JPH0596516A - Method and apparatus for molding fine pieces - Google Patents

Abstract

(57) [Summary] [Purpose] A necessary and sufficient amount of fine pieces is supplied to the product cavity to efficiently form the fine pieces. A mold 28 having a product cavity 36, an inlet 30 and an outflow passage 38 communicating with the product cavity 36, a supply passage 26 having an opening / closing valve 22 communicating with the inlet, and an opening / closing valve 46 opening to the inlet. A molding apparatus having the discharge passages 44 and 48 is prepared. While detecting the pressure in the inlet between the cavity and the opening of the discharge passage, the slurry in which the solvent of the supercritical fluid and the fine particles are mixed is introduced at high pressure into the cavity from the supply passage through the inlet. Meanwhile, the solvent in the slurry is caused to flow out from the outflow passage, and the open / close valve 22 is closed and the open / close valve 46 is opened when the detected pressure reaches a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for molding fine particles such as powders, whiskers and fibers, and more particularly to the use of a high pressure solvent composed of a substance having a boiling point lower than room temperature. The present invention relates to a method for molding a resin and a molding apparatus used for carrying out the method.

[0002]

2. Description of the Related Art The molding of fine pieces improved so that a predetermined amount of fine pieces can be reliably and reliably supplied to a product cavity regardless of the size or shape of the fine piece molded body to be formed. As one of the methods, for example, as described in Japanese Patent Application No. 3-177625 and the application filed by the same applicant as the present applicant, a product cavity, an inlet and a discharge passage communicating with the cavity, And a mixing tank, and a molding apparatus having a passage means having an on-off valve in the middle of which the mixing tank and the introduction port are connected to each other, and a solvent having a boiling point lower than room temperature is prepared. And storing a slurry in which fine particles to be molded are mixed in the mixing tank, while detecting the pressure in the inlet or the passage means between the cavity and the on-off valve, the slurry Substantially drained of solvent in said slurry while through the inlet at 10 kg / cm ² or more pressure is introduced into the cavity to the mold outer than said discharge passage, the detected pressure is a predetermined value There has already been proposed a method for molding a fine piece in which the on-off valve is closed at the stage when it has reached the end.

According to this method, when the fine pieces are filled up to the upstream side of the site where the pressure is detected in the inlet or the passage means, the fine pieces filled up to the upstream side of the site where the pressure is detected. Since the pressure at the portion where the pressure is detected by the pressure drop due to the piece becomes substantially atmospheric pressure, the on-off valve is closed when the detected pressure reaches, for example, substantially atmospheric pressure or a predetermined value close to it. By valveing, it is possible to reliably supply a predetermined amount of fine particles to the product cavity without excess or deficiency.

As one of the molding apparatuses for easily and surely carrying out such a method, for example, the above-mentioned Japanese Patent Application No. 3-1.
No. 77625 specification and drawings, a mold having a product cavity, an inlet and a discharge passage communicating with the cavity, a mixing tank, and the mixing tank and the inlet are connected in communication. There has already been proposed a molding apparatus having a passage means having an opening / closing valve and a pressure detecting means for detecting the pressure in the inlet or the pressure in the passage means between the inlet and the opening / closing valve.

According to this molding apparatus, since the pressure detecting means for detecting the pressure in the inlet or the pressure in the passage means between the inlet and the on-off valve is provided, the pressure in the inlet or the passage means. It is possible to reliably detect that the fine pieces have been filled up to the upstream side of the site where is detected, and thus the method described above can be easily and reliably performed.

[0006]

However, in the method and apparatus according to the above-mentioned proposal, even if the opening / closing valve is closed at the stage when the detected pressure reaches a predetermined value, the downstream side of the opening / closing valve Since the slurry remaining in the passage means flows toward the cavity due to the pressure gradient in the passage means, fine particles are also filled in the inlet or the conduit upstream of the portion where the pressure is detected by the pressure detecting means. , Fine particles may be clogged in these parts. Therefore, in such a case, not only the amount of the excessively molded portion removed from the molded body after the completion of molding becomes large, but also the fine pieces excessively filled in the introduction port or the passage means before the next molding is performed. It has to be removed, and there is a problem that the molding efficiency is poor.

