JPH08112700A - Device for controlling pressurizing force of hydraulic press - Google Patents

Abstract

PURPOSE: To obtain a pressurizing force control device, in which the pressurizing force of a hydraulic press is accurately controlled to a necessary pressurizing force. CONSTITUTION: A correcting value of the resistance in a line is outputted by the detected value P2 of a first pressure sensor 2 arranged in the first pipe line 11 in the pressurizing side oil chamber 1A of a hydraulic cylinder 1, the detected value P3 of a second pressure sensor 3 arranged in the line 13 in the back pressure side oil chamber 1B, the detected value V of a velocity sensor 4 to the piston 15 of the hydraulic cylinder 1, a pressurizing force setting 17 and a first computing element 7, second computing element 8 and third computing element 9 contained in a pressurizing force control unit 6. The pressurizing force of the hydraulic press is controlled by continuously and correctively controlling a pressure control valve 5 arranged in the first pipe line 11 during pressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for precise control in the field of controlling the pressing force of a hydraulic press.

[0002]

2. Description of the Related Art In a conventional pressurizing force control device for a hydraulic press, a pressure sensor detects a pressure in a pressurizing side oil chamber of a hydraulic cylinder, and a control amount calculated from the detected value and a set value of a pressurizing force setter is applied. The pressure was controlled. In this case, when the pressure of the back pressure side oil chamber cannot be ignored, the pressure of the hydraulic press was controlled based on the pressure calculated from the pressure of the pressure side oil chamber and the pressure of the back pressure side oil chamber. .

[0003]

In the above-mentioned conventional pressurizing force control device, it is desirable to directly attach the pressure sensor to the oil chamber of the hydraulic cylinder, but due to structural limitations of the hydraulic press such as ease of attachment and maintenance. In some cases, the hydraulic cylinder may have to be attached to a conduit away from the oil chamber.
In such a case, between the pressure detected by the pressure sensor and the pressure in each oil chamber, there is a difference in pressure loss due to the line resistance from the pressure sensor to the oil chamber. This pressure loss varies depending on the flow rate of oil flowing through the pipe line, which has a drawback that it causes an error in the pressing force during press working.

An object of the present invention is to eliminate these drawbacks, and to provide a pressurizing force control device for a hydraulic press which controls the pressure so that an error does not occur in the pressurizing force depending on the mounting position of the pressure sensor.

[0005]

In order to achieve the above-mentioned object, a first pipe provided in a first pipeline of a pressure side oil chamber of a hydraulic cylinder.
A first arithmetic unit for obtaining a measured pressing force from a detection value of the pressure sensor and a detection value of a second pressure sensor provided in the second pipe line of the back pressure side oil chamber, and a speed sensor for detecting the piston speed of the hydraulic cylinder. (Or the speed may be obtained from a position sensor that detects the piston position), and the pressure loss due to the line resistance from the first pressure sensor to the pressurizing side oil chamber and the second pressure sensor to the back pressure side oil chamber. Each is calculated, the pressing force loss due to this pressure loss is calculated, and then the second calculating unit that calculates the net pressing force from the measured pressing force and the pressing force loss, and the value from this net pressing force and the pressing force setter are applied. The 3rd which operates the pressure control valve which controls the oil pressure of the pipeline leading to the pressure side oil chamber
The pressurizing force of the hydraulic press is controlled by the arithmetic unit and the pressure control valve to configure a pressurizing force control device of the hydraulic press.

[0006]

The first computing unit has a detection value of the first pressure sensor provided in the pipe line to the pressurizing side oil chamber and a detection value of the second pressure sensor provided in the pipe line to the back pressure side oil chamber. From the pressure sensor, the second calculator calculates the pressure loss due to the line resistance from the detected value of the speed sensor that detects the operating speed of the hydraulic cylinder, and then the pressure loss from this pressure loss. Further, the net pressure is calculated from the obtained pressure and the measured pressure, and the third calculator calculates the operation amount of the pressure control valve from the net pressure and the value from the pressure setting device, and the pressure control valve Output to. With this operation amount, the pressure control valve provided in the conduit leading to the pressure side oil chamber of the hydraulic cylinder is operated to obtain a required pressing force.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a hydraulic press during pressurization according to an embodiment of the present invention. Pressure side oil chamber 1 of hydraulic cylinder 1
A is the first pipeline 11, and the back pressure side oil chamber 1B is the second pipeline 1
3 is connected to the directional control valve 16. Further, the first pressure sensor 2 and the pressure control valve 5 are connected to the first pipeline 11, and the second pressure sensor 3 is connected to the second pipeline 13. The direction switching valve 16 is connected to the hydraulic power source 12 and the tank 14, and the pressure control valve 5 is connected to the tank 14.

The piston 15 descends and the parts (not shown)
The pressurizing side oil chamber 1 of the hydraulic cylinder 1
Pressure oil is supplied to A, and oil is discharged from the back pressure side oil chamber 1B. The pressure side oil chamber 1A has a pressure P0 and the back pressure side oil chamber 1B has a pressure P1.
The pressing force F necessary for press working is generated in the.

