Fluid pressure circuit

Abstract

Provided is a fluid pressure circuit capable of accumulating fluid with a wide range of pressures.　The fluid pressure circuit includes: a drive body 1; and a plurality of accumulators 6a, 6b that accumulate fluid in accordance with a fluid pressure supplied from the drive body 1 side. The plurality of accumulators 6a, 6b have different accumulation characteristics.

Description

Fluid Pressure Circuit

[0001] The present invention relates to a hydraulic circuit, and more particularly to a hydraulic circuit having an accumulator for storing hydraulic fluid.

[0002] In various fields, fluid pressure circuits are known that drive actuators using hydraulic fluid such as hydraulic oil delivered from a fluid supply device such as a pump. In such fluid pressure circuits, for example, oil discharged from a hydraulic cylinder device as an actuator when the hydraulic cylinder device contracts is stored in an accumulator, and is regenerated when the hydraulic cylinder device extends.

[0003] For example, a fluid pressure circuit is known in which a hydraulic fluid discharged from a hydraulic cylinder device is pressurized by a pressure booster device and stored in an accumulator (see Patent Document 1). An example of such a fluid pressure circuit, shown in Figure 4, is mainly composed of a hydraulic pump 501, a directional control valve 502, a hydraulic cylinder device 503, an electromagnetic switching valve 504, a pressure booster device 505, an accumulator 506, and a tank 507.

[0004] The directional control valve 502 is a spring-center type six-port three-position switching valve. When the directional control valve 502 is in the neutral position 502-1, the oil discharged from the hydraulic pump 501 is discharged to the tank 507.

[0005] Furthermore, when the directional control valve 502 is in the left position 502-2, the oil discharged from the hydraulic pump 501 is supplied to the first oil chamber 503-1 of the hydraulic cylinder device 503, and part of the oil in the second oil chamber 503-2 of the hydraulic cylinder device 503 is discharged to the tank 507 via the orifice 517, and the other part flows to the electromagnetic control valve 504. This causes the workpiece W to descend.

[0006] When the directional control valve 502 is in the right position 502-3, a portion of the oil discharged from the hydraulic pump 501 is supplied to the second oil chamber 503-2 of the hydraulic cylinder device 503, and the oil in the first oil chamber 503-1 of the hydraulic cylinder device 503 is discharged to the tank 507. This causes the workpiece W to rise.

[0007] The electromagnetic switching valve 504 is a four-port two-position type electromagnetic switching valve.

[0008] The pressure booster 505 includes a case 508 and a piston 509. The case 508 includes a large-diameter cylindrical portion 508a, a small-diameter cylindrical portion 508b, and a partition wall 508c. The partition wall 508c is annular and separates the large-diameter cylindrical portion 508a from the small-diameter cylindrical portion 508b. The piston 509 includes a large-diameter portion 509a, a small-diameter portion 509b, and a shaft portion 509c, and is enclosed within the case 508 so as to be slidable in the axial direction.

[0009] When the solenoid controlled directional control valve 504 is demagnetized, it is located at a first position 504-1, and oil supplied from the hydraulic cylinder device 503 side is introduced into the oil chamber 505-1 of the pressure booster device 505, and oil in the oil chamber 505-2 is discharged into the tank 507. This causes the piston 509 to move to the right, and the oil in the oil chamber 505-3 is pushed out and flows into the accumulator 506 through the check valve 510. At the same time, negative pressure is created in the oil chamber 505-4 of the pressure booster device 505, and oil in the tank 507 is sucked in through the check valve 511.

[0010] On the other hand, when the solenoid directional control valve 504 is switched to the second position 504-2, the oil supplied from the hydraulic cylinder device 503 side is introduced into the oil chamber 505-2 of the pressure booster device 505, and the oil in the oil chamber 505-1 is discharged into the tank 507. This causes the piston 509 to move to the left, pushing out the oil in the oil chamber 505-4 and flowing into the accumulator 506 through the check valve 512. At the same time, the pressure inside the oil chamber 505-3 of the pressure booster device 505 becomes negative, and the oil in the tank 507 is sucked in through the check valve 513.

