JP5428948B2 - Hydraulic die cushion device and control method thereof - Google Patents

Description

  The present invention relates to a hydraulic die cushion device and a control method thereof.

  The hydraulic die cushion device is provided in a press machine that molds the work piece between the upper mold and the lower mold. Is a device that generates a reaction force and a push-up force (pressing force against a slide that is a movable part of a press machine: cushion force) for press-molding a workpiece. The hydraulic die cushion device includes a die cushion pad to which a lower mold is attached, a hydraulic cylinder that drives the die cushion pad, and a control device that controls the hydraulic cylinder to generate the cushion force.

  The hydraulic die cushion device configured as described above generates a cushioning force by increasing the pressure of the hydraulic cylinder. Since a large cushioning force is required during molding of the workpiece, the hydraulic cylinder is boosted to a high pressure of, for example, about 10 to 30 Mpa. When the hydraulic die cushion pad reaches the bottom dead center in a state where the workpiece is sandwiched between the upper die and the lower die, the molding of the workpiece is finished. Then, since the slide is separated from the die cushion pad, control (locking control) for holding the position of the die cushion pad is performed by the control device.

  In Patent Document 1 below, when the die cushion pad reaches the bottom dead center, the electric servo motor is driven to retract the die cushion pad from the bottom dead center position to the lower side by a predetermined retraction height. A die cushion control device that performs control is disclosed. By performing such control, the workpiece is prevented from jumping up at the moment when the die cushion pad reaches the bottom dead center and the slide rises.

JP 2007-2371874 A

  By the way, if the die cushion pad jumps up at the bottom dead center described above, the die cushion pad vibrates greatly, and there is a possibility that the mechanical load is applied and the life of the hydraulic die cushion device is shortened. Further, when the die cushion pad bounces, not only the above-described workpiece bounces but also a large sound due to vibration is generated, resulting in noise. Therefore, the die cushion pad bounce needs to be suppressed as much as possible.

  In the above-mentioned Patent Document 1, the electric servo motor is driven to perform the control to retract the die cushion pad to the lowering side to prevent the die cushion pad from jumping up, but the control on the electric servo motor becomes complicated. There is a problem. Further, since the control for the electric servo motor is complicated, it is difficult to accurately control the timing of retracting the die cushion pad, and there is a problem that the jumping up of the die cushion pad cannot be sufficiently suppressed.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a hydraulic die cushion device and a control method thereof that can effectively suppress the jumping of the die cushion pad at the bottom dead center.

In order to solve the above problems, a hydraulic die cushion device according to the present invention comprises a contact member (22) that is in contact with a contact object (10) and that can move in one axis in conjunction with the movement of the contact object, and the contact member. In a hydraulic die cushion device (20) comprising a hydraulic cylinder (23) for driving the hydraulic cylinder, a pressure accumulator (26) communicating with the hydraulic cylinder and storing oil used in the hydraulic cylinder, and the hydraulic cylinder, The valve device (27) for opening and closing the oil flow path between the pressure accumulator and the oil in the hydraulic cylinder is discharged and stored in the pressure accumulator when the contact member reaches bottom dead center. And a control device (30) for controlling the valve device.
In the hydraulic die cushion device according to the present invention, the control device controls the valve device in consideration of a response time required for the valve device to change from a closed state to an open state.
Further, the hydraulic die cushion device according to the present invention is characterized in that the control device controls the valve device at a time point before the response time from a time point when the contact member reaches bottom dead center.
The hydraulic die cushion device of the present invention includes pressure sensors (29a to 29c) for detecting the pressure state of the hydraulic cylinder, and the control device detects the pressure state of the hydraulic cylinder detected by the pressure sensor. When the pressure reaches a preset pressure state, the valve device is controlled to be closed from the open state.
In the hydraulic die cushion device of the present invention, the valve device is a logic valve that takes two states, an open state and a closed state.
In the hydraulic die cushion device of the present invention, the hydraulic cylinder holds oil between the first piston (P1) connected to the contact member and the first piston, And a second piston (P2) for decompressing.
The hydraulic die cushion device according to the present invention includes a movable plate (24) connected to the second piston and the control device, and the first piston and the second piston are moved by moving the movable plate. And a motor (25) that pressurizes and depressurizes the oil sandwiched therebetween.
The control method of the die cushion device of the present invention includes a contact member (22) that contacts the contact object (10) and can move in one axis in conjunction with the movement of the contact object, and a hydraulic cylinder that drives the contact member ( 23), a pressure accumulator (26) in which the oil in the hydraulic cylinder is discharged and communicated with the hydraulic cylinder when the contact member reaches bottom dead center. ), The valve device (27) for opening and closing the flow path between the hydraulic cylinder and the pressure accumulator is controlled.

