Title: Electronically-commutated electric motor comprising coils with parallel axes
Abstract: The invention relates to an electronically commutated electric motor having a multi-pole magnetized permanent magnet, a plurality of flux guide units each of which features at least one flux collector section and one flux concentrator section, whereby each flux guide unit picks up a radial magnetic flux from the permanent magnet and redirects it into a transversal magnetic flux, and having a plurality of coils each of which is allocated to a flux guide unit and is arranged axially parallel to the permanent magnet.
Patent Number: 6,998,755 Issued on 02/14/2006 to Kloepzig, et al.
| Inventors:
|
Kloepzig; Markus (Spaichingen, DE);
Oelsch; Jürgen (Hohenroth, DE)
|
| Assignee:
|
Minebea Co., Ltd. (Nagamo-Ken, JP)
|
| Appl. No.:
|
487273 |
| Filed:
|
August 21, 2002 |
| PCT Filed:
|
August 21, 2002
|
| PCT NO:
|
PCT/EP02/09358
|
| 371 Date:
|
July 30, 2004
|
| 102(e) Date:
|
July 30, 2004
|
| PCT PUB.NO.:
|
WO03/026106 |
| PCT PUB. Date:
|
March 27, 2003 |
Foreign Application Priority Data
| Sep 19, 2001[DE] | 101 46 123 |
| Current U.S. Class: |
310/254; 310/216 |
| Current Intern'l Class: |
H02K 1/12 (20060101) |
| Field of Search: |
310/49 R,156.01,216-218,254-259,190
|
References Cited [Referenced By]
U.S. Patent Documents
| 4029980 | Jun., 1977 | Gamble.
| |
| 4353602 | Oct., 1982 | Habermann.
| |
| 4680494 | Jul., 1987 | Grosjean.
| |
| 5659217 | Aug., 1997 | Petersen.
| |
| 5691583 | Nov., 1997 | Suzuki et al.
| |
| 5854526 | Dec., 1998 | Sakamoto.
| |
| 6774512 | Aug., 2004 | Takagi et al.
| |
| Foreign Patent Documents |
| 1018142 | Oct., 1957 | DE.
| |
| 19818035 | Oct., 1999 | DE.
| |
| 63077364 | Jul., 1988 | JP.
| |
Primary Examiner: Lam; Thanh
Attorney, Agent or Firm: Comtois; Mark C., Duane Morris, LLP
Claims
The invention claimed is:
1. An electronically commutated electric motor comprising: a multi-pole permanent
magnet (
18), a plurality of flux guide units (
24,
26,
28)
each of the flux guide units having at least one flux collector section (
36,
38,
40) and one flux concentrator section (
30,
32,
34), wherein each flux guide unit (
24,
26,
28) detects
a radial magnetic flux from the permanent magnet (
18) and redirects the
radial magnetic flux to a corresponding transversal magnetic flux; and a plurality
of coils (
52,
54,
56), each coil in communication with a flux
guide unit (
24,
26,
28); wherein the flux guide units (
24,
26,
28) are nested within each other such that the flux collector
sections (
36) of a flux guide unit (
24) passes through a cavity (
72,
78) of another flux guide unit (
26,
28).
2. The electric motor according to claim 1, wherein the permanent magnet is arranged
annularly on the rotor (
10).
3. The electric motor according to claim 1, further comprising a back yoke (
16)
for receiving the permanent magnet (
18).
4. The electric motor according to claim 1, wherein the coils (
52,
54,
56) are arranged on a corresponding coil core (
46,
48,
50).
5. The electric motor according to claim 4, wherein the coil cores (
46,
48,
50) are coupled to a back iron yoke (
58).
6. The electric motor according to claim 4, wherein the flux guide units (
24,
26,
28) are arranged coaxially one on top of one other such that
the flux collector sections (
36) and coil cores (
46) of pass through
cutouts (
72,
78) in an inner flux guide unit (
26,
28).
7. The electric motor according to claim 1, wherein the flux concentrator section
(
30,
32,
34) of a flux guide unit (
24,
26,
28)
is essentially concentric with the permanent magnet (
18).
8. The electric motor according to claim 1, wherein the flux collector sections
(
36,
38,
40) are arranged circumferentially about an associated
flux concentrator (
30,
32,
34).
9. The electric motor according to claim 1, wherein each flux guide unit (
24,
26,
28) is associated with a phase of the electric motor.
10. The electric motor according to claim 1, wherein one or four coils (
52,
54,
56) are provided for each phase of the electric motor.
