JP2001137948A - Ram moving method in press brake and press brake using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ram moving method capable of increasing productivity by reducing shock in reversing so as to increase an action gain of a ram, and a press brake using the ram moving method. SOLUTION: In order to switch up/down movement of hydraulic cylinders 13L, 13R for reversing up/down movement of a ram 5U, a controller 18 controls an AC servo motor 39, rotation of a bidirectional piston pump 31 is reversed. At this time, a ram moving speed command part 65 of the controller 18 conducts a pattern command by which after reversing, a moving speed of the ram 5U is held fixed only during a prescribed warming up time and then a moving speed of the ram 5U is changed up to a prescribed speed. A command position counter 67 reads a ram position from the ram moving pattern, the read value and the actual ram 5U position detected from a ram position detector 11 are added by an adder 73, a rotation of the AC servo motor 39 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ram moving method for a press brake in which a ram is moved up and down by a hydraulic cylinder, and a press brake using the ram moving method.

[0002]

2. Description of the Related Art In a press brake in which a ram is moved up and down by a hydraulic cylinder to perform a bending process in cooperation with a punch and a die, a bidirectional fluid pump may be used to operate the hydraulic cylinder. A simplified hydraulic circuit provided for such a hydraulic cylinder is shown in FIG.

In such a hydraulic circuit, pipes 101 and 103 connected to an upper cylinder chamber or a lower cylinder chamber of a hydraulic cylinder (not shown) are connected to a bidirectional fluid pump 107 rotated by a servomotor 105. I have. Further, the pipes 101 and 103 are each provided with a check valve 10.
9 and 111 are connected to the oil tank 113.

Accordingly, the bidirectional fluid pump 107 is rotated by the servomotor 105, and the pipe 101 or the pipe 1 is rotated.
Hydraulic oil is supplied to the upper or lower cylinder chamber (not shown) through 03, and the ram moves up and down. At this time, hydraulic oil is supplied from the oil tank 113 via the check valve 109 or the check valve 111.

In such a hydraulic circuit, the bidirectional fluid pump 107 is rotated by instructing the servo motor 105 to move the ram up and down in a pattern as shown in FIG. That is, the ram increases speed at a constant acceleration, moves at a constant speed when a predetermined speed is reached, and decreases the speed at a constant deceleration.

[0006]

However, according to such a conventional technique, at the time of reversal in which the moving direction of the ram changes, one of the check valves 109 (or the check valve 111) is subjected to a negative pressure. May be open. At this time, if the bidirectional fluid pump 107 reverses and a sudden positive pressure is applied, the open check valve 109 is opened.
The hydraulic oil may flow backward until the (or check valve 111) closes, resulting in poor responsiveness. As shown in FIG. 8, the actual ram moves in an unstable manner. For this reason, there is a problem that the shock at the time of reversal is large, the operating gain of the ram cannot be increased, and the productivity is reduced.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above-mentioned problems of the prior art. The shock at the time of reversal is reduced, thereby increasing the operating gain of the ram and improving the productivity. It is an object of the present invention to provide a ram moving method for a press brake and a press brake using the ram moving method.

[0008]

According to a first aspect of the present invention, there is provided a method for moving a ram in a press brake, comprising the steps of: In the ram moving method of the press brake for performing the bending by vertically moving, after the bidirectional fluid pump is reversed to reverse the vertical movement of the ram, a warm-up time or a distance for temporarily maintaining the ram speed constant for a predetermined time or Providing a predetermined distance, and then controlling the bidirectional fluid pump to change the ram speed to the predetermined speed.

Therefore, when the rotation of the bidirectional fluid pump is reversed to switch the vertical movement of the hydraulic cylinder in order to reverse the vertical movement of the ram, after the reversal, a predetermined length of warm-up time or a predetermined distance of the ram is required. The moving speed is held constant, and then the ram is moved up and down by changing the moving speed of the ram to a predetermined speed.

