There is provided a shift device for a straddle-type vehicle that is configured to cause a transmission device to perform a shift change in accordance with rotation of a shift shaft. The shift device includes: a shift lever provided with an operation portion that is configured to receive a shift operation; a shift sensor provided on the shift shaft so as to be integrally rotatable with the shift shaft; and a shift rod that couples the shift lever and the shift sensor. The shift sensor is configured to detect the shift operation on the shift lever in accordance with a movement of the shift rod. The operation portion and the shift sensor are positioned at the same side in a manner of sandwiching the shift rod.

A drive device includes: an actuator rotating, around a rotation axis, a shift drum having a lead groove formed on an outer peripheral surface; and an angle correction unit correcting a detection value of a rotation angle sensor that detects a rotation angle of the shift drum. The angle correction unit calculates the rotation angle of the shift drum at a reference position as a learning angle based on a correspondence between a displacement amount of a first engaging portion and a change amount of the rotation angle of the shift drum per a predetermined time of rotation of the shift drum at a predetermined speed. Then, the angle correction unit corrects the detection value of the rotation angle sensor based on an amount of deviation between the learning angle and a design angle.

A shift mechanism switches power transmission paths among a first transmission shaft, a second transmission shaft, and a third transmission shaft that are concentrically arranged on a rotational axis. The shift mechanism has a drive drum that is provided so as to be coaxial with the rotational axis and pivotable about the rotational axis, and a first driven drum and a second driven drum that are arranged on the rotational axis so as to be concentric with the drive drum and move along the rotational axis as the drive drum pivots. As the first driven drum moves, a first shift sleeve advances and retreats, and the first transmission shaft and the second transmission shaft are connected and disconnected. In addition, as the second driven drum moves, a second shift sleeve advances and retreats, and the second transmission shaft and the third transmission shaft are connected and disconnected.

A shift mechanism switches power transmission paths among a first transmission shaft, a second transmission shaft, and a third transmission shaft that are concentrically arranged on a rotational axis. The shift mechanism has a drive drum that is provided so as to be coaxial with the rotational axis and pivotable about the rotational axis, and a first driven drum and a second driven drum that are arranged on the rotational axis so as to be concentric with the drive drum and move along the rotational axis as the drive drum pivots. As the first driven drum moves, a first shift sleeve advances and retreats, and the first transmission shaft and the second transmission shaft are connected and disconnected. In addition, as the second driven drum moves, a second shift sleeve advances and retreats, and the second transmission shaft and the third transmission shaft are connected and disconnected.

[Technical problem] To provide a power transmission mechanism for a four-wheel drive vehicle in which a prime mover is disposed at a low position to lower the center of gravity of the vehicle while a driving path from a transmission to a front wheel differential mechanism is also shortened. [Solutions] In a power transmission mechanism for a four-wheel drive vehicle, the power of a prime mover is transmitted to a front wheel differential mechanism which is disposed in front of the prime mover, and to a rear wheel differential mechanism which is disposed behind a transmission, through the transmission which is disposed behind the prime mover. The transmission comprises a front and rear wheel drive shaft that extends along the longitudinal direction of the vehicle body. The transmission is arranged separately from the prime mover and a rear axle drive device. The rear end portion of the front and rear wheel drive shaft is connected to an input shaft of the rear wheel differential mechanism. The front end portion of the front and rear wheel drive shaft is connected to an input shaft of the front wheel differential mechanism via a front wheel power transmission shaft that extends along the longitudinal direction of the vehicle body and passes through the space beneath the prime mover. The front wheel differential mechanism, the prime mover, the transmission, and the rear wheel differential mechanism are arranged along the longitudinal direction of the vehicle body at the center of the vehicle width of the vehicle.

A transmission includes a shift drum, an angular sensor, and a control unit. The control unit has reference values of the output values at a first rotation angle and a second rotation angle of the shift drum. The control unit is configured to obtain the output values at the first rotation angle and the second rotation angle as a first output value and a second output value, respectively. The control unit is configured to correct the output value output between the first rotation angle and the second rotation angle based on a difference between the first output value and the reference value at the first rotation angle and a difference between the second output value and the reference value at the second rotation angle.

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 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.

This transmission device includes a mode changeover switch (59) on which a mode changeover operation between a manual mode (M2) and an automated mode (M1) is externally performed, other operation unit (80) on which a predetermined shift operation is externally performed separately from the mode changeover switch (59), and a control unit (60) configured to control a mode changeover between the manual mode (M2) and the automated mode (M1). The control unit (60) executes the mode changeover between the manual mode (M2) and the automated mode (M1) on the basis of the mode changeover operation on the mode changeover switch (59). When the shift operation on the other operation unit (80) has been performed, the control unit (60) executes the mode changeover between the manual mode (M2) and the automated mode (M1).

A shift drum angle detecting device includes: a first angle sensor configured to output a first sensor output value corresponding to a shaft rotational angle of a first sensor shaft integrally rotating with a shift drum; and a second angle sensor configured to output a second sensor output value corresponding to a shaft rotational angle of a second sensor shaft rotating at an increased speed as a result of a speed increasing mechanism increasing the rotation of the first sensor shaft. A first sensor switching angle where the maximum value and the minimum value of the first sensor output value are switched and a second sensor switching angle where the maximum value and the minimum value of the second sensor output value are switched are set to be different from each other in rotational angle of the shift drum. Such device precisely detects any rotational angle of the shift drum.