JPS63255582A - Closed circuit pressure controller for reciprocation type cylinder - Google Patents

Abstract

PURPOSE:To prevent the generation of peak pressure in a suction circuit by installing a means for accelerating the output of the valve opening and closing signals for a no-leak valve by a prescribed time by the output of the drive stop signal for a hydraulic pump in the case when the pressure of an accumulator is lowered to a set value. CONSTITUTION:A pump stop control circuit 36 controls the drive of a hydraulic pump 21 by increasing and decreasing the pressure of an accumulator 26. A signal processing circuit 37 for outputting the drive signal supplied into the hydraulic pump 21 late by a prescribed time in comparison with the valve opening signal supplied to a no-leak valve 28 and the valve closing signal early in the case when the pressure of the accumulator 26 for high pressure is lowered to a set value. Therefore, the generation of peak pressure in the suction circuit, accompanied with the delay of the opening operation of the no-leak valve, is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) This invention relates to an improvement in a closed circuit pressure control device for a reciprocating type sill.

(Prior Art) As a closed circuit for a reciprocating cylinder used in an injection molding machine, the applicant has proposed a circuit configured as shown in FIG. 3 (see Japanese Patent Application No. 183952/1983). ).

1 is a reciprocating type sill, 2 is a reversible rotary hydraulic pump, and 3 is an electric motor (servo motor) that drives the hydraulic pump 2. A discharge port (Out) of the hydraulic pump 2 is connected via a discharge circuit 5 to an oil chamber A that drives the piston 4 of the cylinder 1 forward. In the middle of this discharge circuit 5, an accumulator 6 for high pressure and a check valve 7 for preventing backflow of pressure oil are interposed, and in parallel with these, the upstream of the check valve 7 and the downstream of the accumulator 6 are short-circuited. No-leak valve 8 (solenoid valve)
is provided.

A suction port (In) of the hydraulic pump 2 is connected to the other oil chamber B of the cylinder 1 through a suction circuit 9. Further, the drain (D) of the hydraulic pump 2 is connected to a low pressure accumulator 10. This accumulator 10 is connected to the discharge circuit 5 via a check valve 11 and to the suction circuit 9 via a check valve 12.
When the check valve 11 or 12 on the low pressure side opens depending on the pressure of the suction circuit 9, the check valve 12 or 11 on the high pressure side closes.

The controller 13 controls the energization of the electric motor 3, that is, the drive of the hydraulic pump 2 and the opening and closing of the no-leak valve 8. Based on this, the accumulating force of the accumulator 6, that is, the pressurizing force of the shilling 1 is also controlled. Reference numeral 15 indicates a drive circuit for the electric motor 3.

That is, the control unit 13 rotates the hydraulic pump 2 in forward and reverse directions so as to supply the hydraulic oil in the oil chamber B or A to the oil chamber A or B when the cylinder 1 is reciprocating. In addition, when pressurizing the piston 4 in the forward position after the forward movement of the cylinder 1, the pressure of the high-pressure accumulator 6 is used. When increasing this pressure (holding force of the cylinder 1), the no-leak valve 8 is closed and the hydraulic pressure is increased. Rotate pump 2 forward. Since the discharge circuit 5 becomes high pressure due to the rotation of the hydraulic pump 2,
The check valve 11 is closed and the check valve 12 is opened, and the pressure oil in the low-pressure accumulator 10 is pressurized by the hydraulic pump 2 from the suction circuit 9 and sent to the high-pressure accumulator 6. This increased pressure holds the piston 4 under pressure, and the hydraulic pump 2 is stopped when the pressure of the accumulator 6 reaches a set high pressure value.

On the other hand, when lowering the pressure in the high-pressure accumulator 6, the no-leak valve 8 is opened and the hydraulic pump 2 is rotated in the opposite direction. At this time, the pressure oil in the high-pressure accumulator 6 is returned from the discharge circuit 5 through the hydraulic pump 2 to the suction circuit 9, and then back to the low-pressure accumulator 10 via the check valve 12, so that the pressure in the high-pressure accumulator 6 is adjusted to the set low pressure. When the value is reached, the hydraulic pump 2 is stopped and the no-leak valve 8 is closed at the same time.

