A door moving apparatus includes a motor unit, a first gear, a second gear, an endless belt, a drum, and a rotator. The first gear is mounted on a rotary shaft of the motor unit. The second gear includes a diameter larger than a diameter of the first gear and teeth more than the first gear. The endless belt passes over the first gear and the second gear. A rotary power of the second gear is transmitted to the drum via a rotary power transmission mechanism. The rotator is configured to reduce a separation of the endless belt from a preset running path.

A door moving apparatus includes a motor unit, a first gear, a second gear, an endless belt, a drum, and a rotator. The first gear is mounted on a rotary shaft of the motor unit. The second gear includes a diameter larger than a diameter of the first gear and teeth more than the first gear. The endless belt passes over the first gear and the second gear. A rotary power of the second gear is transmitted to the drum via a rotary power transmission mechanism. The rotator is configured to reduce a separation of the endless belt from a preset running path.

A transmission includes an input shaft coupled to a prime mover, a countershaft, main shaft, and an output shaft, with gears between the countershaft and the main shaft. A shift actuator selectively couples the input shaft to the main shaft by rotatably coupling gears between the countershaft and the main shaft. The shift actuator is mounted on an exterior wall of a housing including the countershaft and the main shaft. An integrated actuator housing is operationally coupled to the shift actuator and a linear clutch actuator. The linear clutch actuator is a self-adjusting actuator, and the transmission includes a self-adjusting clutch.

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.

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.

A gear pair includes a first gear and a second gear that are engaged and paired with each other, wherein the arithmetic average roughness Ra of the tooth surface of the first gear is less than 0.10, and the arithmetic average roughness Ra of the tooth surface of the second gear is equal to or greater than 0.15. An improvement of the transmission efficiency is achieved due to the improved composite roughness of the gear pair. Accordingly, both of the improvement of the transmission efficiency of the gears and an improvement of the pitting fatigue life are achieved at low cost.

A gear pair includes a first gear and a second gear that are engaged and paired with each other, wherein the arithmetic average roughness Ra of the tooth surface of the first gear is less than 0.10, and the arithmetic average roughness Ra of the tooth surface of the second gear is equal to or greater than 0.15. An improvement of the transmission efficiency is achieved due to the improved composite roughness of the gear pair. Accordingly, both of the improvement of the transmission efficiency of the gears and an improvement of the pitting fatigue life are achieved at low cost.

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 method of manufacturing a gear is provided. The method includes forming a plurality of gear teeth in a surface of a gear, the gear teeth having tooth faces defining tooth edges including tooth edge flanks and tooth edge top land and generating a convex contour at an edge break of at least one of the tooth edge flanks and tooth edge top land.