EP3184259A1 - Impact tool - Google Patents
Impact tool Download PDFInfo
- Publication number
- EP3184259A1 EP3184259A1 EP16205945.5A EP16205945A EP3184259A1 EP 3184259 A1 EP3184259 A1 EP 3184259A1 EP 16205945 A EP16205945 A EP 16205945A EP 3184259 A1 EP3184259 A1 EP 3184259A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- weight
- tool
- pressed state
- controller
- electric motor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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- 238000001514 detection method Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 abstract description 3
- 238000004891 communication Methods 0.000 description 15
- 230000005540 biological transmission Effects 0.000 description 8
- 238000005553 drilling Methods 0.000 description 8
- 230000000694 effects Effects 0.000 description 4
- 230000000994 depressogenic effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
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- 239000000203 mixture Substances 0.000 description 1
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- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D11/00—Portable percussive tools with electromotor or other motor drive
- B25D11/005—Arrangements for adjusting the stroke of the impulse member or for stopping the impact action when the tool is lifted from the working surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D17/00—Details of, or accessories for, portable power-driven percussive tools
- B25D17/04—Handles; Handle mountings
- B25D17/043—Handles resiliently mounted relative to the hammer housing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D17/00—Details of, or accessories for, portable power-driven percussive tools
- B25D17/24—Damping the reaction force
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D2217/00—Details of, or accessories for, portable power-driven percussive tools
- B25D2217/0073—Arrangements for damping of the reaction force
- B25D2217/0076—Arrangements for damping of the reaction force by use of counterweights
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D2250/00—General details of portable percussive tools; Components used in portable percussive tools
- B25D2250/195—Regulation means
- B25D2250/201—Regulation means for speed, e.g. drilling or percussion speed
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25D—PERCUSSIVE TOOLS
- B25D2250/00—General details of portable percussive tools; Components used in portable percussive tools
- B25D2250/221—Sensors
Definitions
- the present invention relates to an impact tool which performs a hammering operation on a workpiece by linearly driving a tool accessory along a prescribed hammering axis.
- Japanese laid-open patent publication No. 2008-073836 A discloses an impact tool in which a counter weight is provided on a swinging member for reciprocally move a cylindrical piston.
- This impact tool is configured such that the swinging member reciprocally moves the cylindrical piston and thereby linearly drives a tool bit to perform a hammering operation, and is configured such that the counter weight reduces vibration caused during the hammering operation.
- An impact tool of this type is configured such that, in a non-pressed state that a tool bit is not pressed against a workpiece, in order to secure user's safety and to promptly proceed to a hammering operation when the user switches to a pressed state by pressing the tool bit against the workpiece, a driving mechanism is placed in a driving state while impact driving of the tool bit is prevented when it is still in the non-pressed state in which the hammering operation is not yet started.
- the above-described impact tool is configured such that the swinging member is moved by driving of the driving mechanism even in the non-pressed state. Therefore, in the non-pressed state, unnecessary vibration may be caused by reciprocating movement of the counter weight. In view of this point, a countermeasure focusing on vibration of an impact tool in a non-pressed state is desired to be provided.
- an impact tool which performs a hammering operation on a workpiece by linearly driving a tool accessory along a prescribed hammering axis.
- the impact tool has a brushless motor, a driving mechanism that drives the tool accessory by an output of the brushless motor, a vibration suppressing mechanism having a movable weight, and a controller that controls driving ofthe brushless motor.
- a pressed state which is defined as a state that a prescribed pressing force is applied to the tool accessory
- the controller drives the brushless motor at a first rotation speed.
- a non-pressed state which is defined as a state that the prescribed pressing force is not applied to the tool accessory, the controller drives the brushless motor at a second rotation speed lower than the first rotation speed.
- the impact tool may be configured to cause the tool accessory not only to perform hammering motion by linearly driving the tool accessory along the prescribed hammering axis, but to perform rotating motion by rotating the tool accessory around the hammering axis, or it may be configured to simultaneously perform the hammering motion and the rotating motion.
- the impact tool specifically includes an electric hammer and an electric hammer drill.
- the driving mechanism may typically consist of a piston which is caused to reciprocate by the output of the brushless motor, and a striking element which is moved via pressure fluctuations caused in the air chamber by reciprocating movement of the piston and collides with the tool accessory.
- the user presses the tool accessory against a workpiece. By this user's operation, the impact tool is placed in the pressed state. Upon completion of the hammering operation, the user moves the tool accessory away from the workpiece. By this user's operation, the impact tool is placed in the non-pressed state.
- the controller is typically formed by disposing a switching element for controlling a plurality of coils provided in the brushless motor, a central processing unit (CPU) and a condenser on a substrate.
- the controller is configured to determine whether the impact tool is placed in the pressed state or the non-pressed state and then switch the rotation speed of the brushless motor.
- a structure for determining whether the impact tool is placed in the pressed state or the non-pressed state a structure based on detection of a load on the brushless motor, or a structure using a sensor for detecting a region of the driving mechanism which is moved together with the tool accessory when it is switched to the pressed state may be appropriately used.
- first rotation speed and the second rotation speed are preset in the controller, and the controller is configured to select the first rotation speed in the pressed state and to select the second rotation speed in the non-pressed state.
- the structure of switching between the first rotation speed and the second rotation speed may be a structure of instantaneously or gradually switching from one to the other speed. Further, the second rotation speed may be set to zero.
- the vibration suppressing mechanism is a counter weight which is configured such that the weight is mechanically connected to a prescribed region of the driving mechanism and the weight is caused to directly reciprocate by movement of the driving mechanism.
- the vibration suppressing mechanism is a dynamic vibration reducer which has a weight elastic member connected to the weight and is configured such that the weight is caused to reciprocate by movement of the driving mechanism.
- vibration when the impact tool performs a hammering operation, vibration can be effectively suppressed by the counter weight or the dynamic vibration reducer.
- the counter weight may be typically configured such that the weight is mechanically connected to a prescribed region of the driving mechanism via a cam mechanism or a link mechanism. Alternatively, the weight may be directly connected to part of the driving mechanism. With this structure, the weight can be caused to perform steady and periodic motion in a prescribed phase.
- the dynamic vibration reducer may be configured to vibrate the weight elastic member or the weight by movement of the driving mechanism.
- it may be configured to vibrate the weight elastic member by mechanically connecting the weight elastic member to a prescribed region of the driving mechanism via a cam mechanism or a link mechanism and to thereby vibrate the weight.
- it may be configured to vibrate the weight via fluctuations of air pressure by movement of the driving mechanism.
- the weight elastic member may typically be a coil spring.
- the weight elastic member may consist of a single elastic body, or it may consist of a first elastic body connected to one side of the weight and a second elastic body connected to the other side of the weight.
- the weight may be configured to be moved linearly in the direction of the hammering axis.
- the weight may be configured to be rotated around the hammering axis.
- a moving direction of the weight appropriate to the impact tool can be selected, so that the design freedom of the vibration suppressing mechanism can be ensured.
- the impact tool may further has a housing for housing at least part of the driving mechanism, a handle to be held by a user, and a handle elastic member.
- the handle is connected to the housing via the handle elastic member, so that the handle and the housing can be configured to be movable with respect to each other.
- vibration which is caused in the housing during hammering operation and transmitted to the handle can be suppressed.
- the handle elastic member may be a coil spring or rubber.
- the handle and the housing are only enough to be movable with respect to each other via the handle elastic member.
- another component may be disposed between the handle and the handle elastic member or between the housing and the handle elastic member.
- the controller may be disposed within the handle.
- the weight can be distributed to the handle with the controller, so that the vibration proofing effect can be enhanced.
- the impact tool may further have a sensor that detects behavior of the impact tool during a prescribed operation.
- the controller can control driving of the brushless motor based on a detection result of the sensor.
- the controller for controlling driving of the brushless motor is utilized to further control the driving of the brushless motor based on the detection result of the sensor, so that the controller can more finely control the brushless motor.
- the sensor typically includes an acceleration sensor.
- the controller can detect the behavior of the impact tool. For example, when the prescribed operation by the impact tool is a "drilling operation by rotating the tool accessory", the controller can detect behavior that the tool accessory is locked in a hole formed by the drilling operation and the impact tool is caused to rotate on the tool accessory. Upon detection of such behavior, the controller can control to stop the brushless motor.
- the brushless motor may be driven by a battery, and the handle may have a mounting part for the battery.
- the weight can be distributed to the handle with the battery, so that the vibration proofing effect can be enhanced.
- the handle and the housing are connected to each other via an elastic member, transmission of vibration to the handle is suppressed. Therefore, for example, a connection terminal of the mounting part and a connection terminal of the battery can be prevented from being welded with each other.
- FIGS. 1 to 8 First to fourth embodiments of an impact tool according to the present invention are now described with reference to FIGS. 1 to 8 .
- components or mechanisms having structures or functions identical or similar to those of the first embodiment are given the same designations and reference signs and may not be described.
- FIG. 2 is a partially cutaway sectional view taken along line I-I in FIG. 1 .
- An electric hammer 100 is explained as a representative example of the impact tool according to the present invention.
- the electric hammer 101 is configured to perform a chipping operation on a workpiece (such as concrete) by causing a tool bit 119 coupled to a front end region of a body 101 to perform hammering motion in its longitudinal direction.
- the tool bit 119 extends along its hammering axis.
- the tool bit 119 is removably coupled to the body 101 via a cylindrical tool holder 131.
- the tool bit 119 is inserted into a bit insertion hole of the tool holder 131 and held such that it is prevented from rotating around an axis of the tool holder 131 with respect to the tool holder 131.
- the tool bit 119 is an example embodiment that corresponds to the "tool accessory" according to the present invention.
- the body 101 mainly includes a body housing 103, a barrel 104 and an outer housing 105.
- the body housing 103 mainly includes a motor housing 103a that houses an electric motor 110, and a gear housing 103b that houses a first motion converting mechanism 120 and a second motion converting mechanism 160.
- the barrel 104 is configured as a cylindrical member for housing a striking mechanism 140 and part ofthe tool holder 131 and connected to the body housing 103.
- the motor housing 103a, the gear housing 103b and the barrel 104 are made of aluminum.
- the barrel 104, the gear housing 103b and the motor housing 103a are arranged in this order in the longitudinal direction of the tool bit 119 and joined to each other to be fixedly assembled together.
- the barrel 104 is arranged closest to the tool bit 119 and the motor housing 103 a is arranged farthest from the tool bit 119 in the longitudinal direction of the tool bit 119.
- the motor housing 103a and the gear housing 103b may be formed in one piece.
- the body housing 103 is an example embodiment that corresponds to the "housing" according to the present invention.
- the outer housing 105 is arranged on the outside of the body housing 103 as shown in FIG. 1 .
- the outer housing 105 has a cylindrical shape extending in the longitudinal direction of the tool bit 119 and is arranged to entirely cover the body housing 103.
- the outer housing 105 has an upper housing 106 and a lower housing 107.
- a pair of handgrips 109 for operating the electric hammer 100 in chipping operation are provided on the upper housing 106.
- the handgrips 109 are symmetrically arranged with respect to an axis extending in the longitudinal direction of the tool bit 119 and extend straight in a direction crossing the axis.
- Each of the handgrips 109 has one end fixed to the upper housing 106 in a cantilever form.
- the handgrip 109 is an example embodiment that corresponds to the "handle" according to the present invention.
- the user performs a chipping operation while holding the handgrips 109 with hands and pointing the tool bit 119 downward. Therefore, for the sake of convenience, in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101), the tool bit 119 side is defined as the lower side and the handgrip 109 side is defined as the upper side.
- the handgrip 109 is an example embodiment that corresponds to the "handle" according to the present invention.
- the lower housing 107 is integrally connected to the body housing 103.
- a guide shaft 108A is disposed between the upper housing 106 and the motor housing 103a.
- the guide shaft 108A has a shaft support part 106a which is integrally connected to the upper housing 106.
- An upper end of the guide shaft 108A is fitted in a recess 106b of the shaft support part 106a, and a lower end of the guide shaft 108A is fitted in a recess 103a1 of the motor housing 103a.
- a middle region of the guide shaft 108A is inserted through an annular part 106c of the shaft support part 106a.
- the guide shaft 108A has a flange 108A1 in a region below the annular part 106c.
- a coil spring 108b is disposed between the flange 108A1 and the recess 103a1 of the motor housing 103a. In the electric hammer 100, four such guide shafts 108A and four such coil springs 108b are provided.
- the upper housing 106 and the motor housing 103a are connected via the coil springs 108b.
- the coil spring 108b is an example embodiment that corresponds to the "handle elastic member" according to the present invention.
- the handgrip 109 and the body housing 103 are configured to be movable with respect to each other.
- the upper housing 106 and the lower housing 107 are connected via an annular bellows 108a.
- the bellows 108a is made of vinyl or rubber and configured to be expandable and contractable.
- the bellows 108a prevents entry of dust into the handgrips 109 and the body housing 103.
- the coil springs 108b and the bellows 108a form a connecting mechanism 108.
- An electric switch 109e for driving and stopping the electric motor 110 and an operation part 109d for switching on and off the electric switch 109e are provided in one of the handgrips 109 as shown in FIG. 1 .
- the operation part 109d of the electric hammer 100 is formed by a switch lever.
- the operation part 109d is provided to be turned in a direction crossing the longitudinal direction of the handgrip 109.
- the operation part 109d is held in a position to protrude outward (upward) from an outer surface of the handgrip 109 by a biasing force of a built-in spring (not shown) provided in the electric switch 109e.
- the operation part 109d is pressed with a user's finger, the operation part 109d is turned inward into the handgrip 109 and the electric switch 109e is switched on, so that the electric motor 110 is driven.
- the electric motor 110 is formed by a brushless motor. As shown in FIG. 3 , a controller 112 for controlling driving of the electric motor 110 is disposed between an outer surface of the body housing 103 and an inner surface of the outer housing 105. The controller 112 is formed by disposing a switching element for controlling a plurality of coils provided in the electric motor 110, a central processing unit (CPU) and a condenser on a substrate.
