Hydraulic drive device

Abstract

This hydraulic drive device supplies a hydraulic fluid to a hydraulic cylinder having a head-side port and a rod-side port, and is provided with: a hydraulic pump motor having a suction port and a discharge port; the electric motor is connected with the hydraulic pump motor; a direction control valve for switching the connection target of the head-side port to the discharge port and the suction port; a regeneration valve that opens and closes a regeneration channel that connects the head-side port and the rod-side port; and an unloading valve connecting the discharge channel and the tank, wherein the discharge channel connects the discharge port and the direction control valve.

Description

Technical Field

[0001] The present disclosure relates to a hydraulic drive device for supplying and discharging a hydraulic fluid to and from a hydraulic cylinder having a head-side port and a rod-side port. Background Art

[0002] As a hydraulic drive device for driving a hydraulic cylinder, for example, there is known a hydraulic drive device such as that disclosed in Patent Document 1. In the hydraulic drive device such as that disclosed in Patent Document 1, during the boom lowering operation, the hydraulic pump motor is driven by the working fluid discharged from the head side port of the boom cylinder to rotate. 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, energy consumption can be suppressed by regenerating fluid energy of the working fluid into electrical energy. However, in addition to energy consumption, the hydraulic drive device of Patent Document 1 is also required to improve operability.

[0005] Therefore, an object of the present disclosure is to provide a hydraulic drive device capable of improving operability while suppressing energy consumption.

[0006] Means of solving the problem: The hydraulic drive device disclosed in the present invention is a hydraulic drive device that supplies working fluid to a hydraulic cylinder having a head side port and a rod side port, and comprises: a hydraulic pump motor having a suction port and a discharge port; an electric motor connected to the hydraulic pump motor; a directional control valve that switches the connection object of the head side port to the discharge port and the suction port respectively; a regeneration valve that opens and closes a regeneration channel that connects the head side port and the rod side port; and an unloading valve that connects the discharge channel to a tank, and the discharge channel connects the discharge port and the directional control valve.

[0007] According to the present disclosure, the directional control valve connects the head side port and the suction port, and the unloading valve connects the discharge channel and the tank. Therefore, when the hydraulic cylinder contracts, the working fluid is pushed out from the head side port and supplied to the suction port of the hydraulic pump motor. As a result, the electric motor can be driven via the hydraulic pump motor, so energy can be recovered by the electric motor. Therefore, energy consumption in the hydraulic drive device can be suppressed.

[0008] Furthermore, according to the present disclosure, the regeneration valve opens and closes the regeneration passage connecting the head side port and the rod side port. By opening the regeneration valve when the working fluid is pushed out from the head side port, a part of the pushed out working fluid is regenerated in the rod side port. Thus, the working fluid can be quickly supplied to the rod side port, so the operability can be improved.

[0009] Effect of the invention: According to the present disclosure, it is possible to reduce the size of the hydraulic drive device while suppressing energy consumption.

[0010] 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

[0011] Figure 1 is a circuit diagram showing the structure of a hydraulic drive device according to a first embodiment of the present disclosure; Figure 2 It is shown Figure 1 A circuit diagram showing the flow of working fluid when the boom cylinder is extended in a hydraulic drive device; Figure 3 It is shown Figure 1 A circuit diagram showing the flow of working fluid when the boom cylinder is retracted in a hydraulic drive device; Figure 4 1 is a circuit diagram showing the structure of a hydraulic drive device according to a second embodiment of the present disclosure. DETAILED DESCRIPTION

[0012] Hereinafter, the hydraulic drive device 1, 1A according to the first and second embodiments of the present disclosure will be described with reference to the above-mentioned drawings. In addition, the concept of direction used in the following description is used for the convenience of description, and does not limit the direction of the structure of the invention to the direction. In addition, the hydraulic drive device 1, 1A described below is only one embodiment of the present disclosure. Therefore, the present disclosure is not limited to the embodiment, and additions, deletions, and changes can be made within the scope of the main purpose of the invention.

[0013] [First embodiment] 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 has a boom, a dipper, and an attachment (such as a bucket). The hydraulic excavator can perform various operations by moving the boom, the dipper, and the attachment (such as a bucket). The hydraulic excavator has a boom cylinder 2.

[0014] The boom cylinder 2 as an example of a hydraulic cylinder has a head side port 2a and a rod side port 2b. The boom cylinder 2 is provided on the boom. The boom cylinder 2 moves the boom by extending and retracting. To explain in more detail, when working fluid (such as a liquid such as oil or water) is supplied to the head side port 2a and the working fluid is discharged from the rod side port 2b, the boom cylinder 2 extends. As a result, the boom rises. On the other hand, the boom cylinder 2 contracts by discharging the working fluid from the head side port 2a and supplying the working fluid to the rod side port 2b. As a result, the boom descends. In addition, in the present embodiment, the boom cylinder 2 bears the dead weight of the boom in the direction of contraction. Therefore, the boom cylinder 2 discharges the working fluid from the head side port 2a by the dead weight of the boom, and contracts by sucking the working fluid from the rod side port 2b.