The pressure P0 of the pressure side oil chamber 1A and the first conduit 11
The detection value P2 of the first pressure sensor 2 provided in the above, the pressure P1 of the back pressure side oil chamber 1B and the detection value P3 of the second pressure sensor 3 provided in the second pipeline 13 are affected by the pipeline resistance, respectively. Therefore, pressure loss occurs. This pressure loss is due to the pressure loss proportional to the square of the flow rate due to the conduit resistance of the fluid flowing through the conduit.

The first calculator 7 of the pressure control device 6 detects the detection signal (P2) from the first pressure sensor 2 and the second pressure sensor 3.
Detection signal (P3) is input, and the respective pressure values are multiplied by the areas of the pressurizing side and the back pressure side of the hydraulic cylinder 1 which are stored in advance, and the difference is calculated to obtain the measured pressurizing force. The pressing force is output to the second computing unit 8.

The second calculator 8 detects the speed (V) of the speed sensor 4 which detects the speed of the piston 15 of the hydraulic cylinder 1.
Is input, and the speed value V and the areas of the pressure side and the back pressure side of the hydraulic cylinder 1 stored in advance and the first,
From the area of the second pipelines 11 and 13 and the physical property value of oil, the pressure loss due to the pipeline resistance is calculated, and the net pressure is calculated from the pressure loss obtained from this pressure loss and the measured pressure from the first calculator 7. Is output to the third computing unit 9.

The third computing unit 9 determines the pressure connected to the first conduit 11 based on the input value of the predetermined pressing force from the pressing force setting unit 17 and the net pressing force from the second computing unit 8. The operation amount of the control valve 5 is obtained and output to the pressure control valve 5.

In operation, the piston 15 of the hydraulic cylinder 1 placed in the ascending limit is operated by the directional control valve 16 in response to a command from a press control device (not shown), so that the pressure oil from the hydraulic power source is supplied. Is supplied to the pressure side oil chamber 1A,
At the same time, when the oil is drained from the back pressure side oil chamber 1B, the descent starts.

The output signals of the first pressure sensor 2 provided in the first conduit 11 and the second pressure sensor 3 provided in the second conduit 13 are output to the first calculator 7 and to the speed sensor 4 provided to the piston 15. The output signal is constantly input to the second computing unit 8 and the third computing unit 9
Thus, the pressure control valve 5 is constantly controlled.

These sensors 2, 3, 4 and the arithmetic unit 7,
The pressurizing force control device 6 composed of 8 and 9 performs a feedback control of a series of detection and control until the press working is completed, thereby controlling the pressurizing force F to be accurate.

[0016]

As is apparent from the above description, according to the present invention, since the control is performed so that an error due to the pressure loss of the pipeline does not occur, an accurate pressing force can be continuously obtained during the press working, Highly accurate press working is possible.

Further, even if the flow rate in the pipeline changes and the descending speed of the hydraulic cylinder changes, it is possible to continuously control the accurate pressing force. Further, since the pressure sensor can be attached at any position, piping to the hydraulic cylinder becomes easy.

Further, it can be applied not only to press working but also to pressure control such as cushion, counter punch and knockout.

[Brief description of drawings]

FIG. 1 is an explanatory view of a hydraulic press showing an embodiment of the present invention.

[Explanation of symbols]

1 is a hydraulic cylinder, 1A is a pressure side oil chamber, 1B is a back pressure side oil chamber, 2 is a first pressure sensor, 3 is a second pressure sensor, 4 is a speed sensor, 5 is a pressure control valve, and 6 is a pressure control device. , 7 is a first arithmetic unit, 8 is a second arithmetic unit, 9 is a third arithmetic unit, 11 is a first pipeline, 12 is a hydraulic source, 13 is a second pipeline, 14 is a tank, 15 is a piston, 16 Is a direction switching valve, 17 is a pressurizing force setter, F is a pressurizing force, P0 is a pressure in the pressurizing side oil chamber 1A, and P is a P pressure.
1 is the pressure of the back pressure side oil chamber 1B, P2 is the detection value of the first pressure sensor 2, P3 is the detection value of the second pressure sensor 3, and V is the detection value of the speed sensor 4.

Claims (1)

[Claims] 1. A hydraulic press having a hydraulic cylinder, wherein a detection value of a first pressure sensor provided in a first pipe line to the pressurizing side oil chamber of the hydraulic cylinder and a second pipe line to the back pressure side oil chamber. And a detection value of the first pressure sensor, a detection value of a speed sensor that detects a piston speed of the hydraulic cylinder, and a detection value of the first pressure sensor. From the detected value of the second pressure sensor, the pressure loss due to the line resistance to the pressurizing side oil chamber and the back pressure side oil chamber is calculated, and the pressurizing pressure loss due to this pressure loss is calculated to obtain the measured pressurizing force. And a second calculator that calculates a net pressure from the pressure loss, and the net pressure and the values of the pressure setting device, which are connected to the first pipeline to the oil chamber on the pressure side. Operation amount of the pressure control valve that controls the pressure of the pressure chamber side oil chamber A third calculator that calculates and outputs the value to the pressure control valve is operated to control the hydraulic pressure of the pressure side oil chamber to control the pressurizing force of the hydraulic press during press working. A pressure control device for a hydraulic press, which is controlled.