Hydraulic drive device

Abstract

To provide a hydraulic driving device capable of downsizing itself while suppressing the consumption of energy.SOLUTION: The hydraulic driving device for supplying working liquid to a hydraulic cylinder having a head side port and a rod side port includes a hydraulic pump motor having a suction port and a discharge port, an electric motor connected to the hydraulic pump motor, a direction control valve for switching the connection destination of the head side port between the discharge port and the suction port, a regeneration valve for opening / closing a regeneration passage linking the head side port to the rod side port, and an unload valve for connecting a discharge passage linking the discharge port to the direction control valve, to a tank.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a hydraulic drive device that supplies and discharges hydraulic fluid to 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, a hydraulic drive device such as Patent Document 1 is known. In the hydraulic drive device as in Patent Document 1, in the boom lowering operation, the hydraulic pump motor is rotationally driven by the hydraulic fluid discharged from the head-side port of the boom cylinder. Thereby, the potential energy of the boom can be regenerated into electric energy.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the hydraulic drive device of Patent Document 1, energy consumption can be suppressed by regenerating the fluid energy of the hydraulic fluid into electric energy. However, in the hydraulic drive device of Patent Document 1, in addition to energy consumption, an improvement in operability is required.

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

Means for Solving the Problems

[0006] The hydraulic drive device of this disclosure is a hydraulic drive device for supplying working fluid to a hydraulic cylinder having a head-side port and a rod-side port, and comprises a hydraulic pump motor having an intake port and a discharge port, an electric motor connected to the hydraulic pump motor, a directional control valve for switching the connection destination of the head-side port to the discharge port and the intake port, respectively, a regeneration valve for opening and closing a regeneration passage connecting the head-side port and the rod-side port, and an unload valve for connecting a discharge passage connecting the discharge port and the directional control valve to a tank.

[0007] According to this disclosure, a directional control valve connects the head-side port to the suction port, and an unload valve connects the discharge passage to the tank. Therefore, when the hydraulic cylinder retracts, the working fluid is pushed out from the head-side port and supplied to the suction port of the hydraulic pump motor. This allows the motor to be driven via the hydraulic pump motor, enabling energy regeneration by the motor. Therefore, energy consumption in the hydraulic drive system can be reduced.

[0008] Furthermore, according to this disclosure, the regeneration valve opens and closes a 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 portion of the pushed-out working fluid is regenerated in the rod-side port. This allows for a rapid supply of working fluid to the rod-side port, thereby improving operability. [Effects of the Invention]

[0009] According to this disclosure, it is possible to miniaturize the hydraulic drive device while reducing energy consumption. [Brief explanation of the drawing]

[0010] [Figure 1] This is a circuit diagram showing the configuration of a hydraulic drive device according to the first embodiment of the present disclosure. [Figure 2] Figure 1 is a circuit diagram showing the flow of the working fluid when extending the boom cylinder in the hydraulic drive device. [Figure 3]Figure 1 is a circuit diagram showing the flow of the working fluid when the boom cylinder is retracted in the hydraulic drive device. [Figure 4] This is a circuit diagram showing the configuration of a hydraulic drive device according to a second embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, the hydraulic drive devices 1 and 1A of the first and second embodiments of this disclosure will be described with reference to the aforementioned drawings. Note that the concept of direction used in the following description is for convenience of explanation and does not limit the orientation of the invention's configuration to that direction. Furthermore, the hydraulic drive devices 1 and 1A described below are merely one embodiment of this disclosure. Therefore, this disclosure is not limited to these embodiments, and additions, deletions, and modifications are permitted without departing from the spirit of the invention.

[0012] [First Embodiment] The hydraulic drive device 1 shown in Figure 1 is installed in, 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 this embodiment, the work vehicle is a hydraulic excavator. The hydraulic excavator is equipped with a boom, an arm, and an attachment (for example, a bucket). The hydraulic excavator can perform various tasks by moving the boom, arm, and attachment (for example, a bucket). The hydraulic excavator is equipped with a boom cylinder 2.

[0013] A boom cylinder 2, an example of a hydraulic cylinder, has a head-side port 2a and a rod-side port 2b. The boom cylinder 2 is installed on the boom. The boom cylinder 2 moves the boom by extending and retracting. More specifically, the boom cylinder 2 extends when working fluid (e.g., oil or water) is supplied to the head-side port 2a and working fluid is discharged from the rod-side port 2b. This causes the boom to rise. On the other hand, the boom cylinder 2 contracts when working fluid is discharged from the head-side port 2a and working fluid is supplied to the rod-side port 2b. This causes the boom to lower. In this embodiment, the boom cylinder 2 is supported by the weight of the boom in the direction of contraction. Therefore, the boom cylinder 2 contracts by discharging working fluid from the head-side port 2a and drawing working fluid in from the rod-side port 2b due to the weight of the boom.