[0015] <Hydraulic drive unit> The hydraulic drive device 1 supplies and discharges working fluid to the boom cylinder 2. Thus, the hydraulic drive device 1 drives the boom cylinder 2. In more detail, the hydraulic drive device 1 supplies and discharges working fluid to the head side port 2a and the rod side port 2b respectively. Thus, the hydraulic drive device 1 extends and retracts the boom cylinder 2. In addition, the hydraulic drive device 1 regenerates energy of the working fluid discharged from the head side port 2a of the boom cylinder 2. The hydraulic drive device 1 that functions in this way includes a hydraulic pump motor 11, an electric motor 12, a directional control valve 13, a regeneration valve 14, and an unloading valve 15. In addition, the hydraulic drive device 1 includes an operating device 16, a temperature sensor 17, and a control device 18.

[0016] <Hydraulic pump motor> The hydraulic pump motor 11 has a suction port 11a and a discharge port 11b. The hydraulic pump motor 11 also has a shaft portion 11c. The suction port 11a is connected to the tank 20 via a suction passage 21. In addition, a check valve 19 is provided in the middle of the suction passage 21. The check valve 19 allows the flow of the working fluid from the tank 20 to the suction port 11a and prevents the flow in the reverse direction.

[0017] The hydraulic pump motor 11 operates as follows when the shaft 11c is driven to rotate. That is, the hydraulic pump motor 11 sucks working fluid from the suction port 11a. Then, the hydraulic pump motor 11 discharges working fluid from the discharge port 11b. On the other hand, when the working fluid is supplied to the suction port 11a, the hydraulic pump motor 11 rotates the shaft 11c. Then, the hydraulic pump motor 11 discharges the working fluid from the discharge port 11b. The hydraulic pump motor 11, in this embodiment, is a variable capacity swash plate pump and has a regulator 11d. The regulator 11d changes the tilt angle of the swash plate based on the input capacity instruction. In this way, the piston capacity of the hydraulic pump motor 11 changes. That is, the hydraulic pump motor 11 can change the discharge flow rate and the suction flow rate.

[0018] <Motor> The electric motor 12 is connected to the hydraulic pump motor 11. In more detail, the electric motor 12 is connected to the shaft 11c. The electric motor 12 drives the hydraulic pump motor 11 by rotation so that the working fluid is discharged from the hydraulic pump motor 11. In more detail, the electric motor 12 drives the shaft 11c by rotation so that the working fluid is discharged from the discharge port 11b. In addition, the electric motor 12 generates electricity by receiving the supply of working fluid and rotating the hydraulic pump motor 11 (in more detail, the shaft 11c). That is, the electric motor 12 cooperates with the hydraulic pump motor 11 to regenerate the fluid energy of the working fluid into electrical energy. In addition, the electric motor 12 changes the rotation speed (in more detail, the rotation speed of the shaft 11c) according to the input rotation speed command.

[0019] <Directional control valve> The directional control valve 13 is connected to the suction port 11a and the discharge port 11b of the hydraulic pump motor 11, respectively. In more detail, the directional control valve 13 is connected to the suction port 11a side of the hydraulic pump motor 11 relative to the check valve 19 in the suction passage 21. In addition, the directional control valve 13 is connected to the discharge port 11b via the discharge passage 22. The directional control valve 13 is connected to the head side port 2a of the boom cylinder 2. In addition, the directional control valve 13 is connected to the rod side port 2b of the boom cylinder 2 and the tank 20.

[0020] The directional control valve 13 switches the connection object of the head side port 2a to the discharge port 11b and the suction port 11a respectively according to the input action command. In addition, when the head side port 2a is connected to the discharge port 11b, the directional control valve 13 connects the rod side port 2b to the tank 20. On the other hand, when the head side port 2a is connected to the suction port 11a, the directional control valve 13 connects the rod side port 2b to the discharge port 11b. In addition, when the rod side port 2b is connected to the discharge port 11b, the directional control valve 13 allows the flow of the working fluid from the discharge port 11b to the rod side port 2b, and blocks the flow of the working fluid in the opposite direction. In addition, when the head side port 2a is connected to the suction port 11a, the directional control valve 13 controls the opening between the head side port 2a and the suction port 11a according to the action command (hereinafter referred to as "the opening of the directional control valve 13"). In this embodiment, the directional control valve 13 is an electrical slide valve. However, the directional control valve 13 is not limited to the electric spool valve.

