JP2002316300A - Method of controlling hydraulic cylinder and method of controlling hydraulic cylinder of press brake as well as controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling a hydraulic cylinder which is capable of improving productivity by generating a high pressure in spite of a fluctuation in load and the method of controlling the hydraulic cylinder in a press brake. SOLUTION: A directional control valve 17 moves to locate a lower table 5L in a command position and the lower table 5L is vertically moved by the hydraulic cylinder 3. There is however a difference between the command position and the actual ram position detected by ram position detecting means 11 and usually a controller 131 controls the directional control valve 17 so as to diminish this difference. In shifting from the fast feed operation of the lower table 5L of the press brake 1 to a pressurization operation, the pressure of the hydraulic cylinder 3 is detected by pressure detecting means 25 and when the pressure rises above the prescribed threshold, the directional control valve 17 is clamped in the pressurization operation position regardless of the amount of the deviation between the command position with respect to the lower table 5L and the actual position of the lower table 5L, by which the pressurization operation is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for switching a plurality of characteristics of a hydraulic cylinder by a single switching valve based on a deviation amount between a command position for a ram moved by a hydraulic cylinder and an actual ram position. The present invention relates to a method for controlling a hydraulic cylinder for moving a ram up and down, a method for controlling a hydraulic cylinder in a press brake, and a control device.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a press brake 101 for controlling a controlled object having a plurality of characteristics with one valve. This press brake 1
At 01, the lower table 103L as a ram having a die D opposed to the above-mentioned punch P exchangeably mounted at the upper end thereof is moved up and down with respect to the upper table 103U at which the punch P is exchangeably mounted at the lower end. Then, the work is bent.

The lower table 103L has a hydraulic cylinder 10
5 to move up and down. The hydraulic cylinder 105 is a double cylinder having two diameters, a large diameter cylinder 107 and a small diameter cylinder 109. The actual position of the lower table 103L is determined by the lower table position detector 1
11 detects the vertical position.

A small-diameter cylinder chamber 113 and a large-diameter cylinder chamber 115 of a double cylinder are connected to a four-port switching valve 117, respectively. The switching valve 117 is connected to a hydraulic pump 121 that is driven to rotate by a motor 119, and the hydraulic pump 121 is connected to a tank 123.

[0005] In the switching valve 117, the motor 12
5, the spool is moved, and the position of the spool is detected by a spool position sensor 127. By moving the spool, the hydraulic path is switched, and the flow rate in the hydraulic path is switched steplessly. The large-diameter cylinder chamber 115 has a check valve 1
It communicates with the tank 123 via 29.

FIG. 7 shows the press brake 101 described above.
Of the hydraulic circuit control device 131 is shown. The control device 131 has a ram position controller 133 and a valve position controller 135. The ram position controller 133 sends a ram position and speed command to the valve position controller 135 based on the difference (ram position deviation amount) between the actual ram position detected by the lower table position detector 111 and the ram position command.

The valve position controller 135 amplifies the command sent from the ram position controller 133 by the amplifier 137, controls the motor 125 of the switching valve 117 to move the spool, and sends the spool to the large-diameter cylinder 107 and the small-diameter cylinder 109. Supply hydraulic oil.

More specifically, when the switching valve 117 is set to the fast-forward position (the state shown in FIG. 8B) and hydraulic oil is supplied only to the small-diameter cylinder 109, the relationship between the amount of supplied hydraulic oil and the sectional area of the cylinder is obtained. Lower table 10
3L can be moved up at high speed. Further, the switching valve 117 is moved to the pressure feed operation position (FIG. 8A).
When the hydraulic oil is supplied to both the small-diameter cylinder 109 and the large-diameter cylinder 107 in the state shown in FIG. 1, a high pressure can be generated in the lower table 103L.

FIGS. 9A to 9C show a ram speed (command speed and actual speed), a valve position, and a hydraulic cylinder 105.
Are shown. As shown by the solid line in FIG. 9A, the command speed is switched before the high pressure is generated in the lower table 103L after the lower valve 103L is moved at a high speed by setting the switching valve 117 to the fast-forward position. The valve 117 is set to the pressure feeding operation position, and a command is issued to reduce the moving speed of the lower table 103L to the pressure feeding speed.

