Permanent magnet motor

• US 4,225,798 A
• Filed: 01/13/1978
• Issued: 09/30/1980
• Est. Priority Date: 01/13/1978
• Status: Expired due to Term

• Current Assignee: Edward L. Barrett
• Original Assignee: Edward L. Barrett
• Inventors: Barrett, Edward L.
• Primary Examiner(s): Skudy, R.
• Application Number:
  US05/869,317
• Time in Patent Office: 991 Days
• Field of Search: 310/68 R, 310/49, 310/68 C, 310/43, 310/83, 310/40 MM, 310/154, 310/51, 310/42, 310/172, 310/168, 310/46, 310/242, 310/71, 310/249, 310/111, 310/89, 310/155, 310/254, 310/216 , 310/258, 310/259, 310/218, 310/66, 49/340, 49/341, 49/349, 74/425, 74/424.5, 74/458
• US Class Current: 310/154.36
• CPC Class Codes: H02K 23/04 having permanent magnet excitation
• CPC Class Codes: H02K 5/148 Slidably supported brushes
• CPC Class Codes: H02K 7/081 specially adapted for worm gear drives H02K7/09 takes precedence
• CPC Class Codes: H02K 7/1166 comprising worm and worm-wheel structural association with bearings specially adapted for worm gear drives H02K7/081

Abstract

A dynamo-electric machine comprises an armature and a permanent magnet field structure including at least two permanent magnets and at least two field shoes. Each field shoe has an arcuate surface which forms one side of an air gap between the shoe and the armature, and is configured to direct magnetic flux from the permanent magnets to the arcuate surface in such a manner that the magnetic lines of force emanating from the arcuate surface and extending through the armature are of substantially uniform distribution and intensity, thereby providing a uniform magnetic field through the armature. This is accomplished by making the shoe of variable thickness to have a cross-sectional area varying substantially in proportion to the density of magnetic flux carried by the shoe at points therealong, so that the density of magnetic flux is substantially constant throughout the shoe and the shoe provides a substantially uniform distribution of magnetic flux across the arcuate surface and through the armature. To further enhance a uniform distribution of magnetic flux through the armature, the arcuate surface of the shoe is nonconcentric with the periphery of the armature to provide a nonuniform air gap having a reluctance which decreases with increasing distance from the magnets, thereby to encourage a flow of magnetic flux to areas of the arcuate surface remote from the magnets. The resulting construction provides a very thin D.C. motor especially adapted for mounting in the relatively narrow confines of a vehicle door to provide a powerful drive for electric window regulators for automotive vehicles.

Claims

1. A dynamo-electric machine comprising an armature and a permanent magnet field structure including two permanent magnets and two field shoes each having two portions which mate with associated ones of said magnets and an arcuate surface between said portions which forms one side of an air gap between the field shoe and the armature, the improvement residing in the field shoes being configured to direct magnetic flux from the permanent magnets associated therewith to said arcuate surfaces in such a manner that the magnetic lines of force emanating from the arcuate surfaces and extending through the armature are uniformly distributed over the armature with substantially uniform intensity, said arcuate surface of each said field shoe extending from the portions of said field shoe which mate with said magnets to a plane situated approximately midway between said magnets, each field shoe progressively increasing in thickness to both sides of said plane from the area adjacent said plane to adjacent said portions of the field shoe which mate with said magnets, and then progressively decreasing in thickness from those portions to ends of the field shoe, the thickness of the field shoe between said area adjacent said plane and the ends of the field shoe, and therefore the cross-sectional area thereof, varying substantially in proportion to the density of magnetic flux carried by the field shoe at points therealong, so that the density of magnetic flux is substantially constant throughout the field shoe and the field shoe provides a substantially uniform intensity distribution of magnetic flux across said armature surface, said arcuate dimension of each said field shoe being nonconcentric with the periphery of said armature and defining between said arcuate surface and said armature periphery an air gap which progressively increases in width to both sides of said plane from a minimum dimension in the area adjacent said plane to a greater dimension in the areas adjacent said portions of the field shoe which mate with said magnets, said width of said air gap from said plane to said mating portions increasing substantially in accordance with the length of the field shoe therealong, whereby the reluctance of said air gap from said areas adjacent said mating portions to said area adjacent said plane progressively decreases to encourage a flow of flux through said field shoe from said areas adjacent said mating portions to said area adjacent said plane, the varying width of said air gap assisting in the establishment of a uniform flux distribution through the armature, each portion of said arcuate surface of each said field shoe to each side of said plane being the mirror image of the other, each shoe having at its two ends a flat surface extending parallel to a diameter of the armature, intersecting the arcuate surface, being substantially parallel to the corresponding surfaces of the other shoe and comprising said portions of mating with said magnets, said magnets being rectangular and abutting flush against respective flat surfaces of said shoes, the dimensions of said magnets abutting against said surfaces and along a diameter of the armature being greater than the dimensions of said magnets perpendicular to said surfaces, said magnets being elongate in the directions parallel to said surfaces of said shoes, and said magnets and shoes defining a field structure that is relatively elongate in the direction parallel to the surfaces of said shoes and to a diameter of the armature and of minimum width in the direction transverse to the surfaces of said shoes, and including a commutator at one axial end of said armature, a brush assembly mounted at the corresponding end of said field structure, said brush assembly comprising two brushes and two brush holders mounted along the long dimension of said structure parallel to said surfaces of said shoes and to a diameter of the armature with each brush and brush holder situated adjacent and parallel to a respective one of said magnets, the dimension of each said magnet in the long dimension of said structure accommodating a relatively long brush and a relatively long brush holder, two electrical terminals, and a bi-metallic overload protector connected in series circuit between one of said brushes and one of said electrical terminals.

