Abstract: A resin molding mold, by which a resin worm wheel for a worm speed reducer is molded, includes a plurality of tooth forming portions provided such that the tooth forming portions are disposed at predetermined intervals on a circumference of the resin molding mold. The tooth forming portions each include a projection portion provided in a part of a tooth-flank forming surface by which a tooth flank is formed.

Abstract: A power transmission coupling that couples an output shaft of an electric motor and a worm shaft together includes a first rotation element coupled to the output shaft, a second rotation element coupled to the worm shaft, and an intermediate element formed of an elastic body and interposed between the first rotation element and the second rotation element. The intermediate element forms a unit integrally including an annular support portion, power transmission portions extending radially from the support portion and interposed between engaging protrusions of the first rotation element and the second rotation element, a spacer arranged inward of the support portion in a radial direction to apply a preload to the worm shaft in an axial direction, and a coupling portion that couples the support portion and the spacer together.

Abstract: A worm reduction gear satisfies following relational Formula (1) and Formula (2): 3?D2/D1?1.7??(1) 0.1°?????0.5°??(2) where D1 is an outside diameter of a worm, D2 is an outside diameter of a hob for cutting a worm wheel to form tooth spaces, and ? is a pressure angle of the worm wheel and ? is a pressure angle of the worm at an intermeshing pitch circle of the worm and the worm wheel.

Abstract: A center axis of a worm shaft is offset in an offset direction with respect to a plane that is orthogonal to a center axis of a worm wheel and that passes through a central position of the worm wheel in a tooth width direction. A bias member biases a second end of the worm shaft in a preloading direction in which a center distance between the worm shaft and the worm wheel decreases. When the worm shaft is configured like a right-hand thread, in a left-handed coordinate system, a direction toward a first end of the worm shaft in an axial direction (a direction toward an electric motor) corresponds to a thumb direction. The preloading direction corresponds to an index finger direction. The offset direction corresponds to a middle finger direction.

Abstract: An electric power steering device includes a worm which is swingably connected to the rotation shaft of an electric motor through a joint. A first end portion and second end portion of the worm are supported by a first bearing and a second bearing, respectively. A pair of elastic members elastically urge the worm to an axial neutral position. An annular leaf spring which is held by a housing urges the second end portion toward a worm wheel through the second bearing. A synthetic resin member having a sliding contact surface which is in contact with the leaf spring is integrally disposed on the second bearing.

Abstract: An electric power steering system includes a joint that connects a rotary shaft of an electric motor with a worm shaft of a speed reducer. The joint includes a first rotational element that has a boss into which a first end portion of the worm shaft is press-fitted, and a flange extending radially from the boss. The first bearing is held by a housing and supports the first end portion so that the first end portion is rotatable and movable in an axial direction. A first elastic body, which urges the worm shaft in the axial direction toward the electric motor through the first rotational element, is provided between an inner ring of the first bearing and the flange.

Abstract: A shaft coupling structure includes a rotating shaft, a worm shaft, a first member, a second member, and an intermediate member that is an elastic member. The intermediate member is interposed between the first member and the second member. Coupling protrusions of the first member that extend in an axial direction are each inserted between second radial protrusions of the intermediate member and between a plurality of first radial protrusions of the second member. Protruding portions of the first radial protrusions engage with the corresponding recessed portions of the second radial protrusions in the axial direction. When a relative rotation angle between the first member and the second member is smaller than a predetermined angle, ends of each of the second radial protrusions in a circumferential direction each projects in the circumferential direction with respect to a corresponding end of the corresponding first radial protrusion in the circumferential direction.

Abstract: A worm reduction gear satisfies following relational Formula (1) and Formula (2): 3?D2/D1?1.7??(1) 0.1°?????0.5°??(2) where D1 is an outside diameter of a worm, D2 is an outside diameter of a hob for cutting a worm wheel to form tooth spaces, and ? is a pressure angle of the worm wheel and ? is a pressure angle of the worm at an intermeshing pitch circle of the worm and the worm wheel.

Abstract: In a speed reducer of an electric power steering system, a first bearing supports a first end portion of a worm so that the first end portion is movable in an axial direction. Elastic members elastically support the worm in the axial direction. A second bearing supports a second end portion of the worm. An urging member oscillates and urges the worm. The sum of first frictional resistance in the axial direction between an inner ring of the first bearing and the worm and second frictional resistance in the axial direction between the urging member and an outer circumference of an outer ring of the second bearing is less than engagement frictional resistance in the axial direction of the worm.