The present invention has been made in view of the above problems in the method and apparatus for molding fine pieces according to the above proposal, and regardless of the size or shape of the fine piece molded body to be formed, the fine piece molding is performed. It is possible to supply a necessary and sufficient predetermined amount of fine pieces corresponding to the body to the product cavity, which enables efficient molding of the fine pieces without causing problems such as clogging of the passage means with the fine pieces. An object of the present invention is to provide an improved method and apparatus for molding fine pieces.

[0008]

According to the present invention, the above-mentioned object is to provide a mold having a product cavity, an inlet and an outlet passage communicating with the cavity, and a supply mold in the middle of communicating with the inlet. It has a supply passage means having a control on-off valve and a discharge passage means having a discharge control on-off valve opened at the introduction port, and the introduction port has a cross-sectional area that gradually increases toward the cavity. Prepare a molding apparatus configured, the boiling point is higher than room temperature while detecting the pressure in the inlet between the cavity and the opening of the discharge passage means with the discharge control on-off valve closed. while introducing through said inlet from said supply passage means at substantially 10 kg / cm ² or more pressure and fines to be formed with a solvent consisting of lower materials are mixed slurry into said cavity The solvent in the slurry is allowed to flow out of the mold through the outflow passage, and the supply control on / off valve is closed and the discharge control on / off valve is opened at a stage when the detected pressure reaches a predetermined value. A method for molding a fine piece to be opened, a molding die having a product cavity and an inlet and an outlet passage communicating with the cavity, and a supply passage means having a supply control opening / closing valve in the middle of communication with the inlet. A pressure detecting means for detecting the pressure in the inlet, and a discharge passage having a discharge control opening / closing valve opening to the inlet on the side opposite to the cavity with respect to the portion where the pressure is detected by the pressure detecting means. Means and the inlet is configured to gradually increase in cross-sectional area toward the cavity.

[0009]

According to the molding method of the present invention, when the fine pieces are filled up to the upstream side of the site where the pressure is detected in the inlet, the fine pieces filled upstream of the site where the pressure is detected are filled. Due to the pressure drop due to, the pressure at the portion where the pressure is detected becomes substantially atmospheric pressure. Therefore, by closing the supply control on-off valve and opening the discharge control on-off valve at the time when the detected pressure becomes substantially atmospheric pressure or a predetermined value close to it, excess fine particles are removed. It is possible to reliably prevent the slurry from being supplied to the inlet, and to discharge the slurry remaining in the supply passage means and the inlet downstream of the supply control opening / closing valve to the outside of the supply passage means and the inlet through the discharge passage means. This makes it possible to supply a predetermined amount of fine pieces necessary and sufficient for forming the fine piece molded body to the product cavity.

Further, according to the molding apparatus of the present invention, since the pressure detecting means for detecting the pressure in the inlet is provided,
It is possible to reliably detect that the fine pieces have been filled up to the upstream side of the pressure detection site in the inlet, and the site where the pressure is detected by the pressure detection means is opposite to the cavity. Since it has a discharge passage means having a discharge control opening / closing valve opened on the side of the inlet, it is possible to discharge excess slurry more efficiently from the inside of the inlet, which facilitates the above method. It can be implemented reliably.

According to the molding method and apparatus of the present invention,
Since the cross-sectional area of the inlet gradually increases toward the cavity, it is easy to take out the fine piece molded body having an integral convex portion formed by molding the fine piece in the inlet. Further, even if the fine pieces remain in the supply passage means and the introduction port, it is possible to easily remove the fine pieces remaining after taking out the fine piece molded body from the molding die. ..

The solvent used in the method of the present invention is a supercritical fluid composed of a substance having a boiling point lower than room temperature, and a solvent having a boiling point lower than room temperature, and subjected to a pressure of substantially 10 kg / cm ² or more. Regardless of whether the solvent is a liquid in a pressurized state or a solvent in a gaseous state that is pressurized to a pressure of 10 kg / cm ² or more at a critical pressure or less, the cavity is close to the inlet. The pressure gradually decreases from a pressure of substantially 10 kg / cm ² or more to a pressure close to the atmospheric pressure in the vicinity of the outflow passage, and this pressure gradient causes fine particles to be generated in the vicinity of the outflow passage of the product cavity. While this is being pressed against the wall surface of the part, it is finally gradually molded to the inlet, and this phenomenon progresses rapidly, so that a dense and homogeneous molded body of fine pieces can be efficiently and inexpensively formed.

