Abstract: A reduction gear is provided. The reduction gear includes: a worm made of a metal; and a worm wheel having gear teeth engaged with the worm, wherein at least the gear teeth of the worm wheel are made of a synthetic resin containing reinforcing fibers, and wherein an engagement surface of the gear teeth is so processed that a containing ratio of the reinforcing fibers of a surface layer is lower than that of the reinforcing fiber of an inner portion. By improving initial acquaintanceship of the engagement surface of the teeth gear of the worm wheel, it is possible to increase a durability-allowable transmission tongue. In addition, by reducing a friction of the worm, it is possible to provide a reduction gear with the worm having a lengthened lifetime.

Abstract: A reduction gear in which an engaging surface of gear teeth is processed so that grease for lubricating the engaging surface is sufficiently supplied over the entire of the engaging surface, thereby reducing the friction caused on the engaging surface, and increasing the durability of the gear teeth is provided. In a reduction gear which includes a worm made of metal and a worm wheel having gear teeth which engage with the worm, wherein at least the gear teeth of the worm wheel are made of synthetic resin, and in which an engaging surface of the gear teeth is lubricated by grease, the engaging surface has over an entire surface a plurality of grease reservoir grooves formed along a sliding line of the engaging surface.

Abstract: In a method of machining gear teeth 2 of worm wheel 1 by causing a worm (not shown) on which abrasive or grinding material is added to mesh with the gear teeth 2 of the worm wheel 1, at least the gear teeth of said worm wheel being made of a synthetic resin, and rotating the worm, the machining is performed in such a state that the angle formed by the axis of the worm wheel and the virtual helical axis in forming the gear teeth of the worm wheel is made substantially equal to the angle formed by the axis of said worm wheel and the helical axis of said worm.

Abstract: An object of the present invention is to provide a grease composition for resin lubrication which is capable of keeping good the sliding lubrication between a resin member and a metal member, and between a metal member and another metal member over the long term. The present invention provides a grease composition for resin composition which is characterized by including a base, a thickener, and at least one of a nonpolar wax and a polar wax. Further, the grease composition for resin lubrication is applied to a telescopic shaft for vehicle steering or an electric power steering apparatus, thereby to improve the durability, and to achieve a longer life.

Abstract: For lubrication of a reduction gear, at least a Ca sulfonate additive is added to a lubricating grease made by an urea compound as a thickener and a synthetic hydrocarbon oil as a base oil.

Abstract: In a worm wheel (41) and a method of manufacturing the same, the worm wheel has a metal worm wheel element (51) in which an axial bore (55) is formed at a rotational center and a synthetic resin gear ring (53) attached on the outer circumference of the worm wheel element, and a centering guide portion (77) that is coaxial with the axial bore (55) is formed on one surface of the metal worm wheel element (51).

Abstract: An electric power steering apparatus having an electric motor for generating steering auxiliary force and a reduction gear device for reducing a rotating speed of the motor by a gear mechanism connected to a rotating shaft of the electric motor, wherein at least one of reduction gears in the gear mechanism is a gear made of a synthetic resin which is lubricated by grease in which lubrication durability at a high temperature is improved while starting torque of rotation at a low temperature is kept low.

Abstract: An electric power steering apparatus can maintain suitable backlash in a temperature changing atmosphere even if a gear consisting of a metallic cylindrical core portion and a toothed resin outer ring portion. The thickness of the resin outer ring portion is suitably determined by the coefficients of linear thermal expansion of a driving gear, a driven gear, a housing, the addendum of the driven gear and the center distance between the driving gear and the driven gear. Even if the temperature of the atmosphere changes, the positional relation between the gears is unchanged. Thus, the backlash is substantially unaltered.