Automotive alternator and automotive alternator brush abrasion detection system

Abstract

A brush holding apparatus is mounted to an inner wall surface of a rear bracket and a cap mounted to a head portion of a brush holder portion is exposed through an opening in the rear bracket. Brushes are housed inside brush insertion apertures of the brush holder portion and are placed in elastic contact with slip rings by springs. An abrasion detection terminal is insert molded into the brush holder portion, a contact thereof projecting inside one of the brush insertion apertures and coming into contact with the corresponding spring when the brushes are abraded by a predetermined amount.

What is claimed is:  
     
         1 . An automotive alternator comprising: 
 a case;    a shaft rotatably supported in said case;    a rotor fixed to said shaft and disposed inside said case for generating a rotating magnetic field, said rotor being provided with: 
 a rotor coil in which a magnetic flux is generated on passage of an electric current; and  
 a plurality of magnetic poles magnetized by said magnetic flux generated in said rotor coil;  
   a stator mounted to said case so as to cover an outer circumferential side of said rotor, said stator being provided with a stator winding in which an electromotive force is generated by said rotating magnetic field generated by said rotor;    a pair of electric current supplying members disposed so as to be separated in an axial direction on a first end portion of said shaft and be able to rotate together with said shaft, said pair of electric current supplying members being electrically connected in series by means of said rotor coil; and    a brush holding apparatus disposed inside said case so as to be positioned radially outside said pair of electric current supplying members, wherein: 
 said brush holding apparatus is provided with: 
 a brush holder portion in which a pair of brush insertion apertures is formed such that an aperture direction of each of said brush insertion apertures is perpendicular to a center axis of said shaft, said pair of brush insertion apertures being separated in an axial direction of said shaft;  
 a cap removably mounted to a head portion of said brush holder portion for covering said pair of brush insertion apertures;  
 a pair of brushes each housed inside said pair of brush insertion apertures so as to be able to move freely in said aperture direction;  
 a pair of brush terminals constituting input and output terminals of said brushes;  
 a pair of lead wires each having a first end linked to a first end portion of said brushes and a second end linked to said brush terminals;  
 electrically-conductive elastic members disposed inside each of said brush insertion apertures for placing a second end of each of said brushes in elastic contact with said electric current supplying members by forcing said brushes toward said shaft; and  
 an abrasion detection terminal disposed in at least one of said pair of brush insertion apertures, said abrasion detection terminal having a contact for contacting at least one of said elastic members when said brushes are abraded by a predetermined amount; and  
 
   an opening is disposed in said case radially outside said brush holder portion so as to expose said cap.    
     
     
         2 . The automotive alternator according to  claim 1 , wherein: 
 each of said elastic members is constituted by a coil spring.    
     
     
         3 . The automotive alternator according to  claim 2 , wherein: 
 said coil spring is disposed in a compressed state between said brush and said brush terminal.    
     
     
         4 . The automotive alternator according to  claim 3 , wherein: 
 said brush is formed into a substantially rectangular parallelepiped in which a cross section perpendicular to a longitudinal direction is a rectangular shape,    said coil spring is formed into a cylindrical shape,    said brush and said coil spring are disposed such that a center of said rectangular shape of said brush and a center of said cylindrical shape of said coil spring are substantially aligned, and    a relationship between a length of a short side (E) and a length of a long side (F) of said rectangular shape and an outside diameter (D) of said coil spring satisfies an expression E<D<F.    
     
     
         5 . The automotive alternator according to  claim 4 , wherein: 
 said brush insertion aperture is formed with an aperture shape having an internal shape substantially matching a composite external shape formed by superposing said cylindrical shape of said coil spring onto said rectangular shape of said brush in a longitudinal direction of said brush.    
     
     
         6 . The automotive alternator according to  claim 1 , wherein: 
 said lead wire is linked to a central portion of a first end surface of said brush, and a flexible tube is mounted to said lead wire.    
     
     
         7 . An automotive alternator comprising: 
 a case;    a shaft rotatably supported in said case;    a rotor fixed to said shaft and disposed inside said case for generating a rotating magnetic field, said rotor comprising: 
 a rotor coil in which a magnetic flux is generated on passage of an electric current; and  
 a plurality of magnetic poles magnetized by said magnetic flux generated in said rotor coil;  
   a stator mounted to said case so as to cover an outer circumferential side of said rotor, said stator being provided with a stator winding in which an electromotive force is generated by said rotating magnetic field generated by said rotor;    a pair of electric current supplying members disposed so as to be separated in an axial direction on a first end portion of said shaft projecting out of said case and be able to rotate together with said shaft, said pair of electric current supplying members being electrically connected in series by means of said rotor coil; and    a brush holding apparatus removably disposed on an outer end surface of said case so as to be positioned radially outside said pair of electric current supplying members, wherein: 
 said brush holding apparatus is provided with: 
 a brush holder portion in which a pair of brush insertion apertures is formed such that an aperture direction of each of said brush insertion apertures is perpendicular to a center axis of said shaft, said pair of brush insertion apertures being separated in an axial direction of said shaft;  
 a cap removably mounted to a head portion of said brush holder portion for covering said pair of brush insertion apertures;  
 a pair of brushes each housed inside said pair of brush insertion apertures so as to be able to move freely in said aperture direction;  
 a pair of brush terminals constituting input and output terminals of said brushes;  
 a pair of lead wires each having a first end linked to a first end portion of said brushes and a second end linked to said brush terminals;  
 electrically-conductive elastic members disposed inside each of said brush insertion apertures for placing a second end of each of said brushes in elastic contact with said electric current supplying members by forcing said brushes toward said shaft; and  
 an abrasion detection terminal disposed in at least one of said pair of brush insertion apertures, said abrasion detection terminal being provided with a contact for contacting at least one of said elastic members when said brushes are abraded by a predetermined amount; and  
 
   a cover is removably mounted to an outer wall surface of said case from an axial direction of said shaft so as to envelop said brush holding apparatus.    
     
     
         8 . The automotive alternator according to  claim 7 , wherein: 
 each of said elastic members is constituted by a coil spring.    
     
     
         9 . The automotive alternator according to  claim 8 , wherein: 
 said coil spring is disposed in a compressed state between said brush and said brush terminal.    
     
     
         10 . The automotive alternator according to  claim 9 , wherein: 
 said brush is formed into a substantially rectangular parallelepiped in which a cross section perpendicular to a longitudinal direction is a rectangular shape,    said coil spring is formed into a cylindrical shape,    said brush and said coil spring are disposed such that a center of said rectangular shape of said brush and a center of said cylindrical shape of said coil spring are substantially aligned, and    a relationship between a length of a short side (E) and a length of a long side (F) of said rectangular shape and an outside diameter (D) of said coil spring satisfies an expression E<D<F.    
     
     
         11 . The automotive alternator according to  claim 10 , wherein: 
 said brush insertion aperture is formed with an aperture shape having an internal shape substantially matching a composite external shape formed by superposing said cylindrical shape of said coil spring onto said rectangular shape of said brush in a longitudinal direction of said brush.    
     
     
         12 . The automotive alternator according to  claim 8 , wherein: 
 said lead wire is linked to a central portion of a first end surface of said brush, and a flexible tube is mounted to said lead wire.