JP2001341038A - Electrohydraulic clamp circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy saving electrohydraulic clamp circuit with a simple circuit constitution having no power loss due to a throttle element and providing compatibility between an accumulator circuit capable of maintaining clamping pressure for a long time in an interrupted state of power feed and a variable secondary clamping pressure control circuit with small power consumption utilizing torque control by a motor. SOLUTION: This electrohydraulic clamp circuit has a hydraulic pump motor 1, the motor 2 capable of torque control, a driver 3, a hydraulic cylinder 4, and a hydraulic control part comprised by sequentially providing in a clamp side passage 12a of the hydraulic pump motor 1, a pressure takeout passage 12c to a three port solenoid valve 10, insertion of an external drain type pilot check valve 7 operable by the solenoid valve 10, and a branch for an accumulator 5 and a pressure sensing part 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an application of an electric hydraulic circuit to, for example, a work clamping device of a machine tool.

[0002]

2. Description of the Related Art Conventionally, as this type of electro-hydraulic circuit, for example, the one shown in FIG. 3 (Japanese Patent Laid-Open No. 11-82411) is known. This electric hydraulic circuit is a circuit 51 in which pilot checks 53 and 54 are inserted into input / output ports 51 and 52 of a double rod type double acting cylinder 50, respectively.
a and 52b are connected at one end, and the other end is connected to suction / discharge ports 61 and 62 of a pump 60 capable of normal and reverse rotation.
The hydraulic fluid in the left and right chambers of the cylinder 50 is replaced by rotating the pump
a is moved forward and backward. Relief valve 61
The feed check valves 61b and 62b are provided for replenishment when the operating fluid becomes insufficient due to liquid leakage or the like, and one end thereof is provided for the suction / discharge port 61, 62. And the other end is reservoir 8
Connected to 0. Also, although not shown, when operating the piston rod using a single rod type double acting cylinder, the inflow and outflow amounts of the left and right chambers of the cylinder are not the same. When the feed check valve is pressurized and closed, a pilot-operated open / close switching valve that operates at this pressure and connects the opposite pump port to the reservoir 80 is provided instead of the other feed check valve.

[0003]

However, the above-mentioned conventional electric hydraulic circuit does not include an accumulator and a hydraulic control circuit for operating the accumulator, and does not show that pressure control can be performed in an energy saving state. In other words, there is a disadvantage that the clamp pressure cannot be maintained for a long time in the energy saving state, or it can not be clamped again by changing the pressure sometimes. Therefore, an object of the present invention is to hold the clamp pressure with an accumulator for a long time, for example, in a state where the electric motor is stopped and the supply of power is cut off, and use the torque control by the electric motor to reduce the clamp pressure with less power consumption when necessary. An object of the present invention is to provide an electro-hydraulic clamp circuit which can be variably controlled, has no throttle element in the circuit, saves energy, and has a simple circuit configuration. In addition, it is possible to collect the discharge power of the accumulator via the driver using the power generation action of the electric motor via the hydraulic pump / motor.

[0004]

In order to achieve the above object, an electric hydraulic clamping circuit according to the present invention basically has an electric motor capable of controlling torque in at least one direction and reversing as shown in FIG. 2, a driver 3 for the electric motor 2 having a power input 15 and a signal input 14,
A hydraulic pump / motor 1 driven by the electric motor 2 and also serving as a hydraulic motor; a main line group 12 connecting the reservoir 11 and the hydraulic cylinder 4 with the hydraulic pump / motor 1 interposed; The three-port solenoid valve 1 is sequentially connected to the clamp side pipe line 12a of the hydraulic pump / motor 1.
And a hydraulic control unit provided with an insertion of an external drain type pilot check valve 7 operable by the solenoid valve 10 and a branch for the accumulator 5 and the pressure sensing unit 6. Characterized by

[0005]

