Hydraulic drive device

Abstract

A hydraulic drive device for supplying a hydraulic fluid to a plurality of hydraulic cylinders including a first hydraulic cylinder, the hydraulic drive device being provided with: a plurality of hydraulic drive systems that correspond to each of the plurality of hydraulic cylinders and supply the hydraulic fluid to the corresponding hydraulic cylinders; and at least one communication valve that communicates the plurality of hydraulic drive systems with each other in accordance with an input communication command, each of the plurality of hydraulic drive systems including a hydraulic drive motor, an electric motor, a directional control valve, and a first hydraulic drive system that is a hydraulic drive system corresponding to the first hydraulic cylinder, and a second hydraulic drive system that is a hydraulic drive system corresponding to the second hydraulic cylinder. Comprising a first direction control valve as a direction control valve, and the first direction control valve enables the working fluid to flow from the first hydraulic cylinder to the hydraulic pump motor according to an input first operation command.

Description

Technical Field

[0001] The present invention relates to a hydraulic drive device for supplying working fluid to a hydraulic cylinder. Background Art

[0002] A hydraulic drive device drives a hydraulic cylinder by supplying working fluid to the hydraulic cylinder. For example, a known hydraulic drive device is disclosed in Patent Document 1. The drive device disclosed in Patent Document 1 includes multiple drive circuits. One of the multiple drive circuits includes a pump motor that generates electricity using return fluid from the hydraulic cylinder. Meanwhile, the other drive circuits are operated by the electricity generated by the pump motor. More specifically, the other drive circuits include electric pumps. The generated electricity then drives the electric pumps.

[0003] Prior art literature: Patent Literature: Patent Document 1: Japanese Patent Application Laid-Open No. 2004-190845. Summary of the Invention

[0004] Problems to be solved by the invention: The drive device of Patent Document 1 uses a pump-motor with a capacity that corresponds to the flow rate of fluid returning from the fluid pressure actuator, i.e., the return flow rate. Therefore, a pump-motor with a capacity that corresponds to the size of the hydraulic cylinder must be used. This makes miniaturization of the pump-motor difficult.

[0005] Therefore, an object of the present invention is to provide a hydraulic drive device capable of reducing the size of a hydraulic pump and motor.

[0006] Means of solving the problem: The hydraulic drive device of the present invention is a hydraulic drive device that supplies working fluid to multiple hydraulic cylinders including a first hydraulic cylinder, and is equipped with: multiple hydraulic drive systems, which respectively correspond to the multiple hydraulic cylinders and supply working fluid to the corresponding hydraulic cylinders; and at least one connecting valve, which connects the multiple hydraulic drive systems to each other according to an input connection instruction, and the multiple hydraulic drive systems each include: a hydraulic pump motor, which rotates when discharging working fluid and being supplied with working fluid; an electric motor, which drives the hydraulic pump motor by rotation so that the working fluid is discharged from the hydraulic pump motor and generates electricity by being driven by the rotation of the hydraulic pump motor; and a directional control valve, which switches the flow direction of the working fluid flowing between the hydraulic pump motor and the corresponding hydraulic cylinder according to an action instruction. The first hydraulic drive system corresponding to the first hydraulic cylinder includes a first directional control valve as the directional control valve, and the first directional control valve causes the working fluid to flow from the first hydraulic cylinder to the hydraulic pump motor according to the input first action instruction.

[0007] According to the present invention, at least one connecting valve is provided for interconnecting multiple hydraulic drive systems in response to an input connection command. Therefore, when a connection command is output to the connecting valve while the working fluid is flowing from the first hydraulic cylinder to the hydraulic pump and motor via the first directional control valve, the working fluid returning from the first hydraulic cylinder can be distributed to the hydraulic pumps and motors of the multiple hydraulic drive systems. Consequently, the working fluid returning from the first hydraulic cylinder can be regenerated by the multiple hydraulic pumps and motors. Consequently, the capacity of the first hydraulic pump and motor can be reduced, thereby miniaturizing the first hydraulic pump and motor.

[0008] Effects of the invention: According to the present invention, the hydraulic pump and motor can be reduced in size.

[0009] The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 1 is a circuit diagram showing the structure of the hydraulic drive device of this embodiment; Figure 2 It shows Figure 1 Flowchart of the sequence of the boom regeneration method of the hydraulic drive device. DETAILED DESCRIPTION

[0011] A hydraulic drive device 1 according to an embodiment of the present invention will be described below with reference to the aforementioned drawings. The directional concepts used in the following description are for ease of explanation and do not limit the orientation of the structure of the invention to these directions. The hydraulic drive device 1 described below is merely one embodiment of the present invention. Therefore, the present invention is not limited to the embodiment described above, and additions, deletions, and modifications may be made without departing from the spirit of the invention.

[0012] Figure 1 The hydraulic drive device 1 shown is equipped on, for example, a work vehicle (not shown). Work vehicles include construction vehicles such as hydraulic excavators and hydraulic cranes, and industrial vehicles such as lifts. In the present embodiment, the work vehicle is a hydraulic excavator. The hydraulic excavator is provided with a plurality of hydraulic cylinders 3 to 5 for moving an attachment. In the present embodiment, the attachment of the hydraulic excavator is a bucket, and the hydraulic excavator is provided with at least a boom cylinder 3 as a first hydraulic cylinder, a bucket cylinder 4 as a second hydraulic cylinder, and an arm cylinder 5 as a third hydraulic cylinder. The hydraulic cylinders 3 to 5 are respectively provided on the boom, the bucket, and the arm. The hydraulic excavator moves the bucket separately by extending and retracting the three hydraulic cylinders 3 to 5. As a result, the hydraulic excavator can perform various operations.

[0013] <Hydraulic drive unit> The hydraulic drive system 1 drives hydraulic cylinders 3 to 5. In this embodiment, the hydraulic drive system 1 drives at least the aforementioned boom cylinder 3, bucket cylinder 4, and arm cylinder 5. The hydraulic drive system 1 includes first to third hydraulic drive systems 11 to 13 and two communication valves 14 and 15. Furthermore, the hydraulic drive system 1 includes an operating device 16 and a control device 17.

[0014] Multiple hydraulic drive systems Each hydraulic drive system 11-13 corresponds to a respective hydraulic cylinder 3-5. In this embodiment, the first hydraulic drive system 11 corresponds to the boom cylinder 3, the second hydraulic drive system 12 corresponds to the bucket cylinder 4, and the third hydraulic drive system 13 corresponds to the arm cylinder 5. The hydraulic drive systems 11-13 then supply working fluid (for example, liquids such as oil and water) to the corresponding hydraulic cylinders 3-5. The first to third hydraulic drive systems 11-13 each include a hydraulic pump motor 21, 31, 41, an electric motor 22, 32, 42, and a directional control valve 23, 33, 43, respectively. Furthermore, the first and third hydraulic drive systems 11 and 13 also include regeneration valves 24 and 44. The structures of the first to third hydraulic drive systems 11-13 are described in detail below.

[0015] <First Hydraulic Drive System> The first hydraulic drive system 11 supplies working fluid to the boom cylinder 3. Furthermore, the first hydraulic drive system 11 regenerates the fluid energy of the working fluid discharged from the boom cylinder 3 into electrical energy. Furthermore, the first hydraulic drive system 11 regenerates the working fluid discharged from the head-side port 3a of the boom cylinder 3 to the rod-side port 3b. As described above, the first hydraulic drive system 11 includes a first hydraulic pump-motor 21, a first electric motor 22, and a first directional control valve 23. Furthermore, the first hydraulic drive system 11 also includes a first regeneration valve 24.

