JPH10249598A - Lower limit position controller of hydraulic press and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lower limit position controller of a hydraulic press and a method therefor which precisely positions the lower limit position of a slide in forming with the press. SOLUTION: In this lower limit position controlling method, a hydraulic cylinder 2 to drive a slide 4 vertically in straight line is controlled with a servo valve 17, the working speed of the slide 4 in the time of pressing and lowering and its speed switching position are controlled, the slide lowering limit position is positioned and a work is punched. In this case, the time variation of the slide pressing force being peculiar to the work in the time of punching is pre-stored as the pressure decrease, by comparing the pressure decrease of the slide 4 to calculate when the work w is machined in a prescribed machining speed with the above stored pressed decrease of the slide, punching the work is detected, the position of the slide 4 in the completed time of this punching is detected, the control command to switch the speed of the slide 4 to a prescribed positioning speed being later than the above machining speed from the positioning speed switching position on this side by a prescribed distance from this punching position in the next punching time is outputted to the servo valve 17 and positioning of the lowering limit position of the slide 4 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a lower limit position of a slide for suppressing vibration and noise at the time of punching of a hydraulic press and improving forming accuracy at the time of drawing.

[0002]

2. Description of the Related Art Press machines are classified into mechanical types and hydraulic types. Hydraulic presses are used in a wide range of fields because they have the advantage that the operation of a slide can be changed in various ways according to processing conditions. I have. In order to set various processing conditions, control methods relating to the operation of a hydraulic press, that is, a slide motion have been conventionally proposed. For example,
In Japanese Patent Application Laid-Open No. 08-150500, in order to enable high-precision machining in a process of machining a work using an upper mold attached to a slide of a hydraulic press and a lower mold attached to a bolster, A method of controlling a slide motion in two modes, a pressure priority mode and a position priority mode, has been proposed as shown in FIG. Looking at the control method of the slide in the pressure priority mode in FIG. 9, first, the slide descends at a high speed from the upper limit position where the operation is started, and reaches the machining area just before the work. Then, the slide descends while processing the work at a predetermined processing speed, but when the pressing force reaches a predetermined value at a position before reaching the lower limit position, the slide stops at that position and the pressing force is reduced for a predetermined time. Hold. On the other hand, in the position priority mode,
If the predetermined pressing force is not reached even when the slide reaches the lower limit position, the slide holds the pressing force at the lower limit position for a certain period of time. Then, after processing, it rises at a low speed to a predetermined position, and then rises at a high speed to an upper limit position to complete the processing cycle. By controlling such a slide motion, it is possible to prevent an excessive force from being applied to a work or a mold, so that high-precision processing is possible, and
It is said that there are effects such as prevention of mold damage.

[0003]

However, in drawing, there are products in which the height (thickness) of the molding must be within a specified value as in so-called crushing. However, the speed in a conventional hydraulic press,
In the position control method, the slide may go too low at the lower limit position, and therefore, there is a problem that the conventional method cannot be applied to a work requiring a high precision standard as described above. Also, in the punching process, after the completion of the punching, the pressing force of the slide is sharply reduced due to a so-called breakthrough, and the slide may be pushed further below a predetermined lower limit position or may vibrate. For this reason, there is a problem that the service life of the mold and the press is shortened, and the working environment is deteriorated for the worker due to noise, vibration, and the like, which causes mental and physical pain.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a hydraulic press lower limit position control device and method capable of improving the positioning accuracy of the slide lower limit position.

[0005]

In order to achieve the above object, the invention according to the first aspect is directed to a slide 4 which is linearly driven vertically by a hydraulic cylinder 2.
And a servo valve 17 for controlling the operation of the hydraulic cylinder 2
And a slide position detecting means 8 for detecting the position of the slide 4, and a motion setting means 15 for setting control conditions such as at least a processing speed when the slide 4 is pressurized and lowered and its speed switching position. The lower limit position control device of the hydraulic press that performs the punching of the work w by controlling the operation of the slide 4 based on the control condition
Pressing force detecting means 10 and 11 installed in the upper chamber 2a and the lower chamber 2b of the hydraulic cylinder 2 and detecting respective pressures of the upper chamber 2a and the lower chamber 2b; Load detecting means 21 for calculating the pressing force of the slide 4 on the basis of the pressure signal from the pressure sensor, and a pressure gradient for calculating and outputting a pressure reduction rate when the pressing force detected by the load detecting means 21 decreases with time. The calculating means 22 and the pressure reduction rate at the time of punching specific to the workpiece w are stored in advance, and the pressure gradient calculating means 2 is used during the first machining.
When the pressure reduction rate calculated in Step 2 becomes larger than the stored pressure reduction rate, it is determined that the punching is completed, and the rupture determination means 23 which takes in the position data of the slide 4 at the time of the punching from the slide position detection means 8. A position feedback unit 24 that feeds back the position data obtained by the fracture determination unit 23 as a punching position, and a minute distance before the punching position at the time of the next and subsequent machining based on the fed back position data, and A position setting means 25 for setting the positioning speed switching position for starting the positioning control of the lower limit position by switching the speed of the slide 4 to a positioning speed lower than the processing speed, and the positioning newly set by the position setting means 25. Speed switching position, motion setting means 1
5, a motion storage means 26 for storing the positioning speed and the control condition inputted by 5; a speed calculation means 27 for calculating a speed value based on a temporal displacement of the position data detected by the slide position detection means 8; The processing speed of the slide 4 calculated by the speed calculating means 27 and the positioning speed near the lower limit position are compared with the corresponding set values stored in the motion storage means 26, and the deviation of the speed is reduced. And a servo valve command output for receiving the output value from the servo valve output calculating means 28 and transmitting the control command to the servo valve 17. And means 29.

