US20120139456A1 - Electric operating machine - Google Patents

Electric operating machine Download PDF

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Publication number
US20120139456A1
US20120139456A1 US13/389,574 US201013389574A US2012139456A1 US 20120139456 A1 US20120139456 A1 US 20120139456A1 US 201013389574 A US201013389574 A US 201013389574A US 2012139456 A1 US2012139456 A1 US 2012139456A1
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US
United States
Prior art keywords
battery
operating machine
voltage
electric operating
electric
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.)
Abandoned
Application number
US13/389,574
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English (en)
Inventor
Nobuhiro Takano
Kazuhiko Funabashi
Hideyuki Tanimoto
Chikai Yoshimizu
Hiromi Ozawa
Yoshihiro Hoshi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koki Holdings Co Ltd
Original Assignee
Hitachi Koki Co Ltd
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Filing date
Publication date
Application filed by Hitachi Koki Co Ltd filed Critical Hitachi Koki Co Ltd
Assigned to HITACHI KOKI CO., LTD. reassignment HITACHI KOKI CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FUNABASHI, KAZUHIKO, HOSHI, YOSHIHIRO, OZAWA, HIROMI, TAKANO, NOBUHIRO, TANIMOTO, HIDEYUKI, YOSHIMIZU, CHIKAI
Publication of US20120139456A1 publication Critical patent/US20120139456A1/en
Abandoned legal-status Critical Current

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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00—Programme-control systems
    • G05B19/02—Programme-control systems electric
    • G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
    • G05B19/048—Monitoring; Safety
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01D—HARVESTING; MOWING
    • A01D69/00—Driving mechanisms or parts thereof for harvesters or mowers
    • A01D69/02—Driving mechanisms or parts thereof for harvesters or mowers electric
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4221—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells with battery type recognition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/569—Constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/574—Devices or arrangements for the interruption of current
    • H01M50/579—Devices or arrangements for the interruption of current in response to shock
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00306—Overdischarge protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/0031—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits using battery or load disconnect circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0063—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with circuits adapted for supplying loads from the battery
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K3/00—Details of windings
    • H02K3/04—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors
    • H02K3/26—Windings characterised by the conductor shape, form or construction, e.g. with bar conductors consisting of printed conductors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
    • H02K7/145—Hand-held machine tool
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/02—Providing protection against overload without automatic interruption of supply
    • H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
    • H02P29/027—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the fault being an over-current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00304—Overcurrent protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00308—Overvoltage protection
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to an electric operating machine driven by a motor.
  • electric operating machines having a motor that drives a rotary blade attract attention and are increasingly used.
  • electric power as power source, electric operating machines (lawn mowers) are quiet, discharge no exhaust gas, and excellent in running cost.
  • Patent Literature 1 discloses an electric lawn mower having adjustable motor rotation speed. This electric lawn mower has a converter to change the voltage applied to the motor so as to change the motor rotation speed. Then, the blade rotation speed can be changed according to the lawn grass to mow or the lawn shape. Electric driving produces low driving noise.
  • the electric lawn mower described in the Patent Literature 1 changes the rotation speed according to the battery output. Therefore, when a battery of different output is mounted, the motor does not rotate at a desired rotation speed, which is inconvenient. Furthermore, batteries have different weights depending on their output. When a battery of different output is mounted, the weight balance of the electric lawn mower is changed, which may lower the operability.
  • the present invention is made in view of the above problems and a purpose of the present invention is to provide an electric operating machine that can control the rotation speed of the motor regardless of the output of the battery mounted and allow for mounting/dismounting of batteries of different outputs. Furthermore, another purpose of the present invention is to provide an electric operating machine that is lightweight and well-balanced and therefore excellent in operability.
  • the electric operating machine is:
  • an electric operating machine comprising:
  • a power source part including a battery mounting part for mounting a battery
  • the power source part further includes a voltage measuring part measuring the voltage applied to the electric motor and outputting it to the voltage conversion part is further provided;
  • the voltage conversion part adjusts the output voltage so that the voltage output from the voltage measuring part has a given level.
  • a battery of any voltage is mounted on or dismounted from the battery mounting part.
  • the power source part of the electric operating machine may further comprise an overcurrent protection part blocking the current running toward the electric motor when the current running toward the electric motor exceeds a given value.
  • the electric operating machine may further comprise a first announcing part announcing that an overcurrent is running when the current running toward the electric motor exceeds a given value.
  • the power source part of the electric operating machine may further comprise an overdischarge protection part blocking the current running toward the electric motor when the voltage output from the battery becomes lower than a predetermined voltage.
  • the electric operating machine may further comprise a second announcing part announcing that the battery is overly discharging when the voltage output from the battery becomes lower than a predetermined voltage.
  • the power source part of the electric operating machine may further comprise a voltage determination part determining the predetermined voltage based on battery information of the battery that is output from the battery.
  • the power source part of the electric operating machine may further comprise a battery abnormality stop part blocking the current running toward the electric motor according to battery abnormality signals output from the battery when the battery undergoes an abnormal event.
  • the battery abnormality stop part may block the current running toward the electric motor until the battery is dismounted from the battery mounting part since it receives the battery abnormality signals.
