JP2012115847A - Die cushion control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die cushion control device capable of reducing power consumption and excluding restriction of cycle time.SOLUTION: The die cushion control device controls a die cushion device comprising a cushion pad and an actuator in conjunction with elevating operation of a slide. Before the slide comes into contact with the cushion pad, the amount of operation of the actuator is so varied in a ramp-like manner or a step-like manner in a shorter time than its own natural period that a desired cushion force can be obtained at a first timing, and then the amount of operation is varied in the step-like manner in an opposite direction at a second timing which is set within a settable period of time when the cushion force decreases from the first maximum value to its half value.

Description

 The present invention relates to a die cushion control device.

  2. Description of the Related Art Conventionally, there has been known a press device including a die cushion device including a cushion pad to which a lower mold is fixed and an actuator for driving the cushion pad (see Patent Document 1 below). This press device performs the position control and force control of the cushion pad in conjunction with the lifting and lowering operation of the slide to which the upper die is fixed, thereby sandwiching the workpiece between the upper die and the lower die, A reaction force for wrinkle pressing and a push-up force (cushion force) for press molding are obtained.

  As a control method of the die cushion device, the cushion pad is moved down just before the slide and the cushion pad contact (specifically, immediately before the upper mold and the lower mold collide with the workpiece sandwiched). A technique called pre-acceleration for mitigating the impact of time is known (see Patent Document 2 below).

  In addition, after the contact between the slide and the cushion pad, as a control method for quickly setting the cushion force to the target value (in other words, realizing high-speed response), a state in which a constant cushion force is generated in advance before the contact between the two The actuator is controlled so that the cushioning force in the downward direction is generated instantaneously to the extent that the cushion pad does not descend in consideration of the response of the actuator immediately before contact (preload). ) The method is known.

  When a hydraulic cylinder is used as the actuator of the die cushion device, the control of the cushioning force is realized by torque control of a servo motor that drives the piston of the hydraulic cylinder. FIG. 3 shows the time change of the torque command value for the servo motor during the press operation. As shown in this figure, the torque command value is held at 0 (N · m) during a period (standby period) from the press start timing (slide descent start timing) t0 to the preload start timing t1.

  Then, the torque command value increases in a ramp shape from the preload start timing t1, and after reaching the constant value, is kept constant until the preaccelerator start timing t2. That is, the period from t1 to t2 is the preload execution period. If the torque command value is changed abruptly (stepwise), vibration is generated in the cushion force, and thus it is necessary to increase the torque command value in a ramp shape as described above. As shown in FIG. 4, since the cushion force vibrates even when the ramp time is short, it is necessary to set the ramp time to be equal to or greater than the natural cycle of the hydraulic cylinder (specifically, an integral multiple of the natural cycle).

Then, during the period from the pre-accelerator start timing t2 to the contact timing (molding start timing) t3 between the slide and the cushion pad, the torque command value changes stepwise in the negative direction so that a downward cushion force is generated. That is, the period from t2 to t3 is the pre-accelerator implementation period. The time between t2 and t3 is set to such a time that the cushion pad does not descend in consideration of the response of the hydraulic cylinder.
After the contact timing (molding start timing) t3 between the slide and the cushion pad, the torque command value is feedback-controlled to a constant value so that the cushion force becomes the target cushion force.

  By controlling the torque command value for the servo motor of the die cushion device as described above, combining the preload and preaccelerator reduces the rise time of the cushion force after the slide and cushion pad contact and suppresses overshoot. As a result, the cushioning force can be quickly set to the target value (high-speed response can be realized).

JP 2007-038238 A Japanese Examined Patent Publication No. 7-106478

As described above, when preloading is performed, before starting the pre-accelerator, it is necessary to increase the torque command value in a ramp shape over a time longer than the natural period of the hydraulic cylinder to suppress the vibration of the cushion force. If the natural period becomes longer due to a small spring coefficient of the hydraulic cylinder or a large mass (motor inertia, etc.), the preload time becomes longer, resulting in restrictions on the cycle time and increased power consumption. Occurs.
Further, in the above control method, it is necessary to generate a large acceleration in the cushion pad before the contact between the slide and the cushion pad. Therefore, a high-performance actuator is required, resulting in an increase in cost.

