U.S. patent application number 10/201161 was filed with the patent office on 2003-03-27 for permanent magnet rotating electric machine.
Invention is credited to Fukushima, Tadashi, Ishii, Kohei, Kikuchi, Satoshi, Koharagi, Haruo, Noma, Keiji, Sato, Kazuo, Senoh, Masaharu, Takahashi, Miyoshi, Yamamoto, Kouki.
Application Number | 20030057785 10/201161 |
Document ID | / |
Family ID | 18782214 |
Filed Date | 2003-03-27 |
United States Patent
Application |
20030057785 |
Kind Code |
A1 |
Koharagi, Haruo ; et
al. |
March 27, 2003 |
Permanent magnet rotating electric machine
Abstract
A permanent magnet rotating electric machine includes a stator
having a plurality of teeth formed in a stator core, concentrated
wound armature windings wound around the plurality of teeth, and a
rotor having a plurality of holes formed in a rotor core for
accommodating permanent magnets. Permanent magnets are inserted
into the plurality of holes of the rotor. The permanent magnets are
each formed or arranged as a convex "V" and "U" with respect to the
shaft of the rotor.
Inventors: |
Koharagi, Haruo; (Taga-gun,
JP) ; Senoh, Masaharu; (Narashino-shi, JP) ;
Noma, Keiji; (Inba-gun, JP) ; Ishii, Kohei;
(Tokyo, JP) ; Sato, Kazuo; (Sakura-shi, JP)
; Kikuchi, Satoshi; (Hitachi-shi, JP) ; Takahashi,
Miyoshi; (Hitachi-shi, JP) ; Yamamoto, Kouki;
(Hitachinaka-shi, JP) ; Fukushima, Tadashi;
(Hitachi-shi, JP) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
18782214 |
Appl. No.: |
10/201161 |
Filed: |
July 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10201161 |
Jul 24, 2002 |
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09796788 |
Feb 27, 2001 |
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6441525 |
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Current U.S.
Class: |
310/156.56 |
Current CPC
Class: |
H02K 21/16 20130101;
H02K 1/2766 20130101 |
Class at
Publication: |
310/156.56 |
International
Class: |
H02K 021/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2000 |
JP |
2000-300546 |
Claims
What is claimed is:
1. A permanent magnet rotating electric machine comprising: a
stator having a plurality of teeth formed in a stator core,
concentrated wound armature windings wound around said plurality of
teeth; a rotor having a plurality of holes formed in a rotor core
for accommodating permanent magnets; and permanent magnets inserted
into said plurality of holes of said rotor; wherein said permanent
magnets are each formed or arranged as a convex "V" and "U" with
respect to said shaft of said rotor.
2. A permanent magnet rotating electric machine according to claim
1, wherein a width of said interpole core between said permanent
magnets at an inside-diameter side of said rotor is wider than a
width of said interpole core between said permanent magnets at an
outside-diameter side of said rotor.
3. A compressor configured in such a manner as to be driven by a
permanent magnet rotating electric machine, said permanent magnet
rotating electric machine comprising: a stator having a plurality
of teeth formed in a stator core, concentrated wound armature
windings wound around said plurality of teeth; a rotor having a
plurality of holes formed in a rotor core for accommodating
permanent magnets; and permanent magnets inserted into said
plurality of holes of said rotor; wherein said permanent magnets
are each shaped or arranged like a convex "V" or "U" with respect
to said shaft of said rotor.
4. An air conditioner having a compressor configured in such a
manner as to be driven by a permanent magnet rotating electric
machine, said permanent magnet rotating electric machine
comprising: a stator having a plurality of teeth formed in a stator
core, concentrated wound armature windings wound around said
plurality of teeth; a rotor having a plurality of holes formed in a
rotor core for accommodating permanent magnets; and permanent
magnets inserted in said plurality of holes of said rotor; wherein
said permanent magnets are each shaped or arranged as a convex "V"
or "U" with respect to said shaft of said rotor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to a permanent
magnet rotating electric machine having rare earth permanent
magnets for a field system, which are provided in a rotor, and more
particularly, to a permanent magnet rotating electric machine that
is mounted in, for example, a compressor of an air conditioner and
that has concentrated wound stator windings.
[0003] 2. Description of the Related Art
[0004] Generally adopted permanent magnet rotating electric
machines of such a type employ permanent magnets of various shapes.
