JP4334090B2 - Bidirectional fluid pump control method for hydraulic cylinder and press brake using this bidirectional fluid pump control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bidirectional fluid pump control method for a hydraulic cylinder in a press brake that performs bending by a hydraulic cylinder operated by a bidirectional fluid pump, and a press brake using the bidirectional fluid pump control method.
[0002]
[Prior art]
2. Description of the Related Art Conventionally known press brakes that move a ram up and down by a hydraulic cylinder use a bidirectional fluid pump to supply hydraulic fluid that operates the hydraulic cylinder.
[0003]
Since this bidirectional fluid pump is used at a high rotation speed and a high pressure, there is an advantage that the capacity of a servo motor that rotationally drives the bidirectional fluid pump can be reduced.
[0004]
[Problems to be solved by the invention]
However, the bidirectional fluid pump as described above generates noise when used at a high rotation speed. In addition, when used at high rotation and high pressure, there is a characteristic that a larger noise is generated.
[0005]
Therefore, as shown in FIG. 6, when bending is performed by moving the ram up and down in accordance with the ram movement pattern (solid line in FIG. 6) indicating the speed command value, the time T1 when the punch comes into contact with the workpiece and thereafter Since the actual ram moving speed (shown by the broken line in FIG. 6) decreases and deviates from the ram speed command value during the bending process of FIG. 7, in order to eliminate this deviation and bring the actual speed closer to the command speed, FIG. As shown, the rotational speed of the servo motor is increased to make the bidirectional fluid pump high. Accordingly, there is a problem that noise increases as shown in FIG.
[0006]
Further, as shown by a two-dot chain line in FIG. 6, when the punch comes into contact with the workpiece and the bidirectional fluid pump during the subsequent bending process is used at a high pressure, the noise is further increased. There is a problem that occurs.
[0007]
The object of the present invention has been made paying attention to the problems of the prior art as described above, and is a bidirectional hydraulic cylinder capable of reducing noise generated by a bidirectional fluid pump that operates the hydraulic cylinder. It is an object of the present invention to provide a fluid pump control method and a press brake using the bidirectional fluid pump control method.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a bidirectional fluid pump control method for a hydraulic cylinder according to a first aspect of the present invention comprises operating a bidirectional fluid pump, rotating a servo motor, and bending a ram by a hydraulic cylinder. In the bidirectional fluid pump control method of the hydraulic cylinder to be moved up and down, the oil pressure in the bidirectional fluid pump is measured and the change amount of the oil pressure is calculated in advance so as to reduce the noise when the bidirectional fluid pump rotates. Based on the determined pressure-ram moving speed relationship and pressure change amount-ram moving speed relationship, the ram moving speed with respect to the pressure detected at a certain time and the ram moving speed with respect to the pressure change amount at this time are obtained, Compare the ram movement speed against the pressure and the ram movement speed against the amount of change in pressure. To command to determine the rotational speed of the servo motor to the speed corresponding to the ram moving speed to obtain the speed, and is characterized in.
[0009]
Therefore, the oil pressure of the bidirectional fluid pump that is driven to rotate by the servo motor to operate the hydraulic cylinder is detected, the amount of change in the oil pressure is obtained, and it is determined in advance to reduce the noise during the rotation of the bidirectional fluid pump. Based on the pressure-ram movement speed relationship and the pressure change-ram movement speed relationship, the lower ram movement speed is selected to reduce noise at any time, and the rotation speed corresponding to the selected ram movement speed. To the servo motor.
