Source: http://www.google.com/patents/US6512318?dq=6480844
Timestamp: 2014-09-23 02:52:58
Document Index: 227601436

Matched Legal Cases: ['art.\n10', 'art. 20', 'art.\n23', 'art.\n28', 'art 14', 'art 16', 'art 14', 'art 16', 'art 14', 'arts 16']

Patent US6512318 - Self-starting electric brushless motor having permanent magnet and ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign in<nobr>Advanced Patent Search</nobr>PatentsA self-starting brushless electric motor having a first motor (stator) with poles arranged in a row, said poles constituting ferromagnetic poles or permanent-magnet poles, a second motor part (rotor) with poles arranged in a row, said poles consisting of ferromagnetic poles or permanent-magnet poles...http://www.google.com/patents/US6512318?utm_source=gb-gplus-sharePatent US6512318 - Self-starting electric brushless motor having permanent magnet and reluctance polesAdvanced Patent SearchPublication numberUS6512318 B2Publication typeGrantApplication numberUS 09/752,512Publication dateJan 28, 2003Filing dateJan 3, 2001Priority dateMay 30, 1995Fee statusPaidAlso published asCN1077347C, CN1191640A, EP0829128A1, EP0829128B1, EP1363384A2, EP1363384A3, US6204587, US20020047447, WO1996038903A1Publication number09752512, 752512, US 6512318 B2, US 6512318B2, US-B2-6512318, US6512318 B2, US6512318B2InventorsVilmos T�r�k, Walter Wissmach, Roland SchaerOriginal AssigneeToeroek Vilmos, Walter Wissmach, Roland SchaerExport CitationBiBTeX, EndNote, RefManPatent Citations (11), Referenced by (5), Classifications (18), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetSelf-starting electric brushless motor having permanent magnet and reluctance polesUS 6512318 B2Abstract A self-starting brushless electric motor having a first motor (stator) with poles arranged in a row, said poles constituting ferromagnetic poles or permanent-magnet poles, a second motor part (rotor) with poles arranged in a row, said poles consisting of ferromagnetic poles or permanent-magnet poles and being arranged opposite the row of poles on the first motor part, wherein the motor part with salient ferromagnetic poles or, if both motor parts have salient ferromagnetic poles, at least one of the motor parts has a permanent-magnet pole, and also a magnetizing winding on the first motor part. The system of poles formed by the pole rows is magnetically asymmetrical in the direction in which the motor parts are movable in relation to each other.
What is claimed is: 1. A self-starting brushless electric motor, comprising ferromagnetic first and second motor parts having a preferential direction of relative movement and being separated by an air gap,
the first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, each pole group of the first pole line comprising at least one reluctance pole and a permanent-magnet pole spaced from the reluctance pole, the permanent-magnet pole having a magnetization direction transverse to the air gap, the second motor part having a plurality of poles arranged in a second pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across the air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a magnetic field linking the first and the second pole lines through the pole group upon energization of the winding system to cause relative movement of the motor parts in said preferential direction of relative movement, wherein at least one of said poles of at least one of said pole groups of the first pole line and each pole of the second pole line comprise a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the motor parts and which is of a length, as measured along the pole lines, such that when any two poles on the two motor parts are magnetically aligned with one another as a result of energization of the winding, the auxiliary pole part of one of the poles of the second pole line extends at least to the vicinity of the permanent-magnet pole of said at least one pole group. 2. The electric motor of claim 1 wherein the at least one reluctance pole of each pole group of the first pole line comprises two reluctance poles between which said permanent-magnet pole is disposed and wherein the poles of the second pole line are reluctance poles.
3. The electric motor of claim 1 wherein said one of said poles of said at least one of said pole groups which comprises a main pole part and an auxiliary pole part is the permanent-magnet pole.
4. The electric motor of claim 1 wherein the poles of the second pole line are permanent-magnet poles that alternate in polarity from one pole to the next along the second pole line.
5. The electric motor of claim 1 wherein said auxiliary pole part is of a length, as measured along the pole lines, such that when any two poles of the first and second pole lines are magnetically aligned with one another as a result of energization of the winding, the auxiliary pole part of at least one of the poles of the second pole line slightly overlaps said permanent-magnetic pole.
