U.S. patent number RE31,278 [Application Number 06/206,159] was granted by the patent office on 1983-06-14 for brushless d-c motor.
This patent grant is currently assigned to Papst Motoren GmbH & Co., KG. Invention is credited to Fritz Schmider.
United States Patent |
RE31,278 |
Schmider |
June 14, 1983 |
Brushless D-C motor
Abstract
A preferably axial air gap motor has coreless armature stator
windings and a permanent magnet rotor. Sensors, such as Hall
generators, are provided to sense the rotary position of the rotor
and control switching of current to the respective armature
windings. The stator armature windings have a maximum of two
magnetically active coil sections per pole of the multi-polar
rotor, preferably arranged as flat round coils located on the
stator in diametrically arranged configuration, the angular spacing
between imaginary diametrical lines through the coils being,
however, non-uniform over the rotor circumference, and matched to
the spacing of rotor poles, the larger angular gaps between the
coils providing space on the stator for the sensors and electronic
circuitry. In a preferred embodiment, the rotor has numbers of
poles divisible by eight.
Inventors: |
Schmider; Fritz (Hornberg,
DE) |
Assignee: |
Papst Motoren GmbH & Co.,
KG (St. Georgen, DE)
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Family
ID: |
5915970 |
Appl.
No.: |
06/206,159 |
Filed: |
November 12, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
576650 |
May 12, 1975 |
04125792 |
Nov 14, 1978 |
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Foreign Application Priority Data
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May 18, 1974 [DE] |
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2424290 |
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Current U.S.
Class: |
310/268;
310/156.34 |
Current CPC
Class: |
H02K
29/08 (20130101) |
Current International
Class: |
H02K
29/06 (20060101); H02K 29/08 (20060101); H02K
003/04 (); H02K 029/02 () |
Field of
Search: |
;318/138,254,318
;310/68,156,268 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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269277 |
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Mar 1969 |
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AU |
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1538749 |
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Dec 1966 |
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DE |
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1907822 |
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Feb 1969 |
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DE |
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2143752 |
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Sep 1971 |
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DE |
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2240717 |
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Aug 1972 |
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DE |
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2423665 |
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May 1974 |
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DE |
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1412365 |
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Aug 1965 |
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FR |
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1551886 |
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Nov 1968 |
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FR |
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1138156 |
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Dec 1968 |
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GB |
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1218897 |
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Jan 1971 |
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GB |
|
1237776 |
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Jun 1971 |
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GB |
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1240604 |
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Jul 1971 |
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GB |
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1262980 |
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Feb 1972 |
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GB |
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1323342 |
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Jul 1973 |
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GB |
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Other References
Radio Mentor (German Mag. "ME"), vol. 40, No. 2, (1974), pp.
56-58..
|
Primary Examiner: Hickey; Robert J.
Attorney, Agent or Firm: Kasper; Horst M.
Claims
What is claimed is:
1. A slow speed brushless speed controlled d-c motor having a
coreless stator winding and a rotary multipolar permanent magnet
rotor which in operation interacts with a rotary field produced by
the coreless stator winding, and a sensor arrangement controlled by
the rotary position of the rotor connected to control current flow
through the stator winding;
wherein the stator winding has a maximum of two magnetically active
coil sections per pole of the multipolar rotor two coil sections
forming a set;
the coil sections are located in two superposed layers; and a
number of coil sections (62) corresponding to the number of pairs
of poles are interconnected and symmetrically distributed in one
layer and the same number of coil sections (63) are symmetrically
distributed in the second layer of the two layer winding, the coil
sections of the second layer being displaced by an angle (.alpha.)
relative to the coils of the first layer;
wherein the displacement angle (.alpha.) is an odd multiple of
90.degree.-el and the maximum width of the coils is about
360.degree.-el; means deriving a control signal representative of
speed of rotation of the rotor;
and means controlling current flow through said stator coil
sections in dependence on said control signal.
2. Motor according to claim 1, wherein the displacement angle
(.alpha.) is 90.degree. electrical.
3. Motor according to claim 2, wherein the coil sections in one
plane are connected in series.
4. Motor according to claim 2, wherein the coil sections in one
plane are wound in bifilar manner (62', 62") and are connected in
series.
5. Motor according to claim 2, wherein the coil sections in one
plane are unidirectionally connected in series so that, when
current flows through them, they produce magnetic fields having the
same direction.
6. Motor according to claim 1, wherein the motor is an axial air
gap motor;
and the coil sections are constructed as flat circular coils (62,
63).
7. Motor according to claim 1, wherein the motor is an eight-pole
motor;
and two diametrically opposite interconnected coil sections form an
interconnected set.
8. Motor according to claim 7, wherein the coil sections are
located on the motor such that imaginary lines passing through the
diametrically opposite coil sections of the sets form an angle with
each other of 90.degree.-el. or an odd multiple thereof.
9. Motor according to claim 7, wherein the coil sections are
located on the motor such that imaginary lines passing through the
diametrically opposite coils of the pairs of coils form an angle of
450.degree.-el. and 270.degree.-el. respectively and wherein the
sensor arrangement (68, 69, 107) for determining the rotary
position of the rotor (44) is located between the coils including
the larger angular range of 450.degree.-el.