According to the first aspect of the present invention, in punching a work, the slide descends at a high speed from an upper limit position to a position a predetermined distance before the work, and is switched from this position to a predetermined processing speed to press the work. While descending.
During the downward movement of the slide, the workpiece is punched by the pressing force of the slide. The work of the work is completed by this punching, and the slide returns from the lower limit position to the upper limit position. The pressing force of the slide is constantly detected,
The punching of the work is determined by the magnitude of the time change of the pressing force of the slide, that is, the pressure reduction rate. The pressure reduction rate of this slide is also always calculated, and is constantly compared with a pressure reduction rate which is stored in advance as a value unique to the workpiece and is a reference for punching determination. When the pressure reduction rate of the slide becomes larger than the pressure reduction rate serving as the criterion for the punching determination, it is determined that the punching of the workpiece is completed. Also, the position of the slide is constantly monitored, and this slide position is detected when the work punching is completed. When the punching of the workpiece is determined, a positioning speed switching position that is a predetermined distance before the punching position is set as a new control condition. Then, from the next punching operation, the slide descends from the positioning speed switching position at a predetermined positioning speed which is lower than the processing speed, and the slide is punched to finish the processing. When the slide is descending at a positioning speed lower than the processing speed in this way, the servo valve is in a state of being greatly throttled. Therefore, when the servo valve is switched from the descending direction of the slide to the ascending direction when the punching of the work is detected, the followability of the slide is significantly improved as compared with the conventional case where the slide is not switched to the positioning speed. . Therefore, the amount of slide can be suppressed, and the life of the mold can be improved. In addition, since the pressurized oil is supplied to the lower chamber of the hydraulic cylinder immediately after the punching is completed, the damper effect is increased by the hydraulic cylinder, and the vibration of the slide can be suppressed by a large effect. As a result, the vibration of the slide can be suppressed and the vibration can be damped faster, so that the life of the hydraulic press can be improved.

In the invention according to a second aspect, the position setting means 25 detects the punching position each time each punching operation is performed, and based on the detected position, the positioning speed of the slide 4 in the next processing operation. The lower limit position control device for a hydraulic press according to claim 1 for updating the switching position is provided.

According to the second aspect of the present invention, a slide position at the time of punching is detected each time a workpiece is processed, and a lower limit positioning start position of the slide is set. Each time, based on the updated positioning speed switching position data,
Perform punching. This makes it possible to accurately detect the punching position even when the thickness variation of the workpiece is relatively large, and to reliably suppress the amount of protrusion at the time of punching and the vibration of the slide. Thereby, the life of the mold and the hydraulic press can be improved.

According to a third aspect of the present invention, the position setting means 25 detects the punching position every predetermined number of times of the punching process, and based on the detected position, the position of the slide 4 at the next processing is determined. A lower limit position control device for a hydraulic press according to claim 1 for updating the positioning speed switching position.

According to the third aspect of the present invention, the slide position at the time of punching is detected every predetermined number of times during work processing, and the lower limit positioning start position is newly set and updated. Then, molding is performed at the predetermined number of times under the newly set conditions. As a result, even if the thickness of the work gradually changes, the punching position is accurately detected, and the amount of protrusion and the vibration of the slide at the time of punching can be reliably suppressed. Thereby, the life of the mold and the hydraulic press can be improved. This method is particularly effective when the thickness of the work gradually increases or decreases.

Further, the invention according to claim 4 is characterized in that the slide 4 which is linearly driven vertically by the hydraulic cylinder 2,
A servo valve 17 for controlling the operation of the hydraulic cylinder 2,
Slide position detecting means 8 for detecting the position of slide 4
And motion setting means 15 for setting at least control conditions such as a processing speed when the slide 4 is pressurized and lowered and a speed switching position thereof. The operation of the slide 4 is controlled based on the set control conditions. A lower limit position control device for a hydraulic press for drawing a workpiece w, a motion storage means 26 for storing the control conditions inputted by the motion setting means 15, and a position data detected by the slide position detection means 8. A speed calculating means 27 for calculating a speed value based on a time displacement; and an overshoot when a predetermined speed from a lower limit position is reached to a positioning speed switching position during lowering at the set low processing speed. The predetermined low speed value and the speed performance are set so as to be a lower predetermined speed which is positioned at the lower limit position. Means for calculating the control value of the servo valve 17 for reducing the deviation from the speed value calculated by the means 27 and controlling the position of the slide 4; and output values from the servo valve output calculating means 28 In response to this, a servo valve command output means 29 for transmitting the control command to the servo valve 17 is provided.

According to the fourth aspect of the present invention, the slide descends at a high speed from the upper limit position to a position before the work by a predetermined distance,
From this position, the workpiece is switched to a predetermined processing speed and descends while processing the work. During this downward movement, the slide descends from the positioning speed switching position, which is a predetermined distance before the lower limit position, at a positioning speed lower than the processing speed. When the slide reaches the lower limit position and the machining is completed, the servo valve is switched at that moment, and the slide is switched from the descending stroke to the ascending stroke and rises to the upper limit position.
As described above, when the slide is descending at a positioning speed even slower than the processing speed, the servo valve is largely throttled, so that the slide reaches the lower limit position and the servo valve is switched. The slide switching followability is much better than the conventional case where the slide is not switched to the positioning speed. As a result, overtravel due to a response delay of the servo valve or the like is reduced, and a high positioning accuracy of the lower limit position of the slide is obtained, so that a molded product with high accuracy which cannot be obtained conventionally can be processed.

According to a fifth aspect of the present invention, the lower limit position of the hydraulic press according to any one of the first to fourth aspects, further comprising setting display means 30 for displaying setting data of the control conditions and control data during molding. It has the configuration of the control device.

According to the fifth aspect of the present invention, the setting data of the slide control condition during molding and the control data during molding can be displayed and constantly monitored, so that the control condition can be easily set.

