U.S. patent number RE44,037 [Application Number 12/646,584] was granted by the patent office on 2013-03-05 for rotating electric machine having rotor embedded-permanent-magnets with inner-end magnetic gaps and outer-end magnetic gaps, and electric car using the same electric machine.
This patent grant is currently assigned to Hitachi, Ltd.. The grantee listed for this patent is Noriaki Hino, Shigeru Kakugawa, Masashi Kitamura, Takashi Kobayashi, Yutaka Matsunobu, Fumio Tajima, Takashi Yasuhara. Invention is credited to Noriaki Hino, Shigeru Kakugawa, Masashi Kitamura, Takashi Kobayashi, Yutaka Matsunobu, Fumio Tajima, Takashi Yasuhara.
United States Patent |
RE44,037 |
Tajima , et al. |
March 5, 2013 |
Rotating electric machine having rotor embedded-permanent-magnets
with inner-end magnetic gaps and outer-end magnetic gaps, and
electric car using the same electric machine
Abstract
A permanent magnet rotating electric machine comprises a stator
having stator windings wound round a stator iron core and a
permanent magnet rotor having a plurality of inserted permanent
magnets in which the polarity is alternately arranged in the
peripheral direction in the rotor iron core. The rotor iron core of
the permanent magnets is composed of magnetic pole pieces,
auxiliary magnetic poles, and a stator yoke, and furthermore has
concavities formed on the air gap face of the magnetic pole pieces
of the rotor iron core of the permanent magnets, gently tilting
from the central part of the magnetic poles to the end thereof. In
a permanent magnet rotating electric machine, effects of iron loss
are reduced, and an electric car using highly efficient permanent
magnet rotating electric machine are realized.
Inventors: |
Tajima; Fumio (Hitachi,
JP), Matsunobu; Yutaka (Hitachinaka, JP),
Kitamura; Masashi (Mito, JP), Hino; Noriaki
(Mito, JP), Kobayashi; Takashi (Hitachiota,
JP), Kakugawa; Shigeru (Hitachi, JP),
Yasuhara; Takashi (Yotsukaido, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Tajima; Fumio
Matsunobu; Yutaka
Kitamura; Masashi
Hino; Noriaki
Kobayashi; Takashi
Kakugawa; Shigeru
Yasuhara; Takashi |
Hitachi
Hitachinaka
Mito
Mito
Hitachiota
Hitachi
Yotsukaido |
N/A
N/A
N/A
N/A
N/A
N/A
N/A |
JP
JP
JP
JP
JP
JP
JP |
|
|
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
34918340 |
Appl.
No.: |
12/646,584 |
Filed: |
December 23, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11052753 |
Dec 19, 2006 |
7151335 |
|
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Reissue of: |
11611206 |
Dec 15, 2006 |
7521832 |
Apr 21, 2009 |
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Foreign Application Priority Data
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Mar 10, 2004 [JP] |
|
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2004-066465 |
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Current U.S.
Class: |
310/156.48;
310/156.53; 310/156.56; 310/156.54; 310/156.57 |
Current CPC
Class: |
B60L
7/14 (20130101); B60L 15/2009 (20130101); B60L
50/66 (20190201); B60L 50/51 (20190201); H02K
1/2766 (20130101); B60L 2240/12 (20130101); H02K
29/03 (20130101); Y02T 10/64 (20130101); Y02T
10/645 (20130101); B60L 2240/423 (20130101); Y02T
10/705 (20130101); H02K 2201/03 (20130101); Y02T
10/7005 (20130101); Y02T 10/7275 (20130101); H02K
2213/03 (20130101); B60L 2270/145 (20130101); Y02T
10/70 (20130101); Y02T 10/72 (20130101); B60L
2240/421 (20130101); Y02T 10/641 (20130101) |
Current International
Class: |
H02K
1/12 (20060101); H02K 1/27 (20060101); H02K
21/14 (20060101); H02K 21/12 (20060101) |
Field of
Search: |
;310/156.48,156.53,156.54,156.56,156.57,156.51-156.52,156.55,156.58,156.49,216.004,261.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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5-103453 |
|
Apr 1993 |
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JP |
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5-103453 |
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Apr 1993 |
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JP |
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8-251846 |
|
Sep 1996 |
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JP |
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8-251846 |
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Sep 1996 |
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JP |
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9-261901 |
|
Oct 1997 |
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JP |
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9-261901 |
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Oct 1997 |
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JP |
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10-146031 |
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May 1998 |
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JP |
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10-262359 |
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Sep 1998 |
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JP |
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10-262359 |
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Sep 1998 |
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JP |
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11-27913 |
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Jan 1999 |
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JP |
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11-27913 |
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Jan 1999 |
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JP |
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11-164501 |
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Jun 1999 |
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JP |
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11-164501 |
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JP |
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2000-50546 |
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Feb 2000 |
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JP |
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2000-60038 |
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2000-60038 |
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JP |
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2000-116085 |
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JP |
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2000-116085 |
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JP |
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2000-295805 |
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JP |
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2000-295805 |
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Oct 2000 |
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JP |
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2001-178047 |
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Jun 2001 |
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JP |
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2001-178047 |
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Jun 2001 |
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JP |
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2001-286110 |
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Oct 2001 |
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JP |
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2001-286110 |
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Oct 2001 |
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JP |
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2002-78260 |
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Mar 2002 |
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JP |
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2002-78260 |
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Mar 2002 |
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JP |
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2002-171730 |
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Jun 2002 |
|
JP |
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2002-171730 |
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Jun 2002 |
|
JP |
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2002-209350 |
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Jul 2002 |
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JP |
|
2002-209350 |
|
Jul 2002 |
|
JP |
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2004-328956 |
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Nov 2004 |
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JP |
|
Other References
Hirose, Keiichi, Introduction to Electric Machine Design (Second
Edition), The Institute of Electrical Engineers of Japan, Aug. 31,
1951, pp. 159-161, Meisei University, Denki Sekkei Gairon. cited by
applicant .