- the electric motor 110 and the controller 112 are example embodiments that correspond to the "brushless motor" and the "controller", respectively, according to the present invention.
- the user performs a hammering operation on a workpiece while pressing the tool bit 119 against the workpiece.
- This state that a prescribed pressing force is applied to the tool bit 119 is defined as a pressed state of the electric hammer 100.
- the user may move the electric hammer 100 toward other workpiece. In such a case, while the user is moving the electric hammer 100, the electric motor 110 is kept on, but the tool bit 119 is not pressed against the workpiece.
- This state that the prescribed pressing force is not applied to the tool bit 119 is defined as a non-pressed state of the electric hammer 100.
- the user can perform a hammering operation on a plurality of workpieces by switching the electric hammer 100 between the pressed state and the non-pressed state.
- the pressed state and the non-pressed state are example embodiments that correspond to the "pressed state” and the “non-pressed state", respectively, according to the present invention.
- the controller 112 controls the electric motor 110 to be driven in a prescribed range of rotation speed. Specifically, the controller 112 controls the electric motor 110 to rotate in the prescribed range of rotation speed such that the rotation speed of the electric motor 110 does not significantly fluctuate by load on the electric motor 110 during hammering operation.
- the prescribed range of rotation speed at which the electric motor 110 is driven in the pressed state is defined as a first rotation speed.
- the first rotation speed is an example embodiment that corresponds to the "first rotation speed" according to the present invention.
- the controller 112 controls the electric motor 110 to be driven at lower rotation speed than the first rotation speed.
- This lower rotation speed than the first rotation speed, at which the electric motor 110 is driven in the non-pressed state, is defined as a second rotation speed.
- the second rotation speed is an example embodiment that corresponds to the "second rotation speed" according to the present invention.
- the controller 112 is configured to detect load on the electric motor 110 and thereby determine whether the electric hammer 100 is placed in the pressed state or the non-pressed state. More specifically, a threshold is set for a current to be supplied to the electric motor 110, and the controller 112 is configured to determine that the electric hammer 100 is placed in the non-pressed state when the current does not exceed the threshold and to determine that the electric hammer 100 is placed in the pressed state when the current exceeds the threshold.
- the electric motor 110 is driven by alternate current supplied via a feeding part 180 as shown in FIG. 1 .
- the feeding part 180 is formed by a power cable.
- the electric motor 110 is arranged such that a motor shaft 111 of the electric motor 110 extends in a direction crossing a longitudinal axis of the tool bit 119 and parallel to a longitudinal axis of the handgrip 109.
- Rotation of the electric motor 110 is converted into linear motion by the first motion converting mechanism 120 and transmitted to the striking mechanism 140, and the tool bit 119 is struck in the longitudinal direction (downward as viewed in FIG. 1 ) via the striking mechanism 140.
- rotation of the electric motor 110 is converted into linear motion by the second motion converting mechanism 160 and transmitted to a counter weight 190.
- the counter weight 190 is configured to linearly move in the longitudinal direction of the tool bit 119 at a timing when an impact force is generated by striking of the tool bit 119. With this structure, the counter weight 190 suppresses vibration caused in the electric hammer 100.
- the motor shaft 111, the first motion converting mechanism 120 and the second motion converting mechanism 160 are example embodiments that correspond to the "rotary shaft", the “driving mechanism” and the “vibration suppressing mechanism", respectively, according to the present invention.
- the counter weight 190 is an example embodiment that corresponds to the "weight” and the "counter weight” according to the present invention.
- the first motion converting mechanism 120 is formed by a first crank mechanism disposed below the electric motor 110 and including a first crank shaft 121, a first connecting rod 123 and a piston 125.
- the first motion converting mechanism 120 is driven by the electric motor 110 via a gear speed reducing device 113 having a plurality of gears.
- the piston 125 forms a driving element for driving the striking mechanism 140 (see FIG. 1 ).
- the piston 125 is arranged to slide within a cylinder 141 in the longitudinal direction of the tool bit 119.
- the first crank shaft 121 is arranged in parallel to the motor shaft 111 of the electric motor 110.
- An eccentric shaft part 121 a is integrally formed with the first crank shaft 121 and rotatably connected to the first connecting rod 123.
- the striking mechanism 140 mainly includes a cylinder 141, a striking element in the form of a striker 143, and an intermediate element in the form of an impact bolt 145.
- the striker 143 is slidably disposed within the cylinder 141.
- the impact bolt 145 is slidably disposed within the tool holder 131 and transmits kinetic energy of the striker 143 to the tool bit 119.
- the cylinder 141 is coaxially arranged with the tool holder 131 above the tool holder 131.
- An air chamber 141a is formed between the piston 125 and the striker 143 within the cylinder 141.
- the striker 143 is driven via pressure fluctuations caused in the air chamber 141a by sliding movement of the piston 125. Then the striker 143 collides with the impact bolt 145 and strikes the tool bit 119 via the impact bolt 145.
- the cylinder 141 has a vent 141b as shown in FIG. 1 .
- the vent 141b is configured to provide communication between the inside of the cylinder 141 and the inside of the barrel 104.
- the striker 143 When the electric hammer 100 is in the pressed state, the striker 143 is placed in an upper position via the tool bit 119 and the impact bolt 145 and blocks communication between the air chamber 141a and the vent 141b. Thus, when the piston 125 is driven, the pressure of the air chamber 141a fluctuates, so that the striker 143 can be driven.
- the striker 143 moves the tool bit 119 and the impact bolt 145 downward.
- the air chamber 141a is expanded to a region of the cylinder 141 having the vent 141b.
- the air chamber 141a communicates with the inside of the barrel 104 via the vent 141b. Therefore, when the piston 125 moves in a direction of compressing air of the air chamber 141a (downward), the air is released into the barrel 104 via the vent 141b.
- the second motion converting mechanism 160 is formed by a second crank mechanism including a second crank shaft 161, an eccentric shaft 163 and a second connecting rod 165.
- the second crank shaft 161 is arranged on an extension of an axis of the first crank shaft 121 of the first crank mechanism and rotated by the eccentric shaft part 121a of the first crank shaft 121.
- the eccentric shaft 163 is arranged in parallel to the second crank shaft 161 in a position displaced a prescribed distance in a radial direction from the center of rotation of the second crank shaft 161.
- One end of the second connecting rod 165 is connected to the eccentric shaft 163 so as to be rotatable around the eccentric shaft 163.
- the other end of the second connecting rod 165 is connected to a connecting shaft 166 provided on the counter weight 190 so as to be rotatable around the connecting shaft 166.
- the connecting shaft 166 is arranged in parallel to the eccentric shaft 163.
- the counter weight 190 is configured as a cylindrical member which is slidably fitted onto the cylinder 141.
- the counter weight 190 reciprocates between a front position closest to the tool bit 119 and a rear position farthest from the tool bit 119.
- the cylindrical counter weight 190 may be shaped to partially surround the cylinder 141.
- the user When performing a hammering operation on a workpiece with the electric hammer 100 having the above-described structure, the user holds a pair of the handgrips 109 with hands and presses the tool bit 119 pointed downward against a workpiece. Specifically, the user performs a hammering operation while keeping the electric hammer 100 in the pressed state.
- the electric motor 110 When the user presses the operation part 109d with a finger of the hand holding the one handgrip 109 to turn on the electric switch 109e, the electric motor 110 is driven. Then the tool bit 119 is linearly driven via the first motion converting mechanism 120 and the striking mechanism 140 and can perform a hammering operation on the workpiece.
- the controller 112 determines that the electric hammer 100 is placed in the pressed state and controls the electric motor 110 to rotate at the first rotation speed.
- the counter weight 190 is caused to reciprocate in the longitudinal direction of the tool bit 119 via the second motion converting mechanism 160.
- the counter weight 190 is set to move substantially in opposite phase to movement of the striker 143. Specifically, the counter weight 190 moves upward when the striker 143 moves downward, while the counter weight 190 moves downward when the striker 143 moves upward. By this movement, the counter weight 190 suppresses vibration caused in the electric hammer 100 during operation.
- the handgrips 109 (the upper housing 106) and the body housing 103 (the motor housing 103a) are moved in the longitudinal direction of the tool bit 119 with respect to each other while being guided by the guide shafts 108A under the biasing force of the coil springs 108b.
- the coil springs 108b are expanded and contracted by the kinetic energy of vibration caused during hammering operation, so that transmission of vibration from the body housing 103 to the handgrips 109 is suppressed.
- vibration-proof handle and the counter weight 190 vibration which is caused during hammering operation and transmitted to the user holding the handgrips 109 is suppressed.
- the operability of the electric hammer 100 is improved.
- the controller 112 detects that the current supplied to the electric motor 110 is below a threshold and controls the electric motor 110 to rotate at the second rotation speed.
- the striker 143 In the non-pressed state, where the electric motor 110 is rotationally driven at the second rotation speed, the first crank shaft 121 and the second crank shaft 161 are driven. Immediately after the electric hammer 100 is switched from the pressed state to the non-pressed state, the striker 143 is driven by driving of the piston 125. In the non-pressed state, however, the tool bit 119 and the impact bolt 145 are located in a lower position. Therefore, the striker 143 moves down to the impact bolt 145 located in this lower position. As a result, the striker 143 moves down to below the vent 141b. Thus, the air chamber 141a communicates with the inside of the barrel 104, so that the tool bit 119 is prevented from being driven by driving of the first crank shaft 121.
- the counter weight 190 is caused to reciprocate by driving of the second crank shaft 161
- the electric motor 110 is driven at the second rotation speed, so that vibration caused by the reciprocating movement of the counter weight 190 can be reduced.
- the electric hammer 100 can suppress vibration related to hammering operation by the second motion converting mechanism 160 and the coil springs 108b. Further, in the non-pressed state, the electric motor 110 is driven at the second rotation speed, so that vibration caused by the reciprocating movement of the counter weight 190 can be reduced. Specifically, the electric hammer 100 can effectively suppress vibrations caused in the pressed state and the non-pressed state.
- An electric hammer 200 of the second embodiment is different from the electric hammer 100 of the first embodiment mainly in the structures of the handle and the vibration suppressing mechanism.
- the electric hammer 200 is an example embodiment that corresponds to the "impact tool" according to the present invention.
- the body 101 mainly includes a body housing 203 and a handgrip 109 connected to the body housing 203.
- the body housing 203 is an example embodiment that corresponds to the "housing" according to the present invention.
- a barrel 104 is connected to the body housing 203 and houses a striking mechanism 140.
- a side grip 109A to be held by a user can be removably attached onto the barrel 104. The structure of the side grip 109A is not described here for convenience sake.
- the handgrip 109 to be held by a user is arranged on a side opposite from the tool bit 119 in the longitudinal direction of the tool bit 119 as shown in FIG. 4 .
- the tool bit 119 side is defined as a lower side and the handgrip 109 side is defined as an upper side in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101).
- a direction crossing the vertical direction is defined as a transverse direction
- a direction crossing the vertical direction and the transverse direction is defined as a thickness direction.
- An operation part 109d is provided in the handgrip 109 as shown in FIG. 4 .
- the operation part 109d of the electric hammer 200 is configured to be slidable in the thickness direction to switch on and off an electric switch 109e.
- a controller 112 drives the electric motor 110.
- the body housing 203 and the handgrip 109 are connected by a connecting mechanism 108 as shown in FIG. 5 .
- the connecting mechanism 108 has a bellows 108a and a coil spring 108b. With this structure, the body housing 203 and the handgrip 109 can move with respect to each other.
- the electric motor 110 is a brushless motor and is arranged such that the motor shaft 111 extends in a direction crossing the longitudinal axis of the tool bit 119.
- the electric motor 110 and the handgrip 109 are arranged on the longitudinal axis of the tool bit 119.
- the controller 112 is configured to drive the electric motor 110 at the first rotation speed in the pressed state and to drive the electric motor 110 at the second rotation speed in the non-pressed state.
- the controller 112 is housed in the handgrip 109.
- a cable for electrically connecting the controller 112 and the electric motor 110 is wired between the controller 112 and the electric motor 110 through the inside of the bellows 108a. In FIGS. 4 and 5 , the cable is not shown for convenience sake.
- rotation of the electric motor 110 is transmitted to a first motion converting mechanism 120 via a gear speed reducing device 113, and thereafter converted into linear motion by the first motion converting mechanism 120 and transmitted to the striking mechanism 140. Then the tool bit 119 is struck in the longitudinal direction via the striking mechanism 140. Further, rotation of the electric motor 110 is transmitted to a second motion converting mechanism 160 via the first motion converting mechanism 120, and thereafter converted into linear motion by the second motion converting mechanism 160 and transmitted to a dynamic vibration reducer 290.
- the first motion converting mechanism 120, the gear speed reducing device 113 and the striking mechanism 140 have the same structures as those of the first embodiment, respectively, and are not described.
- the second motion converting mechanism 160 mainly includes a second crank shaft 161 which is rotated by an eccentric shaft part 121a of a first crank shaft 121 of the first motion converting mechanism 120, an eccentric shaft 163 integrally formed with the second crank shaft 161, and an second connecting rod 165 which is linearly moved in the longitudinal direction of the tool bit 119 by rotation of the eccentric shaft 163.
- the second connecting rod 165 drives the dynamic vibration reducer 290.
- the dynamic vibration reducer 290 mainly includes an annular weight 291 configured to surround the outer circumferential surface of the cylinder 141 entirely in the circumferential direction, and biasing springs 292, 293 disposed on the upper and lower sides of the weight 291.
- the biasing springs 292, 293 apply respective spring forces to the weight 291 in the longitudinal direction of the tool bit 119 when the weight 291 moves in the longitudinal direction of the tool bit 119.
- the weight 291, the dynamic vibration reducer 290 and the biasing spring 292 or 293 are example embodiments that correspond to the "weight”, the "dynamic vibration reducer” and the "weight elastic member", respectively, according to the present invention.
