EP1416096B1 - Hydraulic excavator with a hydraulic circuit - Google Patents
Hydraulic excavator with a hydraulic circuit Download PDFInfo
- Publication number
- EP1416096B1 EP1416096B1 EP03256761A EP03256761A EP1416096B1 EP 1416096 B1 EP1416096 B1 EP 1416096B1 EP 03256761 A EP03256761 A EP 03256761A EP 03256761 A EP03256761 A EP 03256761A EP 1416096 B1 EP1416096 B1 EP 1416096B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- pressure
- bucket
- pilot
- boom
- boom raising
- 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.)
- Expired - Lifetime
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
- F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
- F15B11/166—Controlling a pilot pressure in response to the load, i.e. supply to at least one user is regulated by adjusting either the system pilot pressure or one or more of the individual pilot command pressures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2221—Control of flow rate; Load sensing arrangements
- E02F9/2225—Control of flow rate; Load sensing arrangements using pressure-compensating valves
- E02F9/2228—Control of flow rate; Load sensing arrangements using pressure-compensating valves including an electronic controller
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2221—Control of flow rate; Load sensing arrangements
- E02F9/2232—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps
- E02F9/2235—Control of flow rate; Load sensing arrangements using one or more variable displacement pumps including an electronic controller
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2221—Control of flow rate; Load sensing arrangements
- E02F9/2239—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance
- E02F9/2242—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance including an electronic controller
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/226—Safety arrangements, e.g. hydraulic driven fans, preventing cavitation, leakage, overheating
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2285—Pilot-operated systems
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2292—Systems with two or more pumps
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2278—Hydraulic circuits
- E02F9/2296—Systems with a variable displacement pump
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
- F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
- F15B11/162—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for giving priority to particular servomotors or users
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
- F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
- F15B11/167—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load using pilot pressure to sense the demand
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
- F15B2211/205—Systems with pumps
- F15B2211/2053—Type of pump
- F15B2211/20546—Type of pump variable capacity
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/305—Directional control characterised by the type of valves
- F15B2211/3056—Assemblies of multiple valves
- F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/305—Directional control characterised by the type of valves
- F15B2211/3056—Assemblies of multiple valves
- F15B2211/3059—Assemblies of multiple valves having multiple valves for multiple output members
- F15B2211/30595—Assemblies of multiple valves having multiple valves for multiple output members with additional valves between the groups of valves for multiple output members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/31—Directional control characterised by the positions of the valve element
- F15B2211/3105—Neutral or centre positions
- F15B2211/3116—Neutral or centre positions the pump port being open in the centre position, e.g. so-called open centre
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/32—Directional control characterised by the type of actuation
- F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/50—Pressure control
- F15B2211/575—Pilot pressure control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
- F15B2211/6309—Electronic controllers using input signals representing a pressure the pressure being a pressure source supply pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
- F15B2211/6313—Electronic controllers using input signals representing a pressure the pressure being a load pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/63—Electronic controllers
- F15B2211/6303—Electronic controllers using input signals
- F15B2211/6306—Electronic controllers using input signals representing a pressure
- F15B2211/6316—Electronic controllers using input signals representing a pressure the pressure being a pilot pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/60—Circuit components or control therefor
- F15B2211/635—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements
- F15B2211/6355—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements having valve means
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/76—Control of force or torque of the output member
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/78—Control of multiple output members
Definitions
- This invention relates to a hydraulic circuit of a hydraulic excavator.
- Japanese Patent Application Publication No. Hei 8-13547 discloses that a pump pressure is increased to more than a load pressure of the boom cylinder by throttling a flow rate for supply to the bucket cylinder on composite operations including the above three operations.
- a hydraulic excavator of the present invention comprises a boom, an arm, a bucket and a hydraulic circuit.
- the hydraulic circuit comprises a boom cylinder for actuating the boom of a hydraulic excavator; an arm cylinder for actuating the arm of the excavator, a bucket cylinder for actuating the bucket of the excavator, a first hydraulic pump, and a second hydraulic pump, and is constructed such that pressure oil provided from the first hydraulic pump is fed in parallel to both boom cylinder and bucket cylinder through a boom control valve and a bucket control valve, while pressure oil provided from the second hydraulic pump is fed in parallel to both boom cylinder and arm cylinder through a boom control valve for confluence and a control valve for the arm, wherein each of the control valves is a hydraulic pilot switching valve adapted to operate in accordance with the amount of operation of an operating means, the hydraulic circuit further comprising a pilot pressure control means which, in accordance with the amount of an arm pulling operation and that of a boom raising operation, reduces a pilot pressure fed
- the pilot pressure fed to the bucket control valve is reduced to diminish the stroke of the same valve, whereby a throttling effect of the control valve itself is exerted to increase the pump pressure and there is ensured a boom raising operation.
