Abstract: A rotation limiting device including: a first member having a first protrusion; a second member having a second protrusion disposed on an axial one side with respect to the first protrusion, the second member being disposed coaxially with the first member and configured to rotate relative to the first member; and at least one intermediate member supported in a relatively rotatable manner with respect to the first member and the second member, the intermediate member including a side plate portion disposed between the first protrusion and the second protrusion in an axial direction, an intermediate side first protrusion protruding toward an axial other side from an axial other side surface of the side plate portion, and an intermediate side second protrusion protruding toward the axial one side from an axial one side surface of the side plate portion.

Abstract: A holder has a holder engagement portion in at least a position sandwiching a pad from both sides in a third direction orthogonal to both a first direction that is an urging direction of an elastic member and a second direction that is an axial direction of a worm accommodation portion. The pad has a pad engagement portion that comes into contact with the holder engagement portion on at least one of both side portions in the third direction. Based on contact between the holder engagement portion and the pad engagement portion, displacement of the pad in the third direction with respect to the holder is regulated.

Abstract: A rack portion (21) includes a hardened layer (26) over an entire circumference on a radially outer portion including the rack teeth (20). A depth (tb) of a portion of the hardened layer (26) on an opposite side to the rack teeth (20) in a radial direction is shallower than a depth (ts) of portions of the hardened layer (26) on both sides of the rack teeth (20) in a tooth width direction.

Abstract: The gear housing including a wheel housing section, a worm housing section, and a one side rib that protrudes from a side surface on one side in the axial direction of a bottom portion for wheel of the wheel housing section and connects a fitting tubular portion for wheel of the wheel housing section and a fitting tubular portion for worm on one side in the axial direction of the worm housing section into which a bearing for worm or a bearing holder holding the bearing for worm is internally fitted.

Abstract: Provided is a mechanical structural member that can suppress deformation and has high precision and excellent quality. In a mechanical structural member (triangular threaded shaft 31) in which grooves (32) and teeth (33) are formed by plastic working and a hardened layer (31a) is formed on a surface of the teeth (33), the mechanical structural member has a sorbite structure, and Rockwell hardness in a region P excluding the hardened layer (31a) is 13 to 28 (HRC). A variation in the Rockwell hardness in the region P excluding the hardened layer (31a) is within 6 (HRC).

Abstract: Provided is a mechanical structural member that can reduce deformation and has high precision and excellent quality. The mechanical structural member has a groove (32) and a tooth (33) formed by plastic working, and includes a hardened layer (31a) with a uniform martensitic single phase structure formed on a surface by induction hardening, a core region (31b) having a sorbite structure, and a boundary layer (31c) in which a sorbite structure and a martensite structure are mixed, formed between the core region (31b) and the hardened layer (31a). Rockwell hardness in the core region is 13 to 28 (HRC), and a variation in the Rockwell hardness is within 6 (HRC).

Abstract: A holder has a holder engagement portion in at least a position sandwiching a pad from both sides in a third direction orthogonal to both a first direction that is an urging direction of an elastic member and a second direction that is an axial direction of a worm accommodation portion. The pad has a pad engagement portion that comes into contact with the holder engagement portion on at least one of both side portions in the third direction. Based on contact between the holder engagement portion and the pad engagement portion, displacement of the pad in the third direction with respect to the holder is regulated.