JP2672091B2 - Closed circuit pressure controller for reciprocating cylinder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a closed circuit pressure control device for a reciprocating cylinder. (Prior Art) A closed circuit of a reciprocating cylinder used in an injection molding machine or the like is proposed by the applicant of the present invention, which is configured as shown in FIG. 3 (see Japanese Patent Application No. 61-183952). ). 1 is a reciprocating cylinder, 2 is a reversible rotary hydraulic pump, 3 is
Is an electric motor (servo motor) for driving the hydraulic pump 2. The 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 in the forward direction. An accumulator 6 for high pressure and a check valve 7 for preventing a backflow of pressure oil are provided in the middle of the discharge circuit 5, and the upstream side of the check valve 7 and the downstream side of the accumulator 6 are short-circuited in parallel with these. No leak valve 8 (solenoid valve)
Is provided. The suction port (In) of the hydraulic pump 2 is connected to the other oil chamber B of the cylinder 1 by the suction circuit 9, and the drain port (D) of the hydraulic pump 2 is connected to the low pressure accumulator 10. This accumulator 10 has a check valve 11
Connected to the discharge circuit 5 via the check valve 12 and to the suction circuit 9 via the check valve 12, and the check valves 11 and 12 are connected to the discharge circuit 5 and the suction circuit 9 respectively.
When the low pressure side check valve 11 or 12 is opened according to the pressure of 1, the high pressure side check valve 12 or 11 is closed. The controller 13 controls the energization of the electric motor 3, that is, the drive of the hydraulic pump 2 and the opening / closing of the no-leak valve 8. The controller 13 outputs a signal from the pressure sensor 14 for detecting the pressure in the high pressure accumulator 6. Based on this, the accumulated pressure of the accumulator 6, that is, the applied pressure of the cylinder 1 is also controlled. Reference numeral 15 represents a drive circuit of the electric motor 3. That is, the control unit 13 rotates the hydraulic pump 2 forward and backward 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 reciprocates. Further, after the forward movement of the cylinder 1, the pressure of the high pressure accumulator 6 is used when the piston 4 is pressurized at the forward position, and 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 has a 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 of the low pressure accumulator 10 is pressurized from the suction circuit 9 by the hydraulic pump 2 and sent to the high pressure accumulator 6. The piston 4 is pressurized and held by this rising pressure,
The hydraulic pump 2 is stopped when the pressure of the accumulator 6 reaches the set high pressure value. On the other hand, when lowering the pressure of the high pressure accumulator 6, the no-leak valve 8 is opened and the hydraulic pump 2 is rotated in the reverse direction. At this time, the pressure oil of the high-pressure accumulator 6 is opened from the discharge circuit 5 to the suction circuit 9 through the hydraulic pump 2 and the no-leak valve 8 is opened. It is returned to the low pressure accumulator 10 via the valve 12, and when the pressure of the high pressure accumulator 6 reaches the set low pressure value, the drive of the hydraulic pump 2 is stopped and the no-leak valve 8 is closed. (Problems to be Solved by the Invention) In such an apparatus, when the pressure of the high-pressure accumulator 6 is lowered, the controller 13 outputs a drive signal to the hydraulic pump 2 and a valve open signal to the no-leak valve 8 at the same time. However, there is a time delay (operation delay) from the receipt of the valve opening signal from the controller 13 to the actual switching of the no-leak valve 8, and during that time the no-leak valve 8 is not fully opened. Nevertheless, since the hydraulic pump 2 is driven, as shown in FIG.