11. The electric motor according to claim 5, wherein an outer flux guide unit
(
24) and the back iron yoke (
58) each accommodate bearings (
60,
62) to support a rotor shaft (
14).
12. The electric motor according to claim 1, wherein each flux guide unit (
24,
26,
28) comprises a number of flux collector sections (
36,
38,
40) which are regularly spaced in a circle concentric to the
permanent magnet (
18).
13. The electric motor according to claim 1, wherein the motor is an inner rotor
motor or an outer rotor motor.
14. The electric motor according to claim 1, wherein the flux collector sections
(
36,
38,
40) are attached to the inner circumference of a
flux concentrator section (
30,
32,
34).
15. The electric motor according to claim 12, wherein a flux collector (
36,
38,
40) and a flux concentrator (
30,
32,
34)
substantially form a right angle.
16. The electric motor according to claim 1, wherein the flux collector sections
(
36,
38,
40) are interposed between the magnet (
18)
and the coils (
52,
54,
56).
17. The electric motor according to claim 1, wherein the electric motor is an
electronically commutated DC motor.
18. The electric motor according to claim 1, wherein at least one coil is axially
parallel to the permanent magnet (
18).
19. The electric motor according to claim 1, wherein the permanent magnet is
concentric with a shaft (
14) of the rotor (
10).
20. The electric motor according to claim 4, wherein at least one coil core (
46,
48,
50) is axially parallel to the permanent magnet (
18).
21. The electric motor according to claim 4, wherein at least one coil core (
46,
48,
50) communicates with at least one flux concentrator (
30,
32,
34).
22. The electric motor according to claim 1, wherein at least one flux collector
(
36,
38,
40) is axially parallel to the permanent magnet (
18).
Description
This application claims priority to the filing date of German Patent Application
No. 101 46 123.2 filed Sep. 19, 2001, and the PCT Application No. PCT/EP02/09358
filed Aug. 21, 2002; the specification of both of these appications are incorporated
herein in their entirety.
FIELD OF THE INVENTION
The invention relates to an electronically commutated electric motor with an
n-pole radially or diametrically magnetized permanent magnet that combines the
advantages of a radial flux design and a transversal flux design. For this purpose,
the invention proposes a new design for an electronically commutated electric motor.
BACKGROUND OF THE INVENTION
A description of the prior art concerning high-performance electronically commutated
electric motors is cited by Hendershot in "Design of Brushless Permanent Magnet
Motors". According to this, an electronically commutated electric motor consists
of the following characteristic components:
1. Stationary stator and rotor in a radial flux design
The stator consists, for example, of a laminated iron ring and a winding mostly
made up of three phases. The laminations of the iron ring are subdivided into the
characteristic parts of tooth, hammer and back iron yoke. The winding is inserted
in the area enclosed by the tooth, hammer and back iron yoke. The area in which
the winding is inserted is called a "slot". The iron ring can be designed to suit
various slot configurations.
The rotor consists of a back iron yoke and the permanent magnet generating the
flux. The permanent magnet can be composed of several segments; it is preferably
made from a single piece and n-pole radially or diametrically magnetized. The number
of poles (P) corresponds to the number of magnetized pole areas with alternating
polarity. The rotor can be designed as an inner or outer rotor motor. For outer
rotor motors, the stator is designed with the back iron yoke located inside and
the tooth and hammer pointing towards the outside. For inner rotor motors the stator
is designed with the back iron yoke on the outside and the tooth and hammer pointing
towards the inside. The magnet on the rotor of an outer rotor motor is located
inside and the back iron yoke outside. The magnet on the rotor of an inner rotor
motor is located outside and the back iron yoke inside.
This motor design is based on the radial flux principle; i.e. the magnetic flux
penetrates the coils in relation to the permanent magnet and its rotational axis
in an essentially radial direction. The required offset in the phases of the motor
depends on the number of slots, poles and phases and is set by placing the phase
windings in different areas of the stator.
2. Commutation device
The motor should be designed with a commutation device which, dependent on the
position of the rotor, selects the energizing pattern for the coils that generates
maximum torque. The commutation device mostly takes the form of Hall position sensors
in combination with a sensor magnet and a MOSFET power amplifier. Here, the Hall
position sensors detect the momentary position of the rotor and trigger the MOSFET
power amplifier in the required manner.
