JP6702491B1 - Die cushion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress surge pressure generated from a hydraulic cylinder in die cushion pressure control. A die cushion device includes a hydraulic cylinder (10) for moving a cushion pad (14) up and down, a hydraulic pump (P) for supplying hydraulic oil from an oil tank (T) to the hydraulic cylinder (10), A relief valve (20) that returns the hydraulic oil discharged from the hydraulic cylinder (10) to the oil tank, a pressure sensor (PS) that detects the pressure of the hydraulic oil that is the die cushion pressure of the hydraulic cylinder (10), and a hydraulic pump. A control device (40) for controlling the flow rate and pressure of hydraulic oil supplied from (P) to the hydraulic cylinder (10). The control device (40) controls the rotation speed of the hydraulic pump (P) so that the pressure of the hydraulic oil detected by the pressure sensor (PS) becomes the die cushion pressure command value, and at the same time, controls the pressure sensor (PS). When the detected pressure of the hydraulic oil is equal to or higher than the set pressure of the relief valve (20), the hydraulic pump (P) is rotated in the reverse direction. [Selection diagram] Figure 1

Description

The present invention relates to a die cushion device of a press machine.

2. Description of the Related Art Conventionally, as a die cushion device for a press machine, there is an air type device that controls die cushion pressure by air pressure.

However, in the air type die cushion device, there is a problem that the cylinder diameter becomes large and the device becomes large in size, and since pressure of air having compressibility is used, pressure adjustment and precise position control are difficult. There's a problem.

Therefore, in order to solve such a problem, a die cushion device using a hydraulic cylinder is used in a press machine (for example, see JP-A-2006-142312 (Patent Document 1)).

Japanese Patent Laid-Open No. 2006-142312

In the die cushion device using the hydraulic cylinder, since hydraulic oil having a lower compressibility than air is used, a large surge pressure is generated in the hydraulic circuit when an external force is generated during press molding, which adversely affects molding. There is.

The present disclosure proposes a die cushion device that suppresses surge pressure generated from a hydraulic cylinder in die cushion pressure control of a press machine.

The die cushion device of the present disclosure is
A hydraulic cylinder that moves the cushion pad up and down,
A first hydraulic pump for supplying hydraulic oil from an oil tank to the hydraulic cylinder;
A relief valve for returning the hydraulic oil discharged from the hydraulic cylinder to the oil tank,
A pressure sensor that detects the pressure of the hydraulic oil in the flow path between the hydraulic cylinder and the first hydraulic pump;
A control device for controlling the rotational speed of the first hydraulic pump according to the pressure of the hydraulic oil detected by the pressure sensor,
The control device is
When the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than a predetermined pressure value, the first hydraulic pump is reversely rotated.

According to the present disclosure, during press forming of a press machine, the control device rotates the hydraulic pump according to the pressure of the hydraulic oil in the flow path between the hydraulic cylinder and the first hydraulic pump detected by the pressure sensor. Control the number. In such die-cushion pressure control of a press machine, when a surge pressure is generated in the hydraulic cylinder during press forming and the pressure of the hydraulic oil detected by the pressure sensor exceeds a predetermined pressure value, the control device operates the hydraulic pump. Reverse rotation. By performing the pressure control by the hydraulic pump with high accuracy and high speed, it is possible to suppress the surge pressure generated from the hydraulic cylinder in the die cushion pressure control.

A die cushion device according to one aspect of the present disclosure is
The pressure sensor detects the pressure of hydraulic oil, which is the die cushion pressure of the hydraulic cylinder,
The control device is
By controlling the rotational speed of the first hydraulic pump according to the pressure of the hydraulic oil detected by the pressure sensor, the flow rate and the pressure of the hydraulic oil supplied from the first hydraulic pump to the hydraulic cylinder are controlled. As well as
The rotational speed of the first hydraulic pump is controlled so that the pressure of the hydraulic oil detected by the pressure sensor becomes a die cushion pressure command value,
When the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than the preset pressure of the relief valve that is the predetermined pressure value, the first hydraulic pump is reversely rotated.

According to the present disclosure, at the time of press molding of a press machine, the control device controls the rotational speed of the hydraulic pump according to the pressure of the hydraulic oil detected by the pressure sensor (corresponding to the die cushion pressure). Controls the flow rate and pressure of hydraulic fluid supplied from the hydraulic cylinder to the hydraulic cylinder. In the die cushion pressure control of such a press machine, surge pressure is generated in the hydraulic cylinder during press forming, and the pressure of the working oil, which is the die cushion pressure of the hydraulic cylinder, is the set pressure of the relief valve that is the above predetermined pressure value. When the pressure rises above, the relief valve operates to return the hydraulic oil discharged from the hydraulic cylinder to the oil tank, and when the pressure of the hydraulic oil detected by the pressure sensor becomes equal to or higher than the set pressure of the relief valve, the control device controls the hydraulic pump. Rotate in reverse. By performing the pressure control by the hydraulic pump with high accuracy and high speed, it is possible to suppress the surge pressure generated from the hydraulic cylinder in the die cushion pressure control.

Further, in the die cushion device according to one aspect of the present disclosure,
The first hydraulic pump is disposed closer to the first hydraulic pump than a connection point of the flow path between the hydraulic cylinder and the first hydraulic pump to which the relief valve is connected. Equipped with a check valve that regulates the flow of hydraulic oil to the
The set pressure of the relief valve is controlled by the pressure of the hydraulic oil discharged from the first hydraulic pump,
When the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than the set pressure of the relief valve, the control device reversely rotates the first hydraulic pump to open the relief valve.

According to the present disclosure, when the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than the set pressure of the relief valve, the control device causes the hydraulic pump to rotate in the reverse direction. At this time, the relief valve operates to return the working oil discharged from the hydraulic cylinder to the oil tank.

Further, in the die cushion device according to one aspect of the present disclosure,
A second hydraulic pump for controlling the set pressure of the relief valve,
The control device is
When the pressure of the hydraulic oil detected by the pressure sensor becomes equal to or higher than the set pressure of the relief valve, the first hydraulic pump is rotated in the reverse direction so that the pressure of the hydraulic oil detected by the pressure sensor becomes the die cushion pressure. While controlling the rotational speed of the hydraulic first pump so that the command value is obtained,
After the reverse rotation of the first hydraulic pump is started, when the pressure of the hydraulic oil detected by the pressure sensor reaches the die cushion pressure command value, the set pressure of the relief valve is increased to close the relief valve. The rotation speed of the second hydraulic pump is controlled.

According to the present disclosure, when the pressure of the hydraulic oil detected by the pressure sensor becomes equal to or higher than the set pressure of the relief valve, the control device causes the hydraulic pump to rotate in the reverse direction so that the pressure of the hydraulic oil detected by the pressure sensor is changed to The rotation speed of the hydraulic pump is controlled so that the cushion pressure command value is achieved. After the reverse rotation of the hydraulic pump is started, when the pressure of the hydraulic oil detected by the pressure sensor reaches the die cushion pressure command value, the controller sets the relief valve to raise the set pressure of the relief valve and close the relief valve. Controls the speed of the hydraulic pump.

A die cushion device according to one aspect of the present disclosure is
The discharge side of the first hydraulic pump is connected to the vent port of the relief valve,
The pressure sensor detects the vent pressure of the relief valve,
The control device is
While controlling the rotation speed of the first hydraulic pump according to the vent pressure of the relief valve detected by the pressure sensor,
The control device is
When the vent pressure of the relief valve detected by the pressure sensor is equal to or higher than the predetermined pressure value, the first hydraulic pump is reversely rotated.

Here, rotating the first hydraulic pump in reverse means rotating the first hydraulic pump in a rotation direction opposite to the rotation direction in which the hydraulic oil is discharged.

According to the present disclosure, in die cushion pressure control during press forming of a press machine, when the pressure of the hydraulic oil discharged from the hydraulic cylinder becomes equal to or higher than the set pressure of the relief valve, the relief valve operates and the hydraulic oil is discharged from the hydraulic cylinder. Return the working oil to the oil tank. If an external force is applied to the cushion pad during this press forming and surge pressure is generated in the hydraulic cylinder, the surge pressure pushes the relief valve valve element to move it, compressing the vent chamber and increasing the relief valve vent pressure. To do. Then, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the control device causes the first hydraulic pump to rotate in the reverse direction. By performing the pressure control by the first hydraulic pump with high accuracy and high speed, it is possible to suppress the surge pressure generated from the hydraulic cylinder in the die cushion pressure control.