Japanese Office Action dated Dec. 5, 2006 with English translation
(forty-one (41) pages). cited by applicant .
Japanese office action dated Sep. 8, 2009 with partial English
translation (9 pages). cited by applicant.
|
Primary Examiner: Nguyen; Tran
Attorney, Agent or Firm: Crowell & Moring LLP
Claims
What is claimed is:
1. A permanent magnet electric rotating machine, comprising: a
stator; a rotor having a rotor iron core and being arranged
opposite said stator with a rotation air gap therebetween; a
plurality of magnetic poles in said rotor iron core and arranged in
a peripheral direction of said rotor in which polarity is
alternately arranged; a plurality of auxiliary magnetic pole
portions arranged in the peripheral direction between said magnetic
poles; and bridge portions which connect magnetic pole piece
portions formed between said magnetic poles and a surface of said
rotor with said auxiliary magnetic pole portions, .Iadd.each of
said magnetic pole piece portions formed between two permanent
magnets of each of said magnetic poles and an outer surface of the
rotor, .Iaddend.wherein .Iadd.said two permanent magnets of
.Iaddend.each said magnetic pole .[.has two permanent magnets of.].
.Iadd.have .Iaddend.common polarity and .Iadd.are .Iaddend.in a
V-shape arrangement opening towards said stator, a core portion of
said rotor iron core and a first magnetic gap are provided between
each of the inner ends of said two permanent magnets, said core
portion being provided to connect said magnetic pole piece portions
with said rotor iron core .[.radically.]. .Iadd.radially
.Iaddend.inward of said magnetic poles, and second magnetic gaps
are provided between outer ends of said two permanent magnets and
said bridge portions.
2. A permanent magnet rotating electric machine according to claim
1 wherein said rotor iron is further composed of concavities formed
on an air gap face of said magnetic pole pieces.
3. A permanent magnet rotating electric machine according to claim
2, wherein: a change in a length of the rotation air gap at a
central part of said magnetic poles at a position of said
concavities is smaller than a change in the length of the rotation
air gap at an end of said magnetic poles.
4. A permanent magnet rotating electric machine according to claim
2, wherein: a length of the rotation air gap of said auxiliary
magnetic pole portions is smaller than the length of the rotation
air gap of said magnetic pole pieces.
5. A permanent magnet rotating electric machine according to claim
2, wherein: said concavities are within an electrical angle range
of 20.degree. to 30.degree. from said magnetic pole center where
there are two slots of said stator iron core per pole and per
phase.
6. A permanent magnet rotating electric machine according to claim
2, wherein: said concavities are within an electrical angle range
of 15.degree. to 45.degree. from said magnetic pole center where
there is one slot of said stator iron core per pole and per
phase.
7. An electric car comprising a permanent magnet rotating electric
machine, wheels driven by said permanent magnet rotating electric
machine, and control means for controlling drive torque outputted
by said permanent magnet rotating electric machine, wherein: said
permanent magnet rotating electric machine is composed of a stator;
a rotor having a rotor iron core and being arranged opposite said
stator with a rotation air gap therebetween; a plurality of
magnetic poles in said rotor iron core and arranged in a peripheral
direction of said rotor in which polarity is alternately arranged;
a plurality of auxiliary magnetic pole portions arranged in the
peripheral direction between said magnetic poles; and bridge
portions which connect magnetic pole piece portions formed between
said magnetic poles and a surface of said rotor with said auxiliary
magnetic pole portions, .Iadd.each of said magnetic pole piece
portions formed between two permanent magnets of each of said
magnetic poles and an outer surface of the rotor, .Iaddend.wherein
.Iadd.said two permanent magnets of .Iaddend.each said magnetic
pole .[.has two permanent magnets of.]. .Iadd.have .Iaddend.common
polarity and .Iadd.are .Iaddend.in a V-shape arrangement opening
towards said stator, a core portion of said rotor iron core and a
first magnetic gap are provided between each of the inner ends of
said two permanent magnets, said core portion being provided to
connect said magnetic pole piece portions with said rotor iron core
radially inward of inside said magnetic poles, and second magnetic
gaps are provided between outer ends of said two permanent magnets
and said bridge portions.
8. An electric car according to claim 7, wherein said rotor iron
core is further composed of magnetic pole pieces positioned on an
air gap face of said permanent magnets for forming a magnetic path
of said permanent magnets, auxiliary magnetic poles projected up to
said air gap face of said permanent magnets for producing reluctant
torque, and a stator yoke positioned on a reversed air gap face of
said permanent magnets for forming a magnetic path of said
auxiliary magnetic poles and said permanent magnets, and further
includes concavities formed on an air gap face of said magnetic
pole pieces.
9. An electric car according to claim 8, wherein: said concavities
are within an electrical angle range of 20.degree. to 30.degree.
from said magnetic pole center where there are two slots of said
stator iron core per pole and per phase.
