WO1997023027B1

WO1997023027B1 - Method of fabricating a rotor for a motor and the rotor produced thereby

Info

Publication number: WO1997023027B1
Application number: PCT/US1996/019490
Authority: WO
Filing date: 1996-12-10
Publication date: 1997-08-21

Abstract

A method for manufacturing a rotor structure (10) for a motor using a square shaft member (12) and four magnet members (18A-D) and the structure produced thereby. The method comprises the steps of: (a) mounting to each of the lateral surface of the shaft the back surface of one of the four magnets thereby to form a single circumferential layer of magnets about the shaft, the four magnets being mounted such that: (i) a portion of the back surface of each of the four magnets extends past an edge of the shaft for at least a predetermined distance thereby to define about the circumference of the shaft a total of four overhanging areas; and (ii) one side surface of each of the four magnets abuts against an overhanging area; and (b) thereafter forming the single circumferential layer of the four magnets into a continuous circular contour centered on the axis of the shaft.

Claims

AMENDED CLAIMS

[received by the International Bureau on 16 July 1997 (16 07.97). new claims 5-7 added; remaining claims unchanged ( 1 page)]

5. A rotor structure for a motor, said rotor structure formed by a method using

a shaft member having an axis of elongation extending therethrough and having four planar lateral surfaces thereon, the shaft having a square configuration with four edges when viewed in a cross sectional plane perpendicular to the axis, and

four magnet members each of which has a planar back surface, two planar side surfaces and a front surface,

the method comprising the steps of

(a) mounting to each lateral surface of the shaft the back surface of one of the four magnets thereby to form a single circumferential layer of magnets about the shaft, the four magnets being mounted such that:

(i) a portion of the back surface of each of the four magnets extends past an edge of the shaft for at least a predetermined distance thereby to define about the circumference of the shaft a total of four overhanging areas; and

(ii) one side surface of each of the four magnets abuts against an overhanging area; and

(b) thereafter forming the single circumferential layer of the four magnets into a continuous circular contour centered on the axis of the shaft.

6. The rotor structure of claim 5 wherein the back surfaces of each of the four magnets are of equal length.

7 The rotor structure of claim 5 wherein each planar side surface is orthogonal to the planar back surface. STATEMENT UNDER ARTICLE 19OΪ

The International Search Report, mailed 22 May 1997, lists two "Y" references, US-A- 4,748,359 to Yahara et al. ("Yahara patent"), and USSR Patent 1,636,930 ("USSR patent"). Original claims 1- 4 and new claims 5, 6 and 7 include an inventive step over these references.

Neither patent suggests the unique method of mounting planar magnet

members to a shaft and thereafter forming the magnets into a continuous circular contour centered on the axis of the shaft. Yet these elements are explicitly required by the claims. Neither cited patent suggests, for example, the post-mounting forming step of element (b) of claim 1.

In addition, product-by-process claims 5 through 7 require structural elements, separate and apart from the method steps, that are not found in the cited patents. For example, claims 5 through 7 require a square shaft and a continuous circular contour formed about a front surface of the magnet members, wherein the magnet members each overhang the shaft and abut each other in the overhanging area. These are

explicit structural requirements, neither taught nor suggested by the cited patents.

The Yahara patent discloses fully machined magnets having only two planar surfaces. The side abutting the rotor is not planar, but incorporates two curved areas that must fit about the roughly octagonal rotor [see Fig. 1]. The magnets do not overhang the shaft, as required by the instant claims. Accordingly, the magnets of the Yahara patent will suffer from the very fit problems the present invention is designed to prevent, namely: each of the magnets to be mounted to the shaft is machined and shaped on both its inner and outer surface prior to its attachment to the shaft. This manufacturing technique places a premium upon accurate dimensioning of the parts during the machining process. Any errors made during the machining of the magnets may result in difficulty in mounting the magnets to the shaft or in the creation of gaps between the magnets and the shaft, between adjacent magnets, or between the magnets and the sleeve. [Specification, at page 1, lines 12-19]

The magnets of the USSR patent also suffer from these limitations. First, they are formed as a double layer, not a single layer of magnets as explicitly claimed in the present application. Moreover, these magnets must also be formed to tight tolerances, because they are layered within other rows of magnets. The outer layer of magnets do

not abut, as required by claims 5 through 7. In addition, the outer layer of magnets

have gaps, as prohibited by claims 5 through 7, which require a continuous circular contour. The structural combination of a single layer of overhanging and abutting magnets, each having three planar surfaces, and fourth sides jointly forming a continuous circular contour, is not disclosed or suggested by the Yahara et al. patent or the USSR patent Accordingly, claims 1 through 4 and new claims 5, 6 and 7 reflect an inventive step over these patents.