JP2014190433A - Working machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic shovel capable of restraining over-revolution of an engine.SOLUTION: The working machine comprises: an engine 7; a closed circuit 108 having a second hydraulic pump 10 in the engine 7, an arm cylinder 3 driven by working oil emitted from the second hydraulic pump 10, a proportional control valve 34 for generating load pressure to an emission side of the second hydraulic pump 10, an accumulator 36, and a flow passage switch part 109 for switching a flow passage of the working oil emitted from the second hydraulic pump 10 to any of the arm cylinder 3, the proportional control valve 34, and the accumulator 36; a closed circuit 107 having a first hydraulic pump 9 that is driven by the engine 7 and whose emission flow rate and emission direction can be controlled, and a boom cylinder 1 driven by the working oil emitted from the first hydraulic pump 9; and a power transmission device 8 for transmitting power of the first hydraulic pump 9 to the second hydraulic pump 10.

Description

  The present invention relates to a work machine such as a hydraulic excavator, and more particularly to a work machine having a fluid pressure actuator driven by a fluid discharged from a fluid pressure pump.

  In recent years, in a working machine such as a hydraulic excavator, hydraulic oil discharged from a pressure generation source such as a hydraulic pump is directly sent to a hydraulic actuator such as a hydraulic cylinder, and the hydraulic oil after driving the hydraulic actuator is supplied to the hydraulic actuator. There is known a hydraulic circuit called a closed circuit connected so as to return to the back.

  In the system using this closed circuit, the hydraulic oil discharged from the hydraulic pump is sent to the hydraulic actuator by adjusting the flow rate through the throttle, and the hydraulic oil after driving the hydraulic actuator is discharged to the tank. There is no hydraulic oil pressure loss due to throttling compared to a hydraulic circuit system called open circuit. Further, the method using the closed circuit tends to reduce the fuel consumption because the energy of the return hydraulic oil discharged from the hydraulic actuator can be regenerated by the hydraulic pump.

  Patent Document 1 discloses a conventional technique related to a work machine that performs a regenerative operation in a system using this type of closed circuit. In Patent Document 1, a plurality of closed circuits and open circuits are provided in the hydraulic circuit. Then, by providing a distribution circuit for supplying hydraulic oil supplied to the open circuit to the closed circuit, optimum power is supplied according to the load of the hydraulic actuator.

  A hydraulic pump is attached to each of the closed circuit and the open circuit, and each hydraulic pump is connected to one engine (drive source) via a power transmission device. When the motor / generator is connected to the power transmission device and the engine load is small, the motor / generator is driven by the power of the engine and the battery connected to the motor / generator is charged. When the engine load is large, the motor / generator is driven by the electric power stored in the battery, and the drive of the engine is assisted through the power transmission device.

Japanese Patent Laid-Open No. 2005-76781

  In the prior art disclosed in Patent Document 1 described above, when the charge amount of the battery is maximum (full charge), the regenerative energy of the closed-circuit hydraulic pump cannot be absorbed, and the regenerative energy that cannot be absorbed is given to the engine. The engine may overspeed, i.e. overrev. In addition, it is possible to assume a general closed circuit configuration that is not equipped with the motor / generator and battery in the prior art disclosed in Patent Document 1 described above, and that is not a so-called hybrid type. Since there is no means for absorbing the heat, that is, the motor / generator and the battery, the possibility of overrev becomes even higher than in the case of Patent Document 1.

  The present invention has been made from the actual situation in the above-described prior art, and an object thereof is to provide a work machine capable of suppressing the overrev of the drive source.

  In order to achieve this object, the present invention provides a work machine body, a drive source provided in the work machine body, a fluid pressure pump driven by the drive source, and a fluid discharged from the fluid pressure pump. A fluid pressure actuator driven by a fluid pressure, a load pressure generating section for generating a load pressure on the discharge side of the fluid pressure pump, and a fluid flow path for fluid discharged from the fluid pressure pump through the fluid pressure actuator and the load pressure generation A fluid pressure circuit having a flow path switching unit for switching to any one of the above, a closed circuit fluid pressure pump driven by the drive source and capable of controlling a discharge flow rate and a discharge direction, and the closed circuit fluid pressure pump. A closed circuit having a closed-circuit fluid pressure actuator driven by a discharged fluid, and a power transmission unit for transmitting the power of the closed-circuit fluid pressure pump to the fluid pressure pump. It is characterized in.

  In the present invention configured as described above, when the closed circuit fluid pressure pump is driven by the fluid discharged from the closed circuit fluid pressure actuator to generate regenerative power, the regenerative power is fluidized via the power transmission unit. The fluid pressure pump of the pressure circuit is transmitted to drive the fluid pressure pump. Then, by switching the flow path of the fluid discharged from the fluid pressure pump to the load pressure generating section at the flow path switching section, the regenerative power that drives the fluid pressure pump can be consumed by the load pressure generating section. it can. Therefore, when the energy of the fluid discharged from the closed circuit fluid pressure actuator is large, this energy can be prevented from being transmitted to the drive source via the closed circuit fluid pressure pump. It becomes possible to suppress.

  Further, the present invention is the above invention, further comprising a tank for storing fluid discharged from the fluid pressure pump, and a flow path connecting the tank and the fluid pressure pump. It is a pressure loss part provided on the road.

  In the present invention configured as described above, when regenerative power is generated by the closed circuit fluid pressure pump of the closed circuit, the fluid pressure pump of the fluid pressure circuit is driven by the regenerative power, and the fluid to be discharged is discharged from the discharge port of the fluid pressure pump. And a pressure loss unit provided on a flow path connecting the tank and the tank. Thereby, regenerative power can be consumed in a pressure loss part. Therefore, when the energy of the fluid discharged from the closed circuit fluid pressure actuator is large, this energy can be prevented from being transmitted to the drive source via the closed circuit fluid pressure pump. It becomes possible to suppress.

  Moreover, the present invention is characterized in that, in the above-mentioned invention, the load pressure generating unit is an energy storage unit that stores energy of fluid discharged from the fluid pressure pump.

  In the present invention configured as described above, when regenerative power is generated by the closed circuit fluid pressure pump of the closed circuit, the fluid pressure pump of the fluid pressure circuit is driven by the regenerative power, and the discharged fluid is sent to the energy storage unit. Can do. Thereby, regenerative power can be stored in an energy storage part. Therefore, when the energy of the fluid discharged from the closed circuit fluid pressure actuator is large, this energy can be prevented from being transmitted to the drive source via the closed circuit fluid pressure pump. It becomes possible to suppress. Moreover, since the energy stored in the energy storage unit can be reused, a work machine with higher energy efficiency can be obtained.

  Further, the present invention is the above invention, wherein a plurality of the fluid pressure circuits are provided, and the power transmission section is driven when the closed circuit fluid pressure pump is driven by the fluid discharged from the closed circuit fluid pressure actuator. The fluid pressure pump that is not used for driving the fluid pressure actuator among the fluid pressure pumps of the plurality of fluid pressure circuits is preferentially selected, and the selected fluid pressure pump is driven and discharged. It is characterized in that a fluid to be introduced flows into the load pressure generating section.

  In the present invention configured as described above, when regenerative power is generated by a closed circuit fluid pressure pump of a closed circuit, the fluid pressure not used for driving the fluid pressure actuator among the fluid pressure pumps of the plurality of fluid pressure circuits. The pump is preferentially selected, the selected fluid pressure pump is driven by the regenerative power, and the fluid to be discharged can be sent to the load pressure generator. As a result, among the plurality of fluid pressure circuits, an available fluid pressure pump can be appropriately driven, and the regenerative energy generated by the fluid discharged from the closed circuit fluid pressure actuator can be consumed by the load pressure generating unit. When the energy of the fluid discharged from the fluid pressure actuator is large, it is possible to more efficiently suppress this energy from being transmitted to the drive source via the closed circuit fluid pressure pump. It can be suppressed efficiently.

  The present invention relates to a fluid pressure actuator driven by a fluid discharged from a fluid pressure pump driven by a drive source, a load pressure generating unit for generating a load pressure on the discharge side of the fluid pressure pump, and a fluid pressure pump. A fluid pressure circuit having a flow path switching unit that switches a flow path of a fluid to be discharged to either a fluid pressure actuator or the load pressure generating unit, and a closed circuit that is driven by a drive source and can control a discharge flow rate and a discharge direction. A closed circuit having a fluid pressure pump for a circuit, a closed circuit fluid pressure actuator driven by fluid discharged from the closed circuit fluid pressure pump, and the power of the closed circuit fluid pressure pump to the fluid pressure pump And a power transmission unit for transmitting. With this configuration, the present invention drives the closed circuit fluid pressure pump with the fluid discharged from the closed circuit fluid pressure actuator, and the power of the closed circuit fluid pressure pump is supplied to the fluid pressure circuit via the power transmission unit. The fluid pressure pump is driven to drive the fluid pressure pump. Then, by switching the flow path of the fluid discharged from the fluid pressure pump to the load pressure generating section at the flow path switching section, the power driving the fluid pressure pump can be consumed by the load pressure generating section. . Therefore, when the energy of the fluid discharged from the closed circuit fluid pressure actuator is large, this energy can be prevented from being transmitted to the drive source via the closed circuit fluid pressure pump. Can be suppressed. Problems, configurations, and effects other than those described above will be made clear from the following description of embodiments.

