Hydraulic drive system

Abstract

The hydraulic drive system includes a hydraulic pump that supplies working fluid to a hydraulic actuator; an inlet control valve that controls the flow rate of the working fluid from the hydraulic pump to the hydraulic actuator; an outlet control valve that controls the flow rate of the working fluid from the hydraulic actuator to a tank; and a regeneration valve that supplies the working fluid discharged from the hydraulic actuator to the hydraulic actuator; the outlet control valve and the regeneration valve are connected to the hydraulic actuator in parallel.

Description

Technical Field

[0001] This invention relates to a hydraulic drive system capable of regenerating the working fluid discharged from a hydraulic actuator. Background Technology

[0002] In hydraulic drive systems, the working fluid discharged from the hydraulic actuator is regenerated to achieve energy-saving effects. For example, the hydraulic drive device described in Patent Document 1 is known as such a hydraulic drive system.

[0003] Existing technical documents: Patent documents: Patent document 1: Japanese Patent Application Publication No. 2018-28358. Summary of the Invention

[0004] The problem the invention aims to solve: In the hydraulic drive system of Patent Document 1, the working fluid discharged to the meter out line is regenerated in the hydraulic cylinder via a regeneration line. Therefore, since the working fluid discharged to the meter out line is directly regenerated in the hydraulic cylinder, the regeneration flow rate varies depending on the posture and load of the attachments mounted on the hydraulic cylinder. Thus, the posture and load of the attachments affect the cylinder's responsiveness to rod operation. Furthermore, when the working fluid is discharged to the tank during regeneration, it is introduced into the tank through a control valve and a regeneration release valve. Therefore, the pressure loss of the working fluid during regeneration is significant.

[0005] Therefore, the object of the present invention is to provide a hydraulic drive system capable of suppressing the impact of changes in regeneration flow rate on the responsiveness of a hydraulic actuator.

[0006] In addition, the present invention can provide a hydraulic drive system that can reduce pressure loss in the working fluid during regeneration.

[0007] Solution methods: The hydraulic drive system of the present invention includes: a hydraulic pump for supplying working fluid to a hydraulic actuator; an inlet control valve for controlling the flow rate of working fluid from the hydraulic pump to the hydraulic actuator; an outlet control valve for controlling the flow rate of working fluid discharged from the hydraulic actuator to a tank; and a regeneration valve for supplying working fluid discharged from the hydraulic actuator to the hydraulic actuator; the outlet control valve and the regeneration valve are connected to the hydraulic actuator in parallel.

[0008] According to the present invention, the flow rate of the working fluid flowing within each of the inlet control valve, outlet control valve, and regeneration valve can be independently controlled. Therefore, the outlet flow rate can be adjusted according to changes in the regeneration flow rate. This suppresses the impact of regeneration flow rate variations on the responsiveness of the hydraulic actuator.

[0009] Furthermore, according to the present invention, the working fluid discharged to the tank is discharged from the hydraulic actuator to the tank without passing through the regeneration valve. Therefore, it is possible to reduce the pressure loss of the working fluid discharged to the tank.

[0010] Invention effects: According to the present invention, the effect of changes in regeneration flow rate on the responsiveness of the hydraulic actuator can be suppressed.

[0011] In addition, according to the present invention, the pressure loss generated in the working fluid during regeneration can be reduced.

[0012] The above-mentioned objects, other objects, features and advantages of the present invention will become clear from the following detailed description of preferred embodiments with reference to the accompanying drawings. Attached Figure Description

[0013] Figure 1 This is a hydraulic circuit diagram illustrating a hydraulic drive system according to an embodiment of the present invention. Figure 2 yes Figure 1 A block diagram of the control device of the hydraulic drive system that involves the opening control of the regeneration valve. Figure 3 yes Figure 1 A block diagram of the control device of the hydraulic drive system involving the opening control of the liquid outlet control valve. Figure 4 This is a hydraulic circuit diagram illustrating a hydraulic drive system according to another embodiment of the present invention. Detailed Implementation

[0014] The hydraulic drive system 1 according to an embodiment of the present invention will now be described with reference to the aforementioned accompanying drawings. Furthermore, the concept of direction used in the following description is for ease of explanation and is not intended to limit the structural orientation of the invention to that direction. Additionally, the hydraulic drive system 1 described below is only one embodiment of the present invention. Therefore, the present invention is not limited to this embodiment, and additions, deletions, and modifications can be made without departing from the spirit of the invention.