[0014] <Hydraulic drive device> The hydraulic drive unit 1 supplies and discharges working fluid to the boom cylinder 2. This drives the boom cylinder 2. More specifically, the hydraulic drive unit 1 supplies and discharges working fluid to the head-side port 2a and the rod-side port 2b, respectively. This causes the hydraulic drive unit 1 to extend and retract the boom cylinder 2. The hydraulic drive unit 1 also regenerates energy from the working fluid discharged from the head-side port 2a of the boom cylinder 2. The hydraulic drive unit 1, which functions in this way, comprises a hydraulic pump motor 11, an electric motor 12, a directional control valve 13, a regeneration valve 14, and an unload valve 15. The hydraulic drive unit 1 also comprises an operating device 16, a temperature sensor 17, and a control device 18.

[0015] <Hydraulic pump motor> The hydraulic pump motor 11 has an intake port 11a and a discharge port 11b. The hydraulic pump motor 11 also has a shaft 11c. The intake port 11a is connected to the tank 20 via an intake passage 21. A check valve 19 is interposed in the intake passage 21. The check valve 19 allows the flow of working fluid from the tank 20 to the intake port 11a and prevents flow in the reverse direction.

[0016] When the shaft 11c is rotated, the hydraulic pump motor 11 operates as follows: The hydraulic pump motor 11 draws in working fluid from the suction port 11a. The hydraulic pump motor 11 then discharges working fluid from the discharge port 11b. On the other hand, when working fluid is supplied to the suction port 11a, the hydraulic pump motor 11 rotates the shaft 11c. The hydraulic pump motor 11 then discharges working fluid from the discharge port 11b. In this embodiment, the hydraulic pump motor 11 is a variable displacement swashplate pump and has a regulator 11d. The regulator 11d changes the tilt angle of the swashplate based on the input displacement command. This changes the piston displacement of the hydraulic pump motor 11. That is, the hydraulic pump motor 11 can change the discharge flow rate and the suction flow rate.

[0017] <Electric motor> The electric motor 12 is connected to the hydraulic pump motor 11. More specifically, the electric motor 12 is connected to the shaft 11c. The electric motor 12 rotates the hydraulic pump motor 11, thereby discharging working fluid from the hydraulic pump motor 11. More specifically, the electric motor 12 rotates the shaft 11c, thereby discharging working fluid from the discharge port 11b. The electric motor 12 also generates electricity by receiving the supply of working fluid and causing the hydraulic pump motor 11 (more specifically, the shaft 11c) to rotate. In other words, the electric motor 12 works in cooperation with the hydraulic pump motor 11 to regenerate the fluid energy of the working fluid into electrical energy. Furthermore, the electric motor 12 changes its rotational speed (more specifically, the rotational speed of the shaft 11c) according to the input rotational speed command.

[0018] <Direction control valve> The direction control valve 13 is respectively connected to the suction port 11a and the discharge port 11b of the hydraulic pump motor 11. To explain in more detail, the direction control valve 13 is connected to the suction port 11a side of the hydraulic pump motor 11 from the check valve 19 in the suction passage 21. Also, the direction control valve 13 is connected to the discharge port 11b via the discharge passage 22. The direction control valve 13 is connected to the head side port 2a of the boom cylinder 2. Also, the direction control valve 13 is connected to the rod side port 2b of the boom cylinder 2 and the tank 20.

[0019] The direction control valve 13 switches the connection destination of the head side port 2a to the discharge port 11b and the suction port 11a respectively according to the input operation command. Further, when the direction control valve 13 connects the head side port 2a to the discharge port 11b, it connects the rod side port 2b to the tank 20. On the other hand, when the direction control valve 13 connects the head side port 2a to the suction port 11a, it connects the rod side port 2b to the discharge port 11b. Incidentally, when the direction control valve 13 connects the rod side port 2b to the discharge port 11b, it allows the flow of the working fluid from the discharge port 11b to the rod side port 2b and blocks the reverse flow of the working fluid. Also, when the direction control valve 13 connects the head side port 2a to the suction port 11a, it controls the opening degree between the head side port 2a and the suction port 11a (hereinafter, also referred to as the "opening degree of the direction control valve 13") according to the operation command. In the present embodiment, the direction control valve 13 is an electric spool valve. However, the direction control valve 13 is not limited to an electric spool valve.

