JP3319899B2 - Decompression method and apparatus in cold isostatic pressurizing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing pressure after compaction in a cold isostatic press used for powder compacting and the like, and an apparatus for implementing the method.

[0002]

2. Description of the Related Art As means for cold-pressing a powder body,
Conventionally, a rubber press method has been widely used. In this method, a rubber bag in which a preformed powder body is sealed is accommodated in a high-pressure molding container, and a hydrostatic pressure is supplied into the high-pressure molding container to increase the pressure. , The powder is uniformly compressed from the entire circumference of the internal powder, and is pressed and molded.

When the press product thus formed is taken out, if the pressure of the high-pressure molding container is rapidly reduced, the pressure-molded powder body, which has not yet been in a stable state, expands unevenly and cracks the product. appear. For this reason, it is necessary to reduce the pressure with a predetermined pressure reducing characteristic that does not cause such cracks. However, cracks are likely to occur especially when the inside of the high-pressure molded container that generates a large pressure difference from the internal pressure formed by high pressure is under atmospheric pressure. Since it is close to the time, in order to shorten the removal time of the molded product, the pressure in the high-pressure molding container is relatively quickly reduced from the start of depressurization to a predetermined depressurized state, from which the product does not crack. The pressure is gradually reduced at a predetermined pressure reduction rate. That is, during the decompression work, the decompression is performed by dividing the pressure into a primary decompression, which reduces the pressure relatively quickly, and a secondary decompression, which decreases the pressure gradually.

Various decompression means have been proposed. In particular, in order to accurately perform secondary decompression, for example, as disclosed in JP-A-57-109597, the pressure of a pressurizing medium for molding is reduced. A hydraulic pressure is applied to the other side of the receiving piston, and the hydraulic pressure is controlled by a signal from a pre-programmed control device while detecting the pressure of the pressurized medium to be reduced. It is proposed by the present applicant that the pressure medium is depressurized at a predetermined speed by retreating at a predetermined speed.

Further, as shown in Japanese Patent Application Laid-Open No. 60-12298, for example, by switching the hydraulic circuit of a reciprocating type pressure intensifier used at the time of pressure molding, the pressure in the pressure intensifying cylinder is reduced when the pressure intensifying piston is retracted. The applicant of the present invention has proposed a device in which a pressure medium is sucked, and the suction speed is adjusted to a predetermined pattern by a control device to reduce the pressure.

[0006]

As the above-mentioned various conventional pressure reducing means, the former (JP-A-57-109597) is used.
Uses a piston in which a pressurized medium and a hydraulic pressure are opposed to each other as a secondary pressure reducing device, so it is necessary to reduce the pressure only by moving the piston in one stroke, and the size of the cylinder and piston must be increased. As a result, the size of the entire apparatus is increased. Further, since a hydraulic servo valve is used for pressure reduction control, it is inevitably somewhat expensive.

On the other hand, the latter (Japanese Patent Application Laid-Open No. 60-12298) draws a pressurized medium into a pressure-increasing cylinder upon depressurization, so that a part of the powder is filled in the pressurized medium in a high-pressure molding container. When mixed, the powder may enter the intensifier cylinder and damage the inner surface or the like of the cylinder.

Therefore, according to the present invention, the secondary pressure reduction can be accurately performed in accordance with a predetermined pressure reduction characteristic,
It is an object of the present invention to provide a depressurizing method and apparatus in a cold isostatic pressurizing apparatus which can be inexpensive and small in size and does not damage equipment such as an intensifier.

[0009]

In order to solve the above-mentioned problems, the present invention performs cold isostatic pressurization by a primary booster pump and an intensifier, and controls the selection of a plurality of throttle valves and discharges the primary booster pump when the pressure is reduced. A pressure reducing method in a cold isostatic pressurizing apparatus that performs decompression with a predetermined depressurizing characteristic by an amount control, and a cold isostatic pressurizing apparatus including a primary pressurizing pump and an intensifier, including an on-off valve. A pressure-reducing throttle adjusting device constituted by arranging a plurality of pressure-reducing throttle valves in parallel, and a discharge amount adjusting device for a primary booster pump are provided. By providing a control device for performing related control so as to have a pressure reducing characteristic, the pressure reducing device in the cold isostatic pressurizing device is configured.

[0010]

Since the present invention is constructed as described above, it is commercialized by performing a primary pressurization by the operation of a primary pressurizing pump at the time of cold isostatic pressurization and then performing a final high pressure pressurization by an intensifier. When the pressure is reduced by opening the pressure reducing valve, and when the pressure is excessively reduced than the predetermined pressure reducing characteristic, the discharge amount of the primary pressure increasing pump is increased to approach the predetermined pressure reducing characteristic. The discharge amount of the pump is adjusted by opening the throttle valve with a small flow rate among the throttle valves, and when the pressure is still too small, the throttle valve with a larger flow rate or the throttle valve is opened by simultaneously opening a plurality of throttle valves. The control is performed in association with the pressure reduction amount control by adjusting the discharge amount of the pump.