Further, the high-pressure solvent forming the slurry lowers its pressure rapidly in the process of passing through the product cavity and the outflow passage, and due to the pressure gradient, it efficiently passes through the outflow passage from the inside of the product cavity. Outflow into the atmosphere. Therefore, in the process in which the molded product of the fine pieces is formed in the product cavity as described above, the solvent is efficiently removed from the molded product in the process of forming, whereby the molding of the fine pieces and the removal of the solvent are simultaneously performed. Since this is also carried out, a molded body of fine pieces can be formed efficiently and at low cost.

[0014]

[Supplementary Explanation of Means for Solving the Problems] The solvent in the method of the present invention is any substance which has a boiling point lower than room temperature and which can be pressurized to a pressure of substantially 10 kg / cm ² or more. However, CO ₂ , air, N _{2 and the} like are preferable in terms of price, safety, easiness of handling and the like.

When the pressure of the slurry when it is supplied to the forming die is 10 kg / cm ² or less, a steep pressure gradient required for forming fine pieces can be formed in the product cavity of the forming die. Therefore, a high-density molded body cannot be efficiently formed. Therefore, in the method of the present invention, the pressure of the slurry when it is supplied to the mold is 1
It is set to 0 kg / cm ² or more.

The present invention will be described below in detail with reference to the accompanying drawings.

[0017]

Embodiment 1 FIG. 1 is a schematic configuration diagram showing a first embodiment of a molding apparatus according to the present invention.

In FIG. 1, 10 indicates a mixing tank,
Although not shown in the figure, the mixing chamber 12 of the mixing tank is connected by a conduit 14 to a cylinder for storing CO ₂ therein. The mixing chamber 12 is heated to a predetermined temperature by a heater 16, and a stirrer 20 is provided in the mixing chamber 12 for stirring the fine pieces 18 to be formed and charged in the mixing chamber. Has been.

The mixing chamber 12 is connected to a slurry inlet 30 of a molding die 28 by a conduit 26 having a normally closed electromagnetic on-off valve 22 as a supply control on-off valve and a pump 24 on the way. In the illustrated embodiment, the mold 28 comprises an upper mold 32 and a lower mold 34 which, when fitted together, define a slurry inlet 30 and a product cavity 36 communicating with the inlet. It is like this. The product cavity 36 communicates with the atmosphere through a minute gas outflow passage 38 formed as a minute gap between the parting surfaces of the upper mold 32 and the lower mold 34.

In the illustrated embodiment, the slurry inlet 3
0 has a conical taper shape that opens toward the product cavity 36, so that its cross-sectional area gradually increases toward the product cavity. The molding die 28 is provided with a pressure detecting passage 40 that opens to the slurry introducing port 30 at one end, and a pressure sensor 42 is provided at the other end of the passage 40, whereby the pressure P in the slurry introducing port is detected. It is supposed to be done. Further, the molding die 28 is provided with a slurry discharge passage 44 communicating with the slurry introduction port 30 on the side opposite to the product cavity with respect to the opening of the passage 40, and the discharge control opening / closing is provided at the other end of the passage. A discharge conduit 48 having a normally-open electromagnetic on-off valve 46 as a valve is connected.

As shown in the figure, the electromagnetic on-off valves 22, 46 and the pump 24 are controlled by an electronic control unit 50. The control device 50 is, for example, a CPU, RAM, RO
A general microcomputer having an M and an input / output port device may be used.
The electromagnetic on-off valve and pump are controlled according to the control flow shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing a molding start command switch not shown in FIG.

First, in the first step 10, the control signal is output to the electromagnetic opening / closing valve 46 to close the valve, and in step 20, the control signal is output to the electromagnetic opening / closing valve 22. As a result, the on-off valve is opened, and then the pump 24 is operated in step 30.

In the next step 40, after waiting for a predetermined time such as 1 second, in step 50 the pressure sensor 4
A signal indicating the pressure P in the slurry inlet detected by 2 is read, and in step 60, it is determined whether or not the pressure P is less than or equal to a threshold value Pc (a positive constant lower than the slurry supply pressure). If it is determined that the pressure P is not less than or equal to Pc, the process returns to step 50, and if it is determined that the pressure P is less than or equal to Pc, the process proceeds to step 70.

