A gear assembly comprising first and second gears configured to mesh with each other, the first gear comprising inner and outer ring elements and a resilient ring element disposed between and coupled to the inner and outer ring elements, the outer ring element comprising first gear teeth which mesh with second gear teeth of the second gear, wherein the first and second gears each comprise a positioning ring axially spaced apart from the first and second gear teeth, the positioning rings being configured to engage each other and limit the position of the first and second gear teeth relative to each other.

A gear assembly comprising first and second gears configured to mesh with each other, the first gear comprising inner and outer ring elements and a resilient ring element disposed between and coupled to the inner and outer ring elements, the outer ring element comprising first gear teeth which mesh with second gear teeth of the second gear, wherein the first and second gears each comprise a positioning ring axially spaced apart from the first and second gear teeth, the positioning rings being configured to engage each other and limit the position of the first and second gear teeth relative to each other.

The planetary gear unit in which sliding resistance between a double helical gear and a peripheral member is reduced is provided. The planetary gear unit comprises: pinion gears individually having two rows of oppositely-oriented helical gears in an axial direction; a first pushing member that elastically pushes at least one of the pinion gears toward in a predetermined axial direction; and a second pushing member that elastically pushes at least one of the remaining pinion gears in the opposite axial direction.

The planetary gear unit in which sliding resistance between a double helical gear and a peripheral member is reduced is provided. The planetary gear unit comprises: pinion gears individually having two rows of oppositely-oriented helical gears in an axial direction; a first pushing member that elastically pushes at least one of the pinion gears toward in a predetermined axial direction; and a second pushing member that elastically pushes at least one of the remaining pinion gears in the opposite axial direction.

A tolerance ring is interposed between an output side rotary shaft and a rotor shaft. For this reason, even in a case where a backlash formed in a spline fitting portion between the output side rotary shaft and the rotor shaft is not eliminated, the rotary shafts of both of the output side rotary shaft and the rotor shaft are held by the tolerance ring without a backlash, and rattling noise can be suppressed. An oil supply groove for supplying a lubricant between an annular portion of the tolerance ring and the output side rotary shaft is provided inside an annular groove formed in the output side rotary shaft. With this, it is possible to suppress degradation of the durability of the tolerance ring without performing special processing on the tolerance ring.

A tolerance ring is interposed between an output side rotary shaft and a rotor shaft. For this reason, even in a case where a backlash formed in a spline fitting portion between the output side rotary shaft and the rotor shaft is not eliminated, the rotary shafts of both of the output side rotary shaft and the rotor shaft are held by the tolerance ring without a backlash, and rattling noise can be suppressed. An oil supply groove for supplying a lubricant between an annular portion of the tolerance ring and the output side rotary shaft is provided inside an annular groove formed in the output side rotary shaft. With this, it is possible to suppress degradation of the durability of the tolerance ring without performing special processing on the tolerance ring.

Disclosed herein is a joint unit including two facing gears that include respective two bevel gear members that face each other, and an intermediate gear that has a bevel gear member meshing with both the two bevel gear members. One of the two facing gears and the intermediate gear includes a first member including an inner circumferential portion of the bevel gear member of the one of the two facing gears and the intermediate gear; a second member including an outer circumferential portion of the bevel gear member of the one of the two facing gears and the intermediate gear; and a resilient member attached to one of the first member and the second member for normally urging the other of the first member and the second member to move in a direction along the directions of rotation of the one of the two facing gears and the intermediate gear.

Disclosed herein is a joint unit including two facing gears that include respective two bevel gear members that face each other, and an intermediate gear that has a bevel gear member meshing with both the two bevel gear members. One of the two facing gears and the intermediate gear includes a first member including an inner circumferential portion of the bevel gear member of the one of the two facing gears and the intermediate gear; a second member including an outer circumferential portion of the bevel gear member of the one of the two facing gears and the intermediate gear; and a resilient member attached to one of the first member and the second member for normally urging the other of the first member and the second member to move in a direction along the directions of rotation of the one of the two facing gears and the intermediate gear.

An optical device including a lens and a control member configured such that motion of the control member produces a change in the optical power provided along an optical axis of the lens. The optical device further includes a framework, a motor and a driving member. The motor includes an output shaft rotatively coupled to said driving member. The motor and the control member are mounted in the framework such that the driving member and the control member mechanically cooperate. The driving member is rotatably mounted in the framework. The optical device comprises biasing means for maintaining the driving member in a predetermined axial position along the output shaft axis and relative to the framework. This optical device can be used in an optometric equipment.

An optical device including a lens and a control member configured such that motion of the control member produces a change in the optical power provided along an optical axis of the lens. The optical device further includes a framework, a motor and a driving member. The motor includes an output shaft rotatively coupled to said driving member. The motor and the control member are mounted in the framework such that the driving member and the control member mechanically cooperate. The driving member is rotatably mounted in the framework. The optical device comprises biasing means for maintaining the driving member in a predetermined axial position along the output shaft axis and relative to the framework. This optical device can be used in an optometric equipment.