WO1998046888A1 - Dispositif d'alimentation en huile sous pression - Google Patents

Dispositif d'alimentation en huile sous pression Download PDF

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Publication number
WO1998046888A1
WO1998046888A1 PCT/JP1998/001662 JP9801662W WO9846888A1 WO 1998046888 A1 WO1998046888 A1 WO 1998046888A1 JP 9801662 W JP9801662 W JP 9801662W WO 9846888 A1 WO9846888 A1 WO 9846888A1
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
valve
throttle
hydraulic pilot
pilot valve
Prior art date
Application number
PCT/JP1998/001662
Other languages
English (en)
Japanese (ja)
Inventor
Nobumi Yoshida
Yousuke Oda
Naoki Ishizaki
Kenji Morino
Mutsumi Ono
Takashi Hori
Original Assignee
Komatsu Ltd.
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Komatsu Ltd. filed Critical Komatsu Ltd.
Publication of WO1998046888A1 publication Critical patent/WO1998046888A1/fr

Links

Classifications

    • 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
    • E02F9/2004—Control mechanisms, e.g. control levers
    • 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
    • E02F9/2217—Hydraulic or pneumatic drives with energy recovery arrangements, e.g. using accumulators, flywheels
    • 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
    • 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
    • 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
    • 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
    • F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • 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
    • 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
    • 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
    • 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