In step 70, the supply of the control signal to the electromagnetic opening / closing valve 22 is stopped to close the opening / closing valve, and in step 80, the supply of the control signal to the electromagnetic opening / closing valve 46 is stopped. By doing so, the on-off valve is opened, and then the operation of the pump 24 is stopped in step 90, whereby the control by the control flow shown in FIG. 2 is completed.

Next, a first embodiment of the molding method of the present invention, which is carried out by using the molding apparatus configured as described above, will be described.

According to the present invention, a powder compact mainly composed of silicon nitride powder was formed by using CO ₂ in a supercritical state as a solvent and using the compacting apparatus constructed as described above.

First, a raw material powder consisting of 9.6 kg of silicon nitride powder (average particle size 0.5 μm), 200 g of yttrium oxide (average particle size 0.1 μm) and 200 g of alumina powder (average particle size 0.1 μm). 18 was loaded into the mixing chamber 12 of the mixing tank 10. Next, with the solenoid on-off valve 22 closed, CO ₂ 15 is supplied into the mixing chamber 12 from a cylinder (not shown) via the conduit 14 while pressurizing with a pump (not shown). temperature of CO ₂ by heating the CO ₂ by the heater 16 80
It was brought into a supercritical state at a temperature of 120 ° C. and a pressure of 120 kg / cm ² .

Next, the stirrer 20 is rotated for 3 hours to stir and mix the raw material powder and CO _{2 in a} supercritical state,
As a result, a slurry of raw material powder using CO ₂ in a supercritical state as a solvent was formed. Next, the electromagnetic on-off valve 46 is closed,
By opening the electromagnetic opening / closing valve 22 and operating the pump 24, 300 kg / a part of the slurry in the mixing chamber 20
It was pressurized to cm ² and injected into the product cavity 36 of the molding die 28. When the pressure P reaches Pc (= 20 kg / cm ² ), the on-off valve 22 is closed, the on-off valve 46 is opened, the pump 24 is stopped, and thereby the slurry supply is stopped and the conduit is 26 and the excess slurry in the inlet 30 were discharged through the passage 44 and the conduit 48.

Although not visually observable in this case, the supercritical CO ₂ in the slurry introduced into the product cavity 36 is communicated with the atmosphere by the gas outlet passage 38. Therefore, it is presumed that the pressure in the cavity was gradually decreased, and the gas became a gas at substantially atmospheric pressure from the supercritical state and was released into the atmosphere. Further, in the product cavity 36, a pressure gradient is generated in which the pressure gradually decreases from the vicinity of the slurry introduction port 30 toward the gas outflow passage, and this pressure gradient causes the raw material powder to be in a portion near the gas outflow passage of the molding die. It is speculated that it was gradually pressed while being pressed against the inner wall surface.

Next, the molding die 28 is disassembled, the powder compact 52 molded in the product cavity 36 is taken out, and its size, shape, and density are investigated, and it is found that this compact has the same size and shape as the product cavity 36. It has been confirmed that it has a corresponding exact size and shape, a uniform density throughout and no defects such as shrinkage or cracking.
Further, in this case, the powder compact can be easily taken out from the lower mold of the molding die, and the raw material powder is filled only to the downstream side of the opening of the slurry discharge passage 44 in the inlet port 30, and the conduit 26 It was confirmed that a large amount of the raw material powder did not remain in the inside so that it was clogged.

As a solvent, CO _{2 in} a liquid state pressurized to 100 kg / cm ² was used, and a part of the slurry was added to 200
Product cavity 3 of molding die 28 by pressurizing to kg / cm ^2.
When injected into 6 and as solvent, 15 kg / cm ²
Similarly, the raw material powder can be satisfactorily molded by using CO _{2 in} a gas state pressurized to a pressure of 60 kg / cm ² and injecting the slurry into the product cavity of the molding die. It was

As in the case of the above-mentioned embodiment, in the former case, the liquid CO ₂ in the slurry introduced into the product cavity gradually lowers its pressure in the cavity, and the CO ₂ in the liquid state becomes a normal gas. It is presumed that the gas was released into the atmosphere in this state. In the latter case, the high-pressure gaseous CO ₂ in the slurry introduced into the product cavity gradually lowers its pressure in the cavity, and It is presumed that the gas state was substantially atmospheric pressure and was released into the atmosphere.