1 is a side view of a hydraulic excavator according to a first embodiment of the present invention. It is a hydraulic circuit diagram which shows the drive control apparatus mounted in the hydraulic shovel shown in FIG. FIG. 3 is a hydraulic circuit diagram showing a flow of hydraulic oil and energy when energy generated when the boom of the drive control device shown in FIG. 2 is lowered can be regenerated. FIG. 3 is a hydraulic circuit diagram showing the flow of hydraulic oil and energy when energy generated when the boom of the drive control device shown in FIG. 2 is lowered cannot be regenerated. FIG. 3 is a hydraulic circuit diagram showing the flow of hydraulic oil and energy when regenerative energy is used when the boom of the drive control device shown in FIG. 2 is raised. It is a hydraulic circuit diagram which shows the drive control apparatus which concerns on 2nd Embodiment of this invention. It is a hydraulic circuit diagram which shows the drive control apparatus which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a side view of a hydraulic excavator according to the first embodiment of the present invention. FIG. 2 is a hydraulic circuit diagram showing a drive control device mounted on the hydraulic excavator shown in FIG.

<Configuration>
A hydraulic excavator 100 that is a first embodiment of a work machine according to the present invention is a hydraulically driven excavator. Specifically, as shown in FIG. 1, the excavator 100 includes a lower traveling body 101 having a crawler type traveling device, and an upper portion as a working machine main body that is pivotably mounted on the lower traveling body 101. And a revolving body 102. The upper swing body 102 is provided with a cab 103 as a driver's seat on which an operator boardes. The lower traveling body 101 and the upper turning body 102 are attached to be turnable via a turning device 104.

  A base end portion of the boom 2 is rotatably attached to the front side of the upper swing body 102. The boom 2 operates via a boom cylinder 1 which is a hydraulic pressure rod cylinder as a closed circuit fluid pressure actuator that is driven by supplied hydraulic oil (pressure oil). Moreover, the base end part of the arm 4 is attached to the front-end | tip part of the boom 2 so that rotation is possible. The arm 4 operates via an arm cylinder 3 which is a hydraulic piece rod cylinder as a fluid pressure actuator driven by supplied hydraulic oil. Furthermore, the base end part of the bucket 6 is attached to the front-end | tip part of the arm 4 so that rotation is possible. The bucket 6 operates via a bucket cylinder 5 that is a hydraulic rod cylinder as a fluid pressure actuator that is driven by supplied hydraulic oil. These boom cylinder 1, boom 2, arm cylinder 3, arm 4, bucket cylinder 5, and bucket 6 constitute a front work machine 105.

  In addition, a hydraulic drive control device 106 as a drive control device for driving the excavator 100 is mounted on the upper swing body 102 of the excavator 100. As shown in FIG. 2, the hydraulic drive control device 106 shows only a portion for driving the boom 2 and the arm 4 in the hydraulic excavator 100 shown in FIG. 1, and other traveling devices of the lower traveling body 101 are shown. A description of a portion that drives a fluid pressure actuator such as a hydraulic motor to be driven and a turning motor that drives the turning device 104 is omitted.

  As shown in FIG. 2, the hydraulic drive control device 106 includes an engine 7 that is a power source as a drive source. The engine 7 is connected to a power transmission device 8 as a power transmission unit that distributes the power of the engine 7. The power transmission device 8 includes a first hydraulic pump 9 as a closed circuit fluid pressure pump for driving the boom cylinder 1 and a second hydraulic pump 10 as a fluid pressure pump for driving the arm cylinder 2. And a charge pump 11 for replenishing hydraulic oil to the negative pressure line of the hydraulic pressure drive control device 106 is connected. Here, the first and second hydraulic pumps 9 and 10 and the charge pump 11 are pressure drive sources for pumping hydraulic oil.

  Furthermore, the power transmission device 8 is a gear transmission device such as a speed reducer configured by a gear, for example. Specifically, the power transmission device 8 appropriately transmits the driving rotational force of the engine 7 to the first and second hydraulic pumps 9 and 10 and the charge pump 11 to drive, for example, the first hydraulic pump 9. When the engine 7 functions as a hydraulic motor, the driving rotational force supplied from the first hydraulic pump 9 is appropriately transmitted to the second hydraulic pump 10 and the charge pump 11 to drive the engine 7. Assist.

  The first and second hydraulic pumps 9 and 10 are capable of controlling the discharge flow rate and the discharge direction, and function as a hydraulic motor when the hydraulic oil is supplied, and the hydraulic oil when the driving rotational force is supplied. It functions as a hydraulic pump that sucks and discharges water. Specifically, the first and second hydraulic pumps 9 and 10 include a bi-tilt swash plate mechanism (not shown) having a pair of input / output ports and a bi-tilt swash plate of the bi-tilt swash plate mechanism. And a pair of regulators 9a and 10a for adjusting the inclination angle of the hydraulic oil, and controls the discharge direction and the suction direction of the hydraulic oil from the input / output ports of the two inclined swash plate mechanisms. The regulators 9a and 10a are electrically connected to a controller 12 as a control unit, receive an operation signal output from the controller 12, and based on the received operation signal, the first and second hydraulic pumps 9, 10 suction / discharge flow rates and suction / discharge directions are controlled.

  A pair of flow paths 13 and 14 are connected to the suction and discharge ports of the first hydraulic pump 9. The flow paths 13 and 14 are connected to the boom cylinder 1 via a pair of flow paths 15 and 16 to form a closed circuit 107 which is a fluid pressure closed circuit as a hydraulic circuit. Here, the flow path 15 is connected to a head chamber 1a for extending a cylinder rod 1d that is attached to the cylinder 1c of the boom cylinder 1 so as to be extendable and contractible. The flow path 16 is connected to a rod chamber 1b for retracting the cylinder rod 1d of the boom cylinder 1. The boom cylinder 1 is expanded and contracted by supplying hydraulic oil discharged from the first hydraulic pump 9. In other words, the boom cylinder 1 changes its retracting direction according to the supply direction of the hydraulic oil discharged from the first hydraulic pump 9.

  Further, check valves 17a and 17b are attached to the flow paths 15 and 16, respectively. Each of these check valves 17a, 17b is connected to a tank 18 that stores hydraulic oil discharged from the first and second hydraulic tanks 9, 10. In other words, the check valves 17a and 17b are operated when the flow passages 15 and 16 become negative pressure or when the boom cylinder 1 operates at high speed, and the hydraulic oil in the cylinder 1c of the boom cylinder 1 becomes insufficient in flow rate. In this case, hydraulic oil is supplied from the tank 18 to the flow paths 15 and 16.

  Furthermore, relief valves 19a and 19b are attached to the flow paths 15 and 16, respectively. These relief valves 19a and 19b connect the flow paths 15 and 16 to the tank 18 when the pressure in the flow paths 15 and 16 becomes equal to or higher than a predetermined pressure. The hydraulic oil is released to the tank 18 to protect the closed circuit 107 including the flow paths 15 and 16. A flushing valve 20 is attached between the flow paths 15 and 16. The flushing valve 20 discharges surplus of the hydraulic oil supplied to the flow paths 15 and 16 to the tank 18.

  On the other hand, a charge check valve 21 is attached to the discharge port side of the charge pump 11. The charging check valve 21 is attached between the flow paths 13 and 14. The suction port side of the charge pump 11 is connected to the tank 18. A charge relief valve 22 is attached to the discharge port side of the charge pump 11. The charge relief valve 22 adjusts the charge pressure of the charge check valve 21. Therefore, when the pressure of the hydraulic oil in the flow paths 13 and 14 falls below the pressure set by the charge relief valve 22, the charge check valve 21 is connected to the flow paths 13 and 14 from the charge pump 11. Supply discharged hydraulic fluid.

  Next, a pair of flow paths 23, 24 are connected to the suction / discharge port of the second hydraulic pump 10, and are connected to the proportional switching valves 32, 33 via these flow paths 23, 24. Further, the proportional switching valves 32 and 33 are connected to the arm cylinder 3 via the flow paths 25 and 26 to form a closed circuit 108 which is a hydraulic circuit as a fluid pressure circuit. Here, the proportional switching valve 32 performs on / off control of the supply of hydraulic oil between the flow path 23 and the flow path 25. The proportional switching valve 33 blocks the flow path 24, connects the flow path 24 to the flow path 26, adjusts the flow rate between the flow paths 24, 26, and connects the flow path 24 to the tank 18. The flow rate between the flow path 24 and the tank 18 is adjusted or controlled.

  Further, the flow path 25 is connected to a head chamber 3a for extending a cylinder rod 3d attached to the cylinder 3c of the arm cylinder 3 so as to be extendable and contractible. The flow path 26 is connected to a rod chamber 3b for retracting the cylinder rod 3d of the arm cylinder 3. The arm cylinder 3 expands and contracts when the hydraulic oil discharged from the second hydraulic pump 10 is supplied. That is, the retracting direction of the arm cylinder 3 varies depending on the supply direction of the hydraulic oil discharged from the second hydraulic pump 10.

  Also, check valves 27a and 27b are attached to the flow paths 25 and 26, respectively. Each of these check valves 27 a and 27 b is connected to the tank 18. These check valves 27a and 27b are used when the flow passages 25 and 26 have a negative pressure or when the arm cylinder 3 operates at high speed and the hydraulic oil in the arm cylinder 3 becomes insufficient in flow rate. Hydraulic oil is supplied from the tank 18 to the flow paths 25 and 26.