10. Motor according to claim 1, wherein the coil sections form a
single winding;
and the means controlling current flow through said coil sections
control the current to flow therethrough, alternately, in opposite
directions to produce magnetic fields having, sequentially,
opposite direction of flux.
11. A brushless d-c motor having a coreless stator winding and a
rotary multipolar permanent magnet rotor which in operation
interacts with a rotary field produced by the coreless stator
winding, and a sensor arrangement controlled by the rotary position
of the rotor connected to control current flow through the stator
winding;
wherein the stator winding has a maximum of two magnetically active
coil sections per pole of the multipolar rotor, for each m coil, a
magnetically active m coil section and a magnetically active m+1
coil section per pole are provided, and the successive coil
sections are displaced relative to one another by the same
angle;
respective m-th and (m+)th magnetically active coil sections are
combined to form a single coil;
and wherein the coil sections are formed by a single coil (99, 100,
101, 102, 138, 139, 142, 143) per pole, of approximately n times
the number of ampere turns of an equivalent set of overlapping
individual m coils displaced by 90.degree.-el. to provide said
rotary field, said single coils being arranged in non-overlapping
manner to obtain a single layer winding.
12. Motor according to claim 11, wherein the motor is an axial air
gap motor;
and the coil sections are constructed as flat circular coils (62,
63).
13. Motor according to claim 11, wherein the motor is an eight-pole
motor;
and two diametrically opposite interconnected coil sections form an
interconnected set.
14. Motor according to claim 11, wherein the permanent magnet rotor
has a number of poles integrally divisible by 4.
15. Motor according to claim 11, wherein, the placement of said
single coils and their number of ampere turns is symmetrical
relative to the motor axis of rotation.
16. Motor according to claim 15, wherein the motor has a number of
poles of at least 8; and wherein n = 2.
17. Motor according to claim 16, wherein (FIG. 4) the motor is an
8-pole motor, four bifilar coils are provided, two pairs of coils
(99, 101; 100, 102) each are unidirectionally connected in series
and two coils of each pair of coils are located diametrically
opposite each other with respect to the axis of rotation of the
motor.
18. Motor according to claim 17, wherein the coils are located on
the motor such that imaginary lines passing through the
diametrically opposite coils of the pairs of coils form an angle of
450.degree.-el. and 270.degree.-el. respectively and wherein the
sensor arrangement (68, 69, 107) for determining the rotary
position of the rotor (44) is located between the coils including
the larger angular range of 450.degree.-el.
19. Motor according to claim 15, wherein (FIG. 14) the motor is a
16-pole motor and wherein n is equal to or less than four.
20. Motor according to claim 15, wherein (FIG. 14) the motor is a
16-pole motor, four coils (138, 139, 142, 143) are provided, two
pairs of coils each are connected in series and two coils of each
pair of coils are located diametrically opposite each other with
respect to the axis of rotation of the motor.
21. Motor according to claim 20, wherein the coils are located on
the motor such that imaginary lines passing through the
diametrically opposite coils of the pairs of coils form an angle of
450.degree.-el. or less.
22. Motor according to claim 15, wherein (FIG. 16) the motor is a
24-pole motor and wherein n is equal to or less than 5.
23. Motor according to claim 15, wherein (FIG. 16) the motor is a
24-pole motor, four coils are provided, two pairs of coils each are
connected in series, and two coils of each pair of coils are
located diametrically opposite each other with respect to the axis
of rotation of the motor.
24. Motor according to claim 23, wherein the coils are located on
the motor such that imaginary lines passing through the
diametrically opposite coils of the pairs of coils form an angle of
about 97.5.degree. mechanical.
25. Motor according to claim 11, wherein the motor is a flat, axial
air gap motor and the coils are shaped as flat, circular coils.
26. Motor according to claim 11, in combination with a speed
control circuit; and transducer means provided supplying an actual
speed pulse value signal having a pulse count per rotor rotation
which is high relative to the motor speed.
27. Motor according to claim 11, wherein the motor is a slow speed
motor adapted for direct drive of
phonograph reproducing apparatus, further including speed control
means deriving a control signal representative of speed of rotation
of the rotor;
and means controlling current flow through said coil sections in
dependence on said control signal.
28. Motor according to claim 11, in combination with a speed
control circuit; and transducer means supplying an actual speed
pulse signal having a pulse count per rotor rotation which is high
relative to the motor speed.
29. Motor according to claim 11, wherein the motor is an axial air
gap motor.
30. Motor according to claim 11, wherein the coil sections form a
single winding;
and the means controlling current flow through said coil sections
control the current to flow therethrough, alternately, in opposite
directions to produce magnetic fields having, sequentially,
opposite direction of flux.
31. Axial air gap motor comprising a permanent magnet rotor (54)
having alternate zones of magnetization forming magnet poles;
a coreless stator winding comprising at least four coils
(99-102);
transducer means interacting with the magnetic field of the rotor
to provide a rotor position signal;
and circuit means selectively energizing the coils to provide a
rotary field for interaction with the rotor poles,
wherein
the coils are flat coils in which two coils, each form a pair
located opposite each other with respect to the axis of rotation of
the rotor
oppositely located coils of one pair are connected in series and
unidirectionally wound to provide for current flow therethrough in
the same direction;
and the coils are distributed non-uniformly circumferentially with
respect to said axis of rotation such that imaginary lines passing
through the opposite coils of a pair form alternatingly electrical
angles with respect to each other which are odd whole number
multiples of 90.degree.-el.