[0015] Hydraulically driven machinery, such as construction machinery, industrial machinery, and industrial vehicles, possesses hydraulic actuators and hydraulic drive systems. Furthermore, hydraulically driven machinery can cause various structural movements by activating the hydraulic actuators. Thus, hydraulically driven machinery can perform various tasks. For example, a hydraulic actuator may be... Figure 1The hydraulic cylinder 2 is shown. The hydraulic cylinder 2 can perform various structural actions through extension and retraction. To explain in more detail, the hydraulic cylinder 2 inserts a rod 2b retractably into a cylinder tube 2a. Furthermore, a rod-side port 2c and a head-side port 2d are formed on the cylinder tube 2a. Moreover, by supplying and discharging working fluid to each port 2c and 2d, the rod 2b moves forward and backward relative to the cylinder tube 2a, i.e., the hydraulic cylinder 2 extends and retracts.

[0016] The hydraulic drive system 1 supplies and discharges working fluid to the hydraulic cylinder 2. Specifically, the hydraulic drive system 1 is connected to each of the ports 2c and 2d of the hydraulic cylinder 2. Furthermore, the hydraulic cylinder 2 is retracted by supplying working fluid to the rod-side port 2c and discharging working fluid from the head-side port 2d. Additionally, the hydraulic drive system 1 retracts the hydraulic cylinder 2 by supplying working fluid to the head-side port 2d and discharging working fluid from the rod-side port 2c. In more detail, the hydraulic drive system 1 includes, for example, a hydraulic pump 11, an inlet control valve 12, an outlet control valve 13, a regeneration valve 14, three pressure sensors 15-17, an operating device 18, and a control device 19.

[0017] The hydraulic pump 11 is driven to discharge working fluid by rotation. That is, the hydraulic pump 11 is connected to a drive source. The drive source is an engine E or an electric motor. In this embodiment, the drive source is an engine E. The hydraulic pump 11 discharges working fluid by being driven to rotate by the engine E. Furthermore, in this embodiment, the hydraulic pump 11 is a swashplate pump or a swashplate pump.

[0018] The inlet control valve 12 is located between the hydraulic pump 11 and the hydraulic cylinder 2. That is, the inlet control valve 12 is connected to ports 2c and 2d of both the hydraulic pump 11 and the hydraulic cylinder 2. In this embodiment, the inlet control valve 12 is connected to the rod-side port 2c via the rod-side passage 21a and to the head-side port 2d via the head-side passage 21b. Furthermore, the inlet control valve 12 can control the direction and flow rate of the working fluid supplied from the hydraulic pump 11 to the hydraulic cylinder 2 according to the input inlet command. That is, the inlet control valve 12 can supply the working fluid from the hydraulic pump 11 to either port 2c or 2d of the hydraulic cylinder 2, and can control the inlet flow rate as the flow rate of the supplied working fluid. Specifically, in this embodiment, the inlet control valve 12 is an electronically controlled spool valve. That is, the inlet control valve 12 has a valve core 12a and two electromagnetic proportional control valves 31L and 31R. The valve core 12a switches the flow direction of the working oil by moving and can control the opening degree of the inlet control valve 12.

[0019] Two electromagnetic proportional control valves 31L and 31R can apply pilot pressures in mutually opposing directions to the valve core 12a. Furthermore, the two electromagnetic proportional control valves 31L and 31R output pilot pressures corresponding to the input fluid inlet command, causing the valve core 12a to move to a position corresponding to the pressure difference between the two pilot pressures. That is, the two electromagnetic proportional control valves 31L and 31R move the valve core 12a to a position corresponding to the input fluid inlet command. This supplies working fluid in the direction and flow rate corresponding to the input fluid inlet command to the hydraulic cylinder 2.

