JP2010005625A - Control device for cushion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a cushion apparatus with which excessive overshoot is prevented and the accuracy of control of a cushion load is improved. <P>SOLUTION: A slide 5 is moved and controlled according to the operation motion of a slide and the control device 10 is provided with a slid speed predicting part 11, a cushion load predicting part 13 and a cushion load controlling part 15. The slide speed predicting part 11 calculates a slide speed at a future point of time by a prescribed time from the present point of time as a slide speed predicted value on the basis of the operation motion of the slide. The cushion load predicting part 13 calculates the cushion load at future point of time as a load predicted value on the basis of the slide speed predicted value. The cushion load controlling part 15 performs the control for reducing the generated cushion load when the load predicted value exceeds largely the amount of the allowable maximum overshoot than the target value of a set load. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control device for a cushion device.

  The cushion device is a device that applies a cushion load to the slide while being retracted by the slide moving toward the cushion device. The slide is controlled to move according to the driving motion of the slide.

The cushion device is used, for example, for wrinkle press forming of a press machine. As shown in FIG. 3, the press machine performs press molding by sandwiching the workpiece 1 between the upper mold 21 and the lower mold 23. The upper die 21 is attached to the slide 5 that moves up and down. In the case of performing the wrinkle press forming of the workpiece 1, the cushion device 3 is moved by the movable portion 7 that is lowered together with the upper die 21 while the workpiece 1 is sandwiched between the cushion device 3 and the upper die 21 at the time of press molding. Have
The movable part 7 is, for example, a blank holder 7a that comes into contact with the workpiece 1 during press molding and descends together with the upper die 21 while the workpiece 1 is sandwiched between the upper die 21 and a blank holder 7a. The cushion pin 7b that supports the cushion pin 7b from below, the cushion plate 7c that supports the cushion pin 7b from below, and the pressing member 7d that presses the cushion plate 7c from below. When the cushion device 3 uses a hydraulic cylinder, the pressing member 7d is a piston of the hydraulic cylinder.

  In the cushion device 3 using a hydraulic cylinder, during press molding, the piston 7d is held at a predetermined standby position by position control, and when it is detected that the piston 7d is pushed by the descending slide 5, load control (that is, (Hydraulic control). That is, at the same time as switching to load control, it is necessary to open the servo valve to the opening calculated by the flow rate calculation (the servo valve is in the amount of oil flowing from the lower chamber of the hydraulic cylinder to the lower chamber and the upper chamber of the hydraulic cylinder. This controls the amount of oil that flows from outside the upper chamber). If the above switching timing is early, the rise of the cushion load is delayed, and if it is late, excessive overshoot occurs, so switching must be performed at an appropriate timing.

Examples of the determination conditions for executing such switching include the following (1) and (2).
(1) The cushion load value is equal to or less than the switching load determination value (for example, a value that is 50% of the set load target value), and the piston stroke is equal to or less than the switching stroke determination value.
(2) The press angle passes the switching angle. The press angle is, for example, the rotation angle of the crankshaft for raising and lowering the slide, and the switching angle is obtained based on the press angle at which the upper mold contacts the cushion device, the set load target value, the press speed, etc. deep.

As a prior art document of the present invention, for example, there is Patent Document 1 below.
JP2007-301591

The method (1) described above has a problem that overshoot becomes excessive when the set load target value is low in high-speed operation.
On the other hand, in the method (2) described above, a calculation formula for obtaining an optimum switching angle from the set load target value and the press speed has not been established, and it is necessary to adjust the switching angle based on the result of actual machine adjustment. .

  Accordingly, an object of the present invention is to provide a control device for a cushion device that can prevent an overshoot from becoming excessive and improve the control accuracy of the cushion load by a new method.

In order to achieve the above object, according to the present invention, there is provided a control device for a cushion device, comprising:
The cushion device is a device that generates a cushion load while being retracted by a slide that moves toward the cushion device, and the slide is controlled to move according to an operation motion of the slide. A speed prediction unit, a cushion load prediction unit, and a cushion load control unit are provided.
The slide speed prediction unit calculates a slide speed at a future time as a slide speed prediction value based on the driving motion of the slide for a predetermined time from the current time,
The cushion load prediction unit calculates a future cushion load as a load prediction value based on the slide speed prediction value,
The cushion load control unit performs control to reduce the generated cushion load when the predicted load value is larger than the allowable maximum overshoot amount from the set load target value. An apparatus is provided.

