JP4820674B2 - Die cushion control device for press machine - Google Patents

Description

  The present invention relates to a die cushion control device for a press machine used for drawing or the like, and relates to a die cushion control device that controls the operation of a die cushion pad in synchronization with the operation of a slide.

  2. Description of the Related Art Conventionally, as a die cushion control device that controls the lifting / lowering operation of a die cushion pad driven by a servomotor, for example, a device proposed in Patent Document 1 is known. In the die cushion control device according to Patent Document 1, the cushion stroke of the die cushion is controlled by position control until the upper die of the slide comes into contact with the die cushion pad with the workpiece interposed therebetween. When a change in the current of the servo motor when a load is applied to the die cushion pad is detected, the position control is switched to the pressure control based on the detection signal of the current change, and a preset cushion pressure is applied to the die cushion pad. In such a die cushion control device, since the position control can be switched to the pressure control, the drawing process can be performed satisfactorily.

JP-A-10-202327 (page 3)

  However, if an overshoot that greatly exceeds the target pressure during pressure control occurs in the actual generated pressure due to the impact load when the upper die contacts (touches) the workpiece, Deviation from pressure continues to occur downward. In particular, when there is an integral element in the pressure control portion, the deviation accumulates, and the undershoot occurs greatly due to the reaction. Due to this undershoot, the die cushion should have been lowered along with the slide. Occurs, and accurate pressure control cannot be performed.

  The objective of this invention is providing the die cushion control apparatus which can prevent reliably the detachment | leave phenomenon of a die cushion and a slide.

A die cushion control device for a press machine according to claim 1 of the present invention is applied to a pressure command signal output unit that outputs a first pressure command signal corresponding to a pressure target value based on a predetermined pressure pattern, and a die cushion pad. A pressure detection unit that detects a generated pressure; and a pressure comparison unit that outputs a pressure deviation signal corresponding to a deviation between a pressure target value based on the pressure pattern and a pressure detection value based on a pressure detection signal from the pressure detection unit; A pressure control unit that outputs a pressure speed command signal based on the pressure deviation signal; a speed control unit that outputs a motor current command signal based on the pressure speed command signal; and a current corresponding to the motor current command signal A servo amplifier for supplying an electric servo motor for driving the die cushion, the pressure target value, and a generated pressure that overshoots exceeding the pressure target value, And a deviation canceller to substantially zero the deviation over a predetermined time period, the end of the predetermined time is a pressure detection value to the overshoot until nearing a substantially peak pressure at the end of the predetermined time A pressure pattern that gently converges from a detected value to the pressure target value using a predetermined time constant is used as a new pressure pattern, and after the predetermined time has elapsed, the new pressure pattern is converged to the pressure target value. The second pressure command signal corresponding to the pressure pattern is replaced with the first pressure command signal .

A die cushion control device for a press machine according to a second aspect of the present invention is the die cushion control device according to the first aspect, wherein the pressure control unit integrates a pressure deviation signal output from the pressure comparison unit. It is characterized by having a vessel .
A die cushion control device for a press machine according to claim 3 of the present invention is the die cushion control device for a press machine according to claim 1 or 2, wherein a position command corresponding to a position target value based on a predetermined position pattern is provided. A position command signal output unit for outputting a signal; a position detection means for detecting the position of the die cushion pad; and a deviation between a position target value based on the position pattern and a position detection value based on a position detection signal from the position detection means. Any one of a position comparison unit that outputs a position deviation signal according to the position, a position control unit that outputs a position speed command signal based on the position deviation signal, the position speed command signal, and the pressure speed command signal A position / pressure control switching unit that outputs one as a speed command signal, and the speed control unit is output from the position / pressure control switching unit. A motor current command signal is output based on the degree command signal and the position control based on the position speed command signal is switched to the pressure control based on the pressure speed command signal. Is made substantially zero.

  According to the first aspect of the present invention, even when the generated pressure is generated by greatly overshooting the pressure target value when the upper mold of the slide comes into contact with the workpiece, the deviation between the generated pressure and the pressure target value is eliminated. Since the section is set to 0 “zero”, the pressure deviation signal is also 0, and it is possible to prevent the occurrence of a large undershoot due to the accumulation of deviations, and it is possible to reliably prevent the load from being lost by suppressing the separation phenomenon between the slide and the die cushion.

  According to the second aspect of the present invention, the generated pressure converging unit smoothly converges the peak pressure at the time of overshooting to the pressure target value, so that undershooting can be prevented more reliably.

Next, specific embodiments of the die cushion control device according to the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration diagram of a press machine according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of the die cushion 13 according to the first embodiment.

  A press machine 1 shown in FIG. 1 includes a slide 4 that is supported by a main body frame 2 so as to be movable up and down and is driven up and down by a slide drive mechanism 3, and a bolster 6 that is disposed opposite to the slide 4 and attached to a bed 5. And. An upper die 7 is attached to the lower surface of the slide 4, and a lower die 8 is attached to the upper surface of the bolster 6. Thus, press work (drawing) is performed on the work 9 disposed between the upper die 7 and the lower die 8 by the lifting and lowering operation of the slide 4.

  Among these configurations, the bed 5 has a built-in die cushion 13. The die cushion 13 includes a required die cushion pin 14, a die cushion pad 15 that is supported by the bed 5 so as to be movable up and down in the bed 5, and a die cushion pad drive mechanism 16 that drives the die cushion pad 15 up and down. It is configured with.

  Each die cushion pin 14 is inserted into a hole formed in each of the bolster 6 and the lower mold 8 and penetrating in the vertical direction. The upper end of each die cushion pin 14 is in contact with a blank holder 17 disposed in the recess of the lower mold 8, and the lower end thereof is in contact with the die cushion pad 15.

