U.S. patent application number 09/362467 was filed with the patent office on 2002-04-25 for thrust-controllable rotary synchronous machine.
Invention is credited to MATSUBARA, SATORU, NISHIDA, SATOSHI, SEKIYAMA, TOKUZOU, SHIBUYA, HIROSHI.
Application Number | 20020047433 09/362467 |
Document ID | / |
Family ID | 26459394 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020047433 |
Kind Code |
A1 |
SEKIYAMA, TOKUZOU ; et
al. |
April 25, 2002 |
THRUST-CONTROLLABLE ROTARY SYNCHRONOUS MACHINE
Abstract
Rotary synchronous machine includes a stator and a rotor. The
stator includes a magnetic field core and an armature core
magnetically separated from each other. The rotor includes a
plurality of magnetic substance segments which are magnetically
separated from each other in a direction of rotation but are
magnetically coupled with both of the magnetic field core and
armature core. The rotor and magnetic field core are arranged to
cause an axial thrust to the rotor depending on the intensity of
electric currents passed through filed windings. Namely, the rotor
and magnetic field core are arranged in such a manner that magnetic
attraction (magnetic coupling) occurs between the rotor and the
magnetic field core in a same direction as a rotational axis or at
a predetermined non-normal angle relative to the rotational axis.
Thus, thrust is produced based on the magnetic attraction between
the rotor and the magnetic field core., and this thrust corresponds
to the intensity of the electric currents passed through filed
windings. Consequently, a traveling position of the rotor in the
axial direction can be controlled by providing the magnetic field
cores adjacent to opposite sides of the rotor and appropriately
controlling the intensity of the filed currents.
Inventors: |
SEKIYAMA, TOKUZOU;
(GUNMA-KEN, JP) ; MATSUBARA, SATORU; (GUNMA-KEN,
JP) ; NISHIDA, SATOSHI; (GUNMA-KEN, JP) ;
SHIBUYA, HIROSHI; (GUNMA-KEN, JP) |
Correspondence
Address: |
DAVID L. FEHRMAN
MORRISON & FOERSTER L L P
555 WEST FIFTH STREET ,SUIT 3500
LOS ANGELES
CA
90013-1024
US
|
Family ID: |
26459394 |
Appl. No.: |
09/362467 |
Filed: |
July 28, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09362467 |
Jul 28, 1999 |
|
|
|
09301761 |
Apr 29, 1999 |
|
|
|
Current U.S.
Class: |
310/156.55 ;
310/156.01; 310/156.54 |
Current CPC
Class: |
B29C 2045/5024 20130101;
F16C 32/0495 20130101; B29C 2045/504 20130101; B29C 2045/5032
20130101; H02K 2201/18 20130101; H02K 19/103 20130101; H02K 21/046
20130101; H02K 7/09 20130101; B29C 45/5008 20130101; H02K 16/00
20130101; H02K 7/12 20130101; H02K 19/24 20130101 |
Class at
Publication: |
310/156.55 ;
310/156.54; 310/156.01 |
International
Class: |
H02K 021/12; H02K
019/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 1, 1998 |
JP |
10-122228 |
Claims
What is claimed is:
1. A rotary synchronous machine comprising: a stator; an armature
core provided on said stator and having armature windings
sequentially wound thereon in a direction of rotation; a rotor
including a plurality of magnetic substance segments which are
magnetically coupled with said armature core but are magnetically
separated from each other in the direction of rotation; and a
magnetic field core that is provided on said stator in
magnetically-separated relation to said armature core but is
magnetically coupled with said armature core via said rotor, said
magnetic field core having field windings positioned thereon for
producing rotating magnetic poles and thus producing said rotor
with an axial thrust corresponding to intensity of electric
currents passed through the field windings.
2. A rotary synchronous machine comprising: a stator; a cylindrical
armature core provided along an inner surface of said stator and
having armature windings that extend along a direction of rotation
and are sequentially received in slots formed radially in said
armature core; a rotor including a plurality of cylindrical
magnetic substance segments that are magnetically coupled with the
inner surface of said armature core but are magnetically separated
from each other in the direction of rotation; a first magnetic
field core that is provided on said stator in
magnetically-separated relation to said armature core but is
magnetically coupled with one side surface of the cylindrical
magnetic substance segments of said rotor, said first magnetic
field core having field windings positioned thereon for producing
rotating magnetic poles; and a second magnetic field core that is
provided on said stator in magnetically-separated relation to said
armature core but is magnetically coupled with another side surface
of the cylindrical magnetic substance segments of said rotor, said
second magnetic field core having field windings positioned thereon
for producing rotating magnetic poles.
3. A rotary synchronous machine as recited in claim 2 which further
comprises a current control device that controls intensity of
electric currents to be supplied to said first magnetic field core
and second magnetic field core, to thereby control an axial thrust
of said rotor.
4. A rotary synchronous machine as recited in claim 2 wherein a
cylindrical permanent magnet is provided around an outer peripheral
surface of said cylindrical magnetic substance segments of said
rotor.
5. A rotary synchronous machine as recited in claim 4 wherein the
cylindrical magnetic substance segments of said rotor is tapered at
least one end portion thereof to provide a conically slanted
surface and said first magnetic field core and second magnetic
field core are provided to be magnetically coupled with the
conically slanted surface of said rotor.
6. A rotary synchronous machine as recited in claim 2 wherein the
cylindrical magnetic substance segments of said rotor is tapered at
least one end portion thereof to provide a conically slanted
surface and said first magnetic field core and second magnetic
field core are provided to be magnetically coupled with the
conically slanted surface of said rotor.
7. A rotary synchronous machine including a plurality of rotary
synchronous machine structures connected together along an axis of
a same rotation shaft, at least one of the plurality of rotary
synchronous machine structures being an improved rotary synchronous
machine structure, said improved rotary synchronous machine
structure comprising: a stator; an armature core provided on said
stator and having armature windings sequentially wound thereon in a
direction of rotation; a rotor including a plurality of magnetic
substance segments which are magnetically coupled with said
armature core but are magnetically separated from each other in the
direction of rotation; and a magnetic field core that is provided
on said stator in magnetically-separated relation to said armature
core but is magnetically coupled with said armature core via said
rotor, said magnetic field core having field windings positioned
thereon for producing rotating magnetic poles and thus producing
said rotor with an axial thrust corresponding to intensity of
electric currents passed through the field windings.