[0020] The discharge control valve 13 is located between the hydraulic pump 11 and the tank 10. Specifically, the discharge control valve 13 is connected to each of the ports 2c and 2d of the hydraulic cylinder 2 and the tank 10. In this embodiment, the discharge control valve 13 is connected to the rod-side passage 21a and the head-side passage 21b in parallel with the inlet control valve 12. Furthermore, the discharge control valve 13 can control the direction and flow rate (discharge flow rate) of the working fluid discharged from the hydraulic cylinder 2 to the tank 10 according to the input discharge command. That is, the discharge control valve 13 can switch the direction of the discharged working fluid from ports 2c and 2d of the hydraulic cylinder 2 to either side of the tank 10 and control the discharge flow rate. Additionally, the discharge control valve 13 can independently control the flow rate passing through it, separate from the flow rate supplied to the hydraulic cylinder 2 through the inlet control valve 12. Specifically, in this embodiment, the discharge control valve 13 is an electronically controlled spool valve. That is, the liquid outlet control valve 13 has a valve core 13a and two electromagnetic proportional control valves 32L and 32R. The valve core 13a switches the flow direction of the working oil by moving and can control the opening degree of the liquid outlet control valve 13.

[0021] Two electromagnetic proportional control valves 32L and 32R can apply pilot pressures in mutually opposing directions to the valve core 13a. Furthermore, the two electromagnetic proportional control valves 32L and 32R output pilot pressures corresponding to the input discharge command, causing the valve core 13a to move to a position corresponding to the pressure difference between the two pilot pressures. That is, the two electromagnetic proportional control valves 32L and 32R move the valve core 13a to the position corresponding to the input discharge command. As a result, working fluid in the direction and flow rate corresponding to the input discharge command is discharged from the hydraulic cylinder 2.

[0022] The regeneration valve 14 is connected to the hydraulic cylinder 2 in parallel with the discharge control valve 13. The regeneration valve 14 regenerates the working fluid discharged from the hydraulic cylinder 2 back into the hydraulic cylinder 2. In this embodiment, the regeneration valve 14 is located in the regeneration passage 23 connecting the rod-side passage 21a and the head-side passage 21b. More specifically, the regeneration valve 14 can open and close the regeneration passage 23 according to the input regeneration valve command. A check valve 20 is provided in the regeneration passage 23. In this embodiment, the check valve 20 is located in the regeneration passage 23 closer to the head-side passage 21b than the regeneration valve 14. Furthermore, the check valve 20 allows forward flow from the rod-side port 2c to the head-side port 2d in the regeneration passage 23 and prevents reverse flow. Therefore, the hydraulic drive system 1 can regenerate the working fluid from the rod-side port 2c to the head-side port 2d. Additionally, the regeneration valve 14 can adjust its opening degree according to the input regeneration valve command. Thus, the regeneration valve 14 can regenerate the working fluid to the hydraulic cylinder 2 at a regeneration flow rate corresponding to the input regeneration valve command. Furthermore, the regeneration valve 14 can independently control the flow rate through it, in contrast to the flow rates through the inlet control valve 12 and the outlet control valve 13. In this embodiment, the regeneration valve 14 is an electromagnetic proportional control valve.

[0023] The first and second pressure sensors 15 and 16 detect the hydraulic pressure supplied to and discharged from the rod-side port 2c and the head-side port 2d, respectively. More specifically, the first pressure sensor 15 is connected to the rod-side passage 21a. That is, the first pressure sensor 15 detects the hydraulic pressure (rod pressure Pcr) of the working fluid supplied to and discharged from the rod-side port 2c. On the other hand, the second pressure sensor 16 is connected to the head-side passage 21b. That is, the second pressure sensor 16 detects the hydraulic pressure (head pressure Pch) of the working fluid supplied to and discharged from the head-side port 2d. Furthermore, the third pressure sensor 17 detects the hydraulic pressure (discharge pressure) of the working fluid discharged from the hydraulic pump 11. Moreover, the three pressure sensors 15-17 output the detected hydraulic pressure to the control device 19.

[0024] The operating device 18 outputs an operating command to the control device 19 to actuate the hydraulic cylinder 2. The operating device 18 may be, for example, an operating valve or an electric joystick. More specifically, the operating device 18 has an operating lever 18a as an example of an operating element. The operating lever 18a is configured to be operable by an operator. Furthermore, the operating device 18 outputs an operating command to the control device 19 corresponding to the amount of operation of the operating lever 18a. In this embodiment, the operating lever 18a is configured to be rocking. Moreover, the operating device 18 outputs an operating command to the control device 19 corresponding to the amount of rocking of the operating lever 18a.

