Hydraulic drive device

Abstract

A hydraulic drive device for driving a hydraulic cylinder by supplying and discharging a hydraulic fluid to a head-side port and a rod-side port, the hydraulic drive device being provided with: a hydraulic pump motor that discharges the hydraulic fluid and is rotationally driven by the supplied hydraulic fluid; the electric motor is connected with the hydraulic pump motor; a direction control valve that switches the direction of the hydraulic fluid flowing between the hydraulic pump motor and the head-side port; a regeneration valve that opens and closes a regeneration channel that connects the head-side port and the rod-side port; a pressure sensor that detects an inflow pressure of the hydraulic pump motor; and a control device for controlling the operation of each of the direction control valve and the regeneration valve, the control device controlling the opening degree of the regeneration valve on the basis of the inflow pressure of the working fluid detected by the pressure sensor when the regeneration passage is opened by the regeneration valve and the head-side port and the hydraulic pump motor are connected by the direction control valve.

Description

Technical Field

[0001] The present disclosure relates to a hydraulic drive device for supplying and discharging a working fluid to and from a head-side port and a rod-side port of a hydraulic cylinder, respectively. 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, an excessive load may be applied to the boom instantaneously. In this case, an excessive load is applied to the motor in order to regenerate energy. It is desirable to suppress such an excessive load from being applied to the motor.

[0005] Therefore, an object of the present disclosure is to provide a hydraulic drive device capable of suppressing an excessive load on a motor during regeneration.

[0006] Means of solving the problem: The hydraulic drive device disclosed in the present invention is a hydraulic drive device that drives a hydraulic cylinder by supplying and discharging working fluid to a head side port and a rod side port respectively, and comprises: a hydraulic pump motor that discharges working fluid and is rotationally driven by the supplied working fluid; an electric motor connected to the hydraulic pump motor; a directional control valve that switches the direction of the working fluid flowing between the hydraulic pump motor and the head side port; a regeneration valve that opens and closes a regeneration channel that connects the head side port and the rod side port; a pressure sensor that detects the inflow pressure of the hydraulic pump motor; and a control device that controls the respective actions of the directional control valve and the regeneration valve, wherein the control device controls the opening of the regeneration valve according to the inflow pressure of the working fluid detected by the pressure sensor when the regeneration channel is opened by the regeneration valve and the head side port and the hydraulic pump motor are connected by the directional control valve.

[0007] According to the present disclosure, the opening of the regeneration valve is controlled according to the inflow pressure. Therefore, when an excessive load is applied to the motor during regeneration, pressure loss can be generated through the regeneration valve. Thus, during regeneration, an excessive load acting on the motor is suppressed.

[0008] Effect of the invention: According to the present disclosure, it is possible to suppress an excessive load on the motor during regeneration.

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

[0010] Figure 1 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 flowchart of the sequence of boom cylinder extension and retraction processing performed by the hydraulic drive device; Figure 3 It is shown in Figure 1 A circuit diagram showing the flow of working fluid when the boom cylinder is extended in a hydraulic drive device; Figure 4 It is shown in Figure 1 A circuit diagram showing the flow of working fluid when the boom cylinder is retracted in a hydraulic drive device; Figure 5 1 is a circuit diagram showing the structure of a hydraulic drive device according to a second embodiment of the present disclosure. DETAILED DESCRIPTION

[0011] 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.

[0012] [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.

[0013] 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. The boom cylinder 2 is driven by supplying and discharging working fluid (for example, liquid such as oil or water) to and from the head side port 2a and the rod side port 2b, respectively. To explain in more detail, when the working fluid is supplied to the head side port 2a and discharged from the rod side port 2b, the boom cylinder 2 extends. Thus, 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. Thus, 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.

[0014] <Hydraulic drive unit> 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 drives the boom cylinder 2, that is, causes the boom cylinder 2 to extend and retract. 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 suction side pressure sensor 17, a stroke sensor 18, and a control device 19.

