JP5688316B2 - Electric fluid pressure actuator - Google Patents

Description

  The present invention relates to an electric fluid pressure actuator that is operated by a working fluid from a fluid pressure pump driven by an electric motor.

  2. Description of the Related Art Conventionally, an electric fluid pressure actuator is used in which a fluid pressure pump is driven by an electric motor and a rod of a fluid pressure cylinder is advanced and retracted by a working fluid supplied from the fluid pressure pump. Patent Document 1 discloses a hydraulic drive unit in which a hydraulic pump driven by an electric motor and a tank for storing hydraulic oil are arranged in parallel with a hydraulic cylinder. In this hydraulic drive unit, the rod of the hydraulic cylinder is advanced and retracted by switching between forward and reverse rotation of the electric motor.

JP 2006-132683 A

  However, in the hydraulic drive unit as in Patent Document 1, in order to improve the output of the hydraulic cylinder, it is necessary to increase the operating pressure using a large-capacity hydraulic pump or an electric motor. For this reason, there is a possibility that the apparatus becomes larger and the power consumption increases.

  The present invention has been made in view of the above problems, and an object thereof is to provide an electric fluid pressure actuator that can improve the output of a fluid pressure cylinder without using a large capacity fluid pressure cylinder or an electric motor. And

  The present invention includes a fluid pressure pump capable of discharging a working fluid in both directions, an electric motor that drives the fluid pressure pump, a fluid pressure cylinder having a rod that moves forward and backward with the working fluid discharged from the fluid pressure pump, An electric fluid pressure actuator comprising: an accumulator capable of accumulating a part of the working fluid discharged from the fluid pressure pump, wherein the fluid pressure cylinder includes a first piston to which the rod is connected; The first piston defines a piston-side fluid chamber and a rod-side fluid chamber into which the first piston is slidably inserted and the working fluid discharged in both directions from the fluid pressure pump is guided. The first cylinder portion, the second piston connected to the first cylinder portion, the second piston is slidably inserted, and the rod is inserted into the second piston. A back pressure chamber that imparts thrust in a direction to exit, and a second cylinder portion defined on a back surface of the second piston, and the working fluid is guided from the fluid pressure pump to the piston-side fluid chamber. In this case, the working fluid accumulated in the accumulator is guided to the back pressure chamber based on the discharge pressure of the fluid pressure pump.

  In the present invention, the working fluid discharged from the fluid pressure pump is guided to the piston-side fluid chamber to retreat the rod, and at the same time, based on the pressure of the working fluid guided from the fluid pressure pump to the piston-side fluid chamber, The second piston connected to one cylinder is slid in the direction in which the rod is retracted by the thrust of the back pressure chamber to which the working fluid is guided from the accumulator. Therefore, the rod withdrawal operation by the working fluid from the fluid pressure pump is assisted by the working fluid from the accumulator. Therefore, the output of the fluid pressure cylinder can be improved without using a large capacity cylinder or an electric motor.

It is a circuit diagram of the electric fluid pressure actuator concerning an embodiment of the invention. It is a circuit diagram of an electric fluid pressure actuator when a fluid pressure pump rotates in one direction and a fluid pressure cylinder extends. It is a circuit diagram of an electric fluid pressure actuator when the fluid pressure pump rotates in the other direction and the fluid pressure cylinder contracts.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the configuration of an electrohydraulic actuator 100 as an electrohydraulic actuator according to an embodiment of the present invention will be described with reference to FIG. The electric hydraulic actuator 100 uses hydraulic pressure as the fluid pressure.

  The electric hydraulic actuator 100 includes a hydraulic pump 1 as a fluid pressure pump that can discharge hydraulic oil in both directions, an electric motor 2 that drives the hydraulic pump, and a rod 15 that moves forward and backward by the hydraulic oil discharged from the hydraulic pump 1. And a hydraulic cylinder 10 as a fluid pressure cylinder.