6. The electric motor of claim 5 wherein the at least one reluctance pole of each pole group of the first pole line comprises two reluctance poles between which said permanent-magnet pole is disposed and wherein the poles of the second pole line are reluctance poles.
7. The electric motor of claim 5 wherein said at least one of said poles of said at least one of said pole groups which comprises a main pole part and an auxiliary pole part is the permanent-magnet pole.
8. The electric motor of claim 5 wherein the poles of the second pole line are permanent-magnet poles that alternate in polarity from one pole to the next along the second pole line.
9. The electric motor of claim 1 wherein all poles of the second pole line are substantially uniformly spaced-apart.
10. The electric motor of claim 9 wherein the at least one reluctance pole of each pole group of the first pole line comprises two reluctance poles between which said permanent-magnet pole is disposed.
11. The electric motor of claim 10 wherein at least one of the reluctance poles of each pole group of the first pole line is magnetically asymmetrical.
12. The electric motor of claim 10 wherein the two reluctance poles of each pole group of the first pole line are magnetically symmetrical.
13. A self-starting brushless electric motor, comprising
a ferromagnetic first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, a ferromagnetic second motor part having a plurality of poles arranged in spaced-apart relation in a second pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a magnetic field linking the first and the second pole lines through the pole group upon energization of the coil, wherein at least one of the first pole line and the second pole line includes a magnetic asymmetry providing a preferential direction of relative movement of the motor parts upon energization of the winding system, the first pole line comprises permanent-magnet poles only, each pole group of the first pole line comprises two permanent-magnet poles polarized in opposite directions transverse to the air gap, and the second pole line includes a plurality of reluctance poles. 14. The electric motor of claim 13 wherein at least one pole of each pole group of the first pole line is an asymmetrical pole providing magnetic asymmetry in the first pole line and comprising a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the first motor part and which is of a length, as measured along the pole lines, such that when any two poles of the two pole lines are magnetically aligned with one another, the auxiliary pole part of the at least one asymmetrical pole of the first pole line extends at least to the vicinity of an adjacent pole of the second pole line.
15. The electric motor of claim 13 wherein at least one pole of each pole group of the first pole line is an asymmetrical pole providing magnetic asymmetry in the first pole line and comprising a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the first motor part and which is of a length, as measured along the pole lines, such that when any two poles of the two pole lines are magnetically aligned with one another, the auxiliary pole part of the at least one asymmetrical pole of the first pole line slightly overlaps an adjacent pole of the second pole line.
16. The electric motor of claim 15 wherein all poles of the first pole line are asymmetrical.
17. The electric motor of claim 13 wherein the poles of the second pole line are substantially uniformly spaced asymmetrical reluctance poles.
18. The electric motor of claim 17 wherein each reluctance pole comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length, as measured along the pole lines, such that whenever two poles of the two pole lines are magnetically aligned with one another, the auxiliary pole part of a permanent-magnet pole of the first pole line slightly overlaps the auxiliary pole part of a reluctance pole of the second pole line.
19. A self-starting brushless electric motor, comprising
a ferromagnetic first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, a ferromagnetic second motor part having a plurality of poles arranged in spaced-apart relation in a second pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a unidirectional magnetic field linking the first and the second pole lines through the pole group upon energization of the coil, wherein each pole group of the first pole line comprises at least one reluctance pole and a permanent-magnet pole spaced from the reluctance pole and providing a preferential direction of relative movement of the motor parts upon energization of the winding system, the permanent-magnet pole has a magnetization direction transverse to the air gap, and opposite to the direction of the magnetic field produced by the associated winding coil, the second pole line includes a plurality of reluctance poles substantially evenly spaced along the second pole line, in each pole group of the first pole line the permanent-magnet pole is positioned asymmetrically relative to two successive poles of the second pole line when one of said two successive poles is magnetically aligned with the at least one reluctance pole as a result of energization of the winding coil and the permanent-magnet pole is located opposite the space between the two successive poles of the second pole line such that it will be closer to magnetic alignment with said one of the two successive poles than with the other, and each pole of the second pole line comprises a main pole part and an auxiliary pole part projecting in the direction opposite to the preferential direction of relative movement of the second motor part. 20. The electric motor of claim 19 wherein the at least one reluctance pole of each pole group of the first motor part comprises two reluctance poles between which the permanent-magnet pole is disposed.