  In the control device for the cushion device of the present invention described above, the slide speed prediction unit calculates a slide speed at a future time as a slide speed prediction value for a predetermined time from the current time based on the operation motion of the slide, and predicts a cushion load. The unit calculates a cushion load at a future time point as a load predicted value based on the predicted slide speed value, and the cushion load control unit determines that the predicted load value is larger than the allowable maximum overshoot amount from the set load target value. When it greatly exceeds, control to reduce the generated cushion load is performed, so that the cushion load is suppressed when the future cushion load is likely to exceed the allowable maximum overshoot amount. Thereby, it is possible to prevent the overshoot from becoming excessive, and the control accuracy of the cushion load is improved.

  According to a preferred embodiment of the present invention, the cushion load prediction unit includes a load detection unit that detects a current cushion load, and based on the detected current cushion load and the predicted slide speed value, Calculate the cushion load.

  As described above, the cushion load prediction unit can calculate the cushion load at the future time point based on the current cushion load and the predicted slide speed value at the future time point.

  According to a preferred embodiment of the present invention, the cushion load prediction unit stores a load prediction model and applies the slide speed prediction value to the load prediction model to calculate a cushion load at a future time point.

  Thus, the cushion load at the future time can be calculated based on the load prediction model created in advance.

According to a preferred embodiment of the present invention, the cushion device includes a movable part that is retracted by the slide, and a drive part that generates a cushion load that is a force pushing the movable part toward the slide.
The cushion load control unit controls the cushion load by controlling the drive unit.

  Thus, the cushion load control unit can control the cushion load by controlling the drive unit of the cushion device.

According to a preferred embodiment of the present invention, the cushion device is a die cushion device of a press machine for press-molding a workpiece between an upper die and a lower die,
The upper mold is attached to the slide,
The cushion device is a device that moves down together with the upper die while a workpiece is sandwiched between the upper die and the upper die.

  Thus, by using the cushion device as a die cushion device, the control accuracy of the die cushion is improved, and a higher quality press-molded product can be produced.

  According to the above-described present invention, it is possible to prevent the overshoot from becoming excessive and to improve the control accuracy of the cushion load by a new method.

  The best mode for carrying out the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the common part in each figure, and the overlapping description is abbreviate | omitted.

  FIG. 1 shows a case where a control device for a cushion device according to the present invention is applied to a press machine. The configuration of the press machine may be the same as that described with reference to FIG.

In the embodiment of the present invention, the cushion device 3 is a device that generates a cushion load while being retracted by the slide 5 moving toward the cushion device 3. In the example of FIG. 1, the cushion device 3 uses a hydraulic cylinder. The cushion device 3 includes a movable portion 7 that is retracted by the slide 5 and a drive portion 9 that generates a cushion load that is a force pushing the movable portion 7 toward the slide 5. In the example of FIG. 1, the drive unit 9 includes a hydraulic cylinder 9a, a hydraulic source 9b that supplies hydraulic pressure to the lower chamber of the hydraulic cylinder 9a, a conduit 9c that connects the hydraulic source 9b and the lower chamber, and the conduit And a servo valve 9d provided in 9c.
The slide 5 is controlled to move according to the driving motion of the slide. Slide operation motion is, for example, motion data that defines the relationship between each press angle or each slide position and slide speed during press molding, or motion data that defines the relationship between each time point and slide position during press molding. It may be. The press angle may be, for example, a rotation angle of a crankshaft that rotates to raise and lower the slide 5. Moreover, the slide 5 may be driven by a servo motor via a crankshaft, for example. For example, the current speed or position of the slide 5 is detected, and the movement of the slide 5 may be controlled by controlling the servo motor in accordance with the detected value and the operation motion of the slide.

According to the embodiment of the present invention, the control device 10 of the cushion device 3 includes a slide speed prediction unit 11, a cushion load prediction unit 13, and a cushion load control unit 15.
The slide speed prediction unit 11 calculates a slide speed at a future time point as a slide speed prediction value for a predetermined time from the present time based on the driving motion of the slide. Specifically, the predicted slide speed value is calculated based on the detected value of the press angle or slide position, the detected value of the press speed or slide speed, and the operation motion of the slide. Such processing is performed momentarily by the slide speed prediction unit 11 during one press molding cycle. One press molding cycle is a period from the time when the slide 5 starts to descend until the time when the upper die 21 comes into contact with the workpiece 1 and the slide 5 further descends to the bottom dead center and rises again to a predetermined position. .