[0016] [First hydraulic pump motor] The first hydraulic pump-motor 21 discharges working fluid. Furthermore, the first hydraulic pump-motor 21 rotates when the working fluid is supplied. More specifically, the first hydraulic pump-motor 21 includes a shaft 21a and a pump port 21b. When the shaft 21a is rotationally driven, the first hydraulic pump-motor 21 discharges working fluid from the pump port 21b. On the other hand, when the working fluid is supplied to the pump port 21b, the first hydraulic pump-motor 21 rotates the shaft 21a. Furthermore, in this embodiment, the first hydraulic pump-motor 21 is a variable capacity swash plate pump and includes a regulator 21c. The regulator 21c changes the pump capacity of the first hydraulic pump-motor 21 based on an input first capacity instruction.

[0017] [First motor] The first electric motor 22 drives the first hydraulic pump-motor 21 by rotation, thereby discharging the working fluid from the first hydraulic pump-motor 21. Furthermore, the first electric motor 22 generates electricity by being driven by the first hydraulic pump-motor 21. That is, the first electric motor 22 recovers the fluid energy of the working fluid into electrical energy by cooperating with the first hydraulic pump-motor 21. In more detail, the first electric motor 22 is connected to the shaft 21a. The first electric motor 22 drives the shaft 21a by rotation, thereby discharging the working fluid from the pump port 21b. Furthermore, the first electric motor 22 generates electricity when the first hydraulic pump-motor 21 drives the shaft 21a by rotation. In addition, the first electric motor 22 changes the rotation speed according to the input first rotation speed command.

[0018] [First directional control valve] The first directional control valve 23 is connected to the first hydraulic pump-motor 21 via a pump passage 25. Furthermore, the first directional control valve 23 is connected to the boom cylinder 3. More specifically, the first directional control valve 23 is connected to the head-side port 3a and the rod-side port 3b of the boom cylinder 3. Furthermore, the first directional control valve 23 is connected to the tank 18.

[0019] The first directional control valve 23 switches the flow direction of the hydraulic fluid between the first hydraulic pump-motor 21 and the boom cylinder 3 in response to the input first actuation command. Specifically, the first directional control valve 23 directs the flow of hydraulic fluid from the boom cylinder 3 to the first hydraulic pump-motor 21 in response to the input first actuation command. Furthermore, the first directional control valve 23 directs the flow of hydraulic fluid from the first hydraulic pump-motor 21 to the boom cylinder 3 (in this embodiment, the head-side port 3a of the boom cylinder 3) in response to the first actuation command. Furthermore, in this embodiment, the first directional control valve 23 directs the flow of hydraulic fluid in either the head-side supply direction or the rod-side supply direction in response to the input first actuation command. The head-side supply direction refers to the flow of hydraulic fluid from the first hydraulic pump-motor 21 to the head-side port 3a, while the rod-side supply direction refers to the flow of hydraulic fluid from the first hydraulic pump-motor 21 to the rod-side port 3b. Furthermore, the first directional control valve 23 can block the flow between the first hydraulic pump-motor 21 and the boom cylinder 3. Furthermore, the opening degree of the first directional control valve 23 is controlled according to the first operation command when regenerating the hydraulic fluid from the boom cylinder 3 to the first hydraulic pump-motor 21 .

[0020] [First regeneration valve] The first regeneration valve 24 is connected to the head-side port 3a and the rod-side port 3b of the boom cylinder 3. The first regeneration valve 24 connects the head-side port 3a with the rod-side port 3b in response to a first regeneration command. Furthermore, when the head-side port 3a and the rod-side port 3b are connected, the first regeneration valve 24 allows the flow of working fluid in the first regeneration direction and blocks flow in the opposite direction. The first regeneration direction refers to flow from the head-side port 3a to the rod-side port 3b. Thus, when the first regeneration valve 24 supplies working fluid to the rod-side port 3b, the working fluid discharged from the head-side port 3a is regenerated in the rod-side port 3b.

[0021] Second hydraulic drive system The second hydraulic drive system 12 supplies hydraulic fluid to the bucket cylinder 4. As described above, the second hydraulic drive system 12 includes a second hydraulic pump-motor 31, a second electric motor 32, and a second directional control valve 33. Furthermore, the second hydraulic pump-motor 31 and the second electric motor 32 have the same structure as the aforementioned first hydraulic pump-motor 21 and the first electric motor 22. Therefore, regarding the structure of the second hydraulic pump-motor 31 and the second electric motor 32, reference will be made to the description of the aforementioned first hydraulic pump-motor 21 and the first electric motor 22, and their detailed description will be omitted. Furthermore, the regulator 31c of the second hydraulic pump-motor 31 changes the discharge flow rate according to the second capacity instruction, and the second electric motor 32 changes the speed according to the second speed instruction.

[0022] [Second directional control valve] The second directional control valve 33 is connected to the second hydraulic pump-motor 31 via a pump passage 35 and is also connected to the bucket cylinder 4. The second directional control valve 33 switches the flow direction of the hydraulic fluid between the second hydraulic pump-motor 31 and the bucket cylinder 4 in response to a second actuation command. More specifically, the second directional control valve 33 connects the second hydraulic pump-motor 31 to one of the rod-side port 4a and the head-side port 4b of the bucket cylinder 4 in response to the second actuation command. Furthermore, the second directional control valve 33 connects the other of the rod-side port 4a and the head-side port 4b to the tank 18 in response to the second actuation command. Thus, the second directional control valve 33 directs the hydraulic fluid discharged from the second hydraulic pump-motor 31 toward one of the rod-side port 4a and the head-side port 4b. Furthermore, the second directional control valve 33 can block the flow between the second hydraulic pump-motor 31 and the bucket cylinder 4.

[0023] <Third hydraulic drive system> The third hydraulic drive system 13 supplies working fluid to the boom cylinder 5. Furthermore, the third hydraulic drive system 13 regenerates the working fluid discharged from the rod-side port 5a of the boom cylinder 5 to the head-side port 5b. As previously described, the third hydraulic drive system 13 includes a third hydraulic pump-motor 41, a third electric motor 42, and a third directional control valve 43. Furthermore, the third hydraulic drive system 13 also includes a second regeneration valve 44. Furthermore, the third hydraulic pump-motor 41 and the third electric motor 42 have the same structure as the aforementioned first hydraulic pump-motor 21 and the first electric motor 22. Therefore, regarding the structure of the third hydraulic pump-motor 41 and the third electric motor 42, refer to the description of the aforementioned first hydraulic pump-motor 21 and the first electric motor 22, and their detailed description will be omitted. Furthermore, the regulator 41c of the third hydraulic pump-motor 41 changes the discharge flow rate according to the third capacity instruction, and the third electric motor 42 changes the speed according to the third speed instruction.

[0024] [Third directional control valve] The third directional control valve 43 is connected to the third hydraulic pump motor 41 via the pump channel 45, and is also connected to the boom cylinder 5. The third directional control valve 43 switches the flow direction of the working fluid flowing between the third hydraulic pump motor 41 and the boom cylinder 5 according to the third action instruction. Specifically, the third directional control valve 43 switches the flow direction of the working fluid from the third hydraulic pump motor 41 to one of the rod side port 5a and the head side port 5b of the boom cylinder 5 according to the third action instruction. In addition, the third directional control valve 43 connects the other side of the rod side port 5a and the head side port 5b to the tank 18. In addition, the third directional control valve 43 can cut off the connection between the third hydraulic pump motor 41 and the boom cylinder 5 according to the third action instruction.