 The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a die cushion control device capable of realizing reduction in power consumption, elimination of constraint on cycle time, and reduction in cost.

  In order to solve the above-mentioned problem, in the present invention, as a first solution means for a die cushion control device, a die cushion that controls a die cushion device composed of a cushion pad and an actuator in conjunction with a lifting and lowering operation of a slide. The control device is configured to change the operation amount of the actuator in a ramp shape or a step shape in a time shorter than the natural period so that a desired cushion force can be obtained at a first timing before the slide and the cushion pad are contacted. Then, the operation amount is changed stepwise in the opposite direction at a second timing set within a settable period until the cushion force decreases from the initial maximum value to the half value.

  Further, in the present invention, as a second solving means related to the die cushion control device, in the first solving means, the target cushion force after the contact between the slide and the cushion pad and the speed of the slide are selected. The second timing is changed within the settable period.

In the present invention, when preloading is performed, the operation amount is shorter than the natural period without performing vibration suppression control (increasing the operation amount in a ramp shape over a time longer than the natural period of the actuator). Therefore, the preload time can be shortened and the power consumption can be reduced and the cycle time can be eliminated.
Further, in the present invention, since the pre-acceleration is started at the second timing set within the settable period until the cushion force is reduced from the initial maximum value to the half value thereof, the actuator exceeds the maximum acceleration that can be output independently. Preacceleration can be performed with acceleration. Therefore, an actuator having a low performance can be used, and the cost of the actuator can be reduced.

It is a schematic block diagram of the press apparatus A in this embodiment. It is explanatory drawing regarding the control method of the die cushion apparatus 2 in this embodiment. It is the 1st explanatory view about the control method of the conventional die cushion device. It is the 2nd explanatory view about the control method of the conventional die cushion device.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a press apparatus A in the present embodiment. As shown in FIG. 1, a press device A is a servo press device that performs press molding by holding a workpiece W between an upper die D1 and a lower die D2, and includes a slide device 1 and a die cushion device 2. And the control device 3.

  The slide device 1 includes a slide 10 and a slide drive mechanism 20. The slide 10 is a mold fixing member that is supported in the press device A so as to be movable up and down in the vertical direction, and an upper mold D1 for press-molding the workpiece W is attached to the lower surface thereof.

 The slide drive mechanism 20 implements a lifting / lowering operation (slide motion control) of the slide 10, and includes a servo motor 21 that is rotationally controlled by the control device 3, and a pinion gear 22 that is attached to the rotation shaft of the servo motor 21. A main gear 23 meshing with the pinion gear 22, a crankshaft 24 connected to the rotation shaft of the main gear 23, a connecting rod 25 connecting the eccentric portion of the crankshaft 24 and the upper surface of the slide 10. And a main gear angle sensor 26 (for example, an encoder or a resolver) installed on the rotation shaft of the main gear 23.

 That is, the slide drive mechanism 20 converts the rotation operation of the servo motor 21 into the raising / lowering operation of the slide 10 via the pinion gear 22, the main gear 23, the crankshaft 24, and the connecting rod 25. The main gear angle sensor 26 outputs a main gear angle signal indicating the rotation angle of the main gear 23 to the control device 3.

   The die cushion device 2 includes a cushion pad 30 that fixes and supports the lower mold D2 from below, and a hydraulic cylinder drive mechanism (actuator) 40 that drives the cushion pad 30. The hydraulic cylinder drive mechanism 40 realizes cushion force control of the cushion pad 30, and includes a hydraulic cylinder 41, a movable plate 42, a servo motor 43 that is rotationally controlled by the control device 3, and pressure sensors 44 a to 44 c. It consists of and.

   The hydraulic cylinder 41 has a cylindrical shape in which an internal space is partitioned into an upper chamber R1, a middle chamber R2, and a lower chamber R3 by an upper piston 41a connected to the cushion pad 30 and a lower piston 41b connected to the movable plate 42. The upper chamber R1, the middle chamber R2, and the lower chamber R3 are filled with oil. The movable plate 42 is a flat plate member in which holes having screw grooves are formed at both ends, and a ball screw 35a coaxially connected to the servo motor 43 is inserted into each of these holes.