[0010]

However, in such a conventional technique, the hydraulic pump 121 is
A "constant discharge type gear pump" is used, which always supplies hydraulic oil while maintaining a constant rotation speed. When the pressure increases rapidly, a load is also applied to the hydraulic pump 121, and the rotation speed decreases or the rotation speed decreases. However, even if they are the same, the leakage flow rate increases, and the discharge amount of hydraulic oil decreases.

That is, the time t when the pressure of the hydraulic cylinder 105 is generated due to the contact of the punch P with the workpiece W
When it reaches 1, even if the command speed is commanding a constant speed,
The actual lower table 103L comes into contact with the work W and the speed is reduced (indicated by a broken line in FIG. 9A). At this time, the motor 119 increases the rotation speed and
The L speed approaches the command speed, but the motor 119
The speed is reduced due to the response delay of the vehicle.

When the speed of the lower table 103L decreases as described above, a difference between the command speed of the lower table 103L and the actual speed occurs, and the amount of ram position deviation increases.
The switching valve 117 is switched to the "fast-forward operation position". For this reason, there is a problem that a high pressure cannot be generated in the lower table 103L, and the material cannot be bent. Further, in order to avoid this state, the command speed of the lower table 103L can be set lower than the pressurizing feed speed, but there is a problem that productivity is reduced.

An object of the present invention is to pay attention to the above-mentioned problems of the conventional technology, and it is possible to generate a high pressure even if the load fluctuates, thereby improving productivity. It is an object of the present invention to provide a hydraulic cylinder control method and a hydraulic cylinder control method and control device in a press brake.

[0014]

According to a first aspect of the present invention, there is provided a method of controlling a hydraulic cylinder according to the present invention, wherein a deviation between a command position for a ram moved by the hydraulic cylinder and an actual ram position is provided. A method for controlling a hydraulic cylinder in which a single switching valve switches a plurality of characteristics of the hydraulic cylinder to move a ram up and down by a single switching valve, wherein a pressure in the hydraulic cylinder or an actual position or a ram speed of the ram is determined. Detecting and controlling the position of the switching valve according to the pressure or the actual position or the ram speed.

Accordingly, the switching valve is moved to position the ram at the command position, and the ram is moved up and down by the hydraulic cylinder. However, there is a difference between the commanded position and the actual ram position, and the switching valve is normally controlled to reduce the difference, but it depends on the pressure in the hydraulic cylinder or the actual ram position or ram speed. Thus, the switching valve is controlled to be switched regardless of the difference between the command position and the actual ram position.

According to a second aspect of the present invention, there is provided a method for controlling a hydraulic cylinder in a press brake, wherein one switching valve is used based on a deviation amount between a command position for a ram moved by the hydraulic cylinder and an actual ram position. Switching the multiple characteristics of the hydraulic cylinder to move the ram up and down,
In the control method of the hydraulic cylinder in the press brake that performs a bending process on the work by the cooperation of the punch and the die, when shifting from the rapid feed operation of the ram to the pressing operation, the pressure in the hydraulic cylinder is detected, When the pressure in the hydraulic cylinder is equal to or higher than a predetermined threshold value, the switching valve is clamped at the pressurizing operation position regardless of the deviation amount between the command position for the ram and the actual position of the ram. It is a feature.

Accordingly, the switching valve is moved to position the ram at the command position, and the ram is moved up and down by the hydraulic cylinder. However, there is a difference between the command position and the actual ram position. Normally, the switching valve is controlled to reduce the difference, but when the press brake shifts from the ram fast-forward operation to the pressurizing operation. The pressure in the hydraulic cylinder is detected, and when the pressure exceeds a predetermined threshold value, the switching valve is pressed regardless of the deviation between the command position for the ram and the actual position of the ram. And continue the pressurizing operation.

According to a third aspect of the present invention, there is provided a control device for a hydraulic cylinder in a press brake, wherein one switching valve is used to control the ram moved by the hydraulic cylinder based on a deviation amount between a command position and an actual ram position. Switching the multiple characteristics of the hydraulic cylinder to move the ram up and down,
A control device for a hydraulic cylinder in a press brake that performs bending on a workpiece by cooperation between a punch and a die, comprising: a ram position detection unit that detects a position of the ram; and a pressure detection unit that detects a pressure in the hydraulic cylinder. A command position for the ram and a command position for the ram when the pressure in the hydraulic cylinder detected by the pressure detecting means at the time of shifting the ram from the rapid traverse operation to the pressurizing operation becomes equal to or higher than a predetermined threshold value. A valve movement pattern switching unit for clamping the switching valve to the pressurizing operation position regardless of the deviation amount from the actual position.