  Furthermore, relief valves 29a and 29b are attached to the flow paths 25 and 26, respectively. The relief valves 29a and 29b connect the flow paths 25 and 26 to the tank 18 when the pressure in the flow paths 25 and 26 is equal to or higher than a predetermined pressure. The hydraulic oil is released to the tank 18 to protect the closed circuit 108 including the flow paths 25 and 26. A flushing valve 30 is attached between the flow paths 25 and 26. The flushing valve 30 discharges excess of the hydraulic oil supplied to the flow paths 25 and 26 to the tank 18.

  On the other hand, a charge check valve 31 is attached to the discharge port side of the charge pump 11. The charging check valve 31 is attached between the flow paths 23 and 24. The charge check valve 31 is discharged from the charge pump 11 to each of the flow paths 23 and 24 when the pressure of the hydraulic oil in the flow paths 23 and 24 falls below the pressure set by the charge relief valve 22. Supply hydraulic oil. That is, the charge relief valve 22 adjusts the charge pressure of the charge check valve 31.

  Further, a proportional switching valve 34 that is a pressure loss portion serving as a load pressure generating portion and a pressure accumulation switching valve 35 are connected to the intake / exhaust port of the second hydraulic pressure pump 10 through a flow path 23. The proportional switching valve 34 controls the flow rate of the hydraulic oil discharged to the tank 18. Further, the pressure accumulation switching valve 35 adjusts the shut-off state in which the flow path 23 is shut off, the check valve state in which the flow direction of the hydraulic oil is limited to one direction from the flow path 23 to the accumulator 36, and the flow rate of the supplied hydraulic oil Switch the proportional valve state. An accumulator 36 is connected to the pressure accumulation switching valve 35 as a load pressure generating unit that generates a load pressure on the discharge side of the second hydraulic pump 10. The accumulator 36 is provided on the flow path 23 and functions as an energy storage unit that stores energy of hydraulic oil discharged from the second hydraulic pump 10. The accumulator 36 is configured to store pressure with hydraulic oil flowing in via the pressure accumulation switching valve 35 and to discharge hydraulic fluid with the stored pressure.

  Further, a relief valve 37 is connected between the pressure accumulation switching valve 35 and the accumulator 36. The relief valve 37 is connected to the tank 18, and when the pressure accumulated in the accumulator 36 becomes equal to or higher than a predetermined pressure, the hydraulic oil accumulated in the accumulator 36 is released to the tank 18. This accumulator 36 is protected. Here, the supply destination of the hydraulic oil discharged from the second hydraulic pump 10, that is, the oil passage, is supplied to the arm cylinder 3 and the accumulator 36 by the proportional switching valves 32, 33, 34, the pressure accumulation switching valve 35 and the relief valve 37. A flow path switching unit 109 that switches to any one of the tanks 18 is configured.

  Next, the controller 12 is electrically connected to the regulator 9 a of the first hydraulic pump 9, the regulator 10 a of the second hydraulic pump 10, the proportional switching valves 32, 33, 34 and the pressure accumulation switching valve 35. 12 to control. The controller 12 is connected to levers 28a and 28b. The lever 28a determines the expansion / contraction direction of the boom cylinder 1 according to the direction of inclination, and determines the target speed of the boom cylinder 1 according to the degree of inclination. The lever 28b determines the expansion / contraction direction of the arm cylinder 3 according to the direction of inclination, and determines the target speed of the arm cylinder 3 according to the degree of inclination. Therefore, the controller 12 receives input signals of the boom cylinder 1 and the arm cylinder 3 from the levers 28a and 28b and the target speed, a pressure sensor (not shown) in each of the closed circuits 107 and 108, a tilt angle sensor, an engine The regulators 9a and 10a, the proportional switching valves 32, 33 and 34, and the pressure accumulation switching valve 35 are controlled based on various sensor information obtained from the rotational speed sensor 7.

<Action>
Next, the operation of the hydraulic drive control device 106 mounted on the excavator 1 according to the first embodiment will be described for each operation mode of the excavator 1. In each operation mode, the tilt angle of both the tilting swash plates of the first and second hydraulic pumps 9 and 10 and the proportional switching are set so that the fuel consumption of the engine 7 is improved by a signal from the controller 12. The opening and closing of the valves 32, 33, 34 and the pressure accumulation switching valve 35 are controlled.

(1) When stopped In FIG. 2, when the levers 28a and 28b are not operated (when not operated), the first and second hydraulic pumps are operated by the regulators 9a and 9b in response to a command from the controller 12. Each of the tilting plates 9 and 10 is controlled to the minimum tilting angle. Further, in response to a command from the controller 12, all of the proportional switching valves 32, 33, 34 and the power storage proportional valve 35 are closed, and the driving of the boom cylinder 1 and the arm cylinder 3 is held in a stopped state.

(2) During the boom lowering operation During the boom lowering operation, the pressure on the head chamber 1a side of the boom cylinder 1 is high due to the weight of the boom 2, the arm 4 and the bucket 6 shown in FIG. When the lever 28a is operated so that the boom cylinder 1 is contracted, the bilaterally inclined swash plate of the first hydraulic pump 9 is controlled by the regulator 9a in accordance with a command from the controller 12, and this first hydraulic pressure is controlled. The discharge side of the pump 9 is raised to the flow path 14 side. At this time, since the suction side of the first hydraulic pump 9 becomes the flow path 13 connected to the head chamber 1a of the boom cylinder 1, the pressure on the suction side is higher than the discharge side of the first hydraulic pump 9. For this reason, the 1st hydraulic pump 9 receives supply of hydraulic fluid, and acts as a hydraulic motor.

  Further, since the flow rate of the hydraulic oil returning from the head chamber 1a of the boom cylinder 1 to the first hydraulic pump 9 is larger than the flow rate of the hydraulic oil supplied to the rod chamber 1b of the boom cylinder 1, an excess amount of this hydraulic oil Is returned to the tank 18 from the flow path 16 through the flushing valve 20. The driving force (energy) generated by the first hydraulic pump 9 acting as a hydraulic motor is transmitted to the second hydraulic pump 10 via the power transmission device 8, and the second hydraulic pump 10 Used as driving force.

(With regeneration)
Here, referring to FIG. 3, the flow in the case where the energy generated by driving the first hydraulic pump 9 can be regenerated in the accumulator 36 when the first hydraulic pump 9 acts as a hydraulic motor. explain. FIG. 3 is a hydraulic circuit diagram showing the flow of hydraulic oil and energy when energy generated when the boom of the drive control device shown in FIG. 2 is lowered can be regenerated.

  Specifically, when the accumulator 36 is capable of accumulating pressure below a predetermined pressure, the accumulator switching valve 35 is switched to the check valve state and the proportional switching valves 32, 33, 34 are shut off in response to a command from the controller 12. Switch to state. Then, in accordance with a command from the controller 12, the tilting swash plate of the second hydraulic pump is controlled by the regulator 10a, and the discharge side of the second hydraulic pump 10 is raised to the flow path 23 side. At this time, the command from the controller 12 to the regulator 10a is that the amount of energy obtained based on the various sensor information described above when the first hydraulic pump 9 is driven as a hydraulic motor, and the pressure in the accumulator 36. Is calculated by the controller 12 based on the above.

  Further, the second hydraulic pump 10 is driven by the driving force transmitted from the first hydraulic pump 9 via the power transmission device 8, and the hydraulic oil passes through the check valve 31 from the tank 18 via the charge pump 11. And supplied to the second hydraulic pump 10. Then, the hydraulic oil discharged by the second hydraulic pump 10 flows into the accumulator 36 through the flow path 23 and the pressure accumulation switching valve 35, and is accumulated in the accumulator 36 to the first hydraulic pump 9. Regenerates and accumulates energy.

(No regeneration)
Next, the flow in the case where the energy generated by driving the first hydraulic pump 9 cannot be regenerated in the accumulator 36 when the first hydraulic pump 9 acts as a hydraulic motor will be described with reference to FIG. To do. FIG. 4 is a hydraulic circuit diagram showing the flow of hydraulic oil and energy when energy generated when the boom of the drive control device shown in FIG. 2 is lowered cannot be regenerated.

  Specifically, when the accumulator 36 cannot store pressure at a predetermined pressure or higher (accumulation is impossible), each of the proportional switching valves 32 and 33 and the pressure storage switching valve 35 is turned off by a command from the controller 12. Can be switched. Then, in accordance with a command from the controller 12, the tilting swash plate of the second hydraulic pump 10 is controlled by the regulator 10a, and the discharge side of the second hydraulic pump 10 is raised to the flow path 23 side. Then, the second hydraulic pump 10 is driven by the driving force transmitted from the first hydraulic pump 9 via the power transmission device 8, and the hydraulic oil passes through the check valve 31 from the tank 18 via the charge pump 11. And supplied to the second hydraulic pump 10.

  Further, the hydraulic oil discharged by the second hydraulic pump 10 flows into the proportional switching valve 34 via the flow path 23, and the energy of the hydraulic oil when passing through the proportional switching valve 34. Is converted into heat energy and consumed, and then returned to the tank 18. At this time, a command from the controller 12 to the proportional switching valve 34 and the regulator 10a is calculated by the controller 12 based on the amount of energy regenerated when the first hydraulic pump 9 is driven as a hydraulic motor.

(3) During boom lowering / arm dump combined operation In FIG. 2, when the lever 28a is operated so that the boom cylinder 1 contracts, the regulator 9a is operated in the same manner as in the boom lowering single operation described in (2) above. The discharge side of the first hydraulic pump 9 is raised to the flow path 14 side, and this first hydraulic pump 9 acts as a hydraulic motor.

