Hydraulic drive device

Abstract

[Problem] To provide a hydraulic drive device capable of retrogradation and capable of reducing the size of a hydraulic pump motor. [Solution] A hydraulic drive device for supplying and discharging a hydraulic fluid to a hydraulic cylinder, the hydraulic drive device being provided with: a plurality of hydraulic pump motors each having a suction port and a discharge port; a plurality of electric motors connected to the plurality of hydraulic pump motors, respectively; and a direction control valve which is connected to the outlet throttle passage and which discharges the working fluid from the hydraulic cylinder to the outlet throttle passage by connecting the hydraulic cylinder to the outlet throttle passage, the suction ports of each of the plurality of hydraulic pump motors being connected in parallel to the outlet throttle passage.

Description

Technical Field

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

[0002] As a hydraulic drive device for driving a hydraulic cylinder, for example, a hydraulic drive device such as that disclosed in Patent Document 1 is known. In a hydraulic drive device such as that disclosed in Patent Document 1, during a boom lowering operation, a hydraulic pump motor is rotationally driven by hydraulic oil discharged from a head-side port of a boom cylinder. Thus, the potential energy of the boom can be regenerated into electrical energy.

[0003] Prior art literature: Patent Literature: Patent document 1: Japanese Patent Application Publication No. 2021-181789. Summary of the invention

[0004] Problems to be solved by the invention: In the hydraulic drive device of Patent Document 1, the potential energy of the boom is regenerated into electric energy by a single hydraulic pump-motor for the boom cylinder. Therefore, in the hydraulic drive device of Patent Document 1, if all the working fluid discharged from the boom cylinder is sucked in by a single hydraulic pump-motor during regeneration, the hydraulic pump-motor will be large.

[0005] Therefore, an object of the present invention is to provide a hydraulic drive device that can be regenerated and can reduce the size of a hydraulic pump and motor.

[0006] Means of solving the problem: The hydraulic drive device of the first invention is a hydraulic drive device for supplying and discharging working fluid to a hydraulic cylinder, and comprises: a plurality of hydraulic pump motors having a suction port and a discharge port; a plurality of electric motors respectively connected to the plurality of hydraulic pump motors; and a directional control valve connected to an outlet throttling channel, and the working fluid is discharged from the hydraulic cylinder to the outlet throttling channel by connecting the hydraulic cylinder to the outlet throttling channel, and the suction port of each of the plurality of hydraulic pump motors is connected in parallel with the outlet throttling channel.

[0007] According to the first invention, the suction ports of the plurality of hydraulic pumps and motors are connected in parallel to the outlet throttle passage. Therefore, the fluid energy of the working fluid discharged from the hydraulic cylinder can be regenerated into electrical energy by the plurality of hydraulic pumps and motors. Therefore, during regeneration, the flow rate of the working fluid sucked into each of the hydraulic pumps and motors, that is, the suction flow rate, can be suppressed. Thus, each of the hydraulic pumps and motors can be miniaturized.

[0008] The hydraulic drive device of the second invention is a hydraulic drive device for supplying and discharging working fluid to multiple hydraulic actuators including a first hydraulic actuator serving as a hydraulic cylinder, and comprises: multiple hydraulic pump motors having a suction port and a discharge port, the discharge ports being respectively connected to the multiple hydraulic actuators; multiple electric motors being respectively connected to the multiple hydraulic pump motors; and a directional control valve being connected to an outlet throttling channel, and discharging working fluid from the first hydraulic actuator to the outlet throttling channel by connecting the first hydraulic actuator to the outlet throttling channel, and the suction ports of the multiple hydraulic pump motors are respectively connected to the outlet throttling channel.

[0009] According to the second invention, the discharge ports of the hydraulic pump and motor are connected to different hydraulic actuators, so that multiple hydraulic actuators can be operated simultaneously. On the other hand, the suction ports of the hydraulic pump and motor are connected in parallel to the outlet throttle passage. Therefore, the fluid energy of the working fluid discharged from the first hydraulic actuator can be regenerated into electrical energy through the multiple hydraulic pumps and motors. Therefore, during regeneration, the flow rate of the working fluid sucked into each of the hydraulic pumps and motors, that is, the suction flow rate, can be suppressed. As a result, each of the hydraulic pumps and motors can be miniaturized.

[0010] Effect of the invention: According to the first and second inventions, the hydraulic pump and motor can be regenerated and reduced in size.

[0011] 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

[0012] Figure 1 A circuit diagram showing the structure of the hydraulic drive device of this embodiment; Figure 2 Graphs showing flow rates required of the first to third hydraulic pump-motors by each hydraulic cylinder relative to the operation amount of each operation in the hydraulic drive device of the present embodiment, (a) is a graph showing the boom required flow rate, (b) is a graph showing the arm required flow rate, and (c) is a graph showing the bucket required flow rate; Figure 3 A flowchart showing the sequence of causing each hydraulic cylinder to perform telescopic motion in the hydraulic drive device of the present embodiment; Figure 4 of Figure 4 (a) to (c) are graphs showing each required flow rate for each of the first to third hydraulic pump-motor relative to the operation amount of each operation when the second operation is performed simultaneously with the boom lowering operation; Figure 5 of Figure 4(a) to (c) are graphs showing each required flow rate for each of the first to third hydraulic pump-motor relative to the operation amount of each operation when the third operation is performed simultaneously with the boom lowering operation. DETAILED DESCRIPTION

[0013] Hereinafter, a hydraulic drive device 1 according to an embodiment of the present invention will be described with reference to the above-mentioned drawings. In addition, the concept of direction used in the following description is a concept used for the convenience of description, and does not limit the direction of the structure of the invention to the direction. The hydraulic drive device 1 described below is only one embodiment of the present invention. Therefore, the present invention is not limited to the embodiment, and additions, deletions, and changes can be made within the scope of the main purpose of the invention.

[0014] Figure 1 The hydraulic drive device 1 shown is equipped on, for example, a work vehicle (not shown). The work vehicle is, for example, a construction vehicle such as a hydraulic excavator and a hydraulic crane, and an industrial vehicle such as a lift. In the present embodiment, the work vehicle is a hydraulic excavator. The hydraulic excavator is provided with a plurality of hydraulic actuators 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 actuator, a dipper arm cylinder 4 as a second hydraulic actuator, and a bucket cylinder 5 as a third hydraulic actuator. The hydraulic cylinders 3 to 5 are respectively provided on the boom, the dipper arm, and the bucket. The hydraulic excavator moves the boom, the dipper arm, and the bucket respectively by extending and retracting the three hydraulic cylinders 3 to 5 respectively. Thus, the hydraulic excavator can perform various operations.

[0015] The hydraulic drive device 1 supplies and discharges working fluid to a plurality of hydraulic cylinders 3 to 5. In the present embodiment, the hydraulic drive device 1 supplies and discharges working fluid to at least the aforementioned boom cylinder 3, the arm cylinder 4, and the bucket cylinder 5. The hydraulic drive device 1 includes a plurality of hydraulic pump motors 11 to 13, a plurality of electric motors 14 to 16, and a first directional control valve 17. In more detail, the hydraulic drive device 1 is provided with at least the same number of hydraulic pump motors 11 to 13 and electric motors 14 to 16 as the number of hydraulic cylinders 3 to 5. In the present embodiment, the hydraulic drive device 1 includes three hydraulic pump motors (i.e., the first to third hydraulic pump motors) 11 to 13, and three electric motors (i.e., the first to third electric motors) 14 to 16. In addition, the hydraulic drive device 1 further includes a second directional control valve 18, a third directional control valve 19, a regeneration valve 20, a plurality of unloading valves 21 to 23, and a merging mechanism 24. In this embodiment, the hydraulic drive device 1 is provided with three unloading valves (ie, first to third unloading valves) 21 to 23 , which is the same number as the hydraulic pump motors 11 to 13 . The hydraulic drive device 1 also includes an operating device 26 and a control device 27 .

[0016] [Hydraulic pump motor] The first to third hydraulic pump motors 11 to 13 have suction ports 11a to 13a and discharge ports 11b to 13b, respectively. The suction ports 11a to 13a of the first to third hydraulic pump motors 11 to 13 are connected in parallel to the meter-out passage 31 described later. In addition, the suction ports 11a to 13a of the first to third hydraulic pump motors 11 to 13 are connected to the tank 28 via the meter-out passage 31 and the tank passages 28a to 28c. The tank passages 28a to 28c connect the tank 28 to the meter-out passage 31. In addition, check valves 29a to 29c are provided in the middle of the tank passages 28a to 28c. The check valves 29a to 29c allow the working fluid to flow from the tank 28 to the meter-out passage 31 and prevent the flow in the opposite direction.

