Abstract: A housing structure includes: a first housing having a fitting inner tubular portion that has an inner tubular end surface and a first bolt fastening portion that has a first bolt aligning surface formed at a position away from the inner tubular end surface in the radial direction, the first housing supporting a first end of an assist shaft via a first bearing; and a second housing having a fitting outer tubular portion having an outer tubular end surface and a second bolt fastening portion that has a second bolt aligning surface that mates with the first bolt aligning surface, the second housing supporting a second end of the assist shaft via a second bearing. A first gap is provided between the inner tubular end surface and an inner tubular opposite surface, and a second gap is provided between the outer tubular end surface and an outer tubular opposite surface.

Abstract: A housing extends in an axial direction of a rack shaft connected to a pinion shaft so as to cover at least the rack shaft, and has an end portion on which a cover member is fitted to cover the end portion. The housing includes a holding portion that has an inner side sinking in a radial direction of the housing, and holds the cover member, and a plurality of convex portions that protrude in the radial direction of the housing, and are circumferentially disposed on a downstream side of the holding portion in a fit-in direction of the cover member, while separating from the holding portion by a predetermined distance in the fit-in direction.

Abstract: A structure of a bush bearing includes: a bush on which a groove is formed; and an endless annular-shaped elastic member which is installed in the groove of the bush, and that supports a rack shaft, in which an inner circumferential surface of the bush includes a first inner circumferential surface that is in slide contact with an outer circumferential surface of the rack shaft, which is positioned opposite to a formation position of rack teeth, a second inner circumferential surface that faces the outer circumferential surface of the rack shaft with a gap interposed between the outer circumferential surface and the second inner circumferential surface, and the groove formed in a formation range of the first inner circumferential surface has a depth shallower than that of the groove formed in a formation range of the second inner circumferential surface.