In the present social environment, automobile demands further reduction of fuel consumption and light weight.
Now that the reduction of vehicle weight is being pursued, even a slight looseness in each element of an automobile may become a source of vibration and noise due to the lowered rigidity of such an automobile.
The quietness of vehicles is urged, spline backlash in the spline mechanism exhibits a problem in some cases.
A propeller shaft, a part of the automobile driving system, also has a sliding spline mechanism as shown in Fig. 1.
Such a propeller shaft is required to have functions of transmitting high torque driving forces, and absorbing the variation of the vehicle driveline overall length at the same time.
Vibration and noise are apt to occur if when torque is applied, there is a significant balance fluctuation or great sliding resistance due to spline backlash.
Therefore, it is necessary to reduce both the spline backlash and sliding resistance for the propeller shaft at the same time.