Further, in the die cushion device according to one aspect of the present disclosure,
A second hydraulic pump having a discharge side connected to a vent port of the relief valve,
The pressure sensor detects the vent pressure of the relief valve,
The control device is
While controlling the rotation speed of the first hydraulic pump according to the vent pressure of the relief valve detected by the pressure sensor,
The set pressure of the relief valve is controlled by controlling the vent pressure of the relief valve with the pressure of the hydraulic oil discharged from the second hydraulic pump,
When the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the first hydraulic pump and the second hydraulic pump are reversely rotated.

According to the present disclosure, the hydraulic oil discharged from the hydraulic cylinder during the action of the die cushion is returned to the oil tank via the second hydraulic pump that is rotated in the reverse direction, so that heat generation (oil temperature rise) in the relief valve is prevented. Can be avoided.

Further, in the die cushion device according to one aspect of the present disclosure,
When the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the first hydraulic pump and the second hydraulic pump are reversely rotated, and the second hydraulic pressure is reversely rotated. The rotational speed of the second hydraulic pump is controlled so that the hydraulic fluid discharged from the hydraulic cylinder via the pump is returned to the oil tank so that the die cushion pressure of the hydraulic cylinder becomes the die cushion pressure command value. With
After the reverse rotation of the first hydraulic pump is started, when the die cushion pressure of the hydraulic cylinder reaches the die cushion pressure command value, the set pressure of the relief valve is increased more than before the reverse rotation is started, and the relief valve is closed. First, the rotation speed of the first hydraulic pump is controlled.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the control device causes the first hydraulic pump and the second hydraulic pump to rotate in the reverse direction to cause the hydraulic cylinder to rotate. By controlling the rotation speed of the second hydraulic pump so that the die cushion pressure becomes the die cushion pressure command value, the working oil discharged from the hydraulic cylinder is returned to the oil tank via the second hydraulic pump. You can When the die cushion pressure of the hydraulic cylinder reaches the die cushion pressure command value after the reverse rotation of the first hydraulic pump is started, the rotation speed of the first hydraulic pump is controlled to start the reverse rotation of the set pressure of the relief valve. Raise it higher than before and close the relief valve.

Further, in the die cushion device according to one aspect of the present disclosure,
The control device is
The set pressure of the relief valve is controlled by controlling the vent pressure of the relief valve with the pressure of the hydraulic oil discharged from the first hydraulic pump.

Further, in the die cushion device according to one aspect of the present disclosure,
When the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the first hydraulic pump is rotated in the reverse direction so that the working oil discharged from the hydraulic cylinder via the relief valve is discharged. While returning to the oil tank, the rotation speed of the first hydraulic pump is controlled so that the die cushion pressure of the hydraulic cylinder becomes the die cushion pressure command value.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the control device causes the first hydraulic pump to rotate in the reverse direction to relieve the hydraulic oil discharged from the hydraulic cylinder. While returning to the oil tank via the valve, the rotational speed of the first hydraulic pump can be controlled so that the die cushion pressure of the hydraulic cylinder becomes the die cushion pressure command value.

Further, in the die cushion device according to one aspect of the present disclosure,
The oil passage between the hydraulic cylinder and the first hydraulic pump and the oil passage is disposed closer to the first hydraulic pump than a connection point to which the relief valve is connected. A check valve for restricting the flow of hydraulic oil to the hydraulic pump 1 is provided.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value and the first hydraulic pump is reversely rotated, the check valve causes the hydraulic cylinder to move to the first hydraulic pump. By restricting the flow of the hydraulic oil of (3), all the hydraulic oil discharged from the hydraulic cylinder can be returned to the oil tank via the relief valve.

Further, in the die cushion device according to one aspect of the present disclosure,
A solenoid valve is provided on the oil passage between the hydraulic cylinder and the first hydraulic pump and closer to the first hydraulic pump than a connection point of the oil passage to which the relief valve is connected.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than a predetermined pressure value and the first hydraulic pump is rotated in the reverse direction, the electromagnetic valve is closed to remove the first hydraulic pressure from the hydraulic cylinder. The flow of hydraulic oil to the pump can be reliably stopped, and the vent pressure of the relief valve detected by the pressure sensor becomes stable, so that stable control is possible.

Further, in the die cushion device according to one aspect of the present disclosure,
A throttle for connecting the connection point side and the pressure sensor is provided,
The die cushion device, wherein the pressure sensor detects a pressure of hydraulic oil that is a die cushion pressure of the hydraulic cylinder.

According to the present disclosure, during the transient period when surge pressure occurs in the hydraulic cylinder during die cushion pressure control, the effect of a sudden pressure change on the die cushion pressure control is exerted by the effect of the throttles connected to both ends of the check valve. It can be avoided and the stability of control can be secured.

It is a schematic block diagram of a die cushion device of a 1st embodiment of this indication. It is a graph which shows operation of the above-mentioned die cushion device. It is a schematic block diagram of the die cushion apparatus of 2nd Embodiment of this indication. It is a graph which shows operation of the above-mentioned die cushion device. It is a schematic block diagram of the die cushion apparatus of 3rd Embodiment of this indication. It is a graph which shows operation|movement of the die cushion apparatus of 3rd Embodiment. It is a schematic block diagram of the die-cushion apparatus of 4th Embodiment of this indication. It is a graph which shows operation|movement of the die cushion apparatus of 4th Embodiment. It is a schematic block diagram of the die-cushion apparatus of 5th Embodiment of this indication. It is a graph which shows operation|movement of the die cushion apparatus of 5th Embodiment. It is a schematic block diagram of the die cushion apparatus of 6th Embodiment of this indication. It is a graph which shows operation of the die cushion device of a 6th embodiment.

Hereinafter, embodiments will be described. In the drawings, the same reference numerals represent the same or corresponding parts.

[First Embodiment]
FIG. 1 is a schematic block diagram of a die cushion device according to a first embodiment of the present disclosure.

As shown in FIG. 1, the die cushion device according to the first embodiment includes a hydraulic cylinder 10 that moves a cushion pad 14 up and down, a hydraulic pump P that supplies hydraulic oil from an oil tank T to the hydraulic cylinder 10, and a hydraulic pressure. A motor M that drives the pump P, a relief valve 20 that returns the hydraulic oil discharged from the hydraulic cylinder 10 to the oil tank T, a pressure sensor PS that detects the pressure of the hydraulic oil that is the die cushion pressure of the hydraulic cylinder 10, A check valve 30 that restricts the flow of hydraulic oil from the hydraulic cylinder 10 to the hydraulic pump P and a control device 40 that controls the flow rate and pressure of hydraulic oil supplied from the hydraulic pump P to the hydraulic cylinder 10 are provided. The hydraulic pump P is an example of a first hydraulic pump.

The hydraulic cylinder 10 has a cylinder tube 11, a piston 12 that reciprocates in the cylinder tube 11, and a piston rod 13 whose one end is connected to the piston 12. A cushion pad 14 is connected to the other end of the piston rod 13 of the hydraulic cylinder 10. The cushion pad 14 is supported by the hydraulic cylinder 10. The cushion pad 14 is provided with a position sensor (not shown) that detects the position of the cushion pad 14. A position signal indicating the position of the cushion pad 14 is output from the position sensor to the control device 40.

The check valve 30 is arranged closer to the hydraulic pump P than a connection point of the flow valve between the hydraulic cylinder 10 and the hydraulic pump P to which the relief valve 20 is connected. The port 10 a of the hydraulic cylinder 10 is connected to the discharge side of the hydraulic pump P via the check valve 30.

A pressure sensor PS is connected to the port 10a of the hydraulic cylinder 10. A pressure signal is output from the pressure sensor PS to the control device 40.

Further, the port 10 a of the hydraulic cylinder 10 is connected to the inlet port 21 of the relief valve 20, and the outlet port 22 of the relief valve 20 is connected to the oil tank T. The relief valve 20 is a pilot operated relief valve, and the discharge side of the hydraulic pump P is connected to the vent port 23 (pilot port) of the relief valve 20. As a result, the discharge pressure (pilot pressure) of the hydraulic pump P is supplied to the vent port 23 of the relief valve 20, and the set pressure Pp of the relief valve 20 is controlled.