- the boom raising operation is ensured not by throttling an inlet-side passage (main passage) in the bucket control valve, but by reducing the pilot pressure fed to the same valve. Therefore, even if the pump flow rate decreases due to a decrease of engine speed, there is no fear of occurrence of cavitation because the tank flow rate is also throttled at the same time.
- the pilot pressure control means is constructed such that a tank line communicating with a tank is connected a bucket digging-side pilot line, and a bucket digging-side switching valve whose degree of opening changes in accordance with a boom raising pilot pressure, as well as a first throttle means, are provided in the tank line, further, a second throttle means is provided in the pilot line upstream of the tank line.
- a boom raising switching valve whose degree of opening changes in accordance with an arm pulling pilot pressure is connected to a boom raising pilot line, and a boom raising pilot pressure as an output of the boom raising switching valve is fed to a pilot port of the bucket digging-side switching valve.
- variable throttle means whose degree of opening can be adjusted.
- the pilot pressure control means may comprise an electromagnetic proportional pressure reducing valve disposed in the bucket digging-side pilot line of the bucket control valve, an arm pulling detector means for detecting the amount of the arm pulling operation, a boom raising detector means for detecting the amount of the boom raising operation, and a controller which issues to the electromagnetic proportional pressure reducing valve a command of a secondary pressure proportional to the amount of the arm pulling operation and that of the boom raising operation detected by both detector means.
- the pilot pressure control means may comprise a boom raising pressure detector means for detecting a boom raising-side pressure of the boom cylinder and a pump pressure detector means for detecting an operating pressure of the first hydraulic pump, wherein the command of the secondary pressure to the electromagnetic proportional pressure reducing valve may be issued on condition that the operating pressure of the first hydraulic pump is higher than the boom raising-side pressure.
- Working attachments in a hydraulic excavator are composed of a boom, an arm, a bucket, and hydraulic cylinders (boom cylinder, arm cylinder, bucket cylinder) for actuating those components.
- Various works including excavating and loading works, are carried out by various operations, including boom raising/boom lowering, arm pushing/arm pulling, and bucket digging or bucket-in/bucket dump or bucket-out operations.
- both a boom cylinder which requires a large flow rate and a bucket cylinder for which a small flow rate will do are actuated usually by a common hydraulic pump.
- a boom cylinder and a bucket cylinder are actuated by a first hydraulic pump, while an arm cylinder is actuated by a second hydraulic pump, and in this state a portion of pressure oil fed from the second hydraulic pump is allowed to join the pressure oil in the boom cylinder to ensure a required boom operation speed.
- the numeral 1 denotes a first hydraulic pump.
- a bucket cylinder 2 and a boom cylinder 3 are connected to the first hydraulic pump 1 in parallel through a bucket control valve 4 and a boom control valve 5, respectively.
- Numeral 6 denotes a second hydraulic pump.
- the boom cylinder 3 and an arm cylinder 7 are connected to the second hydraulic pump 6 in parallel through a boom control valve 8 for confluence and an arm control valve 9, respectively.
- the mark T denotes a tank.
- the control valves 4, 5, 8, and 9 are constructed as hydraulic pilot valves (hydraulic pilot switching valves) adapted to operate switchingly in accordance with pilot pressures provided from remote control valves 10, 11, and 12 for bucket, boom, and arm, respectively, which serve as operating means.
- the bucket control valve 4 and the boom control valve 5 are set to respective left-hand positions (bucket digging position and boom raising position) in the figure, while the boom control valve 8 for confluence and the arm control valve 9 are set to respective righthand positions (confluent position, arm pulling position) in the figure.
- pressure oil is fed from the first hydraulic pump 1 to both bucket and boom cylinders 2, 3 and from the second hydraulic pump 6 to both boom and arm cylinders 3, 7 at flow rates proportional to control valve operation quantities, whereby the cylinders 2, 3, and 7 extend.
- Fig. 1 as pilot lines for the supply of a pilot pressure to each of the control valves 4, 5, 8, and 9, there are shown only a bucket digging-side pilot line 13, a boom raising-side pilot line 14, a confluent pilot line 15 connected in parallel with the pilot line 14, and an arm pulling-side pilot line 16.
- bucket dump-side, boom lowering-side, confluence stop-side, and arm pushing-side pilot lines are not shown.
- a tank line 17 is connected to the pilot digging-side pilot line 13.
- a bucket digging-side switching valve 18 as a hydraulic pilot valve whose degree of opening changes in accordance with a pilot pressure, and a first throttle 19 (throttle valve), are provided in the tank line 17. Further, a second throttle 20 (throttle valve) is provided in the pilot line 13 upstream (on the hydraulic pump side) of the tank line 17.
- a pilot pressure control means is constituted by these components.
- a pilot port of the bucket digging-side switching valve 18 is connected to the boom raising-side pilot line 14 through a control line 21.
- a boom raising-side switching valve 22 as a hydraulic pilot valve whose degree of opening changes in accordance with an arm pulling pilot pressure.