[0015] <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 24 is provided in the suction passage 21. The check valve 24 allows the flow of the working fluid from the tank 20 to the suction port 11a and prevents the flow in the reverse direction.

[0016] 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. In the present embodiment, the hydraulic pump motor 11 is a variable capacity swash plate pump and has a regulator 11d. The regulator 11d changes the tilt angle of the swash plate according to the input capacity instruction. In this way, the pump 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.

[0017] <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 rotating the hydraulic pump motor 11 (more specifically, the shaft 11c) by receiving the supply of working fluid. 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 (more specifically, the rotation speed of the shaft 11c) according to the input rotation speed command.

[0018] <Directional control valve> The directional control valve 13 switches the direction of the working fluid flowing between the hydraulic pump motor 11 and the head side port 2a. 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 than the check valve 24 in the suction passage 21. In addition, the directional control valve 13 is connected to the discharge port 11b via the discharge passage 22. In addition, 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.

[0019] 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.

[0020] <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.

[0021] <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 to 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.

[0022] <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.

[0023] <Suction side pressure sensor> The suction side pressure sensor 17 detects the inflow pressure of the hydraulic pump motor 11. The inflow pressure is the pressure of the working fluid flowing into the suction port 11a of the hydraulic pump motor 11, and is also called the suction pressure. In more detail, the suction side pressure sensor 17 is connected to the suction passage 21. The suction side pressure sensor 17 detects the hydraulic pressure of the suction passage 21 as the inflow pressure. Then, the suction side pressure sensor 17 outputs the detected inflow pressure.

[0024] <Stroke sensor> The stroke sensor 18, which is an example of a speed sensor, is a sensor for detecting the speed of the boom cylinder 2. To explain in more detail, the stroke sensor 18 detects the stroke amount of the boom cylinder 2. Then, the stroke sensor 18 outputs the detected stroke amount. In addition, the speed sensor can be a speed sensor, an acceleration sensor, an angle sensor, and an inertial measurement unit (abbreviated as: IMU), as long as it is a sensor that can calculate the speed of the boom cylinder 2 based on other detection results. In addition, the speed sensor detects the speed of the stroke in the boom cylinder 2. The acceleration sensor detects the acceleration of the stroke in the boom cylinder 2. The angle sensor detects the angle of the boom. The IMU detects the acceleration and rotation speed of the boom.

[0025] <Control device> The control device 19 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 19 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 19 controls the flow of the working fluid in the hydraulic drive device 1. In addition, the control device 19 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 19 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 19 controls the discharge flow rate and the suction flow rate of the hydraulic pump motor 11.

[0026] Furthermore, the control device 19 changes the discharge flow rate and the suction flow rate of the hydraulic pump motor 11 according to the detection result of the stroke sensor 18 in this embodiment. Thus, the control device 19 performs feedback control on the speed or acceleration (speed in this embodiment) of the boom cylinder 2. In addition, the control device 19 controls the operation of the directional control valve 13 and the regeneration valve 14 according to the inflow pressure detected by the suction side pressure sensor 17. In more detail, the control device 19 controls the opening of the directional control valve 13 and the regeneration valve 14 according to the inflow pressure detected by the suction side pressure sensor 17.

[0027] <Operation of the hydraulic drive unit> In the hydraulic drive device 1, when the operating device 16 is operated (in this embodiment, the operating lever 16a is operated), an operating signal is output from the operating device 16. The control device 19 controls the operation of the direction control valve 13, the regeneration valve 14, and the unloading valve 15 according to the operation signal. In addition, the control device 19 controls the operation of the electric motor 12 and the hydraulic pump motor 11 according to the operation signal and the detection result of the stroke sensor 18. As a result, the control device 19 extends and retracts the boom cylinder 2 in the direction and speed corresponding to the operation signal (in this embodiment, the operation direction and operation 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 19 controls the opening of the direction control valve 13 and the regeneration valve 14 according to the inflow pressure of the hydraulic pump motor 11. As a result, the excessive increase in the load of the electric motor 12 is suppressed.

