JPS61242966A - Method of joining ceramic rotor and metal rotation shaft - 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] [Field of Application of the Invention] The present invention relates to a method of joining a ceramic rotating body and a metal rotating shaft, and particularly relates to a ceramic rotating body suitable for application to parts that require heat resistance. This invention relates to a method of joining a body and a metal rotating shaft.

[Background of the invention]

As an example of a method for joining a ceramic rotating body and a metal rotating shaft, for example, as described in Japanese Patent Application Laid-Open No. 55-140771, a ceramic rotating body and a metal rotating shaft are bonded together by thermal expansion of both. There is a method of joining by differential shrink fit.

However, with this method, the shrink-fit effect disappears at high temperatures, so the shaft of the ceramic rotating body must be lengthened for parts that will be used at high temperatures, and the shrink-fit must be performed on the low-temperature side, away from the high-temperature side. Must be.

On the other hand, methods of shrink fitting or joining at a low temperature have the following problems.

(1) It is difficult to integrally mold a long ceramic shaft and a ceramic rotating body, resulting in poor yield, and is also prone to defects and low reliability.

(2) In the case of a long ceramic rotating body with a shaft, the machining time of the ceramic part is correspondingly long, which is an economical problem.

(3) If the ceramic shaft or the joint between ceramic and metal breaks during operation, the lubricating oil in the bearing will flow into the high temperature side, creating a safety problem.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems of the prior art, and is a combination of a ceramic rotating body and a metal rotating shaft, which makes it possible to inexpensively produce a ceramic rotating body with a metal rotating shaft that has improved heat resistance. Its purpose is to provide a binding method.

[Summary of the invention]

In the method of joining a ceramic rotating body and a metal rotating shaft according to the present invention, a boss portion that protrudes concentrically with the axis of the ceramic rotating body is provided concentrically with the axis of the metal rotating shaft. The boss is inserted into a hole having a diameter larger than the diameter of the boss so that a minute gap is maintained between the outer circumferential surface of the boss and the inner circumferential surface of the hole, and the end surface of the boss and the bottom of the hole are connected. They are brought into contact to form an in-phase junction.

Additionally, the idea behind developing the present invention is as follows.

In view of the problems of the prior art described above, namely reliability, economy and safety, the shaft of the ceramic rotating body is shortened and a ceramic rotating body with a long metal rotating shaft is used.

However, in this case, heat resistance becomes a problem in the shrink-fit structure as described above. Therefore, we considered using the characteristic that ceramics have lower thermal conductivity than metals to improve the low thermal conductivity of the joint structure. That is,
The structure is such that the joints are not directly exposed to high-temperature atmosphere, and also blocks heat transfer from the metal rotating shaft. In order to maintain a gap between the outer peripheral surface of the boss of the ceramic rotating body and the inner surface of the hole provided in the metal rotating shaft, the diameter of the hole is increased, and the end surface of the boss is joined to the bottom surface of the hole.

As a result, the metal rotating shaft and the ceramic boss are not in direct contact with each other and are not directly exposed to a high temperature atmosphere, so that the thermal load on the joint can be reduced.

In addition, the joining position was located at a location farther away from the oil ring groove toward the lower temperature side. This was designed to cool the joints using bearing lubricating oil.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a cross-sectional view of a joining part of a turbocharger rotor showing a method of joining a ceramic impeller and a metal rotating shaft according to an embodiment of the present invention, and FIG. 2 shows the turbocharger of FIG. 1 and a conventional one. In an experimental comparison with a metal turbocharger,
FIG. 3 is a diagram showing the relationship between turbine inlet temperature and junction temperature.

In this embodiment, the present invention is applied to a turbocharger component that requires heat resistance.

In FIG. 1, 1 is Si related to the ceramic rotating body.
3N, an impeller made of impeller; 2, a boss protruding concentrically with the rotation axis; 3, Cr-Mo related to the metal rotation axis;
The steel rotating shaft 4 is a hole formed in the stepped large diameter portion 3a of the rotating shaft 3 so as to be concentric with the rotation axis, and the hole 4 is machined to have an inner diameter larger than the outer diameter of the boss portion 2. There is.