[0020] <Regenerative valve> The regeneration valve 14 opens and closes a regeneration passage 23 that connects the head-side port 2a and the rod-side port 2b. The regeneration valve 14 is interposed in the regeneration passage 23. The regeneration valve 14 opens and closes the regeneration passage 23 in response to a regeneration command. Further, the regeneration valve 14 allows the flow of the hydraulic fluid in the regeneration direction and blocks the reverse flow when the regeneration passage 23 is open. The regeneration direction is the flow from the head-side port 2a to the rod-side port 2b. Thereby, the regeneration valve 14 regenerates the hydraulic fluid discharged from the head-side port 2a to the rod-side port 2b. The regeneration valve 14 restricts the opening degree in response to a regeneration command. The regeneration valve 14 is, for example, an electromagnetic proportional control valve.

[0021] <Unloading valve> The unloading valve 15 connects a discharge passage 22 that connects the discharge port 11b and the direction control valve 13 to the tank 20. More specifically, the unloading valve 15 connects the discharge passage 22 to the tank 20 in response to an input unloading command. Thereby, the hydraulic pump motor 11 can be unloaded. In the present embodiment, the unloading valve 15 is an electromagnetic on-off valve. However, the unloading valve 15 may be an electromagnetic proportional control valve capable of controlling the opening degree.

[0022] <Operating device> The operating device 16 is for operating the boom (more specifically, the boom cylinder 2). The operating device 16 has an operating lever 16a. The operating lever 16a is configured to be operable. The operating device 16 outputs an operation signal according to the operation direction and operation amount of the operating lever 16a. The operating device 16 is, for example, an electric joystick. However, the operating device 16 may be a pilot-operated valve. In this case, the operating device 16 outputs an operation signal according to the output pressure of the pilot-operated valve. Further, the operating device 16 may be a touch panel. In this case, the operating device 16 outputs an operation signal according to the input operation and program.

[0023] <Temperature sensor> The temperature sensor 17 detects the coil temperature of the electric motor 12. More specifically, the temperature sensor 17 directly or indirectly detects the coil temperature of the electric motor 12. In this embodiment, the temperature sensor 17 is installed in the casing of the electric motor 12. The temperature sensor 17 indirectly detects the coil temperature by detecting the temperature of the casing of the electric motor 12. The temperature sensor 17 then outputs the detected temperature of the casing of the electric motor 12.

[0024] <Control device> The control device 18 controls the operation of the directional control valve 13, the regeneration valve 14, and the unload valve 15 in response to the input operation signals. More specifically, the control device 18 controls the operation of the directional control valve 13, the regeneration valve 14, and the unload valve 15 by outputting operation commands, regeneration commands, and unload commands in response to the operation signals. In this way, the control device 18 controls the flow of the working fluid in the hydraulic drive device 1. The control device 18 also controls the operation of the hydraulic pump motor 11 and the electric motor 12 in response to the operation signals. More specifically, the control device 18 controls the operation of the hydraulic pump motor 11 and the electric motor 12 by outputting capacity commands and rotational speed commands in response to the operation signals. In this way, the control device 18 controls the discharge flow rate and suction flow rate of the hydraulic pump motor 11. Furthermore, 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. More specifically, the control device 18 controls the opening degree of the directional control valve 13 and the regeneration valve 14 based on the coil temperature detected by the temperature sensor 17.

[0025] <Operation of the hydraulic drive device> In the hydraulic drive unit 1, when the operating device 16 is operated (in this embodiment, the operating lever 16a is operated), an operation 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 unload valve 15 according to the operation signal. The control device 18 also controls the operation of the electric motor 12 and the hydraulic pump motor 11 according to the operation signal. As a result, the control device 18 extends and retracts the boom cylinder 2 in a direction and speed corresponding to the operation signal (in this embodiment, the operating direction and amount of the operating lever 16a). In the hydraulic drive unit 1, when the boom is lowered (i.e., when the boom cylinder 2 is retracted), a portion of the working fluid discharged from the head-side port 2a of the boom cylinder 2 is regenerated into the rod-side port 2b. In addition, the remaining portion of the working fluid discharged from the head-side port 2a is used for energy recovery in the hydraulic drive unit 1. Furthermore, the control device 18 controls the opening degree of the directional control valve 13 and the regeneration valve 14 based on the coil temperature of the electric motor 12. This prevents the coil temperature of the electric motor 12 from rising excessively.