[0025] [Second regeneration valve] The second regeneration valve 44 is connected to the rod-side port 5a and the head-side port 5b of the boom cylinder 5. The second regeneration valve 44 connects the rod-side port 5a and the head-side port 5b in response to the second regeneration command. Furthermore, when the rod-side port 5a and the head-side port 5b are connected, the second regeneration valve 44 allows the flow of working fluid in the second regeneration direction and blocks flow in the opposite direction. The second regeneration direction refers to flow from the rod-side port 5a to the head-side port 5b. Thus, when the second regeneration valve 44 supplies working fluid to the head-side port 5b, the working fluid discharged from the rod-side port 5a is regenerated in the head-side port 5b.

[0026] <Connecting valve> The two connecting valves 14 and 15 connect the first to third hydraulic drive systems 11 to 13 to each other according to the input connection instruction. In more detail, the first connecting valve 14 is connected to the pump channel 25 of the first hydraulic drive system 11 and the pump channel 35 of the second hydraulic drive system 12. The first connecting valve 14 is opened according to the input first connection instruction. As a result, the two pump channels 25 and 35 are connected, so the working fluid can flow back and forth between the pump channels 25 and 35. The second connecting valve 15 is connected to the pump channel 35 of the second hydraulic drive system 12 and the pump channel 45 of the third hydraulic drive system 13. The second connecting valve 15 connects the two pump channels 35 and 45 according to the input second connection instruction. As a result, the working fluid can flow back and forth between the pump channels 35 and 45.

[0027] <Operating device> The operating device 16 is operated by a driver or the like to move the boom cylinder 3, bucket cylinder 4, and arm cylinder 5. Specifically, the operating device 16 can operate each cylinder 3-5 individually. The operating device 16 outputs an operating signal corresponding to the direction and amount of operation (hereinafter referred to as the "operation state") of each operation performed on each cylinder 3-5 (hereinafter referred to as "each operation"). The operating device 16 includes, for example, a plurality of operating levers 16a and 16b. In this embodiment, the operating device 16 includes two operating levers 16a and 16b. The operating levers 16a and 16b can be operated in various directions (for example, tilting). The operating device 16 outputs an operating signal based on the direction (for example, the tilting direction) and amount (for example, the tilting amount) of each operating lever 16a and 16b as the operation state of each operation. Alternatively, the operating device 16 may take other forms, such as an operating panel, and may output operating signals based on operations performed on the operating panel or a pre-stored program.

[0028] <Control device> The control device 17 receives an operation signal from the operating device 16. The control device 17 then outputs an operation command to the first to third hydraulic drive systems 11 to 13, respectively, based on the operating status of each operation, thereby controlling the operation of the directional control valves 23, 33, and 43. More specifically, the control device 17 outputs a first operation command based on the operating status of a first operation on the boom cylinder 3, thereby operating the first directional control valve 23. Furthermore, the control device 17 outputs a second operation command based on the operating status of a second operation on the bucket cylinder 4, thereby operating the second directional control valve 33. Furthermore, the control device 17 outputs a third operation command based on the operating status of a third operation on the arm cylinder 5, thereby operating the third directional control valve 43.

[0029] The control device 17 operates the first regeneration valve 24 by outputting a first regeneration command. The control device 17 operates the second regeneration valve 44 by outputting a second regeneration command. The control device 17 outputs first and second communication commands based on the operating states of the first to third operations. Consequently, the control device 17 opens and closes the first and second communication valves 14 and 15.

[0030] The control device 17 controls the discharge flow rate or intake flow rate of the hydraulic pump-motor 21, 31, and 41, respectively, by controlling the operation of the electric motors 22, 32, and 42 and the regulators 21c, 31c, and 41c. For example, the control device 17 calculates the discharge flow rate or intake flow rate of the hydraulic pump-motor 21, 31, and 41, respectively, based on the operating state of each operation. Based on the calculated discharge flow rate or intake flow rate, the control device 17 calculates the rotational speed of each electric motor 22, 32, and 42 and the pump capacity of each hydraulic pump-motor 21, 31, and 41, respectively. The control device 17 then outputs first to third rotational speed commands corresponding to the rotational speed to each electric motor 22, 32, and 42, and outputs first to third capacity commands corresponding to the pump capacity to each hydraulic pump-motor 21, 31, and 41, respectively. Thus, the control device 17 controls the discharge flow rate or intake flow rate of the hydraulic pump-motor 21, 31, and 41, respectively, based on the operating state of each operation.

[0031] <Operation of the hydraulic drive unit> In the hydraulic drive system 1, when the operating device 16 is operated (in this embodiment, the operating levers 16a and 16b are operated), an operating signal corresponding to the operating state of each operation is output from the operating device 16. After the operating signal is output, the control device 17 causes each cylinder 3 to 5 to extend or retract in a direction corresponding to the operating direction of each operation and at a speed corresponding to the amount of operation of each operation.

[0032] To explain in more detail, the control device 17 outputs speed commands corresponding to the operating state of each operation to the electric motors 22, 32, and 42. Furthermore, the control device 17 outputs displacement commands corresponding to the operating state of each operation to the hydraulic pump-motors 21, 31, and 41, respectively. Consequently, the control device 17 causes the electric motors 22, 32, and 42 and the hydraulic pump-motors 21, 31, and 41 to discharge or inhale hydraulic fluid at a flow rate corresponding to the amount of operation of each operation, in accordance with the operating direction of each operation. Furthermore, the control device 17 outputs motion commands corresponding to the operating state of each operation to each hydraulic drive system 11-13. In this manner, the directional control valves 23, 33, and 43 connect the hydraulic pump-motor 21, 31, and 41 to the corresponding hydraulic cylinders 3-5. Consequently, each cylinder 3-5 expands and contracts in a direction corresponding to the operating direction of each operation and at a speed corresponding to the amount of operation. The following describes the expansion and contraction of each cylinder in response to each operation.

[0033] [Extension action of each cylinder] For example, when a first operation (specifically, a boom-up operation) is performed on the operating device 16 to extend the boom cylinder 3, the control device 17 outputs a first speed command and a first displacement command corresponding to the operating state of the first operation. Consequently, hydraulic fluid is discharged from the first hydraulic pump-motor 21 at a flow rate corresponding to the amount of operation of the first operation. Furthermore, the control device 17 outputs a first motion command to the first hydraulic drive system 11 based on the operating state of the first operation. This connects the first hydraulic pump-motor 21 to the head-side port 3a of the boom cylinder 3 via the first directional control valve 23. This switches the flow direction of the hydraulic fluid to the head-side supply direction. Furthermore, in this embodiment, during the boom-up operation, the opening between the first hydraulic pump-motor 21 and the head-side port 3a is fully open. Therefore, hydraulic fluid flows in the head-side supply direction at a flow rate corresponding to the amount of operation of the first operation. Consequently, the boom cylinder 3 extends at a speed corresponding to the amount of operation of the first operation.

[0034] Furthermore, when the amount of operation of the first operation is greater than a predetermined boom confluence threshold, the control device 17 opens the first connecting valve 14. Furthermore, the control device 17 outputs a second speed command and a second capacity command corresponding to the operating state of the first operation. Thus, in addition to the first hydraulic pump-motor 21, the second hydraulic pump-motor 31 also discharges working fluid. The working fluids discharged from the hydraulic pump-motor 21 and 31 respectively merge with each other through the first connecting valve 14 and are supplied to the boom cylinder 3 (more specifically, the head-side port 3a). This allows the boom cylinder 3 to be extended at a faster speed. Therefore, the first hydraulic pump-motor 21 can be miniaturized.