  The electrohydraulic actuator 100 includes an accumulator 20 capable of accumulating a part of hydraulic fluid discharged from the hydraulic pump 1, and a pair of supply / discharge passages 3 connecting the hydraulic pump 1 and the hydraulic cylinder 10. A supply / discharge flow path 4, an operation check valve 5 and an operation check valve 6 disposed in each of the supply / discharge flow paths 3 and 4, and a tank 31 for storing hydraulic oil are provided.

  The hydraulic pump 1 is a gear pump in which a pump chamber that moves by rotation of a gear sucks hydraulic oil from one direction and discharges it from the other direction, with a pair of gears engaged with each other as a pump chamber. The hydraulic pump 1 rotates in both directions according to the rotation direction of the electric motor 2 and can discharge hydraulic oil in the direction according to the rotation.

  The electric motor 2 is driven based on a signal emitted from a controller (not shown) input from a switch (not shown) operated by an operator to a controller (not shown).

  The hydraulic cylinder 10 includes a piston 11 to which a rod 15 is connected, a cylinder part 12 into which the piston 11 is slidably inserted, a piston 13 connected to the cylinder part 12, and a piston 13 to be slidably inserted. The cylinder part 14 is provided. The piston 11 corresponds to the first piston, the cylinder portion 12 corresponds to the first cylinder portion, the piston 13 corresponds to the second piston, and the cylinder portion 14 corresponds to the second cylinder portion.

  In the hydraulic cylinder 10, the cylinder portion 14 is fixed, and the free end of the rod 15 is connected to an external load (not shown). The hydraulic cylinder 10 expands and contracts as the rod 15 advances and retreats with respect to the cylinder portion 14, and moves the load accordingly.

  The piston 11 is connected to a load via a rod 15 that protrudes from the cylinder portion 12. When the piston 11 slides in the cylinder part 12, the rod 15 advances and retreats with respect to the cylinder part 12.

  The cylinder part 12 is a double-acting cylinder in which the piston 11 can slide in accordance with the pressure of hydraulic oil. In the cylinder portion 12, a piston-side oil chamber 12a as a piston-side fluid chamber and a rod-side oil chamber 12b as a rod-side fluid chamber are defined by the piston 11. The piston-side oil chamber 12a and the rod-side oil chamber 12b are expanded and contracted by the hydraulic oil discharged in both directions from the hydraulic pump 1, respectively.

  The piston 13 is connected to the bottom surface 12c of the piston-side oil chamber 12a in the cylinder portion 12 via a rod 13a. When the piston 13 slides in the cylinder portion 14, the cylinder portion 12 slides integrally with the piston 13, and the cylinder portion 12 advances and retreats with respect to the cylinder portion 14.

  The piston 13 is formed with a larger diameter than the piston 11. That is, the pressure receiving area of the piston 13 is larger than the pressure receiving area of the piston 11.

  The rod 13a projects from the cylinder portion 12 to the outside. The proximal end portion of the rod 13 a is connected to the piston 13, and the distal end portion is connected to the cylinder portion 12.

  The cylinder part 14 is formed in series with the cylinder part 12. In the cylinder portion 14, a back pressure chamber 14 a and a rod side fluid chamber 14 b are defined by the piston 13.

  The back pressure chamber 14 a is defined on the back surface 13 b of the piston 13. The hydraulic oil accumulated in the accumulator 20 is guided to the back pressure chamber 14a based on the discharge pressure of the hydraulic pump 1 when being guided from the hydraulic pump 1 to the piston side oil chamber 12a. When the hydraulic oil is supplied and expanded, the back pressure chamber 14a imparts thrust to the piston 13 in the direction in which the rod 15 retracts.

  The back pressure chamber 14a can discharge internal hydraulic oil by switching pilot switching valves 21 and 22, which will be described later. As a result, the piston 13 can slide in the direction in which the back pressure chamber 14a is contracted. The rod 13a enters the cylinder portion 14 while contracting the back pressure chamber 14a by its own weight or by a force input from the external load via the rod 15.