[0017] The discharge ports 11b to 13b of the first to third hydraulic pump motors 11 to 13 are connected to the hydraulic cylinders 3 to 5, respectively. In the present embodiment, the discharge port 11b of the first hydraulic pump motor 11 is connected to the boom cylinder 3. The discharge port 12b of the second hydraulic pump motor 12 is connected to the arm cylinder 4. The discharge port 13b of the third hydraulic pump motor 13 is connected to the bucket cylinder 5.

[0018] Furthermore, the first to third hydraulic pump motors 11 to 13 have shafts 11c to 13c. When the shafts 11c to 13c are driven to rotate, the first to third hydraulic pump motors 11 to 13 suck working fluid from the suction ports 11a to 13a and discharge working fluid from the discharge ports 11b to 13b. On the other hand, when working fluid is supplied to the suction ports 11a to 13a, the first to third hydraulic pump motors 11 to 13 rotate the shafts 11c to 13c.

[0019] In addition, the first to third hydraulic pump-motor 11 to 13 are variable capacity swash plate pumps in the present embodiment. That is, the first to third hydraulic pump-motor 11 to 13 each have a regulator 11d to 13d. The regulator 11d to 13d changes the pump capacity of each of the first to third hydraulic pump-motor 11 to 13 based on the first to third capacity instructions inputted thereto.

[0020] [Electric Motor] The first to third electric motors 14 to 16 are connected to the first to third hydraulic pump-motors 11 to 13, respectively. To explain in more detail, the first to third electric motors 14 to 16 are connected to the first to third hydraulic pump-motors 11 to 13, respectively, via shafts 11c to 13c. The first to third electric motors 14 to 16 respectively drive the first to third hydraulic pump-motors to rotate so as to discharge the working fluid from each of them. Furthermore, the first to third electric motors 14 to 16 generate electricity by being driven to rotate by the first to third hydraulic pump-motors 11 to 13, respectively. That is, the first to third electric motors 14 to 16 respectively cooperate with the first to third hydraulic pump-motors 11 to 13, respectively, to regenerate the fluid energy of the working fluid into electrical energy. The first to third electric motors 14 to 16 respectively change the rotation speed according to the input first to third rotation instructions, respectively.

[0021] [First directional control valve] The first directional control valve 17 is connected to the meter-out passage 31. The first directional control valve 17 is connected to the boom cylinder 3. The first directional control valve 17 discharges the working fluid from the boom cylinder 3 to the meter-out passage 31 by connecting the boom cylinder 3 to the meter-out passage 31. In more detail, the first directional control valve 17 is connected to the head side port 3a and the rod side port 3b of the boom cylinder 3, respectively. The first directional control valve 17 connects the head side port 3a to the meter-out passage 31. Thus, the working fluid is discharged from the head side port 3a of the boom cylinder 3 to the meter-out passage 31. The first to third hydraulic pump motors 11 to 13 (in more detail, suction ports 11a to 13a) are connected in parallel to the meter-out passage 31. The first directional control valve 17 is connected to the first hydraulic pump motor 11 via the first pump passage 32. In addition, the first directional control valve 17 is connected to the tank 28.

[0022] The first directional control valve 17 switches the flow direction of the working fluid flowing between the first hydraulic pump motor 11 and the boom cylinder 3 according to the input first motion command. In more detail, the first directional control valve 17 switches the connection destination of each port 3a, 3b of the boom cylinder 3 according to the first motion command. For example, the first directional control valve 17 connects the head side port 3a of the boom cylinder 3 to the outlet meter-out passage 31 according to the first motion command, and connects the discharge port 11b of the first hydraulic pump motor 11 to the rod side port 3b of the boom cylinder 3. In this embodiment, in the first directional control valve 17, a check valve 17a is interposed between the discharge port 11b and the rod side port 3b. The check valve 17a allows the flow from the discharge port 11b to the rod side port 3b and prevents the flow in the opposite direction. In addition, the first directional control valve 17 connects the rod side port 3b of the boom cylinder 3 to the tank 28 according to the first motion command, and connects the discharge port 11b of the first hydraulic pump motor 11 to the head side port 3a of the boom cylinder 3. Furthermore, the first directional control valve 17 can cut off the connection between the first hydraulic pump / motor 11 and the boom cylinder 3 .

[0023] [Second directional control valve] The second directional control valve 18 is connected to the second hydraulic pump motor 12 via the second pump passage 33. In more detail, the second directional control valve 18 is connected to the discharge port 12b of the second hydraulic pump motor 12. In addition, the second directional control valve 18 is also connected to the boom cylinder 4. The second directional control valve 18 switches the flow direction of the working fluid flowing between the second hydraulic pump motor 12 and the boom cylinder 4 according to the second action instruction. In more detail, the second directional control valve 18 connects the discharge port 12b of the second hydraulic pump motor 12 to one of the rod side port 4a and the head side port 4b of the boom cylinder 4 according to the second action instruction. In addition, the second directional control valve 18 connects the other of the rod side port 4a and the head side port 4b to the tank 28 according to the second action instruction. Thus, the second directional control valve 18 causes the working fluid discharged from the second hydraulic pump motor 12 to flow to one of the rod side port 4a and the head side port 4b. In addition, the second directional control valve 18 can cut off the connection between the second hydraulic pump motor 12 and the boom cylinder 4.

[0024] [Third directional control valve] The third directional control valve 19 is connected to the third hydraulic pump motor 13 via the third pump passage 34. In more detail, the third directional control valve 19 is connected to the discharge port 13b of the third hydraulic pump motor 13. Moreover, the third directional control valve 19 is also connected to the bucket cylinder 5. The third directional control valve 19 switches the flow direction of the working fluid flowing between the third hydraulic pump motor 13 and the bucket cylinder 5 according to the third action instruction. Specifically, the third directional control valve 19 connects the discharge port 13b of the third hydraulic pump motor 13 to one of the rod side port 5a and the head side port 5b of the bucket cylinder 5 according to the third action instruction. Moreover, the third directional control valve 19 connects the other of the rod side port 5a and the head side port 5b to the tank 28 according to the third action instruction. In addition, the third directional control valve 19 can cut off the connection between the third hydraulic pump motor 13 and the bucket cylinder 5.

[0025] [Regeneration valve] The regeneration valve 20 is connected to the head side port 3a and the rod side port 3b of the boom cylinder 3. The regeneration valve 20 connects the head side port 3a with the rod side port 3b according to the regeneration command. In addition, the regeneration valve 20 allows the flow of the working fluid from the head side port 3a to the rod side port 3b while connecting the head side port 3a with the rod side port 3b, and blocks the flow in the opposite direction. Thus, when the regeneration valve 20 supplies the 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.

[0026] [Unloading valve] The first to third unloading valves 21 to 23 discharge at least a portion of the working fluid discharged from the discharge ports 11b to 13b of the first to third hydraulic pump motors 11 to 13 to the tank 28. In more detail, each of the first to third unloading valves 21 to 23 is connected to each of the first to third pump passages 32 to 34. Each of the first to third unloading valves 21 to 23 operates in accordance with each of the first to third unloading instructions input. Then, the first to third unloading valves 21 to 23 adjust the opening between the discharge ports 11b to 13b and the tank 28 in accordance with each of the first to third unloading instructions input.

[0027] [Confluence mechanism] The merging mechanism 24 merges the working fluids discharged from the respective discharge ports 11b to 13b of the first to third hydraulic pump motors 11 to 13. In more detail, the merging mechanism 24 is connected to the three pump channels 32 to 34, respectively. The merging mechanism 24 connects the first pump channel 32 with the third pump channel 34, and also connects the second pump channel 33 with the third pump channel 34. Then, the merging mechanism 24 merges the working fluids discharged from the first to third hydraulic pump motors 11 to 13, respectively, by switching the connection states of the three pump channels 32 to 34. In the present embodiment, the merging mechanism 24 includes a first merging valve 41 and a second merging valve 42.

[0028] The first confluence valve 41 makes the working fluid discharged from the discharge ports 11b and 13b of the first and third hydraulic pump motors 11 and 13 merge. In more detail, the first confluence valve 41 is connected to the first pump channel 32 and the third pump channel 34. The first confluence valve 41 is opened according to the input first confluence instruction. As a result, the first pump channel 32 is connected to the third pump channel 34, so that the working fluid can flow back and forth between the two pump channels 32 and 34.

[0029] The second merging valve 42 merges the working fluid discharged from the discharge ports 12b and 13b of the second and third hydraulic pump motors 12 and 13, respectively. In more detail, the second merging valve 42 is connected to the second pump channel 33 and the third pump channel 34. The second merging valve 42 is opened in response to the input second merging command. As a result, the second pump channel 33 is connected to the third pump channel 34, so that the working fluid can flow back and forth between the two pump channels 33 and 34.