[0026] [Boom cylinder extension operation] The following describes 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 operation signal is output from the operating device 16. Then, the control device 18 operates the directional control valve 13 in response to the operation signal. More specifically, the control device 18 outputs an operation command to the directional control valve 13 in response to the operation signal. As a result, the directional control valve 13 connects the discharge port 11b to the head-side port 2a and the rod-side port 2b to the tank 20, as shown in Figure 2. The suction port 11a is then blocked from the head-side port 2a and the rod-side port 2b by the directional control valve 13. The control device 18 also outputs a rotation speed command and a volume command in response to the operation signal. As a result, the hydraulic pump motor 11 discharges 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 via the directional control valve 13 (arrow A1 in Figure 2). On the other hand, working fluid is discharged from the rod-side port 2b to the tank 20 via the directional control valve 13 (arrow A2 in Figure 2). This causes the boom cylinder 2 to extend at a speed corresponding to the operation signal (see arrow A and dashed line in Figure 2). Therefore, the boom can be raised at a speed corresponding to the operation signal.

[0027] [Boom cylinder retraction operation] In the hydraulic drive unit 1, when the operating device 16 is operated to retract the boom cylinder 2, an operation signal is output from the operating device 16. In response to this, the control device 18 operates the directional control valve 13, the regeneration valve 14, and the unload valve 15. More specifically, the control device 18 outputs an operation command to the directional control valve 13 in response to the operation signal. As a result, the control device 18 connects the head-side port 2a to the suction port 11a via the directional control valve 13, as shown in Figure 3. The control device 18 also outputs a regeneration command to the regeneration valve 14. As a result, the control device 18 opens the regeneration passage 23 via the regeneration valve 14. This connects the head-side port 2a and the rod-side port 2b. Furthermore, the control device 18 outputs an unload command to the unload valve 15. As a result, the control device 18 connects the discharge passage 22 to the tank 20 via the unload valve 15. This unloads the hydraulic pump motor 11.

[0028] As described above, when the directional control valve 13, regeneration valve 14, and unload valve 15 are operated, the working fluid flows as follows. That is, the boom cylinder 2 is subjected to the weight of the boom in the direction of contraction. Therefore, the boom cylinder 2 is contracted by the weight of the boom. As a result, working fluid is discharged from the head-side port 2a. A portion of the discharged working fluid is supplied to the rod-side port 2b through the regeneration passage 23. That is, a portion of the working fluid is regenerated from the head-side port 2a to the rod-side port 2b (see arrow B1 in 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 arrow B2 in Figure 3). The remaining portion then rotates the electric motor 12 via the hydraulic pump motor 11 and is discharged from the discharge port 11b to the tank 20 via the unload valve 15. By rotating the electric motor 12, the electric motor 12 generates electricity. As a result, the fluid energy of the remaining portion is recovered as electrical energy. In other words, the potential energy of the boom is regenerated into electrical energy. Thus, energy can be recovered from the discharged working fluid.

[0029] Furthermore, the control device 18 retracts the boom cylinder 2 at a speed corresponding to the operation signal by controlling the suction flow rate of the hydraulic pump motor 11. More specifically, the control device 18 outputs a rotation speed command and a volume command corresponding to the operation signal. This allows the hydraulic pump motor 11 to flow the hydraulic fluid at a flow rate corresponding to the operation signal into the suction port 11a, thereby controlling the flow rate of the hydraulic fluid discharged from the head-side port 2a of the boom cylinder 2 to a flow rate corresponding to the operation signal. As a result, the flow rate of the hydraulic fluid regenerated at the rod-side port 2b is controlled to a flow rate corresponding to the operation signal, allowing the boom cylinder 2 to retract at a speed corresponding to the operation signal (see arrow B and dashed line in Figure 3). This allows the boom to be lowered at a speed corresponding to the operation signal.

[0030] Furthermore, the control device 18 restricts the opening of the regeneration valve 14 when predetermined conditions are met. Also, when predetermined conditions are met, the control device 18 restricts the opening between the head-side port 2a and the intake port 11a using the directional control valve 13. In other words, when predetermined conditions are met, the control device 18 restricts the opening of the directional control valve 13. In this embodiment, the predetermined condition is that the coil temperature of the electric motor 12 is above a predetermined temperature. That is, the control device 18 restricts the opening of the regeneration valve 14 to prevent the coil temperature of the electric motor 12 from becoming excessively high, and also restricts the opening between the head-side port 2a and the intake port 11a using the directional control valve 13.

