Rotary fluid machine

Abstract

A rotary fluid machine is provided that includes a rotor rotatably housed within a casing, a hollow rotating shaft (113) that rotates integrally with the rotor, and a fixed shaft (102) that is relatively rotatably fitted into the inner periphery of the rotating shaft (113); in which the rotating shaft (113) is formed by shrink-fitting an outer sleeve (21) made of metal around the outer periphery of an inner sleeve (85) made of ceramic, etc. having a lower coefficient of thermal expansion than that of metal, and the fixed shaft (102) is formed by shrink-fitting an outer sleeve (88) made of metal around the outer periphery of an inner sleeve (87) made of ceramic, etc. having a lower coefficient of thermal expansion than that of metal. Since thermal expansion of the outer sleeves (21, 88) fitted around the outer peripheries of the inner sleeves (85, 87) is suppressed due to residual tensile stress of the outer sleeves (21, 88), intimate contact between the outer sleeves (21, 88) and the inner sleeves (85, 87) can be maintained.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a rotary fluid machine for interconverting the pressure energy of a gas-phase working medium and the rotational energy of a rotor. BACKGROUND ART [0002] A rotary fluid machine disclosed in Japanese Patent Application Laid-open No. 2000-320543 is equipped with a vane piston unit in which a vane and a piston are combined; the piston, which is slidably fitted in a cylinder provided radially in a rotor, interconverts the pressure energy of a gas-phase working medium and the rotational energy of the rotor via a power conversion device comprising an annular channel and a roller, and the vane, which is radially and slidably supported in the rotor, interconverts the pressure energy of the gas-phase working medium and the rotational energy of the rotor. [0003] In such a rotary fluid machine, a rotary valve for supplying and discharging a high temperature gas-phase working medium is formed between the outer peripheral face of a fi...

AI Technical Summary

Benefits of technology

The present invention proposes a rotary fluid machine that reduces the increase in leakage and abnormal wear by minimizing the variation in clearance between the sliding surfaces of a fixed shaft and a rotating shaft due to thermal expansion. This is achieved by shrink-fitting an outer sleeve made of metal around the inner sleeve made of a material having a lower coefficient of thermal expansion than that of metal. The inner periphery of the rotating shaft, which is supported by the fixed shaft and rotates integrally with the rotor, is formed by shrink-fitting the outer sleeve around the outer periphery of the inner sleeve. The outer sleeve is made of metal and is shrink-fitted around the inner sleeve, which is made of a material having a lower coefficient of thermal expansion than that of metal. This results in a stable clearance between the sliding surfaces of the fixed and rotating shafts, suppressing the overall thermal expansion of the rotating shaft and reducing the likelihood of leakage and abnormal wear.

Problems solved by technology

If an attempt is made to ensure the sealing characteristics of the rotary valve by means of a seal, there is the problem of a decrease in the durability of the seal, which is exposed to a high temperature gas-phase working medium, and if an attempt is made to ensure the sealing characteristics by means of a lubricating oil, the lubricating oil undesirably contaminates the working medium.

However, since the difference in temperature of the rotary valve between when it is hot and when it is cold is extremely large, the clearance varies due to thermal expansion, and there is a possibility that abnormal wear or leakage might occur.

That is, when a high temperature gas-phase working medium is supplied to the rotary valve through the interior of the fixed shaft when cold, the fixed shaft, which is on the inside, thermally expands first, and the rotating shaft, which is on the outside, thermally expands after a time lag, the clearance therebetween decreases, and abnormal wear is caused due to the contact.

In order to avoid this problem, the use of a material such as ceramic that has a small coefficient of thermal expansion for both the fixed shaft and the rotating shaft can be considered, but the sliding surfaces of materials of the same type have poor sliding characteristics, and there is a possibility that the friction might increase or that seizing might occur.

Furthermore, when an attempt is made to apply a low friction material in order to improve the sliding characteristics, there is the problem that it is difficult to coat ceramic.

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