[0011] If the area of ​​the left side surface of large diameter portion 509a of piston 509 is A, the area of ​​the right side surface of large diameter portion 509a is B, the area of ​​the right side surface of small diameter portion 509b is C, and the area of ​​the left side surface of small diameter portion 509b is D, then according to Pascal's principle, when solenoid directional control valve 504 is in a de-energized state, the oil pushed out from oil chamber 505-3 is increased in pressure by up to A / C times and flows into accumulator 506. Also, when solenoid directional control valve 504 is in an energized state, the oil pushed out from oil chamber 505-4 is increased in pressure by up to B / D times and flows into accumulator 506. Therefore, by repeatedly energizing and de-energizing solenoid directional control valve 504, oil increased in pressure by pressure booster 505 continuously flows into accumulator 506.

[0012] JP 2017-15130 A (page 7, Figure 2)

[0013] In the fluid pressure circuit as shown in FIG. 4, the pressure in the second oil chamber 503-2 of the hydraulic cylinder device 503, i.e., the input pressure to the pressure booster device 505, may vary greatly depending on the conditions of use of the hydraulic cylinder device 503, for example, whether or not a load is acting on the workpiece W.

[0014] For example, when the load on the workpiece W is large and the input pressure to the pressure intensifier 505 is as high as 7 MPa, if the pressure intensifier 505 has a pressure intensifier ratio of 3 and the enclosed gas pressure of the accumulator 506 is 7 MPa, as shown in FIG. 5 , the output pressure is intensified to 21 MPa due to the pressure intensifier 505's pressure intensifier ratio, and therefore a large amount of liquid can be stored in the accumulator 506.

[0015] On the other hand, when the load on the workpiece W is small and the input pressure to the pressure booster 505 is low at 3 MPa, as shown in FIG. 6, the output pressure is only boosted up to 9 MPa due to the boost ratio of the pressure booster 505, and there is a risk that the amount of liquid stored in the accumulator 506 will be small.

[0016] The present invention has been made in view of the above-mentioned problems, and has as its object to provide a fluid pressure circuit capable of storing fluids with a wide range of pressures.

[0017] In order to solve the above problems, the fluid pressure circuit of the present invention includes a driver and a plurality of accumulators that accumulate fluid in accordance with the fluid pressure supplied from the driver, the plurality of accumulators having different accumulation characteristics. This allows the use of a plurality of accumulators with different accumulation characteristics in accordance with the pressure, thereby enabling the accumulation of a wide range of fluid pressures.

[0018] The system may further include a switching valve that switches the supply destination of the fluid to at least one of the accumulators. In this way, the supply destination of the fluid can be selected by the switching valve, and the fluid can be preferentially accumulated in a desired accumulator.

[0019] The switching valve may switch the supply destination to one of the accumulators. In this case, since the switching valve supplies fluid to one accumulator, movement of fluid between accumulators with different accumulation characteristics is prevented. Therefore, it is possible to prevent fluid accumulated in a high-pressure accumulator from flowing to a low-pressure accumulator.

[0020] A pressure sensor for detecting the pressure of the fluid may be provided between the driver and the accumulator. This allows the switching valve to be switched in accordance with the pressure of the fluid detected by the pressure sensor. This improves the accuracy of control of the fluid pressure circuit in response to changes in conditions.

[0021] The driving body may be an extendable hydraulic cylinder device. In this case, even if the hydraulic pressure of the return oil from the hydraulic cylinder device fluctuates, it can be accumulated by using a plurality of accumulators with different accumulation characteristics.

[0022] A pressure booster may be provided between the driver and the accumulator, whereby the high fluid pressure boosted by the pressure booster can be accumulated in the accumulator.

[0023] The system may further include a regeneration switching valve that selectively regenerates the fluid stored in the plurality of accumulators. In this case, the accumulator that stores the fluid at an optimum pressure can be selected by the regeneration switching valve and used for regeneration.

[0024] Fig. 1 is a schematic diagram showing a fluid pressure circuit in a first embodiment of the present invention; Fig. 2 is a diagram showing the relationship between the output pressure of a pressure booster device and the amount of fluid stored in an accumulator in the first embodiment; Fig. 3 is a schematic diagram showing a fluid pressure circuit in a second embodiment of the present invention; Fig. 4 is a schematic diagram showing a conventional fluid pressure circuit; Fig. 5 is a diagram showing the relationship between the output pressure of a pressure booster device and the amount of fluid stored in an accumulator when the input pressure of the pressure booster device is high in the conventional case; Fig. 6 is a diagram showing the relationship between the output pressure of a pressure booster device and the amount of fluid stored in an accumulator when the input pressure of the pressure booster device is low in the conventional case.

