{TECHNICAL FIELD}
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The present invention relates to a fluid pressure circuit, and more particularly, to a fluid pressure circuit that includes an accumulator for accumulating working fluid.
{BACKGROUND ART}
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A fluid pressure circuit that utilizes working fluid, such as hydraulic oil, sent out from a fluid supply device, such as a pump, to drive an actuator is known in various fields. In such a fluid pressure circuit, for example, oil discharged from a hydraulic cylinder device as an actuator is accumulated in an accumulator in accordance with the contraction operation of the hydraulic cylinder device and is regenerated during the extension operation of the hydraulic cylinder device.
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For example, a fluid pressure circuit that increases the pressure of working fluid discharged from a hydraulic cylinder device with a booster and accumulates the working fluid in an accumulator is known (see Patent Citation 1). A fluid pressure circuit illustrated in FIG. 4, which is an example of such a fluid pressure circuit, mainly includes a hydraulic pump 501, a directional control valve 502, a hydraulic cylinder device 503, an electromagnetic switching valve 504, a booster 505, an accumulator 506, and a tank 507.
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The directional control valve 502 is a spring-centered six-port/three-position type switching valve. In a case where the directional control valve 502 is in a neutral position 502-1, oil discharged from the hydraulic pump 501 is discharged to the tank 507.
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Further, in a case where the directional control valve 502 is in a left position 502-2, oil discharged from the hydraulic pump 501 is supplied to a first oil chamber 503-1 of the hydraulic cylinder device 503, a part of oil present in a second oil chamber 503-2 of the hydraulic cylinder device 503 is discharged to the tank 507 through an orifice 517, and the other part of the oil flows to the electromagnetic switching valve 504. Accordingly, a workpiece W is moved down.
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In a case where the directional control valve 502 is in a right position 502-3, a part of oil discharged from the hydraulic pump 501 is supplied to the second oil chamber 503-2 of the hydraulic cylinder device 503 and oil present in the first oil chamber 503-1 of the hydraulic cylinder device 503 is discharged to the tank 507. Accordingly, the workpiece W is moved up.
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The electromagnetic switching valve 504 is a four-port/two-position type electromagnetic switching valve.
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The booster 505 includes a case 508 and a piston 509. The case 508 includes a large-diameter tubular portion 508a, a small-diameter tubular portion 508b, and a partition wall portion 508c. The partition wall portion 508c has an annular shape, and partitions the large-diameter tubular portion 508a and the small-diameter tubular portion 508b. The piston 509 includes a large-diameter portion 509a, a small-diameter portion 509b, and a shaft portion 509c, and is enclosed in the case 508 to be slidable in an axial direction.
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The electromagnetic switching valve 504 is located at a first position 504-1 in a demagnetized state, oil supplied from the hydraulic cylinder device 503 is introduced into an oil chamber 505-1 of the booster 505, and oil present in an oil chamber 505-2 is discharged to the tank 507. Accordingly, the piston 509 is moved to a right side, and oil present in the oil chamber 505-3 is extruded and flows into the accumulator 506 through a check valve 510. At the same time, negative pressure is generated in an oil chamber 505-4 of the booster 505, so that oil present in the tank 507 is sucked into the oil chamber 505-4 through the check valve 511.
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On the other hand, in a case where the electromagnetic switching valve 504 is switched to a second position 504-2, oil supplied from the hydraulic cylinder device 503 is introduced into the oil chamber 505-2 of the booster 505 and oil present in the oil chamber 505-1 is discharged to the tank 507. Accordingly, the piston 509 is moved to a left side, and oil present in the oil chamber 505-4 is extruded and flows into the accumulator 506 through a check valve 512. At the same time, negative pressure is generated in the oil chamber 505-3 of the booster 505, so that oil present in the tank 507 is sucked into the oil chamber 505-3 through a check valve 513.