8. A rotary synchronous machine as recited in claim 7 wherein at
least another of said rotary synchronous machine structures is
another improved rotary synchronous machine structure which
comprises: a stator; a cylindrical armature core provided along an
inner surface of said stator and having armature windings that
extend along a direction of rotation and are sequentially received
in slots formed radially in said armature core; a rotor including a
plurality of cylindrical magnetic substance segments that are
magnetically coupled with the inner surface of said armature core
but are magnetically separated from each other in the direction of
rotation; a first magnetic field core that is provided on said
stator in magnetically-separated relation to said armature core but
is magnetically coupled with one side surface of the cylindrical
magnetic substance segments of said rotor, said first magnetic
field core having field windings positioned thereon for producing
rotating magnetic poles; a second magnetic field core that is
provided on said stator in magnetically-separated relation to said
armature core but is magnetically coupled with another side surface
of the cylindrical magnetic substance segments of said rotor, said
second magnetic field core having field windings positioned thereon
for producing rotating magnetic poles; and a current control device
that controls intensity of electric currents to be supplied to said
first magnetic field core and second magnetic field core, to
thereby control an axial thrust of said rotor.
9. A rotary synchronous machine including a plurality of rotary
synchronous machine structures connected together along an axis of
a same rotation shaft, at least one of the plurality of rotary
synchronous machine structures being an improved rotary synchronous
machine structure, said improved rotary synchronous machine
structure comprising: a stator; a cylindrical armature core
provided along an inner surface of said stator and having armature
windings that extend along a direction of rotation and are
sequentially received in slots formed radially in said armature
core; a rotor including a plurality of cylindrical magnetic
substance segments that are magnetically coupled with the inner
surface of said armature core but are magnetically separated from
each other in the direction of rotation; a first magnetic field
core that is provided on said stator in magnetically-separated
relation to said armature core but is magnetically coupled with one
side surface of the cylindrical magnetic substance segments of said
rotor, said first magnetic field core having field windings
positioned thereon for producing rotating magnetic poles; and a
second magnetic field core that is provided on said stator in
magnetically-separated relation to said armature core but is
magnetically coupled with another side surface of the cylindrical
magnetic substance segments of said rotor, said second magnetic
field core having field windings positioned thereon for producing
rotating magnetic poles.
10. A rotary synchronous machine as recited in claim 9 wherein said
at least one of said rotary synchronous machine structures further
comprises a current control device that controls intensity of
electric currents to be supplied to said first magnetic field core
and second magnetic field core, to thereby control an axial thrust
of said rotor.
Description
RELATED APPLICATION
[0001] This application is a continuation-in-part application of
our corresponding U.S. application Ser. No. 09/301,761 filed Apr.
29, 1999, which is now pending.
BACKGROUND OF THE INVENTION
[0002] The present invention relates generally to rotary
synchronous machines having field and armature windings provided on
a stator, and more particularly to a rotary synchronous machine
capable of optionally controlling thrust developed in an axial
direction of a rotation shaft.
[0003] Synchronous motors are available in a variety of designs,
such as the rotating-armature, rotating-field and inductor types.
The rotating-armature type synchronous motors comprise a magnetic
field pole provided on a stator, and an armature winding provided
on a rotor. The rotating-field type synchronous motors comprise an
armature winding provided on a stator, and a magnetic field pole
provided on a rotor. The magnetic field pole in the rotating-field
type synchronous motors is typically a permanent magnets positioned
on the rotor, or a magnetic field winding that is excited by direct
current. Further, the inductor-type synchronous motors comprise a
magnetic field pole and an armature winding provided on a stator,
and an inductor provided on a rotor and having gear-like teeth and
slots.
[0004] Since the armature winding is provided on the stator as
mentioned, the rotating-field type synchronous motors are
substantially free from mechanical damages and breakage and permit
easy insulation, so that they are widely used today as drive means
for rotating the spindles of various machine tools and others.
[0005] However, such rotating-field type synchronous motors where
the field pole comprises a permanent magnet positioned on the rotor
are disadvantageous in that the permanent magnet itself is
expensive and must be secured firmly enough to not accidentally
detach from the rotor and also in that it is difficult to provide
large capacity because the magnetic field produced is always
constant. The rotating-field type synchronous motors where the
field pole comprises a magnetic field winding provided on the rotor
are also disadvantageous in that they essentially require slip
rings and a rotary transformer in order to supply field current to
the rotor, resulting in a complex structure.
[0006] The rotary drive means do not produce a thrust in an axial
direction thereof although they give rotational force, i.e.,
torque. Therefore, in cases where both rotational force and axial
thrust are required, it has been customary to provide a linear
drive means separate from the rotary drive means, so as to control
the rotational force and axial thrust by the different drive means.
However, because at least two separate drive means were necessary
for the control of the rotational force and axial thrust, a
relatively large space was required. Thus, in most cases, it has
been conventional for the entire rotary drive means to be
controlled by the linear drive means.
SUMMARY OF THE INVENTION
[0007] It is therefore an object of the present invention to
provide a thrust-controllable rotary synchronous machine which is,
by itself, capable of simultaneously controlling both rotational
force and axial thrust.
[0008] In order to accomplish the above-mentioned object, the
present invention provides a rotary synchronous machine which
comprises: a stator; an armature core provided on the stator and
having armature windings sequentially wound thereon in a direction
of rotation; a rotor including a plurality of magnetic substance
segments which are magnetically coupled with the armature core but
are magnetically separated from each other in the direction of
rotation; and a magnetic field core that is provided on the stator
in magnetically-separated relation to the armature core but is
magnetically coupled with the armature core via the rotor, the
magnetic field core having field windings positioned thereon for
producing rotating magnetic poles and thus providingducing, in the
rotor, an axial thrust corresponding to intensity of electric
currents passed through the field windings.
[0009] On the stator, the magnetic field core and armature core are
magnetically separated from each other. On the rotor, a plurality
of magnetic substance segments are magnetically separated from each
other in a direction of rotation but are magnetically coupled with
both of the magnetic field core and armature core. Thus, N and S
rotating magnetic poles produced on the magnetic field core are
coupled together via the rotor and armature core, to form closed
magnetic circuitry. Because the rotor and armature core are coupled
in a direction normal to the rotation axis, magnetic attraction
between the rotor and armature core will contribute only to
rotational force. The rotor and magnetic field core, on the other
hand, are arranged to cause an axial thrust to the rotor depending
on the intensity of the electric currents passed through the filed
windings. Namely, the rotor and magnetic field core are arranged in
such a manner that magnetic attraction (magnetic coupling) occurs
between the rotor and the magnetic field core in a same direction
as the rotational axis or at a predetermined non-normal angle
relative to the rotational axis. Thus, thrust is produced based on
the magnetic attraction between the rotor and the magnetic field
core, and this thrust corresponds to the intensity of the electric
currents passed through the field windings. Consequently, a
traveling position of the rotor in the axial direction can be
controlled by providing the magnetic field cores adjacent to
opposite sides of the rotor and appropriately controlling the
intensity of the field currents.
