JP2001205342A - Ram position control method and ram position controller in press brake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ram position control method and an apparatus therefor in a press brake by which a ram is positioned at command position regardless of a pressure/oil temperature of a hydraulic oil supplied from a hydraulic pump to a hydraulic cylinder. SOLUTION: A hydraulic pump 35 is operated by rotating a servo motor 43 in conforming to a position command from a position command part 71, the hydraulic oil is supplied to hydraulic cylinders 13R, 13L to move a ram 5U vertically. A height position of the ram 5U at this time is detected by a position detector 11 to be feed-backed, further the hydraulic oil pressure in the hydraulic cylinders 13R, 13L at this time is detected by a pressure sensor 21 as well as an oil temperature of the hydraulic oil is detected by an oil temperature sensor 19, a monitor part 81 obtains a position correcting quantity from the relation of a deviation quantity of a ram position for the pressure/oil temperature which is obtained in advace and stored in a memory 83, and outputs a corrected position command to a servo motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ram position control method and a ram position control device for a press brake for performing bending by relatively vertically moving an upper table or a lower table as a ram.

[0002]

2. Description of the Related Art FIG. 5 shows a flow of ram position control in a press brake 101 which is well known in the related art. The press brake 101 moves the upper table 103U, which is a ram on which the punch P is mounted, up and down by a hydraulic cylinder 105 to bend the work in cooperation with a die D mounted on the lower table 103L. is there.

That is, a position command from the position command unit 107 is sent to a gain determining unit 111 via an adder 109. The gain determining unit 111 determines the ram operation gain, amplifies the command by the amplifier 113, and
15 to issue a command. The hydraulic pump 117 is operated by the servomotor 115, and the hydraulic cylinder 105 is operated.
Moves up and down to move the upper table 103U up and down.

The vertical position of the upper table 103U is detected by a ram position detector 119 and fed back to the adder 109 via a position counter 121 to form a servo loop.

[0005]

However, in such a conventional technique, as shown in the zero pump efficiency characteristic of FIG. In order to hold the table 103U at a fixed position, it is necessary to rotate the hydraulic pump 117. However, as shown in FIG. 6, since the rotation speed of the hydraulic pump 117 varies depending on the pressure and oil temperature of the hydraulic oil, the upper table 103 which is a ram
There is a problem that U cannot be positioned at the command position.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above-mentioned problems of the prior art, and a ram is provided regardless of the pressure and oil temperature of hydraulic oil supplied from a hydraulic pump to a hydraulic cylinder. It is an object of the present invention to provide a ram position control method using a hydraulic cylinder capable of positioning at a command position and a device therefor.

[0007]

According to a first aspect of the present invention, there is provided a method for controlling a ram position using a hydraulic cylinder, comprising the steps of: A ram position control method of a press brake in which a ram is moved up and down using a hydraulic cylinder operated by hydraulic oil, and a work is bent in cooperation with a punch and a die, wherein the servo motor is controlled based on a position command. Rotate and feed back a position signal from a ram position detector that detects the position of the ram at this time, and determine the position from the relationship of the deviation amount of the ram position with respect to the pressure and oil temperature in the hydraulic cylinder obtained in advance. A correction value is obtained, the position command is corrected, and the servomotor is rotated.

Accordingly, the hydraulic pump is operated by rotating the servomotor in accordance with the position command, and the hydraulic oil is supplied to the hydraulic cylinder to move the ram up and down. The height position of the ram at this time is detected and fed back by the ram position detector, and the pressure and the oil temperature of the hydraulic oil in the hydraulic cylinder at this time are detected, and the pressure and the oil temperature obtained in advance are determined. A position correction amount is obtained from the relationship between the ram position deviation amounts, and a corrected position command is issued to the servomotor.