[0030] <Operation device> The operating device 26 is operated by the driver or the like to move the boom cylinder 3, the arm cylinder 4, and the bucket cylinder 5. To explain in more detail, the operating device 26 outputs an operating signal corresponding to the operating direction and operating amount (hereinafter referred to as "operating state") of the operation of each hydraulic cylinder 3 to 5 (hereinafter referred to as "each operation"). The operating device 26 includes, for example, a plurality of operating levers 26a and 26b. In the present embodiment, the operating device 26 includes two operating levers 26a and 26b. The operating levers 26a and 26b can be operated in various directions (for example, dumping). The operating device 26 outputs an operating signal using the operating direction (for example, dumping direction) and operating amount (for example, dumping amount) of the operating levers 26a and 26b as the operating state of each operation. In addition, the operating device 26 may also be in other forms such as an operating panel, or may output an operating signal based on an operation on an operating panel or a pre-stored program.

[0031] <Control device> The control device 27 inputs an operation signal from the operation device 26. Then, the control device 27 operates the first to third directional control valves 17 to 19 according to the input operation signal. In more detail, the control device 27 outputs a first action instruction according to the operation state of the first operation as the operation of the boom cylinder 3, thereby operating the first directional control valve 17. In addition, the control device 27 outputs a second action instruction according to the operation state of the second operation as the operation of the boom cylinder 4, thereby operating the second directional control valve 18. In addition, the control device 27 outputs a third action instruction according to the operation state of the third operation as the operation of the bucket cylinder 5, thereby operating the third directional control valve 19. The control device 27 outputs a regeneration instruction according to the operation state of the first operation. As a result, the control device 27 operates the regeneration valve 20. In addition, the control device 27 outputs the first and second communication instructions. As a result, the control device 27 opens the first and second confluence valves 41 and 42.

[0032] The control device 27 controls the discharge flow rate or the suction flow rate of each of the first to third hydraulic pump motors 11 to 13 according to the input operation signal. Figure 2 As shown in the graphs (a) to (c), the flow rates required by the hydraulic cylinders 3 to 5 for the first to third hydraulic pump-motor 11 to 13 are set in accordance with the operation amount of each operation. Figure 2 (a) shows the boom required flow rate. Figure 2 (b) shows the required flow rate of the boom. Figure 2 The bucket required flow rate is shown in (c). In addition, the boom required flow rate is the flow rate that the boom cylinder 3 requires of the first to third hydraulic pump motors 11 to 13 relative to the operation amount of the first operation. The arm required flow rate is the flow rate that the arm cylinder 4 requires of the first to third hydraulic pump motors 11 to 13 relative to the operation amount of the second operation. The bucket required flow rate is the flow rate that the bucket cylinder 5 requires of the second and third hydraulic pump motors 12 and 13 relative to the operation amount of the third operation. Again, Figure 2 In (a) to (c), the solid lines represent the required flow rates required for the first hydraulic pump-motor 11 , the dashed lines represent the required flow rates required for the second hydraulic pump-motor 12 , and the double-dashed lines represent the required flow rates required for the third hydraulic pump-motor 13 .

[0033] The control device 27 calculates the required discharge flow rate and the required regeneration flow rate of each of the first to third hydraulic pump motors 11 to 13 based on each required flow rate and the operation state of each operation. The required discharge flow rate is the discharge flow rate required for each of the first to third hydraulic pump motors 11 to 13. The required regeneration flow rate is the regeneration flow rate, that is, the suction flow rate, required for each of the first to third hydraulic pump motors 11 to 13. The calculation method of the required discharge flow rate and the required regeneration flow rate will be described in detail later. The control device 27 calculates the rotation speed of each of the motors 14 to 16 and the pump capacity of each of the first to third hydraulic pump motors 11 to 13 based on the calculated required discharge flow rate and required regeneration flow rate. Then, the control device 27 outputs the first to third rotation instructions corresponding to the rotation speed to each of the motors 14 to 16, and outputs the first to third capacity instructions corresponding to the pump capacity to the first to third hydraulic pump motors 11 to 13. Thus, the control device 27 controls the discharge flow rate of each of the first to third hydraulic pump-motor 11 to 13 to the required discharge flow rate (or controls the suction flow rate to the required regeneration flow rate) according to the operation state of each operation.

[0034] The control device 27 controls the operation of the first to third unloading valves 21 to 23 according to the input operation signal. In more detail, the control device 27 calculates the required discharge flow rate and the required regeneration flow rate of each of the first to third hydraulic pump motors 11 to 13 as described above. Then, the control device 27 outputs the first to third unloading instructions corresponding to the difference between the required discharge flow rate and the required regeneration flow rate to the first to third hydraulic pump motors 11 to 13, thereby controlling the opening degree of each of the first to third unloading valves 21 to 23.

[0035] <Operation of the hydraulic drive unit> In the hydraulic drive device 1, when the operating device 26 is operated (in this embodiment, the operating levers 26a and 26b are operated), an operating signal corresponding to the operating state of each operation is output from the operating device 26. After the operating signal is output, the control device 27 causes each hydraulic cylinder 3 to 5 to extend and retract in a direction corresponding to the operating direction of each operation and at a speed corresponding to the operating amount of each operation.

[0036] To explain in more detail, the control device 27 outputs speed instructions corresponding to the operating state of each operation to the first to third electric motors 14 to 16, respectively. Furthermore, the control device 27 outputs capacity instructions corresponding to the operating state of each operation to the first to third hydraulic pump-motors 11 to 13, respectively. Thus, the control device 27 causes the first to third hydraulic pump-motors 11 to 13 to discharge or inhale working fluid at a flow rate corresponding to the operating amount of each operation. Furthermore, the control device 27 outputs the first to third action instructions according to the operating state of each operation. In this way, the first to third directional control valves 17 to 19 connect the first to third hydraulic pump-motors 11 to 13 to the corresponding hydraulic cylinders 3 to 5, respectively. Thus, the hydraulic cylinders 3 to 5 extend and retract in a direction corresponding to the operating direction of each operation and at a speed corresponding to the operating amount. hereinafter, refer to Figure 3 The flow chart illustrates the extension and retraction actions of the hydraulic cylinders 3 to 5 caused by various operations.

[0037] The control device 27 starts when the operating device 26 is operated (in this embodiment, the operating levers 26a and 26b are operated). Figure 3 The process shown. In this way, the process proceeds to step S1. In step S1, which is a boom lowering operation determination process, it is determined whether a boom lowering operation, which is one of the first operations, has been performed. In the present embodiment, the control device 27 determines whether the operating lever 26a on one side has been tilted forward to lower the boom. When the operating lever 26a on one side is tilted forward, the control device 27 determines that a boom lowering operation has been performed. In this way, the process proceeds to step S2. On the other hand, when the operating lever 26a on one side is not operated or tilted backward, the control device 27 determines that a boom lowering operation has not been performed. In this way, the process proceeds to step S7. In addition, the boom lowering operation is not limited to the case where the operating lever 26a is tilted forward. The aforementioned method for determining the boom lowering operation is merely an example, and the control device 27 may determine that a boom lowering operation has been performed when the operating device 26 performs an operation corresponding to the boom lowering operation.

[0038] In step S2, which is the unloading valve full opening process, the control device 27 fully opens the first to third unloading valves 21 to 23. Then, when lowering the boom, the control device 27 regenerates the fluid energy of the working fluid discharged from the head side port 3a of the boom cylinder 3 into electric energy, that is, performs boom lowering regeneration. The boom lowering regeneration will be described in further detail below.

[0039] The control device 27 operates the first directional control valve 17 by outputting a first operation command. Thus, the head side port 3a of the boom cylinder 3 is connected to the meter-out passage 31 through the first directional control valve 17. Moreover, the discharge port 11b of the first hydraulic pump motor 11 is connected to the rod side port 3b of the boom cylinder 3 via the check valve 17a. In addition, the control device 27 calculates the required regeneration flow rate of each of the first to third hydraulic pump motors 11 to 13 based on the operation amount of the boom lowering operation. In the present embodiment, the required regeneration flow rate of each of the first to third hydraulic pump motors 11 to 13 is calculated based on the boom required flow rate of each of the first to third hydraulic pump motors 11 to 13 and the operation amount of the boom lowering operation. Then, the control device 27 outputs the first to third rotation speed commands and the first to third capacity commands corresponding to the required regeneration flow rates of each of the first to third hydraulic pump motors 11 to 13. As a result, the suction flow rates of the first to third hydraulic pump motors 11 to 13 are controlled to be the required regeneration flow rates. Furthermore, the control device 27 fully opens the first to third unloading valves 21 to 23. In this way, the working fluid flows as follows.