  • the electric operating machine may further comprise a third announcing part announcing that the battery undergoes an abnormal event when the battery undergoes an abnormal event.
  • the voltage measuring part applies to the voltage conversion part a voltage according to the pulling rate of the trigger.
  • the power source part of the electric operating machine may further comprise a trigger switch part blocking the current running toward the electric motor when the pulling rate of the trigger is lower than a given rate and allowing a current to run through the electric motor when the pulling rate of the trigger is equal to or higher than the given rate.
  • the power source part of the electric operating machine may further comprise a main switch part blocking the current running from the battery to the trigger switch part when it is turned OFF and allowing the current when it is turned ON.
  • the electric operating machine may further comprise a first light emitting part emitting light when the main switch part is ON.
  • the electric operating machine may further comprise a remaining battery level display displaying the remaining battery level according the voltage output from the battery.
  • the power source part of the electric operating machine may comprise a constant voltage circuit outputting a constant voltage from the voltage output from the battery.
  • the electric operating machine may further comprise a sound reproducing part operating upon application of a voltage output from the constant voltage circuit, decoding sound data, and reproducing sound information.
  • the electric operating machine may comprise a speaker amplifying the sound information and making sound by a voltage output from the constant voltage circuit.
  • the electric motor is a coreless motor.
  • the electric operating machine may further comprise a coupling part on whose one end the power source part is arranged and on whose other end the electric motor is arranged.
  • the electric operating machine may comprise a second light emitting part emitting light when the electric motor is powered.
  • the electric operating machine may further comprise a fourth announcing part announcing the power supply when the electric motor is powered.
  • the coreless motor includes a rotor and a stator
  • the rotor includes a fixed output shaft
  • one of the rotor and stator comprises a disc-shaped coil substrate including multiple nearly annular coils arranged in the circumferential direction around the output shaft when seen in the axial direction of the output shaft;
  • the other of the rotor and stator comprises a magnet generating a magnetic flux passing through the coil substrate in the axial direction of the output shaft.
  • the electric operating machine according to the second aspect of the present invention is:
  • an electric operating machine comprising:
  • a power source part comprising a mounting part to which a lithium rechargeable battery is detachably mounted;
  • a coupling part holding the coreless motor at one end and holding the power source part at the other end characterized in that:
  • the coreless motor includes a rotor and a stator
  • the rotor includes a fixed output shaft
  • one of the rotor and stator comprises a disc-shaped coil substrate including multiple nearly annular coils arranged in the circumferential direction around the output shaft when seen in the axial direction of the output shaft;
  • the other of the rotor and stator comprises a magnet generating a magnetic flux passing through the coil substrate in the axial direction of the output shaft.
  • the electric operating machine according to the third aspect of the present invention is:
  • an electric operating machine comprising:
  • a power source part comprising a mounting part to which a rechargeable battery is detachably mounted;
  • a grip part extending in the longitudinal direction of the coupling part, including a trigger operable by the operator for controlling the drive of the coreless motor, and being continued from or close to the power source part;
  • a handle provided on the coupling part at a distance from the power source part and grip part for being held by the operator, characterized in that:
  • the coreless motor includes a rotor and a stator
  • the rotor includes a fixed output shaft
  • one of the rotor and stator comprises a disc-shaped coil substrate including multiple nearly annular coils arranged in the circumferential direction around the output shaft when seen in the axial direction of the output shaft;
  • the other of the rotor and stator comprises a magnet generating a magnetic flux passing through the coil substrate in the axial direction of the output shaft;
  • the coreless motor is heavier than the rechargeable battery mounted on the mounting part and the gravity center of the electric operating machine is located on the coreless motor side with respect to the handle.
  • the coreless motor may comprise an aluminum alloy motor case housing the rotor.
  • the electric operating machine according to the first aspect of the present invention can control the rotation speed of the motor regardless of the battery output and allow for mounting/dismounting of batteries of different outputs. Furthermore, the electric operating machines according to the second and third aspects of the present invention are lightweight and well-balanced and therefore excellent in operability.
  • FIG. 1 An illustration showing the appearance of an electric operating machine according to an embodiment of the present invention
  • FIG. 2 An enlarged view of the operation part of the electric operating machine in FIG. 1 ;
  • FIG. 3 A cross-sectional view of the drive part of the electric operating machine in FIG. 1 ;
  • FIG. 4 An exploded cross-sectional view of the rotor of the electric operating machine in FIG. 1 ;
  • FIG. 7 An illustration showing the connection in the operation part of the electric operating machine in FIG. 1 ;
  • FIG. 8 An illustration showing a modification example of the electric operating machine in FIG. 1 ;
  • FIG. 8 An illustration showing the connection in the operation part of the electric operating machine in FIG. 8 ;
  • FIG. 11 A circuit diagram of a specific example of the booster circuit and speed adjustment part of the power supply circuit in FIG. 10 ;
  • FIG. 12 A circuit diagram of a specific example of the current detection part of the power supply circuit in FIG. 10 ;
  • FIG. 14 An illustration showing a modification example of the electric operating machine in FIG. 1 ;
  • FIG. 16 An illustration showing a belt for holding the electric operating machine in FIG. 14 ;
  • FIG. 17 An illustration showing the working manner with the electric operating machine in FIG. 14 .