For electronically commutated motors of the described construction, many different
combinations of numbers of poles (2P) and of slots (n) are known. Through the choice
of the number of poles and slots, the motor can be adapted to various requirements,
such as a trapezoid torque waveform, sinoid torque waveform, low detent torque
etc. For especially low detent torque a cant of 2π/n for the pole transitions
between the magnets is frequently suggested.
The main disadvantages of the standard motor design for electronically commutated
motors lie in the costly manufacturing processes to fabricate the windings for
inner rotor motors, and the lack of a stationary housing and the high costs of
magnets for outer rotor motors.
3. Stator and rotor in a transversal flux design
For each motor phase in a transversal flux machine, a rotor section with a permanent
magnet, or with a permanent magnet section, is provided that has magnetized, alternating
poles. The stator has flux guide units with claws to redirect the radial magnetic
flux into a transversal magnetic flux, whereby the claws extend parallel to the
rotational axis of the permanent magnet net and in the vicinity of the magnetic
pole surfaces of the permanent magnet. Each flux guide unit belonging to a phase
of the transversal flux machine encloses a concentrically wound toroid coil which,
in relation to the permanent magnets, is essentially enclosed by the magnetic flux
in a longitudinal direction. For each multiphase transversal flux machine, several
such rotor/stator units are arranged next to each other on one axis or stacked
one on top of the other, whereby the required offset of the phases is achieved
by using several permanent magnets or magnet sections which are offset in relation
to each other, or by stacking the stator units with the appropriate offset in the
angle of rotation. Each phase thus has its own pole or armature system having a
rotor with a permanent magnet, a stator and a dedicated toroid coil. The number
of flux collectors or claws corresponds to the number of poles.
An example of a known transversal flux machine with further references to the
prior art can be found in DE 198 18 035 A1.
Although the transversal flux design has the advantage of a simpler winding
technique for the coils, it requires a higher magnetic volume compared to the radial
flux machine to generate a comparable magnetic flux. Moreover, the transversal
flux machine has the disadvantage that the number of magnetic poles has to correspond
to the number of flux collectors or claws on the flux guide units which goes to
restrict the means of influencing the torque waveform for the transversal flux machine.
U.S. Pat. No. 5,854,526 describes a direct current motor having a multi-pole
permanent magnet and several flux guide units. Each flux guide unit has a flux
collector section and flux concentrator section, whereby each flux guide unit picks
up a radial magnetic flux from the permanent magnet and redirects it into a transversal
magnetic flux. In addition, the motor has several coils arranged axially parallel
to the permanent magnet. The purpose of the motor design revealed in this patent
is to provide a low-cost DC motor with a large torque and good performance which
can be manufactured with precision.
DE 1 018 142 describes a self-running synchronous motor with two coaxially attached
coils that have serrate pole plates made of ferromagnetic material at their ends
featuring an approximately even number of annular teeth. The teeth of two pole
plates belonging to different coils are combined together to form one tooth. The
purpose of this arrangement is to increase the number of pole divisions per unit
of length.
The object of the present invention is to provide a new principle for an electronically
commutated electric motor which has coils that are easy to wind, which can achieve
a comparable performance in relation to known radial flux machines and which allows
any desired combination of the number of poles of the permanent magnet and the
number of slots of the stator to enable the torque waveform to be influenced according
to requirements.
SUMMARY OF THE INVENTION
This object has been achieved through an electronically commutated electric
motor having the characteristics outlined in claim 1. Preferred embodiments
of the invention are given in the sub-claims.
The electric motor presented in the invention has a rotor with magnet segments
or with a one-piece multi-pole magnetized permanent magnet, and several flux guide
units each of which have at least one flux collector section, preferably several
flux collector sections, whereby the flux guide unit picks up a radial magnetic
flux from the permanent magnet and redirects it into a transversal magnetic flux.
The electric motor additionally includes several coils each of which is allocated
to one of the flux guide units and arranged axially parallel to the permanent magnet
and its rotational axis.
By nesting several flux guide units for several phases of the electric motor
within
each other, as described in further detail below, it is possible to realize a multiphase
electric motor which operates with a single radially magnetized permanent magnet
and, for each phase, features one or more annular axially parallel coils which,
however, in contrast to the conventional transversal flux machine are not concentric
to the permanent magnet but rather (for an inner rotor motor) arranged on its outer
circumference parallel to the rotational axis of the permanent magnet. For an outer
rotor motor, the coils are accordingly arranged on the inner circumference of the
permanent magnet. This allows the coils to be more easily wound than is the case
with radial flux machines and it also allows for a more compact construction than
is the case with conventional transversal flux machines. In particular, the invention
allows the use of simple pre-fabricated coils, so-called preformed coils, which
makes the electric motor considerably easier to manufacture.
