JPH01249227A - Pressure controller for press die cushion - Google Patents

Abstract

PURPOSE:To obtain controllability all over the region from a low voltage to a high voltage by providing a gain constant electronic switch in a gain control circuit of a pressure control unit of a press die cushion. CONSTITUTION:A pressure control signal generating device 8 selects a cushion pattern by a computer 10 and reads out an angle data, a voltage data according to a pattern number. A crank angle is detected from a synchronous oscillator 11 and inputted into a pressure control generator 8. A set pressure instruction signal is outputted from an angle data crank angle and a voltage data to a pressure control unit 7. The pressure control unit 7 compares an inputted signal and a feedback signal from a pressure tranducer 17 detecting the primary side pressure of a servovalve 5 with a signal corrected by a constant K2 to output a deviation to a gain control circuit 18. The circuit 18 switches gain constants K1, KP, KI automatically by gain constant switching circuit 19 according to a set pressure instruction signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a pressure control device for a hydraulically controlled duct installed in a press.

[Conventional technology]

As shown in FIG. 3, a pressure control device for a hydraulically controlled ductition installed in a conventional press includes a servo valve d provided between a hydraulic cylinder b and an oil tank C provided in a traction unit a. Desired cushioning characteristics are obtained by controlling the opening degree of this servo valve d by a pressure control unit e.

In the figure, f is a signal generator that generates a pressure control signal in synchronization with the crank angle input from a synchro transmitter g installed on the main shaft of the press, j is a sequencer, and h is a station necessary for control. It is a converter that sends the pattern to sequencer j.

[Problem to be solved by the invention]

In the pressure control device for a hydraulically controlled ductus as described above, when controlling the hydraulic pressure in the hydraulic cylinder b, the primary side flow rate of the servo valve d changes nonlinearly, and the characteristics of the servo valve d also change between the closed end and the open end. Although it is partially linear, the linearity collapses on the side, but it is non-linear overall.

Therefore, when the pressure of hydraulic cylinder b is gain adjusted on the low pressure side, a linear control result shown by the solid line is obtained in response to the command shown by the broken line in FIG.
As shown in FIG. 4(b), the control result becomes nonlinear.

Conversely, if the gain is adjusted on the high pressure side as shown in Figure 5 (b), the control result will become non-linear on the low pressure side as shown in Figure 5 (a). As shown in FIG. 4 (c) and FIG. 5 (c), there was a problem that satisfactory controllability could not be obtained.

This invention was made with the aim of improving the above-mentioned conventional problems, and aims to provide a pressure control device for a press die cushion that can obtain sufficient controllability over the entire range from low pressure to high pressure. .

[Means and operations for solving the problem] In order to achieve the above object, the present invention has a servo valve provided between a hydraulic cylinder and an oil tank provided in a die cushion unit of a breather. In a press die cushion pressure control device that is controlled via a pressure control unit by a set pressure command signal output from a pressure control signal generator according to a cushion pattern, a gain adjustment provided in the pressure control unit is provided. By installing a gain constant switching circuit in the circuit that automatically switches the gain constant according to the set pressure command signal input from the pressure control signal generator, linear control is achieved over the entire range from the low pressure side to the high pressure side. The present invention provides a pressure control device for a press die cushion capable of achieving high performance.

〔Example〕

An embodiment of the present invention will be described in detail with reference to the drawings.

In the figure, 1 is a die cushion unit installed in a press, and has an air cylinder 1a and a hydraulic cylinder 1b. tion pad 2 is provided.

The hydraulic cylinder 1b and the oil tank 4 provided in the hydraulic unit 3 are connected via a servo valve 5 and a suction pipe 6 for replenishing released oil, and the servo valve 5 is connected to a pressure control unit 7. It is now controlled by.

Further, a set pressure command signal is inputted to the pressure control unit 7 from a pressure control signal generator 8.

The pressure control signal generator 8 is equipped with a data setter 9, and a pattern N set in the data setter 9 is provided.
The O1 angle data and voltage data are set to pattern N by selecting a cushion pattern using the personal computer 10.

It is read out according to the

On the other hand, a synchro transmitter 11 installed on the main shaft of the press
The crank angle is detected and inputted to the pressure control signal generator 8, and this signal is sent to the S/D converter 1.
Interface 1 after being converted into a digital signal by 2
3 to the point detection circuit 14, point data is detected from the angle data read from the data setter 9 and the crank angle signal from the synchro transmitter 11, and is output to the voltage selection circuit 15.

The voltage selection circuit 15 selects a voltage from the voltage data according to the input point data, converts the obtained voltage into analog by the D/A converter 16, and outputs it to the pressure control unit 7 as a set pressure command signal. It has become.

The pressure control unit 7 compares the input signal with a signal obtained by correcting the feedback signal from the pressure transducer 17 that detects the primary side pressure of the servo valve 5 by a constant of 2, and outputs the deviation to the gain adjustment circuit 18. do.

The gain adjustment circuit 18 adjusts the gain constant K 1 according to the set pressure command signal input from the pressure control signal generator 8.
, K P , and K I , and by switching the gain constants on the low-voltage side and the high-voltage side, the results shown in Fig. 2 (a), (b), and (c) are obtained. As shown, sufficient controllability can be obtained over the entire range from the low pressure side to the high pressure side.

The broken lines in Figure 2 (a), (b), and (c) are command signals,
Solid lines indicate control results.

〔Effect of the invention〕

As detailed above, the present invention provides a gain constant switching circuit for automatically switching the gain constant according to a set pressure command signal output from a pressure control signal generator in a gain adjustment circuit of a pressure control unit. Therefore, sufficient controllability can be obtained over the entire range from the low pressure side to the high pressure side.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being a block diagram, FIGS.
The figure is an explanatory diagram of the conventional method, and FIGS. 4(a), (b), and (c) and FIGS. 5(a), (b), and (c) are explanatory diagrams of the same operation. 1 is a die cushion unit, 1b is a hydraulic cylinder, 4
is an oil tank, 5 is a servo valve, 7 is a pressure control unit, 8
is a pressure control signal generator, 18 is a gain adjustment circuit, 1
9 is a gain constant switching circuit. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] A servo valve 5 provided between a hydraulic cylinder 1b and an oil tank 4 provided in a die cushion unit 1 of a press is controlled by a set pressure outputted from a pressure control signal generator 8 according to a cushion pattern input in advance. In a press die cushion pressure control device that is controlled via a pressure control unit 7 by a command signal, a pressure control signal generator 8 inputs a signal to a gain adjustment circuit 18 provided in the pressure control unit 7. A press die cushion pressure control device comprising a gain constant switching circuit 19 that automatically switches the gain constant according to a set pressure command signal.