[0025] The control device 19 is connected to the regeneration valve 14, three pressure sensors 15-17, four electromagnetic proportional control valves 31L, 31R, 32L, and 32R, and the operating device 18. Furthermore, the control device 19 controls the opening of the regeneration valve 14 and the discharge control valve 13. Thus, the control device 19 causes the hydraulic cylinder 2 to discharge working fluid at a flow rate corresponding to the operating signal from the operating device 18. More specifically, the control device 19 controls the opening of the regeneration valve 14 according to the load state of the hydraulic cylinder 2, thereby causing the working fluid at the regeneration flow rate to be regenerated from the rod-side port 2c to the head-side port 2d via the regeneration valve 14. Additionally, the control device 19 controls the opening of the discharge control valve 13 to discharge the working fluid at the discharge flow rate (obtained by subtracting the regeneration flow rate from the discharge flow rate) into the tank 10. More specifically, to control the opening of the regeneration valve 14, as... Figure 2 As shown, the control device 19 includes a target discharge flow rate calculation unit 41, a regeneration ratio calculation unit 42, a piping pressure estimation unit 43, and a regeneration valve opening calculation unit 44. Furthermore, in order to adjust the discharge flow rate according to the regeneration flow rate, such as... Figure 3 As shown, the control device 19 includes a target discharge flow calculation unit 41, a regeneration flow estimation unit 45, and an inlet control valve opening calculation unit (M / O control valve opening calculation unit) 46.

[0026] The target discharge flow rate calculation unit 41 calculates the target discharge flow rate discharged from the hydraulic cylinder 2 based on the operation command from the operating device 18. In this embodiment, the target discharge flow rate calculation unit 41 calculates the target discharge flow rate based on a mapping diagram showing the correspondence between the operation command and the target discharge flow rate. Alternatively, the target discharge flow rate can also be calculated based on a formula.

[0027] The regeneration ratio calculation unit 42 calculates the regeneration ratio based on the load condition of the hydraulic cylinder 2. The regeneration ratio is the ratio of the regenerated flow rate to the target discharge flow rate discharged from the hydraulic cylinder 2. That is, the regeneration ratio is the ratio of the flow rate that should be regenerated relative to the target discharge flow rate discharged from the hydraulic cylinder 2. In addition, the load condition is the load (driving force or braking force) of the hydraulic cylinder 2. Moreover, the load condition is calculated by at least one of the hydraulic pressure at the rod-side port 2c (rod pressure Pcr detected by the first pressure sensor 15) and the hydraulic pressure at the head-side port 2d (head pressure Pch detected by the second pressure sensor 16). Alternatively, the discharge pressure (discharge pressure detected by the third pressure sensor 17) can be used instead of the hydraulic pressure at the head-side port 2d. Moreover, the regeneration ratio is set according to the rod pressure Pcr detected by the first pressure sensor 15 and the head pressure Pch detected by the second pressure sensor 16. In this embodiment, the regeneration ratio is set low when the head pressure Pch is high and high when the head pressure Pch is low. Furthermore, the regeneration ratio can also be set based on the load of the hydraulic cylinder 2 calculated from the difference between the rod pressure Pcr and the head pressure Pch. Moreover, the load of the hydraulic cylinder 2 is negative when the rod 2b is pushed and extended by the load. In this embodiment, the regeneration ratio is set to decrease when the absolute value of the load increases, causing the rod 2b to extend. However, the relationship between the regeneration ratio and the load state of the hydraulic cylinder 2 is not limited to the aforementioned relationship. When the first and second pressure sensors 15 and 16 detect hydraulic pressure, the regeneration ratio calculation unit 42 calculates the regeneration ratio based on the detection results.

[0028] The piping pressure estimation unit 43 estimates the downstream pressure of the regeneration valve 14. That is, the piping pressure estimation unit 43 estimates the pressure (piping pressure Ph) of the working fluid flowing through the piping section 23a between the regeneration valve 14 and the check valve 20 in the regeneration passage 23. More specifically, the piping pressure estimation unit 43 estimates the pressure based on the rod pressure Pcr (discharge pressure) detected by the first pressure sensor 15, the head pressure Pch (supply pressure) detected by the second pressure sensor 16, and the target regeneration opening. The target regeneration opening is the target regeneration opening of the regeneration valve 14 calculated by the regeneration valve opening calculation unit 44, which will be detailed later. In other words, the piping pressure estimation unit 43 estimates the piping pressure Ph based on the rod pressure Pcr, the head pressure Pch, the target regeneration opening, and the opening (prescribed value) of the check valve 20. Furthermore, when estimating the piping pressure Ph, it is not necessarily necessary to refer to the head pressure Pch. By using the head pressure Pch, the piping pressure Ph can be estimated with higher accuracy.