  The rod side fluid chamber 14b is filled with a compressible gas such as air. The rod-side fluid chamber 14b contracts when the back pressure chamber 14a is expanded by the hydraulic oil guided from the accumulator 20, and expands when the internal hydraulic fluid is discharged and the back pressure chamber 14a contracts.

  The accumulator 20 is provided so as to be able to communicate with the back pressure chamber 14a via a pilot switching valve 21 and a check valve 23 which will be described later. Since the check valve 23 is provided, the hydraulic oil flows only in one direction from the accumulator 20 to the back pressure chamber 14a.

  The accumulator 20 is provided so as to be able to communicate with the supply / discharge flow path 4 via a pilot switching valve 22 and a check valve 24 described later. Since the check valve 24 is provided, the hydraulic oil flows only in one direction from the supply / discharge channel 4 to the accumulator 20.

  The supply / discharge flow path 3 is a flow path that connects the hydraulic pump 1 and the piston-side oil chamber 12a. The supply / discharge flow path 3 is provided with an operation check valve 5 for stopping the flow of hydraulic oil when the hydraulic pump 1 is stopped, and a slow return valve 8 for preventing hunting of the hydraulic cylinder 10.

  The operation check valve 5 is closed when the electric motor 2 is stopped and the hydraulic pump 1 is stopped, and the flow of hydraulic oil in the supply / discharge passage 3 is blocked. Thereby, when the electric motor 2 stops, the flow of hydraulic oil stops and the length of the hydraulic cylinder 10 is maintained.

  The operation check valve 5 is opened when the electric motor 2 rotates and hydraulic fluid is introduced from the hydraulic pump 1 to the piston-side oil chamber 12a. Thereby, when the rod 15 retreats from the cylinder part 12, hydraulic oil can be supplied from the hydraulic pump 1 to the piston-side oil chamber 12a.

  The operation check valve 5 is connected to the supply / discharge channel 4 on the opposite side via a pilot channel 5a. The operation check valve 5 is pilot-driven by the pressure of the hydraulic oil in the supply / discharge flow path 4 and is opened. As a result, when the hydraulic oil is supplied from the hydraulic pump 1 to the rod-side oil chamber 12b and the rod 15 enters the cylinder portion 12, the hydraulic oil can be returned from the piston-side oil chamber 12a to the hydraulic pump 1. Become.

  The slow return valve 8 is a throttle valve provided between the piston-side oil chamber 12 a and the operation check valve 5. The slow return valve 8 provides resistance by restricting the flow path of the hydraulic oil discharged from the piston-side oil chamber 12a by the sliding of the piston 11 in the direction in which the rod 15 enters the cylinder portion 12. By providing the slow return valve 8, a hunting phenomenon in which the piston 11 intermittently vibrates intermittently when the rod 15 enters the cylinder portion 12 due to the weight of the load connected to the tip portion of the rod 15. Is prevented.

  The supply / discharge passage 3 includes a relief passage 43 for returning the working oil to the tank when the pressure of the working oil between the piston-side oil chamber 12a and the operation check valve 5 rises, and the operation check valve 5 and the hydraulic pump. 1 is connected to a relief channel 41 that returns the hydraulic oil to the tank when the pressure of the hydraulic oil rises to 1. A relief valve 43a and a relief valve 41a are provided in the relief channel 43 and the relief channel 41, respectively. As a result, when the rod 15 retreats from the cylinder portion 12 to become a stroke end or when an overload occurs, the hydraulic oil in the supply / discharge passage 3 is returned to the tank 31.

  The supply / discharge channel 4 is a channel that connects the hydraulic pump 1 and the rod-side oil chamber 12b. The supply / discharge flow path 4 is provided with an operation check valve 6 that stops the flow of hydraulic oil when the hydraulic pump 1 is stopped.

  The operation check valve 6 is closed when the electric motor 2 is stopped and the hydraulic pump 1 is stopped, thereby blocking the flow of hydraulic oil in the supply / discharge passage 4. Thereby, when the electric motor 2 stops, the length of the hydraulic cylinder 10 is maintained.