  Between each side surface of the die cushion pad 15 and the inner wall surface of the bed 5 facing each side surface, one or more guide members (not shown) for guiding the die cushion pad 15 in the vertical direction are provided. Each guide member includes a pair of inner guide and outer guide that engage with each other. The inner guide is attached to each side surface of the die cushion pad 15, and the outer guide is attached to the inner wall surface of the bed 5. Thus, the die cushion pad 15 is supported in the bed 5 so as to be movable up and down.

  As shown in FIG. 2, the die cushion pad drive mechanism 16 includes an electric servo motor 21 as a drive source, a ball screw mechanism 22 as an elevator means for the die cushion pad 15, an electric servo motor 21 and a ball screw mechanism. A winding transmission mechanism 23 and a connecting member 24 arranged in a power transmission path between the die cushion pad 15 and the electric servomotor 21 are configured to be able to transmit each other's power freely.

  The electric servo motor 21 is a rotary AC servo motor having a rotation shaft, and the rotation speed and the rotation force of the rotation shaft are controlled by controlling the motor current (current) i supplied to the electric servo motor 21. It has become. A main body portion of the electric servo motor 21 is fixed to a beam 25 laid between the inner wall surfaces of the bed 5. The electric servo motor 21 is additionally provided with an encoder (position detecting means) 36. The encoder 36 detects the angle and angular velocity of the rotating shaft of the electric servomotor 21 and outputs the detected values as a motor rotation angle detection signal θ and a motor rotation angular velocity detection signal ω, respectively. The motor rotation angle detection signal θ and the motor rotation angular velocity detection signal ω output from the encoder 36 are input to the controller 41 described later.

  The ball screw mechanism 22 includes a screw portion 26 and a nut portion 27 that is screwed to the screw portion 26. The rotary power input from the nut portion 27 is converted into linear power by the screw portion 26 and output. It has a function to do. The lower end portion of the screw portion 26 is disposed so as to be able to advance and retreat in a space formed in the central portion of the connecting member 24, and the lower end portion of the nut portion 27 is coupled to the upper end portion of the connecting member 24. The connecting member 24 is supported by the beam 25 via a bearing device 28 including required bearings and a bearing housing that accommodates the bearings.

  In the winding transmission mechanism 23, a timing belt 31 is wound between a small pulley 29 fixed to the rotating shaft of the electric servomotor 21 and a large pulley 30 fixed to the lower end portion of the connecting member 24. Is made up of.

  With the above configuration, the rotational power of the electric servomotor 21 is transmitted to the nut portion 27 in the ball screw mechanism 22 via the small pulley 29, the timing belt 31, the large pulley 30, and the connecting member 24, and is transmitted to the nut portion 27. The screw portion 26 in the ball screw mechanism 22 is moved in the vertical direction by the rotational power thus generated, and the die cushion pad 15 is driven up and down. Further, the urging force applied to the die cushion pad 15 is controlled by controlling the motor current i to the electric servomotor 21.

  Incidentally, in this die cushion 13, a plunger rod 80 is connected to the lower end portion of the die cushion pad 15. The plunger rod 80 is slidably supported at its side by a cylindrical plunger guide 82. The plunger guide 82 has a function of guiding the plunger rod 80 and the die cushion pad 15 connected to the plunger rod 80 in the up and down direction. A cylinder 80A having a downward opening is formed in the lower portion of the plunger rod 80, and a piston 81 is slidably accommodated in the cylinder 80A.

  A hydraulic chamber 83 is formed on the inner wall surface of the cylinder 80A and the upper surface of the piston 81, and the hydraulic chamber 83 is filled with pressure oil. The axial center of the hydraulic chamber 83 is the same as that of the plunger rod 80 and the ball screw mechanism 22. The pressure oil port of the hydraulic chamber 83 is connected to a hydraulic circuit, and pressure oil is exchanged between the hydraulic chamber 83 and the hydraulic circuit. The pressure oil in the hydraulic chamber 83 relaxes the impact generated when the upper mold 7 and the work 9 come into contact with each other, and is discharged to the tank when the hydraulic pressure exceeds a predetermined value. The pressure oil in the hydraulic chamber 83 has such an overload protection function.

  The lower end of the piston 81 is in contact with the upper end of the screw portion 26 in the ball screw mechanism 22. A spherical concave surface 81A is formed at the lower end of the piston 81, and a spherical convex surface is formed at the upper end of the screw portion 26 facing the concave surface 81A. On the contrary, a convex surface may be formed at the lower end of the piston 81 and a concave surface may be formed at the upper end of the screw portion 26. A rod-like member such as the screw portion 26 is strong against an axial force acting on the end portion, but is weak against a bending moment. If the upper end of the threaded portion 26 is spherical, even if the die cushion pad 15 is inclined and a bending moment is generated at the upper end of the threaded portion 26, only the axial force acts on the entire threaded portion 26. Such a structure can prevent the screw portion 26 from being damaged by the eccentric load.

  In the die cushion 13, the pressure in the hydraulic chamber 83 is detected in the hydraulic circuit described above. The port of the hydraulic chamber 83 communicates with a pipe 85 constituting a hydraulic circuit, and a pressure gauge (pressure detection means) 93 is provided in the middle of the pipe 85. The pressure gauge 93 detects the pressure in the hydraulic chamber 83, that is, the load generated on the die cushion pad 15. A pressure detection signal Pr is output from the pressure gauge 93 toward the controller 41.

  Next, the configuration of the die cushion control device 40 that controls the die cushion 13 will be described below with reference to the functional block diagram of FIG. 3 and the control block diagram of FIG.

  The die cushion control device 40 shown in FIGS. 3 and 4 includes a controller 41 and a servo amplifier 42 that supplies a motor current i corresponding to a motor current command signal ic output from the controller 41 to the electric servomotor 21. It has.