[0029] The regeneration valve opening calculation unit 44 calculates the regeneration valve command based on the target discharge flow rate, regeneration ratio, head pressure Pch, and rod pressure Pcr. More specifically, the regeneration valve opening calculation unit 44 multiplies the target flow rate calculated by the target discharge flow rate calculation unit 41 by the regeneration ratio calculated by the regeneration ratio calculation unit 42. This calculates the target regeneration flow rate in the regeneration valve 14. Furthermore, the regeneration valve opening calculation unit 44 calculates the target regeneration opening degree based on the calculated target regeneration flow rate, the piping pressure Ph, and the rod pressure Pcr detected by the first pressure sensor 15. The target regeneration opening degree is the opening degree in the regeneration valve 14 to allow the aforementioned target regeneration flow rate to flow to the head port 2d. When the regeneration valve opening calculation unit 44 calculates the target regeneration opening degree, it outputs a regeneration valve command corresponding to the target regeneration opening degree to the regeneration valve 14. Thus, when the rod port 2c has a higher pressure than the head port 2d, the working fluid with the target regeneration flow rate is regenerated from the rod port 2c to the head port 2d through the regeneration valve 14.

[0030] The regeneration flow estimation unit 45 estimates the regeneration flow rate based on the opening degree of the regeneration valve 14. More specifically, the regeneration flow estimation unit 45 estimates the regeneration flow rate based on the pressure difference across the regeneration valve 14 and the target regeneration opening degree. In this embodiment, the pressure difference across the regeneration valve 14 is calculated by subtracting the piping pressure Ph from the rod pressure Pcr. The rod pressure Pcr is detected by the first pressure sensor 15. Furthermore, the piping pressure Ph is estimated by the piping pressure estimation unit 43. Moreover, the target regeneration opening degree is calculated by the regeneration valve opening calculation unit 44.

[0031] The M / O control valve opening calculation unit 46 calculates the target discharge flow rate. More specifically, the M / O control valve opening calculation unit 46 calculates the target discharge flow rate by subtracting the regeneration flow rate from the target discharge flow rate. Here, the target discharge flow rate is calculated by the target discharge flow rate calculation unit 41. Additionally, the regeneration flow rate is calculated by the regeneration flow rate estimation unit 45. Furthermore, the M / O control valve opening calculation unit 46 calculates the target discharge opening degree based on the calculated target discharge flow rate, the rod pressure Pcr detected by the first pressure sensor 15, and the specified tank pressure. The target discharge opening degree is the opening degree that the discharge control valve 13 should open to discharge the target discharge flow rate into the tank 10. Alternatively, the target discharge opening degree can be calculated based on the downstream pressure of the discharge control valve 13 instead of the tank pressure. The downstream pressure of the discharge control valve 13 is detected by a pressure sensor (not shown) or estimated by a pressure estimation method. When the M / O control valve opening calculation unit 46 calculates the target discharge opening degree, it outputs a discharge control valve command (M / O control valve command) corresponding to the target discharge opening degree to the electromagnetic proportional control valves 32L and 32R. For example, when the control device 19 discharges working fluid from the lever-side port 2c, it outputs an M / O command to the electromagnetic proportional control valve 32L. As a result, the working fluid with the target discharge flow rate is discharged to the tank 10 through the discharge control valve 13. That is, the working fluid with the target discharge flow rate can be discharged from the hydraulic cylinder 2 through the regeneration valve 14 and the discharge control valve 13.