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fluid pressure circuit according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0026] A fluid pressure circuit according to a first embodiment will be described with reference to Figures 1 and 2. In the following description, the left and right sides of Figure 1, as viewed from the front, will be taken as the valve positions of the directional control valves and the left and right sides of the pressure booster.

[0027] The hydraulic circuit as a fluid pressure circuit according to the first embodiment utilizes working fluid discharged from a hydraulic cylinder device of a work machine, a construction machine, a material handling vehicle, an automobile, or the like, and stores the working fluid pressurized by a pressure booster in an accumulator to be regenerated in the hydraulic cylinder device.

[0028] As shown in FIG. 1, the hydraulic circuit 101 is mainly composed of a hydraulic cylinder device 1 which is an actuator serving as a driving body, a hydraulic pump 2, a directional control valve 3, an electromagnetic control valve 4, a pressure booster 5, accumulators 6a and 6b, a supply destination control valve 7 which serves as a control valve, a tank 8, a regenerative control valve 9, a pressure sensor 10, check valves 11 to 16, and pipelines 21 to 36.

[0029] The hydraulic pump 2 supplies pressure oil. The pressure oil delivered from the hydraulic pump 2 passes through the pipelines 21 and 22 and the check valve 11 and flows into the directional control valve 3.

[0030] Although the hydraulic pump 2 in this embodiment is a fixed displacement type, it may be a variable displacement type.

[0031] The directional control valve 3 is a spring-center type, three-position, six-port hydraulic control valve. When the directional control valve 3 is in the neutral position 3-1, it connects the line 21 to the line 23. The line 23 is connected to the tank 8. Therefore, all of the pressure oil delivered from the hydraulic pump 2 is discharged into the tank 8.

[0032] When a hydraulic signal is applied to the left side of the directional control valve 3, the spool moves to the right and the directional control valve 3 switches to the left position 3-2. When the directional control valve 3 is in the left position 3-2, the pipe 22 is connected to the pipe 24 and the pipe 25 is connected to the pipe 27.

[0033] Therefore, the pressurized oil delivered from the hydraulic pump 2 flows into the first oil chamber 1-1 of the hydraulic cylinder device 1, and the pressurized oil in the second oil chamber 1-2 of the hydraulic cylinder device 1 is discharged into the tank 8 via the orifice 17, and a portion of the oil flows into the solenoid directional control valve 4 through a pipe 28 branching from the pipe 25. This causes the hydraulic cylinder device 1 to contract, and the workpiece W moves down.

[0034] On the other hand, when a hydraulic signal is applied to the right side of the directional control valve 3, the spool moves leftward and the directional control valve 3 switches to the right position 3-3. When the directional control valve 3 is in the right position 3-3, it connects the line 22 to the line 25 and the line 24 to the line 27.

[0035] Therefore, the pressurized oil delivered from the hydraulic pump 2 flows into the second oil chamber 1-2 of the hydraulic cylinder device 1, and the pressurized oil in the first oil chamber 1-1 of the hydraulic cylinder device 1 is discharged into the tank 8. As a result, the hydraulic cylinder device 1 extends and the workpiece W rises.

[0036] The solenoid controlled directional control valve 4 is a spring offset type two-position four-port solenoid controlled directional control valve. When the solenoid controlled directional control valve 4 is in the offset position 4-1, it connects the line 28 to the line 29 and also connects the line 30 to the line 26.

[0037] When an electric signal is applied to the solenoid 4a and the solenoid 4a is excited, the spool moves and switches to the onset position 4-2. When the solenoid-operated directional control valve 4 is in the onset position 4-2, the line 28 is connected to the line 30 and the line 29 is connected to the line 26.

[0038] The pressure booster 5 is mainly composed of a case 51 and a piston 52 .

[0039] The case 51 is formed in a stepped cylindrical shape and includes a large-diameter cylindrical portion 51a, a small-diameter cylindrical portion 51b, a partition wall portion 51c, and disk portions 51d and 51e.

