JP2018030164A - Die cushion device - Google Patents

Abstract

To raise and lower a die cushion of a die cushion device at a low cost.
A die cushion pad 14 is disposed below a slide 8 of a press machine, and a hydraulic cylinder 18 supporting the pad 14 is moved up and down together with the pad 14 when a workpiece 10 of the press machine is formed. The magnetostrictive sensor 28 detects the stroke of the cylinder 18 when the workpiece 10 is formed. A plurality of stroke ranges of the pad 14 at the time of forming the workpiece 10, the upward or downward direction of the pad 14 corresponding to these ranges, and the pressure of the hydraulic cylinder 18 are set in the setting unit 30. Based on the stroke detected by the magnetostrictive sensor 28, the control unit 26 determines the upward or downward direction of the hydraulic cylinder, and reads the pressure corresponding to the determined direction and the detected stroke from the setting unit 30. The proportional valve 22 provided in the hydraulic cylinder 18 is controlled so that the pressure is supplied to the cylinder 18.
[Selection] Figure 1

Description

  The present invention relates to a die cushion device used with a press machine, and more particularly to a device capable of adjusting a pressing force to a workpiece.

  2. Description of the Related Art Conventionally, there is a technique for improving the formability by adjusting the characteristics of the pressing force applied to the workpiece of the die cushion device during drawing in a press machine in accordance with the processing characteristics of the workpiece. An example thereof is disclosed in Patent Document 1.

  In the technique of Patent Document 1, a die cushion is connected to a piston of an oil cylinder through a rod, and an oil chamber of the oil cylinder whose volume changes as the piston moves up and down is connected to an oil tank through an electromagnetic solenoid valve. . A pressure sensor is attached to the oil chamber, and the detected value is supplied to a control unit that controls the electromagnetic solenoid valve. An air chamber is provided in the die cushion, and this air chamber is connected to an air tank. The die cushion is lowered by the pressure applied by the slide of the press machine, the air in the air chamber is compressed, and the hydraulic oil in the oil cylinder flows out to the oil tank. The pressure of is adjusted. When the slide is raised, the piston of the oil cylinder raises the die cushion by the compressed air pressure, so that the piston is also raised, and oil is supplied from the oil tank to the oil chamber. The pressure adjustment when the die cushion is lowered is performed by the control unit adjusting the throttle of the electromagnetic solenoid in accordance with the oil chamber pressure detected by the pressure sensor.

JP-A-10-76323

  In the technique of Patent Document 1, when the die cushion is lowered together when the slide is lowered, the pressure can be adjusted. By the way, when the molding method requires a complicated process to be performed while weaving and raising in the molding direction, the pressure of the die cushion cannot be changed when it is raised or lowered. For example, if you stop using air, use a servo valve instead of an electromagnetic solenoid, and perform feedback control based on the pressure of the pressure sensor, you can also control the lifting and lowering of the die cushion. Since it must be used, it is expensive.

  An object of the present invention is to provide a die cushion device capable of controlling the raising and lowering of a die cushion at a low cost.

  In the die cushion device according to one aspect of the present invention, the die cushion pad is disposed below the slide of the press machine. In a press machine, for example, an upper die is attached to a slide, a lower die is placed on a bolster, a work is placed between the upper die and the lower die, and the slide moves downward on the bolster side. The workpiece is pressed between the upper die and the lower die. The die cushion pad is disposed, for example, below the bolster and is coupled to a die cushion pin that supports the workpiece. A fluid pressure cylinder supports the die cushion pad. The fluid pressure cylinder can be lifted and lowered together with the die cushion pad when the workpiece of the press machine is formed. A hydraulic cylinder or an air cylinder can be used as the fluid pressure cylinder. The fluid pressure cylinder is driven by fluid from a fluid pressure source, the fluid pressure cylinder is partitioned into two chambers, for example by a piston, fluid is supplied to one of the chambers and fluid is discharged from the other chamber, The fluid can be raised and lowered by supplying the fluid to the other room and discharging the fluid from the other room. A proportional valve is provided in the fluid pressure cylinder so as to adjust the pressure of the fluid in the fluid pressure cylinder when the workpiece of the press machine is formed. The proportional valve can be provided, for example, so as to adjust the pressure of the fluid supplied from the fluid pressure source to each of the two chambers of the fluid pressure cylinder, or the fluid discharged from each of the two chambers of the fluid pressure cylinder. The pressure at the time of supplying the fluid to one of the two chambers of the fluid pressure cylinder and the pressure at the time of discharging can also be adjusted. Further, the proportional valve may be composed of a pilot type pressure regulating valve and a pilot pressure regulating valve that regulates the pilot pressure of the pressure regulating valve. Stroke detecting means detects the stroke of the fluid pressure cylinder or the die cushion pad during the forming of the workpiece of the press machine. A plurality of stroke ranges of the die cushion pad or the fluid pressure cylinder at the time of forming the workpiece of the press machine, and directions of ascending or descending of the die cushion pad or the fluid pressure cylinder respectively corresponding to the plurality of stroke ranges And the pressure of the fluid pressure cylinder corresponding to each of the plurality of stroke ranges are set in a setting unit. The stroke range may set both an upper limit value and a lower limit value of each stroke range, or when each stroke range is arranged over time, the upper limit value of each stroke range is the next stroke range. In the case of repeatedly matching the lower limit value, only one of the upper limit value and the lower limit value can be set. Based on the stroke detected by the stroke detection means of the fluid pressure cylinder or the die cushion pad, the control unit determines the upward or downward direction of the fluid pressure cylinder or the die cushion pad, and the determined direction The pressure corresponding to the detected stroke is read from the setting unit, and the proportional valve controls the pressure in the fluid pressure cylinder to the read pressure.