32. Motor according to claim 31, wherein the permanent magnet rotor
has a number of poles integrally divisible by 4.
33. Motor according to claim 31, wherein the motor is an eight-pole
motor, four coils are provided and the coils are spaced by angles
of 270.degree.-el. and 450.degree.-el., respectively.
34. Motor according to claim 31, wherein the rotor has a number of
poles integrally divisible by eight, at least four coils are
provided, arranged in coil pairs and spaced mechanically,
approximately circumferentially with respect to the axis of
rotation of the rotor to interact with the magnetic field of the
permanent magnet rotor as determined by the relationship:
wherein the "large angle" and "small angle" columns respectively
relate to the mechanical angles between said imaginary diametrical
lines, the circumferentially non-uniform placement of said coils
resulting in alternately larger and smaller included angles
therebetween.
35. Motor according to claim 31, wherein the transducer means are
arranged on a carrier plate (107) arranged between two adjacent
flat coils.
36. Motor according to claim 31, wherein the coils are constructed
as circular coils (62, 63).
37. Motor according to claim 31, wherein the coils are located
diametrically opposite each other with respect to the axis of
rotation of the rotor.
38. Motor according to claim 31, wherein the transducer means and
at least part of the energization circuit means are located in the
space between the coils spaced circumferentially from each other by
the greater one of said angles.
39. Motor according to claim 33, wherein the sensor arrangement
(68, 69, 107) for determining the rotary position of the rotor (44)
is located between the coils including the larger angular range of
450.degree.-el.
40. Motor according to claim 31, wherein the motor is a slow speed
motor adapted for direct drive of
phonograph reproducing apparatus, further including speed control
means deriving a control signal representative of speed of rotation
of the rotor;
and means controlling current flow through said coil sections in
dependence on said control signal.
41. Motor according to claim 31, in combination with a speed
control circuit; and transducer means supplying an actual speed
pulse signal having a pulse .[.counter.]. .Iadd.count .Iaddend.per
rotor rotation which is high relative to the motor speed.
42. Electric motor comprising a permanent magnet rotor (54) having
alternate zones of magnetization forming magnet poles;
a coreless stator winding comprising at least four thin coils
(99-103);
transducer means interacting with the magnetic field of the rotor
to provide a rotor position signal;
and circuit means selectively energizing the coils to provide a
rotary field for interaction with the rotor poles,
wherein
the coils are thin flat coils in which two coils, each, form a pair
located opposite each other with respect to the axis of rotation of
the rotor and wherein oppositely located coils are connected in
series to provide for current flow therethrough in the same
direction;
and the coils are distributed non-uniformly circumferentially with
respect to said axis of rotation such that imaginary lines passing
centrally through opposite coils of a pair form alternatingly
electrical angles with respect to each other which are odd whole
number multiples of 90.degree.-el.
43. Motor according to claim 42, wherein the coils are bifilar
coils.
44. Motor according to claim 42, wherein the permanent magnet rotor
has a number of poles integrally divisible by 4.
45. Motor according to claim 42, wherein the motor is an eight-pole
motor, four coils are provided and the coils are spaced by angles
of 270.degree.-el. and 450.degree.-el., respectively.
46. Motor according to claim 42, wherein said motor is an axial air
gap motor.
47. Brushless d-c motor having a .[.coreless.]. permanent magnet
rotor;
and a .Iadd.coreless .Iaddend.stator coil arrangement having two
sets of coil sections (a, b) forming a single layer winding to
generate a rotary field on the rotor,
wherein the coil sections of any set being symmetrically placed
along the circumference of the rotor, one set being offset with
respect to the other by (2k + 1).times.90.degree.-el., wherein k=0,
1, 2, 3, 4 . . . n;
at least two coil sections form a set and these coil sections are
serially connected and unidirectionally wound with respect to each
other, and spaced along the circumference by whole multiples of
360.degree.-el.
48. Motor according to claim 47, wherein the coil sections in one
plane are wound in bifilar manner (62', 62") and are connected in
series.
49. Motor according to claim 47, wherein the coil sections form a
single winding;
and means are provided controlling current flow through said coil
sections, alternately, in opposite direction.
50. Motor according to claim 47, wherein the motor is a slow speed
motor adapted for direct drive of phonograph reproducing apparatus,
further including speed control means deriving a control signal
representative of speed of rotation of the rotor;
and means controlling current flow through said coil sections in
dependence on said control signal.
51. Motor according to claim 47, in combination with a speed
control circuit; and transducer means supplying an actual speed
pulse signal having a pulse count per rotor rotation which is high
relative to the motor speed.