Embodiment 2 FIG. 3 is a schematic configuration diagram showing a second embodiment of the molding apparatus according to the present invention, and FIG. 4 is a flow chart showing a control flow achieved by the electronic control unit of this embodiment. In FIG. 3, the parts substantially the same as those shown in FIG. 1 are designated by the same reference numerals as those shown in FIG. 1, and in FIG. Substantially the same steps as those shown in FIG. 2 are given the same step numbers as the step numbers given in FIG.

In this embodiment, the on-off valve 22 in the first embodiment is replaced with a three-port three-position switching type control valve 54 having three ports a to c. The other end of the conduit 26a, which is connected to the mixing tank 10 at one end, is connected to the a port, and the molding die 28 is connected to the b port at one end.
Is connected to the other end of the conduit 26b, and the c port is connected at one end to the other end of a conduit 56 connected to a high pressure gas cylinder (not shown).

The control valve 54 has a first position 54a which shuts off communication with all ports, and a port b which shuts off port c.
The control unit 50 is adapted to switch between a second position 54b for communicating connection with the port and a third position 54c for blocking connection of the a port and communicating connection between the c port and the b port.
First position 5 when no more control signal is supplied
4a is maintained.

The control valve 54, the electromagnetic on-off valve 46, and the pump 24 in this embodiment are controlled by the electronic control unit 50 according to the flow chart shown in FIG.

Step 20 that follows step 10
, The control valve 54 is switched to its second position 54b, thereby connecting the conduits 26a and 26b in communication. Steps 30 to 60 are executed in the same manner as in the case of the first embodiment, and when it is judged in step 50 that the molding of the fine pieces is completed, the control valve 54 is set to the first step in step 70. It is switched to the one position 54a, which cuts off the communication of all ports.

Next, at step 80, the solenoid opening / closing valve 46
Is opened, the slurry in the inlet 30 and the conduit 26b is discharged through the passage 44 and the conduit 48, and then in step 82, the control valve 54 is moved to the third position 5 thereof.
4c, whereby high pressure gas is introduced into conduit 26b. In the next step 84, the high pressure gas introduced as described above is maintained for a time sufficient for the fine particles remaining in conduit 26b and inlet 30 to be expelled via passageway 44 and conduit 48, and then At step 90, the operation of the pump 24 is stopped, then at step 92 the control valve 54 is switched to its first position 54a, and the control according to the flow chart shown in FIG. 4 is completed.

Therefore, according to this embodiment, the high pressure gas is caused to flow after the completion of the molding, so that the conduit 26b and the inlet 30 are formed.
Since fine particles remaining inside can be removed, it is possible to form a high-quality molded product having a desired composition even when powder molded products are continuously manufactured using raw material powders having different compositions. ..

The conduit 26 is passed through the conduit 56 and the control valve 54.
high pressure gas introduced into the b is not limited to CO ₂ in the supercritical state, for example it may be any high-pressure gas such critical points following CO ₂ and compressed air.

As a second embodiment of the molding method of the present invention using the molding apparatus constructed as described above, in step 84, the pressure is about 60 kg / cm ² via the conduit 56 and the control valve 54.
The raw material powder was molded under the same procedure and conditions as in Example 1 except that the high-pressure CO ₂ was introduced for about 20 seconds.

As a result, the molded body formed in this embodiment also has an accurate size and shape corresponding to the size and shape of the product cavity 36 and has a uniform density throughout.
It was confirmed that defects such as shrinkage and cracks did not occur at all. Also in the case of this embodiment, the powder compact can be easily taken out from the lower die of the molding die, and the raw material powder is filled only to the downstream side of the opening of the slurry discharge passage 44 in the inlet 30. Therefore, it was confirmed that almost no raw material powder remained in the conduit 26.

Embodiment 3 FIG. 5 is a schematic structural view showing a third embodiment of the molding apparatus according to the present invention, FIG. 6 is an enlarged partial vertical sectional view showing the mixing tank shown in FIG. 5, and FIG. It is a flowchart which shows the control flow achieved by the electronic control apparatus of an example. In FIG. 5, the parts substantially the same as those shown in FIG. 1 are designated by the same reference numerals as those shown in FIG. 1, and in FIG. Substantially the same steps as those shown in FIG. 2 are given the same step numbers as the step numbers given in FIG.