[0040] That is, the working fluid is discharged from the head side port 3a of the boom cylinder 3. The discharged working fluid flows from the head side port 3a to the outlet throttle passage 31. Thereafter, the working fluid is supplied to the first to third hydraulic pump motors 11 to 13 through the outlet throttle passage 31, respectively. The first to third hydraulic pump motors 11 to 13 are driven by the supplied working fluid. Therefore, the first to third electric motors 14 to 16 generate electricity. Thus, the fluid energy of the working fluid is recovered as electrical energy by the first to third hydraulic pump motors 11 to 13 and the first to third electric motors 14 to 16. At this time, the first to third unloading valves 21 to 23 are fully opened by the control device 27. Therefore, the working fluid discharged from the first to third hydraulic pump motors 11 to 13 is directly discharged to the tank 28. That is, the first to third hydraulic pump motors 11 to 13 are in an unloaded state. Therefore, the fluid energy of the working fluid can be efficiently recovered as electrical energy. In addition, the control device 27 outputs the first action command and the regeneration command at the time of boom lowering recovery. As a result, the regeneration valve 20 is opened, so that the rod-side port 3b and the head-side port 3a communicate with each other. As a result, part of the working fluid discharged from the head-side port 3a is regenerated in the rod-side port 3b.

[0041] In this way, in the hydraulic drive device 1, a part of the working fluid discharged from the head side port 3a of the boom cylinder 3 is regenerated in the rod side port 3b, and the remaining part is returned to the first to third hydraulic pump motors 11 to 13. As a result, the boom cylinder 3 is retracted and the boom is lowered. In addition, the control device 27 controls the flow rate of the working fluid flowing to the rod side port 3b through the regeneration valve 20 by controlling the suction flow rate of each of the first to third hydraulic pump motors 11 to 13 to each required regeneration flow rate. In this way, the working fluid of the flow rate corresponding to the operation state of the first operation can flow to the rod side port 3b. As a result, the boom cylinder 3 can be retracted at a speed corresponding to the operation state of the first operation. That is, the boom can be lowered at a speed corresponding to the operation state of the first operation. In addition, by controlling the suction flow rate of each of the first to third hydraulic pump motors 11 to 13 to each required regeneration flow rate, the power generation of the first to third electric motors 14 to 16 is controlled. When the boom lowering regeneration starts, the process moves to step S3.

[0042] In step S3, which is a simultaneous operation determination process, it is determined whether at least one of the second operation and the third operation is not performed while the boom lowering operation is in progress. To explain in more detail, the control device 27 obtains the operation status of each operation based on the input operation signal. Then, the control device 27 determines whether any one of the second operation and the third operation is not performed while the boom lowering operation is in progress based on the operation status of each operation. When it is determined that at least one of the second operation and the third operation is not performed while the boom lowering operation is in progress, the aforementioned boom lowering resuscitation is continued until the boom lowering operation is completed or at least one of the second operation and the third operation is performed while the boom lowering operation is in progress, and the process is terminated. On the other hand, when it is determined that at least one of the second operation and the third operation is performed while the boom lowering operation is in progress, the process proceeds to step S4.

[0043] In step S4, which is a hydraulic pump motor flow control process, the discharge flow rate or regeneration flow rate of each of the first to third hydraulic pump motors 11 to 13 is controlled according to the operating state of each operation. In more detail, the control device 27 calculates the required discharge flow rate and the required regeneration flow rate for each of the first to third hydraulic pump motors 11 to 13 based on each required flow rate and the operating state of each operation. In the present embodiment, the required regeneration flow rate of each of the first and third hydraulic pump motors 11 to 13 is the required flow rate of the boom of each of the first and third hydraulic pump motors 11 to 13. On the other hand, the discharge flow rate of each of the first to third hydraulic pump motors 11 to 13 is the total flow rate of the arm required flow rate and the bucket required flow rate for each of the first and third hydraulic pump motors 11 to 13.

[0044] The control device 27 calculates the control flow rate in each of the first and third hydraulic pump-motor 11 to 13. In more detail, the control device 27 selects the larger flow rate of the required discharge flow rate and the required regeneration flow rate as the control flow rate. Then, the control device 27 controls the operation of each of the first and third hydraulic pump-motor 11 to 13 and the first to third electric motors 14 to 16 based on the control flow rate. In more detail, the control device 27 outputs the first to third speed instructions and the first to third capacity instructions according to the control flow rate. As a result, the discharge flow rate or the suction flow rate of the first to third hydraulic pump-motor 11 to 13 is controlled to the control flow rate. For example, for the hydraulic pump-motor for which the required discharge flow rate is selected among the first to third hydraulic pump-motor 11 to 13, the discharge flow rate is controlled to the required discharge flow rate. On the other hand, for the hydraulic pump-motor for which the required regeneration flow rate is selected among the first to third hydraulic pump-motor 11 to 13, the suction flow rate is controlled to the required regeneration flow rate. When the discharge flow rate or the regeneration flow rate is controlled, the process moves to step S5.

[0045] In step S5, which is a merging mechanism opening and closing process, the merging mechanism 24 is opened and closed according to the respective required flow rates. In more detail, the control device 27 opens and closes the first and second merging valves 41 and 42 according to the arm required flow rates and bucket required flow rates of the first to third hydraulic pump motors 11 to 13 and the operating state of each operation. For example, when the operating amount of the second and third operations is small, the second and third hydraulic pump motors 12 and 13 supply working fluid to each hydraulic cylinder 4 and 5 independently of each other. Therefore, the control device 27 keeps the first and second merging valves 41 and 42 in a closed state.

[0046] On the other hand, when the operation amount of the second operation becomes larger, the boom cylinder 4 is required to be supplied with working fluid from the first and third hydraulic pump motors 11 and 13 in addition to the second hydraulic pump motor 12 in stages. The control device 27 first opens the second merging valve 42 to merge the working fluid of the third hydraulic pump motor 13 with the working fluid of the second hydraulic pump motor 12 and supplies it to the boom cylinder 4. In addition, when the flow rate of the working fluid is required, the control device 27 opens the first merging valve 41 in stages to further merge the working fluid of the first hydraulic pump motor 11 with the working fluid of the second hydraulic pump motor 12 and supplies it to the boom cylinder 4. Furthermore, when the operation amount of the third operation becomes larger, the bucket cylinder 5 is required to be supplied with working fluid from the second hydraulic pump motor 12 in addition to the third hydraulic pump motor 13. Therefore, the control device 27 opens the second merging valve 42. As a result, the working fluid of the second hydraulic pump motor 12 merges with the working fluid of the third hydraulic pump motor 13 and supplies it to the bucket cylinder 5. When the merging mechanism 24 is opened and closed according to the operation amounts of the second and third operations, the process proceeds to step S6.

[0047] In step S6, which is the unloading valve opening control process, the opening of the first to third unloading valves 21 to 23 is controlled according to the difference between the required discharge flow rate and the required regeneration flow rate in each of the first to third hydraulic pump-motor 11 to 13. Thus, the flow rate from the first to third hydraulic pump-motor 11 to 13 to each hydraulic cylinder 3 to 5 is controlled. That is, the control device 27 performs excess flow discharge control through the first to third unloading valves 21 to 23. Explaining the excess flow discharge control in more detail, the control device 27 calculates the difference between the required regeneration flow rate and the required discharge flow rate (for example, the value obtained by subtracting the required discharge flow rate from the required regeneration flow rate) for each of the first to third hydraulic pump-motor 11 to 13. Then, the control device 27 controls the opening of the first to third unloading valves 21 to 23 according to the difference between the required discharge flow rate and the required regeneration flow rate in each of the first to third hydraulic pump-motor 11 to 13.

[0048] Specifically, for each of the first to third hydraulic pump-motors 11 to 13, the control device 27 closes the corresponding first to third unloading valves 21 to 23 for the hydraulic pump-motors whose required discharge flow rate is greater than the required regeneration flow rate (i.e., the difference is negative). As a result, for the hydraulic pump-motors whose required discharge flow rate is greater than the required regeneration flow rate, the entire flow rate of the required discharge flow rate can be used for driving the hydraulic cylinders 3 to 5. On the other hand, for each of the first to third hydraulic pump-motors 11 to 13, the control device 27 controls the opening of the corresponding first to third unloading valves 21 to 23 for the hydraulic pump-motors whose required discharge flow rate is less than the required regeneration flow rate (i.e., the difference is positive). More specifically, the control device 27 controls the opening of each of the first to third unloading valves 21 to 23 based on the first to third differences. As a result, the control device 27 discharges the remaining flow rate obtained by subtracting the required discharge flow rate from the required regeneration flow rate from the corresponding first to third unloading valves 21 to 23 to the tank 28. Thus, the control device 27 supplies the necessary flow rate of the hydraulic fluid to each of the hydraulic cylinders 3 to 5. When the openings of the first to third unloading valves 21 to 23 are controlled based on the first to third differences, the flow ends.