[0021] <Regeneration valve> The regeneration valve 14 opens and closes the regeneration channel 23 connecting the head side port 2a and the rod side port 2b. The regeneration valve 14 is disposed in the regeneration channel 23. The regeneration valve 14 opens and closes the regeneration channel 23 according to the regeneration instruction. In addition, the regeneration valve 14 allows the flow of the working fluid in the regeneration direction while opening the regeneration channel 23, and blocks the flow in the opposite direction. The regeneration direction refers to the flow from the head side port 2a to the rod side port 2b. Thus, the regeneration valve 14 regenerates the working fluid discharged from the head side port 2a to the rod side port 2b. The regeneration valve 14 throttles the opening according to the regeneration instruction. The regeneration valve 14 is, for example, an electromagnetic proportional control valve.

[0022] <Unloading valve> The unloading valve 15 connects the discharge channel 22 to the tank 20, and the discharge channel 22 connects the discharge port 11b and the directional control valve 13. In more detail, the unloading valve 15 connects the discharge channel 22 to the tank 20 according to the input unloading command. In this way, the hydraulic pump motor 11 can be unloaded. In this embodiment, the unloading valve 15 is an electromagnetic on-off valve. However, the unloading valve 15 can also be an electromagnetic proportional control valve whose opening can be controlled.

[0023] <Operation device> The operating device 16 is a device for operating the boom (more specifically, the boom cylinder 2). The operating device 16 has an operating rod 16a. The operating rod 16a is configured to be operable. The operating device 16 outputs an operating signal corresponding to the operating direction and operating amount of the operating rod 16a. The operating device 16 is, for example, an electric joystick. However, the operating device 16 may also be a pilot operating valve. In this case, the operating device 16 outputs an operating signal corresponding to the output pressure of the pilot operating valve. In addition, the operating device 16 may also be a touch panel. In this case, the operating device 16 outputs an operating signal according to the input operation or program.

[0024] <Temperature sensor> The temperature sensor 17 detects the coil temperature of the motor 12. In more detail, the temperature sensor 17 directly or indirectly detects the coil temperature of the motor 12. In the present embodiment, the temperature sensor 17 is provided in the housing of the motor 12. The temperature sensor 17 detects the coil temperature indirectly by detecting the temperature of the housing of the motor 12. Then, the temperature sensor 17 outputs the detected temperature of the housing of the motor 12.

[0025] <Control device> The control device 18 controls the operation of the directional control valve 13, the regeneration valve 14, and the unloading valve 15 according to the input operation signal. In more detail, the control device 18 controls the operation of the directional control valve 13, the regeneration valve 14, and the unloading valve 15 by outputting an operation command, a regeneration command, and an unloading command corresponding to the operation signal. Thus, the control device 18 controls the flow of the working fluid in the hydraulic drive device 1. In addition, the control device 18 controls the operation of the hydraulic pump motor 11 and the electric motor 12 according to the operation signal. In more detail, the control device 18 controls the operation of the hydraulic pump motor 11 and the electric motor 12 by outputting a capacity command and a speed command corresponding to the operation signal. Thus, the control device 18 controls the discharge flow rate and the suction flow rate of the hydraulic pump motor 11. In addition, the control device 18 controls the operation of the directional control valve 13 and the regeneration valve 14 based on the coil temperature detected by the temperature sensor 17. In more detail, the control device 18 controls the opening of the directional control valve 13 and the regeneration valve 14 based on the coil temperature detected by the temperature sensor 17.

[0026] <Operation of the hydraulic drive unit> In the hydraulic drive device 1, when the operating device 16 (in this embodiment, the operating lever 16a is operated), an operating signal is output from the operating device 16. The control device 18 controls the operation of the directional control valve 13, the regeneration valve 14, and the unloading valve 15 according to the operating signal. In addition, the control device 18 controls the operation of the electric motor 12 and the hydraulic pump motor 11 according to the operating signal. As a result, the control device 18 extends and retracts the boom cylinder 2 in the direction and speed corresponding to the operating signal (in this embodiment, the operating direction and the operating amount of the operating lever 16a). In the hydraulic drive device 1, when the boom is lowered (that is, when the boom cylinder 2 is retracted), part of the working fluid discharged from the head side port 2a of the boom cylinder 2 is regenerated in the rod side port 2b. In addition, in the hydraulic drive device 1, the remaining part of the working fluid discharged from the head side port 2a is regenerated by energy. In addition, the control device 18 controls the opening of the directional control valve 13 and the regeneration valve 14 based on the coil temperature of the electric motor 12. As a result, the excessive increase in the coil temperature of the electric motor 12 is suppressed.