For example, Domestic Republication of PCT International
Publication No. WO97/31422 describes a permanent magnet rotating
electric machine that comprises a stator, into which concentrated
wound armature windings are inserted in such a way as to surround a
plurality of teeth formed in a stator core, and a rotor having
permanent magnets inserted into a plurality of holes, which are
formed in a rotor core and used for accommodating permanent
magnets. Improvement in efficiency of this rotating electric
machine, that is, what is called output enhancement is achieved by
utilizing reluctance torque.
[0005] However, although the efficiency of this permanent magnet
rotating electric machine is increased by effectively utilizing
reluctance torque, no consideration is given to the efficiency of a
system during driven by what is called a position sensorless
inverter in the case of 120 degree energization.
[0006] In the case of this conventional machine, consideration is
given only to the efficiency of a motor. Especially, in a rotor
structure employing concentrated windings and utilizing reluctance
torque, reluctance increases. Thus, the power factor of the
rotating electric machine decreases for that, while electric
current flowing therethrough increases. This increase in electric
current results in reduction in inverter efficiency. Consequently,
the system efficiency decreases, far from increasing.
[0007] The present invention is accomplished in view of the
aforementioned problems.
[0008] Accordingly, an object of the present invention is to
provide a permanent magnet rotating electric machine comprising a
stator having concentrated windings and a rotor into which
permanent magnets are embedded that can increase the system
efficiency even when the rotating electric machine is driven by a
position sensorless inverter in the case of 120 degree
energization.
SUMMARY OF THE INVENTION
[0009] When a permanent magnet rotating electric machine is driven
by a position sensorless inverter in the case of 120 degree
energization, the performance of the machine is not determined only
by the efficiency of the rotating electric machine or motor but is
finally determined by the degree of the system efficiency defined
as a product of the inverter efficiency and the efficiency of the
rotating electric machine. For example, when the efficiency of the
rotating electric machine is enhanced, an output current of the
inverter increases in the case that the power factor of the motor
decreases. Further, when the output current of the inverter
increases, the voltage drop occurring in a control device of the
inverter increases. Consequently, the inverter efficiency is
reduced, so that the system efficiency is reduced, far from being
enhanced. Thus, according to an aspect of the present invention,
there is provided a permanent magnet rotating electric machine
comprising a stator, into which concentrated wound armature
windings are inserted in such a way as to surround a plurality of
teeth formed in a stator core, and a rotor having rare earth
permanent magnets inserted into a plurality of permanent magnet
holes, which are formed in a rotor core and used for accommodating
permanent magnets. In this rotating electric machine, the permanent
magnets are each shaped like a convex "V" or "U" with respect to
the shaft of the rotor. Moreover, the machine is configured so that
the width of the interpole core at the outside-diameter side of the
rotor is narrow, while the width of the interpole core at the
inside-diameter side of the rotor is wide. Further, a ratio of
width W1, which is narrowed at the outside-diameter side of the
rotor, of an interpole core between the permanent magnets to width
Xg of a gap between the stator core and the rotor core is set in
such a manner as to satisfy the following condition:
10.8.ltoreq.W1/Xg.ltoreq.13.2. Incidentally, the shaping of the
permanent magnets like a convex "V" or "U" includes the shaping of
the permanent magnets like an arc, and also includes the arranging
of the permanent magnets like a letter "V" or "U" by combining the
permanent magnets with each other.
[0010] Consequently, the present invention provides a permanent
magnet rotating electric machine that enhances system efficiency
when the reluctance thereof is set at an optimum value, and the
machine is driven by a position sensorless inverter in the case of
120 degree energization.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] Other features, objects and advantages of the present
invention will become apparent from the following description of
preferred embodiments with reference to the drawings in which like
reference characters designate like or corresponding parts
throughout several views, and in which:
[0012] FIG. 1 is a cross sectional view of a permanent magnet
rotating electric machine according to a first embodiment of the
present invention;
[0013] FIG. 2 is a cross sectional view of a rotor of the first
embodiment of the present invention;
[0014] FIG. 3 is a graph illustrating the characteristics of the
rotating electric machine according to the first embodiment of the
present invention; and
[0015] FIG. 4 is a cross sectional view of a rotor of a second
embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] First Embodiment
[0017] Hereinafter, a first embodiment of the present invention is
described with reference to FIGS. 1, 2, and 3.