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In a case where the area of a left surface of the large-diameter portion 509a of the piston 509 is denoted by A, the area of a right surface of the large-diameter portion 509a is denoted by B, the area of a right surface of the small-diameter portion 509b is denoted by C, and the area of a left surface of the small-diameter portion 509b is denoted by D, the pressure of oil extruded from the inside of the oil chamber 505-3 in a demagnetized state of the electromagnetic switching valve 504 according to Pascal's principle is increased up to a maximum of A/C times and the oil flows into the accumulator 506. Further, the pressure of oil extruded from the inside of the oil chamber 505-4 in an excited state of the electromagnetic switching valve 504 is increased up to a maximum of B/D times and the oil flows into the accumulator 506. Accordingly, oil of which the pressure is increased by the booster 505 as the excitation and demagnetization of the electromagnetic switching valve 504 are repeated continuously flows into the accumulator 506.
{CITATION LIST}
{Patent Literature}
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Patent Citation 1:
JP 2017-15130 A (Page 7,
FIG. 2)
{SUMMARY OF INVENTION}
{Technical Problem}
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In the fluid pressure circuit illustrated in FIG. 4, a pressure in the second oil chamber 503-2 of the hydraulic cylinder device 503, that is, a pressure input to the booster 505 may vary significantly depending on use conditions of the hydraulic cylinder device 503, for example, whether or not a load acts on the workpiece W.
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For example, when a boost ratio of the booster 505 is set to 3 times and a filler gas pressure of the accumulator 506 is set to 7 MPa in a case where a load acting on the workpiece W is large and a pressure input to the booster 505 is high at 7 MPa, an output pressure is increased up to 21 MPa according to the boost ratio of the booster 505 as illustrated in FIG. 5. Accordingly, a large amount of oil accumulated in the accumulator 506 can be ensured.
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On the other hand, in a case where a load acting on the workpiece W is small and a pressure input to the booster 505 is low at 3 MPa, an output pressure is increased only up to 9 MPa according to the boost ratio of the booster 505 as illustrated in FIG. 6. For this reason, there is a concern that the amount of oil accumulated in the accumulator 506 is reduced.
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The present invention has been made in view of such problems, and an object of the present invention is to provide a fluid pressure circuit that can accumulate fluid having a pressure in a wide range.
{Solution to Problem}
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In order to solve the problems, a fluid pressure circuit according to the present invention includes: a driver; and a plurality of accumulators configured to accumulate fluid according to a fluid pressure supplied from the driver, wherein the plurality of accumulators have different accumulation characteristics. According to the aforesaid feature of the present invention, since the plurality of accumulators having different accumulation characteristics can be utilized according to a pressure, a fluid pressure in a wide range can be accumulated.
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It may be preferable that the fluid pressure circuit further includes a switching valve configured to switch a supply destination of the fluid to at least one of the accumulators. According to this preferable configuration, since a supply destination of the fluid can be selected by the switching valve, the fluid can be preferentially accumulated in any accumulator.
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It may be preferable that the switching valve switches the supply destination to one of the accumulators. According to this preferable configuration, since the switching valve supplies the fluid to one accumulator, the fluid is prevented from moving between the accumulators having different accumulation characteristics. For this reason, the fluid accumulated in the accumulator of which the pressure is high can be prevented from flowing to the accumulator of which the pressure is low.
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It may be preferable that a pressure sensor configured to detect the pressure of the fluid is provided between the driver and the accumulators. According to this preferable configuration, the switching valve can be switched according to the pressure of the fluid detected by the pressure sensor. For this reason, the accuracy of control of the fluid pressure circuit with respect to a change in situations can be improved.
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It may be preferable that the driver is a hydraulic cylinder device configured for extending and contracting. According to this preferable configuration, even though the pressure of return oil of the hydraulic cylinder device fluctuates, the plurality of accumulators having different accumulation characteristics can be utilized to accumulate the oil.
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It may be preferable that a booster is provided between the driver and the accumulators. According to this preferable configuration, the high pressure of the fluid that is increased by the booster can be accumulated.
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It may be preferable that the fluid pressure circuit further include a regenerative switching valve configured to selectively regenerate the fluid accumulated in the plurality of accumulators. According to this preferable configuration, the accumulator that accumulates fluid having an optimum pressure can be selected by the regenerative switching valve and used for regeneration.
{BRIEF DESCRIPTION OF DRAWINGS}
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- FIG. 1 is a schematic diagram illustrating a fluid pressure circuit according to a first embodiment of the present invention.