  According to the present invention, the pressure accumulator communicated with the hydraulic cylinder and the valve device for opening and closing the oil flow path between the hydraulic cylinder and the pressure accumulator are provided, and the hydraulic cylinder when the contact member reaches the bottom dead center. Since the valve device is controlled by the control device so that the oil inside is discharged and stored in the pressure accumulator, there is an effect that the jumping of the die cushion pad at the bottom dead center can be effectively suppressed. As a result, the mechanical load applied to the hydraulic die cushion device is reduced, so that the life of the device can be extended and noise can be prevented.

It is a side view showing a schematic structure of a press provided with a hydraulic die cushion device by one embodiment of the present invention. It is a flowchart which shows operation | movement of a press machine provided with the hydraulic die cushion apparatus by one Embodiment of this invention. It is a figure which shows an example of the cushion force generate | occur | produced with the hydraulic cylinder 23 at the time of a press.

  Hereinafter, a hydraulic die cushion device and a control method thereof according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side view showing a schematic configuration of a press equipped with a hydraulic die cushion device according to an embodiment of the present invention. As shown in FIG. 1, the press machine 1 includes a slide 10 (contact object) and a hydraulic die cushion device 20. The slide 10 collides (contacts) with the hydraulic die cushion device 20. The sandwiched panel P (workpiece) is press-molded.

  The slide 10 is configured to be capable of reciprocating in the vertical direction, and an upper mold D1 for press-molding the panel P is attached to the lower part thereof. Specifically, the slide 10 is reciprocated by a crank mechanism including a crankshaft 11 that is rotationally driven by a main motor (not shown), and a connecting rod 12 that connects an eccentric portion of the crankshaft 11 and an upper portion of the slide 10. Is possible.

  The crank mechanism is provided with a rotation angle sensor 13 for detecting the rotation angle of the crankshaft 11, and the speed of the slide 10 and the slide 10 are changed according to the rotation angle detected by the rotation angle sensor 13. The point of collision is required. The detection result of the rotation angle sensor 13 is output to a control device (not shown) that controls the operation of the slide 10 and a control device 30 that controls the operation of the hydraulic die cushion device 20.

  The hydraulic die cushion device 20 includes a cushion pin 21, a die cushion pad 22 (contact member), a hydraulic cylinder 23, a moving plate 24, a motor 25, an accumulator 26 (pressure accumulator), a logic valve 27 (valve device), a stroke sensor 28, And pressure sensors 29a to 29c, and generates a reaction force for wrinkle pressing and a cushion force for press-molding the panel P under the control of the control device 30.

  The die cushion pad 22 is disposed below the slide 10 and supports the lower mold D <b> 2 via the cushion pin 21. The die cushion pad 22 can move vertically downward in conjunction with the movement of the slide 10 when the slide 10 collides (contacts). The phrase “contact” in this specification means that the slide 10 and the die cushion pad 22 are indirectly touched via the die cushion pin 21, the upper mold D 1, the lower mold D 2, and the panel P. means.

  The hydraulic cylinder 23 includes a piston P <b> 1 (first piston) and a piston P <b> 2 (second piston), and the cushion force is controlled by driving the motor 25. The piston P1 has one end connected to the lower portion of the die cushion pad 22 and the other end dividing the interior of the hydraulic cylinder 23 into an upper chamber 23a and an intermediate chamber 23b. One end of the piston P2 is connected to the movable plate 24, and the other end partitions the inside of the hydraulic cylinder 23 into an intermediate chamber 23b and a lower chamber 23c. The upper chamber 23a, the middle chamber 23b, and the lower chamber 23c partitioned by the pistons P1 and P2 are filled with oil.

  The movable plate 24 is a flat plate member in which holes having screw grooves are formed at both ends. Each hole formed in the movable plate 24 is provided with a cylindrical feed member 25a having a thread formed on the side surface and configured to be rotatable about a shaft by a motor 25. Each axis of the feed member 25a is set in the vertical direction. When the feed member 25a is rotated at the same speed by the motor 25, the movable plate 24 can be translated in the vertical direction.

