Clutch drive unit and straddle type vehicle

A clutch drive unit for mutually switching between transmission and blocking of drive force in a clutch of a straddle type vehicle, the vehicle including

• an engine configured to generate the drive force by fuel combustion,
• a transmission configured to change, for the drive force of the engine, a rotation speed by a plurality of gear trains forming a plurality of gear stages with different transmission gear ratios from one another, and
• the clutch configured to selectively switch, by pressing force of a push rod, between transmission and blocking of the drive force from the engine to the transmission,
• the clutch drive unit comprising:
• a clutch actuator including a drive shaft to be rotatably driven;
• a transmission gear including a large gear configured to engage with the drive shaft and a small gear provided concentric with respect to the large gear;
• a crank arm comprising a tooth portion engaged with the small gear and configured to be rotated by a drive force of the clutch actuator transmitted from the transmission gear, the crank arm being coupled with the drive shaft;
• an output pin provided on one side of the crank arm, the output pin configured to press an output rod;
• a receiving pin provided on other side of the crank arm and at a position with a longer distance from a center of rotation of the crank arm than a distance between the output pin and the center of rotation of the crank arm;
• a master cylinder configured to generate hydraulic pressure for pushing the push rod, the hydraulic pressure being generated by rotation of the crank arm which causes the output pin to press the output rod and to slide the output rod in a cylinder;
• and
• an extendable body
• comprising an elastic body configured to produce pressing force toward the center of rotation of the crank arm, and
• rotatable about a holder receiving pin contacting one end of the extendable body while other end of the extendable body is in contact with the receiving pin, within a range of an angle θ2 at which a pressing direction of the pressing force of the elastic body is toward the center of rotation of the crank arm and an angle θ1 at which the pressing direction of the pressing force of the elastic body is against reactive force moment based on reactive force acting on the crank arm from the clutch through each of the push rod and the output rod, to cause pressing moment in a direction opposite to the reactive force moment to act on the crank arm, wherein
• the extendable body provides the crank arm with the pressing force of the elastic body such that the pressing moment is greater than the reactive force moment, and
• the distance between the center of rotation of the crank arm and the output pin is shorter than a distance between the center of rotation of the crank arm and a center of rotation of the transmission gear.