  In the die cushion device configured as described above, when the press machine starts to press the workpiece, the die cushion pad descends, and the stroke of the die cushion pad or the hydraulic cylinder is detected by the stroke detecting means and supplied to the control unit. The A control part selects from the stroke range which contains the detected stroke inside. The selected stroke range may be both descending and ascending. In this case, for example, the moving direction of the die cushion pad is determined according to the detected stroke, and the proportional valve is controlled so that the pressure in the fluid pressure cylinder changes to the pressure in the stroke range corresponding to the determined direction. . Therefore, depending on the detected stroke, the pressure on the die cushion pad can be adjusted to a desired value whether it is lowered or raised, and the adjustment does not require a servo valve or feedback control. is there.

  The control unit can determine the direction by comparing the detection value supplied at that time with the detection value supplied last time each time the detection value of the stroke detection means is supplied. . By determining whether the deviation between the current stroke detection value and the previous stroke detection value is positive or negative, it is possible to determine whether it is a decrease or an increase.

  The stroke detecting means may be a sensor provided in the fluid pressure cylinder. For example, the stroke detection means can be provided outside the fluid pressure cylinder. However, when oil is used as the fluid, the stroke detection means may be contaminated with oil and become unusable. Such a problem does not arise by providing it inside.

  As described above, in the die cushion device according to the present invention, the control for raising and lowering the die cushion pad and the fluid pressure cylinder can be performed at low cost without using a servo valve or feedback control.

It is a schematic block diagram of the press machine using the die cushion apparatus of one Embodiment of this invention. It is a figure which shows the data set to the setting part of the die cushion apparatus of FIG. It is a figure which shows the change of the cushion stroke of the die cushion apparatus of FIG. 1, and die cushion pressure. It is a flowchart which shows operation | movement of the control part of the die cushion apparatus of FIG. It is a figure which shows another example of the set data of the die cushion apparatus of FIG. It is a figure which shows the change of the cushion stroke and cushion pressure of the die cushion apparatus controlled based on the data of FIG.

  A die cushion device according to an embodiment of the present invention is used in a press machine. As shown in FIG. 1, the press machine has a bolster 2 on which a lower mold 4 is disposed. A press slide 8 to which an upper mold 6 is attached is disposed above the lower mold 4. The workpiece 10 is disposed between the lower die 4 and the upper die 6 and the press slide 8 is lowered to press the workpiece 10 into a form determined by the lower die 4 and the upper die 6.

  The workpiece 10 is attached to a cushion pin 12 of a die cushion device. The cushion pin 12 is attached to the die cushion pad 14. The die cushion pad 14 is attached to a frame 16 disposed on the lower surface side of the bolster 2 so as to be slidable in the vertical direction. A cushion pin 12 is attached to the upper surface of the die cushion pad 14. Accordingly, when the upper die 6 comes into contact with the workpiece 10 and further presses the workpiece 10 against the lower die 4, the die cushion 14 is lowered together with the cushion pins 12.

  A fluid pressure cylinder, for example, an elevating part 18 a of a hydraulic cylinder 18 is attached to the lower surface of the die cushion pad 14, and a fixing part 18 b of the hydraulic cylinder 18 is fixed to an upper surface of a base 20 attached to the frame 16. . Therefore, the elevating part 18 a can be lowered together with the die cushion pad 14. A piston (not shown) is provided in the fixed portion 18b, and the fixed portion 18b is partitioned into two chambers by the piston, and the piston is coupled to the elevating portion 18a.