- FIG. 2 is a diagram illustrating a relationship between the output pressure of a booster and the amount of oil accumulated in an accumulator in the first embodiment.
- FIG. 3 is a schematic diagram illustrating a fluid pressure circuit according to a second embodiment of the present invention.
- FIG. 4 is a schematic diagram illustrating a fluid pressure circuit in a conventional art.
- FIG. 5 is a diagram illustrating a relationship between the output pressure of a booster in a case where the input pressure of a booster is high and the amount of oil accumulated in an accumulator in the conventional art.
- FIG. 6 is a diagram illustrating a relationship between the output pressure of a booster in a case where the input pressure of the booster is low and the amount of oil accumulated in the accumulator in the conventional art.
{DESCRIPTION OF EMBODIMENTS}
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Modes for carrying out a fluid pressure circuit according to the present invention will be described below on the basis of embodiments.
{First embodiment}
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A fluid pressure circuit according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. Right and left sides as viewed from the front of FIG. 1 will be described as valve positions of a directional control valve or the right and left sides of a booster.
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A hydraulic circuit as the fluid pressure circuit according to the first embodiment is to utilize working fluid discharged from a hydraulic cylinder device of a working machine, a construction machine, a cargo handling/transport vehicle, an automobile, or the like to accumulate working fluid, of which the pressure is increased by a booster, in an accumulator and to cause the hydraulic cylinder device to regenerate the working fluid.
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As illustrated in FIG. 1, a hydraulic circuit 101 mainly includes a hydraulic cylinder device 1 that is an actuator as a driver, a hydraulic pump 2, a directional control valve 3, an electromagnetic switching valve 4, a booster 5, accumulators 6a and 6b, a supply destination switching valve 7 as a switching valve, a tank 8, a regenerative switching valve 9, a pressure sensor 10, check valves 11 to 16, and pipelines 21 to 36.
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The hydraulic pump 2 supplies pressure oil. The pressure oil sent out 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.
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Meanwhile, the hydraulic pump 2 of the present embodiment may be a fixed displacement hydraulic pump or a variable displacement hydraulic pump.
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The directional control valve 3 is a spring-centered three-position/six-port hydraulic switching valve. The directional control valve 3, which is in a neutral position 3-1, connects the pipeline 21 to the pipeline 23. The pipeline 23 is connected to the tank 8. For this reason, the total amount of the pressure oil sent out from the hydraulic pump 2 is discharged to the tank 8.
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In a case where a hydraulic signal is applied to the left side of the directional control valve 3, a spool is moved to a right side and the directional control valve 3 is switched to a left position 3-2. The directional control valve 3, which is in the left position 3-2, connects the pipeline 22 to the pipeline 24 and connects the pipeline 25 to the pipeline 27.
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For this reason, the pressure oil sent out from the hydraulic pump 2 flows into a first oil chamber 1-1 of the hydraulic cylinder device 1, pressure oil present in a second oil chamber 1-2 of the hydraulic cylinder device 1 is discharged to the tank 8 through an orifice 17, and a part of the pressure oil flows into the electromagnetic switching valve 4 through a pipeline 28 branching off from the pipeline 25. Accordingly, the hydraulic cylinder device 1 contracts, so that a workpiece W is moved down.
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On the other hand, in a case where a hydraulic signal is applied to the right side of the directional control valve 3, the spool is moved to a left side and the directional control valve 3 is switched to a right position 3-3. The directional control valve 3, which is in the right position 3-3, connects the pipeline 22 to the pipeline 25 and connects the pipeline 24 to the pipeline 27.
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For this reason, the pressure oil sent out from the hydraulic pump 2 flows into the second oil chamber 1-2 of the hydraulic cylinder device 1, and the pressure oil present in the first oil chamber 1-1 of the hydraulic cylinder device 1 is discharged to the tank 8. Accordingly, the hydraulic cylinder device 1 extends, so that the workpiece W is moved up.
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The electromagnetic switching valve 4 is a spring-offset two-position/four-port electromagnetic switching valve. The electromagnetic switching valve 4, which is in an offset position 4-1, connects the pipeline 28 to the pipeline 29 and connects the pipeline 30 to the pipeline 26.