 That is, the hydraulic cylinder drive mechanism 40 converts the rotation operation of the servo motor 43 into the lifting / lowering operation of the cushion pad 30 via the ball screw 35a, the movable plate 42, and the hydraulic cylinder 41. Here, when the movable plate 42 is moved upward by driving the servo motor 43, the hydraulic pressure in the middle chamber R <b> 2 of the hydraulic cylinder 41 is increased, and an upward cushion force is generated in the cushion pad 30. On the other hand, when the movable plate 42 is moved downward by driving the servo motor 43, the hydraulic pressure in the middle chamber R2 is reduced, and a downward cushioning force is generated in the cushion pad 30.

   The pressure sensors 44a to 44c detect the hydraulic pressure of the upper chamber R1, the hydraulic pressure of the middle chamber R2, and the hydraulic pressure of the lower chamber R3, respectively, and output a hydraulic pressure detection signal indicating the detection result to the control device 3. Is.

 The control device 3 performs overall control of the entire operation of the press device A (in other words, performs slide motion control and cushion force control), and includes an operation panel 50, a press controller 60, a first motor driver 70, and a cushion controller. 80 and a second motor driver 90.

 The operation panel 50 provides various setting keys for the operator to input setting data (slide motion data, press speed, target cushion force, etc.) necessary for the press operation of the press apparatus A, and instructs the start or stop of the press operation. Press start / stop key, and a display panel for informing the operator of the operation state and setting data of the press apparatus A. The operation panel 50 outputs the setting data input by the operator to the press controller 60, and displays the operation state and setting data of the press apparatus A provided from the press controller 60 on the display panel.

Based on the setting data (slide motion data, press speed) input from the operation panel 50 and the main gear angle signal input from the main gear angle sensor 26, the press controller 60 draws a desired slide motion. The servo motor 21 is controlled so as to move up and down (slide motion control).
The first motor driver 70 generates a motor drive signal in accordance with control by the press controller 60 and outputs the motor drive signal to the servo motor 21.

 The cushion controller 80 (die cushion control device) is input from setting data (target cushion force) obtained from the press controller 60, a main gear angle signal input from the main gear angle sensor 26, and pressure sensors 44a to 44c. Based on the hydraulic pressure detection signal, the servo motor 43 is controlled so that the target cushion force is generated in the cushion pad 30 (cushion force control).

Specifically, the cushion controller 80 estimates the slide position from the main gear angle, and the torque command value (operation amount) for the servo motor 43 so that a target cushion force corresponding to the slide position is generated in the cushion pad 30. To control. In the present embodiment, when the torque command value for the servo motor 43 is increased in the positive direction, the movable plate 42 moves upward to generate an upward cushion force on the cushion pad 30, and the torque command for the servo motor 43 is generated. When the value is increased in the negative direction, the movable plate 42 moves downward and a downward cushioning force is generated on the cushion pad 30.
The second motor driver 90 generates a motor drive signal corresponding to the torque command value input from the cushion controller 80 and outputs the motor drive signal to the servo motor 43.

Next, the press operation by the press apparatus A configured as described above will be described in detail.
First, when receiving a press start instruction via the operation panel 50, the press controller 60 slides based on preset slide motion data and press speed, and a main gear angle signal input from the main gear angle sensor 26. Start motion control. Thereby, the slide 10 starts to descend while drawing a desired slide motion.

 On the other hand, as shown in FIG. 2, the cushion controller 80 sets the torque command value to 0 (N · m) in the period (standby period) from the press start timing (slide 10 descent start timing) t0 to the preload start timing t10. Hold on. FIG. 2 shows changes over time in the torque command value and cushion force for the servo motor 43 during the press operation.

 When the cushion controller 80 detects the preload start timing t10 based on the main gear angle signal, the cushion controller 80 starts preloading. Specifically, at the preload start timing t10, the cushion controller 80 increases the torque command value in the positive direction in a ramp shape in a time shorter than the natural cycle of the hydraulic cylinder drive mechanism 40, and after reaching a certain value, starts the pre accelerator. Hold constant until timing t11.