21. The electric motor of claim 20 wherein the permanent-magnet pole of each pole group of the first pole line is movable along the first pole line between a first position for causing the preferential direction of relative movement to have a first sense and a second position for causing the preferential direction of relative movement to have a second sense opposite to the first sense.
22. The electric motor of claim 21 wherein each pole of the second pole line comprises a main pole part and two auxiliary pole parts each projecting in the direction of the second pole line from a respective end of the main pole part.
23. The electric motor of claim 22 wherein each auxiliary pole part of each pole of the second pole line is of a length, as measured along pole lines, such that when any two poles of the two pole lines are magnetically aligned with one another as a result of energization of the winding coil and the permanent-magnet pole is in one of the first and second positions, an auxiliary pole part of at least one pole of the second pole line extends at least to the vicinity of a permanent-magnet pole of a pole group of the first pole line.
24. The electric motor of claim 23 wherein the length of each auxiliary pole part of each pole of the second pole line, as measured along pole lines, is such that when any two poles of the two pole lines are magnetically aligned with one another as a result of energization of the winding coil and the permanent-magnet pole is in one of the first and second positions, the auxiliary pole part of at least one pole of the second pole line slightly overlaps the permanent-magnet pole of a pole group of the first pole line.
25. The electric motor of claim 20 wherein all poles of each pole group of the first motor part are magnetically symmetrical.
26. The electric motor of claim 25 wherein the permanent-magnet pole of each pole group of the first pole line is movable along the first pole line between a first position for causing the preferential direction of relative movement to have a first sense and a second position for causing the preferential direction of relative movement to have a second sense opposite to the first sense.
27. The electric motor of claim 26 wherein each pole of the second pole line comprises a main pole part and two auxiliary pole parts each projecting in the direction of the second pole line from a respective end of the main pole part.
28. The electric motor of claim 27 wherein each auxiliary pole part of each pole of the second pole line is of a length, as measured along pole lines, such that when any two poles of the two pole lines are magnetically aligned with one another as a result of energization of the winding coil and the permanent-magnet pole is in one of the first and second positions, an auxiliary pole part of at least one pole of the second pole line extends at least to the vicinity of a permanent-magnet pole of a pole group of the first pole line.
29. The electric motor of claim 28 wherein the length of each auxiliary pole part of each pole of the second pole line, as measured along pole lines, is such that when any two poles of the two pole lines are magnetically aligned with one another as a result of energization of the winding coil and the permanent-magnet pole is in one of the first and second positions, the auxiliary pole part of at least one pole of the second pole line slightly overlaps the permanent-magnet pole of a pole group of the first pole line.
30. A self-starting brushless electric motor, comprising
a ferromagnetic first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, a ferromagnetic second motor part having a plurality of permanent-magnet poles of alternating polarities arranged in a second pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a magnetic field linking the first and the second pole lines through the pole group upon energization of the coil, at least one of the first pole line and the second pole line includes a magnetic asymmetry providing a preferential direction of relative movement of the motor parts upon energization of the winding system, and each pole group of the first pole line comprises two reluctance poles separated by a pole-free space, at least one of said reluctance poles being asymmetrical, wherein the second pole line comprises a plurality of permanent-magnet poles that alternate in polarity from one pole to the next along the second pole line and having a magnetization direction transverse to the air gap and adjacent like-polarity permanent-magnet poles of the second pole line are simultaneously magnetically alignable with the two reluctance poles of a pole group of the first pole line, and wherein the at least one asymmetrical reluctance pole of each pole group of the first pole line comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the first motor part and which is of a length, as measured along the pole lines, such that when adjacent like-polarity permanent-magnet poles of the second pole line are magnetically aligned with the two reluctance poles of a pole group of the first pole line, the auxiliary pole part extends at least to the vicinity of the permanent-magnet pole of the second pole line which is positioned between said adjacent like-polarity permanent-magnet poles. 31. The electric motor of claim 30 wherein the permanent-magnet poles of the second pole line are asymmetrical and each permanent-magnet pole comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length, as measured along the pole lines, such that when adjacent like-polarity permanent-magnet poles of the second pole line are magnetically aligned with the two reluctance poles of a pole group of the first pole line, the auxiliary pole part slightly overlaps the auxiliary pole part of said at least one asymmetrical reluctance pole.