10. An electric car according to claim 8, wherein: said concavities
are within an electrical angle range of 15.degree. to 45.degree.
from said magnetic pole center where there is one slot of said
stator iron core per pole and per phase.
Description
CLAIM OF PRIORITY
The present application claims priority from Japanese application
serial no. 2004-66465, filed on Mar. 10, 2004, the content of which
is hereby incorporated by reference into this application.
FIELD OF THE INVENTION
The present invention relates to a permanent magnet rotating
electric machine suitable for use for an electric car and the
electric car using it.
BACKGROUND OF THE INVENTION
A motor used to drive an electric car, particularly an electric
vehicle and a hybrid electric vehicle, is desired to be small,
light, and highly efficient. In recent years, by development of a
highly efficient magnet material, as a drive motor for an electric
car (particularly an electric vehicle and a hybrid electric
vehicle), in consideration of the respect that it can be made
smaller, lighter, and more highly efficient than an induction motor
and a reluctance motor, a permanent magnet motor has been used
predominantly. The reason is that the permanent magnet motor can
generate a large amount of magnetic flux without supplying a large
current. Particularly, in a region of high torque at a low speed,
the characteristic can be realized. On the other hand, at a high
speed, an occurrence of iron loss and an occurrence of high voltage
due to the magnetic flux amount often come into a problem.
As a rotor structure of a motor used for an electric car,
particular an electric vehicle and a hybrid electric vehicle, in
consideration of countermeasures for an occurrence of iron loss and
an occurrence of high voltage and retention of permanent magnets,
an embedding type permanent magnet rotating electric machine for
embedding permanent magnets in a laminated silicone steel plate is
known. Furthermore, as described in Japanese Patent Laid-Open No.
Hei09(1997)-261901, as a structure of reducing the rate of torque
by magnets and reducing the magnetic flux amount of permanent
magnets, a structure of arranging auxiliary salient poles between
permanent magnets is known. In this structure, since the magnetic
flux of the permanent magnets is little, the iron loss at a
comparatively high speed is little, while in a region requiring low
speed torque, reluctant torque is produced by the auxiliary salient
poles and little magnetic torque can be compensated for.
SUMMARY OF THE INVENTION
However, even in the structure described in Japanese Patent
Laid-Open No. Hei09(1997)-261901, particularly in a case of a drive
motor used in a hybrid electric vehicle, the iron loss due to the
magnetic flux of the permanent magnets becomes braking force and
increases fuel expenses of the car, so that the iron loss in a
high-speed region comes into a problem.
Further, as a motor used to drive an electric car, particularly an
electric vehicle and a hybrid electric vehicle, the reduction in
the torque ripple is important from the viewpoint of
comfortableness to ride in and noise reduction, though this respect
is not taken into account in conventional motors.
The first object of the present invention is to provide a highly
efficient permanent magnet rotating electric machine capable of
more reducing effects of iron loss and an electric car using
it.
Further, the second object of the present invention is to provide a
permanent magnet rotating electric machine of a low torque ripple
capable of reducing the torque ripple and an electric car using
it.
(1) To accomplish the above first object, the present invention is
a permanent magnet rotating electric machine comprising a stator
having stator windings wound round a stator iron core and a
permanent magnet rotor having a plurality of inserted permanent
magnets in which the polarity is alternately arranged in the
peripheral direction in the rotor iron core, wherein the iron core
of the permanent magnet rotor is composed of magnetic pole pieces
positioned on the air gap face of the permanent magnets for forming
the magnetic path of the permanent magnets, auxiliary magnetic
poles projected up to the air gap face of the permanent magnets for
producing reluctant torque, and a stator yoke positioned on the
reversed air gap face of the permanent magnets for forming the
magnetic path of the auxiliary salient poles and permanent magnets,
and the iron core has concavities formed on the air gap face of the
magnetic pole pieces of the rotor iron core of the permanent
magnets, gently tilting from the central part of the magnetic poles
to the end thereof.
By use of such a constitution, the effect of iron loss can be
reduced more and high efficiency can be realized.
(2) In (1) mentioned above, the change in the air gap length at the
central part of the magnetic poles at the position of the
concavities is preferably smaller than the change in the air gap
length at the end of the magnetic poles.
(3) In (1) mentioned above, the air gap length of the auxiliary
salient pole portion is preferably smaller than the air gap length
of the magnetic pole piece portion.
(4) To accomplish the above second object, the present invention is
a permanent magnet rotating electric machine comprising a stator
having stator windings wound round a stator iron core and a
permanent magnet rotor having a plurality of inserted permanent
magnets in which the polarity is alternately arranged in the
peripheral direction in the rotor iron core, wherein the iron core
of the permanent magnet rotor is composed of magnetic pole pieces
positioned on the air gap face of the permanent magnets for forming
the magnetic path of the permanent magnets, auxiliary magnetic
poles projected up to the air gap face of the permanent magnets for
producing reluctant torque, and a stator yoke positioned on the
reversed air gap face of the permanent magnets for forming the
magnetic path of the auxiliary salient poles and permanent magnets,
and the iron core has concavities formed on the air gap face of the
magnetic pole pieces of the rotor iron core of the permanent
magnets on both sides of the magnetic pole center at a position
within the range from an electrical angle of 20.degree. to
30.degree. from the magnetic pole center when the number of slots
of the stator iron core per pole and per phase is 2 or at a
position within the range from an electrical angle of 15.degree. to
45.degree. from the magnetic pole center when the number of slots
of the stator iron core per pole and per phase is 1.