52. Motor according to claim 47, wherein said motor is an axial air
gap motor. .Iadd. 53. Axial air gap motor comprising a permanent
magnet rotor (54) having alternate zones of magnetization forming
magnet poles;
a coreless stator winding comprising at least four coils
(99-102);
transducer means interacting with the rotor to provide a rotor
position signal;
and circuit means selectively energizing the coils to provide a
rotary field for interaction with the rotor poles,
wherein
the coils are flat coils in which two coils located opposite each
other with respect to the axis of rotation of the rotor form a
pair;
oppositely located coils of one pair are connected to produce
magnetic fields having the same direction;
and the coils are distributed non-uniformly circumferentially with
respect to said axis of rotation such that imaginary lines passing
through the opposite coils of a pair form alternatingly electrical
angles with respect to each other which are odd whole number
multiples of 90.degree.-el. .Iaddend..Iadd. 54. Motor according to
claim 53, wherein the permanent magnet rotor has a number of poles
integrally divisible by 4. .Iaddend..Iadd. 55. Motor according to
claim 53, wherein the motor is an eight-pole motor, four coils are
provided and the coils are spaced by angles of 270.degree.-el and
450.degree.-el, respectively. .Iaddend. .Iadd. 56. Motor according
to claim 53, wherein the rotor has a number of poles integrally
divisible by eight, at least four coils are provided, arranged in
coil pairs and spaced mechanically, approximately circumferentially
with respect to the axis of rotation of the rotor to interact with
the magnetic field of the permanent magnet rotor as determined by
the relationship: .Iaddend.
wherein the "large angle" and "small angle" columns respectively
relate to the mechanical angles between said imaginary diametrical
lines, the circumferentially non-uniform placement of said coils
resulting in alternately larger and smaller included angles
therebetween. .Iaddend..Iadd. 57. Motor according to claim 53,
wherein the transducer means are arranged on a carrier plate (107)
arranged between two adjacent flat coils. .Iaddend..Iadd. 58. Motor
according to claim 53, wherein the coils are constructed as
circular coils (62, 63). .Iaddend. .Iadd. 59. Motor according to
claim 53, wherein the coils are located diametrically opposite each
other with respect to the axis of rotation of the rotor.
.Iaddend..Iadd. 60. Motor according to claim 53, wherein the
transducer means and at least part of the energization circuit
means are located in the space between the coils spaced
circumferentially from each other by the greater one of said
angles. .Iaddend..Iadd. 61. Motor according to claim 55, wherein
the sensor arrangement (68, 69, 107) for determining the rotary
position of the rotor (44) is located between the coils including
the larger angular range of 450.degree.-el. .Iaddend. .Iadd. 62.
Motor according to claim 53, wherein the motor is a slow speed
motor adapted for direct drive of
phonograph reproducing apparatus, further including speed control
means deriving a control signal representative of speed of rotation
of the rotor;
and means controlling current flow through said coil in dependence
on said control signal. .Iaddend..Iadd. 63. Motor according to
claim 53, in combination with a speed control circuit; and
transducer means supplying an actual speed pulse signal having a
pulse counter per rotor rotation which is high relative to the
motor speed. .Iaddend. .Iadd. 64. Motor according to claim 53
wherein said transducer means interacting with the rotor comprises
at least one galvanomagnetic sensor element. .Iaddend. .Iadd. 65.
Motor according to claim 75, said sensor element comprising a
Hall-Generator. .Iaddend. .Iadd. 66. Electric motor comprising a
permanent magnet rotor (54) having alternate zones of magnetization
forming magnet poles;
a coreless stator winding comprising at least four thin coils
(99-103);
transducer means interacting with the rotor to provide a rotor
position signal;
and circuit means selectively energizing the coils to provide a
rotary field for interaction with the rotor poles,
wherein
the coils are thin flat coils and two coils, located opposite each
other with respect to the axis of rotation of the rotor form a pair
and wherein oppositely located coils are connected to provide for
current flow therethrough in the same direction;
and the coils are distributed non-uniformly circumferentially with
respect to said axis of rotation such that imaginary lines passing
centrally through opposite coils of a pair form alternatingly
electrical angles with respect to each other which are odd whole
number multiples of 90.degree.-el. .Iaddend..Iadd. 67. Motor
according to claim 64, wherein the coils are bifilar coils.
.Iaddend..Iadd. 68. Motor according to claim 64, wherein the
permanent magnet rotor has a number of poles integrally divisible
by 4. .Iaddend..Iadd. 69. Motor according to claim 64, wherein the
motor is an eight-pole motor, four coils are provided and the coils
are spaced by angles of 270.degree.-el and 450.degree.-el.,
respectively. .Iaddend. .Iadd. 70. Motor according to claim 64,
wherein said motor is an axial air gap motor. .Iaddend. .Iadd. 71.
Motor according to claim 64 wherein said transducer means
interacting with the rotor comprises at least one galvanomagnetc
sensor element. .Iaddend. .Iadd. 72. Brushless d.c. motor having a
permanent magnet rotor;
and a coreless stator coil arrangement having two sets of coil
sections (a, b) forming a single layer winding to generate a rotary
field on the rotor,
wherein the coil sections of any set being symmetrically placed
along the circumference of the rotor, one set being offset with
respect to the other by (2k+1).times.90.degree.-el, wherein k=0, 1,
2, 3, 4 . . . n;
at least two coil sections form a set and these coil sections are
connected to provide for current flow therethrough in the same
direction and spaced along said circumference by whole multiples of
360.degree.-el. .Iadd. 73. Motor according to claim 69, wherein the
coil sections in one plane are wound in bifilar manner (62', 62")
and are connected in series. .Iaddend..Iadd. 74. Motor according to
claim 69, wherein the coil sections are serially connected and
unidirectionally wound with respect to each other. .Iaddend..Iadd.