- pilot pressures P1, P2, and P3 proportional to operation quantities are exerted on pilot lines 13, 14, 15, and 16.
- the switching valve 22 opens at a degree of opening proportional to the pilot pressure P3. Further, a pilot pressure P2a proportional to the degree of opening of the switching valve 22 is fed to the pilot port of the bucket digging-side switching valve 18, whereby the switching valve 18 opens at a degree of opening proportional to the pilot pressure P2a.
- the bucket digging-side pilot pressure P1 is reduced to an intermediate pressure (e.g., one half or so) by the second throttle 20.
- an intermediate pressure e.g., one half or so
- valve stroke is diminished not by throttling an inlet-side passage of the bucket control valve 4 but by reducing the pilot pressure fed to the valve 4, to ensure a boom raising operation. Consequently, even in the event of decrease of the pump flow rate due to a lowering of the engine speed which is a pump drive source, the tank flow rate is also throttled at the same time by the valve 4. As a result, there no longer is any fear of occurrence of cavitation.
- the construction can be made simpler than in case of providing a throttle means in the main passage. Accordingly, the cost of parts and that of assembly can be reduced and it becomes easy to later install the hydraulic circuit to an existing machine.
- the bucket digging-side switching valve 18 When both boom raising and arm pulling operations are not performed substantially simultaneously, the bucket digging-side switching valve 18 does not operate, so that there is no throttling action for the bucket digging-side pilot pressure and a bucket digging operation is performed at a normal speed.
- the degree of reduction in the bucket digging-side pilot pressure be adjustable in accordance with the weight of the bucket and the operator' s taste in operation characteristic.
- adjustment of the degree of pressure reduction can be made by the selection and replacement of both throttles 19 and 20.
- variable throttles are used as both first and second throttles 19' and 20'.
- variable throttles when the bucket is replaced or the operator is changed in a single machine, the degree of pressure reduction can be adjusted freely by adjusting the degree of opening of both throttles 19' and 20'.
- an electromagnetic proportional pressure reducing valve (hereinafter referred to simply as "pressure reducing valve") 23 is disposed in the bucket digging-side line 13, as shown in Fig. 3 .
- pressure sensors 25 and 26 for detecting the boom raising pilot pressure P2 and the arm pulling pilot pressure P3 and sending them to a controller 24.
- Secondary pressure command signals proportional to both pilot pressures P2 and P3 are sent to the pressure reducing valve 23 from the controller 24 to reduce the bucket digging-side pilot pressure.
- steps S1 and S2 the boom raising pilot pressure P2 and the arm pulling pilot pressure P3 are read.
- steps S3 and S4 it is respectively determined whether a boom raising operation and an arm pulling operation are being performed.
- steps S5 and S6 the sum of both pilot pressures P2 and P3 is plotted along the axis of abscissa and a secondary pressure (pressure after reduction) of the pressure reducing valve 23 is plotted along the axis of ordinate, then on the basis of a preset throttle characteristic a secondary pressure command signal is outputted to the pressure reducing valve 23 as a proportional valve.
- the selection and change of a characteristic with respect to each of boom raising, bucket digging, and arm pulling operations can be done more easily by adjustment (e.g., using a trimmer) through the controller 24.
- pressure sensors 27 and 28 for detecting a boom raising-side (cylinder head) pressure of the boom cylinder 3 and an operating pressure (pump pressure) of the first hydraulic pump 1, as shown in Fig. 5 .
- pump pressures detected by the pressure sensors 27 and 28 are inputted to the controller 24 and a bucket digging-side pilot pressure reducing action is exerted on the premise that the pump pressure is higher than the boom raising-side pressure.
- the boom raising pilot pressure P2, arm pulling pilot pressure P3, boom cylinder pressure, and the pressure of the first hydraulic pump 1 are read in steps S1 to S4.
- steps S5 and S6 it is determined whether a boom raising operation and an arm pulling operation are being performed or not. Thereafter, in step S7, a comparison is made between pump pressure and cylinder pressure. Only when the pump pressure is higher than the cylinder pressure, a secondary pressure of the pressure reducing valve as a proportional valve is calculated and outputted in steps S8 and S9.
- a hydraulic pilot type pressure reducing valve as a pilot control means may be provided in the bucket digging-side pilot line 13.
- electromagnetic switching valves are used as both bucket digging-side and boom raising-side switching valves 18, 22, and the switching valves 18 and 22 may be controlled by the controller in accordance with the boom raising-side pilot pressure and the arm pulling-side pilot pressure both detected by the pressure sensors.
- the pressure oil provided from the first hydraulic pump 1 is used for both bucket cylinder and boom cylinder, while the pressure oil from the second hydraulic pump 6 is used for boom cylinder confluence and for the arm cylinder.
- the present invention is also applicable to the case where the pressure oil from the second hydraulic pump 6 is not used for boom cylinder confluence.