  The operation check valve 6 is opened when the electric motor 2 rotates and the hydraulic oil is guided from the hydraulic pump 1 to the rod side oil chamber 12b. As a result, hydraulic oil can be supplied from the hydraulic pump 1 to the rod-side oil chamber 12b when the rod 15 enters the cylinder portion 12.

  The operation check valve 6 is connected to the supply / discharge channel 3 on the opposite side via a pilot channel 6a. The operation check valve 6 is pilot-driven by the pressure of the hydraulic oil in the supply / discharge passage 3 and is opened. As a result, the hydraulic oil can be returned from the rod side oil chamber 12b to the hydraulic pump 1 when the rod 15 retreats from the cylinder portion 12.

  The supply / discharge flow path 4 includes a relief flow path 44 for returning the hydraulic oil to the tank when the pressure of the hydraulic oil between the rod side oil chamber 12b and the operation check valve 6 rises, the operation check valve 6 and the hydraulic pump. 1 is connected to a relief flow path 42 that returns the hydraulic oil to the tank when the hydraulic oil pressure increases with respect to 1. A relief valve 44a and a relief valve 42a are provided in the relief channel 44 and the relief channel 42, respectively. As a result, when the rod 15 enters the cylinder portion 12 to become a stroke end or an overload occurs, the hydraulic oil in the supply / discharge passage 4 is returned to the tank 31.

  The tank 31 stores hydraulic oil for compensating a later-described flow rate difference between the suction flow rate and the discharge flow rate in the hydraulic pump 1. Further, the hydraulic oil discharged from the back pressure chamber 14a is returned to the tank 31 when pilot switching valves 21 and 22 (to be described later) are switched.

  The electrohydraulic actuator 100 includes a pilot switching valve 30 for adjusting the flow rate of hydraulic oil before and after the hydraulic pump 1 and an emergency manual valve 50 that can be manually operated by an operator.

  When the piston 11 slides inside the cylinder part 12, the volume of expansion and contraction of the piston side oil chamber 12 a and the rod side oil chamber 12 b is compared with the piston side oil chamber 12 a as much as the rod 15 is inserted. And the volume by which the rod side oil chamber 12b is expanded and contracted is smaller. Thereby, when the rod 15 retreats from the cylinder part 12, the volume of the hydraulic oil supplied to the piston side oil chamber 12a is the same as the volume of the hydraulic oil discharged from the rod side oil chamber 12b by the movement of the piston 11. It becomes large compared. Similarly, when the rod 15 enters the cylinder portion 12, the volume of the hydraulic oil discharged from the piston-side oil chamber 12a by the movement of the piston 11 is compared with the volume of the hydraulic oil supplied to the rod-side oil chamber 12b. And get bigger. Therefore, by providing the pilot switching valve 30, the flow rate difference between the suction flow rate and the discharge flow rate in the hydraulic pump 1 is compensated.

  The pilot switching valve 30 is a three-position switching valve having a first position 30a, a second position 30b, and a third position 30c. When the hydraulic pump 1 is stopped, the pilot switching valve 30 is switched so that both ends are urged by springs and the second position 30b communicates. At this time, the pilot switching valve 30 blocks between the supply / discharge flow paths 3 and 4 and the tank 31.

  When the hydraulic oil discharged from the hydraulic pump 1 is guided to the piston-side oil chamber 12a, the pilot switching valve 30 is pilot-driven by the hydraulic oil pressure in the supply / discharge passage 3 so that the first position 30a communicates. To be switched. At this time, the pilot switching valve 30 communicates between the supply / discharge flow path 4 and the tank 31. As a result, the hydraulic oil can be guided from the tank 31 to the supply / discharge passage 4 by the volume of the rod 15 to supplement the suction flow rate of the hydraulic pump 1.

  When the hydraulic oil discharged from the hydraulic pump 1 is guided to the rod-side oil chamber 12b, the pilot switching valve 30 is pilot-driven by the hydraulic oil pressure in the supply / discharge passage 4 so that the third position 30c communicates. To be switched. At this time, the pilot switching valve 30 communicates between the supply / discharge flow path 3 and the tank 31. As a result, the hydraulic oil can be returned from the supply / discharge passage 3 to the tank 31 by the volume of the rod 15.