  At the same time, when the lever 28b is operated so that the arm cylinder 3 contracts (dumps), the regulator 10a controls the both inclined swash plates of the second hydraulic pump 10 in accordance with a command from the controller 12. The discharge side of the second hydraulic pump 10 is raised to the flow path 24 side. At this time, the proportional switching valve 32 is fully opened by the command from the controller 12, and the flow path 24 and the flow path 26 are connected by the proportional switching valve 33.

  Further, when the arm cylinder 3 is contracted, the flow rate of the hydraulic oil returning from the head chamber 3 a of the arm cylinder 3 to the second hydraulic pump 10 is the flow rate of the hydraulic oil supplied to the rod chamber 3 b of the arm cylinder 3. Therefore, the surplus hydraulic fluid is returned from the flow path 26 to the tank 18 via the flushing valve 30. At this time, the energy consumed by the second hydraulic pump 10 is regenerated by the first hydraulic pump 9 based on the pressure ratio between the hydraulic oil pressure in the flow path 23 and the hydraulic oil pressure in the flow path 24. The opening degree of the proportional control valve 33 is calculated by the controller 12 so as to be equal to or larger than the amount, and the proportional control valve 33 is controlled to the calculated opening degree.

(4) During boom lowering / arm cloud combined operation When the lever 28a is operated so that the boom cylinder 1 contracts, the first operation is performed by the regulator 9a in the same manner as in the boom lowering single operation described in (2) above. The discharge side of the hydraulic pump is raised to the flow path 14 side, and the first hydraulic pump 9 acts as a hydraulic motor.

  At the same time, when the lever 28b is operated so that the arm cylinder 3 extends (cloud), the bi-tilt swash plate of the second hydraulic pump 10 is controlled by the regulator 10a in accordance with a command from the controller 12. The discharge side of the second hydraulic pump 10 is raised to the flow path 23 side. At this time, the proportional switching valve 33 is fully opened and the flow path 24 and the flow path 26 are connected by a command from the controller 12.

  Further, when the arm cylinder 3 is extended, the flow rate of the hydraulic oil returning from the rod chamber 3 b of the arm cylinder 3 to the second hydraulic pump 10 is the flow rate of the hydraulic oil supplied to the head chamber 3 a of the arm cylinder 3. Less. For this reason, the shortage of the suction flow rate of the second hydraulic pump 10 is added from the charge pump 11 to the flow path 24 via the charge check valve 31. At this time, based on the pressure ratio between the flow path 23 and the flow path 24, the proportional control valve 32 is opened so that the amount of energy consumed by the second hydraulic pump 10 is equal to or greater than the amount of energy regenerated by the first hydraulic pump 9. The degree is calculated by the controller 12, and the proportional control valve 32 is controlled to the calculated opening degree.

(5) When the boom is lifted up alone When the lever 28a is operated so that the boom cylinder 1 is extended, the bilaterally inclined swash plate of the first hydraulic pump 9 is moved by the regulator 9a according to a command from the controller 12. Under control, the discharge side of the first hydraulic pump 9 is raised to the flow path 13 side. Further, the hydraulic oil discharged from the first hydraulic pump 9 is supplied from the flow path 13 to the head chamber 1 a of the boom cylinder 1 via the flow path 15. On the other hand, the hydraulic oil in the rod chamber 1 b of the boom cylinder 1 is returned from the flow path 16 to the first hydraulic pump 9 via the flow path 14.

  At this time, the flow rate of the hydraulic oil returning from the rod chamber 1b of the boom cylinder 1 to the first hydraulic pump 9 is smaller than the flow rate of the hydraulic oil supplied from the first hydraulic pump 9 to the head chamber 1a of the boom cylinder 1. For this reason, the shortage of hydraulic oil that returns from the rod chamber 1 b of the boom cylinder 1 to the first hydraulic pump 9 is supplied from the charge pump 12 to the first hydraulic pump 9 via the charging check valve 21 and the flow path 14. Is done.

(With regeneration)
Here, the flow in the case of using (reusing) the energy accumulated in the accumulator 36 will be described with reference to FIG. FIG. 5 is a hydraulic circuit diagram showing the flow of hydraulic oil and energy when regenerative energy is used when the boom of the drive control device shown in FIG. 2 is raised.

  Specifically, when energy is accumulated in the accumulator 36, that is, hydraulic oil is accumulated, the pressure accumulation switching valve 35 is switched to the proportional valve state by the command from the controller 12, and the proportional switching valve 33 is switched to flow. The path 24 and the tank 18 are connected, and each of the proportional switching valves 32 and 34 is switched to the shut-off state. Then, the opening degree of the pressure accumulation switching valve 35 is adjusted by a command from the controller 12, and the pressure of the hydraulic oil in the flow path 23 is increased. In addition, in a state where the pressure of the hydraulic oil in the flow path 23 is higher than the pressure of the hydraulic oil in the flow path 24, the regulator 10a inclines both sides of the second hydraulic pump 10 according to a command from the controller 12. The swash plate is controlled, and the hydraulic oil passing through the second hydraulic pump 10 is started up so as to be discharged from the flow path 23 to the flow path 24.

  At this time, the pressure of the hydraulic fluid on the suction side of the second hydraulic pump 10 increases. For this reason, the second hydraulic pump 10 acts as a hydraulic motor in response to the supply of hydraulic oil from the accumulator 36. The driving force (energy) generated by the second hydraulic pump 10 acting as a hydraulic motor is transmitted to the first hydraulic pump 9 via the power transmission device 8, and the driving force of the first hydraulic pump 9 is transmitted. Used as The flow rate of the hydraulic oil discharged from the second hydraulic pump 10 is calculated by the controller 12 based on the amount of energy used in the first hydraulic pump 9 and the pressure of the hydraulic oil in the flow path 23, It is controlled by this controller 12.

(6) During boom raising / arm dump combined operation In FIG. 2, when the lever 28a is operated so that the boom cylinder 1 extends, the regulator 9a is operated similarly to the above-described boom raising single operation (5). The discharge side of the first hydraulic pump 9 is raised to the flow path 13 side. Then, the shortage of hydraulic oil returning from the rod chamber 1b of the boom cylinder 1 to the first hydraulic pump 9 is supplied from the charge pump 12 to the first hydraulic pump 9 via the charging check valve 21 and the flow path 14. The

  At the same time, when the lever 28b is operated so that the arm cylinder 3 contracts, the discharge of the second hydraulic pump 10 is performed by the regulator 10a as in the above-described (3) combined boom lowering / arm dumping operation. The proportional switch valve 32 is fully opened, and the proportional switch valve 33 connects the flow path 24 and the flow path 26. Here, when the pressure of the hydraulic oil in the flow path 23 is higher than the pressure of the hydraulic oil in the flow path 24, the second hydraulic pump 10 receives the hydraulic oil supplied from the flow path 23 and the hydraulic pump 10 Acts as

  The opening degree of the proportional control valve 33 is calculated by the controller 12 so that the energy consumption amount of the first hydraulic pump 9 is equal to or larger than the energy amount regenerated by the second hydraulic pump 10, and the calculated opening degree The proportional control valve 33 is controlled. At this time, when the pressure of the hydraulic oil in the flow path 24 is higher than the pressure of the hydraulic oil in the flow path 23, the proportional control valve 33 is fully opened by a command from the controller 12.

(7) During boom raising / arm cloud combined operation When the lever 28a is operated so that the boom cylinder 1 is extended, the first operation is performed by the regulator 9a as in the case of the boom raising single operation of (5) described above. The discharge side of the hydraulic pump 9 is raised to the flow path 13 side. Then, the shortage of hydraulic oil returning from the rod chamber 1b of the boom cylinder 1 to the first hydraulic pump 9 is supplied from the charge pump 12 to the first hydraulic pump 9 via the charging check valve 21 and the flow path 14. The

  At the same time, when the lever 28b is operated so that the arm cylinder 3 extends, the regulator 10a controls the second hydraulic pump 10 in the same manner as the boom lowering / arm cloud combined operation (4) described above. The discharge side is raised to the flow path 23 side, the proportional switching valve 33 is fully opened, and the flow path 24 and the flow path 26 are connected. At this time, when the internal pressure of the flow path 24 is higher than the internal pressure of the flow path 23, the second hydraulic pump 10 acts as a hydraulic motor. Then, as in the above-described boom raising / arm dump combined operation (6), the proportional control valve is set so that the amount of energy consumed by the first hydraulic pump 9 is equal to or greater than the amount of energy regenerated by the second hydraulic pump 10. The opening degree of 32 is controlled. At this time, when the pressure of the hydraulic oil in the flow path 23 is higher than the pressure of the hydraulic oil in the flow path 24, the proportional control valve 32 is fully opened by a command from the controller 12.

(8) At the time of arm dump alone operation When the lever 28b is operated so that the arm cylinder 3 contracts, the second operation is performed by the regulator 10a in the same manner as the boom lowering / arm dump combined operation of (3) described above. The discharge side of the hydraulic pump 10 is raised to the flow path 24 side, the proportional switching valve 32 is fully opened, and the flow path 24 and the flow path 26 are connected by the proportional switching valve 33. Further, based on the pressure ratio between the flow path 23 and the flow path 24, the opening degree of the proportional control valve 33 is calculated by the controller 12 so that the pressure of the hydraulic oil in the flow path 24 is increased. The proportional control valve 33 is controlled.

