US5047682A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Permanent magnet excited electric motor
Assignee: Papst Licensing GmbH and Co KG
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Filing: 1988-10-05
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Granted: 1991-09-10
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Expires: 2008-10-05
Abstract
Abstract A permanent magnet excited electric motor is provided with a low circumferential hump-like protrusion on the face of each electromagnetic pole to partially decrease the air gap between the stator and rotor and act as a so-called magnetic cam 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 electromagnetic poles and the gaps between the permanent magnet poles.
Inventors
- 👤 Martin Burgbacher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 03:19
CPC Classifications
H; H02; H02K; H02K29/00; H02K29/03; H02K21/00; H02K21/12; H02K21/14; H02K21/22; H02K2213/00; H02K2213/03; Y; Y10; Y10T; Y10T74/00; Y10T74/21; Y10T74/2101
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
235 words
An electromagnetic direct current motor excited by permanent magnets comprising a laminated core having radially extending slots with slot openings at a coaxial surface of the core, the coaxial surface being cylindrical; at least one winding forming electromagnetic poles defined in 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 separating each polarity, the faces of the electromagnetic poles facing the faces of the permanent magnets and being separated by an air gap defined therebetween, one of the electromagnetic poles as an entity or the permanent magnets as an entity being the stator and the other the rotor; no more than one raised portion on each of the electromagnetic pole surfaces extending radially into the air gap, the circumferential width of the raised portion being small compared to the electromagnetic pole pitch such that the electromagnetic pole pitch is many times the circumferential width of the raised portion; and the raised portions being located circumferentially on the surface of the laminated core such that the distance measured in the direction of rotor rotation from the center of a core slot defined between any given pair of electromagnetic poles to the center of a raised portion on the electromagnetic pole adjacent the given pair is equal to n times the permanent magnet pole pitch, n being a whole number.
Claim 2
Dependent Claim
235 words
An electromagnetic direct current motor excited by permanent magnets comprising a laminated core having radially extending slots with slot openings at a coaxial surface of the core, the coaxial surface being cylindrical; at least one winding forming electromagnetic poles defined in 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 separating each polarity, the faces of the electromagnetic poles facing the faces of the permanent magnets and being separated by an air gap defined therebetween, one of the electromagnetic poles as an entity or the permanent magnets as an entity being the stator and the other the rotor; no more than one raised portion on each of the electromagnetic pole surfaces extending radially into the air gap, the circumferential width of the raised portion being small compared to the electromagnetic pole pitch such that the electromagnetic pole pitch is many times the circumferential width of the raised portion; and the raised portions being located circumferentially on the surface of the laminated core such that the distance measured in the direction of rotor rotation from the center of a core slot defined between any given pair of electromagnetic poles to the center of a raised portion on the electromagnetic pole adjacent the given pair is equal to n times the permanent magnet pole pitch, n being a whole number.
Claim 3
Dependent Claim
45 words
An electromagnetic direct current motor according to claim 1, wherein the motor is a small brushless dc motor and wherein the stator includes the laminated core and electromagnetic poles and the rotor includes the permanent magnet poles, the rotor poles being of relatively high inductance.
Claim 4
Dependent Claim
32 words
A motor according to claim 2, wherein the raised portions are provided at the stator pole centers, and wherein the ratio of the number of stator poles to rotor poles is 3:2.
Claim 5
Dependent Claim
28 words
A motor according to claim 3, wherein the circumferential extent of the raised portion corresponds to from 0.5 to 1 times the width of the stator slot opening.
Claim 6
Dependent Claim
44 words
A motor according to any one of claims 2-4, wherein the air gap is maximally wide immediately adjacent the raised portions, the width of the air gap decreasing to the value above the raised portion as the air gap approaches the stator pole tips.
Claim 7
Dependent Claim
30 words
A motor according to claim 5, wherein at an effective air gap of from 0.3 to 0.6 mm, the height of the raised portion is from 0.1 to 0.3 mm.
Claim 8
Dependent Claim
44 words
A motor according to claim 5, wherein the electromagnetic pole faces are pointed in a radial direction towards the air gap and wherein the circumferential extent of the raised portion corresponds to from 0.3 to 0.8 times the width of the stator slot opening.
Claim 9
Dependent Claim
32 words
A motor according to claim 7, wherein the height of the raised portion is approximately from 0.05 to 0.15 mm at an effective air gap width of from 0.3 to 0.6 mm.
Claim 10
Dependent Claim
27 words
A motor according to claim 8, wherein the width of the air gap decreases progressively from immediately adjacent the raised portion circumferentially toward an adjacent slot opening.
Claim 11
Dependent Claim
28 words
A motor according to claim 8, wherein the width of the air gap decreases in steps from immediately adjacent the raised portion circumferentially toward an adjacent slot opening.
Claim 12
Dependent Claim
18 words
A motor according to claim 3, wherein the stator winding provided with a cylindrical air gap is multiphased.
Claim 13
Dependent Claim
14 words
A motor according to claim 11, wherein the stator winding is wound without overlap.
Claim 14
Dependent Claim
24 words
A motor according to claim 2, wherein the pattern of magnetization of the rotor in the circumferential direction is distributed in a trapezoidal shape.
Claim 15
Dependent Claim
15 words
A motor according to claim 13, wherein the rotor magnet is a rare earth magnet.
Claim 16
Dependent Claim
13 words
A motor according to claim 12, wherein the stator is a three-phase stator.
Claim 17
Dependent Claim
19 words
A motor according to claim 15, wherein the motor is provided with 6 stator poles and 4 rotor poles.
Claim 18
Dependent Claim
31 words
A motor according to claim 9, wherein adjacent the raised portion, the air gap width immediately decreases sharply, then increases and finally decreases again as it approaches the stator pole tips.
Claim 19
Dependent Claim
14 words
A motor according to claim 6 having an outside diameter of approximately 40 mm.
Claim 20
Dependent Claim
14 words
A motor according to claim 6 having an outside diameter of approximately 25 mm.
Claim 21
Dependent Claim
30 words
A motor according to claim 10 wherein adjacent the raised portion, the air gap immediately decreases sharply, then increases and finally decreases again as it approaches the stator pole tips.
Claim 22
Dependent Claim
14 words
A motor according to claim 8 having an outside diameter of approximately 40 mm.
Claim 23
Dependent Claim
14 words
A motor according to claim 8 having an outside diameter of approximately 25 mm.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-09-09 | 1995-03-11 | 1995-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-09-09 | 1999-03-11 | 1999-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-09-09 | 2003-03-11 | 2003-09-10 | $7700.00 | Window Closed / Lapsed |