[0028] Below, refer to Figure 2 The flowchart further details the boom cylinder extension and retraction process for extending and retracting the boom cylinder 2. In the hydraulic drive device 1, when the operating device 16 is operated to extend and retract the boom cylinder 2, an operating signal is output from the operating device 16. In this way, the boom cylinder extension and retraction process is started, and the process is transferred to step S1. In step S1, which is a boom lowering operation determination process, the control device 19 determines whether the operation of the operating device 16 is a boom lowering operation (i.e., an operation to retract the boom cylinder 2). In more detail, the control device 19 detects the operating direction of the operating lever 16a based on the operating signal. Then, the control device 19 determines whether it is a boom lowering operation based on the operating direction of the operating lever 16a. For example, when the operating lever 16a is operated in the first direction, the control device 19 determines that it is a boom raising operation. In this way, the process is transferred to step S2. On the other hand, when the operating lever 16a is operated in the second direction, the control device 19 determines that it is a boom lowering operation. In this way, the process is transferred to step S3.

[0029] In step S2, which is the boom cylinder extension process, the control device 19 extends the boom cylinder 2. In more detail, the control device 19 operates the directional control valve 13 according to the operation signal. For example, the control device 19 outputs an operation command corresponding to the operation signal to the directional control valve 13. As a result, the directional control valve 13, such as Figure 3As 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. In addition, the opening between the discharge port 11b and the head side port 2a in the directional control valve 13 is fully open in this embodiment. 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 19 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 3 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 3 As a result, the boom cylinder 2 extends at a speed corresponding to the operation signal (see arrow A2). Figure 3 The boom can be raised at a speed corresponding to the operation signal. Afterwards, if the boom raising operation is completed, the control device 19 ends the boom cylinder extension and retraction process.

[0030] In step S3 as the boom cylinder retracting process, the control device 19 retracts the boom cylinder 2. In more detail, the control device 19 operates the directional control valve 13, the regeneration valve 14, and the unloading valve 15 according to the operation signal. For example, the control device 19 outputs an operation command corresponding to the operation signal to the directional control valve 13. Thus, the control device 19, as shown in FIG. Figure 4 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 19 outputs a regeneration command to the regeneration valve 14. As a result, the control device 19 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 19 outputs a unloading command to the unloading valve 15. As a result, the control device 19 connects the discharge passage 22 to the tank 20 through the unloading valve 15. In this way, the hydraulic pump motor 11 is unloaded.

[0031] 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 4 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 4Then, 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.

[0032] Furthermore, the control device 19 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 19 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 4 The boom can thereby be lowered at a speed corresponding to the operation signal. When the boom cylinder 2 is retracted according to the boom lowering operation, the process proceeds to step S4.

[0033] In addition, the control device 19 performs the following feedback control during the boom lowering operation. That is, the control device 19 changes the suction flow rate of the hydraulic pump motor 11 according to the detection result of the stroke sensor 18. In more detail, the control device 19 outputs a capacity command and a speed command according to the detection result of the stroke sensor 18, thereby changing the suction flow rate of the hydraulic pump motor 11. In this way, the speed of the boom cylinder 2 is feedback-controlled by the control device 19. As a result, hunting generated in the boom cylinder 2 is suppressed.

[0034] In step S4, which is an inflow load determination process, the control device 19 determines whether the inflow load, which is a load flowing into the electric motor 12, is greater than or equal to a prescribed value I1. In more detail, the control device 19 estimates the inflow load I based on the inflow pressure detected by the suction side pressure sensor 17. Specifically, the control device 19 calculates the suction flow rate of the hydraulic pump motor 11 based on the speed command and the capacity command. Then, the control device 19 estimates the inflow load I based on the suction flow rate and the inflow pressure. The control device 19 determines whether the inflow load I is greater than or equal to a prescribed value I1. When the inflow load I is less than the prescribed value I1, the process proceeds to step S5. On the other hand, when the inflow load I is greater than or equal to the prescribed value I1, the process proceeds to step S6.

