JP2008291863A - Hydraulic drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic drive unit of simple and compact structure capable of accurately controlling the rod position even in the case where noload is applied to an actuator cylinder. <P>SOLUTION: There are assembled in the same unit an oil pressure supply device for supplying and sucking operating fluid inside a reservoir tank to/from one of a head side cylinder chamber and a rod side cylinder chamber of an actuator cylinder with a two-way rotary hydraulic pump to be driven for rotation by a servo motor and an air pressure supply device comprising an air pump for pressure-feeding air to the other cylinder chamber when the operating fluid is sucked by the hydraulic pump, an air tank pressurized by the air from the air pump and housing air discharged from the other cylinder chamber, and a pressure control valve for controlling the pressure inside the air tank to a predetermined upper limit pressure or less, and the number of revolution of the servo motor is controlled by the control device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic drive unit for driving a rod of an actuator cylinder forward and backward.

  2. Description of the Related Art Some hydraulic drive devices that perform forward / backward drive of rods of actuator cylinders by hydraulic control use a constant displacement bidirectional rotary pump. Since this bidirectional rotary pump supplies hydraulic oil in both forward and reverse directions, both ports of the bidirectional rotary pump 42 are connected to the inlet / outlet port H of the head side cylinder chamber S1 of the actuator cylinder 50 and the rod as shown in FIG. Only by connecting to the inlet / outlet port R of the side cylinder chamber S2, a control valve is not required, and the cylinder rod can be driven forward and backward with a simple hydraulic circuit comprising a self-supply valve and a safety valve.

  That is, the hydraulic oil in the reservoir tank 43 is supplied from one port to the head-side cylinder chamber S1 by the forward rotation of the pump 42, and the hydraulic oil in the rod-side cylinder chamber S2 is sucked from the other port of the pump 42 to the tank. By returning to 43, the cylinder rod 51 can be driven forward, and by the reverse rotation of the pump 42, hydraulic oil is supplied from the other port to the rod side cylinder chamber S2, and the hydraulic oil in the head side cylinder chamber S1 is pumped. The cylinder rod 51 can be retracted by suctioning from one of the ports and returning it to the tank 43.

  If the bidirectional rotary hydraulic pump is used in this way, a hydraulic supply device can be configured as a compact unit 41 having no hydraulic piping with a simple hydraulic circuit that circulates hydraulic oil in a substantially closed system (for example, Patent Document 1). reference.).

  The bidirectional rotary hydraulic pump 42 is rotationally driven by a servo motor M. The servo motor M is driven by a control device 60 from a position detection signal of the cylinder rod 51 from the position sensor 53 and a pressure sensor 45. Feedback control is performed based on the pressure detection signal of the pump discharge hydraulic oil.

  In addition, since the bidirectional rotary pump 42 is a constant capacity type in which the swash plate of the piston pump is fixed, the discharge flow rate is determined by the rotational speed of the pump. By controlling the pump rotation speed over a wide range from low speed to high speed, the pump discharge flow rate is efficiently controlled.

  Therefore, if such a constant displacement pump is used, it is very efficient compared to a case where loss such as hydraulic internal leakage is large, such as a variable displacement pump that changes the displacement of the pump at a constant high speed. A hydraulic supply system can be configured.

JP 2006-329241 A

  In the conventional hydraulic pressure supply apparatus as described above, when hydraulic fluid is fed from the pump 42 using the discharge circuit between the pump 42 and the head side cylinder chamber S1, the suction circuit is provided between the pump 42 and the rod side cylinder chamber S2. On the other hand, when hydraulic oil is sent from the pump 42 to the rod side cylinder chamber S2 using the discharge circuit between the rod side cylinder chamber S2 and the rod side cylinder chamber S2, a suction circuit is provided between the pump 42 and the head side cylinder chamber S1.

  Therefore, when performing position control such as positioning the rod at a predetermined initial position in a state where there is no load on the cylinder, the hydraulic oil to either the head side or the rod side is corrected each time position error correction is performed. It was necessary to completely reduce the discharge pressure to 0 MPa.

  However, in such error correction, since the discharge pressure is reduced to 0 MPa, it is likely to be affected by the residual air in the cylinder, so position control in units of several μm is difficult and is currently required. There was no choice but to control the position with a lower accuracy than the current one. On the other hand, in order to maintain the pressure in the circuit and ensure high-precision controllability, it is necessary to take measures to provide a sequence valve in the passage, but this complicates the circuit, There was a problem that the size of the apparatus was increased.

