JPS63120602A - Manufacture of ceramic turbine rotor - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic turbine rotor by injection molding.

[Prior Art 1] A ceramic turbo rotor used in a turbocharger for an automobile engine includes a shaft, a hub portion integrally connected to one end of the shaft, and a wing portion formed on the outer peripheral surface of the hub. Consists of.

Conventionally, ceramic turbo rotors are manufactured by first mixing ceramic powder and thermoplastic resin, injection molding the mixture, degreasing it by heating, and then firing it.

However, ceramic turbo rotors manufactured by such conventional methods tend to have internal defects, resulting in problems with dimensional accuracy and strength. I think the internal defects are caused by the mixture of thick internal parts and thin parts in the ceramic turbo rotor. That is, during degreasing, the thermoplastic resin is removed relatively well from the thin walled portions.

However, when attempting to sufficiently degrease the thick walled portion (hub), internal defects such as cracks and density distribution tend to occur due to the pressure of gas generated by decomposition of the thermoplastic resin. Also,
If the thick portions are not sufficiently degreased, the resin remaining inside will decompose and gasify during firing, and the resulting pressure will tend to cause cracks and the like.

In order to solve this problem, for example, Japanese Utility Model Application No. 57-57201 discloses a method of forming small holes along a substantially radial direction within the thickness of a molded body before the degreasing process of the molded body. In addition, the Tokuko Sho 5
No. 6-41403 proposes a method in which a shaft and a hub are molded separately, the fired shaft is inserted into an unfired hub, and the two are heated together and joined by shrinkage as sintering progresses. ing.

[Problems to be Solved by the Invention] The above-mentioned method, for example, the method of improving degreasing performance by providing holes in a thick-walled portion, has problems in terms of strength and performance of the thick-walled portion in which the holes are provided. Furthermore, in the method of forming the parts into parts and then joining them during firing, it is necessary to improve the machining accuracy of the shaft and the hole in order to eliminate defects at the joined parts, which causes the number of man-hours to be increased.

The present invention was devised in view of the above circumstances, and proposes an injection molding method that reduces the molded product time by 12 m and does not adversely affect performance and strength.

[Means for Solving the Problems] The method for manufacturing a ceramic turbine rotor of the present invention includes a step of inserting a previously formed and pre-fired shaft portion and injection molding to form a molded body having m portions, and injection molding. The method is characterized by comprising a step of degreasing the molded body obtained in step 1, a step of covering the degreased molded body and subjecting it to hydrostatic pressure, and then a step of firing.

The shaft part is a porous body having communicating holes of 0.1 μm or more after being molded and pre-fired, and after molding, at least one end of the shaft part protrudes from the four parts.

The shaft portion is a porous body that is degreased and calcined after injection molding and has 20% or more of communicating pores of 0.1 μm or more. The fact that this shaft part is a porous body means that when degreasing the molded body,
The thermoplastic resin present in the inner layer of the wing near the shaft is discharged to the outside through the porous body. In addition, it is necessary that the shaft portion protrude from the wing portions to facilitate the thermoplastic resin being discharged through the porous body as a passageway. As a result, 12 m is discharged to the outside through the surface of the molded body and the internal shaft portion, thereby improving the degreasing efficiency and reducing the time.

The step of inserting the shaft and injection molding to produce a four-part molded body can be easily obtained by a conventional method. Since this molded body does not have a thick-walled shape, moldability is improved. The material composition of the material needs to have a similar shrinkage rate and is preferably the same as that of the shaft part.

The degreasing process is carried out by a conventional method, either directly under normal pressure or reduced pressure, or by burying the molded body in a batt material and heating it. Either method can be applied.

As described above, since the shaft portion is used as an exhaust passage for the thermoplastic resin, the degreasing is improved, the degreasing is completed in a short period of time, the occurrence of internal distortion due to residue is prevented, and the cause of cracking is suppressed. In the hydrostatic pressing process, if there is a large difference in shrinkage between the insert part and the molded part during firing, it may cause cracking, so the degree of shrinkage is adjusted by uniformly applying pressure to the entire molded body.

