JPH0829364B2 - Die cushion device for press machine - Google Patents

Description

The present invention relates to a die cushion device for a press machine.

[Prior Art] FIG. 4 shows an example of a conventional die cushion device of a press machine. A lower die c is provided on a bolster plate b provided on a bed a, and the bolster plate b is further provided. A blank holder e, which penetrates and receives the material d at the upper end, is provided, and a cushion pad g provided at the lower end of the blank holder e is supported on a die cushion h composed of a plurality of stages of air cylinders. The upper die i is not processed, and the material d is clamped by pressing the material d against the blank holder e so that the material i is clamped. Further, the die cushion h is lowered while compressing the die cushion h in the clamped state. By doing so, the material d is formed by the upper and lower molds i and c. In the figure, j indicates a soundproof wall provided so as to cover the press device, and k indicates an opening / closing door provided for moving the mold in and out of the soundproof wall j.

[Problems to be Solved by the Invention] However, in the press machine as described above, when the upper die i is pre-accelerated and hits the material d first (the upper die i and the blank holder e clamp the material). ), The blank holder e
Causes a loud noise (metal sound) when hitting a stopper (not shown) at the raised upper limit position, and particularly a striking impact sound when the upper die i hits the material d for the first time, which is a problem. .

Therefore, conventionally, a heavy soundproof wall j is provided, and at this time, an opening / closing door k is provided on the soundproof wall j in order to replace the upper and lower molds c and i. In spite of having a very large and expensive structure, the sound insulation was not so effective.

Further, in the die cushion h by the air cylinder as described above, since the cushion force is obtained by compressing the air in the air cylinder, the size is increased, and the cushion force is increased with the descending stroke. However, there is a problem that the clamping force is excessively increased on the material, which causes cracks and wrinkles in the material d.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to freely adjust the pressing force using a small hydraulic cylinder and to prevent the generation of a large noise accompanying the press work. .

[Means for Solving the Problems] The present invention includes an upper mold that can move up and down, a lower mold that does not move up and down, and a blank holder that can move up and down to clamp a material between the upper mold and the lower mold. In a die cushion device of a press machine, the blank holder is supported by a hydraulic cylinder so that it can be moved up and down, a flow path equipped with an accumulator capable of accumulating pressure is connected to the upper oil chamber of the hydraulic cylinder, and pressure oil is supplied to the lower oil chamber of the hydraulic cylinder. Connect a flow path equipped with a servo valve that supplies and discharges, and input the detection signal from the position detector that detects the position of the upper die to set the relationship between the upper die position and the pressing force. The die cushion device of the press machine is provided with a control device for sending a control signal for adjusting the flow rate to the servo valve based on the setting signal of.

[Operation] Therefore, in the present invention, since the hydraulic cylinder is used, the device can be downsized as compared with the case where the conventional air cylinder is used, and the detection signal indicating the position of the upper die is input from the position detector. The control device sends a control signal to the servo valve based on the setting signal from the setting device, and the servo valve controls the pressing force of the hydraulic cylinder by supplying / discharging pressure oil to / from the lower oil chamber. When the servo valve is opened to a certain degree during lowering and the lower oil chamber is opened, pressure oil from the accumulator is supplied to the upper oil chamber, the blank holder descends, and noise when clamping the material by the upper die. To prevent the occurrence of
Further, the lowering speed of the blank holder can be adjusted by changing the opening of the servo valve.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

 FIG. 1 is an explanatory view of one embodiment of the present invention.

A vertically oriented hydraulic cylinder 2, 3 is arranged on the lower surface of the fixed base 1, and a piston rod extending through the fixed base 1 upwardly through pistons 4, 5 fitted in the hydraulic cylinder 2, 3 so as to move up and down. Attach 6, 7 as a unit.

A cushion pad 8 is attached to the upper ends of the piston rods 6 and 7, and a blank holder 9 is attached on the cushion pad 8.

A flow path 17 including a pump 13, a check valve 14, a switching valve 15, and a servo valve 16 is connected between the lower oil chambers 10 and 11 of the hydraulic cylinders 2 and 3 and the tank 12 to connect the lower oil chambers 10 and 11. Allows pressure oil to be supplied to and discharged from 11, 11.

Also, the upper oil chambers 18 and 19 of the hydraulic cylinders 2 and 3 and the flow passage 17
A flow passage 25 including a first accumulator 20, a pressure reducing valve 21, a switching valve 22, a second accumulator 23, and a switching valve 24 capable of accumulating pressure is connected between the check valve 14 and the downstream of the check valve 14.
The pressure oil can be supplied to and discharged from the upper oil chambers 18, 19.

