Hydrodynamic bearing device and spindle motor using the same

Abstract

A hydrodynamic bearing device being low in torque, low in power consumption, high in reliability and best suited for miniaturization and a spindle motor using the same. The hydrodynamic bearing device in accordance with the present invention, dynamic pressure generation grooves being provided on at least one of a shaft or a sleeve, and a lubricant being present in a clearance where the above-mentioned shaft and the above-mentioned sleeve are opposed to each other, is characterized in that the above-mentioned lubricant contains diesters obtained from a divalent alcohol having 4 to 8 carbon atoms and having no alkyl side chain at the β position and one or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms.

1 . A hydrodynamic bearing device, dynamic pressure generation grooves being provided on at least one of a shaft or a sleeve, and a lubricant being present in a clearance where said shaft and said sleeve are opposed to each other, wherein said lubricant contains diesters obtained from a divalent alcohol having 4 to 8 carbon atoms and having no alkyl side chain at the β position and one or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms, and said clearance is a radial clearance of 1 to 5 μm.  
     
     
         2 . A hydrodynamic bearing device in accordance with  claim 1 , wherein said one or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms are two or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms.  
     
     
         3 . A hydrodynamic bearing device in accordance with  claim 2 , wherein at least one of said two or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms is a straight-chain type saturated monovalent fatty acid.  
     
     
         4 . A hydrodynamic bearing device in accordance with  claim 3 , wherein said two or more kinds of saturated monovalent fatty acids having 9 to 13 carbon atoms are saturated monovalent fatty acids having the same number of carbon atoms.  
     
     
         5 . A hydrodynamic bearing device in accordance with  claim 1 , wherein said divalent alcohol having 4 to 8 carbon atoms and having no alkyl side chain at the β position is 3-methyl-1,5-pentanediol, and said saturated monovalent fatty acid having 9 to 13 carbon atoms is a saturated monovalent fatty acid having 9 or 10 carbon atoms.  
     
     
         6 . A hydrodynamic bearing device in accordance with  claim 1 , wherein the number of inorganic foreign particles being included in said lubricant and larger than the minimum dimension of said clearance is 1000 or less per hydrodynamic bearing device.  
     
     
         7 . A spindle motor comprising said hydrodynamic bearing device in accordance with  claim 1 .  
     
     
         8 . A hydrodynamic bearing device, dynamic pressure generation grooves being provided on at least one of a shaft and a sleeve, and a lubricant being present in a clearance where said shaft and said sleeve are opposed to each other, wherein said lubricant contains esters obtained from a divalent alcohol having 4 to 8 carbon atoms and having no alkyl side chain at the β position, one or more kinds of saturated dibasic acids having 6 to 10 carbon atoms and one or more kinds of saturated monovalent fatty acids having 5 to 13 carbon atoms, and said clearance is a radial clearance of 1 to 5 μm.  
     
     
         9 . A hydrodynamic bearing device in accordance with  claim 8 , wherein said one or more kinds of saturated monovalent fatty acids having 5 to 13 carbon atoms are two or more kinds of saturated monovalent fatty acids having 5 to 13 carbon atoms.  
     
     
         10 . A hydrodynamic bearing device in accordance with  claim 9 , wherein at least one of said two or more kinds of saturated monovalent fatty acids having 5 to 13 carbon atoms is a straight-chain type saturated monovalent fatty acid.  
     
     
         11 . A hydrodynamic bearing device in accordance with  claim 10 , wherein said two or more kinds of saturated monovalent fatty acids having 5 to 13 carbon atoms are saturated monovalent fatty acids having the same number of carbon atoms.  
     
     
         12 . A hydrodynamic bearing device in accordance with  claim 8 , wherein said divalent alcohol having 4 to 8 carbon atoms and having no alkyl side chain at the β position is 3-methyl-1,5-pentanediol, and said saturated monovalent fatty acid having 5 to 13 carbon atoms is a saturated monovalent fatty acid having 7 to 10 carbon atoms.  
     
     
         13 . A hydrodynamic bearing device in accordance with  claim 8 , wherein the number of inorganic foreign particles being included in said lubricant and larger than the minimum dimension of said clearance is 1000 or less per hydrodynamic bearing device.  
     
     
         14 . A spindle motor comprising said hydrodynamic bearing device in accordance with  claim 8.