[0035] In step S5, which is the first opening control process, the control device 19 controls the opening of the regeneration valve 14 according to the inflow load I. In more detail, the control device 19 makes the opening R of the regeneration valve 14 greater than the prescribed first regeneration opening R1, for example, fully open. In addition, the control device 19 also makes the opening between the head side port 2a and the suction port 11a, that is, the opening D of the directional control valve 13 greater than the prescribed first regeneration opening D1, for example, fully open. In this way, by making the regeneration valve 14 and the directional control valve 13 fully open, the pressure loss generated in the working fluid can be suppressed, so that more energy can be regenerated into electrical energy. In addition, the first regeneration opening R1 and the first regeneration opening D1 do not necessarily have to be fully open, as long as they are more than 85% of the full opening. Afterwards, if the boom lowering operation is completed, the control device 19 ends the boom cylinder extension and retraction process.

[0036] In step S6, which is the second opening control process, the control device 19 throttles the opening of the regeneration valve 14. In more detail, the control device 19 throttles the opening R of the regeneration valve 14 from the first regeneration opening R1. That is, the control device 19 throttles the opening R of the regeneration valve 14 to the second regeneration opening R2 (for example, an opening between 20% or more and less than 85% of the fully open state). As a result, pressure loss occurs 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 second regeneration opening R2 is not limited to the aforementioned numerical range, as long as it is smaller than the first regeneration opening R1.

[0037] Furthermore, the control device 19 throttles the opening of the directional control valve 13. To explain in more detail, the control device 19 throttles the opening D of the directional control valve 13 from the first regeneration opening D1. That is, the control device 19 throttles the opening D of the directional control valve 13 to the second regeneration opening D2 (for example, an opening between 20% and less than 85% of the fully open state). 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 second regeneration opening D2 is not limited to the aforementioned numerical range, as long as it is smaller than the first regeneration opening D1.

[0038] 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. As a result, the fluid energy flowing into the hydraulic pump motor 11 is reduced. Therefore, during regeneration, the inflow load of the electric motor 12 is suppressed. After the opening of the regeneration valve 14 and the directional control valve 13 is throttled, if the boom lowering operation is completed, the control device 19 ends the boom cylinder extension and retraction process.

[0039] In addition, the control device 19 controls the pump capacity of the hydraulic pump motor 11 and the rotation speed of the electric motor 12 according to the inflow load during regeneration. In more detail, the control device 19 limits the output capacity command and the rotation speed command according to the estimated inflow load. Thus, the pump capacity of the hydraulic pump motor 11 and the rotation speed of the electric motor 12 are respectively limited. In this way, the suction flow rate of the hydraulic pump motor 11 can be suppressed. Thus, the energy regenerated by the electric motor 12 during regeneration can be reduced. Therefore, it is possible to suppress excessive load (for example, output power exceeding the rated output power) from acting on the electric motor 12.

[0040] In the hydraulic drive device 1 of the present embodiment, the opening of the regeneration valve 14 is controlled according to the inflow pressure. Therefore, when an excessive load is applied to the motor 12 during regeneration, pressure loss can be generated through the regeneration valve 14. Thus, during regeneration, an excessive load is suppressed from acting on the motor 12.

[0041] Furthermore, in the hydraulic drive device 1 of the present embodiment, when the inflow load is greater than a predetermined value, the control device 19 throttles the opening of the regeneration valve 14. Therefore, pressure loss can be generated. Thus, the load of the motor 12 during regeneration can be reduced. Therefore, the motor 12 can be prevented from becoming overloaded. On the other hand, by increasing the opening of the regeneration valve 14 when the inflow load is less than a predetermined value, the pressure loss during regeneration can be suppressed. Thus, the regeneration efficiency in the hydraulic drive device 1 can be maintained high.