[0011]

An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, water supplied from a water supply pump 2 is supplied to a high-pressure molding container 1 containing a rubber bag in which a pre-formed powder body is sealed by a primary booster pump 4 driven by an inverter motor 3. Raise the plumbing drain 5,
The primary high-pressure water is supplied through the water supply / drain valve 6 and the water supply / drain pipe 7,
The primary pressure of the powder inside is increased.

A high-pressure water supply pipe 8 is connected to the high-pressure molding vessel 1, and after the primary pressurization, water from the water supply pump 2, which is pressurized by a reciprocating intensifier 10, is supplied to the high-pressure molding vessel 1. The primary pressurized powder is pressurized to the final molding pressure to produce a product. This pressure state is maintained for a period a as shown in FIG.
Is a primary pressurization period, during which the pressure is rapidly increased to a predetermined pressure by a low-pressure pump with a large discharge amount, and then, during the secondary pressurization period of the period b, the pressure is increased by a high-pressure pump with a small discharge amount and the predetermined final molding Pressure. Thereafter, in the period c, the high pressure state is maintained for a predetermined time.

When the product thus formed is removed from the high-pressure molding container 1, the pressure of the high-pressure molding container 1 is reduced to atmospheric pressure.
A primary pressure reducing line 13 having a primary pressure reducing throttle 11 and a primary switching valve 12, and a first secondary pressure reducing line 16a, similarly having a first secondary pressure reducing throttle 14a and a first secondary switching valve 15a. A second pressure reducing valve having a secondary pressure reducing throttle 14b and a second secondary switching valve 15b
The secondary decompression line 16b, the third secondary decompression line 14c, and the third secondary decompression line 16c provided with the third secondary switching valve 15c are branched.

The water supply / drain passage 5 is provided with a pressure detector 17, and a detection signal is input to a control device 18. The control device 6 outputs a frequency signal to the inverter motor 3, and outputs the primary switching valve 12, the first A switching operation signal is output to the secondary switching valve 15a, the second secondary switching valve 15b, the third secondary switching valve 15c, and the water supply / drain valve 6.

In the decompression device, after the high pressure is formed in the high pressure molding container 1 and the high pressure state is maintained for a predetermined time as described above, the function of the check valve of the water supply / drain valve 6 is released by the signal of the control device 6. And the primary switching valve 12 is opened. Thereby, the high-pressure water in the high-pressure molding container 1 passes through the water supply / drainage pipe 6 and the primary switching valve 12 and drains into the tank while being regulated by the restriction set by the primary pressure-reducing restriction 11. This aperture amount is small, and therefore, as shown in a period d in FIG.
It rapidly drops to a predetermined pressure.

This pressure reduction state is detected by a pressure detector 17, and when it is detected that the pressure has been reduced to a predetermined pressure, the controller 18 closes the primary switching valve 12, and the first secondary switching valve 1
By opening 5a, the pressure reduction rate is reduced. At this time, if the actual decompression speed is faster than the set decompression speed, the control device 6 increases the drive speed of the inverter motor 3 to increase the discharge amount, and decreases the reduction speed of the pressure in the water supply / drain passage 5. Thereby, the secondary decompression speed in the high-pressure molding container 1 is reduced. Since the pump operated at this time is a low-pressure pump having a large discharge amount, a rapid pressure change does not occur at the time of operation, and a highly responsive and accurate pressure control can be performed by the inverter motor.

In the course of the secondary pressure reduction control, when the pressure reduction speed is rapid and the maximum discharge amount of the primary pressure increase pump 4 controlled by the inverter motor 3 cannot be satisfied,
In order to use the second secondary throttle 14b having a throttle larger than the first secondary throttle 14a, the first secondary switching valve 15a is closed and the second secondary switching valve 15b is opened. Thereafter, the inverter motor 3 is similarly controlled by the signal of the pressure detector 17,
By adjusting the discharge amount of the primary booster pump, the pressure is adjusted so as to match the predetermined pressure reduction characteristic.

If the actual depressurizing speed is still too high even in this depressurizing control state, a secondary restrictor having a larger restrictor can be prepared in advance and selected. Also at this time, the discharge amount control of the primary booster pump by the control of the inverter motor 3 is performed.

