A gear is provided that has excellent continuous moldability for practical use, and both high slidability and high durability. The provided gear is a molded resin constructed of a resin composition comprising a thermoplastic resin (A) and cellulose nanofibers (B) with an average fiber diameter of 1000 nm or smaller, and having a number average molecular weight of the thermoplastic resin (A) in the range of 10,000 to 150,000, wherein a sliding surface of the gear with another gear teeth has an arithmetic mean surface roughness Sa of 3.0 μm or lower.

Plural ejector pins are made to project before a molten resin containing reinforcing fibers is injected into an inside of a cavity through pin point gates in a web forming portion in the inside of the cavity and at positions outside the pin point gates in a radial direction. The ejector pins are retracted from the inside of the cavity after a flow of the molten resin containing reinforcing fibers injected into the inside of the cavity through the pin point gates impinges on the ejector pins and is divided and before a tooth portion forming portion in the inside of the cavity is filled with the molten resin containing reinforcing fibers. Accordingly, weld lines which extend along the radial direction are formed at positions outside the ejector pins in the radial direction, and the molten resin is filled in portions formed after the ejector pins are retracted.

A steering reaction force apparatus for a vehicle includes: a housing that is openable and closable by a cover unit, a stator unit fixed to an inside of the housing, a rotor unit disposed to face the stator unit and to be rotated by electromagnetic interaction with the stator unit, a transmission shaft unit connected to the rotor unit to rotate in conjunction with the rotor unit, a power transmission unit disposed inside the rotor unit to transmit a rotational force of the transmission shaft unit to a steering shaft, and a retainer unit to support the power transmission unit with respect to the cover unit.

A space and an elastic member have a first part where a distance between an outer peripheral surface of a metal bush and an inner peripheral surface of a resin member is a first distance, a second part where the distance between the outer peripheral surface and the inner peripheral surface is a second distance different from the first distance, and a third part where the distance between the outer peripheral surface and the inner peripheral surface is a third distance different from the first distance in a cross section along a radial direction of a resin gear. The first part is provided between the second part and the third part in an axial direction of the resin gear.

A multi-piece gearwheel comprising an inner core section and an external toothed ring with external teething is presented. The core section has intermeshing teeth extending radially outwards, which have an undercut in cross-section in the radial direction. The toothed ring has recesses that originate from an inner side of the tooth ring and extend radially outwards, wherein the recesses are at least partially complementary to the intermeshing teeth, and wherein the intermeshing teeth are received in the recesses. Furthermore, a gearbox for an electromechanically-assisted steering system is described.

A gear of a speed reducer of an actuator includes: an insert component; a center portion; an outer peripheral portion; a connecting portion; a gate mark; a weld-line portion; and a rib-shaped portion. The center portion surrounds the insert component. The outer peripheral portion includes a toothed portion and a toothless portion. The weld-line portion is formed in at least one of the center portion, the connecting portion and the outer peripheral portion at a location which is on a radially inner side of the toothless portion. The rib-shaped portion is formed in at least one of the center portion, the connecting portion and the outer peripheral portion at a location which includes the weld-line portion. The rib-shaped portion has a wall thickness that is larger than a wall thickness of another circumferential portion.

A resin gear includes an annular metal bush and an annular resin member provided around the metal bush. The metal bush and the resin member are disposed so as to be relatively rotatable in a direction of rotation of the resin gear. A plurality of spaces entering an outer peripheral surface of the metal bush and an inner peripheral surface of the resin member are formed, so as to be aligned along the direction of rotation, between the metal bush and the resin member. The space has, in at least one end portion in an axial direction of the resin gear, inner surfaces intersecting with the axial direction. An elastic member is disposed in the space. The elastic member engages with the inner surfaces.

A light-weight gear including: an annular tooth portion made of metal; a shaft extending along a central axis of the tooth portion and made of metal; and a coupling element configured to couple the shaft to the tooth portion and made of a resin, in which a joining part between the shaft and the coupling element and a joining part between the tooth portion and the coupling element are provided with irregularities configured to be engaged with one another in a circumferential direction, and corners of the irregularities are rounded to release a stress. Also, provided is a manufacturing method of a light-weight gear including: disposing the tooth portion and the shaft in a mold and injecting a molten resin into a cavity of the mold, thereby simultaneously performing injection molding of the coupling element and joining the coupling element to the tooth portion and the shaft.

A gear includes: an outer circumferential rim provided integrally with a plurality of tooth portions disposed side-by-side in a circumferential direction on an outer circumferential surface; and a plurality of reinforcing ribs disposed inside the outer circumferential rim to be spaced from each other in the circumferential direction by thinning portions, wherein a position where each of the plurality of reinforcing ribs and the outer circumferential rim are joined corresponds, in the circumferential direction, to a position of a tooth groove between the plurality of tooth portions.

A gear manufacturing method, the gear including an annular gear portion including teeth on an outer periphery, an annular support portion provided on an inner peripheral surface of the gear portion and supporting the gear portion, and a core portion provided inside the support portion, the method includes: a support portion molding step of molding the support portion by disposing the gear portion and the core portion in an annular mold and filling a resin between the gear portion and the core portion; and a support portion cooling step of cooling the support portion molded in the support portion molding step, a radial gap between the teeth of the gear portion and the mold before the support portion molding step is set to be smaller than a radial shrinkage amount of the support portion in the support portion cooling step.