  Here, since the movable plate 24 is connected to one end of the piston P2, when the movable plate 24 moves in the vertical direction, the piston P2 moves integrally with the movable plate 24 in the vertical direction. When the movable plate 24 is moved upward by driving the motor 25, the oil sandwiched between the pistons P1 and P2 is pressurized, so that the cushioning force of the hydraulic cylinder 23 can be increased. On the other hand, when the movable plate 24 is moved downward by driving the motor 25, the oil sandwiched between the piston P1 and the piston P2 is decompressed, so that the cushioning force of the hydraulic cylinder 23 can be reduced. it can.

  The accumulator 26 is communicated with the hydraulic cylinder 23 and stores oil filled in the middle chamber 23b partitioned by the pistons P1 and P2. Specifically, when the panel P is press-molded, when the die cushion pad 22 reaches the bottom dead center, the oil filled in the middle chamber 23b is discharged and stored in the accumulator 26. This is to suppress jumping (vibration) that occurs when the die cushion pad 22 reaches the bottom dead center and is separated from the slide 10.

  The logic valve 27 is a valve that is in one of two states, an open state and a closed state. The logic valve 27 is provided in a pipe connecting the hydraulic cylinder 23 and the accumulator 26, and is controlled under the control of the control device 30. Thus, the flow path of the pipe between the hydraulic cylinder 23 and the accumulator 26 is opened or closed. The reason why the logic valve is used as a valve for opening and closing the flow path between the hydraulic cylinder 23 and the accumulator 26 is that the opening and closing control is easy and the response time required to change from the closed state to the open state is short. .

  The stroke sensor 28 is a sensor that detects the amount of movement of the die cushion pad 22 in the vertical direction. The pressure sensors 29a to 29c are sensors that detect the hydraulic pressure of the upper chamber 23a, the hydraulic pressure of the middle chamber 23b, and the hydraulic pressure of the lower chamber 23c, respectively. Although not shown in FIG. 1, the detection results of the stroke sensor 28 and the pressure sensors 29 a to 29 c are output to the control device 30.

  The control device 30 controls the motor 25 using the detection results of the rotation angle sensor 13, the stroke sensor 28, and the pressure sensors 29 a to 29 c to adjust the cushion force generated in the hydraulic cylinder 23. Further, by controlling the logic valve 27 using the detection results of the rotation angle sensor 13 and the pressure sensors 29a to 29c, the jump (vibration) generated when the die cushion pad 22 reaches the bottom dead center and the slide 10 is separated. Suppress.

  Here, in order to suppress the spring-up of the die cushion pad 22, it is necessary to reduce the cushioning force of the hydraulic cylinder 23 at an accurate timing when the die cushion pad 22 reaches the bottom dead center and the press molding of the panel P is completed. That is, it is necessary to perform control so that the oil sandwiched between the pistons P1 and P2 is discharged and stored in the accumulator 26 when the die cushion pad 22 reaches bottom dead center. Therefore, the control device 30 controls the logic valve 27 in consideration of the response time required for the logic valve 27 to change from the closed state to the open state.

Specifically, the detection result of the rotation angle sensor 13 when the die cushion pad 22 reaches bottom dead center is θ0 [degree], the rotation angular velocity of the crankshaft 11 is ω [degree / sec], and the response time of the logic valve 27 Is td [sec], the control device 30 performs control to turn the logic valve 27 from the closed state to the open state at the timing when the rotation angle sensor 13 detects the angle θ1 [degree] represented by the following equation (1). Do. That is, the control device 30 controls the logic valve 27 at a time point before the time when the die cushion pad 22 reaches the bottom dead center by the response time of the logic valve 27.
θ1 = θ0−ω × td (1)

  In addition, the control device 30 determines that the pressure state of the hydraulic cylinder 23 detected by the pressure sensors 29a to 29c when the die cushion pad 22 is stopped at a preset position (locking position) near the bottom dead center. When the preset pressure state is reached, the logic valve 27 is controlled from the open state to the closed state. Specifically, the control of the logic valve 27 is performed when it is determined from the detection results of the pressure sensors 29a to 29c that the residual pressure in the hydraulic cylinder 23 has disappeared.

  Next, operation | movement of the press machine in the said structure is demonstrated. FIG. 2 is a flowchart showing an operation of a press machine including a hydraulic die cushion device according to an embodiment of the present invention. First, the slide 10 provided in the press machine 1 and the die cushion pad 22 of the hydraulic die cushion device 20 are respectively arranged at predetermined height positions by the control of the control device 30 or the like before starting the molding of the panel P. (Step S11). Then, it is determined whether or not the panel P is disposed on the lower mold D2 supported on the die cushion pad 22 via the cushion pin 21 (step S12).