  • the present invention relates to a hydraulic oil supply device that supplies hydraulic oil discharged from a hydraulic pump to a plurality of actuators, such as a boom cylinder that swings a boom of a hydraulic shovel up and down and an arm cylinder that swings an arm up and down.
  • the hydraulic oil is supplied to the boom cylinder by the boom operation valve and the oil is supplied by the arm operation valve.
  • One that supplies pressurized oil to a cylinder is known.
  • the ground is excavated on a flat surface by swinging the boom upward, swinging the arm downward, and moving the bucket blade attached to the tip of the arm along the ground.
  • clearance work may be performed.
  • the boom operation valve is set to the extension position to supply pressure oil to the extension chamber of the boom cylinder
  • the arm operation valve is set to the extension position to supply pressure oil to the extension chamber of the arm cylinder.
  • the weight of the boom (including the weight of the arm and the bucket) is applied to the extension chamber, and a holding pressure is generated.
  • the boom cylinder does not extend unless the holding pressure is exceeded.
  • the arm cylinder is extended by the arm's own weight (actually, the weight of the bucket and the weight of the bucket cylinder), so the boom operation valve and the arm operation When the valves are simultaneously switched, the arm swings down before the boom swings up.
  • a boom operation valve 3 and an arm operation valve 4 are provided in the discharge path 2 of the hydraulic pump 1.
  • the first output circuit 6 and the second output circuit 7 of the boom hydraulic pilot valve 5 are connected to the first pressure receiving section 8 and the second pressure receiving section 9 of the boom operation valve 3.
  • the boom hydraulic pilot valve 5 By operating the boom hydraulic pilot valve 5, the discharge pressure oil of the pilot hydraulic pump 10 is supplied to the first pressure receiving section 8 or the second pressure receiving section 9 as pilot pressure oil, and the boom operation valve 3 is operated. From the neutral position A to the extended position B or the contracted position C.
  • the first output circuit 14 and the second output circuit 15 of the arm hydraulic pilot valve 13 are connected to the first pressure receiving section 16 and the second pressure receiving section 17 of the arm operation valve 4.
  • the hydraulic pilot valve 13 for the arm By operating the hydraulic pilot valve 13 for the arm, the discharge pressure oil of the hydraulic pump 10 for the pilot is supplied to the first pressure receiving section 16 or the second pressure receiving section 17 as pilot pressure oil, and the arm is operated. Move control valve 4 from neutral position A to extended position B or contracted position C.
  • the arm cylinder 18 extends or contracts, and the arm 19 swings downward or upward.
  • the first output circuit 14 of the arm hydraulic pilot valve 13 is provided with a switching valve 20 that can be switched between a communication position D and a throttle communication position E.
  • the switching valve 20 is in the communication position D at the spring 21 and the pressure receiving section 22
  • the throttle communication position E is reached with the pressure oil acting on the throttle.
  • the pressure receiving part 22 is connected to the first output circuit 6 of the hydraulic pilot valve 5 for boom in a circuit 23 and is laid.
  • the boom operation valve 3 In the pressure oil supply device, the boom operation valve 3 is in the extended position B, and the switching valve 20 is in the throttle communication position E with the pressure oil, so that the first output circuit 14 of the arm hydraulic pilot valve 13 is connected to the first output circuit 14.
  • the output pressure oil is supplied to the first pressure receiving portion 16 of the arm operation valve 4 through the throttle 24 of the switching valve 20.
  • the pressure rise in the first pressure receiving portion 16 of the arm operation valve 4 is slowed down by the throttle 24, so that the boom operation valve 3 and the arm operation valve 4 are in the extended positions B, B and the boom
  • boom operation valve 3 When swinging 1 2 upward and swinging arm 19 downward, boom operation valve 3 extends first to reach position B, and boom 12 and arm 19 swing almost simultaneously upward and downward. .
  • the pressure rise time of the first pressure receiving portion 16 of the arm operation valve 4 is delayed only by the flow resistance due to the throttle 24, so that the pressure rise time of the first pressure receiving portion 16 is reduced.
  • an object of the present invention is to provide a pressure oil supply device capable of solving the problem that the arm swings downward first when the arm weight is large and then the boom swings upward.
  • the discharge pressure oil of the hydraulic pump 1 is supplied to the first actuator.
  • a first actuator that operates the first actuator in a direction against external force by supplying the first actuator, a first hydraulic pilot valve that outputs pressure oil for switching the first operation valve, and a hydraulic pressure.
  • a second operation valve that operates in a direction in which the second actuator is operated by an external force, and pressure oil that switches the second operation valve is output.
  • a control unit for setting the pressure reducing unit to a reduced pressure state for a predetermined time.
  • the pressure reducing means is maintained in the reduced pressure state for the predetermined time by utilizing the fact that the output pressure of the first hydraulic pilot valve rises to the predetermined pressure. It switches after operation valve 1 switches. As a result, the pressure oil is supplied to the first actuator and then the supply of the pressure oil to the second actuator starts. The first actuator operates first, and then the second actuator operates.
  • the packet does not bite into the ground, and the ground can be excavated on a flat surface.
  • a throttle 40 and an accumulator 41 are provided in a circuit 23 connected to the output circuit of the first hydraulic pilot valve in the first aspect of the invention as a control means, and a pressure difference between the upstream and downstream of the throttle 40 is provided.
  • This is a pressure oil supply device in which the pressure reducing means is in a reduced pressure state.
  • the output pressure oil of the first hydraulic pilot valve is stored in the accumulator 41 via the throttle 40, so that a differential pressure is generated around the throttle 40. This pressure difference causes the pressure reducing means to be in a reduced pressure state.
  • the pressure reducing means is reduced in pressure until the output pressure oil of the first hydraulic pilot valve is accumulated in the accumulator 41, and the output pressure oil of the second hydraulic pilot valve is reduced. As the pressure is reduced, the second control valve does not switch.
  • the first operating valve is switched to start supplying hydraulic oil to the first actuator, and then the second operating valve is switched.
  • pressurized oil is supplied to the second actuator.
  • the time during which the output pressure of the pressure reducing means rises to the predetermined pressure can be changed.
  • the third invention is the same as the first invention, except that the second hydraulic pilot valve This is a pressure oil supply device in which a pressure reducing valve 30 is provided in a circuit connecting the pressure receiving portion of the second operation valve to serve as a pressure reducing means.
  • the conventional device can be easily improved.
  • the pressure reducing valve 30 of the third aspect is pushed toward the communication position by the pressure supplied to one of the pressure receiving chambers, and is directed to the drain position by the pressure supplied to the other pressure receiving portion.
  • a throttle 40 and an accumulator 41 are provided in the circuit 23 connected to the output circuit of the first hydraulic pilot valve as control means, and the wake of this throttle 40 is assumed.
  • the pressure oil supply device is connected to the one pressure receiving chamber, and the upstream side of the throttle 40 is connected to the other pressure receiving chamber.