[0018] FIG. 1 is a cross sectional view of a permanent magnet
rotating electric machine according to a first embodiment of the
present invention. As shown in this figure, in a permanent magnet
rotating electric machine 1, a stator 6 is configured by winding
armature windings 5 (consisting of concentrated U-phase windings
5A, concentrated V-phase windings 5B, and concentrated W-phase
windings 5C) in a plurality of slots 4 that are formed together
with teeth 3 of the stator core 2.
[0019] A rotor 7 consists of a rotor core 8, rare earth permanent
magnets 10 respectively placed in permanent magnet inserting holes
9 arranged like four convex "V"s (illustrated as corresponding to
four poles in this embodiment) with respect of a shaft (not shown)
of the rotor 7, and a shaft fitting hole 11 into which the shaft
(not shown) is fitted. The rotor 7 is rotatably supported through a
gap formed between the stator 6 and the rotor 7 so that the width
Xg of the gap is the difference between the outside diameter of the
rotor 7 and the inside diameter of the stator 6.
[0020] Each of the V-shaped pattern elements is composed of the two
rare earth permanent magnets 10 respectively inserted into the two
permanent magnet inserting holes 9 arranged like a letter "V". Each
of the permanent magnet inserting holes 9 and the rare earth
permanent magnets 10 has a rectangular section, as viewed from a
longitudinal direction of the shaft of the rotor 7. Each of the
V-shaped pattern element is formed by arranging the two permanent
magnet inserting holes 9, and thus, the two rare earth permanent
magnets 10 to be respectively inserted to these holes 9 so that the
longitudinal axes of the two inserting holes 9 or the two permanent
magnets 10 intersect with each other at an angle at the side of the
shaft of the rotor 7.
[0021] FIG. 2 is an enlarged cross sectional view of the rotor of
the first embodiment shown in FIG. 1. As shown in FIG. 2, rivet
holes 12 for fixing the rotor core 8 are formed in the rotor 7. The
width W1 of each interpole core 13 between adjacent ones of the
V-shaped pattern elements is such that the width thereof at the
outside-diameter side of the rotor 7 is relatively narrow and that
the width thereof at the inside-diameter side of the rotor 7 is
relatively wide.
[0022] FIG. 3 is a graph illustrating the characteristics of the
rotating electric machine according to the first embodiment of the
present invention. Abscissas represent W1/Xg, while ordinates
represent various kinds of efficiency or power factor (normalized
by setting the maximum motor efficiency at 1.0 and setting the
maximum inverter efficiency at 1.0 (pu)) obtained during the
rotating electric machine is driven by a position sensorless
inverter in the case of 120 degree energization. Thus, a curve
connecting black circles, a curve connecting white circles, and a
curve connecting white squares respectively represent the motor
efficiency, the inverter efficiency, and the system efficiency
obtained by using the ratio (W1/Xg) as a parameter. Incidentally,
"pu" values are values represented according to a per-unit method.
In this case, the maximum value of the motor efficiency is set at
1.0 pu (that is, what is called 100%). Similarly, the maximum value
of the inverter efficiency is set at 1.0 pu. The motor efficiency
and the inverter efficiency represent change in the motor
efficiency and change in the inverter efficiency, which are
expressed as percentages of the parameter W1/Xg. This embodiment
can be applied to a motor used for driving a compressor (not shown)
of an air conditioner (not shown). Usually, under constraints due
to the compressor, it is preferable that the width of the gap is
0.4 to 0.6 mm.
[0023] This desirable range of the width of the gap is determined
according to the manner of assembling the compressor. That is, the
rotor is pressed into the shaft operating in cooperation with a
scroll of the compressor, while the stator is shrinkage fitted into
an inner circumferential part of a compressor container. However,
strictly speaking, the inner circumference of the stator is out of
round. Thus, the position of the rotor is determined between the
inner circumference of the stator and the outer circumference of
the rotor through a spacer with reference to the inner
circumference of the stator. Therefore, the width of the gap may
vary about 0.2 mm. Thus, to assemble the compressor by taking
sufficient allowable change in width of the gap into consideration,
preferably, the width of the gap is 0.4 to 0.6 mm.