  The ascending / descending portion 18a is lifted by supplying a fluid, for example, pressure oil, from a fluid pressure source, for example, a hydraulic pump 22, to one room in the fixed portion 18b via a pressure oil supply path. Is discharged to the hydraulic pump 22, for example, via the pressure oil discharge path, and the lowering of the elevating part 18a supplies the pressure oil to the other room of the fixed part 18b and discharges the pressure oil from the one room Is done by doing. The pressure oil is supplied to one room or the other room via a switching valve (not shown), and the pressure oil is also discharged from the other room or one room via the switching valve.

  A mechanical relief valve 23 is provided on the lower surface of the base 20. The relief valve 23 is of a pilot pressure type, and the pilot pressure is supplied to the proportional relief valve 24, and the control unit 26 controls the relief pressure of the proportional relief valve 24, so that the pilot of the relief valve 23 is controlled. The pressure is controlled, and the pressure of the pressure oil supplied to or discharged from one chamber of the cylinder 18 is controlled to apply a pressing force, for example, a die cushion pressure, when the die cushion pad 14 is raised or lowered. The relief valve 23 and the proportional relief valve 24 constitute a proportional valve. The pilot pressure oil of the mechanical relief valve 23 discharged from the proportional relief valve 24 is returned to the hydraulic pump 22 through the discharge path of the proportional relief valve 24.

  The die cushion pressure is adjusted by the control unit 26 controlling the proportional relief valve 24. Since this adjustment is performed in accordance with the stroke of the die cushion pad 14, a stroke detecting means, for example, a magnetostrictive sensor 28 is provided in the hydraulic cylinder 18 so as to detect this stroke. The stroke detected by the magnetostrictive sensor 28 is supplied to the control unit 26. The value of the stroke increases as the die cushion pad 14 is lowered from the reference position (stroke 0), for example, the position where the upper mold 6 is in contact with the cushion pin 12, and is lowered from the reference position to 120 mm, for example.

  The relationship between the die cushion stroke and the die cushion pressure is determined by the user as shown in FIG. 3, for example. In the drawing, as indicated by a two-dot chain line, the press slide 8 descends and rises from the top dead center to the bottom dead center, maintains the elevated state, descends, and maintains the lowered state. The die cushion pressure is determined corresponding to the die cushion stroke during this period. It is determined that a die cushion pressure of 300 kN is applied while the die cushion pad 14 is lowered from the reference position 0 of the die cushion stroke to the die cushion stroke 20 mm as the press slide 8 is lowered. The die cushion pressure in the die cushion stroke range from 0 to 20 mm is the pressure at the start of molding. It is determined that a die cushion pressure of 250 kN is applied while the die cushion pad 14 is lowered from the die cushion stroke 20 to 40 mm as the press slide 8 is further lowered. It is determined that a die cushion pressure of 200 kN is applied while the die cushion pad 14 descends from the die cushion stroke 40 to 60 mm as the press slide 8 further descends. It is determined that a die cushion pressure of 300 kN is applied while the die cushion pad 14 rises from the die cushion stroke 60 to 50 mm as the press slide 8 rises. It is determined that a die cushion pressure of 150 kN is applied while the die cushion pad 14 is lowered from the cushion stroke 60 to 80 mm as the press slide 8 is lowered. It is determined that a die cushion pressure of 100 kN is applied while the die cushion pad 14 is lowered from the die cushion stroke 80 to 120 mm (position corresponding to the press slide 8 reaching the bottom dead center) as the press slide 8 is lowered. Is done. It is determined that a die cushion pressure of 300 kN is applied while the die cushion pad 14 stops at a die cushion stroke of 120 mm as the press slide 8 stops. The die cushion pad 14 is lifted by, for example, the press slide 8 being lifted, so that the force holding the die cushion pad 14 is weakened, and the force applied by the hydraulic cylinder 18 to the die cushion pad 14 is increased. It happens.

  The stroke ranges described above and the set pressures corresponding to these stroke ranges are set in the setting unit 30 by the user as shown in FIG. However, what is set as setting 1 to setting 6 in FIG. 2 is a range excluding the stroke range of the die cushion stroke 0 to 20 mm. The set pressure of the die cushion stroke from 0 to 20 mm is the pressure at the start of molding as described above, and is set to 300 kN as an initial value separately.