[0027] [Extension action of boom cylinder] The following will describe in more detail the case of extending and retracting the boom cylinder 2. In the hydraulic drive device 1, when the operating device 16 is operated to extend the boom cylinder 2, an operating signal is output from the operating device 16. In this way, the control device 18 operates the directional control valve 13 according to the operating signal. In more detail, the control device 18 outputs an operating instruction corresponding to the operating signal to the directional control valve 13. As a result, the directional control valve 13, such as Figure 2As shown, the discharge port 11b is connected to the head side port 2a, and the rod side port 2b is connected to the tank 20. Then, the suction port 11a is cut off from the head side port 2a and the rod side port 2b by the directional control valve 13. In addition, the control device 18 outputs a speed command and a capacity command corresponding to the operation signal. As a result, the hydraulic pump motor 11 discharges the working fluid at a flow rate corresponding to the operation signal from the discharge port 11b. The discharged working fluid is guided to the head side port 2a ( Figure 2 On the other hand, the working fluid is discharged from the rod side port 2b to the tank 20 via the directional control valve 13 ( Figure 2 As a result, the boom cylinder 2 extends at a speed corresponding to the operation signal (see arrow A2). Figure 2 Therefore, the boom can be raised at a speed corresponding to the operation signal.

[0028] [Retraction action of boom cylinder] In the hydraulic drive device 1, when the operating device 16 is operated to retract the boom cylinder 2, an operating signal is output from the operating device 16. In this way, the control device 18 operates the directional control valve 13, the regeneration valve 14, and the unloading valve 15 according to the operating signal. In more detail, the control device 18 outputs an operation command corresponding to the operating signal to the directional control valve 13. As a result, the control device 18, as shown in FIG. Figure 3 As shown, the head side port 2a is connected to the suction port 11a through the directional control valve 13. In addition, the control device 18 outputs a regeneration command to the regeneration valve 14. As a result, the control device 18 opens the regeneration passage 23 through the regeneration valve 14. In this way, the head side port 2a is connected to the rod side port 2b. In addition, the control device 18 outputs a unloading command to the unloading valve 15. As a result, the control device 18 connects the discharge passage 22 to the tank 20 through the unloading valve 15. In this way, the hydraulic pump motor 11 is unloaded.

[0029] As described above, when the directional control valve 13, the regeneration valve 14, and the unloading valve 15 are operated, the working fluid flows as follows. That is, the boom cylinder 2 bears the deadweight of the boom in the direction of contraction. Therefore, the boom cylinder 2 contracts due to the deadweight of the boom. As a result, the working fluid is discharged from the head side port 2a. A part of the discharged working fluid is supplied to the rod side port 2b through the regeneration passage 23. That is, a part of the working fluid is regenerated from the head side port 2a to the rod side port 2b (refer to Figure 3 On the other hand, the remaining portion is supplied to the suction port 11a of the hydraulic pump motor 11 via the directional control valve 13 (see Figure 3Then, the remaining part is discharged from the discharge port 11b to the tank 20 through the unloading valve 15 after the motor 12 is rotated by the hydraulic pump motor 11. The motor 12 generates electricity by rotating the motor 12. As a result, the remaining part of the fluid energy is recovered as electrical energy. In other words, the potential energy of the boom is recovered as electrical energy. In this way, the discharged working fluid can be regenerated.

[0030] Furthermore, the control device 18 controls the suction flow rate of the hydraulic pump motor 11, thereby causing the boom cylinder 2 to retract at a speed corresponding to the operation signal. To explain in more detail, the control device 18 outputs a rotation speed command and a capacity command corresponding to the operation signal. As a result, the hydraulic pump motor 11 can cause the working fluid of a flow rate corresponding to the operation signal to flow into the suction port 11a, so that the flow rate of the working fluid discharged from the head side port 2a of the boom cylinder 2 can be controlled to a flow rate corresponding to the operation signal. In this way, the flow rate of the working fluid regenerated in the rod side port 2b is controlled to a flow rate corresponding to the operation signal, so the boom cylinder 2 can be retracted at a speed corresponding to the operation signal (refer to Figure 3 As a result, the boom can be lowered at a speed corresponding to the operation signal.

[0031] In addition, the control device 18 throttles the opening of the regeneration valve 14 when the prescribed condition is met. Furthermore, the control device 18 throttles the opening between the head side port 2a and the suction port 11a through the directional control valve 13 when the prescribed condition is met. In other words, the control device 18 throttles the opening of the directional control valve 13 when the prescribed condition is met. In the present embodiment, the prescribed condition is that the coil temperature of the motor 12 is above the prescribed temperature. That is, the control device 18 throttles the opening of the regeneration valve 14 to suppress the coil temperature of the motor 12 from becoming excessively high, and throttles the opening between the head side port 2a and the suction port 11a through the directional control valve 13.

