US4998032A
Expired / Lapsed
US
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Permanent magnet excited electric motor
Assignee: Papst Licensing GmbH and Co KG
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Filing: 1988-07-13
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Granted: 1991-03-05
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Expires: 2008-07-13
Abstract
Abstract A permanent magnet excited motor is provided with a plurality of low circumferential hump-like protrusions on the face of each stator pole to partially decrease the air gap between the stator and rotor and act as so-called magnetic cams to exert a force on the rotor to smooth an otherwise uneven parasitic slot torque that occurs between the interaction of slot openings of the stator poles and the gaps between the permanent magnet poles of the rotor.
Inventors
- 👤 Martin Burgbacher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 07:40
CPC Classifications
H; H02; H02K; H02K29/00; H02K29/03; H02K21/00; H02K21/12; H02K21/14; H02K21/22
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
243 words
A brushless dc motor excited by permanent magnets comprising a laminated stator core having radially extending slots with slot orifices at a coaxial surface of the core, the coaxial surface being cylindrical; at least one winding forming electromagnetic poles defined in the sectors between the slots; a plurality of radially thin, annular permanent magnets arranged in alternating polarities in the general form of a ring with a gap circumferentially separating each polarity and formed to rotate with respect to the stator, each magnet forming a rotor pole of a relatively high induction, the faces of the electromagnetic poles facing the faces of the permanent magnets and being separated by a generally cylindrical air gap defined therebetween; a plurality of raised portions on each of the stator pole coaxial surfaces extending radially into the air gap, the circumferential width of the raised portions being small compared to the stator pole pitch such that the stator pole pitch is many times the circumferential width of the raised portions; and one of the raised portions on each of the stator faces being located around the circumference of the stator core such that the distance measured in the direction of rotor rotation from the center of a stator slot defined between any given pair of stator poles to the center of said one raised portion on the stator pole adjacent the given pair is equal to n times the rotor pole pitch, n being a whole number.
Claim 2
Dependent Claim
243 words
A brushless dc motor excited by permanent magnets comprising a laminated stator core having radially extending slots with slot orifices at a coaxial surface of the core, the coaxial surface being cylindrical; at least one winding forming electromagnetic poles defined in the sectors between the slots; a plurality of radially thin, annular permanent magnets arranged in alternating polarities in the general form of a ring with a gap circumferentially separating each polarity and formed to rotate with respect to the stator, each magnet forming a rotor pole of a relatively high induction, the faces of the electromagnetic poles facing the faces of the permanent magnets and being separated by a generally cylindrical air gap defined therebetween; a plurality of raised portions on each of the stator pole coaxial surfaces extending radially into the air gap, the circumferential width of the raised portions being small compared to the stator pole pitch such that the stator pole pitch is many times the circumferential width of the raised portions; and one of the raised portions on each of the stator faces being located around the circumference of the stator core such that the distance measured in the direction of rotor rotation from the center of a stator slot defined between any given pair of stator poles to the center of said one raised portion on the stator pole adjacent the given pair is equal to n times the rotor pole pitch, n being a whole number.
Claim 3
Dependent Claim
35 words
A motor according to claim 1, wherein the raised portions are each provided in the stator pole middle and the ratio of the stator pole number to the rotor pole number is 3 to 2.
Claim 4
Dependent Claim
29 words
A motor according to claim 1, wherein the circumferential extent of the raised portion corresponds to from 0.5 to 1 times the circumferential width of the stator slot orifice.
Claim 5
Dependent Claim
47 words
A motor according to claim 3, wherein the air gap directly next to the raised portion as seen in the circumferential direction has the maximum dimension, which dimension decreases in the direction of the stator pole ends, preferably to a value equal to that above the cog.
Claim 6
Dependent Claim
30 words
A motor according to claim 4, wherein the height of the raised portion is from 0.1 to 0.3 mm with an effective air gap of from 0.3 to 0.6 mm.