- the weight 291 is arranged to slide with its periphery in contact with an inner wall surface (cylindrical surface) of the barrel 104.
- the upper and lower biasing springs 292, 293 are compression coil springs.
- the upper spring 293 is configured such that its one end is held in contact with a flange of a slide sleeve 210 and the other end is held in contact with the weight 291.
- the lower spring 292 is configured such that its one end is held in contact with the weight 291 and the other end is held in contact with a ring-like member 211 fixed to the barrel 104.
- the slide sleeve 210 and the ring-like member 211 form spring receiving members.
- the slide sleeve 210 can slide in the longitudinal direction of the tool bit 119 with respect to the periphery of the cylinder 141 and is held in contact with the second connecting rod 165. Thus, the slide sleeve 210 is slid by the second motion converting mechanism 160.
- the dynamic vibration reducer 290 is configured such that the weight 291 is driven in opposite phase to the striker 143.
- the user When performing a hammering operation on a workpiece with the electric hammer 200 having the above-described structure, the user holds the handgrip 109 and presses the electric hammer 200.
- the electric motor 110 is driven.
- the tool bit 119 is linearly driven via the first motion converting mechanism 120 and the striking mechanism 140 and can perform a hammering operation on the workpiece.
- the controller 112 determines that the electric hammer 200 is placed in the pressed state and controls the electric motor 110 to rotate at the first rotation speed.
- the dynamic vibration reducer 290 is forcibly driven by the second motion converting mechanism 160. Therefore, the dynamic vibration reducer 290 effectively suppresses vibration caused in the body housing 203 during hammering operation. Furthermore, the handgrip 109 moves with respect to the body housing 203 via the coil springs 108b, so that transmission of vibration to the handgrip 109 is further effectively suppressed.
- the controller 112 detects that the current supplied to the electric motor 110 is below a threshold and controls the electric motor 110 to rotate at the second rotation speed.
- the dynamic vibration reducer 290 is driven by driving of the second crank shaft 161
- the electric motor 110 is driven at the second rotation speed, so that vibration caused by driving of the dynamic vibration reducer 290 can be reduced.
- the electric hammer 200 can suppress vibration related to hammering operation by the second motion converting mechanism 160 and the coil springs 108b. Further, in the non-pressed state, the electric motor 110 is driven at the second rotation speed, so that vibration caused by driving of the dynamic vibration reducer 290 can be reduced. Specifically, the electric hammer 200 can effectively suppress vibrations caused in the pressed state and the non-pressed state.
- the third embodiment of the present invention is now described with reference to FIGS. 6 and 7 .
- the structure of the impact tool according to the third embodiment is explained based on an electric hammer drill 300 which is capable of performing a hammering operation by linearly driving a tool bit along a prescribed hammering axis and a drilling operation of drilling a workpiece by rotating the tool bit around the hammering axis.
- the electric hammer drill 300 is an example embodiment that corresponds to the "impact tool" according to the present invention.
- the electric hammer drill 300 is configured to be switched by a user among a hammer mode for hammering operation, a drill mode for drilling operation and a hammer drill mode for simultaneously performing hammering and drilling operations.
- the structure for switching the operation mode is not described for convenience sake.
- the body 101 of the electric hammer drill 300 mainly includes a body housing 303 and a handgrip 109 connected to the body housing 303.
- the body housing 303 is an example embodiment that corresponds to the "housing" according to the present invention.
- the body housing 303 houses an electric motor 110, a controller 112, a first motion converting mechanism 120, a striking mechanism 140, and a rotation transmitting mechanism 151 and a dynamic vibration reducer 390 (see FIG. 7 ).
- the handgrip 109 is arranged on a side of the body housing 303 opposite from the tool bit 119 in the longitudinal direction of the tool bit 119.
- the tool bit 119 side is defined as a front side and the handgrip 109 side is defined as a rear side in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101).
- the handgrip 109 has a grip part 109a extending in a vertical direction of the hammer drill 300 (a direction crossing the longitudinal direction of the tool bit 119) as shown in FIG. 6 .
- the handgrip 109 is connected to the body housing 303 by a connecting mechanism 108 in an upper connecting region 109b.
- a coil spring 108b of the connecting mechanism 108 is arranged to extend between a spring receiving part 108c provided in the body housing 303 and a spring receiving part 108d provided in the handgrip 109.
- the handgrip 109 is connected to the body housing 303 by a pivot 108e in a lower connecting region 109c.
- the handgrip 109 and the body housing 303 can rotate on the pivot 108e with respect to each other under the biasing force of the coil spring 108b. With this structure, transmission of vibration of the body housing 303 to the handgrip 109 can be suppressed.
- An operation part 109d is provided in the handgrip 109 as shown in FIG. 6 .
- the electric motor 110 is driven via the controller 112.
- the operation part 109d of the hammer drill 300 is a trigger which is depressed by a user.
- the electric motor 110 is a brushless motor and is arranged such that the motor shaft 111 extends in a direction crossing the longitudinal axis of the tool bit 119.
- the electric motor 110 is arranged in a position displaced from the longitudinal axis of the tool bit 119.
- the electric motor 110 is disposed in a lower part of the hammer drill 300, and a cylinder 141 and a tool holder 131 which are coaxially arranged with the tool bit 119 are disposed in an upper part of the hammer drill 300.
- the controller 112 is configured to drive the electric motor 110 at the first rotation speed in the pressed state and to drive the electric motor 110 at the second rotation speed in the non-pressed state.
- the hammer drill 300 has an acceleration sensor 112a, and the controller 112 is configured to control driving of the electric motor 110 based on the detection result of the acceleration sensor 112a.
- the acceleration sensor 112a is an example embodiment that corresponds to the "sensor" according to the present invention. When the acceleration sensor 112a detects an inclined state of the hammer drill 300, the controller 112 can detect the behavior of the hammer drill 300.
- the hammer drill 300 is configured such that the controller 112 controls to stop driving of the electric motor 110 when the acceleration sensor 112a exhibits prescribed behavior in the drill mode or hammer drill mode of the hammer drill 300.
- This prescribed behavior includes such behavior that the tool bit 119 is locked in a hole formed by drilling operation and the hammer drill 300 is caused to rotate on the tool bit 119.
- the hammer drill 300 can be provided with a function of preventing specific behavior in drilling operation simply by providing the controller 112 for controlling driving of the brushless motor (the electric motor 110) with an additional function of controlling driving of the electric motor 110 based on the detection result of the acceleration sensor 112a.
- the acceleration sensor 112a is disposed in the controller 112 as shown in FIG. 6 .
- the acceleration sensor 112a may be disposed elsewhere in the body 101, and a plurality of acceleration sensors 112a may be provided.
- rotation of the electric motor 110 is transmitted to the first motion converting mechanism 120 disposed in the upper part of the hammer drill 300, and thereafter converted into linear motion by the first motion converting mechanism 120 and transmitted to the striking mechanism 140. Then the tool bit 119 is struck in the longitudinal direction via the striking mechanism 140. Further, rotation of the electric motor 110 is transmitted to the tool holder 131 via the rotation transmitting mechanism 151, and the tool bit 119 is rotated around its axis via the tool holder 131.
- the first motion converting mechanism 120 and the striking mechanism 140 have the same structures as those of the first embodiment, respectively, and are not described.
- a cylinder side communication opening 141c is formed in the cylinder 141 of the hammer drill 300 as shown in FIG. 6 .
- the rotation transmitting mechanism 151 mainly includes a driven gear 153, a mechanical torque limiter 155, an intermediate shaft 157 and a small bevel gear 159 as shown in FIG. 6 .
- the driven gear 153 is engaged with a pinion gear provided on the motor shaft 111 and rotated.
- the driven gear 153 is connected to the intermediate shaft 157 via the mechanical torque limiter 155.
- the mechanical torque limiter 155 is configured to interrupt torque transmission between the driven gear 153 and the intermediate shaft 157 when acted upon by torque exceeding a prescribed value.
- the small bevel gear 159 is provided on an upper end of the intermediate shaft 157 and engages with a large bevel gear 132 provided on a rear end of the tool holder 131. With this structure, the rotation transmitting mechanism 151 transmits rotation of the electric motor 110 to the tool holder 131.
- the dynamic vibration reducer 390 has a weight 391, a biasing spring 392 disposed on the front side of the weight 391, and a biasing spring 393 disposed on the rear side of the weight 391.
- the weight 391, the dynamic vibration reducer 390 and the biasing springs 392, 393 are example embodiments that correspond to the "weight”, the "dynamic vibration reducer” and the “weight elastic member”, respectively, according to the present invention. Only one dynamic vibration reducer 390 is shown in FIG. 7 , but another dynamic vibration reducer 390 is disposed on the opposite side of the hammering axis from the one dynamic vibration reducer 390.
- the dynamic vibration reducer 390 is disposed in a dynamic vibration reducer arrangement space.
- the dynamic vibration reducer arrangement space includes a first space 394 in which the biasing spring 392 is disposed and a second space 395 in which the biasing spring 393 is disposed.
- the weight 391 is disposed in the dynamic vibration reducer arrangement space via a cylindrical member 396. More specifically, a large-diameter part of the weight 391 is held in contact with the cylindrical member 396 so as to be reciprocally slidable. The large-diameter part of the weight 391 prevents communication between the first space 394 and the second space 395.
- the first space 394 has a dynamic vibration reducer side first communication opening 394a which communicates with the barrel space.
- the first space 394 communicates with the air chamber 141a via the dynamic vibration reducer side first communication opening 394a and the barrel space.
- the second space 395 has a dynamic vibration reducer side second communication opening 395a which communicates with the crank chamber 121b.
- the second space 395 communicates with the crank chamber 121b via the dynamic vibration reducer side second communication opening 395a.
- the weight 391 reciprocates in the back and forth direction by driving of the piston 125.
- the dynamic vibration reducer 390 is configured to move the weight 391 in a phase opposite to the moving direction of the piston 125. Based on this movement, the dynamic vibration reducer 390 is designed such that the weight 391 is driven in a phase opposite to the moving direction of the striker 143.
- the user When performing a hammering operation on a workpiece with the hammer drill 300 having the above-described structure, the user holds the handgrip 109 and presses the hammer drill 300.
- the electric motor 110 is driven.
- the tool bit 119 is linearly driven via the first motion converting mechanism 120 and the striking mechanism 140 and can perform a hammering operation on the workpiece.
- the controller 112 determines that the hammer drill 300 is placed in the pressed state and controls the electric motor 110 to rotate at the first rotation speed.
- the operation part 109d of the hammer drill 300 is a trigger.
- the weight 391 of the dynamic vibration reducer 390 is moved in a phase opposite to the moving direction of the striker 143. Therefore, during hammering operation, the dynamic vibration reducer 390 effectively reduces vibration caused in the body housing 303. Furthermore, the handgrip 109 reciprocally rotates on the pivot 108e with respect to the body housing 303 via the coil spring 108b, so that transmission of vibration to the handgrip 109 is further effectively suppressed.
- the controller 112 detects that the current supplied to the electric motor 110 is below a threshold and controls the electric motor 110 to rotate at the second rotation speed.
- the piston 125 In the non-pressed state, where the electric motor 110 is rotationally driven at the second rotation speed, the piston 125 is driven.
- the dynamic vibration reducer 390 is driven, but in this state where the electric motor 110 is rotationally driven at the second rotation speed, vibration caused by driving of the dynamic vibration reducer 390 is reduced, compared with the state where the electric motor 110 is driven at the first rotation speed.
- the hammer drill 300 is configured such that the ring-like member 141 d shown in FIG. 6 closes the vent 141b of the cylinder 141 in the pressed state and opens the vent 141b in the non-pressed state.
- the tool bit 119 is prevented from being driven by driving of the piston 125.
- the structure relating to this function is not described for convenience sake.
- the hammer drill 300 can suppress vibration related to hammering operation by the dynamic vibration reducer 390 and the coil spring 108b. Further, in the non-pressed state, since the electric motor 110 is driven at the second rotation speed, vibration caused by driving of the dynamic vibration reducer 390 can be reduced. Specifically, the hammer drill 300 can effectively suppress vibrations caused in the pressed state and the non-pressed state.
- an electric hammer drill 400 of the fourth embodiment is configured to be switched by a user among a hammer mode, a drill mode and a hammer drill mode.
- the body 101 of the electric hammer drill 400 mainly includes a body housing 403 and a handgrip 109 connected to the body housing 403.
- the body housing 403 houses an electric motor 110, a controller 112, a first motion converting mechanism 120, a striking mechanism 140, a rotation transmitting mechanism 151 and a counter weight 490.
- the handgrip 109 is arranged on a side of the body housing 403 opposite from the tool bit 119 in the longitudinal direction of the tool bit 119.
- the tool bit 119 side is defined as a front side and the handgrip 109 side is defined as an rear side in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101).
- the side on which the tool bit 119 is arranged is defined as an upper side and the side on which the controller 112 is arranged is defined as a lower side.
- the handgrip 109 has a grip part 109a extending in a vertical direction of the hammer drill 400 (a direction crossing the longitudinal direction of the tool bit 119).
- the handgrip 109 has an upper connecting region 109b and a lower connecting region 109c which are connected to the body housing 403 by respective connecting mechanisms 108.
- the handgrip 109 and the body housing 403 can move with respect to each other under the biasing force of the coil spring 108b, so that transmission of vibration of the body housing 403 to the handgrip 109 can be suppressed.
- a battery mounting part 109f for mounting a battery (a feeding part 180) is provided on the underside of the handgrip 109.
- the battery mounting part 109f is an example embodiment that corresponds to the "mounting part" according to the present invention.
- a cable for electrically connecting the feeding part 180 and the controller 112 is wired between the feeding part 180 and the electric motor 110 through the inside of a lower bellows 108a. In FIG. 8 , the cable is not shown for convenience sake.
- a trigger which forms an operation part 109d is provided in the handgrip 109.
- the electric motor 110 is driven via the controller 112.
- the electric motor 110 is a brushless motor.