[0035] Furthermore, in the hydraulic drive system 1, when a second operation (specifically, a bucket tip-in operation) is performed on the operating device 16 to extend the bucket cylinder 4, the control device 17 outputs a second rotation speed command and a second displacement command based on the operating state of the second operation. Furthermore, the control device 17 outputs a second motion command corresponding to the operating state of the second operation to the second hydraulic drive system 12. Consequently, the bucket cylinder 4 extends at a speed corresponding to the amount of operation of the second operation.

[0036] Furthermore, when a third operation (specifically, an operation to retract the boom) is performed on the operating device 16 in order to extend the boom cylinder 5, the control device 17 operates as follows. That is, the control device 17 calculates the posture of the boom based on the respective angles of the boom and the boom. For example, angle sensors are provided on the boom and the boom, respectively. The control device 17 calculates the posture of the boom based on the detection results obtained from the angle sensors, respectively. Then, the control device 17 determines whether the deadweight of the boom acts in the extension direction based on the calculation result, that is, performs a deadweight extension judgment. Alternatively, the control device 17 may perform a deadweight extension judgment based on the hydraulic pressure of the rod-side port 5a and the head-side port 5b.

[0037] When the arm's own weight is not acting on the arm cylinder 5 in the extension direction, the control device 17 outputs a third action command corresponding to the operating state of the third operation to the third hydraulic drive system 13. This connects the rod-side port 5a to the tank 18 via the third directional control valve 43. Furthermore, the control device 17 controls the opening between the rod-side port 5a and the tank 18 based on the amount of operation of the third operation. Furthermore, the control device 17 outputs a third speed command and a third displacement command corresponding to the operating state of the third operation. As a result, hydraulic fluid at a flow rate corresponding to the amount of operation of the third operation is supplied from the third hydraulic pump-motor 41 to the head-side port 5b and simultaneously discharged from the rod-side port 5a to the tank 18 via the third directional control valve 43. Consequently, the arm cylinder 5 extends at a speed corresponding to the amount of operation of the third operation. Furthermore, as the amount of operation of the third operation increases, the control device 17 opens the second connecting valve 15 to allow the hydraulic fluid from the second hydraulic pump-motor 31 to merge with the hydraulic fluid from the third hydraulic pump-motor 41. This enables faster extension of the arm cylinder 5. Furthermore, when the operation amount of the third operation becomes larger, the control device 17 opens the first communication valve 14 to allow the hydraulic fluid of the first hydraulic pump-motor 21 to merge with the hydraulic fluid of the second hydraulic pump-motor 31. This allows the arm cylinder 5 to be extended more quickly.

[0038] On the other hand, when the deadweight of the boom acts on the boom cylinder 5 in the extension direction, the control device 17 performs boom regeneration processing. That is, the control device 17 opens the second regeneration valve 44 by outputting a second regeneration instruction to the second regeneration valve 44. As a result, the rod side port 5a is connected to the head side port 5b. The control device 17 cuts off the connection between the third hydraulic pump motor 41 and the boom cylinder 5 through the third directional control valve 43. That is, the rod side port 5a, the head side port 5b, the third hydraulic pump motor 41, and the tank 18 are cut off from each other by the third directional control valve 43. As a result, the working fluid discharged from the rod side port 5a can be regenerated in the head side port 5b. In addition, the insufficient working fluid is sucked into the head side port 5b from the replenishment circuit not shown in the figure. As a result, the boom cylinder 5 extends at a speed corresponding to the operation amount of the third operation.

[0039] [Contraction action of each cylinder] When a second operation (specifically, a bucket tilt-out operation) is performed on the operating device 16 to retract the bucket cylinder 4, the control device 17 outputs a second rotational speed command and a second displacement command corresponding to the operating state of the second operation. Furthermore, the control device 17 outputs a second motion command corresponding to the operating state of the second operation to the second hydraulic drive system 12. This connects the second hydraulic pump-motor 31 to the rod-side port 4a of the bucket cylinder 4 via the second directional control valve 33. Consequently, the bucket cylinder 4 retracts at a speed corresponding to the amount of operation of the second operation.

[0040] Furthermore, when a third operation (specifically, an arm extension operation) is performed on the operating device 16 to retract the arm cylinder 5, the control device 17 outputs a third speed command and a third displacement command based on the operating state of the third operation. Furthermore, the control device 17 outputs a third motion command corresponding to the operating state of the third operation to the third hydraulic drive system 13. This connects the third hydraulic pump-motor 41 to the rod-side port 5a of the arm cylinder 5 via the third directional control valve 43. Consequently, the arm cylinder 5 retracts at a speed corresponding to the amount of the third operation.

[0041] Furthermore, when the amount of operation during the third operation exceeds a predetermined boom merging threshold, the control device 17 opens the second connecting valve 15. Furthermore, the control device 17 outputs a second speed command and a second displacement command corresponding to the operating state of the third operation. This causes the second hydraulic pump-motor 31 to discharge hydraulic fluid in addition to the third hydraulic pump-motor 41. The hydraulic fluids discharged from the hydraulic pump-motor 31 and 41 merge through the second connecting valve 15 and are supplied to the boom cylinder 5. This allows the boom cylinder 5 to be retracted at a faster rate.

[0042] [Retraction of the boom cylinder] Furthermore, when the first operation (specifically, the boom lowering operation) is performed on the operating device 16 in order to retract the boom cylinder 3, the control device 17 performs regeneration control. That is, in the hydraulic drive device 1, when the boom cylinder 3 is retracted in order to lower the boom, the fluid energy of the working fluid is regenerated into electrical energy. Furthermore, the control device 17 performs regeneration control while performing regeneration control. That is, in the hydraulic drive device 1, the working fluid discharged from the head side port 3a is regenerated in the rod side port 3b. Furthermore, in the hydraulic drive device 1, the number of hydraulic pump motors 21, 31, 41 used in regeneration is changed according to the operating states (mainly the operating amount) of the first to third operations. Hereinafter, with reference to Figure 2 The flowchart shown here explains the regeneration control by the control device 17. When the first operation is a boom lowering operation, the control device 17 proceeds to step S1.

[0043] In step S1, the regeneration determination process, it is determined whether the first operation variable BO is greater than or equal to a predetermined regeneration start threshold BO1 (i.e., BO ≥ BO1). If the first operation variable BO is less than the regeneration start threshold BO1 (for example, when the operation variable is zero), it is determined that energy regeneration is not required. Thus, regeneration control ends. On the other hand, if the first operation variable BO is greater than or equal to the regeneration start threshold BO1, the process proceeds to step S2.

[0044] In step S2, which is the regeneration start process, energy regeneration is performed using the first hydraulic pump-motor 21. That is, the control device 17 outputs a first drive instruction corresponding to the operating state of the first operation to the first hydraulic drive system 11. In this way, the head side port 3a of the boom cylinder 3 and the first hydraulic pump-motor 21 are connected through the first directional control valve 23. At this time, the control device 17 keeps the connecting valves 14 and 15 closed. As a result, the working fluid returns from the head side port 3a of the boom cylinder 3 to the first hydraulic pump-motor 21. The first hydraulic pump-motor 21 is driven to rotate by the flowing working fluid. As a result, the electric motor 22 generates electricity. Therefore, the fluid energy of the working fluid can be regenerated into electrical energy using the first hydraulic pump-motor 21.