[0015] The invention according to claim 6 is characterized in that the slide 4
The servo cylinder 17 controls the hydraulic cylinder 2 that linearly drives the slider 4 in the vertical direction, controls the operating speed when the slide 4 is pressurized and lowered, and the speed switching position, positions the slide lower limit position, and punches the workpiece w. In the method of controlling the lower limit position of the hydraulic press, the time change of the slide pressing force at the time of punching specific to the work w is stored in advance as a pressure reduction rate, and the work w is processed at a predetermined processing speed at the first processing. By comparing the calculated pressure reduction rate of the slide 4 with the stored pressure reduction rate of the slide 4, the completion time of the punching of the work w is detected, and the position of the slide 4 at the time of the completion of the punching is detected. ,
At the next and subsequent punching operations, a control command for switching the speed of the slide 4 from the positioning speed switching position that is a predetermined distance before the punching position to a predetermined positioning speed that is lower than the processing speed is output to the servo valve 17. The method controls the positioning of the lower limit position of the slide 4.

According to the present invention, the pressure reduction rate at the time of punching specific to the work is stored in advance, and the pressure reduction rate generated at the time of punching the work is compared with the stored pressure reduction rate. Thus, punching of the work is detected, and the position of the slide at the time of punching is detected. Then, based on the punching position, a positioning speed switching position is set by a predetermined distance before the punching position,
The lower limit position of the slide is determined by switching the slide speed from this position to a predetermined positioning speed which is lower than the processing speed. As a result, the protrusion amount of the slide after punching the work is reduced, and the vibration of the slide 4 is rapidly reduced, so that the life of the mold and the hydraulic press can be improved. In addition, since the process from the detection of the punching position of the slide to the setting of the positioning speed switching position can be automatically performed in this manner, the lower limit position can be easily set without depending on the skill and experience of the operator.

Further, according to a seventh aspect of the present invention, the slide 4
Is controlled by a servo valve 17 to control the operating speed when the slide 4 is pressurized and lowered and the speed switching position, and position the lower limit position of the slide to draw the work w. In the method for controlling the lower limit position of a hydraulic press, when the slide 4 comes down to a positioning speed switching position that is a predetermined position before the lower limit position while the slide 4 is moving down at the processing speed, the speed of the slide 4 is further reduced to a predetermined speed lower than the processing speed. In this method, the positioning of the lower limit position of the slide 4 is controlled by switching to the positioning speed.

According to the present invention, the positioning speed switching position is set in advance by a predetermined distance from the lower limit position of the slide before machining the work. And
The lower limit position of the slide is determined by switching the slide speed from this position to the predetermined positioning speed lower than the processing speed from the processing speed. According to this method, the lower limit position of the slide 4 can be positioned with high accuracy, and a highly accurate product can be formed.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view of a main part of a hydraulic press on which a mold and a work are mounted. The hydraulic press 1 is equipped with a C frame 5, a bed 9 is provided below the C frame 5, and the bed 9 holds the bolster 3 above. A hydraulic cylinder 2 is mounted on an upper portion of the C frame 5, and a slide 4 that moves up and down at a position facing the bolster 3 is fixed to a lower end of the hydraulic cylinder 2.
When the upper mold d1 attached to the slide 4 is lowered from the upper limit position to the lower limit position by the hydraulic cylinder 2, the work w placed on the lower mold d2 attached to the bolster 3 is pressed and processed. You. After the work w is pressed at the lower limit position of the slide 4 for a predetermined time, the slide w
Rises to the initial upper limit position, and the machining cycle is completed.

In the vicinity of the opening of the C frame 5,
An auxiliary frame 7 having a shape similar to that of the opening is mounted. The lower end of the auxiliary frame 7 is attached to the side surface of the C frame 5 by a pin 6 so as to be freely displaceable in the vertical direction. Further, at predetermined positions on the upper end side of the auxiliary frame 7 and the rear side of the slide 4, slide position detecting means 8 including a linear sensor or the like is provided. The slide position detecting means 8 includes a sensor rod 8a at a rear portion of the slide 4 mounted so that an axial direction thereof is parallel to a vertical movement direction of the slide 4, and the auxiliary frame described above in a state where the sensor rod 8a is inserted. 7 comprises a sensor head 8b. As the slide 4 moves up and down with respect to the sensor head 8b to which the sensor rod 8a is fixed, the position of the slide 4 moves from the position detecting unit incorporated inside the sensor head 8b to the upper surface of the bolster 3 Is detected as the height from

Referring to FIG. 2, the hardware structure of the lower limit position control device for the hydraulic press according to the present invention will be described. The upper chamber 2a, the lower chamber 2b and the uppermost chamber 2 of the hydraulic cylinder 2 in FIG.
c, the servo valve 1 via the low speed / high speed switching valve 18
A working oil of a predetermined pressure is supplied from 7 or discharged from each of these chambers. The piston outer chamber 2d in the cylinder is open to the atmosphere. Inside the upper chamber 2a and the lower chamber 2b, respective pressure detecting means 10 and 11 each comprising a pressure sensor for detecting the pressure in the cylinder chamber are mounted. By the pressing force detecting means 10 and 11,
The hydraulic oil pressure controlled by the servo valve 17 and the like is constantly detected, and the detection signal is transmitted to the controller 20.
Is input to Further, the slide position detecting means 8 as described above is provided near the slide 4, and the position of the slide 4 is always detected. The detected signal is input to the controller 20 similarly to the pressure signal.

The motion setting means 15 instructs the controller 20 on a predetermined control value set for controlling the slide motion. This motion setting means 15
Is configured by a device including a portion for inputting a set value such as a setting switch, a portion for displaying the input set value, and the like.

The controller 20 is mainly composed of a microcomputer or the like having a high-speed arithmetic processing function, and has a central function of a device for controlling the slide 4 according to the present invention. The controller 20 converts the various input signals described above into signals for controlling the servo valve 17 by performing predetermined processing described later, and controls the servo valve 17. The servo valve 17 receiving this control signal controls the pressure, flow rate, and the like of the hydraulic oil that drives the hydraulic cylinder 2. Then, the controlled hydraulic oil passes through the circuit of the low-speed / high-speed switching valve 18 and the hydraulic cylinder 2
, Or discharged from the cylinder, the position, speed and pressure of the slide 4 attached to the hydraulic cylinder 2 are controlled.

