United States Patent [19]
`Nishiyama et ai.
`
`[54] MOTOR
`
`[75]
`
`Inventors: Noriyoshi Nishiyama, Izumiotsu;
`Tomokazu Nakamura, Katano;
`Yasufumi Ikkai, Kobe; Yukio Honda,
`Katano; Hiroshi Murakami, Suita;
`Shinichiro Kawano, Kadoma, all of
`Japan
`
`[73]
`
`Assignee: Matsushita Electric Industrial Co.,
`Ltd., Osaka, Japan
`
`[ * ]
`
`Notice:
`
`This patent issued on a continued pros(cid:173)
`ecution application filed under 37 CFR
`1.53( d), and is subject to the twenty year
`patent term provisions of 35 U.S.c.
`154(a)(2).
`
`[21]
`
`Appl. No.:
`
`08/945,460
`
`[22] PCT Filed:
`
`Feb. 21, 1997
`
`[86] PCTNo.:
`
`PCT/JP97/00489
`
`§ 371 Date:
`
`Feb. 2,1998
`
`§ 102(e) Date: Feb. 2, 1998
`
`[87] PCT Pub. No.: W097/31422
`
`PCT Pub. Date: Aug. 28, 1997
`
`[30]
`
`Foreign Application Priority Data
`
`Feb. 23, 1996
`
`[JP]
`
`Japan ...................................... 8-35988
`
`Int. CI? ....................................................... H02K 1/27
`[51]
`[52] U.S. CI. .......................... 310/156; 310/254; 310/259;
`310/162; 310/42; 310/179
`[58] Field of Search ..................................... 310/254,258,
`310/259, 216, 217, 218, 156, 162, 166,
`168, 179, 42; 29/596
`
`111111
`
`1111111111111111111111111111111111111111111111111111111111111
`US006049153A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,049,153
`*Apr. 11,2000
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3/1992 Mikulic ................................... 310/156
`5,097,166
`5,583,387 12/1996 Tankeuchi et al. ..................... 310/217
`5,729,072
`3/1998 Hirano et al. ........................... 310/258
`5,861,693
`1/1999 Takahashi et al. ...................... 310/113
`FOREIGN PATENT DOCUMENTS
`
`62-160048
`63-242157
`5-284677
`5-292714
`6-98514
`6-66277
`7-20050
`7-236240
`7-255138
`7-303357
`8-19196
`
`7/1987
`10/1988
`10/1993
`11/1993
`4/1994
`9/1994
`4/1995
`9/1995
`10/1995
`11/1995
`1/1996
`
`Japan ............................... H02K 3/28
`Japan ..................................... 310/156
`Japan ............................... H02K 1/16
`Japan ............................. H02K 17/12
`Japan ..................................... 310/156
`Japan ............................. H02K 21/14
`Japan ............................... H02K 1/27
`Japan ............................... H02K 1/27
`Japan ............................... H02K 1/27
`Japan ............................. H02K 19/10
`Japan ............................... H02K 1/18
`
`OTHER PUBLICATIONS
`Japanese language search report for Int'l Appln. No. PCT/
`JP97/00489.
`English translation of Japanese language search report for
`Int'l Appln. No. PCT/JP97/00489.
`Primary Examiner---Nestor Ramirez
`Assistant Examiner~urt Mullins
`Attorney, Agent, or Firm-Ratner & Prestia
`ABSTRACT
`[57]
`
`A motor comprises a stator core having plural teeth and slots
`provided among the teeth, a winding applied on the teeth by
`a turn, and a rotor incorporating plural permanent magnets.
`The rotor is rotated and driven by utilizing reluctance torque
`in addition to magnetic torque. Since the winding is not
`crossed, the size of the coil end is reduced.
`
`21 Claims, 7 Drawing Sheets
`
`5-ri---f---=-
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`3
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`140
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`130
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`14
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`Page 1 of 16
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`PETITIONERS' EXHIBIT 1011
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`u.s. Patent
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`tnet
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`00021,1r..pA
`Apr. 11, 2000
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`Sheet 1 of 7
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`6,049,153
`6,049,153
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`Fig. I
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`II
`I ........