The cushion load prediction unit 13 calculates a cushion load at a future time point as a load prediction value based on the slide speed prediction value. Specifically, the cushion load prediction unit 13 includes a load detection unit 13a that detects the current cushion load, and based on the detected current cushion load and the predicted slide speed value, calculates a cushion load at a future time. Calculated as a predicted load value. The cushion load may be detected based on the detected value of the hydraulic pressure in the lower chamber of the hydraulic cylinder 9a. When hydraulic pressure is also supplied to the upper chamber of the hydraulic cylinder 9a, the cushion load may be detected based on the lower chamber hydraulic pressure detection value and the upper chamber hydraulic pressure detection value.
Further, the cushion load prediction unit 13 stores a load prediction model, and applies the current slide speed prediction value and the detected current cushion load value to the load prediction model, so that the cushion load at a future time point is applied. Is calculated as a predicted load value. Details of the load prediction model will be described later.
Such processing is performed momentarily by the cushion load prediction unit 13 during one press molding cycle.

The cushion load control unit 15 controls the cushion load by controlling the drive unit 9 (servo valve 9d in the example of FIG. 1). According to the present embodiment, the cushion load control unit 15 performs control to reduce the generated cushion load when the predicted load value is larger than the allowable maximum overshoot amount from the set load target value. The cushion load control unit 15 includes a feedback control unit 15a, an overshoot suppression unit 15b, and an addition unit 15c.
The feedback control unit 15a compares the detected current cushion load value with the current set load target value, and if they match, the servo having the same value as the servo valve opening command value output immediately before is detected. The valve opening command value is output, the current opening of the servo valve 9d is maintained, and if both do not match, the servo valve opening command value corresponding to the deviation between the two is output. For example, if the detected current cushion load value is smaller than the set load target value, the servo valve opening command value that is smaller than the servo valve opening command value output immediately before by the deviation between the two Is output to reduce the opening of the servo valve 9d. On the other hand, if the detected current cushion load value is larger than the set load target value, the servo valve opening command value that is increased by the servo valve opening command value output immediately before according to the deviation between the two. Is output to increase the opening of the servo valve 9d. Thereby, feedback control is performed for causing the actual cushion load to follow the set load target value. The set load target value is stored in the feedback control unit 15a.
The overshoot suppressing unit 15b compares the predicted load value at a future time point with the set load target value at the future time point, and the predicted load value is determined to be an allowable maximum overshoot from the set load target value at a future time point. If it exceeds the amount (ie, if the difference between the predicted load value and the set load target value at a future time is greater than the allowable maximum overshoot amount), the current time (or the current and the future in question) The correction value is output at a desired point in time. For example, a correction value having a value corresponding to the deviation between the predicted load value and the set load target value at the future time is output. Preferably, the correction value is larger as the deviation is larger. On the other hand, when the predicted load value does not greatly exceed the allowable maximum overshoot amount from the set load target at the future time point, no correction value is output (or a correction value of zero is output). The set load target value and the allowable maximum overshoot amount are stored in the overshoot suppressing unit 15b.
The adding unit 15c adds the correction value from the overshoot suppressing unit 15b to the servo valve opening command value from the feedback control unit 15a. The servo valve opening command value corrected in this way is input to the servo valve 9d, and the opening of the servo valve 9d is set to the opening indicated by the servo valve opening command value.
Such processing is performed momentarily by the cushion load control unit 15 during one press molding cycle.

The future time point (that is, the predetermined time T ₁ ) will be described based on the control cycle time T ₂ of the feedback control unit 15a.
The time required for one control cycle of the feedback control unit 15a is T ₂ (for example, 1 to 5 msec). That, _{T 2} is the time it takes the following (1) to (3) to perform once. (1) The load detection unit 13a detects a cushion load, (2) the feedback control unit 15a outputs the servo valve opening command value based on the detected cushion load value, and (3) the servo valve opening command. The opening degree of the servo valve 9d is adjusted by the value. (1) to (3) are repeated in this order. In this case, the above-described future time point may be, for example, a time point that is 1T _{2 to} 10T ₂ from the current time point (ie, T ₁ = 1T _{2 to} 10T ₂ ). The time T ₁ from the present time to the future time may be the same as the time required to perform the following (A) to (E) once. (A) The load detection unit 13a detects the cushion load, (B) the slide speed prediction unit 11 outputs the slide speed prediction value, and the current cushion load value and the slide speed prediction value detected in (A). The cushion load predicting unit 13 outputs the load predicted value based on (C), the overshoot suppressing unit 15b outputs the correction value based on the load predicted value, and (D) adding based on the corrected value. The portion 15c outputs the corrected servo valve opening command value, and (E) the opening of the servo valve 9d is adjusted by the servo valve opening command value. (A) to (E) are repeated in this order. Further, when it is desired to adjust the T ₂ and the T ₁ with respect to each other, a delay circuit for delaying the signal may be provided at an appropriate location.