An oil ring groove 6 is formed in the large diameter portion 3a of the Cr-Mo steel rotary shaft 3, and this oil ring groove 6 is for sealing the lubricating oil of the bearing portion 7.

The boss portion 2 of such a Si3N4 impeller 1 is made of Cr-
M o Insert the boss part 2 into the hole 4 of the steel rotating shaft 3 so that the outer circumferential surface of the boss part 2 and the inner circumferential surface of the hole 4 do not contact each other, that is, maintain a small gap. The end surface 2a and the bottom surface 4a of the hole 4 were brought into contact, and diffusion bonding, which is one of the solid phase bonding methods, was performed via the AQ insert material 5 to bond them.

This joining position is determined by adjusting the depth of the hole 4 and the length of the boss portion 2 so that it is located away from the oil ring groove 6 toward the lower temperature side.

FIG. 2 shows the results of a comparative experiment on the relationship between the turbine input cogas temperature and the joint temperature for the turbocharger of this embodiment and a conventional Cr-Mo steel turbocharger.

In FIG. 2, solid lines and black circles indicate data for the turbocharger of this embodiment, and broken lines and black triangles indicate data for a conventional metal turbocharger.

According to the results of this experiment, as is clear from the figure, the junction temperature of this example is low.

As the turbine inlet temperature increases, the temperature of the joint increases, and at a turbine inlet temperature of 950°C, the joint temperature of this example is about 320°C.

Therefore, it can be seen that there is no problem in heat resistance even when joining using low melting point AQC (melting point: about 660° C.) as an insert material.

The reason why the temperature of the joint does not rise compared to the conventional example is that the outer periphery of the boss part 2 of the Si3N4 impeller and the Cr
-Mo There is no direct contact with the inner periphery of the hole 4 in the steel rotating shaft, the joint is not directly exposed to a high-temperature gas atmosphere, and it is indirectly cooled with bearing lubricating oil. This is due to a number of things.

According to this embodiment, the heat resistance of the turbocharger rotor is improved and the following effects are achieved.

In conventional joining by shrink fit, the machining dimensional accuracy between the boss part of the ceramic rotating body and the fitting hole provided in the metal rotating shaft must be ±5 μm or less, but in the case of this example, it is ±50 μm. It may be a degree. Therefore, processing costs are reduced.

Furthermore, for parts whose metal rotating shafts have a diameter of 5 mm or less, conventionally it has not been possible to provide a sufficient shrink fit allowance from the viewpoint of dimensional accuracy in machining, making shrink fit practically impossible. However, with the joining method of this embodiment, joining is possible regardless of the diameter of the metal rotating shaft.

In addition, in the above-mentioned embodiment, S of the turbocharger rotor
L, N4 impeller and Cr-Mo@lie
i Although an example of joining a rotating shaft has been described, the present invention is not limited to this, and can be applied to parts consisting of a ceramic rotating body and a metal rotating shaft that require heat resistance, within the range where the same effect is expected. , is a method that can be applied universally.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide a method for joining a ceramic rotating body and a metal rotating shaft, which allows manufacturing a ceramic rotating body with a metal rotating shaft with improved heat resistance at low cost. can.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a joining part of a turbocharger rotor showing a method of joining a ceramic impeller and a metal rotating shaft according to an embodiment of the present invention, and FIG. 2 shows the turbocharger of FIG. 1 and a conventional one. In an experimental comparison with a metal turbocharger,
FIG. 3 is a diagram showing the relationship between turbine inlet temperature and junction temperature.

Claims (1)

[Scope of Claims] 1. A boss protruding in the same direction as the axis of the ceramic rotating body is inserted into a hole having a diameter larger than the diameter of the boss, which is provided concentrically with the axis of the metal rotating shaft. , the boss is inserted so that an outer circumferential surface of the boss and the inner circumferential surface of the hole maintain a small gap, and the end face of the boss is brought into contact with the bottom of the hole to perform solid phase welding. A method of joining a ceramic rotating body and a metal rotating shaft. 2. In the method described in claim 1, an oil ring groove is provided in the metal rotating shaft, and the joint portion between the boss end face of the ceramic rotating body and the inner bottom surface of the metal rotating shaft is separated from the oil ring groove. A method of joining a ceramic rotating body and a metal rotating shaft, which are positioned on the low temperature side.