- the controller 112 is configured to drive the electric motor 110 at the first rotation speed in the pressed state and to drive the electric motor 110 at the second rotation speed in the non-pressed state.
- the electric motor 110 is arranged such that the motor shaft 111 extends in a direction crossing the longitudinal axis of the tool bit 119.
- the electric motor 110 is arranged in a position displaced from the longitudinal axis of the tool bit 119.
- Rotation of the electric motor 110 is transmitted to the first motion converting mechanism 120 disposed above the electric motor 110, and thereafter converted into linear motion by the first motion converting mechanism 120 and transmitted to the striking mechanism 140.
- the tool bit 119 is struck in the longitudinal direction via the striking mechanism 140.
- rotation of the electric motor 110 is transmitted to the tool holder 131 via the rotation transmitting mechanism 151, and the tool bit 119 is rotated around its axis via the tool holder 131.
- rotation of the electric motor 110 is transmitted to a counter weight 490 via the first motion converting mechanism 120.
- the first motion converting mechanism 120 mainly includes a driven gear 117, an intermediate shaft 116, a swinging shaft 118, a movable cylinder 142 and a striking mechanism 140.
- the driven gear 123 is integrally formed with the intermediate shaft 116.
- the swinging shaft 118 is configured to rotate together with the intermediate shaft 116 and has a rotary member 118a and a shaft member 118b.
- the rotary member 118a has an outer surface inclined with respect to the extending direction of the intermediate shaft 116.
- the shaft member 118b has an annular region which is connected to the rotary member 118a via a steel ball, and a shaft-like region which protrudes upward from the annular region and is rotatably connected to the movable cylinder 142.
- the movable cylinder 142 is a cylindrical member having a bottom and is disposed within the tool holder 131 so as to be reciprocally slidable.
- a striker 143 is disposed within the movable cylinder 142 so as to be reciprocally slidable, and an air chamber 142a is formed between the bottom of the movable cylinder 142 and the striker 143.
- an impact bolt 145 is disposed in front of the striker 143 so as to be reciprocally slidable.
- the swinging shaft 118 reciprocally moves the movable cylinder 142 when the intermediate shaft 116 is rotated by rotation of the motor 110. Then the striker 143 is caused to collide with the impact bolt 145 via pressure fluctuations of the air chamber 142a by the reciprocating movement of the movable cylinder 142, and the too bit 119 is moved forward via the impact bolt 145.
- the tool holder 131 has a striker holding part 131a and an O-ring 131b fitted in the striker holding part 131a. Further, the striker 143 has a front end large-diameter part.
- the striker 143 When the hammer drill 400 is placed in the pressed state, the striker 143 is placed in a rear position via the tool bit 119 and the impact bolt 145. In this state, the impact bolt 145 is located in an inside region of the O-ring 131 b of the striker holding part 131a.
- the striker 143 moves the tool bit 119 and the impact bolt 145 forward.
- the impact bolt 145 is no longer located in the inside region of the O-ring 131b.
- the striker 143 is moved forward by driving of the movable cylinder 142, the front end large-diameter part of the striker 143 moves over the O-ring 131b.
- the pressure of the air chamber 142a decreases by the movement of the movable cylinder 142, the front end large-diameter part is engaged with the O-ring 131b, so that the striker 143 is prevented from moving.
- the tool bit 119 is prevented from being driven.
- the rotation transmitting mechanism 151 mainly includes a driven gear 154 which can rotate together with the intermediate shaft 116, and a tool holder gear 133 which engages with the driven gear 154 and can rotate together with the tool holder 131.
- the driven gear 154 is rotated by the intermediate shaft 116 and rotationally drives the tool holder gear 133, so that the rotation transmitting mechanism 151 can rotate the tool bit 119 held by the tool holder 131.
- the counter weight 490 has an upper end region 490a which is rotatably journaled to the body housing 403 and a lower end region 490b which is connected to a lower end of the annular region of the shaft member 118b.
- the upper end region 490a and the lower end region 490b of the counter weight 490 are arranged on the opposite sides of the swinging axis of the shaft member 118b.
- the counter weight 490 is moved in a phase opposite to the moving direction of the movable cylinder 142.
- the user When performing a hammering operation on a workpiece with the hammer drill 400 having the above-described structure, the user holds the handgrip 109 and presses the hammer drill 400.
- the electric motor 110 is driven.
- the tool bit 119 is linearly driven via the first motion converting mechanism 120 and the striking mechanism 140 and can perform a hammering operation on the workpiece.
- the controller 112 determines that the hammer drill 400 is placed in the pressed state and controls the electric motor 110 to rotate at the first rotation speed.
- the counter weight 490 is driven by movement of the swinging shaft 118. Therefore, during hammering operation, the counter weight 490 effectively reduces vibration caused in the body housing 403. Furthermore, the handgrip 109 reciprocally moves with respect to the body housing 403 via the coil spring 108b, so that transmission of vibration to the handgrip 109 is further effectively suppressed.
- the controller 112 detects that the current supplied to the electric motor 110 is below a threshold and controls the electric motor 110 to rotate at the second rotation speed.
- the hammer drill 400 can suppress vibration related to hammering operation by the counter weight 490 and the coil spring 108b. Further, in the non-pressed state, since the electric motor 110 is driven at the second rotation speed, vibration caused by driving of the counter weight 490 can be reduced. Specifically, the hammer drill 400 can effectively suppress vibrations caused in the pressed state and the non-pressed state.
- Embodiments of the present invention are not limited to the above-described structures of the first to fourth embodiments, but may have other structures.
- the hammering axis of the tool bit 119 may be arranged in parallel to the output shaft of the electric motor 110.
- the structures of the first to fourth embodiments may be appropriately used in combination.
- the structures relating to the counter weight 190 of the first embodiment, the dynamic vibration reducer 290 ofthe second embodiment, the dynamic vibration reducer 390 ofthe third embodiment and the counter weight 490 ofthe fourth embodiment may be appropriately used in other embodiments.
- the impact tool according to this invention can be provided with the following features. Each of the features can be used separately or in combination with the other, or in combination with the claimed invention.
- the weight elastic member has a first elastic body connected to one side of the weight, and a second elastic body connected to the other side of the weight.
- the counter weight is configured such that one end region of the counter weight is rotatably journaled to the housing and the other end region is connected to the driving mechanism.
- the sensor for detecting behavior of the impact tool during the prescribed operation comprises an acceleration sensor.
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Abstract
Description
- The present invention relates to an impact tool which performs a hammering operation on a workpiece by linearly driving a tool accessory along a prescribed hammering axis.
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Japanese laid-open patent publication No. 2008-073836 A - An impact tool of this type is configured such that, in a non-pressed state that a tool bit is not pressed against a workpiece, in order to secure user's safety and to promptly proceed to a hammering operation when the user switches to a pressed state by pressing the tool bit against the workpiece, a driving mechanism is placed in a driving state while impact driving of the tool bit is prevented when it is still in the non-pressed state in which the hammering operation is not yet started. Thus, the above-described impact tool is configured such that the swinging member is moved by driving of the driving mechanism even in the non-pressed state. Therefore, in the non-pressed state, unnecessary vibration may be caused by reciprocating movement of the counter weight. In view of this point, a countermeasure focusing on vibration of an impact tool in a non-pressed state is desired to be provided.
- Accordingly, it is an object of the present invention to provide a further rational technique for reducing vibration in a non-pressed state.
- The above-described problem is solved by the present invention. According to a preferred aspect of the present invention, an impact tool is provided which performs a hammering operation on a workpiece by linearly driving a tool accessory along a prescribed hammering axis. The impact tool has a brushless motor, a driving mechanism that drives the tool accessory by an output of the brushless motor, a vibration suppressing mechanism having a movable weight, and a controller that controls driving ofthe brushless motor. In a pressed state which is defined as a state that a prescribed pressing force is applied to the tool accessory, the controller drives the brushless motor at a first rotation speed. Further, in a non-pressed state which is defined as a state that the prescribed pressing force is not applied to the tool accessory, the controller drives the brushless motor at a second rotation speed lower than the first rotation speed.
- In the impact tool according to this aspect, in the non-pressed state, since the brushless motor is driven at the second rotation speed, movement of the weight can be suppressed compared with in the pressed state. Thus, vibration caused by movement of the weight in the non-pressed state can be suppressed.
- The impact tool may be configured to cause the tool accessory not only to perform hammering motion by linearly driving the tool accessory along the prescribed hammering axis, but to perform rotating motion by rotating the tool accessory around the hammering axis, or it may be configured to simultaneously perform the hammering motion and the rotating motion. The impact tool specifically includes an electric hammer and an electric hammer drill. The driving mechanism may typically consist of a piston which is caused to reciprocate by the output of the brushless motor, and a striking element which is moved via pressure fluctuations caused in the air chamber by reciprocating movement of the piston and collides with the tool accessory.
- When performing a hammering operation with the impact tool, the user presses the tool accessory against a workpiece. By this user's operation, the impact tool is placed in the pressed state. Upon completion of the hammering operation, the user moves the tool accessory away from the workpiece. By this user's operation, the impact tool is placed in the non-pressed state.
- The controller is typically formed by disposing a switching element for controlling a plurality of coils provided in the brushless motor, a central processing unit (CPU) and a condenser on a substrate. The controller is configured to determine whether the impact tool is placed in the pressed state or the non-pressed state and then switch the rotation speed of the brushless motor. As a structure for determining whether the impact tool is placed in the pressed state or the non-pressed state, a structure based on detection of a load on the brushless motor, or a structure using a sensor for detecting a region of the driving mechanism which is moved together with the tool accessory when it is switched to the pressed state may be appropriately used.
- Further, the first rotation speed and the second rotation speed are preset in the controller, and the controller is configured to select the first rotation speed in the pressed state and to select the second rotation speed in the non-pressed state. The structure of switching between the first rotation speed and the second rotation speed may be a structure of instantaneously or gradually switching from one to the other speed. Further, the second rotation speed may be set to zero.
- According to a further aspect of the impact tool of the present invention, the vibration suppressing mechanism is a counter weight which is configured such that the weight is mechanically connected to a prescribed region of the driving mechanism and the weight is caused to directly reciprocate by movement of the driving mechanism. Alternatively, the vibration suppressing mechanism is a dynamic vibration reducer which has a weight elastic member connected to the weight and is configured such that the weight is caused to reciprocate by movement of the driving mechanism.
- In the impact tool according to this aspect, when the impact tool performs a hammering operation, vibration can be effectively suppressed by the counter weight or the dynamic vibration reducer.
- The counter weight may be typically configured such that the weight is mechanically connected to a prescribed region of the driving mechanism via a cam mechanism or a link mechanism. Alternatively, the weight may be directly connected to part of the driving mechanism. With this structure, the weight can be caused to perform steady and periodic motion in a prescribed phase.
- Further, the dynamic vibration reducer may be configured to vibrate the weight elastic member or the weight by movement of the driving mechanism. Typically, it may be configured to vibrate the weight elastic member by mechanically connecting the weight elastic member to a prescribed region of the driving mechanism via a cam mechanism or a link mechanism and to thereby vibrate the weight. Alternatively, it may be configured to vibrate the weight via fluctuations of air pressure by movement of the driving mechanism.
- The weight elastic member may typically be a coil spring. The weight elastic member may consist of a single elastic body, or it may consist of a first elastic body connected to one side of the weight and a second elastic body connected to the other side of the weight.
- According to a further aspect of the impact tool of the present invention, the weight may be configured to be moved linearly in the direction of the hammering axis. Alternatively, the weight may be configured to be rotated around the hammering axis. In the impact tool according to this aspect, a moving direction of the weight appropriate to the impact tool can be selected, so that the design freedom of the vibration suppressing mechanism can be ensured.
- According to a further aspect of the impact tool of the present invention, the impact tool may further has a housing for housing at least part of the driving mechanism, a handle to be held by a user, and a handle elastic member. The handle is connected to the housing via the handle elastic member, so that the handle and the housing can be configured to be movable with respect to each other.
- In the impact tool according to this aspect, vibration which is caused in the housing during hammering operation and transmitted to the handle can be suppressed.
- Further, typically, the handle elastic member may be a coil spring or rubber. The handle and the housing are only enough to be movable with respect to each other via the handle elastic member. For example, another component may be disposed between the handle and the handle elastic member or between the housing and the handle elastic member.
- According to a further aspect of the impact tool of the present invention, the controller may be disposed within the handle. In the impact tool according to this aspect, the weight can be distributed to the handle with the controller, so that the vibration proofing effect can be enhanced.
- According to a further aspect of the impact tool of the present invention, the impact tool may further have a sensor that detects behavior of the impact tool during a prescribed operation. With this structure, the controller can control driving of the brushless motor based on a detection result of the sensor. In the impact tool according to this aspect, the controller for controlling driving of the brushless motor is utilized to further control the driving of the brushless motor based on the detection result of the sensor, so that the controller can more finely control the brushless motor.
- The sensor typically includes an acceleration sensor. When the acceleration sensor detects an inclined state of the impact tool, the controller can detect the behavior of the impact tool. For example, when the prescribed operation by the impact tool is a "drilling operation by rotating the tool accessory", the controller can detect behavior that the tool accessory is locked in a hole formed by the drilling operation and the impact tool is caused to rotate on the tool accessory. Upon detection of such behavior, the controller can control to stop the brushless motor.
- According to a further aspect of the impact tool of the present invention, the brushless motor may be driven by a battery, and the handle may have a mounting part for the battery.
- In the impact tool according to this aspect, the weight can be distributed to the handle with the battery, so that the vibration proofing effect can be enhanced. Particularly in the structure in which the handle and the housing are connected to each other via an elastic member, transmission of vibration to the handle is suppressed. Therefore, for example, a connection terminal of the mounting part and a connection terminal of the battery can be prevented from being welded with each other.
- According to the invention, a further rational technique for reducing vibration in a non-pressed state can be provided.