The control device 40 receives the die cushion pressure command signal indicating the die cushion pressure command value, the position signal indicating the position of the cushion pad 14, and the pressure signal from the pressure sensor PS, and outputs a drive signal for driving the motor M. Thus, the rotation speed of the hydraulic pump P is controlled. The die cushion pressure command signal is input from a main machine controller (not shown) of the press machine or the like.

FIG. 2 shows the operation of the die cushion device.

As shown in FIG. 2, in the press forming of the press machine, immediately before an external force is generated during the action of the die cushion, the pressure of the hydraulic oil detected by the pressure sensor PS by the control device 40 is set to the die cushion pressure command value. The rotational speed of the hydraulic pump P is controlled, the flow rate of the hydraulic pump P is kept constant, and the pressure of the vent port 23 is set to the pressure corresponding to the die cushion pressure command value.

Then, when an external force is generated during the action of the die cushion, the surge pressure is superimposed on the die cushion pressure, and when the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pp of the relief valve 20, the relief valve 20 operates. Then, the hydraulic oil discharged from the hydraulic cylinder 10 is returned to the oil tank T via the relief valve 20. At this time, the pressure of the hydraulic oil detected by the pressure sensor PS becomes equal to or higher than the set pressure Pp of the relief valve 20, and the control device 40 causes the hydraulic pump P to rotate in the reverse direction.

After that, the control device 40 controls the rotation speed of the hydraulic pump P so that the pressure of the hydraulic oil detected by the pressure sensor PS returns to the die cushion pressure command value.

As described above, according to the die cushion device having the above-described configuration, the hydraulic pump P is controlled by the control device 40 according to the pressure of the working oil (corresponding to the die cushion pressure) detected by the pressure sensor PS during the press forming of the press machine. By controlling the number of revolutions of the hydraulic pump P, the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump P to the hydraulic cylinder 10 are controlled. In the die cushion pressure control of the press machine, when a surge pressure is generated in the hydraulic cylinder 10 during press forming and the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pp of the relief valve 20, the relief valve 20 is activated. When the operating oil discharged from the hydraulic cylinder 10 is returned to the oil tank T and the pressure of the operating oil detected by the pressure sensor PS becomes equal to or higher than the set pressure Pp of the relief valve 20, the control device 40 causes the hydraulic pump P to operate. Rotate in reverse. By performing the die cushion pressure control by the hydraulic pump P with high accuracy and high speed, the surge pressure generated from the hydraulic cylinder 10 can be suppressed.

Further, in the die cushion device, the set pressure Pp of the vent port 23 of the pilot operated relief valve 20 is directly controlled by the hydraulic pump P, as compared with the balance piston type relief valve having a slow response. The surge pressure can be surely suppressed without causing the operation delay of.

[Second Embodiment]
FIG. 3 is a schematic block diagram of the die cushion device according to the second embodiment of the present disclosure. 3, the same components as those in FIG. 1 are designated by the same reference numerals.

As shown in FIG. 3, the die cushion device according to the second embodiment includes a hydraulic cylinder 10 that moves a cushion pad 14 up and down, a hydraulic pump P1 that supplies hydraulic oil from an oil tank to the hydraulic cylinder 10, and a hydraulic pump. A motor M1 that drives P1, a relief valve 20 that returns the hydraulic oil discharged from the hydraulic cylinder 10 to the oil tank T, a pressure sensor PS that detects the pressure of the hydraulic oil that is the die cushion pressure of the hydraulic cylinder 10, and a hydraulic pressure. The controller 140 controls the flow rate and pressure of the hydraulic oil supplied from the pump P1 to the hydraulic cylinder 10. The hydraulic pump P1 is an example of a first hydraulic pump.

Further, the die cushion device includes a hydraulic pump P2 that controls the set pressure Pp of the relief valve 20 and a motor M2 that drives the hydraulic pump P2. The hydraulic pump P2 is an example of a second hydraulic pump and has a smaller capacity than the hydraulic pump P1.

The port 10a of the hydraulic cylinder 10 is connected to the discharge side of the hydraulic pump P1.

A pressure sensor PS is connected to the port 10a of the hydraulic cylinder 10. A pressure signal is output from the pressure sensor PS to the control device 140. A position sensor (not shown) is provided on the cushion pad 14 supported by the hydraulic cylinder 10, and the position sensor outputs a position signal indicating the position of the cushion pad 14 to the control device 40.

Further, the port 10 a of the hydraulic cylinder 10 is connected to the inlet port 21 of the relief valve 20, and the outlet port 22 of the relief valve 20 is connected to the oil tank T. The relief valve 20 is a pilot operated relief valve, and connects the discharge side of the hydraulic pump P2 to the vent port 23 of the relief valve 20. As a result, the discharge pressure (pilot pressure) of the hydraulic pump P2 is supplied to the vent port 23 of the relief valve 20, and the set pressure Pp of the relief valve 20 is controlled.

The control device 140 receives the die cushion pressure command signal indicating the die cushion pressure command value, the position signal indicating the position of the cushion pad 14 and the pressure signal from the pressure sensor PS, and outputs a drive signal for driving the motors M1 and M2. By doing so, the rotational speeds of the hydraulic pumps P1 and P2 are controlled respectively. The die cushion pressure command signal is input from a main machine controller (not shown) of the press machine or the like.

FIG. 4 shows the operation of the die cushion device.

As shown in FIG. 4, in the press forming of the press machine, immediately before an external force is generated during the action of the die cushion, the pressure of the hydraulic oil detected by the pressure sensor PS by the control device 140 is set to the die cushion pressure command value. The rotational speed of the hydraulic pump P1 is controlled to keep the flow rate of the hydraulic pump P1 constant. At this time, the controller 40 controls the rotation speed of the hydraulic pump P2 so that the set pressure Pp of the vent port 23 of the relief valve 20 becomes a pressure corresponding to the die cushion pressure command value.

Then, when an external force is generated during the action of the die cushion, the surge pressure is superimposed on the die cushion pressure, and when the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pp of the relief valve 20, the relief valve 20 operates. Then, the hydraulic oil discharged from the hydraulic cylinder 10 is returned to the oil tank T via the relief valve 20. At this time, the pressure of the hydraulic oil detected by the pressure sensor PS becomes equal to or higher than the die cushion pressure command value, and the control device 140 causes the hydraulic pump P1 to rotate in the reverse direction.

After that, the control device 140 controls the hydraulic pump P1 to an appropriate rotational speed so that the pressure of the hydraulic oil detected by the pressure sensor PS returns to the die cushion pressure command value. Further, the control device 140 controls the rotation speed of the hydraulic pump P2 so that the set pressure Pp of the relief valve 20 becomes higher than the pressure immediately before the external force is generated during the action of the die cushion so that the discharge pressure of the hydraulic pump P2 is higher. The relief valve 20 is closed by changing

According to the die cushion device having the above-described configuration, during the press forming of the press machine, the rotation speed of the hydraulic pump P1 is controlled by the control device 140 according to the pressure of the hydraulic oil detected by the pressure sensor PS (corresponding to the die cushion pressure). By controlling, the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump P1 to the hydraulic cylinder 10 are controlled. In the die cushion pressure control of the press machine, when a surge pressure is generated in the hydraulic cylinder 10 during press forming and the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pp of the relief valve 20, the relief valve 20 is activated. When the operating oil discharged from the hydraulic cylinder 10 is returned to the oil tank T and the pressure of the operating oil detected by the pressure sensor PS becomes equal to or higher than the set pressure Pp of the relief valve 20, the control device 140 causes the hydraulic pump P1 to operate. Rotate in reverse. By performing the die cushion pressure control by the hydraulic pump P1 with high accuracy and high speed, the surge pressure generated from the hydraulic cylinder 10 can be suppressed.

Further, in the die cushion device, the set pressure Pp of the vent port 23 of the pilot-operated relief valve 20 is directly controlled by the hydraulic pump P2, as compared with the balanced-piston relief valve having a slow response. The surge pressure can be surely suppressed without causing the operation delay of.