The permanent magnet of the present invention is either a single piece or made
up of segments and arranged on a rotor with a back yoke ring, and the coils are
on coil cores which are coupled with the flux concentrator and a back iron yoke.
In a preferred embodiment of the invention, each flux concentrator section of a
flux guide unit forms a ring or a ring section which is essentially concentric
to the permanent magnet. In this context, a ring is not necessarily circular in
shape and the flux concentrator can rather be formed as a polygon, an oval or suchlike.
The flux collectors are arranged at the inner circumference of the flux concentrator
rings (for an inner rotor motor design; for an outer rotor motor, at the outer
circumference) and extend essentially parallel to the rotational axis of the permanent
magnet and are located in the vicinity of its poles. The function of the flux collector
sections is similar to that of the hammer in the stator stack of a radial flux
machine so that in the electric motor of the present invention, almost any required
combination of numbers of poles and of slots can be realized.
The motor presented in the invention can take the form, for example, of any known
design variations for three-phase electronically commutated DC motors that operate
with concentrated windings. These include, for example, the variations of six slots
(according to the flux collector sections) with four poles, nine slots with six
poles, twelve slots with eight poles and all other variations which satisfy the equation
number of slots (no. of flux collector sections)=1.5×number of poles.
Moreover, special designs such as 12 slots with 10 poles and 12 slots with
14 poles etc. can be realized. By concentrating the magnetic flux of the individual
flux collector sections in the associated flux concentrator section, the number
of coils per phase can also be varied.
According to the invention, for each phase of the electric motor, several
coils, preferably one or two coils, can be provided which are arranged on coil
cores which are connected to the respective flux concentrator section of an associated
flux guide unit. The coil core sections extend essentially parallel to the rotational
axis of the permanent magnet and are connected at the end lying opposite the flux
concentrator section to a common magnetic back yoke ring. This design even allows
the number of coils per phase to be varied.
A particularly compact design of the electric motor of the present invention
is
achieved in that the flux guide units are coaxially arranged one on top of the
other and nesting into each other in such a way that the flux collector sections
and the coil cores of an outer flux guide unit, both of which extend parallel to
the axis of the permanent magnet, pass through an inner flux guide unit through
appropriate cutouts. The flux collector sections of the individual flux guide units
are offset in relation to each other in such a way that they end up lying regularly
spaced in a concentric circle around the permanent magnet.
In a particularly preferred embodiment of the invention, this outermost flux
guide
unit and the back iron yoke can be designed in such a way that they each carry
bearings to support a rotor shaft. To magnetically de-couple the rotor and stator,
the rotor shaft can, for example, be made of a magnetically non-conductive material,
or any other suitable form of de-coupling, for example in the bearings, can be
provided. By accommodating the shaft bearings in the magnetic ring, the motor flanges
normally required for this purpose are no longer needed.
All parts of the magnetic ring, i.e. in particular the flux guide units and the
magnetic back yoke ring can be manufactured as simple molded sheet-metal parts
which means that the motor can be manufactured quickly and effectively. As an option,
parts of the iron ring can also be made from sheet metal.
The electric motor presented in the invention enables many different combinations
in the number of poles and slots—as is usual for radial flux machines—to
be realized in a transversal flux arrangement, whereby the coils can take the form
of toroid coils which are much easier to wind. The arrangement of the axially parallel
coils on the circumference of the permanent magnet allows the flux guide units
and coils for the respective phases to be nested into each other in such a way
that for all phases a single multi-polar permanent magnet can be used, which results
in a more compact design than is usual for transversal flux machines. The invention
has the additional advantage that the bearings for the rotor shaft can be accommodated
in the magnetic ring so that additional motor flanges are not necessary.
