JP5440838B2 - Hydraulic die cushion device and its position control method - Google Patents

Description

  The present invention relates to a hydraulic die cushion device for a press machine and a position control method thereof.

In a press machine, a work is moved up and down, and a workpiece (workpiece) is sandwiched between an upper mold fixed to the lower surface of the slide when the slide is lowered and a lower mold arranged below the slide. Press to process.
The die cushion device is a device that sandwiches a workpiece between an upper die and a blank holder during press processing in a press machine and applies a wrinkle holding force (cushion force) to the workpiece.

  Conventionally, various types of hydraulic die cushion devices for press machines have been proposed (for example, Patent Documents 1 to 3).

Japanese Patent No. 3591807, “Control Method of Hydraulic Die Cushion Device” JP 2007-222926 A, “Die cushion load control device and press machine equipped with cushion load control device” JP 2008-149346 A, “Die Cushion Device for Press Machine and Die Cushion Operation Control Method”

  The hydraulic die cushion device generally includes a hydraulic cylinder having a piston rod that moves up and down a die cushion (a blank holder, a cushion pad, and a cushion pin) and a servo valve that supplies or discharges hydraulic oil to or from the hydraulic cylinder.

  FIG. 1 is a diagram illustrating a cushion operation of the die cushion device. As shown in this figure, after the slide passes through the bottom dead center, the work is taken out by the work take-out device while the die cushion is locked (stopped). The die cushion is released from the blank holder (or the cushion pin) positioned at the top of the die cushion device after the workpiece take-out device is sufficiently separated from the die cushion and starts to rise.

  In conventional hydraulic die cushion devices, the cushion position is usually controlled by feedforward control and position feedback control, and when a lift occurs after pressing, a damper is used to generate surge pressure and overshoot during stoppage. It was suppressed. This damper includes a mechanical damper such as a shock absorber and a soft damper that performs a damper operation in a controlled manner.

  In the conventional hydraulic die cushion device, when a mechanical damper is used to suppress surge pressure at the time of stopping, the device cost increases. Further, when using a soft damper, the soft damper needs to be adjusted because it is necessary to set the start timing and the damper speed according to the rising speed.

  In the case of a conventional hydraulic die cushion device, locking (stopping) of the die cushion device is performed by fully closing the servo valve, so that pressure oil remains in the hydraulic cylinder during locking, and this pressure oil (residual pressure) There was a problem that the blank holder slightly raised when the slide was raised.

  The present invention has been developed to solve the above-described problems. That is, it is an object of the present invention to suppress the occurrence of surge pressure and overshoot at the time of stopping without increasing the device cost and adjusting time, and pressure oil (residual pressure at the time of locking) Is to provide a hydraulic die cushion device and a position control method thereof.

According to the present invention, a hydraulic die cushion device that sandwiches a workpiece between an upper die of a press machine and a blank holder and moves the workpiece up and down while applying an upward cushion force to the blank holder,
A hydraulic cylinder having a piston rod that moves the blank holder up and down;
A servo valve for supplying or discharging hydraulic oil to the hydraulic cylinder;
A servo valve control device for controlling the servo valve,
The servo valve control device includes a cylinder model for calculating a cylinder movement amount after a predetermined predicted time from a cylinder position of the hydraulic cylinder, an upper chamber pressure, a lower chamber pressure, and a spool position of the servo valve;
A regulator that calculates a servo valve command value so as to reach the target position after the predicted time elapses from the target position and current position of the hydraulic cylinder and the amount of cylinder movement, and controls the servo valve based on the servo valve command value A hydraulic die cushion device is provided.

  The servo valve command value is limited to a predetermined limit value or less, and the servo valve is controlled by the output value of the limiter.

Further, according to the present invention, the press machine includes a hydraulic cylinder having a piston rod that moves the blank holder up and down, a servo valve that supplies or discharges hydraulic oil to the hydraulic cylinder, and a servo valve control device that controls the servo valve. A position control method for a hydraulic die cushion device that sandwiches a workpiece between an upper die and a blank holder and moves the workpiece vertically while applying an upward cushion force to the blank holder,
Calculate the amount of cylinder movement after a predetermined predicted time from the cylinder position of the hydraulic cylinder, the upper chamber pressure, the lower chamber pressure, and the spool position of the servo valve,
From the target position and current position of the hydraulic cylinder, and the amount of cylinder movement, calculate the servo valve command value so that it reaches the target position after the predicted time has elapsed,
A position control method for a hydraulic die cushion device is provided, wherein the servo valve is controlled by the servo valve command value .