Accordingly, the switching valve is moved to position the ram at the command position, and the ram is moved up and down by the hydraulic cylinder. However, there is a difference between the command position and the actual ram position detected by the ram position detecting means. Usually, the control device controls the switching valve so as to reduce this difference. When shifting from the rapid traverse operation to the pressurizing operation, the pressure in the hydraulic cylinder is detected by the pressure detecting means, and when the pressure exceeds a predetermined threshold value, the command position for the ram and the actual position of the ram The pressurizing operation is continued by clamping the switching valve to the pressurizing operation position irrespective of the deviation amount from the above.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows an example of a hydraulic circuit of the press brake 1 according to the present invention. Since the same hydraulic cylinders 3 and hydraulic circuits are provided on the left and right in the press brake 1, here, the left hydraulic cylinder 3 and the hydraulic circuit will be described as an example.

In the press brake 1, a lower ram having a die D opposed to the punch P at an upper end thereof is exchangeably mounted on an upper table 5U having a lower end at which a punch P is exchangeably mounted. The table 5L is moved up and down by the hydraulic cylinder 3 to bend the work.

The hydraulic cylinder 3 is a double cylinder having two diameters, a large-diameter cylinder 7 and a small-diameter cylinder 9. The actual position of the lower table 5L, which is moved up and down by the hydraulic cylinder 3, is used as ram position detecting means. Is detected by the lower table position detector 11.

The small-diameter cylinder chamber 13 and the large-diameter cylinder chamber 15 in the hydraulic cylinder 3 are connected to a four-port switching valve 17, respectively.
By switching the number 7, a plurality of characteristics such as the operation of only the small-diameter cylinder 9 or the operation of the large-diameter cylinder 7 and the small-diameter cylinder 9 can be switched.

The switching valve 17 is connected to a hydraulic pump 21 rotated and driven by a motor 19, and the hydraulic pump 21 is connected to a tank 23. Further, between the large-diameter cylinder chamber 15 of the large-diameter cylinder 7 and the switching valve 17, a pressure sensor 25 as pressure detecting means for measuring the pressure in the large-diameter cylinder chamber 15 is provided.

In the switching valve 17, the position of the spool 31 moved by the motor 27 is detected by a spool position sensor 29. By the movement of the spool 31, the hydraulic path is switched or the flow rate in the hydraulic path is switched steplessly. The large-diameter cylinder chamber 15 is connected to the tank 23 via a check valve 33.

FIG. 1 shows a control device of the hydraulic circuit of the press brake 1. The ram position controller 35 as a control device includes a CPU 37 as a central processing unit and a ROM 39 and a RAM 41 as storage devices. The ram position controller 35 sends a command to the motor 27 of the switching valve 17 via the amplifier 43 to command the valve opening. As a result, the switching valve 17 is switched to perform switching of the vertical direction of the lower table 5L, the small-diameter cylinder 9 and the large-diameter cylinder 7, and the like.

As the lower table 5L moves up and down, the actual position of the lower table 5L detected by the lower table position detector 11 is fed back to the ram position controller 35. The pressure in the hydraulic cylinder 3 detected by the pressure sensor 25 is also changed by the ram position controller 3.
5 is fed back.

As described above in the section of the prior art (see FIG. 9C), the speed of the lower table 5L decreases due to the response delay of the motor 19, and the difference between the commanded speed and the actual speed (ram position deviation). Switching valve 17
Is switched to the fast-forward position (see FIG. 8B), and as a result, no pressure is generated. In order to solve this problem and to generate pressure, as shown in FIG. 3, the position of the switching valve 17 is changed to a pressurizing feed operation position (FIG. 8 (FIG. 8) where the large diameter cylinder 7 and the small diameter cylinder 9 operate. See A)).

Therefore, a ram position controller 35 is constructed as shown in FIG. That is, when the target position is set by the target position command unit 45 of the lower table 5L, the ram position controller 35 performs a speed distribution process for moving the lower table 5L to the target position by the speed distribution processing unit 47. A command is issued via a command position counter 49.