[0010] According to another aspect of the present invention, there
is provided a rotary synchronous machine which comprises: a stator;
a cylindrical armature core provided along an inner surface of the
stator and having armature windings that extend along a direction
of rotation and are sequentially received in slots formed radially
in the armature core; a rotor including a plurality of cylindrical
magnetic substance segments that are magnetically coupled with the
inner surface of the armature core but are magnetically separated
from each other in the direction of rotation; a first magnetic
field core that is provided on the stator in magnetically-separated
relation to the armature core but is magnetically coupled with one
side surface of the cylindrical magnetic substance segments of the
rotor, the first magnetic field core having field windings
positioned thereon for producing rotating magnetic poles; a second
magnetic field core that is provided on the stator in
magnetically-separated relation to the armature core but is
magnetically coupled with another side surface of the cylindrical
magnetic substance segments of the rotor, the second magnetic field
core having field windings positioned thereon for producing
rotating magnetic poles; and a current control device that controls
intensity of electric currents to be supplied to the first magnetic
field core and second magnetic field core, to thereby control an
axial thrust of the rotor. In this rotary synchronous machine, a
pair of the magnetic field cores are provided adjacent to opposite
sides of the rotor, and the axial thrust of the rotor is controlled
by the current control device controlling the intensity of the
currents passed through the two magnetic field cores.
[0011] In a preferred implementation of the present invention, a
cylindrical permanent magnet is provided around an outer peripheral
surface of the cylindrical magnetic substance segments of the
rotor. If the surface of the cylindrical permanent magnet opposed
to the rotor is excited to assume the S pole and the surface of the
magnet opposed to the armature core is excited to assume the N
pole, the surfaces of the magnetic substance segments opposed to
the first and second magnetic field cores are excited to assume the
S pole; conversely, if the surface of the cylindrical permanent
magnet opposed to the rotor is excited to assume the N pole and the
surface of the magnet opposed to the armature core is excited to
assume the S pole, then the surfaces of the magnetic substance
segments opposed to the first and second magnetic field cores are
excited to assume the N pole. Thus, the rotor is caused to rotate
in response to the electric currents passed through the armature
windings even when no field currents are supplied. Then, both the
rotational force and the axial thrust can be controlled by
controlling the intensity of the field currents. In this case, the
axial thrust can be controlled finely by causing the field
currents, to be supplied to the first and second magnetic filed
cores, to be in phase with each other and producing magnetic
attraction between the first and second magnetic filed cores and
the rotor. Further, the axial thrust can be controlled greatly by
causing the field currents, to be supplied to the first and second
magnetic filed cores, to be in opposite phase and producing
magnetic attraction between the first magnetic field core and the
rotor while producing magnetic repulsion between the second
magnetic field core and the rotor.
[0012] In another preferred implementation, the cylindrical
permanent magnet of the rotor is tapered at least one end portion
thereof to provide a conically slanted surface and the first
magnetic field core and second magnetic field core are provided to
be magnetically coupled with the conically slanted surface of the
rotor. By thus tapering the rotor, a sufficient traveling distance
of the rotor greater than a gap between the magnetic substance
segments and the magnetic field cores can be guaranteed even
through the gap width is small, and it is possible to reduce the
necessary field currents and substantially improve the thrust
characteristics.
[0013] According to still another aspect of the present invention,
there is provided a rotary synchronous machine which includes a
plurality of improved rotary synchronous machine structures
connected together along an axis of a same rotation shaft, and each
of the improved rotary synchronous machine structures comprises: a
stator; an armature core provided on the stator and having armature
windings sequentially wound thereon in a direction of rotation; a
rotor including a plurality of magnetic substance segments which
are magnetically coupled with the armature core but are
magnetically separated from each other in the direction of
rotation; and a magnetic field core that is provided on the stator
in magnetically-separated relation to the armature core but is
magnetically coupled with the armature core via the rotor, the
magnetic field core having field windings positioned thereon for
producing rotating magnetic poles and thus causing, to the rotor,
an axial thrust corresponding to intensity of electric currents
passed through the field windings. This multi-stage arrangement can
produce a sufficiently great axial thrust.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For better understanding of the present invention, the
preferred embodiments of the invention will be described in detail
below with reference to the accompanying drawings, in which:
[0015] FIG. 1 is a sectional view of a thrust-controllable rotary
synchronous motor according to a preferred embodiment of the
present invention, taken longitudinally through a rotation shaft
thereof;
[0016] FIG. 2 is a sectional view of the rotary synchronous motor
taken along the line A-A of FIG. 1;
[0017] FIG. 3 is a sectional view of the rotary synchronous motor
taken along the line B-B of FIG. 1;
[0018] FIG. 4A is a diagram of one of magnetic field cores shown in
FIG. 1;
[0019] FIG. 4B is a sectional view taken along the line C-C of FIG.
4A;
[0020] FIG. 5 is a diagram illustrating an exemplary wiring
organization between armature and field windings in the rotary
synchronous motor of FIG. 1;
[0021] FIG. 6 is a diagram illustrating another embodiment of a
four-pole rotor of FIG. 2;
[0022] FIG. 7 is a diagram illustrating still another embodiment of
the four-pole rotor of FIG. 2;
[0023] FIG. 8 is a longitudinal sectional view of a rotary
synchronous motor in accordance with another embodiment of the
present invention which comprises a plurality of the linear motor
structures of FIG. 1 connected in series with each other;
[0024] FIG. 9 is a longitudinal sectional view of a rotary
synchronous motor in accordance with still another embodiment of
the present invention;
[0025] FIG. 10 is a diagram illustrating still another embodiment
of the four-pole rotor of FIG. 2;
[0026] FIG. 11 is a longitudinal sectional view of a rotary
synchronous motor in accordance with still another embodiment of
the present invention;
[0027] FIG. 12 is a graph showing relationship between a traveling
distance and thrust in the case where the side surface of the rotor
extend parallel to the rotational axis along the full length of the
rotor as in the synchronous motor of FIG. 1 and in the case where
the rotor has opposite end portions tapered relative to the
rotational axis; and
[0028] FIG. 13 is a is a block diagram illustrating an A.C. servo
motor system employing the synchronous motor according to the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] In FIGS. 1, 2 and 3, there is shown a thrust-controllable
rotary synchronous motor according to one embodiment of the present
invention, of which FIG. 1 is a sectional view of the synchronous
motor taken longitudinally through its rotation shaft, FIG. 2 is a
sectional view of the synchronous motor taken along the line A-A of
FIG. 1, particularly showing a detailed structure of a magnetic
filed core 6. Further, FIG. 3 is a sectional view of the
synchronous motor taken along the line B-B of FIG. 1.