[0032] Furthermore, the control device 19 controls the opening degree of the inlet control valve 12 according to the operation command from the operating device 18. More specifically, the control device 19 calculates the direction of the working oil supply and the target supply flow rate based on the operation command from the operating device 18. Then, the control device 19 calculates the target inlet flow rate by subtracting the aforementioned target regeneration flow rate from the calculated target supply flow rate. The target inlet flow rate is the flow rate that should be supplied to the hydraulic cylinder 2 via the inlet control valve 12. Additionally, the control device 19 calculates the opening degree of the inlet control valve 12 based on the target inlet flow rate and the pressure difference across the inlet control valve 12. The pressure difference across the inlet control valve 12 is calculated by the control device 19 based on the hydraulic pressure detected by either the first or second pressure sensors 15, 16 and the third pressure sensor 17. Moreover, the control device 19 outputs inlet control valve commands (M / I control valve commands) corresponding to the calculated opening degree to the electromagnetic proportional control valves 31L and 31R. For example, when supplying working fluid to the head-side port 2d, the control device 19 outputs an M / I command to the electromagnetic proportional control valve 31L. Therefore, working fluid with a target inlet flow rate is supplied from the inlet control valve 12 to the hydraulic cylinder 2. Furthermore, working fluid with a target supply flow rate is supplied to the hydraulic cylinder 2.

[0033] In the hydraulic drive system 1 with this structure, when the rod 2b is extended and subjected to a load in the extension direction, the working fluid can be regenerated from the rod-side port 2c to the head-side port 2d. Furthermore, during regeneration, the control device 19 controls the opening of the inlet control valve 12, the regeneration valve 14, and the outlet control valve 13 in the following manner: When the operating rod 18a is operated, the operating device 18 outputs an operating command to the control device 19 corresponding to the amount of operation of the operating rod 18a. Then, the control device 19 outputs a regeneration valve command to the regeneration valve 14. Specifically, when outputting the operating command, the control device 19 calculates the target discharge flow rate and regeneration ratio in the target discharge flow rate calculation unit 41 and the regeneration ratio calculation unit 42, respectively, and estimates the piping pressure Ph in the piping pressure estimation unit 43. Additionally, the control device 19 calculates the target regeneration opening degree in the regeneration valve opening calculation unit 44 based on the target discharge flow rate, the regeneration ratio, and the piping pressure Ph. Furthermore, the control device 19 outputs a regeneration valve command corresponding to the target regeneration opening degree to the regeneration valve 14 in the regeneration valve opening calculation unit 44. As a result, the working fluid with a regeneration flow rate corresponding to the load state of the hydraulic cylinder 2 is regenerated from the rod-side port 2c to the head-side port 2d.

[0034] Furthermore, in order to control the opening of the discharge control valve 13, the control device 19 estimates the regeneration flow rate in the regeneration flow estimation unit 45. Additionally, the control device 19 calculates the target discharge opening degree in the M / O control valve opening calculation unit 46 based on the target discharge flow rate and the regeneration flow rate. Moreover, the control device 19 outputs an M / O control valve command to the electromagnetic proportional control valve 32L in the M / O control valve opening calculation unit 46 according to the target discharge opening degree. Thus, the working fluid at the target discharge flow rate can be discharged from the rod-side port 2c of the hydraulic cylinder 2 to the tank 10 via the inlet control valve 12. In other words, the target discharge flow rate and the target regeneration flow rate can be integrated, allowing the working fluid at the target discharge flow rate to be discharged from the rod-side port 2c.

[0035] Furthermore, in order to control the opening of the inlet control valve 12, the control device 19 outputs an M / I command corresponding to the operation command and regeneration flow rate to the electromagnetic proportional control valve 31L. Thus, the opening of the inlet control valve 12 is controlled according to the operation command and regeneration flow rate. That is, the working fluid with the target inlet flow rate is supplied from the hydraulic pump 11 to the head port 2d of the hydraulic cylinder 2 via the inlet control valve 12. Therefore, the target inlet flow rate and the target regeneration flow rate can be integrated, and the working fluid with the target supply flow rate can be supplied to the head port 2d.

[0036] In the hydraulic drive system 1 with this structure, regeneration can be performed from the lever-side port 2c to the head-side port 2d, while simultaneously discharging working fluid with high precision from the lever-side port 2c at a target discharge flow rate corresponding to the operating command. Therefore, the hydraulic cylinder 2 can be operated at a speed corresponding to the operating amount of the operating lever 18a of the operating device 18. This improves the operability of the hydraulic cylinder 2.