  • the electric operating machine is an electric lawn mower 1 including a motor that drives a rotary blade.
  • the battery mounting part 11 is used to mount a battery 50 .
  • the battery mounting part 11 supplies the output of the battery 50 to the power supply circuit 16 .
  • the main switch 12 is a switch turning ON/OFF the power supply circuit 16 .
  • the power supply circuit 16 is put in the standby mode.
  • the power supply circuit 16 is not activated and supplies no electric power while the main switch 12 is OFF.
  • the trigger 13 is a switch controlling the value of electric power supplied to the drive part 30 from the power supply circuit 16 .
  • the trigger 13 is pulled in the standby mode while the main switch 12 is ON, the electric power according to the pulling rate of the trigger 13 is supplied to the drive part 30 from the power supply circuit 16 .
  • the remaining battery level display 14 is, for example, a liquid crystal screen that changes display according to the output of the battery 50 . Checking on the screen displayed by the remaining battery level display 14 , the user of the electric lawn mower 1 can know the approximate remaining operation time.
  • the main LED 15 is a first light emitting part emitting light when the main switch 12 is turned ON. Since the main LED 15 emits light when the main switch 12 is turned on, the operator can easily confirm that the main switch 12 is ON/OFF.
  • the power supply circuit 16 converts the voltage output from the battery 50 to a voltage of a value corresponding to the pulling rate of the trigger 13 regardless of the output voltage magnitude from the battery 50 and outputs it.
  • the power supply circuit 16 further include a function of protecting the battery 50 and drive part 30 against overcurrent and overvoltage, imposing mandatory OFF on the output according to the output voltage of the battery 50 or the value of current supplied to the drive part 30 . Details of operation and a specific circuit of the power supply circuit 16 will be described later.
  • the battery 50 is, for example, a lithium ion rechargeable battery.
  • the battery 50 comprises a substrate, multiple battery cells provided on the substrate, and plus and minus terminals provided on the substrate.
  • the battery 50 also comprises an LD terminal. When a circuit provided on the substrate of the battery 50 detects overdischarge from the battery cells, abnormal signals are output from the LD terminal.
  • the battery 50 also comprises an ID terminal. Battery information such as specification of the battery 50 stored in the memory on the substrate of the battery 50 is output from the ID terminal.
  • the battery 50 applies a voltage between the plus and minus terminals to the power supply circuit 16 .
  • the electric lawn mower 1 further comprises a speaker, a radio, and a sound reproducing device, which are driven by the electric power supplied from the operation part 10 .
  • the coupling part 20 includes a hollow tube made of a lightweight, rigid material such as aluminum alloy and reinforced plastic.
  • the coupling part 20 mechanically connects the operation part 10 and drive part 30 and supplies the electric power output from the power supply circuit 16 to the drive part 30 via a conductive wire running through the inside thereof.
  • the user uses the electric lawn mower 1 .
  • the operation part 10 and drive part 30 are provided on the coupling part 20 at a distance as described above; therefore, the gravity center of the electric lawn mower 1 is away from the operation part 10 .
  • the user receives a proper weight, improving the operability.
  • the drive part 30 rotates the attached blade 39 with the input electric power.
  • the drive part 30 consists of, for example, a coreless motor.
  • the drive part 30 consisting of a coreless motor assures a higher level of quietness. Furthermore, a lithium ion battery is used to drive the coreless motor; a lightweight, low power consumption electric lawn mower 1 having extended operation time can be constructed. Furthermore, using a booster circuit 300 as described later, sufficiently high rotation speed operation is available with a small capacity battery.
  • the running indicator LED 40 is a second light emitting part emitting light while the drive part 30 is powered.
  • the running indicator LED 40 consists of, for example, an organic EL.
  • the running indicator LED 40 emits light while the drive part 30 is powered. Then, the running indicator LED 40 emits light even if the drive part 30 does not rotate because of, for example, shortage in torque. In this way, the user can know whether or not the drive part 30 is powered from the running indicator LED 40 .
  • the running indicator LED 40 allows the user to know whether or not the drive part 30 is driven.
  • the battery 50 is detachably fitted in the battery mounting part 11 in the direction from the top surface to bottom surface. With the battery 50 being fitted in the battery mounting part 11 , the output terminals of the battery 50 are connected to the input terminals of the operation part 10 .
  • the drive part 30 consisting of a coreless motor primarily comprises, as shown in FIG. 3 , a motor case 29 , a coil substrate 31 , a central shaft (output shaft) 32 , a brush 33 , a commutator 34 , an upper yoke 35 , a lower yoke 36 , a magnet part 37 , and a brush cap 38 .
  • the motor case 29 immobilizes the upper yoke 35 , lower yoke 36 , and brush cap 38 .
  • the coil substrate 31 is secured by the central shaft 32 passing through the center of the motor case 29 .
  • the commutator 34 is fixed to one surface of the coil substrate 31 .
  • the upper yoke 35 is fixed to the motor case 29 at a not-shown position.
  • the lower yoke 36 is fitted in and fixed to the motor case 29 .
  • the magnet part 37 is fixed to one surface of the lower yoke 36 .
  • the brush cap 38 is fixed to the motor case 29 .