SHORT DESCRIPTION OF THE DRAWINGS
These and other advantages of the invention can be derived from the following
description of preferred embodiments with reference to the drawings. In the figures:
FIG. 1 shows a schematic cross-section through the electric motor in accordance
with a first embodiment of the invention along the line B—B in FIG. 2;
FIG. 2 shows a schematic longitudinal view through the electric motor in accordance
with a first embodiment of the invention along the line A—A in FIG. 1;
FIG. 3 shows a perspective exploded view of the electric motor in accordance
with a first embodiment of the invention;
FIG. 4 shows a bottom view of an assembly which includes three pre-mounted flux
guide units in accordance with a second embodiment of the invention;
FIG. 5 shows a bottom view of an assembly which includes three pre-mounted flux
guide units in accordance with a third embodiment of the invention;
FIG. 6 shows a bottom view of an assembly which includes three pre-mounted flux
guide units in accordance with a fourth embodiment of the invention;
FIG. 7 shows a punched/bent part which can be used to manufacture a flux guide
unit in accordance with the fourth embodiment of the invention;
FIG. 8 shows a bottom view of an assembly which includes three pre-mounted flux
guide units in accordance with a fifth embodiment of the invention;
FIG. 9 shows a bottom view of an assembly which includes three pre-mounted flux
guide units in accordance with a sixth embodiment of the invention;
FIG. 10 shows a punched/bent part which can be used to manufacture a flux guide
unit in accordance with the sixth embodiment of the invention;
FIG. 11 shows a schematic longitudinal view through the electric motor in accordance
with a seventh embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In FIGS. 1 and 2, a preferred embodiment of an electronically commutated DC motor
in accordance with the invention is shown, whereby FIG. 1 is a cross-section of
the motor along the line B-B in FIG. 2 and FIG. 2 is a longitudinal view of the
motor along the line A—A in FIG. 1.
The electric motor of the invention has a rotor
10 and a stator
12,
whereby the illustrated motor is constructed according to the principle of an inner
rotor motor. However, the invention can be equally applied to outer rotor motors,
whereby the technician can reverse the structure of the motor described below in
order to design it as an outer rotor motor.
The rotor
10 includes a rotor shaft
14, a back yoke
16 which
is located on the rotor shaft
14 and a multi-pole magnetized permanent magnet
18, which can take the form of a permanent magnet ring or a segmented permanent
magnet. FIG. 1 shows a permanent magnet
18 with eight poles
20,
22,
without the invention of course being restricted to a specific number of poles.
The electric motor shown in FIG. 1 and 2 has three flux guide units
24,
26,
28 each having an annular flux concentrator section
30,
32,
34 and, in the embodiment illustrated, four flux collector sections
36,
38,
40. The flux guide units
24,
26,
28
are magnetically de-coupled by means of a layer made of a paramagnetic or diamagnetic
material
42,
44, such as aluminum.
Opposite the flux guide units
24,
26,
28 is a common
back iron yoke
58 that carries three coil cores
46,
48,
50
each of which accommodates a toroid coil
52,
54,
56 which
extend axially parallel to the rotor shaft
14 and the permanent magnet
18.
The coils
52,
54,
56 for the inner rotor construction illustrated
in the figures, are equally distributed around the circumference of the permanent
magnet
18 as shown in FIG. 1.
At the ends located opposite to the back iron yoke
58, the coil cores
46,
48,
50 are connected to the associated flux concentrator sections
30,
32,
34 of the flux guide units
24,
26,
28.
A magnetic circuit is formed via the flux collector sections, the flux concentrator
sections, the coil cores and the back iron yoke, whereby, in operation, the toroid
coils
52,
54,
56 are transversally penetrated by the magnetic field.
Finally, in FIG. 2 bearings
60,
62 are also shown which are
used to support the rotor shaft
14, whereby a first bearing
60 is
supported by the outer flux guide unit
24 and the second bearing
62
is supported by the back iron yoke
58.
In the illustrated embodiment of the electric motor presented in the invention,
three flux guide units
24,
26,
28 with their associated coils
52,
54,
56 are provided for the three phases of an electronically
commutated DC motor that can be energized via a commutation device in a manner
known to the technician. A particularly compact design is achieved when the flux
guide units
24,
26,
28 are nested within each other and the
outermost flux guide unit
24 as well as the back iron yoke
58 can
accommodate the bearings
60,
62 for the rotor shaft
14.
A preferred design for the flux guide units, the back iron yokes and the coil
cores
can be more clearly seen from FIG. 3. It should be noted that all figures are schematic
views of the invention, whereby the individual components of the electric motor
presented in the invention can be realized in various ways. The components can,
for example, be turned, milled or formed through punch/bending processes.
FIG. 3 schematically shows the electric motor in accordance with the invention
in a perspective exploded view. FIG. 3 shows the disc-shaped back iron yoke which
is formed from a flat annular disc made from a magnetically conductive material
and has holes (not illustrated) to attach the coil cores
46,
48,
50 as well as a bearing carrier at its center (not illustrated in FIG. 3)
to accommodate the rotor shaft bearing. The coil cores
46,
48,
50
can be attached to the back iron yoke
58 via the holes by means, for example,
of screws or rivets (not illustrated). Each coil core carries a toroid coil
52,
54 or
56 respectively.