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`9
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`5
`2
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`5
`~
`12 6 7
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`60"
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`5
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`21
`6
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`a6Pn.0ab.2Ua
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`3
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`130
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`14
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`
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`aP
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`Page 2 of 16
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`u.s. Patent
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`Apr. 11, 2000
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`Sheet 2 of 7
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`6,049,153
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`Fig.2
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`lOb
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`Fig.3
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`6
`
`lOa 5 7 10b ll
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`120
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`12
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`120
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`15
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`130 140
`3",
`_--'-:==:::c;::::===I= h
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`14
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`14
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`Page 3 of 16
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`u.s. Patent
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`US. Patent
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`Apr. 11,2000
`Apr. 11, 2000
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`Sheet 3 of 7
`Sheet 3 0f 7
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`6,049,153
`6,049,153
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`Fig.4
`Fig.4
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`§§§
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`§§§§§v§
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`§§§
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`24
`42
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`7
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`Page 4 of 16
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`Page 4 of 16
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`u.s. Patent
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`Apr. 11, 2000
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`Sheet 4 of 7
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`6,049,153
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`FJg.5
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`39
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`37
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`F
`~
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`34
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`Page 5 of 16
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`u.s. Patent
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`Apr. 11,2000
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`Sheet 5 of 7
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`6,049,153
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`Fig.6
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`d
`
`~
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`58
`
`,/
`51
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`q r 60a
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`~:::,--:::---,5 90
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`___ -"11.
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`::=4:=:~ 600
`:---1-57
`54
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`Page 6 of 16
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`u.s. Patent
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`Apr. 11, 2000
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`Sheet 6 of 7
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`6,049,153
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`Fig.7
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`82
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`Fig.8
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`81
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`75
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`73
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`80
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`77
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`Page 7 of 16
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`u.s. Patent
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`Apr. 11, 2000
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`Sheet 7 of 7
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`6,049,153
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`List of Reference Numerals In Drawing Figures
`
`1
`
`2
`
`3
`
`5
`
`7
`
`8
`
`9
`
`Motor
`
`Stator
`
`Rotor
`
`Core element
`
`Tooth
`
`Slot
`
`Slot forming recess
`
`12 Magnetic pole
`
`13
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`14
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`15
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`Rotor core
`
`Permanent magnet
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`Cut-off portion
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`Page 8 of 16
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`6,049,153
`
`1
`MOTOR
`
`This Application is a U.S. National Phase Application of
`PCT International Application PCT/JP97/00489.
`
`TECHNI CAL FIELD
`
`The present invention relates to a synchronous motor
`comprising a stator for generating a rotary magnetic field,
`for rotating and driving by making use of a reluctance
`torque.
`
`BACKGROUND ART
`
`In a conventional general synchronous motor, a stator is
`formed by integrally projecting plural teeth from a ring(cid:173)
`shaped yoke to its inner circumferential side. This stator is
`fabricated by laminating stator plates having plural teeth
`projecting to the inner circumferential side. It also comprises
`a stator core forming slots among these teeth, and windings
`are wound in these slots by distributed winding. The dis(cid:173)
`tributed winding is a winding method for winding distant
`teeth through slots. The rotor is composed by burying plural
`permanent magnets for magnetic poles in the outer circum(cid:173)
`ference of the rotor core, and mounting a rotary shaft in the
`center.
`In this way, by burying permanent magnets inside the
`rotor, the buried permanent magnet motor can utilize not
`only the magnet torque but also the reluctance torque, in
`which the reluctance torque is generated in addition to the
`magnet torque by the permanent magnets, as an inductance 30
`difference occurs between the inductance Ld in the direction
`of the d-axis which is a direction for coupling the center of
`the permanent magnet and the rotor center, and the induc(cid:173)
`tance Lq in the direction of the q-axis which is a direction
`rotated 90 degrees of electrical angle from the d-axis. This
`relation is shown in formula (1).