[0030] This rotary synchronous motor is of a type which has four
magnetic poles and is driven by three-phase alternating currents.
As shown, the synchronous motor includes a cylindrical stator frame
1 and the rotation shaft 4 rotatably mounted in the stator frame 1
via bearings 2 and 3 located on opposite ends of the shaft 4. The
rotation shaft 4 is also slidable in its longitudinal or axial
direction via the bearings 2 and 3. Within the cylindrical stator
frame 1, an armature core 5 and two magnetic field cores 6 and 7
are also provided on the central and end inner surfaces of the
stator frame 1, respectively, and a rotor 8 having an alternating
sequence of magnetic substance segments 81 to 84 and non-magnetic
substance segments 85 to 88 is mounted on the rotation shaft 4.
[0031] The armature core 5 comprises a cylindrical laminated iron
core provided along the inner peripheral surface of the stator
frame 1, which has 24 radial slots formed along the inner periphery
thereof and around the rotation shaft 4 as shown in FIG. 2. In the
individual radial slots of the armature core 5 are received
three-phase armature windings (armature windings), one winding
portion or coil in each of the slots. The laminated iron core of
the armature core 5 comprises a plurality of thin silicon steel
rings stacked in the axial direction.
[0032] The magnetic field cores 6 and 7 are similar annular iron
rings mounted on the opposed, flat inner end surfaces of the stator
frame 1 adjacent to opposite ends of the rotor 8. FIG. 4A is a
diagram of one of the magnetic field cores (magnetic field core 6
in the illustrated example) as viewed from the rotor 8, and FIG. 4B
is a sectional view taken along the line C-C of FIG. 4A. For
simplicity of illustration, no field windings are shown in these
figures. As shown in FIGS. 4A and 4B, each of the magnetic field
cores 6 and 7 has 24 radial slots formed in its inner surface
facing the end surface of the rotor 8. In the radial slots of the
magnetic field cores 6 and 7 are received two (first and second)
sets of three-phase field windings. Each of the magnetic field
cores 6 and 7 comprises a plurality of thin silicon steel rings
stacked in the radial direction of the core and hence of the
rotation shaft 4.
[0033] As typically shown in FIG. 2, the three-phase armature
windings on the armature core 5 comprise two (first and second)
sets of U-phase, V-phase and W-phase windings that are positioned
to be shifted from each other by 120 electrical degrees. In the
specification and drawings, the armature windings are denoted by
upper-case alphanumerics while the field windings are denoted by
lower-case alphanumerics.
[0034] The first and second U-phase armature windings are
positioned on the armature core 5 via eight slots in ascending
order of winding portion numbers, i.e.,
"U1"-"U2"-"U3"-"U4"-"U5"-"U6"-"U7"-"U8". The first and second
V-phase armature windings are positioned on the armature core 5 via
eight slots in ascending order of winding portion numbers, i.e.,
"V1"-"V2"-"V3"-"V4"-"V5"-"V6"-"V7"-"V8". Similarly, the first and
second W-phase armature windings are positioned on the armature
core 5 via eight slots in ascending order of winding portion
numbers, i.e., "W1"-"W2"-"W3"-"W4"-"W5"-"W6"-"W7"-"W8". The
U-phase, V-phase and W-phase armature windings are positioned to be
shifted from each other by 120 electrical degrees as earlier noted;
that is, the U-phase, V-phase and W-phase armature windings are
displaced with respect to each other, in the clockwise direction,
by four slots.
[0035] Similarly to the three-phase armature windings, the
three-phase field windings located on the magnetic field core 6, as
shown in FIG. 3, comprise two (first and second) sets of u-phase,
v-phase and w-phase windings that are positioned to be shifted from
each other by 120 electrical degrees.
[0036] The u-phase field windings comprise the first u-phase
winding wound on the magnetic field core 6 to extend from a winding
start portion ua to a winding end portion ub via four slots, and
the second u-phase winding wound on the magnetic field core 6 to
extend from a winding start portion uc to a winding end portion ud
via four slots. The v-phase field windings comprise the first
v-phase winding wound on the magnetic field core 6 to extend from a
winding start portion va to a winding end portion vb via four
slots, and the second v-phase winding wound on the magnetic field
core 6 to extend from a winding start portion vc to a winding end
portion vd via four slots. Similarly, the w-phase filed windings
comprise the first w-phase winding wound on the magnetic field core
6 to extend from a winding start portion wa to a winding end
portion wb via four slots, and the second w-phase winding wound on
the magnetic field core 6 to extend from a winding start portion wc
to a winding end portion wd via four slots.
[0037] The three-phase field windings on the magnetic field core 7
are similar in structure to the three-phase field windings on the
magnetic field core 6 and positioned in symmetry therewith about
the rotor 8.
[0038] The respective three-phase field windings on the magnetic
field cores 6 and 7 are positioned to be shifted from the
corresponding armature windings by 90 electrical degrees. More
specifically, the u-phase field windings are positioned to be
shifted in the clockwise direction from the U-phase armature
windings by three slots (90 electrical degrees), the v-phase field
windings are also positioned to be shifted in the clockwise
direction from the V-phase armature windings by three slots (90
electrical degrees), and the w-phase magnetic field windings are
also positioned to be shifted in the clockwise direction from the
W-phase armature windings by three slots (90 electrical degrees).
Note that the shift amounts may be approximately in the
neighborhood of 90.degree., rather than exactly 90.degree.,
depending on the specific structure of the synchronous motor.
