JPS60116923A - Shaft fastening tool - Google Patents

Abstract

PURPOSE:To eliminate crack in ceramic shaft and to increase fastening force of shaft as the temperature rises by forming the fastening tool through lamination of material having different thermal expansion factor into a coil. CONSTITUTION:A laminated strip board 3 of material having different thermal expansion factor is formed into a coil then the shaft fastening area is increased to construct a fastening tool 4. The shaft to be fastened such as a ceramic shaft 5 and a metal shaft 6 are pressure inserted to the inside of said fastening tool 4 under normal temperature then both shafts are fastened. Consequently, even upon temperature rise, the fastening tool 4 itself will contract to increase the fastening force thus to improve the reliability under high temperature resulting in prevention of crack in ceramic shaft 5 due to thermal stress.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a fastener between shafts, and is particularly suitable for use in a shaft fastening part of a ceramic turbocharger or an X-ray target used under high temperature conditions. Regarding fasteners.

[Background of the Invention] Bonding and mechanical fastening have been considered for fastening a ceramic shaft and a virtual shaft, or for fastening ceramic shafts together. For example, in joining and fastening a ceramic shaft and a metal shaft, methods have been considered in which the end face of the ceramic shaft is metallized and joined to the end face of the metal shaft via a brazing material, or direct diffusion bonding without using a brazing material. However, when these types of joints are used to connect shafts to each other, cracks occur in the ceramic shafts due to the generation of thermal stress.
It is difficult to obtain a reliable one.

Furthermore, brazing materials with low melting points have limitations in their use in high-temperature environments.

On the other hand, for mechanically fastening a ceramic shaft and a metal shaft, a method using, for example, shrink fit has been considered. However, in this method, when a metal shaft is inserted into a ceramic shaft and tightened, the ceramic shaft, which has low tensile strength and low deformability, may be damaged if thermal stress is generated due to a rise in temperature. In addition, if the combination is reversed and shrink-fitted, there is a large difference in thermal expansion between the two, so as the temperature rises, the fastening force decreases and the original function is no longer achieved. Another possible method is to use a metal with a low coefficient of thermal expansion, such as molybdenum, for the shaft fastening portion, but these materials are generally expensive.

As described above, it has been difficult to provide a highly reliable product at a low cost with the conventional method of coupling shafts together.

[Purpose of the invention]

An object of the present invention is to provide a reliable method that can connect a ceramic shaft and a metal shaft or ceramics together under high-temperature conditions without causing cracks in the ceramic shaft, and that the joining force between the shafts increases as the temperature rises. The objective is to provide fasteners with high performance.

[Summary of the invention]

In order to achieve this object, the shaft-to-shaft fastener of the present invention is characterized in that materials having different coefficients of thermal expansion are formed into a laminated band shape and formed into a coil shape.

[Embodiments of the invention]

Before describing specific embodiments of the present invention, the principle of the fastener of the present invention will be explained with reference to FIGS. 1 to 4. As shown in FIGS. 1(a) and 1(b), a material 1 having a thickness of a thermal expansion coefficient α1 and a thickness h2 having a coefficient of thermal expansion α2 smaller than the coefficient of thermal expansion α1 of the material 1. A laminated strip plate 3 having a width is made with the material 2, and a cylinder having a radius R is formed by this laminated strip plate 3 as shown in FIG. Then, when the temperature change of AT is given to the cylinder, the plate thickness is h2
and thermal expansion coefficient α1. The amount of contraction AR in the radius of curvature can be calculated using α2 as a parameter, but if we focus only on the theoretical parameters and consider h, = h2 = h, α1>α2, the amount of contraction is 7! IR can be expressed as follows.

AR=R=4hR/ (4b+3!lT(α1-α2)
R) - (α1+α2)/2・ATR Here, material 1 is 18-8 stainless steel (α1≠18X
10-6), and material 2 is carbon tR (α2= 12
X 10-6) R=30mm, h=2mm, ΔT
= 7 assuming 500℃! When IR is added, AR-0,7
It becomes 5mn. In other words, the radius will be reduced by 0.75 mm.

The fastener according to the present invention utilizes the above-mentioned principle, and the laminated strip 3 shown in FIG. 1 is formed into a coil shape as shown in FIGS. 3(a) and 3(b). This is an increase in Then, the shafts to be fastened, for example, a ceramic shaft and a metal shaft, are inserted into the inside of this fastener by press-fitting or the like at room temperature, and both shafts are fastened. As a result, even if the temperature rises, the fastener itself shrinks and the tightening force increases, improving reliability under high temperatures and preventing cracks from occurring in the ceramic shaft due to thermal stress.

In addition, especially when fastening a metal shaft and a ceramic shaft, since the coefficient of thermal expansion of the metal shaft is large, the metal shaft insertion portion C of the fastener should be formed into a cylindrical shape, as shown in Fig. 4. This enables even more reliable fastening.

Next, specific embodiments of the present invention will be described with reference to FIGS. 5 to 8. FIG. 5 shows an example in which ceramics 5 are fastened together using the fastener 4 explained in FIG. 3. In this configuration, the diameter of the fastener 4 decreases as the temperature rises to maintain the fastening force, making it possible to obtain a highly reliable fastening part in a high temperature range, and also preventing cracks from occurring in the ceramic shaft 5. .

FIG. 6 shows an example in which a ceramic shaft 5 and a metal shaft 6 are fastened together using the fastener 4' described in FIG. 4. That is, the ceramic shaft 5 is inserted into the coiled portion of the fastener 4' by press-fitting or the like, and the metal shaft 6 is inserted into the cylindrical portion C by press-fitting or the like.

In FIG. 7, a fastener 4' and a metal shaft 6 are integrated, and a ceramic shaft 5 is inserted into the coiled part of the fastener 4'.
An example is shown in which the ceramic shaft 5 and the metal shaft 6 are fastened together.

FIG. 8 shows an example in which the shaft 8 of the ceramic rotor 7 and another shaft 9 are fastened together using the fastener 4 shown in FIG.

[Effects of the Invention] As explained above, according to the present invention, a ceramic shaft and a metal shaft or ceramic shafts that are used under high temperature conditions can be fastened together without causing cracks in the ceramic shaft, and moreover, the temperature rise Since the fastening force increases as the speed increases, a highly reliable shaft fastening section can be provided. Furthermore, since there is no need to use an expensive material with a low coefficient of thermal expansion such as molybdenum, it can be manufactured at low cost.

[Brief explanation of drawings]

1 to 4 are shown to explain the present invention in detail, and FIG. 1(a) is a plan view of a laminated strip;
Figure 3(b) is an end view thereof, Figure 2 is a side view of the laminated strip formed into a cylindrical shape, Figure 3(a) is a front view showing an example of the fastener according to the present invention, Figure 3(b) 4 is a front view showing another example of the fastener, and FIGS. 5 to 8 are front views showing specific embodiments of the present invention.

Claims (1)

[Claims] 1. A shaft-to-shaft fastener used under high temperature conditions, comprising:
A fastener between shafts, characterized by laminated strips made of materials with different coefficients of thermal expansion and formed into a coil shape. 2. A axial fastener according to claim 1, characterized in that a portion thereof is formed into a cylindrical shape by laminated strips.