[0045] Furthermore, during regeneration, the control device 17 outputs a first actuation command and simultaneously outputs a first regeneration command to the first regeneration valve 24. This opens the first regeneration valve 24, connecting the rod-side port 3b to the head-side port 3a. Furthermore, by outputting the first actuation command corresponding to the amount of the first operation, the control device 17 controls the opening of the first directional control valve 23 to the opening corresponding to the first actuation command. This limits the flow rate of the working fluid returning from the head-side port 3a to the first hydraulic pump-motor 21, allowing a portion of the working fluid discharged from the head-side port 3a to be regenerated in the rod-side port 3b. Furthermore, the control device 17 outputs a first speed command and a first displacement command based on the amount of the first operation, thereby controlling the flow rate of the working fluid drawn into the first hydraulic pump-motor 21 to the flow rate corresponding to the amount of the first operation. This generates electricity in the first electric motor 22 corresponding to the amount of the first operation. When the first hydraulic pump-motor 21 regenerates the fluid energy of the working fluid into electrical energy, the process proceeds to step S3.

[0046] In step S3, the bucket drive determination process, a determination is made as to whether the second operation variable BU is less than or equal to the first predetermined value BU1 (i.e., BU ≤ BU1). If the second operation variable BU is greater than the first predetermined value BU1 (e.g., when the bucket cylinder 4 is actuated), the process ends. Therefore, during regeneration control, energy regeneration is performed using only the first hydraulic pump-motor 21. On the other hand, if the second operation variable BU is less than or equal to the first predetermined value BU1 (e.g., when the operation variable is zero), the process proceeds to step S4.

[0047] In step S4, the merging determination process, a determination is made as to whether the manipulated variable AM ​​of the third operation is below the aforementioned boom merging threshold AM1 (i.e., AM ≤ AM1). If the manipulated variable AM ​​of the third operation is greater than the boom merging threshold AM1 (for example, when the boom cylinder 5 is rapidly extended), the process ends. Therefore, during regeneration control, only the first hydraulic pump-motor 21 is used for energy regeneration. On the other hand, if the manipulated variable AM ​​of the third operation is below the boom merging threshold AM1, the process proceeds to step S5.

[0048] In step S5, the first operation amount determination process, it is determined whether the first operation amount BO is greater than or equal to a predetermined first communication threshold BO2 (> BO1) (i.e., BO ≥ BO2). If the first operation amount BO is less than the first communication threshold BO2, the process ends. Therefore, during regeneration control, only the first hydraulic pump-motor 21 is used for energy regeneration. On the other hand, if the first operation amount BO is greater than or equal to the first communication threshold BO2, the process proceeds to step S6.

[0049] In step S6, the first connection process, the control device 17 outputs a first connection command to the first connection valve 14. This opens the first connection valve 14, connecting the head-side port 3a of the boom cylinder 3 to the second hydraulic pump-motor 31. Furthermore, the control device 17 maintains isolation between the second hydraulic pump-motor 31 and the bucket cylinder 4 via the second directional control valve 33. This also supplies the hydraulic fluid discharged from the head-side port 3a to the second hydraulic pump-motor 31. Furthermore, the control device 17 outputs first and second speed commands, as well as first and second displacement commands, corresponding to the amount of operation of the first operation. This controls the flow rates of hydraulic fluid drawn into the first and second hydraulic pump-motor 21 and 31, respectively, to flow rates corresponding to the amount of operation of the first operation. Consequently, the first and second electric motors 22 and 32 generate electricity corresponding to the amount of operation of the first operation. When the fluid energy of the hydraulic fluid is recovered as electrical energy by the first and second hydraulic pump-motor 21 and 31, the process proceeds to step S7.

[0050] In step S7, the arm drive determination process, a determination is made as to whether the manipulated amount AM of the third operation is less than or equal to the second predetermined value AM2 (< AM1) (i.e., AM ≤ AM2). If the manipulated amount AM of the third operation is greater than the second predetermined value AM2 (for example, when the arm cylinder 5 is actuated), the process proceeds to step S8. On the other hand, if the manipulated amount AM of the third operation is less than or equal to the first predetermined value AM2 (for example, when the manipulated amount is zero), the process proceeds to step S10.

[0051] In step S8, which is the deadweight extension judgment process, it is determined whether the boom cylinder 5 is extended due to the load. In more detail, the control device 17, similar to the aforementioned deadweight extension judgment, determines whether the deadweight of the boom acts in the direction of extending the boom cylinder 5 during the boom retraction operation. When the control device 17 determines that the third operation is not the boom retraction operation, or the deadweight of the boom does not act in the direction of extending the boom cylinder 5, the process ends. Therefore, in the regeneration control, the first and second hydraulic pump motors 21 and 31 are used to regenerate energy. On the other hand, when the control device 17 determines that the third operation is a boom retraction instruction and the deadweight of the boom acts in the direction of extending the boom cylinder 5, it transfers to step S9.

[0052] In step S9, the arm cylinder regeneration process, the control device 17 executes the aforementioned arm regeneration process. Specifically, the control device 17 outputs a second regeneration command to the second regeneration valve 44, thereby opening the second regeneration valve 44. This allows the hydraulic fluid discharged from the rod-side port 5a to the tank 18 to be regenerated in the head-side port 5b. Once regeneration is complete, the process ends. Therefore, during regeneration control, energy is regenerated using the first and second hydraulic pump-motor 21 and 31.

[0053] In step S10, the second operation amount determination process, a determination is made as to whether the operation amount BO of the first operation is greater than or equal to a predetermined second communication threshold BO3 (>BO2) (i.e., BO ≥ BO3). If the operation amount BO of the first operation is less than the second communication threshold BO3, the process ends. Therefore, during regeneration control, energy regeneration is performed using the first and second hydraulic pump-motor 21 and 31. On the other hand, if the operation amount BO of the first operation is greater than or equal to the second communication threshold BO3, the process proceeds to step S11.

[0054] In the second connection process, the control device 17 outputs a second connection command to the second connection valve 15. This opens the second connection valve 15, connecting the head-side port 3a of the boom cylinder 3 to the third hydraulic pump-motor 41. Furthermore, the control device 17 maintains isolation between the third hydraulic pump-motor 41 and the arm cylinder 5 via the third directional control valve 43. This also supplies the hydraulic fluid discharged from the head-side port 3a to the third hydraulic pump-motor 41. Furthermore, the control device 17 outputs first to third speed commands and first to third displacement commands corresponding to the amount of the first operation. This controls the flow rate of hydraulic fluid drawn into the first to third hydraulic pump-motor 21, 31, and 41, respectively, to a flow rate corresponding to the amount of the first operation. Consequently, the first to third electric motors 22, 32, and 42 generate electricity corresponding to the amount of the first operation. In other words, during regeneration control, energy is regenerated using the first to third hydraulic pump-motor 21, 31, and 41. The process then ends.

[0055] In addition, there are cases where a force application operation is performed during the boom lowering operation. When a force application operation is performed, the control device 17 performs the force application control described below. In addition, regarding whether a force application operation is performed, the control device 17 determines, for example, based on the respective hydraulic pressures of the head side port 3a and the rod side port 3b of the boom cylinder 3. During the force application control, the control device 17 outputs a first speed instruction and a first capacity instruction corresponding to the operating state of the first operation. As a result, working fluid is discharged from the first hydraulic pump-motor 21. In addition, the control device 17 connects the rod side port 3b of the boom cylinder 3 and the first hydraulic pump-motor 21 through the first directional control valve 23, and makes the opening between the rod side port 3b and the first hydraulic pump-motor 21 an opening corresponding to the operating amount of the first operation. As a result, working fluid of a flow rate corresponding to the operating amount of the first operation flows in the rod side supply direction. Therefore, the control device 17 can cause the boom cylinder 3 to retract at a speed corresponding to the operating amount of the first operation.