[0010] The press brake of the invention according to claim 2 is
A press brake that performs a bending process by operating a bidirectional fluid pump by a control device controlling a servo motor, operating a hydraulic cylinder with hydraulic oil from the bidirectional fluid pump to vertically move a ram, After the control device reverses the rotation of the bidirectional fluid pump to reverse the vertical movement of the ram, a warming-up time or distance for once maintaining the ram speed constant is provided for a predetermined time or a predetermined distance, and then the ram speed is predetermined. A ram moving speed pattern command unit for commanding a preset ram moving speed pattern to change to a speed of up to a speed; a command position counter for reading a ram position from a ram speed commanded by the ram moving speed pattern command unit; A ram position detector for detecting the ram position and the ram position read by the command position counter. Is characterized in that said adding ram position signal from the ram position detector ram is provided with an adder for commanding said servo motor so as to be positioned at a desired position.

Therefore, the control device controls the servomotor to reverse the rotation of the bidirectional fluid pump in order to switch the vertical movement of the hydraulic cylinder in order to reverse the vertical movement of the ram. At this time, after the reversal, the ram moving speed pattern command unit of the control device keeps the ram moving speed constant for a predetermined length of warm-up time or a predetermined distance, and then changes the ram moving speed to the predetermined speed. Executes the pattern command of the set ram movement speed pattern. The command position counter reads the ram position from the ram moving speed pattern, and adds the read value and the actual ram position detected by the ram position detector with an adder so that the ram is positioned at a desired position. Control the rotation of the motor.

[0012]

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

FIGS. 4 and 5 show the entirety of the press brake 1 according to the present invention. The press brake 1 has side plates 3L, 3R standing upright and left and right, and has an upper table 5U as a ram on the upper front end face 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.

At the lower end of the upper table 5U, a punch P is provided exchangeably via a plurality of intermediate plates 7.
A die D is provided in the die holder 9 provided at the upper end of the lower table 5L so as to be exchangeable.

An example of a linear scale 11 as a ram position detector for measuring the height position of the upper table 5U is provided, and the distance between the punch P and the die D is determined from the height of the punch P to bend. It detects whether processing has been completed, detects bending angles, and secures safety.

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, respectively. An upper table 5U is attached.

Next, referring to FIG.
The hydraulic circuit for L and 13R and the control device 18 will be described. The left and right hydraulic cylinders 13L, 13R
Is provided with a hydraulic circuit that is completely the same as that described above, and therefore, the right hydraulic cylinder 13R and the hydraulic circuit will be described below.

The upper cylinder chamber 19U of the hydraulic cylinder 13R for vertically moving the upper table 5U, which is a ram, is connected to a prefill valve 23 by a pipe 21 and further to a pipe 2
5 is connected to the oil tank 27.

The upper cylinder chamber 19U is provided with a pipe 2
9 is connected to one side of a bidirectional piston pump 31 as a bidirectional fluid pump capable of bidirectional rotation. A pipe 33 is connected to the pipe 29 on the way, and is connected to the oil tank 27 via a check valve 35 and a suction filter 37. The bidirectional piston pump 31 is driven to rotate by an AC servomotor 39 as a servomotor controlled by the control device 18.

On the other hand, a pipe 41 is connected to the lower cylinder chamber 19L of the hydraulic cylinder 13R, and a counter balance valve 43 and a sequence switching valve 45 which is an electromagnetic poppet valve are provided in parallel. The counterbalance valve 43 and the sequence switching valve 45 are connected to the other side of the bidirectional piston pump 31 by a pipe 47. A pipe 49 is connected to the pipe 47 on the way, and the pipe 49 is connected to the oil tank 27 via a check valve 51 and a suction filter 53.

A throttle valve 55 and a high-pressure priority type shuttle valve 57 are provided between the pipe 41 and the pipe 29. A pipe 59 is connected to the discharge side of the high-pressure priority type shuttle valve 57, and the pipe 59 is provided with a relief valve 61 and further provided with a pipe 63 connected to the oil tank 27.