[0039] The rotor 8 in the illustrated example is generally in a
cylindrical shape and provided around the peripheral surface of the
rotation shaft 4. The rotor 8 includes an alternating sequence of
four magnetic substance segments 81 to 84 and four non-magnetic
substance segments 85 to 88 provided axially along the rotation
shaft 4, or along a direction of magnetic flux flowing from
magnetic poles (N and S poles) produced on the magnetic field cores
6 and 7. The non-magnetic substance segment 85 to 88 act to
separate the magnetic substance segments 81 to 84 from each other
to ensure that the magnetic substance segments 81 to 84 are not
magnetically coupled with each other in the circumferential
direction or direction of rotation of the rotor 8. However, the
magnetic substance segments 81 to 84 are magnetically coupled with
the outer peripheral surface of the armature core 5 and the inner
end surface of the magnetic field cores 6 and 7. More specifically,
if the spacing of the magnetic substance segments 81 to 84 from the
non-magnetic substance segments 85 to 88 is chosen to be about 3-10
mm, then it will suffice that the spacing of the magnetic substance
segments 81 to 84 from the armature core 5 and the magnetic field
cores 6 and 7 is about 0.5-3 mm. By the magnetic substance segments
81 to 84 being thus magnetically separated from each other by the
intervening non-magnetic substance segments 85 to 88, the magnetic
flux flowing from the N poles of the magnetic field cores 6 and 7
are easily directed into the armature core 5 by way of the magnetic
substance segments 81 to 84.
[0040] The following three-phase alternating currents iu, iv and
iw, phase-shifted from each other by 120 electrical degrees, are
passed through the three-phase windings on the magnetic field core
6:
[0041] iu=im.multidot.sin.omega.t
[0042] iv=im.multidot.sin(.omega.t-2.pi./3)
[0043] iw=im.multidot.sin(.omega.t-4.pi./3) where im represents a
maximum electric current value.
[0044] By such currents iu, iv and iw flowing through the
three-phase field windings on the magnetic field core 6, the
magnetic poles producing magnetic flux directed toward the magnetic
substance segments 82 and 84 of the rotor 8 (i.e., N poles) and the
magnetic poles absorbing magnetic flux from the magnetic substance
segments 81 and 83 toward the magnetic field core 6 (i.e., S
poles), as shown in FIG. 3, are both caused to occur and rotate in
the clockwise direction on the flat end surface of the field core 6
facing the rotor 8. Similar three-phase alternating currents iu, iv
and iw are passed through the three-phase field windings on the
other magnetic field core 7, so that the magnetic poles (N and S
poles) are both caused to occur and rotate in the clockwise
direction on the flat end surface of the core 7 facing the rotor
8.
[0045] Magnetic fields in and around the magnetic poles (N and S
poles) produced by the three-phase currents assume a sinusoidal
magnetic flux distribution in the direction of rotation, and the
magnetic flux can be expressed as follows if the maximum magnetic
flux is represented by .PHI. and the pole center is represented by
.theta.=0:
.PHI.=.PHI.m.multidot.cos.theta.
[0046] If the currents flowing through the three-phase field
windings are controlled in such a manner that the pole center of
the magnetic fields produced by the field windings coincides with
an "easiest-to-magnetize" surface portion of the rotor 8, the rotor
8 will be magnetized in a predetermined direction and assume a
magnetic flux density that can be approximately expressed by
B=Bm.multidot.cos .theta.
[0047] Namely, the magnetic substance segments 81 to 84 of the
rotor 8 are magnetized in predetermined directions in response to
the magnetic poles (N and S poles) produced on the magnetic field
cores 6 and 7. For example, by the currents iu, iv, iw, N poles are
produced on the surfaces of the field cores 6 and 7 facing the
magnetic substance segments 82 and 84 and S poles are produced on
the surfaces of the field cores 6 and 7 facing the magnetic
substance segments 81 and 83, in response to which S poles are
produced on the flat surfaces of the magnetic substance segments 82
and 84 facing the magnetic field cores 6 and 7 and N poles are
produced on the curved surfaces of the magnetic substance segments
82 and 84 facing the armature core 5.
[0048] Similarly, N poles are produced on the flat surfaces of the
magnetic substance segments 81 and 83 facing the magnetic field
cores 6 and 7 and S poles are produced on the curved surfaces of
the magnetic substance segments 81 and 83 facing the armature core
5.
[0049] Namely, as typically shown in FIG. 1, the magnetic flux
.PHI.1 flowing from the two N poles of the field core 6 enters the
magnetic substance segments 82 and 84 through their S-pole flat
surfaces. Similarly, the magnetic flux .PHI.2 flowing from the two
N poles of the other magnetic field core 7 enters the magnetic
substance segments 82 and 84 through their S-pole flat surfaces.
The magnetic flux .PHI.1 and .PHI.2, having thus entered the
magnetic substance segments 82 and 84, enters the armature core 5
via their N-pole curved surfaces, passes along the outer peripheral
portion of the core 5, and then enters the magnetic substance
segments 81 and 83 via their S-pole curved surfaces. After this,
the magnetic flux .PHI.1 and .PHI.2 enters the S-pole flat surfaces
of the magnetic field cores 6 and 7 from the N-pole flat surfaces
of the magnetic substance segments 81 and 83. The magnetic flux
.PHI.1 and .PHI.2, having entered the magnetic field cores 6 and 7,
passes therethrough to reach the respective N poles. Thus, in this
rotary synchronous machine, predetermined closed magnetic circuits
are formed by the magnetic field cores 6 and 7, rotor 8 and
armature core 5.
[0050] The rotary synchronous machine arranged in the above-noted
manner gives rise to attraction between the opposed surfaces of the
magnetic substance segments 81 to 84 and the magnetic field cores 6
and 7, on the basis of the magnetic flux .PHI.1 and .PHI.2 produced
via the cores 6 and 7. The magnitude of the attraction depends on
the magnitude of the magnetic flux .PHI.1 and .PHI.2. Therefore, if
the magnetic flux .PHI.1 produced via the magnetic field core 6 is
equal in magnitude to the magnetic flux .PHI.2 produced via the
magnetic field core 7, the attraction occurring on the opposed
surfaces cancels each other, so that the rotary synchronous machine
will generate torque T based solely on the magnetic flux .PHI.1 and
.PHI.2.
[0051] On the other hand, the following three-phase alternating
currents IU, IV and IW, phase-shifted from each other by 120
electrical degrees, are passed through the three-phase windings on
the armature core 5:
[0052] IU=Im.multidot.sin .omega.t
[0053] IV=Im.multidot.sin(.omega.t-2.pi./3)
[0054] IW=Im.multidot.sin(.omega.t-4.pi./3)
[0055] Because the three-phase armature windings are phase-shifted
from the corresponding field windings by 120 electrical degrees in
this case, torque T is developed in accordance with the well-known
Fleming's rule, which causes rotation of the rotor 8 (i.e., the
rotation shaft 4). In this case, only the intensities of the
currents passed through the field and armature windings have to be
controlled in order to control the intensity of this torque T.