By use of such a constitution, the torque ripple can be
reduced.
(5) To accomplish the above first object, the present invention is
an electric car comprising a permanent magnet rotating electric
machine, wheels driven by the permanent magnet rotating electric
machine, and a control means for controlling drive torque outputted
by the permanent magnet rotating electric machine, wherein the
permanent magnet rotating electric machine is composed of a stator
having stator windings wound round a stator iron core and a
permanent magnet rotor having a plurality of inserted permanent
magnets in which the polarity is alternately arranged in the
peripheral direction in the rotor iron core, and the iron core of
the permanent magnet rotor is composed of magnetic pole pieces
positioned on the air gap face of the permanent magnets for forming
the magnetic path of the permanent. magnets, auxiliary magnetic
poles projected up to the air gap face of the permanent magnets for
producing reluctant torque, and a stator yoke positioned on the
reversed air gap face of the permanent magnets for forming the
magnetic path of the auxiliary salient poles and permanent magnets,
and the iron core has concavities formed on the air gap face of the
magnetic pole pieces of the rotor iron core of the permanent
magnets, gently tilting from the magnetic pole central part to the
end.
By use of such a constitution, an electric car of low vibration and
low noise can be obtained.
(6) To accomplish the above second object, the present invention is
an electric car comprising a permanent magnet rotating electric
machine, wheels driven by the permanent magnet rotating electric
machine, and a control means for controlling drive torque outputted
by the permanent magnet rotating electric machine, wherein the
permanent magnet rotating electric machine is composed of a stator
having stator windings wound round a stator iron core and a
permanent magnet rotor having a plurality of inserted permanent
magnets in which the polarity is alternately arranged in the
peripheral direction in the rotor iron core, and the iron core of
the permanent magnet rotor is composed of magnetic pole pieces
positioned on the air gap face of the permanent magnets for forming
the magnetic path of the permanent magnets, auxiliary magnetic
poles projected up to the air gap face of the permanent magnets for
producing reluctant torque, and a stator yoke positioned on the
reversed air gap face of the permanent magnets for forming the
magnetic path of the auxiliary salient poles and permanent magnets,
and the iron core has concavities formed on the air gap face of the
magnetic pole pieces of the rotor iron core of the permanent
magnets on both sides of the magnetic pole center at a position
within the range from an electrical angle of 20.degree. to
30.degree. from the magnetic pole center when the number of slots
of the stator iron core per pole and per phase is 2 or at a
position within the range from an electrical angle of 15.degree. to
45.degree. from the magnetic pole center when the number of slots
of the stator iron core per pole and per phase is 1.
By use of such a constitution, an electric car of low vibration and
low noise can be obtained.
According to the present invention, an electric car in which the
effect of iron loss can be reduced more, and a highly efficient
permanent magnet rotating electric machine can be obtained, and
fuel expenses can be reduced, and low vibration and noise can be
realized can be obtained.
According to the present invention, a permanent magnet rotating
electric machine of a low torque ripple can be obtained and an
electric car of low vibration and noise can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view showing the constitution of the
permanent magnet rotating electric machine of the first embodiment
of the present invention.
FIG. 2 is a cross sectional view showing the constitution of the
permanent magnet rotating electric machine of the first embodiment
of the present invention.
FIG. 3 is an enlarged cross sectional view showing the detailed
constitution of the rotor of the permanent magnet rotating electric
machine of the first embodiment of the present invention.
FIG. 4 is an illustration for the air gap length of the magnetic
pole pieces of the rotor of the permanent magnet rotating electric
machine of the first embodiment of the present invention.
FIG. 5 is an illustration for iron loss of the rotor of the
permanent magnet rotating electric machine of the first embodiment
of the present invention.
FIG. 6 is an illustration for iron loss of the rotor of the
permanent magnet rotating electric machine of the first embodiment
of the present invention.
FIG. 7 is a cross sectional view showing the constitution of the
permanent magnet rotating electric machine of the second embodiment
of the present invention.
FIG. 8 is a cross sectional view showing the constitution of the
permanent magnet rotating electric machine of the third embodiment
of the present invention.
FIG. 9 is an illustration for the relationship between the
concavities 77 and the torque ripple formed on the outer periphery
of the magnetic pole pieces of the rotor of the permanent magnet
rotating electric machine of the third embodiment of the present
invention.
FIG. 10 is an illustration for the relationship between the
concavities 77 and the torque ripple formed on the outer periphery
of the magnetic pole pieces of the rotor of the permanent magnet
rotating electric machine of the third embodiment of the present
invention.
FIG. 11 is a block diagram showing the constitution of the machine
driving system of the electric car loading the permanent magnet
rotating electric machine of each embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the constitution of the permanent magnet rotating
electric machine Of the first embodiments of the present invention
will be explained with reference to FIGS. 1 to 6. Here, as an
example, an example of a permanent magnet motor in which a rotating
electric machine has a winding structure of distribution winding as
a stator and a rotor has 8 poles will be explained.
Firstly, by referring to FIGS. 1 and 2, the whole constitution of
the permanent magnet rotating electric machine of this embodiment
will be explained.
FIGS. 1 and 2 are cross sectional views showing the constitution of
the permanent magnet rotating electric machine of the first
embodiment of the present invention. FIG. 1 is a cross sectional
view in the parallel direction with the rotation axis and FIG. 2 is
a cross sectional view in the perpendicular direction to the
rotation axis and a view in the A-A direction shown in FIG. 1.