`
`10
`
`2
`In the distributed winding, moreover, by turning windings
`plural times, a winding ring is formed, and this winding ring
`is inserted into the teeth, and the periphery of the winding
`ring becomes longer than the periphery of the teeth. Still
`5 more, in the distributed winding, since the teeth are wound
`through slots, the windings cross each other. Thus, in the
`distributed winding, the winding projects from the stator
`end, and the windings cross each other to increase the size
`of the coil end.
`Hence, if attempted to drive the motor efficiently by
`making use of the reluctance torque, the motor size becomes
`larger. To the contrary, if the motor is reduced in size, the
`output of the motor drops.
`In the air-conditioner, refrigerator, electric vehicle, etc.,
`15 however, a motor of large output and small size is required.
`Incidentally, the magnetic pole portion at the end of the
`teeth in the stator is formed wider in the peripheral direction.
`Between the adjacent magnetic pole portions, however,
`since openings are formed for laying down windings in the
`20 slots, the interval of ends of teeth must be formed wider in
`the peripheral direction. That is, because of the distributed
`winding, an opening for inserting the winding ring in the
`teeth is needed. Incidentally, the gap between the stator inner
`circumference and the rotor outer circumference is generally
`25 set uniform on the whole periphery except for the openings
`of the slots.
`In such conventional constitution, at the stator side, since
`there is an opening for a slot between magnetic pole
`portions, an insulating portion in the peripheral direction is
`formed in the distribution of the magnetic flux leaving the
`magnetic pole portions, which produced a problem of occur-
`rence of cogging torque during rotor rotation. At the rotor
`side, when the distribution of the magnetic flux leaving its
`outer circumference is brought closer to sine waveform, the
`35 cogging torque can be decreased, but since the gap between
`the stator inner circumference and rotor outer circumference
`is uniform, the magnetic resistance in this gap is constant on
`the whole periphery, and in the joining portions of the ends
`of the permanent magnets, the magnetic flux distribution
`40 changes suddenly, and the cogging torque increases. Thus,
`the cogging torque increasing factors are combined at the
`stator side and rotor side, and a large cogging torque is
`caused.
`
`T ~Pn{ <jJaxI q+1Iz(Ld-Lq)xldxI q}
`
`(1)
`
`where Pn: number of pole pairs
`<jJa: interlinkage magnetic flux
`Ld: d-axis inductance
`Lq: q-axis inductance
`Iq: q-axis current
`Id: d-axis current
`Formula (1) shows a voltage equation of dp conversion.
`For example, in a surface magnet motor, since the perme(cid:173)
`ability of the permanent magnet is nearly equal to that of air,
`both inductance Ld and Lq in formula (1) are nearly equal
`values, and the reluctance torque portion expressed in the
`second term enclosed in braces in formula (1) does not
`occur.
`In addition to the magnet torque, by utilizing the reluc(cid:173)
`tance torque, if desired to increase the torque of the driving
`motor, according to formula (1), it is enough to increase the
`difference of (Ld-Lq). The inductance L, which expresses
`the degree of ease of passing of magnetic flux, is propor(cid:173)
`tional to N2 (number of turns of teeth), and hence by
`increasing the number of turns on the teeth, the difference of
`(Ld-Lq) becomes larger, so that the reluctance torque can be
`increased. However, if the number of turns is increased in
`order to utilize the reluctance torque more, as the number of
`turns increases, the winding group projecting to the stator
`end surface, that is, the coil end becomes larger. Hence, to
`rotate and drive the motor efficiently, if attempted to make
`use of the reluctance torque, the coil end becomes larger, and
`the motor itself is increased in size.
`
`45
`
`SUMMARY OF THE INVENTION
`The motor of the invention comprises a stator core having
`plural teeth and slots provided among these teeth, a winding
`making a single turn around the teeth, and a rotor incorpo(cid:173)
`rating plural permanent magnets, being constituted to rotate
`50 and drive by making use of reluctance torque, in which the
`winding does not cross because of a single turn, and the coil
`end can be decreased in size.