[0031] More specifically, the control device 18 estimates the coil temperature based on the casing temperature detected by the temperature sensor 17. Then, when the control device 18 connects the head-side port 2a to the suction port 11a using the directional control valve 13 (i.e., when retracting the boom cylinder 2), it determines whether the coil temperature is above a predetermined temperature. If the coil temperature is below the predetermined temperature, the control device 18 opens the regeneration valve 14 to a predetermined regeneration opening or greater, for example, fully open. The control device 18 also opens the opening between the head-side port 2a and the suction port 11a to a predetermined regenerative opening or greater, for example, fully open, using the directional control valve 13. Note that the regeneration opening and regenerative opening do not necessarily have to be fully open; they only need to be 85% or more of the fully open position. In this way, by fully opening the regeneration valve 14 and the directional control valve 13, pressure loss in the working fluid can be suppressed, allowing for greater energy to be recovered as electrical energy.

[0032] On the other hand, if the coil temperature is above a predetermined temperature, the control device 18 restricts the opening of the regeneration valve 14. More specifically, the control device 18 restricts the opening of the regeneration valve 14 from a predetermined regeneration opening. That is, the control device 18 restricts the opening of the regeneration valve 14 to, for example, between 50% and 85% of the fully open state. This causes a pressure loss in the working fluid flowing through the hydraulic drive device 1. Therefore, the fluid energy of the working fluid supplied to the hydraulic pump motor 11 can be reduced. Note that the opening of the regeneration valve 14 is not limited to the numerical range described above, but can be any smaller than the predetermined regeneration opening.

[0033] Furthermore, the control device 18 also restricts the opening between the head-side port 2a and the suction port 11a using the directional control valve 13. More specifically, the control device 18 restricts the opening between the head-side port 2a and the suction port 11a from a predetermined regenerative opening using the directional control valve 13. For example, the control device 18 restricts the opening between the head-side port 2a and the suction port 11a to, for example, between 50% and less than 85% from the fully open state. This suppresses the reduction in the hydraulic pressure of the hydraulic fluid supplied to the rod-side port 2b while causing a pressure loss in the hydraulic fluid supplied to the hydraulic pump motor 11. Therefore, the fluid energy of the hydraulic fluid supplied to the hydraulic pump motor 11 can be reduced. Note that the opening restricted between the head-side port 2a and the suction port 11a is not limited to the numerical range described above, but is only required to be smaller than the predetermined regenerative opening.

[0034] In this way, the fluid energy of the working fluid is reduced by the regeneration valve 14 and the directional control valve 13 in the hydraulic drive device 1. This makes it possible to suppress the energy regenerated by the electric motor 12. Therefore, it is possible to prevent the coil temperature of the electric motor 12 from rising excessively.

[0035] In the hydraulic drive device 1 of this embodiment, the directional control valve 13 connects the head-side port 2a to the suction port 11a, and the unload valve 15 connects the discharge passage 22 to the tank 20. Therefore, when the boom cylinder 2 retracts, 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, and energy regeneration can be performed by the electric motor 12. Therefore, energy consumption in the hydraulic drive device 1 can be reduced.

[0036] Furthermore, 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 portion of the pushed-out working fluid is regenerated in the rod-side port 2b. This allows for a rapid supply of working fluid to the rod-side port 2b, thereby improving operability.

[0037] Furthermore, 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 unload valve 15 according to the input operation signals. Therefore, the control device 18 can electrically control the directional control valve 13, the regeneration valve 14, and the unload valve 15.

[0038] Furthermore, in the hydraulic drive device 1 of this embodiment, when energy regeneration is performed by the electric motor 12, the discharge passage 22 is connected to the tank 20 by the unload valve 15. This makes it possible to suppress the rise in the discharge pressure of the hydraulic pump motor 11. Therefore, the regeneration efficiency of the electric motor 12 can be improved.

[0039] Furthermore, in the hydraulic drive device 1 of this embodiment, pressure loss can be generated in the working fluid by restricting the opening of the regeneration valve 14 when predetermined conditions are met. This makes it possible to reduce the energy regenerated by the motor 12 when energy regeneration is performed by the motor 12. As a result, the load on the motor 12 can be reduced.

