Dust core

Abstract

A dust core is produced by pressure-molding at least a ferromagnetic powder and an insulating material. The dust core has high magnetic permeability representing the direct current superimposition characteristics, has reduced core loss and has increased mechanical strength. The insulating material comprises a methyl-phenyl silicone resin, wherein the amount of a trifunctional methyl-phenyl silicone resin contained in the methyl-phenyl silicone resin is in a range from 20 to 70 mol % of all silicone resins.

What is claimed is:  
     
         1 . A dust core comprising: 
 ferromagnetic powder; and    an insulating binder, in which said powder is dispersed; wherein the insulating binder is a silicone resin comprising phenyl groups.    
     
     
         2 . A dust core according to  claim 1 , wherein the silicone resin is an alkyl-phenyl silicone resin.  
     
     
         3 . A dust core according to  claim 2 , wherein the alkyl-phenyl silicone resin is a methyl-phenyl silicone resin.  
     
     
         4 . A dust core according to  claim 3 , wherein the methyl-phenyl silicone resin has a phenyl content in the range from 15 mol % to 60 mol %, based on the total moles of methyl-phenyl silicone resin.  
     
     
         5 . A dust core according to  claim 1 , wherein the amount of the silicone resin is in a range from 0.3 to 5% by weight, based on the weight of ferromagnetic powder.  
     
     
         6 . A dust core according to  claim 5 , wherein the silicone resin is an alkyl-phenyl silicone resin.  
     
     
         7 . A dust core according to  claim 6 , wherein the alkyl-phenyl resin is a methyl-phenyl resin.  
     
     
         8 . A dust core according to  claim 7 , wherein the methyl-phenyl silicone resin has a phenyl content in the range from 15 mol % to 60 mol %, based on the total moles of methyl-phenyl silicone resin.  
     
     
         9 . A dust core comprising: 
 ferromagnetic powder; and    an alkyl-phenyl silicone insulating binder, in which said powder is dispersed; wherein the alkyl-phenyl silicone resin comprises from 20 mol % to 70 mol % of a trifunctional methyl-phenyl silicone resin, based on the total moles of alkyl-phenyl silicone resin.    
     
     
         10 . A dust core comprising ferromagnetic powder and an insulating material, the insulating material comprising a silicone resin, wherein the silicone resin includes a phenyl group, and wherein the amount of silicon resin contained in the dust core is in a range of from 0.5 to 3.0 wt % based on the ferromagnetic powder.  
     
     
         11 . A dust core according to  claim 10 , wherein the silicone resin is an alkyl-phenyl silicone resin.  
     
     
         12 . A dust core according to  claim 11 , wherein the alkyl-phenyl resin is a methyl-phenyl resin.  
     
     
         13 . A dust core according to  claim 12 , wherein the methyl-phenyl silicone resin has a phenyl content in the range from 15 mol % to 60 mol %, based on the total moles of methyl-phenyl silicone resin.  
     
     
         14 . A method of producing a dust core comprising pressure molding ferromagnetic powder and an insulating material, the insulating material comprising a silicone resin, wherein the silicone resin includes a phenyl group.