[0040] The large-diameter cylindrical portion 51a and the small-diameter cylindrical portion 51b are separated by an annular partition wall 51c. The left end of the large-diameter cylindrical portion 51a is closed by a disk portion 51d, and the right end of the small-diameter cylindrical portion 51b is closed by a disk portion 51e.

[0041] The piston 52 includes a large-diameter cylindrical portion 52a, a small-diameter cylindrical portion 52b, and a connecting shaft portion 52c, the axes of which are arranged substantially in the same straight line.

[0042] The large diameter columnar portion 52a has a diameter slightly smaller than the inner diameter of the large diameter cylindrical portion 51a of the case 51. The large diameter columnar portion 52a is slidable along the inner circumferential surface of the large diameter cylindrical portion 51a.

[0043] The small diameter columnar portion 52b has a diameter that is slightly smaller than the inner diameter of the small diameter cylindrical portion 51b of the case 51. The small diameter columnar portion 52b is slidable along the inner circumferential surface of the small diameter cylindrical portion 51b.

[0044] The connecting shaft 52c has a diameter slightly smaller than the inner diameter of the partition wall 51c of the case 51. The connecting shaft 52c is slidable along the inner circumferential surface of the partition wall 51c of the case 51.

[0045] The pressure booster 5 includes a first input chamber 5-1, a second input chamber 5-2, a first output chamber 5-3, and a second output chamber 5-4.

[0046] The first input chamber 5-1 is a space surrounded by the large-diameter cylindrical portion 51a, the disk portion 51d, and the large-diameter columnar portion 52a, and the conduit 29 is connected thereto.

[0047] The second input chamber 5-2 is a space surrounded by the large-diameter cylindrical portion 51a, the partition wall portion 51c, and the large-diameter columnar portion 52a, and the conduit 30 is connected thereto.

[0048] The first output chamber 5-3 is a space surrounded by the small diameter cylindrical portion 51b, the disk portion 51e and the small diameter columnar portion 52b, and the conduit 31 and the conduit 35 are connected thereto.

[0049] The second output chamber 5-4 is a space surrounded by the small diameter cylindrical portion 51b, the partition wall portion 51c and the small diameter columnar portion 52b, and the conduits 33 and 34 are connected to the second output chamber 5-4.

[0050] When the electromagnetic switching valve 4 is in a demagnetized state, i.e., in the offset position 4-1, the pressurized oil flowing through the pipe 28 flows into the first input chamber 5-1 of the pressure booster 5 via the pipe 29, and the pressurized oil in the second input chamber 5-2 of the pressure booster 5 is discharged to the tank 8 via the pipes 30 and 26.

[0051] This causes the piston 52 to move to the right, and the pressurized oil in the first output chamber 5-3 flows into the supply destination switching valve 7 through the line 31, the check valve 13, and the line 36. At the same time, negative pressure is created in the second output chamber 5-4, and oil in the tank 8 is sucked in through the check valve 14 and the line 33.

[0052] The pressure-receiving area C of the right side surface of the small-diameter cylindrical portion 52b of the piston 52 is smaller than the pressure-receiving area A of the left side surface of the large-diameter cylindrical portion 52a. Therefore, the pressure of the pressurized oil pushed out from the first output chamber 5-3 by the piston 52 moving to the right can be increased up to A / C times.

[0053] When the solenoid switching valve 4 is in an excited state, i.e., in the onset position 4-2, the pressurized oil flowing through the pipe 28 flows into the second input chamber 5-2 of the pressure booster 5 via the pipe 30, and the pressurized oil in the first input chamber 5-1 of the pressure booster 5 is discharged to the tank 8 via the pipes 29 and 26.

[0054] This causes the piston 52 to move to the left, and the pressurized oil in the second output chamber 5-4 flows into the supply destination switching valve 7 through the line 34, the check valve 15, and the line 36. At the same time, negative pressure is created in the first output chamber 5-3, and oil in the tank 8 is sucked in through the check valve 16 and the line 35.

[0055] The pressure-receiving area D of the left side surface of the small-diameter cylindrical portion 52b of the piston 52 is smaller than the pressure-receiving area B of the right side surface of the large-diameter cylindrical portion 52a. Therefore, the pressure of the pressurized oil pushed out from the second output chamber 5-4 by the piston 52 moving leftward can be increased by up to B / D times.

