Transmission and shift control system

A shift control system comprising:

• a start clutch that transmits and outputs a torque from an engine according to a fastening adjustment;
• a transmission that shifts gears through a shifting movement of a meshing clutch according to a vehicle speed to output the torque transmitted and output from the start clutch to drive wheels;
• a clutch actuator that performs the fastening adjustment of the start clutch;
• a shift actuator that causes the shifting movement of the meshing clutch;
• a torque detector that detects a transmitting torque toward the drive wheels;
• a clutch controller that controls the clutch actuator to perform the fastening adjustment so that a transmission torque of the start clutch is reduced during an interval just before and after shifting a gear while maintaining engine output transmitting torque detected by the torque detector at the time of shifting the gear and preventing an excessive shock torque due to the shifting.

The shift control system according to claim 1, wherein:

• the transmission comprises:
• multiple stage shift gears fixed to or relatively rotatably supported with driving force transmission shafts;
• a plurality of clutch rings each having meshing parts on both sides for meshing with the respective shirt gears that take two speeds or more away from each other, so as to connect the respective shift gears to the driving force transmission shafts and perform a shifted output;
• a shift operation part that selectively operates the clutch rings;
• guide parts that are provided for respective stages of the shift gears between the clutch rings and the driving force transmission shafts so that, when meshing engagements of the clutch rings of an upper stage and a lower stage are simultaneously performed through the operation of the shift operation part, axial forces oriented in opposite directions that are a meshing-engagement direction and a meshing-release direction are generated on the clutch rings of the upper stage and the lower stage.