  • the brush 33 is supported and biased toward the commutator 34 by a spring that the motor case 29 includes.
  • the motor case 29 is a hollow case made of a lightweight, rigid material such as aluminum alloy and reinforced plastic.
  • the coil substrate 31 is a nearly disc-shaped plate on which multiple coils are arranged.
  • the central shaft 32 Passing through the coil substrate 31 and commutator 34 , the central shaft 32 is secured to the coil substrate 31 .
  • the coil substrate 31 and commutator 34 rotates as one piece as the central shaft 32 rotates.
  • the electric power supplied from the operation part 10 via a conductive wire passing through the inside of the coupling part 20 is supplied to the coil substrate 31 via the brush 33 .
  • the commutator 34 consists of commutator segments and insulating segments connected to the coil substrate 31 and alternately arranged in a circle around the central shaft.
  • the commutator 34 allows only one direction of current supplied from the brush 33 to run to the coil substrate 31 .
  • the magnet part 37 has planar magnets magnetized in the axial direction and arranged in the circumferential direction, forming a magnetic circuit via the upper and lower yokes 35 and 36 .
  • the rotor of the coreless motor comprises a central shaft 32 , a flange 132 , and, from the top in FIG. 4 , a commutator 34 and a coil substrate 31 consisting of five coil substrate parts 131 .
  • the commutator 34 and coil substrate 31 are each a printed-wiring board composed of an insulator substrate and a conductor pattern.
  • a conductor pattern for commutator segments 134 making contact with the brush 33 is formed on the top surface of the commutator 34 .
  • the conductor pattern has an annular form around the central shaft 32 seen in the axial direction of the central shaft 32 .
  • Each commutator segment 134 has a through-hole penetrating the commutator 34 at the outer end.
  • a conductor pattern on the top surface of the coil substrate part 131 provides multiple coil segments 131 a arranged in a radial pattern about the central shaft 32 and bent in given directions about the axis of the central shaft 32 .
  • each coil segment 131 c is connected to the corresponding commutator segment 134 via a through-hole at the inner end.
  • Each coil segment 131 c has multiple through-holes penetrating the coil substrate part 131 at the outer end.
  • a conductor pattern on the bottom surface of the coil substrate part 131 is nearly equal to the coil segments 131 a and 131 c shown in FIGS. 5 and 6 and provides multiple not-shown coil segments arranged in a radial pattern about the central shaft 32 .
  • the outer end of each not-shown coil segment is connected to the corresponding coil segment on the top surface via solder filled in the through-hole.
  • the inner end of each not-shown coil segment is connected to the corresponding commutator segment 134 of the commutator 34 via solder filled in the through-hole.
  • the multiple coil segments 131 a and 131 c and multiple not-shown coil segments in the coil region constitute multiple coils in the form of a nearly horizontal U-shape (an example of a nearly annular form) seen in the axial direction of the central shaft 32 .
  • the multiple coils are arranged in the circumferential direction around the central shaft 32 .
  • the ends of the coils are connected to the corresponding commutator segments 134 of the commutator 34 .
  • the conductor pattern for the commutator segments 134 of the commutator 34 has a thickness larger than the coil segments of the coil substrate parts in order to curb damage due to abrasion by the brush 33 .
  • Not-shown insulating layers are interposed between the commutator 34 and coil substrate 31 and between multiple coil substrate parts 131 .
  • the magnetic flux generation means is not restricted to this structure as long as the magnetic flux passes through the coils of the coil substrate 31 in the axial direction of the central shaft 32 .
  • the magnetic flux generation means can consist of multiple permanent magnets, electromagnets, or only coils.
  • the blade 39 rotates in conjunction with the central shaft 32 rotates. As the blade 39 rotates, the target is mowed.
  • FIG. 7 The connection between the operation part 10 and trigger 13 of the electric lawn mower 1 in FIG. 1 is shown in detail in FIG. 7 .
  • the grip 22 is formed integrally with the operation part 10 and provided along the periphery of the coupling part 20 .
  • the grip 22 is provided with a rotation shaft 25 , to which the trigger 13 is coupled.
  • a wire 24 is connected to the trigger 13 .
  • the trigger 13 is coupled to a variable speed switch 26 provided in the operation part 10 via the wire 24 .
  • the grip 22 may be close to the operation part 10 with a space therebetween, which is regarded as equivalent to a situation where the grip 22 is next to the operation part 10 .
  • the wire 24 When the trigger 13 is pulled, the wire 24 is tugged about the rotation shaft 25 .
  • the wire 24 transfers the pulling rate of the trigger 13 to the variable speed switch 26 .
  • the variable speed switch 26 supplies the pulling rate of the trigger 13 to the power supply circuit 16 .
  • the power supply circuit 16 adjusts the output voltage according to the pulling rate of the trigger 13 .
  • the electric lawn mower 1 can have a U-shaped handle 23 as shown in FIG. 8 in place of the D-shaped handle 21 .
  • the U-shaped handle 23 is provided on the coupling part 20 at a distance from the operation part 10 and the trigger 13 is provided at one end of the U-shaped handle 23 .
  • the U-shaped handle 23 consists of a U-shaped hollow pipe and has grips 22 at the ends.
  • the trigger 13 is provided to one of the grips 22 .