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FIG. 1 is a sectional view showing an electric hammer according to a first embodiment of the invention. -
FIG. 2 is a sectional view showing a connecting mechanism according to the first embodiment. -
FIG. 3 is an enlarged view showing a driving mechanism according to the first embodiment. -
FIG. 4 is a sectional view showing an electric hammer according to a second embodiment of the invention. -
FIG. 5 is an enlarged view showing a driving mechanism according to the second embodiment. -
FIG. 6 is a sectional view showing an electric hammer drill according to a third embodiment of the invention. -
FIG. 7 is a sectional view showing a vibration suppressing mechanism according to the third embodiment. -
FIG. 8 is a sectional view showing an electric hammer drill according to a fourth embodiment of the invention. - First to fourth embodiments of an impact tool according to the present invention are now described with reference to
FIGS. 1 to 8 . In the description of the second to fourth embodiments, components or mechanisms having structures or functions identical or similar to those of the first embodiment are given the same designations and reference signs and may not be described. - The first embodiment of the present invention is now described with reference to
FIGS. 1 to 3 .FIG. 2 is a partially cutaway sectional view taken along line I-I inFIG. 1 . Anelectric hammer 100 is explained as a representative example of the impact tool according to the present invention. As shown inFIG. 1 , theelectric hammer 101 is configured to perform a chipping operation on a workpiece (such as concrete) by causing atool bit 119 coupled to a front end region of abody 101 to perform hammering motion in its longitudinal direction. Specifically, thetool bit 119 extends along its hammering axis. - As shown in
FIG. 1 , thetool bit 119 is removably coupled to thebody 101 via acylindrical tool holder 131. Thetool bit 119 is inserted into a bit insertion hole of thetool holder 131 and held such that it is prevented from rotating around an axis of thetool holder 131 with respect to thetool holder 131. Thetool bit 119 is an example embodiment that corresponds to the "tool accessory" according to the present invention. - As shown in
FIG. 1 , thebody 101 mainly includes abody housing 103, abarrel 104 and anouter housing 105. Thebody housing 103 mainly includes amotor housing 103a that houses anelectric motor 110, and agear housing 103b that houses a firstmotion converting mechanism 120 and a secondmotion converting mechanism 160. Thebarrel 104 is configured as a cylindrical member for housing astriking mechanism 140 and part ofthetool holder 131 and connected to thebody housing 103. Themotor housing 103a, thegear housing 103b and thebarrel 104 are made of aluminum. Thebarrel 104, thegear housing 103b and themotor housing 103a are arranged in this order in the longitudinal direction of thetool bit 119 and joined to each other to be fixedly assembled together. Thebarrel 104 is arranged closest to thetool bit 119 and themotor housing 103 a is arranged farthest from thetool bit 119 in the longitudinal direction of thetool bit 119. Themotor housing 103a and thegear housing 103b may be formed in one piece. Thebody housing 103 is an example embodiment that corresponds to the "housing" according to the present invention. - The
outer housing 105 is arranged on the outside of thebody housing 103 as shown inFIG. 1 . Theouter housing 105 has a cylindrical shape extending in the longitudinal direction of thetool bit 119 and is arranged to entirely cover thebody housing 103. Theouter housing 105 has anupper housing 106 and alower housing 107. A pair ofhandgrips 109 for operating theelectric hammer 100 in chipping operation are provided on theupper housing 106. Thehandgrips 109 are symmetrically arranged with respect to an axis extending in the longitudinal direction of thetool bit 119 and extend straight in a direction crossing the axis. Each of thehandgrips 109 has one end fixed to theupper housing 106 in a cantilever form. Thehandgrip 109 is an example embodiment that corresponds to the "handle" according to the present invention. In use of theelectric hammer 100, the user performs a chipping operation while holding thehandgrips 109 with hands and pointing thetool bit 119 downward. Therefore, for the sake of convenience, in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101), thetool bit 119 side is defined as the lower side and thehandgrip 109 side is defined as the upper side. Thehandgrip 109 is an example embodiment that corresponds to the "handle" according to the present invention. - The
lower housing 107 is integrally connected to thebody housing 103. - As shown in
FIG. 2 , aguide shaft 108A is disposed between theupper housing 106 and themotor housing 103a. Theguide shaft 108A has ashaft support part 106a which is integrally connected to theupper housing 106. An upper end of theguide shaft 108A is fitted in arecess 106b of theshaft support part 106a, and a lower end of theguide shaft 108A is fitted in a recess 103a1 of themotor housing 103a. Further, a middle region of theguide shaft 108A is inserted through anannular part 106c of theshaft support part 106a. Theguide shaft 108A has a flange 108A1 in a region below theannular part 106c. Acoil spring 108b is disposed between the flange 108A1 and the recess 103a1 of themotor housing 103a. In theelectric hammer 100, foursuch guide shafts 108A and foursuch coil springs 108b are provided. - Thus, the
upper housing 106 and themotor housing 103a are connected via the coil springs 108b. Thecoil spring 108b is an example embodiment that corresponds to the "handle elastic member" according to the present invention. With this structure, thehandgrip 109 and thebody housing 103 are configured to be movable with respect to each other. - The
upper housing 106 and thelower housing 107 are connected via anannular bellows 108a. Thebellows 108a is made of vinyl or rubber and configured to be expandable and contractable. Thebellows 108a prevents entry of dust into thehandgrips 109 and thebody housing 103. The coil springs 108b and thebellows 108a form a connectingmechanism 108. - An
electric switch 109e for driving and stopping theelectric motor 110 and anoperation part 109d for switching on and off theelectric switch 109e are provided in one of thehandgrips 109 as shown inFIG. 1 . Theoperation part 109d of theelectric hammer 100 is formed by a switch lever. Theoperation part 109d is provided to be turned in a direction crossing the longitudinal direction of thehandgrip 109. When theoperation part 109d is not operated, theoperation part 109d is held in a position to protrude outward (upward) from an outer surface of thehandgrip 109 by a biasing force of a built-in spring (not shown) provided in theelectric switch 109e. When theoperation part 109d is pressed with a user's finger, theoperation part 109d is turned inward into thehandgrip 109 and theelectric switch 109e is switched on, so that theelectric motor 110 is driven. - The
electric motor 110 is formed by a brushless motor. As shown inFIG. 3 , acontroller 112 for controlling driving of theelectric motor 110 is disposed between an outer surface of thebody housing 103 and an inner surface of theouter housing 105. Thecontroller 112 is formed by disposing a switching element for controlling a plurality of coils provided in theelectric motor 110, a central processing unit (CPU) and a condenser on a substrate. Theelectric motor 110 and thecontroller 112 are example embodiments that correspond to the "brushless motor" and the "controller", respectively, according to the present invention. - The user performs a hammering operation on a workpiece while pressing the
tool bit 119 against the workpiece. This state that a prescribed pressing force is applied to thetool bit 119 is defined as a pressed state of theelectric hammer 100. After performing a hammering operation on a prescribed workpiece, the user may move theelectric hammer 100 toward other workpiece. In such a case, while the user is moving theelectric hammer 100, theelectric motor 110 is kept on, but thetool bit 119 is not pressed against the workpiece. This state that the prescribed pressing force is not applied to thetool bit 119 is defined as a non-pressed state of theelectric hammer 100. Thus, the user can perform a hammering operation on a plurality of workpieces by switching theelectric hammer 100 between the pressed state and the non-pressed state. The pressed state and the non-pressed state are example embodiments that correspond to the "pressed state" and the "non-pressed state", respectively, according to the present invention. - When the user performs a hammering operation while pressing the
electric hammer 100, thecontroller 112 controls theelectric motor 110 to be driven in a prescribed range of rotation speed. Specifically, thecontroller 112 controls theelectric motor 110 to rotate in the prescribed range of rotation speed such that the rotation speed of theelectric motor 110 does not significantly fluctuate by load on theelectric motor 110 during hammering operation. The prescribed range of rotation speed at which theelectric motor 110 is driven in the pressed state is defined as a first rotation speed. The first rotation speed is an example embodiment that corresponds to the "first rotation speed" according to the present invention. - When the user places the
electric hammer 100 in the non-pressed state, thecontroller 112 controls theelectric motor 110 to be driven at lower rotation speed than the first rotation speed. This lower rotation speed than the first rotation speed, at which theelectric motor 110 is driven in the non-pressed state, is defined as a second rotation speed. The second rotation speed is an example embodiment that corresponds to the "second rotation speed" according to the present invention. - The
controller 112 is configured to detect load on theelectric motor 110 and thereby determine whether theelectric hammer 100 is placed in the pressed state or the non-pressed state. More specifically, a threshold is set for a current to be supplied to theelectric motor 110, and thecontroller 112 is configured to determine that theelectric hammer 100 is placed in the non-pressed state when the current does not exceed the threshold and to determine that theelectric hammer 100 is placed in the pressed state when the current exceeds the threshold. - The
electric motor 110 is driven by alternate current supplied via afeeding part 180 as shown inFIG. 1 . The feedingpart 180 is formed by a power cable. As shown inFIG. 2 , theelectric motor 110 is arranged such that amotor shaft 111 of theelectric motor 110 extends in a direction crossing a longitudinal axis of thetool bit 119 and parallel to a longitudinal axis of thehandgrip 109. Rotation of theelectric motor 110 is converted into linear motion by the firstmotion converting mechanism 120 and transmitted to thestriking mechanism 140, and thetool bit 119 is struck in the longitudinal direction (downward as viewed inFIG. 1 ) via thestriking mechanism 140. Further, rotation of theelectric motor 110 is converted into linear motion by the secondmotion converting mechanism 160 and transmitted to acounter weight 190. Thecounter weight 190 is configured to linearly move in the longitudinal direction of thetool bit 119 at a timing when an impact force is generated by striking of thetool bit 119. With this structure, thecounter weight 190 suppresses vibration caused in theelectric hammer 100. Themotor shaft 111, the firstmotion converting mechanism 120 and the secondmotion converting mechanism 160 are example embodiments that correspond to the "rotary shaft", the "driving mechanism" and the "vibration suppressing mechanism", respectively, according to the present invention. Thecounter weight 190 is an example embodiment that corresponds to the "weight" and the "counter weight" according to the present invention. - As shown in
FIG. 3 , the firstmotion converting mechanism 120 is formed by a first crank mechanism disposed below theelectric motor 110 and including afirst crank shaft 121, a first connectingrod 123 and apiston 125. The firstmotion converting mechanism 120 is driven by theelectric motor 110 via a gearspeed reducing device 113 having a plurality of gears. Thepiston 125 forms a driving element for driving the striking mechanism 140 (seeFIG. 1 ). Thepiston 125 is arranged to slide within acylinder 141 in the longitudinal direction of thetool bit 119. Thefirst crank shaft 121 is arranged in parallel to themotor shaft 111 of theelectric motor 110. Aneccentric shaft part 121 a is integrally formed with thefirst crank shaft 121 and rotatably connected to the first connectingrod 123. - As shown in
FIG. 1 , thestriking mechanism 140 mainly includes acylinder 141, a striking element in the form of astriker 143, and an intermediate element in the form of animpact bolt 145. Thestriker 143 is slidably disposed within thecylinder 141. Theimpact bolt 145 is slidably disposed within thetool holder 131 and transmits kinetic energy of thestriker 143 to thetool bit 119. Thecylinder 141 is coaxially arranged with thetool holder 131 above thetool holder 131. Anair chamber 141a is formed between thepiston 125 and thestriker 143 within thecylinder 141. Thestriker 143 is driven via pressure fluctuations caused in theair chamber 141a by sliding movement of thepiston 125. Then thestriker 143 collides with theimpact bolt 145 and strikes thetool bit 119 via theimpact bolt 145. - The
cylinder 141 has avent 141b as shown inFIG. 1 . Thevent 141b is configured to provide communication between the inside of thecylinder 141 and the inside of thebarrel 104. - When the
electric hammer 100 is in the pressed state, thestriker 143 is placed in an upper position via thetool bit 119 and theimpact bolt 145 and blocks communication between theair chamber 141a and thevent 141b. Thus, when thepiston 125 is driven, the pressure of theair chamber 141a fluctuates, so that thestriker 143 can be driven. - Immediately after the
electric hammer 100 is switched from the pressed state to the non-pressed state, first, thestriker 143 moves thetool bit 119 and theimpact bolt 145 downward. In this state, theair chamber 141a is expanded to a region of thecylinder 141 having thevent 141b. Thus, theair chamber 141a communicates with the inside of thebarrel 104 via thevent 141b. Therefore, when thepiston 125 moves in a direction of compressing air of theair chamber 141a (downward), the air is released into thebarrel 104 via thevent 141b. On the other hand, when thepiston 125 moves in a direction of expanding air of theair chamber 141a (upward), the air is led from the inside of thebarrel 104 into theair chamber 141a via thevent 141b. Specifically, even if thepiston 125 is driven, pressure fluctuations enough to lift thestriker 143 from the lower position are not caused in theair chamber 141a. Thus, in the unloaded state, thetool bit 119 is prevented from being driven. - As shown in
FIG. 3 , the secondmotion converting mechanism 160 is formed by a second crank mechanism including asecond crank shaft 161, aneccentric shaft 163 and a second connectingrod 165. Thesecond crank shaft 161 is arranged on an extension of an axis of thefirst crank shaft 121 of the first crank mechanism and rotated by theeccentric shaft part 121a of thefirst crank shaft 121. Theeccentric shaft 163 is arranged in parallel to thesecond crank shaft 161 in a position displaced a prescribed distance in a radial direction from the center of rotation of thesecond crank shaft 161. One end of the second connectingrod 165 is connected to theeccentric shaft 163 so as to be rotatable around theeccentric shaft 163. The other end of the second connectingrod 165 is connected to a connectingshaft 166 provided on thecounter weight 190 so as to be rotatable around the connectingshaft 166. The connectingshaft 166 is arranged in parallel to theeccentric shaft 163. Thecounter weight 190 is configured as a cylindrical member which is slidably fitted onto thecylinder 141. Thecounter weight 190 reciprocates between a front position closest to thetool bit 119 and a rear position farthest from thetool bit 119. Thecylindrical counter weight 190 may be shaped to partially surround thecylinder 141. - When performing a hammering operation on a workpiece with the
