Abstract: A rack-and-pinion steering system includes a pinion shaft having pinion teeth, a rack shaft on which rack teeth are formed which mesh with the pinion teeth; and a rack bush which supports the rack shaft slidably in an axial direction thereof. An outer circumferential surface of the rack shaft includes a first area which is a concave formed on an outer circumferential surface of the rack shaft and extending in the axial direction and a second area which is an area of the outer circumferential surface excluding the first area and lies adjacent to an end portion of the first area in the axial direction. The rack teeth are formed in the first area. A chamfered portion or a rounded portion is provided on a boundary between the end portion of the first area and the second area to chamfer or round a corner portion on the boundary.

Abstract: A rack bush for supporting a rack shaft in a rack-and-pinion steering system so that the rack shaft slides in an axial direction thereof includes a teeth side support portion and a back side support portion. Rack teeth are formed in a first area of an outer circumferential surface of the rack shaft. The teeth side support portion contacts a second area of the outer circumferential surface to support the rack shaft from a teeth side where the rack teeth are formed. The second area lies adjacent to the first area in the axial direction. The back side support portion contacts a third area of the outer circumferential surface to support the rack shaft from a back side other than the teeth side. The third area is positioned out of the first area in a circumferential direction around an axis of the rack shaft.

Abstract: A rack-and-pinion steering system includes a pinion shaft having pinion teeth, a rack shaft on which rack teeth are formed which mesh with the pinion teeth; and a rack bush which supports the rack shaft slidably in an axial direction thereof. An outer circumferential surface of the rack shaft includes a first area which is a concave formed on an outer circumferential surface of the rack shaft and extending in the axial direction and a second area which is an area of the outer circumferential surface excluding the first area and lies adjacent to an end portion of the first area in the axial direction. The rack teeth are formed in the first area. A chamfered portion or a rounded portion is provided on a boundary between the end portion of the first area and the second area to chamfer or round a corner portion on the boundary.

Abstract: A rack bush for supporting a rack shaft in a rack-and-pinion steering system so that the rack shaft slides in an axial direction thereof includes a teeth side support portion and a back side support portion. Rack teeth are formed in a first area of an outer circumferential surface of the rack shaft. The teeth side support portion contacts a second area of the outer circumferential surface to support the rack shaft from a teeth side where the rack teeth are formed. The second area lies adjacent to the first area in the axial direction. The back side support portion contacts a third area of the outer circumferential surface to support the rack shaft from a back side other than the teeth side. The third area is positioned out of the first area in a circumferential direction around an axis of the rack shaft.

Abstract: In a shaft coupling structure, a lower joint yoke has a slit that axially extends from its open end portion, and a guide cover is fitted around an input shaft so as to be rotatable together with the input shaft. The guide cover is formed of a guide portion that protrudes radially outward from the input shaft and that is engageable with the slit of the lower joint yoke, and a cover portion that covers an opening portion of a valve housing and that is fitted around the input shaft. The guide portion and the cover portion are formed integrally with each other.