JPS5918159B2 - Pressure reduction method and device in cold isostatic pressurization equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and improved proposal for a depressurizing means after pressure molding in a cold isostatic press device used for powder molding and the like.

During pressure molding of powder, hydrostatic pressure is supplied into a high-pressure molding container, as is well known as a rubber press.
A cold isostatic press device for pressure-molding a powder sealed in a container is frequently used as a wet-forming press means for powder.

The outline of this device is that the desired powder is set in a preformed shape and sealed inside a high-pressure molded container with a plug that can be opened and closed tightly via a rubber bag, support, etc., and pressurized water is supplied into the container. The powder is then pressure-molded as the pressure increases, and after the pressure-molding process, the high pressure medium in the container is reduced and the pressed product is taken out. The secondary and stepwise processes are of course automatically controlled according to a predetermined decompression rate or a decompression program based on its pattern.

In this process of pressure reduction, particularly important factors are the secondary pressure reduction start pressure and the secondary pressure reduction rate or their pattern, and if they are incorrect, cracks or cracks will occur in the pressure-molded product inside the container.

The speed and pattern of this secondary pressure reduction depend on the type, composition, and shape of the material to be molded, and it is necessary to set a pressure reduction program suitable for them. The control is performed from beginning to end by a mechanical throttling means, which causes the following problem.

In other words, the opening of the needle valve or orifice provided in the pressure medium circuit is driven by a stepping motor, servo valve, etc., and the pressure is reduced by controlling the flow rate, according to the finger cooling signal from the program setting device. However, direct mechanical throttling of the pressure medium through these valves or orifices will cause the needle valve or orifice itself to wear out due to erosion, making it difficult to perform stable control. , there may be variations in the pressure reduction program, or the pressure reduction rate may change due to changes in viscosity due to temperature changes in the pressure medium, making it impossible to obtain satisfactory reproducibility and requiring pressure to be maintained during pressure reduction. In some cases, there are problems such as inability to compensate for leaks from gaskets, etc., and there is a need for improvement as a pressure reduction control system that can provide stable results over a long period of time.

The present invention has been made to contribute to solving the above-mentioned problems in such a cold isostatic pressing apparatus, and includes:
The feature is that powder or other material to be molded is sealed in a high-pressure molding container, and the material to be molded is pressure-molded by applying hydrostatic pressure within the container. When reducing the pressure of the pressure medium according to a preset pressure reduction rate and other pressure reduction programs, after the primary pressure reduction by a mechanical throttling means in the pressure medium circuit, the pressure of the pressure medium is adjusted to a hydraulic pressure that can be controlled according to the pressure reduction program. Converted,
The secondary pressure reduction of the pressure medium is carried out through the hydraulic control, and its feature is that the device for performing the above pressure reduction includes a primary pressure reduction circuit equipped with mechanical throttling means, and a pressure reduction circuit in the high-pressure molded container. A secondary pressure reduction circuit is equipped with a hydraulic-hydraulic opposing cylinder, which integrally interlocks and connects an introduction cylinder that introduces the hydraulic pressure of the hydraulic pressure unit and a hydraulic cylinder that introduces the hydraulic pressure of the hydraulic unit via a servo valve. The secondary pressure reduction circuit is connected in parallel to the container, and includes a pressure detector for detecting pressure medium pressure, a pressure reduction program setting device for setting a pressure reduction program in advance, and a detection signal of the pressure detector. A servo amplifier is provided for comparing the setting signal from the pressure reduction program setting device and outputting a signal for operating the servo valve.

The present invention will be described in detail below based on the illustrated embodiments. FIG. 1 is an overall explanatory diagram of the method and apparatus of the present invention, FIG. 2 is a sectional view of an example of the structure of a high-pressure molded container, and FIG. FIG. 4 shows an explanatory diagram of one example of a pressure reduction program setting device. In FIG. 1, 1 is a high-pressure molding container; As illustrated in the figure, a main body 21 of the container is provided with a pressure medium inlet 20 for high-pressure liquid as hydrostatic pressure at the bottom, an opening of the main body 21 is sealed via a nut 22 or the like so that it can be opened and closed, and an air vent 23 is provided. As shown in the figure, a powder 28 filled in a rubber bag 27 equipped with a rubber stopper 26 is enclosed via a support 29 in the container main body 21. Pressure molding is performed by supplying high pressure water or other hydraulic medium from the pressure medium inlet 20 and increasing the pressure thereof.

Reference numeral 2 denotes an air vent valve communicating with the air vent hole 23, and 3 is a pressurizing pump, from which a supply circuit 30 is connected via a check valve 4 to the pressure medium inlet 20 by an appropriate pipe line as a pressure medium supply source. They are communicated with each other, and the pressure medium is supplied into the high-pressure molded container 1 and its pressure is increased.

Reference numeral 9 denotes a pressure detector I for detecting the pressure of the pressure medium during pressure molding and the pressure of the pressure medium when performing primary depressurization, and the pressure is indicated by the indicator 13 after passing through the pressure amplifier 11. .