- the bucket digging-side pilot pressure may be reduced in accordance with the boom raising-side pilot pressure (a pressure raising operation quantity).
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- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Civil Engineering (AREA)
- Structural Engineering (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Mechanical Engineering (AREA)
- Operation Control Of Excavators (AREA)
- Fluid-Pressure Circuits (AREA)
- Earth Drilling (AREA)
Abstract
Description
- This invention relates to a hydraulic circuit of a hydraulic excavator.
- In a hydraulic excavator with a two-pump type hydraulic circuit, when simultaneous operations of a boom raising, an arm pulling, and a bucket digging are performed in the air, pressure oil provided from both pumps are fed to a bucket cylinder and an arm cylinder in preference to a boom cylinder since a boom raising operation is an operation with heavy load than a bucket digging or an arm pulling of which its own weight in itself acts in a direction of working. As a result, there is a problem that an operation can not operate working attachments according to his will.
- In this regard, with a flow rate control valve provided at an inlet-passage of a control valve for a bucket cylinder,
Japanese Patent Application Publication No. Hei 8-13547 EP-A1-0715029 ) discloses that a pump pressure is increased to more than a load pressure of the boom cylinder by throttling a flow rate for supply to the bucket cylinder on composite operations including the above three operations. - In this case, on a condition of a full stroke of control valve for bucket, its inlet flow rate is throttled but a returning flow rate to a tank is not throttled. This causes problems that, especially, rotation speed of an engine as pump driving source is lowered due to a work load, a pump flow rate decreases and shortage of an inlet flow rate leads to cavitation.
- Since a main flow rate is throttled, a later installation of the flow rate control valve to the existing machine is difficult to handle and the installation like this is costly. Furthermore, it is difficult to deal with an adjustment with regard to an increase and decrease of a bucket weight (a load of the bucket cylinder).
- It is an object of the present invention to provide a hydraulic circuit in a hydraulic excavator capable of ensuring a boom raising operation at the time of simultaneous operation of working attachments, including a boom, with no fear of occurrence of cavitation, easy to be installed later, and easy to adjust against an increase or decrease of the bucket weight.
- A hydraulic excavator of the present invention comprises a boom, an arm, a bucket and a hydraulic circuit. The hydraulic circuit comprises a boom cylinder for actuating the boom of a hydraulic excavator; an arm cylinder for actuating the arm of the excavator, a bucket cylinder for actuating the bucket of the excavator, a first hydraulic pump, and a second hydraulic pump, and is constructed such that pressure oil provided from the first hydraulic pump is fed in parallel to both boom cylinder and bucket cylinder through a boom control valve and a bucket control valve, while pressure oil provided from the second hydraulic pump is fed in parallel to both boom cylinder and arm cylinder through a boom control valve for confluence and a control valve for the arm, wherein each of the control valves is a hydraulic pilot switching valve adapted to operate in accordance with the amount of operation of an operating means, the hydraulic circuit further comprising a pilot pressure control means which, in accordance with the amount of an arm pulling operation and that of a boom raising operation, reduces a pilot pressure fed to a bucket digging-side pilot port of the bucket control valve when boom raising, arm pulling, and bucket digging operations are performed substantially simultaneously. The pilot pressure control means is constructed such that the pilot pressure fed to the bucket digging side pilot port of the bucket control valve is reduced by a throttle means.
- According to the present invention constructed as above, when two operations of both boom raising operation and bucket digging operation or three operations of these two operations plus an arm pulling operation are performed at a time, the pilot pressure fed to the bucket control valve is reduced to diminish the stroke of the same valve, whereby a throttling effect of the control valve itself is exerted to increase the pump pressure and there is ensured a boom raising operation.
- That is, the boom raising operation is ensured not by throttling an inlet-side passage (main passage) in the bucket control valve, but by reducing the pilot pressure fed to the same valve. Therefore, even if the pump flow rate decreases due to a decrease of engine speed, there is no fear of occurrence of cavitation because the tank flow rate is also throttled at the same time.
- Besides, since the pilot pressure for the bucket control valve is reduced, the construction of the hydraulic circuit is simpler and the cost thereof is lower than in the technique wherein the main flow rate is throttled, and a later installation of the hydraulic circuit becomes easier.
- Preferably, the pilot pressure control means is constructed such that a tank line communicating with a tank is connected a bucket digging-side pilot line, and a bucket digging-side switching valve whose degree of opening changes in accordance with a boom raising pilot pressure, as well as a first throttle means, are provided in the tank line, further, a second throttle means is provided in the pilot line upstream of the tank line.
- Preferably, a boom raising switching valve whose degree of opening changes in accordance with an arm pulling pilot pressure is connected to a boom raising pilot line, and a boom raising pilot pressure as an output of the boom raising switching valve is fed to a pilot port of the bucket digging-side switching valve.
- As the first and second throttle means there may be used variable throttle means whose degree of opening can be adjusted.