[0056] The hydraulic drive device 1 of this embodiment is equipped with a first connecting valve 14 that connects the first and second hydraulic drive systems 11 and 12 to each other in response to an input first connecting command. Therefore, when the first directional control valve 23 is used to cause hydraulic fluid to flow from the boom cylinder 3 to the first hydraulic pump-motor 21, the first connecting command is output to the first connecting valve 14. This allows the hydraulic fluid returning from the boom cylinder 3 to be distributed to the first and second hydraulic pump-motor 21 and 31. Consequently, the hydraulic fluid returning from the boom cylinder 3 can be regenerated by the first and second hydraulic pump-motor 21 and 31. This reduces the capacity of the first hydraulic pump-motor 21, leading to a more compact design.

[0057] Furthermore, the hydraulic drive device 1 of this embodiment is equipped with first and second connecting valves 14 and 15, respectively, which connect the first to third hydraulic drive systems 11 to 13 to each other in response to input connection commands. Therefore, when the first directional control valve 23 returns hydraulic fluid from the boom cylinder 3 to the first hydraulic pump-motor, a connection command is output to the first and second connecting valves 14 and 15, respectively. This allows the hydraulic fluid returning from the boom cylinder 3 to be distributed to the first to third hydraulic pump-motor 21, 31, and 41. Consequently, the hydraulic fluid returning from the boom cylinder 3 can be regenerated by the first to third hydraulic pump-motor 21, 31, and 41. This further reduces the capacity of the first hydraulic pump-motor 21, thereby further miniaturizing the first hydraulic pump-motor 21.

[0058] Furthermore, in the hydraulic drive system 1 of this embodiment, communication valves 14 and 15 are connected to the pump passages 25, 35, and 45 of the interconnected hydraulic drive systems 11 to 13. Therefore, by shutting off the second and third directional control valves 33 and 43 during regeneration, more hydraulic fluid can flow to the hydraulic pump-motor 31 and 41. This improves the regeneration efficiency of the hydraulic drive system 1.

[0059] Furthermore, in the hydraulic drive system 1 of this embodiment, the hydraulic fluid discharged from the head-side port 3a can be regenerated in the rod-side port 3b via the first regeneration valve 24. This can suppress the flow rate returning from the boom cylinder 3 to the first hydraulic pump-motor 21, thereby further reducing the size of the first hydraulic pump-motor 21.

[0060] Furthermore, in the hydraulic drive device 1 of this embodiment, the opening of the first directional control valve 23 is controlled based on a first motion command corresponding to the amount of operation of the first operation, and the communication valves 14 and 15 are operated based on the amount of operation of the first operation. Therefore, the opening of the first directional control valve 23 and the communication via the communication valves 14 and 15 are both controlled based on the amount of operation of the first operation. Therefore, when the opening of the first directional control valve 23 is increased based on the amount of operation of the first operation, and the return flow rate of the working fluid increases, the hydraulic drive systems 11 to 13 can be connected, allowing the working fluid to be distributed and supplied to the first to third hydraulic pump-motor 21, 31, and 41. This can prevent the first hydraulic pump-motor 21 from not being regenerated and thus reducing the regeneration efficiency.

[0061] Furthermore, in the hydraulic drive system 1 of this embodiment, the control device 17 outputs a first regeneration command to the first regeneration valve 24 during regeneration. This allows a portion of the hydraulic fluid discharged from the head-side port 3a of the boom cylinder 3 to be regenerated to the rod-side port 3b, while the remaining flow rate is regenerated. This suppresses the return flow rate of the hydraulic fluid to the first hydraulic pump-motor 21, enabling the first hydraulic pump-motor 21 to be miniaturized.

[0062] Furthermore, in the hydraulic drive device 1 of this embodiment, when the operation amount of the first operation is greater than or equal to the first communication threshold value and the operation amount of the second operation is less than the first predetermined value during regeneration, the first communication valve 14 is opened. Therefore, when the return flow rate from the boom cylinder 3 is large and the operation amount of the second operation is small, the working fluid returning from the boom cylinder 3 can be distributed to the first and second hydraulic drive systems 11 and 12. This can suppress the flow rate of the working fluid returning to the first hydraulic pump-motor 21 during regeneration. Therefore, the first hydraulic pump-motor 21 can be miniaturized. Furthermore, because regeneration is performed by the first and second hydraulic pump-motor 21 and 31, more fluid energy can be regenerated into electrical energy.

[0063] Furthermore, in the hydraulic drive device 1 of this embodiment, the second communication valve 15 is also opened when the operation amount of the first operation is greater than or equal to the second communication threshold value and the operation amount of the third operation is less than the second predetermined value during regeneration. Therefore, when the return flow rate from the boom cylinder 3 is high and the operation amounts of the second and third operations are small, the hydraulic fluid returning from the boom cylinder 3 can be distributed to the first to third hydraulic pump-motor 21, 31, and 41, respectively. This suppresses the flow rate of hydraulic fluid returning to the first hydraulic pump-motor 21 during regeneration. Consequently, the first hydraulic pump-motor 21 can be miniaturized. Furthermore, because regeneration is performed by the first to third hydraulic pump-motor 21, 31, and 41, more fluid energy can be regenerated into electrical energy.

[0064] In the hydraulic drive device 1 of this embodiment, when the arm cylinder 5 extends under load, the second regeneration valve 44 is opened. Therefore, part of the hydraulic fluid discharged from the rod-side port 5a of the arm cylinder 5 can be regenerated in the head-side port 5b.

[0065] Furthermore, the hydraulic drive system 1 of the present embodiment can realize the aforementioned functions in a construction machine or the like including a boom, a bucket, and an arm.

[0066] <Other Implementation Methods> The hydraulic drive device 1 of this embodiment can also be applied to construction vehicles and industrial vehicles other than hydraulic excavators, and can also be applied to other work machines. In addition, the hydraulic drive device 1 can be applied to any device as long as it is a vehicle or machine that supplies working fluid to drive multiple hydraulic cylinders. In addition, the number of hydraulic cylinders supplied by the hydraulic drive device 1 can also be two or more than four. In addition, when the number of hydraulic cylinders is two, the number of connecting valves becomes one. In addition, the hydraulic drive system of the hydraulic drive device 1 does not necessarily have to be the same as the number of hydraulic cylinders. In addition, the hydraulic cylinders 3 to 5 are not limited to the boom cylinder 3, the bucket cylinder 4, and the dipper cylinder 5, but can also be other hydraulic cylinders. In addition, the structure of the hydraulic drive system 11 to 13 is not limited to the structure described above, and can also be provided with other valves such as a pressure relief valve, a check valve, and an electromagnetic proportional valve.

[0067] In the hydraulic drive device 1 of this embodiment, the method for determining the number of hydraulic pump-motors 21, 31, and 41 used in regeneration control is not limited to the aforementioned process. Furthermore, the first and third hydraulic drive systems 11 and 13 do not necessarily need to include regeneration valves 24 and 44, respectively. The first hydraulic drive system 11 can also supply hydraulic fluid to hydraulic cylinders other than the boom cylinder 3. The same applies to the second and third hydraulic drive systems 12 and 13. The amount of operation for each operation is not necessarily limited to the amount of operation of the operating levers 16a and 16b; it can also be a value corresponding to the amount of operation of the operating levers 16a and 16b. Furthermore, the first to third hydraulic pump-motors 21, 31, and 41 can be fixed-displacement pumps, bent-axis pumps, gear pumps, and the like. When the first to third hydraulic pump-motors 21, 31, and 41 are fixed-displacement pumps, the control device 17 controls the discharge and intake flow rates by the rotational speed of the electric motors 22, 32, and 42.

