A synchronizer of a transmission may include bottom key disposed on a hub to be slidable in a radial direction of the hub; a top key disposed radially outside the bottom key to be slidable in an axial direction of the hub; a sleeve disposed outside the hub and sliding in the axial direction to slide the top key in the axial direction to press a synchro-ring; a key spring disposed between the bottom key and the hub to press the bottom key and the top key toward an internal side of the sleeve; and a motion converting portion converting relative motion generated in a circumferential direction of the hub between the top key and the bottom key into axial relative motion of the top key to the bottom key toward the synchro-ring.

A groove follower is provided for cooperating with a shift groove of a shift drum of a multi-step sequential transmission for a motor vehicle, comprising a groove follower body, comprising at least one contact surface for contacting a lateral face of the shift groove of the shift drum, wherein at least part of the at least one contact surface is formed as part of an outer surface of a three-dimensional helix with a helix diameter and a helix pitch.

A dog clutch includes a gear (40) mounted on a power transmission shaft (30), first and second dog rings (10, 20), a fork (60), springs (65), and cam grooves (31). The cam grooves (31) each include a first slope surface (36) inclined from the axial direction toward the positive rotation direction as the first slope surface (36) approaches the gear (40) and a second parallel surface (37) parallel to the axial direction. The first dog ring (10) includes first cam protrusions (16) to be engaged with the respective first slope surfaces (36), and the second dog ring (20) includes second cam protrusions (26) to be engaged with the respective second parallel surfaces (37). This structure prevents the dog rings and the fork from coming into contact with each other, thereby avoiding generation of abrasion and increasing the transmission efficiency.

A transmission mechanism includes a first gear coaxially fixed to a rotational shaft having a hollow shape, a second gear, and a third gear. The second and third gears are rotatably and coaxially disposed on an outer periphery of the rotational shaft such that the second and third gears are opposed to each other. A gear select clutch is disposed between the second and third gears, and configured to select one of a state in which the second and first gears are coupled and the third and first gears are decoupled, and a state in which the third and first gears are coupled and the second and first gears are decoupled. A clutch operation unit is configured to couple an operation shaft disposed in a hollow part of the rotational shaft to operate the gear select clutch by advancing and retreating the operation shaft in an axial direction.

A shift control apparatus of an automatic transmission includes: an input detecting unit configured to detect a real rotational speed of the input shaft; an output detecting unit configured to detect a real rotational speed of the output shaft; an estimating unit configured to estimate an estimated rotational speed of the input shaft, which corresponds to a shift request, by multiplying the real rotational speed of the output shaft by a target gear ratio; and a control unit configured to control the rotation of the input shaft based on a detection result from the input detecting unit. The control unit controls the rotation of the input shaft such that an upper-limiting rotational speed of a variation in real rotational speed of the input shaft is lower than the estimated rotational speed.

A bicycle transmission hub includes: a hub shaft to input a rotation force is input, the hub shaft having first pawls arranged on the outer peripheral surface thereof; a transmission controller for controlling the first pawls to appear and disappear; driving gears, each having a ratchet formed on the inner peripheral surface thereof to receive a rotation force by the first pawls, the driving gears having a different number of teeth, the hub shaft extending through the center of each driving gear; driven gears engaged with the driving gears, respectively, having a different number of teeth, and rotating; an output wheel rotating while being coupled to a driving gear adjacent thereto among the driving gears and having a second pawl disposed on the outer peripheral surface thereof; and a hub shell having a ratchet formed on the inner peripheral surface thereof to receive a rotation force by the second pawl.

Provided is a speed-switchable reduction gear including: an input shaft; an output shaft; a plurality of output-side geared-wheels mounted on the output shaft; a shifter for selecting the output-side geared-wheel to be used; a shifter-side first bearing and a non-shifter-side second bearing provided to each the output-side geared-wheel; and a plurality of dividing walls each provided in each cell between the first and second bearings. The output shaft has an axial lubricating-oil flow path and a plurality of supply flow paths. Each dividing wall divides each cell into a first cell adjacent to the first bearing and a second cell adjacent to the second bearing and allows lubricating oil to be supplied from the supply flow paths into the first and second cells so as to make pressure of lubricating oil in the first cell higher than that in the second cell.

A synchronizer of a transmission may include bottom key disposed on a hub to be slidable in a radial direction of the hub; a top key disposed radially outside the bottom key to be slidable in an axial direction of the hub; a sleeve disposed outside the hub and sliding in the axial direction to slide the top key in the axial direction to press a synchro-ring; a key spring disposed between the bottom key and the hub to press the bottom key and the top key toward an internal side of the sleeve; and a motion converting portion converting relative motion generated in a circumferential direction of the hub between the top key and the bottom key into axial relative motion of the top key to the bottom key toward the synchro-ring.

A shift system for shifting a gear unit has at least one movably disposed selector shaft and at least one switch element. The selected position of the switch element is changed by movement of the selector shaft relative to the switch element. A drive shaft is rotatable about a centre axis. In a first selected position of the switch element, it can be connected to co-rotate at least in one direction of rotation to a component of the gear unit. In a second selected position of the switch element, it can be disconnectable from the component of the gear unit in each direction of rotation. At least a part of the switch element co-rotates with a rotation of the drive shaft about the centre axis, so that relative movement of the switch element with respect to the selector shaft is generated. A gear unit has such a switch system.

A constant mesh type transmission for a straddled vehicle includes an input shaft; a plurality of drive gears; an output shaft; a plurality of driven gears; and a gear stage setting mechanism, including a ratchet mechanism. The ratchet mechanism includes a n-th speed accelerating pawl, a n-th speed decelerating pawl, a (n+1)-th speed accelerating pawl, a (n+1)-th speed decelerating pawl, a rotary cam, and a plurality of sliders. The rotary cam has a plurality of cam portions on an outer peripheral surface thereof which position the respective guide object parts such that the plurality of sliders raise an accelerating pawl and a decelerating pawl corresponding to a selected gear stage and lower an accelerating pawl and a decelerating pawl corresponding to a non-selected gear stage.