[0049] In step S7, which is the unloading valve full closing process, the control device 27 fully closes the first to third unloading valves 21 to 23. Then, the control device 27 operates (extends or contracts) the hydraulic cylinders 3 to 5 according to the operation state of each operation. For example, when each operation is performed to operate the hydraulic cylinders 3 to 5, the control device 27 calculates the required discharge flow rates of the first to third hydraulic pump motors 11 to 13 based on the required flow rates and the operation state of each operation. The control device 27 outputs the first to third speed instructions and the first to third capacity instructions corresponding to the required discharge flow rates of the first to third hydraulic pump motors 11 to 13. As a result, the working fluid of the flow rate corresponding to the operation amount of each operation is discharged from the first to third hydraulic pump motors 11 to 13. In addition, the control device 27 outputs the first to third action instructions respectively according to the operation state of each operation. In this way, the corresponding first to third directional control valves 17 to 19 are operated. In this embodiment, the first to third directional control valves 17 to 19 are fully opened in the operating state. Therefore, the working fluid of the flow rate corresponding to the operation amount of each operation flows to the hydraulic cylinders 3 to 5. Therefore, the hydraulic cylinders 3 to 5 operate at speeds corresponding to the operation amounts of the respective operations.

[0050] Furthermore, the control device 27 opens the merging mechanism 24, or more specifically, opens the first and second merging valves 41 and 42, when the operation amount of each operation becomes larger. The first merging valve 41 is opened, so that the working fluids of the first and third hydraulic pump motors 11 and 13 merge. Thus, more working fluid can be supplied to, for example, the bucket cylinder 5. Furthermore, the second merging valve 42 is opened, so that the working fluids of the second and third hydraulic pump motors 12 and 13 merge. Thus, more working fluid can be supplied to, for example, the boom cylinder 4. In addition, the first and second merging valves 41 and 42 are opened, so that the working fluids of the first to third hydraulic pump motors 11 to 13 merge. Thus, more working fluid can be supplied to, for example, the boom cylinder 4. By supplying more working fluid in this way, the hydraulic cylinders 3 to 5 can operate at a faster speed corresponding to the operation amount of each operation.

[0051] The following describes the action of the hydraulic drive device 1 when the boom lowering operation is performed alone. When the boom lowering operation is performed alone, in step S1, the control device 27 determines whether the boom lowering operation has been performed. Then, in step S2, the control device 27 fully opens the first to third unloading valves 21 to 23. In addition, the control device 27 performs boom lowering regeneration. As a result, the fluid energy of the working fluid discharged from the head side port 3a of the boom cylinder 3 can be regenerated into electrical energy through the first to third hydraulic pump motors 11 to 13 and the first to third electric motors 14 to 16. Because it is a boom lowering operation alone, in step S3, the control device 27 determines that at least one of the second operation and the third operation is not performed while the boom lowering operation is being performed. In this way, the process ends.

[0052] Next, refer to Figure 4 The operation of the hydraulic drive system 1 when the second operation is performed simultaneously with the boom lowering operation will be described. Figure 4 (a) to (c) are graphs showing the required flow rates of the first to third hydraulic pump motors 11 to 13 relative to the operation amount of each operation when the second operation is performed simultaneously with the boom lowering operation. When the second operation is performed simultaneously with the boom lowering operation, in step S1, the control device 27 determines that the boom lowering operation is performed. Then, in step S2, the control device 27 fully opens the first to third unloading valves 21 to 23. Then, the control device 27 performs boom lowering regeneration. In step S3, the control device 27 determines that the second operation is performed simultaneously with the boom lowering operation. In step S4, the control device 27 calculates the control flow rates of the first to third hydraulic pump motors 11 to 13 based on the required flow rates and the operation amounts of the boom lowering operation and the second operation. In the present embodiment, the required regeneration flow rate (i.e., the boom required flow rate) is calculated as the control flow rate of the first hydraulic pump motor 11, and the required discharge flow rate (arm required flow rate) is calculated as the control flow rate of the second hydraulic pump motor 12. On the other hand, as the control flow rate of the third hydraulic pump-motor 13, when the operation amount of the second operation is small, the required regeneration flow rate is calculated, and when the operation amount of the second operation becomes large, the required discharge flow rate is calculated.

[0053] In step S5, when the operation amount of the second operation is small, the control device 27 keeps the first and second merging valves 41 and 42 closed. On the other hand, when the operation amount of the second operation becomes larger, the control device 27 opens the second merging valve 42. As a result, the working fluid from the third hydraulic pump motor 13 merges with the working fluid from the second hydraulic pump motor 12. Furthermore, when the operation amount of the second operation becomes larger, the control device 27 opens the first merging valve 41. As a result, in addition to the working fluid from the third hydraulic pump motor 13, the working fluid from the first hydraulic pump motor 11 also merges with the working fluid from the second hydraulic pump motor 12. In this way, the boom cylinder 4 can be operated faster by merging.

[0054] In step S6, the control device 27 controls the opening of the first to third unloading valves 21 to 23 according to the first to third differences. For example, in the second hydraulic pump motor 12, because the required discharge flow rate is always greater than the required regeneration flow rate (that is, the second difference is negative), the second unloading valve 22 becomes fully closed. On the other hand, the magnitude relationship between the required discharge flow rate and the required regeneration flow rate of the first and third hydraulic pump motors 11 and 13 changes according to the operation amount of the second operation. When the operation amount of the second operation is small, the required discharge flow rate is less than the required regeneration flow rate in each of the first and third hydraulic pump motors 11 and 13 (that is, the first and third differences are positive). Therefore, the control device 27 controls the opening of the first and third unloading valves 21 and 23 according to the first and third differences.

[0055] For example, when the required discharge flow rate of the first and third hydraulic pump-motor 11, 13 is zero, the first and third unloading valves 21, 23 are fully opened. Then, the control device 27 gradually closes the opening of the first and third unloading valves 21, 23 according to the first and third differences, because the required discharge flow rate increases as the operation amount of the second operation increases. As a result, the flow rate of the working fluid that merges with the working fluid from the second hydraulic pump-motor 12 can be increased while maintaining the suction flow rate in the first and third hydraulic pump-motor 11, 13 at the required regeneration flow rate. Thereafter, when the operation amount of the second operation further increases and the required discharge flow rate in each of the first and third hydraulic pump-motor 11, 13 further exceeds the required regeneration flow rate, the corresponding first and third unloading valves 21, 23 are closed. Furthermore, when the operation amount of the second operation is gradually reduced, the opening of each of the first and third unloading valves 21, 23 is gradually changed from the fully closed state to the fully open state according to the first and third differences, in the reverse order of the above. Then, the process ends.

[0056] In addition, refer to Figure 5 The operation of the hydraulic drive system 1 when the third operation is performed simultaneously with the boom lowering operation will be described. Figure 5 (a) to (c) are graphs showing the required flow rates of the first to third hydraulic pump motors 11 to 13 relative to the operation amount of each operation when the third operation is performed simultaneously with the boom lowering operation. When the third operation is performed simultaneously with the boom lowering operation, in step S1, the control device 27 determines that the boom lowering operation is performed. Then, in step S2, the control device 27 fully opens the first to third unloading valves 21 to 23. Then, the control device 27 performs boom lowering regeneration. In step S3, the control device 27 determines that the third operation is performed simultaneously with the boom lowering operation. In step S4, the control device 27 calculates the control flow rates of the first to third hydraulic pump motors 11 to 13 based on the required flow rates and the operation amounts of the boom lowering operation and the third operation. In the present embodiment, the required regeneration flow rate (i.e., the boom required flow rate) is calculated as the control flow rate of the first hydraulic pump motor 11, and the required discharge flow rate (bucket required flow rate) is calculated as the control flow rate of the third hydraulic pump motor 13. On the other hand, as the control flow rate of the second hydraulic pump-motor 12, when the operation amount of the third operation is small, the required regeneration flow rate is calculated, and when the operation amount of the third operation becomes large, the required discharge flow rate is calculated.

[0057] In step S5, when the operation amount of the third operation is small, the control device 27 keeps the first and second merging valves 41 and 42 closed. On the other hand, when the operation amount of the third operation becomes large, the control device 27 opens the second merging valve 42. As a result, the working fluid from the second hydraulic pump-motor 12 merges with the working fluid from the third hydraulic pump-motor 13. In this way, the bucket cylinder 5 can be operated more quickly.

[0058] In step S6, the control device 27 controls the opening of the second and third unloading valves 22 and 23 according to the second and third differences. For example, in the third hydraulic pump motor 13, the required discharge flow rate is always greater than the required regeneration flow rate (that is, the third difference is negative), so the third unloading valve 23 becomes fully closed. On the other hand, the magnitude relationship between the required discharge flow rate and the required regeneration flow rate of the second hydraulic pump motor 12 changes according to the operation amount of the third operation. When the operation amount of the third operation is small, the required discharge flow rate of the second hydraulic pump motor 12 is less than the required regeneration flow rate (that is, the second difference is positive). Therefore, the control device 27 controls the opening of the second unloading valve 22 to an opening corresponding to the second difference.