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In a case where an electrical signal is applied to a solenoid 4a and the solenoid 4a is excited, a spool is moved and the electromagnetic switching valve 4 is switched to an onset position 4-2. The electromagnetic switching valve 4, which is in the onset position 4-2, connects the pipeline 28 to the pipeline 30 and connects the pipeline 29 to the pipeline 26.
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The booster 5 mainly includes a case 51 and a piston 52.
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The case 51 is formed in a stepped cylindrical shape including a large-diameter cylindrical portion 51a, a small-diameter cylindrical portion 51b, a partition wall portion 51c, and disk portions 51d and 51e.
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The large-diameter cylindrical portion 51a and the small-diameter cylindrical portion 51b are partitioned by the annular partition wall portion 51c. A left end of the large-diameter cylindrical portion 51a is closed by the disk portion 51d, and a right end of the small-diameter cylindrical portion 51b is closed by the disk portion 51e.
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The piston 52 includes a large-diameter columnar portion 52a, a small-diameter columnar portion 52b, and a connecting shaft portion 52c, and axial centers thereof are arranged substantially on the same straight line.
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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 can slide along the inner peripheral surface of the large-diameter cylindrical portion 51a.
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The small-diameter columnar portion 52b has a diameter slightly smaller than the inner diameter of the small-diameter cylindrical portion 51b of the case 51. The small-diameter columnar portion 52b can slide along the inner peripheral surface of the small-diameter cylindrical portion 51b.
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The connecting shaft portion 52c has a diameter slightly smaller than the inner diameter of the partition wall portion 51c of the case 51. The connecting shaft portion 52c can slide along the inner peripheral surface of the partition wall portion 51c of the case 51.
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The 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.
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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 pipeline 29 is connected to the first input chamber 5-1.
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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 pipeline 30 is connected to the second input chamber 5-2.
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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 pipelines 31 and 35 are connected to the first output chamber 5-3.
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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 pipelines 33 and 34 are connected to the second output chamber 5-4.
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In a case where the electromagnetic switching valve 4 is in a demagnetized state, that is, is in the offset position 4-1, pressure oil flowing through the pipeline 28 flows into the first input chamber 5-1 of the booster 5 through the pipeline 29 and pressure oil present in the second input chamber 5-2 of the booster 5 is discharged to the tank 8 through the pipelines 30 and 26.
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Accordingly, the piston 52 is moved to the right side, and pressure oil present in the first output chamber 5-3 flows into the supply destination switching valve 7 through the pipeline 31, the check valve 13, and the pipeline 36. At the same time, negative pressure is generated in the second output chamber 5-4, so that oil present in the tank 8 is sucked into the second output chamber 5-4 through the check valve 14 and the pipeline 33.
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A pressure-receiving area C of a right surface of the small-diameter columnar portion 52b of the piston 52 is smaller than a pressure-receiving area A of a left surface of the large-diameter columnar portion 52a. For this reason, the pressure of pressure oil, which is extruded from the inside of the first output chamber 5-3 as the piston 52 is moved to the right side, can be increased up to A/C times.
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In a case where the electromagnetic switching valve 4 is in an excited state, that is, is in the onset position 4-2, pressure oil flowing through the pipeline 28 flows into the second input chamber 5-2 of the booster 5 through the pipeline 30 and pressure oil present in the first input chamber 5-1 of the booster 5 is discharged to the tank 8 through the pipelines 29 and 26.
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Accordingly, the piston 52 is moved to the left side, and pressure oil present in the second output chamber 5-4 flows into the supply destination switching valve 7 through the pipeline 34, the check valve 15, and the pipeline 36. At the same time, negative pressure is generated in the first output chamber 5-3, so that oil present in the tank 8 is sucked into the first output chamber 5-3 through the check valve 16 and the pipeline 35.
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A pressure-receiving area D of a left surface of the small-diameter columnar portion 52b of the piston 52 is smaller than a pressure-receiving area B of a right surface of the large-diameter columnar portion 52a. For this reason, the pressure of pressure oil, which is extruded from the inside of the second output chamber 5-4 as the piston 52 is moved to the left side, can be increased up to B/D times.