Further, in the die cushion device, the hydraulic oil discharged from the hydraulic cylinder 10 during the die cushion action is returned to the oil tank T via the reversely rotated hydraulic pump P1. Therefore, heat is generated in the relief valve 20 (oil temperature). Rise) can be avoided.

The reverse rotation of the hydraulic pump P1 causes the motor M1 to rotate in the reverse direction, and the electric energy generated by the motor M1 is consumed by the regenerative resistance.

In the conventional air-type die cushion device, the cylinder diameter becomes large and the device becomes large, and it is difficult to perform pressure adjustment and precise position control because the pressure of air having compressibility is used. Although there are problems, these problems can be solved in the first and second embodiments.

[Third Embodiment]
FIG. 5 is a schematic block diagram of a die cushion device according to the third embodiment of the present disclosure.

In the die cushion device of the third embodiment, as shown in FIG. 5, a hydraulic cylinder 10 for vertically moving a cushion pad 14 of a press machine (not shown), and hydraulic oil from an oil tank T are supplied to the hydraulic cylinder 10. The hydraulic pump P to be supplied, the motor M for driving the hydraulic pump P, the relief valve 20 for returning the hydraulic oil discharged from the hydraulic cylinder 10 to the oil tank T, and the flow of the hydraulic oil from the hydraulic cylinder 10 to the hydraulic pump P. A check valve 30 that regulates the pressure, a pressure sensor PS that detects the vent pressure of the relief valve 20, and a control device 240 that controls the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump P to the hydraulic cylinder 10. .. The hydraulic pump P is an example of a first hydraulic pump.

The hydraulic cylinder 10 has a cylinder tube 11, a piston 12 that reciprocates in the cylinder tube 11, and a piston rod 13 whose one end is connected to the piston 12. A cushion pad 14 is connected to the other end of the piston rod 13 of the hydraulic cylinder 10. The cushion pad 14 is supported by the hydraulic cylinder 10. The cushion pad 14 is provided with a position sensor (not shown) that detects the position of the cushion pad 14. A position signal indicating the position of the cushion pad 14 is output from the position sensor to the control device 240.

The check valve 30 is disposed on the hydraulic pump P side of an oil passage between the hydraulic cylinder 10 and the hydraulic pump P and a connection point of the oil passage on which the relief valve 20 is connected. The port 10 a of the hydraulic cylinder 10 is connected to the discharge side of the hydraulic pump P via the check valve 30.

A pressure sensor PS is connected between the discharge side of the hydraulic pump P and the check valve 30. A pressure signal representing the vent pressure of the relief valve 20 is output from the pressure sensor PS to the control device 240.

Further, the port 10 a of the hydraulic cylinder 10 is connected to the inlet port 21 of the relief valve 20, and the outlet port 22 of the relief valve 20 is connected to the oil tank T. The relief valve 20 is a pilot operated relief valve, and the discharge side of the hydraulic pump P is connected to the vent port 23 of the relief valve 20. As a result, the discharge pressure of the hydraulic pump P is supplied to the vent port 23 of the relief valve 20, and the set pressure Pset of the relief valve 20 is controlled.

The controller 240 receives the die cushion pressure command signal indicating the die cushion pressure command value, the position signal indicating the position of the cushion pad 14, and the pressure signal from the pressure sensor PS, and outputs a drive signal for driving the motor M. Thus, the rotation speed of the hydraulic pump P is controlled. The die cushion pressure command signal is input from a main machine controller (not shown) of the press machine or the like.

FIG. 6 shows the operation of the die cushion device. In FIG. 6, the horizontal axis represents time [arbitrary scale], and the vertical axis represents pressure [arbitrary scale] and flow rate [arbitrary scale].

As shown in FIG. 6, in press molding of a press machine, immediately before a slide (not shown) collides with the cushion pad 14 and external force is generated, the relief valve 20 detected by the pressure sensor PS is detected by the control device 240. The rotational speed of the hydraulic pump P is controlled so that the die cushion pressure of the hydraulic cylinder 10 becomes the die cushion pressure command value based on the vent pressure of. At this time, the control device 240 controls the rotation speed of the hydraulic pump P so that the pressure of the vent port 23 of the relief valve 20 becomes the set vent pressure Pv.

Then, when a slide (not shown) collides with the cushion pad 14 and an external force is generated, surge pressure is superimposed on the die cushion pressure, and the die cushion pressure of the port 10 a of the hydraulic cylinder 10 becomes the set pressure Pset of the relief valve 20. If it becomes above, the relief valve 20 will operate and will return the hydraulic fluid discharged from the hydraulic cylinder 10 to the oil tank T via the relief valve 20.

Here, if the set vent pressure is Pv and the differential pressure spring surface pressure of the relief valve 20 is Pd, the set pressure Pset of the relief valve 20 is
Pset=Pv+Pd
It is represented by.

When the surge pressure is superimposed on the die cushion pressure and the vent pressure of the relief valve 20 detected by the pressure sensor PS becomes equal to or higher than the predetermined pressure value Pv, the control device 240 causes the hydraulic pump P to rotate in the reverse direction. In this embodiment, the predetermined pressure value Pv is the same as the set vent pressure Pv, but the predetermined pressure value Pv>the set vent pressure may be set.

After that, the cushion pad 14 is pushed down at a predetermined speed by sliding, and the control device 240 controls the rotational speed of the hydraulic pump P so that the vent pressure detected by the pressure sensor PS returns to the set vent pressure Pv.

As described above, in the die cushion device having the above-described configuration, the control device 240 controls the rotational speed of the hydraulic pump P in accordance with the vent pressure detected by the pressure sensor PS during press forming of the press machine, so that the hydraulic pump The flow rate and pressure of the hydraulic oil supplied from P to the hydraulic cylinder 10 are controlled. Further, in the die cushion pressure control of the press machine, when a surge pressure is generated in the hydraulic cylinder 10 during press forming and the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pset of the relief valve 20, the relief valve. 20 operates to return the hydraulic oil discharged from the hydraulic cylinder 10 to the oil tank T, and when the vent pressure of the relief valve 20 detected by the pressure sensor PS becomes equal to or higher than a predetermined pressure value Pv, the control device 240 causes the hydraulic pump to operate. Rotate P in reverse.

In the die cushion device described above, the surge pressure generated from the hydraulic cylinder 10 can be suppressed by performing the die cushion pressure control by the hydraulic pump P with high precision and high speed.

In the die cushion device, the vent pressure of the pilot-operated relief valve 20 is directly controlled by the hydraulic pump P, as compared with the balanced-piston relief valve, which has a slow response, so that an operation delay of the relief valve 20 occurs. The surge pressure can be suppressed without fail.

When the vent pressure of the relief valve 20 detected by the pressure sensor PS becomes equal to or higher than the predetermined pressure value Pv, the control device 240 causes the hydraulic pump P to rotate in the reverse direction so that the die cushion pressure of the hydraulic cylinder 10 becomes equal to the die cushion pressure. By controlling the rotation speed of the hydraulic pump P so that the command value is achieved, the hydraulic oil discharged from the hydraulic cylinder 10 can be returned to the oil tank T via the relief valve 20.

Further, when the vent pressure of the relief valve 20 detected by the pressure sensor PS becomes equal to or higher than the predetermined pressure value Pv and the hydraulic pump P is reversely rotated, the check valve 30 operates from the hydraulic cylinder 10 to the hydraulic pump P. By restricting the flow of oil, all the hydraulic oil discharged from the hydraulic cylinder 10 can be returned to the oil tank T via the relief valve 20.

Further, in the die cushion device described above, even when the hydraulic pump P has a large pump capacity, stable control with good responsiveness is possible so that the discharge side does not become negative pressure when the hydraulic pump P rotates in the reverse direction. Therefore, it is not necessary to add a vacuum check valve for supplying the hydraulic oil from the oil tank T between the discharge side of the hydraulic pump P and the check valve 30 or to devise a mechanism for limiting the reverse rotation.

[Fourth Embodiment]
FIG. 7 is a schematic block diagram of a die cushion device according to the fourth embodiment of the present disclosure. The die cushion device of the fourth embodiment has the same configuration as the die cushion device of the third embodiment except for the solenoid valve 50 and the control device 340.