Further, the servo valve command value is limited to a predetermined limit value or less, and the servo valve is controlled by the output value of the limiter.

  According to the apparatus and method of the present invention, the servo valve control device predicts the servo valve position after a predetermined predicted time and controls the servo valve, so that surge pressure is generated at the time of stoppage or overshoot occurs. Even if the blank holder rises due to pressure oil (residual pressure) at the time of locking, the servo valve is controlled by predicting these phenomena before the forecast time, so prevent these phenomena beforehand Can do.

According to a preferred embodiment of the present invention, a cylinder model calculates a cylinder movement amount after a predetermined predicted time from a cylinder position of the hydraulic cylinder, an upper chamber pressure, a lower chamber pressure, and a servo valve spool position. can do.
Further, the regulator can calculate the servo valve command value from the target position and current position of the hydraulic cylinder and the cylinder movement amount so that the target position is reached after the predicted time has elapsed.
Therefore, it is possible to control the servo valve by predicting the servo valve position after a predetermined prediction time has elapsed.

  Therefore, by controlling the servo valve according to the calculated servo valve command value, the hydraulic cylinder moves to the target position after the predicted time has elapsed, so that the equipment cost is not increased and adjustment time is not required. The occurrence of surge pressure and overshoot can be suppressed, and the rise of the blank holder due to pressure oil (residual pressure) during locking can be prevented.

Furthermore, the servo valve command value is limited to a predetermined limit value or less by a limiter, and the servo valve is controlled by the output value of the limiter, so that the servo valve is prevented from opening too much and the maximum rising speed of the cushion is limited. be able to.

It is a figure which shows the cushion operation | movement of a die cushion apparatus. It is a block diagram of the hydraulic die cushion apparatus by this invention. It is a block diagram of the servo valve control apparatus by this invention. 1 is a flow diagram of a hydraulic die cushion method according to the present invention. It is operation | movement explanatory drawing of the hydraulic die cushion apparatus by this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

FIG. 2 is a configuration diagram of a hydraulic die cushion device according to the present invention.
The pressing device (not shown) lowers the upper die fixed to the lower surface of the slide that moves up and down with respect to the lower die fixed to the upper surface of the bolster, and moves the workpiece (not shown) between the lower die and the upper die. The (work material) is pressurized and press-molded into a predetermined shape.

In FIG. 2, reference numeral 1 denotes a blank holder. When a workpiece is press-molded with an upper die and a lower die, the blank holder 1 allows the peripheral portion of the lower surface of the workpiece to be placed between the upper die when the workpiece is press-molded. Supporting and wrinkling the workpiece.
That is, the hydraulic die cushion device 10 of the present invention is configured to sandwich a workpiece between the upper die of the press machine and the blank holder 1 and to move the workpiece up and down while applying an upward cushioning force to the blank holder 1. Yes.
In addition, a cushion pad may be used instead of the blank holder 1, and the periphery of the lower surface of the workpiece may be supported between the upper die by a cushion pin and the workpiece may be pressed.

  In FIG. 2, the hydraulic die cushion device 10 of the present invention includes a hydraulic cylinder 12, a servo valve 14, and a servo valve control device 20.

The hydraulic cylinder 12 has a piston rod 11 that moves the blank holder 1 up and down.
In this example, the hydraulic cylinder 12 is arranged upward and vertically, and the blank holder 1 is fixed to the tip (upper end) of the piston rod 11 so as to move up and down integrally.

In FIG. 2, pressure gauges 15 and 16 are provided on the rod side (upper side) and the piston side (lower side) of the hydraulic cylinder 12, respectively, and the upper chamber pressure P _u (t ₀ ) and lower chamber pressure of the hydraulic cylinder 12 are provided. P _d (t ₀ ) is detected. The detected values P _u (t ₀ ) and P _d (t ₀ ) are respectively input to the servo valve control device 20. Note that t ₀ in the parentheses below indicates the current value.
Furthermore, a position detector 17 for detecting the cylinder position x (t ₀ ) of the hydraulic cylinder 12 is provided, and the detected value x (t ₀ ) is input to the servo valve control device 20. In this example, the position detector 17 is arranged so as to detect the position of the blank holder 1, but the cylinder position x (t ₀ ) may be directly detected.
Hereinafter, the cylinder position x (t ₀ ) of the hydraulic cylinder 12 is simply referred to as “cylinder position”.