Abstract: A power transmission coupling that couples an output shaft of an electric motor and a worm shaft together includes a first rotation element coupled to the output shaft, a second rotation element coupled to the worm shaft, and an intermediate element formed of an elastic body and interposed between the first rotation element and the second rotation element. The intermediate element forms a unit integrally including an annular support portion, power transmission portions extending radially from the support portion and interposed between engaging protrusions of the first rotation element and the second rotation element, a spacer arranged inward of the support portion in a radial direction to apply a preload to the worm shaft in an axial direction, and a coupling portion that couples the support portion and the spacer together.

Abstract: A center axis of a worm shaft is offset in an offset direction with respect to a plane that is orthogonal to a center axis of a worm wheel and that passes through a central position of the worm wheel in a tooth width direction. A bias member biases a second end of the worm shaft in a preloading direction in which a center distance between the worm shaft and the worm wheel decreases. When the worm shaft is configured like a right-hand thread, in a left-handed coordinate system, a direction toward a first end of the worm shaft in an axial direction (a direction toward an electric motor) corresponds to a thumb direction. The preloading direction corresponds to an index finger direction. The offset direction corresponds to a middle finger direction.

Abstract: An electric power steering device includes a worm which is swingably connected to the rotation shaft of an electric motor through a joint. A first end portion and second end portion of the worm are supported by a first bearing and a second bearing, respectively. A pair of elastic members elastically urge the worm to an axial neutral position. An annular leaf spring which is held by a housing urges the second end portion toward a worm wheel through the second bearing. A synthetic resin member having a sliding contact surface which is in contact with the leaf spring is integrally disposed on the second bearing.

Abstract: In a speed reducer of an electric power steering system, a first bearing supports a first end portion of a worm so that the first end portion is movable in an axial direction. Elastic members elastically support the worm in the axial direction. A second bearing supports a second end portion of the worm. An urging member oscillates and urges the worm. The sum of first frictional resistance in the axial direction between an inner ring of the first bearing and the worm and second frictional resistance in the axial direction between the urging member and an outer circumference of an outer ring of the second bearing is less than engagement frictional resistance in the axial direction of the worm.

Abstract: An electric power steering system includes a joint that connects a rotary shaft of an electric motor with a worm shaft of a speed reducer. The joint includes a first rotational element that has a boss into which a first end portion of the worm shaft is press-fitted, and a flange extending radially from the boss. The first bearing is held by a housing and supports the first end portion so that the first end portion is rotatable and movable in an axial direction. A first elastic body, which urges the worm shaft in the axial direction toward the electric motor through the first rotational element, is provided between an inner ring of the first bearing and the flange.

Abstract: A worm wheel of a worm drive includes an annular synthetic resin member having tooth portions meshing with a worm shaft and a core having an outside diameter portion joined to an inside diameter portion of the synthetic resin member. The outside diameter portion of the core has first joining tooth portions that protrude outward in a radial direction and are joined to the inside diameter portion of the synthetic resin member. Each of the first joining tooth portions includes a widening portion whose width in a circumferential direction increases toward the outside in the radial direction.

Abstract: A gear includes a metal core and a synthetic resin tooth body. The metal core includes a cylindrical portion, and a disc portion that extends inwardly in a radial direction from one end of the cylindrical portion. The synthetic resin tooth body is coupled to the cylindrical portion of the metal core. A plurality of rotation prevention grooves is formed on the outer peripheral portion of the cylindrical portion, and a plurality of rotation prevention grooves is formed on the inner peripheral portion of the cylindrical portion.

Abstract: A shaft coupling mechanism includes a coupling base body coupled to a rotating shaft; a coupling base body coupled to a steering shaft; rotation transmitting members which are disposed between the rotating shaft and the steering shaft through the both coupling base bodies and transmit the rotation of the rotating shaft in an R direction to the steering shaft; an intermediate interposed member disposed between the rotation transmitting members; and a coupling means for coupling the rotation transmitting members to each other.

Abstract: A gear includes a metal core and a synthetic resin tooth body. The metal core includes a cylindrical portion, and a disc portion that extends inwardly in a radial direction from one end of the cylindrical portion. The synthetic resin tooth body is coupled to the cylindrical portion of the metal core. A plurality of rotation prevention grooves is formed on the outer peripheral portion of the cylindrical portion, and a plurality of rotation prevention grooves is formed on the inner peripheral portion of the cylindrical portion.