In the control unit 18 for controlling the AC servomotor 39, the ram moving speed pattern command unit 65 for commanding the moving speed pattern of the upper table 5U as a ram is provided.
The ram movement speed pattern command unit 65 reverses the up and down movement of the upper table 5U and stops increasing the movement speed, as in the case of the movement speed pattern shown in FIG. Is moved at a constant speed for a predetermined warm-up time TW, and thereafter, is instructed to increase the moving speed again. Then, the command position counter 67 reads the position of the upper table 5U from the moving speed pattern from the ram moving speed pattern command unit 65.

On the other hand, the position signal 71 from the linear scale 11 for detecting the position of the upper table 5U is fed back by the position counter 71, and the adder 73 outputs the feedback signal and the command position read by the command position counter 67 described above. to add. A ram operation gain determination unit 75 determines a gain from the signal added by the adder 73, amplifies the gain with an amplifier 77, and issues a command to the AC servomotor 39.

With the above structure, the upper cylinder chamber 19U and the lower cylinder chamber 19L are filled with hydraulic oil, the bidirectional piston pump 31 is stopped, and the piston 19R is at the top dead center. When the upper table 5U is rapidly lowered by 13R, the sequence switching valve 45 is switched to connect the pipes 41 and 47, and the bidirectional piston pump 31 is rotated by the AC servomotor 39.

When the bending process is performed by descending further,
With the sequence switching valve in the state shown in FIG. 1, the hydraulic oil from the lower cylinder chamber 19 </ b> L passes through the pipe 41, the counterbalance valve 43, and the pipe 47, and
The flow returns to 1 and is further supplied from the pipe 29 to the upper cylinder chamber 19U of the hydraulic cylinder 13R. Thereby, the piston 19R descends, and the upper table 5U descends to perform bending.

Since the cross-sectional area of the lower surface of the piston 19R is smaller than that of the upper surface, the amount of the hydraulic oil injected into the upper cylinder chamber 19U is smaller than that of the lower cylinder chamber 19L. Since the amount of the returning hydraulic oil is small, the hydraulic oil is replenished from the oil tank 27 via the check valve 51.

When the hydraulic oil in the upper and lower cylinder chambers 19U and 19L has a high pressure, a part of the hydraulic oil passes from the relief valve 61 via the high pressure priority type shuttle valve 57 to the pipe 63 to protect the circuit. To return to the oil tank 27.

On the other hand, when the upper table 5U is raised by reversing the hydraulic cylinder 13R based on the pattern signal from the ram moving speed pattern command unit 65, the reversing command causes the AC servomotor 39 to move in the opposite direction to the above case. To rotate the bidirectional piston pump 31 in reverse,
Hydraulic oil from the upper cylinder chamber 19U with the piston 19R lowered is supplied to the pipe 29, the bidirectional piston pump 31,
The gas is supplied to the lower cylinder chamber 19L through the pipe 47, the switching valve 45, the pipe 41, and the like. As a result, the piston 19R rises and the upper table 5U starts to rise.

Then, the ram movement speed pattern command section 65
The command position counter 67 reads the ram moving speed pattern from the controller, and when the piston 19R reaches a predetermined rising speed, the rising of the speed is stopped and the speed is stopped at a constant speed for a predetermined warming-up time TW.
Command to ensure that 1 is closed. After that, when the warm-up time TW elapses and the check valve 51 is closed to prevent the backflow of the hydraulic oil from occurring, the AC servomotor 39 is controlled to accelerate until the rising speed of the upper table 5U reaches a predetermined speed. I do.

When the pressure of the hydraulic oil injected into the lower cylinder chamber 19L becomes higher than a predetermined value, the prefill valve 23 is opened by the pilot signal 79, and the upper cylinder chamber 19L is opened.
From U, the oil is sent to the oil tank 27 through the prefill valve 23.

From the above results, the bidirectional piston pump 3
After reversing 1, the warm-up time TW for keeping the moving speed constant once while the moving speed of the upper table 5U is low is provided, and the check valve 3 is turned on before a large positive pressure is applied.
As shown in FIG. 3, since the shock absorber 5 and 51 are closed, the shock at the time of rising due to the surge pressure, which has conventionally been considered a problem (see FIG. 8), is reduced, and the upper table 5U during movement is reduced. Vibration can be prevented. As a result, the operating gain of the upper table 5U can be increased to improve productivity.