  Further, it is conceivable to use a spring as the return force of the cylinder rod as a simple configuration, but it is often difficult to design in consideration of the load and stroke. In addition, hydraulic control using an accumulator or the like is conceivable, but the accumulator is troublesome because it is subject to the high-pressure gas safety law.

  In view of the above problems, an object of the present invention is to provide a hydraulic drive unit capable of highly accurate rod position control even when there is no load on an actuator cylinder, while having a simple and compact configuration.

  In order to achieve the above object, the hydraulic drive unit according to the first aspect of the present invention supplies and sucks the hydraulic oil in the reservoir tank to one of the head side cylinder chamber or the rod side cylinder chamber of the actuator cylinder. A hydraulic pressure supply device including a bidirectional rotary hydraulic pump and a servo motor that rotationally drives the hydraulic pump, and air is pumped to the other cylinder chamber when the hydraulic pump draws hydraulic oil to one of the cylinder chambers. An air pump that is pressurized with air from the air pump and that stores air discharged from the other cylinder chamber when hydraulic oil is supplied to one of the cylinder chambers by the hydraulic pump, and a pressure in the air tank A pneumatic pressure supply device comprising a pressure regulating valve for regulating the pressure below a predetermined upper limit pressure; It includes a control unit for controlling the number of revolutions of Bomota, and said hydraulic pressure supply device and the air pressure supply device is one that has been assembled in the same unit.

  According to a second aspect of the present invention, the hydraulic drive unit according to the first aspect of the present invention is the hydraulic drive unit according to the first aspect, wherein the hydraulic pressure supply device has a second flow path between the one cylinder chamber and the reservoir tank. And a shut-off valve that is disposed in the second flow path and is switched by the control device between a flow path on the cylinder chamber side and a flow path on the reservoir tank side between a closed state and a communication state. is there.

  A hydraulic drive unit according to a third aspect of the present invention is the hydraulic drive unit according to the first or second aspect, wherein the pneumatic device is disposed in a flow path between the air pump and the air tank. And a switching valve that switches the flow path to release the air from the air pump to the atmosphere when the pressure of the air in the air tank becomes equal to or higher than a predetermined pressure.

  Furthermore, the hydraulic drive unit according to the invention of claim 4 is the hydraulic drive unit according to any one of claims 1 to 3, wherein both the hydraulic pump and the air pump are driven by the servo motor, A position sensor for detecting a rod position of a cylinder, a pressure sensor for detecting a pressure of hydraulic pressure acting on one of the cylinder chambers, and a pressure sensor for detecting a pressure of air pressure acting on the other of the cylinder chambers, The control device controls the rotational speed of the servo motor based on detection signals from these sensors.

  The present invention operates on one cylinder chamber on the head side and on the rod side of the actuator cylinder by a hydraulic pressure supply device and a pneumatic pressure supply device assembled in the same unit, without using a complicated sequence valve or a cumbersome accumulator. Since oil can be supplied to and discharged from the other cylinder chamber in synchronization with each other, even when there is no load on the actuator cylinder, a constant air pressure load is applied to the hydraulic oil in one cylinder chamber. Since the pressure acts, there is an effect that the position control of the cylinder rod by the hydraulic control can be performed with high accuracy which has been difficult in the past.

  The hydraulic drive unit of the present invention is a hydraulic supply unit that supplies and sucks hydraulic oil in a reservoir tank to one of a head side cylinder chamber or a rod side cylinder chamber of an actuator cylinder by a bidirectional rotary hydraulic pump driven by a servo motor. In the same unit as the apparatus, when the hydraulic oil is sucked into one cylinder chamber by the hydraulic pump, air is pumped to the other cylinder chamber by the air pump and pressurized with air from the air pump to the air tank. An air pressure supply device is provided for storing air discharged from the other cylinder chamber when hydraulic oil is supplied to the one cylinder chamber by the pump.