FIG. 3 also shows an outer, a middle and an inner flux guide unit
24,
26 or
28 respectively in further detail.
The outer flux guide unit
24 has an annular flux concentrator section
30 and four flux collector sections
36 on its inner circumference
extending perpendicular to it. The flux concentrator section
30 features
a central hole with a bearing carrier
68 to accommodate the bearing
60
supporting the rotor shaft
14. The flux concentrator section
30 additionally
features holes
70 distributed around its circumference for the purpose of
attaching the coil core
46 by means of screws or suchlike.
The flux guide units
24,
26,
28 have a basically similar
structure to each other but are so adapted that they can be nested within each other.
The middle flux guide unit
26 features an annular flux concentrator
32
and four flux collector sections
38 on its inner circumference extending
perpendicular to it. The flux concentrator section
32 features a central
opening
72 to let the flux collector sections
36 of the outer flux
guide unit
24 pass through, whereby in a mounted condition, the flux collector
sections
36 and the flux collector sections
38, which lie on the
same radius, are offset in relation to each other in such a way that they end up
lying next to each other as shown in FIG. 1. Moreover, the flux concentrator section
32 features an opening
74 to let the coil core
46 belonging
to the outer flux guide unit
24 pass through, as can be seen in FIG. 2.
Finally, the flux concentrator section
32 features holes
76 distributed
around its circumference for the purpose of attaching the coil core
48 by
means of screws or suchlike.
The inner flux guide unit
28 is designed essentially in the same way as
the middle flux guide unit
26 and includes a flux concentrator section
34
and four flux collector sections
40 on the inner circumference of and extending
perpendicular to the flux concentrator section
34; a central opening
78
to let the flux collector sections
36,
38 of the outer and middle
flux guide units
24,
26 pass through, whereby the flux collector
sections
30,
32,
34, are offset in relation to each other
in such a way that they end up lying next to each other as shown in FIG. 1. In
the flux concentrator section
34 of the inner flux guide unit
28,
two openings
80,
82 are provided to let the coil core
46 allocated
to the outer flux guide unit
24 and the coil core
48 allocated to
the middle flux guide unit
26 pass through. Finally, flux concentrator section
34 of the inner flux guide unit
28 also features holes
84
for the purpose of attaching the coil core
50 by means of screws or suchlike.
FIG. 3 shows that the coil core
46 allocated to the outer flux guide
unit
24 is essentially the same length as or slightly longer than the flux
collector sections
36 of the outer flux guide unit
24; the coil core
48 allocated to the middle flux guide unit
26 is the same length
as or slightly longer than the flux collector sections
38 of the middle
flux guide unit
26, and the coil core
50, allocated to the inner
flux guide unit
28 is the same length as or slightly longer than the flux
collector sections
40 of the inner flux guide unit
28.
When the flux guide units
24,
26,
28 and the back iron
yoke
38 with the attached coil cores
46,
48,
50 are
mounted in the finished electric motor, the flux collector sections
36,
38,
40 extend in an alternating sequence at the inner circumference
of the flux concentrator sections
30,
32,
34, parallel to
the rotational axis of the permanent magnet and in the vicinity of its poles, whereby
the flux collector sections of the outer flux guide units pass through the openings
72,
78.
The coil cores
46,
48,
50 with the toroid coils
52,
54,
56 wound on them extend outside the flux collector sections
36,
38,
40 axially parallel to the permanent magnet, whereby the coil
cores carrying the coils are distributed equally around the circumference of the
permanent magnet. It should be noted that instead of one coil per phase and flux
guide unit of the electric motor, two or three coils, for example, could be provided.
The coil cores
46,
48 of the outer flux guide units
24,
26
pass through openings
74,
80,
82 in the inner flux guide units
which are provided for this purpose. The length of the coil cores
46,
48,
50 is calculated so that the free ends of the coil cores lie in one plane
and can be connected to the back iron yoke
58.
In the electric motor of the present invention, for the toroid coils
52,
54,
56, simple pre-fabricated coils, so-called preformed coils, can
be used making the winding process considerably easier than in the case of conventional
radial flux machines. All parts of the magnetic circuit and in particular the flux
guide units
24,
26,
28 and the back iron yoke
58 can
be made from formed sheet metal parts which goes to simplify the manufacturing
process even further. Even a laminated stator, as in a conventional radial flux
machine, can be used.