32. The electric motor of claim 30 wherein the at least one asymmetrical reluctance pole of each pole group of the first pole line comprises two reluctance poles.
33. A self-starting brushless electric motor, comprising
a ferromagnetic first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, a ferromagnetic second motor part having a plurality of poles in a second pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a magnetic field linking the first pole line and the second pole line through the pole group upon energization of the coil, wherein each pole group of the first motor part comprises two symmetrical reluctance poles separated by a pole-free space, wherein the second pole line includes a magnetic asymmetry providing a preferential direction of relative movement of the motor parts upon energization of the winding system and the poles in the second pole line include a plurality of asymmetrical permanent-magnet poles that alternate in polarity from one pole to the next along the second pole line and having a magnetization direction transverse to the air gap, and wherein each asymmetrical permanent-magnet pole of the second pole line comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length, as measured along the pole lines, such that when the two poles of a pole group of the first pole line are magnetically aligned with a pair of adjacent like-polarity permanent-magnet poles of the second pole line, the auxiliary pole part of the permanent-magnet positioned between said like-polarity permanent-magnet poles extend at least to the vicinity of one of the two reluctance poles of said pole group. 34. A self-starting brushless electric motor, comprising
a ferromagnetic first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, a ferromagnetic second motor part having a plurality of poles arranged and substantially uniformly distributed in a second pole line and magnetically alignable with the poles of the pole groups of the first pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a magnetic field linking the first and the second pole lines through the pole group upon energization of the coil, wherein at least one of the first pole line and the second pole line includes a magnetic asymmetry providing a preferential direction of relative movement of the motor parts upon energization and deenergization of the winding system, each pole group of the first pole line comprises at least one reluctance pole and a permanent-magnet pole spaced from the reluctance pole, and wherein the permanent-magnet pole of each pole group has a magnetization direction transverse to the air gap and is asymmetrical in shape with respect to a line transverse to the first pole line and comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the first motor part and which is of a length as measured along the pole lines such that when any two poles on the two motor parts are magnetically aligned with one another as a result of energization of the winding coil, the auxiliary pole part of the permanent-magnet pole extends at least to the vicinity of an adjacent pole of the second pole line. 35. The electric motor of claim 34 wherein the at least one reluctance pole of each pole group of the first pole line comprises two reluctance poles between which the permanent-magnet pole is disposed, wherein the poles of the second pole line consists of reluctance poles which are spaced apart substantially uniformly along the pole lines such that any two adjacent reluctance poles of the second pole line are simultaneously magnetically alignable with the two reluctance poles of any one pole group of the first pole line, and wherein each reluctance pole of the second pole line comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length, as measured along the pole lines, such that when any two adjacent reluctance poles of the second pole line are magnetically aligned with the two reluctance poles of a pole group of the first pole line, the auxiliary pole part of one of said two aligned reluctance poles of the second pole line extends at least to the vicinity of the auxiliary pole part of the permanent-magnet pole of that pole group.
36. The electric motor of claim 35 wherein the auxiliary pole part of said one aligned reluctance pole slightly overlaps the auxiliary pole part of the permanent-magnet pole.
37. The electric motor of claim 34 wherein the at least one reluctance pole of each pole group of the first pole line comprises two reluctance poles between which the permanent-magnet pole is disposed, and wherein the poles of the second pole line are permanent-magnet poles.
38. The electric motor of claim 37 wherein each pole of the second pole line is asymmetrical in shape with respect to a line transverse to the second pole line and comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length, as measured along the pole lines, such that when any two adjacent poles of the second pole line are magnetically aligned with respectively said at least one reluctance pole of a pole group of the first pole line and the permanent-magnet of that pole group, the auxiliary pole parts of said adjacent permanent-magnet poles extend at least to the vicinity of said one reluctance pole and the permanent-magnet of the said pole group.