[0042] In addition, in the hydraulic drive device 1 of the present embodiment, when the inflow load is greater than a predetermined value, the control device 19 throttles the opening of the directional control valve 13. Therefore, pressure loss can be generated. As a result, the load of the motor 12 during regeneration can be reduced. Therefore, the motor 12 can be prevented from becoming overloaded. On the other hand, by increasing the opening of the directional control valve 13 when the inflow load is less than a predetermined value, the pressure loss during regeneration can be suppressed. As a result, the regeneration efficiency in the hydraulic drive device 1 can be maintained high.

[0043] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 19 controls the rotation speed of the electric motor 12 according to the inflow pressure. Therefore, by reducing the rotation speed of the electric motor 12, the suction flow rate of the hydraulic pump motor 11 can be suppressed. Thus, the load on the electric motor 12 can be suppressed. Therefore, the electric motor 12 is suppressed from becoming an overload state.

[0044] In addition, in the hydraulic drive device 1 of the present embodiment, the control device 19 controls the pump capacity of the hydraulic pump motor 11 according to the inflow pressure. Therefore, by reducing the pump capacity of the hydraulic pump motor 11, the suction flow rate of the hydraulic pump motor 11 can be suppressed. As a result, the load on the motor 12 can be suppressed. Therefore, the motor 12 is suppressed from becoming overloaded.

[0045] In the hydraulic drive device 1 of this embodiment, the discharge passage 22 is connected to the tank 20 via the unloading valve 15 when the electric motor 12 is regenerated. 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 maintained high.

[0046] [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.

[0047] Figure 5 The hydraulic drive system 1A of the second embodiment shown includes a hydraulic pump motor 11A, an electric motor 12, a directional control valve 13A, and a regeneration valve 14. The hydraulic drive system 1A also includes an operating device 16, a pressure sensor 17A, a stroke sensor 18, and a control device 19A.

[0048] <Hydraulic pump motor> The hydraulic pump motor 11A has a first port 11Aa, a second port 11Ab, and a shaft portion 11c. The first port 11Aa is connected to the tank 20 via the tank passage 21A. Furthermore, the second port 11Ab is connected to the pump passage 22A. The hydraulic pump motor 11A, when the shaft portion 11c is driven to rotate in the forward direction, sucks the working fluid from the first port 11Aa and discharges the working fluid from the second port 11Ab. On the other hand, the hydraulic pump motor 11A rotates the shaft portion 11c in the reverse direction when the working fluid is supplied to the second port 11Ab. Then, the hydraulic pump motor 11A discharges the working fluid from the first port 11Aa. Furthermore, the hydraulic pump motor 11A is a variable capacity swash plate pump in the present embodiment and has a regulator 11d.

[0049] <Directional control valve> The directional control valve 13A switches the direction of the working fluid flowing between the hydraulic pump motor 11A and the head side port 2a. The directional control valve 13A is connected to the second port 11Ab of the hydraulic pump motor 11A via the pump passage 22A. The directional control valve 13A is connected to the head side port 2a and the rod side port 2b of the boom cylinder 2. In addition, the directional control valve 13A is connected to the tank 20.

[0050] The directional control valve 13A connects the second port 11Ab to the head side port 2a when an action command is input. In addition, the directional control valve 13A opens and closes between the rod side port 2b and the tank 20 according to the input action command. Thus, the directional control valve 13A can switch the direction of the working fluid flowing between the hydraulic pump motor 11A and the head side port 2a. Furthermore, when the working fluid flows from the head side port 2a to the second port 11Ab, the directional control valve 13A controls the opening between the head side port 2a and the second port 11Ab (i.e., the opening of the directional control valve 13A) according to the action command. In the present embodiment, the directional control valve 13A is an electrical slide valve. However, the directional control valve 13A is not limited to an electrical slide valve.

[0051] <Pressure sensor> The pressure sensor 17A detects the inflow pressure of the hydraulic pump motor 11A. In more detail, the pressure sensor 17A is connected to the pump channel 22A. The pressure sensor 17A detects the hydraulic pressure of the working fluid flowing in the pump channel 22A. Therefore, the pressure sensor 17A detects the hydraulic pressure of the working fluid flowing in the pump channel 22A as the inflow pressure during regeneration. The pressure sensor 17A outputs the detected inflow pressure.