Although not described in detail, the controller 41 is mainly composed of an input interface for converting and shaping various input signals, a microcomputer, a high-speed numerical arithmetic processor, and the like, and performs arithmetic on input data according to a predetermined procedure. A computer apparatus that performs a logical operation and an output interface that converts the operation result into a control signal and outputs the control signal. The controller 41 includes a die cushion pad position calculation unit 43, a die cushion pad speed calculation unit 44, a position command signal output unit 45, a position comparison unit 46, a position control unit 47, a pressure command signal output unit 48, and a pressure comparison unit 49. , Pressure control unit 50, position / pressure control switching unit 51, speed comparison unit 52, speed control unit 53, output switching unit 101, timer 102, pressure holding unit 103, and time constant processing unit 104 are provided. ing. These functional units are formed by software or the like processed by the computer. In the present embodiment, the deviation canceling unit 100 of the present invention is formed by the output switching unit 101 and the timer 102, and the output switching unit 101, the timer 102, the pressure holding unit 103, and the time constant processing unit 104 provide the present invention. the generated pressure convergence unit 1 50 is formed.

  The die cushion pad position calculation unit 43 receives a motor rotation angle detection signal θ from an encoder 36 attached to the electric servomotor 21, and the die cushion pad 15 having a predetermined relationship with the motor rotation angle based on this input signal. And a result of outputting the result as a die cushion pad position detection signal (position detection signal) hr.

  The die cushion pad speed calculation unit 44 receives the motor rotation angular speed detection signal ω from the encoder 36, and the speed (elevating speed) of the die cushion pad 15 having a predetermined relationship with the motor rotation speed based on this input signal. And outputs the result as a die cushion pad speed detection signal υr.

The position command signal output unit 45 obtains a position target value of the die cushion pad 15 by referring to a preset position pattern 54, and generates and outputs a position command signal hc based on the obtained position target value. It has a function. Here, the position pattern 54 indicates a desired correspondence between time (or press angle or slide position) and die cushion pad position.

  The position comparison unit 46 compares the position command signal hc output from the position command signal output unit 45 with the die cushion pad position detection signal hr from the die cushion pad position calculation unit 43, and outputs a position deviation signal eh. It has a function to do.

The position control unit 47 includes a coefficient unit 55 that receives the position deviation signal eh from the position comparison unit 46, multiplies the input signal by a predetermined position gain K1, and outputs a position corresponding to the position deviation signal eh. It has a function to generate and output the industrial speed command signal υhc.

  The pressure command signal output unit 48 obtains a pressure (cushion pressure) target value to be generated in the die cushion pad 15 by referring to a preset pressure pattern 56, and the obtained pressure target value (hereinafter, target). The pressure command signal Pc based on the pressure may be generated and output. Here, the pressure pattern 56 indicates a desired correspondence between time (or press angle or slide position) and pressure generated in the die cushion pad 15.

  The pressure comparison unit 49 has a function of comparing the pressure command signal Pc from the pressure command signal output unit 48 with the pressure detection signal Pr from the pressure gauge 93 and outputting a pressure deviation signal ep.

The pressure control unit 50 receives the pressure deviation signal ep from the pressure comparison unit 49, multiplies the input signal by a predetermined proportional gain K2, and outputs the coefficient unit 71 and the pressure deviation signal ep from the pressure comparison unit 49. An integrator 72 that inputs and integrates and outputs the input signal (the symbol s in the block is a Laplace operator), and an output signal from the integrator 72 is input and a predetermined integral gain K3 is input to the input signal. And a coefficient unit 73 that multiplies and outputs, and has a function of generating and outputting a pressure speed command signal υpc by adding the output signal from the coefficient unit 73 to the output signal from the coefficient unit 71.

  In this pressure control unit 50, a pressure deviation signal is transmitted from the pressure control unit 50 by performing a proportional + integral operation (PI operation) that combines a proportional operation (P operation) and an integration operation (I operation). A pressure speed command signal υpc that is large enough to match ep and increases as long as there is a pressure deviation signal ep is output, so that the detected pressure matches the target pressure quickly and accurately. .

The position / pressure control switching unit 51 switches between position control for controlling the position of the die cushion pad 15 and pressure control for controlling the pressure generated in the die cushion pad 15. A switch 60 for switching the connection with the c contact and a position / pressure comparison unit 61 for selecting a switching operation of the switch 60 are provided.
When the contact b is connected to the contact a by the switch 60 (hereinafter, this connection operation is referred to as “ba contact connection operation”), the position speed command signal υhc from the position controller 47 compares the speed. On the other hand, when the b contact and the c contact are connected by the switch 60 (hereinafter, this connection operation is referred to as “bc contact connection operation”), the pressure control unit 50 The speed command signal υpc for pressure flows to the speed comparison unit 52.

The position / pressure comparison unit 61 compares the pressure speed command signal υpc from the pressure control unit 50 with the position speed command signal υhc from the position control unit 47, and selects the smaller one of the two. Has been.
Here, the switching logic of the position / pressure comparison unit 61 will be described with reference to FIGS. FIG. 5 shows a position speed command signal υhc. In FIG. 5, when the position pattern (position target value) of the die cushion pad 15 is always set to 0 (standby position), the position of the die cushion pad 15 is set to the standby position before the upper mold 7 contacts the workpiece 9. Therefore, the position deviation signal eh is 0, and the position speed command signal υhc is 0. Thereafter, when the preliminary acceleration of the die cushion pad 15 is started, the position speed command signal υhc is increased to the side where the die cushion pad 15 is lowered, and then the preliminary acceleration is performed at a constant speed. When the upper die 7 reaches a position (touch position) in contact with the workpiece 9 during the preliminary acceleration, the die cushion pad 15 starts to lower below the position target as the upper die 7 is lowered. The deviation signal eh gradually increases, and the position speed command signal υhc which attempts to return to the upper position accordingly increases upward.