  Next, the load prediction model will be described.

  The load prediction model uses the following [Equation 1].

dP indicates the hydraulic pressure fluctuation in the lower chamber of the hydraulic cylinder 9a. That is, assuming that the hydraulic pressure in the lower chamber at a time point that is a predetermined time after the current time is Pf and the hydraulic pressure in the lower chamber at the current time is Pc, dP = Pf−Pc.
K is the bulk modulus. K may be a fixed value (for example, 980 MPa). The volume modulus of elasticity changes depending on the volume mixing ratio of bubbles at pressure and atmospheric pressure. For example, the volume mixing ratio can be calculated from the data measurement result. Using the calculated volume mixing ratio and the pressure value before the slide contact (that is, before the slide 5 exerts a force on the cushion device 3), the volume elastic modulus may be calculated and used as fixed.
S is a cross-sectional area of the cylindrical hydraulic cylinder 9a.
V is the volume of the lower chamber of the hydraulic cylinder 9a. Preferably, V includes the volume of the conduit 9c from the servo valve 9d to the lower chamber of the hydraulic cylinder 9a.
dx is a pushing stroke of the piston 7d of the hydraulic cylinder 9a. That is, dx = xf−xc (≧ 0) where xf is the piston position at a future time from the present time by the predetermined time and xc is the current piston position.
a is a coefficient of oil amount which flows out from the lower chamber of the hydraulic cylinder 9a to the outside of the lower chamber depending on the opening degree of the servo valve 9d. a may be a function of the pressure in the lower chamber of the current hydraulic cylinder 9a.
Isv is the current servo valve opening command value.
The product of a and Isv is the amount of oil that flows from the lower chamber of the hydraulic cylinder 9a to the outside of the lower chamber between the present time and the future time when the current servo valve opening command value is maintained.

In [Expression 1], K, S, a, and Isv are set in advance and stored in the cushion load prediction unit 13.
The dx may be calculated by the cushion load prediction unit 13 as a product of the current slide speed detection value (or the slide speed prediction value) and the predetermined time. The cushion load predicting unit 13 substitutes the calculated dx into [Equation 1] to calculate dP, and adds the calculated dP to the detected cushion load value at the present time, whereby the cushion at the future time point is calculated. A load (that is, a predicted load value) is calculated.

  The fact that the above [Equation 1] can actually be used will be described.

  The relational expression between the pushing stroke when the piston 7d is pushed in with the oil sealed and the pressure increase in the lower chamber of the hydraulic cylinder 9a is shown in [Equation 2]. Each symbol in [Expression 2] is the same as in [Expression 1].

FIG. 2 is an explanatory diagram of the control by the cushion load control unit 15. In this figure, a white circle indicates a predicted load value at a future time, and a black circle indicates a detected cushion load value at the present time.
At the time points t1, t2, and t5, the predicted load value is equal to or less than the set load target value at a future time point, so the overshoot suppressing unit 15b does not function and outputs a zero correction value. Therefore, the servo valve command value from the feedback control unit 15a is directly input to the servo valve 9d without being corrected.
On the other hand, at the time points t3 and t4, the load predicted value exceeds the allowable maximum overshoot amount from the set load target at a future time point, so the overshoot suppressing unit 15b outputs the above-described correction value. Therefore, the corrected servo valve opening command value is input to the servo valve 9d.
At the time point t6, the load predicted value is larger than the set load target value, but the load predicted value does not exceed the allowable maximum overshoot amount from the set load target at a future time point. Without correction, a zero correction value is output. Therefore, the servo valve command value from the feedback control unit 15a is directly input to the servo valve 9d without being corrected.