  • the power supply circuit 16 comprises, as shown in FIG. 10 , input terminals I 1 , I 2 , I 3 , and I 4 , a main switch circuit 100 , a trigger switch circuit 200 , a booster circuit 300 , a speed adjustment circuit (speed adjustment part, voltage measuring part) 400 , a control circuit 500 , a current detection circuit 600 , a battery voltage detection circuit 700 , a battery abnormality detection circuit 800 , a constant voltage circuit 900 , and output terminals O 1 and O 2 .
  • the input terminal I 1 is connected to the plus terminal (+) of the battery 50 ; the input terminal I 2 , to the minus terminal ( ⁇ ) of the battery 50 ; the input terminal I 3 , to the LD terminal of the battery 50 ; and the input terminal I 4 , to the ID terminal of the battery 50 .
  • the running indicator LED 40 and drive part 30 are series-connected between the output terminals O 1 and O 2 .
  • the input terminal I 1 is connected to the main switch circuit 100 .
  • the input terminal I 2 is grounded.
  • the input terminal I 3 is connected to the battery abnormality detection circuit 800 .
  • the input terminal I 4 is connected to the control circuit 500 .
  • the output of the main switch circuit 100 is supplied to the trigger switch circuit 200 , battery voltage detection circuit 700 , constant voltage circuit 900 , and anode of the main LED 15 .
  • the cathode of the main LED 15 is connected to the remaining battery level display 14 .
  • the main switch circuit 100 consists of, for example, a switch activated as the main switch 12 is turned ON and a self-arc extinguishing element such as IGBT (insulated gate bipolar transistor) and MOSFET (metal oxide semiconductor field effect transistor).
  • the speed adjustment circuit 400 is so connected as to provide feedback on the output of the booster circuit 300 to the booster circuit 300 .
  • the speed adjustment circuit 400 consists of, for example, a voltage dividing resistor and a variable resistor having a resistance varied according to the pulling rate of the trigger 13 .
  • the control circuit 500 receives the output of the constant voltage circuit 900 , output of the current detection circuit 600 , output of the battery voltage detection circuit 700 , and the input to the input terminal I 4 .
  • the output of the control circuit 500 is supplied to the main switch circuit 100 , trigger switch circuit 200 , and speaker 910 .
  • the control circuit 500 is, for example, a microcomputer.
  • the current detection circuit 600 is connected to the output terminal O 2 at one terminal and grounded at the other terminal.
  • the current detection circuit 600 is, for example, an ampere meter.
  • the output of the battery abnormality detection circuit 800 is supplied to the main switch circuit 100 .
  • the battery voltage detection circuit 700 is, for example, an off-latch circuit.
  • the power supply circuit 16 having the above-described structure is driven by a voltage applied between the input terminals I 1 and I 2 .
  • the main switch circuit 100 is a switch associated with ON/OFF of the main switch 12 .
  • the main switch circuit 100 is turned ON when the main switch 12 is turned ON.
  • the main switch circuit 100 is turned OFF when the main switch 12 is turned OFF.
  • the main switch circuit 100 is further turned ON/OFF by the control circuit 500 while the main switch 12 is ON.
  • the main switch circuit 100 supplies the electric power output from the battery 50 to the trigger switch circuit 200 , constant voltage circuit 900 , and remaining battery level display 14 . While the main switch 12 is OFF, the main switch circuit 100 blocks the electric power supplied from the battery 50 .
  • the trigger witch circuit 200 is a switch associated with the trigger 13 .
  • the trigger switch circuit 200 is turned ON when the pulling rate of the trigger 13 is equal to or higher than a given value.
  • the trigger switch circuit 200 is further turned ON/OFF by the control circuit 500 . While the trigger switch circuit 200 is ON, the trigger switch circuit 200 supplies the electric power supplied from the main switch circuit 100 to the booster circuit 300 . While the trigger switch circuit 200 is OFF, the trigger switch circuit 200 blocks the electric power.
  • the booster circuit 300 boosts the electric power supplied from the trigger switch circuit 200 and outputs it from the output terminal O 1 .
  • the output of the booster circuit 300 is adjusted by the speed adjustment circuit 400 .
  • the booster circuit 300 adjusts the output so that the voltage input from the speed adjustment circuit 400 always stays constant.
  • the voltage boosted by the booster circuit 300 is applied to the drive part 30 connected to the output terminals O 1 and O 2 .
  • the speed adjustment circuit 400 is a circuit measuring the voltage applied to the motor and adjusting the output of the booster circuit 300 according to the pulling rate of the trigger 13 .
  • the speed adjustment circuit 400 provides feedback on the output of the booster circuit 300 , whereby the booster circuit 30 outputs a voltage of a target value.
  • the speed adjustment circuit 400 supplies the voltage divided between the voltage dividing resistor and variable resistor to the booster circuit 300 .
  • the control circuit 500 mandatorily turns OFF the main switch circuit 100 or trigger switch circuit 200 , for example, when the current running toward the drive part 30 exceeds the rated value of the drive part 30 or when the voltage output from the battery 50 becomes lower than a given value.