 When the torque command value is changed in this way, as the lower piston 41b is pushed upward by the servo motor 43, the cushion force of the cushion pad 30 increases, and the pushing amount of the lower piston 41b is maximized. The cushioning force is the maximum value. When the pushing amount of the lower piston 41b is maximized, the force that pushes the lower piston 41b downward is maximized, the lower piston 41b is pushed downward, and the cushioning force is reduced.

 The cushion controller 80 grasps the change in the cushion force as described above based on the hydraulic pressure detection signals input from the pressure sensors 44a to 44c, and sets the cushion force until the cushion force decreases from the initial maximum value to its half value. The pre-accelerator is started at the pre-accelerator start timing t11 set within the possible period (the torque command value is changed stepwise in the negative direction).

 When the cushion controller 80 detects the contact timing t12 (molding start timing) between the slide 10 and the cushion pad 30 based on the main gear angle signal, the cushion controller 80 feedback-controls the torque command value so that the cushion force becomes the target cushion force. .

 As described above, in the present embodiment, when preloading is performed, the torque suppression control (the torque command value is increased in a ramp shape over a time longer than the natural period of the actuator) is performed as in the related art. Since the command value is increased in a ramp shape in a time shorter than the natural period, the preload time can be shortened. As a result, it is possible to reduce power consumption and eliminate restrictions on the cycle time.

 In the present embodiment, since the pre-accelerator is started at the pre-accelerator start timing t11 set within the settable period until the cushion force decreases from the initial maximum value to its half value, the actuator (hydraulic cylinder drive mechanism 40 ) Can be pre-accelerated at an acceleration greater than the maximum acceleration that can be produced independently. Therefore, an actuator having a low performance can be used, and the cost of the actuator can be reduced.

 The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and it is needless to say that the embodiment can be changed without departing from the gist of the present invention. For example, the present invention includes the following modifications in addition to the above embodiment.

(1) In the above embodiment, the case where the torque command value is increased in a ramp shape in a time shorter than the natural period at the time of preloading is illustrated, but the present invention is not limited to this, and the torque command value is stepped. It may be increased.

(2) In the above embodiment, the pre-accelerator start timing t11 is fixed. However, the present invention is not limited to this, and the pre-accelerator start timing t11 depends on the target cushion force after the contact between the slide 10 and the cushion pad 30 and the speed of the slide 10. The cushion controller 80 may have a function of changing the pre-accelerator start timing t11 within the settable period. For example, when the slide speed is fast and the target cushion force is small, the pre-accelerator start timing t11 is set so as to be close to the timing when the cushion force becomes the first maximum value. Conversely, when the slide speed is slow and the target cushion force is high, the pre-accelerator start timing t11 is delayed.

(3) In the above embodiment, the hydraulic cylinder drive mechanism 40 is exemplified as the actuator used in the die cushion device 2, but the present invention is not limited to this, and the present invention is applied to any actuator that constitutes a vibration system. be able to. Further, the operation amount of the actuator is not limited to the torque command value.

 A ... press device, 1 ... slide device, 2 ... die cushion device, 3 ... control device, 10 ... slide, 20 ... slide drive mechanism, 30 ... cushion pad, 40 ... hydraulic cylinder drive mechanism (actuator), 50 ... operation panel , 60 ... press controller, 70 ... first motor driver, 80 ... cushion controller (die cushion control device), 90 ... second motor driver

Claims (2)

A die cushion control device that controls a die cushion device composed of a cushion pad and an actuator in conjunction with a lift operation of a slide,
Before the contact between the slide and the cushion pad, the amount of operation of the actuator is changed in a ramp shape or a step shape in a time shorter than the natural period so that a desired cushion force can be obtained at a first timing, and then the cushion force The die cushion control device is characterized in that the operation amount is changed stepwise in the opposite direction at a second timing set within a settable period from when the first maximum value is reduced to its half value.   2. The die cushion control according to claim 1, wherein the second timing is changed within the settable period in accordance with a target cushion force after contact between the slide and the cushion pad and a speed of the slide. apparatus.

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