JPH0510223A - Shaping method for extremely small ceramic part - Google Patents

Abstract

PURPOSE:To provide a shaping method for an extremely small ceramic part in which a hole having a curvature, is easily formed on the ceramic part and the hole shape is formed with high precision. CONSTITUTION:In the shape forming method for an extremely small ceramic part, a plastic substance 20 is attached at the top edge 19 of an injection hole forming pin 5, which is advanced toward a pin insertion hole 18, and the plastic substance 20 is pushed onto the wall surface 27 of a cavity 3, and then the injection hole forming pin 5 is slightly retreated and held in the state where a curvature 17 is formed on the peripheral surface by the surface tension of the plastic substance 20. Then, slurry S is poured into the cavity 3 through a slurry pouring passage 2, and the moisture of the slurry S is adsorbed to a porous part 30, and solidification is generated, and the shape of the curvature 17 is printed on the body part 7, and body part 7 is applied with a curvature 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for imparting a shape to a very small ceramic part, which is produced from a slurry of ceramics containing ceramic particles.

[0002]

2. Description of the Related Art Conventionally, as a molding method for manufacturing a small precision component such as a tip of an injection nozzle using a ceramic material containing ceramic particles, an injection molding method or a slip casting method using a wax core is used. A method in which a wax core is heated and eluted is known.

Further, as a method for casting silicon nitride ceramics by sludge casting, there is a method disclosed in JP-A-64-5977. The molding method is as follows. Add 0.1 to 0.7% by weight of ammonium salt of polyacrylic acid as a deflocculating agent to the slurry of silicon nitride ceramics to the powder of the slurry, and add an acrylic emulsion as a binder into the slurry. It is cast-molded.

A jet nozzle having a nozzle tip made of ceramics is disclosed in Japanese Utility Model Laid-Open No. 58-122778.
There is one disclosed in the publication. In this injection nozzle, each injection hole formed in the nozzle tip is made of a ceramic member, and the ceramic member is shrink-fitted to the valve seat portion of the nozzle body.

Further, in the case of forming a deformed injection hole at the tip of the injection nozzle, machining, laser processing,
It is generally formed by electric discharge machining.

[0006]

However, in the above-mentioned conventional injection molding method, since the composition is filled in the mold by high pressure, for example, the injection hole forming pin (diameter: 0.3 mm) of the injection nozzle of the diesel engine is used. ), Etc. may be damaged when pressurized.

Further, the method of heating and elution of the wax core after molding by slip casting has a problem in accuracy, it is not possible to form a highly accurate hole or the like, and it is caused by shrinkage of the inking portion during molding drying. Cracks may occur. Further, the molding method disclosed in Japanese Patent Laid-Open No. 64-5977 has the same problem.

In order to solve the above problems, the present applicant has developed a ceramic member molding method, a ceramic member molding apparatus, and an injection nozzle manufactured by the molding method.
I applied for it as Japanese Patent Application No. 2-415086. However, in the method for molding a ceramic member according to the present invention, although a deformed injection hole can be formed, a method of forming the injection hole in a shape having a curved surface on the inlet side of the injection hole, that is, a shape having a curvature on the inner peripheral wall surface, It is not disclosed. Regarding the shape of the injection hole of the fuel injection nozzle, by forming a shape in which the inner wall surface around the inlet side has a curvature,
It is possible to reduce the pressure loss of the fuel pressure in the fuel injection.

Further, when the inner surface of the injection hole is curved with respect to the injection hole of the fuel injection nozzle such as the injection nozzle disclosed in Japanese Utility Model Laid-Open No. S58-122778, machining is performed. The current situation. However, the method of giving curvature to the inner surface of the injection hole by machining has a problem that the production efficiency is low and the cost is high.

Further, in general, a complicated shape is formed inside a deformed injection hole of a fuel injection nozzle, a molded body is produced in a state in which a leasable core is included, and the core is leached by heating or the like. Methods such as sintering are also known. However,
The elution of the core by heating or the like to give the inner surface of the injection hole a curvature has a problem that the shape accuracy of the injection hole is not reliable.

Therefore, an object of the present invention is to solve the above-mentioned problems, to facilitate the formation of a hole having a curvature in a ceramic component, and to form the hole shape with high precision, For example, if the holes are the injection holes of the fuel injection nozzle, the pressure loss of the fuel pressure of the fuel injected from the injection holes can be reduced, and a large amount of compacts can be fired at the time of firing, which facilitates extremely mass production. Another object of the present invention is to provide a method for imparting a shape to an extremely small ceramic component.

