JP4636646B2 - Ram position control method and ram position control apparatus for press brake - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ram position control method and a ram position control apparatus in a press brake that performs bending by relatively moving an upper table or a lower table as a ram up and down.
[0002]
[Prior art]
FIG. 5 shows the flow of ram position control in the press brake 101, which has been well known conventionally. The press brake 101 moves the upper table 103U, which is a ram mounted with the punch P, up and down by the hydraulic cylinder 105, and bends the workpiece in cooperation with the die D mounted on the lower table 103L. is there.
[0003]
That is, the position command from the position command unit 107 is sent to the gain determination unit 111 via the adder 109. The gain determination unit 111 determines the ram operation gain, amplifies the command by the amplifier 113, and issues a command to the servo motor 115. The servo motor 115 operates the hydraulic pump 117, and the hydraulic cylinder 105 moves up and down to move the upper table 103U up and down.
[0004]
The upper and lower positions of the upper table 103U are detected by the ram position detector 119 and fed back to the adder 109 via the position counter 121, thereby constituting a servo loop.
[0005]
[Problems to be solved by the invention]
However, in such a conventional technique, as shown in the pump efficiency zero characteristic of FIG. 6, oil leakage occurs in the hydraulic pump 117 so that the upper table 103U as a ram is held at a fixed position. For this, the hydraulic pump 117 needs to be rotated. However, as shown in FIG. 6, since the rotational speed of the hydraulic pump 117 varies depending on the pressure of the hydraulic oil and the oil temperature, there is a problem that the upper table 103U, which is a ram, cannot be positioned at the command position.
[0006]
The object of the present invention has been made by paying attention to the above-mentioned problems of the prior art, and the ram is set to the command position regardless of the pressure and temperature of the hydraulic oil supplied from the hydraulic pump to the hydraulic cylinder. It is an object to provide a ram position control method and apparatus using a hydraulic cylinder that can be positioned.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a ram position control method using a hydraulic cylinder of the invention according to claim 1 is a method in which a servo motor operates a hydraulic pump and a hydraulic cylinder operated by hydraulic oil supplied from the hydraulic pump is provided. In a ram position control method in a press brake in which a ram is moved up and down using a punch and a die to bend the workpiece, the servo motor is rotated based on a position command. The position signal from the ram position detector for detecting the position is fed back, and the ram position deviation amount is obtained from the relationship between the characteristics of the pump and the ram position deviation amount with respect to the pressure and oil temperature in the hydraulic cylinder obtained in advance. the ram position deviation determined by correcting the position command as a correction value to rotate the servo motor, the It is an butterfly.
[0008]
Therefore, the servo motor is rotated according to the position command to operate the hydraulic pump, and 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 a ram position detector and fed back, and the pressure and oil temperature of the hydraulic oil in the hydraulic cylinder at this time are detected, and the pressure and oil temperature obtained in advance are detected. A position correction amount is obtained from the relationship between the ram position deviation amounts, and a corrected position command is issued to the servo motor.
[0009]
In the ram position control device using the hydraulic cylinder of the invention according to claim 2, the servo motor operates the hydraulic pump, and the ram is moved up and down using the hydraulic cylinder operated by the hydraulic oil supplied from the hydraulic pump. A ram position control device for a press brake that bends a workpiece by cooperating with a die and a ram position detection unit that commands the position of the ram and detects and feeds back the position of the ram , A memory for storing in advance the relationship between the pump characteristics and the ram position deviation amount with respect to the pressure and oil temperature in the hydraulic cylinder, and the pressure and oil from the pressure sensor and the oil temperature sensor provided in the hydraulic cylinder. The ram position is determined from the relationship between the pressure and oil temperature stored in the memory and the ram position deviation based on the temperature monitored. Calculating deviations, is to a monitoring unit configured to correct the position command a ram position deviation amount this determined as a correction value, characterized in that it comprises a.