On the other hand, the pressure reduction by the first secondary throttle 14a and the primary booster pump 4 controlled by the inverter motor 3
When the pressure reduction control is performed by the discharge amount control of the inverter motor 3, the pressure reduction speed is lower than a predetermined pressure reduction speed.
If the depressurizing speed is still slow even after stopping the operation, the third secondary throttle 14c having a throttle smaller than the first secondary throttle 14a is used. Therefore, the first secondary switching valve 15a is closed and the third secondary switching is performed. The valve 15c is opened. Thereafter, similarly, the inverter motor 3 is controlled by the signal of the pressure detector 17 and the discharge amount of the primary booster pump is adjusted, so that the pressure is adjusted so as to match the predetermined pressure reduction characteristic.

If the actual depressurizing speed is still too slow even in this depressurized state, a secondary restrictor having a smaller restrictor is prepared in advance and selected, or the first secondary restrictor 14a and the second secondary restrictor 14a are selected. It is also possible to use both of 14b. Even at these times, the inverter motor 3
Is controlled so as to match the predetermined pressure reduction characteristics.

By such secondary pressure reduction control, a predetermined secondary pressure reduction in the period e in FIG. 2 is performed. Next, when the pressure becomes almost the atmospheric pressure, the secondary pressure reduction control is stopped and the period e
Natural drainage is performed using a large opening throttle.

In the above embodiment, the throttle amount control of the throttle valve at the time of pressure reduction is performed by selecting a plurality of throttle valves. However, one throttle valve is a variable throttle valve, and the throttle amount is controlled. It can be arbitrarily controlled by the device.

The discharge rate of the primary booster pump can be controlled by various means such as controlling the discharge rate by adjusting the inclination angle of the swash plate pump or controlling the discharge rate of the discharge fluid to the outside, in addition to controlling the discharge rate by the inverter motor. is there.

[0024]

Since the present invention is constructed as described above, it is possible to accurately perform secondary decompression in accordance with a predetermined decompression characteristic, and to use a special device such as a conventional hydraulic-hydraulic opposed piston. This eliminates the necessity of sucking all of the reduced pressure in one step of the piston without any need, so that a small and inexpensive device can be obtained. Further, since a decompression piston is not used, the piston is not damaged by powder or the like mixed in the pressurized medium. Further, since the primary booster pump used as the pressurizing means is used as the secondary depressurizing adjusting means, the apparatus becomes inexpensive, and the primary booster pump is usually a low-pressure pump having a large discharge amount. By performing pressure adjustment at the time, stable control can be performed.

[Brief description of the drawings]

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

FIG. 2 is a pressure diagram.

[Explanation of symbols] 1 ... high pressure vessel, 2 ... water supply pump,
3 ... Inverter motor, 4 ... Primary booster pump, 5 ... Supply / drainage channel, 6 ... Supply / drainage valve, 7 ... Supply / drainage pipe, 8 ... High pressure supply pipe, 10 ... Pressure booster, 11 ... Primary pressure reducing throttle, 12 ... Primary switching valve, 13 … Primary decompression pipeline, 14… secondary decompression throttle, 15
… Secondary switching valve, 16… Secondary pressure reducing line, 1
8. Control device.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-60897 (JP, A) JP-A-61-150798 (JP, A) JP-A-62-121099 (JP, A) 103596 (JP, U) JP-A 1-1114198 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B30B 11/00 B22F 3/04 B30B 5/02

Claims (6)

(57) [Claims] The present invention is characterized in that cold isostatic pressurization is performed by a primary booster pump and an intensifier, and at the time of depressurization, depressurization is performed with a predetermined depressurization characteristic by controlling the throttle amount of a throttle valve and controlling the discharge amount of the primary booster pump. A decompression method in a cold isostatic press. 2. A cold isostatic pressurizing apparatus comprising a primary booster pump and a pressure intensifier, comprising a depressurizing throttle adjusting device and a discharge adjusting device of the primary booster pump, wherein both adjusting devices have predetermined pressure reducing characteristics. A pressure reducing device in a cold isostatic pressurizing device, comprising a control device for performing related control. 3. The pressure reducing device in the cold isostatic pressurizing device according to claim 2, wherein the discharge amount adjusting device is an inverter motor for driving a primary boosting pump. 4. A pressure reducing device in a cold isostatic pressurizing device according to claim 2, further comprising a control device for controlling the pressure reducing throttle adjusting device by selecting a plurality of throttle valves. 5. The depressurizing device in the cold isostatic pressurizing device according to claim 2, further comprising a control device for controlling the depressurizing throttle adjusting device including the variable throttle valve throttle amount adjusting device. 6. A discharge amount adjusting device is controlled by a deviation signal between a predetermined decompression speed and an actual decompression speed, and when a shortage occurs, a throttle amount is controlled and a discharge amount is relatedly controlled. The pressure reducing device in the cold isostatic pressing device according to any one of the above.