- The pilot pressure control means may comprise an electromagnetic proportional pressure reducing valve disposed in the bucket digging-side pilot line of the bucket control valve, an arm pulling detector means for detecting the amount of the arm pulling operation, a boom raising detector means for detecting the amount of the boom raising operation, and a controller which issues to the electromagnetic proportional pressure reducing valve a command of a secondary pressure proportional to the amount of the arm pulling operation and that of the boom raising operation detected by both detector means.
- Further, the pilot pressure control means may comprise a boom raising pressure detector means for detecting a boom raising-side pressure of the boom cylinder and a pump pressure detector means for detecting an operating pressure of the first hydraulic pump, wherein the command of the secondary pressure to the electromagnetic proportional pressure reducing valve may be issued on condition that the operating pressure of the first hydraulic pump is higher than the boom raising-side pressure.
- In this case, since there is performed feedback of the pump pressure, there is no fear of the bucket digging operation speed decreasing to a greater extent than necessary with consequent impairment of operability.
- In the above construction provided with the throttle means, since pressure is reduced by the throttle means, there can be attained a simpler construction, a lower cost of parts, and a still easier later installation of the hydraulic circuit.
- It also becomes easy to increase or decrease the weight of the bucket and adjust the degree of pressure reduction according to an operator' s taste in operation characteristics. This adjustment is further facilitated by the construction which uses a variable throttle means.
- On the other hand, in the construction using a pressure reducing valve adapted to operate in accordance with a command provided from the controller, the selection and change of a characteristic with respect to each of boom raising, bucket digging, and arm pulling operations can be done more easily by adjustment using the controller.
-
-
Fig. 1 is a view of a hydraulic circuit according to a first embodiment of the present invention; -
Fig. 2 is a view of a hydraulic circuit according to a second embodiment of the present invention; -
Fig. 3 is a view of a hydraulic circuit according to a third embodiment of the present invention; -
Fig.4 is an explanatory flow chart of an operation of the third embodiment; -
Fig. 5 is a view of a hydraulic circuit according to a fourth embodiment of the present invention; and -
Fig. 6 is an explanatory flow chart of an operation of the fourth embodiment. - Working attachments in a hydraulic excavator are composed of a boom, an arm, a bucket, and hydraulic cylinders (boom cylinder, arm cylinder, bucket cylinder) for actuating those components. Various works, including excavating and loading works, are carried out by various operations, including boom raising/boom lowering, arm pushing/arm pulling, and bucket digging or bucket-in/bucket dump or bucket-out operations.
- In this case, as to a hydraulic pump - cylinder combination, both a boom cylinder which requires a large flow rate and a bucket cylinder for which a small flow rate will do, are actuated usually by a common hydraulic pump.
- In each of the following embodiments, reference will be made to a two-pump type hydraulic circuit as an example. According to this construction, a boom cylinder and a bucket cylinder are actuated by a first hydraulic pump, while an arm cylinder is actuated by a second hydraulic pump, and in this state a portion of pressure oil fed from the second hydraulic pump is allowed to join the pressure oil in the boom cylinder to ensure a required boom operation speed.
- The
numeral 1 denotes a first hydraulic pump. Abucket cylinder 2 and aboom cylinder 3 are connected to the firsthydraulic pump 1 in parallel through a bucket control valve 4 and aboom control valve 5, respectively. - Numeral 6 denotes a second hydraulic pump. The
boom cylinder 3 and anarm cylinder 7 are connected to the secondhydraulic pump 6 in parallel through aboom control valve 8 for confluence and anarm control valve 9, respectively. The mark T denotes a tank. - The
control valves remote control valves boom control valve 5 are set to respective left-hand positions (bucket digging position and boom raising position) in the figure, while theboom control valve 8 for confluence and thearm control valve 9 are set to respective righthand positions (confluent position, arm pulling position) in the figure. - According to this construction, pressure oil is fed from the first
hydraulic pump 1 to both bucket andboom cylinders hydraulic pump 6 to both boom andarm cylinders cylinders - In
Fig. 1 , as pilot lines for the supply of a pilot pressure to each of thecontrol valves side pilot line 13, a boom raising-side pilot line 14, aconfluent pilot line 15 connected in parallel with thepilot line 14, and an arm pulling-side pilot line 16. On the other hand, bucket dump-side, boom lowering-side, confluence stop-side, and arm pushing-side pilot lines are not shown. - In this hydraulic circuit, a