[0032] To explain in more detail, the control device 18 estimates the coil temperature based on the temperature of the housing detected by the temperature sensor 17. Then, when the head side port 2a is connected to the suction port 11a through the directional control valve 13 (that is, when the boom cylinder 2 is retracted), the control device 18 determines whether the coil temperature is above the specified temperature. When the coil temperature is lower than the specified temperature, the control device 18 makes the opening of the regeneration valve 14 above the specified regeneration opening, for example, fully open. In addition, the control device 18 also makes the opening between the head side port 2a and the suction port 11a above the specified regeneration opening, for example, fully open, through the directional control valve 13. In addition, the regeneration opening and the regeneration opening do not necessarily have to be fully open, as long as they are 85% or more of the full opening. In this way, the pressure loss generated in the working fluid can be suppressed by making the regeneration valve 14 and the directional control valve 13 fully open, so that more energy can be regenerated as electrical energy.

[0033] On the other hand, when the coil temperature is above the specified temperature, the control device 18 throttles the opening of the regeneration valve 14. To explain in more detail, the control device 18 throttles the opening of the regeneration valve 14 starting from the specified regeneration opening. That is, the control device 18 throttles the opening of the regeneration valve 14 from the fully open state to between 50% and less than 85%, for example. As a result, a pressure loss is generated in the working fluid flowing in the hydraulic drive device 1. Therefore, the fluid energy of the working fluid supplied to the hydraulic pump motor 11 can be reduced. In addition, the opening of the regeneration valve 14 is not limited to the aforementioned numerical range, as long as it is less than the specified regeneration opening.

[0034] Furthermore, the control device 18 also throttles the opening between the head side port 2a and the suction port 11a through the directional control valve 13. To explain in more detail, the control device 18 throttles the opening between the head side port 2a and the suction port 11a from a specified regeneration opening through the directional control valve 13. For example, the control device 18 throttles the opening between the head side port 2a and the suction port 11a from a fully open state to a range between 50% or more and less than 85%. As a result, it is possible to suppress the reduction in the hydraulic pressure of the working fluid supplied to the rod side port 2b, while causing a pressure loss in the working fluid supplied to the hydraulic pump motor 11. Therefore, the fluid energy of the working fluid supplied to the hydraulic pump motor 11 can be reduced. In addition, the throttled opening between the head side port 2a and the suction port 11a is not limited to the aforementioned numerical range, as long as it is less than the specified regeneration opening.

[0035] In this way, in the hydraulic drive device 1, the fluid energy of the working fluid is reduced by the regeneration valve 14 and the directional control valve 13. Thus, the energy regenerated by the electric motor 12 is suppressed. Therefore, the coil temperature of the electric motor 12 can be suppressed from excessively rising.

[0036] In the hydraulic drive device 1 of the present embodiment, the directional control valve 13 connects the head side port 2a to the suction port 11a, and the unloading valve 15 connects the discharge passage 22 to the tank 20. Therefore, when the boom cylinder 2 contracts, the working fluid is pushed out from the head side port 2a and supplied to the suction port 11a of the hydraulic pump motor 11. As a result, the electric motor 12 can be driven via the hydraulic pump motor 11, so energy can be recovered by the electric motor 12. Therefore, the energy consumption in the hydraulic drive device 1 can be suppressed.

[0037] In the hydraulic drive device 1, the regeneration valve 14 opens and closes the regeneration passage 23 connecting the head side port 2a and the rod side port 2b. Therefore, by opening the regeneration valve 14 when the working fluid is pushed out from the head side port 2a, a part of the pushed out working fluid is regenerated in the rod side port 2b. Thus, the working fluid can be quickly supplied to the rod side port 2b, so that the operability can be improved.

[0038] In the hydraulic drive device 1 of this embodiment, the control device 18 controls the operation of the directional control valve 13, the regeneration valve 14, and the unloading valve 15 according to the input operation signal. Therefore, the control device 18 can electrically control the directional control valve 13, the regeneration valve 14, and the unloading valve 15.

[0039] In the hydraulic drive device 1 of this embodiment, when the electric motor 12 regenerates energy, the discharge passage 22 is connected to the tank 20 via the unloading valve 15. This can suppress the increase in the discharge pressure of the hydraulic pump motor 11. Therefore, the regeneration efficiency of the electric motor 12 can be improved.