The pressure in the suction circuit 9 rises and the pressure in the suction circuit 9 rises. As a result, one check valve 11 opens and the other check valve 12 closes. This causes a problem that the holding force (pressing force) is suddenly reduced. Further, even when the pressure of the accumulator 6 drops below the set value, the no-leak valve 8 has not been closed at the time of stopping the hydraulic pump 2 due to a time delay, so leakage from the no-leak valve 8 causes the high-pressure accumulator 6 to leak. There is also a problem that the pressure drops below the set value. (Means for Solving Problems) In order to solve such problems, the present invention provides a reversible rotary hydraulic pump with a discharge circuit in one oil chamber of a reciprocating cylinder and a suction circuit in the other oil chamber. Connected to each of these discharge circuits, a check valve that blocks the reverse flow of the accumulator and pressure oil, and a normally closed no-leak valve in parallel with this check valve are installed, and the accumulator is controlled by controlling the drive of the hydraulic pump and the no-leak valve. In a closed-circuit pressure control device for a reciprocating cylinder that keeps the cylinder in a pressurized state based on the accumulated pressure of, the output of the open / close signal to the no-leak valve is driven to the hydraulic pump when the pressure of the accumulator is reduced to the set value. A signal processing means for advancing the operation delay time of the no-leak valve from the output of the signal and the stop signal is additionally provided. (Operation) When lowering the pressure of the high-pressure accumulator, the open / close signal to the no-leak valve is output earlier than the drive signal and the stop signal to the hydraulic pump by the operation time delay of the no-leak valve. Since the no-leak valve actually opens and closes at the same time, peak pressure rises in the suction circuit due to the no-leak valve opening operation delay, and the no-leak valve closing operation delay causes the high-pressure accumulator pressure to fall below the set value. There is no such thing as a drop. (Embodiment) In FIG. 1, 20 is a reciprocating cylinder, 21 is a hydraulic pump, 22 is an electric motor (servo motor), and 23 is a hydraulic pump 21.
Discharge circuit (Out) connected to the oil chamber A that drives the piston 24 of the cylinder 20 to the forward side, and 25 connects the suction port (In) of the pump 21 and the other oil chamber B of the cylinder 20. Suction circuit, 26 is a high-pressure accumulator installed in the discharge circuit 23, 27 is a check valve for blocking backflow of pressure oil, 28 is a no-leak valve installed in parallel with the check valve 27, and 29 is a hydraulic pump. twenty one
An accumulator for low pressure connected to the drain port (D) of the accumulator 29 is connected to the discharge circuit 23 via the check valve 30 and to the suction circuit 25 via the check valve 31. The check valves 30 and 31 are connected to the discharge circuit 23 and the suction circuit 25.
The low pressure side opens and the high pressure side closes at the same time according to the pressure. And 33 is energization of the electric motor 22, that is, the hydraulic pump 21.
Is a controller for controlling the driving of the motor and the opening / closing of the no-leak valve 28, 34 is a drive circuit for the electric motor 22, and 35 is a pressure sensor for detecting the pressure in the accumulator 26 for high pressure. In this case, when the pressure of the high-pressure accumulator 26 (holding force of the cylinder 20) is raised or lowered, the controller 33 performs an operation of lowering the set pressure by a predetermined value ΔP to resist the flow of backflowing pressure oil. And a pump stop control circuit 36 for controlling the drive of the hydraulic pump 21 so as to apply the drive signal to the hydraulic pump 21 when the pressure of the high pressure accumulator 26 is reduced to a set pressure. A signal processing circuit 37 that delays the opening operation delay time Δt _{2 of the} no-leak valve 28 more quickly and outputs the closing signal to the no-leak valve 28 earlier than the stop signal of the hydraulic pump 21 by the closing operation delay time Δt _{3 of the} no-leak valve 28. Attached. Therefore, when the controller 33 reduces the pressure of the high pressure accumulator 26 as the pressure holding force of the cylinder 20,
The no-leak valve 28 is opened to rotate the hydraulic pump 21 in the reverse direction. At this time, as shown in FIG. 2, the signal processing circuit 37 outputs the drive signal to the hydraulic pump 21 to the no-leak valve from the open signal to the no-leak valve 28. Since the opening delay time Δt _{2 of the} valve 28 is output late, the drive timing of the hydraulic pump 21 coincides with the actual opening timing of the no-leak valve 28. The suction circuit 25 is pressurized by driving 21 so that the peak pressure does not rise. In this case, the high pressure accumulator 26
