JPS6278169A - Bonded structure of ceramic axis - 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 improvement in a joint between a ceramic shaft and a metal shaft in engine parts such as ceramic turbochargers, gas turbine rotors, and pistons.

(Prior art) Conventionally, when joining a ceramic shaft and a metal shaft, the end of the ceramic shaft is tightly fitted to the end of the metal shaft. However, the joint was exposed to high temperatures.
In the former case, since the metal part of the fitting part is thin, it is likely to be deformed due to a decrease in mechanical strength, and there is a risk that the ceramic shaft will separate from the fitting part due to expansion of the metal shaft. In the latter case, a reduction in strength due to oxidation of the brazed portion of the joint is unavoidable. In order to improve the drawbacks of the above conventional ones, a sleeve is joined to the outer periphery of the joint between the ceramic shaft and the metal shaft,
Proposals have been made to increase bonding strength and prevent oxidation of the brazing filler metal. (% Application No. 59-210279) (Problems to be Solved by the Invention) However, when the joint is covered with the above-mentioned sleeve, the surface of the ceramic shaft adjacent to the joint is exposed to the wax interposed between the sleeve and the sleeve. During use, the edge portion held by the ceramic shaft, which is subject to strong clamping force from the solder tank, may be damaged. In addition, if the amount of brazing material is reduced to prevent the formation of wax deposits on the surfaces of the sleeve and ceramic shaft, the amount of brazing material will not be sufficiently interposed on the inner surface of the sleeve, creating a void, which will prevent a uniform tightening force from acting on the entire surface. It is something.

(Means for solving the problem) Therefore, we investigated the residual stress caused by the difference in thermal expansion of the ceramic shaft that is brazed to the metal shaft. On the other hand, as shown in FIG. 3, it is recognized that stress concentration occurs near the joint, and then it decreases smoothly with distance. On the other hand, as shown in FIG. 1, the relationship between the length 2) at which the sleeve (3) is brazed to the ceramic shaft and the diameter 0 of the ceramic shaft, that is, A/D is 0.1.02, 0. 3
, 0.4 jump = On/D = 0), the stress generated by the bending due to one vibration and the screw torque due to the change in rotational speed is shown in Fig. 4. The joining length (gripping length) is 0.3.

When 0.40, there is a large stress concentration at the edge (η),
It is recognized that when there is no gripping length, a large stress concentration occurs at the joint. Figure 5 is a combination of the results of Figures 3 and 4, and when viewed from Figure 6, which shows the maximum stress, the grip length is 0.05 D~
It is clear that between 0.2 D the stress concentration is reduced. Therefore, based on the above findings, the present invention aims to improve the drawbacks of the conventional joint by brazing the end of the ceramic shaft to the metal shaft and shrink-fitting or brazing the joint to the outer periphery of the joint. Todoroki υ, the grip length of the sleeve with the ceramic shaft is 0 if the diameter of the ceramic shaft is D.
．． 05 to 0.2D. In other words, the above 0
．． If it is smaller than 05D, stress concentration will occur at the joint, and the
．． If it is larger than 2D, stress concentration may occur at the edge portion.

(Function) Since the structure is as described above, if the ceramic shaft, which is joined to the metal shaft at the end and tightly fitted with a sleeve around this joint, rotates, vibrates, or bends, The length of the grip) is 0.05D to 0.05D on the above axis.
In the case of 2D, the stress acting on the joint portion and the stress acting on the gripping edge portion are balanced - they are different.

In addition to the stress mentioned above, thermal stress is generated when the ceramic shaft is used at high temperatures, but in the structure of this invention, the sleeve tends to expand in the axial direction, and no stress is applied to the ceramic shaft. 1) Since this stress is proportional to the gripping length of the sleeve, a problem will occur if it exceeds the above-mentioned limited range, but within the scope of the present invention, thermal stress will not have any effect.

(Example) An example in which this is applied to a ceramic turbocharger shown in FIG. 2 will be described. The same parts as in FIG. 1 will be described with the same reference numerals.

(1) is a turbine rotor shaft with a diameter IQu+ made of ceramic, and (2) is a shaft with N
i.

It is a metal shaft that is joined to a joint (5) that is brazed through a stress buffer plate made of three layers of Ni-W alloy and Ni, and at the same time, a sleeve that tightly fits onto the joint (5). (3) is brazed to the metal shaft (2), and the sleeve (3) is
Some of them are ceramic! I\II (11) is also fitted and brazed (4). In the figure, (6) is 7 rd.

The above turbine rotor was assembled into an engine, different lengths were prepared, and an idling cycle test (Go-8TOP test) was conducted with the engine fully open, and the following results were obtained.

As above, the grip length t3) is 13/D=0.
It is clear that when the value is between 05 and 02, no breakage occurs from either the joint 1 or the edge.

In this invention, the ceramic materials are preferably heat-resistant ceramics such as silicon nitride and silicon carbide, and the metal materials are carbon steel, alloy steel, stainless steel, maraging steel, heat-resistant steel such as Inconel, hollow steel, Fe -N
i-Co alloy (:I74-) titanium and the like are preferred. In addition to the above metal materials, the sleeve material is preferably a low expansion or low Young's modulus material such as tungsten, silver, zirconium, molybdenum, steel, or a shape memory alloy.

As the brazing material, Ag-Cu eutectic brazing, Au-Cu-Pd brazing, Ni, or Ni alloy brazing can be used.

(Effects of the invention) Through the above, this invention is suitable for joining ceramic shafts and metal shafts.
Since the grip length of the sleeve that fits tightly into the joint is within a specified range, the generated stress can be reduced and the ceramic shaft can be prevented from breaking at the joint or edge. It has a certain effect.

[Brief explanation of drawings]

Fig. 1 shows the joining structure of the ceramic shaft body of the present invention, Fig. 2 is a partial vertical cross-sectional view of this applied to the rotor of a turbocharger, and Figs. These are various materials showing the invention. DESCRIPTION OF SYMBOLS 1... Ceramic shaft, 2... Metal shaft, 3... Sleeve, 4... Brazing metal, 5... Joining part, 6... Bleed, 7... Edge part. Patent Applicant Representative Patent Attorney Miyuki Fujiki Figure 3 Figure 5 Capital %, /'i:: Gai ζ and rsr - 3 Forces and Q Soviet Captives Figure 4 Figure 6 B/ WπA Hishik

Claims (1)

[Claims] A ceramic shaft and a metal shaft are brazed together, and a sleeve is tightly fitted around the outer periphery of this joint by shrink fitting or brazing,
If the diameter of the ceramic shaft is D and the length of the sleeve that fits tightly onto the ceramic shaft is l, then l/D is 0.05 to 0.
2. The joining structure of the ceramic shaft body.