(9) At the time of arm cloud single operation When the lever 28b is operated so that the arm cylinder 3 extends, the second operation is performed by the regulator 10a in the same manner as in the boom lowering / arm cloud combined operation of (4) described above. The discharge side of the hydraulic pump 10 is raised to the flow path 23 side, the proportional switching valve 33 is fully opened, and the flow path 24 and the flow path 26 are connected. Further, based on the pressure ratio between the flow path 23 and the flow path 24, the opening degree of the proportional control valve 32 is calculated and controlled by the controller 12 so that the pressure of the hydraulic oil in the flow path 23 is increased.

<Effect>
As described above, according to the excavator 1 according to the first embodiment, the controller 12 controls the first and second hydraulic pumps 9 for each of the nine operation modes in accordance with the operation of the levers 28a and 28b. 10, the proportional switching valves 32, 33 and 34 and the pressure accumulation switching valve 35 are controlled. In particular, when the energy of the hydraulic oil discharged from the boom cylinder 1 on the closed circuit 107 side is large and the first hydraulic pump 9 is driven as a hydraulic motor by this hydraulic oil, a high regenerative torque is generated. The power of the hydraulic pump 9 is transmitted to the second hydraulic pump 10 via the power transmission device 8. Then, the second hydraulic pump 10 is driven by the transmitted power, and the hydraulic oil discharged from the second hydraulic pump 10 is accumulated in the accumulator 36.

  When the boom is raised, that is, when the boom cylinder 1 is driven to extend, the hydraulic oil accumulated in the accumulator 36 is supplied to the second hydraulic pump 10 to drive the second hydraulic pump 10. The power of the second hydraulic pump 10 can be transmitted to the first hydraulic pump 9 via the power transmission device 8, and the driving of the first hydraulic pump 9 can be assisted. Accordingly, the hydraulic oil accumulated in the accumulator 36 can be reused, and the load on the engine 7 when the first hydraulic pump 9 is driven can be reduced. Therefore, since the fuel consumption required for driving the hydraulic excavator 1 can be improved, the energy efficient hydraulic excavator 1 can be obtained. At the same time, when the first hydraulic pump 9 is driven as a hydraulic motor, the transmission of power from the first hydraulic pump 9 to the engine can be suppressed. The overrev of the engine 7 that exceeds the number can be suppressed.

  Further, when the accumulator 36 is in a saturated state and the hydraulic oil cannot be accumulated in the accumulator 36, the regenerative torque generated when the first hydraulic pump 9 is driven as a hydraulic motor is used as the second hydraulic pressure. Used to drive the pump 10. Then, the hydraulic oil discharged by driving the second hydraulic pump 10 is discharged to the tank 18 through the proportional switching valve 34. As a result, when the hydraulic oil discharged from the second hydraulic pump 10 passes through the proportional switching valve 34, the energy (pressure) of the hydraulic oil can be converted into thermal energy, and the first hydraulic pump 9 The regenerated energy can be consumed. Therefore, even when the hydraulic oil cannot be stored in the accumulator 36, the regenerative energy when the first hydraulic pump 9 is driven as a hydraulic motor can be consumed, and the transmission of this regenerative energy to the engine 7 is suppressed. Therefore, the overrev of the engine 7 can be suppressed.

  Here, when the hydraulic oil discharged from the boom cylinder 1 is directly accumulated in the accumulator 36 when the boom is lowered, the pressure of the hydraulic oil flowing into the accumulator 36 fluctuates due to the operation of the boom cylinder 1. Regeneration is not easy. In addition, when priority is given to pressure accumulation in the accumulator 36, the operability of the boom cylinder 1 or the like may be deteriorated. On the other hand, when priority is given to the operability of the boom cylinder 1 or the like, the regeneration efficiency in the accumulator 36 may be deteriorated.

  Therefore, in the first embodiment described above, the flow rate of hydraulic oil discharged from the boom cylinder 1 when the boom is lowered is controlled by the first hydraulic pump 9, and this first hydraulic pump 9 acts as a hydraulic motor. The second hydraulic pump 10 is driven by the regenerative torque generated in this case to accumulate pressure in the accumulator 36. That is, the speed of the boom cylinder 1 is adjusted by the first hydraulic pump 9, and the pressure accumulation in the accumulator 36 corresponding to the regenerative energy in the first hydraulic pump 9 is adjusted by the second hydraulic pump 10. Therefore, the operability of the first hydraulic pump 9 can be ensured, and the second hydraulic pump 10 can stably store hydraulic oil in the accumulator 36, that is, regenerate energy.

  Furthermore, the pressure oil discharged from the boom cylinder 1 when the boom is lowered is converted into regenerative torque by the first hydraulic pump 9. Further, when the pressure on the suction side is higher than the discharge side of the second hydraulic pump 10 during the arm operation, the pressure oil discharged from the arm cylinder 3 is converted into regenerative torque by the second hydraulic pump 10. At this time, by adjusting the flow rate of the hydraulic oil with the proportional switching valve 32, a load can be applied to the second hydraulic pump 10, and the regenerative energy of the first and second hydraulic pumps 9 and 10 is consumed. Therefore, the overrev of the engine 7 can be suppressed.

  In particular, when hydraulic oil is accumulated in the accumulator 36, the second hydraulic pump 10 is driven as a hydraulic motor by the hydraulic oil accumulated in the accumulator 36, thereby assisting in driving the engine 7. Can do. At this time, by adjusting the driving of the second hydraulic pump 10, even when the pressure of the hydraulic oil accumulated in the accumulator 36 fluctuates, the engine 7 can be stably assisted.

[Second Embodiment]
FIG. 6 is a hydraulic circuit diagram showing a drive control apparatus according to the second embodiment of the present invention. The second embodiment differs from the first embodiment described above in that the first embodiment is different from the hydraulic drive control device 106 in which the hydraulic circuit for driving the arm cylinder 3 is a closed circuit 108 in the second embodiment. The hydraulic circuit for driving the arm cylinder 3 is a hydraulic pressure drive control device 106A in which the open circuit 110 is an open circuit 110. In the second embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

<Configuration>
Specifically, in the second embodiment, as shown in FIG. 6, one of the suction and discharge ports of the second hydraulic pump 10 is connected via a flow path 39 to the switching valve 40, the proportional switching valve 34, and the relief valve 37. And the pressure accumulation switching valve 35. The other of the suction and discharge ports of the second hydraulic pump 10 is connected to the tank 18 to form an open circuit 110 as a fluid pressure circuit. The switching valve 40 switches between conduction and interruption of the flow path 39 according to a command from the controller 12.

  The proportional switching valve 34 controls the flow rate of the hydraulic oil discharged to the tank 18 according to a command from the controller 12. The relief valve 37 releases the hydraulic oil to the tank 18 and protects the open circuit 110 including the flow path 39 when the pressure of the hydraulic oil in the flow path 39 exceeds a predetermined pressure. Further, an accumulator 36 is connected to the flow path 39 via a pressure accumulation switching valve 35. The pressure accumulation control valve 35 is connected to each of the switching valve 40, the relief valve 37, and the switching control valve 34.

  Further, a proportional switching valve 44 as a control valve is connected to one of the suction and discharge ports of the second hydraulic pump 10 through a flow path 39, a switching valve 40 and a check valve 43. A counter balance valve 45 and an arm cylinder 3 are connected to the proportional switching valve 44 via flow paths 47 and 48, respectively. That is, a counter balance valve 45 and a proportional switching valve 44 are connected to the arm cylinder 3 via flow paths 47 and 48, and the proportional switching valve 44 is connected to the tank 18 to form an open circuit 110. .

  The check valve 43 prevents the backflow of hydraulic oil from the proportional switching valve 44 to the switching valve 40. The proportional switching valve 44 switches the connection destination of the check valve 43 and the tank 18 to the counter balance valve 45 or the flow path 48 according to a command from the controller 12 and adjusts the flow rate of the hydraulic oil passing through the proportional switching valve 44. To do. Further, the counter balance valve 45 suppresses the weight drop of the arm cylinder 3, and is connected to the head chamber 3 a of the arm cylinder 3 via the flow path 47. On the other hand, the flow path 48 is connected to the rod chamber 3 b of the arm cylinder 3. Furthermore, relief valves 29a and 29b are provided between the flow paths 47 and 48, and the tank 18 is connected between the relief valves 29a and 29b.

  As in the first embodiment, the controller 12 is based on input signals of the boom cylinder 1 and the arm cylinder 3 from the levers 28a and 28b and the target speed, and sensor information in each closed circuit 107 and open circuit 110. The regulator 9a of the first hydraulic pump 9, the regulator 10a of the second hydraulic pump 10, the switching valve 40, the proportional switching valves 34 and 44, and the pressure accumulation switching valve 35 are controlled.

<Action>
Next, the operation of the hydraulic drive control device 106A mounted on the excavator 1 according to the second embodiment will be described for each operation mode of the excavator 1. In each operation mode, the tilt angle of the both tilt swash plates of the first and second hydraulic pumps 9 and 10 and the switching valve are set so that the fuel consumption of the engine 7 is improved by the signal from the controller 12. 40, the opening and closing of the proportional switching valves 34 and 44 and the pressure accumulation switching valve 35 are controlled.

(1) When stopped When the levers 28a and 28b are not operated, both tilt swash plates of the first and second hydraulic pumps 9 and 10 are controlled to the minimum tilt angle, and the switching valve 40 and proportional switching are performed. All of the valves 34 and 44 and the power storage proportional valve 35 are closed, and the driving of the boom cylinder 1 and the arm cylinder 3 is maintained.