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The supply destination switching valve 7 is a spring-centered three-position/four-port electromagnetic switching valve. The supply destination switching valve 7, which is in a neutral position 7-1, closes the pipeline 36.
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The supply destination switching valve 7 includes solenoids 7a and 7b. The solenoids 7a and 7b are electrically connected to a control device (not illustrated).
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In a case where an electrical signal is applied to the left solenoid 7a and the solenoid 7a is excited, a spool is moved to the right side and the supply destination switching valve 7 is switched to a left position 7-2. The supply destination switching valve 7, which is in the left position 7-2, connects the pipeline 36 to the accumulator 6a and connects the accumulator 6b to the pipeline 32.
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On the other hand, in a case where an electrical signal is applied to the right solenoid 7b and the solenoid 7b is excited, the spool is moved to the left side and the supply destination switching valve 7 is switched to a right position 7-3. The supply destination switching valve 7, which is in the right position 7-3, connects the pipeline 36 to the accumulator 6b and connects the accumulator 6a to the pipeline 32.
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Each of the accumulators 6a and 6b is a so-called gas type accumulator in which a bladder filled with nitrogen gas is built in a case having high stiffness. A filler gas pressure in the bladder of the accumulator 6a of the present embodiment is set to 3 MPa, and a filler gas pressure of the accumulator 6b is set to 7 MPa. As described above, the accumulation characteristics of the accumulators 6a and 6b in which oil can be accumulated are different from each other.
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The accumulators 6a and 6b are independently connected to the supply destination switching valve 7.
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Meanwhile, the filler gas pressures of the accumulators 6a and 6b are not limited to the present embodiment, and can be freely changed in a case where other filler gas pressures are to be applied. Further, the accumulator may be a weight type accumulator, a spring type accumulator, and the like without being limited to a gas type accumulator, and the structure of the accumulator may be any structure, such as a bladder type structure or a piston type structure.
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The regenerative switching valve 9 is a spring-offset two-position/two-port hydraulic switching valve. The regenerative switching valve 9, which is in an offset position 9-1, closes the pipeline 32.
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In a case where a hydraulic signal is applied to the right side of the regenerative switching valve 9, a spool is moved and the regenerative switching valve 9 is switched to an onset position 9-2. The regenerative switching valve 9, which is in the onset position 9-2, connects the pipeline 32 to the pipeline 37.
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The pipeline 37 is connected to the pipeline 25 through the check valve 12. Further, the pressure sensor 10 that detects oil pressure in the second oil chamber 1-2 of the hydraulic cylinder device 1 is connected to the pipeline 25.
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In such a hydraulic circuit 101, a part of the pressure oil present in the second oil chamber 1-2 of the hydraulic cylinder device 1 can be accumulated in the accumulators 6a and 6b during the contraction operation of the hydraulic cylinder device 1 and the pressure oil accumulated in the accumulators 6a and 6b can be regenerated during the extension operation of the hydraulic cylinder device 1.
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Next, the contraction operation of the hydraulic cylinder device 1 will be described.
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During the contraction operation of the hydraulic cylinder device 1, the electromagnetic switching valve 4 is alternately switched to the offset position 4-1 and the onset position 4-2 and oil, of which the pressure is increased as the piston 52 of the booster 5 repeatedly reciprocates, continues to be supplied to the supply destination switching valve 7. Meanwhile, a boost ratio of the booster 5 is set to three times in the present embodiment.
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The pressure of the oil supplied to the electromagnetic switching valve 4 in a state where an external force is applied to the workpiece W is higher than that in a state where an external force is hardly applied to the workpiece W.
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The supply destination switching valve 7 is controlled to switch to either the left position 7-2 or the right position 7-3 by the control device (not illustrated) on the basis of the oil pressure detected by the pressure sensor 10.
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Specifically, the control device switches the supply destination switching valve 7 to the left position 7-2 in a case where the oil pressure detected by the pressure sensor 10 is less than 7 MPa, and switches the supply destination switching valve 7 to the right position 7-3 in a case where the oil pressure detected by the pressure sensor 10 is 7 MPa or more.