Further, in FIGS. 1 and 2, the same numerals indicate the same
parts.
As shown in FIG. 1, a permanent magnet rotating electric machine 1
includes a stator 2, a rotor 3, and end brackets 9A and 9B. The
stator 2 has a stator iron core 4 and stator windings 5. The rotor
3 has a rotor iron core 7 composed of a magnetic substance and a
shaft 8. Further, the rotor 3, via the shaft 8 fit into the rotor
iron core 7, is rotatably held by bearings 10A and 10B fit into the
end brackets 9A and 9B. Further, the constitution shown in the
drawing has no frame on the outer periphery of the stator iron core
4. However, a frame may be used if necessary.
On the shaft 8 of the rotor 3, a magnetic pole position sensor PS
for detecting the position of the rotor 3 and a position sensor E
are installed. According to the position of the rotor detected by
the magnetic pole position sensor PS for detecting the position of
the rotor 3 and the position sensor E, a 3-phase current is
supplied to the stator windings 5, thus a rotating magnetic field
is generated. Magnetic attraction and repulsion force are generated
between the rotating magnetic field and the permanent magnets of
the rotor 3, thus continuous rotary power is generated. Here, when
the current phase is properly selected, in the low speed and large
torque region, the composite torque of the torque by permanent
magnet torque 6 and the torque by auxiliary salient poles 71 is
controlled so as to be maximized.
On the other hand, in the high speed region where the induced
voltage of the permanent magnets is higher than the terminal
voltage of the motor, the current vector is moved forward, thus the
rotating magnetic field by the stator winding current is controlled
by weak field control so as to be applied to the center of the
permanent magnets 6 as demagnetizing force. By doing this, the
magnetic flux of the permanent magnets 6 is effectively reduced,
thus the iron loss of the rotating electric machine can be reduced
and a highly efficient operation can be performed.
Next, as shown in FIG. 2, the stator iron core 4 is composed of a
circular ring shaped stator yoke 41 and iron core teeth 42. Between
the neighboring stator teeth 42, slots 43 for storing the stator
windings 5 are installed. Here, round the stator windings 5,
general 3-phase (phase U, phase V, phase W) distribution windings
are wound. The number of stator teeth 42 is 48 and the number of
slots 43 is also 48. The number of stator teeth (salient poles) 42
per phase is 16.
The rotor iron core 7 has insertion holes 70 for the permanent
magnets 6 arranged at even intervals in the peripheral direction.
The permanent magnets 6 are inserted into the insertion holes 70.
The number of poles of the rotor 3 is 8 and the number of insertion
holes 70 is 16. For example, permanent magnets 6A1 and 6A2 inserted
into two insertion holes 70A1 and 70A2 constitute the same pole,
thus one pole is formed. For example, assuming the polarity of the
permanent poles 6A1 and 6A2 as pole S, the polarity of the
neighboring permanent magnets 6B1 and 6B2 in the peripheral
direction becomes pole N and mutual polarity is obtained in the
peripheral direction. The insertion holes 70A1 and 70A2 are
arranged symmetrically with respect to line in the radial direction
of the rotor iron core 7 and in a V shape. Therefore, two permanent
magnets 6B1 and 6B2 are arranged per magnetic pole, so that the
flux density per magnetic pole is increased.
The rotor iron core 7 has magnetic pole pieces 72 installed on the
outer periphery of the permanent magnets 6. The magnetic pole
pieces 72 form a magnetic circuit through which the magnetic flux
generated by the permanent magnets 6 flows toward the stator 2 via
the air gap formed between the rotor 3 and the stator 2.
The permanent magnets 6 forming the respective magnetic poles
adjoin each other via the auxiliary salient poles 71 which are a
part of the rotor iron core 7. The auxiliary magnetic poles 71
bypass the magnetic circuit of the magnets and directly generate
the magnetic flux on the stator side by the electromotive force of
the stator. The magnetic pole pieces 72 and the auxiliary salient
poles 71 are connected by bridges 73 to increase the mechanical
strength thereof.
Between the magnets 6A1 and 6A2 and the bridges 73, triangular air
gaps 75A1 and 75A2 are respectively formed and between the magnets
6A1 and 6A2 forming the same pole, a triangular air gap 75A3 is
formed. Air exists inside the air gaps 75A1, 75A2, and 75A3 and the
leakage flux is reduced.
The inner peripheral side of the insertion holes 70, the auxiliary
salient poles 71, and the air gaps 75A1, 75A2, and 75A3 is a rotor
yoke 74 constituting the magnetic path of the permanent magnets 6.
By the above constitution, the so-called embedding type permanent
magnet rotating electric machine is formed.
The aforementioned control by weak field current, by increasing the
current, can reduce the basic wave part of the iron loss, though
the high frequency component of the iron loss is increased
inversely and after all, the iron loss may not be reduced.
On the other hand, when the air gap length is increased, the iron
loss by high frequency waves is decreased. However, in
correspondence to an increase in the air gap length, the torque is
reduced. Therefore, it is important to suppress an increase in the
iron loss at a high speed while suppressing the reduction in an
occurrence of torque.
