Fluid dynamic bearing motor, and recording-medium driving apparatus

Abstract

A fluid dynamic bearing includes a shaft member engaged with a circular plate extending radially outward therefrom; a support including a cylinder rotatably accommodating the shaft member, an outer surface of the support having a tapered portion toward an axial upper surface thereof opposing the circular plate; a stopper, an inner surface of the stopper having a constant diameter in an axial direction in a portion opposite to the tapered portion of the support so as to form a tapered gap with respect to an outer surface of the support located under the axial upper surface of the support; and a working fluid placed between the inner surface of the stopper and the outer surface of the support.

1 . A fluid dynamic bearing comprising:
 a shaft member engaged with a circular plate extending radially outward therefrom;   a support including a cylinder rotatably accommodating the shaft member, an outer surface of the support having a tapered portion toward an axial upper surface thereof opposing the circular plate;   a stopper, an inner surface of the stopper having a constant diameter in an axial direction in a portion opposite to the tapered portion of the support so as to form a tapered gap with respect to an outer surface of the support located under the axial upper surface of the support; and   a working fluid placed between the inner surface of the stopper and the outer surface of the support.   
     
     
         2 . The fluid dynamic bearing of  claim 1 , wherein the support includes a flange portion formed at an axial end of the cylinder, and
 the stopper interferes with the flange portion to thereby prevent the shaft member from ascending.   
     
     
         3 . The fluid dynamic bearing of  claim 2 , wherein a lower end of the inner surface of the stopper extends below the cylinder in an axial direction. 
     
     
         4 . The fluid dynamic bearing of  claim 2 , wherein the support is press-fitted and fixed to an inner surface of a boss extending upward from a stator in an axial direction, and
 the cylinder is formed above the boss.   
     
     
         5 . The fluid dynamic bearing of  claim 1 , wherein a thrust bearing portion is formed between the axial upper surface of the support and the circular plate, and
 a through-hole extending axially is formed in the support radially inside of the thrust bearing portion.   
     
     
         6 . The fluid dynamic bearing of  claim 5 , wherein the thrust bearing portion includes a pressure-generating groove in a thrust surface thereof, and
 the through-hole is connected to the pressure-generating groove.   
     
     
         7 . The fluid dynamic bearing of  claim 1 , wherein the stopper is engaged with a yoke protruding from the circular plate in an axial downward direction. 
     
     
         8 . The fluid dynamic bearing of  claim 7 , wherein the stopper is fixed to an inner surface of the yoke using an adhesive or by welding to prevent oil from leaking between the yoke and the stopper. 
     
     
         9 . The fluid dynamic bearing of  claim 7 , wherein the stopper is fixed to both a lower surface of the circular plate and an inner surface of the yoke. 
     
     
         10 . A motor comprising:
 a fluid dynamic bearing according to  claim 1 ; and   a drive unit configured to rotate the shaft member of the fluid dynamic bearing relative to the support.   
     
     
         11 . A recording-medium driving apparatus comprising:
 a motor according to  claim 10 ; and   a fixing portion to fix a recording medium to the motor.   
     
     
         12 . A fluid dynamic bearing comprising:
 a shaft member engaged with a circular plate extending radially outward therefrom;   a sleeve including a cylinder rotatably accommodating the shaft member, a portion of an outer surface of the sleeve increasing in diameter in an axial upward direction, and a flange portion being formed at an axial end of the cylinder;   a stopper, a portion of an inner surface of the stopper having a constant diameter in an axial direction so as to form a tapered gap between the stopper and the sleeve, the stopper interfering with the flange portion so as to prevent the shaft member from ascending; and   a working fluid placed between the inner surface of the stopper and the outer surface of the sleeve located under the axial upper surface,   wherein the working fluid fills gaps between the shaft member and the inner surface of the sleeve, between the upper surface of the sleeve and the circular plate, and up to between the outer surface of the sleeve and the inner surface of the stopper.   
     
     
         13 . The fluid dynamic bearing of  claim 12 , wherein a lower end of the inner surface of the stopper extends further downwards than the cylinder in an axial direction. 
     
     
         14 . The fluid dynamic bearing of  claim 12 , wherein the sleeve is press-fitted and fixed to an inner surface of a boss extending upward from a stator In an axial direction, and
 the cylinder is formed above the boss.   
     
     
         15 . The fluid dynamic bearing of  claim 12 , wherein a thrust bearing portion is formed between the axial upper surface of the sleeve and the circular plate, and
 a through-hole extending axially is formed in the sleeve radially inside of the thrust bearing portion.   
     
     
         16 . The fluid dynamic bearing of  claim 15 , wherein the thrust bearing portion includes a pressure-generating groove in a thrust surface thereof, and
 the through-hole is connected with the pressure-generating groove.   
     
     
         17 . The fluid dynamic bearing of  claim 12 , wherein the stopper is engaged with a yoke protruding from the circular plate in an axial downward direction. 
     
     
         18 . The fluid dynamic bearing of  claim 17 , wherein the stopper is fixed to an inner surface of the yoke using an adhesive or by welding to prevent oil from leaking between the yoke and the stopper. 
     
     
         19 . The fluid dynamic bearing of  claim 17 , wherein the stopper is fixed to both a lower surface of the circular plate and an inner surface of the yoke. 
     
     
         20 . A motor comprising:
 a fluid dynamic bearing according to  claim 12 ; and   a drive unit configured to rotate the shaft member of the fluid dynamic bearing relative to the sleeve.   
     
     
         21 . A recording-medium driving apparatus comprising:
 a motor according to  claim 20 ; and   a fixing portion to fix a recording medium to the motor.