[0059] For example. When the required discharge flow rate is zero, the second unloading valve 22 is fully opened. Then, the control device 27 gradually closes the opening of the second unloading valve 22 according to the second difference because the required discharge flow rate increases as the operation amount of the third operation increases. As a result, it is possible to increase the flow rate of the working fluid that merges with the working fluid from the third hydraulic pump motor 13 while maintaining the suction flow in the second hydraulic pump motor 12 at the required regeneration flow rate. Thereafter, when the operation amount of the third operation further increases and the required discharge flow rate further exceeds the required regeneration flow rate, the second unloading valve 22 is closed. Furthermore, when the operation amount of the third operation is gradually reduced, the opening of the second unloading valve 22 gradually changes from a fully closed state to a fully open state according to the second difference, in the opposite order to the above. Thereafter, the process ends.

[0060] In the hydraulic drive device 1 of the present embodiment, the suction ports 11a to 13a of the first to third hydraulic pump motors 11 to 13 are connected in parallel to the meter-out passage 31. Therefore, the fluid energy of the working fluid discharged from the boom cylinder 3 can be regenerated into electrical energy through the first to third hydraulic pump motors 11 to 13. Therefore, the suction flow rate in each of the first to third hydraulic pump motors 11 to 13 can be suppressed during regeneration. As a result, each of the first to third hydraulic pump motors 11 to 13 can be miniaturized.

[0061] In the hydraulic drive device 1 of the present embodiment, the merging mechanism 24 merges the working fluid discharged from the discharge ports 11b to 13b of the first to third hydraulic pump motors 11 to 13 and supplies the fluid to the hydraulic cylinders 3 to 5. Therefore, the discharge flow rate from the first to third hydraulic pump motors 11 to 13 can be suppressed. Thus, the first to third hydraulic pump motors 11 to 13 can be miniaturized.

[0062] In addition, in the hydraulic drive device 1 of the present embodiment, the opening degree of each of the first to third unloading valves 21 to 23 can be adjusted. Therefore, the flow rate of the remaining portion of the working fluid discharged from the discharge ports 11b to 13b of the first to third hydraulic pump-motor 11 to 13 that is not discharged to the tank 28, that is, the flow rate of the working fluid supplied to each hydraulic cylinder 4, 5 can be controlled by the opening degree of the first to third unloading valves 21 to 23. As a result, the flow rate of the remaining portion of the working fluid that is not discharged to the tank 28 can be more accurately controlled and utilized while regenerating by the first to third hydraulic pump-motor 11 to 13 during regeneration. That is, the working fluid whose flow rate is more accurately controlled can be supplied from the second and third hydraulic pump-motor 12, 13 to the arm cylinder 4 and the bucket cylinder 5, respectively.

[0063] Furthermore, in the hydraulic drive device 1 of the present embodiment, the discharge ports 11b and 12b of the first and second hydraulic pump motors 11 and 12 are respectively connected to the boom cylinder 3 and the arm cylinder 4, so that the boom cylinder 3 and the arm cylinder 4 can be operated simultaneously. On the other hand, the suction ports 11a and 12a of the first and second hydraulic pump motors 11 and 12 are respectively connected to the outlet throttle passage 31 in parallel. Therefore, the fluid energy of the working fluid discharged from the boom cylinder 3 can be regenerated into electrical energy by the first and second hydraulic pump motors 11 and 12. Therefore, during the regeneration action, the suction flow rate of each of the first and second hydraulic pump motors 11 and 12 can be suppressed. Therefore, each of the first and second hydraulic pump motors 11 and 12 can be miniaturized.

[0064] In addition, in the hydraulic drive device 1 of the present embodiment, the first unloading valve 21 can adjust the opening degree. Therefore, the flow rate of the working fluid discharged from the discharge port 11b of the first hydraulic pump-motor 11 (that is, the flow rate of the remaining portion not discharged to the tank 28) can be controlled by the opening degree of the first unloading valve 21. As a result, the flow rate of the remaining portion of the working fluid not discharged to the tank 28 can be more accurately controlled and utilized while regenerating by the first and second hydraulic pump-motor 11 and 12 during regeneration. For example, the remaining portion of the working fluid can be used to merge the working fluid from the first hydraulic pump-motor 11 through the merging mechanism 24 and supply it to the boom cylinder 4, and the flow rate of the merged working fluid can be more accurately controlled.

[0065] In addition, in the hydraulic drive device 1 of the present embodiment, the second unloading valve 22 can adjust the opening degree. As a result, a part of the working fluid guided from the boom cylinder 3 to the second hydraulic pump motor 12 can be supplied to the arm cylinder 4, and the fluid energy of the remaining working fluid can be regenerated as electrical energy. Therefore, the working fluid discharged from the boom cylinder 3 can be effectively used.

[0066] In addition, in the hydraulic drive device 1 of the present embodiment, the merging mechanism 24 can merge the working fluid discharged from the respective discharge ports 11b and 12b of the first and second hydraulic pump motors 11 and 12. Therefore, the discharge flow rate from the first and second hydraulic pump motors 11 and 12 can be suppressed. Thus, each of the first and second hydraulic pump motors 11 and 12 can be miniaturized. In addition, since the flow rate of the working fluid that merges from the first hydraulic pump motor 11 can be controlled by the first unloading valve 21, the controllability of the boom cylinder 4 can be ensured even when merging.

[0067] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 27 controls the opening of the second unloading valve 22 according to the difference between the required regeneration flow rate and the required discharge flow rate. As a result, the excess flow rate not supplied to the boom cylinder 4 can be used as electric energy for regeneration. As a result, the energy consumption in the hydraulic drive device 1 can be suppressed.

[0068] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 27 controls the opening of the first unloading valve 21 according to the first difference, and controls the opening of the second unloading valve 22 according to the second difference. As a result, the surplus flow that is not supplied from the first to second hydraulic pump motors 11 and 12 to the boom cylinder 4 can be used as electric energy recovery. As a result, the energy consumption in the hydraulic drive device 1 can be suppressed.

[0069] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 27 controls the opening of the second unloading valve 22 according to the second difference, and controls the opening of the third unloading valve 23 according to the third difference. As a result, the surplus flow that is not supplied from the second and third hydraulic pump motors 12 and 13 to the arm cylinder 4 and the bucket cylinder 5, respectively, can be regenerated as electric energy. As a result, the energy consumption in the hydraulic drive device 1 can be suppressed.

[0070] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 27 controls the opening of the second unloading valve 22 according to the second difference, and controls the opening of the third unloading valve 23 according to the third difference. As a result, the surplus flow that is not supplied from the second and third hydraulic pump motors 12 and 13 to the arm cylinder 4 and the bucket cylinder 5, respectively, can be recovered as electric energy. As a result, the energy consumption in the hydraulic drive device 1 can be suppressed. In addition, since the flow of the working fluid that merges from the second and third hydraulic pump motors 12 and 13 can be controlled by the second and third unloading valves 22 and 23, respectively, the controllability of the flow of the working fluid after the merging can be ensured.

[0071] <Other embodiments> 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 working 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 converging valves becomes one. In addition, the hydraulic pump motor equipped with the hydraulic drive device 1 does not necessarily have to be the same as the number of hydraulic actuators. In addition, the hydraulic cylinders 3 to 5 are not limited to the boom cylinder 3, the dipper cylinder 4, and the bucket cylinder 5, and can also be other hydraulic cylinders.

[0072] In the hydraulic drive device 1 of the present embodiment, the first to third hydraulic pump motors 11 to 13 are connected in parallel with the outlet meter-out passage 31, but the number of hydraulic pump motors connected in parallel with the outlet meter-out passage 31 may be two or more than four. In addition, the second hydraulic actuator to which the second hydraulic pump motor 12 supplies the working fluid may also be the bucket cylinder 5. Similarly, the third hydraulic actuator to which the third hydraulic pump motor 13 supplies the working fluid may also be the boom cylinder 4. The aforementioned process is only an example of the telescopic operation of each cylinder, and other processes may also be used. In addition, the hydraulic drive device 1 does not necessarily have to be provided with the regeneration valve 20, and may also be provided with a regeneration valve that is different from the regeneration valve 20 and that connects the two ports 4a and 4b of the boom cylinder 4. In addition, the first to third hydraulic pump motors 11 to 13 may be fixed capacity type pumps, or may be bent axis pumps and gear pumps, etc. When the first to third hydraulic pump motors 11 to 13 are fixed capacity type pumps, the control device 27 controls the discharge flow rate and the suction flow rate by the rotation speed of the motors 14 to 16.

