A DC motor is provided for use in a starter that starts an ermine. The DC motor includes a commutator and a brush. The commutator is formed of copper or a copper alloy whose copper percentage content is higher than or equal to 99 mass %. The brush is arranged in sliding contact with a surface of the commutator. Moreover, the brush is formed of a sintered compact that contains graphite, copper and at least one metal sulfide solid lubricant. The percentage content of copper in the sintered compact is 30-70 mass %. The at least one metal sulfide solid lubricant includes tungsten disulfide. The percentage content of tungsten disulfide in the sintered compact is higher than or equal to 6.5 mass %.

A DC motor is provided for use in a starter that starts an ermine. The DC motor includes a commutator and a brush. The commutator is formed of copper or a copper alloy whose copper percentage content is higher than or equal to 99 mass %. The brush is arranged in sliding contact with a surface of the commutator. Moreover, the brush is formed of a sintered compact that contains graphite, copper and at least one metal sulfide solid lubricant. The percentage content of copper in the sintered compact is 30-70 mass %. The at least one metal sulfide solid lubricant includes tungsten disulfide. The percentage content of tungsten disulfide in the sintered compact is higher than or equal to 6.5 mass %.

A starter includes a motor configured with a direct current motor. The direct current motor has a brush and a commutator. The brush is a sintered material formed of graphite and a copper powder. The commutator is formed of either copper or a copper alloy that has a copper content of 99% or more. A surface of is a sliding portion of the commutator which has sliding movement with the brush is provided with a graphite cover-layer that contains graphite as a main component. The graphite cover-layer contains a hard compound which has a Vickers hardness higher than 10 GPa and a metal sulfide solid lubricant.

A starter includes a motor configured with a direct current motor. The direct current motor has a brush and a commutator. The brush is a sintered material formed of graphite and a copper powder. The commutator is formed of either copper or a copper alloy that has a copper content of 99% or more. A surface of is a sliding portion of the commutator which has sliding movement with the brush is provided with a graphite cover-layer that contains graphite as a main component. The graphite cover-layer contains a hard compound which has a Vickers hardness higher than 10 GPa and a metal sulfide solid lubricant.

A bus bar engaged with each brush holder and electrically connected to positive brushes. A rotor has coils and protrusions extending in an outward direction and electrically connecting the coils to commutator segments. Each brush portion end surface faces the outward direction, the bus bar has an engagement portion with an end facing the inward direction, and the end of the engagement portion is further in the outward direction than the end surface portion. The brush has an end facing the first direction, the bus bar has an end facing a second direction, and the end of the bus bar is further in the second direction than the end of the brush facing the first direction. Each protrusion end faces the second direction, and the end of the bus bar facing the first direction is further in the second direction than the end of the protrusion facing the second direction.

A bus bar engaged with each brush holder and electrically connected to positive brushes. A rotor has coils and protrusions extending in an outward direction and electrically connecting the coils to commutator segments. Each brush portion end surface faces the outward direction, the bus bar has an engagement portion with an end facing the inward direction, and the end of the engagement portion is further in the outward direction than the end surface portion. The brush has an end facing the first direction, the bus bar has an end facing a second direction, and the end of the bus bar is further in the second direction than the end of the brush facing the first direction. Each protrusion end faces the second direction, and the end of the bus bar facing the first direction is further in the second direction than the end of the protrusion facing the second direction.

A DC motor is provided that can suppress a commutator from wearing. A DC motor including a commutator formed of copper or a copper alloy of 99% or more copper, and a brush pressed against and in contact with the commutator, wherein the brush is composed of a sintered compact including graphite and copper powder, hard compound particles higher in hardness than any of the copper or the copper alloy and the graphite or the copper powder are contained in at least one of the commutator and the brush and are scattered on or near a contact surface of the commutator with the brush at least during use.

A DC motor is provided that can suppress a commutator from wearing. A DC motor including a commutator formed of copper or a copper alloy of 99% or more copper, and a brush pressed against and in contact with the commutator, wherein the brush is composed of a sintered compact including graphite and copper powder, hard compound particles higher in hardness than any of the copper or the copper alloy and the graphite or the copper powder are contained in at least one of the commutator and the brush and are scattered on or near a contact surface of the commutator with the brush at least during use.

An angle grinder includes a housing, an output shaft, and a motor. The motor includes a stator assembly, a rotor assembly including a motor shaft configured to rotate about a first axis, a commutator, and a carbon brush. The commutator includes a bushing, configured to connect the commutator to the motor shaft, a plurality of commutator segments, sequentially distributed in a circumferential direction around the first axis and arranged around the bushing, and an insulating member, configured to bond the bushing and the plurality of commutator segments so as to constitute a whole.

An electrical contact device includes a high electric potential-side contact and a low electric potential-side contact having a lower electric potential than the high electric potential-side contact. The high electric potential-side contact and the low electric potential-side contact are configured to be brought into and out of contact with each other. At least one of the high electric potential-side contact and the low electric potential-side contact is formed of a low-boiling point material whose boiling point is lower than 2562 C. or a mixed material that contains the low-boiling point material.