JP3107985B2 - Pressure control device of hydraulic press - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for controlling a pressing force of a hydraulic press.

[0002]

2. Description of the Related Art In order to control the pressing force of a conventional hydraulic press,
As the main valve, a manual valve such as a balance piston type valve or a logic valve, an electromagnetic relief valve, or a servo valve is used. In the case of a manual valve, adjustment for setting the pressure is performed by manually adjusting the mechanism of the valve itself.In the case of an electromagnetic relief valve or servo valve, feedback control of the hydraulic pressure is performed for the command pressure value. ing.

In some cases, an accumulator is connected to a main circuit of a hydraulic cylinder to suppress fluctuations in pressure with respect to a set pressure.

[0004]

In the case of a hydraulic press, a press load does not act on the slide until the slide descends and the upper mold contacts the lower mold, but a large load acts simultaneously with the contact. is there. Thus, when the load changes suddenly, the response delay occurs in the manual valve, the electromagnetic relief valve, and the servo valve conventionally used for the pressure control of the cylinder, and a surge pressure occurs in the pilot circuit,
Overshoot may occur or the slide speed may change rapidly.

[0005] In these cases, it becomes a source of vibration of the press machine and adversely affects noise, machine durability, mold life, and machining accuracy. In the latter case, machining accuracy, mold life, and machine accuracy are also affected. Deterioration of durability occurs.

In order to prevent these problems, the setting of the manual valve is changed in accordance with the processing method, the control is performed by controlling the electromagnetic relief valve or the servo valve, or the pulsation of the pressure is taken by an accumulator provided in the main circuit. There are cases.

However, the method of changing the setting of the manual relief valve has the disadvantage that the adjustment is troublesome and cannot respond to disturbances, and the accumulator provided in the main circuit is disadvantageous in that it is large and expensive. There is.

In response to feedback control of an electromagnetic relief valve and a servo valve, the control device is expensive,
A valve having a large capacity such as used in a main circuit of a hydraulic press has a problem in that the response is slow and cannot be sufficiently coped with.

An object of the present invention is to solve the above-mentioned problem at the time of contact with a mold, which adversely affects press working, without requiring complicated and inexpensive adjustment and control.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention controls the pressure of a hydraulic cylinder of a hydraulic press using a hydraulic cylinder. In a relief mechanism consisting of a main valve consisting of a povet valve and a pilot relief valve controlling the main valve, a damper consisting of an elastic body whose volume changes due to hydraulic pressure acting on the pilot circuit between the main valve and the pilot relief valve is optional. And a volume adjustment device provided so that it can be used selectively, and the load acting on the slide,
In a state where a sudden change occurs, a sudden increase in the pressure of the pilot circuit is absorbed by the volume adjusting device, and the main valve is operated to prevent a sudden change in the pressure in the main circuit.

[0011]

A volume control device is provided in the pilot chamber of the main valve of the relief mechanism and in the pilot circuit between the pilot relief valves to absorb sudden pressure changes in the pilot circuit. In the state where the press load does not act on the slide of the hydraulic press,
The pressure of the main circuit connected to the hydraulic cylinder is also significantly lower than the set pressure, is naturally lower than the cracking pressure of the pilot relief valve, and the pilot relief valve is closed.

In this state, when the mold contacts and the pressure of the main circuit increases, the pressure of the pilot circuit connected to the main circuit via the throttle valve also increases, and reaches the cracking pressure of the pilot relief valve. Then, the pilot relief valve starts to open. When the pressure of the main circuit rises above the set pressure, the pressure oil is discharged from the pilot relief valve, the main valve opens, the pressure oil is discharged from the main circuit, and the pressure of the main circuit does not rise significantly above the set pressure. Become like

However, if the pressure in the main circuit rises rapidly, the pressure in the pilot circuit will momentarily exceed due to the delay in the operation of the pilot relief valve, and the operation of the main valve will also be delayed. Circuit pressure is over.

According to the present invention, when the volume control device is provided in the pilot circuit between the main valve and the pilot relief valve, even if the pilot relief valve is the same as the prior art, the instantaneously rising pilot pressure is absorbed by the volume control device. As a result, the main valve is quickly operated, the pressure oil is discharged from the main circuit, and the pressure of the main circuit is maintained at the set pressure.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. FIG. 1 shows a hydraulic circuit according to an embodiment of the present invention. The hydraulic cylinder 6 of the hydraulic press is composed of a cylinder 7 and a piston 8, and a slide 9 for attaching an upper die 16 is connected to the piston 8. Hydraulic cylinder 6
Are fixed to the frame 18 of the hydraulic press. A bolster 19 is fixed to the lower part of the frame 18,
Is attached.

The operation direction of the hydraulic cylinder 6 is switched by the main switching valve 3 by pressure oil discharged from the variable discharge hydraulic pump 1 driven by the motor 2 and driven. The slide 9 is on top before the pressing cycle starts. When the main switching valve 3 enters the position 3A and the processing cycle starts, the pressure oil flows into the main circuit 4, and the oil returns from the rising circuit 5 to the tank, and the piston 8 and the slide 9 start lowering.

The main circuit 4 is provided with a relief mechanism 25, and the pilot circuit 11 is connected to the main circuit 4 of the poppet-type main valve 10 through the orifice 12, thereby obtaining a supply of pressure oil. A pilot relief valve 13 for setting a pressure is connected to the pilot circuit 11 through an orifice 21, and connected to an electromagnetic relief valve 24 used for safety and rapid discharge of a relief mechanism 25, and further a volume control device. 26. The pilot circuit 11 and the dampers 14, 22, 23 of the volume adjusting device 26 are constituted by a switching valve 15 that shuts off communication with an arbitrary combination.

