Source: http://www.google.com/patents/US5760520?dq=7,013,345/
Timestamp: 2013-12-20 06:55:41
Document Index: 444912174

Matched Legal Cases: ['arts 3', 'art 3', 'art 3', 'arts 3', 'art 3', 'art 3', 'art 3', 'art 3', 'art 3']

Patent US5760520 - Motor - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA motor has a stator and a rotor that is formed of two rotor parts fitted on a rotor shaft in a fashion preventing the rotor from rotating relative to the rotor shaft. The rotor parts carry permanent magnets arranged with a fixed pitch angle over their outer peripheral faces. The rotor shaft has a single...http://www.google.com/patents/US5760520?utm_source=gb-gplus-sharePatent US5760520 - MotorAdvanced Patent SearchPublication numberUS5760520 APublication typeGrantApplication numberUS 08/778,711Publication dateJun 2, 1998Filing dateDec 27, 1996Priority dateDec 27, 1995Fee statusPaidPublication number08778711, 778711, US 5760520 A, US 5760520A, US-A-5760520, US5760520 A, US5760520AInventorsMasahiro Hasebe, Yasuo YamaguchiOriginal AssigneeAisin Aw Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (11), Referenced by (47), Classifications (9), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetMotorUS 5760520 AAbstract A motor has a stator and a rotor that is formed of two rotor parts fitted on a rotor shaft in a fashion preventing the rotor from rotating relative to the rotor shaft. The rotor parts carry permanent magnets arranged with a fixed pitch angle over their outer peripheral faces. The rotor shaft has a single key for engaging with both an engagement groove of the first rotor and an engagement groove of the second rotor. The engagement groove of each steel plate forming the rotor parts is formed in a position shifted 1/2 of the skew angle from the pole center of a given one of the permanent magnets. The steel plates of the first rotor part and the steel plates of the second rotor part face in opposite directions when fitted to the key of the rotor shaft, thereby providing the predetermined skew angle between the two rotor parts.
What is claimed is: 1. A motor comprising:a rotor shaft; a rotor axially divided into a plurality of rotor parts including at least first and second rotor parts, each of which is fitted on the rotor shaft in a manner that prevents rotation relative to the rotor shaft, and each of said rotor parts having circumferentially spaced magnet fittings, said magnet fittings holding a plurality of permanent magnets in respective circumferentially positions spaced to define a pitch angle therebetween; and a stator disposed radially outward from the rotor, said rotor shaft comprising engaging means extending axially of the rotor shaft for fitting into both a first engagement fitting of said first rotor part and a second engagement fitting of said second rotor part such that the first engagement fitting of said first rotor part aligns with the second engagement fitting of said second rotor part, said engagement fittings being radially aligned with said engaging means along a first radial line, each of said first rotor part and said second rotor part comprising a laminate of a plurality of steel plates, each of the steel plates having a plate fitting, the plate fittings of the steel plates of said first and second rotor parts forming said first and second engagement fittings, respectively, the steel plates of said second rotor part being reversed on said rotor shaft relative to the steel plates of said first rotor part so that a center of a given one of said magnet fittings of said first rotor part, defined by position relative to said first engagement fitting, defines a second radial line at a predetermined angle +θ with said first radial line and a center of said given one of said magnet fittings of said second rotor part, in the same position relative to said second engagement fitting, defines a third radial line at a a predetermined angle -θ with said first radial line, θ being greater than 0 and less than P/2 where P is said pitch angle. 2. A motor according to the claim 1, wherein said predetermined angle θ is determined as follows:if 0&lt;θ≦P/4, &#952;={(n/2)+(1/4)} if P/4&lt;θ&lt;P/2, &#952;=(P/2)-{(n/2)+(1/4)} where S is a slot pitch angle of the stator, and n is an integer. 3. A motor according to claim 1, wherein said predetermined angle θ is determined as follows:if 0&lt;θ≦P/4, &#952;={n+(n+(1/2)} if P/4&lt;θ&lt;P/2, &#952;=(P/2)-{n+(1/2)} where S is a slot pitch angle of the stator, and n is an integer. Description
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the present invention are described in detail hereinafter with reference to the accompanying drawings. The overall construction of a motor in accordance with a first embodiment, FIGS. 1 and 2, comprises a rotor shaft 2 rotatably supported at its opposite ends on a case 10 by bearings 11, and a rotor 3 having first and second rotor parts 3a, 3b. (Hereinafter, the Roman letters "a" and "b" attached to reference Arabic numerals indicate elements related to the first rotor part 3a and the second rotor part 3b, respectively.) Each of the first and second rotor parts 3a, 3b is fitted on the rotor shaft 2 in a manner that prevents the rotor from rotating relative to the rotor shaft 2, and has a number of circumferential recesses 31 corresponding to the number of magnetic poles of the motor (six according to this embodiment). Each circumferential recess 31 embraces a permanent magnet 32 so that the permanent magnets 32 are arranged over the circumference with a fixed pitch angle. A stator 4 comprises a plurality of cores 40 that are laminated in the direction of the axis and disposed radially outward from the rotor 3 by fitting their outer peripheral faces to the case 10 in a rotation-inhibiting manner, and coils (not shown) inserted into slots formed in the core laminate 40. The motor further comprises a resolver 5 fixed to an end of the rotor shaft 2 for rotating together with the rotor shaft 2 and for detecting a magnetic pole position, coil ends 41 protruding from the opposite ends of the stator core laminate 40, and clamp plates 21 that clamp the permanent magnets 32 and laminated rotor cores 30, as shown in FIG. 1. In FIG. 2, the permanent magnets disposed on the first rotor part 3a are omitted to avoid a complicated illustration.
