A vehicle power unit has a transmission apparatus including a transmission, and a transmission actuating mechanism including a speed reduction gear train having multiple speed reduction stages for transmitting power from a drive gear on a drive shaft of a shift motor to a driven gear on a drum turning shaft of a shift drum. The speed reduction gear train has a speed reduction ratio ranging from 23 to 45, and the shift motor is a DC electric motor that produces a pulsating cogging torque having a maximum value ranging from 0.04 to 0.07 Nm. The vehicle power unit enables the transmission actuating mechanism to be made up of a reduced number of parts and to be simple in structure, making the transmission apparatus small in size, and ensures quicker and smoother gear changes with an electric motor.

A cylindrical shift drum is rotatable around a third rotational axis. The cylindrical shift drum includes at least one lead groove in an outer circumferential surface of the cylindrical shift drum. A shift fork shaft extending in parallel to the third rotational axis is disposed opposite to the outer circumferential surface. At least one shift fork includes a main portion slidably supported by the shift fork shaft and a pin portion rotatably supported by the main body portion. The main body portion includes a fork portion to be engaged with at least one shifter gear. The pin portion is inserted in one of the at least one lead groove. The cylindrical shift drum is to be rotated to guide the pin portion along the one of the at least one lead groove to move the at least one shift fork to shift the at least one shifter gear.

A gear-shifting device for a vehicle is provided and includes a guide body that has a first end portion connected to a control shaft, installed so that a second end portion is rotated at the first end portion as an axis in a rotational displacement that corresponds to a selecting path to perform a selecting operation, and installed to be moved in a substantially straight displacement that corresponds to a shifting path along an axis direction of the first end portion to perform a shifting operation. A guide unit is disposed to distinguish each shifting path on the selecting path in which the second end portion of the guide body is rotated and is configured to guide the second end portion of the guide body to be movable along the shifting path.

A vehicle manual transmission includes: shift fork shafts; shift forks; sleeves; and gear pieces. Each of the shift forks is coupled with the shift fork shaft so as to be moved together. Each of the sleeves has an annular shape. The sleeve includes an annular sliding groove to be fitted to the shift fork on an outer peripheral surface of the sleeve. The sleeve includes peripheral edges forming annular planes as viewed in the longitudinal direction of the shift fork shaft. Each of the gear pieces includes outer peripheral teeth to be meshed with inner peripheral teeth formed on an inner peripheral surface of the sleeve when the sleeve is moved in accordance with the gear shift operation. The shift fork shaft or the shift fork includes a restricting member that abuts to the peripheral edge so as to restrict a movement of the sleeve in a longitudinal direction.

A gearbox of a power unit includes a transmission, a shift drum provided with lead grooves, a shift drum feed mechanism, and a drive side-shift fork and driven side-shift forks respectively provided with engaging portions to be engaged with the lead grooves. At least one lead groove is a common lead groove with which the engaging portion of the drive side-shift fork and the engaging portion of the driven side-shift fork are engaged at an angular interval, which is a positive multiple integral of a feed angle of the shift drum, with respect to a rotation center of the shift drum. The drive side-shift fork and driven side-shift fork, whose engaging portions are engaged with the common lead groove, are guided by the same axially shifted groove portions provided in the common lead groove, and thereby establish speeds of the transmission.

Actuation device for a transmission system includes an electric motor kinematically connected to a speed reducer and an output shaft of the speed reducer of axis of rotation, the output shaft being arranged to pivot through three adjacent angular sectors, a first angular sector, a second angular sector adjacent to the first angular sector, and a third angular sector adjacent to the second angular sector. An actuation cam is rigidly connected to the output shaft for rotation therewith. A receiving part is axially movable along a main axis perpendicular to the axis of rotation, comprising a receiving recess for receiving the actuation cam formed by two surfaces parallel to each other and perpendicular to the main axis.

A gearbox (1) is placed in a drive train between an electric motor (12) and an engine (13) of a vehicle. The gearbox (1) is placed in direct connection to an output shaft (2) of the electric motor (12). The gear box (1) has means to place it in three different modes.

An apparatus for moving a shift rail of a transmission may include a control shaft provided to be moved in a direction perpendicular to a plurality of shift rails by an actuator, a plurality of rollers protruding from one selected among a corresponding one of the shift rails and the control shaft, the rollers being formed on one of facing sides of the shift rail and the control shaft, and a cam protruding in an S-shaped form from a remaining one selected among the corresponding shift rail and the control shaft, on which no roller is formed, the cam being provided to selectively move the shift rails in an axial direction by moving while coming into contact at opposite sides thereof with the rollers depending on a distance by which the control shaft is moved.

A transmission according to an embodiment includes a shift fork swingably supported by a case to move a movable element in an axial direction in accordance with the motion of a second shaft to two shift positions; two first protrusions provided on the second shaft and spaced apart from each other in the axial direction; and a second protrusion provided on the shift fork, and when the second shaft is in one of select positions, is positioned between the two first protrusions and overlaps with the first protrusions viewed from the axial direction. A protruding direction of the first protrusions and a protruding direction of the second protrusion are orthogonal to a swinging center of the shift fork when viewed in the axial direction. The second protrusion protrudes from the shift fork toward the swinging center. The second shaft is positioned between the second protrusion and the swinging center.

A gear-shifting device for a vehicle is provided and includes a guide body that has a first end portion connected to a control shaft, installed so that a second end portion is rotated at the first end portion as an axis in a rotational displacement that corresponds to a selecting path to perform a selecting operation, and installed to be moved in a substantially straight displacement that corresponds to a shifting path along an axis direction of the first end portion to perform a shifting operation. A guide unit is disposed to distinguish each shifting path on the selecting path in which the second end portion of the guide body is rotated and is configured to guide the second end portion of the guide body to be movable along the shifting path.