75. Motor according to claim 69, wherein the motor is a slow speed
motor adapted for direct drive of phonograph reproducing apparatus,
further including speed control means deriving a control signal
representative of speed of rotation of the rotor;
and means controlling current flow through said coil sections in
dependence on said control signal. .Iaddend..Iadd. 76. Motor
according to claim 69, in combination with a speed control circuit;
and transducer means supplying an actual speed pulse signal having
a pulse count per rotor rotation which is high relative to the
motor speed. .Iaddend..Iadd. 77. Motor according to claim 69,
wherein said motor is an axial air gap motor. .Iaddend..Iadd. 78.
Motor according to claim 77, said sensor element comprising a
Hall-Generator. .Iaddend.
Description
Cross reference to related patent and application: U.S. Pat. No.
3,845,339; U.S. Ser. No. 402,259, now U.S. Pat. No. 3,924,166,
Doemen, both assigned to the assignee of the present
application.
The invention relates to brushless d-c motors with a coreless
stator winding and a multipolar permanent magnet rotor which, in
operation, interacts with a rotary field produced by the coreless
stator winding, controlled by the rotary position of the rotor by
means of a sensor arrangement.
A motor of this type is known from U.S. Pat. No. 3,845,339,
assigned to the assignee of this application. This motor may be
used as a slow speed motor for direct drive of record players at
331/3 or 45 r.p.m.; for such use it is preferably constructed as an
8-pole motor. Its coreless (i.e. air-core) stator winding is a
two-layer winding, wherein two layers of 8 series-connected bifilar
windings are used; per motor pole 4 magnetically active coil
sections are used.
This motor has excellent running characteristics and the described
arrangement with 16 coils has the special advantage of permitting
the use of the control system invention described in U.S. Ser. No.
402,259, now U.S. Pat. No. 3,924,166, Doemen, assigned to the
assignee of this application, which makes the use of a
tacho-alternator unnecessary.
It is an object of the invention to improve this known motor
without any loss of its qualities.
Subject matter of the present invention: A motor, generally of the
type described in U.S. Pat. No. 3,845,339, and preferably a flat or
axial air gap motor has, preferably, a 4-phase stator winding with
a maximum of two magnetically active coil sections per pole of the
multipolar rotor.
If individual coils are used, as in the motor of U.S. Pat. No.
3,845,339, the number of coils in such a motor can be halved; in
that case, for comparable power output, larger coils are required
whose coil width is approximately twice as large as that of the
hitherto used coils. These larger coils can be manufactured and
assembled more easily, so that a cheaper motor is obtained.
Furthermore, larger free sections are obtained between the
magnetically active coil sections which can be utilized for the
positioning of switching members, e.g. of sensors in the manner of
Hall generators. The motor according to U.S. Pat. No. 3,845,339
uses narrow webs to separate the individual, trapezoidally wound
coils causing a not inconsiderable pitch factor; the wider,
magnetically active coil sections according to the invention have
no such web so that the pitch factor is improved. Thus, there is
only a small loss of powder with the same size of motor as compared
with one having twice the number of coils. The larger number of
smaller coils, given a predetermined motor size, results in a
better copper factor; the somewhat smaller copper factor obtained
with an arrangement according to the invention is, however,
compensated by the better pitch factor.
According to a feature of the invention, the motor can
advantageously be so constructed that round coils are used and the
motor is a flat motor. Round coils are much easier to manufacture
than trapezoidal coils and lead to only a slight power loss as
compared with trapezoidal coils.
In the case of motors with a number of poles which is integrally
divisible by at least 4 and preferably 8, a particularly simple
construction is obtained in that in place of each set of n
unidirectional coils being displaced relative to one another by
360.degree. electrical, or a multiple thereof, there is provided a
single coil having approximately n times the number of ampere turns
of the particular set of individual coils and said single coils are
arranged in non-overlapping fashion to obtain a single layer
winding. Such a construction is particularly suitable for 8-, 16-
or 24-pole motors where, as a result of the invention, a
particularly simple winding arrangement is obtained which leaves
plenty of space on the stator for the arrangement of electrical
components, e.g. Hall generators or other sensors, resistors,
transistors or other compounds. This provides a further
simplification in that, e.g. the signals from the sensors for the
rotor rotation position can be partly processed on the stator
itself, so that as compared with the known motor, the number of
supply lines is reduced which further simplifies assembly.
The invention will be described by way of example with reference to
the accompanying drawings, wherein:
FIG. 1 is a longitudinal section through a first embodiment of a
brushless d-c motor according to the invention along the line 1--1
of FIG. 2;
FIG. 2 is a section along the line 2--2 of FIG. 1;
FIG. 3 is a circuit diagram schematically showing the circuit and
the winding direction for the upper layer of the stator winding of
FIG. 1;
FIG. 4 is a second embodiment of a stator winding for the motor of
FIG. 1;
FIG. 5 is a section along the line 5--5 of FIG. 4;
FIG. 6 is a detail of the attachment of the stator plate according
to FIG. 5 in section along the line 6--6 of FIG. 4;
FIG. 7 is a circuit diagram showing schematically the circuit and
winding direction of the 4 coils of the stator arrangement
according to FIG. 4;
FIG. 8 is a schematic developed fragmentary of a prior art
motor;
FIGS. 9 and 10 are two schematic developed fragmentary views for
explaining the principles of the present invention, to the same
scale as FIG. 8;
FIG. 11 is a schematic view of a winding according to the invention
for a 12-pole motor;
FIG. 12 is a schematic view of a winding according to the invention
for a 20-pole motor;
FIGS. 13 and 14 are schematic views of two variants of a winding
according to the invention for a 16-pole motor;
FIGS. 15 and 16 are schematic views of two variants of a winding
according to the invention for a 24-pole motor; and
FIG. 17 is a schematic view of a control circuit for a brushless
d-c motor according to the invention.
