For promoting the high efficiency of motors, there is known a permanent magnet (PM) motor that adopts a rare metal (rare earth) such as a neodymium magnet as a magnetic body. Use of the rare metal raises various problems including prices due to scarcity.
In this respect, there are known various motors that can obtain sufficient characteristics by effectively using a ferrite magnet not using the rare metal.
The motor prevailing at present is configured of a radial-air-gap motor with an air gap in the same direction with an output shaft, but in this configuration, the ferrite magnet is required to be arranged along a rotational direction of the output shaft, and it is necessary to increase a volume of the ferrite magnet for obtaining the same performance with the neodymium magnet. As a result, the motor becomes large in size.
As to a motor that secures performance and prevents the motor from growing in size, there is known an axial-air-gap motor as disclosed in Patent Literature 1, for example. The axial-air-gap motor is configured such that a magnet is arranged largely in a radial direction vertical to an output shaft direction. Therefore, the length of the motor in the output shaft direction is made short, that is, a so-called flattened motor is made possible, thus preventing the motor from growing in size.
Here, a stator of the axial-air-gap motor disclosed in Patent Literature 1 is configured as follows. First, an insulator (bobbin) is provided on the periphery of a teeth iron core having a shape of an approximately trapezoidal cylinder to be integral therewith by resin molding, and a coil is wound around the insulator to obtain a plurality of pole members. Thereafter, the plurality of pole members are arranged without a gap in an annual shape (in a donut shape) pointing the cylindrical teeth toward the rotational shaft direction, and finally, all the pole members arranged in the annual shape are molded as a whole by insert molding of resin to form the annually integrated stator.
Patent Literature 2 discloses a stator in an axial-air-gap motor having the approximately same configuration with Patent Literature 1. This stator can be produced by, for lining up a plurality of pole members in an annual shape, providing a hook portion for connection to an insulator of the adjacent pole member in one corner of an end part in an insulator in an inner diameter side, providing a hook groove portion for engaging to a hook portion provided in an opposite adjacent pole member in the other corner part, connecting the insulators in close contact with each other without a gap, and thereafter, resin-molding the entire pole members.
USPTO Backgrounds
USPTO Backgrounds