Magnetic disk apparatus

Abstract

The hole that penetrates the axial direction in the hub, the force of the axial direction by fluid force that operates on the spindle motor is reduced during the rotation. Fluctuation of fluid power is reduced by this hole. The rotary precision of the axial direction improves. Against the oil leakage from the bearing equipment, magnetic fluid is used as a lubrication fluid of the bearing. Magnetic fluid is magnetized with the permanent magnet arranged in the bearing equipment, and oil leakage is prevented. Against scattering of the oil particle, the groove for dynamic pressure generation is in the opening of bearing equipment. The oil particle is kept inside the bearing equipment.

What is claimed is:  
     
         1 . A spindle motor used in an information storage apparatus at least to reproduce an information from a rotating disk comprising: 
 a member which form a part of a case on which the spindle motor is installed;    a rotary axis;    a bearing device which support said rotary axis to be able to rotate against said member;    a cup-shaped hub to install the disk, which having a motor to rotate the disk and said bearing device in the inside, and    a passage for the air circulation, which connects the inside of said hub with the outside.    
     
     
         2 . A spindle motor as claimed in  claim 1 , wherein an outside opening of said passage is arranged at an portion of said hub which is situated on opposite side of said member with respect to said disk.  
     
     
         3 . A spindle motor as claimed in  claim 1 , wherein said disk is a plurality of magnetic disk stacked up on said hub, and an outside opening of said passage is arranged at an portion of said hub which is situated on opposite side of said member with respect to the disk stacked on the top.  
     
     
         4 . A spindle motor as claimed in  claim 1 , wherein 
 said bearing device is comprising a seal ring, a radial bearing, a permanent magnet, another radial bearing and a thrust bearing arranged along said rotating shaft from a opening side;    said radial bearings are dynamic pressure sliding bearings; and    magnetic fluid is used as a lubricant for bearings.    
     
     
         5 . A spindle motor as claimed in  claim 1 , wherein a filter is positioned in said passage.  
     
     
         6 . An information storage apparatus at least to reproduce an information from a disk rotated by a spindle motor as claimed in  claim 1 , wherein a cover is provided to cover said disk, and an outside opening of said passage is provided so as to connect the inside of the hub with a space formed by said disk and said cover.  
     
     
         7 . A spindle motor used in an information storage apparatus at least to reproduce an information from a rotating disk comprising: 
 a member which form a part of a case on which the spindle motor is installed;    a rotary axis;    a bearing device which support said rotary axis to be able to rotate against said member;    a cup-shaped hub to install the disk, which having said bearing device in the inside;    a motor structurally connecting to said rotary axis; and    a means for forcing back the fruid leaked from said bearing device into said bearing device, which is adjacent to an opening of said bearing device.    
     
     
         8 . A spindle motor as claimed in  claim 7 , wherein said means is a spiral groove forming either in an opening of said bearing device or on a surface of said hub opposite to said opening.  
     
     
         9 . A spindle motor as claimed in  claim 7 , wherein said means is a spiral groove forming in said opening of said bearing device, and a annular recess is formed on a surface of said hub opposite to said opening.  
     
     
         10 . A spindle motor as claimed in  claim 7 , wherein said means is a spiral groove forming on an inner surface of a seal ring provided at a side of said opening.  
     
     
         11 . An information storage apparatus at least to reproduce an information from a disk rotated by a spindle motor as claimed in  claim 7 , wherein a cover is provided to cover said disk.  
     
     
         12 . A spindle motor as claimed in  claim 1 , wherein a spiral groove is formed either in an opening of said bearing device or on a surface of said hub opposite to said opening.  
     
     
         13 . A spindle motor as claimed in  claim 1 , wherein a spiral groove is formed forming on an inner surface of a seal ring provided at a side of said opening.  
     
     
         14 . A spindle motor as claimed in  claim 1 , wherein 
 a member which form a part of a case on which the spindle motor is installed;    a rotary axis;    a bearing device which support said rotary axis to be able to rotate against said member;    a cup-shaped hub to install the disk, which having a motor to rotate the disk and said bearing device in the inside, and    a passage for the air circulation, which connects the inside of said hub with the outside.    said bearing device comprising a seal ring, a radial bearing, a permanent magnet, another radial bearing and a thrust bearing arranged along said rotating shaft from a side of an opening;    said radial bearings are dynamic pressure sliding bearings; magnetic fluid is used as a lubricant for bearings;    said disk is a plurality of magnetic disk stacked up on said hub in the direction of the axis of rotation;    a spiral groove is formed either in an opening of said bearing device or on a surface of said hub opposite to said opening;    a spiral groove is formed forming on an inner surface of a seal ring provided at a side of said opening;    said passage is provided with said hub as a penetration hole of the axial direction that connects the inside and the outside the hub;    a filter made of a fluorine resin or comprising fibers coated with a fluorocarbon resin is positioned in said penetration hole: and    whereby said spiral groove force back the fruid leaked from said bearing device into said bearing device.