In the above construction, in the clamping process, power is supplied to the electric motor 2 from the power input unit 15 through the driver 3 and simultaneously the hydraulic pump / motor 1 (hereinafter referred to as the pump 1) is driven in accordance with the signal from the signal input unit 14. In the discharge section of the pump 1, the clamp side pipe 12
a, the check member of the external drain type pilot check valve 7 is automatically opened, the piston rod of the hydraulic cylinder 4 is advanced, and after the piston rod reaches the clamp position and stops, the pressure is accumulated in the accumulator 5. Start. Here, if the set pressure is detected by the pressure sensor 6 such as the pressure switch 6 ′, the motor 2 is stopped via the driver 3. When the motor 2 is stopped, the check member of the pilot check valve 7 automatically closes, and the accumulator 5 for the clamp pressure is closed.
Is maintained. Since the branch of the take-out pipe 12c to the solenoid valve 10 is on the pump 1 side of the pilot check valve 7, even if the solenoid valve 10 has an internal leak, the accumulated pressure of the accumulator 5 may be consumed for this reason. And the clamping pressure is maintained for a long time. Next, in the unclamping step and the pressure control step, first, the pump 1 is rotated forward by appropriate means (not shown),
Is excited, the pilot oil of a relatively low pressure temporarily flows into the pilot piston of the pilot check valve 7 which is an external drain type, so that the pilot piston can be pressed and the check member of the pilot check valve 7 can be pressed. It can be forcibly opened against the accumulated pressure.
As a result, the accumulated pressure of the accumulator 5 causes the pump 1 to reversely act against the driving torque of the electric motor 2 to act as a hydraulic motor, and after consuming power, the oil flow is discharged to the reservoir 11. Here, if the drive torque of the electric motor 2 is sufficiently reduced to stop the pump 1, the unclamping process is completed.
Further, if the pump 1 is rotated forward again so as to compensate for the leakage of the hydraulic circuit by securing the driving torque, the low-pressure clamping pressure may be manually adjusted by visual observation of the pressure gauge 16 even in the region below the operating pressure of the accumulator 5 at this time. Can be adjusted. In other words, variable pressure control can be obtained even with the pilot check valve 7 utilizing the torque control by the driver 3 and the electric motor 2. As is clear from the above, the clamp pressure can be held for a long time in a state in which the supply of power is cut off by using the accumulated pressure of the accumulator 5, while the clamp pressure can be varied with less power consumption by the torque control by the electric motor 2. In addition, the circuit can be controlled, and in addition, the circuit has no loss due to the throttle element, saves energy and has a simple circuit configuration.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. FIG. 1 shows a basic embodiment of an electro-hydraulic clamp circuit. This electro-hydraulic clamp circuit includes a motor 2 ′ capable of controlling torque, such as an electric servomotor, a power input unit 15 and a signal input unit 14. A driver 3 for the electric motor 2 'having the following structure; a constant displacement hydraulic pump / motor 1' (hereinafter referred to as a pump 1 ') which can be driven by the electric motor 2' and be a hydraulic motor; A main line group 12 connecting the reservoir 11 and the single-acting hydraulic cylinder with spring 4 ′ therebetween, a one-side line 12 b divided by the pump 1 ′ and connected to the reservoir 11, a hydraulic control unit, In the clamp side line 12a which is the other side line of the pump 1 ', a pressure extraction line 12c for the three-port solenoid valve 10 is operated in order from the discharge port of the pump 1' and the solenoid valve 10. An external drain type pilot check valve 7 is inserted, and an accumulator 5 and a hydraulic pressure control unit having a branch for a pressure switch 6 ′ and a pressure gauge 16 which are pressure sensing units are provided. The operation of the electric hydraulic clamp circuit having the above configuration will be described below. The piston rod of the single-acting hydraulic cylinder 4 ′ with spring is at the retreat end at the beginning, and in the clamping stroke, power is supplied to the electric motor 2 ′ from the power input unit 15 through the driver 3 while the pump 1 ′ is connected to the signal input unit 14 at the same time. In accordance with the signal, the engine is driven forward at a variable speed, the hydraulic oil is sucked up from the reservoir 11 in the following order, the pressure in the clamp side pipe line 12a is increased, and then the check member of the external drain type pilot check valve 7 is automatically opened to open the hydraulic cylinder. The piston rod 4 'is advanced against the spring force, and after the piston rod reaches the clamp position and stops, pressure accumulation in the accumulator 5 is started. Here, if the pressure switch 6 'detects the set pressure, the motor 2' is stopped via the driver 3 by a method not shown, the check member of the pilot check valve 7 is automatically closed, and the accumulator 5 has a clamp. Pressure is maintained. Since the branch of the take-out line 12c to the solenoid valve 10 is on the pump 1 'side of the pilot check valve 7, even if the solenoid valve 10 has an internal leak, the accumulated pressure of the accumulator 5 is consumed for this purpose. And the clamping pressure is maintained for a long time. Next, in the unclamping step and the pressure control step, if the pump 1 'is first rotated forward and the solenoid valve 10 is excited immediately before and after the pump 1', the pilot piston portion of the pilot check valve 7, which is of an external drain type, is relatively small. Since the pilot oil which requires only a low pressure flows temporarily, the pilot member can be pressed and the check member of the pilot check valve 7 can be forcibly opened. As a result, the accumulated pressure of the accumulator 5 reverses the pump 1 ′ against the driving torque of the electric motor 2 ′ and acts as a hydraulic motor, so that the oil flow consuming power is discharged to the reservoir 11. Here, if the driving torque of the electric motor 2 'is sufficiently reduced, the piston rod of the hydraulic cylinder 4' returns to the original retracted end, and the unclamping process ends.