[0040] In addition, in the hydraulic drive device 1 of the present embodiment, it is possible to generate pressure loss in the working fluid by throttling the opening of the regeneration valve 14 when a predetermined condition is satisfied. Thus, when energy is regenerated by the motor 12, the energy regenerated by the motor 12 can be suppressed. Thus, the load applied to the motor 12 can be reduced.

[0041] In addition, in the hydraulic drive device 1 of this embodiment, it is possible to generate pressure loss in the working fluid by throttling the opening between the head side port 2a and the suction port 11a when a predetermined condition is satisfied. Thus, when energy is regenerated by the motor 12, the energy regenerated by the motor 12 can be suppressed. Thus, the load applied to the motor 12 can be reduced.

[0042] In addition, in the hydraulic drive device 1 of the present embodiment, the coil temperature being above a predetermined temperature is a predetermined condition. Therefore, when the coil temperature is above a predetermined temperature when energy is regenerated by the motor 12, the energy regenerated by the motor 12 can be suppressed. Thus, an excessive increase in the coil temperature of the motor 12 can be suppressed.

[0043] [Second embodiment] The hydraulic drive device 1A of the second embodiment has a similar structure to the hydraulic drive device 1 of the first embodiment. Therefore, the structure of the hydraulic drive device 1A of the second embodiment will be mainly described in terms of differences from the hydraulic drive device 1 of the first embodiment, and the same structures will be given the same reference numerals and their description will be omitted.

[0044] Figure 4 The hydraulic drive system 1A of the second embodiment shown includes a hydraulic pump motor 11A, an electric motor 12, a directional control valve 13, a regeneration valve 14, and an unloading valve 15. The hydraulic drive system 1 also includes an operating device 16, a suction side pressure sensor 17A, and a control device 18A.

[0045] <Suction side pressure sensor> The suction side pressure sensor 17A detects the inflow pressure of the hydraulic pump motor 11A. The inflow pressure is the pressure of the working fluid flowing into the suction port 11a of the hydraulic pump motor 11A, and is also called the suction pressure. In more detail, the suction side pressure sensor 17A is connected to the suction passage 21. The suction side pressure sensor 17A detects the hydraulic pressure of the suction passage 21 as the inflow pressure. Then, the suction side pressure sensor 17A outputs the detected inflow pressure.

[0046] <Control device> The control device 18A, like the control device 18 of the first embodiment, controls the operation of the directional control valve 13, the regeneration valve 14, and the unloading valve 15 according to the input operation signal. Furthermore, the control device 18A controls the operation of the directional control valve 13 and the regeneration valve 14 based on the inflow pressure detected by the suction side pressure sensor 17A.

[0047] <Operation of the hydraulic drive unit> In the hydraulic drive device 1A, when the operating device 16 (in this embodiment, the operating lever 16a is operated), an operating signal is output from the operating device 16. The control device 18A, like the control device 18 of the first embodiment, controls the operation of the direction control valve 13, the regeneration valve 14, and the unloading valve 15 according to the operating signal. As a result, the boom cylinder 2 is extended and retracted in a direction corresponding to the operating direction and at a speed corresponding to the operating amount.

[0048] In addition, the control device 18A throttles the opening of the regeneration valve 14 when a predetermined condition is satisfied, and throttles the opening between the head side port 2a and the suction port 11a through the directional control valve 13. In the present embodiment, the predetermined condition is that the inflow load of the hydraulic pump motor 11A is greater than a predetermined value. That is, the control device 18A throttles the opening of the regeneration valve 14 to suppress the inflow load of the hydraulic pump motor 11A from becoming excessively large, and throttles the opening between the head side port 2a and the suction port 11a through the directional control valve 13.

[0049] To explain in more detail, the control device 18A calculates the inflow load of the hydraulic pump motor 11A based on the inflow pressure detected by the suction side pressure sensor 17A. In the present embodiment, the control device 18A calculates the inflow load based on the inflow pressure and the capacity instruction (i.e., the pump capacity of the hydraulic pump motor 11A) and the speed instruction (i.e., the speed of the electric motor 12). Then, when the head side port 2a is connected to the suction port 11a through the directional control valve 13 (i.e., when the boom cylinder 2 is retracted), the control device 18A determines whether the inflow load is greater than a predetermined value.

[0050] When the inflow load is less than a specified value, the control device 18A makes the opening of the regeneration valve 14 equal to or greater than a specified regeneration opening. Furthermore, the control device 18A also makes the opening between the head side port 2a and the suction port 11a equal to or greater than a specified regeneration opening through the directional control valve 13. In this way, by making the regeneration valve 14 and the directional control valve 13 respectively have a specified regeneration opening and a specified regeneration opening, the pressure loss generated in the working fluid can be suppressed, so that more energy can be regenerated as electrical energy.