[0056] The supply destination switching valve 7 is a spring center type three-position four-port electromagnetic switching valve. When the supply destination switching valve 7 is in the neutral position 7-1, the supply destination switching valve 7 closes the pipeline 36.

[0057] The supply destination switching valve 7 has solenoids 7a and 7b, which are electrically connected to a control device (not shown).

[0058] When an electric signal is applied to the left solenoid 7a, the spool of the destination switching valve 7 moves to the right and the destination switching valve 7 switches to the left position 7-2. When the destination switching valve 7 is in the left position 7-2, the supply destination switching valve 7 connects the line 36 to the accumulator 6a and connects the accumulator 6b to the line 32.

[0059] On the other hand, when an electric signal is applied to the right solenoid 7b, the spool of the destination switching valve 7 moves leftward and the valve 7 switches to the right position 7-3. When the destination switching valve 7 is in the right position 7-3, it connects the line 36 to the accumulator 6b and the accumulator 6a to the line 32.

[0060] The accumulators 6a and 6b are so-called gas-type accumulators, each incorporating a bladder filled with nitrogen gas in a highly rigid case. In this embodiment, the accumulator 6a has a gas pressure of 3 MPa filled in the bladder, while the accumulator 6b has a gas pressure of 7 MPa filled in the bladder. Thus, the accumulators 6a and 6b have different oil storage characteristics.

[0061] The accumulators 6 a and 6 b are connected to the supply destination switching valve 7 independently of each other.

[0062] The pressure of the gas charged into the accumulators 6a, 6b is not limited to that of this embodiment, and can be freely changed as long as the pressure of the gas charged is different. Furthermore, the accumulator is not limited to a gas type, and may be a weight type or a spring type accumulator, and the accumulator may have any structure, such as a bladder type or a piston type.

[0063] The regenerative switching valve 9 is a spring offset type two-position two-port hydraulic switching valve. When the regenerative switching valve 9 is in the offset position 9-1, the line 32 is closed.

[0064] When a hydraulic signal is applied to the right side of the regenerative switching valve 9, the spool moves and switches to the onset position 9-2. The solenoid 4a in the onset position 9-2 connects the line 32 to the line 37.

[0065] The pipe 37 is connected to the pipe 25 via a check valve 12. The pipe 25 is also connected to a pressure sensor 10 that detects the oil pressure in the second oil chamber 1-2 of the hydraulic cylinder device 1.

[0066] In such a hydraulic circuit 101, a part of the pressurized oil in the second oil chamber 1-2 of the hydraulic cylinder device 1 is accumulated in the accumulators 6a, 6b when the hydraulic cylinder device 1 is contracted, and the pressurized oil accumulated in the accumulators 6a, 6b can be regenerated when the hydraulic cylinder device 1 is extended.

[0067] Next, the contraction operation of the hydraulic cylinder device 1 will be described.

[0068] During the contraction operation of the hydraulic cylinder device 1, the electromagnetic switching valve 4 is alternately switched between the offset position 4-1 and the onset position 4-2, and the piston 52 of the pressure booster 5 is repeatedly reciprocated to continuously supply pressurized oil to the supply destination switching valve 7. In this embodiment, the pressure boost ratio of the pressure booster 5 is set to 3 times.

[0069] The pressure of the oil supplied to the electromagnetic switching valve 4 is higher when an external force is applied to the workpiece W than when almost no external force is applied to the workpiece W.

[0070] The supply destination switching valve 7 is controlled by a control device (not shown) to switch between a left position 7 - 2 and a right position 7 - 3 based on the oil pressure detected by a pressure sensor 10 .

[0071] Specifically, when the oil pressure detected by the pressure sensor 10 is less than 7 MPa, the control device switches the supply destination switching valve 7 to the left position 7-2, and when the oil pressure detected by the pressure sensor 10 is 7 MPa or higher, the control device switches the supply destination switching valve 7 to the right position 7-3.

[0072] As an example, if the oil pressure detected by the pressure sensor 10 is 3 MPa, the oil is boosted to 9 MPa due to the boost ratio of the booster device 5 and flows into the supply destination switching valve 7. The supply destination switching valve 7 switches to the left position 7-2, so that the oil flows into the accumulator 6a, whose charged gas pressure is 3 MPa. As a result, as shown in Figure 2, a sufficient amount of oil can be accumulated in the accumulator 6a even if the input oil pressure is low.