According to a second aspect of the present invention, there is provided a ram position control device using a hydraulic cylinder, wherein a servomotor operates a hydraulic pump, and the ram is moved up and down using a hydraulic cylinder operated by hydraulic oil supplied from the hydraulic pump. A ram position control device for a press brake that performs a bending process on a workpiece by cooperation of a punch and a die, and detects a position of the ram, and detects and feeds back the position of the ram. A ram position detector, a memory for storing a relationship between a pressure and an oil temperature in the hydraulic cylinder and a ram position deviation amount, and a pressure and an oil temperature from a pressure sensor and an oil temperature sensor provided in the hydraulic cylinder. And the ram position deviation amount is determined from the relationship between the pressure and oil temperature stored in the memory and the ram position deviation amount based on these values. A monitoring unit for correcting the position command and is characterized in that it comprises an.

Therefore, the hydraulic pump is operated by rotating the servo motor in accordance with the position command from the position command unit, and the hydraulic oil is supplied to the hydraulic cylinder to move the ram up and down.
The height position of the ram at this time is detected by the ram position detector and fed back, and the pressure of the hydraulic oil in the hydraulic cylinder at this time is detected by the pressure sensor, and the oil temperature of the hydraulic oil is detected by the oil temperature sensor. Then, the monitoring unit monitors the pressure and the oil temperature, obtains a position correction amount from the relationship between the deviation amount of the ram position with respect to the pressure and the oil temperature obtained in advance and stored in the memory, and obtains a position command to the servomotor. Is corrected.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIGS. 2 and 3 show the entirety of the press brake 1 according to the present invention. The press brake 1 has side plates 3L, 3R erected on the left and right. An upper table 5U as a ram is provided on the upper front end surface of the side plates 3L, 3R so as to be movable up and down.
A lower table 5L is provided on the lower front surface of the R.

An intermediate plate 7 is provided at the lower end of the upper table 5U.
The punch P is provided so as to be exchangeable via the. Also,
A die D is provided at the upper end of the lower table 5L via a die base 9 so as to be exchangeable.

A linear scale 11 is provided as a ram position detector for measuring the height position of the upper table 5U, and the distance between the punch D and the die D is obtained from the height of the punch P to complete the bending process. Detection of whether or not it has been done, detection of the bending angle, and security are performed.

Hydraulic cylinders 13L and 13R are provided on the upper front surfaces of the left and right side plates 3L and 3R, respectively, and the piston rods 17L and 17R mounted on the pistons 15L and 15R of the hydraulic cylinders 13L and 13R are described above. An upper table 5U is attached. The hydraulic cylinders 13L and 13R are provided with an oil temperature sensor 19 for detecting the oil temperature of the hydraulic oil and a pressure sensor 21 for detecting the pressure.

Next, referring to FIG.
The hydraulic circuit for L and 13R will be described. In addition,
Since exactly the same hydraulic circuit is provided for the left and right hydraulic cylinders 13L and 13R, the right hydraulic cylinder 13R and the hydraulic circuit will be described below.

The upper cylinder chamber 23U of the hydraulic cylinder 13R for vertically moving the upper table 5U, which is a ram, is connected to a prefill valve 27 by a pipe 25,
9 is connected to the oil tank 31.

The upper cylinder chamber 23U is provided with a pipe 3
3 is connected to one side of a bidirectionally rotatable bidirectional piston pump 35 as a hydraulic pump. A pipe 37 is connected to the pipe 33 on the way, and is connected to the oil tank 31 via a check valve 39 and a suction filter 41. The bidirectional piston pump 35 is driven to rotate by an AC servomotor 43 as a servomotor.

On the other hand, a pipe 45 is connected to the lower cylinder chamber 23L of the hydraulic cylinder 13R, and a counter balance valve 47 and a sequence switching valve 49 which is an electromagnetic poppet valve are provided in parallel. The counter balance valve 47 and the sequence switching valve 49 are connected to the other side of the bidirectional piston pump 35 by a pipe 51. A pipe 53 is connected to the pipe 51 on the way, and the pipe 53 is connected to the oil tank 31 via a check valve 55 and a suction filter 57.

A throttle valve 59 and a high-pressure priority type shuttle valve 61 are provided between the pipe 45 and the pipe 33. A pipe 63 is connected to the discharge side of the high-pressure shuttle valve 61. The pipe 63 is provided with a relief valve 65 and a pipe 67 connected to the oil tank 31.