In the control device 10 of the cushion device 3 according to the embodiment of the present invention described above, the slide speed predicting unit 11 uses the slide speed at a future time as a slide speed predicted value for a predetermined time from the present time based on the operation motion of the slide. The cushion load prediction unit 13 calculates the future cushion load as a load predicted value based on the predicted slide speed value, and the cushion load control unit 15 calculates the load predicted value at the future time. When the set load target value is much larger than the allowable maximum overshoot amount, control is performed to reduce the generated cushion load.If the future cushion load is likely to exceed the allowable maximum overshoot amount, the cushion load It can be suppressed. Thereby, it is possible to prevent the overshoot from becoming excessive, and the control accuracy of the cushion load is improved.
The cushion load prediction unit 13 can calculate a cushion load at a future time point based on the current cushion load and a predicted slide speed value at a future time point. In this case, a cushion load at a future time can be calculated based on a load prediction model created in advance.

  The present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention.

The set load target value may be constant, or may change according to the detected press angle, slide position, piston position, time, or the like. In this case, the set load target value at the future time point may be calculated as a predicted value from the detected press angle, slide position, piston position or time.
Although the accuracy decreases, the current set load target value can be used instead of the set load target value at the future time point.

    The predicted slide speed value may be used for feed forward control of the slide 5.

  The control device of the cushion device of the present invention may be applied to a cushion device other than the die cushion device of the press machine.

  In order to prevent excessive overshoot as described above, not only the amount of oil flowing out of the lower chamber from the lower chamber of the hydraulic cylinder 9a but also the amount of oil flowing into the upper chamber of the hydraulic cylinder 9a from outside the upper chamber is also controlled. In the case of control, the load prediction model described above may be changed in accordance with this.

  The present invention is applicable not only to a cushion device using a hydraulic cylinder but also to a cushion device using an air cylinder. In this case, the volume elastic modulus of the hydraulic cylinder is changed to the volume elastic modulus of the air cylinder.

It is a block diagram at the time of applying the control apparatus of the cushion apparatus of this invention to the cushion apparatus of a press machine. It is explanatory drawing of control by a cushion load control part. It is a figure which shows the cushion apparatus of a press machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece, 3 Cushion device, 5 Slide, 7 Movable part, 7a Blank holder, 7b Cushion pin, 7c Cushion plate, 7d Pressing member (piston), 9 Drive part, 9a Hydraulic cylinder, 9b Hydraulic source, 9c Pipe line , 9d Servo valve, 10 Control device, 11 Slide speed prediction unit, 13 Cushion load prediction unit, 13a Load detection unit, 15 Cushion load control unit, 15a Feedback control unit, 15b Overshoot suppression unit, 15c Addition unit, 21 Upper metal Mold, 23 lower mold,

Claims (5)

A control device for the cushion device,
The cushion device is a device that generates a cushion load while being retracted by a slide that moves toward the cushion device, and the slide is controlled to move according to an operation motion of the slide. A speed prediction unit, a cushion load prediction unit, and a cushion load control unit are provided.
The slide speed prediction unit calculates a slide speed at a future time as a slide speed prediction value based on the driving motion of the slide for a predetermined time from the current time,
The cushion load prediction unit calculates a future cushion load as a load prediction value based on the slide speed prediction value,
The cushion load control unit performs control to reduce the generated cushion load when the predicted load value is larger than the allowable maximum overshoot amount from the set load target value. apparatus.   The cushion load prediction unit includes a load detection unit that detects a current cushion load, and calculates a cushion load at a future time based on the detected current cushion load and the predicted slide speed. The control device for the cushion device according to claim 1.   The said cushion load prediction part memorize | stores a load prediction model, applies the said slide speed prediction value to the said load prediction model, and calculates the cushion load of the future time point, The Claim 1 or 2 characterized by the above-mentioned. The control apparatus of the cushion apparatus of description. The cushion device includes a movable part that is retracted by the slide, and a drive part that generates a cushion load that is a force pushing the movable part toward the slide.
The said cushion load control part controls the said cushion load by controlling the said drive part, The control apparatus of the cushion apparatus in any one of Claims 1-3 characterized by the above-mentioned. The cushion device is a die cushion device for a press machine that press-molds a workpiece between an upper die and a lower die,
The upper mold is attached to the slide,
The control device for a cushion device according to any one of claims 1 to 4, wherein the cushion device is a device that descends with the upper die while a workpiece is sandwiched between the upper die and the upper die. .

Images