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 vertically moving the upper table 5U has been described. However, the same applies to the press brake for vertically moving the lower table 5L.

Further, a method of performing warm-up in which the ram speed is kept constant until the ram moving distance becomes a constant distance may be used.

[0034]

As described above, in the ram moving method of the press brake according to the first aspect of the present invention, the rotation of the bidirectional fluid pump is reversed so as to switch the vertical movement of the hydraulic cylinder in order to reverse the vertical movement of the ram. In this case, after the reversal, the moving speed of the ram is kept constant for a predetermined length of warm-up time, and then the moving speed of the ram is changed to the predetermined speed to move the ram up and down. Shock at the time of rising, which has been regarded as a problem, can be reduced, and vibration of the ram during movement can be prevented. Thereby, the operation gain of the ram can be increased to improve the productivity.

In the press brake according to the second aspect of the present invention, the control device controls the servomotor to reverse the rotation of the bidirectional fluid pump in order to switch the vertical movement of the hydraulic cylinder in order to reverse the vertical movement of the ram. At this time, the ram moving speed pattern command unit of the control device, after reversing, keeps the ram moving speed constant for a predetermined length of warm-up time, and thereafter changes the ram moving speed to the predetermined speed. The command position counter reads the ram position from the ram moving speed pattern, and adds the value to the actual ram position detected by the ram position detector with an adder, and the ram moves. Since the rotation of the servomotor is controlled so as to be located at a desired position, it is possible to reduce the shock at the time of rising, which has conventionally been a problem, and to prevent the vibration of the ram during movement. Thereby, the operation gain of the ram can be increased to improve the productivity.

[Brief description of the drawings]

FIG. 1 is a circuit and a block diagram showing a configuration of a hydraulic circuit and a control device of a press brake according to the present invention.

FIG. 2 is a graph showing a ram moving speed pattern.

FIG. 3 is a graph showing an actual moving speed of a ram when a movement is commanded according to the ram moving speed pattern of FIG. 2;

FIG. 4 is a front view showing the entire press brake according to the present invention.

FIG. 5 is a side view as viewed from a direction V in FIG. 4;

FIG. 6 is a schematic view showing a main part of a hydraulic circuit of a conventional press brake.

FIG. 7 is a graph showing a conventional ram moving speed pattern.

8 is a graph showing the actual moving speed of the ram when movement is commanded according to the ram moving speed pattern of FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 press brake 5U upper table (ram) 11 linear scale (ram position detector) 13L, 13R hydraulic cylinder 18 controller 31 bidirectional piston pump (bidirectional fluid pump) 39 AC servo motor (servo motor) 65 ram moving speed pattern Command part 67 Command position counter 73 Adder

Claims (2)

[Claims] 1. A ram moving method in a press brake in which a ram is moved up and down by a hydraulic cylinder which is moved up and down in accordance with a rotation direction of a bidirectional fluid pump, wherein the ram is moved up and down to reverse the up and down movement of the ram. After inverting the directional fluid pump, a warm-up time or distance for temporarily maintaining the ram speed constant is provided for a predetermined time or a predetermined distance, and thereafter, the bidirectional fluid pump is controlled so as to change the ram speed to the predetermined speed. Ram movement method in press brake. 2. A press for performing a bending process by controlling a servomotor to operate a bidirectional fluid pump and operating a hydraulic cylinder with hydraulic oil from the bidirectional fluid pump to move the ram up and down. A brake, wherein after the control device reverses the rotation of the bidirectional fluid pump to reverse the vertical movement of the ram, a warming-up time or a distance for once maintaining the ram speed constant is provided for a predetermined time or a predetermined distance, A ram moving speed pattern command unit for commanding a preset ram moving speed pattern for changing the ram speed to a predetermined speed, a command position counter for reading a ram position from the ram speed commanded by the ram moving speed pattern command unit, and A ram position detector for detecting the position of the ram, and A press brake, comprising: an adder that adds a ram position and a ram position signal from the ram position detector to instruct the servo motor to position the ram at a desired position.