2. A dynamo-electric machine comprising an armature and a permanent magnet field structure including at least two permanent magnets and at least two field shoes each having two portions associated with said magnets and an arcuate surface between said portions which forms one side of an air gap between the field shoe and the armature, the improvement residing in the field shoes being configured to direct magnetic flux from the permanent magnets associated therewith to said arcuate surfaces in such a manner that the magnetic lines of force emanating from the arcuate surfaces and extending through the armature are uniformly distributed over the armature with substantially uniform intensity, said arcuate surface of each said field shoe extending from the portions of said field shoe associated with said magnets to a plane situated approximately midway between said magnets, each field shoe progressively increasing in thickness to both sides of said plane from the area adjacent said plane to adjacent said portions of the field shoe associated with said magnets, and then progressively decreasing in thickness from those portions to ends of the field shoe, the thickness of the field shoe between said area adjacent said plane and the ends of the field shoe, and therefore the cross-sectional area thereof, varying substantially in proportion to the density of magnetic flux carried by the field shoe at points therealong, so that the density of magnetic flux is substantially constant throughout the field shoe and the field shoe provides a substantially uniform intensity distribution of magnetic flux across said armature surface, wherein said arcuate dimension of each said field shoe is nonconcentric with the periphery of said armature and defines between said arcuate surface and said armature periphery an air gap which progressively increases in width to both sides of said plane from a minimum dimension in the area adjacent said plane to a greater dimension in the areas adjacent said portions of the field shoe associated with said magnets, said with of said air gap from said plane to said portions associated with said magnets increasing substantially in accordance with the length of the field shoes therealong, whereby the reluctance of said air gap from said areas adjacent said portions to said area adjacent said plane progressively decreases to encourage a flow of flux through said field shoe from said areas adjacent said portions to said area adjacent said plane, the varying width of said air gap assisting in the establishment of a uniform flux distribution through the armature, wherein each portion of said arcuate surface of each said field shoe to each side of said plane is the mirror image of the other, each shoe having at its two ends a flat surface extending parallel to a diameter of the armature and comprising said portions associated with said magnets, said magnets being rectangular and abutting flush against respective flat surfaces of said shoes, the dimensions of said magnets abutting against said surfaces and along a diameter of the armature being greater than the dimensions of said magnets perpendicular to said surfaces, and including seal means between said surfaces and said magnets for sealing and bonding said magnets with and to said field shoes to form a sealed substantially cylindrical cavity for said armature, including two magnets spaced equally from one another and two field shoes extending between said magnets, the flat surfaces of each shoe intersecting the arcuate surface thereof and being substantially coplanar and parallel to the corresponding surfaces of the other shoe, wherein said magnets are elongate in the directions parallel to said surfaces of said shoes, and said magnets and shoes define a field structure that is relatively elongate in the direction parallel to the surface of said shoes and to a diameter of the armature and of minimum width in the direction transverse to the surfaces of said shoes, and including a commutator at one axial end of said armature and a brush assembly mounted at the corresponding end of said field structure, said brush assembly comprising two brushes and two brush holders mounted along the long dimension of said structure parallel to said surfaces of said shoes and to a diameter of the armature with each brush and brush holder situated adjacent and parallel to a respective one of said magnets, the dimension of each said magnet in the long dimesion of said structure accommodating a relatively long brush and a relatively long brush holder.