[0040] Furthermore, in the hydraulic drive device 1 of this embodiment, pressure loss can be generated in the working fluid by narrowing the opening between the head-side port 2a and the suction port 11a when predetermined conditions are met. This makes it possible to reduce the energy regenerated by the electric motor 12 when energy regeneration is performed by the electric motor 12. As a result, the load on the electric motor 12 can be reduced.

[0041] Furthermore, in the hydraulic drive device 1 of this embodiment, a predetermined condition is that the coil temperature is above a predetermined temperature. Therefore, when energy regeneration is performed in the electric motor 12 and the coil temperature is above the predetermined temperature, the energy regenerated by the electric motor 12 can be suppressed. This prevents the coil temperature in the electric motor 12 from rising excessively.

[0042] [Second Embodiment] The hydraulic drive device 1A of the second embodiment has a similar configuration to the hydraulic drive device 1 of the first embodiment. Therefore, the configuration of the hydraulic drive device 1A of the second embodiment will mainly be described in terms of the differences from the hydraulic drive device 1 of the first embodiment, and identical components will be denoted by the same reference numerals and their description will be omitted.

[0043] The hydraulic drive device 1A of the second embodiment shown in Figure 4 comprises a hydraulic pump motor 11A, an electric motor 12, a directional control valve 13, a regeneration valve 14, and an unload valve 15. The hydraulic drive device 1 also comprises an operating device 16, a suction-side pressure sensor 17A, and a control device 18A.

[0044] <Intake 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. More specifically, the suction-side pressure sensor 17A is connected to the suction passage 21. The suction-side pressure sensor 17A detects the fluid pressure in the suction passage 21 as the inflow pressure. The suction-side pressure sensor 17A then outputs the detected inflow pressure.

[0045] <Control device> The control device 18A controls the operation of the directional control valve 13, the regeneration valve 14, and the unload valve 15 in response to input operation signals, similar to the control device 18 of the first embodiment. In addition, 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 intake side pressure sensor 17A.

[0046] <Operation of the hydraulic drive device> In the hydraulic drive device 1A, when the operating device 16 is operated (in this embodiment, the operating lever 16a is operated), an operation signal is output from the operating device 16. The control device 18A, like the control device 18 in the first embodiment, also controls the operation of the directional control valve 13, the regeneration valve 14, and the unload valve 15 in response to the operation signal. As a result, the boom cylinder 2 extends and retracts in a direction corresponding to the operating direction and at a speed corresponding to the amount of operation.

[0047] Furthermore, when predetermined conditions are met, the control device 18A restricts the opening of the regeneration valve 14 and also restricts the opening between the head-side port 2a and the suction port 11a using the directional control valve 13. In this embodiment, the predetermined condition is that the inflow load of the hydraulic pump motor 11A is greater than or equal to a predetermined value. That is, in order to prevent the inflow load of the hydraulic pump motor 11A from becoming excessively large, the control device 18A restricts the opening of the regeneration valve 14 and also restricts the opening between the head-side port 2a and the suction port 11a using the directional control valve 13.

[0048] More specifically, 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 this embodiment, the control device 18A calculates the inflow load based on the inflow pressure, along with the capacity command (i.e., the pump capacity of the hydraulic pump motor 11A) and the rotational speed command (i.e., the rotational speed of the electric motor 12). Then, when the directional control valve 13 connects the head-side port 2a to the suction port 11a (i.e., when the boom cylinder 2 is retracted), the control device 18A determines whether the inflow load is above a predetermined value.

[0049] When the inflow load is below a predetermined value, the control device 18A sets the opening of the regeneration valve 14 to a predetermined regeneration opening or greater. The control device 18A also sets the opening between the head-side port 2a and the suction port 11a to a predetermined regenerative opening or greater using the directional control valve 13. In this way, by setting the regeneration valve 14 and the directional control valve 13 to predetermined regeneration and regenerative openings, respectively, pressure loss in the working fluid can be suppressed, allowing for greater energy to be recovered as electrical energy.