Furthermore, a flow passage 27 having a pilot check valve 26 is connected between the flow passage 25 downstream of the switching valve 24 and the tank 12, and the pilot check valve 26 and the flow passage 25 are switched upstream from the pressure reducing valve 21. A flow path 29 equipped with a valve 28 is connected so that the pilot check valve 26 can be opened and closed.

A pressure sensor which detects the hydraulic pressures of the lower oil chamber 11 and the upper oil chamber 19 of the hydraulic cylinder 3 separately and inputs the detection signals 30 and 31 to the pressing force by taking the deviation between the two. 33, 34 are provided, and further a position detector such as a rotary encoder 42 for detecting the rotational angle position of the press drive device 36 for raising and lowering the upper die 35 (that is, the position of the upper die 35) is provided. Detection signal 37 and the comparator
A control device for inputting a deviation signal 38 from 32 as well as a setting signal 40 that sets the relationship between the pressing force from the setter 39 and the rotational angle position
41 is provided, and the servo valve 16 is controlled by a control signal 43 from the control device 41.

In the figure, 44 is a lower mold fixed to the bolster plate, 45 is a material, and 46 is a relief valve.

Next, the operation will be described. The switching valve 15 is switched to the D side to shut off the flow path 17, and the switching valve 24 is switched to the H side so that the pressure oil does not reach the upper oil chambers 18 and 19 of the hydraulic cylinders 2 and 3, and the pressure reducing valve 21 After setting the pressure to be accumulated in the accumulator 23 (lower pressure than the accumulator 20) and switching the switching valve 22 to the E side, the pump 13 is operated to supply pressure oil through the flow path 25 to supply the accumulator 20 and the accumulator. The pressure is accumulated in 23, and after the pressure accumulation is completed, the switching valve 22 is switched to the F side to shut off the accumulator 23 and the pump 13 (hereinafter, the pump 13
Is used for accumulating the accumulator 20), and the switching valve 24 is switched to the G side so that the accumulator 23 and the upper oil chambers 18 and 19 are communicated with each other.

When the upper die 35 is raised, the switching valve 15 is switched to the C side and the servo valve 16 is switched to the B side to supply the oil from the accumulator 20 to the lower oil chambers 10 and 11 and to the upper oil chamber 1.
The blank holder 9 which has discharged the 8 and 19 oils and has accumulated the pressure in the accumulator 23 is raised to the set upper limit position, and in this state, the servo valve 16 is brought into the closed state shown in the drawing.

Then, the upper mold 35 comes down and the blank holder 9
After the material 45 is clamped between and, the material 45 is molded between it and the lower die 44.

However, when the material 45 is clamped, a large impact sound is emitted. Therefore, the switching valve 15 is switched to the D side so that the pump 13 accumulates pressure in the accumulator 20 and the flow path 17
After making it communicate with the tank 42, the control device 41 that inputs the detection signal 37 from the rotary encoder 42 detects the position immediately before the upper die 35 hits the material 45, and the servo valve 16 is turned on for the required time. Just adjust to the B side, supply the pressure oil of the accumulator 23 to the upper oil chambers 18 and 19 via the flow passage 25, and return it from the lower oil chambers 10 and 11 to the oil tank 12 via the flow passages 13 and 16. ,
The blank holder 9 is lowered.

At this time, as shown in FIG. 2, the amount of oil discharged is set so that the lowering speed of the upper mold 35 when the upper mold 35 comes into contact with the material 45 and the lowering speed of the blank holder 9 become substantially equal. It is controlled by the servo valve 16. As a result, the material 45 is gently clamped by the upper mold 35 and the blank holder 9 and almost no impact noise can be prevented.

After the clamp, the cushion pad 8 is pushed down through the blank holder 9 by the lowering of the upper mold 35, and the pressing force is generated by the compression operation of the lower oil chambers 10 and 11. At this time, the servo valve 16 is adjusted to the B side so as to return the oil in the lower oil chambers 10 and 11 to the oil tank 12 while squeezing the oil through the flow path 17, and the returned amount is a control signal from the control device 41. As shown in FIG. 3, by controlling by the 43, adjustment according to the setting signal 41 by the setting device 40 so that the holding force required by the conditions such as the material, size, and drawing depth of the material 45 (Fig. Then, it can be gradually decreased). At this time, the detection signals 30, 31 from the pressure sensors 33, 34, that is, the comparator 32
The deviation signal 38 from is fed back to the control device 41 to perform reliable control.

