JPS61205103A - Manufacture of ceramic hollow shape body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an injection molding method for hollow ceramic bodies.
In particular, the present invention relates to a method for manufacturing ceramic products having complicated hollow shapes used for sub-combustion chambers for internal combustion engines and the like.

(Prior art) Press molding, slurry casting, extrusion molding, etc. have long been known as methods for molding ceramic products, but in recent years injection molding has also been used for the purpose of molding complex shapes. These manufacturing methods have been used differently depending on the shape of the product. However, recently, as the idea of substituting ceramics for conventional metal products to achieve higher performance and efficiency has come to be considered, precision casting, etc., has increased the demand for ceramic products with the same shape and dimensional accuracy as metal products. It's here. Among these complex-shaped products, the hollow shape is the most difficult to mold using conventional ceramic techniques.

(Problems to be Solved by the Invention) The slurry casting method, the blow molding method, etc. are known for forming hollow shapes. Regarding the shape, high dimensional accuracy cannot be obtained using these conventional ceramic methods, making mass production difficult.

Injection molding has also attracted attention for its ability to mass-produce ceramic products with high dimensional accuracy, but in the case of hollow shapes, no matter how you set the parting line, there will be undercuts and the molded product will separate. I couldn't type it. For this reason, the product was divided into two products by dividing them into two products, each of which was molded separately and then joined or mechanically fixed. However, this increased the number of parts and the number of manufacturing steps, which led to higher manufacturing costs. Another problem was that the reliability of the product, such as the gas sealing properties at the joint surfaces, was reduced.

For this reason, the hollow part is made by ceramic injection molding using a core.
A method has been proposed in which the core is removed by heating and combustion (Japanese Unexamined Patent Publication No. 145104/1983), but in this case,
Since the molded body may be damaged due to the difference in thermal expansion between the core and the molded body due to heating, there is a drawback that the core material and ceramic injection molding raw material are limited to those that do not cause such damage.

The present invention was made with the aim of solving all of these problems and manufacturing products with complex hollow shapes in one piece, making it possible to mass-produce ceramic products with complex hollow shapes with high dimensional accuracy. It is meant to be.

(Means for Solving the Problems) The present invention involves attaching a soluble core to an injection molding mold, injecting a ceramic injection molding raw material into the mold, and then moving the injection molded body together with the core from the mold. This is a method for producing a hollow ceramic body whose main component is to take out the core, dissolve and remove the core with a solvent, and then sinter it.

(Function) Hereinafter, the manufacturing process of the present invention will be explained in detail in the order shown in FIG. First, in the ceramic injection molding raw material preparation process,
Ceramic raw materials include silicon nitride, silicon carbide, zirconia, alumina, etc., but when thermal shock resistance is required, such as in an internal combustion IR fly-side sub-combustion chamber, it is preferable to use silicon nitride.

Further, as the plasticizer, an organic thermoplastic substance is suitable, and waxes and thermoplastic resins (polyethylene resin, polystyrene resin, acrylic resin, etc.) are used. The type and amount of these plasticizers added need to be changed depending on the properties of the ceramic raw material powder, product shape, etc. In order to make injection molding easier, the plasticity of the injection base is increased and the plasticity gradually increases over a wide temperature range. In order to obtain characteristics that change, it is possible to use combinations of the above-mentioned plasticizers, or to add various plasticizers, lubricants, etc. as an accessory.

It is also necessary to select a plasticizer that will not be soaked in by the solvent used to dissolve the core mentioned in the note.

These ceramic raw material powders and the plasticizing agent are mixed and kneaded using a mixer such as a pressurized and heated kneader. In the case of a plasticizer mainly composed of waxes, a ceramic injection molding raw material that can be injection molded can be prepared by kneading at about 100° C. for about 1 hour. In order to prevent air from being drawn into the ceramic injection molding raw material and to make the molding process easier, it is recommended to extrude it into a noodle shape using a screw extruder, etc., and then cut it into a pellet shape by cutting it into a length of about 5 mm. .

The next step is to inject the ceramic injection molding raw material into an injection mold provided with a core having a predetermined shape, solidify the molded product, and then remove the molded product from the injection mold.

The shape of the core corresponds to the hollow part of a ceramic product, and the core can be manufactured by a press molding method, an injection molding method, or the like. In order to have a smooth injection molding surface, it is desirable that the surface roughness of the core be small.

The material of the core is soluble in the solvent used in the core melting and removal process described later, has an appropriate thermal expansion coefficient for ceramic injection molding, and has corrosion resistance for ceramic injection molding raw materials. , selected to withstand injection molding pressures and temperatures.

The material soluble in the solvent may be an organic or inorganic material, but water-soluble materials are particularly preferred from the viewpoint of ease of handling and economy, and urea resin and polyethylene oxide resin are preferably selected. Urea resin is particularly preferred because it is thermosetting and does not deform at injection molding temperatures. It goes without saying that thermoplastic polyethylene oxide resin can also be used if consideration is given to its thermal deformation.