The controller 20 is connected to a display 16 composed of, for example, a liquid crystal display screen, a CRT, or an LED for displaying a numerical value. Information for monitoring data and the like is provided.

FIG. 3 is a block diagram showing a lower limit position control apparatus and method according to the present invention. The pressure signals transmitted from the pressing force detecting means 10 and 11 are taken into the controller 20, and the load detecting means 21 calculates the product of the pressure and the pressure receiving area of the hydraulic cylinder upper chamber 2 a and the pressure of the hydraulic cylinder lower chamber 2 b. And the product of the pressure receiving area and the product of the pressure receiving area. This pressure is
The input is constantly input to the pressure gradient calculating means 22, and is monitored by the pressure gradient calculating means 22 as a time change of the pressing force of the slide 4. This time change of the pressing force is represented by a pressing force-time diagram having a pressing force P on the vertical axis and a pressing time t on the horizontal axis, where P is the pressing force of the slide 4 and t is the pressing time. Expressed as a rate of change. The rate of change of the pressing force, that is, the rate of change of the pressure, is always calculated by the pressure gradient calculating means 22. Here, the pressure change rate when the applied pressure decreases with time is set to a positive value, and this pressure change rate is expressed as a pressure decrease rate Pc. The pressure reduction rate Pc is represented by “Pc = ΔP / Δt” in a mathematical expression, and is calculated by the pressure gradient calculator 22. When the pressure reduction rate Pc becomes larger than the pressure reduction rate at the time of punching specific to the work, it can be detected that the work w has been punched.

Here, the above-described determination of punching will be described with reference to FIG. This figure shows the relationship between the slide position of the slide 4 and the operation elapsed time, and the relationship between the slide pressure and the operation elapsed time. That is, slide 4 on the vertical axis
, The horizontal axis represents the operation diagram of the slide 4 representing the time t from when the slide 4 starts at the upper limit position U, the vertical axis represents the pressing force P of the slide 4, and the horizontal axis represents the operation diagram. And a pressing force diagram representing the same time t are shown as a pair.

In the punching operation, when the slide 4 reaches the processing area, its speed is switched to the processing speed and further lowered. At this time, the pressing force of the slide 4 increases with time, and when the pressing force reaches the maximum value Pn, plastic deformation of the work w starts. Then, when the pressure reduction rate Pc of the slide 4 becomes larger than a predetermined value specific to the work, the deformation speed of the work w cannot follow the processing speed, the work w is punched out, and the pressing force of the slide 4 rapidly decreases. Here, in the pressing force-time curve, a point at which punching occurs is represented by a punching point Bp, a pressing force of the slide 4 at the punching point Bp is represented by a punching pressure Pb, and a pressure reduction rate during punching is represented by a symbol Pbc. The pressure reduction rate Pbc at the time of punching is represented by a mathematical expression “Pbc = ΔPb / Δt”, and can be obtained from past empirical data and theoretical values of the work w.

The pressure reduction rate Pbc at the time of punching is a value peculiar to each work w, and is stored in the rupture determining means 23 shown in FIG. 3 as a reference value for punching determination. Slide 4 calculated by the pressure gradient calculating means 22
The value of the pressure decrease rate Pc (= ΔP / Δt) is always input to the rupture determination means 23 and is compared with the stored reference value (= the pressure decrease rate Pbc at the time of punching). Then, the pressure reduction rate Pc of the slide 4 is determined by the breaking determination means 23 to be equal to the pressure reduction rate Pb at the time of punching.
If it is determined to be larger than c, it is determined that the punching of the work w has been completed. Slide 4 when punching is completed
Is taken from the slide position detecting means 8 to the break determining means 23 and transmitted to the position feedback means 24 as a punching position.

The position data of the slide 4 at the time of completion of the punching is used to set a new control condition for the slide 4.
By the position feedback means 24, the position setting means 2
5 is transmitted. The setting means 25 having received the position data sets a positioning speed switching position at which the slide 4 is further lowered at a position short of the minute distance where the punching of the work w is completed, as a new control condition. The positioning speed switching position of the slide 4 is calculated by an algorithm incorporated in the position setting means 25. The speed switching position is determined as a position where punching does not occur before the speed switching of the slide 4 even if the thickness variation of the workpiece w and the positioning accuracy are considered, and the position calculation method is determined. The speed switching position data thus obtained is fed back from the position setting means 25 to the motion storage means 26, and is updated as one of the control conditions of the slide 4 which is already input from the motion setting means 15 and stored in the motion storage means 26. Is done.

The updated control condition data of the motion storage means 26 is transmitted to the servo valve output calculation means 28 together with the speed data of the slide 4 calculated by the speed calculation means 27. Here, the method of obtaining the speed data may be detected by, for example, a normal speed sensor,
It may be obtained as a temporal displacement of the position data detected by the slide position detecting means 8. An output value for controlling the servo valve 17 such as the electromagnetic flow rate proportional control valve is calculated by the servo valve output calculating means 28. From the positioning speed switching position to the lower limit position, an output value for performing position control is obtained. This calculated value is output by the servo valve command output means 29 to the servo valve 17 which is an element constituting the hydraulic circuit, and the servo valve 17 controls the flow rate, pressure, flow direction and the like of the hydraulic oil. The controlled hydraulic oil drives the hydraulic cylinder 2 via the low-speed / high-speed switching valve 18, and the position and speed of the slide 4 are controlled to predetermined conditions. Also slide 4
The control condition of the setting display means 30 such as a liquid crystal display
Is displayed as setting data, and the operating condition of the slide 4 is also clearly indicated on the setting display means 30 by color display or marking, so that the operating state of the slide 4 can be easily monitored.

