Turbine wheel

1. A turbine wheel provided with a groove having a bottom surface extending circumferentially and a pair of side wall surfaces forming an opening, the turbine wheel comprising:

a balance weight that is arranged in the groove, the balance weight being configured to be insertable from any circumferential position of the opening of the groove, the balance weight having a through-hole opened toward one of the pair of side wall surfaces of the groove; and

a retaining member that contacts a portion of the one of the pair of side wall surfaces of the groove in a state of being inserted in the through-hole of the balance weight, to thereby cause the balance weight to abut against other one of the pair of side wall surfaces of the groove and be retained in the groove, wherein

the groove has a plurality of engagement recesses provided at intervals in a circumferential direction at the bottom surface or an engagement protrusion protruding from the bottom surface, the engagement protrusion being fitted to one of a plurality of fitting recesses provided at intervals in the circumferential direction at the bottom surface, and

the balance weight has an engagement protrusion that engages with one of the engagement recesses of the groove to restrict a circumferential shift of the balance weight in the groove or an engagement groove that engages with the engagement protrusion of the groove to restrict a circumferential shift of the balance weight in the groove.

2. The turbine wheel according to claim 1 , wherein

the groove has the engagement recesses, and

the balance weight includes

a body section having the through-hole, and

the engagement protrusion formed integrally with the body section.

3. The turbine wheel according to claim 1 , wherein

the groove has the engagement recesses, and

the balance weight includes

a body section that has the through-hole and a fitting recess, the fitting recess being provided in a portion facing the bottom surface of the groove, and

the engagement protrusion fitted to the fitting recess of the body section.

4. The turbine wheel according to claim 2 , wherein

the balance weight has

a rear surface that faces the bottom surface of the groove,

a front surface that is positioned on a side opposite to the rear surface, and faces the opening of the groove,

a first side surface that is connected to the rear surface and the front surface, and faces the one of the pair of side wall surfaces of the groove, and

a second side surface that is connected to the rear surface and the front surface, is positioned on a side opposite to the first side surface, and faces the other one of the pair of side wall surfaces of the groove, and

the balance weight is formed such that a length from a ridge located between the front surface and the second side surface to an end portion of a tip surface of the engagement protrusion of the balance weight is shorter than a length from an opening edge of the opening of the groove to an end portion of an opening edge of one of the engagement recesses of the groove, the end portion of the tip surface being on a side where the first side surface is located, the opening edge of the opening of the groove being on a side where the one of the pair of side wall surfaces is located, the end portion of the opening edge of one of the engagement recesses being on a side where the other one of the pair of side wall surfaces is located.

5. The turbine wheel according to claim 1 , wherein

a corner portion located on a side of the one of the pair of side wall surfaces in the groove is formed in a concave curved surface, and

the retaining member is formed such that a tip section of the retaining member makes line contact with a portion of the concave curved surface of the corner portion of the groove.