[0073] <Exemplary Embodiment> The hydraulic drive device in the first aspect is a hydraulic drive device for supplying and discharging working fluid to a hydraulic cylinder, and comprises: a plurality of hydraulic pump motors having a suction port and a discharge port; a plurality of electric motors respectively connected to the plurality of hydraulic pump motors; and a directional control valve connected to an outlet throttling channel, and the working fluid is discharged from the hydraulic cylinder to the outlet throttling channel by connecting the hydraulic cylinder to the outlet throttling channel, and the suction port of each of the plurality of hydraulic pump motors is connected in parallel with the outlet throttling channel.

[0074] According to the above aspect, the suction ports of the plurality of hydraulic pumps and motors are connected in parallel to the outlet throttle passage. Therefore, the fluid energy of the working fluid discharged from the hydraulic cylinder can be regenerated into electrical energy by the plurality of hydraulic pumps and motors. Therefore, during regeneration, the flow rate of the working fluid sucked into each of the hydraulic pumps and motors, that is, the suction flow rate, can be suppressed. Thus, each of the hydraulic pumps and motors can be miniaturized.

[0075] The hydraulic drive device according to the second aspect may be the hydraulic drive device according to the first aspect, further comprising a merging mechanism that merges the working fluid discharged from the respective discharge ports of the plurality of hydraulic pumps and motors and supplies the working fluid to the hydraulic cylinder.

[0076] According to the above aspect, the merging mechanism merges the working fluid discharged from the discharge ports of the hydraulic pump and motor and supplies the combined working fluid to the hydraulic cylinder. Therefore, the discharge flow rate from each hydraulic pump and motor can be suppressed. Thus, the plurality of hydraulic pumps and motors can be miniaturized.

[0077] The hydraulic drive device according to the third aspect may be the hydraulic drive device according to the first or second aspect, further comprising: a plurality of unloading valves for discharging at least a portion of the working fluid discharged from the discharge ports of the plurality of hydraulic pumps and motors into a tank; The plurality of unloading valves adjust opening degrees.

[0078] According to the above aspect, the opening degree of each unloading valve can be adjusted. Therefore, the flow rate of the working fluid discharged from the discharge port of each hydraulic pump and motor (that is, the flow rate of the remaining portion not discharged to the tank) can be controlled by the opening degree of the unloading valve. As a result, the flow rate of the remaining portion of the working fluid not discharged to the tank can be more accurately controlled and utilized while regenerating by a plurality of hydraulic pumps and motors during regeneration.

[0079] The hydraulic drive device of the fourth aspect is a hydraulic drive device for supplying and discharging working fluid to multiple hydraulic actuators including a first hydraulic actuator serving as a hydraulic cylinder, and comprises: multiple hydraulic pump motors having a suction port and a discharge port, the discharge ports being respectively connected to the multiple hydraulic actuators; multiple electric motors being respectively connected to the multiple hydraulic pump motors; and a directional control valve being connected to an outlet throttling channel, and discharging working fluid from the first hydraulic actuator to the outlet throttling channel by connecting the first hydraulic actuator to the outlet throttling channel, and the suction ports of the multiple hydraulic pump motors are respectively connected to the outlet throttling channel.

[0080] According to the above aspect, since the discharge ports of the hydraulic pumps and motors are connected to different hydraulic actuators, multiple hydraulic actuators can be operated simultaneously. On the other hand, the suction ports of the hydraulic pumps and motors are connected in parallel to the outlet throttle passage. Therefore, the fluid energy of the working fluid discharged from the first hydraulic actuator can be regenerated into electrical energy through the multiple hydraulic pumps and motors. Therefore, the flow rate of the working fluid sucked into each of the hydraulic pumps and motors, that is, the suction flow rate, can be suppressed during regeneration. As a result, each of the hydraulic pumps and motors can be miniaturized.

[0081] The hydraulic drive device in the fifth aspect may also be the hydraulic drive device in the fourth aspect, comprising a first unloading valve, wherein the multiple hydraulic pumps and motors include a first hydraulic pump and motor connected to the first hydraulic actuator, and the first unloading valve discharges at least a portion of the working fluid discharged from the discharge port of the first hydraulic pump and motor to a tank and adjusts the opening.

[0082] According to the above aspect, the first unloading valve can adjust the opening degree. Therefore, the flow rate of the working fluid discharged from the discharge port of the first hydraulic pump-motor (that is, the flow rate of the remaining portion not discharged to the tank) can be controlled by the opening degree of the first unloading valve. As a result, the flow rate of the remaining portion of the working fluid not discharged to the tank can be more accurately controlled and utilized while regenerating by the plurality of hydraulic pumps and motors during regeneration.

[0083] The hydraulic drive device in the sixth aspect may also be the hydraulic drive device in the fifth aspect, comprising a second unloading valve, wherein the multiple hydraulic pump-motors include a second hydraulic pump-motor connected to a second hydraulic actuator which is one of the multiple hydraulic actuators, and the second unloading valve discharges at least a portion of the working fluid discharged from the discharge port of the second hydraulic pump-motor to a tank and adjusts the opening.

[0084] According to the above aspect, the second unloading valve can adjust the opening degree. Therefore, a part of the working fluid directed from the first hydraulic actuator to the second hydraulic pump motor can be supplied to the second hydraulic actuator, and the fluid energy of the remaining working fluid can be recovered as electric energy. Therefore, the working fluid discharged from the first hydraulic actuator can be effectively used.

[0085] The hydraulic drive device in the seventh aspect may also be the hydraulic drive device in the sixth aspect, comprising a merging mechanism, wherein the discharge port of the first hydraulic pump motor is connected to the first hydraulic actuator, and the discharge port of the second hydraulic pump motor is connected to the second hydraulic actuator, and the merging mechanism merges the working fluid discharged from the respective discharge ports of the first hydraulic pump motor and the second hydraulic pump motor.

[0086] According to the above aspect, the merging mechanism can merge the working fluid discharged from the respective discharge ports of the first and second hydraulic pump motors. Therefore, the discharge flow rates from the first and second hydraulic pump motors can be suppressed. As a result, each of the first and second hydraulic pump motors can be miniaturized. In addition, since the flow rate of the working fluid merging from the first hydraulic pump motor can be controlled by the first unloading valve, the controllability of the second hydraulic actuator can be ensured even when the working fluid merges.

[0087] The hydraulic drive device of the eighth aspect may also be a hydraulic drive device of the sixth or seventh aspect, comprising: a control device, which controls the action of the directional control valve and the second unloading valve according to an input signal, the control device operates the directional control valve according to the input signal to connect the first hydraulic actuator to the outlet throttling channel and calculates a required regeneration flow rate as the flow regenerated from the first hydraulic actuator to the second hydraulic pump motor and a required discharge flow rate as the flow discharged from the second hydraulic pump motor based on the input signal, and controls the opening of the second unloading valve according to the difference between the required regeneration flow rate and the required discharge flow rate.

[0088] According to the above aspect, the control device controls the opening of the second unloading valve according to the difference between the required regeneration flow rate and the required discharge flow rate. Thus, the surplus flow rate not supplied to the second hydraulic actuator can be used as electric energy for regeneration. Thus, the energy consumption in the hydraulic drive device can be suppressed.

[0089] The hydraulic drive device of the ninth aspect may be the hydraulic drive device of the seventh aspect, further comprising: a control device that controls the operation of the directional control valve, the merging mechanism, the first unloading valve, and the second unloading valve based on an input signal, wherein the control device calculates a required regeneration flow rate, which is a flow rate regenerated from the first hydraulic actuator to the first hydraulic pump-motor and the second hydraulic pump-motor, and a required discharge flow rate, which is a flow rate discharged from the first hydraulic pump-motor and the second hydraulic pump-motor, respectively, based on the input signal, when the directional control valve is operated based on the input signal to connect the first hydraulic actuator to the meter-out passage and the working fluid discharged from the respective discharge ports of the first hydraulic pump-motor and the second hydraulic pump-motor are combined through the merging mechanism and supplied to the second hydraulic actuator, respectively, and controls the opening of the first unloading valve based on a first difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the first hydraulic pump-motor, and controls the opening of the second unloading valve based on a second difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the second hydraulic pump-motor.

[0090] According to the above aspect, the control device controls the opening of the first unloading valve according to the first difference, and controls the opening of the second unloading valve according to the second difference. As a result, the surplus flow not supplied from the two hydraulic pump motors to the hydraulic actuator can be recovered as electric energy. As a result, the energy consumption in the hydraulic drive device can be suppressed.

