BACKGROUND

1. Field

The present disclosure relates to a transmission and a centrifugal compressor equipped with the transmission.

2. Description of Related Art

As disclosed in Japanese Laid-Open Patent Publication No. 2004-308757, a transmission that transmits driving force between a low speed shaft and a high speed shaft has been known. The transmission disclosed in the document includes a transmission housing, an annular ring portion that rotates as a low speed shaft rotates, a high speed shaft arranged on the inner side of the ring portion, and rollers that are arranged between the ring portion and the high speed shaft. The rollers each have an outer circumferential surface that contacts both of the inner circumferential surface of the ring portion and the outer circumferential surface of the high speed shaft. The document also discloses that at least one of the rollers is a movable roller.

Some transmissions include a movable bearing that rotatably supports a movable roller. In this case, the movable bearing must support the movable roller such that the movable roller is movable. The movable bearing thus may be movable.

In such a configuration, displacement or dimensional errors may cause the movable bearing to be caught on the transmission housing. In this case, the movable bearing may hinder the movement of the movable roller. Also, sliding motion between the movable bearing and the transmission housing may wear components.

SUMMARY

Accordingly, it is an objective of the present disclosure to provide a transmission and a centrifugal compressor equipped with a transmission that allows a movable bearing to move smoothly.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In a first general aspect, a transmission is provided that includes a transmission housing member, an annular ring portion that is provided in the transmission housing member and rotates as a low speed shaft rotates, a high speed shaft that is arranged on an inner side of the ring portion, at least three rollers that are provided between the ring portion and the high speed shaft and contact both of an inner circumferential surface of the ring portion and an outer circumferential surface of the high speed shaft, and radial bearings with which the rollers are rotatably supported by the transmission housing member. The rollers include a movable roller that moves in a rotation direction of the ring portion in response to rotation of the ring portion, and a fixed roller that is fixed so as not to move in the rotation direction of the ring portion. The radial bearings include a movable bearing that rotatably supports the movable roller. The transmission housing member includes a first supporting surface that contacts the movable bearing so as to restrict the movable roller to a first position, and a second supporting surface that is provided at a position spaced apart from first supporting surface in the rotation direction and contacts the movable bearing so as to restrict the movable roller to a second position. Movement of the movable roller is performed within a movement range from the first position to the second position. The movement range includes a specified range in which the movable roller is not supported, in a radial direction of the high speed shaft, by the transmission housing member with the movable bearing in between, but is supported by being held between the ring portion and the high speed shaft.

In a second general aspect, a transmission is provided that includes a transmission housing member, an annular ring portion that is provided in the transmission housing member and rotates as a low speed shaft rotates, a high speed shaft that is arranged on an inner side of the ring portion, at least three rollers that are provided between the ring portion and the high speed shaft and contact both of an inner circumferential surface of the ring portion and an outer circumferential surface of the high speed shaft, and roller bearings with which the at least three rollers are rotatably supported by the transmission housing member. The at least three rollers include at least one movable roller that moves, in response to rotation of the ring portion, between a first position and a second position that is spaced apart from the first position in a rotation direction of the ring portion, and at least two fixed rollers that are fixed so as not to move in the rotation direction of the ring portion. The roller bearings include a movable bearing that rotatably supports the movable roller. The transmission housing member includes, as surfaces that define a movable bearing accommodating chamber that accommodates the movable bearing, a bottom surface, and an accommodating side surface that extends from the bottom surface and includes the first supporting surface and the second supporting surface. The movable bearing accommodating chamber is arranged on an outer side of the high speed shaft in a radial direction of the high speed shaft. The accommodating side surface includes a first supporting surface that contacts the movable bearing so as to support the movable bearing when the movable roller is at the first position, and a second supporting surface that is provided at a position spaced apart from the first supporting surface in the rotation direction, and contacts the movable bearing so as to support the movable bearing when the movable roller is at the second position. The accommodating side surface includes a separated surface provided at a position separated from the movable bearing and on an outer side of the movable bearing in the radial direction of the high speed shaft. A clearance exists between the separated surface and the movable bearing regardless of a position of the movable bearing.

Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.