[0052] <Control device> The control device 19A controls the operation of the directional control valve 13A, the regeneration valve 14, and the unloading valve 15 in accordance with the input operation signal, similarly to the control device 19 of the first embodiment. Furthermore, in the present embodiment, the control device 19A changes the discharge flow rate and the suction flow rate of the hydraulic pump motor 11A in accordance with the detection result of the stroke sensor 18. In addition, the control device 19A controls the opening of the directional control valve 13A and the regeneration valve 14 in accordance with the inflow pressure detected by the pressure sensor 17A.

[0053] <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), the boom cylinder extension process is executed similarly to the hydraulic drive device 1 of the first embodiment. The boom cylinder extension process executed by the control device 19A is similar to the boom cylinder extension process executed by the control device 19 of the first embodiment. The following mainly describes the differences between the boom cylinder extension process executed by the control device 19A and the boom cylinder extension process executed by the control device 19 of the first embodiment.

[0054] In step S2, which is the boom cylinder extension process, the control device 19A extends the boom cylinder 2. To explain in more detail, the control device 19A actuates the directional control valve 13A according to the operation signal. For example, the control device 19A outputs an action instruction corresponding to the operation signal to the directional control valve 13A. As a result, the directional control valve 13A connects the second port 11Ab to the head side port 2a, and connects the rod side port 2b to the tank 20. Then, the control device 19A outputs a speed instruction and a capacity instruction corresponding to the operation signal. As a result, the hydraulic pump motor 11A discharges the working fluid of the flow rate corresponding to the operation signal from the second port 11Ab. Therefore, the boom can be lifted at a speed corresponding to the operation signal. Afterwards, if the boom lifting operation is completed, the control device 19A ends the boom cylinder extension and retraction process.

[0055] In step S3, which is a boom cylinder retraction process, the control device 19A retracts the boom cylinder 2. To explain in more detail, the control device 19A actuates the directional control valve 13A and the regeneration valve 14 according to the operation signal. For example, the control device 19A outputs an operation command corresponding to the operation signal to the directional control valve 13A. As a result, the control device 19A connects the head side port 2a to the second port 11Ab through the directional control valve 13A, and cuts off the connection between the rod side port 2b and the tank 20. In addition, the control device 19A outputs a regeneration command to the regeneration valve 14, thereby opening the regeneration passage 23 through the regeneration valve 14. In this way, in the boom cylinder 2 that is subjected to the dead weight of the boom in the retraction direction, 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. In addition, the remaining part is guided to the hydraulic pump motor 11A. Then, energy recovery is performed in the electric motor 12. The control device 19A controls the suction flow rate in the same manner as the control device 19 of the first embodiment, thereby causing the boom cylinder 2 to retract at a speed corresponding to the operation signal, and performs feedback control on the speed or acceleration of the boom cylinder 2 based on the detection result of the stroke sensor 18. In this way, when the boom cylinder 2 is retracted in accordance with the boom lowering operation, the process proceeds to step S4.

[0056] In step S4, which is an inflow load determination process, the control device 19A estimates the inflow load I based on the inflow pressure detected by the pressure sensor 17A. Specifically, the control device 19A calculates the suction flow rate of the hydraulic pump motor 11A based on the speed command and the capacity command. Then, the control device 19A estimates the inflow load I based on the suction flow rate and the inflow pressure. When the estimated inflow load I is less than the specified value I1, the process proceeds to step S5. On the other hand, when the inflow load I is greater than the specified value I1, the process proceeds to step S6.

[0057] The hydraulic drive system 1A of the present embodiment achieves the same operational effects as those of the hydraulic drive system 1 of the first embodiment.