  Therefore, in the present invention, the hydraulic oil is supplied to and discharged from one cylinder chamber on the head side and the rod side of the actuator cylinder by the hydraulic pressure supply device, and air is supplied to the other cylinder chamber by the air pressure supply device. Even when there is no load on the actuator cylinder, the load pressure is constantly applied by air pressure to the hydraulic oil in one cylinder chamber. Can be done with precision. That is, according to the present invention, although it is a simple and compact unit configuration, even if there is no load on the actuator, position control in units of several μm, which has been difficult in the past, is possible without reducing the hydraulic pressure to 0 MPa. .

  The air pressure supply device includes a pressure adjustment valve that adjusts the pressure in the air tank to a predetermined upper limit pressure or less, thereby preventing rupture damage of the tank due to excessive pressurization.

  Further, in the hydraulic pressure supply device, a second flow path is provided between one cylinder chamber and the reservoir tank, and a shutoff valve is disposed in the second flow path so that the cylinder chamber side and the reservoir tank side are arranged. If the control device switches the flow paths between the cylinder chamber side and the reservoir tank side, the flow path between the cylinder chamber side and the reservoir tank side is switched to the communication state, so that one cylinder chamber can transfer to the reservoir tank. It is possible to increase the moving speed of the cylinder rod by speeding up the return of the hydraulic oil. In particular, when hydraulic fluid is supplied to or discharged from the head side cylinder chamber, the return speed of the cylinder rod can be increased. Further, if such return of the hydraulic oil is performed only by the second flow path by the shut-off valve, the pump side operation is not necessary, so that energy saving can be achieved in driving the apparatus.

  Further, in the pneumatic device, when the air pressure in the air tank exceeds a predetermined pressure in the flow path between the air pump and the air tank, the flow path is switched to release the air from the air pump to the atmosphere. By arranging the switching valve, when air is sent into the other cylinder chamber, air can be sent and stored in the air tank up to a predetermined pressure at the same time, and the danger of sending air more than necessary can be avoided. .

  As the air pump, it is convenient to use a compressor, and a dedicated motor may be provided as a power source separately from the hydraulic pump side and driven by the control device in synchronization with each other. If it is driven together, the configuration of the apparatus becomes simpler and more compact, and the control apparatus only needs to drive and control only this servo motor.

  In this case, the control device detects a position sensor that detects a rod position of the cylinder, a pressure sensor that detects a hydraulic pressure acting on one of the cylinder chambers, and a pneumatic pressure that acts on the other of the cylinder chambers. Based on each detection signal from the pressure sensor, the control command inputted in advance is adjusted to control the rotation speed of the servo motor, thereby efficiently performing high-precision pump rotation speed control by electrical feedback control. be able to.

  The discharge flow rate control by the pump rotation speed control is performed in a state where the displacement of the pump is constant, but in the case of a swash plate type piston pump, a fixed capacity provided with a fixed swash plate whose angle is fixed in advance. Although it is convenient to use a type pump, it may be used in a state where the angle of a variable displacement pump with a variable swash plate angle is constant. In this case, the hydraulic drive unit is not limited to use in the hydraulic drive system based on the rotational speed control, and can be widely used in other hydraulic drive systems not based on the rotational speed control.

  As an embodiment of the present invention, a hydraulic drive unit using a bidirectional rotary constant displacement hydraulic pump and driven to rotate by the same servo motor as a compressor as an air pump is shown in the hydraulic circuit of FIG.

  The hydraulic drive unit 1 in the present embodiment drives the cylinder rod 21 by supplying and discharging hydraulic fluid to the head side cylinder chamber S1 of the actuator cylinder 20 and supplying and discharging air to the rod side cylinder chamber S2. The hydraulic pressure supply device and the pneumatic pressure supply device are assembled in the same unit.

  The hydraulic drive unit 1 includes a pump port P that is an inlet / outlet port of a hydraulic pressure supply device, an air port A that is an inlet / outlet port of a pneumatic circuit, and a tank port T as an inlet port to the reservoir tank 3 for hydraulic oil. It is. In this embodiment, the pump port P communicates with the inlet / outlet port H of the head side cylinder chamber S1 through the hydraulic oil passage 4b, and the air port A passes through the inlet / outlet of the rod side cylinder chamber S2 through the air passage 8b. The tank port T communicates with the port R, and the tank port T communicates with the head side cylinder chamber S1 via the second flow path 13b.