The servo valve 14 is a servo valve capable of switching the flow direction provided in the middle of the hydraulic piping connecting the hydraulic cylinder 12 and the hydraulic unit 13, supplying hydraulic oil from the hydraulic unit 13 to the hydraulic cylinder 12, and The hydraulic oil is discharged to the hydraulic unit 13.
The flow rate Q of hydraulic fluid supplied from the servo valve 14 to the hydraulic cylinder 12 is proportional to the opening degree I _sv (t ₀ ) of the servo valve. The opening degree I _sv (t ₀ ) is input to the servo valve control device 20. The opening degree I _sv (t ₀ ) is, for example, −100 to 100%.

The servo valve control device 20 controls the servo valve 14 by predicting the servo valve position after the elapse of a predetermined prediction time t. Here, the predicted time t is a time (for example, 0.1 sec) that is about 1 to 10 times the scan time of the control device.
The servo valve command value I _cmd output from the servo valve control device 20 is, for example, −100 to 100%, and the servo valve opening I _sv moves to that position in accordance with the servo valve command value I _cmd .

FIG. 3 is a block diagram of a servo valve control device according to the present invention.
In this figure, the servo valve control device 20 of the present invention has a cylinder model 22, a regulator 24 and a limiter 26. The servo valve control device 20 is, for example, a computer (PC), and the cylinder model 22, the regulator 24, and the limiter 26 are computer programs installed in the computer. In addition, this invention is not limited to this structure, You may comprise the cylinder model 22, the regulator 24, and the limiter 26 as a separate control controller or an integrated control controller, respectively.
A programmable logic controller (PLC) or other control device may be used instead of the computer.

The cylinder model 22 is based on the cylinder position x (t ₀ ), the upper chamber pressure P _u (t ₀ ), the lower chamber pressure P _d (t ₀ ), and the servo valve spool position I _sv (t ₀ ) of the hydraulic cylinder 12. The cylinder movement amount Δx (t) after the predicted time t has elapsed is calculated.

The regulator 24 determines the servo valve command value I _cmd so that the target position is reached after the predicted time t has elapsed from the target value x (t) of the cylinder position, the current position x (t ₀ ), and the cylinder movement amount Δx (t). Calculate

The limiter 26 limits the servo valve command value I _cmd to a predetermined limit value or less.
That is, when the servo valve command value I _cmd is less than the limit value, the servo valve command value I _cmd is output to the servo valve, and when the servo valve command value I _cmd exceeds the limit value, the limit value is set to the servo valve. The command value I _cmd is output to the servo valve.

2 and 3, the servo valve position I _sv (t), the lower chamber cylinder force F _d (t), the upper chamber cylinder force F _u (t), and the cylinder force F _c (t) after the predicted time t has elapsed. The cylinder movement amount Δx (t) can be expressed by Equations (1) to (5) of Equation 1.
Here, equation (1) is a prediction equation of servo valve position I _sv (t), equations (2) and (3) are lower chamber cylinder force F _d (t) and upper chamber cylinder force F _u (t), equation (4) ) Is a cylinder force F _c (t), and Expression (5) is an expression representing the cylinder movement amount Δx (t).
K _qd is the volume modulus of the lower chamber cylinder, K _qu is the volume modulus of the upper chamber cylinder, S _d is the lower chamber pressure area, _Su is the upper chamber pressure area, τ is the time constant of the control system, K _sv the flow coefficient of the servo valve, M _c cushion own weight, xi] is the dynamic friction coefficient, t ₀ is the current time, t is the predicted future time.

  FIG. 4 is a flow diagram of a hydraulic die cushion method according to the present invention. In this figure, the method of the present invention comprises steps (strokes) S1 to S6.

In step S1, the sensor input, that is, the cylinder position x (t ₀ ) of the hydraulic cylinder 12, the upper chamber pressure P _u (t ₀ ), the lower chamber pressure P _d (t ₀ ), and the servo valve spool position I _sv ( From t ₀ ), cylinder speed Δx (t ₀ ), upper chamber cylinder force F _u (t ₀ ), and lower chamber cylinder force F _d (t ₀ ) are calculated.
The cylinder speed Δx (t ₀ ) is obtained from the time derivative of the cylinder position x (t ₀ ). The upper chamber cylinder force F _u (t ₀ ) and the lower chamber cylinder force F _d (t ₀ ) are the upper chamber pressure receiving area S _u , the lower chamber pressure receiving area S _d and the pressure (upper chamber pressure P _u (t ₀ )). And the lower chamber pressure P _d (t ₀ )).

In step S2, the upper chamber cylinder force F _u (t) and the lower chamber cylinder force F _d (t) after the elapse of the predicted time t are calculated by the equations (1), (2), and (3).