[0051] On the other hand, when the inflow load is greater than a specified value, the control device 18A throttles the opening of the regeneration valve 14. More specifically, the control device 18A throttles the opening of the regeneration valve 14 from a specified regeneration opening. As a result, pressure loss occurs in the working fluid flowing in the hydraulic drive device 1A. Therefore, the fluid energy of the working fluid can be reduced. In addition, the control device 18A also throttles the opening between the head side port 2a and the suction port 11a through the directional control valve 13. More specifically, the control device 18A throttles the opening between the head side port 2a and the suction port 11a from a specified regeneration opening. As a result, the hydraulic pressure of the working fluid supplied to the rod side port 2b can be reduced, and at the same time, pressure loss occurs in the working fluid supplied to the hydraulic pump motor 11A. Therefore, the fluid energy of the working fluid supplied to the hydraulic pump motor 11A can be reduced. In this way, by reducing the fluid energy of the working fluid, the energy regenerated by the motor 12 can be suppressed. As a result, the inflow load of the motor 12 can be suppressed from becoming excessively large.

[0052] In the hydraulic drive device 1A of the present embodiment, the inflow load being greater than a predetermined value is a predetermined condition. Therefore, when the inflow load is greater than a predetermined value, when the electric motor 12 performs energy regeneration, the energy regenerated by the electric motor 12 can be suppressed. Thus, the inflow load of the electric motor 12 can be suppressed from becoming excessively large.

[0053] Otherwise, the hydraulic drive system 1A of the present embodiment exerts the same operational effects as those of the hydraulic drive system 1 of the first embodiment.

[0054] <Other embodiments> In the hydraulic drive device 1, 1A of the present embodiment, the hydraulic cylinder to which the working fluid is supplied may be a hydraulic cylinder other than the boom cylinder 2, such as a boom cylinder and a lift cylinder. The directional control valve 13 and the regeneration valve 14 do not necessarily have to be valves with adjustable openings, as long as at least one of the directional control valve 13 and the regeneration valve 14 is configured to have an adjustable opening. The control device 18, 18A does not necessarily have to throttle the openings of both the directional control valve 13 and the regeneration valve 14 when the prescribed conditions are met. The control device 18, 18A only has to throttle the opening of at least one of the directional control valve 13 and the regeneration valve 14. In addition, the control device 18, 18A may selectively throttle the openings of the directional control valve 13 and the regeneration valve 14 according to the coil temperature or the inflow load. For example, the control device 18, 18A first throttles the opening of the regeneration valve 14 as the coil temperature rises, and then throttles the opening of the directional control valve 13. In addition, the object of the prescribed conditions is not limited to the coil temperature and the inflow load. In addition, the driving source of the hydraulic pump motor 11 , 11A is not limited to the electric motor 12 , and may be a hybrid driving source of the electric motor 12 and an engine.

[0055] <Exemplary Embodiment> The hydraulic drive device in the first aspect is a hydraulic drive device that supplies working fluid to a hydraulic cylinder having a head side port and a rod side port, and comprises: a hydraulic pump motor having a suction port and a discharge port; an electric motor connected to the hydraulic pump motor; a directional control valve that switches the connection object of the head side port to the discharge port and the suction port respectively; a regeneration valve that opens and closes a regeneration channel that connects the head side port and the rod side port; and an unloading valve that connects the discharge channel to a tank, and the discharge channel connects the discharge port and the directional control valve.

[0056] According to the above aspect, the directional control valve connects the head side port to the suction port, and the unloading valve connects the discharge passage to the tank. Therefore, when the hydraulic cylinder contracts, the working fluid is pushed out from the head side port and supplied to the suction port of the hydraulic pump motor. As a result, the electric motor can be driven via the hydraulic pump motor, so energy can be regenerated by the electric motor. Therefore, energy consumption in the hydraulic drive device can be suppressed.

[0057] Furthermore, according to the above aspect, the regeneration valve opens and closes the regeneration passage connecting the head side port and the rod side port. When the working fluid is pushed out from the head side port, the regeneration valve is opened, and a part of the pushed out working fluid is regenerated in the rod side port. Thus, the working fluid can be quickly supplied to the rod side port, so that the operability can be improved.

[0058] The hydraulic drive device in the second aspect may be the hydraulic drive device in the first aspect, further comprising: a control device that controls the operations of the directional control valve, the regeneration valve, and the unloading valve based on input signals.

[0059] According to the above aspect, the control device controls the operation of the directional control valve, the regeneration valve, and the unloading valve according to the input signal. Therefore, the control device can electrically control the directional control valve, the regeneration valve, and the unloading valve.

[0060] The hydraulic drive device in the third aspect may be the hydraulic drive device in the second aspect, wherein the control device connects the discharge passage to the tank through the unloading valve when the head side port is connected to the suction port through the directional control valve.