  • the control circuit 500 executes programs stored in the memory in advance so as to turn OFF the main switch circuit 100 or trigger switch circuit 200 according to the current running toward the drive part 30 , which is detected by the current detection circuit 600 , and the voltage output from the battery 50 , which is detected by the battery voltage circuit 700 . Furthermore, when the control circuit 500 detects no electric power being supplied to the drive part 30 for a given period of time while the main switch circuit 100 is ON, the control circuit 500 automatically turns OFF the main switch circuit 100 .
  • the control circuit 500 receives battery information from the ID terminal via the input terminal 4 .
  • the control circuit 500 makes reference to a table stored in the internal memory in advance and reads the voltage at which the battery starts overly discharging based on the battery information. For example, the control circuit 500 obtains an overdischarge voltage of 8 V if the battery information includes a rated voltage of 14.4 V and an overdischarge voltage of 10 V if the battery information includes a rated voltage of 18 V.
  • the control circuit 500 automatically turns OFF the main switch circuit 100 when the output voltage of the battery 50 becomes lower than the overdischarge voltage.
  • the overdischarge voltage is a reference voltage where the battery 50 reaches a state of overdischarge when the actual output voltage of the batter 50 constantly decreases. Also, the overdischarge voltage is larger than this output voltage by a predetermined value. When the output voltage of the battery 50 falls below the overdischarge voltage, the main switch circuit 100 is automatically turned OFF as overdischarge occurs shortly thereafter.
  • the battery abnormality detection circuit 800 turns OFF the main switch circuit 100 when it receives signals from the LD terminal and mandatorily keeps the main switch circuit 100 OFF until it receives no input from the LD terminal or the battery 50 is dismounted.
  • the speaker 910 makes sound based on input sound information.
  • the control circuit 500 instructs the speaker 910 to make sound for the case of overcurrent.
  • the speaker 910 announces the overdischarge.
  • the speaker 910 announces that the battery 50 undergoes an abnormal event.
  • the sound reproducing circuit 920 operates on the output of the constant voltage circuit 900 .
  • the sound reproducing circuit 920 decodes sound data such as music data stored in the internal memory and outputs them to the speaker 910 .
  • the radio 930 has an antenna.
  • the radio 930 tunes the antenna properties and receives radio waves of a particular frequency, detects sound information superimposed on carrier waves from the received radio waves, and outputs the detected sound information to the speaker. These operations are performed on the output of the constant voltage circuit 900 ; therefore, they are activated as the main switch circuit 100 is turned ON.
  • the booster circuit 300 consists of, for example, a smoothing circuit 301 , a booster circuit 310 , a rectifier diode 320 , and a smoothing capacitor 330 .
  • the speed adjustment circuit 400 consists of a series circuit composed of a voltage dividing resistor 410 , a voltage dividing resistor 420 , a variable resistor 430 .
  • the smoothing capacitor 301 is parallel-connected between the trigger switch circuit 200 and booster circuit 310 .
  • the booster circuit 310 is series-connected between the trigger switch circuit 200 and rectifier diode 320 .
  • the rectifier diode 320 is series-connected between the booster circuit 310 and output terminal O 1 .
  • the smoothing capacitor 330 is parallel-connected between the rectifier diode 320 and output terminal O 1 .
  • the speed adjustment circuit 400 is connected between the output terminals O 1 and 02 .
  • the output of the speed adjustment circuit 400 is connected to the booster circuit 310 .
  • the voltage dividing resistors 410 and 420 are series-connected and the variable resistor 430 is further series-connected thereto.
  • the smoothing capacitor 301 removes extra vibration of the voltage supplied from the trigger switch circuit 200 so as to smooth the waveform.
  • the booster circuit 310 is a booster chopper circuit consisting of, for example, an FET (field effect transistor) 311 , a switching IC (integrated circuit) 312 , and a choke coil 313 .
  • the booster circuit 310 boosts the input voltage by means of the flyback effect of the choke coil 313 and outputs the boosted voltage.
  • the FET 311 is turned ON when a voltage equal to or higher than a threshold voltage is applied to the gate terminal by the switching IC 312 , allowing a current to run between the source and drain terminals.
  • the FET 311 is turned OFF when a voltage lower than the threshold voltage is applied to the gate terminal, allowing no current to run between the source and drain terminals.
  • the switching IC 312 applies a high level of voltage equal to or higher than a threshold voltage of the FET 311 or a low level of voltage lower than the threshold voltage to the gate terminal of the FET 311 to turn ON/OFF the FET 311 according to the voltage input from the speed adjustment circuit 400 .
  • the switching IC 312 adjusts the ON/OFF switching frequency of the voltage applied to the gate terminal of the FET 311 so that the voltage input from the speed adjustment circuit 400 has a target value. For example, the switching IC 312 increases the ON/OFF switching speed of the FET 311 when the voltage input from the speed adjustment circuit 400 is lower than a target value, and decreases the ON/OFF switching speed of the FET 311 when the voltage input from the speed adjustment circuit 400 is higher than the target value.
  • the choke coil 313 yields flyback effect as the ON/OFF switching of the FET 311 occurs.
  • the flyback effect causes the voltage between the terminals of the choke coil 313 to rise.
  • the rectifier diode 320 rectifies the output of the booster circuit 310 .
  • the smoothing capacitor 330 removes extra vibration of the voltage rectified by the rectifier diode 320 so as to smooth the waveform.