In this embodiment, the electromagnetic on-off valve 22 is provided in the conduit 14, and the pump 24 is on-off valve 2.
2 and a cylinder 58 which is connected to the other end of the conduit 14 and which stores high-pressure CO ₂ therein. Pump 24
An accumulator 60 is provided between the on-off valve 22 and the on-off valve 22, and the pressure Pa in the accumulator is a pressure sensor 62.
Is detected by the.

The mixing vessel 10 is provided with a fine piece supply device 64. As shown in detail in FIG. 6, the mixing tank 1
Reference numeral 0 is composed of a main body member 68 and a lid member 70 which are fixed to each other by bolts 66 and cooperate with each other to define the mixing chamber 12, and the fine piece supply device 64 is fixed to the lid member 70. The fine piece supply device 64 has a hopper 72, and the communication between the internal passage 74 and the mixing chamber 12 is controlled by a valve device 76.

The valve device 76 includes a valve element 80 supported by a base portion of the hopper 72 by a rod portion so as to be capable of reciprocating along an axis 78, and a nut screwed to an upper end of the rod portion of the valve element 80 in the drawing. The compression coil spring 86 elastically mounted between the spring seat 84 fixed to the rod portion by 82 and the base portion of the hopper 72 brings the umbrella portion to the valve closed position where it comes into contact with the valve seat 88 provided on the lid member 70. Being energized. Thus, the valve device 76 pushes the rod portion of the valve element downward in the figure along the axis 78 against the spring force of the compression coil spring 86, without loosening the bolt 66 and removing the lid member from the main body member. The predetermined amount of fine pieces in the hopper 72 can be supplied into the mixing chamber 12.

Also, in the illustrated embodiment, the body member 68
And lid member 70 are provided with passageways 90 and 92 to which conduits 26 and 14, respectively, are connected. The passage 90 communicates with the tip of the inverted conical lower end of the mixing chamber 12, and the passage 92 is provided at a position laterally offset from the passage 90, whereby the first and second passages are provided. Even if the fine pieces in the mixing chamber 12 are not stirred by the stirrer 20 as in the embodiment, the flow of a high-pressure solvent such as CO _{2 in} a supercritical state supplied into the mixing chamber through the conduit 14 and the passage 92. A substantially uniform slurry is formed by the stirring action by the. Needless to say, an agitator similar to the agitator 20 in the first and second embodiments may be provided in the mixing chamber 12.

Further, in the embodiment shown in the drawings, the filter described in Japanese Patent Application No. 3-169236 and the drawing of the same applicant as the applicant of the present invention is provided in the product cavity 36 of the molding die 28. Similarly to the above, a filter 94 that allows passage of a fluid such as a supercritical fluid and blocks passage of fine particles is disposed in proximity to the gas outflow passage 38.

Solenoid on-off valves 22 and 4 in this embodiment
6. The pump 24 is controlled by the electronic control unit 50 according to the flow chart shown in FIG.

In this embodiment, the pump 24 is operated in step 12 after step 10, and the pressure Pa in the accumulator 60 detected by the pressure sensor 62 in step 14 is read. If it is determined in step 14 whether the pressure Pa is equal to or higher than the upper limit threshold Psu, and if it is determined that the pressure Pa is not equal to Psu or higher, the process returns to step 14. When it is determined that the pressure Pa is equal to or higher than Psu, the pump 24 is stopped in step 18 and then step 2
Go to 0.

Steps 20 to 80 are executed in the same manner as in the case of the first embodiment. In step 100, it is judged whether or not the next molding is performed, and it is judged that the next molding is not performed. When it is performed, the control according to the flowchart shown in FIG. 7 is terminated, and when it is determined that the next molding is performed, the process proceeds to step 110. In step 110, the pressure Pa in the accumulator 60 detected by the pressure sensor 62 is read, and in step 120 it is determined whether or not the pressure Pa is less than or equal to the lower limit threshold Psl. When it is determined that the pressure Pa is equal to or lower than Psl, the process returns to step 10, and when it is determined that the pressure Pa is not equal to or lower than Psl, step 130 is performed.
Then, after the on-off valve 46 is closed, the process returns to step 20.