Therefore, in this embodiment, on the peripheral part of the rotor
iron core 7, that is, on the air gap face of the magnetic pole
pieces 72, concavities 76 gently tilting from the central part of
the magnetic poles to the end thereof are formed. Particularly,
since the concavities 76 gently tilting from the central part of
the magnetic poles to the end thereof are formed on the air gap
face of the magnetic pole pieces of the rotor iron core, when the
air gap length at the central part of the auxiliary salient poles
71 and the magnetic pole pieces 72 which greatly contribute to an
occurrence of torque and do not affect an occurrence of iron loss
is reduced and the air gap portion of the magnetic pole pieces from
the center of the magnetic poles to the end thereof causing high
frequency iron loss rather than an occurrence of torque is
increased as shown in FIG. 2, consistency of a reduction in the
iron loss with insurance of an occurrence of torque can be
realized. This respect will be explained by referring to FIG. 3 and
the subsequent drawings.
Next, by referring to FIG. 3, the detailed constitution of the
rotor of the permanent magnet rotating electric machine of this
embodiment.
FIG. 3 is an enlarged cross sectional view showing the detailed
constitution of the rotor of the permanent magnet rotating electric
machine of the first embodiment of the present invention. FIG. 3
shows the essential section shown in FIG. 2 which is enlarged.
Further, the same numerals as those shown in FIG. 2 indicate the
same parts.
The line connecting the center of the permanent magnets 6A1 and 6A2
constituting the same pole, that is, the center of the air gap 75A3
and the center of the rotor 3, that is, the center of the shaft 8
is assumed as L1. The insertion holes 70A and 70A2 are arranged so
as to be symmetrical with respect to the line L1. Therefore, the
permanent magnets 6A1 and 6A2 are also arranged so as to be
symmetrical with respect to the line L1. The line L1 is a line
indicating the central part of one magnetic pole.
Further, the lines connecting the centers of bridges 73A1 and 73A2
and the center of the rotor 3, that is, the center of the shaft 8
are assumed respectively as L2 and L3. The range between the lines
L2 and L3 forms one magnetic pole. The angle .zeta.1 of one
magnetic pole is an electric angle of 180.degree. and is composed
of 8 poles, so that it is a mechanical angle of 45.degree..
Further, the angle .theta.2 in the drawn example is an electric
angle of 130.degree..
Lines L4 and L5 are lines connecting the right corner of the
permanent magnet 6A1 and the left corner of the permanent magnet
6A2 and the center of the rotor 3, that is, the center of the shaft
8.
Here, at the position of the central part of the magnetic poles,
the air gap length between the outer peripheral part of the rotor 3
and the inner peripheral part of the stator 2 is assumed as G1, and
the air gap length at the positions on the outer periphery of the
rotor 3 where concavities 76A1 and 76A2 are formed are assumed as
G2, and the air gap length at the end of the magnetic poles is
assumed as G3. The air gap lengths G1 and G2 are longer than the
air gap length G3 and in the rotor 3, in the neighborhood of the
center of the magnetic pole portion thereof, the concavities 76 are
formed on the outer periphery. Moreover, the air gap length G1 is
shorter than the air gap length G2 and on the air gap face of the
magnetic pole pieces 72, the concavities 76 gently tilting from the
center of the magnetic poles to the end thereof are formed. An
example of it is that the air gap length G1 is 0.5 mm, and the air
gap length G2 is 1.5 mm, and the air gap length G3 is 0.3 mm.
Here, by referring to FIG. 4, the air gap length of the magnetic
pole pieces of the rotor of the permanent magnet rotating electric
machine of this embodiment will be explained concretely.
FIG. 4 is an illustration for the air gap length of the magnetic
pole pieces of the rotor of the permanent magnet rotating electric
machine of the first embodiment of the present invention.
The air gap length G1 is assumed as 0.5 mm, and the air gap length
G2 is assumed as 1.5 mm, and between them, the change in the air
gap length, as shown by a solid line of X1 in FIG. 4, is in a shape
convex downward. Namely, the change in the air gap length at the
central part of the magnetic poles is smaller than the change in
the air gap length at the end of the magnetic poles. Further, in
the drawing, the dashed line X2 is a straight line and the
alternate long and short dashed line X3 is a curve convex
upward.
Here, by referring to FIGS. 5 and 6, the iron loss of the rotor of
the permanent magnet rotating electric machine of this embodiment
will be explained. Further, the values shown in FIGS. 5 and 6 are
values obtained by theoretical calculation and are different from
the values indicated in the explanation shown in FIG. 4.
FIGS. 5 and 6 are illustrations for iron loss of the rotor of the
permanent magnet rotating electric machine of the first embodiment
of the present invention.
FIG. 5 shows, in the high speed rotating region, the whole iron
loss Wfe for the weak field current when the air gap length is
fixed and the breakdown of the basic wave part and harmonic part.
The drawing shows that, as mentioned above, when the weak field
current is increased, the basic wave part of the iron loss is
reduced, while the harmonic part is increased, and the whole iron
loss is not reduced.
FIG. 6 shows the torque T when the air gap length is changed at a
fixed weak field current and changes in the iron loss Wfe. The iron
loss Wfe1 indicates an iron loss when the air gap length G is kept
at 0.5 mm. The iron loss Wfe2 indicates an iron loss when the air
gap length G is changed evenly and the drawing shows that when the
air gap length is increased, the iron loss mainly due to a
reduction in the harmonic part is suddenly reduced and the occurred
torque T is reduced due to a reduction in the basic wave part of
the magnetic flux density.