[0024] As is seen from FIG. 3, the motor efficiency changes
according to the ratio (W1/Xg) and takes a maximum value when the
ratio (W1/Xg) is close to 12. In contrast, although the inverter
efficiency changes according to the ratio (W1/Xg), the inverter
efficiency takes a maximum value when the ratio (W1/Xg) is equal to
or less than 10. The performance of the compressor depends upon the
system efficiency that is the product of the inverter efficiency
and the motor efficiency. The lower limit value of the ratio
(W1/Xg) for optimizing the system efficiency is determined by the
motor efficiency, while the upper limit value thereof is determined
by the inverter efficiency. When the value of the ratio (W1/Xg) is
in the range of 10.8 to 13.2, the system efficiency is almost
constant and takes a maximum value. Thus, the optimum range of the
value of the ratio (W1/Xg) is given by:
0.8.ltoreq.W1/Xg.ltoreq.13.2.
[0025] Incidentally, although the width of the interpole core 13 is
set in this embodiment so that the width thereof at the
inside-diameter side of the rotor 7 is wider than the width thereof
at the outside-diameter side of the rotor 7, needless to say, the
width of the interpole core 13 may be set so that the width thereof
at the inside-diameter side of the rotor 7 is equal to the width
thereof at the outside-diameter side thereof.
[0026] Second Embodiment
[0027] Next, another permanent magnet rotating electric machine,
which is a second embodiment of the present invention, is described
with reference to FIG. 4. Incidentally, the description of
constituent elements, which are the same as the constituent
elements of the first embodiment, is omitted herein. Further, the
following description describes only the differences between the
first embodiment and the second embodiment.
[0028] As shown in FIG. 4, the second embodiment has rare earth
permanent magnets 10 that are shaped like a convex letter "U" or
arc with respect to the shaft of the rotor 7. Even when the
U-shaped rare earth permanent magnets are provided instead of the
V-shaped rare earth permanent magnets of the first embodiment, the
shape of the interpole core portion 13 of the second embodiment is
similar to that of the interpole core portion of the first
embodiment. Consequently, the second embodiment can have effects
similar to those of the first embodiment.
[0029] As is obvious from the foregoing description, according to
the present invention, in the permanent magnet rotating electric
machine employing a stator that has concentrated windings, the rare
earth permanent magnets are each shaped like a convex "V" or "U"
with respect to the shaft of the rotor. Moreover, the ratio of the
width W1 of the interpole core between the permanent magnets to the
width Xg of the gap between the stator core and the rotor core is
set in such a manner as to meet the following condition:
0.8.ltoreq.W1/Xg.ltoreq.13.2.
[0030] Thus, the rotating electric machine can operate in a state
in which the system efficiency obtained as the product of the motor
efficiency and the inverter efficiency is close to a maximum value
thereof. Therefore, when the present invention is applied to a
compressor, the efficiency of the compressor is enhanced.
Consequently, the present invention has an advantage in that the
present invention can provide energy savings to an air conditioner
using such a compressor.
[0031] As described above, the present invention provides, for
instance, a permanent magnet rotating electric machine (that is,
the first machine) having a stator, into which concentrated wound
armature windings are inserted in such a way as to surround a
plurality of teeth formed in a stator core, and a rotor having rare
earth permanent magnets inserted into a plurality of permanent
magnet holes, which are formed in a rotor core and used for
accommodating permanent magnets. In this rotating electric machine,
the permanent magnets are each shaped like a convex "V" or "U" with
respect to the shaft of the rotor. Moreover, the ratio of the width
W1 of the interpole core between the permanent magnets to the width
Xg of the gap between the stator core and the rotor core is set in
such a manner as to satisfy the following condition:
0.8.ltoreq.W1/Xg.ltoreq.13.2.
[0032] Furthermore, an embodiment (hereunder referred to as a
second machine) of this permanent magnet rotating electric machine
is configured so that the width of the interpole core between the
permanent magnets at the inside-diameter side of the rotor is wider
than the width of the interpole core between the permanent magnets
at the outside-diameter side of the rotor. Moreover, the present
invention provides a compressor configured in such a manner as to
be driven by one of the first and second machines. Furthermore, the
present invention provides an air conditioner having the
aforementioned compressor.
[0033] Thus, according to the present invention, there is provided
a permanent magnet rotating electric machine that can increase the
system efficiency even when the rotating electric machine having a
stator, which employs a concentrated windings, and also having a
permanent-magnet-embedded type rotor is driven by a position
sensorless inverter in the case of 120 degree energization.
[0034] Although the preferred embodiments of the present invention
have been described above, it should be understood that the present
invention is not limited thereto and that other modifications will
be apparent to those skilled in the art without departing from the
sprint of the invention.
[0035] The scope of the present invention, therefore, should be
determined solely by the appended claims.
* * * * *