[0073] Also, if the oil pressure detected by pressure sensor 10 is 7 MPa, the oil is boosted to 21 MPa due to the boost ratio of booster device 5 and flows into supply destination switching valve 7. Supply destination switching valve 7 switches to the right position 7-3, so that oil flows into accumulator 6b, whose charged gas pressure is 7 MPa. As a result, as shown in Figure 2, a sufficient amount of oil can be accumulated in accumulator 6b, and even if the input oil pressure is high, oil will not flow into accumulator 6a, which has a relatively low strength, preventing failure of accumulator 6a.

[0074] Next, the extension operation of the hydraulic cylinder device 1 will be described.

[0075] Returning to FIG. 1, during the extension operation of the hydraulic cylinder device 1, the supply destination switching valve 7 is controlled to switch to either the left position 7-2 or the right position 7-3 by a control device (not shown) based on the oil pressure detected by the pressure sensor 10, in the same manner as described above.

[0076] Furthermore, the regenerative switching valve 9 is switched from the offset position 9-1 to the onset position 9-2, whereby the oil accumulated in either the accumulator 6a or 6b is regenerated into the second oil chamber 1-2 of the hydraulic cylinder device 1 via the pipe 32, the pipe 37, the check valve 12, and the pipe 25.

[0077] As an example, when the oil pressure detected by the pressure sensor 10 is low (for example, less than 7 MPa), that is, when almost no external force is applied to the workpiece W, the supply destination switching valve 7 switches to the left position 7-2, and the oil stored in the accumulator 6a is regenerated into the second oil chamber 1-2 of the hydraulic cylinder device 1.

[0078] Furthermore, when the oil pressure detected by the pressure sensor 10 is high (for example, 7 MPa or higher), that is, when an external force is applied to the workpiece W, the supply destination switching valve 7 switches to the right position 7-3, and the oil stored in the accumulator 6b is regenerated into the second oil chamber 1-2 of the hydraulic cylinder device 1.

[0079] As explained above, accumulators 6a, 6b with different storage characteristics can be selected depending on the oil pressure supplied from supply destination switching valve 7, so oil with a wide range of pressures from 3 MPa to 21 MPa can be effectively stored.

[0080] Furthermore, when accumulating oil over a wide range of pressures in a single accumulator, it is necessary to prepare a special case with a large capacity and strength sufficient to withstand the upper limit pressure of the accumulation. However, the hydraulic circuit 101 of this embodiment is capable of accumulating oil over a wide range of pressures by using general accumulators 6a, 6b with different accumulation characteristics, and therefore the hydraulic circuit 101 can be configured more simply than when accumulating oil over a wide range of pressures in a single accumulator.

[0081] Furthermore, the accumulators 6a and 6b are independently connected to a supply destination switching valve 7, which switches the oil supply destination to either the accumulator 6a or 6b. This prevents oil from moving between the accumulators 6a and 6b, which have different accumulation characteristics. For example, it is possible to prevent high-pressure oil accumulated in the high-pressure accumulator 6b from flowing to the low-pressure accumulator 6a. This allows the oil pressure in the accumulator 6b to be maintained at a high level.

[0082] Furthermore, a pressure sensor 10 is provided, and the supply destination switching valve 7 can be switched in accordance with the oil pressure detected by the pressure sensor 10. Therefore, it is possible to improve the accuracy of control in response to changes in the oil pressure input to the accumulators 6a and 6b.

[0083] In addition, the oil flowing out from the second oil chamber 1-2 of the hydraulic cylinder device 1 is boosted by the booster device 5, which widens the range of oil pressure input to the accumulators 6a and 6b, but the oil can be effectively stored by using the accumulators 6a and 6b, which have different storage characteristics depending on the input oil pressure.

[0084] Furthermore, the regeneration switching valve 9 allows the accumulators 6 a and 6 b to be selected for regeneration depending on the force required for the extension operation of the hydraulic cylinder device 1 .

[0085] In this embodiment, the directional control valve 3, the electromagnetic control valve 4, the supply destination control valve 7, and the regenerative control valve 9 are spool type valves, but they may also be poppet type or slide type valves.

