Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1989-06-06
1991-08-27
Beha, Jr., William H.
Electrical generator or motor structure
Dynamoelectric
Rotary
310217, H02K 504
Patent
active
050436163
DESCRIPTION:
BRIEF SUMMARY
1. Technical Field
The present invention relates to a construction of a motor having mounting legs, and more particularly, to a construction of an induction type motor in which, an induction motor, a connection of core laminates of a stator core, as well as a connection of motor-mounting legs to a motor housing, are assembled by joining those elements together without welding, to thereby prevent generation of magnetic noise during the rotation of the motor.
2. Background Art
Induction motors, especially variable speed induction motors driven via a transistor inverter, are used as rotary drive source for machine tools and other industrial machines, and in the known method of fabricating and assembling the induction motors, welding is often used for interconnecting core laminates of a stator core after stacking. Alternatively, in some conventional small output induction motors, the stacked core laminates are connected by a mechanical staking method. Nevertheless, the staking method for connecting core laminates is not applicable to intermediate output type motors because, in the intermediate or larger output type motors, the size of the stator core is larger, and therefore, the staking of the core laminates by using a press machine is difficult from the view point of the capability of the press machine. As a result, in induction motors of more than an intermediate output, a tungsten-inert gas welding or a metal-inert gas welding method is employed for connecting the core laminates.
Moreover, many induction type motors are used which have a construction such that mounting legs for fixing the induction motor to a driven unit such as a machine tool are separately manufactured and attached to the outer periphery of the body of the motor. In this case, the mounting legs are often connected to front and rear housings or around the stator core of a non-shell type induction motor by welding. When the welding connection is incorporated in the construction of a motor, however, the welded portions are subjected to intense heat, and a weld bead is applied to the to-be-welded portions under a high temperature. As a result, shrinkage of the welded portions and the weld bead occurs during cooling of the welded portions, and consequently, often the bore of a stator core in which a rotor element of the motor is inserted and arranged via a small gap is deformed, causing a deterioration in the roundness and axial straightness of the bore. Accordingly, the gap between the outer periphery of the rotor element and the inner face of the bore of the stator core is not even, and this uneven gap between the rotor periphery and the stator bore causes an uneven distribution of the density of magnetic flux when an electric excitation current is supplied to the stator element, which results in a generation of magnetic noise when the motor is rotated. Particularly, in the case of variable speed induction type motors driven via a transistor inverter, the frequency of the magnetic noise is as high as more than 1 kHz during high speed rotation of the motor, resulting in a generation of sharp metallic sounds, and therefore, a problem of noise pollution arises. Accordingly, to prevent the generation of magnetic noise in such motors, an improvement in the fabrication and assembly of the motors, particularly an improvement in the design of the construction of stators, is required so that a deformation of the stator cores does not occur during the fabricating and assembly of the stator cores.
DISCLOSURE OF THE INVENTION
Therefore, an object of the present invention is to provide a construction of an electric motor which is able to satisfy the above-mentioned requirement.
Another object of the present invention is to provide an electric motor having mounting legs that are not welded to the motor.
A further object of the present invention is to provide a construction of an electric induction motor assembled by employing only a connection by threaded screws and tie-bolts.
To realize the above objects of the present invention, there is provided an
REFERENCES:
patent: 2023259 (1935-12-01), Anderson
patent: 4216399 (1980-08-01), Bartheld
patent: 4636673 (1987-01-01), McDonald
Katsuzawa Yukio
Masuya Michi
Beha Jr. William H.
Fanuc Ltd.
Rebsch D.
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