`Moreover, in the core composed by combining plural
`independent core elements in an annular form, since the
`55 winding is turned in the portion of a slot recess formed at
`both sides of the teeth of the core element, and the winding
`is turned in a state of the core element, the winding can be
`applied on the stator in neat arrangement. Moreover, since
`the winding is not turned in the adj acent state of the teeth,
`60 it is not necessary to keep a wide opening between the ends
`of the teeth, so that the interval of the ends of the teeth can
`be narrowed.
`Further, in the stator core composed by coupling ends of
`plural core elements, and folding the core element group
`65 with bent ends into an annular form, since the winding is
`turned in the slot shape recess portion formed at both sides
`of the teeth of the core elements, when winding around the
`
`Page 9 of 16
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`

`

`6,049,153
`
`4
`FIG. 4 is a diagram showing a core element of embodi(cid:173)
`ment 1,
`FIG. 5 is a sectional view of a motor in embodiment 2 of
`the invention,
`FIG. 6 is a sectional view of a motor in embodiment 3 of
`the invention,
`FIG. 7 is a sectional view of a motor in embodiment 4 of
`the invention,
`FIG. 8 is a sectional view of a motor in embodiment 5 of
`the invention.
`
`10
`
`3
`teeth, the end interval of teeth can be widened, and the
`winding can be applied around the teeth in neat arrangement.
`Moreover, since the ends are coupled, position setting when
`assembling is easy.
`Further, the clearance between the confronting surface of 5
`teeth of the permanent magnet and the outer circumference
`of the rotor core is wider in the central part than in the end
`portion of the permanent magnet, and the reluctance torque
`can be utilized effectively.
`Further, since the shape of the permanent magnet is
`projecting toward the center of the rotor in its middle, the
`reluctance torque can be utilized effectively.
`Further, since the width between the adjacent permanent
`magnets is 0.15 to 0.20 of the width of teeth confronting two
`magnetic poles (two permanent magnets), the torque ripple
`of the motor can be suppressed.
`Further, the leading end of the magnetic pole portion of
`the inner circumferential side of the teeth is projecting in the
`peripheral direction across a slight gap between the ends of
`the teeth, and the gap between the teeth and rotor outer
`circumference is nearly constant, so that useless magnetic
`flux does not flow at the ends of the teeth.
`Further, as the leading end of the magnetic pole portion of
`the inner circumferential side of the teeth is projecting in the
`peripheral direction so as to connect between ends of the
`teeth, the gap between the teeth and rotor outer circumfer(cid:173)
`ence may be continuous.
`Further, by setting the width b of the opposite sides of the
`ends of teeth at b<0.6 mm, the magnetic flux is saturated at
`the ends of the teeth.
`Further, the incorporated permanent magnets are thinner
`in the permanent magnet positioned ahead in the rotor
`rotating direction than at the permanent magnet rear portion,
`so that the quantity of the permanent magnets may be
`decreased without lowering the torque.
`Further, the profile of the adj acent portions of the perma(cid:173)
`nent magnets is a recess form corresponding to the disk(cid:173)
`shape profile positioned outside of the center of the perma(cid:173)
`nent magnet, and the magnetic resistance is increased in the
`adjacent portions of the permanent magnets, so that the
`magnetic flux distribution may be close to a sine waveform.
`Further, the length of the rotor outer recess positioned
`outside of the adjacent portions of the permanent magnets
`should be properly corresponding to the angle of 0.2 to 0.4
`of the central angle of the one pole portion of the rotor core.
`Further, the gap between the rotor outer recess and teeth
`should be properly two or more times of the gap between the
`rotor outer circumference and the teeth.
`Further, when the incorporated permanent magnets have
`two layers, the q-axis inductance increases, and the reluc(cid:173)
`tance torque portion is maximized.
`Further, the interval is properly a value set larger than If3
`of the width of the teeth.
`Further, when the winding is a flat square wire, the
`occupation rate can be enhanced more than in the case of
`round wire. In particular, the winding of flat square wire is
`suited to concentric concentrated winding around the teeth.
`
`20
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`Referring now to FIG. 1 through FIG. 4, embodiment 1 of
`15 the invention is described below.