tank line 17 is connected to the pilot digging-side pilot line 13. A bucket digging-side switching valve 18 as a hydraulic pilot valve whose degree of opening changes in accordance with a pilot pressure, and a first throttle 19 (throttle valve), are provided in thetank line 17. Further, a second throttle 20 (throttle valve) is provided in thepilot line 13 upstream (on the hydraulic pump side) of thetank line 17. A pilot pressure control means is constituted by these components. - A pilot port of the bucket digging-
side switching valve 18 is connected to the boom raising-side pilot line 14 through acontrol line 21. In thecontrol line 21 is provided a boom raising-side switching valve 22 as a hydraulic pilot valve whose degree of opening changes in accordance with an arm pulling pilot pressure. - In this construction, when there is performed a composite operation of bucket digging, boom raising, and arm pulling, pilot pressures P1, P2, and P3 proportional to operation quantities are exerted on
pilot lines - In this case, when the arm pulling pilot pressure P3 is fed to a pilot port of the boom raising-
side switching valve 22, theswitching valve 22 opens at a degree of opening proportional to the pilot pressure P3. Further, a pilot pressure P2a proportional to the degree of opening of theswitching valve 22 is fed to the pilot port of the bucket digging-side switching valve 18, whereby theswitching valve 18 opens at a degree of opening proportional to the pilot pressure P2a. - On the other hand, the bucket digging-side pilot pressure P1 is reduced to an intermediate pressure (e.g., one half or so) by the
second throttle 20. As a result, by the action of thefirst throttle 19 upon opening of the bucket digging-side switching valve 18, a further reduced pilot pressure is fed to a bucket digging-side pilot port of the bucket control valve 4. - With this action, the stroke of the bucket control valve 4 is diminished and the pump pressure of the first
hydraulic pump 1 increases by a throttling action of the valve 4. Consequently, pressure oil is fed also to theboom cylinder 3 whose load pressure is high, whereby a boom raising operation is ensured. That is, a composite operation of bucket digging, boom raising, and arm pulling, can be done at an operator' s will. - Besides, the valve stroke is diminished not by throttling an inlet-side passage of the bucket control valve 4 but by reducing the pilot pressure fed to the valve 4, to ensure a boom raising operation. Consequently, even in the event of decrease of the pump flow rate due to a lowering of the engine speed which is a pump drive source, the tank flow rate is also throttled at the same time by the valve 4. As a result, there no longer is any fear of occurrence of cavitation.
- Moreover, because of the construction wherein the pilot digging-side pilot pressure is reduced, the construction can be made simpler than in case of providing a throttle means in the main passage. Accordingly, the cost of parts and that of assembly can be reduced and it becomes easy to later install the hydraulic circuit to an existing machine.
- When both boom raising and arm pulling operations are not performed substantially simultaneously, the bucket digging-
side switching valve 18 does not operate, so that there is no throttling action for the bucket digging-side pilot pressure and a bucket digging operation is performed at a normal speed. - In the following embodiments, reference will be made to only different points from the first embodiment.
- It is preferable that the degree of reduction in the bucket digging-side pilot pressure be adjustable in accordance with the weight of the bucket and the operator' s taste in operation characteristic. In the previous first embodiment, adjustment of the degree of pressure reduction can be made by the selection and replacement of both
throttles - In this second embodiment, variable throttles are used as both first and second throttles 19' and 20'.
- With the variable throttles, when the bucket is replaced or the operator is changed in a single machine, the degree of pressure reduction can be adjusted freely by adjusting the degree of opening of both throttles 19' and 20'.
- In this third embodiment, as a pilot pressure control means, an electromagnetic proportional pressure reducing valve (hereinafter referred to simply as "pressure reducing valve") 23 is disposed in the bucket digging-
side line 13, as shown inFig. 3 . There also are providedpressure sensors controller 24. Secondary pressure command signals proportional to both pilot pressures P2 and P3 are sent to thepressure reducing valve 23 from thecontroller 24 to reduce the bucket digging-side pilot pressure. - The operation on this regard will now be described with reference to
Fig. 4 . In steps S1 and S2, the boom raising pilot pressure P2 and the arm pulling pilot pressure P3 are read. Next, in steps S3 and S4, it is respectively determined whether a boom raising operation and an arm pulling operation are being performed. - If both answers are affirmative, then in steps S5 and S6, the sum of both pilot pressures P2 and P3 is plotted along the axis of abscissa and a secondary pressure (pressure after reduction) of the
pressure reducing valve 23 is plotted along the axis of ordinate, then on the basis of a preset throttle characteristic a secondary pressure command signal is outputted to thepressure reducing valve 23 as a proportional valve. - By so doing, as in the first embodiment, it is possible to diminish the stroke of the bucket digging-side control valve in the composite three-operation mode and thereby increase the pump pressure. As a result, it is possible to ensure a boom raising operation.