Regarding the thermal expansion coefficient of the core, it is preferable to use one that is approximately the same as the ceramic injection molding raw material.

The reason for this is to reduce distortion during injection molding and to prevent cracks from occurring in the molded body due to the difference in thermal expansion when the molded body and core are cooled after injection molding.

If it is not possible to match the thermal expansion coefficients of the ceramic injection molding raw material and the core due to the material and shape of the ceramic product, it is possible to perform a core melting and removal process described later.

Although it is essential that the core used in the present invention be soluble in a solvent, the core may also contain a filler for the purpose of adjusting heat resistance, mechanical strength, and even coefficient of thermal expansion. In this case, it is preferable to use the same filler as the raw material for ceramic injection molding.

Since the purpose of the present invention is to obtain a ceramic product with a complex shape by injection molding, it is preferable that the material of the core has isotropic thermal properties.

After the ceramic injection molding raw material is solidified through injection molding, it is taken out from the injection mold.It goes without saying that the solidification is uniform, but when taken out from the injection mold, the molded product has as much temperature distribution as possible. It is better to avoid unevenness.

The next step is to dissolve and remove the core of the injection molded product.

In the core melting and removal process, after the ceramic injection molding raw material has solidified in the above process, the molded body is taken out from the injection mold,
The core is dissolved and removed using a solvent.

The solvent is selected depending on the material of the core, but one that does not dissolve or corrode the plasticizer contained in the ceramic molded body as much as possible is used.

As mentioned above, when the core is water-soluble, water or an aqueous solution containing a surface-active material or the like is used.

Since a ceramic molded body is composed of a ceramic injection molding raw material and a core made of different materials, when this molded body is cooled or heated, it is necessary to make the temperature distribution uniform. This is because if the ceramic injection molding material is not uniformly cooled or heated, thermal stress is generated between the ceramic injection raw material and the core, which tends to cause cracks in the injection molded product.

Therefore, it is necessary to perform the core melting process so that the temperature distribution of the ceramic molded body is uniform. That is, it is effective to keep the temperature of the solvent close to the temperature of the injection molded article.

When the thermal expansion coefficients of the ceramic injection molding raw material and the core are approximately equal, the temperature of the solvent may be room temperature.

In addition, if there is a difference in the coefficient of thermal expansion between the ceramic injection molding raw material and the core, in addition to making the temperature distribution uniform as described above, the temperature of the solvent should be adjusted so as not to cause distortion due to the difference in thermal expansion. It is effective to select

In order to achieve uniform temperature distribution, this is achieved by immersing the molded article in a solvent and circulating the solvent, or by shaking the molded article. Further, in order to increase the dissolution rate of the core, the temperature of the solvent may be higher than the temperature of the injection molded article.

The final step is a step in which the ceramic injection molded body from which the core has been melted and removed is sintered.

Before the sintering process, the plasticizer contained in the ceramic injection molding raw material is removed by heating. Heating conditions may be determined depending on the type and content of the plasticizer, but if the content is large, avoid rapid heating to prevent cracks, or if the raw material for ceramic injection molding is silicon nitride and the plasticizer is When the plasticizer is organic, it is important to thermally decompose the plasticizer as much as possible in an oxidizing or non-oxidizing atmosphere.

Sintering temperature, time, and atmospheric conditions are determined by the ceramic injection raw material. For example, in the case of silicon nitride, the sintering temperature is 1
The process is carried out at 600 to 1900° C. for 1 hour in a nitrogen atmosphere to obtain a hollow ceramic body with excellent thermal shock resistance.

Note that the plasticizer may be removed during this sintering step, and the injection molded product after the removal of the plasticizer is increased in density by isostatic pressing, and then sintered. , it has excellent thermal shock resistance and can lower the sintering temperature.

(Example) In order to form the auxiliary combustion chamber of an internal combustion engine as shown in FIG.
After kneading g at 100°C for 1 hour in a pressure heating kneader, the kneaded material was taken out, and after cooling, extruded a 3ml 1lφ turdle at a temperature of 60°C using a screw set extruder.
It was cut into a pellet shape of 5 mm.

Next, using the pellet, as shown in Fig. 3, a urea resin core A previously molded by injection molding was set in a mold C for molding product B, and the plasticizing temperature was set at 65°C. Mold temperature 45℃, injection pressure 1. Ot/cI/,
Injection time 1 second, holding pressure 1.4t/Cze, holding time 5
Injection molding was carried out at a cold part time of 15 seconds. Remove the molded model from the mold, including the core, and immediately immerse it in running water at 45°C.
The core was dissolved and removed after being left for about 1 hour. The product was then dried and gradually heated to 40°C in a hot air dryer at a heating rate of 3°C/Hr.
The plasticizer was burned off by heating to 0°C.