Claim 7
Dependent Claim
43 words
A motor according to claim 4, wherein the stator pole face ends taper radially to a point toward the air gap and the circumferential extent of the elevation corresponds to from 0.3 to 0.8 times the circumferential width of the stator slot orifice.
Claim 8
Dependent Claim
31 words
A motor according to claim 6, wherein the height of the raised portion is from 0.5 to 0.15 mm with an effective air gap width of from 0.3 to 0.6 mm.
Claim 9
Dependent Claim
17 words
A motor according to claim 4, wherein the reduction in air gap dimension is gradual and continuous.
Claim 10
Dependent Claim
17 words
A motor according to claim 4, wherein the reduction in air gap dimension takes place in steps.
Claim 11
Dependent Claim
28 words
A motor according to claim 1, wherein the stator winding is a multiphase winding with a cylindrical air gap and especially wound to be free of any overlap.
Claim 12
Dependent Claim
21 words
A motor according to claim 1, wherein the magnetization of the rotor is in a trapezoidal pattern in the circumferential direction.
Claim 13
Dependent Claim
24 words
A motor according to claim 10, wherein the stator is a three-phase stator, and wherein 6 stator poles and 4 rotor poles are provided.
Claim 14
Dependent Claim
37 words
A motor according to claim 8, wherein the air gap next to the raised portion soon decreases drastically in dimension, then increases again near the stator pole ends and finally decreases directly at the stator pole ends.
Claim 15
Dependent Claim
14 words
A motor according to claim 1, wherein the outside diameter is about 40 mm.
Claim 16
Dependent Claim
14 words
A motor according to claim 1, wherein the outside diameter is about 25 mm.
Claim 17
Dependent Claim
23 words
A motor according to claim 1, wherein the motor is an outer rotor motor and the rotor is inserted into a memory disk.
Claim 18
Dependent Claim
20 words
A motor according to claim 1 or 8 or 9, wherein 8 rotor poles and 6 stator poles are provided.
Claim 19
Dependent Claim
31 words
A motor according to claim 17, wherein three raised portions are provided and are distributed circumferentially on each stator face at equidistant intervals between the centers of two adjacent stator slots.
Claim 20
Dependent Claim
17 words
A motor according to claim 18, wherein the raised portions run axially parallel to the motor axis.
Claim 21
Dependent Claim
70 words
A motor according to claim 19, wherein the an area of a relative enlargement in the air gap dimension is also provided approximately in the middle between the stator pole middle and the stator pole ends forming another increase and decrease in air gap dimension, where this increase in air gap dimension is smaller radially than that next to the raised portion and that next to the stator pole ends.
Claim 22
Dependent Claim
41 words
A motor according to claim 20, wherein the area of relative enlargement in the air gap dimension in the circumferential direction next to the raised portion in the middle of the stator pole, corresponds approximately to 1/10 the stator pole width.
Claim 23
Dependent Claim
32 words
A motor according to claim 21, wherein the relative enlargement in air gap dimension adjacent the stator pole ends is equal to or less than that next to the middle raised portion.
Claim 24
Dependent Claim
44 words
A motor according to claim 22, wherein the relative enlargement in air gap dimension occurring between the stator pole middle and the stator pole end is smaller than that increase adjacent the stator pole and than that adjacent the end of the stator pole.
Claim 25
Dependent Claim
13 words
A motor according to claim 1, wherein the rotor is an internal rotor.
Claim 26
Dependent Claim
14 words
A motor according to claim 11, wherein the rotor magnet is based on neodymium.
Claim 27
Dependent Claim
15 words
A motor according to claim 11, wherein the rotor magnet is a rare earth magnet.
Claim 28
Dependent Claim
37 words
A motor according to claim 9, wherein the air gap next to the raised portion soon decreases drastically in dimension, then increases again near the stator pole ends and finally decreases directly at the stator pole ends.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1994-03-04 | 1994-09-03 | 1995-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-03-04 | 1998-09-03 | 1999-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-03-04 | 2002-09-03 | 2003-03-05 | $7700.00 | Window Closed / Lapsed |