[0037] Furthermore, the hydraulic drive system 1 of this embodiment can independently control the flow rate of the working fluid flowing in the inlet control valve 12, the outlet control valve 13, and the regeneration valve 14. Therefore, the outlet flow rate can be adjusted in accordance with changes in the regeneration flow rate. As a result, changes in the discharge flow rate from the hydraulic cylinder 2 can be suppressed, and the impact of changes in the regeneration flow rate on the responsiveness of the hydraulic actuator can be suppressed.

[0038] Furthermore, in the hydraulic drive system 1, the discharge control valve 13 is connected to the hydraulic actuator in parallel with the regeneration valve 14. Therefore, the working fluid discharged to the tank 10 is discharged from the hydraulic cylinder 2 to the tank 10 without passing through the regeneration valve 14. This reduces the pressure loss of the working fluid discharged to the tank 10. Consequently, it improves the fuel consumption of the drive source (engine E).

[0039] Furthermore, the hydraulic drive system 1 controls the opening of the regeneration valve 14 and the discharge control valve 13 in a manner that links the regeneration flow rate and the discharge flow rate, thereby maintaining the discharge flow rate from the hydraulic cylinder 2 at a flow rate corresponding to the operating signal. Thus, by adjusting the regeneration flow rate to the optimal flow rate, stable operability can be achieved while maintaining the responsiveness of the hydraulic cylinder 2.

[0040] Furthermore, in the hydraulic drive system 1, the control device 19 calculates the discharge flow rate by subtracting the target regeneration flow rate from the target discharge flow rate. Therefore, since the discharge flow rate is increased or decreased in accordance with changes in the regeneration flow rate, insufficient regeneration flow rate or insufficient discharge flow rate can be suppressed. As a result, the rise in the discharge pressure of the hydraulic pump 11 and the occurrence of cavitation can be suppressed.

[0041] Furthermore, in the hydraulic drive system 1, by arranging the regeneration valve 14 and the outlet control valve 13 in parallel, the piping pressure Ph can be estimated with high accuracy. This improves the estimation accuracy of the regeneration flow rate and stabilizes the control. Additionally, by using the supply pressure detected for estimating the piping pressure Ph, the piping pressure Ph can be estimated with even higher accuracy. This further improves the estimation accuracy of the regeneration flow rate and makes the control more stable.

[0042] Furthermore, in the hydraulic drive system 1, by using the regeneration ratio, the regeneration flow rate can be varied according to the load of the hydraulic actuator. This helps to suppress the rise in discharge pressure of the hydraulic pump 11 or the occurrence of cavitation.

[0043] <Regarding other implementation methods> In the hydraulic drive system 1 of this embodiment, the hydraulic actuator is described using a hydraulic cylinder 2 as an example, but the hydraulic actuator can also be a hydraulic motor. Furthermore, the type of hydraulic cylinder 2 is not limited to a single-rod double-acting cylinder; it can also be a double-rod cylinder or a single-acting cylinder. Moreover, the inlet control valve 12, outlet control valve 13, and regeneration valve 14 are not limited to the aforementioned structures. That is, the inlet control valve 12, outlet control valve 13, and regeneration valve 14 are only required to control their respective openings.

[0044] Furthermore, in the hydraulic drive system 1, the valve cores 12a and 13a of the inlet control valve 12 and the outlet control valve 13 can also be driven by an electric motor or the like. Moreover, in the hydraulic drive system 1, the number of hydraulic actuators connected to the hydraulic pump 11 can be two or more. In this case, the operating device 18 has multiple operating levers 18a corresponding to each hydraulic actuator. Furthermore, when at least two of the multiple operating levers 18a are operated, the control device 19 corrects the target discharge flow rate and the target supply flow rate based on the number of operated levers 18a and their respective operating amounts.

[0045] Furthermore, in the hydraulic drive system 1 of this embodiment, the regeneration ratio varies according to the load state of the hydraulic cylinder 2, but it can also be a fixed value. Additionally, the regeneration ratio can be switched between on and off based on the load state of the hydraulic cylinder 2. Furthermore, in the hydraulic drive system 1 of this embodiment, the control device 19 does not necessarily need to control the opening of the inlet control valve 12, the outlet control valve 13, and the regeneration valve 14 as described above.