`In FIG. 1, a synchronous motor 1 rotates by utilizing
`reluctance torque, as well as magnet torque, and it is
`composed of a stator 2, a rotor 3, and a rotary shaft 4.
`The stator 2 is composed of a ring-shaped frame 21, a
`stator core 22 combining plural independent core elements
`5 made of high permeability material in an annular form, and
`a winding wound around slots 8 formed between teeth 7 of
`each core element 5, and when a current is applied to these
`25 winding groups, a rotary magnetic field is generated.
`The stator core 22 is composed by combining the plural
`core elements 5 in an annular form on the outer circumfer(cid:173)
`ence 6 thereof, and fitting and fixing in the inner circum(cid:173)
`ference of the frame 21, and each outer circumference 6 is
`30 formed in an entire shape of a sector form in which the
`extension line of both side surfaces 6a passes through the
`stator center. In the core elements 5, as specifically shown in
`FIG. 2, slot forming recesses 9 are formed in the inner
`circumferential portion, and slots 8 are formed in the slot
`35 forming recesses 9 in the adjacent teeth 7. At both side
`surfaces 6a, stopping portions 11 composed of engaging
`bumps lOa and engaging recesses lOb for engaging with
`each other when the core elements 5 are combined in an
`annular form are provided, so that the core elements 5 may
`40 be mutually fixed firmly. The core elements 5 are combined
`by welding, or they may be also fixed by crimping by
`forming fitting parts at the side of the core elements 5.
`In this way, the stator 2 is formed by combining plural
`core elements 5. Hence, instead of turning the winding
`45 around the stator 2, the stator 2 can be formed after turning
`the winding around the core element 5. Thus, by winding in
`the state of core elements 5, since the winding is turned in
`every core element 5, single winding (concentrated winding)
`may be formed easily. That is, as shown in FIG. 4, when
`50 turning the winding, there is no disturbing position for
`winding at the side surface of the teeth 7. As a result, the
`winding port of the turning device rotates about the teeth 7,
`so that an arrangement winding may be formed through an
`insulating film 24. Moreover, the turning precision of the
`55 winding 40 may be enhanced, and the arrangement winding
`may be formed easily.
`Thus, by forming the winding of the stator 2 as a single
`winding, mutual crossing of winding at the stator end can be
`suppressed. As a result, since the winding is not crossed at
`60 the end of the rotary shaft direction of the stator 5, the size
`of the coil end can be suppressed. Moreover, by winding in
`the divided state of the stator, the periphery of the teeth 5 and
`one turn of the winding can be equalized in length. As a
`result, the winding does not project at the stator end, and the
`65 coil end may be reduced in size.
`Further, because of winding in the divided state of the
`stator 5, it is not necessary to consider the space of the
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a sectional view of a motor in embodiment 1 of
`the invention,
`FIG. 2 is a partial sectional view of a stator in embodiment
`
`1,
`
`1,
`
`FIG. 3 is a partial sectional view of a rotor in embodiment
`
`Page 10 of 16
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`6,049,153
`
`25
`
`5
`winding port of the winding device when winding, and the
`winding can be overlaid as much as possible. Besides, since
`the stator 5 is divided when winding, the precision of the
`winding device is heightened, and an arrangement winding
`may be formed. As a result, the occupation rate in the slot is
`heightened. Since the reluctance torque is proportional to the
`number of turns, the reluctance torque can be enhanced by
`raising the occupation rate.
`In this way, since the winding around the teeth can be
`turned in a proper length, there is no extra winding, and the
`winding length can be shortened for the total number of
`turns. As a result, the copper loss is decreased, and the heat
`generation of the winding can be decreased.
`Furthermore, since the interval d of the ends of the teeth
`does not require the space for passing the winding through
`the winding port of the device, the interval d of the ends of
`the teeth can be reduced. As a result, gap changes between
`the teeth and rotor outer circumference are smaller, and the
`cogging torque decreases.