Next, when the upper die 35 reaches the lower limit position where the operation changes from descending to ascending, that position is set to the rotary encoder.
The detection signal 37 from 42 is detected by the control device 41, and the control signal 43 from the control device 41 holds the servo valve 16 in the closed state shown in FIG.

As a result, the blank holder 9 temporarily stops its operation (locking operation) at the lowermost position, but the upper mold 35 starts to rise during this period, so that the upper mold 35 is stopped.
Will be demolded from the molded material 45.

Then, adjust the servo valve 16 to the B side to adjust the blank holder 9
The blank holder 9 is also made of material 45 at this time.
Also, as shown in FIG. 2, the rising speed is adjusted by the amount of pressure oil supplied to the lower oil chambers 10 and 11 so as to gently match the rising of the upper mold 35 so as not to collide with the upper mold 35. At this time, as the blank holder 9 rises, the accumulator 23 accumulates pressure again.

Also, when the blank holder 9 reaches the upper limit and returns to the initial posture, a collision noise is generated by hitting a stopper (not shown) at the upper limit. Therefore, the position immediately before the upper limit is detected by the control device 41 which inputs a detection signal such as a limit switch, the servo valve 16 is adjusted in advance to the B side by the control signal 43, and the pressure oil of the accumulator 20 is adjusted. By limiting the supply to the lower oil chamber 14, as shown in FIG. 2, after adjusting so that the upper limit stopper may come loose,
Close the servo valve 16 and stop at the upper limit position.

According to the above, by adjusting the servo valve 16, the lower oil chamber 1
It is possible to adjust the pressing force of 0 and 11, and prevent the generation of impact noise during press work.

When the blank holder 9 is not lowered when clamping the material 45, the switching valve 24 is switched to the H side to shut off the upper oil chambers 18, 19 and the accumulator 23, and the switching valve 28 is switched to the J side. The pilot check valve 26 is opened to open the upper oil chambers 18, 19 to the tank 12.

The present invention is not limited to the above-described embodiment, and the oil in the lower oil chambers 10 and 11 must be returned to the tank 12 from the switching valve 15 to raise the blank holder 9 by accumulating once in the accumulator 20. Can be performed many times, if a large capacity pump 13 is used, the accumulator 20 can be unnecessary, a plurality of hydraulic cylinders can be provided, and the load received by the hydraulic cylinders can be arbitrarily distributed. Needless to say, various changes can be made without departing from the scope of the present invention.

[Effects of the Invention] As described above, according to the die cushion device of the press machine of the present invention, since the blank holder is supported only by the hydraulic cylinder, it can be made smaller than the conventional air cylinder, and the lower oil chamber of the hydraulic cylinder can be made smaller. The pressing force can be freely adjusted by the side servo valve, and the accumulator on the upper oil chamber side can significantly reduce the generation of noise during material clamping.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between relative movement speeds of an upper mold and a blank holder according to the present invention, and FIG. 3 shows an example of control of a pressing force. Diagram, No. 4
The figure is an illustration of a conventional example. In the figure, 2 and 3 are hydraulic cylinders, 4 and 5 are pistons, 8 is a cushion pad, 9 is a blank holder, 10 and 11 are lower oil chambers, 1
2 is a tank, 13 is a pump, 16 is a servo valve, 17 is a flow path, 18,
19 is an upper oil chamber, 20, 23 are accumulators, 25 is a flow path, 30,
31 is a detection signal, 32 is a comparator, 33 and 34 are pressure sensors, 35 is an upper die, 36 is a press driving device, 37 is a detection signal, 38 is a deviation signal, 39 is a setting device, 40 is a setting signal, 41 Is a control device, 42 is a rotary encoder, 43 is a control signal, 44 is a lower mold, and 45 is a lower mold.
Indicates a material.

Claims (1)

[Claims] 1. A die cushion device for a press machine, comprising: an upper mold that can move up and down and a lower mold that does not move up and down, and a blank holder that can move up and down to clamp a material between the upper mold and the lower mold. The blank holder is supported by a hydraulic cylinder so that it can be moved up and down, a flow path equipped with an accumulator that can store pressure is connected to the upper oil chamber of the hydraulic cylinder, and a servo valve that supplies and discharges pressure oil is provided in the lower oil chamber of the hydraulic cylinder. The servo valve is connected based on the setting signal from the setter that connects the flow path and inputs the detection signal from the position detector that detects the position of the upper die to set the relationship between the upper die position and the pressing force. A die cushion device for a press machine, which is provided with a control device for sending a control signal for adjusting a flow rate.