Thus, the molding apparatuses of the first and second embodiments are suitable for continuously producing a large number of the same kind of fine piece moldings, whereas the molding apparatus of the third embodiment is a fine molding machine. Since a predetermined amount of fine pieces can be supplied from the piece supply device 64 into the mixing tank 10, it is particularly suitable for batch-manufacturing various kinds of fine piece molded bodies.

In the molding apparatus of this embodiment, when the determination in step 60 is YES, the electromagnetic opening / closing valve 46 is first opened in step 80, and then the mixing tank 1 is operated.
0, the conduit 26, and the excess fine particles in the inlet 30 are the passages 44.
And its state is maintained for a sufficient time to be discharged through the conduit 48, and then the on-off valve 22 is closed, which causes excess fine particles in the conduit 26 and the inlet 30 as in the second embodiment. Molding equipment may be used so that substantially no pieces remain.

Further, the pump 24 in this embodiment responds to the pressure Pa in the accumulator 60, and when the pressure Pa becomes, for example, a threshold value Psu or more, the discharge pressure thereof is substantially Psu.
It may be a variable discharge pressure pump which is automatically controlled to.

First, 455 g of silicon nitride powder (average particle size 0.5 μm), 30 g of yttrium oxide (average particle size 0.1 μm) and 15 g of alumina powder (average particle size 0.1
The raw material powder 18 consisting of .mu.m) was charged into the mixing chamber 12 of the mixing tank 10 from the fine piece feeder 64. Next, the electromagnetic on-off valve 46 is closed and the pump 24 is operated, whereby CO ₂ is supplied from the cylinder 58 to the accumulator 60 maintained at a temperature of 60 ° C. while being pressurized, and CO ₂ is supplied to the temperature 60.
It was brought to a supercritical state at a temperature of 200 ° C. and a pressure of 200 kg / cm ² or more.

Next, the electromagnetic on-off valve 22 is opened to introduce CO ₂ in the supercritical state into the mixing chamber 12, and a slurry consisting of the raw material powder and the CO _{2 in the} supercritical state is formed in the mixing chamber 12. The slurry was supplied into the product cavity 36 via the conduit 26 and the inlet 30. Pressure P is Pc (= 20k
g / cm ² ) when the pump 24 is stopped,
The on-off valve 22 is closed and the on-off valve 46 is opened, whereby the slurry supply is stopped and the conduit 26 and the inlet 3 are provided.
Excess slurry in 0 was discharged via passage 44 and conduit 48.

The molded body thus formed also has an accurate size and shape corresponding to the size and shape of the product cavity 36, has a uniform density throughout, and has no defects such as shrinkage and cracks. It was confirmed. Also in the case of this embodiment, the powder compact can be easily taken out from the lower die of the molding die, and the raw material powder is filled only to the downstream side of the opening of the slurry discharge passage 44 in the inlet 30. Therefore, it was confirmed that almost no raw material powder remained in the conduit 26.

Although the present invention has been described above in detail with reference to specific embodiments, the present invention is not limited to these embodiments, and various other embodiments within the scope of the present invention. It will be apparent to those skilled in the art that
For example, the fine pieces to be molded are not limited to powder as in the above-mentioned embodiment, but may be in other forms such as whiskers and short fibers.

Regardless of whether or not a plurality of compacts to be formed have the same size and shape, the opening / closing valve 46 is opened and the excess slurry in the conduit 26 and the inlet 30 is discharged. In the step, the mold in which the fine pieces are filled in the product cavity is removed from the conduit 26, and the molds to be filled next are sequentially connected to the conduit to more efficiently manufacture a plurality of molded bodies. May be done.

Further, in FIG. 6, the passages 90 and 92 are shown in FIG.
6 extends in the vertical direction, the passage 92 extends obliquely with respect to the paper surface of FIG.
The high-pressure solvent supplied to the mixing chamber via the above may form a swirl in the mixing chamber so that the fine particles and the solvent are mixed more effectively.