  In the settings 1 to 6, as is clear from FIG. 3, the die cushion pad 14 does not always descend, but as shown in the settings 3 and 6, the die cushion pad 14 rises from the descending position and maintains the raised position. is there. The setting unit 26 simply sets each stroke range and the set pressure corresponding to each stroke range so that the set pressure corresponds to the stroke range including the stroke detected by the magnetostrictive sensor 28. For example, when the proportional relief valve 24 is only controlled, the stroke 50 mm is included in both the setting 2 and the setting 3, and when this stroke is detected, the control unit 26 sets the setting pressure of the setting 2 or the setting 3. Which of these should be set is out of control. Therefore, in the setting unit 30, as shown in FIG. 2, a downward or upward stroke direction is set corresponding to each stroke range. Then, the control unit 26 determines whether the die cushion pad 14 is ascending or descending from the change in the stroke from the magnetostrictive sensor 28, and the stroke range including the detected stroke in the determined direction. The proportional relief valve 24 is controlled so that the set pressure corresponding to is applied to the die cushion pad 14.

  FIG. 4 is a flowchart showing processing performed by the control unit 26 when the die cushion stroke is in the range of 20 to 120 mm. In addition, the process which the control part 26 performs in the range of die cushion stroke 0 to 20 mm is not illustrated. The stroke value of the magnetostrictive sensor 28 is supplied to the control unit 26 at every sampling timing having a predetermined cycle. Each time this stroke value is supplied, the control unit 26 executes the process shown in FIG. Sampling timing is indicated by a broken line in FIG. In this process, the control unit 26 acquires the stroke value supplied this time as S (0) (step S2). Then, the control unit 26 reads out the stroke range including the acquired stroke value from the setting unit 30 (step S4). For example, if the stroke value is set to 30 mm as shown in FIG. 2, 20 to 40 mm of setting 1 is read as a stroke range including 30 mm. If the stroke value is 50 mm, setting 2 and setting 3 are read out as a stroke range including 50 mm. If the stroke value is 110 mm, settings 5 and 6 including 110 mm are read out.

  Subsequent to step S4, S (0) is compared with the stroke value S (-1) supplied at the previous sampling timing and stored as will be described later, and S (0) and S (-1) are compared. Are equal to each other, or whether the S (0) is increased or decreased from S (−1) is determined by the control unit 26 (step S6). The fact that S (0) and S (-1) are equal means that, for example, the stroke value at sampling timing tx1 in FIG. 3 is S (-1), and the stroke value at sampling timing tx2 immediately before tx1 is S. As apparent from (0), the die cushion pad 14 is present at the same position as the previous sampling timing. The fact that S (0) is higher than S (−1) means that, for example, the stroke value at sampling timing tx3 in FIG. 3 is S (0), and the stroke value at sampling timing tx4 immediately before tx3 is S ( As is apparent from -1), this indicates that the die cushion pad 14 is lowered from the position of the previous sampling timing. The fact that S (0) is smaller than S (−1) means that, for example, the stroke value at the sampling timing tx5 in FIG. 3 is S (0), and the stroke value at the sampling timing tx6 immediately before tx5 is S ( As is clear from -1), this indicates that the die cushion pad 14 is raised from the position of the previous sampling timing.

  Accordingly, when it is determined in step S6 that the pressure is increased, the control unit 26 controls the proportional relief valve 24 so that the hydraulic cylinder 18 generates a set pressure in which the downward and direction are selected from the read stroke range. Control (step S8). For example, if S (0) is 50 mm, setting 2 and setting 3 are read in step S4. If the result of determination in step S6 is an increase, setting 2 of 200 kN is set. If it is determined in step S6 that the pressure is reduced or equal, the proportional relief valve 24 is controlled so that the hydraulic cylinder 18 generates a set pressure for which the rise and direction are selected from the read stroke range (step S6). S10). For example, if S (0) is 50 mm, setting 2 and setting 3 are read in step S4. If the result of determination in step S6 is reduced or equal, 300kN of setting 3 is set. The

  Then, following step S8 or S10, when this process is performed next time, in order to use the current stroke value as the previous stroke value, the control unit 26 sets the stroke value of S (0) to S ( -1) (step S12), and the process is terminated.

  With this configuration, the die cushion pressure on the die cushion pad 14 can be controlled using the proportional relief valve 24 based on the stroke value of the magnetostrictive sensor 28 and the data set in the setting unit 30. In particular, without using feedback control, the die cushion pressure can be adjusted not only when the die cushion pad 14 is lowered but also when it is raised according to the change in the stroke of the die cushion pad 14 detected by the magnetostrictive sensor 28. In addition, a laser sensor can be used instead of the magnetostrictive sensor 28. However, in an environment where a lot of oil is used, the oil adheres to the light-shielding portion of the laser sensor, or the oil becomes mist and the laser light is irregularly reflected. Or the laser sensor may become unusable. However, since the magnetostrictive sensor 28 is provided in the hydraulic cylinder 18, it cannot be used even in an environment where a lot of oil is used, and the stroke can be accurately detected.