  In this state, when the pressure of the hydraulic oil accumulated in the accumulator 20 is reduced, a part of the hydraulic oil discharged from the hydraulic pump 1 is guided to the accumulator 20. Therefore, hydraulic oil can be guided from the tank 31 to the supply / discharge flow path 3 by the volume guided to the accumulator 20 to supplement the suction flow rate of the hydraulic pump 1.

  The emergency manual valve 50 has a first position 50 a that closes all ports, and a second position 50 b that communicates the supply / discharge passages 3 and 4 with the tank 31. The emergency manual valve 50 has a switch 51 that can be manually operated by an operator. When the switch 51 is operated by an operator in an emergency, the emergency manual valve 50 is switched to the second position 50 b and guides the hydraulic oil in the supply / discharge passages 3 and 4 to the tank 31. Thereby, the expansion / contraction operation of the hydraulic cylinder 10 is stopped, and the operator can manually expand and contract the hydraulic cylinder 10.

  The electrohydraulic actuator 100 includes a pilot switching valve 21 that is switched based on the pressure of hydraulic oil in the supply / discharge flow path 3 and a pilot switching valve 22 that is switched based on the pressure of hydraulic oil in the supply / discharge flow path 4. The pilot switching valve 21 corresponds to a first pilot switching valve, and the pilot switching valve 22 corresponds to a second pilot switching valve.

  The pilot switching valve 21 is switched to guide the hydraulic oil accumulated in the accumulator 20 to the back pressure chamber 14a using the pressure of the hydraulic oil discharged from the hydraulic pump 1 and guided to the piston-side oil chamber 12a as a pilot pressure. Specifically, it is as follows.

  The pilot switching valve 21 is a two-position switching valve having a first position 21a and a second position 21b. The pilot switching valve 21 has a pilot flow path 21 c connected to the supply / discharge flow path 3.

  When the hydraulic pump 1 is stopped, the pilot switching valve 21 is urged by a spring so that the first position 21a communicates. At this time, the pilot switching valve 21 shuts off the hydraulic fluid guided from the accumulator 20 and allows the back pressure chamber 14a and the tank 31 to communicate with each other.

  When the hydraulic oil discharged from the hydraulic pump 1 is guided to the piston-side oil chamber 12a, the pilot switching valve 21 is configured so that the pressure of the hydraulic oil transmitted from the supply / discharge channel 3 through the pilot channel 21c is a spring force. As a result, pilot driving is performed and the second position 21b is switched so as to communicate with each other.

  At this time, the pilot switching valve 21 shuts off the back pressure chamber 14a and the tank 31 and allows the accumulator 20 and the back pressure chamber 14a to communicate with each other. As a result, the hydraulic oil accumulated in the accumulator 20 is guided to the back pressure chamber 14a.

  Therefore, the hydraulic oil discharged from the hydraulic pump 1 is guided to the piston-side oil chamber 12a and the rod 15 is withdrawn from the cylinder portion 12, and the back pressure chamber 14a is expanded by the hydraulic oil guided from the accumulator 20, and the rod 13a. Retreats from the cylinder portion 14, and the hydraulic cylinder 10 extends.

  The pilot switching valve 22 is switched so that a part of the hydraulic oil discharged from the hydraulic pump 1 is guided to the accumulator 20 using the pressure of the hydraulic oil discharged from the hydraulic pump 1 and guided to the rod side oil chamber 12b as a pilot pressure. It is done. Specifically, it is as follows.

  The pilot switching valve 22 is a two-position switching valve having a first position 22a and a second position 22b. The pilot switching valve 22 has a pilot flow path 22 c connected to the supply / discharge flow path 4.

  When the hydraulic pump 1 is stopped, the pilot switching valve 22 is urged by a spring so that the first position 22a communicates. At this time, the pilot switching valve 22 blocks between the back pressure chamber 14 a and the tank 31 and blocks between the accumulator 20 and the supply / discharge channel 4.