As shown in FIG. 7, the die cushion device according to the fourth embodiment is located on the hydraulic pump P side of the oil passage between the hydraulic cylinder 10 and the hydraulic pump P and the connection point of the oil passage to which the relief valve 20 is connected. A solenoid valve 50 is provided in the.

When the solenoid 53 is excited, the solenoid valve 50 is at the left switching position, and the first port 51 and the second port 52 are in communication with each other. On the other hand, when the solenoid 53 is not excited, the solenoid valve 50 is in the right switching position, and the first port 51 and the second port 52 are closed respectively.

FIG. 8 shows the operation of the die cushion device. In FIG. 8, the horizontal axis represents time [arbitrary scale], and the vertical axis represents pressure [arbitrary scale] and flow rate [arbitrary scale].

As shown in FIG. 8, in the press forming of the press machine, immediately before the external force is generated during the action of the die cushion, the control device 340 controls the hydraulic cylinder 10 based on the vent pressure of the relief valve 20 detected by the pressure sensor PS. The rotation speed of the hydraulic pump P is controlled so that the die cushion pressure of 1 becomes the die cushion pressure command value. At this time, the control device 340 controls the rotation speed of the hydraulic pump P so that the pressure of the vent port 23 of the relief valve 20 becomes the set vent pressure Pv.

When an external force is generated during the action of the die cushion, surge pressure is superimposed on the die cushion pressure, and when the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pset of the relief valve 20, the relief valve 20 operates. Then, the hydraulic oil discharged from the hydraulic cylinder 10 is returned to the oil tank T via the relief valve 20. At this time, when the vent pressure of the relief valve 20 detected by the pressure sensor PS becomes equal to or higher than the predetermined pressure value Pv, the hydraulic pump P is rotated in the reverse direction.

After that, the cushion pad 14 is pushed down at a predetermined speed by sliding, and the control device 340 controls the rotation speed of the hydraulic pump P so that the vent pressure detected by the pressure sensor PS returns to the set vent pressure Pv.

The die cushion device of the fourth embodiment has the same effects as the die cushion device of the third embodiment.

Further, when the vent pressure of the relief valve 20 detected by the pressure sensor PS becomes equal to or higher than the predetermined pressure value Pv and the hydraulic pump P is rotated in the reverse direction, the electromagnetic valve 50 is closed, and therefore the hydraulic cylinder 10 is discharged. All of the working oil that flows can be returned to the oil tank T via the relief valve 20.

The die cushion device according to the fourth embodiment is different from the die cushion device including the check valve 30 according to the third embodiment in that the hydraulic pump P and the hydraulic cylinder 10 are operated even when pressure overshoot or undershoot occurs. By reliably blocking the oil passage between them, stable control becomes possible.

[Fifth Embodiment]
FIG. 9 is a schematic block diagram of a die cushion device according to the fifth embodiment of the present disclosure. 9, the same components as those in FIG. 5 are designated by the same reference numerals.

As shown in FIG. 9, the die cushion device of the fifth embodiment drives a hydraulic cylinder 10 that moves a cushion pad 14 up and down, a hydraulic pump P2 that controls a set pressure Pset of a relief valve 20, and a hydraulic pump P2. Motor M2, hydraulic pump P1 for supplying hydraulic oil from hydraulic tank T to hydraulic cylinder 10, motor M1 for driving hydraulic pump P1, and relief for returning hydraulic oil discharged from hydraulic cylinder 10 to oil tank T The valve 20, the pressure sensor PS2 that detects the vent pressure of the relief valve 20, the pressure sensor PS1 that detects the pressure of hydraulic oil that is the die cushion pressure of the hydraulic cylinder 10, and the hydraulic pumps by controlling the motors M1 and M2. And a control device 440 for controlling the rotational speeds of P1 and P2.

The control device 440 controls the rotational speed of the hydraulic pump P2 to control the flow rate and pressure of the hydraulic oil supplied to the vent port 23 of the relief valve 20. The control device 440 controls the rotational speed of the hydraulic pump P1 to control the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump P1 to the hydraulic cylinder 10.

The hydraulic pump P2 is an example of a second hydraulic pump. The hydraulic pump P1 is an example of a first hydraulic pump. The hydraulic pump P2 has a smaller capacity than the hydraulic pump P1.

The pressure sensor PS2 is connected to the vent port 23 of the relief valve 20. A second pressure signal indicating the vent pressure of the relief valve 20 is output from the pressure sensor PS2 to the control device 440.

The port 10a of the hydraulic cylinder 10 is connected to the discharge side of the hydraulic pump P1. The pressure sensor PS1 is connected to the port 10a of the hydraulic cylinder 10. A first pressure signal representing the die cushion pressure is output from the pressure sensor PS1 to the control device 440.

A position sensor (not shown) is provided on the cushion pad 14 supported by the hydraulic cylinder 10, and the position sensor outputs a position signal indicating the position of the cushion pad 14 to the control device 440.

Further, the port 10 a of the hydraulic cylinder 10 is connected to the inlet port 21 of the relief valve 20, and the outlet port 22 of the relief valve 20 is connected to the oil tank T. The relief valve 20 is a pilot operated relief valve, and connects the discharge side of the hydraulic pump P2 to the vent port 23 of the relief valve 20. As a result, the discharge pressure of the hydraulic pump P2 is supplied to the vent port 23 of the relief valve 20, and the set pressure Pset of the relief valve 20 is controlled.

The control device 440 receives the die cushion pressure command signal indicating the die cushion pressure command value, the position signal indicating the position of the cushion pad 14, and the first and second pressure signals from the pressure sensors PS1 and PS2, and receives the motors M1 and M2. By outputting the first and second drive signals for driving, the rotational speeds of the hydraulic pumps P1 and P2 are respectively controlled. The die cushion pressure command signal is input from a main machine controller (not shown) of the press machine or the like.

FIG. 10 shows the operation of the die cushion device. In FIG. 10, the horizontal axis represents time [arbitrary scale], and the vertical axis represents pressure [arbitrary scale] and flow rate [arbitrary scale].

As shown in FIG. 10, in the press forming of the press machine, immediately before an external force is generated during the action of the die cushion, the pressure of the hydraulic oil detected by the pressure sensor PS1 by the control device 440 becomes the die cushion pressure command value. , Controls the rotation speed of the hydraulic pump P1. At this time, the control device 440 controls the rotation speed of the hydraulic pump P2 so that the pressure of the vent port 23 of the relief valve 20 becomes the set vent pressure Pv1.
Here, the die cushion pressure command value is, when the differential pressure spring surface pressure of the relief valve 20 is Pd,
Die cushion pressure command value ≤ Pset (=Pv1+Pd)
Then, it stands by in a state where there is no inflow from the hydraulic pump P1 to the relief valve 20.

When an external force is generated during the action of the die cushion, the surge pressure is superimposed on the die cushion pressure, and when the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pset of the relief valve 20, the relief valve 20 operates. Then, the hydraulic oil discharged from the hydraulic cylinder 10 is returned to the oil tank T via the relief valve 20. At this time, when the vent pressure of the relief valve 20 detected by the pressure sensor PS2 becomes equal to or higher than the predetermined pressure value Pv1, the control device 440 reversely rotates the hydraulic pump P1. Alternatively, since the pressure of the hydraulic oil detected by the pressure sensor PS1 exceeds the die cushion pressure command value, the hydraulic pump P1 rotates in the reverse direction and the hydraulic oil discharged from the hydraulic cylinder 10 is transferred via the hydraulic pump P1. Return to tank T. In this embodiment, the predetermined pressure value Pv1 is the same as the set vent pressure Pv1, but the predetermined pressure value Pv1>the set vent pressure may be set.

After that, the cushion pad 14 is pushed down at a predetermined speed by sliding, and the control device 440 sets the hydraulic pump P1 to an appropriate rotation speed so that the pressure of the hydraulic oil detected by the pressure sensor PS1 returns to the die cushion pressure command value. Control.

Further, the control device 440 controls the rotational speed of the hydraulic pump P2 so that the pressure in the vent port 23 of the relief valve 20 is higher than the set vent pressure Pv1 immediately before the external force is generated during the action of the die cushion. The relief valve 20 is closed by changing the discharge pressure of the hydraulic pump P2.

