JP2672090B2 - Cylinder closed circuit hydraulic pump controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a cylinder closed circuit hydraulic pump control device. (Prior Art) For example, as a drive closed circuit of a reciprocating cylinder used in an injection molding machine, the one configured as shown in FIG. 3 has been proposed by the present applicant (Japanese Patent Application No. 61-183952).
issue). Reference numeral 1 is a cylinder, 2 is a reversible rotary hydraulic pump, and 3 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 during forward movement. A high-pressure accumulator 6 is provided in the middle of the discharge circuit 5, and a check valve 7 and a solenoid are provided as a valve device that blocks a reverse flow of pressure oil when the piston 4 moves forward and allows a reverse flow on the return side. A normally-closed no-leak valve 8 driven by. The check valve 7 is provided on the upstream side of the accumulator 6, and the no-leak valve 8 is provided in parallel therewith, and short-circuits the upstream side of the check valve 7 and the downstream side of the accumulator 6. The suction port (In) of the hydraulic pump 2 is connected to the other oil chamber B of the cylinder 1 via a suction circuit 9. Further, the drain port (D) of the hydraulic pump 2 is connected to the low pressure accumulator 10 for replenishing and collecting the hydraulic oil in the closed circuit. The accumulator 10 is connected to the upstream side of the check valve 7 of the discharge circuit 5 via the check valve 11 and to the suction circuit 9 via the check valve 12. The check valves 11 and 12 are the discharge circuit 5
Depending on the pressure of the suction circuit 9 and the check valve 11 on the low pressure side or
At the same time that 12 opens, the check valve 12 or 11 on the high-pressure side closes. The controller 13 controls the drive of the electric motor 3 and the no-leak valve 8. The controller 13 opens and closes the no-leak valve 8 based on the detection signal of the pressure sensor 14 provided in the discharge circuit 5 downstream of the check valve 7. The rotation of the hydraulic pump 2 is controlled as described below. Reference numeral 15 represents a drive circuit of the electric motor 3. That is, the controller 13 rotates the hydraulic pump 2 in the forward direction when the cylinder 1 moves forward to supply the hydraulic oil in the oil chamber B to the hydraulic chamber A. In this way, the pressure of the high-pressure accumulator 6 is used to pressurize and hold the cylinder 1 that has made a predetermined stroke in that position. The pressure of the accumulator 6 is detected by the pressure sensor 14, but when the pressure is lower than the set high pressure value, the hydraulic pump 2 is normally rotated by a signal from the controller 13. 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. Therefore, the hydraulic oil of 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 pressure causes the piston 4 to be pressurized and held at the forward position, and the hydraulic pump 2 is stopped when the pressure of the accumulator 6 reaches the set high pressure value. Further, when the cylinder 1 returns, the controller 13 opens the no-leak valve 8 and reversely rotates the hydraulic pump 2. By driving the hydraulic pump 2, the hydraulic oil in the oil chamber A is transferred to the oil chamber B.
When the piston 4 reaches the retracted position, the no-leak valve 8 is closed and the drive of the hydraulic pump 2 is stopped. At this time, since the suction circuit 9 becomes high pressure and the discharge circuit 5 becomes low pressure, the check valve 12 is closed and the check valve 11 is opened.
The pressure oil of the high pressure accumulator 6 returns to the low pressure accumulator 10. (Problems to be Solved by the Invention) By the way, in such a device, in order to increase the pressure in the accumulator 6, after the forward movement of the cylinder 1,
When the hydraulic pump 2 is driven and pressure is accumulated in the high-pressure accumulator 6, the hydraulic pump 2 is stopped when the hydraulic pressure reaches a set high pressure value. In that case, the hydraulic pump 2
Immediately after the stop, as shown in FIG. 4, a peak pressure rises on the suction circuit 9 side, and this peak pressure pressurizes the cylinder 1 on the backward movement side, causing a problem that the cylinder holding force instantaneously decreases. This is because the partial pressure oil in the discharge circuit 5 (pressure oil downstream of the check valve 7) that had been pressurized until just before the hydraulic pump 2 stopped stopped the pump 2 (the electric motor 3 has a zero drive current and is in a free state). , And reversely rotates and flows into the suction circuit 9 on the low pressure side, whereby the pressure relationship between the discharge circuit 5 and the suction circuit 9 is momentarily reversed, and the check valve 11 opens and the check valve 12 Is closed, and in this state, the hydraulic pump 2 continues to rotate due to inertia, so that the peak pressure rises in the suction circuit 9. (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 high pressure accumulator and a valve device that prevents backflow of pressure oil during forward movement of the cylinder and allows backflow on the return side of the cylinder are installed. In a hydraulic pump control device with a cylinder closed circuit that prevents the high pressure of the accumulator from escaping to the hydraulic pump side and keeps the cylinder under pressure, the hydraulic pump is driven when the pressure inside the high pressure accumulator is raised or lowered. When the set pressure to stop is reached, pump control means is added to drive the hydraulic pump for a predetermined time and then stop so as to add resistance to the flow of pressure oil that flows backward. You. (Operation) When the pressure of the high-pressure accumulator reaches the set pressure at which the driving of the hydraulic pump should be stopped, the hydraulic pump is further driven by the pump control means so as to impart resistance to the backward flow of the hydraulic oil. Then stopped. Therefore, the pressure difference between the discharge circuit and the suction circuit does not occur immediately after the pump is stopped, and the peak pressure due to the reverse rotation of the pump does not rise. (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 port (Out) and an oil circuit A that connects the oil chamber A that drives the piston 24 of the cylinder 20 during forward movement, 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 interposed in the discharge circuit 23, 27 is a check valve, 28 is a no-leak valve, and a check valve 27
And the no-leak valve 28 constitutes a valve device that blocks the reverse flow of the pressure oil when the piston 24 moves forward and allows the reverse flow when returning. 29 is a low pressure accumulator connected to the drain port (D) of the hydraulic pump 21.