[0012]

In order to achieve the above object, the present invention is configured as follows. That is,
According to the present invention, a ceramic material is formed into a predetermined shape by using a mold having a cavity partially having a porous portion and having a slurry injection passage leading to the cavity and a pin insertion hole into which a hole forming pin can be inserted. In the method for molding a ceramic component, the step of adhering a plastic substance to the tip of the hole forming pin, advancing the hole forming pin into the pin insertion hole to press the plastic substance against the wall surface of the cavity, and then the hole. A step of slightly retracting the forming pin to maintain the curvature of the peripheral surface of the plastic material due to the surface tension of the plastic material; a step of injecting a slurry into the cavity through the slurry injection passage; The water content of the porous portion is absorbed into the porous portion to solidify the ink, and the curvature shape is transferred to the inlaid portion. That relating to the shape method of applying minimum ceramic parts.

In the method for imparting the shape of the extremely small ceramic component, the extremely small ceramic molded body is a molded body forming the nozzle tip of the fuel injection nozzle.

In the method for imparting a shape to the micro ceramic component, the plastic substance is petrolatum.

[0015]

The method of imparting the shape of the microminiature ceramic component according to the present invention is configured as described above, and operates as follows. That is, in this method for imparting a shape to a micro ceramic component, a plastic substance is attached to the tip of a hole forming pin, the plastic substance is pressed against the wall surface of the cavity, and then the plastic substance is retracted to cause the plastic substance to move by the surface tension of the plastic substance. A curvature is applied to the peripheral surface of the cavity, and the slurry is injected into the cavity in that state, and the porous portion absorbs water to solidify, so after the slurry is solidified, if the hole forming pin is pulled out and taken out from the mold. , The curvature formed in the plastic material is transferred to the ceramic molded body, and the curvature can be imparted to the hole wall surface such as the injection hole formed in the ceramic molded body. It is possible to form a precise curvature with high accuracy.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for imparting a shape to a microminiature ceramic component according to the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a ceramic molding apparatus for achieving the method for imparting a shape to an extremely small ceramic component according to the present invention. FIG. 2 is an enlarged view of a main part of FIG. FIGS. 3, 4, 5, 6, 7 and 8 are explanatory views showing each step of the method for imparting the shape of the microminiature ceramic component according to the present invention, and FIG. 3 shows the injection hole forming pin inserted into the cavity. FIG. 4 is an explanatory view showing a step of attaching a plastic substance to the cavity wall surface, FIG. 5 is an explanatory view showing a step of slightly retracting the injection hole forming pin to give the plastic substance a curvature, 6 is an explanatory view showing a step of injecting the slurry into the cavity, FIG. 7 is an explanatory view showing a step of extracting the injection hole forming pin and the forming pin from the cavity, and FIG. 8 is a step of drying and solidifying the inking portion. It is an explanatory view shown. And
FIG. 9 is a cross-sectional view showing an example of a ceramic part manufactured by the method for imparting a shape to a very small ceramic part according to the present invention.

This embodiment is an application of the method for imparting a shape of a micro ceramic component according to the present invention to a method for imparting a predetermined shape to an injection hole in a method for forming the tip of a fuel injection nozzle. FIG. 9 shows the tip of the fuel injection nozzle, that is, the nozzle tip 22. This nozzle tip 22
However, in this embodiment, only one injection hole 23 is shown in order to make the description easy to understand. The nozzle tip 22 is made of high-temperature high-strength silicon nitride (Si
It is made of ceramics such as ₃ N ₄ ), silicon carbide (SiC), and zirconia. When the end surface 29 of the nozzle tip 22 is joined to the nozzle body of the fuel injection nozzle, the nozzle sack 28 is formed on the inner surface 25 side and the outer surface 2 is formed.
The 6 side is the surface exposed to the combustion chamber. As shown in FIG.
Injection holes 23 formed in the nozzle tip 22 of the fuel injection nozzle
Are formed in a shape having a curvature 24 on the inlet side in the flow direction of the injected fuel.

As shown in the figure, the injection hole 23 formed in the nozzle tip 22 of the fuel injection nozzle is formed into a straight shape with a large opening on the inlet side, that is, a curvature 24, and a small opening on the outlet side. By forming the needle valve of the fuel injection nozzle, when the fuel supplied from the fuel injection pump is injected through the injection hole 23, the pressure loss of the fuel pressure can be reduced and the fuel can be strongly injected into the combustion chamber. Can be jetted. In some cases, the injected fuel injected from the injection holes 23 can be strongly collided with the wall surface of the combustion chamber and dispersed to promote the mixing with the air, and a good combustion state can be secured.

