Abstract: In a commutator of a rotary electric machine, each of commutator segments has a low-resistive layer made of a low-resistive material and a high-resistive layer made of a high-resistive material having a specific resistance higher than that of the low-resistive material. The low-resistive material contains a carbonic material and a binder. The high-resistive material contains a carbonic material, a binder and an inorganic substance such as boron nitride. A mixing ratio of the inorganic material to the high-resistive material is more than 20 wt %. Alternatively, a brush, which makes contact with the commutator segments, can have the high-resistive layer and the low-resistive layer.

Abstract: A brush body 4 of a metal-graphite brush 2 is composed of a commutator side portion 6 which contains graphite, copper and a metal sulfide solid lubricant, and a lead side portion 8 which contains graphite and copper but does not contain any metal sulfide solid lubricant. A lead wire 10 is attached to the lead side portion 8 containing no metal sulfide solid lubricant.

Abstract: In a commutator of a rotary electric machine, each of commutator segments has a low-resistive layer made of a low-resistive material and a high-resistive layer made of a high-resistive material having a specific resistance higher than that of the low-resistive material. The low-resistive material contains a carbonic material and a binder. The high-resistive material contains a carbonic material, a binder and an inorganic substance such as boron nitride. A mixing ratio of the inorganic material to the high-resistive material is more than 20 wt %. Alternatively, a brush, which makes contact with the commutator segments, can have the high-resistive layer and the low-resistive layer.

Abstract: A brush body 4 of a metal-graphite brush 2 is composed of a commutator side portion 6 which contains graphite, copper and a metal sulfide solid lubricant, and a lead side portion 8 which contains graphite and copper but does not contain any metal sulfide solid lubricant. A lead wire 10 is attached to the lead side portion 8 containing no metal sulfide solid lubricant.

Abstract: A metal-graphite brush comprises a brush body which is made by mixing and molding metal powder and graphite powder. 2 mg to 30 mg as amounts of phosphate ion of at least one of phosphoric acid and a phosphate compound is added to 1 g of the brush body of the metal-graphite brush.

Abstract: Ag particles produced by chemical reduction and having a mean particle size of 5 &mgr;m are added by 0.05-3 wt % and Zn are added by 2-10 wt % to a Pb-less brush body containing graphite, Cu and a metal sulfide solid lubricant of a metal-graphite brush.

Abstract: A brush body 4 of a metal-graphite brush 2 is composed of a Pb-less commutator side portion 6 which contains graphite, copper and a metal sulfide solid lubricant, and a lead side portion 8 which contains graphite, copper, the metal sulfide solid lubricant and Pb.

Abstract: A metal-graphite brush has a copper-graphite brush body to which a metal sulfide solid lubricant is added and a lead embedded. Indium is at least added to an interface between the brush body and the lead in a concentration of 0.4-8 wt %.

Abstract: A sulfidation-resistant current-carrying member, such as a commutator, suitable for a direct-current motor in a fuel pump is provided. The current-carrying member for a direct-current motor in a fuel pump includes a commutator composed of a carbon layer having carbon as a principal component and forming a sliding surface at one end, and a metal carbon layer fixedly bound with the carbon layer at the other end and comprising 55 to 90 wt % of metal having brass as a principal component and a remaining portion having carbon as a principal component. By using brass as a primary metal component in the metal carbon layer, it is possible to achieve a commutator with superior resistance to sulfidation.

Abstract: Ag particles produced by chemical reduction and having a mean particle size of 5 &mgr;m are added by 0.05-3 wt % and Zn are added by 2-10 wt % to a Pb-less brush body containing graphite, Cu and a metal sulfide solid lubricant of a metal-graphite brush.

Abstract: A metal-graphite brush comprises a brush body which is made by mixing and molding metal powder and graphite powder. 2 mg to 30 mg as amounts of phosphate ion of at least one of phosphoric acid and a phosphate compound is added to 1 g of the brush body of the metal-graphite brush.

Abstract: 0.4 to 8 wt % of indium is added to a Pb-less metal-graphite brush containing graphite, copper and a metal sulfide solid lubricant.

Abstract: A brush body 4 of a metal-graphite brush 2 is composed of a Pb-less commutator side portion 6 which contains graphite, copper and a metal sulfide solid lubricant, and a lead side portion 8 which contains graphite, copper, the metal sulfide solid lubricant and Pb.

Abstract: A sulfidation-resistant current-carrying member, such as a commutator, suitable for a direct-current motor in a fuel pump is provided. The current-carrying member for a direct-current motor in a fuel pump includes a commutator composed of a carbon layer having carbon as a principal component and forming a sliding surface at one end, and a metal carbon layer fixedly bound with the carbon layer at the other end and comprising 55 to 90 wt % of metal having brass as a principal component and a remaining portion having carbon as a principal component. By using brass as a primary metal component in the metal carbon layer, it is possible to achieve a commutator with superior resistance to sulfidation.

Abstract: Disclosed is a carbon commutator, comprising a plurality of metal segments each having a through-hole, a plurality of carbon segments each having a projecting portion, which contains a metal, being inserted into the through-hole to be deformed so as to join the carbon segment to the metal segment, and a commutator body on which a plurality of the metal/carbon joined segments are arranged fixedly in a manner to form a substantially circular body.