[0058] <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, 13A 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, 13A and the regeneration valve 14 is configured to have an adjustable opening. The control device 19, 19A does not necessarily have to throttle both the directional control valve 13, 13A and the regeneration valve 14 when the inflow load increases. The control device 19, 19A only needs to throttle the opening of at least one of the directional control valve 13, 13A and the regeneration valve 14. In addition, the control device 19, 19A may selectively throttle the opening of the directional control valve 13, 13A and the regeneration valve 14 according to the inflow load. For example, the control device 19, 19A first throttles the opening of the regeneration valve 14 as the inflow load increases, and then throttles the opening of the directional control valve 13, 13A. Furthermore, the control devices 19 and 19A do not necessarily have to limit the pump capacity of the hydraulic pump motor 11 and 11A and the rotation speed of the electric motor 12 when the inflow load increases. In addition, the control devices 19 and 19A do not necessarily have to perform feedback control on the speed or acceleration of the boom cylinder 2. In addition, the driving source of the hydraulic pump motor 11 and 11A is not limited to the electric motor 12, and may be a hybrid driving source of the electric motor 12 and the engine.

[0059] <Exemplary Embodiment> 4. The hydraulic drive device in accordance with claim 1, wherein the hydraulic cylinder is driven by supplying and discharging working fluid to and from a head side port and a rod side port, respectively. The hydraulic drive device comprises: a hydraulic pump motor that discharges working fluid and is rotationally driven by the supplied working fluid; an electric motor connected to the hydraulic pump motor; a directional control valve that switches the direction of the working fluid flowing between the hydraulic pump motor and the head side port; a regeneration valve that opens and closes a regeneration channel that connects the head side port and the rod side port; a pressure sensor that detects the inflow pressure of the hydraulic pump motor; and a control device that controls the respective actions of the directional control valve and the regeneration valve, wherein the control device controls the opening of the regeneration valve according to the inflow pressure of the working fluid detected by the pressure sensor when the regeneration channel is opened by the regeneration valve and the head side port and the hydraulic pump motor are connected by the directional control valve.

[0060] According to the above aspect, the opening of the regeneration valve is controlled according to the inflow pressure. Therefore, when an excessive load is applied to the motor during regeneration, pressure loss can be generated through the regeneration valve. Thus, during regeneration, an excessive load applied to the motor can be suppressed.

[0061] The hydraulic drive device in the second aspect may also be the hydraulic drive device in the first aspect, wherein the control device throttles the opening of the regeneration valve when the inflow load calculated based on the inflow pressure detected by the pressure sensor and the rotational speed of the motor is greater than a specified value.

[0062] According to the above aspect, when the inflow load is greater than a specified value, the control device throttles the opening of the regeneration valve. Therefore, pressure loss can be generated. As a result, the load of the motor during regeneration can be reduced. Therefore, the motor can be prevented from becoming overloaded. On the other hand, by increasing the opening of the regeneration valve when the inflow load is less than a specified value, the pressure loss during regeneration can be suppressed. As a result, the regeneration efficiency in the hydraulic drive device can be maintained at a high level.

[0063] The hydraulic drive device in the third aspect may also be the hydraulic drive device in the first or second aspect, wherein the control device causes the directional control valve to throttle the opening between the head side port and the hydraulic pump motor when the inflow load calculated based on the inflow pressure detected by the pressure sensor and the rotational speed of the electric motor is greater than a specified value.

[0064] According to the above aspect, when the inflow load is greater than a specified value, the control device throttles the opening of the directional control valve. Therefore, pressure loss can be generated. As a result, the load of the motor during regeneration can be reduced. Therefore, the motor can be prevented from becoming overloaded. On the other hand, by increasing the opening of the directional control valve when the inflow load is less than a specified value, the pressure loss during regeneration can be suppressed. As a result, the regeneration efficiency in the hydraulic drive device can be maintained at a high level.

[0065] The hydraulic drive device in a fourth aspect may be the hydraulic drive device in any one of the first to third aspects, wherein the control device controls the rotation speed of the electric motor based on the inflow pressure detected by the pressure sensor.