According to the die cushion device having the above-described configuration, during the press forming of the press machine, the control device 440 rotates the hydraulic pump P1 according to the vent pressure (corresponding to the die cushion pressure) of the relief valve 20 detected by the pressure sensor PS2. By controlling the number, the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump P1 to the hydraulic cylinder 10 are controlled. In the die cushion pressure control of the press machine, when a surge pressure is generated in the hydraulic cylinder 10 during press forming and the die cushion pressure of the port 10a of the hydraulic cylinder 10 becomes equal to or higher than the set pressure Pset of the relief valve 20, the relief valve 20 is activated. The operating oil discharged from the hydraulic cylinder 10 is returned to the oil tank T, and the vent pressure of the relief valve 20 detected by the pressure sensor PS2 becomes equal to or higher than a predetermined pressure value Pv1 or detected by the pressure sensor PS1. Since the pressure of the hydraulic oil thus generated exceeds the die cushion pressure command value, the control device 440 causes the hydraulic pump P1 to rotate in the reverse direction.

In the die cushion device described above, the surge pressure generated from the hydraulic cylinder 10 can be suppressed by performing the die cushion pressure control by the hydraulic pump P1 with high accuracy and high speed.

In the die cushion device, the pressure of the pilot-operated relief valve 20 is directly controlled by the hydraulic pump P2, as compared with the balance-piston relief valve having a slow response. Therefore, the surge pressure can be surely suppressed.

Further, in the die cushion device, the hydraulic oil discharged from the hydraulic cylinder 10 during the die cushion action is returned to the oil tank T via the reversely rotated hydraulic pump P1. Therefore, heat is generated in the relief valve 20 (oil temperature). Rise) can be avoided.

The reverse rotation of the hydraulic pump P1 causes the motor M1 to rotate in the reverse direction, and the electric energy generated by the motor M1 is consumed by the regenerative resistance.

In the conventional air-type die cushion device, the cylinder diameter becomes large and the device becomes large, and it is difficult to perform pressure adjustment and precise position control because the pressure of air having compressibility is used. Although there are problems, these problems can be solved in the third to fifth embodiments.

When the vent pressure of the relief valve 20 detected by the pressure sensor PS2 becomes equal to or higher than the predetermined pressure value Pv1, the control device 440 causes the hydraulic pump P1 and the hydraulic pump P2 to rotate in the reverse direction so that the die cushion pressure of the hydraulic cylinder 10 is increased. By controlling the rotation speed of the first hydraulic pump P1 so that the die cushion pressure command value is achieved, the hydraulic oil discharged from the hydraulic cylinder 10 can be returned to the oil tank T via the hydraulic pump P1.

When the die cushion pressure of the hydraulic cylinder 10 reaches the die cushion pressure command value after the reverse rotation of the hydraulic pump P2 is started, the rotation speed of the hydraulic pump P2 is controlled to set the set pressure of the relief valve 20 before the reverse rotation is started. The relief valve 20 is closed by increasing the set vent pressure Pv1 to the set vent pressure Pv2.

In the die cushion device described above, even if the hydraulic pump P1 has a large pump capacity, a large surge generation due to a response delay due to inertia can be covered by the response of the relief valve 20, so that the surge generation can be minimized. ..

[Sixth Embodiment]
FIG. 11 is a schematic block diagram of a die cushion device according to the sixth embodiment of the present disclosure. The die cushion device of the sixth embodiment has the same configuration as the die cushion device of the third embodiment except for the operations of the diaphragm 60 and the control device 540.

In the die cushion device of the sixth embodiment, throttles 60 are connected to both ends of the check valve 30 as shown in FIG.

FIG. 12 shows the operation of the die cushion device. In FIG. 12, the horizontal axis represents time [arbitrary scale], and the vertical axis represents pressure [arbitrary scale] and flow rate [arbitrary scale].

As shown in FIG. 12, in the press forming of the press machine, immediately before the slide (not shown) collides with the cushion pad 14 and an external force is generated, the control device 540 controls the operation oil detected by the pressure sensor PS. Based on the pressure, the rotational speed of the hydraulic pump P is controlled so that the die cushion pressure of the hydraulic cylinder 10 becomes the die cushion pressure command value. At this time, the rotation speed of the hydraulic pump P is controlled by the control device 540 so that the pressure of the vent port 23 of the relief valve 20 becomes the set vent pressure Pv.

Then, when a slide (not shown) collides with the cushion pad 14 and an external force is generated, surge pressure is superimposed on the die cushion pressure, and the die cushion pressure of the port 10 a of the hydraulic cylinder 10 becomes the set pressure Pset of the relief valve 20. If it becomes above, the relief valve 20 will operate and will return the hydraulic fluid discharged from the hydraulic cylinder 10 to the oil tank T via the relief valve 20.

When the surge pressure is superimposed on the die cushion pressure and the surge pressure detected by the pressure sensor PS via the throttle 60 becomes equal to or higher than the predetermined pressure value Pv, the control device 540 causes the hydraulic pump P to rotate in the reverse direction.

Then, the cushion pad 14 is pushed down at a predetermined speed by the slide, and the control device 540 controls the rotation speed of the hydraulic pump P so that the pressure detected by the pressure sensor PS returns to the set vent pressure Pv. At this time, the die cushion pressure of the hydraulic cylinder 10 is slightly higher than immediately before the surge pressure is generated due to the influence of the passage pressure loss and the flow rate-pressure characteristic of the relief valve 20, and compared with the case of the third embodiment. The die cushion pressure of 10 gradually approaches the die cushion pressure command value.

As described above, in the die cushion device configured as described above, in the die cushion pressure control of the press machine, surge pressure is generated in the hydraulic cylinder 10 during press forming, and the die cushion pressure of the port 10a of the hydraulic cylinder 10 is reduced to the relief valve 20. When the pressure exceeds the set pressure Pset, the relief valve 20 operates to return the hydraulic oil discharged from the hydraulic cylinder 10 to the oil tank T, and the surge pressure detected by the pressure sensor PS via the throttle 60 is a predetermined pressure value. When it becomes equal to or higher than Pv, the control device 540 reversely rotates the hydraulic pump P.

Compared to the die cushion device of the third embodiment, the die cushion device of the sixth embodiment is connected to both ends of the check valve 30 in the transition period when surge pressure occurs in the hydraulic cylinder 10 in the die cushion pressure control. Due to the effect of the restricted throttle 60, it is possible to avoid the influence of a sudden pressure change on the die cushion pressure control, and to secure the control stability.

Although the check valve 30 is used in the sixth embodiment, an electromagnetic valve may be used instead of the check valve as in the fourth embodiment.

In the first to sixth embodiments, the die cushion device including one hydraulic cylinder 10 for moving the cushion pad 14 up and down has been described, but the die cushion device including a plurality of hydraulic cylinders for vertically moving the cushion pad can be used. The invention may be applied.

Although the specific embodiments of the present disclosure have been described, the present disclosure is not limited to the above first to sixth embodiments, and various modifications can be implemented within the scope of the present disclosure.

The die cushion device of the present disclosure is
A hydraulic cylinder that moves the cushion pad up and down,
A hydraulic pump for supplying hydraulic oil from the oil tank to the hydraulic cylinder,
A relief valve for returning the hydraulic oil discharged from the hydraulic cylinder to the oil tank,
A pressure sensor that detects the pressure of the hydraulic oil that is the die cushion pressure of the hydraulic cylinder;
A control device for controlling the flow rate and pressure of the hydraulic oil supplied from the hydraulic pump to the hydraulic cylinder by controlling the rotational speed of the hydraulic pump according to the pressure of the hydraulic oil detected by the pressure sensor. ,
The control device is
The rotational speed of the hydraulic pump is controlled so that the pressure of the hydraulic oil detected by the pressure sensor becomes the die cushion pressure command value,
When the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than the set pressure of the relief valve, the hydraulic pump is reversely rotated.