  • the first pressure receiving portion 51 and the pressure reducing valve portion 5 which push the pressure reducing valve portion 50 toward the communicating position are provided to the pressure reducing valve portion 50 of the second hydraulic pilot valve in the first invention.
  • This is a pressurized oil supply device provided with a second pressure receiving portion 52 for pressing 0 toward the drain position and serving as pressure reducing means.
  • the second hydraulic pilot valve may be improved, and the second hydraulic pilot valve and the pressure receiving portion of the second operation valve may be connected by a circuit, so that the structure is simplified.
  • a sixth aspect of the present invention which facilitates piping and the like, is the first pressure-receiving valve that pushes the pressure reducing valve part 50 toward the communication position with the pressure reducing valve part 50 of the second hydraulic pilot valve in the fifth invention.
  • a second pressure receiving section 52 that pushes the section 51 and the pressure reducing valve section 50 toward the drain position is provided as pressure reducing means, and the pressure is reduced to the circuit 23 connected to the output circuit of the first hydraulic pilot valve.
  • an accumulator 41 are provided as control means, the downstream side of the throttle 40 is connected to the first pressure receiving section 51, and the upstream side of the throttle 40 is connected to the second pressure receiving section 52. Connect to Pressure oil supply device.
  • FIG. 1 is a hydraulic circuit diagram showing a conventional example.
  • FIG. 3B is a chart showing the relationship between the output pressures of the arm hydraulic pilot valve.
  • FIG. 3C is a chart showing the relationship between the output pressures of the pressure reducing valves.
  • FIG. 4 is a hydraulic circuit diagram showing a second embodiment of the present invention.
  • FIG. 5 is a hydraulic circuit diagram showing a third embodiment of the present invention.
  • FIG. 6 is a diagram showing a hydraulic pilot valve for an arm.
  • FIG. 3 is a cross-sectional view showing a specific structure. BEST MODE FOR CARRYING OUT THE INVENTION
  • a pressure reducing valve 30 is provided in the first output circuit 14 of the arm hydraulic pilot valve 13.
  • the pressure reducing valve 30 is pushed toward the communication position F by the pressure acting on the first and second pressure receiving chambers 31 and 32, and is pressed by the pressure acting on the third and fourth pressure receiving chambers 33 and 34. Pushed to drain position G.
  • the output pressure of the pressure reducing valve 30 is determined by the differential pressure between the pressures of the first and second pressure receiving chambers 31 and 32 and the pressures of the third and fourth pressure receiving chambers 33 and 34. It is determined.
  • Output pressure is supplied to the first pressure receiving chamber 31, and input pressure, that is, output pressure of the arm hydraulic pilot valve 13 is supplied to the third pressure receiving chamber 33. Is done.
  • the circuit 23 connected to the first output circuit 6 of the boom hydraulic high-lot valve 5 is provided with a throttle 40 and an accumulator 41.
  • the downstream side of the throttle 40 is connected to the second pressure receiving chamber 32, and the upstream side of the throttle 40 is connected to the fourth pressure receiving chamber 34.
  • the pressures in the third pressure receiving chamber 32 and the fourth pressure receiving chamber 34 of the pressure reducing valve 30 are equal.
  • the pressure in the first pressure receiving portion 16 of the arm operation valve 4 increases at a speed commensurate with the pressure increase speed of the first output circuit 14 (the operation speed of the arm hydraulic pilot valve 13).
  • the boom hydraulic pilot valve 5 is quickly operated to increase the output pressure P1 to a predetermined pressure in a short time, and the output pressure P of the arm hydraulic pilot 13 is increased.
  • the differential pressure across the throttle 40 becomes large and the output pressure P 3 of the pressure reducing valve 30 (that is, the arm operating valve 4
  • the pressure of the first pressure receiving portion 16 gradually rises until the accumulation time of the accumulator 41 elapses, as indicated by the solid line in FIG. 3C, and then reaches a predetermined output pressure.
  • the opening area of the throttle 40 that is, the size of the throttle 40, the pressure storage capacity of the accumulator 41, and the force of the spring 42, the output pressure of the pressure reducing valve 30 increases to a predetermined pressure.
  • the time can be changed.
  • the pressure reducing valve 30 may be switched between the communication position F and the drain position G by a differential pressure across the throttle 40.
  • FIG. 5 shows a third embodiment in which the output pressure of the arm hydraulic pilot valve 13 is reduced.
  • a first pressure receiving section 51 and a second pressure receiving section 52 are provided in a pressure reducing valve section 50 that outputs pressure oil to a first output circuit 14 of an arm hydraulic pilot valve 13,
  • the downstream side of the throttle 40 is connected to the first pressure receiving section 51, and the upstream side of the throttle 40 is connected to the second pressure receiving section 52.
  • the hydraulic pilot valve 13 for the arm pushes the pressure reducing valve section 50 toward the communication position F via the spring 54 by operating the lever 53, and outputs the output pressure to the pressure receiving section 55.
  • the pressure reducing valve section 50 is provided with a first pressure receiving section 51 and a second pressure receiving section 52 to apply a differential pressure before and after the throttle 40.
  • the output pressure can be controlled as in the case of the pressure reducing valve 30.
  • a pump boat 61 and a tank port 62 are formed in the valve body 60, and the pump port 61, the tank boat 62, and the output port 63 are connected and shut off.
  • a spool 64 is provided, the depressurizing spool 64 is biased to the drain position by a spring 65, and the depressurizing spool is pushed by a piston 68 with a plate 67 swinged by a lever 66.
  • the above-described configuration is conventionally known.
  • the first piston chamber 70 (the first pressure receiving section 51) for pushing the spool 64 to the communicating position and the second piston chamber 71 (the second piston chamber) for pushing the depressurizing spool 64 to the drain position.
  • the pressure receiving section 52 2) is formed.
  • auxiliary valve element 72 Attachs the auxiliary valve element 72 to the valve body 60.
  • a throttle 73 and a piston 74 are provided in the auxiliary valve body 72, and the piston 74 is urged by a spring 75 so that an accumulator 76 (accumulator 41) is provided.
  • the upstream side of the throttle 73 is communicated with the second piston chamber 71, and the downstream side of the throttle 73 is communicated with the first piston chamber 70.
  • the present invention is not limited thereto, and the first actuator (in which the holding pressure is applied by an external force) is used. This is applicable when the boom cylinder 11) is operated in a direction against external force and the second actuator (arm cylinder 18) is operated in a direction operated by external force.
  • the boom cylinder 11 becomes the first actuator
  • the boom operation valve 3 becomes the first operation valve that operates the first actuator in the direction against the external force
  • the boom hydraulic pilot valve 5 becomes the first actuator.
  • the arm cylinder 18 serves as a second actuator
  • the arm operation valve 4 serves as a second operation valve that operates the second actuator in a direction to be operated by an external force
  • an arm hydraulic pilot Valve 13 is the second hydraulic pilot valve.
  • the pressure reducing valve 30 and the pressure reducing valve section 50 serve as pressure reducing means.
  • the diaphragm 40 and the accumulator 41 serve as control means for reducing the pressure in the pressure reducing means