FIG. 1 shows a first embodiment of a brushless d-c motor according
to the invention designed by the overall reference numeral 16. It
has a stationary hollow molding 17 with a bearing supporting tube
18 and lateral supporting arms 19, said arms having holes 20 on
their ends for attachment to an apparatus, e.g. the chassis of a
record player.
In the bearing supporting tube 18 is cast a sintered bushing 21.
Bushing 21 journals a shaft 23 whose lower end is provided with a
rounded tip 24 placed on a plastic plate 28 serving as an axial or
thrust bearing. The plastic plate 28 is fitted in a recess 29 of a
cover 30 and located on a rubber plate 31.
The cover 30 serves as a lower termination of a recess 32 of
molding 17. It is secured to molding 17 by screws 33. A gear wheel
34 made of plastic or constructed as a metal die casting is fixed
to shaft 23 inside recess 32; the gear wheel 34 can mesh through a
lateral opening 35 of recess 32 with another gear wheel (not
shown), e.g. in the case of a record player with the mechanism for
a record changer or the pick-up arm. A disk 36 which serves as an
axial auxiliary bearing is arranged between the top of gear wheel
34 and the bottom of the bearing supporting tube 18. A steel
bushing 40 is pressed on the upper end of shaft 23. Bushing 40 has
slot-shaped depressions 41 on its periphery. An approximately
bell-shaped aluminum casting 42 is anchored in depressions 41. A
soft iron plate 43 is cast into aluminum casting 42. It fulfills
two functions: (1) serving as a magnetic return path and (2)
keeping the penetration of a stray field emanating from the motor
directed towards the top of plate 43 as small as possible in order
to avoid hum in case the motor is used in a record player with a
magnetic sound pick-up system.
A magnet ring 44 made of ceramic magnetic material whose privileged
direction is in the axial direction is adhered to plate 43. This
magnet ring is axially alternately oppositely polarized, i.e. for
example North-South, South-North, North-South, etc. In FIG. 1 this
is schematically indicated by the letters N-S. The annular magnet
shown has eight such differently directed magnets which are
uniformly distributed about the said ring. Magnet ring 44
preferably is itself solid and in one piece, but it is also
possible to use individual magnets.
The magnet ring 44 is secured to plate 43 by a magnetizable
adhesive layer which remains plastic until cured. The downwardly
projecting rim 46 of casting 42 has bores 47 used for balancing
purposes. Furthermore, at the bottom of rim 46, a shoulder 48 is
provided against which abuts a soft iron magnetic return plate 49
which is drawn upwardly by the force of magnet ring 44. In the
motor 16 shown approximately in a scale of 1:1 on the original of
the annexed drawings, this force is about 3.5 kg-force. To secure
the return plate 49 during assembly, a plurality of lateral
assembly holes 53 are provided in edge 46 so that the plate 49 can
be gently mounted on shoulder 48 and can, if necessary, be removed
for repair purposes. In operation, plate 49 rotates with the rotor,
indicated by overall reference numeral 54, because it is supported
on shoulder 48 and is in frictional engagement therewith. Thus, the
force of magnet ring 44 does not act on axial bearing 24, 28 which
only has to carry the weight of rotor 54, plate 49 and optionally
additional parts which are mounted on rotor 54, for example, of a
turntable.
The stator, given the overall reference numeral 55, has an inner
bushing 56 which is pressed onto the outside of the bearing
supporting tube 18. It can also, however, be adhered to the bearing
supporting tube 18, or an attachment in accordance with FIG. 6 can
be used.
FIG. 2 shows a plan view of stator 55 prior to assembly. As shown,
it substantially comprises two superimposed pressboard panels 57
and 58 which in each case are provided with four recesses 61 in
each case displaced by 90.degree. mechanical relative to one
another for receiving corresponding round coils 62 (upper layer) or
63 (lower layer). The upper and lower coils are in each case
displaced by 90.degree. el. relative to one another, so that the
magnetically active coil sections 64 of the upper layer and 65 of
the lower layer (FIG. 9) alternate with one another with the same
angular spacings.
Both stator plates 57 and 58 are fixed to the central bushing 56.
In operation they are thus firmly connected to the bearing
supporting tube 18. The coils 62, 63 are in turn firmly secured to
plates 57, 58, e.g. by an adhesive, and form together therewith a
uniform stable structure.
The coils of one layer are in each case connected in series with
the same winding direction as shown in FIG. 3 relative to the
example of coil 62, one wire 62' of the bifilar winding being shown
by a continuous line and the other wire 62" being shown by a dotted
line. Printed conductors 67 which are provided on plates 57, 58 in
a conventional manner are used for connection purposes. Coils 62,
63 require only three terminals. As seen in FIG. 17, all the phase
windings S1 to S4 have one terminal connected to a positive
terminal 168 of a d-c source (not shown).