electric hammer 100 having the above-described structure, the user holds a pair of thehandgrips 109 with hands and presses thetool bit 119 pointed downward against a workpiece. Specifically, the user performs a hammering operation while keeping theelectric hammer 100 in the pressed state. When the user presses theoperation part 109d with a finger of the hand holding the onehandgrip 109 to turn on theelectric switch 109e, theelectric motor 110 is driven. Then thetool bit 119 is linearly driven via the firstmotion converting mechanism 120 and thestriking mechanism 140 and can perform a hammering operation on the workpiece. At this time, thecontroller 112 determines that theelectric hammer 100 is placed in the pressed state and controls theelectric motor 110 to rotate at the first rotation speed. - The
counter weight 190 is caused to reciprocate in the longitudinal direction of thetool bit 119 via the secondmotion converting mechanism 160. Thecounter weight 190 is set to move substantially in opposite phase to movement of thestriker 143. Specifically, thecounter weight 190 moves upward when thestriker 143 moves downward, while thecounter weight 190 moves downward when thestriker 143 moves upward. By this movement, thecounter weight 190 suppresses vibration caused in theelectric hammer 100 during operation. - During hammering operation, the handgrips 109 (the upper housing 106) and the body housing 103 (the
motor housing 103a) are moved in the longitudinal direction of thetool bit 119 with respect to each other while being guided by theguide shafts 108A under the biasing force of the coil springs 108b. Specifically, the coil springs 108b are expanded and contracted by the kinetic energy of vibration caused during hammering operation, so that transmission of vibration from thebody housing 103 to thehandgrips 109 is suppressed. Thus, in theelectric hammer 100 having two vibration proofing devices, or the vibration-proof handle and thecounter weight 190, vibration which is caused during hammering operation and transmitted to the user holding thehandgrips 109 is suppressed. As a result, the operability of theelectric hammer 100 is improved. - When the user switches the
electric hammer 100 from the pressed state to the non-pressed state, thecontroller 112 detects that the current supplied to theelectric motor 110 is below a threshold and controls theelectric motor 110 to rotate at the second rotation speed. - In the non-pressed state, where the
electric motor 110 is rotationally driven at the second rotation speed, thefirst crank shaft 121 and thesecond crank shaft 161 are driven. Immediately after theelectric hammer 100 is switched from the pressed state to the non-pressed state, thestriker 143 is driven by driving of thepiston 125. In the non-pressed state, however, thetool bit 119 and theimpact bolt 145 are located in a lower position. Therefore, thestriker 143 moves down to theimpact bolt 145 located in this lower position. As a result, thestriker 143 moves down to below thevent 141b. Thus, theair chamber 141a communicates with the inside of thebarrel 104, so that thetool bit 119 is prevented from being driven by driving of thefirst crank shaft 121. - Further, although the
counter weight 190 is caused to reciprocate by driving of thesecond crank shaft 161, theelectric motor 110 is driven at the second rotation speed, so that vibration caused by the reciprocating movement of thecounter weight 190 can be reduced. - As described above, in the pressed state, the
electric hammer 100 can suppress vibration related to hammering operation by the secondmotion converting mechanism 160 and the coil springs 108b. Further, in the non-pressed state, theelectric motor 110 is driven at the second rotation speed, so that vibration caused by the reciprocating movement of thecounter weight 190 can be reduced. Specifically, theelectric hammer 100 can effectively suppress vibrations caused in the pressed state and the non-pressed state. - The second embodiment of the present invention is now described with reference to
FIGS. 4 and5 . Anelectric hammer 200 of the second embodiment is different from theelectric hammer 100 of the first embodiment mainly in the structures of the handle and the vibration suppressing mechanism. Theelectric hammer 200 is an example embodiment that corresponds to the "impact tool" according to the present invention. - As shown in
FIG. 4 , thebody 101 mainly includes abody housing 203 and ahandgrip 109 connected to thebody housing 203. Thebody housing 203 is an example embodiment that corresponds to the "housing" according to the present invention. Abarrel 104 is connected to thebody housing 203 and houses astriking mechanism 140. Aside grip 109A to be held by a user can be removably attached onto thebarrel 104. The structure of theside grip 109A is not described here for convenience sake. - The
handgrip 109 to be held by a user is arranged on a side opposite from thetool bit 119 in the longitudinal direction of thetool bit 119 as shown inFIG. 4 . In the second embodiment, for convenience sake, thetool bit 119 side is defined as a lower side and thehandgrip 109 side is defined as an upper side in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101). Further, in theelectric hammer 200 shown inFIG. 4 , a direction crossing the vertical direction is defined as a transverse direction, and a direction crossing the vertical direction and the transverse direction is defined as a thickness direction. - An
operation part 109d is provided in thehandgrip 109 as shown inFIG. 4 . Theoperation part 109d of theelectric hammer 200 is configured to be slidable in the thickness direction to switch on and off anelectric switch 109e. When theelectric switch 109e is switched on, acontroller 112 drives theelectric motor 110. - The
body housing 203 and thehandgrip 109 are connected by a connectingmechanism 108 as shown inFIG. 5 . The connectingmechanism 108 has abellows 108a and acoil spring 108b. With this structure, thebody housing 203 and thehandgrip 109 can move with respect to each other. - As shown in
FIG. 5 , theelectric motor 110 is a brushless motor and is arranged such that themotor shaft 111 extends in a direction crossing the longitudinal axis of thetool bit 119. Theelectric motor 110 and thehandgrip 109 are arranged on the longitudinal axis of thetool bit 119. Like in the first embodiment, thecontroller 112 is configured to drive theelectric motor 110 at the first rotation speed in the pressed state and to drive theelectric motor 110 at the second rotation speed in the non-pressed state. Thecontroller 112 is housed in thehandgrip 109. By this arrangement, in theelectric hammer 200, the weight can be distributed to thehandgrip 109, so that the vibration proofing effect can be enhanced. A cable for electrically connecting thecontroller 112 and theelectric motor 110 is wired between thecontroller 112 and theelectric motor 110 through the inside of thebellows 108a. InFIGS. 4 and5 , the cable is not shown for convenience sake. - As shown in
FIGS. 4 and5 , rotation of theelectric motor 110 is transmitted to a firstmotion converting mechanism 120 via a gearspeed reducing device 113, and thereafter converted into linear motion by the firstmotion converting mechanism 120 and transmitted to thestriking mechanism 140. Then thetool bit 119 is struck in the longitudinal direction via thestriking mechanism 140. Further, rotation of theelectric motor 110 is transmitted to a secondmotion converting mechanism 160 via the firstmotion converting mechanism 120, and thereafter converted into linear motion by the secondmotion converting mechanism 160 and transmitted to adynamic vibration reducer 290. The firstmotion converting mechanism 120, the gearspeed reducing device 113 and thestriking mechanism 140 have the same structures as those of the first embodiment, respectively, and are not described. - As shown in
FIG. 5 , the secondmotion converting mechanism 160 mainly includes asecond crank shaft 161 which is rotated by aneccentric shaft part 121a of afirst crank shaft 121 of the firstmotion converting mechanism 120, aneccentric shaft 163 integrally formed with thesecond crank shaft 161, and an second connectingrod 165 which is linearly moved in the longitudinal direction of thetool bit 119 by rotation of theeccentric shaft 163. The second connectingrod 165 drives thedynamic vibration reducer 290. - As shown in
FIG. 5 , thedynamic vibration reducer 290 mainly includes anannular weight 291 configured to surround the outer circumferential surface of thecylinder 141 entirely in the circumferential direction, and biasingsprings weight 291. The biasing springs 292, 293 apply respective spring forces to theweight 291 in the longitudinal direction of thetool bit 119 when theweight 291 moves in the longitudinal direction of thetool bit 119. Theweight 291, thedynamic vibration reducer 290 and the biasingspring - The
weight 291 is arranged to slide with its periphery in contact with an inner wall surface (cylindrical surface) of thebarrel 104. The upper and lower biasing springs 292, 293 are compression coil springs. Theupper spring 293 is configured such that its one end is held in contact with a flange of aslide sleeve 210 and the other end is held in contact with theweight 291. Thelower spring 292 is configured such that its one end is held in contact with theweight 291 and the other end is held in contact with a ring-like member 211 fixed to thebarrel 104. Thus, theslide sleeve 210 and the ring-like member 211 form spring receiving members. - The
slide sleeve 210 can slide in the longitudinal direction of thetool bit 119 with respect to the periphery of thecylinder 141 and is held in contact with the second connectingrod 165. Thus, theslide sleeve 210 is slid by the secondmotion converting mechanism 160. - When the second connecting
rod 165 moves downward, theslide sleeve 210 is pushed downward by the second connectingrod 165 and compresses the biasing springs 292, 293. When the second connectingrod 165 moves upward, theslide sleeve 210 is pushed upward by the spring forces of the biasing springs 292, 293. Specifically, during hammering operation, the secondmotion converting mechanism 160 forcibly vibrates the biasing springs 292, 293 and thereby theweight 291 is driven. With this structure, vibration caused in thebody housing 203 is effectively suppressed. Thedynamic vibration reducer 290 is configured such that theweight 291 is driven in opposite phase to thestriker 143. - When performing a hammering operation on a workpiece with the
electric hammer 200 having the above-described structure, the user holds thehandgrip 109 and presses theelectric hammer 200. When the user slides theoperation part 109d with a finger of the hand holding thehandgrip 109 to turn on theelectric switch 109e, theelectric motor 110 is driven. Then thetool bit 119 is linearly driven via the firstmotion converting mechanism 120 and thestriking mechanism 140 and can perform a hammering operation on the workpiece. At this time, thecontroller 112 determines that theelectric hammer 200 is placed in the pressed state and controls theelectric motor 110 to rotate at the first rotation speed. - Further, during hammering operation, the
dynamic vibration reducer 290 is forcibly driven by the secondmotion converting mechanism 160. Therefore, thedynamic vibration reducer 290 effectively suppresses vibration caused in thebody housing 203 during hammering operation. Furthermore, thehandgrip 109 moves with respect to thebody housing 203 via the coil springs 108b, so that transmission of vibration to thehandgrip 109 is further effectively suppressed. - When the user switches the
electric hammer 200 from the pressed state to the non-pressed state, thecontroller 112 detects that the current supplied to theelectric motor 110 is below a threshold and controls theelectric motor 110 to rotate at the second rotation speed. - In the non-pressed state, where the
electric motor 110 is rotationally driven at the second rotation speed, thefirst crank shaft 121 and thesecond crank shaft 161 are driven. Like in the first embodiment, as shown inFIG. 4 , avent 141b is formed in thecylinder 141, so that thetool bit 119 is prevented from being driven by driving of thepiston 125. - Further, although the
dynamic vibration reducer 290 is driven by driving of thesecond crank shaft 161, theelectric motor 110 is driven at the second rotation speed, so that vibration caused by driving of thedynamic vibration reducer 290 can be reduced. - As described above, in the pressed state, the
electric hammer 200 can suppress vibration related to hammering operation by the secondmotion converting mechanism 160 and the coil springs 108b. Further, in the non-pressed state, theelectric motor 110 is driven at the second rotation speed, so that vibration caused by driving of thedynamic vibration reducer 290 can be reduced. Specifically, theelectric hammer 200 can effectively suppress vibrations caused in the pressed state and the non-pressed state. - The third embodiment of the present invention is now described with reference to
FIGS. 6 and7 . The structure of the impact tool according to the third embodiment is explained based on anelectric hammer drill 300 which is capable of performing a hammering operation by linearly driving a tool bit along a prescribed hammering axis and a drilling operation of drilling a workpiece by rotating the tool bit around the hammering axis. Theelectric hammer drill 300 is an example embodiment that corresponds to the "impact tool" according to the present invention. Theelectric hammer drill 300 is configured to be switched by a user among a hammer mode for hammering operation, a drill mode for drilling operation and a hammer drill mode for simultaneously performing hammering and drilling operations. The structure for switching the operation mode is not described for convenience sake. - As shown in
FIG. 6 , thebody 101 of theelectric hammer drill 300 mainly includes abody housing 303 and ahandgrip 109 connected to thebody housing 303. Thebody housing 303 is an example embodiment that corresponds to the "housing" according to the present invention. Thebody housing 303 houses anelectric motor 110, acontroller 112, a firstmotion converting mechanism 120, astriking mechanism 140, and arotation transmitting mechanism 151 and a dynamic vibration reducer 390 (seeFIG. 7 ). Thehandgrip 109 is arranged on a side of thebody housing 303 opposite from thetool bit 119 in the longitudinal direction of thetool bit 119. In the third embodiment, for convenience sake, thetool bit 119 side is defined as a front side and thehandgrip 109 side is defined as a rear side in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101). - The
handgrip 109 has agrip part 109a extending in a vertical direction of the hammer drill 300 (a direction crossing the longitudinal direction of the tool bit 119) as shown inFIG. 6 . Thehandgrip 109 is connected to thebody housing 303 by a connectingmechanism 108 in an upper connectingregion 109b. Acoil spring 108b of the connectingmechanism 108 is arranged to extend between aspring receiving part 108c provided in thebody housing 303 and aspring receiving part 108d provided in thehandgrip 109. Further, thehandgrip 109 is connected to thebody housing 303 by apivot 108e in a lower connectingregion 109c. - With this structure, the
handgrip 109 and thebody housing 303 can rotate on thepivot 108e with respect to each other under the biasing force of thecoil spring 108b. With this structure, transmission of vibration of thebody housing 303 to thehandgrip 109 can be suppressed. - An