In step S3, the cylinder movement amount Δx (t) after the elapse of the predicted time t is calculated by the equations (4) and (5). The cylinder movement amount Δx (t) obtained here is a function of the predicted time t and the servo valve command value I _cmd .

In step S4, a difference Δxa between the target position x (t) of the cylinder and the current position x (t ₀ ) is calculated.

In step S5, the predicted time (t) is substituted into the function of Δx, and the servo valve command value I _cmd is calculated so that Δx = Δxa. The predicted time t is a time (for example, 0.1 sec) that is about 1 to 10 times the scan time of the control device.

In step S6, when the servo valve command value I _cmd exceeds the limit value, the limit value is output as the servo valve command value I _cmd .

FIG. 5 is an operation explanatory view of the hydraulic die cushion device according to the present invention. In this figure, (A) shows the target value of the cylinder position, (B) shows the servo valve command value I _cmd , and (C) shows the actual cylinder position. In each figure, the horizontal axis represents elapsed time.

According to the above-described apparatus and method of the present invention, the servo valve control device 20 predicts the servo valve position after the predetermined prediction time t has elapsed and controls the servo valve.
That is, the future servo valve position I _sv is predicted by the internal model (cylinder model 22) constituting the servo valve control device 20 (after the predicted time t has elapsed), and the servo valve command value I _cmd is matched with the predicted value. Calculate
Therefore, even when the target value of the cylinder position changes suddenly as in A2-A3 in FIG. 5A, the servo valve command is not delayed with respect to A2-A3 as in B2-B3 in FIG. The value I _cmd can be varied.
At this time, since the servo valve command value I _cmd becomes an excessive command value when the cushion starts to move, the ascending speed is controlled by the limiter 26.

By predicting the servo valve position as described above, it is possible to set the time required for ascending by simple parameter adjustment to the shortest. As shown in B4-B5 of FIG. When the value exceeds the value, the servo valve is gradually closed, so that generation of surge pressure and overshoot can be prevented, as indicated by C3 in FIG.
Similarly, the rising speed of the cushion can be made variable according to the press speed. Further, it is possible to prevent an increase due to the residual pressure during locking.

  In addition, this invention is not limited to embodiment mentioned above, is shown by description of a claim, and also includes all the changes within the meaning and range equivalent to description of a claim.

1 Blank holder,
10 Hydraulic die cushion device, 11 Piston rod,
12 hydraulic cylinders, 13 hydraulic units, 14 servo valves,
15, 16 pressure gauge, 17 position detector,
20 Servo valve control device,
22 cylinder model, 24 regulator,
26 Limiter

Claims (4)

A hydraulic die cushion device that sandwiches a workpiece between an upper die of a press machine and a blank holder and moves the workpiece up and down while applying an upward cushioning force to the blank holder,
A hydraulic cylinder having a piston rod that moves the blank holder up and down;
A servo valve for supplying or discharging hydraulic oil to the hydraulic cylinder;
A servo valve control device for controlling the servo valve,
The servo valve control device includes a cylinder model for calculating a cylinder movement amount after a predetermined predicted time from a cylinder position of the hydraulic cylinder, an upper chamber pressure, a lower chamber pressure, and a spool position of the servo valve;
A regulator that calculates a servo valve command value so as to reach the target position after the predicted time elapses from the target position and current position of the hydraulic cylinder and the amount of cylinder movement, and controls the servo valve based on the servo valve command value A hydraulic die cushion device characterized by that. 2. The hydraulic pressure according to claim 1 , wherein the servo valve control device includes a limiter that limits the servo valve command value to a predetermined limit value or less, and controls the servo valve based on an output value of the limiter. Die cushion device. A hydraulic cylinder having a piston rod that moves the blank holder up and down, a servo valve that supplies or discharges hydraulic oil to and from the hydraulic cylinder, and a servo valve control device that controls the servo valve. Is a position control method of a hydraulic die cushion device that sandwiches a workpiece between the two and moves it up and down while applying an upward cushioning force to the blank holder,
Calculate the amount of cylinder movement after a predetermined predicted time from the cylinder position of the hydraulic cylinder, the upper chamber pressure, the lower chamber pressure, and the spool position of the servo valve,
From the target position and current position of the hydraulic cylinder, and the amount of cylinder movement, calculate the servo valve command value so that it reaches the target position after the predicted time has elapsed,
A position control method for a hydraulic die cushion device, wherein the servo valve is controlled by the servo valve command value . The position control method according to claim 3 , wherein the servo valve command value is limited to a predetermined limit value or less, and the servo valve is controlled by an output value of a limiter.

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