A control device 69 for controlling the AC servomotor 43 for driving the bidirectional piston pump 35 to rotate is:
A position command unit 71 for commanding the position of the upper table 5U, which is a ram, has an adder 7
The ram operation gain determination section 75 is connected via the third section. Further, the ram operation gain determination unit 75
7 so as to send a command to the AC servomotor 43.

The adder 73 is connected to a position counter 79 which receives the position signal of the upper table 5U sent from the linear scale 11 and detects the actual position. A servo loop in which the 5U position is fed back is configured.

Further, receiving the detection signals from the oil temperature sensor 19 and the pressure sensor 21 provided on the hydraulic cylinder 13R, the pressure and the oil temperature are monitored to monitor the upper table 5U.
A monitoring unit 81 for correcting the position command is provided, and corrects the command signal from the ram operation gain determining unit 75.

The monitoring unit 81 is connected to a memory 83 which stores the relationship between the pump characteristics and the ram position deviation amount with respect to the pressure and the oil temperature as shown in FIG. Have been. Therefore, the monitoring unit 81
Calculates the ram position deviation amount from the memory 83 based on the pressure from the pressure sensor 21 and the oil temperature from the oil temperature sensor 19, and corrects the position command using this as a correction value. The corrected command value is commanded to the AC servomotor 43.

With the above structure, the upper cylinder chamber 23U and the lower cylinder chamber 23L are filled with hydraulic oil, the bidirectional piston pump 35 is stopped, and the piston 15R is at the top dead center. When the upper table 5U is rapidly lowered by 13R, the sequence switching valve 49 is switched to connect the pipes 45 and 51, and the bidirectional piston pump 35 is rotated by the AC servomotor 43.

In the case of performing the bending process by further descending,
The sequence switching valve 49 is set to the state shown in FIG. 1, and the hydraulic oil from the lower cylinder chamber 23L returns to the bidirectional piston pump 35 through the pipe 45, the counter balance valve 47, and the pipe 61, and further from the pipe 33. The hydraulic cylinder 13R is supplied to the upper cylinder chamber 23U. Thereby, the piston 15R descends and the upper table 5U descends to perform bending.

Since the cross-sectional area of the lower surface of the piston 15R is smaller than that of the upper surface, the amount of hydraulic oil injected into the upper cylinder chamber 23U from the lower cylinder chamber 23L to the bidirectional piston pump 35 is smaller. Since the amount of the returning hydraulic oil is small, the hydraulic oil is replenished from the oil tank 31 via the check valve 55.

On the other hand, when raising the upper table 5U, the sequence switching valve 49 is switched to the state shown in FIG. 1, and the AC servo motor 43 is switched by the inversion command from the position command section 71 to the above-described case. By rotating in the opposite direction to reverse the bidirectional piston pump 35, the hydraulic oil from the upper cylinder chamber 23U in a state where the piston 15R is lowered is supplied to the pipe 33, the bidirectional piston pump 35, the pipe 51, the sequence switching valve 49, and the pipe. It is supplied to the lower cylinder chamber 23L through 45 and the like. Thereby, the piston 1
5R rises and the upper table 5U rises.

When the pressure of the hydraulic oil injected into the lower cylinder chamber 23L becomes higher than a predetermined value, the pre-fill valve 27 is opened by the pilot signal 85 and the upper cylinder chamber 23L is opened.
From U, the oil is sent to the oil tank 31 through the prefill valve 27.

When positioning the upper table 5U at a fixed position, the ram operation gain determining section 75 determines the ram operation gain from the position command from the position command section 71 and the position signal from the linear scale 11, and monitors the ram operation gain. The unit 81 monitors the oil temperature from the oil temperature sensor 19 and the pressure from the pressure sensor 21, obtains the ram position deviation amount based on the data stored in the memory 83, corrects the position command, and corrects the position command.
And issues a command to the AC servomotor 43.

From the above results, the upper table 5U can be accurately positioned at a predetermined position without being affected by the pressure and oil temperature of the hydraulic oil.

