A cylindrical double helix gear having an axis and a unitary gear arrangement extending about the axis, wherein the gear arrangement has two axially spaced gear portions with each gear portion comprising a plurality of gear teeth extending about a radial outer surface of the gear arrangement, wherein the gear portions are connected by a flexible spacer portion configured to allow relative movement between the gear portions.

An idle gear assembly comprises an outer ring having gear teeth formed on an external surface thereof and engaged with a crank gear and any one of the left and right balance gears. A bearing includes an inner member and an outer member in a radial direction of the bearing and a plurality of rolling bodies disposed between the inner member and the outer member. A ring has elasticity in a radial direction thereof. A hub has a flange, which is in contact with the bearing, and a penetration hole. The flange and the penetration hole are formed at one side of the hub in an axial direction. A nut is inserted through another side and mounted at a hollow portion of the ring. A bolt is inserted through the insertion hole of the bearing, the penetration hole, and the nut and fixes the bearing and the hub.

An idle gear assembly comprises an outer ring having gear teeth formed on an external surface thereof and engaged with a crank gear and any one of the left and right balance gears. A bearing includes an inner member and an outer member in a radial direction of the bearing and a plurality of rolling bodies disposed between the inner member and the outer member. A ring has elasticity in a radial direction thereof. A hub has a flange, which is in contact with the bearing, and a penetration hole. The flange and the penetration hole are formed at one side of the hub in an axial direction. A nut is inserted through another side and mounted at a hollow portion of the ring. A bolt is inserted through the insertion hole of the bearing, the penetration hole, and the nut and fixes the bearing and the hub.

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.

A torque filter having an impact spring constant includes a pair of left and right arc springs arranged at left and right sides and having spring constant values set based on a torque of a crank shaft which transfers a driving force of an engine as the torque. An impact spring is disposed in which the pair of the left and right arc springs face each other and has a spring constant value set with a threshold torque based on an instant speed change of the crank shaft.

A shift fork shaft 123 has both end portions movably fitted in shaft supports 83e and 116a of a gear transmission 82. Clearances are left between bottom surfaces 83g and 116c of the shaft supports 83e and 116a and both end faces 123c of the shift fork shaft 123. Caps 145 are mounted in both axial ends of the shift fork shaft 123.

A shift fork shaft 123 has both end portions movably fitted in shaft supports 83e and 116a of a gear transmission 82. Clearances are left between bottom surfaces 83g and 116c of the shaft supports 83e and 116a and both end faces 123c of the shift fork shaft 123. Caps 145 are mounted in both axial ends of the shift fork shaft 123.

A vehicle gear includes: a disk portion having a disk shape and a plurality of through holes formed in a circumference direction thereof; and an outer circumference portion having outer circumference teeth formed on an outer circumference side of the disk portion. Further, each of the through holes includes first and second holes (82A, 82B) formed on one and another ends, respectively, thereof in the circumference direction, and a width of the first hole is larger than a width of the second hole in a radial direction of the disk portion.

A gear that can be utilized in an electric actuator has teeth formed on its outer circumference and a central hole formed at its center. An intermediate region is positioned between a peripheral portion near the teeth and a boss near the central hole. The intermediate region has a thickness thinner than the peripheral portion and the boss. A plurality of weight-lightening apertures is circumferentially and equidistantly formed in the intermediate region. A vibration absorbing member of synthetic rubber is formed on both side surfaces of the intermediate region. The vibration absorbing member is integrally connected on each side through the weight-lightening apertures. The vibration absorbing member is attached to the radially outer side rather than an outer diameter of a bearing arranged adjacent to the vibration absorbing member.