  When the hydraulic oil discharged from the hydraulic pump 1 is guided to the rod-side oil chamber 12b, the pilot switching valve 22 is configured so that the pressure of the hydraulic oil transmitted from the supply / discharge channel 4 through the pilot channel 22c is a spring force. As a result, the pilot drive is performed and the second position 22b is switched to communicate with each other.

  At this time, the pilot switching valve 22 makes the accumulator 20 and the supply / discharge flow path 4 communicate with each other. As a result, part of the hydraulic oil discharged from the hydraulic pump 1 and guided to the rod-side oil chamber 12b is guided to the accumulator 20 and accumulated. At the same time, the pilot switching valve 22 communicates between the back pressure chamber 14 a and the tank 31 via the pilot switching valve 21. As a result, the hydraulic oil in the back pressure chamber 14 a is guided to the tank 31.

  Therefore, the hydraulic oil discharged from the hydraulic pump 1 is guided to the rod side oil chamber 12b, the rod 15 enters the cylinder portion 12, and the hydraulic oil in the back pressure chamber 14a is discharged, so that the rod 13a is discharged. The hydraulic cylinder 10 contracts by entering the cylinder portion 14.

  Instead of using the pilot switching valve 21 and the pilot switching valve 22, a pressure sensor for detecting the pressure of hydraulic oil in each of the supply / discharge flow path 3 and the supply / discharge flow path 4 is provided, and the signal of the pressure sensor An electromagnetic switching valve that is switched by a controller based on the above may be used.

  A throttle valve 9 is provided between the pilot switching valve 22 and the supply / discharge flow path 4. Therefore, the volume of the hydraulic oil led to the pilot switching valve 22 among the hydraulic oil discharged from the hydraulic pump 1 is smaller than the volume of the hydraulic oil led to the rod side oil chamber 12b. Therefore, the operation | movement into which the rod 15 approachs into the cylinder part 12 is not prevented by the hydraulic fluid guide | induced to the rod side oil chamber 12b decreasing.

  Hereinafter, the operation of the electrohydraulic actuator 100 will be described with reference to FIGS. 2 and 3.

  First, the case where the hydraulic cylinder 10 extends will be described with reference to FIG.

  When the hydraulic pump 1 rotates in one direction by driving the electric motor 2, hydraulic oil is discharged from the hydraulic pump 1 toward the supply / discharge flow path 3. The hydraulic oil discharged from the hydraulic pump 1 passes through the operation check valve 5 in an open state, passes through the slow return valve 8, and is supplied to the piston side oil chamber 12a of the cylinder portion 12. At this time, the flow rate of the hydraulic oil is not throttled because it can pass through the check valve of the bypass flow path provided in the slow return valve 8.

  When the piston-side oil chamber 12 a is expanded by the hydraulic oil supplied from the hydraulic pump 1, the piston 11 slides in the direction in which the rod 15 retracts from the cylinder part 12. As a result, the rod 15 is withdrawn from the cylinder portion 12. At this time, the operation check valve 6 is opened by the pressure of the hydraulic oil in the supply / discharge channel 3 transmitted through the pilot channel 6a. Therefore, the hydraulic oil in the rod side oil chamber 12b is discharged and returned to the hydraulic pump 1, and the rod side oil chamber 12b contracts.

  The pilot switching valve 30 is pilot-driven by the pressure of the hydraulic oil in the supply / discharge flow path 3 and is switched to the first position 30 a to communicate the tank 31 with the supply / discharge flow path 4. As a result, the suction flow rate that is smaller than the discharge flow rate of the hydraulic pump 1 by the volume of the rod 15 is supplemented by the hydraulic oil supplied from the tank 31 to the supply / discharge flow path 4 via the pilot switching valve 30.

  The pilot switching valve 21 is switched to the second position 21b by the pressure of the hydraulic oil in the supply / discharge passage 3. As a result, the hydraulic oil accumulated in the accumulator 20 passes through the check valve 23 and the pilot switching valve 21 and is supplied to the back pressure chamber 14 a of the cylinder portion 14.