[0068] <Exemplary Embodiments> The hydraulic drive device of the first aspect is a hydraulic drive device that supplies working fluid to multiple hydraulic cylinders including a first hydraulic cylinder, and is equipped with: multiple hydraulic drive systems, which respectively correspond to the multiple hydraulic cylinders and supply working fluid to the corresponding hydraulic cylinders; and at least one connecting valve, which connects the multiple hydraulic drive systems to each other according to an input connection instruction, and the multiple hydraulic drive systems each include: a hydraulic pump motor, which rotates when discharging working fluid and being supplied with working fluid; an electric motor, which drives the hydraulic pump motor by rotation so that the working fluid is discharged from the hydraulic pump motor and generates electricity by being driven by the rotation of the hydraulic pump motor; and a directional control valve, which switches the flow direction of the working fluid flowing between the hydraulic pump motor and the corresponding hydraulic cylinder according to an action instruction. The first hydraulic drive system corresponding to the first hydraulic cylinder includes a first directional control valve as the directional control valve, and the first directional control valve causes the working fluid to flow from the first hydraulic cylinder to the hydraulic pump motor according to the input first action instruction.

[0069] According to the first aspect, at least one connecting valve is provided for interconnecting multiple hydraulic drive systems in response to an input connection command. Therefore, when a connection command is output to the connecting valve while the working fluid is flowing from the first hydraulic cylinder to the hydraulic pump and motor via the first directional control valve, the working fluid returning from the first hydraulic cylinder can be distributed to the hydraulic pumps and motors of the multiple hydraulic drive systems. Consequently, the working fluid returning from the first hydraulic cylinder can be regenerated by the multiple hydraulic pumps and motors. Consequently, the capacity of the first hydraulic pump and motor can be reduced, thereby miniaturizing the first hydraulic pump and motor.

[0070] The hydraulic drive device in the second aspect may also be the hydraulic drive device in the first aspect, wherein the directional control valve is connected to the hydraulic pump motor via a pump channel in each hydraulic drive system, and is capable of cutting off the hydraulic pump motor from the corresponding hydraulic cylinder, and the connecting valve is connected to the pump channel of the connected hydraulic drive system.

[0071] According to the above aspect, the pump passages of the interconnected hydraulic drive systems are connected to a connecting valve. Therefore, by shutting off the directional control valves of hydraulic drive systems other than the first hydraulic drive system during regeneration, more hydraulic fluid can flow to the hydraulic pumps and motors. This improves the regeneration efficiency of the hydraulic drive system.

[0072] The hydraulic drive device in the third aspect may also be the hydraulic drive device in the first or second aspect, wherein the first hydraulic drive system includes: a first regeneration valve connected to the rod side port and the head side port of the first hydraulic cylinder, and connecting the head side port and the rod side port according to a first regeneration instruction to thereby regenerate the working fluid.

[0073] According to the above aspect, the hydraulic fluid discharged from the head-side port can be regenerated in the rod-side port by the first regeneration valve. This can suppress the flow rate returning from the first hydraulic cylinder to the first hydraulic pump-motor, thereby further reducing the size of the first hydraulic pump-motor.

[0074] The hydraulic drive device in the fourth aspect may also be the hydraulic drive device in any one of the first to third aspects, further comprising: a control device which outputs a first action instruction corresponding to an operation amount of a first operation on the first hydraulic cylinder to the first hydraulic drive system, the first directional control valve controls the opening according to the first action instruction when causing the working fluid to flow from the first hydraulic cylinder to the regeneration of the hydraulic pump motor, and the control device outputs a connection instruction according to the operation amount of the first operation.

[0075] According to the above aspect, the opening of the first directional control valve is controlled based on a first motion command corresponding to the amount of the first operation, and the communication valve is operated based on the amount of the first operation. Therefore, the opening of the first directional control valve and the communication established by the communication valve are both controlled based on the amount of the first operation. Therefore, when the opening of the first directional control valve is increased based on the amount of the first operation, the return flow rate increases, and the hydraulic drive system is connected, allowing the hydraulic fluid to be distributed to each hydraulic pump and motor. This prevents a decrease in regeneration efficiency due to a failure of regeneration in a single hydraulic pump and motor.

[0076] The hydraulic drive device in the fifth aspect may also be the hydraulic drive device in the fourth aspect, wherein the first hydraulic drive system includes: a first regeneration valve, which is connected to the head side port and the rod side port of the first hydraulic cylinder, and connects the head side port and the rod side port according to a first regeneration instruction to regenerate the working fluid, and the control device outputs a first regeneration instruction to the first regeneration valve during regeneration.

[0077] According to the above aspect, the control device outputs a first regeneration command to the first regeneration valve during regeneration. Therefore, a portion of the hydraulic fluid discharged from the head-side port of the hydraulic cylinder can be regenerated to the rod-side port while the remaining flow rate is regenerated. This suppresses the return flow rate of the hydraulic fluid to the hydraulic pump and motor of the first hydraulic drive system, thereby enabling a reduction in the size of the hydraulic pump and motor.

[0078] The hydraulic drive device in the sixth aspect may also be the hydraulic drive device in the fourth or fifth aspect, wherein the multiple hydraulic drive systems further include: a second hydraulic drive system, which is arranged corresponding to the second hydraulic cylinder as one of the multiple hydraulic cylinders, and the at least one connecting valve includes: a first connecting valve, which is connected to the first hydraulic drive system and the second hydraulic drive system, and operates according to a first connecting instruction, a second directional control valve serving as the directional control valve of the second hydraulic drive system, switches the flow direction of the working fluid according to a second action instruction, and controls the opening according to the second action instruction, and the control device outputs a second action instruction corresponding to the operation amount of the second operation as an operation on the second hydraulic cylinder, and opens the first connecting valve when the operation amount of the first operation is above the first connecting threshold and the operation amount of the second operation is below the first specified value during resuscitation.

[0079] According to the above aspect, when the operation amount of the first operation is greater than the first connection threshold value and the operation amount of the second operation is less than the first specified value during regeneration, the first connection valve opens. Therefore, when the return flow from the first hydraulic cylinder is large and the operation amount of the second operation is small, the working fluid returned from the first hydraulic cylinder can be distributed to the hydraulic pumps and motors of the first and second hydraulic drive systems. As a result, the flow rate of the working fluid returning to the hydraulic pumps and motors of the first hydraulic drive system during regeneration can be suppressed. Therefore, the hydraulic pumps and motors of the first hydraulic drive system can be miniaturized. In addition, because regeneration is performed by multiple hydraulic pumps and motors, more fluid energy can be regenerated into electrical energy.

[0080] The hydraulic drive device in the seventh aspect may also be the hydraulic drive device in the sixth aspect, wherein the multiple hydraulic drive systems further include: a third hydraulic drive system, which is arranged corresponding to the third hydraulic cylinder as one of the multiple hydraulic cylinders, and the at least one connecting valve further includes: a second connecting valve, which is connected to the second hydraulic drive system and the third hydraulic drive system, and operates according to the second connecting instruction, the third directional control valve serving as the directional control valve of the third hydraulic drive system switches the flow direction of the working fluid according to the third action instruction, and controls the opening according to the third action instruction, the control device outputs a third action instruction corresponding to the operation amount of the third operation as the operation on the third hydraulic cylinder, and opens the second connecting valve when the operation amount of the first operation is above the second connecting threshold greater than the first connecting threshold and the operation amount of the third operation is below the second specified value during resuscitation.