(2) At the time of boom lowering alone operation When the lever 28a is operated so that the boom cylinder 1 contracts, the discharge side of the first hydraulic pump 9 is raised to the flow path 14 side, and this first hydraulic pump 9 acts as a hydraulic motor.

(With regeneration)
Here, when the first hydraulic pump 9 acts as a hydraulic motor and the accumulator 36 can accumulate pressure below a predetermined pressure, the accumulation switching valve 35 is switched to the check valve state, and the switching valve 40 and proportional switching are performed. Each of the valves 34 is switched to the shut-off state. Further, the discharge side of the second hydraulic pressure pump 10 is raised to the flow path 39 side, and the hydraulic oil discharged by the second hydraulic pressure pump 10 is sent to the accumulator 36 via the flow path 39 and the pressure accumulation switching valve 35. It flows in and is accumulated in this accumulator 36.

(No regeneration)
Next, when the first hydraulic pump 9 acts as a hydraulic motor and the accumulator 36 cannot accumulate pressure at a predetermined pressure or higher, each of the pressure accumulation switching valve 35 and the switching valve 40 is switched to a shut-off state. Furthermore, the discharge side of the second hydraulic pump 10 is raised to the flow path 39 side, and the hydraulic oil discharged by the second hydraulic pump 10 flows into the proportional switching valve 34 via the flow path 39, When passing through the proportional switching valve 34, the energy (pressure) of the hydraulic oil is converted into heat energy and consumed, and then returned to the tank 18.

(3) During boom lowering / arm dump combined operation When the lever 28a is operated so that the boom cylinder 1 contracts, the first hydraulic pump 9 is operated in the same manner as in the boom lowering single operation described in (2) above. The discharge side is raised to the flow path 14 side, and the first hydraulic pump 9 acts as a hydraulic motor.

  At the same time, when the lever 28 b is operated so that the arm cylinder 3 contracts, the regulator 10 a of the second hydraulic pump 10 causes the swash plate of the second hydraulic pump 10 to be moved according to a command from the controller 12. The second hydraulic pump 10 is started up such that the discharge side of the second hydraulic pump 10 becomes the flow path 39 side. At this time, the switching valve 40 is fully opened by a command from the controller 12, and the proportional switching valve 44 connects between the check valve 43 and the flow path 48 and between the tank 18 and the flow path 47. . Based on the pressure ratio between the flow path 39 and the tank 18, the amount of energy consumed by the second hydraulic pump 10 is equal to or greater than the amount of energy regenerated by the first hydraulic pump 9, and the target cylinder given by the lever 28b. The opening degree of the proportional control valve 44 and the tilt angle command of the regulator 10a are calculated and controlled by the controller 12 so that the speed is reached.

(4) During boom lowering / arm cloud combined operation When the lever 28a is operated so that the boom cylinder 1 contracts, the first hydraulic pump 9 is operated in the same manner as in the boom lowering single operation described in (2) above. The discharge side is raised to the flow path 14 side, and the first hydraulic pump 9 acts as a hydraulic motor.

  At the same time, when the lever 28b is operated so that the arm cylinder 3 extends, the discharge side of the second hydraulic pump 10 is raised to the flow path 39 side. Further, the switching valve 40 is fully opened, and the proportional switching valve 44 connects between the check valve 43 and the flow path 47 and between the tank 18 and the flow path 48. Based on the pressure ratio between the flow path 39 and the tank 18, the amount of energy consumed by the second hydraulic pump 10 is equal to or greater than the amount of energy regenerated by the first hydraulic pump 9, and the target cylinder given by the lever 28b. The opening degree of the proportional control valve 44 and the tilt angle command of the regulator 10a are calculated and controlled by the controller 12 so that the speed is reached.

(5) During boom raising single operation When the lever 28a is operated so that the boom cylinder 1 extends, the discharge side of the first hydraulic pump 9 is raised to the flow path 13 side. Then, the hydraulic oil discharged from the first hydraulic pump 9 is supplied from the flow path 13 to the head chamber 1a of the boom cylinder 1 via the flow path 15, and the hydraulic oil in the rod chamber 1b of the boom cylinder 1 is The fluid is returned from the channel 16 to the first hydraulic pump 9 through the channel 14.

(With regeneration)
Here, when the hydraulic oil is accumulated in the accumulator 36, the pressure accumulation switching valve 35 is switched to the proportional valve state, and each of the switching valve 40 and the proportional switching valve 34 is switched to the cutoff state. Then, the opening degree of the pressure accumulation switching valve 35 is adjusted, and the pressure of the hydraulic oil in the flow path 39 is increased. Further, the hydraulic oil passing through the second hydraulic pump 10 is discharged from the flow path 39 to the tank 18 in a state where the pressure of the hydraulic oil in the flow path 39 is higher than the pressure of the hydraulic oil in the tank 18. To be launched.

  At this time, the pressure of the hydraulic fluid on the suction side of the second hydraulic pump 10 increases. For this reason, the second hydraulic pump 10 acts as a hydraulic motor in response to the supply of hydraulic oil from the accumulator 36. The flow rate of the hydraulic oil discharged from the second hydraulic pump 10 is such that the amount of regenerative energy generated by the second hydraulic pump 10 becomes the amount of energy used by the first hydraulic pump 9. The controller 12 calculates and controls the pressure based on the pressure of the hydraulic oil in the engine 39.

(6) During boom raising / arm dump combined operation When the lever 28a is operated so that the boom cylinder 1 is extended, the first hydraulic pump 9 is the same as in the above-described boom raising single operation (5). The discharge side is raised to the flow path 13 side.

  At the same time, when the lever 28b is operated so that the arm cylinder 3 contracts, the discharge side of the second hydraulic pump 10 is connected to the flow path 39 as in the above-described (3) combined boom lowering / arm dump operation. The switching valve 40 is fully opened, and the proportional switching valve 44 connects between the check valve 43 and the flow path 48 and between the tank 18 and the flow path 47.

  Here, when hydraulic oil is accumulated in the accumulator 36, the pressure accumulation switching valve 35 is switched to the proportional valve state, the switching valve 40 is switched to the fully open state, and the proportional switching valve 34 is switched to the cutoff state. Further, the opening degree of the pressure accumulation switching valve 35 is adjusted according to the input of the lever 28b, the pressure in the flow path 39 is increased, and the proportional switching valve 44 is connected between the check valve 43 and the flow path 48, The tank 18 and the flow path 47 are connected to each other.

(7) During boom raising / arm cloud combined operation When the lever 28a is operated so that the boom cylinder 1 extends, the first hydraulic pump 9 is the same as in the above-described boom raising single operation of (5). The discharge side is raised to the flow path 13 side.

  At the same time, when the lever 28b is operated so that the arm cylinder 3 extends, the discharge side of the second hydraulic pump 10 is connected to the flow path as in the boom lowering / arm cloud combined operation (4) described above. The switching valve 40 is fully opened, and the proportional switching valve 44 connects between the check valve 43 and the flow path 47 and between the tank 18 and the flow path 48.

  When hydraulic oil is accumulated in the accumulator 36, the pressure accumulation switching valve 35 is switched to the proportional valve state, the switching valve 40 is switched to the fully open state, and the proportional switching valve 34 is switched to the cutoff state. Further, the opening degree of the pressure accumulation switching valve 35 is adjusted according to the input of the lever 28b, the pressure in the flow path 39 is increased, and the proportional switching valve 44 is connected between the check valve 43 and the flow path 48, The tank 18 and the flow path 47 are connected to each other.

(8) At the time of arm dump single operation When the lever 28b is operated so that the arm cylinder 3 contracts, the second hydraulic pump 10 is the same as in the above-described boom lowering / arm dump combined operation of (3). The discharge side is raised to the flow path 39 side, the switching valve 40 is fully opened, and the proportional switching valve 44 connects between the check valve 43 and the flow path 48 and between the tank 18 and the flow path 47. Is done.

  When hydraulic oil is accumulated in the accumulator 36, the pressure accumulation switching valve 35 is switched to the proportional valve state, the switching valve 40 is switched to the fully open state, and the proportional switching valve 34 is switched to the cutoff state. Further, the opening degree of the pressure accumulation switching valve 35 is adjusted according to the input of the lever 28b, the pressure in the flow path 39 is increased, and the proportional switching valve 44 is connected between the check valve 43 and the flow path 48, The tank 18 and the flow path 47 are connected to each other.

(9) At the time of arm cloud single operation When the lever 28b is operated so that the arm cylinder 3 extends, the second hydraulic pump 10 is the same as the above-described boom lowering / arm cloud combined operation of (4). The discharge side is raised to the flow path 39 side, the switching valve 49 is fully opened, and the proportional switching valve 44 connects between the check valve 43 and the flow path 47 and between the tank 18 and the flow path 48, respectively. Is done.

  When hydraulic oil is accumulated in the accumulator 36, the pressure accumulation switching valve 35 is switched to the proportional valve state, the switching valve 40 is switched to the fully open state, and the proportional switching valve 34 is switched to the cutoff state. Further, the opening degree of the pressure accumulation switching valve 35 is adjusted to increase the pressure in the flow path 39, and at the proportional switching valve 44, between the check valve 43 and the flow path 48 and between the tank 18 and the flow path 47. Are connected to each other.

