| 摘要 |
PROBLEM TO BE SOLVED: To prevent a commutator piece from being lifted at a high-speed rotation by setting the inclination angle of the pressure part of upper and lower tab tables that are provided on both side surfaces in a circumferential direction of the commutator piece that is buried into a mold to a specific range. SOLUTION: In a commutator, a commutator piece 2 made of copper alloy is subjected to mold forming by heat-resistance resin 3, two tab tables 4 and 5 are provided on both side surfaces in a circumferential direction in the armature piece 2, and the material for the commutator piece 2 has a tensile strength that is at least three times larger than that of the heat-resistance phenol resin 3. Then, an inclination angleθ1 of the pressure part of the upper tab table 4 is set to a range of 45 deg.±50 deg., an inclination angleθZ of the pressure part of the lower tab table 5 is set to a range of 30 deg.±5 deg., and at the same time the shape of the commutator piece 2 is optimized, thus making nearly equal compression force being applied to resin near the pressure part of the tab table and hence making nearly equal the life of resin and hence suppressing the lifting of the commutator piece at a high-speed rotation.
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