[0010]
Accordingly, the servo motor is rotated in accordance with the position command from the position command unit to operate the hydraulic pump, and hydraulic oil is supplied to the hydraulic cylinder to move the ram up and down. The ram height position 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. The monitoring unit monitors the pressure and oil temperature, calculates the position correction amount from the relationship between the ram position deviation amount and the pressure and oil temperature obtained in advance and stored in the memory, and sends a position command to the servo motor. Correct.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
2 and 3 show the entire press brake 1 according to the present invention. This press brake 1 has side plates 3L and 3R which are erected on the left and right sides, and has an upper table 5U as a ram on the upper front end surface of the side plates 3L and 3R so as to be movable up and down, and a lower portion of the side plates 3L and 3R. A lower table 5L is provided on the front surface.
[0013]
A punch P is replaceably provided at the lower end of the upper table 5U via an intermediate plate 7. A die D is replaceably provided on the upper end of the lower table 5L via a die base 9.
[0014]
In addition, the linear scale 11 is provided as a ram position detector for measuring the height position of the upper table 5U, the distance from the die D is obtained from the height of the punch P, and the bending process is completed. Detecting haze, bending angle, ensuring safety, etc.
[0015]
Hydraulic cylinders 13L and 13R are respectively provided on the upper front surfaces of the left and right side plates 3L and 3R. The above-described upper table 5U is attached to the piston rods 17L and 17R attached to the pistons 15L and 15R of the hydraulic cylinders 13L and 13R. 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.
[0016]
Next, a hydraulic circuit for the hydraulic cylinders 13L and 13R will be described with reference to FIG. Since 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.
[0017]
The upper cylinder chamber 23U of the hydraulic cylinder 13R that moves the upper table 5U as a ram up and down is connected to a prefill valve 27 by a pipe 25 and further connected to an oil tank 31 by a pipe 29.
[0018]
The upper cylinder chamber 23U is connected to one side of a bidirectional piston pump 35 that can rotate in both directions as a hydraulic pump through a pipe 33. 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 rotationally driven by an AC servo motor 43 as a servo motor.
[0019]
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 that 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 this pipe 53 is connected to the oil tank 31 via a check valve 55 and a suction filter 57.
[0020]
In addition, a throttle valve 59 and a high-pressure priority type shuttle valve 61 are provided between the pipe 45 and the pipe 33. A piping 63 is connected to the discharge side of the high-pressure priority type shuttle valve 61, and a piping 67 connected to the relief valve 65 and the oil tank 31 is provided in the piping 63.
[0021]
The control device 69 that controls the AC servo motor 43 that rotationally drives the bidirectional piston pump 35 has a position command unit 71 that commands the position of the upper table 5U that is a ram. A ram operation gain determination unit 75 is connected via an adder 73. Further, the ram operation gain determination unit 75 is connected so as to send a command to the AC servomotor 43 through an amplifier 77.
[0022]
The adder 73 is connected to a position counter 79 that receives the position signal of the upper table 5U sent from the linear scale 11 and detects the actual position. The servo loop to be fed back is configured.
[0023]
Further, a monitoring unit 81 is provided that receives detection signals from the oil temperature sensor 19 and the pressure sensor 21 provided in the hydraulic cylinder 13R and monitors the pressure and oil temperature to correct the position command of the upper table 5U. The command signal from the ram operation gain determination unit 75 is corrected.
[0024]
The monitoring unit 81 is connected to the memory 83, and the memory 83 stores the relationship between the pump characteristic and the ram position deviation amount with respect to the pressure and the oil temperature as shown in FIG. . Therefore, the monitoring unit 81 obtains 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. This corrected command value is commanded to the AC servo motor 43.
[0025]
With the above configuration, 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. In order to rapidly lower the table 5U, the sequence switching valve 49 is switched to connect the piping 45 and the piping 51, and the bidirectional piston pump 35 is rotated by the AC servo motor 43.
[0026]
In the case of further lowering and bending, the sequence switching valve 49 is set to the state shown in FIG. 1, and hydraulic oil from the lower cylinder chamber 23L passes through the pipe 45, the counter balance valve 47, and the pipe 61. It returns to the bidirectional piston pump 35 and is further supplied from the pipe 33 to the upper cylinder chamber 23U of the hydraulic cylinder 13R. As a result, the piston 15R descends and the upper table 5U descends, and bending is performed.