  The hydraulic supply device in the hydraulic drive unit 1 includes a reservoir tank 3, a bidirectional rotary constant displacement hydraulic pump 2 that supplies and discharges hydraulic oil in the tank 3 to and from the pump port P, and rotates the hydraulic pump 2. A servo motor M for driving is provided. The hydraulic circuit of this hydraulic pressure supply measure mainly consists of a single hydraulic fluid passage 4a from the reservoir tank 3 to the pump port P via the hydraulic pump 2, and detects the pressure of the normal direct relief valve 5 and hydraulic fluid. It is a simple one provided with a pressure sensor 6.

  The air pressure supply device in the hydraulic drive unit 1 includes a compressor 7 that pumps air to the air port A, and is pressurized with the air from the compressor and is supplied with hydraulic oil to the head side cylinder chamber S1 by the hydraulic pump 2 on the rod side. An air tank 9 that accommodates air discharged from the cylinder chamber S2 and a pneumatic relief valve 12 as a pressure adjusting valve that adjusts the pressure in the air tank 9 to be equal to or lower than a predetermined upper limit pressure are provided.

  The pneumatic circuit of this pneumatic pressure supply device is mainly composed of an air flow path 8a from the compressor 7 to the air port A, and the pressure of air in the air tank 9 between the compressor 7 and the air tank 9 becomes equal to or higher than a predetermined pressure. And a pneumatic pilot type switching valve 11 that switches the flow path connection and releases the air from the compressor 7 to the atmosphere. The air pressure sensor 10 for detecting the hydraulic pressure acting on the rod side cylinder chamber S2 is disposed on the air tank 9 side.

  In addition, the second flow path 13a from the tank port T to the reservoir tank 3 in the hydraulic drive unit 1 is electromagnetically closed and communicated between the tank port side and the tank side. A shutoff valve 14 is provided for switching between the two.

  In this embodiment, the compressor 7 is driven by a servo motor M that drives the hydraulic pump 2, so that the device design is simpler and more efficient. The servo motor M receives a rotation control command output from the control device 30 based on a control command inputted in advance through the driver 31 and drives / stops the hydraulic pump 2 at a direction and a rotational speed corresponding to the command. The compressor 7 is driven / stopped.

  The actuator cylinder 20 includes a position sensor 23 for detecting the position of the head 22 of the cylinder rod 21 corresponding to the actual position of the load related to the cylinder rod 21, for example, and outputs the detection result to the control device 30. Shall.

  The control device 30 compares the actual position of the cylinder rod 21 obtained from the detection signal from the position sensor 23 with a desired input position in advance, and based on the detection signals from the pressure sensor 6 and the air pressure sensor 10. Feedback control for preparing the command signal.

  Further, the control device 30 can switch the shut-off state between the cylinder chamber S1 side and the reservoir tank 3 side in the second flow path 13a to the communication state by conducting the shut-off valve 14 and performing spool movement by electromagnetic force. Due to this communication state, the hydraulic oil in the head side cylinder chamber S1 is returned directly to the reservoir tank via the filter 15, and the cylinder rod 21 is returned to the head side only by the hydraulic oil suction by the hydraulic pump 2. It can be returned at the moving speed.

  In the hydraulic drive unit 1 according to the present embodiment having the above-described configuration, when the cylinder rod 21 is advanced, the control device 30 is necessary for the servo rod M to move the cylinder rod 21 by a desired movement amount. The hydraulic pump 2 is driven to rotate forward so that the number of rotations corresponds to the discharge flow rate. The hydraulic pump 2 discharges the hydraulic oil in the reservoir tank 3 from the second port to the hydraulic oil passage 4a while sucking the hydraulic oil from the first port. The hydraulic oil discharged from the hydraulic pump 2 is filled into the head side cylinder chamber S1 from the pump port P through the hydraulic oil passage 4b, and the cylinder rod 21 is advanced by the hydraulic pressure. At this time, the air in the rod side cylinder chamber S2 is pushed out to the air flow path 8b and accommodated in the air tank 9.

  When the cylinder rod 21 is retracted and returned, the control device 30 causes the servo motor M to drive the hydraulic pump 2 in the reverse direction so as to suck the hydraulic oil in the head side cylinder chamber S1 from the first port. While returning to the reservoir tank 3 from a 2nd port, the compressor 7 is driven and air is supplied into the rod side cylinder chamber S2 from the air flow path 8a via the air port A and the air flow path 8b. Therefore, the cylinder rod 21 moves back due to the decrease in the hydraulic oil in the head side cylinder chamber S1 and the increase in the air pressure in the rod side cylinder chamber S2.