- Further, the selection and change of a characteristic with respect to each of boom raising, bucket digging, and arm pulling operations, can be done more easily by adjustment (e.g., using a trimmer) through the
controller 24. - In the fourth embodiment, in addition to the construction of the third embodiment, there are provided
pressure sensors boom cylinder 3 and an operating pressure (pump pressure) of the firsthydraulic pump 1, as shown inFig. 5 . According to the construction of this fourth embodiment, pump pressures detected by thepressure sensors controller 24 and a bucket digging-side pilot pressure reducing action is exerted on the premise that the pump pressure is higher than the boom raising-side pressure. - As shown in
Fig. 6 , the boom raising pilot pressure P2, arm pulling pilot pressure P3, boom cylinder pressure, and the pressure of the firsthydraulic pump 1 are read in steps S1 to S4. In steps S5 and S6, it is determined whether a boom raising operation and an arm pulling operation are being performed or not. Thereafter, in step S7, a comparison is made between pump pressure and cylinder pressure. Only when the pump pressure is higher than the cylinder pressure, a secondary pressure of the pressure reducing valve as a proportional valve is calculated and outputted in steps S8 and S9. - By so doing, since there is performed feedback of the pump pressure, there is no fear of the pump pressure becoming lower than necessary and hence there is no fear of drop in speed of the bucket digging operation and impairment of operability.
- As another embodiment, a hydraulic pilot type pressure reducing valve as a pilot control means may be provided in the bucket digging-
side pilot line 13. - Further, as a modification of the first embodiment, there may be adopted a construction wherein electromagnetic switching valves are used as both bucket digging-side and boom raising-
side switching valves valves - According to the constructions of the above embodiments, the pressure oil provided from the first
hydraulic pump 1 is used for both bucket cylinder and boom cylinder, while the pressure oil from the secondhydraulic pump 6 is used for boom cylinder confluence and for the arm cylinder. However, the present invention is also applicable to the case where the pressure oil from the secondhydraulic pump 6 is not used for boom cylinder confluence. - In this case, in the composite bucket digging and boom raising operation mode, the bucket digging-side pilot pressure may be reduced in accordance with the boom raising-side pilot pressure (a pressure raising operation quantity).
- Although embodiments of the present invention have been described above, the scope of protection of the present invention is not limited to the above embodiments.
- Although the invention has been described with reference to the preferred embodiments in the attached figures, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims.
Claims (6)
- A hydraulic excavator, comprising:a boom, an arm, a bucket and a hydraulic circuit wherein the hydraulic circuit comprises, a boom cylinder (3) for actuating said boom, an arm cylinder (7) for actuating said arm, a bucket cylinder (2) for actuating said bucket, a first hydraulic pump (1), and a second hydraulic pump (6), wherein pressure oil provided from said first hydraulic pump (1) is fed in parallel to said boom cylinder and said bucket cylinder (2) through a boom control valve (5) and a bucket control valve (4), while pressure oil from said second hydraulic pump is fed in parallel to said boom cylinder (3) and said arm cylinder (7) through a boom control valve (8) for confluence and an arm control valve (9), and each of said control valves (4, 5, 8,9) is a hydraulic pilot switching valve adapted to operate by a pilot pressure proportional to the amount of operation of an operating means, characterized in that said hydraulic circuit further comprises:a pilot pressure control means for, in accordance with the amount of an arm pulling operation and a boom raising operation, reducing a pilot pressure fed to a bucket digging-side pilot port of said bucket control valve (4) when boom raising, arm pulling, and bucket digging operations are performed substantially simultaneously, wherein said pilot pressure control means is constructed such that the pilot pressure fed to the bucket digging-side pilot port of said bucket control valve is reduced by a throttle means.
- The hydraulic excavator according to claim 1, wherein said pilot pressure control means is constructed such that a tank line (17) communicating with a tank is connected to a bucket digging-side pilot line (13) and a bucket digging-side switching valve (18) of which degree of opening changes in accordance with a boom raising pilot pressure, as well as a first throttle means (19), are provided in said tank line, and a second throttle means (20) is provided in said pilot line upstream of said tank line (17).
- The hydraulic excavator according to claim 2, wherein a boom raising switching valve (22) of which degree of opening changes in accordance with an arm pulling pilot pressure is connected to a boom raising pilot line (14), and a boom raising pilot pressure as an output of said boom raising switching valve (22) is fed to a pilot port of said bucket digging-side switching valve (18).
- The hydraulic excavator according to claim 2 or 3, wherein said first and second throttle means (19, 20) are variable throttle means for being adjusted in the degree of opening.
- The hydraulic excavator according to claim 1, wherein said pilot pressure control means comprising:an electromagnetic proportional pressure reducing valve disposed in the bucket digging-side pilot line of the bucket control valve;an arm pulling detector means for detecting the amount of the arm pulling operation;a boom raising detector means for detecting the amount of the boom raising operation; anda controller adapted to give to said electromagnetic proportional pressure reducing valve a command of a secondary pressure proportional to the amount of the arm pulling operation and the boom raising operation detected by both said detector means.