Referring to the detailed illustration of FIG. 3, each steel plate 30 has a central hole 34 with a circular cross-sectional shape for fitting onto the outer peripheral face of the rotor shaft 2, and a key groove 33, that is, an engagement groove, for fitting to the key 22 provided as engaging means of the rotor shaft 2. The key groove 33 is formed so that its edge is continuous from the circumferential edge of the central hole 34. In accordance with the invention, the key groove 33 is formed in a position shifted a predetermined angle θ (θ.sub.F, θ.sub.R) from the center A (A.sub.F, A.sub.R) of a given one of the six dove-tail recesses 31 for receiving the permanent magnets 32 providing the magnetic poles of the motor. More specifically, the position of the key groove 33 is shifted from the center A by an angle θ that is greater than 0 and less than P/2 (0&lt;θ&lt;P/2) where P is the central angle (the magnetic pole pitch angle) obtained by measuring, along the circumference, the magnetic pole pitch formed by neighboring permanent magnets. According to this embodiment, the central angle P is 60
The steel plates 30 each provided with the thus-positioned key groove 33 are laminated to form the core of the first rotor part 3a and the core of the second rotor part 3b. The steel plates 30a of the first rotor part 3a (shown on the left in FIG. 3, and, hereinafter, the illustrated face is assumed to be the front face) and the steel plates 30b of the second rotor part 3b (shown on the right, in an reversed posture) are inverted from each other in terms of the front and reverse faces when fitted to the key 22 of the rotor shaft 2 (as shown by the illustration at the bottom in FIG. 3). When the steel plates 30a and 30b are thus joined or laid on top of each other in the inverted postures while the key grooves 33 are aligned, the position of a recess 31a of each for 30a of each forward-facing steel plate 30a close to the key groove 33 is shifted the angle θ.sub.F clockwise from the key groove 33, and the position of a recess 31b of each reverse-facing steel plate 30b close to the key groove 33 is shifted the angle θ.sub.R counterclockwise from the key groove 33. Thus, the angle between the centers A.sub.F, A.sub.R of the recesses 31a, 31b becomes θ.sub.F +θ.sub.R.In the embodiment shown in FIG. 3, since the angle θ is set to a large value close to P/2, the recess 31b of the laminate of reverse-facing steel plates 30b comes close to a recess 31a' of the laminate of forward-facing steel plates 30a neighboring the recess 31a corresponding to the recess 31b. Therefore, the angle between the recesses (31a', 31b) of the steel plates 30a, 30b adjacent to each other in the direction of axis becomes P-2θ although the angle between the corresponding recesses 31a, 31b of the steel plates 30a, 30b is 2θ in absolute value.
An embodiment in which the angle θ is set to a small value close to 0 is shown in FIG. 4. When laminates of steel plates 30a, 30b are joined in inverted positions in terms of front and reverse faces, with key grooves 33 aligned, the recess 31a of the laminate of forward-facing steel plates 30a close to the key groove 33 is shifted θ.sub.F counterclockwise from the key groove 33, and the recess 31b of the laminate of reverse-facing steel plates 30b close to the key groove 33 is shifted θ.sub.R clockwise from the key groove 33. Since the angle θ is set to a small value close to 0, the recess 31b of the laminate of reverse-facing steel plates 30b comes close to the corresponding recess 31a of the laminate of the forward-facing steel plates 30a. Thus the angle between the adjacent recesses 31a and 31b of the steel plates 30a, 30b becomes 2θ.