If the pump 1 'is rotated forward again to secure the drive torque and compensate for the leakage of the hydraulic circuit, the low pressure clamping pressure is manually adjusted by visual observation of the pressure gauge 16 even in the region below the operating pressure of the accumulator 5 at this time. Can do it. In other words, variable secondary pressure control can be obtained even with the pilot check valve 7 using the torque control by the driver 3 and the electric motor 2 '. As is apparent from the above, the clamp pressure can be held for a long time in a state where power supply is cut off by using the accumulated pressure of the accumulator 5, while the clamp pressure can be varied with a small power consumption by the torque control by the electric motor 2 '. In addition, the circuit has no loss due to the aperture element, saves energy, and has a simple circuit configuration. Further, in the above circuit, the power at the time of discharging the accumulator 5 may be configured to be recovered via the electric motor 2 '. Further, the pressure switch 6 'may be replaced with a pressure detector, and the pressure may be controlled in a feedback manner regardless of the operation state of the accumulator 5. Further, the hydraulic cylinder is not limited to the one with the spring. FIG. 2 shows another embodiment of the electric hydraulic clamping circuit according to the present invention. In FIG. 1, the hydraulic cylinder 4 'is replaced by a single rod type double-acting cylinder 4 "and the pressure control is performed by feedback control. There is
The same members are denoted by the same reference numerals and description thereof will be omitted. 1 "is a two-way flow, two-way rotary constant displacement hydraulic pump / motor (hereinafter referred to as pump 1"), 2 "is a two-way rotary electric motor that can control torque and also becomes a generator, and 3 'is a power recovery circuit. A driver having an adder which has an adder capable of adding and calculating a signal from the pressure detector 6 "via a signal line 13; a line 9b which branches off from the line 12b on one side and leads to the remaining port of the cylinder 4" The high-pressure priority type shuttle valve is provided between the pilot line branching from the ′ and the control port of the solenoid valve 10 and connects the intermediate port to the pilot portion of the pilot check valve 7. This is a low-pressure priority type shuttle valve interposed between the "" side and the one side pipe line 12b and connecting the intermediate port to the reservoir 11. The operation of the electric hydraulic clamp circuit having the above configuration is as follows. In the clamp stroke, the pump 1 ″ is driven to rotate forward, and the pressure in the clamp-side pipe line 12a rises. Therefore, first, the low-pressure priority type shuttle valve 8 automatically takes the right position, and the one-side pipe line 12b and the pipe line 12b ′. Is opened to the reservoir 11. At this time, the solenoid valve 10 is in the non-excited state, so that the pilot pressure acting on the pilot portion of the pilot check valve 7 is constant regardless of the operating state of the high-pressure priority type shuttle valve 9.
1 and the pilot piston of the pilot check valve 7 keeps its retracted position. The clamp pressure is controlled in a feedback manner, and if the accumulator 5 accumulates to a predetermined value, the electric motor 2 ″ is transmitted from the driver 3 ′ by a method not shown.
Try to cut off the power to. During the clamp stroke, while the piston rod of the cylinder 4 "is moving forward, the amount of oil returned from the cylinder 4" is smaller than the suction amount of the pump 1 ". In the secondary clamp pressure control step of opening the accumulator 5 and holding the clamp pressure at a low pressure, the pressure feedback loop is released by a method (not shown). The pump 1 ″ is rotated forward, and while increasing the discharge pressure, the solenoid valve 10 is energized back and forth to temporarily supply the discharge pressure oil to the pilot piston of the external drain type pilot check valve 7 to force the pilot check valve 7. And the pressure side of the clamp side pipe line 12a is detected after the discharge side of the pump 1 "and the accumulator 5 side of the cylinder 4" are in communication with each other. 6 "
Using the pressure accumulation of the accumulator 5, the pump 1 "is rotated reversely against the driving torque to operate as a hydraulic motor while monitoring the pressure in the accumulator 5, that is, the suction and discharge are reversed, and at this time, the power is electrically recovered. The pump 1 "is again rotated forward so as to compensate for the leakage of the hydraulic circuit as needed, and the secondary clamp pressure is pressure-controlled again in a feedback manner so as to comply with the request of the signal input unit 14. In the descending stroke of the cylinder 4 ″, assuming that the self-weight does not act on the cylinder 4 ″, the pressure feedback is released, the secondary clamping pressure is temporarily released as necessary, and then the torque of the electric motor 2 ″ is reversed to reduce the line 12 b. When the pressure is generated by the pump 1 ", the shuttle valve 8 automatically takes the left position, and at the same time, the cylinder 4" is pressed in the downward direction. At this time, regardless of whether the solenoid valve 10 is excited or not. The shuttle valve 9 automatically works and pushes the pilot piston of the pilot check valve 7 through this through the pressure of the pipe 12b on one side to keep the pilot check valve 7 in communication. Therefore, the shuttle valve 9 is connected to the pipe on the accumulator 5 side of the cylinder 4 ". The path, that is, the clamp-side pipe line 12 a is connected to the reservoir 11 via the shuttle valve 8. At this time, the return oil from the cylinder 4 "is bisected and one is sucked into the pump 1" and the other is supplied to the reservoir 1
Return to 1. The hydraulic cylinder 4 ″ is not limited to a single rod type, but may be a double rod type.