- The hydraulic excavator according to claim 5, wherein said pilot pressure control means comprising:a boom raising pressure detector means for detecting a boom raising-side pressure of said boom cylinder; anda pump pressure detector means for detecting an operating pressure of said first hydraulic pump, and whereinthe command of the secondary pressure to said electromagnetic proportional pressure reducing valve is issued on condition that the operating pressure of said first hydraulic pump is higher than the boom raising-side pressure.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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JP2002318556 | 2002-10-31 | ||
JP2002318556A JP3818252B2 (en) | 2002-10-31 | 2002-10-31 | Hydraulic circuit of excavator |
Publications (2)
Publication Number | Publication Date |
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EP1416096A1 EP1416096A1 (en) | 2004-05-06 |
EP1416096B1 true EP1416096B1 (en) | 2010-10-06 |
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ID=32089592
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP03256761A Expired - Lifetime EP1416096B1 (en) | 2002-10-31 | 2003-10-27 | Hydraulic excavator with a hydraulic circuit |
Country Status (4)
Country | Link |
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EP (1) | EP1416096B1 (en) |
JP (1) | JP3818252B2 (en) |
AT (1) | ATE483861T1 (en) |
DE (1) | DE60334430D1 (en) |
Families Citing this family (14)
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JP4655795B2 (en) | 2005-07-15 | 2011-03-23 | コベルコ建機株式会社 | Hydraulic control device of excavator |
DE602007000412D1 (en) | 2006-03-07 | 2009-02-12 | Mazda Motor | Rear part of a motor vehicle with side airbag device |
JP4931048B2 (en) * | 2006-07-31 | 2012-05-16 | キャタピラー エス エー アール エル | Control device for work machine |
JP5342293B2 (en) * | 2009-03-26 | 2013-11-13 | 住友建機株式会社 | Hydraulic circuit for construction machinery |
JP5272211B2 (en) * | 2009-07-07 | 2013-08-28 | 住友建機株式会社 | Hydraulic circuit for construction machinery |
JP5079827B2 (en) | 2010-02-10 | 2012-11-21 | 日立建機株式会社 | Hydraulic drive device for hydraulic excavator |
JP5475507B2 (en) * | 2010-02-28 | 2014-04-16 | 住友建機株式会社 | Hydraulic control device of excavator |
JP5406087B2 (en) * | 2010-03-18 | 2014-02-05 | ヤンマー株式会社 | Hydraulic circuit of work vehicle |
CA2891709C (en) * | 2012-11-23 | 2017-10-24 | Volvo Construction Equipment Ab | Apparatus and method for controlling preferential function of a construction machine |
US9890801B2 (en) | 2013-03-22 | 2018-02-13 | Hitachi Construction Machinery Tierra Co., Ltd. | Hydraulic drive system for construction machine |
US9394929B2 (en) | 2013-08-01 | 2016-07-19 | Caterpillar Inc. | Reducing dig force in hydraulic implements |
JP6220228B2 (en) * | 2013-10-31 | 2017-10-25 | 川崎重工業株式会社 | Hydraulic drive system for construction machinery |
JP6196567B2 (en) * | 2014-03-06 | 2017-09-13 | 川崎重工業株式会社 | Hydraulic drive system for construction machinery |
JP7207060B2 (en) * | 2019-03-22 | 2023-01-18 | コベルコ建機株式会社 | Working machine hydraulic drive |
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US172650A (en) * | 1876-01-25 | Improvement in hydraulic elevators | ||
JP2607258B2 (en) * | 1988-03-30 | 1997-05-07 | 日立建機株式会社 | Hydraulic control circuit of work machine |
JP2892939B2 (en) * | 1994-06-28 | 1999-05-17 | 日立建機株式会社 | Hydraulic circuit equipment of hydraulic excavator |
JP3612256B2 (en) * | 1999-12-22 | 2005-01-19 | 新キャタピラー三菱株式会社 | Hydraulic circuit of work machine |
DE10047175A1 (en) * | 2000-09-22 | 2002-04-11 | Mannesmann Rexroth Ag | Method and control arrangement for controlling hydraulic consumers |
JP3901470B2 (en) * | 2001-05-15 | 2007-04-04 | 新キャタピラー三菱株式会社 | Fluid pressure circuit control system |
JP2003232303A (en) * | 2002-02-12 | 2003-08-22 | Shin Caterpillar Mitsubishi Ltd | Fluid pressure circuit |
-
2002
- 2002-10-31 JP JP2002318556A patent/JP3818252B2/en not_active Expired - Fee Related
-
2003
- 2003-10-27 EP EP03256761A patent/EP1416096B1/en not_active Expired - Lifetime
- 2003-10-27 AT AT03256761T patent/ATE483861T1/en not_active IP Right Cessation
- 2003-10-27 DE DE60334430T patent/DE60334430D1/en not_active Expired - Lifetime
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DE60334430D1 (en) | 2010-11-18 |
ATE483861T1 (en) | 2010-10-15 |
EP1416096A1 (en) | 2004-05-06 |
JP2004150198A (en) | 2004-05-27 |
JP3818252B2 (en) | 2006-09-06 |
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