Although the armature currents may also produce magnetic flux, the
flux has only a negligible influence because reluctance of the
rotor is set to be great in the direction of the magnetic flux and
thereby difficult to magnetize.
[0056] If, on the other hand, the magnetic flux .PHI.1 produced via
the magnetic field core 6 is different in magnitude from the
magnetic flux .PHI.2 produced via the magnetic field core 7, an
axial thrust will occur in the rotor 8 (i.e., the rotation shaft 4)
depending on magnitudinous relation between the flux .PHI.1 and
.PHI.2. Namely, if the magnitude of the magnetic flux .PHI.1
produced via the magnetic field core 6 is smaller than the
magnitude of the magnetic flux .PHI.2 produced via the magnetic
field core 7, an axial thrust in a "+Z" direction occurs in the
rotor 8 ( rotation shaft 4); however, if the magnitude of the
magnetic flux .PHI.1 produced via the magnetic field core 6 is
greater than the magnitude of the magnetic flux .PHI.2 produced via
the magnetic field core 7, an axial thrust in a "-Z" direction
occurs in the rotor 8 (rotation shaft 4).
[0057] Namely, the magnitude of the thrust thus produced depends on
a difference between field currents IfL and IfR fed to the magnetic
field cores 6 and 7, i.e., a difference between the magnetic flux
.PHI.1 and .PHI.2. Therefore, the axial thrust can be controlled by
adjusting the respective intensities of the field currents IfL and
IfR. It should also be obvious that the torque T can be controlled
as desired by controlling the field currents IfL and IfR to the
magnetic field cores 6 and 7. In addition, the magnitude of the
axial thrust can be controlled while the torque T remains constant,
in which case it is only necessary to control the respective
intensities of the magnetic flux .PHI.1 and .PHI.2 while keeping
constant a total value of the magnetic flux .PHI.1 and .PHI.2.
[0058] For accurate positioning control of the rotation shaft 4 in
the axial direction, the synchronous machine preferably includes a
linear position detector capable of detecting a positional
relationship between the stator frame 1 and the rotation shaft 4,
so as to adjust the field currents IfL and IfR on the basis of a
position signal from the linear position detector. In this case, it
is essential to control the field currents IfL and IfR so that the
torque T is kept constant.
[0059] The rotary synchronous machine arranged in the
above-mentioned manner achieves the superior benefit that the
rotating power and axial thrust can be simultaneously controlled by
just controlling the field currents to be supplied to field coils,
without addition of any extra thrust-producing component.
[0060] FIG. 5 is a diagram illustrating exemplary wiring between
the armature and field windings in the rotary synchronous motor. In
the instance where the armature and field windings are mechanically
positioned to be phase-shifted from each other by 90 electrical
degrees as shown in FIG. 2, the armature and field windings can be
wound in series with each other, and the motor can be controlled
via a single inverter as an A.C. motor having series winding
characteristics. In this case, a desired axial thrust can be
generated by adding a separate thrust-controlling winding to the
field windings and controlling the intensity of the field currents
to be supplied to the field windings. If, on the other hand, the
armature and field windings are mechanically positioned to be in
phase with each other in stead of being phase-shifted by 90
electrical degrees, it suffices that the field and armature
currents are phase-shifted from each other by 90 electrical degrees
via different inverters; in this case too, a desired axial thrust
can be generated by adding a separate thrust-controlling winding to
the field windings and controlling the intensity of the field
currents to be supplied to the field windings.
[0061] FIGS. 6 and 7 are both diagrams illustrating other
embodiments of the four-pole rotor 8 of FIG. 2. In the rotor 8a of
FIG. 6, the magnetic substance segments 81 to 84 provided along the
direction of passage of the magnetic flux produced by the field
windings (i.e., axially along the rotation shaft) are magnetically
separated from each other more finely by additional non-magnetic
substance segments 8A to 8F in the rotational or angular direction
of the rotor 8a. For simplicity of illustration, no reference
characters are attached to the additional non-magnetic substance
segments separating the magnetic substance segments 82 to 84 in
FIG. 6. Degree of the magnetic separation attained by the
additional non-magnetic substance segments 8A to 8F in this
embodiment is far smaller than that attained by the main
non-magnetic substance segments 85 to 88 having been described
earlier in relation to FIG. 2. For example, if the thickness (as
measured in the rotational direction of the rotor) of each of the
main non-magnetic substance segments 85 to 88 is between about 3-10
mm, the thickness (as measured in the angular direction of the
rotor) of each of the additional non-magnetic substance segments 8A
to 8F may be chosen to be between about 0.3-3 mm. With this rotor
8a thus arranged, it is possible to effectively preclude influences
of the magnetic flux produced by the armature currents, i.e., the
armature reaction.
[0062] Rotor 8b of FIG. 7 is similar to the rotor 8a of FIG. 6 in
that the magnetic substance segments 81 to 84 provided along the
direction of passage of the magnetic flux produced by the field
windings (i.e., along the rotation shaft) are magnetically
separated from each other more finely by additional non-magnetic
substance segments 8G to 8L in the rotational (angular) direction
of the rotor 8b. The rotor 8b, however, is different from the rotor
8a in that the respective thicknesses (as measured in the
rotational direction of the rotor) of the individual magnetic
substance segments 81 to 84 as separated by the additional
non-magnetic substance segments 8G to 8 correspond to a sinusoidal
distribution of densities of the magnetic flux produced by the
magnetic field cores. For simplicity of illustration, no reference
characters are attached to the non-magnetic substance segments
separating the magnetic substance segments 82 to 84 in FIG. 7.
[0063] While the magnetic substance segments 81 to 84 separated by
the additional non-magnetic substance segments 8A to 8F all have a
same thickness in the rotor 8a of FIG. 6, the magnetic substance
segments 81 to 84 separated by the additional non-magnetic
substance segments 8G to 8L have different thicknesses
corresponding to the sinusoidal distribution of the magnetic flux
densities in the rotor 8b of FIG. 7. That is, in each of the
magnetic substance segments 81 to 84 of the rotor 8b, a portion
closer to the adjacent main non-magnetic substance segments 85, 86;
86, 87; 87, 88; 88, 85 than the other portions is smaller in
thickness than the other portions, with a portion located centrally
between the adjacent main non-magnetic substance segments having
the greatest thickness. In other words, the respective thicknesses
of the additional non-magnetic substance segments 8G, 8H, 8J are
chosen to become sequentially smaller in the mentioned order (i.e.,
from 8G to 8J), while the respective thicknesses of the additional
non-magnetic substance segments 8I, 8K, 8L are chosen to become
sequentially greater in the mentioned order (i.e., from 8I to
8L).