  When the above arrangement is completed, the determination result in step S12 is “YES”, the torque of the main motor is controlled by the control of a control device (not shown), and the rotation of the crankshaft 11 is started. Is started (step S13). When the lowering of the slide 10 is started, the control device 30 controls the motor 25 while referring to the detection results of the hydraulic sensors 29a to 29c, and causes the hydraulic cylinder 23 to generate a target cushioning force. Here, the target cushioning force is a cushioning force that should be generated in the hydraulic cylinder 23 when the slide 10 collides with the die cushion pad 22.

  While performing the above control, the control device 30 determines whether or not the slide 10 collides with the die cushion pad 22 based on the detection result of the rotation angle sensor 13 (step S14). If it is determined that the slide 10 has collided with the die cushion pad 22, the determination result in step S14n is “YES”, and the control device 30 applies a certain cushioning force necessary for press-molding the panel P to the hydraulic cylinder 23. The control to generate is performed (step S15). As a result, the slide 10 and the die cushion pad 22 are united vertically by a predetermined distance (stroke) while the panel P is sandwiched between the upper mold D1 and the lower mold D2 with a constant cushioning force. Move down.

  While the control of the cushion force is performed, the control device 30 refers to the detection results of the rotation angle sensor 13 and the stroke sensor 28 to determine whether the die cushion pad 22 has reached the vicinity of the bottom dead center. Judgment is made (step S16). Here, the vicinity of the bottom dead center is a position before the die cushion pad 22 reaches the bottom dead center, and the logic valve 27 is controlled from the closed state to the open state in consideration of the response time of the logic valve 27. Says the position. Specifically, it is a position where the detection result of the rotation angle sensor 13 becomes the angle θ1 shown in the above-described equation (1).

  The control device 30 continues to control the cushioning force shown in step S15 while the determination result in step S16 is “NO”. On the other hand, when the determination result in step S16 is “YES”, the control device 30 performs control to change the logic valve 27 from the closed state to the open state (step S17). By performing such control, the oil sandwiched between the pistons P1 and P2 of the hydraulic cylinder 23 is discharged and accumulated in the accumulator 26 when the die cushion pad 22 reaches bottom dead center.

  When the die cushion pad 22 reaches the bottom dead center, the slide 10 is separated from the die cushion pad 22 and the press molding of the panel P is completed. As a result, the panel P is press-molded according to the upper mold D1 and the lower mold D2. A molded product is obtained. Here, at the timing when the slide 10 is separated from the die cushion pad 22, the cushioning force of the hydraulic cylinder 23 is reduced by the control in step S17 described above. For this reason, even if the slide 10 is separated from the die cushion pad 22, the die cushion pad 22 hardly jumps (vibrates).

  FIG. 3 is a diagram illustrating an example of a cushion force generated in the hydraulic cylinder 23 during pressing. In FIG. 3, time is taken on the horizontal axis, and pressure (cushion force) is taken on the vertical axis. The time t1 on the horizontal axis is the time when the slide 10 collides with the die cushion pad 22, and the time t2 on the horizontal axis is the time when the die cushion pad 22 reaches bottom dead center. As shown in FIG. 3, the cushioning force generated in the hydraulic cylinder 22 suddenly increases at time t1 when the slide 10 collides with the die cushion pad 22, and thereafter until time t2 when the die cushion pad 22 reaches bottom dead center. Has a constant cushioning force.

  Immediately after time t2 when the die cushion pad 22 reaches bottom dead center, conventionally, the slide 10 is separated from the die cushion pad 22, and the cushion cushion force remaining in the hydraulic cylinder causes the die cushion pad to jump up. . For this reason, the cushioning force of the hydraulic cylinder vibrates as indicated by the curve (broken line) denoted by reference numeral F2 in FIG. On the other hand, in the present embodiment, the control is performed to reduce the cushion force by discharging the oil sandwiched between the hydraulic cylinders P1 and P2 at time t2 when the die cushion pad 22 reaches the bottom dead center. However, even if it is separated from the die cushion pad 22, no jumping occurs, and the cushioning force of the hydraulic cylinder 23 hardly oscillates as shown by the curve (solid line) denoted by reference numeral F1 in FIG.