  The setting unit 30 sets both the lower limit value and the upper limit value of the stroke range. For example, when the stroke ranges to be used are arranged in time series, the upper limit value of the preceding stroke range is the lower limit of the next stroke range. If the values match, only the lower limit value can be set. FIG. 5 shows an example of setting of the setting unit 30 in this case. As shown in FIG. 6, in the die cushion stroke range 0 to 20 mm, the die cushion pressure is 300 kN, and in the next die cushion stroke range 20 to 40 mm, When the pressure is 250 kN, the next die cushion stroke range is 40 to 20 mm, the die cushion pressure is 200 kN, the next die cushion stroke is 20 to 80 mm, the die cushion pressure is 150 kN, and the next die cushion stroke is 80 to 50 mm. Is 200 kN, the next die cushion stroke is 50 to 120 mm, the die cushion pressure is 150 kN, and the last die cushion stroke is 120 to 0 mm. In-out output, when arranging each stroke range in a time series, the upper limit of the stroke range of the respectively preceding coincides with the lower limit value of the next stroke range. In this case, the lower limit stroke value and the set pressure and stroke direction in the stroke range having the stroke value as the lower limit value are set in the setting unit 30. If comprised in this way, since only the lower limit should just set the stroke range, a user's setting operation | work will become easy. In this case, as in the above embodiment, the set pressure for the stroke range of 0 to 20 mm is set separately as an initial value.

  In the above embodiment, the pressure at the time of supplying and discharging the pressure oil to one chamber of the hydraulic cylinder 18 is adjusted, but the pressure at the time of supplying or discharging the pressure oil to each of the two chambers of the hydraulic cylinder 18 is adjusted. The adjustment can also be adjusted. Further, although the relief valve 23 and the proportional relief valve 24 are used as the proportional valves, instead of this, a relief valve of a type that is a single relief valve whose pilot pressure can be controlled by the control unit 26 is used. It can also be used as a proportional valve, or any other type of proportional valve that can be controlled by the control unit 26 can be used. Although a hydraulic cylinder is used as the fluid pressure cylinder, an air cylinder can be used instead. Further, although the magnetostrictive sensor 28 is used as the stroke detecting means, a photoelectric sensor or the like can be used instead. In the above embodiment, the magnetostrictive sensor 28 as the stroke detecting means is attached to the hydraulic cylinder 18, but the stroke detecting means may be provided on the die cushion pad 14.

2 Bolster 4 Lower mold 6 Upper mold 8 Press slide 10 Work 12 Cushion pin 14 Die cushion pad 18 Hydraulic cylinder (hydraulic pressure cylinder)
23 Relief valve (Proportional valve 24 Proportional relief valve (Proportional valve)
26 Control Unit 28 Magnetostrictive Sensor (Stroke Detection Unit)
30 Setting section

Claims (3)

A die cushion pad disposed below the slide of the press machine;
A fluid pressure cylinder that supports the die cushion pad and can be moved up and down together with the die cushion pad at the time of molding the workpiece of the press machine;
A proportional valve provided in the fluid pressure cylinder so as to adjust the pressure of the fluid in the fluid pressure cylinder at the time of forming the workpiece of the press machine;
Stroke detecting means for detecting a stroke of the fluid pressure cylinder or the die cushion pad at the time of forming the workpiece of the press machine;
A plurality of stroke ranges of the die cushion pad or the fluid pressure cylinder at the time of forming the workpiece of the press machine, and directions of ascending or descending of the die cushion pad or the fluid pressure cylinder respectively corresponding to the plurality of stroke ranges And a setting unit in which the pressure of the fluid pressure cylinder corresponding to each of the plurality of stroke ranges is set,
Based on the stroke detected by the stroke detecting means of the fluid pressure cylinder or the die cushion pad, the direction of the fluid pressure cylinder or the die cushion pad is raised or lowered, and the detected direction and the detected direction are determined. A controller that reads the pressure corresponding to the stroke from the setting unit and controls the proportional valve so as to adjust the pressure of the fluid pressure cylinder to the read pressure;
Die cushion device having.   2. The die cushion device according to claim 1, wherein the control unit determines the direction every time the detection value of the stroke detection unit is supplied, and the detection value supplied at that time and the detection value supplied last time. Die cushion device that performs by comparing with.   3. The die cushion device according to claim 1, wherein the stroke detecting means is a sensor provided in the fluid pressure cylinder.

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