JPH0424522B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ceramic shaft mounting structure for an impeller.

In recent years, research has been underway to apply ceramics to high-temperature parts in gas turbines and turbochargers, which not only have excellent properties as a heat-resistant material but also have other mechanical properties that are more suitable than metal materials. In particular, if the turbine rotor and rotor shaft are integrally molded from ceramics,
Not only can weight and inertia be effectively reduced, but costs can also be reduced, but in such cases, a compressor impeller made of, for example, a light alloy must be attached to the ceramic rotor shaft, and various problems must be solved. is required.

Figure 1 shows an example of the conventional mounting structure of this type of impeller with a ceramic shaft (Japanese Patent Laid-Open No. 54-68315
1), here 1 is a ceramic rotor shaft (hereinafter referred to as ceramic shaft), and its stepped portion 1
A compressor impeller 2 is fitted into the small diameter shaft portion 1B beyond A, and the impeller 2 is connected to the stepped portion 1A.
The impeller 2 is fixed by tightening a nut 3 to a threaded portion 1C threaded on the end of the shaft portion 1B. 4 indicates a bearing member for the shaft 1.

However, in such a conventional structure for attaching a compressor impeller to a ceramic shaft, the impeller 2 is fixed by screwing a nut 3 into a threaded portion 1C cut into the shaft end of the ceramic shaft 1. Therefore, not only is it costly to process the thread of the ceramic shaft 1, but also the threaded part 1C
Due to the tightening force of the nut 3 and the thermal expansion of the compressor impeller 2, which is generally made of aluminum alloy, etc., the threaded portion 1C is damaged due to tensile stress concentrated on the threaded portion 1C via the nut 3. Easy to do.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic shaft mounting structure for an impeller that eliminates the above-mentioned drawbacks, can be obtained at low cost, and is free from damage.

In order to achieve this object, the present invention provides a ceramic shaft mounting structure for an impeller, in which a stepped small diameter portion of a ceramic shaft is inserted through a mounting hole of an impeller, and is secured by screwing a nut. The sleeve portion of a metal sleeve member having a sleeve portion and a threaded portion integrally formed on the same axis is fitted between the mounting hole of the impeller and the ceramic shaft, and the sleeve portion of the sleeve portion is fitted between the mounting hole of the impeller and the ceramic shaft. A slit in the axial direction is provided from an extending part that extends in the axial direction from the fitting part with the impeller to the fitting part, and a slit is provided in the axial direction from the inner circumferential surface of the end of the extending part where the slit is provided. An engaging portion protruding toward the ceramic shaft is engaged with a locking groove provided on the outer periphery of the ceramic shaft corresponding to the engaging portion by the elasticity of the extending portion having the slit. The metal sleeve part is fixed to the ceramic shaft, the impeller is brought into contact with the stepped part provided on the metal sleeve member, and the nut is screwed into the threaded part, so that the impeller is fixed to the stepped part. It is characterized in that it is brought into pressure contact with the part.

The present invention will be explained in detail below based on the drawings.

FIG. 2 shows one embodiment of the invention, where 11
1 is a metal sleeve member consisting of a threaded portion 12 and a sleeve portion 13. The sleeve portion 13, which is fitted onto the end of the ceramic shaft 1, extends from the impeller 2 to the right in the figure, and the outer diameter of the extending portion 13A is The end face 2A of the hub on the differential user side of the impeller 2 is made larger than the outer diameter of the fitting part 13B with the mounting hole 2A.
A stepped portion 13C is formed at the boundary between the extending portion 13A and the fitting portion 13B at the position. 13D is extension part 1
3A is an engaging portion protruding along the inner circumferential surface of the end portion, and 14 is an extending portion 13A as shown in FIG.
From the middle of the fitting part 13B or the fitting part 1
It is an axially symmetrical slit made up of multiple sections carved throughout 3B. The ceramic shaft 1 to be fitted into the sleeve portion 13 is provided with an annular locking groove 15 extending over the entire circumference at a position corresponding to the engaging portion 13D protruding from the extending portion 13A. Note that the cross-sectional shape of the protruding portion of the engaging portion 13D is formed into a smooth circular arc shape, and the cross-sectional shape of the corresponding groove 15 is also formed to match the shape of the engaging portion 13D.

When attaching the impeller 2 to the ceramic shaft 1 using the mounting structure configured as described above, first, the end of the ceramic shaft 1 is fitted into the sleeve portion 13 of the sleeve member 11, and the engagement provided on the extending portion 13A is inserted. The part 13D is inserted into the locking groove 15 of the ceramic shaft 1.
Insert it into.