The actual position of the lower table 5L detected by the lower table position detector 11 is fed back from the actual position counter 51, and the adder 53 calculates the difference between the commanded position of the lower table 5L and the actual position. The deviation amount is calculated, the position loop gain is determined by the position loop gain determination unit 55, and the position loop gain is multiplied by the aforementioned deviation amount.

On the other hand, the ram position controller 35 monitors the information from the pressure sensor 25 provided on the hydraulic cylinder 3 in real time, and detects the pressure of the hydraulic cylinder 3 at a certain threshold value (for example, the pressure V at a certain level in FIG. 5C). If this is the case, the "ram speed command-valve position conversion" process 57A in which the valve movement pattern switching unit 57 is normally used is automatically replaced with another "ram speed command-valve position conversion" process 57.
Switch to B. The switched "ram speed command-valve position conversion" process 57B has a characteristic of controlling the opening degree, that is, the position of the switching valve 17.

Therefore, referring to FIGS. 5A to 5C, the command speed moves the lower table 5L at a high speed as shown by a solid line in FIG. 5A (see FIG. 5A). )
(A0 to A1 to A2), the switching valve 17 is set to the fast-forward position (B0 to B1 to B2 in FIG. 5B).
The lower table 5L is moved at high speed only by the small-diameter cylinder 9. Before generating a high pressure in the lower table 5L (see (C) in FIG. 5), the speed of the lower table 5L is reduced (A2 to A3 in FIG. 5A), and the switching valve 17 is pressurized and fed. Operating position (B3 in FIG. 5B)
Move to B4).

When the time reaches the time T1 (see FIG. 5C) in which the pressure is generated in the hydraulic cylinder 3 due to the contact of the punch P with the work W, the command speed is commanded to be constant (see FIG. 5C). (A3 to A4 to A5 in FIG. 5A), the actual lower table 5L comes into contact with the work W and the speed is reduced (indicated by a broken line after A4 in FIG. 5A). At this time, the ram position controller 35 attempts to increase the rotation speed of the hydraulic pump 21 so that the lower table 5L speed approaches the command speed, but the speed is reduced due to a response delay of the hydraulic pump 21.

When the speed of the lower table 5L decreases in this way, a difference between the command speed of the lower table 5L and the actual speed occurs, and the amount of ram position deviation increases.
(After A4 during (A)), the switching valve 17 attempts to be in the "fast-forward operation position" in which the moving speed is increased by using only the small-diameter cylinder 9, but when the pressure of the hydraulic cylinder 3 reaches a predetermined threshold value V. As shown in FIG. 5B, the position of the switching valve 17 is clamped in the pressurizing feed position (B5 in FIG. 5B), so that the large-diameter cylinder 7 and the small-diameter cylinder 9 can operate together. To do.
Thereby, as shown in FIG. 5C, the pressure of the hydraulic cylinder 3 increases.

From the above results, the pressure in the hydraulic cylinder 3 is constantly monitored, and when a constant pressure is generated in the hydraulic cylinder 3, the valve movement pattern is automatically changed and clamped at a predetermined position. Since the bending can be performed by generating a high pressure without lowering the moving command speed of the lower table 5L, the productivity can be improved.

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 above-described embodiment of the present invention, the case where the lower table 5L as the lower table 5L is raised by the hydraulic cylinder 3 and the bending is performed in cooperation with the punch P and the die D has been described. The same applies to the case where the upper table 5U is lowered by the cylinder 3 as a ram to perform bending.

In the embodiment of the present invention, the position of the switching valve 17 is controlled by detecting the pressure of the hydraulic cylinder 3 by the pressure sensor 25. In addition, the command position of the lower table 5L is differentiated. "Speed distribution command"
Alternatively, it is also possible to control the position of the switching valve 17 based on the "ram actual speed" detected and fed back by the lower table position detector 11, or the position of the lower table 5L.

[0038]

As described above, in the hydraulic cylinder control method according to the first aspect of the present invention, regardless of the difference between the command position and the actual ram position, the pressure in the hydraulic cylinder or the actual ram position Alternatively, since the switching valve is controlled to be switched according to the ram speed, the ram can be moved according to the situation.

In the method for controlling a hydraulic cylinder in a press brake according to the second aspect of the present invention, when shifting from a rapid traverse operation of the ram to a pressurizing operation in the press brake, regardless of the difference between the command position and the actual ram position. When the pressure in the hydraulic cylinder is detected and the pressure exceeds a predetermined threshold value, the switching valve is clamped at the pressurizing operation position to continue the pressurizing operation. Bending can be performed, and productivity can be improved.