A primary pressure reducing circuit 31 is branched off between the pressurizing pump 3 and the container 1 in the supply circuit 30, and the circuit 31 is equipped with a throttle member 18 such as a needle valve or orifice, and a switching valve 5. By opening the switching valve 5 together with the throttle, the pressure of the pressure medium in the container 1 after pressure molding is primarily reduced.

32 is a secondary pressure reduction circuit according to the present invention, which is branched from a portion of the supply circuit 31 that is closer to the container 1 side than the primary pressure reduction circuit 30, and is connected to the container 1 after the primary pressure reduction through the switching valve 6.
A pressure medium-hydraulic opposing cylinder 7 is provided, into which the pressure medium pressure within is directly introduced.

The cylinder 7 is for converting the pressure medium pressure into hydraulic pressure when performing the secondary pressure reduction of the pressure medium pressure, and the cylinder 7 includes a cylinder 7a for introducing the pressure medium pressure in the container 1;
A structure in which a hydraulic cylinder 7b into which hydraulic pressure is introduced is separated from the hydraulic cylinder 7b via a partition wall, and the head 8a of the piston 8 of the hydraulic cylinder 1b is inserted into the introduction cylinder Ta so as to be freely forward and backward via hydraulic supply and discharge. A hydraulic circuit 33 is attached to the hydraulic cylinder 7b, and a hydraulic unit 16 is attached to the hydraulic cylinder 7b.
, hydraulic pressure is supplied and discharged via the servo valve 17.

The driving servo valve 17 is operated by a pressure reduction program setting device 14 in which a pressure reduction speed or its pattern is set in advance.
The command issued according to the program is compared with the pressure of the pressure medium inside the container 1 detected by the pressure detector 10 and the pressure amplifier 12 provided in the secondary pressure reducing circuit 32, and the appropriate command according to the program is sent to the servo. The piston 8 in the hydraulic cylinder Ib is controlled by the hydraulic circuit 33 via the servo valve 17 to move the head 8a protruding into the introduction cylinder 7a forward and backward, that is, as shown in FIG. In the example, if the head 8a retreats to the right, the pressure medium in the container 1 will expand and be depressurized as the pressure medium introduction space of the introduction cylinder 7a increases. It is designed to reduce the pressure.

The contents of the decompression program setting device 14 are slider type,
There are various methods such as a pinboard method, a magnetic tape method, a card→card reader method, and these will be described later.

The depressurization process according to the present invention will be performed as follows.

That is, the material to be molded 28 filled in the support 29 and the rubber bag 27 is sealed in the container 1 as illustrated in FIG. The medium is supplied into the container 1 from the medium inlet 20, and air is removed from the air vent 23 through the air purge valve 2, the pressure of the pressurized medium by the pump 3 is increased, the molding pressure is detected by the pressure entrainer I9, and the pressure is set at a predetermined pressure. If the pressure has reached , pressurization by the pump 3 is stopped.

In FIG. 3, the vertical axis shows pressure and the horizontal axis shows time, and T1 in the figure is the time required to increase the molding pressure. Pressure molding is performed.

When the pressure forming is completed in this manner, the process moves to a pressure reduction step, and first, as a primary pressure reduction step, primary pressure reduction is performed by throttling by the throttle member 18 in the primary pressure reduction circuit 31 and opening the switching valve 5.

The speed of this primary depressurization is determined by the opening degree of the post-throttling material 18, and in the case of a needle valve, it is changed by manual adjustment, and in the case of an orifice, it is changed by selecting a fixed orifice, and the pressure is detected during this primary depressurization. is performed by the pressure detector I9, and the switching valve 5 is closed at the secondary pressure reduction start pressure P2 shown in the third figure to end the primary pressure reduction, and at time T3 in the same figure.
indicates the time required for primary depressurization.

Next, the switching valve 6 is opened to start the secondary pressure reduction of the present invention by the secondary pressure reduction circuit 32.

That is, in this secondary depressurization, the pressure of the pressure medium in the container 1 which has been subjected to the primary depressurization is detected by the pressure detector 1 [10], and this detected pressure is compared with the pressure of the depressurization curve preset by the depressurization program setting device 14. In comparison, the command signal transmitted by the servo amplifier 15 drives the servo valve 17 in the hydraulic circuit 33 of the hydraulic cylinder 7b in the pressure medium-hydraulic opposing cylinder 7, and the piston 8 in the cylinder Ib is driven.
By supplying appropriate hydraulic pressure to the piston 8, the piston 8 is moved and the accompanying head 8a is moved forward and backward within the introduction cylinder Ta. At this time, if the piston 8 retreats to the right in the figure, the head 8a As the introduction cylinder 7a moves,
The pressure medium in the container 1 communicating with the pressure medium expands, and the secondary pressure reduction of the pressure medium pressure is accurately performed by adjusting the hydraulic cylinder Ib according to the program from the pressure reduction program setting device 14.