It should be noted that the present invention is not limited to the above-described embodiment of the present invention, but by making appropriate changes,
It can be implemented in other aspects. That is, in the embodiment of the invention described above, the press brake 1 for moving the upper table 5U up and down has been described. However, the same applies to the press brake for moving the lower table 5L up and down.

[0033]

As described above, in the ram position control method using the hydraulic cylinder according to the first aspect of the present invention, the hydraulic pump is operated by rotating the servomotor in accordance with the position command, and the hydraulic oil is supplied to the hydraulic cylinder. And move the ram up and down. The height position of the ram at this time is detected and fed back by the ram position detector, and the pressure and oil temperature of the hydraulic oil in the hydraulic cylinder at this time are detected,
The position correction amount is obtained from the relationship between the deviation amount of the ram position with respect to the pressure and the oil temperature obtained in advance, and the corrected position command is issued to the servo motor. Can be accurately positioned.

In the ram position control device using the hydraulic cylinder according to the second aspect of the present invention, the hydraulic pump is operated by rotating the servomotor in accordance with the position command from the position command section, and the hydraulic oil is supplied to the hydraulic cylinder to supply the ram. Is moved up and down. The height position of the ram at this time is detected by the ram position detector and fed back, and the pressure of the hydraulic oil in the hydraulic cylinder at this time is detected by the pressure sensor, and the oil temperature of the hydraulic oil is detected by the oil temperature sensor. Then, the monitoring unit monitors the pressure and the oil temperature, obtains a position correction amount from the relationship between the deviation amount of the ram position with respect to the pressure and the oil temperature obtained in advance and stored in the memory, and obtains a position command to the servomotor. Is corrected, the ram can be accurately positioned at a predetermined position regardless of the pressure and oil temperature of the hydraulic oil.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a ram position control device and a hydraulic circuit using a hydraulic cylinder according to the present invention.

FIG. 2 is a front view showing an entire press brake to which a ram position control method using a hydraulic cylinder according to the present invention is applied.

FIG. 3 is a side view as viewed from a direction III in FIG. 2;

FIG. 4 is a graph showing the relationship between the pressure deviation of the hydraulic oil and the position deviation amount with respect to the oil temperature.

FIG. 5 is a hydraulic circuit of a conventional press brake.

FIG. 6 is a graph showing the relationship between the pump temperature and the oil temperature and pressure.

[Description of Signs] 5U Upper table (ram) 11 Linear scale (ram position detector) 13L, 13R Hydraulic cylinder 19 Oil temperature sensor 21 Pressure sensor 35 Bidirectional piston pump (hydraulic pump) 43 AC servo motor (servo motor) 69 Control device (ram position control device) 71 Position command unit 81 Monitoring unit 83 Memory

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Claims (2)

[Claims] 1. A servo motor operates a hydraulic pump,
A ram position control method for a press brake in which a ram is moved up and down using a hydraulic cylinder operated by hydraulic oil supplied from a hydraulic pump and a work is bent by cooperation of a punch and a die, Is rotated based on a position command, and a position signal from a ram position detector for detecting the position of the ram at this time is fed back, and the ram position with respect to the pressure and oil temperature in the hydraulic cylinder obtained in advance is determined. A position correction value using a hydraulic cylinder, wherein a position correction value is obtained from a relationship between the deviation amounts, the position command is corrected, and the servomotor is rotated. 2. A servo motor operates a hydraulic pump,
A ram position control device in a press brake for vertically moving a ram using a hydraulic cylinder operated by hydraulic oil supplied from the hydraulic pump and bending a work in cooperation with a punch and a die, A position command unit that commands the position of the ram, a ram position detector that detects and feeds back the position of the ram, and a memory that stores the relationship between the pressure and oil temperature in the hydraulic cylinder and the ram position deviation amount. Monitoring the pressure and oil temperature from a pressure sensor and an oil temperature sensor provided in the hydraulic cylinder, and based on the pressure and oil temperature stored in the memory and the relationship between the ram position deviation amount and the ram position. A monitoring unit that obtains a deviation amount and corrects the position command, the ram position control device for a press brake being provided.