As shown in FIG. 2, a Hall generator 68 is secured to plate 58;
displaced by 90.degree. electrical relative thereto a second Hall
generator 69 is provided on the lower plate 57. In conventional
manner, these Hall generators are used for controlling the
commutation of the current between the individual phase windings.
The four series-connected upper round coils 62 form two phase
windings, and the four series-connected round coils 63 of the lower
layer form two further phase windings. FIG. 17 shows the
conventional circuitry for the Hall devices 68, 69.
The coil arrangement according to FIGS. 1 and 2 is explained with
reference to FIGS. 8 and 9. FIG. 8 shows the development of the
motor construction according to U.S. Pat. No. 3,845,339 with ring
magnet 44 and stator 55 which in that case has two coils per pole,
specifically coil 74 in the upper layer and coil 75 in the lower
layer. The width of these coils is not quite a pole pitch, i.e.
about 180.degree. electrical. Here, too, the coils of both the
upper layer and the lower layer each are connected in series but
with alternating winding directions, so that different current
directions occur in the magnetically active coil portions indicated
symbolically by crosses and dots; in conventional manner a cross
represents a current flowing into the plane of the drawing and a
point a current flowing out the plane of the drawing. In the upper
layer of FIG. 8, for example, starting at the left there are first
two adjacent coil sections 76, 77, wherein in each case the current
flows into the plane of the drawing, followed by two adjacent coil
sections 78, 79 where the current flows out of the plane of the
drawing and this is reversed in the next pair of coil sections 80,
81 and so on.
According to the invention, and as illustrated in FIG. 9, coil
section 76, 77 are combined into a single correspondingly larger
coil section 84 with the same current direction as are coil
sections 78, 79 to a correspondingly larger coil section 85 of the
same current direction. The same happens with corresponding coil
sections of the lower layer of FIG. 8, so that in the arrangement
according to FIG. 9, in place of the original two coil sections,
there is now only a single coil section; e.g. coil sections 86, 87,
88, 89 of FIG. 8 are replaced by coil sections 92, 93 in FIG. 9.
Actually, the coil sections in FIG. 9 can be connected in random
manner, e.g. as shown to form round coils with an average diameter
of approximately 360.degree. electrical.
As the arrangement according to FIG. 9 is substantially the
electrical equivalent to that of FIG. 8, it is possible, without
difficulty, to use the circuit according to application Ser. No.
402,259 now U.S. Pat. No. 3,924,166, Doemen therewith.
For specific numbers of poles, the coil arrangement according to
FIG. 2 or FIG. 9 can be further simplified. FIGS. 4 and 5 show this
relative to the example of a stator arrangement 55' for the 8-pole
motor of FIG. 1. This arrangement 55' has a relatively thick
insulating plate 95 which according to FIG. 6 can be fixed in
advantageous manner by means of ribbed nails 96 to protuberances
97, the latter being arranged around the bearing supporting tube
18. Plate 95 has four recesses 98 for receiving four round coils
99, 100, 101 and 102 which are secured in the said recesses by
means of a sealing compound 103, for which purpose lateral
half-moon-shaped recesses 104 are used wherein the sealing compound
is secured. As shown in FIG. 7, all four coils are wound in bifilar
manner and in each case the diametrically opposing coils are
unidirectionally connected in series, i.e. 99 with 101, and 100
with 102, so that once again four phase windings are obtained.
FIGS. 4 and 5 show that a printed circuit board 107 is riveted by
means of rivets 108 to plate 95. It carries the two Hall generators
68 and 69 which are displaced by 90.degree.-el. relative to one
another, as well as resistors 109 and other electrical components
110. This printed circuit board forms a small circuit to which only
seven connecting leads are connected, which represents a
considerable simplification. The assembly of printed circuit board
107 to stator plate 95 is made possible by the large gap between
coils 100 and 101, which according to FIG. 7 is 450.degree.-el. or
112.5.degree. mechanical.
FIG. 10 explains the coil arrangement according to FIGS. 4, 5 and
7. As can be seen in FIG. 9, the coils 64a and 64b have in each
case the same position relative to the poles of rotor magnet 44.
Thus, for example, coil 64b can be omitted and instead coil 64a can
be given twice as many turns so that, for example, coil 101 in FIG.
10 is obtained. In the same way, the two coils 65a and 65b of the
lower layer of FIG. 9 can be combined to form coil 100 of FIG. 10
and the same applies analogously for coils 99 and 102 in FIG. 10.
As a result of skillful combination, a coil arrangement is obtained
which can be placed in a single layer which is obviously very
advantageous from the manufacturing standpoint and also permits the
incorporation of printed circuit board 107.
In general, respective m-th and (m+2) th magnetically active coil
sections are combined to form a single coil, as is clearly apparent
from comparing the arrangement in FIGS. 9 and 10. To obtain
appropriate power output, the coil sections which are combined,
that is, formed by a single coil, such as coils 99, 100, 101, 102,
per pole, have approximately n times the number of ampere turns of
the equivalent set of overlapping individual coils (as explained in
connection with FIG. 9) and which are displaced by 90.degree.-el.
to provide the rotating rotor field. These single coils are
arranged in non-overlapping location to provide for the single
layer winding - see FIG. 10. The usual number for n=2, since
usually two overlapping coils are combined.