(Problem to be Solved by the Invention) In this type of device, when lowering the pressure in the high-pressure accumulator, the controller 13 sends a drive signal to the hydraulic pump 2 and at the same time opens the no-leak valve 8. Although it is designed to output a signal, there is a time delay (operation delay) from when the no-leak valve 8 receives the valve-opening signal from the controller 13 until it actually switches, and during that time, the no-leak valve 8 is not fully opened. Nevertheless, since the hydraulic pump 2 is driven, the pressure in the discharge circuit 5 decreases and the pressure in the suction circuit 9 increases as shown in FIG. 4, which causes one of the check valves 11 to open. Since the other check valve 12 is closed, a peak pressure builds up in the suction circuit 9, causing a problem in that the holding force (pressure force) of the sill 1 is drastically reduced instantaneously. Furthermore, even when the pressure of the accumulator 6 drops below the set value, the no-leak valve 8 is not yet fully closed when the hydraulic pump 2 is stopped due to a time delay.
High pressure accumulator 6 due to leakage from no-leak valve 8
There was also the problem that the pressure of the system would drop below the set value.

(Means for Solving the Problems) In order to solve these problems, the present invention provides a reciprocating hydraulic pump with a discharge circuit in one oil chamber and a suction circuit in the other oil chamber of the reciprocating type cylinder. A check valve that prevents backflow of the accumulator and pressure oil is connected to the discharge circuit, and a normally closed no-leak valve is provided in parallel with the check valve.
In a closed-circuit pressure control device for a reciprocating cylinder that maintains a pressurized cylinder based on the accumulated pressure of an accumulator by controlling the drive of a hydraulic pump and a no-leak valve, no-leak occurs when the pressure of the accumulator is lowered to a set value. A signal processing means is provided that advances the output of the opening/closing signal to the valve by a predetermined time by outputting a drive stop signal to the hydraulic pump.

(Function) When lowering the pressure of the high-pressure accumulator, the open/close signal to the no-leak valve is output a predetermined time earlier than the drive stop signal to the hydraulic pump, that is, the time delay of the no-leak valve. Since this coincides with the timing when the valve actually opens and closes, peak pressure will build up in the suction circuit due to the delay in the opening of the no-leak valve, and the pressure in the high-pressure accumulator will drop below the set value due to the delay in the closing of the no-leak valve. There is no decline.

(Example) In Fig. 1, 20 is a reciprocating type cylinder, 21 is a hydraulic pump, 22 is an electric motor (servo motor), and 23 is a discharge port (Out) of the hydraulic pump 21 and a piston 24 of the cylinder 20 on the reciprocating side. a discharge circuit connecting an oil chamber A driven to a 2
5 is a suction circuit that connects the suction port (In) of the pump 21 and the other oil chamber B of the syringe 20, and 26 is a discharge circuit 23.
27 is a check valve that prevents the backflow of pressure oil, 28 is a no-leak valve that is installed in parallel with the check valve 27, and 29 is connected to the drain port (D) of the hydraulic pump 21. This accumulator 29 is connected to the discharge circuit 2 through a check valve 30.
3 and is also connected to the suction circuit 25 via a check valve 31. Note that the check valves 30 and 31 are configured such that, depending on the pressures of the discharge circuit 23 and the suction circuit 25, the low pressure side opens and the high pressure side closes at the same time.

33 is a controller that controls energization of the electric motor 8! 22, that is, driving the hydraulic pump 21 and opening and closing of the no-leak valve 28; 34 is a drive circuit for the electric motor 22; and 35 is a controller that detects the pressure in the high-pressure accumulator 26. A pressure sensor is shown. In this case, the controller 33 performs an operation to lower the set pressure by a predetermined value ΔP when the pressure of the high-pressure accumulator 26 (holding force of the shilling 20) reaches the set pressure, thereby resisting the flow of pressure oil that flows backward. a pump stop control circuit 36 that controls the drive of the hydraulic pump 21 so as to give the same pressure, and a drive signal to the hydraulic pump 21 and a valve opening signal to the no-leak valve 28 when lowering the pressure of the high pressure accumulator 26 to the set pressure. Predetermined III
A signal processing circuit 37 is provided which outputs a valve closing signal to the no-leak valve 28 a predetermined time Δt3 earlier than a stop signal for the hydraulic pump 21.