39. The electric motor of claim 37 wherein one of said two reluctance poles is asymmetrical in shape with respect to a line transverse to the first pole line and comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the first motor part and which is of a length, as measured along the pole lines, such that when any two adjacent like-polarity poles of the second pole line are magnetically aligned with the two reluctance poles of a pole group of the first pole line, the auxiliary pole part of said at least one reluctance pole of each pole group of the first pole line extends at least to the vicinity of a pole of the second pole line.
40. The electric motor of claim 39 wherein each pole of the second pole line is asymmetrical in shape with respect to a line transverse to the second pole line and comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length, as measured along the pole lines, such that when any two adjacent poles of the second pole line are magnetically aligned with respectively said at least one reluctance pole of a pole group of the first pole line and the permanent-magnet of that pole group, the auxiliary pole parts of said adjacent permanent-magnet poles extend at least to the vicinity of said one reluctance pole and the permanent-magnet of the said pole group.
41. The electric motor of claim 39 wherein the poles of the second pole line are symmetrical in shape with respect to a line transverse to the second pole line.
42. A self-starting brushless electric motor, comprising
a first motor part (11) having a plurality of pole groups comprised of only reluctance poles arranged in a first pole line, a second motor part (16) having a plurality of poles arranged and substantially uniformly distributed in a second pole line and magnetically alignable with the poles of the pole groups of the first pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system (15) on the first motor part comprising a winding coil arranged in association with each pole group to produce an alternating magnetic field linking the first and the second pole lines through the pole group upon energization of the coil, wherein at least one of the first pole line and the second pole line includes a magnetic asymmetry providing a preferential direction relative movement of the motor parts upon both energization and deenergization of the winding system, wherein each pole group of the first pole line comprises at least two reluctance poles separated by a pole-free space, wherein the second pole line includes a plurality of only permanent-magnet poles that alternate in polarity from one pole to the next along the second pole line and having a magnetization direction transverse to the air gap, wherein said at least two reluctance poles of each pole group of the first pole line and adjacent like-polarity poles of the second pole line are substantially equally spaced apart along the pole lines, whereby when said adjacent like-polarity permanent-magnetic poles are magnetically aligned with said at least two reluctance poles, the permanent-magnetic pole positioned between said adjacent like-polarity poles confronts said pole free space separating said at least two reluctance poles. 43. The electric motor of claim 42 wherein the permanent-magnet poles of the second pole lines are asymmetrical in shape with respect to a line transverse to the second pole line and comprise a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length as measured along the pole lines such that when any two poles on the two motor parts are magnetically aligned with one another as a result of the energization of the winding coil, the auxiliary pole part of at least one of the asymmetrical permanent-magnet poles of the second pole line extends at least to the vicinity of an adjacent pole of the first pole line.
44. The electric motor of claim 42 wherein the permanent-magnet poles of the second pole line are magnetically symmetrical and wherein each reluctance pole of the first pole line comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the first motor part and which is of a length, as measured along the pole lines, such that when any two poles on the two motor parts are magnetically aligned with one another as a result of energization of the winding coil, the auxiliary pole part extends at least to the vicinity of an adjacent permanent-magnet pole of the second pole line.