[0091] The hydraulic drive device in the tenth aspect may also be the hydraulic drive device in any one of the sixth to ninth aspects, further comprising: a third unloading valve; and a control device, which controls the operation of the directional control valve, the second unloading valve, and the third unloading valve according to an input signal, the plurality of hydraulic pumps and motors also include a third hydraulic pump and motor connected to a third hydraulic actuator as one of the plurality of hydraulic actuators, the third unloading valve discharges at least a portion of the working fluid discharged from the discharge port of the third hydraulic pump and motor to a tank, and adjusts the opening, and the control device controls the operation of the directional control valve according to the input signal. When the first hydraulic actuator is connected to the outlet meter-out passage, a required regeneration flow rate, which is a flow rate regenerated from the first hydraulic actuator to the second and third hydraulic pump-motors, and a required discharge flow rate, which is a flow rate discharged from the second and third hydraulic pump-motors, are calculated based on input signals, and the opening of the second unloading valve is controlled according to a second difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the second hydraulic pump-motors, and the opening of the third unloading valve is controlled according to a third difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the third hydraulic pump-motors.

[0092] According to the above aspect, the control device controls the opening of the second unloading valve according to the second difference, and controls the opening of the third unloading valve according to the third difference. As a result, the surplus flow not supplied from the two hydraulic pump motors to the second and third hydraulic actuators can be recovered as electric energy. As a result, the energy consumption in the hydraulic drive device can be suppressed.

[0093] The hydraulic drive device in the eleventh aspect may also be the hydraulic drive device in the tenth aspect, further comprising a merging mechanism, wherein the merging mechanism causes the working fluid discharged from the respective discharge ports of the second hydraulic pump-motor and the third hydraulic pump-motor to merge and supply the working fluid to the second hydraulic actuator or the third hydraulic actuator, and the control device, when operating the directional control valve according to an input signal to connect the first hydraulic actuator to the outlet throttling channel and merging the working fluid discharged from the respective discharge ports of the second hydraulic pump-motor and the third hydraulic pump-motor through the merging mechanism, controls the opening of the second unloading valve according to the second difference, and controls the opening of the third unloading valve according to the third difference.

[0094] According to the above aspect, the control device controls the opening of the second unloading valve according to the second difference, and controls the opening of the third unloading valve according to the third difference. As a result, the surplus flow that is not supplied from the two hydraulic pumps and motors to the hydraulic actuator can be recovered as electric energy. As a result, the energy consumption in the hydraulic drive device can be suppressed. In addition, the flow of the working fluid that merges from the second and third hydraulic pumps and motors can be controlled by the second and third unloading valves, respectively, so the controllability of the flow of the working fluid after the merging can be ensured.

[0095] According to the above description, many improvements and other embodiments of the present invention are clear to those skilled in the art. Therefore, the above description should only be interpreted as an example, and is provided for the purpose of teaching the best mode of performing the present invention to those skilled in the art. As long as it does not depart from the gist of the present invention, its specific structure and / or function can be substantially changed.

Claims

1. A hydraulic drive device, characterized in that: It is a hydraulic drive device that supplies and discharges working fluid to the hydraulic cylinder. It comprises: a plurality of hydraulic pump motors having a suction port and a discharge port; a plurality of electric motors connected to the plurality of hydraulic pump motors, respectively; and a directional control valve connected to the outlet meter-out passage, and connected to the hydraulic cylinder to discharge the working fluid from the hydraulic cylinder to the outlet meter-out passage; The suction port of each of the plurality of hydraulic pump motors is connected in parallel to the meter-out passage.

2. The hydraulic drive device according to claim 1, characterized in that: A merging mechanism is provided for merging the hydraulic fluids discharged from the respective discharge ports of the plurality of hydraulic pumps and motors and supplying the hydraulic fluids to the hydraulic cylinder.

3. The hydraulic drive device according to claim 1 or 2, characterized in that: The invention further comprises: a plurality of unloading valves configured to discharge at least a portion of the hydraulic fluid discharged from the discharge ports of the plurality of hydraulic pumps and motors into a tank; The plurality of unloading valves adjust opening degrees.

4. A hydraulic drive device, characterized in that: A hydraulic drive device for supplying and discharging working fluid to a plurality of hydraulic actuators including a first hydraulic actuator as a hydraulic cylinder, It comprises: a plurality of hydraulic pump motors having a suction port and a discharge port, wherein the discharge ports are respectively connected to the plurality of hydraulic actuators; A plurality of electric motors, which are respectively connected to the plurality of hydraulic pump motors; and a directional control valve connected to the throttle-out passage, and configured to discharge the working fluid from the first hydraulic actuator to the throttle-out passage by connecting the first hydraulic actuator to the throttle-out passage; The suction port of each of the plurality of hydraulic pump motors is connected in parallel to the meter-out passage.

5. The hydraulic drive device according to claim 4, characterized in that: Equipped with a first unloading valve, The plurality of hydraulic pumps and motors include a first hydraulic pump and motor connected to the first hydraulic actuator, The first unloading valve discharges at least a portion of the hydraulic fluid discharged from the discharge port of the first hydraulic pump and motor to a tank, and adjusts the opening degree.

6. The hydraulic drive device according to claim 5, characterized in that: Equipped with a second unloading valve, The plurality of hydraulic pump-motors include a second hydraulic pump-motor connected to a second hydraulic actuator that is one of the plurality of hydraulic actuators. The second unloading valve discharges at least a portion of the hydraulic fluid discharged from the discharge port of the second hydraulic pump and motor to a tank, and adjusts the opening degree.

7. The hydraulic drive device according to claim 6, characterized in that: With confluence mechanism, The discharge port of the first hydraulic pump motor is connected to the first hydraulic actuator, The discharge port of the second hydraulic pump motor is connected to the second hydraulic actuator. The merging mechanism merges the hydraulic fluids discharged from the respective discharge ports of the first hydraulic pump-motor and the second hydraulic pump-motor.

8. The hydraulic drive device according to claim 6, characterized in that: The device comprises: a control device for controlling the operation of the directional control valve and the second unloading valve according to an input signal; The control device operates the directional control valve according to an input signal to connect the first hydraulic actuator to the outlet meter-out passage, and calculates a required regeneration flow rate as a flow rate regenerated from the first hydraulic actuator to the second hydraulic pump-motor and a required discharge flow rate as a flow rate discharged from the second hydraulic pump-motor based on the input signal, and controls the opening degree of the second unloading valve according to the difference between the required regeneration flow rate and the required discharge flow rate.

9. The hydraulic drive device according to claim 7, characterized in that: The invention comprises: a control device for controlling the operation of the directional control valve, the merging mechanism, the first unloading valve, and the second unloading valve according to an input signal, The control device calculates a required regeneration flow rate, which is a flow rate regenerated from the first hydraulic actuator to the first hydraulic pump-motor and the second hydraulic pump-motor, and a required discharge flow rate, which is a flow rate discharged from the first hydraulic pump-motor and the second hydraulic pump-motor, respectively, based on the input signal, when the directional control valve is operated in accordance with an input signal to connect the first hydraulic actuator to the meter-out passage and the working fluid discharged from the respective discharge ports of the first hydraulic pump-motor and the second hydraulic pump-motor are combined by the combining mechanism and supplied to the second hydraulic actuator, controls the opening of the first unloading valve in accordance with a first difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the first hydraulic pump-motor, and controls the opening of the second unloading valve in accordance with a second difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the second hydraulic pump-motor.

10. The hydraulic drive device according to claim 6, characterized in that: Also provided: a third unloading valve; and a control device, which controls the actions of the directional control valve, the second unloading valve, and the third unloading valve according to an input signal, The plurality of hydraulic pumps and motors further include a third hydraulic pump and motor connected to a third hydraulic actuator as one of the plurality of hydraulic actuators. The third unloading valve discharges at least a portion of the hydraulic fluid discharged from the discharge port of the third hydraulic pump and motor to a tank and adjusts the opening degree. The control device, when operating the directional control valve in accordance with an input signal to connect the first hydraulic actuator to the meter-out passage, calculates a required regeneration flow rate, which is a flow rate regenerated from the first hydraulic actuator to the second and third hydraulic pump-motors, and a required discharge flow rate, which is a flow rate discharged from the second and third hydraulic pump-motors, respectively, based on the input signal, controls the opening of the second unloading valve in accordance with a second difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the second hydraulic pump-motors, and controls the opening of the third unloading valve in accordance with a third difference, which is a difference between the required regeneration flow rate and the required discharge flow rate related to the third hydraulic pump-motors.

11. The hydraulic drive device according to claim 10, characterized in that: It also has a confluence mechanism. The merging mechanism merges the hydraulic fluid discharged from the respective discharge ports of the second hydraulic pump-motor and the third hydraulic pump-motor and supplies the hydraulic fluid to the second hydraulic actuator or the third hydraulic actuator. The control device controls the opening of the second unloading valve according to the second difference and controls the opening of the third unloading valve according to the third difference when the directional control valve is operated according to the input signal to connect the first hydraulic actuator to the outlet throttling channel and the working fluid discharged from the respective discharge ports of the second hydraulic pump-motor and the third hydraulic pump-motor are merged through the merging mechanism.

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