According to the present disclosure, at the time of press molding of a press machine, the control device controls the rotational speed of the hydraulic pump according to the pressure of the hydraulic oil detected by the pressure sensor (corresponding to the die cushion pressure). Controls the flow rate and pressure of the hydraulic oil supplied from the to the hydraulic cylinder. In such die cushion pressure control of a press machine, when surge pressure is generated in the hydraulic cylinder during press forming and the pressure of the hydraulic oil, which is the die cushion pressure of the hydraulic cylinder, exceeds the set pressure of the relief valve, the relief valve Operates to return the hydraulic oil discharged from the hydraulic cylinder to the oil tank, and when the pressure of the hydraulic oil detected by the pressure sensor becomes equal to or higher than the set pressure of the relief valve, the control device causes the hydraulic pump to rotate in the reverse direction. By performing the pressure control by the hydraulic pump with high accuracy and high speed, it is possible to suppress the surge pressure generated from the hydraulic cylinder in the die cushion pressure control.

Further, in the die cushion device according to one aspect of the present disclosure,
The flow path between the hydraulic cylinder and the hydraulic pump is disposed closer to the hydraulic pump than the connection point to which the relief valve is connected, and regulates the flow of hydraulic oil from the hydraulic cylinder to the hydraulic pump. Equipped with a check valve,
The set pressure of the relief valve is controlled by the pressure of the hydraulic oil discharged from the hydraulic pump,
When the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than the set pressure of the relief valve, the control device reversely rotates the hydraulic pump to open the relief valve.

According to the present disclosure described above, when the pressure of the hydraulic oil detected by the pressure sensor is equal to or higher than the set pressure of the relief valve, the control device causes the hydraulic pump to rotate in the reverse direction. At this time, the relief valve operates to return the working oil discharged from the hydraulic cylinder to the oil tank.

Further, in the die cushion device according to one aspect of the present disclosure,
A relief valve hydraulic pump for controlling the set pressure of the relief valve is provided,
The control device is
When the pressure of the hydraulic oil detected by the pressure sensor becomes equal to or higher than the set pressure of the relief valve, the hydraulic pump is rotated in the reverse direction, and the pressure of the hydraulic oil detected by the pressure sensor becomes the die cushion pressure command value. To control the rotational speed of the hydraulic pump,
After the reverse rotation of the hydraulic pump is started, when the pressure of the hydraulic oil detected by the pressure sensor reaches the die cushion pressure command value, the relief valve is closed so as to raise the set pressure of the relief valve and close the relief valve. Control the number of rotations of the hydraulic pump.

According to the above-mentioned present disclosure, when the pressure of the hydraulic oil detected by the pressure sensor becomes equal to or higher than the set pressure of the relief valve, the control device causes the hydraulic pump to rotate in the reverse direction so that the pressure of the hydraulic oil detected by the pressure sensor is increased. The rotation speed of the hydraulic pump is controlled so that the die cushion pressure command value is obtained. After the reverse rotation of the hydraulic pump is started, when the pressure of the hydraulic oil detected by the pressure sensor reaches the die cushion pressure command value, the controller sets the relief valve to raise the set pressure of the relief valve and close the relief valve. Controls the speed of the hydraulic pump.

The die cushion device of the present disclosure is
A hydraulic cylinder that moves the cushion pad up and down,
A relief valve for returning the hydraulic oil discharged from the hydraulic cylinder to an oil tank,
A first hydraulic pump whose discharge side is connected to the vent port of the relief valve;
A pressure sensor for detecting the vent pressure of the relief valve,
A control device for controlling the rotation speed of the first hydraulic pump according to the vent pressure of the relief valve detected by the pressure sensor,
The control device is
When the vent pressure of the relief valve detected by the pressure sensor is equal to or higher than a predetermined pressure value, the first hydraulic pump is reversely rotated.

Here, rotating the first hydraulic pump in reverse means rotating the first hydraulic pump in a rotation direction opposite to the rotation direction in which the hydraulic oil is discharged.

According to the present disclosure, in die cushion pressure control during press forming of a press machine, when the pressure of the hydraulic oil discharged from the hydraulic cylinder becomes equal to or higher than the set pressure of the relief valve, the relief valve operates and the hydraulic oil is discharged from the hydraulic cylinder. Return the working oil to the oil tank. When an external force is applied to the cushion pad during this press forming and surge pressure is generated in the hydraulic cylinder, the surge pressure pushes the relief valve valve element to move it, compressing the vent chamber and increasing the relief valve vent pressure. To do. Then, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the control device causes the first hydraulic pump to rotate in the reverse direction. By performing the pressure control by the first hydraulic pump with high accuracy and high speed, it is possible to suppress the surge pressure generated from the hydraulic cylinder in the die cushion pressure control.

Further, in the die cushion device according to one aspect of the present disclosure,
A second hydraulic pump for supplying hydraulic oil from the oil tank to the hydraulic cylinder;
The control device is
The set pressure of the relief valve is controlled by controlling the vent pressure of the relief valve with the pressure of the hydraulic oil discharged from the first hydraulic pump,
When the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the second hydraulic pump is reversely rotated.

According to the present disclosure, the hydraulic oil discharged from the hydraulic cylinder during the action of the die cushion is returned to the oil tank via the second hydraulic pump that is rotated in the reverse direction, so that heat generation (oil temperature rise) in the relief valve is prevented. Can be avoided.

Further, in the die cushion device according to one aspect of the present disclosure,
When the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the first hydraulic pump and the second hydraulic pump are reversely rotated, and the second hydraulic pressure is reversely rotated. The rotational speed of the second hydraulic pump is controlled so that the hydraulic fluid discharged from the hydraulic cylinder via the pump is returned to the oil tank so that the die cushion pressure of the hydraulic cylinder becomes the die cushion pressure command value. With
After the reverse rotation of the first hydraulic pump is started, when the die cushion pressure of the hydraulic cylinder reaches the die cushion pressure command value, the set pressure of the relief valve is increased more than before the reverse rotation is started, and the relief valve is closed. First, the rotation speed of the first hydraulic pump is controlled.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the control device causes the first hydraulic pump and the second hydraulic pump to rotate in the reverse direction to cause the hydraulic cylinder to rotate. By controlling the rotation speed of the second hydraulic pump so that the die cushion pressure becomes the die cushion pressure command value, the working oil discharged from the hydraulic cylinder is returned to the oil tank via the second hydraulic pump. You can When the die cushion pressure of the hydraulic cylinder reaches the die cushion pressure command value after the reverse rotation of the first hydraulic pump is started, the rotation speed of the first hydraulic pump is controlled to start the reverse rotation of the set pressure of the relief valve. Raise it higher than before and close the relief valve.

Further, in the die cushion device according to one aspect of the present disclosure,
The control device is
The set pressure of the relief valve is controlled by controlling the vent pressure of the relief valve with the pressure of the hydraulic oil discharged from the first hydraulic pump.

Further, in the die cushion device according to one aspect of the present disclosure,
When the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the first hydraulic pump is rotated in the reverse direction so that the working oil discharged from the hydraulic cylinder via the relief valve is discharged. While returning to the oil tank, the rotation speed of the first hydraulic pump is controlled so that the die cushion pressure of the hydraulic cylinder becomes the die cushion pressure command value.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value, the control device causes the first hydraulic pump to rotate in the reverse direction to relieve the hydraulic oil discharged from the hydraulic cylinder. While returning to the oil tank via the valve, the rotational speed of the first hydraulic pump can be controlled so that the die cushion pressure of the hydraulic cylinder becomes the die cushion pressure command value.

Further, in the die cushion device according to one aspect of the present disclosure,
The oil passage between the hydraulic cylinder and the first hydraulic pump and the oil passage is disposed closer to the first hydraulic pump than a connection point to which the relief valve is connected. A check valve for restricting the flow of hydraulic oil to the hydraulic pump 1 is provided.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than the predetermined pressure value and the first hydraulic pump is reversely rotated, the check valve causes the hydraulic cylinder to move to the first hydraulic pump. By restricting the flow of the hydraulic oil of (3), all the hydraulic oil discharged from the hydraulic cylinder can be returned to the oil tank via the relief valve.

Further, in the die cushion device according to one aspect of the present disclosure,
A solenoid valve is provided on the oil passage between the hydraulic cylinder and the first hydraulic pump and closer to the first hydraulic pump than a connection point of the oil passage to which the relief valve is connected.

