A fork guide groove of a drum member guides a shift fork so that a shifter member is in a reference position not engaged with first and second speed change members when the drum member is placed in a neutral position, is movable between a first speed-change position engaged with the first speed-change member and the reference position when the drum member is placed in a first operational position, and is movable between a second speed-change position engaged with the second speed-change member and the reference position when the drum member is placed in a second operational position. A slider guide groove of the drum member guides a slider member supported by a fork shaft in an axially movable manner so as not to obstruct movement of the shifter member between the reference position and the first speed-change position when the drum member is placed in the first operational position.

A shifting mechanism a shifting mechanism in which a movable member integrated with an engagement pin will not be rotated by a friction acting between a cam groove and the engagement pin. A shifting mechanism comprises: a shift drum that on which a cam groove is formed; a cam sleeve having an engagement pin inserted into the cam groove; a fork shaft reciprocated between predetermined positions by rotating the shift drum; a support stem extending parallel to a center axis of the cam sleeve; and a projection formed integrally with the cam sleeve to come into contact with the support stem when the cam sleeve is rotated.

A device (10) for axially moving a gearbox element (12), including: a shift drum (50) mounted rotatably about an axis of rotation (8) and having a shifting groove (62) formed in its outer casing at least partially circumferentially about the axis of rotation (8), which groove is axially inclinded (64) at least in some areas, a cage (30) holding the gear shift drum (50) with a cage wall (34) delimiting an inner cage space (48) against an outer cage space and a wall slot (70) extending axially through the cage wall (34) and opening the inner cage space (48) towards the outer cage space, a carriage (42) held axially movably between the gear shift drum (50) and the cage wall (34) in the area of the wall slot (70), and a shift fork (46) with two fork legs (80).

An axle assembly that includes a barrel cam. The barrel cam may be rotatable about a barrel cam axis and may be operatively connected to a first shift collar. Rotation of the barrel cam about the barrel cam axis may control movement of the first shift collar along a first axis.

A fork guide groove of a drum member guides a shift fork so that a shifter member is in a reference position not engaged with first and second speed change members when the drum member is placed in a neutral position, is movable between a first speed-change position engaged with the first speed-change member and the reference position when the drum member is placed in a first operational position, and is movable between a second speed-change position engaged with the second speed-change member and the reference position when the drum member is placed in a second operational position. A slider guide groove of the drum member guides a slider member supported by a fork shaft in an axially movable manner so as not to obstruct movement of the shifter member between the reference position and the first speed-change position when the drum member is placed in the first operational position.

A transmission in which multiple shift forks are moved by a shared lead groove of a shift drum has an improved degree of freedom of design of an internal combustion engine as well as an improved degree of freedom of layout of shift forks. The transmission includes multiple shift forks having engaging protrusions that engage with a shared lead groove. At least one shift fork among the multiple shift forks has an opening angle α around a drum rotation center line of a shift drum between a boss center line as a cylindrical center line of a cylindrical boss that is axially supported by a fork shaft of the shift fork, and a fork action part of the engaging protrusion on which the shared lead groove acts in accordance with rotation of the shift drum.

Methods and systems are provided for a transmission housing of a vehicle. In one example, a system comprises a transmission housing comprising at least one cover configured to support a shift fork, wherein the at least one cover is removable from an exterior of the transmission housing.

A transmission in which multiple shift forks are moved by a shared lead groove of a shift drum has an improved degree of freedom of design of an internal combustion engine as well as an improved degree of freedom of layout of shift forks. The transmission includes multiple shift forks having engaging protrusions that engage with a shared lead groove. At least one shift fork among the multiple shift forks has an opening angle α around a drum rotation center line of a shift drum between a boss center line as a cylindrical center line of a cylindrical boss that is axially supported by a fork shaft of the shift fork, and a fork action part of the engaging protrusion on which the shared lead groove acts in accordance with rotation of the shift drum.

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 shift drum has a recess which controls a fork to move one of two cooperating coaxially arranged gears for transmitting torque in a power train of a vehicle. The recess includes a straight section, which upon rotation of the shift drum does not move the fork either to the left or the right, and at least one ramp which does move the fork in one direction (i.e., to the left or the right). The ramp is more complex than a single line, such as having a first portion at a first right-shift portion ramp angle β and a second portion at a second right-shift portion ramp angle γ, perhaps with the intersection between the first right-shift portion ramp angle β and the second right-shift portion ramp angle γ being at the mid-line defined by the straight section of the recess.