[0061]

As is apparent from the above description, according to the molding method of the present invention, the pressure is detected when the fine pieces are filled up to the upstream side of the portion in the inlet where the pressure is detected. The pressure of the portion where the pressure is detected due to the pressure drop due to the fine pieces filled on the upstream side of the portion becomes substantially atmospheric pressure. Therefore, by closing the supply control on-off valve and opening the discharge control on-off valve at the time when the detected pressure becomes substantially atmospheric pressure or a predetermined value close to it, excess fine particles are removed. It is possible to reliably prevent the slurry from being supplied to the inlet, and to discharge the slurry remaining in the supply passage means and the inlet downstream of the supply control opening / closing valve to the outside of the supply passage means and the inlet through the discharge passage means. This makes it possible to supply a predetermined amount of fine pieces necessary and sufficient for forming a fine piece molded body to the product cavity.

Further, according to the molding apparatus of the present invention, since the pressure detecting means for detecting the pressure in the inlet is provided,
It is possible to reliably detect that the fine pieces have been filled up to the upstream side of the pressure detection site in the inlet, and the site where the pressure is detected by the pressure detection means is opposite to the cavity. Since it has the discharge passage means having the discharge control opening / closing valve opened to the inlet on the side, the excess slurry can be discharged efficiently from the inside of the inlet, which facilitates the above method. It can be implemented reliably.

According to the molding method and apparatus of the present invention,
Since the cross-sectional area of the inlet gradually increases toward the cavity, it is easy to take out the fine piece molded body having an integral convex portion formed by molding the fine piece in the inlet. Further, even if the fine pieces remain in the supply passage means and the introduction port, the fine pieces remaining after the fine piece molded body is taken out from the mold can be easily removed as necessary, and thus a large number can be obtained. It is possible to efficiently form the above-mentioned fine piece molded body, and it is possible to form a plurality of fine piece molded bodies with high quality even when the composition of the fine pieces is different.

Further, according to the molding method and the molding apparatus of the present invention, a predetermined amount of fine pieces necessary and sufficient for forming a fine piece molded body can be supplied to the product cavity. Compared to the case without a molding device,
The yield of fine particles and solvent can be improved, and even when multiple molded products with different product cavity sizes and shapes are formed one after another, molding can be performed easily and efficiently without trial molding. can do.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a molding apparatus according to the present invention.

FIG. 2 is a flowchart showing a control flow achieved by the electronic control unit of the first embodiment.

FIG. 3 is a schematic configuration diagram showing a second embodiment of the molding apparatus according to the present invention.

FIG. 4 is a flowchart showing a control flow achieved by the electronic control device of the second embodiment.

FIG. 5 is a schematic configuration diagram showing a third embodiment of the molding apparatus according to the present invention.

6 is an enlarged partial vertical sectional view showing the mixing tank shown in FIG.

FIG. 7 is a flowchart showing a control flow achieved by the electronic control device of the third embodiment.

[Explanation of symbols]

10 ... Mixing tank 15 ... CO ₂ 18 ... Raw powder 22 ... Open / close valve 28 ... Mold 30 ... Slurry inlet 36 ... Product cavity 38 ... Gas outflow passage 42 ... Pressure sensor 44 ... Slurry discharge passage 46 ... Open / close valve 52 ... Powder Molded body

Claims (2)

[Claims] 1. A molding die having a product cavity, an inlet and an outlet passage communicating with the cavity, a supply passage means having a supply control opening / closing valve in the middle of communication with the inlet, and an opening at the inlet. And a discharge passage means having a discharge control on-off valve, and the inlet is provided with a molding apparatus configured so that its cross-sectional area gradually increases toward the cavity, and the discharge control on-off valve is closed. While detecting the pressure in the inlet between the cavity and the opening of the discharge passage means in a valved state, a solvent made of a substance having a boiling point lower than room temperature and fine particles to be molded were mixed. the slurry substantially 10 kg / cm ² or more of said through said inlet from the supply passage means and the solvent of the slurry while introducing into said cavity to the mold outer than the outlet passage at a pressure Issued thereby, the detected method of forming a fine piece for opening the discharge control on-off valve with pressure is closed the supply control on-off valve At a stage has reached a predetermined value. 2. A molding die having a product cavity, an inlet and an outlet passage communicating with the cavity, a supply passage means having a supply control opening / closing valve in the middle of communication with the inlet, and a pressure in the inlet. And a discharge passage means having a discharge control opening / closing valve opening to the inlet on the side opposite to the cavity with respect to the portion where the pressure is detected by the pressure detecting means. The molding apparatus is configured such that the cross-sectional area of the introduction port gradually increases toward the cavity.