Next, a manufacturing method for forming the injection hole 23 having the curvature 24 having the above-described shape on the tip 22 of the fuel injection nozzle by using the ceramic forming apparatus shown in FIG. 1 will be described. This ceramic molding apparatus is suitable for application, for example, to manufacture a nozzle tip of a fuel injection nozzle used in a diesel engine. In this ceramic molding apparatus, a mold 1 is provided with a slurry injection port, that is, a slurry injection passage 2 and a cavity 3 communicating with the slurry injection passage 2, and a metal hole having a polygonal shape at the tip. A through hole 4 and a pin insertion hole 18 for detachably attaching the pin insertion / removal rotary jig 6 having the injection hole forming pin 5 which is a forming pin are formed. The cavity 3 is formed on the lower surface of the mold 1, and the slurry injection passage 2 leads from the upper part of the mold 1 to the cavity 3. The shape of the cavity 3 is the outer shape of the tip of the fuel injection nozzle, that is, the nozzle tip 22. The shape of the injection hole forming pin 5 is formed so as to correspond to the shape of the injection hole 23 formed in the nozzle tip 22, and may be formed in various shapes such as a rectangle and an ellipse.

The mold 1 is set on the positioning table 8.
The upper surface 11 of the positioning table 8 is arranged in contact with the lower surface 12 of the mold 1. A hole 13 is formed in the positioning base 8, and a core 14 and a core 1 that serve as molding pins are formed.
A through hole 15 for raising and lowering the core raising / lowering jig 10 to which 4 is attached is formed. The core lifting jig 10 is detachably fixed to the positioning table 8 by an appropriate fixing means such as a screw, and the core 14 can be installed in the cavity 3 in a projectable state. The core 14 functions as a molding pin for forming the wall surface of the nozzle sack 28.

A porous mold 9 made of gypsum or the like is placed in the hole 13 formed in the positioning table 8. This porous type 9
Cooperates with the mold 1 and the core 14 to form the cavity 3. In other words, a molding die is formed in which a part of the wall surface of the cavity 3 is formed of a porous portion. The porous portion formed by the porous mold 9 has a function of absorbing water from the slurry S injected into the cavity 3 from the slurry injection passage 2 to cause the wall surface of the cavity to be inked and solidify the inlaid portion 7. Have A through hole 16 is formed in the porous mold 9 at a position facing the cavity 3, and the through hole 16 is formed in the core 14.
Is configured to be movable up and down. Core 1
4 is set in a state in which the through hole 16 can be lifted and projected into the cavity 3. By setting the core 14 so as to project into the cavity 3, the core 14 forms the nozzle sack 28 of the fuel injection nozzle.

The ceramic forming apparatus is constructed as described above, and the forming apparatus can be used to achieve the method for imparting the shape of the extremely small ceramic component according to the present invention. That is, the method of imparting the shape to the extremely small ceramic component is to manufacture the nozzle tip 22 which is the extremely small ceramic component of the fuel injection nozzle by slip casting which is one of the ceramic molding methods. That is, in this method for imparting a shape to a micro ceramic component, the cavity 3 having a partly porous portion is formed, and the slurry injection passage 2 leading to the cavity 3 and the pin insertion hole 18 into which the hole forming pin 5 can be inserted are formed. 1 of a ceramic part molding method for molding a ceramic material into a predetermined shape using a metal mold 1
Is one.

In this method for imparting a shape to the extremely small ceramic component, first, the plastic substance 20 is attached to the tip 19 of the injection hole forming pin 5, which is a hole forming pin. The injection hole forming pin 5 to which the plastic substance 20 is attached is indicated by an arrow A in FIG. 2 and FIG.
As shown by, the pin insertion hole 18 is advanced. By further advancing the injection hole forming pin 5, the arrow B in FIG.
As shown by, the plastic material 20 is pressed against the wall surface 27 of the forming pin 14 which is the wall surface of the cavity 3 so that the plastic material 20 becomes larger than the area of the tip 19 of the injection hole forming pin 5 of the forming pin 14. It is attached to the wall surface 27.