According to this secondary pressure reduction, unlike conventional pressure medium throttling operations using valves, orifices, etc., the pressure medium pressure inside the molded container 1 is directly detected and compared with the momentary set pressure in the pressure reduction program setting device 14. However, since it operates on the hydraulic side, which is easy to control, the appropriate depressurization speed and pattern can be obtained smoothly and accurately according to the program, and even if there is a leak from the packing part in each circuit, , since the pressure medium-hydraulic counter cylinder 7 has a pressure increasing function,
It also has a function that can sufficiently compensate for the need to maintain pressure during secondary depressurization, and stable depressurization control with good reproducibility can be easily obtained.

Various types of deceleration program setters are conceivable as the deceleration program setter described above, but in Fig. 3, T4 is the time required for secondary depressurization, and a y b p c indicates each pattern within this time T4. pattern a
, or pattern b or c depends on the material, type, composition, and molding shape of the material to be molded, and must be set arbitrarily. FIG. 4 shows an example of the program setting device 14. As shown in the figure, a plurality of sliders 41 are installed, pressure is plotted on the vertical axis, space is plotted on the horizontal axis, and the decompression pattern is a curved line connecting each adjacent slider position with a straight line. can be obtained.

Therefore, the secondary pressure reduction start pressure P2 is set with the pressure dial 42, and the pressure reduction time T4 is set with the time dial 43, respectively.

In this case, if the number of sliders 41 is increased, a finer decompression pattern can be obtained.As mentioned in this article, it is also possible to use a pinboard method, a magnetic tape, a card→card reader method, etc.

As described above, the present invention is capable of controlling the secondary vacuum start pressure and the secondary vacuum speed or pattern thereof, which produce important results for pressure-molded products, in this type of powder molding, etc., unlike conventional methods. Instead of controlling the pressure of the pressure medium by mechanically restricting its flow path, a pressure medium-hydraulic counter cylinder inserted in the secondary pressure reduction circuit converts the pressure of the pressure medium into oil pressure that is easy to control. Since it is operated according to a secondary depressurization program, mechanical wear and tear is eliminated, stable depressurization control can be easily achieved over a long period of time, and cracks in pressure-molded products can be eliminated.

In addition, it is sufficient to insert a pressure medium-hydraulic opposing cylinder structure in the secondary pressure reduction circuit and communicate with the pressure reduction program setting device, and the necessary mechanism and operation are both simple and easy, and the appropriate and precise cylinder structure that corresponds to the material to be molded can be created. It is excellent in that it can stably obtain the following reduced pressure content.

[Brief explanation of the drawing]

Fig. 1 is an explanatory view of the overall layout of the method and apparatus embodiment of the present invention, Fig. 2 is a sectional view of an example of the high-pressure molded container, Fig. 3 is a pressure one-hour curve diagram of the same pressure molding cycle, and Fig. 4 is It is an explanatory view of the example of the same pressure reduction program setter. 1...High pressure molded container, 3...Pressure pump, 5゜6...Switching valve, 7...Pressure medium-
Hydraulic counter cylinder, 8... Piston, 9, 10
......Pressure detector I, II, 14...Decompression program setting device, 15... Servo amplifier,
16...Hydraulic unit, 17...Servo valve.

Claims (1)

[Scope of Claims] 1. In a device in which powder or other material to be molded is sealed in a high-pressure molding container and the material to be molded is pressure-molded by isostatic pressure within the container, When reducing the pressure of the pressure medium according to a preset pressure reduction rate and other pressure reduction programs, after the primary pressure reduction by a mechanical throttling means in the pressure medium circuit, the pressure of the pressure medium is reduced to a hydraulic pressure that can be controlled according to the pressure reduction program. 1. A method for reducing pressure in a cold isostatic pressurizing device, characterized in that the pressure of the pressure medium is converted and secondary pressure reduction of the pressure medium is performed through the hydraulic control. 2 In the case where powder or other material to be molded is sealed in a high-pressure molding container and the material to be molded is pressure-molded by applying hydrostatic pressure within the container, the pressure of the pressure medium is reduced after the pressure molding. As a device for carrying out the decompression according to a preset depressurization speed and other depressurization programs, it includes a primary decompression circuit 31 equipped with a mechanical throttle means 18, an introduction cylinder 7a that introduces the pressure medium pressure in the high-pressure molded container 1, and a hydraulic unit 16. A secondary pressure reduction circuit 32 is connected in parallel to the high-pressure molded container 1, and is equipped with a hydraulic-hydraulic opposing cylinder 7 integrally connected with a hydraulic cylinder 7b that introduces hydraulic pressure through a servo valve 17. In addition, the secondary pressure reduction circuit 32 includes a pressure detector 10 that detects pressure medium pressure, a pressure reduction program setting device 14 that sets a pressure reduction program in advance, and a detection signal of the pressure detector 10 and a pressure reduction program setting. A pressure reducing device in a cold isostatic pressure pressurizing device, characterized in that it is equipped with a servo amplifier 15 that compares the setting signal from the servo amplifier 14 with a setting signal and outputs a signal for operating the servo valve 17.