A control circuit according to FIG. 17 is particularly suitable for
a stator arrangement according to FIGS. 4, 5 and 7. In FIG. 17,
rotor R is provided with teeth 110 sensed by two series-connected
sensors 111, 112 displaced relative to one another by 180.degree.
mechanical and arranged on the stator, so that a speed-proportional
frequency is obtained, e.g. 400 pulses per revolution. This
frequency f is amplified in an amplifier 113, converted into an
actual speed voltage signal u in a digital-analog converter 114,
smoothed in a low-pass filter 115 and compared with a desired or
command value supplied via a line 116 in a computer 117. The output
signal of comparator 117 is amplified in an amplifier 118 and
controls the motor current via an npn transistor 119
series-connected with the four phase windings S1 to S4 of the
stator. In conventional manner, the outputs of Hall generators 68
and 69 control four npn transistors 122, 123, 124, 125, each of
which controls the current in the phase winding associated
therewith. With the coil arrangement according to FIGS. 4, 5 and 7,
such a regulator can easily regulate the speed of a low speed
brushless d-c motor, e.g. accurately to 331/3 r.p.m.
Obviously, the invention is not restricted to 8-pole motors,
although this number of poles represents a certain optimum because
the coils are still not too small and the magnetization of rotor
magnet 44 represents no difficulties.
FIGS. 11 to 16 show stator arrangements for different numbers of
poles, in each case the series-connected coils are characterized in
the same way. For example, a stator according to the invention for
a 12-pole motor has six coils 130, 131, 132, 133, 134, 135 which
are in each case wound in bifilar manner; the shaded coils 131, 133
and 135 are unidirectionally interconnected in series and form the
first two phase windings of the motor, and the unshaded coils 130,
132 and 134 which are also series-connected from the other two
phase windings. If two Hall generators displaced by 90.degree.-el.
relative to one another are placed on the stator in the correct
angular position, the control circuit of FIG. 7 can be used once
again. This also applies to the stator arrangements according to
FIGS. 13 and 16. In FIGS. 11 to 16 the distances between the
individual coils are given in mechanical degrees.
FIG. 12 shows a stator for a 20-pole motor which has 10 coils.
FIG. 13 shows a stator for a 16-pole motor with eight coils
137-144. The arrangement can be simplified by omitting some of the
symmetrically positioned coils, e.g. coils 137, 141, 140, 144, and
the arrangement according to FIG. 14 is then obtained, which is
extremely simple. On further simplifying in this way the
arrangement of FIG. 4, only two juxtaposed coils would be obtained
and this arrangement would be perfectly usable in special
cases.
FIG. 15 shows a stator for a 24-pole motor and FIG. 16 a further
simplified variant with only four coils. Thus, the number of poles
which can be integrally divided by eight leads to particularly
simple stator arrangements according to the present invention.
It is naturally possible, e.g. in the case of the arrangement
according to FIG. 15, to omit only half the coils and then double
the number of turns on the other coils. It is naturally also
possible in the case of FIGS. 14 and 16 to select others of the
remaining coils, e.g. the arrangement of FIG. 14 may use coils 140,
141 and 137, 144 of FIG. 13 instead of 138, 139 and 142, 143.
If (as known), the individual motor windings are controlled in such
a way that current can flow through the individual windings in both
directions, e.g. if the windings are controlled by a bridge
circuit, then it is possible to use unifilar coils in place of
bifilar coils in all cases. The invention may be used in the same
way. A bifilar coil can of course be replaced by two unifilar coils
arranged adjacent each other and "bifilar" is meant to include this
physical arrangement. It should be pointed out, however, that
bifilar coils, i.e. coils having substantially parallel-wound
wires, usually can be made more conveniently; their electrical
properties are almost identical, which is usually desirable.
As seen specifically in FIGS. 7, 14 and 16, imaginary lines passing
through the diametrically opposite coils of a pair form
alternatingly angles with respect to each other which are unequal.
The inequality can be determined from a consideration of FIGS. 9,
10, and 7, 14 and 16, respectively. Expressed in electrical
degrees, the sum of the angles, in electrical degrees, must be k
.multidot.360, in which k is a whole number of at least unity; the
angles between the coils themselves must be whole multiples of
90.degree.-el.
Various changes and modifications may be made, and features
described in connection with any one of the embodiments may be used
with any of the others within the scope of the inventive
concept.
Since the few coils used in a one layer winding, e.g. the winding
according to FIG. 7, or any of FIGS. 11 to 16, due to their large
copper volume are quite rigid and sturdy, they can be clamped at an
outer or inner portion thereof to a part of the motor structure,
e.g. by flanges as taught in German Patent No. 843,866, FIGS. 1 and
2, whilst the non-clamped portions thereof extend freely - in
cantilever fashion - into the airgap of the rotor without
additional support. This obviates the need for additional support
structure. e.g. the support plate 95 shown in FIG. 4, and makes
possible an extremely simple motor structure both for motors having
a coreless flat winding or for motors having a coreless cylindrical
winding.
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