Next, as shown in FIG. 5, if the injection hole forming pin 5 is slightly retracted in the direction of the arrow C and the injection hole forming pin 5 is held at that position, the plastic material 20 is plasticized by the surface tension. The peripheral surface of the substance 20 is in a state of forming a curvature 17 that becomes a curved surface. Therefore, the state in which the curvature 17 is formed is maintained. The plastic substance 20 is made of a material such as petrolatum, and compared with the slurry S, the slurry S
Although it is harder, it is a softer material than the inlaid portion when the slurry S is solidified and inlaid. Therefore, the slurry S is slurried in a state where the plastic substance 20 is attached to the wall surface 27 of the core 14 which is the forming pin and protrudes into the cavity 3, and the peripheral surface of the plastic substance 20 forms the curvature 17. It is injected into the cavity 3 through the injection passage 2.

As shown in FIG. 6, when the slurry S is injected into the cavity 3, the slurry S infiltrates into the cavity 3 excluding the plastic substance 20 while maintaining the shape of the plastic substance 20, and there, The water content of the slurry S is absorbed by the porous portion 30 of the porous mold 9, and the slurry S is deposited on the wall surface 27 of the cavity 3 and solidified to form the inlaid portion 7.
The inlaid portion 7 does not exist in the portion where the plastic substance 20 and the injection hole forming pin 5 are present, and the incurred portion 7 has a curved peripheral surface of the plastic substance 20 and a straight line of the injection hole forming pin 5. The shape of the peripheral surface is transferred. Therefore, as shown in FIG. 7, the injection hole forming pin 5 is pulled out from the inking portion 7 in a state where the shape retaining property is developed in the inking portion 7, and the straight injection hole 23 is formed in the inking portion 7. To do. Further, the forming pin 14 is pulled out from the inlaid portion 7, but at this time, the plastic substance 20 is in a state of being attached to the inlaid portion 7. With the solidified state of the inlaid portion 7 further advanced, as shown in FIG. 8, the inlaid portion 7 is taken out from the mold 1 and the porous mold 9, and the inlaid portion 7 is sufficiently dried. The dried inlaid portion 7 was put into a firing furnace and heated in a nitrogen atmosphere to burn and burn out the plastic material 20, and the inlaid portion 7 was sintered to obtain a sintered body. This sintered body constitutes the nozzle tip 22.
As shown in, the shape of the curvature 24 is provided on the nozzle sack 28 side of the nozzle tip 22, that is, on the inlet side of the nozzle tip 22.

Next, a specific example of the method for imparting the shape to the extremely small ceramic component will be described. First, a ceramic powder of silicon nitride (Si ₃ N ₄ ), a sintering aid, water and an organic binder were mixed, and then sufficiently mixed by a ball mill to obtain a slurry S. In the method for imparting the shape of the extremely small ceramic component, as the ceramic powder, aluminum titanate, mullite, zirconia, potassium titanate or the like can be used in addition to silicon nitride. In addition to polyvinyl alcohol, a thermoplastic acrylic resin capable of suppressing dimensional shrinkage in the manufacturing process of the ceramic member can be used as the binder.

The slurry S produced as described above is introduced into the cavity 3 from the slurry injection port 2 formed in the nozzle tip making mold of the nozzle tip 22 of the fuel injection nozzle shown in FIGS. 6 and 7, that is, the die 1. Poured. Cavity 3
Moisture is absorbed by the porous mold 9 into the slurry S injected into the cavity S, and the slurry S is infiltrated in the cavity 3 to form an infiltration layer. However, after a predetermined time elapses, when the shape retention property is developed in the infiltration layer. Then, the injection hole forming pin 5 attached to the mold 1 is pulled out from the inlaid portion 7, and the core 14 which is the forming pin attached to the positioning base 8 is removed from the inlaid portion 7. In this state, the inlaid portion 7 is left in the mold, and the porous die 9 further absorbs and discharges water from the inlaid portion 7 to solidify the inlaid portion 7. After the inking portion 7 was solidified to form a molded body of the ceramic member, the molded body was removed from the mold to obtain a nozzle tip molded body having the injection holes 23.

A sintered body of the nozzle tip 22 could be obtained by firing the formed nozzle tip body at 1800 ° C. in a nitrogen atmosphere, for example. The finally obtained nozzle tip 22 is cut into 2 as shown in FIG.
Twenty test pieces having 0 nozzle tip cut surfaces were prepared.
When these test pieces were measured, the size of the straight portion of the injection hole 23 formed in a rectangular cross section was 0.2 × 0.6.
(Mm), the allowable error is 0.02 mm or less,
It was confirmed to be within the allowable error, and in particular, the curvature 24 of radius R0.2 was provided on the inlet side of the injection hole 23. The end surface 29 of the nozzle tip 22 can be joined to the nozzle body using a solder material to complete the fuel injection nozzle. When fuel spray was observed using this fuel injection nozzle, it was confirmed that the air entrainment was improved by about 5% as compared with the conventional straight injection hole.