The nested design allows the flux collector sections
36,
38,
40
of the flux guide units
24,
26,
28 to lie alternately next
to each other on one radius so that a single permanent magnet is sufficient for
a three or more phase electric motor and the result is a particularly compact construction.
By concentrating the magnetic flux in several flux collector sections per phase,
the relationship between the number of flux collector sections, which correspond
to the slots of a radial flux motor, and the poles of the permanent magnet can
be varied almost at will in order to set a required torque waveform as described
in the introductory paragraphs to this application.
By concentrating the magnetic flux via the individual flux collector sections
in the flux concentrator section it is also possible to use one or more coils for
each phase.
FIG. 4 shows a bottom view of an assembly which includes three pre-mounted flux
guide units nested within each other according to a second embodiment of the invention.
The innermost flux guide unit is indicated by
86 and the flux guide units
located further out are indicated by
88 and
90. In this second embodiment,
each flux guide unit has an annular flux concentrator section
86-
1,
88-
1,
90-
1, four flux collector sections
86-
2,
88-
2,
90-
2 and eight coil cores
86-
3,
88-
3,
90-
3, whereby the flux collector sections and
the coil cores are connected to their associated flux concentrator section. In
the finished motor, the flux collector sections
86-
2,
88-
2,
90-
2 extend axially parallel to the permanent magnet and its rotational
axis in the vicinity of the poles of the permanent magnet. They pick up the radial
magnetic flux of the permanent magnet and guide it to the associated flux concentrator
section
86-
1,
88-
1,
90-
1. Coil cores
86-
3,
88-
3,
90-
3 are provided on the
outside of the flux concentrator section
86-
1,
88-
1,
90-
1 which also extend axially parallel to the rotational axis of
the permanent magnet. The coil cores of the outer flux guide units
88,
90
pass through cutouts in the inner circumference of the inner flux concentrator
sections
86-
1,
88-
1. The flux guide units
86,
88,
90 according to the second embodiment of the invention are preferably
manufactured as punched/bent parts as explained below in reference to FIG. 11.
However, the invention is not restricted to a specific means of manufacture and
the flux guide units could also be milled, turned or cast and produced as a single
piece or made up of several components.
FIG. 5 shows a bottom view of an assembly which includes three pre-mounted flux
guide units nested within each other according to a third embodiment of the invention.
The innermost flux guide unit is indicated by
92 and the flux guide units
located further out are indicated by
94 and
96. In this third embodiment,
each flux guide unit has an annular flux concentrator section
92-
1,
94-
1,
96-
1, three flux collector sections
92-
2,
94-
2,
96-
2 and a coil core
92-
3,
94-
3,
96-
3. For the rest, the comments made in respect of the second embodiment
also apply to this third embodiment.
FIG. 6 shows a bottom view of an assembly which includes three pre-mounted flux
guide units nested within each other according to a fourth embodiment of the invention.
The innermost flux guide unit is indicated by
98 and the flux guide units
located further out are indicated by
100 and
102. In this fourth
embodiment, each flux guide unit has an annular flux concentrator section
98-
1,
100-
1,
102-
1, four flux collector sections
98-
2,
100-
2,
102-
2 and two coil cores
98-
3,
100-
3,
102-
3. For the rest, the comments made in respect
of the second embodiment also apply to this fourth embodiment.
FIG. 7 shows a punched/bent part which can be used, for example, in the manufacture
of the flux guide unit
98 in the fourth embodiment of the invention which
is shown in FIG. 10. In FIG. 7, the continuous line indicates the flux guide unit
98 with the annular flux concentrator section
98-
1, the four
flux collector sections
98-
2 and the two coil cores
98-
3
after the punch/bending process, and the broken line indicates the contour of the
punched/bent part before the bending process.
FIG. 8 shows a bottom view of an assembly which includes three pre-mounted flux
guide units nested within each other according to a fifth embodiment of the invention.
In this embodiment, each flux guide unit is divided into two flux guide pieces.
The innermost flux guide unit includes two flux guide pieces
104-
1
and
104-
2, and each of the flux guide units located further out also
include two flux guide pieces
106-
1 and
106-
2 or
108-
1
and
108-
2 respectively. Each of the two flux guide pieces of a flux
guide unit are allocated to one phase of the motor and their flux concentrator
sections lie in one plane. In an alternative embodiment, the flux guide piece
104-
2
can be laid in one plane with the flux guide pieces
106-
1 and
108-
2
and the flux guide piece
104-
1 in one plane with the flux guide pieces
106-
2 and
108-
1 with the purpose of minimizing the
amount of axial space needed by the nested arrangement made up of the three flux
guide units. The axial lengths of the coil cores and flux guide pieces have to
be adjusted accordingly.