[0061] According to the above aspect, when the electric motor regenerates energy, the discharge passage is connected to the tank via the unloading valve, thereby suppressing the increase in the discharge pressure of the hydraulic pump motor, thereby improving the regeneration efficiency in the electric motor.

[0062] The hydraulic drive device in the fourth aspect may also be the hydraulic drive device in the second or third aspect, wherein the control device, when connecting the head side port with the suction port through the directional control valve, throttles the opening of the regeneration valve when the regeneration channel is opened through the regeneration valve and specified conditions are met.

[0063] According to the above aspect, by throttling the opening of the regeneration valve when the specified conditions are met, pressure loss can be generated in the working fluid. Thus, when the motor regenerates energy, the energy regenerated by the motor can be suppressed. Thus, the load applied to the motor can be reduced.

[0064] The hydraulic drive device in the fifth aspect may also be a hydraulic drive device in any one of the second to fourth aspects, wherein the control device, when connecting the head side port with the suction port through the directional control valve, throttles the opening between the head side port and the suction port through the directional control valve when specified conditions are met.

[0065] According to the above aspect, by throttling the opening between the head side port and the suction port when the specified conditions are met, it is possible to generate pressure loss in the working fluid. Thus, when the motor regenerates energy, the energy regenerated by the motor can be suppressed. Thus, the load applied to the motor can be reduced.

[0066] The hydraulic drive device in the sixth aspect may be the hydraulic drive device in the fourth or fifth aspect, further comprising a temperature sensor for detecting the coil temperature of the electric motor, wherein the prescribed condition is that the coil temperature detected by the temperature sensor is above a prescribed temperature.

[0067] According to the above aspect, the predetermined condition is that the coil temperature is above the predetermined temperature. Therefore, when the coil temperature is above the predetermined temperature during energy regeneration by the motor, the energy regenerated by the motor can be suppressed. Thus, the excessive increase in the coil temperature in the motor can be suppressed.

[0068] The hydraulic drive device in the seventh aspect may also be the hydraulic drive device in the fourth or fifth aspect, further comprising a suction side pressure sensor, which detects the inflow pressure of the hydraulic pressure of the suction port of the hydraulic pump motor, and the control device calculates the inflow load of the hydraulic pump motor based on the inflow pressure detected by the suction side pressure sensor, and the specified condition is that the inflow load is above a specified value.

[0069] According to the above aspect, the predetermined condition is that the inflow load is greater than the predetermined value. Therefore, when the inflow load is greater than the predetermined value when the motor regenerates energy, the energy regenerated by the motor can be suppressed. Thus, the inflow load of the motor 12 can be suppressed from becoming excessively large.

[0070] 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 working fluid to a hydraulic cylinder having a head side port and a rod side port. It has: A hydraulic pump motor having a suction port and a discharge port; an electric motor connected to the hydraulic pump motor; a directional control valve for switching the connection object of the head-side port to the discharge port and the suction port, respectively; a regeneration valve that opens and closes a regeneration passage that connects the head-side port and the rod-side port; and An unloading valve connects a discharge passage to a tank, wherein the discharge passage connects the discharge port to the directional control valve.

2. The hydraulic drive device according to claim 1, characterized in that: The invention further comprises a control device for controlling the operation of the directional control valve, the regeneration valve, and the unloading valve according to an input signal.

3. The hydraulic drive device according to claim 2, characterized in that: The control device connects the discharge passage to the tank via the unloading valve when the head-side port is connected to the suction port via the directional control valve.

4. The hydraulic drive device according to claim 2, characterized in that: The control device throttles the opening of the regeneration valve when the regeneration passage is opened by the regeneration valve and a predetermined condition is satisfied when the head-side port is connected to the suction port by the directional control valve.

5. The hydraulic drive device according to claim 2, characterized in that: The control device, when the head-side port is connected to the suction port by the directional control valve, reduces the opening between the head-side port and the suction port by the directional control valve when a predetermined condition is satisfied.

6. The hydraulic drive device according to claim 4 or 5, characterized in that: A temperature sensor for detecting the coil temperature of the motor is also provided. The predetermined condition is that the coil temperature detected by the temperature sensor is equal to or higher than a predetermined temperature.

7. The hydraulic drive device according to claim 4 or 5, characterized in that: A suction side pressure sensor is further provided, which detects the inflow pressure of the hydraulic pressure at the suction port of the hydraulic pump motor. The control device calculates the inflow load of the hydraulic pump motor based on the inflow pressure detected by the suction side pressure sensor. The predetermined condition is that the inflow load is equal to or greater than a predetermined value.

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