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For example, in a case where the oil pressure detected by the pressure sensor 10 is 3 MPa, the pressure of the oil is increased up to 9 MPa according to the boost ratio of the booster 5 and the oil flows into the supply destination switching valve 7. Since the supply destination switching valve 7 is switched to the left position 7-2, the oil flows into the accumulator 6a of which the filler gas pressure is 3 MPa. Accordingly, as illustrated in FIG. 2, a sufficient amount of oil can be accumulated in the accumulator 6a even though oil pressure to be input is low.
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Further, in a case where the oil pressure detected by the pressure sensor 10 is 7 MPa, the pressure of the oil is increased up to 21 MPa according to the boost ratio of the booster 5 and the oil flows into the supply destination switching valve 7. Since the supply destination switching valve 7 is switched to the right position 7-3, the oil flows into the accumulator 6b of which the filler gas pressure is 7 MPa. Accordingly, a sufficient amount of oil can be accumulated in the accumulator 6b as illustrated in FIG. 2, and the breakdown of the accumulator 6a can be prevented since the oil does not flow into the accumulator 6a having relatively low strength even though oil pressure to be input is high.
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Next, the extension operation of the hydraulic cylinder device 1 will be described.
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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 the control device (not illustrated) on the basis of the oil pressure detected by the pressure sensor 10 in the same manner as described above.
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Further, the regenerative switching valve 9 is switched to the onset position 9-2 from the offset position 9-1. Accordingly, the oil accumulated in any one of the accumulators 6a and 6b is regenerated to the second oil chamber 1-2 of the hydraulic cylinder device 1 through the pipeline 32, the pipeline 37, the check valve 12, and the pipeline 25.
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For example, in a case where the oil pressure detected by the pressure sensor 10 is low (for example, less than 7 MPa), that is, in a case where an external force is hardly applied to the workpiece W, the supply destination switching valve 7 is switched to the left position 7-2 and the oil accumulated in the accumulator 6a is regenerated to the second oil chamber 1-2 of the hydraulic cylinder device 1.
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Further, in a case where the oil pressure detected by the pressure sensor 10 is high (for example, 7 MPa or more), that is, in a case where an external force is applied to the workpiece W, the supply destination switching valve 7 is switched to the right position 7-3 and the oil accumulated in the accumulator 6b is regenerated to the second oil chamber 1-2 of the hydraulic cylinder device 1.
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Since the accumulators 6a and 6b having different accumulation characteristics can be selected according to oil pressure supplied from the supply destination switching valve 7 as described above, oil having a pressure in a wide range of 3 MPa to 21 MPa can be effectively accumulated.
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Further, in a case where oil having a pressure in a wide range is accumulated by one accumulator, it is necessary to prepare a special case that has strength to withstand an upper limit of strength for accumulation and a large capacity. However, since the hydraulic circuit 101 according to the present embodiment can utilize general accumulators 6a and 6b having different accumulation characteristics to accumulate oil having a pressure in a wide range, the hydraulic circuit 101 can be formed simply as compared to a case where oil having a pressure in a wide range is accumulated by one accumulator.
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Further, the accumulators 6a and 6b are independently connected to the supply destination switching valve 7, and the supply destination switching valve 7 switches a supply destination of oil to any one of the accumulators 6a and 6b. Accordingly, the movement of oil between the accumulators 6a and 6b having different accumulation characteristics is prevented. For example, high-pressure oil accumulated in the accumulator 6b of which the pressure is high can be prevented from flowing to the accumulator 6a of which the pressure is low. For this reason, oil pressure in the accumulator 6b can be maintained high.
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Furthermore, since the pressure sensor 10 is provided, the supply destination switching valve 7 can be switched according to the oil pressure detected by the pressure sensor 10. For this reason, the accuracy of control with respect to a change in oil pressure input to the accumulators 6a and 6b can be improved.
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In addition, since the pressure of oil flowing out of the second oil chamber 1-2 of the hydraulic cylinder device 1 is increased by the booster 5, the range of oil pressure to be input to the accumulators 6a and 6b is wide. However, the accumulators 6a and 6b having different accumulation characteristics can be utilized according to the oil pressure to be input to effectively accumulate oil.