  At this time, the compressor 7 also sends air to the air tank 9. The air tank 9 is filled with air, and when the internal pressure becomes equal to or higher than the upper limit of the preset pressure, the air is released by the pneumatic relief valve 12, and the pressure in the air tank 9 is kept below the upper limit. Further, a pneumatic pilot type switching valve 11 is arranged in the air flow path 8b, and when the pressure of the air sent from the compressor 7 exceeds a set value, the switching valve 11 is switched and the air sent from the compressor 7 is sent to the atmosphere. In order to escape inside, the pressure in the air tank 9 does not rise dangerously.

  Further, in the hydraulic drive unit 1 according to the present embodiment, when the cylinder rod 21 is positioned and controlled to the initial position, for example, with no load on the actuator cylinder 20, the hydraulic oil in the head side cylinder chamber S1 is controlled. Since the load pressure is steadily applied by the air pressure from the rod side cylinder chamber S2, in the position control of the cylinder rod 21 by hydraulic control, error correction with a high accuracy of several μm is possible.

  In the above embodiments, the hydraulic oil is supplied to and discharged from the head side cylinder chamber and the air is supplied to and discharged from the rod side cylinder chamber. According to the above, even the reverse configuration is effective as well.

1 is a hydraulic circuit diagram showing a schematic overall configuration of a hydraulic drive unit according to an embodiment of the present invention. It is a hydraulic circuit diagram which shows an example of the conventional hydraulic drive unit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,41: Hydraulic drive unit M: Servo motor 2, 42: Bidirectional rotation fixed capacity side hydraulic pump 3, 43: Reservoir tank 4a, 4b: Hydraulic oil flow path 5: Direct relief valve 6, 45: Pressure sensor 7: Compressor (air pump)
8a, 8b: Air flow path 9: Air tank 10: Air pressure sensor 11: Pneumatic pilot type switching valve 12: Pneumatic relief valve 13a, 13b: Second flow path 14: Shut-off valve 15: Filter 20, 50: Actuator cylinder 21, 51: Cylinder rod 22: Cylinder head S1: Head side cylinder chamber S2: Rod side cylinder chamber 22: Cylinder head 23, 53: Position sensor P: Pump port A: Air port T: Tank port 30, 60: Controller 31 :driver

Claims (4)

A bidirectional rotary hydraulic pump that supplies and sucks hydraulic oil in the reservoir tank to one of the head side cylinder chamber or the rod side cylinder chamber of the actuator cylinder, and a servo motor that rotationally drives the hydraulic pump. A hydraulic supply device;
An air pump that pumps air to the other cylinder chamber when the hydraulic oil is sucked to one of the cylinder chambers by the hydraulic pump, and an operation to one of the cylinder chambers by the hydraulic pump while being pressurized with air from the air pump A pneumatic supply device comprising an air tank that accommodates air discharged from the other cylinder chamber when oil is supplied, and a pressure adjustment valve that adjusts the pressure in the air tank to a predetermined upper limit pressure or less;
A controller for controlling the rotational speed of the servo motor,
The hydraulic drive unit, wherein the hydraulic supply device and the pneumatic supply device are assembled in the same unit.   The hydraulic pressure supply device is disposed in the second flow path between the one cylinder chamber and the reservoir tank, and in the second flow path, and blocks the flow paths on the cylinder chamber side and the reservoir tank side. The hydraulic servo system according to claim 1, further comprising a shutoff valve that is switched between a state and a communication state by the control device.   The pneumatic device is disposed in a flow path between the air pump and the air tank, and when the pressure of air in the air tank becomes equal to or higher than a predetermined pressure, the air pressure device is switched from the air pump. The hydraulic servo system according to claim 1, further comprising a switching valve that allows air to escape into the atmosphere. Both the hydraulic pump and the air pump are driven by the servo motor,
A position sensor that detects a rod position of the cylinder, a pressure sensor that detects a hydraulic pressure acting on one of the cylinder chambers, and a pressure sensor that detects a pneumatic pressure acting on the other of the cylinder chambers,
4. The hydraulic drive unit according to claim 1, wherein the control device performs rotation speed control of the servo motor based on detection signals from these sensors. 5.

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