Axial force controlling method and bearing apparatus

1. An axial force controlling method for controlling an axial force applied to a rolling bearing in a bearing apparatus having said rolling bearing and a shaft body, said rolling bearing being mounted to said shaft body such that said rolling bearing fits an outside of said shaft body, said rolling bearing being prevented from dropping off by holding a caulked portion against an outer end face of an inner ring of said rolling bearing, and said caulked portion being formed by bending a cylindrical portion to be caulked on a free end side of said shaft body outward in a diameter direction, said method comprising the following steps for controlling said axial force applied to said rolling bearing through said caulked portion:

defining a first position as a position of an end edge on an inner periphery side of a chamfered portion formed at an inner peripheral shoulder portion of said inner ring;

defining a second position as a caulking starting point on an inner periphery side at a boundary of said cylindrical portion to be caulked and said shaft body;

determining axial forces resultant from said second position having axial displacements both axially inward and outward of said first position;

plotting said axial forces versus a displacement variable proportionate to said axial displacements and setting a minimum axial force to define an acceptable displacement range of said first position and said second position through which said minimal axial force is achieved; and

performing caulking by bending the cylindrical portion beginning at said second position such that an axial displacement of said second position relative to said first position falls within said acceptable displacement range.

2. An axial force controlling method according to claim 1 wherein a coordinate point x of said second position is set the same as an origin of the first position in order to obtain maximum axial force.

3. An axial force controlling method according to claim 2 , wherein a relationship of a radial thickness t of the cylindrical portion to be caulked is set at −0.15≦x/t≦0.05 while a required axial force of more than 2500 kgf is obtained.

4. An axial force controlling method according to claim 1 , wherein said caulked portion of said shaft body is thinner than a remainder of the shaft body.