  • the voltage divided between the voltage dividing resistor 410 and the voltage dividing resistor 420 and variable resistor 430 is supplied to the switching IC 312 .
  • the variable resistor 430 has a resistance varied according to the pulling rate of the trigger 13 .
  • the resistance of the variable resistor 430 drops as the pulling rate of the trigger 13 is increased and rises as the pulling rate of the trigger 13 is decreased.
  • the resistance of the variable resistance 430 drops and the voltage applied to the switching IC 312 from the speed adjustment circuit 400 drops. Then, the switching IC 312 shortens the switching cycle of the FET 311 . As the cycle of switching ON/OFF the FET 311 is shortened, the peak value of the voltage between the terminals of the choke coil 313 rises and the voltage supplied to the switching IC 312 from the speed adjustment circuit 400 rises.
  • the speed adjustment circuit 400 provides feedback on the output of the booster circuit 300 , whereby the booster circuit 300 adjusts the output so that the voltage input from the speed adjustment circuit 400 always stays constant.
  • the above operation is performed also when the voltage supplied to the booster circuit 300 from the trigger switch circuit 200 varies because of the decrease in the output of the battery 50 , the replacement to another battery from the battery 50 , or the like. For example, when the output of the battery 50 drops, the voltage output from the booster circuit 300 accordingly drops. As the output of the booster circuit 300 drops, the voltage supplied to the booster circuit 300 from the speed adjustment circuit 400 drops. Then, the booster circuit 300 further raises the output voltage. The output voltage of the booster circuit 300 is adjusted until the voltage input from the speed adjustment circuit 400 has a target value.
  • the booster circuit 300 and speed adjustment circuit 400 allow the electric lawn mower 1 to operate at a target rotation speed regardless of different output from the battery 50 .
  • the voltage dividing resistors 410 and 420 and variable resistor 430 have relatively high impedances compared with the drive part 30 . Therefore, the speed adjustment circuit 400 consumes almost no electric power.
  • the control circuit 500 , current detection circuit 600 , voltage detection circuit 700 , and battery abnormality detection circuit 800 of the power supply circuit 16 will be described hereafter with reference to FIGS. 12 and 13 .
  • the current detection circuit 600 consists of, for example, a current detection resistor 610 , an operational amplifier 620 , a grounding resistor 621 , a feedback resistor 622 , and a current limiting resistor 630 .
  • the current detection resistor 610 connects the booster circuit 300 , speed adjustment circuit 400 , and drive part 30 and the ground.
  • the terminal of the current detection resistor 610 that is not grounded is connected to the + terminal of the operational amplifier 620 .
  • the output of the operational amplifier 620 is connected to its own ⁇ (minus) terminal via the feedback resistor 622 and further grounded via the grounding resistor 621 . Furthermore, the output of the operational amplifier 620 is supplied to the control circuit 500 via the current limiting resistor 630 .
  • the current detection resistor 610 detects the total current running toward the booster circuit 300 , speed adjustment circuit 400 , and drive part 30 . However, since the current running from the booster circuit 300 and speed adjustment circuit 400 to the ground is much smaller in quantity than the current running toward the drive part 30 , the total current running toward the booster circuit 300 , speed adjustment circuit 400 , and drive part 30 is nearly equal in quantity to the current running toward the drive part 30 .
  • the operational amplifier 620 , grounding resistor 621 , and feedback resistor 622 form a noninverting amplifying circuit.
  • the + terminal of the operational terminal 620 serves as the noninverting input terminal (+) and the ⁇ terminal of the operational terminal 620 serves as the noninverting input terminal ( ⁇ ).
  • the noninverting input terminal (+) of the operational terminal 620 receives the voltage between the current detection resistor 610 and ground.
  • the noninverting input terminal ( ⁇ ) of the operational terminal 620 is grounded via the grounding resistor 621 and receives negative feedback on the output of the operational terminal 620 from the feedback resistor 622 .
  • the amplified output is limited in current by the current limiting resistor 630 and supplied to the control circuit 500 .
  • the control circuit 500 mandatorily turns OFF the trigger switch circuit 200 .
  • the trigger switch circuit 200 is mandatorily turned OFF, the electric power supplied from the main switch circuit 100 is not supplied to the booster circuit 300 even if the trigger 13 is pulled.
  • the current detection resistor 610 , grounding resistor 621 , feedback resistor 622 , and current limiting resistor 630 are selected so that the control circuit 500 receives a signal having a voltage equal to or higher than a threshold when the detected current exceeds a nearly rated value of the drive part 30 (for example, 15 A).
  • the control circuit 500 mandatorily turns OFF the trigger switch circuit 200 .
  • the main switch circuit 100 stays ON and the electric power is supplied to the constant voltage circuit 900 .
  • the control circuit 500 mandatorily turns OFF the trigger switch circuit 200 to stop the power supply to the drive part 30 .
  • the battery voltage detection circuit 700 detects the output voltage of the battery 50 being equal to or lower than a given value, the control circuit 500 mandatorily turns OFF the main switch circuit 100 .
  • the battery voltage detection circuit 700 consists of, for example, as shown in FIG. 13 , a series circuit composed of voltage dividing resistors 710 and 720 .