`Hitherto, in the case of single winding on the stator 2 by 20
`a turning device, it was possible to wind at an occupation
`rate of about 30%. However, after winding on the core
`element 5, when assembled, the wire filling rate in the slot
`8 can be set more than 30%, or the wire filling rate may be
`set even more than 60%.
`The magnetic pole portions 12 of the inner end side from
`the slot forming recesses 9 of the core elements 5 are
`projected long to both sides in the peripheral direction, and
`across a slight gap d between the ends, the magnetic pole 30
`portions 12 of adjacent core elements 5 are connected, so
`that there may be no interruption in the distribution of
`magnetic flux in the peripheral direction from the magnetic
`pole portion 12 of each core element 5. Besides, both sides
`12a of the magnetic pole portion 12 are formed nearly in a 35
`triangular shape so that the width in the radial direction may
`be smaller toward the end, thereby decreasing the magnetic
`leak between the magnetic pole portions 12 of the adjacent
`core elements 5 by increasing the magnetic resistance at
`both sides of the magnetic pole portion 12.
`The slight gap d in embodiment 1 is O<d<O.2 mm. The
`slight gap d is formed by assembling after winding on the
`core element 5, and by opening such small gap, the magnetic
`leak from the winding of the slot 8 can be suppressed, and
`the cogging torque becomes smaller. The gap d of 0<d<0.2 45
`mm is a value obtained by experiments, and the cogging
`torque is decreased efficiently at this value. By not contact(cid:173)
`ing the ends completely, it is effective to suppress flow of
`useless magnetic flux between the adjacent teeth 7.
`This gap d may be set to 0 if the magnetic flux leak 50
`between adjacent core elements 5 can be ignored and there
`is no problem in assembling precision, so that the cogging
`torque can be eliminated.
`On the confronting surfaces of the ends of the teeth 7 (the
`end of teeth 7, being the side confronting between the ends 55
`of the teeth 7), b is properly at b<0.6 mm. By defining b in
`a range of b<0.6 mm, magnetic saturation occurs at the end
`of the teeth 7, and useless magnetic flux leak can be
`decreased.
`On the other hand, the rotor 3 comprises a rotor core 13
`made of high permeability material so that the magnetic flux
`of the rotary magnetic field produced by the winding group
`of the stator 2 may pass easily, and permanent magnets 14
`incorporated in the rotor core 13 at equal intervals in the
`peripheral direction corresponding to the poles on the rotor 65
`3. These permanent magnets 14 are disposed so that the S
`pole and N pole may be alternate in the peripheral direction.
`
`6
`The teeth confronting surface 14a of the permanent
`magnet 14 is linear. The distance between the teeth con(cid:173)
`fronting surface 14a and the outer circumference of the rotor
`13 is wider in the middle part than at the end part of the
`5 permanent magnet 14. Thus, in the outer circumference of
`the rotor 13, having the easily passing portion and hardly
`passing portion of magnetic flux, it is possible to produce an
`inductance difference between the q-axis inductance and
`d-axis inductance, so that it is possible to rotate and drive by
`10 making use of reluctance torque. Incidentally, the shape of
`the permanent magnet 14 may be a shape projecting in the
`middle portion toward the center of the rotor 13.
`On the outer circumference of the rotor core 13, as shown
`specifically in FIG. 3, a second periphery portions 15 is
`15 formed at the adjacent end portions of the permanent mag(cid:173)
`nets 14.
`The outer circumference of the stator 2 is covered with a
`ring-shaped frame 21, and reinforces the core elements 5
`integrated by welding. By using the frame 21 in this manner,
`even in the motor rotating at high speed, the core elements
`are fixed firmly. If the stator main body assembled from the
`core elements 5 has a sufficient strength, it is not necessary
`to reinforce by the frame 21.
`In this constitution, the motor of the invention can be
`driven by utilizing the reluctance torque as well as the
`magnet torque. In spite of the occupation rate of over 60%
`of the slots 8 in the motor, the size of the stator is small.
`Since the output torque of the motor rotated and driven by
`making use of reluctance torque in addition to magnet torque
`is in the relation as shown in formula (1), when the occu(cid:173)
`pation rate of the slots 8 is raised, the difference of Ld-Lq
`becomes larger, and the output torque can be heightened.
