CONNECTION METHOD FOR TURBO CHARGER TURBINE SHAFT

Disclosed is a joining method which helps to achieve an improvement in joining accuracy for wheel and turbine shaft. In the joining method, at least a part of the inner peripheral wall of the fixing hole 3 of the wheel 1 is tapered so as to be reduced in diameter inwardly from the opening of the fitting hole; at one end of the turbine shaft 4 to be joined to the wheel, there are provided a tapered axial abutment portion 7 capable of being brought into close contact with the tapered inner peripheral wall and an insertion portion 6 with a fixed diameter to be inserted into the fitting hole 3, the wheel 1 and the turbine shaft 4 being joined and fixed to each other so as to be coaxial in the rotation axis. In the turbine shaft 4, an axial abutment portion 7 is provided in a part other than the portion 11 to be fused by welding, whereby preventing change in the axial dimension of the turbine shaft 4 at the time of fusion and contraction. The axial abutment portion 7 is tapered, and the inner peripheral wall of the fitting hole in contact therewith is tapered, whereby the wheel 1 and the turbine shaft 4 are brought into close contact with each other while being guided so as to be positioned coaxially. With the provision of the insertion portion 6 along with the axial abutment portion 7, close contact is effected in a stable manner in the axial abutment portion 7 where tapered surfaces come into contact with each other.