As a comparative example, a plastic core made by injection chamber molding was used and placed in a plaster mold,
In the same manner as in the above example, the slurry S was injected into the cavity to produce a nozzle tip. 8 out of 10 nozzle tips
The individual cracks were generated due to shrinkage during drying of the slurry.
In addition, for nozzle tips that did not crack,
The corners of the injection holes were not sharp, and the desired rectangular shape could not be obtained.

[0030]

The method for imparting a shape to a microminiature ceramic component according to the present invention is configured as described above and has the following effects. That is, in the method for imparting a shape to the microminiature ceramic component according to the present invention, a plastic substance is attached to the tip of the hole forming pin, and the hole forming pin is advanced to the pin insertion hole to cause the plastic substance to adhere to the wall surface of the cavity. By pressing, then the hole forming pin is slightly retracted to maintain the curvature of the peripheral surface of the plastic material due to the surface tension of the plastic material, and the slurry is injected into the cavity through the slurry injection passage, Furthermore, since the water content of the slurry is absorbed by the porous portion to solidify the ink and the curvature shape is transferred to the inlaid material, it is possible to form a hole in the micro ceramic component with high accuracy, and The corner of the sectional shape can be formed into a sharp shape, and the extremely small ceramic parts can be manufactured with high efficiency.

Moreover, when a molded body of a nozzle tip of a fuel injection nozzle is manufactured as a minimal ceramic molded body by the method of imparting the shape of the minimal ceramic part and the molded ceramic body is fired to manufacture the nozzle tip,
The curvature is formed on the inlet side of the injection hole, and when fuel is injected into the combustion chamber through the injection hole, the pressure loss of fuel pressure can be reduced, and air entrainment, that is, air entrainment in the combustion chamber is improved. Can be made.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a ceramic molding apparatus for achieving a method for imparting a shape to an extremely small ceramic component according to the present invention.

FIG. 2 is an enlarged view of a main part of the ceramic molding apparatus of FIG.

FIG. 3 is an explanatory view showing a step of inserting the injection hole forming pin into the cavity in the method of imparting the shape to the extremely small ceramic component.

FIG. 4 is an explanatory view showing a step of adhering a plastic material to a cavity wall surface in the method for imparting a shape to this microminiature ceramic component.

FIG. 5 is an explanatory view showing a step of slightly retracting the injection hole forming pin to give a curvature to the plastic material in the method for imparting the shape to the extremely small ceramic component.

FIG. 6 is an explanatory view showing a step of injecting a slurry into a cavity in the method for imparting a shape to this extremely small ceramic component.

FIG. 7 is an explanatory diagram showing a step of extracting the injection hole forming pin and the forming pin from the cavity in the method for imparting the shape of the extremely small ceramic component.

FIG. 8 is an explanatory view showing a step of drying and solidifying the inlaid portion in the method for imparting a shape to this extremely small ceramic component.

FIG. 9 is a cross-sectional view showing an example of a ceramic component manufactured by the method for imparting a shape to a microminiature ceramic component according to the present invention.

[Explanation of symbols]

1 mold 2 Slurry injection passage 3 cavities 5 Injection hole forming pin 7 Meat part 9 Porous type 14 cores (forming pins) 17 Curvature 18 pin insertion hole 20 plastic substances 22 nozzle tip 23 injection holes 24 Curvature 30 Porous part

Claims (3)

[Claims] 1. A ceramic material is formed into a predetermined shape by using a mold having a cavity having a partly porous portion and having a slurry injection passage leading to the cavity and a pin insertion hole into which a hole forming pin can be inserted. In the method of molding a ceramic part, the step of adhering a plastic substance to the tip of the hole forming pin, advancing the hole forming pin to the pin insertion hole to press the plastic substance against the wall surface of the cavity, and then A step of slightly retracting the hole forming pin to maintain a state in which a curvature is formed on the peripheral surface of the plastic material by the surface tension of the plastic material; a step of injecting a slurry into the cavity through the slurry injecting passage; A step of absorbing the water content of the slurry into the porous portion to solidify the ink and transfer the curved shape to the inlaid portion. Forming method for very small ceramic parts. 2. The method for imparting a shape to a micro ceramic component according to claim 1, wherein the micro ceramic molding is a molding that forms a nozzle tip of a fuel injection nozzle. 3. The method for imparting a shape to a microminiature ceramic component according to claim 1, wherein the plastic substance is petrolatum.