45. A self-starting brushless electric motor, comprising
a ferromagnetic first motor part having a plurality of pole groups arranged in spaced-apart relation in a first pole line, a ferromagnetic second motor part having a plurality of poles arranged and substantially uniformly distributed in a second pole line and magnetically alignable with the poles of the pole groups of the first pole line, bearing means supporting the first motor part and the second motor part for relative movement with the first pole line confronting the second pole line across an air gap, and a winding system on the first motor part comprising a winding coil arranged in association with each pole group to produce a magnetic field linking the first and the second pole lines through the pole group upon energization of the coil, wherein at least one of the first pole line and the second pole line includes a magnetic asymmetry providing a preferential direction of relative movement of the motor parts upon energization and deenergization of the winding system, wherein each pole group of the first pole line comprises at least two permanent-magnet poles of alternating polarities having opposite magnetization directions transverse to the air gap, wherein the second pole line includes a plurality of reluctance poles which are asymmetrical in shape with respect to a line transverse to the second pole line and wherein each reluctance pole of the second pole line comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part and which is of a length as measured along the pole lines such that when any two poles on the two motor parts are magnetically aligned with one another, the auxiliary pole part extends at least to the vicinity of an adjacent permanent-magnet pole of the first pole line. 46. The electric motor of claim 45 wherein each permanent-magnet pole of each pole group of the first pole line is asymmetrical in shape with respect to a line transverse to the first pole line and comprises a main pole part and an auxiliary pole part which projects from the main pole part in the preferential direction of relative movement of the second motor part.
This is a continuation of continuation of application Ser. No. 08/973,185, filed Nov. 26, 1997, and claims the benefit of, now U.S. Pat. No. 6,204,587 B1, issued Mar. 20, 2001, which is a 371 of PCT/SE96/00704, filed on May 30, 1996.
This invention relates to a self-starting brushless electric motor of the type which comprises reluctance poles (ferromagnetic salient poles) at least on one of the two relatively moving motor parts and one or more permanent-magnetic poles in the pole system.
The permanent-magnet poles, both symmetrical and asymmetrical, may have skewed ends or edges, i.e. edges running at an angle to the direction of the rotor axis. In some cases such skewing of the edges of the permanent-magnet poles may be extremely beneficial to the function of the motor. Such skewed edges need not be embodied in geometric shapes. It is sufficient for the edges to consist of demarcation lines (demarcation zones) relating to the imprinted magnetic polarisation (in, for example, a permanent-magnet pole), i.e., they are imprinted when the permanent-magnet poles are magnetized.
Assuming that in a rotary motor chosen by way of example both the leading ends and the trailing ends of both the stator poles and the rotor poles extend axially, magnetic asymmetry of a stator pole could in most cases in principle be observed in the following way. The rotor of the motor is replaced with a homogenous ferromagnetic cylinder of the same diameter as the rotor and the flux density in the air gap is measured along an axially extending line on the cylinder surface as the cylinder is rotated to move the line in the preferential direction of rotation past the pole. A graph showing the measured flux density (as averaged over the length of the line) versus the angular position of the line relative to the pole would rise, more or less steadily or in more or less distinct steps, from a point near zero at the leading end of the pole, to a roughly constant value under the main portion of the pole and then decline steeply at the trailing end. If the pole were magnetically symmetric instead, the graph would by symmetrical and resemble a Gaussian curve.
Magnetic pole asymmetry can also be achieved by providing a permanent-magnet pole with different radial dimensions at the leading and trailing ends, respectively, (i.e. by giving the air gap at the pole a width that varies in the direction of the relative movement of the rotor parts) but giving it a uniformly strong magnetization over its entire volume.
In a corresponding manner, magnetic asymmetry resulting from asymmetric positioning of poles may also exist in the rotor. For example, in pole row on a rotor comprising permanent-magnet poles of alternating polarity, the North-pole permanent-magnet poles may be displaced in either direction from a central position between the South-pole permanent-magnet poles with all like poles substantially equally spaced.
It should be noted that in the context of the present invention a pole group (pole unit) may comprise a single pole or a plurality of poles associated with a magnetizing coil.
The invention will now be described in more detail with reference to a number of exemplifying embodiments shown schematically in the accompany drawings.
FIG. 1F is similar to FIG. 1E but shows the starting position. It does not show the rotor in cross-section, but instead shows the rotor in dash-out outline.
FIGS. 13A to 13D are developed view resembling FIG. 1B of pole combinations which differ from each other in respect of the shape and placement of a permanent-magnet pole on the stator.
Moreover, in all embodiments shown in the drawings, the asymmetry of the stator and/or the rotor poles is directed such that the preferential starting directing of the rotor is counterclockwise.