In the control apparatus for a hydraulic cylinder in a press brake according to the third aspect of the present invention, when the press brake shifts from the rapid traverse operation to the pressurizing operation of the ram, the pressure detecting means detects the pressure in the hydraulic cylinder, When the pressure exceeds a predetermined threshold, regardless of the deviation between the command position for the ram and the actual position of this ram, the valve movement pattern switching unit clamps the switching valve to the pressure operation position and pressurizes it. Since the operation is continued, bending can be performed by generating a high pressure, and productivity can be improved.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a hydraulic circuit of a press brake according to the present invention.

FIG. 3 is a graph showing a relationship between a lower table speed and a pressure in a cylinder.

FIG. 4 is a control block diagram of a ram position controller.

5A is a graph showing a lower table speed, FIG. 5B is a valve position, and FIG. 5C is a graph showing a cylinder pressure.

FIG. 6 is a circuit diagram showing a hydraulic circuit of a conventional press brake.

FIG. 7 is a circuit diagram showing a control circuit of a conventional press brake.

8A is an explanatory diagram showing a valve position corresponding to a press-feeding operation position, and FIG. 8B is an explanatory diagram showing a valve position corresponding to a rapid-feeding operation position.

9A is a graph showing the lower table speed, FIG. 9B is a valve position, and FIG. 9C is a graph showing the cylinder pressure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Press brake 3 Hydraulic cylinder 5 Lower table (ram) 11 Lower table position detector (ram position detecting means) 17 Switching valve 25 Pressure sensor (pressure detecting means) 35 Ram position controller (control device) 57 Valve movement pattern switching section P Punch D die

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F15B 9/09 F15B 9/09 CF 11/028 11/02 X F Term (Reference) 3H001 AA03 AA04 AB04 AC02 AC03 AD04 AE13 AE14 3H089 AA13 AA20 BB14 BB15 CC01 DB43 EE33 EE36 FF03 FF07 GG02 JJ03 4E063 BA07 FA02 FA05 FA09 LA01 LA11 LA14 LA17 4E089 EA01 EB01 ED03 ED10 EE01 EE04 4E090 AA01 AB01

Claims (3)

[Claims] 1. A single switching valve switches a plurality of characteristics of the hydraulic cylinder to move the ram up and down based on a deviation amount between a command position for a ram moved by a hydraulic cylinder and an actual ram position. In the method for controlling a hydraulic cylinder, detecting the pressure in the hydraulic cylinder or the actual position or the ram speed of the ram, and controlling the position of the switching valve according to the pressure or the actual position or the ram speed, Characteristic hydraulic cylinder control method. 2. A ram is moved up and down by switching a plurality of characteristics of the hydraulic cylinder by one switching valve based on a deviation amount between a command position for the ram moved by the hydraulic cylinder and an actual ram position. In a control method of a hydraulic cylinder in a press brake that performs bending processing on a work by cooperation of a punch and a die, when shifting from a rapid feed operation of the ram to a pressurizing operation, the pressure in the hydraulic cylinder is detected. When the pressure in the hydraulic cylinder is equal to or higher than a predetermined threshold value, the switching valve is clamped at a pressurizing operation position regardless of a deviation amount between a command position for the ram and an actual position of the ram;
A method for controlling a hydraulic cylinder in a press brake, characterized in that: 3. A ram is moved up and down by switching a plurality of characteristics of the hydraulic cylinder by one switching valve based on a deviation amount between a command position for the ram moved by the hydraulic cylinder and an actual ram position. A control device for a hydraulic cylinder in a press brake for performing a bending process on a work in cooperation with a punch and a die, wherein a ram position detecting means for detecting a position of the ram; and a pressure for detecting a pressure in the hydraulic cylinder. A detecting means, and a command position for the ram when the pressure in the hydraulic cylinder detected by the pressure detecting means at the time of shifting the ram from the rapid traverse operation to the pressurizing operation becomes equal to or higher than a predetermined threshold value. A valve movement pattern switching unit for clamping the switching valve to the pressurizing operation position regardless of the deviation amount from the actual position of the valve. A control device for a hydraulic cylinder in a press brake.