FIGS. 5 to 8 show a control method of the slide 4. 5 and 6 as a first embodiment, and FIGS. 7 and 8 as a second embodiment.
The case of drawing will be described below. First, in the case of punching as the first embodiment, a slide control method is shown in FIG.
FIG. 6 shows a flowchart of the slide control method, which will be described with reference to FIG.

The speed-position diagram of the slide 4 in FIG. 5 shows a speed pattern in which the slide 4 is controlled within its operating range (between the upper limit position and the lower limit position) in the present invention. When the punching process is started, the slide 4 descends while accelerating from the upper limit position Z00, and reaches a predetermined high speed descending speed V05 at the point Zb. The slide 4 reaches the Zc point while maintaining this speed, and descends to the machining start position Z10 while decelerating from the Zc point. This machining start position Z1
At 0, the descending speed of the slide 4 is switched to the processing speed V10, and punching is started. The slide 4 reaches a predetermined processing speed V10 at the Ze point while accelerating, and descends to the Zf point while maintaining this speed. Then, the slide 4 starts to decelerate from the point Zf, and the positioning speed switching position Z2
At 0, the speed is reduced to the positioning speed V20. The positioning speed switching position Z20 of the slide 4 is a position a short distance before the punching position Zh of the workpiece w, and the positioning speed V20 is set to a value lower than the processing speed V10. At the moment when the slide 4 is further lowered and the completion of the punching of the work w is detected at the position Zh of the slide 4, a command to raise the slide 4 is given. Reach Z30. Further, when the slide 4 is pushed in at the time of the completion of the punching, the slide 4 further descends by a minute distance and then stops. At this time, since the positioning speed V20 is set to be lower than the processing speed V10, it is possible to suppress the overshoot amount and the plunge amount due to a response delay of the servo valve 17 or the like. Further, at the moment when the punching is completed, the servo valve 17 is switched from the downward movement of the slide 4 to the upward movement. As a result, the lower limit position Z30 of the slide 4 and the position Zh of the slide 4 when the work punching is completed are substantially the same. After the slide 4 reaches the lower limit position Z30, the machining start position Z at a low ascending speed V30.
10, and further rises to the upper limit position Z00, which is the machining start position, at a high speed ascending speed V00, and the cycle of punching is completed.

According to the flowchart of FIG.
A control method will be described. First, in step S1, a slide control condition is set as a step before starting punching. The setting conditions are as follows: high speed descent speed V05, processing speed V10, positioning speed V20, low speed ascent speed V30, high speed ascent speed V0 as speed data of slide 4.
0 is set, the upper limit position Z00, the processing start position Z10, the positioning speed switching position Z20, the lower limit position Z30 as the position data of the slide 4, and the pressing force P30 of the slide 4 and the punching time peculiar to the work w. Pressure reduction rate Pb
c is set. The control conditions for these punching processes are set based on past experience and the like, but the positioning speed V20 of the slide 4 is set to be lower than the processing speed V10.
The positioning speed switching position Z20 is set to the lower limit position Z30 as an initial value. Further, the lower limit position Z30 of the slide 4 is set to a position where the work w can be punched.

When the control conditions have been set, the punching process is started by a start command. First, in step S2,
When the controller 20 switches the low-speed / high-speed switching valve 18 from the closed state to the high-speed side, the slide 4 descends from the upper limit position Z00 to the machining start position Z10 just before the workpiece at the high-speed descending speed V05. At this time, the upper chamber 2a and the lower chamber 2b are connected to each other and also connected to the pump by the low speed / high speed switching valve 18. In addition, top room 2
c is open to the tank, and the amount of oil supplied to the upper chamber 2a depends on the amount of oil supplied by the servo valve 17 and the amount of oil supplied to the lower chamber 2a.
slide 4 because the amount of oil discharged from b
The descent speed becomes high.

Next, at step S3, at the machining start position Z10 of the slide 4, the low speed / high speed switching valve 18 is switched to the low speed side by the controller 20, and the lower chamber 2b
And the uppermost chamber 2c is opened to the tank, and only the oil amount from the servo valve 17 is supplied to the upper chamber 2a.
The descending speed of the slide 4 is lower than that of the slide 2. Then, in the controller 20, the servo valve output calculating means 28 calculates the control value of the servo valve 17 based on the processing speed V10 set in the motion storage means 26,
The servo valve 17 is controlled by issuing a control command from the servo valve command output means 29. Thus, the descending speed of the slide 4 is switched to the processing speed V10.

Further, in step S4, the slide 4 descends toward the positioning speed switching position Z20 at the processing speed V10. In the controller 20, the speed calculated by the speed calculating means 27 from the amount of change in the position data detected by the slide position detecting means 8, and the processing speed V1 stored in the motion storage means 26 in advance.
From 0, the deviation value of the speed is calculated by the servo valve output calculation means 28 to calculate the control value of the servo valve 17, and the servo valve command output means 29 issues a control command to the servo valve 17. The processing speed V10 is controlled to a predetermined speed.

In step S5, punching is determined, and YES
In the case of, the process proceeds to step 6, and in the case of NO, the process proceeds to step 11. In the first machining, since the positioning speed switching position Z20 of the slide 4 is set to the lower limit position Z30 as an initial value, the workpiece w is moved to the slide 4 at the machining speed V1.
Punching is performed while descending at zero. The pressure decrease rate Pc (= ΔP / Δt) of the slide 4 is calculated by the pressure gradient calculator 22 as described above, and the calculated value is constantly monitored by the rupture determiner 23. This pressure reduction rate Pc is compared with the stored pressure reduction rate Pbc at the time of punching, which is the reference value, and the pressure reduction rate Pc
Is larger than the pressure reduction rate Pbc at the time of punching, it is determined that the punching of the work w has been completed.