The pilot relief valve 13 of the relief mechanism 25 is set to a pressure at which a required pressure can be generated from the start of the lowering of the slide 9. Although not shown, immediately before the upper mold 16 contacts the lower mold 17, the piston 8 is decelerated to an optimal speed for press working, at which time the hydraulic pump 1 reaches the maximum pressure set value and the hydraulic cylinder 6 Can be issued. In this state, the upper die 16 and the lower die 17 come into contact with each other. The switching valve 15 is actuated from the start of the descent to immediately before the contact with the mold so that the slide 9 becomes one of the dampers 14, 22, and 23, or a combination thereof, optimal for the processing pressure selected at the start of the descent. Connect with pilot circuit.

When the slide 9 reaches the lower limit, the slide 9
The main switching valve 3 is moved to position 3B
At the same time, the main valve 10 is set to the minimum pressure by the electromagnetic relief valve 24. The pressure oil from the hydraulic pump 1 passes through the main switching valve 3, and from the ascending circuit 5 to the lower chamber 8 of the piston 8.
B, the piston 8 starts to rise, and the upper chamber 8 of the piston 8
The oil of A returns from the main circuit 4 to the tank through the main switching valve 3 and the main valve 10. When the piston 8 finishes ascending, the main switching valve 3 enters the neutral state 3C, shuts off the pressure oil from the hydraulic pump 1, and stops the movement of the piston 8.

FIG. 2A shows a value when the volume adjusting device 26 is not operated, and FIG. 2B shows a value when the volume adjusting device 26 is not operated. 11
The pressure waveform is shown in FIG. In FIG. 2A, an overshoot state appears in both the main circuit 4 and the pilot circuit 11 and a surge pressure is generated, but in FIG. 2B,
The pressure converges to the set pressure in an undershoot state, and no surge pressure occurs.

FIG. 3 shows a pressure waveform of the main circuit 4 when the damper is operated when the set pressure is changed. In the waveform (A) showing the pressure change of the main circuit 4 when the damper 14 is operated, the effect of the present invention is obtained, but in the waveform (B), the state slightly overshoots.
Further, in the waveform (C), a surge pressure is generated, and a large overshoot state occurs. In the waveforms (D) and (E) in which another damper 22 is operated, the degree of undershoot is large, and it takes too much time to reach the set pressure. It has become.

From these results, there is a range in which the specific damper is more effective depending on the pressure value at the time of pressurization. To apply to a hydraulic press, select and use a plurality of dampers effective for the set pressure. It is necessary to do. Therefore, it is clear that switching the damper stepwise is effective in preventing generation of surge pressure and pressure overshoot.

[0023]

As described above, the hydraulic press according to the present invention can prevent generation of surge pressure when the upper die contacts the lower die. Since no surge pressure is generated, press working can be performed with less vibration, the life of the mold and the durability of the machine are extended, and the processing accuracy of parts is also improved.

Further, since the actual pressure does not exceed the set pressure, it can be used as an inexpensive hydraulic press for cold forging or the like which is processed in an extreme condition where the actual pressing force is not excessively increased.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram according to an embodiment of the present invention.

FIG. 2A is a diagram showing pressure waveforms of a main circuit and a pilot circuit when the volume adjusting device is not operated in the embodiment of the present invention. FIG. 2B is a diagram showing a main waveform when the volume adjusting device is operated in the embodiment of the present invention. Circuit and pilot circuit pressure waveform diagram

FIG. 3 is a pressure waveform diagram of a main circuit due to a capacitance of a damper in an embodiment of the present invention.

[Explanation of symbols]

1 is a hydraulic pump, 2 is a motor, 3 is a main switching valve, 3
A, 3B are positions, 3C is in a neutral state, 4 is a main circuit, 5 is a rising circuit, 6 is a hydraulic cylinder, 7 is a cylinder,
8 is a piston, 8A is an upper chamber, 8B is a lower chamber, 9 is a slide, 10 is a main valve (poppet type), 11 is a pilot circuit, 12 and 21 are orifices, 13 is a pilot relief valve, 14, 22, and 23. Is a damper, 15 is a switching valve, 16 is an upper mold, 17 is a lower mold, 18 is a frame, 19 is a bolster, 24 is an electromagnetic relief valve, 25 is a relief mechanism, 26 is a volume controller, (A) and (B). , (C),
(D), (E) and (F) are waveforms.

Claims (2)

(57) [Claims] In a hydraulic press using a hydraulic cylinder, in a pressure control of a hydraulic cylinder performed by a relief mechanism including a main valve composed of a povet valve and a pilot relief valve for controlling the main valve, a pressure between the main valve and the pilot relief valve is determined. Pie
The lot circuit includes a volume adjusting device, and the volume adjusting device includes:
An elastic body, and the volume of the elastic body is increased by an applied hydraulic pressure.
It can be used arbitrarily according to the processing pressure while changing
Pressure control apparatus for a hydraulic press, characterized in that that. 2. The volume adjusting device according to claim 1,
A pressure control device for a hydraulic press, comprising a switching valve and a plurality of said elastic bodies, wherein said elastic body is switched by said switching valve.