[0046] Alternatively, the hydraulic drive system 1A in another embodiment can also be as follows: Figure 4 The hydraulic drive system 1A is configured as shown. Specifically, it includes a head-side control valve 12A and a rod-side control valve 13A. The head-side control valve 12A connects the head-side port 2d to either the hydraulic pump 11 or the tank 10. Furthermore, the head-side control valve 12A controls the inlet and outlet flow rates to the head-side port 2d. Similarly, the rod-side control valve 13A connects the rod-side port 2c to either the hydraulic pump 11 or the tank 10. Furthermore, the rod-side control valve 13A controls the inlet and outlet flow rates to the rod-side port 2c. Therefore, in the hydraulic drive system 1A, for example, when the rod 2b is extended, the head-side control valve 12A functions as an inlet control valve, and the rod-side control valve 13A functions as an outlet control valve. Otherwise, the hydraulic drive system 1A has the same structure as the hydraulic drive system 1 of this embodiment.

[0047] The hydraulic drive system 1A, configured in this way, can independently control the flow rate of the working fluid flowing in each of the head-side control valve 12A, the rod-side control valve 13A, and the regeneration valve 14. Therefore, the discharge flow rate can be adjusted in response to changes in the regeneration flow rate. This suppresses fluctuations in the discharge flow rate from the hydraulic cylinder 2 and mitigates the impact of regeneration flow rate fluctuations on the responsiveness of the hydraulic actuator. Otherwise, the hydraulic drive system 1A achieves the same effects as the hydraulic drive system 1 of this embodiment.

[0048] Based on the foregoing description, many improvements and other embodiments of the present invention will be apparent to those skilled in the art. Therefore, the foregoing description should be interpreted as illustrative only, provided for the purpose of informing those skilled in the art of the best mode for carrying out the invention. Specific details of its structure and / or function may be substantially changed without departing from the spirit of the invention.

[0049] Symbol explanation: 1. Hydraulic drive system 10 cans 11 Hydraulic pump 12 Inlet control valve 12A lever-side control valve 13 Discharge control valve 13A Head-side Control Valve 14 Regeneration valve 15 First pressure sensor 16 Second pressure sensor 18 Operating device 18a Operating lever (operating element) 19. Control device.

Claims

1. A hydraulic drive system, comprising: A hydraulic pump that supplies working fluid to a hydraulic actuator; An inlet control valve that controls the flow rate of the working fluid from the hydraulic pump to the hydraulic actuator; A discharge control valve that controls the flow rate of working fluid discharged from the hydraulic actuator to the tank; and The working fluid discharged from the hydraulic actuator is supplied to the regeneration valve of the hydraulic actuator; The discharge control valve, the regeneration valve, and the inlet control valve are respectively connected to the hydraulic actuator in parallel.

2. The hydraulic drive system according to claim 1, characterized in that, It also has: An operating device that outputs an operating signal corresponding to the operating amount of the operating component; and A control device that controls the opening of the regeneration valve and the discharge control valve to discharge working fluid from the hydraulic actuator at a flow rate corresponding to the operation signal from the operating device.

3. The hydraulic drive system according to claim 2, characterized in that, The control device estimates the regeneration flow rate based on the opening of the regeneration valve, and controls the opening of the discharge control valve in such a way that the discharge flow rate flows into the tank. This discharge flow rate is the difference between the discharge flow rate from the hydraulic actuator and the estimated regeneration flow rate, controlled according to the operation signal from the operating device.

4. The hydraulic drive system according to claim 2 or 3, characterized in that, It also includes a first pressure sensor that detects the discharge pressure, which is the pressure of the working fluid discharged from the hydraulic actuator; The control device estimates the regeneration flow rate based on the downstream pressure of the regeneration valve and the discharge pressure of the hydraulic actuator; The downstream pressure of the regeneration valve is estimated based on the discharge pressure detected by the first pressure sensor and the opening degree of the regeneration valve.

5. The hydraulic drive system according to claim 4, characterized in that, It has a second pressure sensor that detects the supply pressure, which is the pressure of the working fluid supplied to the hydraulic actuator; The control device estimates the downstream pressure of the regeneration valve based on the discharge pressure detected by the first pressure sensor, the supply pressure detected by the second pressure sensor, and the opening degree of the regeneration valve.

6. The hydraulic drive system according to claim 2, characterized in that, The control device sets the ratio of the regeneration flow rate to the discharge flow rate from the hydraulic actuator, i.e., the regeneration ratio, according to the load state of the hydraulic actuator, and controls the opening of the regeneration valve according to the regeneration ratio.

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