Therefore, when the controller 33 lowers the pressure in the high-pressure accumulator 26 that serves as the pressure holding force for the cylinder 20, it opens the leak valve 28 and reversely rotates the hydraulic pump 21. At this time, the signal processing circuit 37 As shown in FIG. 2, the drive signal to the hydraulic pump 21 is outputted a predetermined time Δc (time delay in the opening operation of the no-leak valve 28) than the opening signal to the no-leak valve 28, so the hydraulic pump 21 Since the drive timing of the 7-leak valve 28 coincides with the timing when the leak valve 28 actually opens, the hydraulic pump 21 is driven when the no-leak valve is not fully opened, so that the suction circuit 25 is pressurized and the peak pressure rises. There is no such thing. In this case, the pressure oil in the high pressure accumulator 26 is 7
- suction channel 2 through leak valve 28 and hydraulic pump 21;
5, it is further returned to the low pressure accumulator 29 via the check valve 31.

When the pressure of the high-pressure accumulator 26 drops to around the set value, the valve closing signal to the no-leak valve 28 is opened at a predetermined time Δ13 (time delay in closing the no-leak valve 28).
Since the 7-leak valve 28 is actually closed when the pressure of the high-pressure accumulator 26 reaches the set value, the pressure does not drop below the set value due to leakage of the no-leak valve 28. . In this case, when the pressure of the high-pressure accumulator 26 reaches the set value, the pump stop control circuit 36 outputs a correction signal that lowers the set value by a predetermined value ΔP, and further provides a predetermined resistance to the flow of pressure oil flowing backward. The hydraulic pump 21 is driven for a time Δt and then stopped. As a result, the pressure oil downstream of the check valve 27 (residual high pressure) is not braked by the hydraulic pump 21, and the suction circuit 2
It gradually flows to 5. Note that the pressure oil in the high-pressure arc umulator 26 is prevented from flowing back toward the hydraulic pump 21 by the check valves 27 and 7-leak valve 28, and the piston 4 is kept pressurized at a set value.

On the other hand, when increasing the pressure of the high-pressure arch umulator 26, the hydraulic pump 21 is closed while the no-leak valve 28 is closed.
When rotated forward, the check valve 30 closes and the check valve 31 opens, so the pressure oil in the low pressure accumulator 29 is sent to the high pressure accumulator 26, and when this pressure reaches the set high pressure value, the pump stops. Control circuit 36 stops hydraulic pump 21 as described above. Further, when the cylinder 20 is reciprocating, the hydraulic pump 21 is rotated in forward and reverse directions to supply hydraulic oil from the oil chamber B or A to the chamber 8 or B.

(Effects of the Invention) In summary, according to the present invention, there is provided a signal processing means that advances the output of the opening/closing signal to the no-leak valve by a predetermined time by outputting a drive stop signal to the hydraulic pump when lowering the pressure of the accumulator to a set value. As an additional feature, the timing when the hydraulic pump stops driving and the actual opening/closing timing of the 7-leak valve are made to coincide, so that peak pressure does not build up in the suction circuit due to a delay in the opening operation of the no-leak valve (time delay). Similarly, it is possible to prevent the pressure of the high-pressure archumulator from falling below a set value due to a delay in the closing operation, and it is possible to accurately control the pressure holding force of the shilling to a predetermined value.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram showing an embodiment of the present invention, Fig. 2 is a timing chart showing an example of its control contents, Fig. 3 is a circuit configuration diagram showing the prior art, and Fig. 4 is a circuit diagram showing its control contents. It is a timing chart which shows an example. 20... Schilling, 21... Hydraulic pump, 23...
・Discharge circuit, 25... Suction circuit, 26... High pressure arc umulator, 27... Check valve, 28.../-
Leak valve, 2...Low pressure accumulator, 30.
31... Check valve, 33... Controller, 37...
・Signal processing circuit. Figure 2 Figure 6

Claims (1)

[Claims] Connect the discharge circuit of the reversible hydraulic pump to one oil chamber of the reciprocating cylinder, and the suction circuit to the other oil chamber.
This discharge circuit is provided with a check valve that prevents backflow of the accumulator and pressure oil, and a normally closed no-leak valve in parallel with this check valve, and by controlling the drive of the hydraulic pump and the no-leak valve, the accumulated pressure of the accumulator is adjusted. In a closed-circuit pressure control device for a reciprocating cylinder that maintains the cylinder in a pressurized state based on the pressure, when the pressure of the accumulator is lowered to the set value, an open/close signal is output to the no-leak valve, and a drive stop signal is output to the hydraulic pump. 1. A closed-circuit pressure control device for a reciprocating cylinder, characterized in that it is equipped with a signal processing means for advancing the pressure by a predetermined amount of time.