Then, in step S6, the position Zh at the time of completion of the punching is taken from the slide position detecting means 8 into the break determining means 23 and transmitted to the position feedback means 24. The position data of the slide 4 at the time of completion of the punching is transmitted to the position setting means 25 by the position feedback means 24 in order to set new control conditions for the slide 4.

When the punching of the work w is completed,
At that moment, in step S7, the controller 20 issues a hydraulic circuit switching command to the servo valve 17 so as to supply hydraulic oil to the lower cylinder chamber 2b and to discharge hydraulic oil from the upper cylinder chamber 2a. Enter the process. Then, in step S8, the slide 4 moves up to the vicinity of the machining start position at the low speed rising speed V30. At this position, the low speed / high speed switching valve 18 is switched to the high speed side, and the slide 4 returns to the upper limit position Z00 at the high speed rising speed V00. .

In the next step S9, the positioning speed switching position Z20 at which the slide 4 is switched to the positioning speed V20 lower than the processing speed V10 by the position setting means 25 based on the position data is set to be a small distance from the punching completion position Zh. A new control condition is set at a position before this. The positioning speed switching position Z20 of the slide 4 is automatically set by an algorithm incorporated in the position setting means 25. In step S10, the positioning speed switching position data is fed back from the position setting means 25 to the motion storage means 26.
, The positioning speed switching position data of the control conditions among the control conditions stored in the motion storage means 26 is updated. The operation of the slide 4 after the completion of the punching in steps 7 and 8 and the setting and feedback of the positioning speed switching position Z20 in steps 9 and 10 may be performed in parallel.

When the first punching operation is completed in this way, since the positioning speed switching position Z20 of the slide 4 is set, no punching occurs at the processing speed V10 of the slide 4 from the next punching operation. That is,
In step S5, NO is determined and the next step S11 is executed.

In step S11, the slide 4 is moved to the positioning speed switching position Z set in step S9.
20, at this position, the descending speed of the slide 4 becomes the positioning speed V which is lower than the processing speed V10.
It is switched to 20. The positioning speed V20 is set in advance based on the shape, dimensions, required accuracy, and the like of the processed product, and is stored in the motion storage unit 26 of the controller 20. In this step S11, the low speed / high speed switching valve 18
Is on the low speed side as it is in step S4, and the speed switching of the slide 4 is performed by the flow control of the servo valve 17 which receives the control command from the controller 20.

In step S12, the positioning speed V is changed from the positioning speed switching position Z20 to the lower limit position Z30.
It descends at 20. This positioning speed V20 is controlled similarly to the processing speed V10 in step S4. That is, in the controller 20, the servo valve output calculating means 28 includes the slide position detecting means 8 and the speed calculating means 2.
7 and the motion storage means 2 in advance.
Then, a deviation value from the processing speed V10 stored in No. 6 is calculated.
Then, the servo valve output calculating means 28 calculates the control value of the servo valve 17 so as to reduce this deviation value,
The servo valve command output means 29 outputs a control command based on the control value to control the servo valve 17 to a predetermined speed.

In step S13, while the slide 4 is being positioned and lowered, the break determination means 23 detects punching of the work w. At the moment when this punching is detected, in the next step 14, the controller 20
Supplies a hydraulic oil to the servo valve 17 to the lower cylinder chamber 2b and issues a hydraulic circuit switching command to discharge the hydraulic oil from the upper cylinder chamber 2a, and the cylinder 4 enters a rising stroke.
Immediately before the switching of the hydraulic circuit, the slide 4 is lowered from the positioning speed switching position Z20 at a positioning speed V20 which is slower than the processing speed V10, and at this time, the servo valve 17 is in a state of being greatly throttled. . Therefore, the switching followability of the slide 4 at the moment when the punching of the work w is completed and the servo valve 17 is switched is improved, so that the amount of slide 4 plunging can be suppressed. As a result, the vibration of the slide 4 can be suppressed, and the decay time of the vibration can be reduced.

After the punching of the slide 4 is completed in this way, in step S15, the slide 4 moves up to the vicinity of the molding start position at the low speed V30, at which position the low speed / high speed switching valve 18 is switched to the high speed side. The slide 4 moves up to the upper limit position Z00 at the high speed rising speed V00.

In the above-described example, the positioning speed switching position Z20 of the slide 4 is set in the first punching process. However, the following setting method can be adopted. That is, each time the work w is punched, the slide position at the time of completion of the punching is detected, and the positioning speed switching position Z20 of the slide 4 is set by the position setting means 25 each time.
Then, the positioning speed switching position Z20 of the slide 4 of the motion storage means 26 is constantly updated, and punching is performed with the updated positioning speed switching position data each time. This method is effective when the thickness variation of the workpiece w is relatively large. Further, the slide position at the time of completion of the punching of the work w may be detected every predetermined number of times, and the position setting means 25 may be used to set the positioning speed switching position Z20 of the slide 4 each time. Then, at the time of setting, the positioning speed switching position Z20 of the slide 4 of the motion storage means 26 is updated, and punching is performed with the updated positioning speed switching position data. This method is effective when the work w is long like a coil material and the thickness gradually increases or decreases. Further, each time the workpiece w is punched, the slide position at the time of completion of the punching is detected, and each time the positioning speed switching position Z20 of the slide 4 is set by the position setting means 25, the positioning speed switching position Z20 is temporarily set. It is also possible to store the data in the position setting means 25, calculate the average value every predetermined number of times, and update the positioning speed switching position Z20 of the slide 4 of the motion storage means 26. Note that the positioning speed switching position Z20 can be automatically set in the flow, or can be manually set by a person and manually input. In the above-described example of the punching process, a hydraulic press having a double-acting cylinder is used, but the same applies to a single-acting case.

