Electric motor
Provided is an electric motor capable of stabilizing a preload applied to a bearing by an annular spring and effectively retarding degradation of the annular spring. The electric motor includes a motor shaft, a rotor, a stator, a housing containing the rotor and the stator in a posture where the motor shaft extends vertically, an upper bearing and a lower bearing supporting the motor shaft, and an annular spring applying a downward preload to the upper bearing. The lower bearing is fixed to the motor shaft and the housing. The housing has a load-receiving surface receiving an upward thrust load overcoming the preload from the upper bearing.
1. An electric motor comprising:
a motor shaft;
a rotor attached to the motor shaft so as to be rotated about the motor shaft;
a stator disposed around of the rotor;
a housing containing the rotor and the stator in a posture where the motor shaft vertically extends;
an upper bearing retained by the housing to rotatably support an upper portion of the motor shaft, the upper portion being on an upper side of the rotor;
a lower bearing retained by the housing to rotatably support a lower portion of the motor shaft, the lower portion being on a lower side of the rotor; and
an annular spring applying a downward preload to the upper bearing, wherein:
the lower bearing is fixed to the motor shaft and the housing to be restrained from axial displacement relative to the motor shaft and the housing;
the housing has a load-receiving surface receiving an upward thrust load from the upper bearing, the upward thrust load overcoming the preload;
the annular spring and the load-receiving surface are disposed on an upper side of the upper bearing;
the annular spring and the load-receiving surface are arranged side by side in a radial direction of the annular spring; and
the electric motor further comprises an insert member which is housed in the housing to be capable of sliding in a vertical direction, the insert member having a preload-transmitting portion and a thrust-load-transmitting portion, the preload-transmitting portion being a portion interposed between the upper bearing and the annular spring so as to transmit the downward preload from the annular spring to the upper bearing, the thrust-load-transmitting portion being a portion interposed between the upper bearing and the load-receiving surface so as to transmit the upward thrust load from the upper bearing to the load-receiving surface.
2. The electric motor as recited in claim 1 , wherein the housing includes a housing body having an upper end and a lower end, the upper end being formed to define an opening inside the upper end, and a cover member attached to the housing body so as to close the opening defined inside the upper end; and the cover member includes an upper cover having the load-receiving surface, a lower cover located under the upper cover, and a shim interposed between the upper cover and the lower cover.
3. The electric motor as recited in claim 1 , wherein the upper bearing includes an inner race and an outer race located radially outward of the inner race, and the annular spring is disposed so as to apply a downward spring force to the outer race of the upper bearing.
4. The electric motor as recited in claim 1 , wherein: the insert member includes a top wall portion covering an upper surface of an outer race of the upper bearing and a peripheral wall portion covering an outer peripheral surface of the outer race; and the annular spring is disposed between the housing and an upper surface of the insert member, the upper surface extending across the top wall and the peripheral wall.
5. The electric motor as recited in claim 1 , wherein the insert member has an inverted L-shaped cross-section.