Electric compressor

Abstract

An electric turbo compressor is an air compressor to be used in a fuel cell system, and includes a housing comprised of a compression casing, a motor casing, and a canceller casing, and the housing houses therein an impeller, a rotary shaft, a thrust canceller (a load cancellation section), and a motor unit. The rotary shaft is supported by a thrust air bearing in its thrust direction, and is axially supported by a radial air bearing in its rotating direction. A thrust load is generated at the rotary shaft when the number of rotations of the impeller increases. The pressure of the compressed air acts to the pressure chamber from the compressed air lead-out section of the compression casing via the compressed air passage, and this pressure acts on the canceller flange of the canceller shaft so as to generate a load towards the rear of the rotary shaft. Therefore, the thrust load is cancelled out.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an electric compressor which compresses gas with the rotation of an impeller, by rotating a rotary shaft and the impeller with a motor unit. [0003] 2. Description of the Related Art [0004] In the conventional electric compressor, for example, there is disclosed a turbo machine equipped with vane wheels (hereinafter referred to as impellers) to both sides of the rotary shaft, in Japanese Patent Laid-Open No. H11-13686 (hereinafter referred to as Patent Document 1). Generally, in this type of compressor, a thrust load proportional to a square of a number of rotations of the impeller generates in the axial direction of the rotary shaft, when the number of rotations of the impeller increases. In the turbo machine disclosed in Patent Document 1, the thrust load is cancelled by making the thrust load generated by the impellers provided to both sides of the rotary shaft to act in a directio...

AI Technical Summary

Benefits of technology

The present invention provides an electric compressor with high compression efficiency and good surge property. The compressor includes a motor unit, a rotary shaft, a motor casing, a compression casing, and an impeller. The rotary shaft is supported by a radial bearing and a thrust air bearing in the axial direction. The thrust air bearing includes a flange portion and front and rear thrust bearings. The motor casing includes a pressure chamber that introduces gas pressure. The rotary shaft is equipped with a load cancellation section that receives the opposite pressure to the load generated by the rotation of the impeller. The load cancellation section cancels out the thrust load generated at the rotary shaft. The electric compressor is capable of maintaining the clearance between the impeller and the compression casing accurately, regardless of the speed of rotation. The load cancellation section reduces the size, weight, and cost of the thrust air bearing. The rotary shaft is preferably hollow tubular shape with a cavity inside, and the load cancellation section is connected to the impeller by the tension shaft via the cavity. This minimizes the variation of the clearance between the impeller and the compression casing.

Problems solved by technology

However, because the pressure of gas corresponding to the thrust load acts on the load cancellation portion in the direction opposite thereto, the thrust load generated at the rotary shaft may be cancelled out.

Therefore, even when the number of rotations of the impeller increases, excessive thrust load is not generated at the rotary shaft.

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