According to the present disclosure, when the vent pressure of the relief valve detected by the pressure sensor becomes equal to or higher than a predetermined pressure value and the first hydraulic pump is rotated in the reverse direction, the electromagnetic valve is closed to remove the first hydraulic pressure from the hydraulic cylinder. The flow of hydraulic oil to the pump can be reliably stopped, and the vent pressure of the relief valve detected by the pressure sensor becomes stable, so that stable control is possible.

10... Hydraulic cylinder 10a... Port 11... Cylinder tube 12... Piston 13... Piston rod 14... Cushion pad 20... Relief valve 21... Inlet port 22... Outlet port 23... Vent port 30... Check valve 40, 140, 240, 340 , 440, 540... Control device 50... Solenoid valve 51... First port 52... Second port 60... Throttle M, M1, M2... Motor P, P1... Hydraulic pump (first hydraulic pump)
P2... Hydraulic pump (second hydraulic pump)
PS, PS1, PS2... Pressure sensor T... Oil tank

Claims (12)

A hydraulic cylinder (10) for moving the cushion pad (14) up and down,
A first hydraulic pump (P, P1) for supplying hydraulic oil from the oil tank (T) to the hydraulic cylinder (10);
A relief valve (20) for returning the hydraulic oil discharged from the hydraulic cylinder (10) to the oil tank,
A pressure sensor (PS, PS2) for detecting the pressure of the hydraulic oil in the flow path between the hydraulic cylinder (10) and the first hydraulic pump (P, P1),
A control device (40, 140, 240, 340, 440, 540) for controlling the rotation speed of the first hydraulic pump (P, P1) according to the pressure of the hydraulic oil detected by the pressure sensor (PS, PS2). ) And
The control device (40, 140, 240, 340, 440, 540) is
A die cushion device, wherein the first hydraulic pump (P, P1) is reversely rotated when the pressure of the hydraulic oil detected by the pressure sensor (PS, PS2) is equal to or higher than a predetermined pressure value. The die cushion device according to claim 1,
The pressure sensor (PS) detects the pressure of hydraulic oil, which is the die cushion pressure of the hydraulic cylinder (10),
The control device (40, 140) is
By controlling the number of revolutions of the first hydraulic pump (P, P1) according to the pressure of the hydraulic oil detected by the pressure sensor (PS), the first hydraulic pump (P, P1) is controlled to operate as described above. While controlling the flow rate and pressure of the hydraulic oil supplied to the hydraulic cylinder (10),
The rotational speed of the first hydraulic pump (P, P1) is controlled so that the pressure of the hydraulic oil detected by the pressure sensor (PS) becomes the die cushion pressure command value.
When the pressure of the hydraulic oil detected by the pressure sensor (PS) is equal to or higher than the preset pressure of the relief valve (20) having the predetermined pressure value, the first hydraulic pump (P, P1) is rotated in the reverse direction. A die cushion device characterized in that The die cushion device according to claim 2,
The flow path between the hydraulic cylinder (10) and the first hydraulic pump (P) is arranged closer to the first hydraulic pump (P) than the connection point to which the relief valve (20) is connected. And a check valve (30) for restricting the flow of hydraulic oil from the hydraulic cylinder (10) to the first hydraulic pump (P),
The set pressure of the relief valve (20) is controlled by the pressure of the hydraulic oil discharged from the first hydraulic pump (P),
The control device (40) reversely rotates the first hydraulic pump (P) when the pressure of the hydraulic oil detected by the pressure sensor (PS) is equal to or higher than the set pressure of the relief valve (20). A die cushion device characterized in that the relief valve (20) is opened. The die cushion device according to claim 3,
A second hydraulic pump (P2) for controlling the set pressure of the relief valve (20),
The control device (140) is
When the pressure of the hydraulic oil detected by the pressure sensor (PS) becomes equal to or higher than the set pressure of the relief valve (20), the first hydraulic pump (P1) is reversely rotated and the pressure sensor (PS) is used. The rotational speed of the first hydraulic pump (P1) is controlled so that the detected pressure of the hydraulic fluid becomes the die cushion pressure command value, and
When the pressure of the hydraulic oil detected by the pressure sensor (PS) reaches the die cushion pressure command value after the reverse rotation of the first hydraulic pump (P1) is started, the set pressure of the relief valve (20) is increased. A die cushion device, characterized in that the rotation speed of the second hydraulic pump (P2) is controlled so as to close the relief valve (20). The die cushion device according to claim 1,
The discharge side of the first hydraulic pump (P) is connected to the vent port (23) of the relief valve (20),
The pressure sensor (PS) detects the vent pressure of the relief valve (20),
The control device (240, 340, 540) is
The rotation speed of the first hydraulic pump (P) is controlled according to the vent pressure of the relief valve (20) detected by the pressure sensor (PS),
When the vent pressure of the relief valve (20) detected by the pressure sensor (PS) is equal to or higher than the predetermined pressure value, the first hydraulic pump (P) is rotated in the reverse direction. .. The die cushion device according to claim 1,
A second hydraulic pump (P2) having a discharge side connected to the vent port (23) of the relief valve (20),
The pressure sensor (PS2) detects the vent pressure of the relief valve (20),
The control device (440) is
The rotation speed of the first hydraulic pump (P1) is controlled according to the vent pressure of the relief valve (20) detected by the pressure sensor (PS2),
The set pressure of the relief valve (20) is controlled by controlling the vent pressure of the relief valve (20) with the pressure of the hydraulic oil discharged from the second hydraulic pump (P2),
When the vent pressure of the relief valve (20) detected by the pressure sensor (PS2) becomes equal to or higher than the predetermined pressure value, the first hydraulic pump (P1) and the second hydraulic pump (P2) are reversely rotated. A die cushion device characterized in that The die cushion device according to claim 6,
When the vent pressure of the relief valve (20) detected by the pressure sensor (PS2) exceeds the predetermined pressure value, the first hydraulic pump (P1) and the second hydraulic pump (P2) are reversed. The die cushion of the hydraulic cylinder (10) is rotated and returned to the oil tank (T) with hydraulic oil discharged from the hydraulic cylinder (10) through the first hydraulic pump (P1) that rotates in the reverse direction. The rotation speed of the first hydraulic pump (P1) is controlled so that the pressure becomes the die cushion pressure command value, and
When the die cushion pressure of the hydraulic cylinder (10) reaches the die cushion pressure command value after the reverse rotation of the second hydraulic pump (P2) is started, the set pressure of the relief valve (20) is set before the reverse rotation is started. A die cushion device, characterized in that the rotation speed of the second hydraulic pump (P2) is controlled so that the relief valve (20) is closed by raising it. The die cushion device according to claim 5,
The control device (240, 340, 540) is
A die characterized in that the set pressure of the relief valve (20) is controlled by controlling the vent pressure of the relief valve (20) with the pressure of the hydraulic oil discharged from the first hydraulic pump (P). Cushion device. The die cushion device according to claim 8,
When the vent pressure of the relief valve (20) detected by the pressure sensor (PS) becomes equal to or higher than the predetermined pressure value, the first hydraulic pump (P) is rotated in the reverse direction to open the relief valve (20). The hydraulic fluid discharged from the hydraulic cylinder (10) through the hydraulic cylinder (10) is returned to the oil tank (T), and the first hydraulic pressure is adjusted so that the die cushion pressure of the hydraulic cylinder (10) becomes a die cushion pressure command value. A die cushion device characterized by controlling the rotational speed of a pump (P). The die cushion device according to claim 8 or 9,
The oil passage between the hydraulic cylinder (10) and the first hydraulic pump (P), and the first hydraulic pump (P) from the connection point of the oil passage to which the relief valve (20) is connected. A die cushion device comprising a check valve (30) disposed on the side of the hydraulic cylinder (10) for restricting the flow of hydraulic oil from the hydraulic cylinder (10) to the first hydraulic pump (P). The die cushion device according to claim 8 or 9,
The oil passage between the hydraulic cylinder (10) and the first hydraulic pump (P), and the first hydraulic pump (P) from the connection point of the oil passage to which the relief valve (20) is connected. A die cushion device comprising a solenoid valve (50) disposed on the side. The die cushion device according to claim 10 or 11,
A throttle (60) for connecting the connection point side and the pressure sensor (PS) is provided,
The die cushion device, wherein the pressure sensor (PS) detects the pressure of the hydraulic oil, which is the die cushion pressure of the hydraulic cylinder (10).

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