29 is connected to the discharge circuit 23 via the check valve 30 and to the suction circuit 25 via the check valve 31. 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 controller 33 reaches a set pressure at which the drive of the hydraulic pump should be stopped when the pressure of the high pressure accumulator 26 is raised or lowered, the controller 33 lowers the pressure in the high pressure accumulator 26 by a predetermined value ΔP, and flows backward. A pump control circuit 36 that drives the hydraulic pump 21 so as to add resistance to the flow of the pressure oil and stops the hydraulic pump 21 when a predetermined time has elapsed is additionally provided. Therefore, the controller 33 supplies the hydraulic oil in the oil chamber B to the oil chamber A by rotating the hydraulic pump 21 in the forward direction when the cylinder 20 moves forward. Then, after the forward movement, the hydraulic pump 21 is further operated,
Pressure oil is supplied from the low-pressure accumulator 29 to the discharge circuit 23 and accumulated in the high-pressure accumulator 26. In this case, the controller 33 controls the drive of the hydraulic pump 21 based on the signal from the pressure sensor 35 so that the pressure in the high pressure accumulator 26 reaches the set high pressure value. When the value is reached, the pump control circuit 36 lowers the pressure in the high pressure accumulator 26 by a predetermined value ΔP, so that the hydraulic pump 21 is driven for a further predetermined time Δt ₁ while reducing the discharge pressure (see FIG. 2). . At this time, the no-leak valve 28 is kept closed. As a result, the partial pressure oil that has been pressurized in the discharge circuit 23 (pressure oil downstream of the check valve 27) tries to flow back to the suction circuit 25 by rotating the pump 21 in the reverse direction. Since the discharge pressure gives resistance to the flow of pressure oil, the pressure relationship between the suction circuit 25 and the discharge circuit 23 does not reverse, and the suction circuit 25
The pressure oil that has flowed back to is returned to the low pressure accumulator 29 through the check valve 31. The check oil 27 and the normally closed no-leak valve 28 prevent the pressure oil in the high pressure accumulator 26 from flowing back to the hydraulic pump 21 side, and the piston 24 is pressurized and held. Further, when the cylinder 20 is returned, the controller 33 opens the no-leak valve 28, reversely rotates the hydraulic pump 21, returns the pressure oil of the high pressure accumulator 26 to the low pressure accumulator 29, and at the same time, operates the hydraulic oil from the oil chamber A. Is supplied to the oil chamber B, and when the piston 24 reaches the retracted position, the no-leak valve 28
Is closed and the drive of the hydraulic pump 21 is stopped. The predetermined value ΔP and the predetermined time Δt ₁ are the discharge circuit 23.
Or the size (diameter or volume) of the suction circuit 25, and the relationship between ΔP and Δt ₁ is not unique. If ΔP is increased, Δt ₁ is decreased, and if ΔP is decreased, Δt ₁ is increased. There is a need. Further, the pump control circuit 36 controls the pressure in the high pressure accumulator 26 to decrease by a predetermined value ΔP when the pump is stopped, but the invention is not necessarily limited to this. In short, the hydraulic pump 2 is braked. However, the control for removing the residual high pressure of the discharge circuit 5 may be performed. (Effects of the Invention) In summary, according to the present invention, when the pressure in the high-pressure accumulator is raised or lowered and the set pressure at which the drive of the hydraulic pump should be stopped has been reached, resistance is imparted to the reverse flow of pressure oil. Since pump control means is added to drive the hydraulic pump for a specified time and then stop, peak pressure does not rise on the suction circuit side immediately after the hydraulic pump is stopped, and the pressure holding force of the cylinder is accurately adjusted to the specified value. The effect that can be controlled to.

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, 36
...... Pump control 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] Connect the discharge circuit of the reversible rotary hydraulic pump to one oil chamber of the reciprocating cylinder, and connect the suction circuit to the other oil chamber of the reciprocating cylinder, and to this discharge circuit, a high pressure accumulator and the reverse flow of pressure oil when the cylinder moves forward. A valve device is installed to prevent backflow when the cylinder moves back, and after the cylinder moves forward, the valve device prevents the high pressure of the accumulator from escaping to the hydraulic pump side and keeps the cylinder pressurized. In the cylinder closed circuit hydraulic pump control device described above, when the pressure in the high pressure accumulator is raised or lowered, a predetermined value is given to apply resistance to the backward flow of pressure oil when the set pressure at which the drive of the hydraulic pump is stopped is reached. A hydraulic pump control device for a cylinder closed circuit, further comprising pump control means for driving the hydraulic pump for a predetermined time and then stopping it.