In this fifth embodiment, each flux guide piece
104-
1,
104-
2,
106-
1,
106-
2,
108-
1,
108-
2
has a flux concentrator section
104-
11,
104-
21,
106-
11,
106-
21,
108-
11,
108-
21 in the form of
a part ring which extends in particular over about ⅓ of a circle. Two flux
collector sections
104-
12,
104-
22,
106-
12,
106-
22,
108-
12,
108-
22 and a coil core
104-
13,
104-
23,
106-
13,
106-
23,
108-
13,
108-
23 are connected to each flux concentrator
section
104-
11,
104-
21,
106-
11,
106-
21,
108-
11,
108-
21 resulting in an overall configuration
of four flux collector sections and two coil cores per flux guide unit. The special
configuration of the flux guide units in the fifth embodiment, which are made up
of two flux guide pieces, can have advantages for the manufacturing process since
the individual flux guide pieces can be more easily formed. Another advantage of
the fifth embodiment is that the flux concentrator sections, each made up of three
flux guide pieces, can be arranged in one plane so that only two planes are needed
for the three flux guide units, which means that the amount of space required for
the entire assembly consisting of the three flux guide units can be reduced.
For the rest, the comments made in respect of the second embodiment also apply
to this fifth embodiment.
FIG. 9 shows a bottom view of an assembly which includes three pre-mounted flux
guide units nested within each other according to a sixth embodiment of the invention.
The embodiment is similar to the embodiment in FIG. 8 although the number of coil
cores for each flux guide unit is doubled. The innermost flux guide unit is indicated
by
110 and the flux guide units located further out are indicated by
112
and
114. In this sixth embodiment, each flux guide unit has an annular flux
concentrator section
110-
1,
112-
1,
114-
1,
four flux collector sections
110-
2,
112-
2,
114-
2
and four coil cores
110-
3,
112-
3,
114-
3.
In contrast to the previous embodiments, the longitudinal coil cores
110-
3,
112-
3,
114-
3 do not extend longitudinally in a circumferential
direction but rather radially to the rotational axis of the permanent magnet of
the electric motors. This embodiment can also have an advantage for the manufacture
of the flux guide units as can be seen in FIG. 14. For the rest, the comments made
in respect of the second embodiment also apply to this sixth embodiment.
FIG. 10 shows a punched/bent piece which can be used, for example, in the manufacture
of the flux guide unit
110 in the sixth embodiment of the invention which
is shown in FIG. 13. FIG. 14 shows the flux guide unit
110 with the annular
flux concentrator section
110-
1, the four flux collector sections
110-
2 and the four coil cores
110-
3 before the punch/bending
process. As can be seen from FIG. 14, the flux guide unit can be manufactured with
the optimum utilization of material.
FIG. 11 shows a schematic longitudinal view through the electric motor in accordance
with a seventh embodiment of the invention which is similar to the view in FIG.
2, whereby in FIG. 11 the rotor and the rotor bearing are not illustrated. In FIG.
11 a first flux guide unit is indicated by
114, a second flux guide unit
is indicated by
116 and a third flux guide unit is indicated by
118.
The embodiment illustrated in FIG. 11 differs from the previous embodiments in
that the coil cores, e.g.
120, are formed as a single piece with the back
iron yoke
122. Thus, in this seventh embodiment, the coil cores, e.g.
120,
are first formed as one piece with the back iron yoke
122, then the coils
124 are placed on the coil cores before the back iron yoke
122, together
with the coils
124, is fitted to the flux guide units
114,
116,
118. For the rest, the comments made for the first embodiment with reference
to FIG. 2 apply.
In designing the rotor shaft
14 from a magnetically non-conductive material,
or by using any other suitable means of magnetically de-coupling the stator and
rotor, it is possible to integrate the bearing carriers
66,
68 for
the rotor shaft bearings
60,
62 into the magnetic circuit and thus
eliminate the need for additional motor flanges. In the preferred embodiment of
the invention, the bearing carriers are integrated into the outer flux collector
24 and the back yoke ring
58.
The characteristics revealed in the above description, the claims and the figures
can be important for the realization of the invention in its various embodiments
both individually and in any combination whatsoever.
*