[0066] According to the above aspect, the control device controls the rotation speed of the electric motor according to the inflow pressure. Therefore, by reducing the rotation speed of the electric motor, the suction flow rate of the hydraulic pump motor can be suppressed. Thus, the load on the electric motor can be suppressed. Therefore, the electric motor is prevented from becoming overloaded.

[0067] The hydraulic drive device in the fifth aspect may be the hydraulic drive device in any one of the first to fourth aspects, wherein the hydraulic pump motor is capable of changing pump capacity, and the control device controls the pump capacity of the hydraulic pump motor according to the inflow pressure detected by the pressure sensor.

[0068] According to the above aspect, the control device controls the pump capacity of the hydraulic pump motor according to the inflow pressure. Therefore, by reducing the pump capacity of the hydraulic pump motor, the suction flow rate of the hydraulic pump motor can be suppressed. As a result, the load on the motor can be suppressed. Therefore, the motor is prevented from becoming overloaded.

[0069] The hydraulic drive device in the sixth aspect may also be a hydraulic drive device in any one of the first to fifth aspects, further comprising a unloading valve, wherein the hydraulic pump motor includes a discharge port for discharging working fluid and a suction port for sucking working fluid, the directional control valve switches the connection objects of the head side port and the rod side port to the discharge port and the suction port respectively, the unloading valve connects the discharge channel to the tank, the discharge channel connects the discharge port and the directional control valve, and the control device operates the unloading valve when connecting the head side port to the suction port through the directional control valve.

[0070] According to the above aspect, when the electric motor is regenerated, 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 maintaining the regeneration efficiency in the electric motor at a high level.

[0071] Explanation of symbols 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 drives the hydraulic cylinder by supplying and discharging working fluid to the head side port and the rod side port respectively. It has: A hydraulic pump motor that discharges working fluid and is rotationally driven by the supplied working fluid; an electric motor connected to the hydraulic pump motor; a directional control valve that switches the direction of the working fluid flowing between the hydraulic pump motor and the head-side port; a regeneration valve for opening and closing a regeneration passage connecting the head-side port and the rod-side port; a pressure sensor for detecting the inflow pressure of the hydraulic pump motor; a control device for controlling the respective operations of the directional control valve and the regeneration valve, The control device controls the opening degree of the regeneration valve according to the inflow pressure of the working fluid detected by the pressure sensor when the regeneration passage is opened by the regeneration valve and the head-side port and the hydraulic pump-motor are connected by the directional control valve.

2. The hydraulic drive device according to claim 1, characterized in that: The control device throttles the opening of the regeneration valve when an inflow load calculated based on the inflow pressure detected by the pressure sensor and the rotation speed of the electric motor is equal to or larger than a predetermined value.

3. The hydraulic drive device according to claim 1 or 2, characterized in that: The control device controls the directional control valve to reduce the opening between the head-side port and the hydraulic pump-motor when an inflow load calculated from the inflow pressure detected by the pressure sensor and the rotation speed of the electric motor is equal to or greater than a predetermined value.

4. The hydraulic drive device according to claim 1 or 2, characterized in that: The control device controls the rotation speed of the electric motor according to the inflow pressure detected by the pressure sensor.

5. The hydraulic drive device according to claim 1 or 2, characterized in that: The hydraulic pump motor is capable of varying the pump capacity, The control device controls a pump capacity of the hydraulic pump motor based on an inflow pressure detected by the pressure sensor.

6. The hydraulic drive device according to claim 1 or 2, characterized in that: It also has a relief valve. The hydraulic pump motor includes a discharge port for discharging the working fluid and a suction port for sucking the working fluid. The directional control valve switches the connection destinations of the head side port and the rod side port to the discharge port and the suction port, respectively. The unloading valve connects the discharge channel to the tank, and the discharge channel connects the discharge port to the directional control valve. The control device operates the unloading valve when the head-side port and the suction port are connected via the directional control valve.

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