  When the back pressure chamber 14 a is expanded by the hydraulic oil supplied from the accumulator 20, the piston 13 slides in the direction in which the rod 13 a retracts from the cylinder portion 14. As a result, the cylinder portion 12 moves in the same direction as the rod 15 with respect to the cylinder portion 14.

  As described above, the hydraulic oil discharged from the hydraulic pump 1 is guided to the piston-side oil chamber 12a and the rod 15 is withdrawn from the cylinder portion 12, and the back pressure chamber 14a is expanded by the hydraulic fluid guided from the accumulator 20 to the rod. 13a retreats from the cylinder part 14, and the hydraulic cylinder 10 extends. Therefore, the retraction operation of the rod 15 by the hydraulic oil from the hydraulic pump 1 is assisted by the hydraulic oil from the accumulator 20. Therefore, the output of the electrohydraulic actuator 100 can be improved without using a large capacity cylinder or electric motor.

  At this time, the rod 13a retracts from the cylinder portion 14 at the initial stage of operation when the rod 15 begins to retract from the cylinder portion 12. Thereafter, the rod 13a stops by stroking to the stroke end while the rod 15 is still leaving the cylinder portion 12. Therefore, high output in the initial operation of the hydraulic cylinder 10 is possible. Therefore, the electrohydraulic actuator 100 is suitable for hydraulic equipment that requires a large output in the initial stage of operation, such as a lifter.

  The assist characteristics can be changed by adjusting the pressure accumulation capacity of the accumulator 20 and the stroke amount of the piston 13.

  Next, a case where the hydraulic cylinder 10 contracts will be described with reference to FIG.

  When the hydraulic pump 1 rotates in the other direction by driving the electric motor 2, hydraulic oil is discharged from the hydraulic pump 1 toward the supply / discharge passage 4. The hydraulic oil discharged from the hydraulic pump 1 passes through with the operation check valve 6 opened, and is supplied to the rod side oil chamber 12b of the cylinder portion 12.

  When the rod side oil chamber 12 b is expanded by the hydraulic oil supplied from the hydraulic pump 1, the piston 11 slides in the direction in which the rod 15 enters the cylinder portion 12. As a result, the rod 15 enters the cylinder portion 12. At this time, the operation check valve 5 is opened by the pressure of the hydraulic oil in the supply / discharge flow path 4 transmitted through the pilot flow path 5a. Therefore, the hydraulic oil in the piston side oil chamber 12a is discharged and returned to the hydraulic pump 1, and the piston side oil chamber 12a contracts.

  The pilot switching valve 30 is pilot-driven by the pressure of the hydraulic oil in the supply / exhaust flow path 4 and is switched to the third position 30 c to connect the tank 31 and the supply / discharge flow path 3. As a result, the suction flow rate of the hydraulic pump 1 that is larger than the discharge flow rate of the hydraulic pump 1 by the volume of the rod 15 is returned to the tank 31.

  The pilot switching valve 22 is switched to the second position 22b by the pressure of the hydraulic oil in the supply / discharge channel 4. As a result, the hydraulic oil in the back pressure chamber 14 a passes through the pilot switching valve 21 and the pilot switching valve 22 and is returned to the tank 31. When the back pressure chamber 14a is contracted by discharging the hydraulic oil, the piston 13 slides in a direction in which the rod 13a enters the cylinder portion 14.

  As described above, the hydraulic oil discharged from the hydraulic pump 1 is guided to the rod-side oil chamber 12b, the rod 15 enters the cylinder portion 12, and the hydraulic oil in the back pressure chamber 14a is discharged, whereby the rod 13a. Enters the cylinder portion 14 and the hydraulic cylinder 10 contracts.

  At the same time, part of the hydraulic oil in the supply / discharge flow path 4 passes through the pilot switching valve 22 and the check valve 24 and is guided to the accumulator 20. Thereby, when the pressure of the hydraulic fluid accumulated in the accumulator 20 is reduced, a part of the hydraulic fluid discharged from the hydraulic pump 1 is guided to the accumulator 20.