That is, if the angle θ is to be set within the range of 0&lt;θ≦P/4,
2&#952;=(2n+1)
If the angle θ is to be set within the range of P/4&lt;θ&lt;P/2,
P-2&#952;=(2n+1)
&#952;={(n/2)+1/4}
&#952;=(P/2)-{(n/2)+(1/4)}
For example, if the slot pitch angle S of the stator 4 is 10 magnet pole pitch angle P of the rotor 3 is 60 n is 0, then the predetermined angle θ becomes 2.5.degree. and 27.5.degree. for the respective ranges.
&#952;={n+(1/2)}
&#952;=(P/2)-{n+(1/2)}
For example, if the slot pitch angle S of the stator 4 is 10 magnet pole pitch angle P of the rotor 3 is 60 n is 0, then the predetermined angle θ becomes 5 25 10
SUMMARY OF THE INVENTION Accordingly, it is a first object of the present invention to provide a motor in which the magnetic poles formed by the permanent magnets of the rotor are provided with a predetermined skew angle while avoiding complicated processing steps and an increase in the number of component part items.
It is preferred that the predetermined angle θ be determined as follows: if 0&lt;θ≦P/4, then θ={(n/2)+(1/4)} if P/4&lt;θ&lt;P/2, then θ=(P/2)-{(n/2)+(1/4)} slot pitch angle of the stator, and n is an integer.
By determining the predetermined angle θ as θ={(n/2)+(1/4)} skew angle 2θ between the first and second rotor parts inverted from each other becomes 1/2 of the slot pitch angle S of the stator, so that the cogging torques of the first and second rotor parts occur at a rate of one cycle per a slot but shifted from each other by half the cycle. Since the cogging torques occurring in the first and second rotor parts thus cancel each other, the torque oscillation caused by cogging torques will be reduced. Thus, by offsetting cogging torques, a significant factor of the torque oscillation of a motor, this preferred construction reduces the entire torque oscillation, besides achieving the advantages mentioned above.
It is also preferred that the predetermined angle θ be determined as follows: if 0&lt;θ≦P/4, then θ={n+(1/2)} P/4&lt;θ&lt;P/2, then θ=(P/2)-{n+(1/2)} pitch angle of the stator, and n is an integer.
By determining the predetermined angle θ as θ={n+(1/2)} or θ=(P/2)-{n+(1/2)} first and second rotor parts inverted from each other becomes an odd-number multiple of the slot pitch angle S of the stator, so that the torque ripples of the first and second rotor parts occur at a rate of one cycle per two slots but shift from each other by half the cycle. Since the torque ripples occurring in the first and second rotor parts thus cancel each other, the torque oscillation caused by torque ripples will be reduced. Thus, by offsetting torque ripples, another significant factor of the torque oscillation of a motor, this preferred construction reduces the entire torque oscillation, besides achieving the advantages mentioned above.
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Smith CorporationBrushless permanent magnet machine with axial modules of rotor magnetization skew and method of producing the sameWO2002041471A1 *Nov 16, 2001May 23, 2002Stefan BeyerRotor for an electric machineWO2003088449A1 *Dec 18, 2002Oct 23, 2003Bosch Gmbh RobertMagnetic return path and permanent-magnet fixing of a rotorWO2007031056A1 *Sep 8, 2006Mar 22, 2007Temic Auto Electr Motors GmbhElectric motorWO2010106497A2 *Mar 16, 2010Sep 23, 2010Control Techniques Dynamics LimitedElectric device rotor and methods for manufactureWO2011048581A2 *Oct 22, 2010Apr 28, 2011Sicor S.P.A.An electric motor with a permanent-magnet rotor and a rotor for an electric motor of this type* Cited by examinerClassifications U.S. Classification310/156.19, 310/156.15International ClassificationH02K15/02, H02K16/02, H02K1/28, H02K1/27Cooperative ClassificationH02K2201/06, H02K1/278European ClassificationH02K1/27B2C5SLegal EventsDateCodeEventDescriptionNov 4, 2009FPAYFee paymentYear of fee payment: 12Nov 4, 2005FPAYFee paymentYear of fee payment: 8Nov 8, 2001FPAYFee paymentYear of fee payment: 4May 14, 1997ASAssignmentOwner name: AISIN AW CO., LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HASEBE, MASAHIRO;YAMAGUCHI, YASUO;REEL/FRAME:008549/0657Effective date: 19970402RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google