Electric motor having magnet mounted to magnet mounting portion of shaft and method for manufacturing the same

An electric motor comprising:

• a stator which is housed in a motor case, and a rotor which comprises a shaft being rotatably supported by the motor case and a rotor body portion having a magnet disposed inside the stator, wherein
• the electric motor has a magnet cover comprising:
• a circular cylinder portion which covers an outer peripheral surface of the magnet;
• a turned-back portion which is arranged in one end portion of the circular cylinder portion and is in contact with one end surface of the rotor body portion;
• and a fastening end portion which is fastened to a flange portion arranged on the shaft so as to cover the other end surface of the rotor body portion;
• and
• an engagement latch portion engaged with the rotor is arranged on the turned-back portion, wherein
• the engagement latch portion extends inward in a radial direction from the turned-back portion,
• two engagement surfaces being flat surfaces are formed in parallel to each other and being flat on the outer peripheral surface of the rotor, and
• the engagement latch portion has top end surfaces extending along a width direction on the engagement surfaces and being parallel to each other to engage with the engagement surfaces,
• when a guide surface is arranged closer to one end surface side of the rotor body portion than the engagement surface, and when the engagement latch portion is moved toward the engagement surface, the guide surface guides the engagement latch portion,
• wherein a plurality of protrusions are arranged on a top end of the engagement latch portion, and the protrusions are engaged with the flat surface.

A method for manufacturing an electric motor, wherein the electric motor comprises:

• a stator which is housed in a motor case, and a rotor which comprises a shaft being rotatably supported by the motor case and a rotor body portion having a magnet disposed inside the stator;
• wherein
• the method for manufacturing the electric motor comprises:
• a working process in which a press working is performed on a magnet cover which has a circular cylinder portion, a turned-back portion that is integrally arranged in one end portion of the circular cylinder portion and protrudes inward in a radial direction, and an engagement latch portion that is integrally arranged on the turned-back portion;
• an assembly process in which the rotor which comprises the rotor body portion having the magnet and the shaft is assembled;
• and
• an insertion process in which the rotor is inserted into the magnet cover, and the engagement latch portion is engaged with the rotor to prevent rotation of the magnet cover with respect to the rotor, wherein
• an inner diameter of the circular cylinder portion is greater than an outer diameter of the magnet, the rotor has a rotor core in which an engagement hole extending in an axial direction is arranged and which is mounted between a magnet mounting portion of the shaft and the magnet, the engagement latch portion extends in the axial direction from the turned-back portion, and
• in the insertion process, the engagement latch portion is engaged with an inner surface in a circumferential direction of the engagement hole,
• wherein a press-fitted portion which is press-fitted into an inner peripheral surface of the engagement hole is arranged in a base end portion of the engagement latch portion;
• and a guide portion is arranged in a top end portion of the engagement latch portion, wherein the guide portion has a width in the circumferential direction smaller than that of the press-fitted portion, and guides the engagement latch portion when the engagement latch portion is inserted into the engagement hole.

A method for manufacturing an electric motor, wherein the electric motor comprises:

• a stator which is housed in a motor case, and a rotor which comprises a shaft being rotatably supported by the motor case and a rotor body portion having a magnet disposed inside the stator;
• wherein
• the method for manufacturing the electric motor comprises:
• a working process in which a press working is performed on a magnet cover which has a circular cylinder portion, a turned-back portion that is integrally arranged in one end portion of the circular cylinder portion and protrudes inward in a radial direction, and an engagement latch portion that is integrally arranged on the turned-back portion;
• an assembly process in which the rotor which comprises the rotor body portion having the magnet and the shaft is assembled;
• and
• an insertion process in which the rotor is inserted into the magnet cover, and the engagement latch portion is engaged with the rotor to prevent rotation of the magnet cover with respect to the rotor, wherein
• the engagement latch portion extends inward in the radial direction from the turned-back portion, an engagement surface is arranged on an outer peripheral surface of the rotor, and
• in the insertion process, the engagement latch portion is engaged with the engagement surface,
• when a guide surface is arranged closer to one end surface side of the rotor body portion than the engagement surface, and when the engagement latch portion is moved toward the engagement surface, the guide surface guides the engagement latch portion,
• wherein a plurality of protrusions are arranged on a top end of the engagement latch portion, and the protrusions are engaged with the flat surface.