  On the other hand, FIG. 6 shows a speed command signal υpc for pressure. In FIG. 6, when the pressure pattern (pressure target value) of the die cushion pad 15 is always set to a constant value, no pressure is generated in the die cushion pad 15 before the upper die 7 contacts the workpiece 9. The signal ep matches the constant value of the pressure pattern, and the pressure speed command signal υpc becomes a value corresponding to the constant value of the pressure pattern. Thereafter, when the upper mold 7 reaches a position (touch position) in contact with the workpiece 9, the die cushion pad 15 is pushed by the upper mold 7 to generate pressure. Since this pressure increases as the die cushion pad 15 descends and approaches the target pressure value set from the beginning, the pressure deviation signal ep gradually decreases, and the pressure speed command signal υpc also decreases accordingly.

As shown in FIG. 7, the position / pressure comparison unit 61 is set to compare the position speed command signal υhc and the pressure speed command signal υpc and select the smaller one of the two. Therefore, when the upper die 7 is lowered before coming into contact with the work 9, the position speed command signal υhc is selected because the position speed command signal υhc is smaller than the pressure speed command signal υpc. By this selection, the switch 60 connects the b contact and the a contact, the position speed command signal υhc flows to the speed comparison unit 52, and position control is performed.
Next, when the upper die 7 reaches the touch position where it comes into contact with the workpiece 9, the position speed command signal υhc increases and the pressure speed command signal υpc decreases. When the magnitude relationship between these speed command signals υhc and υpc is reversed, the position / pressure comparison unit 61 selects a pressure speed command signal υpc smaller than the position speed command signal υhc, and the b and c contacts of the switch 60 Is connected. By this connection switching operation, the pressure speed command signal υpc flows to the speed comparison unit 52, and pressure control is performed.

  Since the position / pressure comparison unit 61 is set so as to always compare the position speed command signal υhc and the pressure speed command signal υpc and select the smaller one of the two, the position control and pressure control Can be automatically switched at an appropriate timing. Therefore, it is possible to minimize the influence of impact and vibration when the upper die 7 comes into contact with the die cushion pad 15 via the workpiece 9, and to switch between position control and pressure control stably and reliably at an appropriate timing. Can be done. In addition, since both the position speed command signal υhc and the pressure speed command signal υpc are constantly monitored, the touch position when the upper die 7 contacts the workpiece 9 can be surely grasped, and quick and reliable switching can be performed. Can be done.

When the position control is selected by the switching operation by the position / pressure control switching unit 51, the speed comparison unit 52 receives the position speed command signal υhc from the position control unit 47 and the die cushion pad speed calculation unit 44. When the pressure control is selected by the switching operation by the position / pressure control switching unit 51 by comparing with the die cushion pad speed detection signal υr, and the pressure deviation signal ev is output. It has a function of comparing the speed command signal υpc and the die cushion pad speed detection signal υr from the die cushion pad speed calculation unit 44 and outputting a speed deviation signal ev.

According to the present embodiment, at the time of pressure control, a pressure speed command signal υpc from the pressure control unit 50 that corresponds to the pressure deviation signal ep and increases as long as the pressure deviation signal ep is present. Is output, the pressure deviation can be reduced quickly and reliably. Therefore, the accuracy of pressure control can be improved.

The speed control unit 53 receives the speed deviation signal ev from the speed comparison unit 52, multiplies the input signal by a predetermined proportional gain K4, and outputs the coefficient unit 62 and the speed deviation signal ev from the speed comparison unit 52. An integrator 63 (symbol s in the block is a Laplace operator) for inputting and integrating the input signal, and an output signal from the integrator 63 is input and a predetermined integral gain K5 is input to the input signal. And a coefficient unit 64 that multiplies and outputs the signal, and adds the output signal from the coefficient unit 64 to the output signal from the coefficient unit 62 to generate a motor current command signal (torque command signal) ic
It has a function to output.

Also in the speed control unit 53, a proportional deviation + integral operation (PI operation) combining a proportional operation (P operation) and an integration operation (I operation) is performed, so that the speed control unit 53 receives a speed deviation signal. A motor current command signal ic having a magnitude corresponding to ev and increasing as long as the speed deviation signal ev is present is output, and the detected speed is quickly and accurately matched to the target speed. In this way, stable position / pressure control can be performed.

  The output switching unit 101 functions as a switch having contacts d, e, f, and g. In the de contact connection operation, the pressure command signal Pc output from the pressure command signal output unit 48 is output to the pressure comparison unit 49 as it is. In the df contact connection operation, the pressure command signal Pc calculated by the time constant processing unit 104 with a predetermined time constant is output to the pressure comparison unit 49. In the dg contact connection operation, the pressure detection signal Pr from the pressure gauge 93 is output to the pressure comparison unit 49 as it is.

  The timer 102 has a function of switching the contact connection operation of the output switching unit 101 by a start signal from the position / pressure comparison unit 61 and holding it for a predetermined time. Specifically, when the upper die touches the workpiece 9 and switches from position control to pressure control, the position / pressure comparison unit 61 switches to the bc contact connection operation at the position / pressure control switching unit 51. At the same time, the position / pressure comparison unit 61 outputs an activation signal to the timer 102. The timer 102 having input the start signal outputs a switching signal so that the output switching unit 101 executes the dg contact connection operation until the time T1 is reached after switching from the position control to the pressure control. To do. Thereafter, until the time T2 is reached after the time T1, the timer 102 outputs a switching signal so that the output switching unit 101 performs the df contact connection operation. Then, after the time T2 has elapsed, the timer 102 outputs a switching signal to cause the output switching unit 101 to execute the de contact connection operation.

  The pressure holding unit 103 detects the pressure detection signal Pr when the time T1 in the timer 102 elapses and the contact connection operation in the output switching unit 101 is switched from the gg contact connection operation to the df contact connection operation. It has a function to hold.