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Further, the accumulators 6a and 6b can be selected to regenerate oil by the regenerative switching valve 9 according to a force required for the extension operation of the hydraulic cylinder device 1.
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Meanwhile, the aspect in which the directional control valve 3, the electromagnetic switching valve 4, the supply destination switching valve 7, and the regenerative switching valve 9 are spool type valves has been exemplified in the present embodiment, but these valves may be poppet type valves, slide type valves, or the like.
{Second embodiment}
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Next, a fluid pressure circuit according to a second embodiment of the present invention will be described with reference to FIG. 3. Meanwhile, the same components as the components described in the first embodiment will be denoted by the same reference numeral, and the repeated description thereof will be omitted.
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As illustrated in FIG. 3, a first switching valve 207 and a second switching valve 208 are disposed between a booster 5 and accumulators 6a and 6b in a hydraulic circuit 201. The first switching valve 207 is disposed closer to the booster 5 than the second switching valve 208.
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The first switching valve 207 is a spring-centered three-position/four-port electromagnetic switching valve. Pipelines 32, 36, 40, and 41 are connected to the first switching valve 207.
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The first switching valve 207, which is in a neutral position 207-1, closes the pipelines 32, 36, 40, and 41.
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The first switching valve 207 includes solenoids 207a and 207b. In a case where an electrical signal is applied to the left solenoid 207a and the solenoid 207a is excited, a spool is moved to the right side and the first switching valve 207 is switched to a left position 207-2. The first switching valve 207, which is in the left position 207-2, causes the pipelines 36 and 40 to communicate with each other and closes the pipelines 32 and 41.
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In a case where an electrical signal is applied to the right solenoid 207b and the solenoid 207b is excited, the spool is moved to the left side and the first switching valve 207 is switched to a right position 207-3. The first switching valve 207, which is in the right position 207-3, causes the pipelines 32 and 41 to communicate with each other and closes the pipelines 36 and 40.
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The second switching valve 208 is a spring-centered three-position/four-port electromagnetic switching valve. The pipelines 40 and 41 and the accumulators 6a and 6b are connected to the second switching valve 208.
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The second switching valve 208, which is in a neutral position 208-1, causes the pipeline 40 to communicate with each of the accumulators 6a and 6b and closes the pipeline 41. A flow passage connecting the pipeline 40 and the accumulator 6b at the neutral position 208-1 is provided with a check valve 210.
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The second switching valve 208 includes solenoids 208a and 208b. In a case where an electrical signal is applied to the left solenoid 208a and the solenoid 208a is excited, a spool is moved to the right side and the second switching valve 208 is switched to a left position 208-2. The second switching valve 208, which is in the left position 208-2, connects the pipeline 41 and the accumulator 6b and closes the pipeline 40 and the accumulator 6a.
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In a case where an electrical signal is applied to the right solenoid 208b and the solenoid 208b is excited, the spool is moved to the left side and the second switching valve 208 is switched to a right position 208-3. The second switching valve 208, which is in the right position 208-3, connects the pipeline 41 and the accumulator 6a and closes the pipeline 40 and the accumulator 6b.
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During the contraction operation of the hydraulic cylinder device 1 of the second embodiment, the first switching valve 207 is switched to the left position 207-2 and the second switching valve 208 is switched to the neutral position 208-1. Accordingly, oil of which the pressure is increased by the booster 5 flows into the accumulators 6a and 6b.
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In a case where oil pressure input from the booster 5 is less than 7 MPa, the oil is accumulated in the accumulator 6a. Meanwhile, since oil pressure input from the booster 5 is lower than the filler gas pressure of the accumulator 6b, the oil is not accumulated in the accumulator 6b. In this case, since the check valve 210 is provided, fluid does not flow to the accumulator 6a from the accumulator 6b and the accumulator 6b can maintain a high pressure.
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On the other hand, in a case where oil pressure input from the booster 5 is 7MPa or more, the oil is accumulated in both the accumulators 6a and 6b. In this case, since the filler gas pressure of the accumulator 6a is lower than the filler gas pressure of the accumulator 6b, oil input from the booster 5 is likely to be accumulated in the accumulator 6a.