[0050] On the other hand, if the inflow load exceeds a predetermined value, the control device 18A restricts the opening of the regeneration valve 14. More specifically, the control device 18A restricts the opening of the regeneration valve 14 from a predetermined regeneration opening. This causes a pressure loss in the working fluid flowing through the hydraulic drive device 1A. Therefore, the fluid energy of the working fluid can be reduced. The control device 18A also restricts the opening between the head-side port 2a and the suction port 11a using the directional control valve 13. More specifically, the control device 18A restricts the opening between the head-side port 2a and the suction port 11a from a predetermined regeneration opening. This suppresses 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 11A. Therefore, the fluid energy of the working fluid supplied to the hydraulic pump motor 11A can be reduced. By reducing the fluid energy of the working fluid in this way, the energy regenerated by the electric motor 12 can be suppressed. This prevents the inflow load to the electric motor 12 from becoming excessively large.

[0051] In the hydraulic drive device 1A of this embodiment, a predetermined condition is that the inflow load is above a predetermined value. Therefore, when energy regeneration is performed by the motor 12 when the inflow load is above a predetermined value, the energy regenerated by the motor 12 can be suppressed. This prevents the inflow load of the motor 12 from becoming excessively large.

[0052] Furthermore, the hydraulic drive device 1A of this embodiment provides the same effects and advantages as the hydraulic drive device 1 of the first embodiment.

[0053] <Other Embodiments> In the hydraulic drive devices 1 and 1A of this embodiment, the hydraulic cylinder supplying the working fluid may be a hydraulic cylinder other than the boom cylinder 2, such as an arm cylinder and a lift cylinder. The directional control valve 13 and the regeneration valve 14 do not necessarily both need to have adjustable opening degrees; it is sufficient if at least one of the directional control valve 13 and the regeneration valve 14 is configured to have adjustable opening degrees. The control devices 18 and 18A do not necessarily need to restrict the opening degrees of both the directional control valve 13 and the regeneration valve 14 when the predetermined conditions are met. The control devices 18 and 18A only need to restrict the opening degree of at least one of the directional control valve 13 and the regeneration valve 14. Furthermore, the control devices 18 and 18A may selectively restrict the opening degrees of the directional control valve 13 and the regeneration valve 14 according to the coil temperature or the inflow load. For example, the control devices 18 and 18A first restrict the opening degree of the regeneration valve 14 as the coil temperature rises, and then restrict the opening degree of the directional control valve 13. Furthermore, the predetermined conditions are not limited to coil temperature and inflow load. Furthermore, the drive source for the hydraulic pump motors 11 and 11A is not limited to the electric motor 12, but may be a hybrid drive source consisting of the electric motor 12 and an engine.

[0054] <Exemplary Embodiment> The hydraulic drive device in the first phase 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 an intake port and a discharge port, an electric motor connected to the hydraulic pump motor, a directional control valve that switches the connection destination of the head-side port to the discharge port and the intake port, respectively, a regeneration valve that opens and closes a regeneration passage connecting the head-side port and the rod-side port, and an unload valve that connects a discharge passage connecting the discharge port and the directional control valve to a tank.

[0055] In the above configuration, the directional control valve connects the head-side port to the suction port, and the unload valve connects the discharge passage to the tank. Therefore, when the hydraulic cylinder retracts, the working fluid is pushed out from the head-side port and supplied to the suction port of the hydraulic pump motor. This allows the electric motor to be driven via the hydraulic pump motor, enabling energy regeneration by the electric motor. Consequently, energy consumption in the hydraulic drive system can be reduced.

[0056] Furthermore, following the above procedure, 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 portion of the pushed-out working fluid is regenerated in the rod-side port. This allows for a rapid supply of working fluid to the rod-side port, thereby improving operability.

[0057] The hydraulic drive device in the second phase may further include a control device that controls the operation of the directional control valve, the regeneration valve, and the unload valve in accordance with the input signal, as in the hydraulic drive device in the first phase.

[0058] According to the above scenario, the control device controls the operation of the directional control valve, the regeneration valve, and the unload valve in accordance with the input signal. Therefore, the control device can electrically control the directional control valve, the regeneration valve, and the unload valve.

[0059] In the third phase, the hydraulic drive device, in the hydraulic drive device of the second phase, may connect the discharge passage to the tank with the unload valve when the control device connects the head-side port to the suction port with the directional control valve.

[0060] According to the above procedure, when energy regeneration is performed by the electric motor, the discharge passage is connected to the tank by an unload valve. This suppresses the rise in discharge pressure of the hydraulic pump motor. Therefore, the regenerative efficiency of the electric motor can be improved.

[0061] In the fourth phase, the hydraulic drive device, in the hydraulic drive device of the second or third phase, may, when the control device connects the head-side port to the suction port with the directional control valve, open the regeneration passage with the regeneration valve and, when predetermined conditions are met, reduce the opening degree of the regeneration valve.