  The time constant processing unit 104 determines a predetermined time constant (in this embodiment, 1 / (1 + Ts) based on the deviation between the pressure detection signal Pr held by the pressure holding unit 103 and the pressure command signal Pc from the pressure command signal output unit 48. )), And a value obtained by adding the pressure detection signal Pr held by the pressure holding unit 103 to the value is calculated as a new pressure command signal Pc and output to the contact f.

The servo amplifier 42 includes a current comparison unit 65, a current control unit 66, and a current detection unit 67. In the servo amplifier 42, the current detector 67 detects the motor current i supplied to the electric servomotor 21, and outputs the detected value as a motor current detection signal ir. Current comparison unit 65 compares motor current command signal ic from speed control unit 53 with motor current detection signal ir from current detection unit 67 and outputs motor current deviation signal ei. The current control unit 66 controls the motor current i to the electric servomotor 21 based on the motor current deviation signal ei from the current comparison unit 65.

  Hereinafter, the position pattern 54 of the position command signal output unit 45 and the pressure pattern 56 of the pressure command signal output unit 48 according to the present embodiment will be described in detail. FIG. 8 shows the position pattern 54 in the present embodiment in association with the slide operation, and FIG. 9 shows the pressure pattern 56 in the present embodiment.

  In the position pattern 54, as shown in FIG. 8, a position h1 corresponding to the standby position of the die cushion pad 15 is first set from time t1 to a predetermined time constant from time t1 to time t2 for preliminary acceleration. The position is set so as to descend to position h2. Then, the upper mold 7 comes into contact with the workpiece 9 at a position h12 in the middle of reaching the position h2 (time t12). Since it is desirable to perform pressure control when the upper die 7 is in contact with the workpiece 9 and the drawing process is performed, the position target value by the position pattern 54 until the time t3 when the slide 4 reaches the bottom dead center is the die cushion. It is set to be higher than the actual position of the pad 15. As a result, the position deviation signal eh increases even when the die cushion pad 15 is lowered, and the pressure speed command signal υpc based on the pressure deviation signal ep smaller than the position deviation signal eh is selected, and the pressure control is performed. To be done. Specifically, as the position pattern 54 at this time, the position command signal hc is output so as to descend to the position h3 with another time constant from the time t2 to the time t3 after the preliminary acceleration to the position h2.

  Next, from time t3 to time t4, the slide 4 turns upward while the die cushion pad 15 is locked at the bottom dead center position. At this position h3, the pressure target value in the pressure pattern 56 described below is set sufficiently high, so that the pressure speed command signal υpc based on the pressure deviation signal ep becomes larger, at time t3. Has switched to position control. Based on this position control, after bottom dead center locking from time t3 to time t4, between time t4 and time t5, the auxiliary lift operation that rises by a predetermined height is performed so that the position h4 is reached at time t5. And after time t5, it is set to return to the position h1 corresponding to the standby position.

  On the other hand, as shown in FIG. 9, the pressure pattern 56 is set to a predetermined value P <b> 1 until time t <b> 12 before the upper die 7 contacts the workpiece 9. The predetermined value P1 is set to a value that is higher by a predetermined ratio than the preload of the die cushion pad 15, so that a predetermined pressure deviation signal ep is generated before the upper die 7 comes into contact with the workpiece 9. . Next, in the range from time t12 to time t3 when the upper die 7 is in contact with the workpiece 9 and drawing is performed, an optimum pressure such as a predetermined value P2 is set in the pressure pattern 56.

  Specifically, at the start of drawing, the pressure target value increases obliquely from the predetermined value P1 to the predetermined value P2 with a predetermined time constant, and thereafter until time t3 until the slide 4 reaches the bottom dead center. During this period, the predetermined value P2 is held. Since it is desirable to perform position control after the slide 4 reaches the bottom dead center (after time t3), the pressure target value is quickly set to a predetermined value P3 and high so that the pressure deviation signal ep increases. Yes.

Next, the relationship between the operation of the die cushion pad 15 and the pressure / position control will be described below. FIG. 10 is a diagram for explaining the operation of the slide 4 and the die cushion pad 15, and the change in the position of the slide 4 and the die cushion pad 15 with the passage of time is represented by a diagram.
In the following description, the die cushion pad position detection signal hr from the die cushion pad position calculation unit 43 is referred to as a “position feedback signal hr”, and the die cushion pad speed detection signal υr from the die cushion pad speed calculation unit 44 is referred to as “position feedback signal hr”. This is referred to as “speed feedback signal υr”, and the pressure detection signal Pr from the pressure gauge 93 is referred to as “pressure feedback signal Pr”.
It shall be called. The position control is referred to as “position feedback control” and the pressure control is referred to as “pressure feedback control”.

  First, since the die cushion pad 15 is at the standby position h1 from the start of the pressing operation to time t1, the position speed command signal υhc is 0, whereas the pressure speed command signal υpc is predetermined. The value corresponds to the value P1. For this reason, between the start of the press working operation and the time t1, the position / pressure comparison unit 61 selects the position speed command signal υhc, and the contact b and contact a are brought into the connected state by the switch 60, and position feedback. Control is performed. Further, since the pressure speed command signal υpc becomes a value corresponding to the predetermined value P1 between the time t1 and the time t12, the position feedback control is continuously performed.

During this position feedback control, the position comparison unit 46 subtracts the position feedback signal hr from the position command signal hc and outputs a position deviation signal eh, and the position control unit 47 uses a position speed command to decrease the position deviation signal eh. The speed comparison unit 52 outputs the speed deviation signal ev by subtracting the speed feedback signal υr from the position speed command signal υhc, and the speed control unit 53 reduces the speed deviation signal ev. A signal (torque command signal) ic is output, and the servo amplifier 42 supplies a motor current i corresponding to the motor current command signal ic to the electric servo motor 21. Thereby, the position of the die cushion pad 15 is controlled so that the position detection value by the encoder 36 follows the preset position pattern 54. The die cushion pad 15 waits at the standby position until time t1, and then performs preliminary acceleration from time t1 to time t2 in order to reduce the impact when the upper die 7 and the work 9 come into contact with each other. Controlled.