<Effect>
As described above, according to the excavator 1 according to the second embodiment, the controller 12 controls the first and second hydraulic pumps 9 for each of the nine operation modes in accordance with the operation of the levers 28a and 28b. 10, the switching valve 40, the proportional switching valves 34 and 44, and the pressure accumulation switching valve 35 are controlled. Then, regenerative energy when the first hydraulic pump 9 acts as a hydraulic motor is transmitted to and driven by the second hydraulic pump 10, and the hydraulic oil discharged from the second hydraulic pump 10 is accumulator 36. To accumulate pressure.

  Even when the hydraulic oil cannot be stored in the accumulator 36, the regenerative energy when the first hydraulic pump 9 acts as a hydraulic motor can be used to drive the second hydraulic pump 10, and this first The energy of the hydraulic oil discharged from the two-hydraulic pump 10 can be consumed as heat energy when passing through the proportional switching valve 34. Therefore, even when the hydraulic circuit for driving the arm cylinder 3 is the open circuit 110, the same effects as those of the first embodiment can be obtained.

[Third Embodiment]
FIG. 7 is a hydraulic circuit diagram showing a drive control apparatus according to the third embodiment of the present invention. The third embodiment is different from the first embodiment described above in that the first embodiment is different from the hydraulic drive control device 106 configured by two closed circuits 107 and 108 in the third embodiment. The hydraulic drive control device 106B has a configuration in which one open circuit 110 is added to two closed circuits 107 and 108. In the third embodiment, the same or corresponding parts as those in the first and second embodiments are denoted by the same reference numerals.

<Configuration>
Specifically, in the third embodiment, as shown in FIG. 7, the open circuit 110 of the second embodiment is combined with the closed circuits 107 and 108 of the first embodiment. The open circuit 110 is configured to drive the bucket cylinder 5. The flow path 47 of the open circuit 110 is connected to a head chamber 5a for extending a cylinder rod 5d attached to the cylinder 5c of the bucket cylinder 5 so as to be extendable and contractible. The flow path 48 of the open circuit 110 is connected to a rod chamber 5b for retracting the cylinder rod 5d of the bucket cylinder 5.

  Furthermore, the open circuit 110 includes a third hydraulic pump 38 configured in the same manner as the second hydraulic pump 10, and the third hydraulic pump 38 is connected to the power transmission device 8. The third hydraulic pressure pump 38 is provided with a regulator 38a for adjusting the inclination angle of the both inclined swash plates of the both inclined swash plate mechanisms of the third hydraulic pressure pump 38. Furthermore, the open circuit 110 includes a proportional switching valve 34 a configured similarly to the proportional switching valve 34, a pressure accumulation switching valve 35 a configured similar to the pressure accumulation switching valve 35, and an accumulator 36 a configured similar to the accumulator 36. The relief valve 37a is configured in the same manner as the relief valve 37.

  For example, when the first hydraulic pump 9 is driven as a hydraulic motor and converted into regenerative energy by hydraulic oil discharged from the boom cylinder 1, the power transmission device 8 includes the second and third hydraulic pumps 10, 38, the second or third hydraulic pump 10, 38 that is not used for driving the arm cylinder 3 or the bucket cylinder 5 is preferentially selected, and the selected second or third hydraulic pump 10, 38 is driven by regenerative energy. That is, the power transmission device 8 further drives the second hydraulic pump 10 that drives the arm cylinder 3 that can supply hydraulic oil or the third hydraulic pump 38 that drives the bucket cylinder 5 with regenerative energy. Then, the hydraulic oil discharged from the second or third hydraulic pumps 10, 38 flows into the accumulators 36, 36a or the proportional control valves 34, 34a and is consumed.

<Action>
Next, the operation of the hydraulic drive control device 106B mounted on the hydraulic excavator 1 according to the third embodiment will be described.

(1) During boom lowering alone operation When the boom cylinder 1 is contracted by the lever 28a (when the boom is lowered), the discharge side of the first hydraulic pump 9 is raised to the flow path 14 side, and the boom cylinder 1 The hydraulic oil discharged from the head chamber 1a flows into the first hydraulic pump 9, and the first hydraulic pump 9 acts as a hydraulic motor.

  At this time, the controller 12 calculates the regenerative energy based on the pressure difference between the hydraulic fluid on the suction side and the discharge side of the first hydraulic pump 9 and the rotational speed of the first hydraulic pump 9. Next, when the calculated regenerative energy can be absorbed and accumulated by any one of the accumulators 36 and 36a, the controller 12 compares the internal pressure of the accumulator 36 with the internal pressure of the accumulator 36a. Then, the second or third hydraulic pumps 10 and 38 connected to the accumulators 36 and 36 a on the lower internal pressure are driven by the regenerative energy converted by the first hydraulic pump 9. Subsequently, the regenerative energy converted by the first hydraulic pump 9 can be consumed by sending the hydraulic oil discharged from the second or third hydraulic pumps 10 and 38 to the accumulators 36 and 36a and accumulating it, It becomes possible to suppress the overrev of the engine 7.

  On the other hand, when the internal pressure of the accumulator 36 and the internal pressure of the accumulator 36a are equal, for example, the third hydraulic pump 38 for driving the bucket 6 that is operated less frequently at the same time as the boom 2 lowering operation is driven by regenerative energy. Then, the hydraulic oil discharged from the third hydraulic pump 38 is sent to the accumulator 36 a to accumulate pressure, and the regenerative energy converted by the first hydraulic pump 8 is consumed, and overrev of the engine 7 is suppressed.

  When the calculated regenerative energy cannot be absorbed by any one of the accumulators 36 and 36a, each of the second and third hydraulic pumps 10 and 38 is driven by the regenerative energy. Then, the hydraulic oil discharged from the second and third hydraulic pumps 10 and 38 is sent to the accumulators 36 and 36a to accumulate pressure, and the regenerative energy converted by the first hydraulic pump 9 is consumed, and the engine 7 Suppresses overrev.

  Further, when either one of the accumulators 36, 36a is in a saturated state, the third or second hydraulic pump 38, 10 connected to the other accumulator 36a, 36 is driven with regenerative energy. The hydraulic oil discharged from the third or second hydraulic pumps 38 and 10 is discharged to the tank 18 via the proportional switching valves 34a and 34, and passes through the proportional switching valves 34a and 34. It is converted into thermal energy and consumed, and the overrev of the engine 7 is suppressed.

(2) During combined boom and arm operation When the boom is lowered, the first hydraulic pump 9 is driven as a hydraulic motor by the hydraulic oil discharged from the head chamber 1a of the boom cylinder 1, and is discharged from the head chamber 1a. The energy that oil has is converted into regenerative energy. At this time, when the arm 4 is operated, when the pressure of the hydraulic fluid on the suction side of the second hydraulic pump 10 is lower than the pressure of the hydraulic fluid on the discharge side of the second hydraulic pump 10, By driving the second hydraulic pump 10 with regenerative energy, this regenerative energy can be consumed, and overrev of the engine 7 can be suppressed.

  On the other hand, when the regenerative energy converted by the first hydraulic pump 9 is larger than the drive energy necessary for driving the second hydraulic pump 10, the regenerative energy is necessary for driving the second hydraulic pump 10. The third hydraulic pump 38 is driven with the remaining regenerative energy obtained by subtracting the drive energy. Then, the hydraulic oil discharged from the third hydraulic pump 38 is sent to the accumulator 36 a to accumulate pressure, thereby consuming regenerative energy and suppressing overrev of the engine 7.

  Further, when the pressure of the hydraulic fluid on the suction side of the second hydraulic pump 10 is higher than the pressure of the hydraulic fluid on the discharge side of the second hydraulic pump 10, the hydraulic fluid discharged from the arm cylinder 3 is used. The second hydraulic pump 10 is driven as a hydraulic motor to convert the energy of the hydraulic oil discharged from the arm cylinder 3 into regenerative energy. The third hydraulic pump 38 is driven by this regenerative energy. Then, the hydraulic oil discharged from the third hydraulic pump 38 is sent to the accumulator 36 a to accumulate pressure, and the regenerative energy generated by the second hydraulic pump 10 is consumed, and the overrev of the engine 7 is suppressed.

  Further, when the accumulator 36a is in a saturated state, the third hydraulic pump 38 connected to the accumulator 36a is driven with regenerative energy, and the hydraulic oil discharged from the third hydraulic pump 38 is supplied to the proportional switching valve 34a. Is discharged to the tank 18 to convert the energy of the hydraulic oil into heat energy when passing through the proportional switching valve 34a, thereby suppressing overrev of the engine 7.

  Further, when operating the arm 4 when raising the boom, when the pressure of hydraulic fluid on the suction side of the second hydraulic pump 10 is higher than the pressure of hydraulic fluid on the discharge side of the second hydraulic pump 10, The second hydraulic pump 10 is driven as a hydraulic motor by the hydraulic oil discharged from the arm cylinder 3, and the energy of the hydraulic oil discharged from the arm cylinder 3 is converted into regenerative energy. And the 1st hydraulic pump 9 is driven with this regenerative energy, the regenerative energy converted with the 2nd hydraulic pump 10 is consumed, and the overrev of the engine 7 is suppressed.

(3) At the time of boom / arm / bucket combined operation When the boom is lowered, the hydraulic fluid discharged from the head chamber 1a of the boom cylinder 1 drives the first hydraulic pump 9 as a hydraulic motor to discharge from the head chamber 1a. The energy of the hydraulic oil to be converted is converted into regenerative energy. At this time, when the arm 4 is operated, if the pressure of the hydraulic fluid on the suction side of the second hydraulic pump 10 is lower than the pressure of the hydraulic fluid on the discharge side of the second hydraulic pump 10, The two-hydraulic pump 10 is driven by regenerative energy to consume this regenerative energy and suppress the overrev of the engine 7.