Next, as a second embodiment, a drawing process will be described with reference to FIGS. FIG. 7 shows a slide control method by a speed-position diagram of the slide 4,
FIG. 8 shows a flowchart of the slide control method, which will be described with reference to FIG. The speed-position diagram of the slide 4 in FIG. 7 shows a speed pattern in which the slide 4 is controlled in its operating range (between the upper limit position and the lower limit position) in the present invention. In the figure, the same reference numerals as those in the case of the punching process in FIG. 5 represent the same configuration. The drawing process is performed in accordance with a preset control value of the slide 4. First, when the slide 4 descends at a high speed from the upper limit position Z00 and reaches the machining start position Z10, the machining speed V1 is shifted from this position to the machining start position Z10.
At 0, it descends at a low speed and reaches a positioning speed switching position Z20 which is a minute distance before the lower limit position Z30. Then, the slide 4 descends from this position toward the lower limit position Z30 at a positioning speed V20 lower than the processing speed V10.
The descending stroke of the slide 4 so far is the same as in the case of punching. Next, in this drawing, when the slide 4 is further lowered and the lower limit position Z30 is detected, the process is switched to the ascending stroke. At this time, an overshoot (so-called overshoot) occurs on the slide 4 due to a response delay of the servo valve 17 or the like. However, since the speed of the slide 4 is set to the positioning speed V20 lower than the processing speed V10, The overshoot amount is smaller than before. As a result, high positioning accuracy of the slide lower limit position, which could not be obtained conventionally, can be secured. The difference between the drawing process and the punching process in the descending process is that the punching process is switched to the ascending process when the punching of the work w is detected, but the drawing process is lowered to a predetermined lower limit position and accurately performed. It is in the place to position. After the slide 4 is switched from descending to ascending in this way, the slide 4 follows the same stroke as the punching, and moves up to the upper limit position Z00.

According to the flowchart of FIG.
A control method will be described. Here, steps having the same processing contents as those in the above-described punching process are denoted by the same reference numerals, and the following description will be simplified. In the flowchart of FIG. 8, in step S21, a slide control condition is set when starting drawing. The setting conditions are as follows: high speed descent speed V05, processing speed V10, positioning speed V20, low speed ascent speed V30, as speed data of slide 4.
The high-speed rising speed V00 is set, the upper limit position Z00, the processing start position Z10, the positioning speed switching position Z20, the lower limit position Z30, and the pressing force P30 of the slide 4 are set as the position data of the slide 4. The difference from the punching process under these setting conditions is that the setting of the pressure reduction rate Pbc at the time of the work punching is unnecessary, and the lower limit position Z30 of the slide 4 is set to a predetermined value from the beginning. It is in.

After the setting of the control conditions is completed, drawing is started by a start command. First, steps S2, S3, and S4 are the same as in the case of punching. That is, the slide 4 descends at a high speed from the upper limit position Z00 to reach the machining start position Z10, descends at a machining speed V10 at a low speed from this position, and moves to the positioning speed switching position Z20.
To reach.

In step S22, the slide 4 is switched to the positioning speed V20 which is lower than the processing speed V10 at the positioning speed switching position Z20 which is a short distance before the lower limit position Z30. This positioning speed V2
“0” is set based on the shape, dimensions, required accuracy, and the like of the drawn product, and is stored in the motion storage unit 26 of the controller 20. The difference from the punching process in this step is that, in this case, the next or subsequent positioning speed switching position Z20 is set based on the position of the slide 4 detected by the first punching, but in the drawing process, the positioning speed switching position Z20 is set. Is set to a predetermined value from the beginning.

In the next step S23, the slide 4 descends at the positioning speed V20 from the positioning speed switching position Z20 to the lower limit position Z30. In this process, unlike the case of the punching process, the phenomenon such as punching does not occur, and the slide 4 descends toward the lower limit position Z30.

Then, in step S24, the slide 4 reaches the initially set lower limit position Z30. Slide 4
Is reliably lowered to the lower limit position Z30 at the low positioning speed V20, so that the overshoot becomes small due to a response delay of the servo valve 17 or the like, and high positioning accuracy of the slide lower limit position can be obtained. Next, in step S15, the slide 4 is switched to the ascending stroke and moves up to the upper limit position as in the case of the punching process. Although the above-described drawing example is a hydraulic press having a double-acting cylinder, the same applies to a single-acting case.

By controlling the positioning of the lower limit position of the slide of the hydraulic press as described above, the amount of slide plunging can be suppressed and the vibration can be rapidly attenuated in the punching process. As a result, effects such as prevention of breakage of the mold and the hydraulic press, improvement of the service life, improvement of a poor working environment due to noise and vibration to the operator, and securing of high-precision product quality are obtained. Also, in drawing, it is possible to keep the slide from going too far.
Very high precision product quality can be obtained. By using a double-acting cylinder, high-speed operation can be performed in a descending area or an ascending area where the slide does not process the work, and it can also contribute to an improvement in work efficiency.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a hydraulic press according to the present invention.

FIG. 2 shows a hardware configuration of a lower limit position control device according to the present invention.

FIG. 3 shows a block diagram of a lower limit position control device and method according to the present invention.

FIG. 4 is a diagram showing a relationship between a slide position and a pressing force with time according to the present invention.

FIG. 5 shows a speed-position diagram of a slide according to the invention.

FIG. 6 shows a flowchart of a slide control method according to the present invention.

FIG. 7 shows a speed-position diagram of a slide according to the invention.

FIG. 8 shows a flowchart of a slide control method according to the present invention.

FIG. 9 shows an example of a slide motion of a hydraulic press.