Further, the iron loss WfeInv shown in the drawing is the
calculation result of the permanent magnet rotating electric
machine having the structure of this embodiment shown in FIGS. 1 to
4. In the reduction comparison of the iron loss at the point where
the torque becomes the same, an iron loss reduction effect of 35%
or higher than the conventional one is shown and in the iron loss
comparison, the iron loss reduction is 30% or more. Therefore,
according to this embodiment, rather than just an increase in the
air gap length, the ratio of (reduction in iron loss)/(reduction in
torque) can be increased.
As a shape of the concavities 76, in any of the lines X1, X2, and
X3 shown in FIG. 4, the reduction in the torque can be suppressed
while reducing the iron loss. Among them, particularly as shown by
the solid line X1 in FIG. 4, as a shape of the concavities 76, when
the change in the air gap length at the central part of the
magnetic poles is made smaller than the change in the air gap
length at the end of the magnetic poles, the air gap distribution
of the magnetic pole pieces 72 can be made larger at the center of
the magnetic poles and smaller at the end thereof and can be made
in a sine wave shape as a whole and the iron loss can be
reduced.
Further, in this embodiment, the air gap length G3 of the auxiliary
salient poles 71 is made smaller than the air gap lengths G1 and G2
of the magnetic pole pieces 72, thus the torque producing ratio of
the auxiliary salient poles 71 not affecting greatly the iron loss
of the permanent magnets 6 is increased and while keeping the
torque reduction little, the iron loss can be reduced.
As explained above, according to this embodiment, the effect of
iron loss can be reduced more and a highly efficient permanent
magnet rotating electric machine can be obtained.
Next, by referring to FIG. 7, the constitution of the permanent
magnet rotating electric machine of the second embodiment of the
present invention will be explained. Here, the whole constitution
of the permanent magnet rotating electric machine of this
embodiment is the same as that shown in FIG. 1.
FIG. 7 is a cross sectional view showing the constitution of the
permanent magnet rotating electric machine of the second embodiment
of the present invention. FIG. 7, similarly to FIG. 2, is a cross
sectional view in the direction perpendicular to the rotation axis
and a view in the direction of A-A. Further, the same numerals as
those shown in FIGS. 1 and 2 indicate the same parts.
In the constitution shown in FIG. 2, 2 permanent magnets constitute
one magnetic pole of the rotor and are arranged in a V shape, while
in this embodiment, as shown in FIG. 7, one permanent magnet 6J
constitutes one magnetic pole of the rotor and is inserted into an
insertion hole 70J in which the long sides of the section in a
rectangular block shape are arranged so as to be directed in the
peripheral direction of the rotor 3.
Although the arrangement of the permanent magnets, that is, the
constitution of the magnetic poles is different from that shown in
FIG. 2, the shape of the concavities 76 of the outer peripheral
part of the rotor 3 formed on the magnetic pole pieces 72,
similarly to that described in detail in FIG. 3, is a shape of
concavities gently tilting from the central part of the magnetic
poles to the end thereof on the air gap face of the magnetic pole
pieces of the rotor iron core. Therefore, the air gap lengths G1
and G2 are the same as those shown in FIG. 4.
Since the permanent magnets are arranged in such a block shape,
compared with the arrangement in the V shape shown in FIG. 2, the
number of magnets per magnetic pole is reduced, so that the
material expenses and the assembly man-hour are reduced, thus the
rotating electric machine can be reduced in cost.
On the other hand, when the permanent magnets are arranged in the
block shape, compared with the arrangement in the V shape, the
magnetic flux density of the magnets on the air gap face side is
reduced, so that in this respect, the torque is slightly
reduced.
As described above, also by this embodiment, the effect of the iron
loss can be reduced more and a highly efficient permanent magnet
rotating electric machine can be obtained.
Next, by referring to FIGS. 8 to 10, the constitution of the
permanent magnet rotating electric machine of the third embodiment
of the present invention will be explained. Here, the whole
constitution of the permanent magnet rotating electric machine of
this embodiment is the same as that shown in FIG. 1.
FIG. 8 is a cross sectional view showing the constitution of the
permanent magnet rotating electric machine of the third embodiment
of the present invention. FIG. 8, similarly to FIG. 2, is a cross
sectional view in the direction perpendicular to the rotation axis
and a view in the direction of A-A. Further, the same numerals as
those shown in FIGS. 1 and 2 indicate the same parts.
In this embodiment, on the outer peripheral part of the magnetic
pole pieces 72 of the rotor 3 of the permanent magnet rotating
electric machine 1, at the position of .theta.4 from the center of
the magnetic poles, concavities 77 are installed. The other
constitution is the same as that shown in FIG. 2. However, the
concavities 76 shown in FIG. 2 are not installed.
Next, by referring to FIGS. 9 and 10, the concavities 77 formed on
the outer periphery of the magnetic pole pieces of the rotor of the
permanent magnet rotating electric machine of this embodiment will
be explained.
FIGS. 9 and 10 are illustrations for the relationship between the
concavities 77 and the torque ripple formed on the outer periphery
of the magnetic pole pieces of the rotor of the permanent magnet
rotating electric machine of the third embodiment of the present
invention.
FIG. 9 shows the torque ripple value Y2 under the maximum torque
occurrence condition when the angle .theta.4 formed between the
center of the magnetic poles and the central position of the
concavities 77 is assumed as a variable. In the example shown in
FIG. 8, when the number of slots per pole and per phase is 2 (48
slots, 3 phases, 8 poles), nspp=2.