  Next, when the upper die 7 and the workpiece 9 are in contact with each other at the position h12 at time t12 during the preliminary acceleration, the position target value of the position pattern 54 still changes toward the position h2, and then changes toward the position h3. To do. However, since the actual die cushion pad 15 descends further below the target position by following the slide 4, a position deviation signal eh exceeding a certain value exists. On the other hand, since the pressure increases when the upper die 7 and the workpiece 9 come into contact with each other, the generated pressure approaches the predetermined value P1 that is the pressure target value of the pressure pattern 56. Accordingly, the pressure deviation signal ep is gradually reduced. When the pressure speed command signal υpc based on the pressure deviation signal ep becomes smaller than the position speed command signal υhc based on the position deviation signal eh, the position / pressure comparison unit 61 selects the pressure speed command signal υpc.

  Thereby, the bc contact connection operation is performed by the switch 60 in the position / pressure control switching unit 51, and the position feedback control is automatically switched to the pressure feedback control. Therefore, the automatic switching operation by the position / pressure control switching unit 51 can surely switch between the position control and the pressure control immediately after the upper mold 7 contacts the workpiece 9. As described above, during the period from time t12 to time t3, the slide 4 and the die cushion pad 15 are integrally lowered and the work 9 is drawn. During this period from time t12 to time t3, pressure feedback control is performed.

During this pressure feedback control, the pressure comparison unit 49 subtracts the pressure feedback signal Pr from the pressure command signal Pc and outputs the pressure deviation signal ep, and the pressure control unit 50 reduces the pressure deviation signal ep. The speed comparison unit 52 outputs the speed deviation signal ev by subtracting the speed feedback signal υr from the pressure speed command signal υpc, and the speed control unit 53 reduces the speed deviation signal ev. A signal (torque command signal) ic is output, and the servo amplifier 42 supplies a motor current i corresponding to the motor current command signal ic to the electric servo motor 21. Thereby, the cushion pressure of the die cushion pad 15 is controlled so that the pressure detection value by the pressure gauge 93 follows the preset pressure pattern 56.

  By the way, when the upper die touches the work 9 at time t12, the actual generated pressure overshoots greatly exceeding the target pressure based on the pressure pattern 56 (see the one-dot chain line of the target pressure in FIG. 10) due to the impact. (Refer to the generated pressure in FIG. 10). Conventionally, undershoot (see the dotted line of the generated pressure in FIG. 10) has occurred due to the accumulation of deviation due to this, and load loss has occurred. Therefore, in this embodiment, when the upper die touches the workpiece 9 and switches from the position feedback control to the pressure feedback control, the timer 102 sends a switching signal to the output switching unit 101 by the activation signal from the position / pressure comparison unit 61. Until the time T1 is reached, the de-contact connection operation so far is switched to the d-g contact connection operation.

  By doing so, the actual pressure feedback signal Pr from the pressure gauge 93 is given as the pressure command signal Pc, and the target pressure exceeds the original target pressure based on the pressure pattern 56 and is shown by a solid line in FIG. As shown, the actual generated pressure is the same. Accordingly, until time T1, the pressure deviation signal ep generated by the deviation between the pressure command signal Pc and the pressure feedback signal Pr becomes 0 “zero”, and even when PI operation control having an integral element is performed, The accumulation of deviation can be eliminated, the undershoot caused by the accumulation can be surely prevented, the separation phenomenon can be prevented, and the load loss can be prevented. The time T1 is a time at which the overshoot generated pressure substantially peaks, and is obtained from experiments and experiences.

Further, in the present embodiment, when the time T1 has elapsed, the timer 102 outputs a switching signal to the output switching unit 101, and the dg contact connection operation is changed to the df contact connection operation until the time T2 is reached. Switch to. At the same time, the timer 102 outputs an activation signal to the pressure holding unit 103 to hold the pressure feedback signal Pr at time T1. By doing so, the time constant processing unit 104 is activated until the time T2 is reached, and the pressure feedback signal Pr held by the pressure holding unit 103 and a predetermined time constant such as 1 / (1 + Ts) The pressure command signal Pc based on the pattern 56 is processed and processed. As a result, as shown by the solid line in the target pressure in FIG. 10, the target pressure is set by a gentle curve based on the time constant after time T1. That is, the target pressure during the time T1 is automatically set so as to converge to the target pressure P2 at the time T2.

  As a result, the generated pressure after time T1 converges gently, and undershoot can be prevented more reliably. This time T2 is obtained from experiments and experiences based on the time required for the generated pressure that repeats overshoot and undershoot to actually converge when the present invention is not applied. Then, after the time T2 has elapsed, the output switching unit 101 returns the df contact connection operation to the de contact connection operation by the switching signal from the timer 102, and gives priority to the pressure command signal Pc based on the pressure pattern 56.

  Here, the operations of the output switching unit 101, the timer 102, the pressure holding unit 103, and the time constant processing unit 104 will be described more simply with reference to the flowchart of FIG. In FIG. 11, the timer 102 monitors the activation signal from the position / pressure control unit 51 and waits for switching from the position feedback control to the pressure feedback control (ST1). When the start signal is input, the timer 102 outputs a switching signal to the output switching unit 101, and the output switching unit 101 starts the dg contact connection operation. As a result, the pressure feedback signal Pr is treated as the pressure command signal Pc, the pressure deviation signal ep is set to 0, the accumulation of deviation due to overshoot is suppressed, and the occurrence of undershoot is prevented (ST2). Next, the timer 102 monitors whether the time T1 has elapsed, and outputs a switching signal to the output switching unit 101 and outputs a start signal to the pressure holding unit 103 when the time T1 has elapsed (ST3).