`That is, since the inductance L is proportional to N2 (number
`of turns), the greater the number of turns, that is, the higher
`the occupation rate in the slots 8, the higher the output
`becomes.
`In the motor driven by utilizing the reluctance torque in
`addition to the magnet torque, when the stator 2 is assembled
`40 after turning a winding about the core elements 5, the
`occupation rate can be enhanced, so that high output and
`small size may be realized.
`Incidentally, it was found by experiments that the torque
`ripple is decreased when the width of the adjacent perma(cid:173)
`nent magnets is 0.15 to 0.20 of the width of the teeth
`confronting two magnetic poles (two permanent magnets)
`(in 8 poles and 12 slots in FIG. 1, three teeth correspond to
`two magnetic poles, and in the case of 8 poles and 24 slots,
`six teeth are equivalent).
`In the rotor 3, in the adjacent end portions of the perma(cid:173)
`nent magnets 14 on the outer circumference of the rotor core
`13, a cut-off portion between rounded portions 15a nearly
`linear to the rotor outer recess is formed. By forming such
`cut-off portion 15, the gap between the stator 2 inner
`circumference and rotor 3 outer circumference becomes
`large in the adjacent end portions of the permanent magnets
`14. Therefore, since the magnetic resistance is large in the
`gap, the magnetic flux distribution in the gap between the
`stator 2 inner circumference and rotor 3 outer circumference
`60 is closer to the sine waveform.
`Meanwhile, the length of the rotor outer recess positioned
`outside of the portion between the adjacent permanent
`magnets is properly a length corresponding to an angle of
`0.2 to 0.4 of the central angle of one pole of the rotor core.
`The spatial gap h between the teeth 7 and cut-off portion
`15 is required to be more than 2 times of the spatial gap
`between the teeth 7 and rotor outer circumference. In
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`7
`embodiment 1, it has been known by experiment that the
`spatial gap of the teeth 7 and the cut-off portion should be
`0.7 to 1 mm.
`Thus, in this embodiment 1, since the cogging torque
`generating factors at both stator 2 side and rotor 3 side can
`be suppressed, a synchronous motor of a small cogging
`torque can be presented.
`By employing such motor in the compressor, refrigerator,
`air-conditioner, electric vehicle, etc., it is effective to reduce
`the size and widen the accommodation space.
`The motor used in an electric vehicle is required to be
`small in size in order to keep a wide space in the
`compartment., and at the same time a motor capable of
`utilizing the current of the charger efficiently is needed. In
`the motor used in the electric vehicle, mostly, a flat square 15
`wire with sectional width of 4 mm or more and height of 1.5
`mm is used. The large current flowing in the winding is 300
`amperes or more. Rotating at 7000 to 15000 by passing a
`large current, it is effective to use a motor of short winding
`length and a small heat generation for the number of turns, 20
`as the motor of the invention. If arrangement winding is
`possible, the occupation rate may be enhanced more than in
`round wires.
`It is very effective to use such motor of the invention in
`a motor passing a large current as in an electric vehicle.
`The description herein relates to a motor using a single
`winding stator, utilizing reluctance torque in addition to
`magnet torque, by burying permanent magnets, but excellent
`effects are also obtained by incorporating gaps with low
`permeability materials or resin materials in the rotor, instead 30
`of the permanent magnets, and rotating and driving by
`utilizing the reluctance torque only. That is, excellent effects
`are obtained if a stator of single winding is used in a
`synchronous motor.
`(Embodiment 2)
`Embodiment 2 is described by referring to FIG. 5.
`In FIG. 5, a synchronous motor 31 rotating mainly in a
`principal rotating direction F, by using reluctance torque in
`addition to magnet torque, and it is composed of a stator 32,
`a rotor 33, and a rotary shaft 34.
`The stator 32 is composed of a ring-shaped frame, a stator
`core combining plural independent core elements 35 made
`of high permeability material in an annular form, and a
`winding wound around slots 38 formed between teeth 37 of
`each core element 35, and when a current is applied to these
`winding groups, it is composed to generate a rotary magnetic
`field.