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During the extension operation of the hydraulic cylinder device 1 of the second embodiment, the first switching valve 207 is switched to the right position 207-3. Further, the second switching valve 208 is switched to the right position 208-3 in a case where the pressure detected by the pressure sensor 10 is low, and is switched to the left position 208-2 in a case where the pressure detected by the pressure sensor 10 is high.
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Accordingly, during the extension operation of the hydraulic cylinder device 1, the oil accumulated in the accumulator 6a is regenerated in a case where the pressure detected by the pressure sensor 10 is low, and the oil accumulated in the accumulator 6b is regenerated in a case where the pressure detected by the pressure sensor 10 is high.
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Further, since the flow passage connecting the pipeline 40 and the accumulator 6b at the neutral position 208-1 of the second switching valve 208 is provided with the check valve 210, the accumulated oil can be prevented from flowing to the accumulator 6a of which the pressure is low from the accumulator 6b of which the pressure is high in a case where the second switching valve 208 is switched to the neutral position 208-1 from the right position 208-3.
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Meanwhile, the first switching valve 207 is switched to the neutral position 207-1 during the non-operation of the hydraulic cylinder device 1. Accordingly, oil can be prevented from flowing into and out of the accumulators 6a and 6b.
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The embodiments of the present invention have been described above with reference to the drawings, but the specific configuration of the present invention is not limited to these embodiments and modifications and additions without departing from the scope of the present invention are also included in the present invention.
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For example, the aspects in which two types of accumulators 6a and 6b having different accumulation characteristics are provided have been exemplified in the first and second embodiments, but three or more types of accumulators may be provided. Further, the number of various accumulators may be freely changed.
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Furthermore, in a case where a plurality of accumulators of each type are provided, for example, the accumulators having the same accumulation characteristics may be connected to each other. That is, the switching valve may supply fluid to the plurality of accumulators having the same accumulation characteristics.
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Moreover, the aspects in which the pressure sensor 10 is provided between the hydraulic cylinder device 1 and the booster 5 have been exemplified in the first and second embodiments, but the pressure sensor may be provided between the booster and the switching valve.
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Further, the driver has been described as the hydraulic cylinder device 1 in the first and second embodiments. However, the driver is not limited to the cylinder device and may be, for example, a pump or the like.
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Furthermore, examples in which oil is accumulated in the accumulator from the booster has been described in the first and second embodiments, but oil may be directly accumulated from a hydraulic cylinder device or a pump without the use of the booster.
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Moreover, the hydraulic circuit including the hydraulic cylinder device 1 as the driver has been exemplified in the first and second embodiments, but the present invention is not limited thereto. For example, the present invention can also be applied to a hydraulic circuit that includes a hydraulic motor as a driver and accumulates a part of return oil during braking in an accumulator and regenerates the return oil during the acceleration of the hydraulic motor, and the like.
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Further, the fluid pressure circuit has been described as a hydraulic circuit in which oil is pumped in the first and second embodiments, but is not limited thereto. The working fluid may be fluid other than oil, and fluid to be applied may be changed as appropriate.
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Furthermore, the case of the booster has been described as a stepped cylindrical case in which cylinders having different radial dimensions are connected to each other in the first and second embodiments, but is not limited thereto. It is preferable that the case has a shape in which an area ratio can be changed.
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Moreover, the aspects in which the booster is a so-called double-acting type booster that increases pressure in a case where a piston is moved to both sides in an axial direction have been exemplified in the first and second embodiments, but the present invention is not limited thereto. The booster may be a single-acting type booster that increases pressure only in a case where a piston is moved to one side in an axial direction.
{REFERENCE SIGNS LIST}
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- 1 Hydraulic cylinder device (actuator, driver)
- 2 Hydraulic pump
- 3 Electromagnetic directional control valve
- 4 Electromagnetic switching valve
- 5 Booster
- 6a, 6b Accumulator
- 7 Supply destination switching valve (switching valve)
- 8 Tank
- 9 Regenerative switching valve
- 10 Pressure sensor
- 11 to 16 Check valve
- 21 to 41 Pipeline
- 101, 201 Hydraulic circuit (fluid pressure circuit)
- 207 First switching valve
- 208 Second switching valve
- A to D Pressure-receiving area