Dynamic Bearing Device

Abstract

A seal member is fixed to a predetermined position on an outer peripheral surface of a shaft portion. During rotation of a shaft member, a lower end surface of the seal member is opposed to an upper end surface of a bearing sleeve through an intermediation of a thrust bearing gap to form a second thrust bearing gap. An outer peripheral surface of the seal member defines between itself and an inner peripheral surface of an upper end portion of a housing a seal space having a predetermined volume.

1 . A dynamic bearing device, comprising: a housing; a bearing sleeve fixed inside the housing; a shaft member making a relative rotation with respect to the housing and the bearing sleeve; a seal member situated at one end of the housing; and a radial bearing portion supporting the shaft member radially in a non-contact manner by a dynamic pressure action of a fluid generated in a radial bearing gap between the bearing sleeve and the shaft member, 
 characterized in that the seal member is provided on the shaft member, with a seal space being provided beside an outer peripheral surface of the seal member.    
   
   
       2 . A dynamic bearing device, comprising: a housing; a bearing sleeve fixed inside the housing; a shaft member making a relative rotation with respect to the housing and the bearing sleeve; a seal member situated at one end of the housing; and a radial bearing portion supporting the shaft member radially in a non-contact manner by a dynamic pressure action of a fluid generated in a radial bearing gap between the bearing sleeve and the shaft member, 
 characterized in that the shaft member has a shaft portion inserted into an inner peripheral surface of the bearing sleeve and a flange portion provided on the shaft portion,    that the seal member is fixed to the shaft member, with a seal space being defined beside an outer peripheral surface of the seal member,    that the dynamic bearing device includes a first thrust bearing portion provided between one end surface of the seal member and one end surface of the bearing sleeve opposed thereto, with the first thrust bearing portion supporting the seal member and the shaft member in a thrust direction in a non-contact manner by a dynamic pressure action of a fluid generated in a thrust bearing gap, and    that the dynamic bearing device includes a second thrust bearing portion provided between one end surface of the flange portion and another end surface of the bearing sleeve opposed thereto, with the second thrust bearing portion supporting the shaft member in the thrust direction in a non-contact manner by a dynamic pressure action of the fluid generated in a thrust bearing gap.    
   
   
       3 . A dynamic bearing device according to  claim 1 , characterized in that a tapered surface gradually diminished in diameter toward outside of the housing is formed on the outer peripheral surface of the seal member.  
   
   
       4 . A dynamic bearing device according to  claim 1 , characterized in that the seal member is fixed to the shaft member by an adhesive, and that an adhesion position of at least one of the seal member and the shaft member is provided with a recess to be filled with the adhesive.  
   
   
       5 . A dynamic bearing device, comprising: a housing; a bearing sleeve fixed inside the housing; a shaft member making a relative rotation with respect to the housing and the bearing sleeve; a seal member situated at one end of the housing; and a radial bearing portion supporting the shaft member radially in a non-contact manner by a dynamic pressure action of a fluid generated in a radial bearing gap between the bearing sleeve and the shaft member, 
 characterized in that the seal member is provided on the shaft member,    that one end surface of the seal member is opposed to one end surface of the bearing sleeve through an intermediation of a thrust bearing gap, and    that an outer peripheral surface of the seal member is provided with a tapered surface gradually diminished in diameter toward outside of the housing and facing a seal space.    
   
   
       6 . A dynamic bearing device according to  claim 1 , characterized in that the radial bearing portion has a dynamic pressure groove as a dynamic pressure generating means.  
   
   
       7 . A dynamic bearing device according to  claim 1 , characterized in that the radial bearing portion is formed by a multi-arc bearing.  
   
   
       8 . A spindle motor for a disk device, comprising the dynamic bearing device according to  claim 1 .  
   
   
       9 . A method of manufacturing a dynamic bearing device comprising: a housing; a bearing sleeve fixed inside the housing; a shaft member having a shaft portion inserted into an inner peripheral surface of the bearing sleeve and a flange portion provided on the shaft portion; a seal member fixed to the shaft member; a radial bearing portion supporting the shaft member radially in a non-contact manner by a dynamic pressure action of a fluid generated in a radial bearing gap between an inner peripheral surface of the bearing sleeve and an outer peripheral surface of the shaft member; a first thrust bearing portion supporting the seal member and the shaft member in a thrust direction in a non-contact manner by a dynamic pressure action of the fluid generated in a thrust bearing gap between one end surface of the seal member and one end surface of the bearing sleeve; and a second thrust bearing portion supporting the shaft member in the thrust direction in a non-contact manner by a dynamic pressure action of the fluid generated in a thrust bearing gap between one end surface of the flange portion and another end surface of the bearing sleeve, the method comprising the steps of: 
 inserting the shaft portion of the shaft member into the inner peripheral surface of the bearing sleeve and attaching the seal member to the shaft portion to thereby interpose the bearing sleeve between the one end surface of the seal member and the one end surface of the flange portion;    adjusting, after the step, an axial relative position of the shaft portion and the seal member to define, between the bearing sleeve and the one end surface of the seal member and between the bearing sleeve and the one end surface of the flange portion, gaps of an amount corresponding to a sum total of the thrust bearing gaps of the first thrust bearing portion and the second thrust bearing portion;    fixing, after the step, the seal member to the shaft portion; and    accommodating an assembly including the bearing sleeve, the shaft member, and the seal member assembled together by the step in the housing.    
   
   
       10 . A dynamic bearing device according to  claim 2 , characterized in that a tapered surface gradually diminished in diameter toward outside of the housing is formed on the outer peripheral surface of the seal member.  
   
   
       11 . A dynamic bearing device according to  claim 2 , characterized in that the seal member is fixed to the shaft member by an adhesive, and that an adhesion position of at least one of the seal member and the shaft member is provided with a recess to be filled with the adhesive.  
   
   
       12 . A dynamic bearing device according to  claim 2 , characterized in that the radial bearing portion has a dynamic pressure groove as a dynamic pressure generating means.  
   
   
       13 . A dynamic bearing device according to  claim 5 , characterized in that the radial bearing portion has a dynamic pressure groove as a dynamic pressure generating means.  
   
   
       14 . A dynamic bearing device according to  claim 2 , characterized in that the radial bearing portion is formed by a multi-arc bearing.  
   
   
       15 . A dynamic bearing device according to  claim 5 , characterized in that the radial bearing portion is formed by a multi-arc bearing.  
   
   
       16 . A spindle motor for a disk device, comprising the dynamic bearing device according to  claim 2 .  
   
   
       17 . A spindle motor for a disk device, comprising the dynamic bearing device according to  claim 5.