[Explanation of symbols]

 Reference Signs List 1 hydraulic press 2 hydraulic cylinder 2a upper chamber 2b lower chamber 2c uppermost chamber 2d piston outer chamber 3 bolster 4 slide d1 upper mold d2 lower mold w work 5 C frame 6 pin 7 auxiliary frame 8 slide position detecting means 8a sensor rod 8b sensor head 9 Bed 10, 11 Pressure detection means 15 Motion setting means 16 Display 17 Servo valve 18 Low speed / high speed switching valve 20 Controller 21 Load detection means 22 Pressure gradient calculation means 23 Break determination means 24 Position feedback means 25 Position setting means 26 Motion Storage means 27 Speed calculation means 28 Servo valve output calculation means 29 Servo valve command output means 30 Setting display means

Claims (7)

[Claims] A slide (4) linearly driven vertically by a hydraulic cylinder (2), a servo valve (17) for controlling the operation of the hydraulic cylinder (2), and a position of the slide (4). A slide position detecting means (8); and a motion setting means (15) for setting at least control conditions such as a processing speed when the slide (4) is pressurized and lowered and a speed switching position thereof. Slides based on (4)
In the lower limit position control device of the hydraulic press that performs the punching of the work (w) by controlling the operation of the hydraulic cylinder (2), the hydraulic cylinder (2) is installed in the upper chamber (2a) and the lower chamber (2b), respectively, and Pressing force detecting means (10) and (11) for detecting the pressures of the upper chamber (2a) and the lower chamber (2b), and slide (based on pressure signals from the pressing force detecting means (10) and (11)). 4) a load detecting means (21) for calculating the applied pressure, and a pressure gradient calculating means (10) for calculating and outputting a pressure reduction rate when the applied pressure detected by the load detecting means (21) decreases with time. 22) and the pressure reduction rate at the time of punching specific to the workpiece (w) is stored in advance, and the pressure reduction rate calculated by the pressure gradient calculation means (22) at the first machining is stored at the stored pressure. When the rate of decrease is greater than the percentage, it is determined that punching is complete, and the slide (4) position data at the time of punching is Breaking position determination means (23) taken in from the position detection means (8); position feedback means (24) for feeding back the position data obtained by the breaking position determination means (23) as a punching position; Based on the data, at the next or subsequent machining, a positioning speed switching position for switching the slide (4) speed to a positioning speed that is smaller than the machining speed by a minute distance before the punching position and starting positioning control of the lower limit position. Position setting means (25) for setting the position, the positioning speed switching position newly set by the position setting means (25), the positioning speed inputted by the motion setting means (15) and the motion for storing the control condition. The velocity value is calculated based on the temporal displacement of the position data detected by the storage means (26) and the slide position detection means (8). Speed calculation means (27) for calculating the machining speed of the slide (4) calculated by the speed calculation means (27) and the positioning speed near the lower limit position, and the correspondence stored in the motion storage means (26). The servo valve output calculating means (28) for calculating the control value of the servo valve (17) so that the deviation of the speed is reduced, and the servo valve output calculating means (28). And a servo valve command output means (29) for transmitting the control command to the servo valve (17) in response to the output value of (1). 2. The position setting means (25) detects the punching position each time each punching operation is performed, and updates the switching speed switching position of the slide (4) in the next processing operation based on the detected position. The lower limit position control device for a hydraulic press according to claim 1, wherein: 3. The position setting means (25) detects the punching position every predetermined number of times of the punching processing, and based on the detected position, determines the positioning speed switching position of the slide (4) in the next processing. 2. The lower limit position control device for a hydraulic press according to claim 1, wherein the control is updated. 4. A slide (4) linearly driven vertically by a hydraulic cylinder (2), a servo valve (17) for controlling operation of the hydraulic cylinder (2), and a position of the slide (4). A slide position detecting means (8); and a motion setting means (15) for setting at least control conditions such as a processing speed when the slide (4) is pressurized and lowered and a speed switching position thereof. Slides based on (4)
A lower limit position control device for a hydraulic press that performs a drawing process on a workpiece (w) by controlling the operation of a motion storage unit (26) that stores the control conditions input by the motion setting unit (15); Speed calculating means for calculating a speed value based on the time displacement of the position data detected by the slide position detecting means (8)
(27), while descending at the set low processing speed, when it comes to the positioning speed switching position a predetermined distance before the lower limit position, it is positioned at the lower limit position without overshooting. The control value of the servo valve (17) for reducing the deviation between the predetermined low speed value and the speed value calculated by the speed calculation means (27) is calculated so that the predetermined low speed is slow, and the slide ( 4) a servo valve output calculating means (28) for performing the position control, and a servo valve command for receiving the output value from the servo valve output calculating means (28) and transmitting this control command to the servo valve (17). A lower limit position control device for a hydraulic press, comprising: output means (29). 5. A lower limit position control device for a hydraulic press according to claim 1, further comprising setting display means for displaying setting data of said control condition and control data during molding. . 6. A hydraulic valve (2) for linearly driving the slide (4) in a vertical direction is controlled by a servo valve (17) to control the operating speed and the speed switching position of the slide (4) when pressurizing and lowering. In the hydraulic press lower limit position control method of controlling and positioning the lower limit position of the slide and punching the work (w), the time change of the slide pressure during punching specific to the work (w) is stored in advance as the pressure reduction rate. The pressure reduction rate of the slide (4) calculated when processing the workpiece (w) at a predetermined processing speed during the first processing is compared with the stored pressure reduction rate of the slide (4). Work by
(w) and the position of the slide (4) at the time of completion of the punching is detected, and at the next and subsequent punching processing, the slide (4) is moved from the positioning speed switching position a predetermined distance before the punching position. A control command for switching the speed of 4) to a predetermined positioning speed lower than the processing speed is output to the servo valve (17) and the slide (4) is output.
Controlling the lower limit position of the hydraulic press. 7. A hydraulic cylinder (2) for linearly driving the slide (4) in a vertical direction is controlled by a servo valve (17) to control the operating speed and the speed switching position of the slide (4) when pressurizing and descending. In the hydraulic press lower limit position control method of controlling and positioning the lower limit position of the slide to draw the work (w), when the slide (4) is moving down at the processing speed, the positioning speed is switched by a predetermined distance before the lower limit position. When the position of the slide (4) is reached, the speed of the slide (4) is switched to a predetermined positioning speed that is lower than the processing speed to control the positioning of the lower limit position of the slide (4). Control method.