JPS58178803A - Turbine shaft - Google Patents

Abstract

PURPOSE:To reduce a manufacturing cost by a method wherein a metallic shaft to be connected to the ceramics shaft integrally formed with the rotor of a turbo charger is formed with an aluminum alloy and these shafts are butt welded. CONSTITUTION:The material quality of a metallic shaft 11 is a pure aluminum or alumnum alloy, and as materials of a turbine rotor 2 and a ceramics shaft 1, a silicon carbide, silicon nitride, aluminum nitride or sialonite etc. are applied. For connecting the metallic shaft 11 and the ceramics shaft 1, a friction welding, laser beam welding, electron beam welding or a high frequency welding etc. are applied. The contact surface of the bearing collar etc. of the metallic shaft 11 is formed with a coated surface 12.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbine shaft, and more particularly to a turbocharger shaft.
It is related to the turbine shaft of ceramic star turbines and gas turbines.

Fig. 1 shows an example of a conventional turbine shaft.
It is also disclosed in the publication. Here, l is a ceramic turbine shaft formed integrally with the ceramic turbine rotor λ, and a fitting part /A of the ceramic shaft l,
The compressor impeller 3 is joined to the metal sleeve l by shrink fitting, press fitting, gluing, or the like. Also,
End 4'B of the metal sleeve V on the side where the fitting hole 4'A is provided
A tapered surface is provided around the periphery, and after the two are fitted by shrink fitting etc., the ceramic shaft / is attached to the end 4'H of the sleeve.
It is exposed to discontinuous, human-sized, and high contact pressure at these points, which prevents it from breaking due to that stress.

J is a 70-ring type bearing provided on the metal sleeve side, and B is a ceramic 70-ting push provided on the ceramic shaft l side, and wear resistance is taken into consideration. r and 9 are washers and nuts used to secure the impeller 3, /θ is a screw cut into the metal sleeve l.

However, in such conventional turbine shafts, the ceramic shaft formed in the rotor 2 and 7 bodies is joined to the metal sleeve l in a fitting manner, and when exposed to high temperatures during operation, the ceramic and metal Since there is a difference in coefficient of thermal expansion between the two, embroidery is likely to occur at the fitting portion. Also, if the interference is too large, the end portion of the sleeve will be damaged due to shrink fitting stress.

To prevent these problems, tightening must be maintained at an appropriate value, and when machining metal sleeve plugs or ceramic shafts, a machining accuracy of less than 1.5 μm is required, leading to an increase in machining costs. . Furthermore, if a large tightening margin is required, a high-strength material such as maraging steel must be used for the sleeve l, which increases the material cost for r1.

In view of the above-mentioned points, an object of the present invention is to provide a lightweight and inexpensive turbine shaft formed by butt-joining a lightweight metal shaft and a ceramic shaft.

In order to achieve such an object, in the present invention, the metal shaft to be joined to the ceramic shaft is formed of aluminum or an aluminum-based alloy that is compatible with the ceramic and easily fused or welded, and such a metal shaft and the ceramic shaft are butted. At the same time, a hard film is formed on the outer peripheral surface of the metal shaft in contact with the bearing.

In the following, the invention will be explained in detail with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, where // is a metal shaft welded in abutment with the ceramic shaft /, and the material of the metal shaft l/ is such that it has a good bonding state with the ceramics. Pure aluminum or aluminum to ensure that it is kept! alloy (hereinafter referred to as aluminum-based metal). Further, as the ceramic material for the turbine rotor tacho and the ceramic shaft 1, it is preferable to use silicon carbide, silicon nitride, aluminum nitride, sialon, or the like. Here, when joining the metal shaft // and the ceramic shaft, for example, a method such as friction welding, laser beam welding, electron beam welding, or high frequency welding may be used. Since the material is selected to be easily compatible with the material when joining, a sufficiently strong bond can be obtained.

In the present invention, since the metal shaft l/ is formed of a 'γ aluminum metal material with relatively low hardness, in order to protect its outer peripheral surface, the contact surface of the metal shaft // with the floating metal S and the thrust bearing (not shown) A coating surface is formed over a range of areas including the contact surface with the collar. This coating direction 12 can be formed by hardening the surface of the metal shaft // by, for example, hard chrome plating, plasma spraying of hard gold, or anodized coating by alumite treatment, etc. Finishing is then carried out to the final dimensions.

The thus obtained coating surface /2 has a surface hardness sufficiently comparable to that of the conventional metal shaft 1, etc., which has been surface hardened using nickel chromium molybdenum #Ili.

By the way, in order to avoid the need for such surface treatment, it is conceivable to extend the ceramic shaft further to the impeller 3 side than the position of the bearing S, etc., as in the case of (3) gas turbine. If the shaft length is long, it becomes difficult to mold the ceramic shaft, which is not preferable.

FIG. 3 shows another embodiment of the present invention, in which a sleeve n is attached to a metal shaft made of the same material as the metal shaft l/ shown in FIG. 1 by shrink fitting or press fitting. The other configuration is the same as the example in Figure 2, and the metal shaft
and the ceramic shaft/ are connected in abutted state. In the turbine shaft configured in this way, the sleeve n is shrink-fitted to the metal shaft made of aluminum metal with a large coefficient of linear expansion, so that the metal shaft I and the sleeve n will remain stable even when exposed to high temperatures during operation. There is no possibility of loosening between the parts, and therefore less tightening is required, resulting in savings in processing costs and material costs. In addition, since only a small amount of tightening is required, the shrink fitting stress is also small.

As explained above, according to the present invention, in the turbine shaft in which the metal shaft is fully joined to the ceramic shaft integrated with the turbine rotor, the metal shaft is formed of an aluminum-based metal material, and the metal shaft f, <1 We butted and welded the metal shaft to the ceramic shaft, and provided an IK hard coating on the outer periphery of the metal shaft in contact with the bearing.
Unlike in the past, there is no need for looseness between the two due to the fitting joint, and strict machining accuracy is not required to obtain the appropriate tightening value at the fitting part, and there is no need for wear resistance in the bearing part. properties can be maintained, and material costs and processing costs can be reduced. In addition, due to the weight reduction of the shaft body,
The moment of inertia is small, and the acceleration/deceleration characteristics of the shaft system are improved.

However, if a hard coating is formed on the outer circumferential surface of the metal shaft by inserting a metal sleeve, the rigidity of the metal shaft will be increased, which will increase the bending strength of the turbine shaft and improve the strength against bending stress generated when the shaft vibrates. do.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the structure of a conventional turbine shaft made by joining a ceramic shaft and a metal shaft, FIG. 2 is a sectional view showing an example of the structure of the turbine shaft of the present invention, and FIG. FIG. 7 is a cross-sectional view of another embodiment of the invention without the configuration thereof; / Ceramic shaft, /A...fitting part, λ-...
Turbine motor, 3. impeller, L sleeve,
4'A--fitting hole, IIB...end,
S...bearing, 6...-button, g.
...Washer? ...Natsuto, /θ...
Screw, //, 2/・metal shaft, /2・-film surface,〃・sleeve. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1) In a turbine shaft formed by joining a metal shaft to a ceramic shaft integral with a ceramic turbine rotor, the metal shaft is formed of aluminum or an aluminum-based alloy material, and the metal shaft and the ceramic shaft are bonded together. A turbine shaft, wherein the metal shaft is welded by butt and has a hard wear-resistant coating surface on at least the shaft support surface of the metal shaft. 2. In the turbine shaft according to claim 1,
The material of the ceramic shaft is silicon carbide, silicon nitride,
A turbine shaft characterized in that it is made of one of aluminum nitride and sialon.