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Operation Control Of Excavators (AREA)
  • Fluid-Pressure Circuits (AREA)

Abstract

Quand on doit mettre en service simultanément un vérin de flèche (11) et un vérin de bras (18), on actionne ce dernier (18) après le premier (11). Une soupape (30) de limitation de pression est située sur un circuit reliant une soupape pilote (13) hydraulique correspondant au bras et une première partie (16) de réception de pression d'une soupape (4) d'actionnement du bras. Une soupape d'étranglement (40) et un accumulateur (41) sont situés sur un circuit (23) relié à un circuit de sortie d'une soupape pilote (5) hydraulique correspondant à la flèche. La soupape (30) de limitation de pression est limitée en pression sous l'effet d'une différence de pression à travers la soupape d'étranglement (40). De ce fait, l'huile sous pression s'écoule vers l'accumulateur (41), de manière à produire une différence de pression à travers la soupape d'étranglement (40), de sorte que la soupape (30) de limitation de pression est limitée en pression jusqu'à ce que l'huile sous pression remplisse totalement l'accumulateur (41) et la soupape (4) d'actionnement du bras est mise en service par commutation après la mise en service de la soupape (3) d'actionnement de la flèche.
PCT/JP1998/001662 1997-04-16 1998-04-10 Dispositif d'alimentation en huile sous pression WO1998046888A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP9868297A JPH10288205A (ja) 1997-04-16 1997-04-16 圧油供給装置
JP9/98682 1997-04-16

Publications (1)

Publication Number Publication Date
WO1998046888A1 true WO1998046888A1 (fr) 1998-10-22

Family

ID=14226287

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP1998/001662 WO1998046888A1 (fr) 1997-04-16 1998-04-10 Dispositif d'alimentation en huile sous pression

Country Status (2)

Country Link
JP (1) JPH10288205A (fr)
WO (1) WO1998046888A1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55178060U (fr) * 1979-06-07 1980-12-20
JPS6389735A (ja) * 1986-09-30 1988-04-20 Hitachi Constr Mach Co Ltd 油圧シヨベルの油圧回路
JPH08326708A (ja) * 1995-05-26 1996-12-10 Hitachi Constr Mach Co Ltd 減圧弁型パイロット弁
JPH093960A (ja) * 1995-06-21 1997-01-07 Sumitomo Constr Mach Co Ltd 油圧ショベルのロードセンシング油圧回路
JPH10114962A (ja) * 1996-10-14 1998-05-06 Sumitomo Constr Mach Co Ltd 油圧ショベル制御回路

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS55178060U (fr) * 1979-06-07 1980-12-20
JPS6389735A (ja) * 1986-09-30 1988-04-20 Hitachi Constr Mach Co Ltd 油圧シヨベルの油圧回路
JPH08326708A (ja) * 1995-05-26 1996-12-10 Hitachi Constr Mach Co Ltd 減圧弁型パイロット弁
JPH093960A (ja) * 1995-06-21 1997-01-07 Sumitomo Constr Mach Co Ltd 油圧ショベルのロードセンシング油圧回路
JPH10114962A (ja) * 1996-10-14 1998-05-06 Sumitomo Constr Mach Co Ltd 油圧ショベル制御回路

Also Published As

Publication number Publication date
JPH10288205A (ja) 1998-10-27

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