operation part 109d is provided in thehandgrip 109 as shown inFIG. 6 . When theoperation part 109d is operated, theelectric motor 110 is driven via thecontroller 112. Theoperation part 109d of thehammer drill 300 is a trigger which is depressed by a user. Theelectric motor 110 is a brushless motor and is arranged such that themotor shaft 111 extends in a direction crossing the longitudinal axis of thetool bit 119. Theelectric motor 110 is arranged in a position displaced from the longitudinal axis of thetool bit 119. Specifically, theelectric motor 110 is disposed in a lower part of thehammer drill 300, and acylinder 141 and atool holder 131 which are coaxially arranged with thetool bit 119 are disposed in an upper part of thehammer drill 300. - As shown in
FIG. 6 , like in the first embodiment, thecontroller 112 is configured to drive theelectric motor 110 at the first rotation speed in the pressed state and to drive theelectric motor 110 at the second rotation speed in the non-pressed state. Further, thehammer drill 300 has anacceleration sensor 112a, and thecontroller 112 is configured to control driving of theelectric motor 110 based on the detection result of theacceleration sensor 112a. Theacceleration sensor 112a is an example embodiment that corresponds to the "sensor" according to the present invention. When theacceleration sensor 112a detects an inclined state of thehammer drill 300, thecontroller 112 can detect the behavior of thehammer drill 300. Thehammer drill 300 is configured such that thecontroller 112 controls to stop driving of theelectric motor 110 when theacceleration sensor 112a exhibits prescribed behavior in the drill mode or hammer drill mode of thehammer drill 300. This prescribed behavior includes such behavior that thetool bit 119 is locked in a hole formed by drilling operation and thehammer drill 300 is caused to rotate on thetool bit 119. Thehammer drill 300 can be provided with a function of preventing specific behavior in drilling operation simply by providing thecontroller 112 for controlling driving of the brushless motor (the electric motor 110) with an additional function of controlling driving of theelectric motor 110 based on the detection result of theacceleration sensor 112a. - The
acceleration sensor 112a is disposed in thecontroller 112 as shown inFIG. 6 . Theacceleration sensor 112a may be disposed elsewhere in thebody 101, and a plurality ofacceleration sensors 112a may be provided. - As shown in
FIG. 6 , rotation of theelectric motor 110 is transmitted to the firstmotion converting mechanism 120 disposed in the upper part of thehammer drill 300, and thereafter converted into linear motion by the firstmotion converting mechanism 120 and transmitted to thestriking mechanism 140. Then thetool bit 119 is struck in the longitudinal direction via thestriking mechanism 140. Further, rotation of theelectric motor 110 is transmitted to thetool holder 131 via therotation transmitting mechanism 151, and thetool bit 119 is rotated around its axis via thetool holder 131. The firstmotion converting mechanism 120 and thestriking mechanism 140 have the same structures as those of the first embodiment, respectively, and are not described. A cylinderside communication opening 141c is formed in thecylinder 141 of thehammer drill 300 as shown inFIG. 6 . A barrel space (not shown) between thecylinder 141 and thebarrel 104 communicates with theair chamber 141a via the cylinderside communication opening 141c. Further, a closed space which forms a crankchamber 121b is formed behind thepiston 125. The first connectingrod 123 and theeccentric shaft part 121a of thefirst crank shaft 121 are disposed in thecrank chamber 121b. - The
rotation transmitting mechanism 151 mainly includes a drivengear 153, amechanical torque limiter 155, anintermediate shaft 157 and asmall bevel gear 159 as shown inFIG. 6 . The drivengear 153 is engaged with a pinion gear provided on themotor shaft 111 and rotated. The drivengear 153 is connected to theintermediate shaft 157 via themechanical torque limiter 155. Themechanical torque limiter 155 is configured to interrupt torque transmission between the drivengear 153 and theintermediate shaft 157 when acted upon by torque exceeding a prescribed value. Thesmall bevel gear 159 is provided on an upper end of theintermediate shaft 157 and engages with alarge bevel gear 132 provided on a rear end of thetool holder 131. With this structure, therotation transmitting mechanism 151 transmits rotation of theelectric motor 110 to thetool holder 131. - As shown in
FIG. 7 , thedynamic vibration reducer 390 has aweight 391, a biasingspring 392 disposed on the front side of theweight 391, and abiasing spring 393 disposed on the rear side of theweight 391. Theweight 391, thedynamic vibration reducer 390 and the biasing springs 392, 393 are example embodiments that correspond to the "weight", the "dynamic vibration reducer" and the "weight elastic member", respectively, according to the present invention. Only onedynamic vibration reducer 390 is shown inFIG. 7 , but anotherdynamic vibration reducer 390 is disposed on the opposite side of the hammering axis from the onedynamic vibration reducer 390. - The
dynamic vibration reducer 390 is disposed in a dynamic vibration reducer arrangement space. The dynamic vibration reducer arrangement space includes afirst space 394 in which thebiasing spring 392 is disposed and asecond space 395 in which thebiasing spring 393 is disposed. Theweight 391 is disposed in the dynamic vibration reducer arrangement space via acylindrical member 396. More specifically, a large-diameter part of theweight 391 is held in contact with thecylindrical member 396 so as to be reciprocally slidable. The large-diameter part of theweight 391 prevents communication between thefirst space 394 and thesecond space 395. - The
first space 394 has a dynamic vibration reducer sidefirst communication opening 394a which communicates with the barrel space. Thus, thefirst space 394 communicates with theair chamber 141a via the dynamic vibration reducer sidefirst communication opening 394a and the barrel space. Thesecond space 395 has a dynamic vibration reducer sidesecond communication opening 395a which communicates with thecrank chamber 121b. Thus, thesecond space 395 communicates with thecrank chamber 121b via the dynamic vibration reducer sidesecond communication opening 395a. - With this structure, the
weight 391 reciprocates in the back and forth direction by driving of thepiston 125. - Specifically, when the
piston 125 moves forward and compresses air of theair chamber 141a, air is sent to thefirst space 394 via the cylinderside communication opening 141c, the barrel space and the dynamic vibration reducer sidefirst communication opening 394a. As a result, the pressure of thefirst space 394 increases, so that theweight 391 is moved rearward. When thepiston 125 moves rearward and compresses air of thecrank chamber 121b, air is sent to thesecond space 395 via thecrank chamber 121b and the dynamic vibration reducer sidesecond communication opening 395a. As a result, the pressure of thesecond space 395 increases, so that theweight 391 is moved forward. Thus, thedynamic vibration reducer 390 is configured to move theweight 391 in a phase opposite to the moving direction of thepiston 125. Based on this movement, thedynamic vibration reducer 390 is designed such that theweight 391 is driven in a phase opposite to the moving direction of thestriker 143. - With this structure, vibration caused in the
body housing 303 particularly during hammering operation can be suppressed. - When performing a hammering operation on a workpiece with the
hammer drill 300 having the above-described structure, the user holds thehandgrip 109 and presses thehammer drill 300. When the user operates theoperation part 109d with a finger of the hand holding thehandgrip 109, theelectric motor 110 is driven. Then thetool bit 119 is linearly driven via the firstmotion converting mechanism 120 and thestriking mechanism 140 and can perform a hammering operation on the workpiece. At this time, thecontroller 112 determines that thehammer drill 300 is placed in the pressed state and controls theelectric motor 110 to rotate at the first rotation speed. Theoperation part 109d of thehammer drill 300 is a trigger. - Further, during hammering operation, the
weight 391 of thedynamic vibration reducer 390 is moved in a phase opposite to the moving direction of thestriker 143. Therefore, during hammering operation, thedynamic vibration reducer 390 effectively reduces vibration caused in thebody housing 303. Furthermore, thehandgrip 109 reciprocally rotates on thepivot 108e with respect to thebody housing 303 via thecoil spring 108b, so that transmission of vibration to thehandgrip 109 is further effectively suppressed. - When the user switches the
hammer drill 300 from the pressed state to the non-pressed state, thecontroller 112 detects that the current supplied to theelectric motor 110 is below a threshold and controls theelectric motor 110 to rotate at the second rotation speed. - In the non-pressed state, where the
electric motor 110 is rotationally driven at the second rotation speed, thepiston 125 is driven. Thus, thedynamic vibration reducer 390 is driven, but in this state where theelectric motor 110 is rotationally driven at the second rotation speed, vibration caused by driving of thedynamic vibration reducer 390 is reduced, compared with the state where theelectric motor 110 is driven at the first rotation speed. - Further, the
hammer drill 300 is configured such that the ring-like member 141 d shown inFIG. 6 closes thevent 141b of thecylinder 141 in the pressed state and opens thevent 141b in the non-pressed state. With this structure, thetool bit 119 is prevented from being driven by driving of thepiston 125. The structure relating to this function is not described for convenience sake. - As described above, in the pressed state, the
hammer drill 300 can suppress vibration related to hammering operation by thedynamic vibration reducer 390 and thecoil spring 108b. Further, in the non-pressed state, since theelectric motor 110 is driven at the second rotation speed, vibration caused by driving of thedynamic vibration reducer 390 can be reduced. Specifically, thehammer drill 300 can effectively suppress vibrations caused in the pressed state and the non-pressed state. - The fourth embodiment of the present invention is now described with reference to
FIG. 8 . Like theelectric hammer drill 300 of the third embodiment, anelectric hammer drill 400 of the fourth embodiment is configured to be switched by a user among a hammer mode, a drill mode and a hammer drill mode. - As shown in
FIG. 8 , thebody 101 of theelectric hammer drill 400 mainly includes abody housing 403 and ahandgrip 109 connected to thebody housing 403. Thebody housing 403 houses anelectric motor 110, acontroller 112, a firstmotion converting mechanism 120, astriking mechanism 140, arotation transmitting mechanism 151 and acounter weight 490. Thehandgrip 109 is arranged on a side of thebody housing 403 opposite from thetool bit 119 in the longitudinal direction of thetool bit 119. In the fourth embodiment, for convenience sake, thetool bit 119 side is defined as a front side and thehandgrip 109 side is defined as an rear side in the longitudinal direction of the tool bit 119 (the longitudinal direction of the body 101). Further, in a direction crossing the longitudinal direction of thetool bit 119, the side on which thetool bit 119 is arranged is defined as an upper side and the side on which thecontroller 112 is arranged is defined as a lower side. - The
handgrip 109 has agrip part 109a extending in a vertical direction of the hammer drill 400 (a direction crossing the longitudinal direction of the tool bit 119). Thehandgrip 109 has an upper connectingregion 109b and a lower connectingregion 109c which are connected to thebody housing 403 by respective connectingmechanisms 108. - With this structure, the
handgrip 109 and thebody housing 403 can move with respect to each other under the biasing force of thecoil spring 108b, so that transmission of vibration of thebody housing 403 to thehandgrip 109 can be suppressed. - A
battery mounting part 109f for mounting a battery (a feeding part 180) is provided on the underside of thehandgrip 109. By this arrangement, in thehammer drill 400, the weight can be distributed to thehandgrip 109, so that the vibration proofing effect can be enhanced. Thebattery mounting part 109f is an example embodiment that corresponds to the "mounting part" according to the present invention. A cable for electrically connecting thefeeding part 180 and thecontroller 112 is wired between the feedingpart 180 and theelectric motor 110 through the inside of alower bellows 108a. InFIG. 8 , the cable is not shown for convenience sake. - A trigger which forms an
operation part 109d is provided in thehandgrip 109. When theoperation part 109d is depressed, theelectric motor 110 is driven via thecontroller 112. Theelectric motor 110 is a brushless motor. Like in the first embodiment, thecontroller 112 is configured to drive theelectric motor 110 at the first rotation speed in the pressed state and to drive theelectric motor 110 at the second rotation speed in the non-pressed state. - The
electric motor 110 is arranged such that themotor shaft 111 extends in a direction crossing the longitudinal axis of thetool bit 119. Theelectric motor 110 is arranged in a position displaced from the longitudinal axis of thetool bit 119. Rotation of theelectric motor 110 is transmitted to the firstmotion converting mechanism 120 disposed above theelectric motor 110, and thereafter converted into linear motion by the firstmotion converting mechanism 120 and transmitted to thestriking mechanism 140. Then thetool bit 119 is struck in the longitudinal direction via thestriking mechanism 140. Further, rotation of theelectric motor 110 is transmitted to thetool holder 131 via therotation transmitting mechanism 151, and thetool bit 119 is rotated around its axis via thetool holder 131. Furthermore, rotation of theelectric motor 110 is transmitted to acounter weight 490 via the firstmotion converting mechanism 120. - The first
motion converting mechanism 120 mainly includes a drivengear 117, anintermediate shaft 116, a swingingshaft 118, amovable cylinder 142 and astriking mechanism 140. The drivengear 123 is integrally formed with theintermediate shaft 116. The swingingshaft 118 is configured to rotate together with theintermediate shaft 116 and has arotary member 118a and ashaft member 118b. Therotary member 118a has an outer surface inclined with respect to the extending direction of theintermediate shaft 116. Theshaft member 118b has an annular region which is connected to therotary member 118a via a steel ball, and a shaft-like region which protrudes upward from the annular region and is rotatably connected to themovable cylinder 142. Themovable cylinder 142 is a cylindrical member having a bottom and is disposed within thetool holder 131 so as to be reciprocally slidable. Astriker 143 is disposed within themovable cylinder 142 so as to be reciprocally slidable, and anair chamber 142a is formed between the bottom of themovable cylinder 142 and thestriker 143. In thetool holder 131, animpact bolt 145 is disposed in front of thestriker 143 so as to be reciprocally slidable. - In the first
motion converting mechanism 120 having the above-described structure, the swingingshaft 118 reciprocally moves themovable cylinder 142 when theintermediate shaft 116 is rotated by rotation of themotor 110. Then thestriker 143 is caused to collide with theimpact bolt 145 via pressure fluctuations of theair chamber 142a by the reciprocating movement of themovable cylinder 142, and the too bit 119 is moved forward via theimpact bolt 145. - The
tool holder 131 has astriker holding part 131a and an O-ring 131b fitted in thestriker holding part 131a. Further, thestriker 143 has a front end large-diameter part. - When the
hammer drill 400 is placed in the pressed state, thestriker 143 is placed in a rear position via thetool bit 119 and theimpact bolt 145. In this state, theimpact bolt 145 is located in an inside region of the O-ring 131 b of thestriker holding part 131a. - Immediately after the