The stator 11 has two diametrically opposite pole groups. Each pole group comprises two salient ferromagnetic poles 13S, also called reluctance poles, spaced from each other circumferentially with a permanent-magnet pole 14A arranged between them. The surfaces of these poles 14A facing the rotor are located on a cylindrical surface that is concentric with the axis of rotation 12A of the rotor. The poles on the stator collectively form a first pole row or pole line.
On the outside of the rotor 12, distributed uniformly around its periphery, are four salient ferromagnetic poles 16A, also called reluctance poles. The surfaces of these poles facing the stator are located on a cylinder that is concentric with the axis of rotation 12A, a short distance from the cylinder containing the pole surfaces of the stator, so that the pole surfaces of the stator and those of the rotor form an air gap 17 between them. The pole pitch of the rotor 12 corresponds to the spacing of the reluctance poles 13S within each pole group on the stator 11. The poles on the rotor collectively from a second pole row or pole line.
In the embodiment shown in FIGS. 1A to 1D, all the poles 13S , 14A on the stator 11 and the poles 16A on the rotor 12 are located in the same plane perpendicular to the axis of rotation, so that during all poles on the rotor pass over and interact with all poles on the stator. The motor may of course have several axially separated sets of pole groups arranged in this manner. Furthermore, instead of being located in closed paths or rows running peripherally around the rotor, the poles on each rotor part may be arranged, for example, on helical paths.
FIG. 1B shows a developed view of one of the pole groups of the stator and the rotor in FIG. 1A as viewed from within the air gap 17 and with the rotor poles displaced axially in relation to the stator pole group. The parallel dash-dot lines R and S indicate the direction of the relative movement between rotor and stator. The dash-dot lines are also lines (alternatively described as paths, circles, or rows) along which the poles are deployed. The dash-dot line L perpendicular thereto represents the centre line between the stator poles. The position of the stator and rotor poles in relation to each other corresponds to the relative position shown in FIG. 1A and is the stable position the rotor assumes in relation to the stator when current is supplied to the winding 15 so that the reluctance poles 13S tend to keep the rotor poles 16A in an attracted or indrawn position with the main pole part opposite to the reluctance poles.
At the same time, the spacing of the other tow rotor poles 16, the upper left and the lower right rotor poles, from the permanent-magnet poles 14A is substantial so that the permanent-magnet poles only apply an insignificant clockwise torque to the rotor.
FIG. 1E includes a graph representative of an exemplary embodiment of the motor shown in FIGS. 1A to 1D which shows the pull-in force F acting between the permanent-magnet poles 14 and the rotor reluctance poles 16 versus the overlap position of d of the leading end 16′′ of the rotor reluctance poles 16 during the pull-in movement from the indrawn position to the starting position. In the right-hand portion of FIG. 1E the indrawn position of the rotor reluctance pole 16A is shown in dash-dot lines.
The graph shows the pull-in force F acting on the rotor reluctance pole 16 for different amounts of overlap (positive and negative) between the auxiliary pole part 14′ of the permanent-magnet pole 14A and the auxiliary pole part 16′ of the rotor reluctance poles 16A in the indrawn position.
From FIG. 1E it is apparent that if the overlap in the indrawn position is −1 mm, that is, if the leading end 16′′ of the reluctance pole 16 is spaced 1 mm in the negative or clockwise direction from the permanent-magnet pole, the pull-in force is quite small. If the leading end 16′′ is opposite the end of the auxiliary pole part 14″ (zero overlap), the pull-in force is substantially greater, and for a positive overlap of about 1 mm the pull-in force on the auxiliary pole part 16″ is at or near its maximum where it is three to four times the pull-in force for a negative overlap of about 1 mm. The asymmetry of the stator permanent-magnet pole 14 in conjunction with the asymmetry of the rotor reluctance pole 16 thus produces a dramatic increase of the initial value of the pull-in force in comparison with the case where only the rotor reluctance pole is asymmetrical as in the motor disclosed in WO92/12567. This increase of the pull-in force broadens the field of application of the motor according to the invention.
