Patent ID: 6877928

Claim:
A construction of coupling spline sections of an automatic transmission, comprising: a rotary shaft section having an outer periphery formed with a spline section; a rotary hollow section having an inner periphery formed with a spline section which is coupled with the spline section of the rotary shaft section so that a portion of the coupling is in a press fitting state; a support member; and a bearing disposed between a part of an outer periphery of the rotary hollow section and the support member, the bearing rotatably bearing the rotary shaft section in such a manner as to transmit a torque between the rotary shaft section and the rotary hollow section, wherein the spline section of the rotary shaft section and the spline section of the rotary hollow section which are disposed at least inside the bearing are coupled with each other in a loose state looser than the press fitting state, wherein the spline section of the rotary shaft section and the spline section of the rotary hollow section are coupled with each other in the loose state on a first end side of the rotary hollow section so that a stress applied to the first end side of the rotary hollow section due to expansion of the rotary shaft section is less than a stress applied in the press fitting state, and wherein the spline section of the rotary shaft section and the spline section of the rotary hollow section are coupled with each other in the press fitting state on a side other than the first end side of the rotary hollow section.