[0027]
Since the cross-sectional area on the lower surface side of the piston 15R is smaller than that on the upper surface side, the hydraulic oil returning from the lower cylinder chamber 23L to the bidirectional piston pump 35 compared to the amount of hydraulic oil injected into the upper cylinder chamber 23U. Therefore, hydraulic oil is replenished from the oil tank 31 through the check valve 55.
[0028]
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 moved in the opposite direction to the above-described case by the reverse command from the position command unit 71. The bidirectional piston pump 35 is rotated in the reverse direction, and the hydraulic oil from the upper cylinder chamber 23U with the piston 15R lowered is supplied to the pipe 33, the bidirectional piston pump 35, the pipe 51, the sequence switching valve 49, the pipe 45, etc. Then, it is supplied to the lower cylinder chamber 23L. As a result, the piston 15R rises and the upper table 5U rises.
[0029]
When the pressure of the hydraulic oil injected into the lower cylinder chamber 23L becomes higher than a predetermined value, the prefill valve 27 is opened by the pilot signal 85 and is sent from the upper cylinder chamber 23U to the oil tank 31 through the prefill valve 27.
[0030]
When positioning the upper table 5U at a certain position, the ram operation gain determination unit 75 determines the ram operation gain from the position command of the position command unit 71 and the position signal from the linear scale 11, and the monitoring unit 81 The oil temperature from the oil temperature sensor 19 and the pressure from the pressure sensor 21 are monitored, the ram position deviation amount is obtained based on the data stored in the memory 83, and the position command is corrected and amplified by the amplifier 77. A command is issued to the AC servo motor 43.
[0031]
From the above results, the upper table 5U can be accurately positioned at a predetermined position without being affected by the pressure and temperature of the hydraulic oil.
[0032]
The present invention is not limited to the embodiment of the invention described above, and can be implemented in other modes by making appropriate modifications. That is, in the above-described embodiment of the invention, the press brake 1 that moves the upper table 5U up and down has been described, but the same applies to the press brake that moves the lower table 5L up and down.
[0033]
【The invention's effect】
As described above, according to the present invention, by rotating the servo motor in accordance with a position command from the position command unit actuates the hydraulic pump supplies hydraulic fluid to the hydraulic cylinder to vertically move the ram. The ram height position 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. The monitoring unit monitors the pressure and oil temperature, calculates the position correction amount from the relationship between the ram position deviation amount and the pressure and oil temperature obtained in advance and stored in the memory, and sends a position command to the servo motor. Therefore, the ram can be accurately positioned at a predetermined position regardless of the pressure of the hydraulic oil and the oil temperature.
[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 seen from the direction III in FIG. 2;
FIG. 4 is a graph showing a relationship between the pressure of hydraulic oil and the positional 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 oil temperature and pressure.
[Explanation of symbols]
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

Claims (2)

In a press brake that operates a hydraulic pump by a servo motor, moves a ram up and down using a hydraulic cylinder that is operated by hydraulic oil supplied from the hydraulic pump, and bends a workpiece by cooperation of a punch and a die In the ram position control method, the servo motor is rotated based on a position command, a position signal from a ram position detector that detects the position of the ram at this time is fed back, and the hydraulic cylinder that is obtained in advance A ram position deviation amount is obtained from the relationship between the pump characteristics and the ram position deviation amount with respect to pressure and oil temperature, and the servo motor is rotated by correcting the position command using the obtained ram position deviation amount as a correction value. A ram position control method using a hydraulic cylinder. In a press brake that operates a hydraulic pump by a servo motor, moves a ram up and down using a hydraulic cylinder that is operated by hydraulic oil supplied from the hydraulic pump, and bends a workpiece by cooperation of a punch and a die A ram position control device, a position command unit for commanding the position of the ram, a ram position detector for detecting and feeding back the position of the ram, a pump characteristic and a ram for pressure and oil temperature in the hydraulic cylinder A memory for storing the relationship between the positional deviation amounts in advance , a pressure sensor and an oil temperature sensor provided in the hydraulic cylinder, and a pressure stored in the memory based on the pressure and the oil temperature. It determined the ram position deviation from the relationship between the oil temperature and the ram position deviation, the position of the ram position deviation amount this determined as a correction value Ram position control device in the press brake, characterized by comprising and a monitoring unit for correcting the command.

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