Next, the molded body from which the plasticizer had been removed was placed in an atmospheric firing furnace, and heated and sintered to 1100°C at a temperature increase rate of 200'C/Hr while flowing nitrogen gas for 1 to 7 minutes.

As a result of investigating the characteristics of the product of the present invention, it was found that there were no defects on the surface or inside thereof from a fluorescence flaw detection test and an X-ray transmission photograph observation, and the dimensional accuracy was within the range of ±0.1111. Also, the density of the substrate is 3.2012/c
c. The four-point bending strength was 75 kg/mm2, and it was confirmed that it was fully suitable for use as a sub-combustion chamber of an internal combustion engine.

(Effects of the Invention) According to the present invention, a product having a complicated hollow shape, such as a sub-combustion chamber of an internal combustion engine, can be manufactured in one piece without being divided.

Therefore, the number of parts and the number of manufacturing steps for the product can be reduced, making it possible to reduce manufacturing costs. Furthermore, since conventional products were manufactured in separate parts, problems related to product reliability such as poor gas sealing properties at joint surfaces can now be resolved by manufacturing them in one piece.

According to the present invention, any shape can be integrally molded as long as there is a hole penetrating through the interior at even one place, so a wide shape comparable to that of metal casting can be molded, which greatly contributes to industrial production.

[Brief explanation of the drawing]

Fig. 1 is a process diagram of the manufacturing process of the present invention, Fig. 2 is a cross-sectional view of a sub-combustion chamber for an internal combustion engine, and Fig. 3 is a urea molded into a mold C for injection molding a sub-combustion chamber for an internal combustion engine. FIG. 3 is an explanatory diagram of injection molding showing that a resin core A is set and that the product is molded in a space indicated by a hatched area B. A... Core B... Product forming part C...
・Amendment to Mold Procedures June 13, 1985 Manabu Shiga, Commissioner of the Japan Patent Office1, Indication of the case 1985 Patent Application No. 449412, Title of invention Method for manufacturing ceramic hollow shaped bodies 3, Amendment Relationship with the case of a person who does a patent application The claims of Patent Applicant 4, Agent 1, from page 1, line 4 of the specification to page 2, line 2 are corrected as follows. "2. Claim L A soluble core is attached to an injection molding mold, a ceramic injection molding raw material is injected into the mold, and then the injection molded body is taken out from the mold together with the core, and the core is A method for manufacturing a hollow ceramic body, the main component of which is sintering after dissolving and removing with a solvent.Turtle: Manufacturing a hollow ceramic body according to claim 1, wherein the soluble core is water-soluble. & A method for producing a ceramic hollow shaped body according to claim 2, wherein the water-soluble core is a water-soluble substance whose main component is area. A method for manufacturing a hollow ceramic body according to claim 1. Apparatus: The hollow ceramic body according to claim 1, 2, or 1114, wherein the hollow ceramic body is a sub-combustion chamber of an internal combustion engine.・2. In line 11 of page 2 of the specification, "same as metal products manufactured by precision casting etc." is corrected to "same as metal products manufactured by precision casting etc." 8, page 5, No. 1! ! Correct "injection base material" in the row to "injection molding raw material". Table same 'M7 page #! Correct "area resin" in line 6 to "a water-soluble substance whose main component is area" 1. Delete "It goes without saying that area resin is 11111" in lines 7 to 12 of the same page. 5. On page 9, line 15, "injection raw materials" is corrected to "injection molding raw materials." 6. Corrected "thermal expansion difference" in line 6 of page 10 to "thermal expansion coefficient difference", and changed it to #! In line 10, ``Immerse in the solvent and remove the solvent'' is corrected to ``Immerse in the solvent and remove the solvent.'' 7. Same page 11 @ 5 Correct "ceramic injection raw material" in line A-6 to "ceramic raw material". 8. Corrected "turdle" in lines 2 to 8 of page 12 to "noodle", and changed "made of area resin" to "made of a water-soluble substance whose main component is area" in lines 6 to 7 of the same page. Corrected to 09. In the same page, page 14, line 5, ``Made of area resin'' is corrected to ``Made of a water-soluble substance whose main component is area.''

Claims (1)

[Claims] 1. A soluble core is attached to an injection molding mold, a ceramic injection molding raw material is injected into the mold, and then the injection molded body is taken out from the mold together with the core, and the core is removed. A method for producing a hollow ceramic body, which comprises dissolving and removing it with a solvent and then sintering it. 2. The method for producing a hollow ceramic body according to claim 1, wherein the soluble core is water-soluble. 3. Claim 2 in which the water-soluble core is made of urea resin
A method for producing a hollow ceramic body as described in Section 1. 4. The method for producing a hollow ceramic body according to claim 1, wherein the ceramic injection molding raw material contains silicon nitride as a main component. 5. The method for manufacturing a hollow ceramic body according to claim 1, 2 or 4, wherein the hollow ceramic body is a sub-combustion chamber of an internal combustion engine.