  On the other hand, when the regenerative energy converted by the first hydraulic pump 9 is larger than the drive energy necessary for driving the second hydraulic pump 10, the regenerative energy is necessary for driving the second hydraulic pump 10. The third hydraulic pump 38 is driven with the remaining regenerative energy obtained by subtracting the drive energy. Then, the hydraulic oil discharged from the third hydraulic pump 38 is sent to the bucket cylinder 5 and driven to consume regenerative energy. Therefore, since transmission of this regenerative energy to the engine 7 can be more efficiently suppressed, overrev of the engine 7 can be more efficiently suppressed.

  Furthermore, when the pressure of the hydraulic fluid on the suction side of the second hydraulic pump 10 is higher than the pressure of the hydraulic fluid on the discharge side of the second hydraulic pump 10 during the arm operation, the hydraulic fluid is discharged from the arm cylinder 3. The second hydraulic pump 10 is driven by hydraulic oil as a hydraulic motor to convert the energy of the hydraulic oil discharged from the arm cylinder 3 into regenerative energy, and the third hydraulic pump 38 is converted by this regenerative energy. Drive. Then, the hydraulic oil discharged from the third hydraulic pump 38 is sent to the bucket cylinder 5 to be driven, the regenerative energy converted by the second hydraulic pump 10 is consumed, and the overrev of the engine 7 is suppressed.

  In this case, when the regenerative energy converted by the second hydraulic pump 10 is larger than the driving energy required for driving the bucket cylinder 5 by the third hydraulic pump 38, the proportional control valve 44 causes the bucket cylinder 5 to The remaining hydraulic oil is sent to the accumulator 36a to accumulate pressure while controlling the flow rate of the hydraulic oil supplied to. As a result, the driving energy of the third hydraulic pump 38 can be increased, the regenerative energy can be consumed, and the overrev of the engine 7 can be suppressed.

  Further, when the accumulator 36a is in a saturated state, the third hydraulic pump 38 connected to the accumulator 36a is driven with regenerative energy. Then, the hydraulic oil discharged from the third hydraulic pump 38 is discharged to the tank 18 through the proportional switching valve 34a, converted into thermal energy, consumed, and the overrev of the engine 7 is suppressed.

<Effect>
As described above, according to the hydraulic excavator 1 according to the third embodiment, the first to third hydraulic pumps 9, 10, 38 and the proportional switching valves 32, 33, 34 are operated according to the operation of the levers 28a, 28b. , 34a, the switching valve 40, and the pressure accumulation switching valves 35, 35a. Then, the regenerative energy when the first or second hydraulic pump 9 or 10 acts as a hydraulic motor is transmitted to the second or third hydraulic pump 10 or 38 and accumulated in the accumulators 36 or 36a. Even if the accumulators 36 and 36a cannot accumulate pressure, the regenerative energy is used to drive the second or third hydraulic pumps 10 and 38 and is passed through the proportional switching valves 34 and 34a as heat energy. Consume. Therefore, even in the hydraulic pressure drive control device 106B in which the plurality of closed circuits 107 and 108 and the open circuit 110 are combined, the same operational effects as those in the first embodiment can be obtained.

[Others]
In addition, this invention is not limited to embodiment mentioned above, Various deformation | transformation aspects are included. For example, the above-described embodiments have been described in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described.

  The first embodiment is a hydraulic drive control device 106 that combines two closed circuits 107 and 108, and the second embodiment is a hydraulic drive control device 106A that combines an open circuit 110 with a closed circuit 107. In the third embodiment, the hydraulic drive control device 106B is a combination of two closed circuits 107 and 108 and one closed circuit 110. However, the first or second hydraulic pump 9 is driven as a hydraulic motor and converted into regenerative energy. If the fluid pressure circuit including 10 is a closed circuit 107, the closed circuits 107 and 108 and the open circuit 110 can be combined as necessary.

  Further, although the proportional switching valves 34 and 34a and the accumulators 36 and 36a are used as means for generating the load pressure, only the proportional switching valves 34 and 34a are used, and the second or third hydraulic pumps 10 and 38 are regenerated with regenerative energy. The hydraulic oil discharged from the second or third hydraulic pumps 10 and 38 can be sent to the proportional switching valves 34 and 34a, and the energy of the hydraulic oil can be converted into heat energy and consumed. Furthermore, as an energy storage unit for storing energy, instead of accumulators 36 and 36a, a hydraulic motor, an electric motor / generator driven by the hydraulic motor, and electric power generated by the electric motor / generator are stored. And a battery to be provided. In this case, the hydraulic motor is driven by the hydraulic oil discharged when the second or third hydraulic pump 10, 38 is driven by regenerative energy, and the electric motor / generator is driven by this hydraulic motor. The electric power generated by the motor / generator is stored in the battery and consumed.

  Further, in each of the above embodiments, the operation of combining the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 has been described. However, the present invention is not limited to this, and the boom cylinder 1, the arm cylinder 3, and the bucket cylinder 5 are not limited thereto. In addition, for example, other hydraulic actuators such as a swing motor that drives the swing device 104 and a travel motor that drives the travel device of the lower traveling body 102 may be applied in appropriate combination. Moreover, it can also be set as the structure which drives the arm cylinder 3 or the bucket cylinder 5 directly with the hydraulic fluid accumulated in the accumulators 36 and 36a.

  In each of the above embodiments, the crawler hydraulic excavator 1 has been described as a working machine. However, the present invention is not limited to this, and for example, a hydraulic actuator such as a wheel loader, a wheel excavator, or a crane. Various working machines to be driven and working machines such as an electric excavator driven by an electric motor instead of the engine 7 can also be used.

1 Boom cylinder (fluid pressure actuator for closed circuit)
1a Head chamber 1b Rod chamber 1c Cylinder 1d Cylinder rod 2 Boom 3 Arm cylinder (Liquid pressure actuator)
3a Head chamber 3b Rod chamber 3c Cylinder 3d Cylinder rod 4 Arm 5 Bucket cylinder (Liquid pressure actuator)
5a Head chamber 5b Rod chamber 5c Cylinder 5d Cylinder rod 6 Bucket 7 Engine (drive source)
8 Power transmission device (power transmission part)
9 First hydraulic pump (liquid pressure pump for closed circuit)
9a Regulator 10 Second hydraulic pump (fluid pressure pump)
10a regulator 11 charge pump 12 controller 13 flow path 14 flow path 15 flow path 16 flow path 17a, 17b check valve 18 tank 19a, 19b relief valve 20 flushing valve 21 charge check valve 22 charge relief valve 23 flow path 24 flow path 25 flow path 26 flow path 27a, 27b check valve 28a, 28b lever 29a, 29b relief valve 30 flushing valve 31 charge check valve 32 proportional switching valve 33 proportional switching valve 34, 34a proportional switching valve (load pressure generating section, pressure loss) Part)
35, 35a Accumulation pressure switching valve 36, 36a Accumulator (load pressure generation unit, energy storage unit)
37, 37a Relief valve 38 Third hydraulic pump (fluid pressure pump)
38a Regulator 39 Flow path 40 Switching valve 43 Check valve 44 Proportional switching valve 45 Counter balance valve 47 Flow path 48 Flow path 100 Hydraulic excavator (work machine)
101 Lower traveling body 102 Upper turning body (work machine main body)
DESCRIPTION OF SYMBOLS 130 Cab 104 Turning apparatus 105 Front work machine 106, 106A, 106B Hydraulic drive control apparatus 107 Closed circuit 108 Closed circuit (fluid pressure circuit)
109 Flow path switching unit 110 Open circuit (fluid pressure circuit)

Claims (4)

The work machine body,
A drive source provided in the work machine body,
A fluid pressure pump driven by the drive source, a fluid pressure actuator driven by a fluid discharged from the fluid pressure pump, a load pressure generating section for generating a load pressure on the discharge side of the fluid pressure pump, and the A fluid pressure circuit having a flow path switching unit that switches a flow path of fluid discharged from a fluid pressure pump to either the fluid pressure actuator or the load pressure generation unit;
A closed circuit fluid pressure pump driven by the drive source and capable of controlling a discharge flow rate and a discharge direction, and a closed circuit fluid pressure actuator driven by a fluid discharged from the closed circuit fluid pressure pump. Closed circuit,
A power transmission unit for transmitting power of the closed-circuit fluid pressure pump to the fluid pressure pump;
A work machine characterized by comprising: The work machine according to claim 1,
A tank for storing fluid discharged from the fluid pressure pump;
A flow path connecting the tank and the fluid pressure pump,
The work pressure generation unit is a pressure loss unit provided on the flow path. The work machine according to claim 1 or 2,
The working machine, wherein the load pressure generation unit is an energy storage unit that stores energy of fluid discharged from the fluid pressure pump. The work machine according to any one of claims 1 to 3,
A plurality of fluid pressure circuits;
When the closed circuit fluid pressure pump is driven by the fluid discharged from the closed circuit fluid pressure actuator, the power transmission unit includes the fluid pressure pumps of the plurality of fluid pressure circuits. The fluid pressure pump that is not used for driving the fluid pressure actuator is preferentially selected, the selected fluid pressure pump is driven, and the fluid to be discharged is caused to flow into the load pressure generating section. machine.

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