[0064] With the rotor 8b thus arranged, magnetic poles (N and S
poles) corresponding to the sinusoidal distribution of the magnetic
flux produced by the magnetic field currents can be produced on the
outer peripheral surface of the rotor 8b, and thus it is possible
to remarkably improve the rotational characteristics of the
synchronous motor.
[0065] Further, FIG. 8 is a longitudinal sectional view
illustrating a rotary synchronous motor according to still another
embodiment of the present invention, which comprises a pair of the
same synchronous motor structures as shown in FIG. 1 that are
connected together in series. Those elements denoted with the same
reference characters as in FIG. 1 are the same in structure as the
counterparts of FIG. 1 and will not be described here to avoid
unnecessary duplication. Thrust control in the rotary synchronous
motor of FIG. 8 is performed in substantially the same manner as in
the above-described embodiment of FIG. 1. Whereas only two
synchronous motors are connected in series in the illustrated
example, three or more such synchronous motors may of course be
connected in series; the thrust and rotational power controllable
by this synchronous motor can be made greater depending on the
number of the series-connected synchronous motor structures.
[0066] FIG. 9 is a longitudinal sectional view illustrating a
rotary synchronous motor according to still another embodiment of
the present invention, which is different the synchronous motor of
FIG. 1 in that a cylindrical permanent magnet 9 is provided along
the outer peripheral surface of the magnetic substance segments 81
to 84 of the rotor 8. Inner surface portion of the cylindrical
permanent magnet 9 in contact with magnetic substance segments 81
and 83 of the rotor 8 is magnetized into the N pole while an outer
surface portion, corresponding to the inner surface portion, of the
permanent magnet 9 opposed to the armature core 5 is magnetized
into the S pole. Therefore, the surfaces of the magnetic substance
segments 81 and 83 of the rotor 8 opposed to the magnetic field
cores 6 and 7 become N poles. Similarly, an inner surface portion
of the cylindrical permanent magnet 9 in contact with the magnetic
substance segments 82 and 84 of the rotor 8 is magnetized into the
S pole while an outer surface portion, corresponding to the inner
surface portion, of the permanent magnet 9 opposed to the armature
core 5 is magnetized into the N pole. Therefore, the surfaces of
the magnetic substance segments 82 and 84 of the rotor 8 opposed to
the magnetic field cores 6 and 7 become S poles.
[0067] The provision of such a cylindrical permanent magnet 9
around the outer periphery of the magnetic substance segments 81 to
84 can rotate the rotor 8 without having to passing field currents
through the field windings. In this case, however, torque control
can not be performed optimally over a wide range because the torque
depends greatly on the intensities of the magnetic poles of the
permanent magnet 9 and armature currents. Thus, the synchronous
motor of the invention is constructed to permit optimum torque
control over a wide range by providing a hybrid-type rotor 8, which
is capable of controlling both the intensity of the magnetic poles
of the permanent magnet 9 by appropriately controlling the
intensity of the electric currents passed through the field
windings and the intensity of the magnetic flux produced from the
field windings. As an alternative, the non-magnetic substance
segments 85 to 88 may of course be replaced by permanent magnets
85A to 88A that are provided between the magnetic substance
segments 81 to 84 of the rotor 8 and the rotation shaft 4 in such
way that the N poles of the permanent magnets 85A to 88A are
opposed to the magnetic substance segments 82 and 84, as shown in
FIG. 10.
[0068] In the illustrated example of FIG. 9, the magnetic field
cores 6 and 7 are energized by the field currents phase-shifted by
90 degrees. If the surface of the magnetic field core 6 opposed to
the rotor 8 is excited to assume the N pole, the surface of the
other magnetic field core 7 opposed to the rotor 8 is excited to
assume the S pole; conversely, if the surface of the magnetic field
core 6 opposed to the rotor 8 is excited to assume the S pole, the
surface of the other magnetic field core 7 opposed to the rotor 8
is excited to assume the N pole. In this way, magnetic repulsion
occurs between the rotor 8 and the magnetic field core 7 while
magnetic attraction occurs between the rotor 8 and the magnetic
field core 6. In this case, the thrust resulting from the magnetic
attraction by the permanent magnet 9 can be maintained without the
field currents, as long as the rotor 8 is in contact with or in
proximity to the magnetic field core 6 or 7. Further, the rotation
shaft 4 may be positioned in the axial or thrust direction by
adjustment of the field currents IfL and IfR similarly to the
embodiment of FIG. 1, and the thrust itself may also be controlled
by adjustment of the field currents IfL and IfR. In addition, a
plurality of the synchronous motor structures as shown in FIG. 9
may be combined together in a multistage fashion as illustrated in
FIG. 8, to thereby produce a greater thrust.
[0069] FIG. 11 is a longitudinal sectional view illustrating a
rotary synchronous motor according to yet another embodiment of the
present invention, which is different the synchronous motor of FIG.
1 in that opposite end portions of the rotor 8C, opposed to the
magnetic field cores 6C and 7C to produce magnetic attraction, are
tapered outwardly relative to the rotational axis to thereby
provide end surfaces slanted at a predetermined angle relative to
the rotational axis. By the tapered configuration of the rotor 8C,
there is established a relationship that the traveling distance Z
of the rotor 8C is greater than a width of a gap d on the magnetic
circuitry between the rotor 8C and the magnetic field cores 6C and
7C (i.e., z>d), so that a sufficient traveling distance Z of the
rotor 8C greater than the gap width d can be quaranteed even
through the gap width d is small and it is possible to reduce the
necessary field currents and substantially improve the thrust
characteristics.
[0070] FIG. 12 is a graph showing relationship between the
traveling distance z and the thrust Fz in the case where the side
surface of the rotor 8C extend parallel to the rotational axis
along the full length of the rotor 8C as in the synchronous motor
of FIG. 1 and in the case where the rotor 8C has opposite end
portions tapered relative to the rotational axis. As apparent from
FIG. 12, in the "fully parallel" configuration where the side
surface of the rotor 8C extend parallel to the rotational axis (the
synchronous motor of FIG. 1), the thrust Fz decreases sharply as
the traveling distance z becomes greater. However, in the "tapered"
configuration of FIG. 11, the thrust decrease can be less than in
the fully parallel configuration irrespective of an increase in the
traveling distance z. This is because the tapered configuration
achieves a greater traveling distance Z than the fully parallel
configuration even when the gap width d is the same.