[0010]
The press brake of the invention according to claim 2 is a press brake that performs bending by operating a bidirectional fluid pump, rotating a servo motor and moving a ram up and down by a hydraulic cylinder, and commanding a movement pattern of the ram. A ram movement speed pattern command unit, a ram position detector that detects the ram position, a command ram position from the ram movement speed pattern command unit, and an actual ram position from the ram position detector. An adder that issues a rotation command to a servo motor that rotationally drives the bidirectional fluid pump to correct the position, a pressure sensor that detects the pressure of the bidirectional fluid pump, and a pressure signal detected by the pressure sensor An arithmetic unit for calculating a pressure change amount, and a ram moving speed and a bidirectional fluid pump for suppressing an appropriate amount of noise of the bidirectional fluid pump. A memory for storing the relationship between the ram moving speed and the pressure change amount, the relationship between the ram moving speed stored in advance in the memory and the pressure of the bidirectional fluid pump, and the ram moving speed. A servo motor rotation speed command unit that compares the relationship between the pressure change amount and the pressure change amount, selects the lower ram movement speed, and commands the servo motor the rotation speed corresponding to the ram movement speed at this time. It is characterized by.
[0011]
Therefore, the servo motor is controlled according to the command pattern from the ram movement speed pattern command unit, the hydraulic cylinder is moved up and down by the bidirectional fluid pump, the actual ram position is detected by the ram position detector, and the command position is determined by the adder. The actual ram position is compared and the servo motor is controlled to perform highly accurate bending. At this time, the oil pressure of the bidirectional fluid pump is detected by the pressure sensor provided in the bidirectional fluid pump. The calculation unit obtains the amount of change in the oil pressure from this pressure, and the pressure-ram moving speed relationship and the amount of pressure change-ram movement determined in advance and stored in the memory to reduce the noise during the rotation of the bidirectional fluid pump. Based on the speed relationship, the ram speed determination unit determines the ram movement speed by selecting the lower ram movement speed to reduce noise at any time. And it commands the speed corresponding to the ram moving speed rotation number command portion servo motor is selected to the servomotor.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
4 and 5 show a press brake 1 according to the present invention. The 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 that can be moved up and down on the upper front end surface of the side plates 3L and 3R and a lower portion of the side plates 3L and 3R. A lower table 5L is provided on the front surface.
[0014]
A punch P is provided at the lower end of the upper table 5U via a plurality of intermediate plates 7 so as to be exchangeable. Moreover, the die D is provided in the die holder 9 provided in the upper end part of the lower table 5L so that replacement | exchange is possible.
[0015]
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.
[0016]
Hydraulic cylinders 13L and 13R are provided on the upper front surfaces of the left and right side plates 3L and 3R, respectively. The above-described upper table 5U is attached.
[0017]
Next, the control device 19 for the hydraulic cylinders 13L and 13R will be described with reference to FIG. Since the same control is performed on the left and right hydraulic cylinders 13L and 13R, in the following, a servo motor that rotationally drives a bidirectional piston pump 21 as a bidirectional fluid pump for the right hydraulic cylinder 13R. The control of the AC servomotor 23 will be described.
[0018]
That is, the control device 19 has a ram moving speed pattern command unit 25 that commands a moving speed pattern of, for example, the upper table 5U that is a ram. The ram moving speed pattern command unit 25 is shown in FIG. The upper table 5U is commanded to move up and down according to the moving speed pattern. Then, the command position counter 27 reads the command position of the upper table 5U from the command pattern from the ram movement speed pattern command unit 25.
[0019]
On the other hand, the position counter 29 reads and feeds back the actual position signal from the linear scale 11 that detects the position of the upper table 5U, and the adder 31 receives this feedback signal and the command position read by the command position counter 27 described above. Add and compare. The ram operation gain determination unit 33 determines the ram operation gain from the signal added by the adder 31. A servo motor rotation speed command unit 35 is connected to the ram operation gain determination unit 33. A signal from the servo motor rotation speed command unit 35 is amplified by an amplifier 37 and a command is issued to the AC servo motor 23.
[0020]
A pressure sensor 39 provided in the bidirectional piston pump 21 and a calculation unit 41 for calculating the amount of change in pressure based on the pressure from the pressure sensor 39, and the relationship between pressure and ram movement speed, which will be described later, and pressure A memory 43 that stores the relationship between the change amount and the ram moving speed is connected to a ram speed clamp value determining unit 45 that determines the moving speed of the upper table 5U that is a ram as will be described later. The ram speed clamp value determination unit 45 is connected to a servo motor rotation number command unit 35 that commands the rotation speed of the AC servo motor 23 corresponding to the ram movement speed determined by the ram operation gain determination unit 33.