  Upon receiving the switching signal from the timer 102, the output switching unit 101 starts the df contact connection operation, and the pressure holding unit 103 holds the pressure feedback signal Pr at time T1. Along with this, the time constant processing unit 104 processes the pressure command signal Pc based on the predetermined time constant and the held pressure feedback signal Pr, and outputs it to the contact f (ST4). As a result, the target pressure after time T1 is changed to a pattern that gently converges, and undershoot is more reliably prevented. Thereafter, the timer 102 waits for the elapse of time T2 to output a switching signal to the output switching unit 101 (ST5), and the output switching unit 101 returns to the df contact connection operation (ST6).

The best configuration, method, and the like for carrying out the present invention have been disclosed above, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of quantity, other details, and the like.
Therefore, the description limited to the shape, quantity, etc. disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

Hereinafter, a first modification of the present invention will be described with reference to FIGS.
In the first modification, instead of the output switching unit 101 of the above embodiment, a first output switching unit 105, a second output switching unit 106, a third output switching unit 107, and a pressure command signal Pc each functioning as a switch. Is provided with a command signal changing unit 108 for changing the value to 0. The timer 102, the first output switching unit 105, the second output switching unit 106, the third output switching unit 107, and the command signal changing unit 108 form the deviation canceling unit 100 of the present invention. The generated pressure converging unit 150 of the present invention is formed by the unit 103, the time constant processing unit 104, the first output switching unit 105, and the third output switching unit 107.

  Specifically, the first output switching unit 105 has contacts h, i, j, and outputs the pressure command signal Pc processed by the time constant processing unit 104 to the pressure comparison unit 49 by the hi contact connection operation. The pressure command signal Pc from the second output switching unit 106 is output to the pressure comparison unit 49 by the hj contact connection operation. The second output switching unit 106 has contacts k, l, m, and receives a pressure command signal Pc from the command signal changing unit 108, that is, a pressure command signal Pc of 0 “zero” at all times by k−1 contact connection operation. It outputs to the contact j of the 1st output switching part 105, and outputs the pressure command signal Pc from the pressure command signal output part 48 to the contact j of the 1st output switching part 105 as it is by k-m contact connection operation. The third output switching unit 107 has contacts n and o, and outputs a pressure detection signal Pr from the pressure gauge 93 to the pressure comparison unit 49 by a no contact contact connection operation. Pressure feedback of the detection signal Pr to the pressure comparison unit 49 is stopped. As described above, the command signal changing unit 108 has a function of always setting the pressure command signal Pr to 0 “zero” to the contact 1 of the second output switching unit 106.

  In this modification, the timer 102 functions as follows. That is, until the time T1 after the upper die contacts the workpiece 9 (t12) and the position control is switched to the pressure control, the timer 102 performs the hj contact connection operation with respect to the first output switching unit 105. To output a switching signal for performing a kl contact connection operation to the second output switching unit 106 and to maintain an open state for the third output switching unit 107 Switch signal is output. As a result, since the pressure command signal Pr of “0” that has passed through the command signal changing unit 108 is input to the pressure comparison unit 49, the target pressure becomes zero as shown in FIG. Further, since the third output switching unit 107 is open, pressure feedback is not performed, and the pressure deviation signal ep is also zero in the pressure comparison unit 49. From this, even when the actual generated pressure overshoots, the deviation is not accumulated, and the subsequent undershoot can be suppressed to prevent the separation phenomenon, thereby preventing the load loss.

  In the period from time T1 to time T2, the timer 102 outputs a switching signal for performing the hi contact connection operation to the first output switching unit 105 and to the third output switching unit 107. A switching signal for performing the no-contact connection operation is output. As a result, as in the above-described embodiment, the target pressure is set so that it gradually converges to the target pressure P2, and undershoot can be prevented more reliably. When the time T2 is exceeded, the timer 102 outputs a switching signal for performing the hj contact connection operation to the first output switching unit 105, and the km contact to the second output switching unit 106. A switching signal for performing the connection operation is output to cause the third output switching unit 107 to maintain the no contact connection operation. As a result, the normal pressure control is restored.

Hereinafter, a second modification of the present invention will be described with reference to FIGS.
In the second modification, the pressure holding unit 103 and the time constant processing unit 104 in the above embodiment are not provided, but instead the pressure storage unit 109, the pressure command signal generation unit 110, and the output switching unit 111 are provided. I have. These parts 109, 110, 111 and the timer 102 form a deviation canceling unit 100 of the present invention, and the deviation canceling unit 100 also serves as the generated pressure converging unit 150.

  The pressure storage unit 109 is composed of an appropriate storage medium such as RAM or ROM, and stores a plurality of pressure waveforms based on the pressure detection signal Pr from the pressure gauge 93. Based on a plurality of pressure waveforms stored in the pressure storage unit 109, the pressure command signal generation unit 110 generates a pressure pattern 112 that is applied until the time T3 elapses from the time when the position control is switched to the pressure control. At the same time, a pressure command signal Pc based on the pressure pattern 112 is output to the output switching unit 111. The output switching unit 111 functions as a switch having contacts p, q, and r. In addition, the timer 102 in this modification example outputs a switching signal so that the output switching unit 111 performs the pq contact connection operation until the time T3 elapses from when the position control is switched to the pressure control. In other cases, a switching signal is output so as to perform a pr contact connection operation.

  Here, as the operation mode of the controller 41, the teaching mode and the normal mode are selected. In the teaching mode, the timer 102 does not function, and the output switching unit 111 always has a pr contact connection. The operation is to be performed. In this teaching mode, the pressure detection signal Pr is stored in the pressure storage unit 109, and the pressure signal generation unit 110 generates a pressure pattern 112 having an overshoot portion that is substantially the same as the generated pressure. When generating the pressure pattern 112, as indicated by a two-dot chain line in FIG. 17, the peak pressure Pp at the first overshoot and the pressure Pf at the convergence at the actual generated pressure gradually change. Is interpolated as follows. For this interpolation, the same time constant as in the above embodiment may be used.