[0081] According to the above aspect, when the operating amount of the first operation is greater than the second connection threshold value and the operating amount of the third operation is less than the second specified value during regeneration, the second connection valve opens. Therefore, when the return flow from the first hydraulic cylinder is large and the operating amounts of the second and third operations are small, the working fluid returned from the first hydraulic cylinder can be distributed to the hydraulic pumps and motors of the first to third hydraulic drive systems. As a result, the flow rate of the working fluid returning to the hydraulic pumps and motors of the first hydraulic drive system during regeneration can be suppressed. Therefore, the hydraulic pumps and motors of the first hydraulic drive system can be miniaturized. In addition, because regeneration is performed by multiple hydraulic pumps and motors, more fluid energy can be regenerated into electrical energy.

[0082] The hydraulic drive device in the eighth aspect may also be the hydraulic drive device in the sixth or seventh aspect, wherein the multiple hydraulic drive systems further include: a third hydraulic drive system, which is arranged corresponding to the third hydraulic cylinder which is one of the multiple hydraulic cylinders, and the third hydraulic drive system includes: a second regeneration valve, which is connected to the head side port and the rod side port of the third hydraulic cylinder, and connects the head side port and the rod side port according to the second regeneration instruction to regenerate the working fluid, and the control device opens the second regeneration valve when the third hydraulic cylinder is stretched due to the load.

[0083] According to the above aspect, when the third hydraulic cylinder contracts under the load, the second regeneration valve is opened, so that a portion of the hydraulic fluid discharged from the rod-side port of the third hydraulic cylinder can be regenerated in the head-side port.

[0084] The hydraulic drive device in the ninth aspect may also be the hydraulic drive device in the seventh or eighth aspect, wherein the first hydraulic drive system supplies working fluid to the boom cylinder serving as the first hydraulic cylinder, the second hydraulic drive system supplies working fluid to the bucket cylinder serving as the second hydraulic cylinder, and the third hydraulic drive system supplies working fluid to the arm cylinder serving as the third hydraulic cylinder.

[0085] According to the above aspect, the aforementioned functions can be realized in a construction machine or the like including a boom, a bucket, and an arm.

[0086] Based on the above description, numerous modifications and alternative embodiments of the present invention will be readily apparent to those skilled in the art. Therefore, the above description should be construed as merely illustrative, and is provided for the purpose of teaching those skilled in the art the best modes for carrying out the present invention. The specific structure and / or functionality may be substantially altered without departing from the spirit of the present invention.

Claims

1. A hydraulic drive device, characterized in that: A hydraulic drive device for supplying working fluid to a plurality of hydraulic cylinders including a first hydraulic cylinder, It has: a plurality of hydraulic drive systems, which respectively correspond to the plurality of hydraulic cylinders and supply working fluid to the corresponding hydraulic cylinders; and at least one connecting valve, which connects the plurality of hydraulic drive systems to each other according to an input connection instruction, Each of the plurality of hydraulic drive systems includes: a hydraulic pump motor that rotates when discharging working fluid and being supplied with working fluid; an electric motor that drives the hydraulic pump motor by rotation so that working fluid is discharged from the hydraulic pump motor and generates electricity by being driven by the hydraulic pump motor by rotation; and a directional control valve that switches the flow direction of the working fluid flowing between the hydraulic pump motor and the corresponding hydraulic cylinder according to an action instruction. The first hydraulic drive system as the hydraulic drive system corresponding to the first hydraulic cylinder includes a first directional control valve as the directional control valve, The first directional control valve allows the hydraulic fluid to flow from the first hydraulic cylinder to the hydraulic pump motor according to a first motion command inputted thereto.

2. The hydraulic drive device according to claim 1, characterized in that: The directional control valve is connected to the hydraulic pump motor via a pump channel in each hydraulic drive system and can cut off the connection between the hydraulic pump motor and the corresponding hydraulic cylinder. The communication valves are respectively connected to the pump channels of the hydraulic drive system that are in communication.

3. The hydraulic drive device according to claim 1, characterized in that: The first hydraulic drive system includes a first regeneration valve connected to a rod-side port and a head-side port of the first hydraulic cylinder, and connecting the head-side port and the rod-side port according to a first regeneration instruction to regenerate working fluid.

4. The hydraulic drive device according to claim 1, characterized in that: The invention further comprises: a control device that outputs a first operation instruction corresponding to an operation amount of a first operation as an operation on the first hydraulic cylinder to the first hydraulic drive system, The first directional control valve controls the opening degree according to the first action instruction when the working fluid flows from the first hydraulic cylinder to the regeneration of the hydraulic pump motor. The control device outputs a connection instruction according to an operation amount of the first operation.

5. The hydraulic drive device according to claim 4, characterized in that: The first hydraulic drive system includes: a first regeneration valve connected to a head side port and a rod side port of the first hydraulic cylinder, and connecting the head side port and the rod side port according to a first regeneration instruction to regenerate the working fluid; The control device outputs a first regeneration command to the first regeneration valve during regeneration.

6. The hydraulic drive device according to claim 4, characterized in that: The plurality of hydraulic drive systems further include: a second hydraulic drive system, which is provided corresponding to a second hydraulic cylinder as one of the plurality of hydraulic cylinders, The at least one communication valve comprises: a first communication valve connected to the first hydraulic drive system and the second hydraulic drive system and operated according to a first communication instruction, The second directional control valve as the directional control valve of the second hydraulic drive system switches the flow direction of the working fluid according to the second action instruction and controls the opening according to the second action instruction. The control device outputs a second action command corresponding to an operation amount of a second operation as an operation on the second hydraulic cylinder, and opens the first communication valve when the operation amount of the first operation is greater than or equal to a first communication threshold value and the operation amount of the second operation is less than or equal to a first specified value during resuscitation.

7. The hydraulic drive device according to claim 6, characterized in that: The plurality of hydraulic drive systems further include: a third hydraulic drive system, which is provided corresponding to a third hydraulic cylinder which is one of the plurality of hydraulic cylinders; The at least one connecting valve further comprises: a second connecting valve connected to the second hydraulic drive system and the third hydraulic drive system and operated according to a second connecting instruction, The third directional control valve as the directional control valve of the third hydraulic drive system switches the flow direction of the working fluid according to the third action instruction and controls the opening according to the third action instruction. The control device outputs a third action instruction corresponding to the operation amount of the third operation as the operation on the third hydraulic cylinder, and opens the second communication valve when the operation amount of the first operation is greater than or equal to a second communication threshold value greater than the first communication threshold value and the operation amount of the third operation is less than or equal to a second prescribed value during resuscitation.

8. The hydraulic drive device according to claim 6, characterized in that: The plurality of hydraulic drive systems further include: a third hydraulic drive system, which is provided corresponding to a third hydraulic cylinder which is one of the plurality of hydraulic cylinders; The third hydraulic drive system includes: a second regeneration valve connected to the head side port and the rod side port of the third hydraulic cylinder, and connecting the head side port and the rod side port according to a second regeneration instruction to regenerate the working fluid; The control device opens the second regeneration valve when the third hydraulic cylinder is extended due to a load.

9. The hydraulic drive device according to claim 7 or 8, characterized in that: The first hydraulic drive system supplies working fluid to a boom cylinder serving as the first hydraulic cylinder. The second hydraulic drive system supplies hydraulic fluid to a bucket cylinder serving as the second hydraulic cylinder. The third hydraulic drive system supplies hydraulic fluid to an arm cylinder serving as the third hydraulic cylinder.

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