A rotary table (1) includes a base body (10), a worm wheel (21), an inner ring (22), a plurality of rolling elements, and a worm screw unit (30). The worm screw unit (30) includes a worm screw (31) held to be rotatable around an axis and having a second gear (31A) meshing with the first gear (215), and a worm screw housing (32) surrounding and holding the worm screw (31) and being fixed to contact the holding surface at a planar contacting surface thereof. One of the holding and contacting surfaces has a cylindrical pin (33) arranged to protrude therefrom. The other of the holding and contacting surfaces has a first recess (11) formed to receive the pin (33), the first recess having a width corresponding to the pin (33) and being elongated in the radial direction of the worm wheel (21).

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.

According to the present embodiments, it is possible to mitigating noise by preventing degradation of lubrication performance due to mixture of greases with different properties in a gear housing.

A motor driven power steering device including a motor and a speed reducer configured to decelerate a rotation speed of the motor, wherein the speed reducer includes a worm gear coupled to a drive shaft of the motor and rotatably installed to a speed reducer housing through a bearing, a worm wheel gear-coupled with the worm gear, and a rotation member mounted between the worm gear and the bearing and configured to circulate a lubrication agent applied between the worm gear and the worm wheel.

The present invention provides a transmission mechanism with which a deterioration in accuracy can be suppressed and a service life can be increased by suppressing lubricant deterioration. A transmission mechanism is provided with a housing, a first rotating member which is accommodated in the housing and which is capable of rotating about a first rotating member axis, and a lubricant which is accommodated in the housing to lubricate the first rotating member, wherein: the transmission mechanism is additionally provided with a first filter member which is accommodated in the housing to filter out dust contained in the lubricant; the lubricant is agitated by means of the rotation of the first rotating member about the first rotating member axis; and the first filter member is provided in the direction in which the lubricant is caused to flow by means of the agitation from the first rotating member.

A motor-driven power steering system for a vehicle is configured such that movement of the worm shaft and a clearance caused by backlash between the worm wheel and the worm shaft may be prevented using the bearing-integrated damper bush which is coupled to the end portion of the worm shaft and is made of steel, and during of rotation of the worm shaft, the lubricant is supplied between the worm shaft and the bearing-integrated damper bush to facilitate lubrication and cooling.

A rotary table (1) includes a base body (10), a worm wheel (21), an inner ring (22), a plurality of rolling elements, and a worm screw unit (30). The worm screw unit (32) includes a worm screw (31) and a worm screw housing (32). The worm screw housing (32) has an opposing surface that faces an outer circumferential surface (21B) of the worm wheel (21). The worm screw housing (32) includes a flange portion (325) that protrudes from the opposing surface and covers a side face (215A) that, of the first gear (215) facing the opposing surface, is on the opposite side from the base body (10) in the axial direction of the worm wheel (21).

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 .Math.m or lower.

A worm reducer includes: a housing including a wheel accommodating portion, and a worm accommodating portion; a worm wheel including wheel teeth disposed on an outer circumferential surface and rotatably supported inside the wheel accommodating portion; and a worm including worm teeth disposed on an outer circumferential surface to mesh with the wheel teeth and rotatably supported inside the worm accommodating portion, wherein a proximal end portion of the worm is connected to a drive shaft such that torque can be transmitted. An inner circumferential surface of the worm accommodating portion includes a housing side step surface which faces a proximal end side in an axial direction of the worm. An outer circumferential surface of the worm includes a worm side step surface which closely faces the housing side step surface in the axial direction at a portion axially deviated from a portion where the worm teeth are disposed.

The invention provides a grease composition for lubricating resins which contains a base oil, a diurea compound represented by formula (I) as a thickener: R.sup.1—NHCONH —R.sup.2—NHCONH—R.sup.3 (I) (wherein R.sup.2 represents a bivalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R.sup.1 and R.sup.3 each independently represent a straight-chain or branched alkyl group having 8 to 22 carbon atoms), and a chained hydrocarbon polymer having a weight-average molecular weight of 20,000 to 300,000.