[0086] Next, a fluid pressure circuit according to a second embodiment will be described with reference to Fig. 3. Components that are the same as those shown in the first embodiment will be given the same reference numerals and redundant description will be omitted.

[0087] 3, the hydraulic circuit 201 includes a first selector valve 207 and a second selector valve 208 disposed between the pressure booster 5 and the accumulators 6a and 6b. The first selector valve 207 is disposed closer to the pressure booster 5 than the second selector valve 208.

[0088] The first switching valve 207 is a spring-center type three-position four-port electromagnetic switching valve. The first switching valve 207 is connected to the lines 32, 36, 40, and 41.

[0089] The first switching valve 207 in the neutral position 207-1 closes the lines 32, 36, 40, and 41.

[0090] The first switching valve 207 has solenoids 207a and 207b. When an electric signal is applied to the left solenoid 207a, the first switching valve 207 is excited, and the spool moves to the right, switching the first switching valve 207 to a left position 207-2. When the first switching valve 207 is in the left position 207-2, the first switching valve 207 communicates between the pipes 36 and 40 and closes between the pipes 32 and 41.

[0091] When an electric signal is applied to the right solenoid 207b, the first switching valve 207 is excited, and the spool moves leftward, switching the first switching valve 207 to a right position 207-3. When the first switching valve 207 is in the right position 207-3, the first switching valve 207 communicates between the pipes 32 and 41 and closes between the pipes 36 and 40.

[0092] The second switching valve 208 is a spring-center type three-position four-port electromagnetic switching valve. The second switching valve 208 is connected to the lines 40 and 41 and the accumulators 6a and 6b.

[0093] The second switching valve 208 in the neutral position 208-1 connects the line 40 to the accumulators 6a and 6b, and closes the line 41. In the neutral position 208-1, a check valve 210 is provided in the flow path connecting the line 40 and the accumulator 6b.

[0094] The second switching valve 208 has solenoids 208a and 208b. When an electric signal is applied to the left solenoid 208a of the second switching valve 208, the spool moves to the right and the second switching valve 208 switches to a left position 208-2. When the second switching valve 208 is in the left position 208-2, it connects the pipe 41 to the accumulator 6b and closes the pipe 40 to the accumulator 6a.

[0095] When an electric signal is applied to the right solenoid 208b, the second selector valve 208 is excited, and the spool moves leftward, switching the second selector valve 208 to a right position 208-3. When the second selector valve 208 is in the right position 208-3, it connects the line 41 to the accumulator 6a and closes the line 40 to the accumulator 6b.

[0096] During the contraction operation of the hydraulic cylinder device 1 of the second embodiment, the first selector valve 207 is switched to the left position 207-2, and the second selector valve 208 is switched to the neutral position 208-1. As a result, the oil pressurized by the pressure booster device 5 flows into the accumulators 6a and 6b.

[0097] When the hydraulic pressure input from the pressure intensifier 5 is less than 7 MPa, it is accumulated in the accumulator 6a. Note that the hydraulic pressure input from the pressure intensifier 5 is lower than the pressure of the gas charged in the accumulator 6b, so it is not accumulated in the accumulator 6b. At this time, since the check valve 210 is provided, fluid does not flow from the accumulator 6b to the accumulator 6a, and the accumulator 6b can maintain a high pressure.

[0098] On the other hand, when the oil pressure input from the pressure intensifier 5 is 7 MPa or higher, it is accumulated in both the accumulators 6a and 6b. At this time, the accumulator 6a has a lower charged gas pressure than the accumulator 6b, so the oil input from the pressure intensifier 5 is more likely to accumulate in the accumulator 6a.

[0099] During the extension / retraction operation of the hydraulic cylinder device 1 of this embodiment 2, the first selector valve 207 is switched to the right position 207-3. Furthermore, the second selector valve 208 is switched to the right position 208-3 when the pressure detected by the pressure sensor 10 is low, and is switched to the left position 208-2 when the pressure detected by the pressure sensor 10 is high.

[0100] Therefore, when the hydraulic cylinder device 1 is extending or retracting, if the pressure detected by the pressure sensor 10 is low, the oil stored in the accumulator 6a is regenerated, and if the pressure detected by the pressure sensor 10 is high, the oil stored in the accumulator 6b is regenerated.