[0062] Following the above procedure, pressure loss can be generated in the working fluid by restricting the opening of the regeneration valve when certain conditions are met. This reduces the amount of energy regenerated by the motor when energy regeneration is performed by the motor. As a result, the load on the motor can be reduced.

[0063] In the fifth phase, the hydraulic drive device is a hydraulic drive device in any one of the second to fourth phases, in which the control device may, when connecting the head-side port to the suction port with the directional control valve, restrict the opening between the head-side port and the suction port with the directional control valve if predetermined conditions are met.

[0064] According to the above procedure, when certain conditions are met, a pressure loss can be generated in the working fluid by narrowing the opening between the head-side port and the suction port. This reduces the amount of energy regenerated by the motor when energy is recovered by the motor. As a result, the load on the motor can be reduced.

[0065] The hydraulic drive device in the sixth phase further includes a temperature sensor for detecting the coil temperature of the electric motor, in addition to the hydraulic drive device in the fourth or fifth phase, and the predetermined condition may be that the coil temperature detected by the temperature sensor is above a predetermined temperature.

[0066] According to the above scenario, the predetermined condition is that the coil temperature is above a predetermined temperature. Therefore, when energy regeneration is performed in the electric motor, if the coil temperature is above the predetermined temperature, the energy regenerated by the electric motor can be suppressed. This prevents the coil temperature in the electric motor from rising excessively.

[0067] The hydraulic drive device in the seventh phase further includes an intake-side pressure sensor that detects the inflow pressure, which is the hydraulic pressure at the intake port of the hydraulic pump motor, in the hydraulic drive device in the fourth or fifth phase, and the control device calculates the inflow load of the hydraulic pump motor according to the inflow pressure detected by the intake-side pressure sensor, and the predetermined condition may be that the inflow load is greater than or equal to a predetermined value.

[0068] According to the above scenario, the predetermined condition is that the inflow load is above a predetermined value. Therefore, when energy regeneration is performed by the motor and the inflow load is above a predetermined value, the energy regenerated by the motor can be reduced. This prevents the inflow load of the motor 12 from becoming excessively large. [Explanation of Symbols]

[0069] 1.1A Hydraulic drive device 2. Boom Cylinder (Hydraulic Cylinder) 2a Head-side port 2b Rod-side port 11,11A Hydraulic pump motor 11a Inhalation port 11b Discharge port 12 Electric motor 13 Directional control valve 14 Regeneration valve 15 Unload valve 17 Temperature sensor 17A Intake side pressure sensor 18,18A Control device 20 tanks 22 Discharge passage 23 Regeneration passage

Claims

1. A hydraulic drive device that supplies working fluid to a hydraulic cylinder having a head-side port and a rod-side port, A hydraulic pump motor having an intake port and a discharge port, An electric motor connected to the aforementioned hydraulic pump motor, A directional control valve that switches the connection destination of the head-side port to the discharge port and the suction port, respectively, A regeneration valve that opens and closes the regeneration passage connecting the head-side port and the rod-side port, An unload valve connects the discharge passage that connects the discharge port and the directional control valve to the tank, The system includes a control device that controls the operation of the directional control valve, the regeneration valve, and the unload valve in response to an input signal. The control device is a hydraulic drive device that connects the head-side port to the suction port using the directional control valve, and connects the discharge passage to the tank using the unload valve.

2. The hydraulic drive device according to claim 1, wherein the control device connects the head-side port to the suction port using the directional control valve, opens the regeneration passage using the regeneration valve, and when predetermined conditions are met, restricts the opening of the regeneration valve.

3. The hydraulic drive device according to claim 1, wherein the control device, when connecting the head-side port to the suction port by the directional control valve, restricts the opening between the head-side port and the suction port by the directional control valve when predetermined conditions are met.

4. The system further includes a temperature sensor for detecting the coil temperature of the electric motor, The hydraulic drive device according to claim 3 or 4, wherein the predetermined condition is that the coil temperature detected by the temperature sensor is at or above a predetermined temperature.

5. The pump motor further includes an intake-side pressure sensor that detects the inflow pressure, which is the liquid pressure at the intake port of the hydraulic pump motor. The control device calculates the inflow load of the hydraulic pump motor according to the inflow pressure detected by the suction-side pressure sensor. The hydraulic drive device according to claim 3 or 4, wherein the predetermined condition is that the inflow load is greater than or equal to a predetermined value.

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