[0021]
2 shows the absolute amount of pressure (indicated by the solid line in FIG. 2) of the bidirectional piston pump 21 and the amount of change in this pressure (indicated by the alternate long and short dash line in FIG. 2) when bending is performed. When the punch P comes into contact with the workpiece, the absolute amount of pressure starts to increase at T1, and the absolute amount of pressure gradually increases during bending.
[0022]
Therefore, the first derivative, which is the amount of change in pressure, rises rapidly from T1 when the punch P comes into contact with the workpiece, and becomes substantially constant while bending at a constant pressure. And when the absolute amount of pressure becomes constant, it becomes zero.
[0023]
FIG. 3A shows the ram moving speed to be set with respect to the amount of change in pressure, which is stored in advance in the memory 43 in consideration of the noise of the bidirectional piston pump 21. FIG. 3B shows the ram moving speed to be set with respect to the absolute amount of pressure, which is stored in advance in the memory 43 in consideration of the noise of the bidirectional piston pump 21.
[0024]
As described above, since the noise increases at the time of high rotation and high pressure of the bidirectional piston pump 21, the pressure change amount A1 and the absolute pressure amount A2 at time Ti are obtained in the graph of FIG. The ram movement speeds B1 and B2 to be set are respectively obtained from A) and (B). When the ram moving speeds B1 and B2 are compared and the lower speed is set as the ram speed clamp value, and the command speed calculated by the ram operation gain determination unit 33 is larger than the ram speed clamp value, the ram speed clamp value is Commands the AC servo motor 23.
[0025]
Therefore, in the example shown in FIG. 2 and FIGS. 3A and 3B, the ram moving speed B1 is adopted, and the ram moving speed B1 and the command speed calculated by the ram operation gain determining unit 33 are changed. The AC servomotor 23 is commanded to the rotation speed corresponding to the smaller value.
[0026]
With the above configuration, the command position counter 27 reads the command position of the upper table 5U according to the pattern from the ram movement speed pattern command unit 25, and this position and the actual position read by the position counter 29 from the position signal of the linear scale 11 are obtained. Compared with the adder 31, the ram operation gain determination unit 33 determines the gain. Here, the rotational speed corresponding to the ram speed determined by the ram speed clamp value determining section 45 in consideration of the absolute amount of pressure detected by the pressure sensor 39 and the amount of change in pressure. Is compared with the rotation speed calculated by the ram operation gain determination section 33, and the smaller rotation speed is commanded to the AC servo motor 23 to drive the bidirectional piston pump 21 to rotate.
[0027]
From the above results, since the number of rotations of the bidirectional piston pump 21 at high rotation and high pressure when the noise is increased is suppressed to the necessary minimum number, the generation of noise can be suppressed to a certain level or less.
[0028]
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 present invention, the press brake 1 that performs the bending process by moving the upper table 5U up and down as a ram has been described, but the same applies to the type that performs the bending process by moving the lower table 5L up and down. It is.
[0029]
【The invention's effect】
As described above, in the bidirectional fluid pump control method for a hydraulic cylinder according to the first aspect of the present invention, the hydraulic pressure of the bidirectional fluid pump that is driven to rotate by a servo motor to operate the upper and lower cylinders is detected and the amount of change in the hydraulic pressure is obtained. Based on the pressure-ram moving speed relationship and the pressure change-ram moving speed relationship which are determined in advance to reduce the noise during rotation of the bidirectional fluid pump, the ram moving speed is set to reduce the noise at any time. Since the slower one is selected and the servo motor is commanded to the rotation speed corresponding to the selected ram moving speed, the noise of the bidirectional fluid pump can be suppressed.