Further, the torque ripple value Y1 shown in FIG. 9 indicates the
characteristic of nspp=2 when the number of slots per pole and per
phase is 1. In this case, the slot width and tooth width are set at
double values of those when the number of slots per pole and per
phase is 2. In the drawing, the positive side of the symbol .theta.
indicates the region applied with the magnetizing force of the
electromotive force by the stator windings in the rotational
direction.
The torque ripple Y2 when the slots (the concavities 77) are not
arranged, is 20 Nm when the number of slots per pole and per phase
is 2. On the other hand, when the position of the concavities 77 is
within the range from an electrical angle .theta.a1 of 15.degree.
to 45.degree. from the central position of the magnetic poles, the
torque ripple can be reduced compared with a case of no concavities
formed.
Further, the torque ripple Y1 when the slots (the concavities 77)
are not arranged is 54 Nm when the number of slots per pole and per
phase is 1. On the other hand, when the position of the concavities
77 is within the range from an electrical angle .theta.a2 of
20.degree. to 30.degree. from the central position of the magnetic
poles, the torque ripple can be reduced compared with a case of no
concavities formed.
FIG. 10 compares the torque ripple (the solid line Z2) when an
electrical angle .theta. is 24.degree. and the hole size is
optimized under the condition that the number of slots per pole and
per phase is 2 with the torque ripple (the solid line Z0) when no
hole is formed. As clearly shown in FIG. 10, when the concavities
77 are formed at a proper position of the magnetic pole pieces, the
torque ripple can be reduced to about 1/3.
As described above, according to this embodiment, the torque ripple
of the permanent magnet rotating electric machine can be
reduced.
Further, for example, in Japanese Patent Application 8-251846 and
Japanese Patent Application 2002-171730, an embedding type magnet
rotor in which slots are arranged on both sides of magnetic pole
pieces are disclosed. However, in the embedding type magnet rotor
described in Japanese Patent Application 8-251846, the slots
arranged on the rotor surface are different in the slot shape and
slot position from those of this embodiment and are formed for
magnetic flux leakage prevention between the magnetic pole pieces
and the auxiliary salient poles but not for iron loss prevention
and torque ripple reduction. Further, in the embedding type magnet
rotor described in Japanese Patent Application 2002-171730, the
slots are different in the slot shape and slot position from those
of this embodiment and are intended to interrupt the magnetic flux
by the reaction of the armature but are not intended to reduce the
iron loss and torque ripple.
Next, by referring to FIG. 11, the constitution of the machine
driving system of an electric car loading the permanent magnet
rotating electric machine of each embodiment of the present
invention will be explained.
FIG. 11 is a block diagram showing the constitution of the machine
driving system of the electric car loading the permanent magnet
rotating electric machine of each embodiment of the present
invention.
In the drawing, the permanent magnet rotating electric machine 1 is
a one described in any of the aforementioned embodiments. A frame
100 of the electric car is supported by 4 wheels 110., 112, 114,
and 116. The electric car is driven by the front wheels, so that
the permanent magnet rotating electric machine 1 is directly
attached to a front axle 154. The control torque of the permanent
magnet rotating electric machine 120 is controlled by a controller
130. As a power source of the controller 130, a battery 140 is
installed, and power is supplied to the permanent magnet rotating
electric machine 1 from the battery 140 via the controller 130, and
the permanent magnet rotating electric machine 1 is driven, and the
wheels 110 and 114 are rotated. The rotation of a handle 150 is
transferred to the two wheels 110 and 114 via a transfer mechanism
composed of a steering gear 152, a tie rod, and a knuckle arm and
the angle of the wheels is changed.
Further, in this embodiment, a case that the front wheels 110 and
114 are driven to rotate by the permanent magnet rotating electric
machine 1 is described. However, the rear wheels 112 and 116 may be
driven to rotate.
When power-running an electric vehicle (at the time of starting,
traveling, acceleration, etc.), the front wheels 110 and 114 are
driven by the motor of the permanent magnet rotating electric
machine 1. The voltage of the battery 140 is supplied to the
permanent magnet rotating electric machine 1 via the controller 130
and the permanent magnet rotating electric machine 1 is driven and
generates rotation output. By doing this, the front wheels 110 and
114 are driven to rotate.
When regenerating the electric vehicle (at the time of stepping on
the brake, easing up on the accelerator, or stopping on the
accelerator), the rotation output of the front wheels 110 and 114
is transferred to the permanent magnet rotating electric machine 1
via the front axle 154 and the permanent magnet rotating electric
machine 1 is driven to rotate. By doing this, the permanent magnet
rotating electric machine 1 operates as a generator. By this
operation, in the stator windings of the permanent magnet rotating
electric machine 1, 3-phase AC power is generated. The generated
3-phase AC power is converted to predetermined DC power by an
inverter and is charged in the battery 140.
Further, in the above description, it is explained that the
permanent magnet rotating electric machine is used to drive the
wheels of an electric car. However, even if the machine is applied
to a hybrid electric car having a hybrid drive mechanism by an
engine and a motor or the so-called engine start device arranged
between an engine and a drive mechanism for starting the engine and
generating power, high efficiency and low noise of the drive
portion of the hybrid electric car can be realized by the same
effect.
As explained above, according to this embodiment, when the
permanent magnet rotating electric machine of low iron loss and low
torque ripple of the present invention is loaded in an electric
car, an electric car characterized by little iron loss at a high
speed, low fuel expenses, low vibration, and low noise can be
obtained by a simple constitution.
* * * * *