Cover with a membrane and pressurize at a predetermined pressure according to a conventional method. The firing step is carried out in a conventional manner. A manufacturing method has been devised in which a sintered turbo rotor can be manufactured by sequentially carrying out the above steps to produce a product free from internal strain cracks.

[Example] Silicon nitride (SiiNa) 92% by weight, yttrium oxide (YtOz>4% by weight, spinel (MGIAIzOa)
After thoroughly mixing the powder with 41m% in a ball mill, it is made into a thermoplastic resin as an injection molding aid! 115% by weight was added and kneaded to create pellets for injection molding.

Using the pellets obtained above, injection mold the shaft part,
After degreasing, temporary firing was performed at 1300° C. for 3 hours. R shaft is electronic! As a result of examination using an I-microscope, the presence of communicating pores of 0.1 μm or more was confirmed.

The pre-fired shaft was fixed to a mold as an insert material, and the pellets were used to mold a turbine rotor having the shape shown in FIG. 1 by injection molding.

The obtained molded body was heated from room temperature to 450°C at a heating rate of 5°C/hour to degrease it.

Next, the degreased molded body was coated for hydrostatic pressurization and heated to 1500k.
Hydrostatic pressurization was performed for 30 seconds at a pressure of Q/cs2.

The hydrostatic pressure coating was then heated to 500° C. under nitrogen gas to remove it, and then fired at 1750° C. for 4 hours under nitrogen gas to obtain a sintered body of a turbine rotor. Since the insert part and the wing part were manufactured with the same composition and the same molding method, the difference in shrinkage rate between the two at the time of dewaxing was 0.3%, and no cracking was observed during degreasing. Also, because the entire molded body was subjected to hydrostatic pressure before firing, the difference in shrinkage rate between the two during firing was 0.6.
%, and no cracking was observed during firing.

Also, as a result of the rotation test, no chips or damage were found.

The ratio of the shaft diameter to the hub diameter (d+/dt-
In the case of a shape in which 0+/Dx) is 2, the time required for degreasing was reduced by 40% compared to the case without a porous shaft.

A turbine rotor having the shape shown in FIGS. 2 and 3 was formed by the same method as in Example 1. No cracking was observed.

[Effect] The present invention performs injection molding by inserting the shaft, so the wall thickness of the wing portion is balanced and moldability is improved, so weld sinkage due to defects due to thick wall is reduced,
Since the joints are glued, there is no need to finish the shaft part with high precision.

Since the insert-molded part does not have a thick interior, the total amount of thermoplastic resin to be degreased and removed is small, and the thermoplastic resin is discharged through the pores of the shaft, so degreasing performance is significantly improved and degreasing can be done in a short time. .

Furthermore, by carrying out the hydrostatic pressurization process, the molded body is pressurized evenly, so there is an advantage that damage due to shrinkage differences during sintering does not occur.

As mentioned above, by applying the method of inserting and molding a shaft part of the present invention to a ceramic turbo rotor having a thick-walled product shape, the thick-walled part is eliminated, and moldability and degreasing properties are significantly improved. This manufacturing method also eliminates defects caused by the difference in shrinkage between the two.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a turbo rotor molded in the shape of Example 1, FIG. 2 is the shape of Example 2, and FIG. 3 is the shape of Example 3. 12.22.32...Shaft 11.21.31...Hub portion patent applicant Toyota Motor Corporation Agent
Patent attorney Hirodo Okawa Patent attorney Akio Maruyama Figure 1

Claims (2)

[Claims] (1) A process of inserting and injection molding a pre-molded and pre-fired shaft part into a molded body with wing parts, a process of degreasing the molded body obtained by injection molding, and a process of coating the degreased molded body. A method for manufacturing a ceramic turbine rotor comprising the steps of hydrostatic pressurization and then firing. (2) The shaft portion is a porous body having a communicating hole of 0.1 μm or more, which is formed and pre-fired, and after molding, at least one end of the shaft protrudes from the wing portion. Manufacturing method of ceramic turbine rotor.