[0071] As shown in FIG. 11, magnetic attraction F is produced
between the rotor 8C and the magnetic field cores 6C and 7C in a
direction normal to the tapered side surface of the rotor 8C. This
magnetic attraction F is split into force in the axial direction
(i.e., thrust) Fz and force Fx in the radial direction. While the
force Fz in the radial direction cancel each other, the force
(thrust) Fz in the axial direction combine with each other in a
single direction, thus giving thrust substantially equal to that
given in the fully parallel (i.e., non-tapered) configuration where
the side surface of the rotor 8C extends parallel to the rotational
axis along the full length of the rotor 8C. With this arrangement,
the synchronous motor of FIG. 11 can function as magnetic bearings
which are advantageous in both the axial and radial directions, by
controlling the magnitudes of the magnetic flux .PHI.1 and .PHI.2.
Note that whereas the rotor 8C of FIG. 11 is shown as tapered at
opposite end portions, only one of the end portions of the rotor
may be tapered.
[0072] FIG. 13 is a block diagram illustrating an A.C. servo motor
system employing the synchronous motor according to the present
invention. The A.C. servo motor system will be described below in
relation to a case where the armature windings and field windings
of the synchronous motor are mechanically positioned to be in phase
with each other, rather than being phase-shifted by 90 electrical
degrees, and field currents and armature currents are supplied to
the filed windings and armature windings such that they are
phase-shifted by 90 electrical degrees.
[0073] To the rotation shaft of the synchronous motor is connected
a detector 26, such as a rotary encoder or rotary resolver, for
detecting a rotating speed and magnetic pole positions of the
motor. The detector 26 feeds signal S2 indicative of a rotating
speed of the motor back to a speed amplifier 21 and also feeds
signal S6 indicative of rotating positions of the magnetic fields
or magnetic pole positions of the motor back to an armature PWM
amplifier 23a and a field PWM amplifier 23f.
[0074] The speed amplifier 21 receives rotating speed instruction
S1 as well as the motor rotating speed signal S2 from the detector
26 to thereby calculate an offset between the speeds indicated by
the signals S1 and S2 and then supplies a current amplifier 22 with
armature current instructing signal (torque signal) S3
corresponding to the thus-calculated speed offset. Armature current
amplifier 22a amplifies a difference between electric current
feedback signal S4 detected by a current detecting isolator 25
(i.e., feedback signal of detected U-phase and V-phase currents)
and the armature current instructing signal S3 from the speed
amplifier 21 and then supplies the armature PWM amplifier 23a with
the amplified current difference as input signal S5. The armature
PWM amplifier 23a, in turn, supplies an armature inverter 24a with
three-phase PWN signal, i.e., inverter control signal S7 on the
basis of the input signal S5 from the current amplifier 22 and
magnetic pole position signal S6 from the detector 26. The armature
inverter 24a is driven by the inverter control signal S7, to supply
armature currents to the armature windings of the individual phases
in the synchronous motor. Control system for the field currents is
similar to that for the armature currents except that it does not
include the speed amplifier 21. This control system for the field
currents includes a magnetic field current amplifier 22f, a
magnetic field PWM amplifier 23f, a magnetic field inverter 24f and
a magnetic field current detecting isolator 25f. Because no speed
amplifier is included in this magnetic field currents control,
magnetic field current instructing signal FS is input directly to
the magnetic field current amplifier 22f. It should be obvious that
whereas only one magnetic field current control is shown in FIG.
13, two such magnetic field current controls must be provided in
corresponding relation to the two sets of the filed windings. Here,
thrust of the synchronous motor is controlled as necessary
depending on the level of the magnetic field current instructing
signal FS.
[0075] With the A.C. servo motor system of FIG. 13 arranged in the
above-mentioned manner, the synchronous motor according to the
present invention is allowed to operate as an A.C. servo motor
rotating at a desired speed and also with a desired thrust.
Whichever rotating position the rotation shaft may be in, the A.C.
servo motor system of FIG. 13 detects the shaft's rotating position
so as to control the respective phases of the three-phase magnetic
field currents in such a manner that the pole center of the
rotation shaft coincides with the pole center of the rotating
magnetic fields. This allows the rotation shaft to be always
revolved with maximum torque.
[0076] The magnetic substance segments in the above-mentioned
embodiments may be made of any of iron material (e.g., pure iron,
soft iron, cast steel, magnetic steel band, or nondirectional or
directional silicon steel), iron-nickel alloy (e.g., Permalloy,
Isoperm or Perminvar), dust core (carbonyl dust core, Permalloy
dust core or Sendust dust core), or ferrite (spinel ferrite,
composite ferrite such as Mn-Zn ferrite, Cu-Zn ferrite, Ni-Zn
ferrite or Cu-Zn-Mg ferrite).
[0077] The embodiments of FIGS. 1 and 11 have been described above
in relation to the case where the magnetic field cores are provided
adjacent to the opposite end portions of the rotor, only one such
magnetic field core may be provided adjacent to one end portion of
the rotor. Where a plurality of the inventive linear motor
structures are connected together in a multi-stage fashion as shown
in FIG. 8, only one such magnetic field core may be provided
adjacent to one end portion of the rotor; in this case, thrust can
be produced only in one direction although no positioning in the
axial direction is permitted. Further, the rotor of FIG. 1 or 11
may be supported only by the bearing 2; particularly, in the case
of FIG. 11, the rotor can function very efficiently by virtue of
magnetic attraction acting in the radial direction.
[0078] Although the present invention has been described so far as
implemented as synchronous motors, the invention may also be
applied as a synchronous power generator, where electromotive force
is induced in the armature windings by supplying the field windings
with currents corresponding to a rotating position of the rotor and
is extracted from the armature windings. In such a case, a position
detector for detecting a rotating position of the rotor may be
provided on the same rotation shaft as the rotor so that the field
currents are controlled depending on the detected rotating
position.
[0079] Further, although the description has been made above about
four-pole/24-slot or double-pole/12-slot synchronous machines, the
numbers of the poles and slots should not be understood as limited
to the above-mentioned, or rather the combination of the numbers
may be selectively varied as necessary. Furthermore, while the
filed windings have been described as single-layer lap windings in
the example of FIG. 3, they may be double-layer lap windings.
[0080] Furthermore, whereas the preferred embodiments have been
described in relation to the case where the rotor is located inside
the armature core, the basic principle of the present invention is
of course applicable to a situation where the rotor is located
outside the armature core, i.e., a so-called "out rotor"
arrangement.
[0081] In summary, the rotary synchronous machine achieves the
superior benefit that it can simultaneously control both rotational
force and axial thrust by itself.
* * * * *