  When the slide 10 is separated from the die cushion pad 22, the control device 30 performs control (locking control) to hold the position of the die cushion pad 22 at a preset locking position near the bottom dead center. While such locking control is performed, the press-molded panel P is removed from the lower mold D2.

  Further, during the above-described locking control, the control device 30 determines whether the pressure state of the hydraulic cylinder 23 detected by the hydraulic sensors 29a to 29c is a preset pressure state (the state in which the residual pressure has disappeared). It is determined whether or not (step S18). And if the judgment result of step S18 becomes "YES", the control apparatus 30 will perform control which makes the logic valve 27 closed from an open state (step S19). As a result, the flow path between the hydraulic cylinder 23 and the accumulator 26 is closed. With the above process, a series of processes for press-molding one panel P is completed. By repeating the process shown in FIG. 2, a plurality of panels P are press-molded.

  As described above, in this embodiment, the accumulator 26 communicating with the hydraulic cylinder 23 and the logic valve 27 for opening and closing the flow path between the hydraulic cylinder 23 and the accumulator 26 are provided, and the die cushion pad 22 is at the bottom dead center. When it reaches, the control device 30 controls the logic valve 27 so that the oil in the hydraulic cylinder 23 (oil sandwiched between the pistons P1 and P2) is discharged and stored in the accumulator 26. For this reason, when the die cushion pad 22 reaches the bottom dead center and the slide 10 is separated from the die cushion pad 22, it is possible to effectively suppress the spring-up of the die cushion pad. As a result, the mechanical load applied to the hydraulic die cushion device 20 can be reduced, the device life can be extended, and noise can be prevented.

  The hydraulic die cushion device and the control method thereof according to one embodiment of the present invention have been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. For example, in the above-described embodiment, the logic valve 27 is used as a valve device that opens and closes the flow path between the hydraulic cylinder 23 and the accumulator 26. However, if the control is easy and the response time is short, the logic valve 27 is not used. It is also possible to use a valve.

10 Slide 20 Hydraulic Die Cushion Device 22 Die Cushion Pad 23 Hydraulic Cylinder 24 Movable Plate 25 Motor 26 Accumulator 27 Logic Valve 29a-29c Hydraulic Sensor 30 Controller P1, P2 Piston

Claims (8)

In a hydraulic die cushion device comprising: a contact member that contacts a contact object and is movable uniaxially in conjunction with the movement of the contact object; and a hydraulic cylinder that drives the contact member;
A pressure accumulator that is in communication with the hydraulic cylinder and stores oil used in the hydraulic cylinder;
A valve device for opening and closing an oil flow path between the hydraulic cylinder and the accumulator;
And a control device that controls the valve device so that oil in the hydraulic cylinder is discharged and stored in the pressure accumulator when the contact member reaches bottom dead center. .   2. The hydraulic die cushion device according to claim 1, wherein the control device controls the valve device in consideration of a response time required for the valve device to change from a closed state to an open state.   3. The hydraulic die cushion device according to claim 2, wherein the control device controls the valve device at a time point before the response time from a time point when the contact member reaches bottom dead center. A pressure sensor for detecting the pressure state of the hydraulic cylinder;
The control device controls the valve device from an open state to a closed state when a pressure state of the hydraulic cylinder detected by the pressure sensor becomes a preset pressure state. Item 4. The hydraulic die cushion device according to Item 3.   5. The hydraulic die cushion device according to claim 4, wherein the valve device is a logic valve that takes two states of an open state and a closed state. The hydraulic cylinder includes a first piston coupled to the contact member;
The hydraulic die cushion device according to any one of claims 1 to 5, further comprising: a second piston for sandwiching oil between the first piston and pressurizing and depressurizing the oil. A movable plate coupled to the second piston;
A motor that is controlled by the control device and that pressurizes and depressurizes oil sandwiched between the first piston and the second piston by moving the movable plate. 6. The hydraulic die cushion device according to 6. In a control method of a hydraulic die cushion device, comprising: a contact member that contacts a contact object and is uniaxially movable in conjunction with the movement of the contact object; and a hydraulic cylinder that drives the contact member;
A flow path between the hydraulic cylinder and the pressure accumulator so that the oil in the hydraulic cylinder is discharged and stored in the pressure accumulator communicated with the hydraulic cylinder when the contact member reaches bottom dead center. A method for controlling a die cushion device, comprising: controlling a valve device that opens and closes the valve.

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