At this time, since the sleeve part 13 is provided with a slit 14, each piece of the sleeve part 13 branched by the slit 14 acts as a spring material, and the engaging part 13D is instantly fitted into the groove 15. After this, the spring force maintains the locked state. Next, the impeller 2 is heated to a high temperature, the impeller 2 is shrink-fitted to the fitting part 13B of the sleeve part 13, the back surface of the impeller 2 is brought into contact with the stepped part 13C, the nut 3 is screwed onto the threaded part 12, and the nut 3 is screwed onto the threaded part 12. The action causes the impeller 2 to be pressed against the stepped portion 13C.

FIG. 4 shows another embodiment of the invention, in which:
Reference numeral 13E represents an engaging portion provided at the end of the extending portion 13A of the sleeve portion 13, and reference numeral 15E represents a locking groove provided around the ceramic shaft 1 at a position corresponding to the engaging portion 13E. In this example, the engaging portion 13E and the locking groove 1
The cross-sectional shape of the ceramic shaft 15E is made into a circular arc shape with a wider gentle curve than the example shown in FIG. The stress concentration that occurs can be alleviated.

In addition, in the above explanation, the case where the engaging part and the locking groove are provided all around the inner circumferential surface of the end of the extending part of the sleeve part and the outer circumferential surface of the ceramic shaft has been described. Although not shown in , for example, the engaging portions and locking grooves are interrupted at one or more points on each circumference, and the engaging portions and locking grooves are provided only in the remaining peripheral portions for locking. It is also possible to make them match. In this way, the tendency of the metal sleeve member to rotate around the ceramic shaft can be restrained.

As explained above, according to the present invention, the ceramic shaft of the impeller is mounted in such a way that the stepped small diameter portion of the ceramic shaft is inserted into the mounting hole of the impeller, and is fixed by screwing the nut. In the structure, the sleeve part of a metal sleeve member having a sleeve part and a threaded part integrally formed on the same axis is fitted between the mounting hole of the impeller and the ceramic shaft, and The slit in the axial direction is provided from an extending part that extends in the axial direction from the fitting part with the impeller to the fitting part, and the slit is provided inward from the inner circumferential surface of the end of the extending part where the slit is provided. an engaging portion protruding toward the engaging portion is engaged with a locking groove provided on the outer periphery of the ceramic shaft corresponding to the engaging portion by the elasticity of the extending portion having the slit; The metal sleeve is fixed to the ceramic shaft, the impeller is brought into contact with a stepped part provided on the metal sleeve member, and the nut is screwed into the threaded part, so that the impeller is fixed to the stepped part. This eliminates the stepped and threaded parts that were previously provided on ceramic shafts, and there is no risk of damage to the ceramic shaft due to stress concentration due to the tightening force of the nut or the notch effect. Moreover, since the freeb part branched by the slit engages the engaging part with the locking groove by screw force, the stress generated by the thermal expansion of the impeller is also transferred to the ceramic shaft through this sleeve part. The spring effect of the sleeve section protects the impeller from damage.

Furthermore, since the engaging portion and the locking groove have a smooth shape and are maintained in pressure contact with each other by the spring force, excessive stress concentration does not occur at the portion of the locking groove.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of the ceramic shaft mounting structure of a conventional impeller, Fig. 2 is a sectional view showing an example of the ceramic shaft mounting structure of the impeller of the present invention, and Fig. 3 is an exploded view of the mounting structure. The perspective view and FIG. 4 are cross-sectional views of an engaging portion and a locking groove in another embodiment of the present invention. 1...Ceramic shaft, 1A...Stepped part, 1B
...Small diameter shaft part, 1C...Threaded part, 2...Impeller, 2A...Mounting hole, 3...Nut, 4...Bearing member, 11...Sleeve member, 12...Threaded part, 13...Sleeve Part, 13A... Extension part, 1
3B...Fitting part, 13C...Stepped part, 13
D, 13E...Engaging portion, 14...Slit, 1
5,15E...Ditch.

Claims (1)

[Claims] 1 In an impeller ceramic shaft mounting structure in which the stepped small diameter part of the ceramic shaft is inserted through the impeller mounting hole and fixed by screwing a nut, the sleeve part and the threaded part are mounted on the same axis. The sleeve portion of the metal sleeve member integrally formed on the center is fitted between the mounting hole of the impeller and the ceramic shaft, and the sleeve portion extends in the axial direction from the fitting portion of the sleeve portion with the impeller. The slit in the axial direction is provided from the extending portion extending from the extending portion to the fitting portion, and the engaging portion protrudes inward from the inner circumferential surface of the end portion of the extending portion where the slit is provided. The metal sleeve is fixed to the ceramic shaft by engaging with a locking groove provided on the outer periphery of the ceramic shaft corresponding to the engaging portion by the elasticity of the extending portion having the slit. and bringing the impeller into contact with a stepped portion provided on the metal sleeve member,
A ceramic shaft mounting structure for an impeller, characterized in that the nut is screwed onto the threaded portion to press the impeller into contact with the stepped portion.