hammer drill 400 is switched from the pressed state to the non-pressed state, first, thestriker 143 moves thetool bit 119 and theimpact bolt 145 forward. Thus, theimpact bolt 145 is no longer located in the inside region of the O-ring 131b. In this state, when thestriker 143 is moved forward by driving of themovable cylinder 142, the front end large-diameter part of thestriker 143 moves over the O-ring 131b. In this state, even if the pressure of theair chamber 142a decreases by the movement of themovable cylinder 142, the front end large-diameter part is engaged with the O-ring 131b, so that thestriker 143 is prevented from moving. Thus, in the unloaded state, thetool bit 119 is prevented from being driven. - The
rotation transmitting mechanism 151 mainly includes a drivengear 154 which can rotate together with theintermediate shaft 116, and atool holder gear 133 which engages with the drivengear 154 and can rotate together with thetool holder 131. - With the above-described structure, the driven
gear 154 is rotated by theintermediate shaft 116 and rotationally drives thetool holder gear 133, so that therotation transmitting mechanism 151 can rotate thetool bit 119 held by thetool holder 131. - The
counter weight 490 has anupper end region 490a which is rotatably journaled to thebody housing 403 and alower end region 490b which is connected to a lower end of the annular region of theshaft member 118b. Thus, thecounter weight 490 is reciprocally rotated in the back and forth direction by swinging of theshaft member 118b. Theupper end region 490a and thelower end region 490b of thecounter weight 490 are arranged on the opposite sides of the swinging axis of theshaft member 118b. Thus, thecounter weight 490 is moved in a phase opposite to the moving direction of themovable cylinder 142. - When performing a hammering operation on a workpiece with the
hammer drill 400 having the above-described structure, the user holds thehandgrip 109 and presses thehammer drill 400. When the user operates theoperation part 109d with a finger of the hand holding thehandgrip 109, theelectric motor 110 is driven. Then thetool bit 119 is linearly driven via the firstmotion converting mechanism 120 and thestriking mechanism 140 and can perform a hammering operation on the workpiece. At this time, thecontroller 112 determines that thehammer drill 400 is placed in the pressed state and controls theelectric motor 110 to rotate at the first rotation speed. - Further, during hammering operation, the
counter weight 490 is driven by movement of the swingingshaft 118. Therefore, during hammering operation, thecounter weight 490 effectively reduces vibration caused in thebody housing 403. Furthermore, thehandgrip 109 reciprocally moves with respect to thebody housing 403 via thecoil spring 108b, so that transmission of vibration to thehandgrip 109 is further effectively suppressed. - When the user switches the
hammer drill 400 from the pressed state to the non-pressed state, thecontroller 112 detects that the current supplied to theelectric motor 110 is below a threshold and controls theelectric motor 110 to rotate at the second rotation speed. - In the non-pressed state, where the
electric motor 110 is rotationally driven at the second rotation speed, the swingingshaft 118 is swung by theintermediate shaft 116. Thus, thecounter weight 490 is driven, but in this state where theelectric motor 110 is rotationally driven at the second rotation speed, vibration caused by driving of thecounter weight 490 can be reduced. - As described above, in the pressed state, the
hammer drill 400 can suppress vibration related to hammering operation by thecounter weight 490 and thecoil spring 108b. Further, in the non-pressed state, since theelectric motor 110 is driven at the second rotation speed, vibration caused by driving of thecounter weight 490 can be reduced. Specifically, thehammer drill 400 can effectively suppress vibrations caused in the pressed state and the non-pressed state. - Embodiments of the present invention are not limited to the above-described structures of the first to fourth embodiments, but may have other structures. Typically, the hammering axis of the
tool bit 119 may be arranged in parallel to the output shaft of theelectric motor 110. - Further, the structures of the first to fourth embodiments may be appropriately used in combination. For example, the structures relating to the
counter weight 190 of the first embodiment, thedynamic vibration reducer 290 ofthe second embodiment, thedynamic vibration reducer 390 ofthe third embodiment and thecounter weight 490 ofthe fourth embodiment may be appropriately used in other embodiments. - The above-described embodiments are representative examples for embodying the present invention, and the present invention is not limited to the structures of the representative embodiments. Correspondences between the features of the embodiments and the features of the invention are as follow:
- The
electric hammer 100, theelectric hammer 200, theelectric hammer drill 300 or theelectric hammer drill 400 is an example embodiment that corresponds to the "impact tool" according to the present invention. Thetool bit 119 is an example embodiment that corresponds to the "tool accessory" according to the present invention. Thebody housing 103, thebody housing 203, thebody housing 303 or thebody housing 403 is an example embodiment that corresponds to the "housing" according to the present invention. Thehandgrip 109 is an example embodiment that corresponds to the "handle" according to the present invention. Thecoil spring 108b is an example embodiment that corresponds to the "handle elastic member" according to the present invention. Theelectric motor 110 and thecontroller 112 are example embodiments that correspond to the "brushless motor" and the "controller", respectively, according to the present invention. The pressed state and the non-pressed state are example embodiments that correspond to the "pressed state" and the "non-pressed state", respectively, according to the present invention. The first rotation speed is an example embodiment that corresponds to the "first rotation speed" according to the present invention. The second rotation speed is an example embodiment that corresponds to the "second rotation speed" according to the present invention. Themotor shaft 111, the firstmotion converting mechanism 120 and the secondmotion converting mechanism 160 are example embodiments that correspond to the "rotary shaft", the "driving mechanism" and the "vibration suppressing mechanism", respectively, according to the present invention. Thecounter weight 190 is an example embodiment that corresponds to the "weight" and the "counter weight" according to the present invention. Theweight 291 or theweight 391 is an example embodiment that corresponds to the "weight" according to the present invention. Thedynamic vibration reducer 290 or thedynamic vibration reducer 390 is an example embodiment that corresponds to the "dynamic vibration reducer" according to the present invention. The biasingspring 292, the biasingspring 293, the biasingspring 392 or the biasingspring 393 is an example embodiment that correspond to the "weight elastic member" according to the present invention. Thecounter weight 490 is an example embodiment that corresponds to the "weight" and the "counter weight" according to the present invention. Theacceleration sensor 112a is an example embodiment that corresponds to the "sensor" according to the present invention. Thebattery mounting part 109f is an example embodiment that corresponds to the "mounting part" according to the present invention. - In view of the nature of the above-described invention, the impact tool according to this invention can be provided with the following features. Each of the features can be used separately or in combination with the other, or in combination with the claimed invention.
- The weight elastic member has a first elastic body connected to one side of the weight, and a second elastic body connected to the other side of the weight.
- The counter weight is configured such that one end region of the counter weight is rotatably journaled to the housing and the other end region is connected to the driving mechanism.
- The sensor for detecting behavior of the impact tool during the prescribed operation comprises an acceleration sensor.
- It is explicitly stated that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure as well as for the purpose of restricting the claimed invention independent of the composition of the features in the embodiments and/or the claims. It is explicitly stated that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure as well as for the purpose of restricting the claimed invention, in particular as limits of value ranges.
-
- 100
- electric hammer
- 101
- body
- 103
- body housing
- 103a
- motor housing
- 103a1
- recess
- 103b
- gear housing
- 104
- barrel
- 105
- outer housing
- 106
- upper housing
- 106a
- shaft support part
- 106b
- recess
- 106c
- annular part
- 107
- lower housing
- 108
- connecting mechanism
- 108A
- guide shaft
- 108A1
- flange
- 108a
- bellows
- 108b
- coil spring (handle elastic member)
- 108c
- spring receiving part
- 108d
- spring receiving part
- 108e
- pivot
- 109
- handgrip
- 109A
- side grip
- 109a
- grip part
- 109b
- upper connecting region
- 109c
- lower connecting region
- 109d
- operation part
- 109e
- electric switch
- 109f
- battery mounting part
- 110
- electric motor
- 111
- motor shaft
- 112
- controller
- 112a
- acceleration sensor
- 113
- gear speed reducing device
- 116
- intermediate shaft
- 117
- driven gear
- 118
- swinging shaft
- 118a
- rotary member
- 118b
- shaft member
- 119
- tool bit
- 120
- first motion converting mechanism
- 121
- first crank shaft
- 121a
- eccentric shaft part
- 121b
- crank chamber
- 123
- first connecting rod
- 125
- piston
- 131
- tool holder
- 131a
- striker holding part
- 131b
- O-ring
- 132
- large bevel gear
- 133
- tool holder gear
- 140
- striking mechanism
- 141
- cylinder
- 141a
- air chamber
- 141b
- vent
- 141c
- cylinder side communication opening
- 141d
- ring-like member
- 142
- movable cylinder
- 142a
- air chamber
- 143
- striker
- 145
- impact bolt
- 151
- rotation transmitting mechanism
- 153
- driven gear
- 154
- driven gear
- 155
- mechanical torque limiter
- 157
- intermediate shaft
- 159
- small bevel gear
- 160
- second motion converting mechanism
- 161
- second crank shaft
- 163
- eccentric shaft
- 165
- second connecting rod
- 166
- connecting shaft
- 170
- bearing holder
- 170a
- needle bearing
- 180
- feeding part
- 190
- counter weight
- 200
- electric hammer
- 203
- body housing
- 210
- slide sleeve
- 211
- ring-like member
- 290
- dynamic vibration reducer
- 291
- weight
- 292
- biasing spring (weight elastic member)
- 293
- biasing spring (weight elastic member)
- 300
- electric hammer drill
- 303
- body housing
- 390
- dynamic vibration reducer
- 391
- weight
- 392
- biasing spring (weight elastic member)
- 393
- biasing spring (weight elastic member)
- 394
- first space
- 394a
- dynamic vibration reducer side first communication opening
- 395
- second space
- 395b
- dynamic vibration reducer side second communication opening
- 396
- cylindrical member
- 400
- electric hammer drill
- 403
- body housing
- 490
- counter weight
- 490a
- upper end region
- 490b
- lower end region
Claims (9)
- An impact tool, which performs a hammering operation on a workpiece by linearly driving a tool accessory (119) along a prescribed hammering axis, comprising:a brushless motor (110),a driving mechanism (120) that drives the tool accessory by an output of the brushless motor (110),a vibration suppressing mechanism (160; 290; 390) having a movable weight (190; 291; 391; 490), anda controller (112) that controls driving of the brushless motor (110), wherein:in a pressed state which is defined as a state that a prescribed pressing force is applied to the tool accessory (119), the controller (112) drives the brushless motor (110) at a first rotation speed, andin a non-pressed state which is defined as a state that the prescribed pressing force is not applied to the tool accessory (119), the controller (112) drives the brushless motor (110) at a second rotation speed lower than the first rotation speed.
- The impact tool as defined in claim 1, wherein the vibration suppressing mechanism (160; 290; 390) comprises a counter weight (190; 291; 391; 490) which is configured such that the weight (190; 490) is mechanically connected to a prescribed region of the driving mechanism (120) and the weight is caused to directly reciprocate by movement of the driving mechanism, or a dynamic vibration reducer (290; 390) which has a weight elastic member (292, 293; 392, 393) connected to the weight (291; 391) and is configured such that the weight (190; 291; 391; 490) is caused to reciprocate by movement of the driving mechanism (120).
- The impact tool as defined in claim 1 or 2, wherein the weight (190; 291; 391; 490) is configured to be moved linearly or rotated with respect to the direction of the hammering axis.
- The impact tool as defined in any one of claims 1 to 3, further comprising:a housing (103; 203; 303; 403) for housing at least part of the driving mechanism (120),a handle (109) to be held by a user, anda handle elastic member (108b), wherein:the handle (109) is connected to the housing (103; 203; 303; 403) via the handle elastic member (108b), so that the handle (109) and the housing (103; 203; 303; 403) can be configured to be movable with respect to each other.
- The impact tool as defined in claim 4, wherein a connecting member (108a) is provided between the handle (109) and the housing (103; 203; 403), wherein the connecting member (108a) covers the handle elastic member (108b) and the connecting member (108a) is expandable and contractable.
- The impact tool as defined in claim 4 or 5, wherein the controller (112) is disposed within the handle (109).
- The impact tool as defined in any one of claims 1 to 6, further comprising:a sensor (112a) that detects behavior of the impact tool during a prescribed operation, wherein:the controller (112) controls driving of the brushless motor (110) based on a detection result of the sensor (112a).
- The impact tool as defined in claim 7, wherein an acceleration sensor (112a) is provided as the sensor (112a).
- The impact tool as defined in any one of claims 4 to 8, wherein the brushless motor (110) is driven by a battery, and the handle (109) has a mounting part (109f) for the battery.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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JP2015254996A JP2017113863A (en) | 2015-12-25 | 2015-12-25 | Impact tool |
Publications (2)
Publication Number | Publication Date |
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EP3184259A1 true EP3184259A1 (en) | 2017-06-28 |
EP3184259B1 EP3184259B1 (en) | 2022-02-16 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP16205945.5A Active EP3184259B1 (en) | 2015-12-25 | 2016-12-21 | Impact tool |
Country Status (2)
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EP (1) | EP3184259B1 (en) |
JP (1) | JP2017113863A (en) |
Cited By (3)
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CN114466726A (en) * | 2019-11-14 | 2022-05-10 | 喜利得股份公司 | Handle for power tool |
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JP2013193142A (en) * | 2012-03-16 | 2013-09-30 | Hitachi Koki Co Ltd | Impact tool |
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EP1637289A1 (en) * | 2004-09-13 | 2006-03-22 | Makita Corporation | Method of manufacturing a power tool |
US20100175903A1 (en) * | 2005-04-11 | 2010-07-15 | Makita Corporation | Electric hammer |
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EP2279831A1 (en) * | 2009-07-31 | 2011-02-02 | Black & Decker Inc. | Vibration Damping System for a Power Tool and in particular for a Powered Hammer |
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Also Published As
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JP2017113863A (en) | 2017-06-29 |
EP3184259B1 (en) | 2022-02-16 |
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