[0007]

As is apparent from the above description, the electric hydraulic clamping circuit of the present invention comprises a motor capable of controlling torque, a hydraulic pump / motor, a hydraulic cylinder, and a hydraulic control unit including an accumulator and the like. Then, since both the holding of the clamp pressure by the accumulator and the variable pressure control by the electric motor are made compatible, the clamping pressure can be held for a long time in a state where the power supply is cut off,
Variable clamp pressure control can be performed with low power consumption, and there is an effect that the loss of the throttle element in the circuit is eliminated and energy is saved and the circuit configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic embodiment of an electric hydraulic clamping circuit according to the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the electric hydraulic clamping circuit of the present invention.

FIG. 3 is a circuit diagram showing a conventional electric hydraulic circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hydraulic pump motor, 2 ... Electric motor which can control torque, 3 ... Driver, 4 ... Hydraulic cylinder, 5 ... Accumulator, 6 ... Pressure sensing part, 7 ... External drain type pilot check valve, 12a ... Clamp side pipeline.

Claims (1)

[Claims] An electric motor capable of controlling torque in at least one direction and capable of reversing; a driver for the electric motor having a power input unit and a signal input unit;
A hydraulic pump / motor 1 driven by the electric motor 2 and also serving as a hydraulic motor; a main line group 12 connecting the reservoir 11 and the hydraulic cylinder 4 with the hydraulic pump / motor 1 interposed; The three-port solenoid valve 1 is sequentially connected to the clamp side pipe line 12a of the hydraulic pump / motor 1.
And a hydraulic control unit provided with an insertion of an external drain type pilot check valve 7 operable by the solenoid valve 10 and a branch for the accumulator 5 and the pressure sensing unit 6. An electric hydraulic clamping circuit.