  While the hydraulic oil is introduced into the accumulator 20 and accumulated, the corresponding hydraulic oil is led from the tank 31 to the supply / exhaust flow path 3 and supplied to the hydraulic pump 1, thereby supplementing the insufficient suction flow rate. .

  According to the above embodiment, the following effects are obtained.

  The hydraulic oil discharged from the hydraulic pump 1 is guided to the piston-side oil chamber 12a to retreat the rod 15, and at the same time, based on the pressure of the hydraulic oil guided from the hydraulic pump 1 to the piston-side oil chamber 12a, the cylinder portion The piston 13 connected to 12 is slid in the direction in which the rod 15 is retracted by the thrust of the back pressure chamber 14 a through which hydraulic oil is guided from the accumulator 20. Therefore, the retraction operation of the rod 15 by the hydraulic oil from the hydraulic pump 1 is assisted by the hydraulic oil from the accumulator 20. Therefore, the output of the electrohydraulic actuator 100 can be improved without using a large capacity cylinder or electric motor.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The present invention can be used as an actuator for saving and automating machines, equipment, jigs and the like.

100 Electric hydraulic actuator (electric fluid pressure actuator)
1 Hydraulic pump (fluid pressure pump)
2 Electric motor 3 Supply / discharge flow path 4 Supply / discharge flow path 5 Operate check valve 6 Operate check valve 10 Hydraulic cylinder (fluid pressure cylinder)
11 Piston (first piston)
12 Cylinder part (first cylinder part)
12a Piston side oil chamber (piston side fluid chamber)
12b Rod side oil chamber (rod side fluid chamber)
13 Piston (second piston)
13a Rod 14 Cylinder part (second cylinder part)
14a Back pressure chamber 15 Rod 20 Accumulator 21 Pilot switching valve 22 Pilot switching valve

Claims (5)

A fluid pressure pump capable of discharging working fluid in both directions;
An electric motor for driving the fluid pressure pump;
An electric fluid pressure actuator comprising a fluid pressure cylinder having a rod that advances and retreats by working fluid discharged from the fluid pressure pump,
An accumulator capable of accumulating pressure by guiding a part of the working fluid discharged from the fluid pressure pump;
The fluid pressure cylinder is
A first piston to which the rod is coupled;
The first piston defines a piston-side fluid chamber and a rod-side fluid chamber into which the first piston is slidably inserted and the working fluid discharged in both directions from the fluid pressure pump is guided. A first cylinder part,
A second piston coupled to the first cylinder portion;
A second cylinder portion in which the second piston is slidably inserted, and a back pressure chamber that applies thrust to the second piston in a direction in which the rod retracts is defined on a back surface of the second piston; With
When the working fluid is led from the fluid pressure pump to the piston-side fluid chamber, the working fluid accumulated in the accumulator is led to the back pressure chamber based on the discharge pressure of the fluid pressure pump. Electric fluid pressure actuator.   A first pilot switching valve that is switched to guide the working fluid accumulated in the accumulator to the back pressure chamber, using the pressure of the working fluid discharged from the fluid pressure pump and guided to the piston-side fluid chamber as a pilot pressure; The electric hydraulic actuator according to claim 1, further comprising:   A second pilot that is switched so that a part of the working fluid discharged from the fluid pressure pump is guided to the accumulator by using the pressure of the working fluid discharged from the fluid pressure pump and guided to the rod side fluid chamber as a pilot pressure. The electric fluid pressure actuator according to claim 1, further comprising a switching valve. A tank in which the working fluid is stored;
The second pilot switching valve is switched to guide the working fluid in the back pressure chamber to the tank using the pressure of the working fluid discharged from the fluid pressure pump and guided to the rod side fluid chamber as a pilot pressure. The electric fluid pressure actuator according to claim 3.   The rod that protrudes from the second cylinder portion is connected to the second piston, and the tip portion of the rod is connected to the bottom surface of the piston-side fluid chamber. The electric hydraulic actuator according to any one of the above.

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