Joining structure of power source and transmission

A joining structure of a power source and a transmission, comprising:

• a joining portion joining a power source and a transmission to each other coaxially with a rotational axis line in a state where a rotary force corresponding to output from the power source is transmittable to the transmission, the joining portion including;
• a first fitting portion centering a first housing of the power source and a second housing of the transmission with each other on the rotational axis line;
• a second fitting portion at which a rotary portion of the transmission is fitted to an output shaft portion of the power source in an axial direction, the second fitting portion centering the rotary portion and the output shaft portion with each other on the rotational axis line;
• a housing spacer fixed to the first housing to be coaxial with the rotational axis line in such a manner that a first flange is fitted into a first hole provided at the first housing;
• and
• a third fitting portion including a protruding portion provided at one of the second housing and the housing spacer and a recessed portion provided at the other of the second housing and the housing spacer, the recessed portion being fitted to the protruding portion in a direction of the rotational axis line and centering the second housing and the housing spacer with each other on the rotational axis line, wherein
• in a case where the transmission is positioned at a position at which the protruding portion of the third fitting portion and the recessed portion of the third fitting portion start fitting to each other, the rotary portion of the transmission is away from a position at which the rotary portion starts fitting to the output shaft portion of the power source by a predetermined distance.