  • the voltage dividing resistor 710 is connected to the output of the main switch circuit 100 at one end and to one end of the voltage dividing resistor 720 at the other end. The other end of the voltage dividing resistor 720 is grounded.
  • the control circuit 500 receives the voltage applied to the voltage dividing resistor 720 . When the received voltage becomes equal to or lower than a voltage at which the battery 50 starts overly discharging, the control circuit 500 mandatorily turns OFF the main switch circuit 100 .
  • the battery voltage detection circuit 700 measures the voltage output from the main switch circuit 100 so as to measure the voltage output from the battery 50 and supplies it to the control circuit 500 .
  • the control circuit 500 mandatorily turns OFF the main switch circuit 100 to stop the output of the battery 50 . In this way, overdischarge of the battery 50 is prevented.
  • the control circuit 500 mandatorily and automatically turns OFF the main switch circuit 100 . In this way, the electric lawn mower 1 is automatically powered off when it is left with the main switch circuit kept ON.
  • control circuit 500 controls the ON/OFF of the main switch circuit 100 and trigger switch circuit 200 upon overdischarge and overcurrent. It is not necessarily the control circuit 500 that is in charge of the control.
  • the following structure can be used when the current running toward the drive part 30 exceeds a given value.
  • a GTO gate turnoff thyristor
  • Zener diode having a breakdown voltage nearly equal to the threshold voltage of this self-arc extinguishing element is connected to the gate of the
  • the operation part 10 and drive part 30 are provided on the coupling part 20 at a distance from each other. They are not necessarily provided at a distance or provided on the coupling part 20 as long as the electric power output from the operation part 10 is supplied to the drive part 30 .
  • the operation part 10 and drive part 30 can be provided at one end of the coupling part 20 side by side or the operation part 10 and drive part 30 can be connected only by a conductive wire without the coupling part 20 .
  • the electric lawn mower 1 can have a blade 39 provided at an angle with respect to the coupling part 20 as shown in FIG. 14 .
  • This allows the operator to maintain his/her natural posture during general operation of the electric lawn mower 1 in which the operator swings his/her hands holding the grip (grip part) 22 (not shown) and D-shaped handle 21 around his/her hip as indicated by the arrow O in FIG. 17 .
  • the electric lawn mower 1 shown in FIG. 14 is designed to have, for example, a total length A of approximately 180 cm and a blade inclination angle B of approximately 38 degrees with respect to the coupling part, whereby the blade 39 is nearly parallel to the ground surface when the distance C between the grip 22 and ground surface is 70 to 90 cm, which is slightly above the hip of the operator.
  • a belt holder 28 holding a belt 65 that can be placed over a shoulder of the operator as shown in FIGS. 15 and 16 is provided between the D-shaped handle 21 and grip 22 . As shown in FIGS. 15 and 17 , the belt 65 is engaged with the belt holder 28 and then the belt 65 is placed over a shoulder of the operator. The weight of the electric lawn mower 1 is received by the shoulder during the operation, less tiring the operator.
  • the operator With the belt 65 being placed over the shoulder, the operator can hold the grip 22 in the rear of the belt holder 28 and applies to the grip 22 a force toward the ground. In this way, the electric lawn mower 1 is supported by the belt holder 28 and grip 22 .
  • the electric lawn mower 1 can be swung about the belt holder 28 simply by applying to the D-shaped handle 21 a force in the swing direction.
  • the blade 39 can easily be moved to the target site, improving the operability.
  • the motor case 29 is made of aluminum alloy.
  • the motor case 29 can be made of resin and a weight can be provided near the drive part 30 to have the gravity center on the drive part 30 side with respect to the D-shaped handle 21 .
  • the motor case 29 made of aluminum alloy provides better cooling action, which curbs rise in the temperature of the coil substrate 31 , and increases the strength, which improves the life.
  • the blade 39 of the electric lawn mower 1 is directly driven by the central shaft 32 of the coreless motor, namely the blade 39 is directly connected to the coreless motor without any gear or the like, curbing mechanical loss. Furthermore, no gear noise occurs, curbing unwanted noise. Furthermore, the coreless motor rotates as a magnetic flux passing through the coil substrate 31 in the axial direction of the central shaft 32 occurs. Therefore, the motor does not protrude in the axial direction of the central shaft 32 even though the motor is provided where the drive part 30 side is (where the blade 39 side is). The drive part 30 can significantly be downsized in the axial direction of the central shaft 32 . Therefore, any reduction in the operability due to the protrusion of the drive part 30 in the axial direction of the central shaft 32 is curbed.
  • the coreless motor in the above embodiment is a coreless motor having a coil substrate 31 in the rotor part and a brush 33 with a magnet part 37 in the stator part. It can be a brushless-type coreless motor comprising a coil substrate in the stator part and a magnet in the rotor part.
  • the gravity center is located on the coreless motor side with respect to the D-shaped handle 21 regardless of any battery, 14.4 V or 18 V lithium ion battery or nickel-cadmium rechargeable battery, being mounted.
  • the structure allowing only lithium ion batteries to be mounted may be used.

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US10547182B2 (en) 2020-01-28
US20170155258A1 (en) 2017-06-01
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WO2011024479A3 (en) 2011-04-21
CN102356365A (zh) 2012-02-15

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