The pressure oil is returned to the suction circuit 25 through the no-leak valve 28 and the hydraulic pump 21, and further to the low pressure accumulator 29 through the check valve 31. Further, when the pressure of the high-pressure accumulator 26 drops near the set value, this time the valve closing signal to the no-leak valve 28 is output earlier by the closing operation delay time Δt _{3 of the} no-leak valve 28, so the pressure of the high-pressure accumulator 26 increases. Since the no-leak valve 28 is actually closed when the set value is reached, the pressure does not drop below the set value due to the leak of the no-leak valve 28. In this case, the pump stop control circuit 36 outputs a correction signal for decreasing the set value by a predetermined value ΔP when the pressure of the high pressure accumulator 26 reaches the set value, and further sets a predetermined value so as to impart resistance to the backward flow of the pressure oil. The hydraulic pump 21 is driven and stopped for the time Δt ₁ . As a result, the pressure oil (remaining high pressure) downstream of the check valve 27 gradually flows into the suction circuit 25 while being braked by the hydraulic pump 21. The check oil 27 and the no-leak valve 28 prevent the pressure oil of the high-pressure accumulator 26 from flowing back to the hydraulic pump 21 side, and pressurize and hold the piston 4 at the set value. On the other hand, when increasing the pressure of the high pressure accumulator 26, if the hydraulic pump 21 is rotated in the forward direction while the no-leak valve 28 is closed, the check valve 30 is closed and the check valve 31 is opened, so the pressure oil of the low pressure accumulator 29 is increased. Is sent to the high pressure accumulator 26, and when this pressure reaches the set high pressure value, the pump stop control circuit 36 stops the hydraulic pump 21 as described above. When the cylinder 20 reciprocates, the hydraulic pump 21 is rotated in the forward and reverse directions to supply the hydraulic oil in the oil chamber B or A to A or B. (Effects of the Invention) In summary, according to the present invention, when the pressure of the accumulator is lowered to the set value, the output of the open / close signal to the no-leak valve is changed from the output of the drive signal and the stop signal to the hydraulic pump to the operation delay time of the no-leak valve. By adding a signal processing means to accelerate it, the drive timing and stop timing of the hydraulic pump are made to coincide with the actual opening and closing timing of the no-leak valve. It is possible to prevent the pressure of the high pressure accumulator from falling below the set value due to the rise of the peak pressure and the delay of the closing operation, and it is possible to obtain the effect that the pressure holding force of the cylinder can be accurately controlled to a predetermined value. To be

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a timing chart showing an example of control contents, and FIG. 3 is a circuit configuration diagram showing prior art. FIG. 4 is a timing chart showing an example of the control contents. 20 …… Cylinder, 21 …… Hydraulic pump, 23 …… Discharge circuit,
25 …… Suction circuit, 26 …… High-voltage accumulator, 27
...... Check valve, 28 ...... No leak valve, 29 ...... Low pressure accumulator, 30,31 ...... Check valve, 33 ...... Controller, 37 ...... Signal processing circuit.

Continuation of front page    (72) Inventor Yoshitake Yonekubo               1805 Asamizodai, Sagamihara-shi 1 Kayaba industry               Sagami Factory Co., Ltd.                (56) References JP-A-63-39315 (JP, A)                 JP 63-99921 (JP, A)

Claims (1)

(57) [Claims] The reversible rotary hydraulic pump discharge circuit is connected to one oil chamber of the reciprocating cylinder, and the suction circuit is connected to the other oil chamber, respectively, and an accumulator and a check valve for preventing backflow of pressure oil are provided in this discharge circuit. A normally closed no-leak valve is installed in parallel with the check valve to control the drive of the hydraulic pump and the no-leak valve to maintain the cylinder in a pressurized state based on the accumulated pressure of the accumulator. In the device, when the pressure of the accumulator is lowered to a set value, a signal processing means for advancing the opening / closing signal output to the no-leak valve by the operation delay time of the no-leak valve from the output of the drive signal and the stop signal to the hydraulic pump is provided. Characteristic reciprocating cylinder closed circuit pressure control device.