[0101] Furthermore, since a check valve 210 is provided in the flow path connecting the conduit 40 and the accumulator 6b when the second switching valve 208 is in the neutral position 208-1, it is possible to prevent accumulated oil from flowing from the accumulator 6b, which has a higher pressure, to the accumulator 6a, which has a lower pressure, when the second switching valve 208 is switched from the right position 208-3 to the neutral position 208-1.

[0102] When the hydraulic cylinder device 1 is not in operation, the first switching valve 207 is switched to the neutral position 207-1, thereby preventing oil from flowing in or out of the accumulators 6a and 6b.

[0103] Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention also includes modifications and additions that do not deviate from the gist of the present invention.

[0104] For example, in the first and second embodiments, two types of accumulators 6a and 6b having different accumulation characteristics are provided, but three or more types of accumulators may be provided. Also, the number of each type of accumulator may be freely changed.

[0105] Furthermore, when a plurality of accumulators of each type are provided, for example, accumulators having the same accumulation characteristics may be connected to each other, i.e., the switching valve may be configured to supply fluid to a plurality of accumulators having the same accumulation characteristics.

[0106] Furthermore, in the first and second embodiments, the pressure sensor 10 is provided between the hydraulic cylinder device 1 and the pressure booster device 5, but the pressure sensor may be provided between the pressure booster device and the switching valve.

[0107] Furthermore, in the first and second embodiments, the driving body is described as the hydraulic cylinder device 1, but the driving body is not limited to the cylinder device and may be, for example, a pump or the like.

[0108] Furthermore, in the first and second embodiments, the pressure is accumulated in the accumulator from the pressure booster, but the pressure may be accumulated directly from a hydraulic cylinder device or a pump without using a pressure booster.

[0109] Furthermore, in the first and second embodiments, the hydraulic circuit has been exemplified as having the hydraulic cylinder device 1 as a driving body, but the present invention is not limited to this. For example, the present invention can be applied to a hydraulic pressure circuit having a hydraulic motor as a driving body, in which a part of the return oil during braking is stored in an accumulator and regenerated when the hydraulic motor is accelerated.

[0110] Furthermore, in Examples 1 and 2, the fluid pressure circuit has been described as a hydraulic circuit in which oil is pumped, but this is not limited to this, and the working fluid may be a fluid other than oil, and the fluid to be applied may be changed as appropriate.

[0111] In addition, in Examples 1 and 2, the case of the booster device is described as having a stepped cylindrical shape made up of a series of cylinders with different radial dimensions, but this is not limited to this, and it is preferable that the case have a shape that allows the area ratio to be changed.

[0112] In addition, in Examples 1 and 2, the pressure booster device is exemplified as a so-called double-acting type that boosts pressure when the piston moves to both sides in the axial direction, but this is not limited to this, and it may be a so-called single-acting type that boosts pressure only when the piston moves to one side in the axial direction.

[0113] REFERENCE SIGNS LIST 1 Hydraulic cylinder device (actuator, driver) 2 Hydraulic pump 3 Electromagnetic directional control valve 4 Electromagnetic control valve 5 Pressure booster 6a, 6b Accumulator 7 Supply destination control valve (control valve) 8 Tank 9 Regenerative control valve 10 Pressure sensor 11-16 Check valves 21-41 Pipes 101, 201 Hydraulic circuit (fluid pressure circuit) 207 First control valve 208 Second control valve A-D Pressure receiving area

Claims

1. A fluid pressure circuit comprising a driver and a plurality of accumulators that accumulate fluid in response to fluid pressure supplied from the driver side, wherein the plurality of accumulators have different accumulation characteristics.

2. The fluid pressure circuit according to claim 1, further comprising a switching valve for switching the destination of the fluid supply to at least one of said accumulators.

3. The fluid pressure circuit according to claim 2, wherein the switching valve switches the supply destination to one of the accumulators.

4. The fluid pressure circuit according to claim 3, further comprising a pressure sensor for detecting the pressure of the fluid provided between said driver and said accumulator.

5. The fluid pressure circuit according to claim 1, wherein said driver is an extendable hydraulic cylinder device.

6. The fluid pressure circuit according to claim 1, further comprising a pressure booster provided between said driver and said accumulator.

7. A fluid pressure circuit according to any one of claims 1 to 6, further comprising a regenerative switching valve for selectively regenerating the fluid stored in said plurality of accumulators.

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