`Permanent magnets 39 are buried inside the rotor 3
`disposed in this stator 32. The shape of permanent magnets
`39 is in V-form, and the permanent magnets project to the
`center of the rotor 33. By thus reverse projecting magnetic
`poles, the inductance difference of the d-axis and q-axis can
`be increased. The permanent magnet 39 is composed of a
`permanent magnet forward portion 39a and a permanent 55
`magnet backward portion 39b in the rotor normal rotating
`direction F. At this time, the thickness of the permanent
`magnet backward portion 39b is greater than the thickness of
`the permanent magnet forward portion 39a.
`Such constitution is based on the following reason. In the 60
`permanent magnet backward portion 39b, the magnetic flux
`produced from the permanent magnet backward portion 39b
`and the magnetic flux produced from the teeth 39 may repel
`each other, possibly causing demagnetization of the perma(cid:173)
`nent magnet backward portion 39b. In order to use a magnet 65
`capable of generating a magnetic force not to cause
`demagnetization, a thick permanent magnet was used.
`
`8
`However, in the motor which rotates almost in the normal
`rotating direction F only, the permanent magnet forward
`portion 39a which is sucked by the suction force from the
`teeth does not cause demagnetization, and it is not required
`to be as thick as the permanent magnet backward portion
`39b. Hence, the permanent magnet forward portion 39a may
`be thinner than the permanent magnet backward portion
`39b. As a result, in the motor rotating almost always in the
`normal direction, if the quantity of permanent magnets is
`10 decreased, the characteristic is not lowered, so that the
`quantity of the permanent magnets can be decreased.
`The teeth confronting surface of the incorporated perma(cid:173)
`nent magnet backward portion 39b projects to the stator 35
`side and is thicker than the permanent magnet forward
`portion 39a. However, the teeth confronting surface of the
`incorporated permanent magnet backward portion 39b may
`be symmetrical to the confronting surface of the permanent
`magnet forward portion 39a, and may project to the rotor
`center side.
`In the buried magnets, a weight for adjusting the balance
`between the forward portion and backward portion (luring
`rotary drive may be buried in the rotor.
`The shape of the permanent magnets is not limited to
`25 V-form, but may be linear or arcuate.
`(Embodiment 3)
`A third embodiment is explained by referring to FIG. 6.
`In FIG. 6, a synchronous motor 51 rotates by making use
`of reluctance torque in addition to magnet torque, and it is
`composed of a stator 52, a rotor 53, and a rotary shaft 54.
`The stator 52 is composed by combining plural indepen(cid:173)
`dent core elements 55 made of high permeability material in
`an annular form. A winding is turned around slots 58 formed
`between teeth 57 of each core element 55, and it is designed
`35 to generate a rotary magnetic field by applying a current in
`the winding group.
`In the rotor 53, four sets of permanent magnets 59, 60
`arranged to have N-pole and S-pole alternately are buried in
`40 the rotor core made of high permeability material, and fixed
`on a rotor shaft 54. The permanent magnet per pole is
`divided into two sections in the rotor radial direction, and is
`composed of an outside permanent magnet 59 and an inside
`permanent magnet 60. The permanent magnets 59, 60 are
`45 formed in a convex arc shape at the rotor center side, and the
`both ends 59a, 60a are extended to the position close to the
`rotor outer circumference. The gap between the outside
`permanent magnet 59 and inside permanent magnet 60 is
`almost a constant width, and a passage 61 of magnetic flux
`50 in the q-axis direction is formed in this gap portion.
`The stator 52 has a specific number of teeth 57, and a
`winding (not shown) is turned around each tooth 57. At this
`time, since the winding is applied on each core element 55,
`a single winding is applied. As an alternating current is given
`to the stator winding, a rotary magnetic flux is generated,
`and by this rotary magnetic flux, magnet torque and reluc(cid:173)
`tance torque act on the rotor 53, so that the rotor 53 is dri