Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1995-04-24
1997-08-12
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
310156, 310254, H02K 122, H02K 2112, H02K 112
Patent
active
056568800
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to the field of dynamo-electric machines; particularly brushless direct-current electric machines (BDCMs) and more particularly to those BDCMs constructed in the pancake, or discoidal style.
BACKGROUND
A BDCM type of electric motor (or generator) confers a number of advantages over prior-art slotted armature motors, such as deletion of the sliding contacts at a commutator, absence of cogging, lighter weight, and higher efficiency. Most BDCMs are constructed in a pattern involving apposed (ie side by side) cylindrical surfaces between which the interaction of magnetic forces operating in a radial direction provides a torque. There is however a need for an efficient economical motor having a flattened, discoidal shape.
OBJECT
It is an object of the present invention to provide an improved discoidal dynamo-electric machine, or one which will at least provide the public with a useful choice.
STATEMENT OF THE INVENTION
In one aspect the invention provides a discoidal dynamo-electric machine having a discoidal stator and a discoidal rotor mounted on a central shaft so that the rotor can be positioned close to and rotate in a plane parallel to that of the stator, wherein the rotor has a circular array of permanent magnets thereon providing a series of closely apposed and alternating permanent magnetic poles.
Preferably the rotor is made of iron or steel, or another ferromagnetic material.
Preferably the windings meander on a repetitive series of radial paths, the number of such paths being preferably equal to the number of poles.
Because the magnetic poles are closely spaced around the rotor it is preferred that there is an even number of between 8 and 64 poles, in its most preferred form of the invention there are about 28 poles.
In another aspect the invention provides a BDCM using ferrite magnets together with a relatively wide air gap between rotor and stator.
In a third aspect this invention provides a pancake or discoidal BDCM in which the windings are upon or within a substrate having a magnetic permeability of less than 20, relative to air.
In a related aspect a ferromagnetic material having a permeability of over 20 may be placed beneath the windings. Preferably this material is selected from a range including powdered ferrite, iron tape, iron wire, or iron sand.
Preferably the magnets are strontium-ferrite and each has a trapezoidal or sector shape.
In a related aspect a ferromagnetic material having a permeability of over 20 may be placed beneath the windings. Preferably this material is selected from the group comprising powdered ferrite, iron or steel tape, iron or steel wire, or iron sand.
DRAWINGS
These and other aspects of this invention, which should be considered in all its novel aspects, will become apparent from the following description, which is given by way of example only, with reference to the accompanying drawings, in which:
FIG. 1a: is an illustration of the face of a first rotor for a preferred dynamoelectric machine.
FIG. 1b: is an illustration of the face of a first stator for use with the rotor of FIG. 1a.
FIG. 2: is a sectional view on a radius through the rotor and stator of a motor of the present invention.
FIG. 3: is a sectional view along a tangent cutting the magnet array, showing flux lines and windings for the rotor and stator of a motor in accordance with FIG. 2.
FIG. 4: is a surface view of the stator of a 28-pole motor.
FIG. 5: is a surface view of the rotor of a 28-pole motor.
FIG. 6: is a surface view of part of a stator having magnetic-field sensors .
First Embodiment--FIGS. 1-3
This first embodiment of a dynamo-electric machine will be described with reference to a brushless DC Motor comprising two disks in a stack, one--a stator (120, 205, 303)--fixed to mountings (not illustrated) and the other--a rotor (100, 204, 305)--capable of rotation about its center on a shaft 201, which is preferably mounted on bearings 121, 202.
Generally there will be an array of windings 122, 301, 302 placed on one face
REFERENCES:
patent: 4167692 (1979-09-01), Sekiya et al.
patent: 4228384 (1980-10-01), Arnold, Jr. et al.
patent: 4629920 (1986-12-01), Hermann
patent: 4633149 (1986-12-01), Welterlin
patent: 4677335 (1987-06-01), Ueda et al.
patent: 4710667 (1987-12-01), Whitely
patent: 4820949 (1989-04-01), Mizobuchi et al.
patent: 5184040 (1993-02-01), Lim
patent: 5396140 (1995-03-01), Goldie et al.
Cadac Limited
Stephan Steven L.
Wallace, Jr. Michael
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