[0030]
In the press brake according to the second aspect of the invention, the servo motor is controlled in accordance with the command pattern from the ram moving speed pattern command section, the hydraulic cylinder is moved up and down by the bidirectional fluid pump, and the actual ram position is detected by the ram position detector. The adder is used to compare the command position and the actual ram position to control the servo motor to perform high-precision bending. At this time, the bidirectional fluid pump is provided with the hydraulic pressure of the bidirectional fluid pump. The pressure-ram moving speed relationship, which is detected in advance and stored in the memory in order to reduce the noise during rotation of the bidirectional fluid pump, and the calculation unit obtains the change amount of the hydraulic pressure from the pressure sensor Based on the relationship between the pressure change and the ram moving speed, the ram speed determining unit has a lower ram moving speed to reduce noise at an arbitrary time. Select determines the ram moving speed, since instructing a rotational speed corresponding to the ram moving speed servo motor speed command unit is selected to the servo motor, it is possible to suppress the noise of the bidirectional fluid pump.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a control device that implements a bidirectional fluid pump control method for a hydraulic cylinder according to the present invention.
FIG. 2 is a graph showing the absolute amount of pressure and the amount of change in pressure during bending.
FIG. 3A is a graph showing the relationship between the ram speed and the amount of change in pressure that should be taken when considering the noise of the bidirectional fluid pump, and FIG. 3B shows the noise of the bidirectional fluid pump. It is a graph which shows the relationship between the ram speed which should be taken when it considers, and the absolute amount of a pressure.
FIG. 4 is a front view showing the entire press brake according to the present invention.
5 is a side view seen from the direction V in FIG. 4. FIG.
FIG. 6 is a graph showing an actual ram speed and pressure with respect to a ram speed command value in a conventional bending process.
7 is a graph showing the rotation speed of a servo motor in the bending process of FIG. 6;
FIG. 8 is a graph showing the magnitude of noise with respect to the rotation speed of the servo motor shown in FIG.
[Explanation of symbols]
1 Press brake 5U Upper table (ram)
11 Linear scale (ram position detector)
13L, 13R Hydraulic cylinder 21 Bidirectional piston pump (bidirectional fluid pump)
23 AC servo motor (servo motor)
25 Ram movement speed pattern command unit 31 Adder 35 Servo motor rotation speed command unit 39 Pressure sensor 41 Calculation unit 45 Memory

Claims (2)

In the bidirectional fluid pump control method of a hydraulic cylinder in which the ram is moved up and down to bend by the hydraulic cylinder by operating the bidirectional fluid pump and rotating the servo motor, the hydraulic pressure in the bidirectional fluid pump is measured. Based on the pressure-ram movement speed relationship and the pressure change-ram movement speed relationship that are determined in advance to reduce the noise during rotation of the bidirectional fluid pump, the change amount of the oil pressure is calculated at a certain time. The ram moving speed with respect to the detected pressure and the ram moving speed with respect to the amount of change in pressure at this time are obtained, and the ram moving speed with respect to the pressure is compared with the ram moving speed with respect to the amount of change in pressure. In order to obtain the moving speed, the rotational speed of the servo motor is determined and commanded to the rotational speed corresponding to the ram moving speed. It bidirectional fluid pump control method for a hydraulic cylinder according to claim. A press brake that operates a bidirectional fluid pump and rotates a servo motor to move a ram up and down by a hydraulic cylinder to perform bending, a ram movement speed pattern command unit that commands a movement pattern of the ram, A ram position detector for detecting a ram position; and the bidirectional fluid for correcting the ram position by comparing a command ram position from the ram movement speed pattern command section with an actual ram position from the ram position detector. An adder that issues a rotation command to a servo motor that rotates the pump; a pressure sensor that detects the pressure of the bidirectional fluid pump; and an arithmetic unit that calculates a pressure change amount from a pressure signal detected by the pressure sensor; In order to suppress the noise of the bidirectional fluid pump to an appropriate amount, the relationship between the ram moving speed and the pressure of the bidirectional fluid pump and the ram moving speed Compares the memory that stores the relationship between the pressure change amount, the relationship between the ram moving speed and the pressure of the bidirectional fluid pump stored in advance in this memory, and the relationship between the ram moving speed and the pressure change amount. And a servo motor rotation speed command section for selecting a lower ram movement speed and instructing the servo motor of a rotation speed corresponding to the ram movement speed at this time.

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