Moreover, FIG. 1E shows that during the counterclockwise pull-in movement of a rotor reluctance pole 16A from the indrawn position to the starting position, the permanent-magnet pole 14A will exert a substantial attraction force on the rotor reluctance pole throughout a circumferential distance which is greater than the circumferential dimension of the permanent-magnet pole 14A: from a position in which the leading end 16′′ is opposite to or only slightly spaced in the clockwise direction from the end 14′′ of the auxiliary pole part 14″ of the permanent-magnet poles 14A up to a point in which the leading end 16′′ is well past the permanent magnet pole.
The embodiments illustrated in the other figures are described only insofar as they differ from the embodiment shown in FIGS. 1A-1D. The same designations are used throughout for all embodiments, the suffix letter A or S indicating asymmetrical or symmetrical. Unless otherwise stated, �symmetry� and �asymmetry� with regard to the poles relates to their magnetic symmetry or asymmetry rather than their geometrical symmetry or asymmetry (which may or may not correspond to the magnetic symmetry or asymmetry).
The motor pole groups of the motor in FIGS. 8A, 8B have only asymmetrical reluctance poles 13A and thus no permanent-magnet poles, and the rotor is very similar to that in FIGS. 4A, 4B and 6A, 6B.
In the motor in FIGS. 9A, 9B, stator pole groups are used which have pole combination corresponding to that in the motor in FIGS. 7A, 7B�an asymmetrical reluctance pole 13A, a symmetrical reluctance pole 13S and an asymmetrical permanent-magnet pole 14A�together with symmetrical permanent-magnet poles 18SN, 18SS of alternating polarity on the rotor.
II. Asymmetrical reluctant poles on the stator
Reluctance poles on the rotor
a. Asymmetrical reluctant poles FIG. 2
b. Symmetrical reluctant poles
More particularly, the motor shown in FIGS. 12A, 12B comprises a stator 11 having reluctance poles 13S similar to those shown in FIGS. 1A to 1D. The rotor 12 also resembles the rotor in FIGS. 1A to 1D, except that its poles 16 are provided with auxiliary pole parts 16′ both at the leading end and at the trailing and the these auxiliary pole parts are of lesser circumferential dimension.
FIGS. 13A and 13D are views corresponding to FIGS. 1B, 2B, 3B etc. and serve to further elucidate the concept of magnetically symmetrical and asymmetrical positioning of a permanent-magnet pole between a pair of reluctance poles on the stator. These four figures show four different shapes of the permanent-magnet pole together with a stator and rotor reluctance pole combination which is the same in all figures and similar to that in FIGS. 1A and 1B. All four figures show the rotor reluctance poles 16A in the starting position, that is magnetically aligned with the permanent-magnet pole 14S (FIG. 13A) or 14A (FIGS. 13B to 13D), the winding associated with the stator pole group being currentless.
In FIGS. 14A and 14B the modification is exemplified for the reluctance poles of the stator of the motor shown in FIGS. 1A-1D, namely the stator reluctance pole 13S to the right in the upper stator pole group. FIG. 14A shows the shortened reluctance pole portion of one plate 11A while FIG. 14B shows the full-length reluctance pole portion of the neighbouring plate 11C. In the region near the air gap 17 this portion is provided with three recesses 11D in the form of elongate openings which have a closed contour and thus are not connected with the curve edge 11E facing the air gap 17. The three recesses are uniformly distributed along the length of the curved edge.
ΔB2=ΔB1 (f1F2){fraction (1/1.2)} is helpful. In this equation, ΔB and f represent respectively the induction swing and the operating frequency, the indices 1 and 2 denoting two different operating conditions. As is immediately apparent from the equation, an increased operating frequency with unchanged iron losses calls for a reduction of the induction swing which is less than directly proportional to the increase of the operating frequency. For example, a doubling of the operating frequency requires a reduction of the induction swing to 56% of its previous value for the iron losses to remain unchanged. At elevated operating frequencies it becomes possible to adjust the iron and copper losses so that they become approximately equal which is optimal for torque generation. Consequently, the flux density may be chosen higher than the flux density corresponding to unchanged iron losses.
These discs may alternatively be designed without individually closed flux paths and are instead connected by axially directed flux paths. Examples of such an arrangement can be found in WO90/02437. The �motor discs� can be magnetized by common coils for two �motor discs� for example.
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