  On the other hand, the operation in the normal mode is performed after the teaching mode. In this normal mode, the output switching unit 111 is set to p− until the time T3 elapses from the time when the position control is switched to the pressure control. In order to perform the q contact connection operation, not the pressure command signal Pc based on the pressure pattern 56 but the pressure command signal Pc based on the pressure pattern 112 substantially the same as the generated pressure is output to the pressure comparison unit 49. As a result, the pressure command signal Pc and the pressure detection signal Pr are substantially the same, the pressure deviation signal ep is also substantially zero, the accumulation of the deviation is eliminated, the undershoot can be reliably prevented, the separation phenomenon can be prevented, and the load loss Can be prevented.

  In addition to the first and second modifications described above, for example, in the above embodiment, a pressure gauge provided in the hydraulic circuit is used as the pressure detection means according to the present invention. It may be a strain gauge or the like. Further, the position detecting means is not limited to the encoder provided in the electric servo motor for driving the die cushion, but may be a linear scale provided between the die cushion pad and the bed. Furthermore, the electric servo motor is not limited to the rotary type, and may be a direct acting type such as a linear servo motor.

  In the above embodiment, the die cushion control device is configured to switch between position control and pressure control. However, the present invention includes the case where pressure control is performed through a stroke.

  INDUSTRIAL APPLICABILITY The present invention can be used for a die cushion control device for controlling a die cushion used in a press machine that performs drawing or the like, and can be suitably used particularly as a die cushion control device for a die cushion driven by an electric servo motor.

1 is a schematic configuration diagram of a press machine according to an embodiment of the present invention. The schematic block diagram of the die cushion which concerns on the said embodiment. The functional block diagram explaining the structure of a die cushion control apparatus. The control block diagram explaining the structure of a die cushion control apparatus. The figure which shows the relationship between time and the speed command signal for positions. The figure which shows the relationship between time and the speed command signal for pressure. Explanatory drawing for demonstrating switching operation | movement between position control and pressure control. The figure which shows a position pattern. The figure which shows a pressure pattern. Operation | movement explanatory drawing of a slide and a die cushion pad. The flowchart for demonstrating operation | movement of an output switching part, a timer, and a pressure holding part. The functional block diagram explaining a 1st modification. The control block diagram explaining a 1st modification. The figure which shows the target pressure and generated pressure in a 1st modification. The functional block diagram explaining the 2nd modification. The control block diagram explaining the 2nd modification. The figure which shows the generated pressure in a 2nd modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Press machine, 9 ... Workpiece, 13 ... Die cushion, 15 ... Die cushion pad, 21 ... Electric servo motor, 40 ... Die cushion control device, 42 ... Servo amplifier, 48 ... Pressure command signal output part, 49 ... Pressure comparison , 56 ... Pressure pattern, 50 ... Pressure control unit, 53 ... Speed control unit, 93 ... Pressure gauge as pressure detection means, 100 ... Deviation canceling unit, 150 ... Generated pressure convergence unit, ep ... Pressure deviation signal, i ... Motor current as current, ic ... motor current command signal, Pc ... pressure command signal, Pr ... pressure detection signal, T1, T2 ... time, υpc ... pressure command signal for pressure.

Claims (3)

In the die cushion control device (40) of the press machine (1) ,
A pressure command signal output unit (48) for outputting a first pressure command signal corresponding to a pressure target value based on a predetermined pressure pattern;
Pressure detecting means (93) for detecting the generated pressure applied to the die cushion pad (15);
A pressure comparator (49) for outputting a pressure deviation signal corresponding to a deviation between a pressure target value based on the pressure pattern and a pressure detection value based on a pressure detection signal from the pressure detection means (93); A pressure control unit (50) for outputting a pressure command signal based on pressure,
A speed controller (53) for outputting a motor current command signal based on the pressure command signal for pressure;
A servo amplifier (42) for supplying a current corresponding to the motor current command signal to the electric servo motor (21) for driving the die cushion (13);
A deviation canceling unit (100) for making the deviation between the pressure target value and the generated pressure overshooting over the pressure target value substantially zero over a predetermined time ;
The end of the predetermined time is until the overshooting pressure detection value almost reaches a peak,
A pressure pattern that gently converges from a pressure detection value at the end of the predetermined time to the pressure target value using a predetermined time constant is a new pressure pattern,
Wherein after a predetermined time elapses, until caused to converge to the target pressure value, press machine a second pressure command signal corresponding to the new pressure pattern and replaces the first pressure command signal ( 1) Die cushion control device (40). In the die cushion control device (40) of the press machine (1) according to claim 1,
The pressure control unit (50) includes an integrator (72) for integrating a pressure deviation signal output from the pressure comparison unit (49), and a die cushion control device for a press machine (1) , (40). In the die cushion control device (40) of the press machine according to claim 1 or 2,
  A position command signal output unit (45) for outputting a position command signal corresponding to a position target value based on a predetermined position pattern;
  Position detecting means (36) for detecting the position of the die cushion pad (15);
  A position comparison unit (46) for outputting a position deviation signal according to a deviation between a position target value based on the position pattern and a position detection value based on a position detection signal from the position detection means (36);
  A position controller (47) for outputting a position speed command signal based on the position deviation signal;
  A position / pressure control switching unit (51) for outputting either the position speed command signal or the pressure speed command signal as a speed command signal;
  The speed control unit (53) outputs a motor current command signal based on the speed command signal output from the position / pressure control switching unit (51),
  At the same time as switching from position control based on the speed command signal for position to pressure control based on the speed command signal for pressure, the deviation canceling unit (100) sets the pressure deviation signal to substantially zero.
  A die cushion control device (40) for a press machine.

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