Rotor, axial gap type motor, method of driving motor, and compressor

A technique of employing a rotor having anti-saliency and being rotatable about a predetermined axis in an axial gap type motor is provided. A plurality of magnets are disposed annularly on a substrate with polarities being symmetric around a shaft hole. For instance, the magnets exhibit N pole and S pole, respectively, on the side of a stator (on this side of sheet of drawing). A plurality of magnetic members are disposed to extend perpendicularly to the direction of a rotation axis, and more specifically, between the magnets.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. National stage application claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2005-011520, filed in Japan on Jan. 19, 2005, the entire contents of which are hereby incorporated herein by reference.

TECHNICAL FIELD

This invention relates to a motor, and particularly to an axial gap type motor in which the gap between a stator and a rotor is provided along a plane perpendicular to the rotation axis.

BACKGROUND ART

Conventionally, many radial gap type motors have been used in which the gap between the stator and rotor is provided along a cylindrical surface parallel to the rotation axis for applications requiring high outputs such as a compressor, machine tool, etc. However, because of the recent higher performance of magnetic materials or the like, the study of employing an axial gap type motor in a compressor or the like has been started.

This is to respond to a request to solve the problem that a stainless pipe or the like for preventing permanent magnets from being scattered by centrifugal force increases gaps or eddy-current loss and a request to apply a plate-like magnet to a cylindrical rotor.

Patent document 6 describes that an axial gap type motor reduces axis and bearing load for compressor application. A rotor employed here has permanent magnets exposed at its surface.

Patent document 1 discloses an axial gap type motor, and employs so-called distributed winding for a stator. In a rotor employed here, permanent magnets magnetized in the axial direction are embedded in a disc part made of a non-magnetic material.

Patent document 2 discloses an axial gap type motor, and employs so-called concentrated winding for a stator. In a rotor employed here, a plurality of permanent magnets are fixed by a non-magnetic ring from their outer sides and by a magnet holder from their inner sides.

Patent document 3 discloses an axial gap type motor having magnetic poles on both sides of a rotor and stators on its both sides. In the rotor employed here, permanent magnets having a plurality of poles are disposed on both sides of a ring-shaped yoke member.

Patent document 4 discloses an axial gap type motor. In a rotor employed here, permanent magnets magnetized in the axial direction are embedded in a disc part made of a non-magnetic material.

Patent document 5 discloses an axial gap type switched reluctance motor.

Patent document 4: Japanese Utility Model No. 3062085

SUMMARY OF THE INVENTION

Problems to be Solved by Invention

However, the rotor shown in Patent document 6, having permanent magnets exposed at its surface, cannot make use of reluctance torque, and in addition, a wide range of operation by flux-weakening control is difficult.

Further, in the rotor shown in Patent document 1 or 4, the disc part of the rotor is made of a non-magnetic material. Thus, a portion of the rotor other than the permanent magnets is merely a structural member having no magnetic function.

In the rotor shown in Patent document 2, the non-magnetic ring is also a mere structural member. There is no mention of the magnet holder being either magnetic or non-magnetic, and even when employing a magnetic material for the magnet holder, it will not exhibit saliency.

In the rotor shown in Patent document 3, the permanent magnets have yokes on the opposite side of gaps, but do not exhibit saliency.

In the switched reluctance motor shown in Patent document 5, the poles of a rotor are cores formed into U shape, and the poles of a stator have cores formed into U shape around which excitation windings are wound. And, they are provided in main parts of separate non-magnetic materials, respectively. One pole of the stator has a pair of magnetic poles when the excitation winding is energized, and one pole of the stator and one pole of the rotor are opposed to each other to form one magnetic path, and there is no exchange of magnetic flux with an adjacent pole.

Therefore, when providing a permanent magnet for the rotor in Patent document 5, the interaction between the energized pole of the stator and the permanent magnet interferes with the interaction with the poles of the rotor composed of the cores formed into U shape. Further, the interaction between a pole of the stator yet to be energized and permanent magnet will cause an increase in cogging torque.

Means for Solving the Problems

A first aspect of a rotor according to this invention (1A;1B;1C;1D;1E;1F;1G;1H;1I;1J,1K;1L;1M) comprises: a plurality of magnets (12a,12b;120a,120b;12a,12b;1a,12b;12a,12b;12cto12f;12a,12b,12g,12h,12a,12b;12a,12b,12g,12h;12,12b;12a,12b,12g,12h;12a,12b;12a,12b), each having a pole face, disposed annularly with polarities being symmetric around a predetermined axis; and a plurality of magnetic members (13a,13b;130a,130b;13a,13b,14a,14b;54a,5b;13a,13b,54cto54f;54gto54j;13a,13b,13g,13h;13a,13b;13a,13b,13g,13h,14a,14b,14g,14h;13a,13b,14a,14b,14g,14h;13a,13b,13g,13h,542,544;13a,13b,542,544;541,545). An inductance (Ld) corresponding to a magnetic flux flowing from outside passing through between a first type of said magnets (12a;120a;12a;12a;12a;12c,12e;12a,12g;12a;12a,12g;12a;12a,12g;12a;12a) having said pole face exhibiting a first polarity with respect to one side of said axis and a second type of said magnets (12b;120b;12b;12b;12b;12d,12f;12b,12h;12b;12b,12h;12b;12b,12h;12b;12b) having said pole face exhibiting a second polarity with respect to said one side is smaller than an inductance (Lq) corresponding to a magnetic flux flowing from said outside to said magnetic members bypassing said magnets.

A second aspect of the rotor according to this invention (1A;1B;1C;1E;1G;1H;1I;1J;1K;1L) is the rotor according to the first aspect, in which said magnetic members (13a,13b;130a,130b;13a,13b;13a,13b;13a,13b,13g,13h;13a,13b;13a,13b,13g,13h;13a,13b;13a,13b,13g,13h;13a,13b) are provided at least between said first type of said magnets (12a;120a;12a;12a;12a,12g;12a;12a,12g;12a;12a,12g;12a) and said second type of said magnets (12b;120b;12b;12b;12b,12h;12b;12b,12h;12b;12b,12h;12b).

A third aspect of the rotor according to this invention is the rotor according to the second aspect, in which surfaces of said magnetic members on said one side lie on almost the same plane as said pole face.

A fourth aspect of the rotor according to this invention (1A;1B;1C;1E;1F;1G;1I;1K) is the rotor according to the second aspect, and further comprises a yoke (11;110;11;11;11;11;11;11) for backing said magnets (12a,12b;120a,120b;12a,12b;12a,12b;12cto12f;12a,12b;12a,12b;12a,12b) from the other side of said axis.

A fifth aspect of the rotor according to this invention (1G;1I;1K) is the rotor according to the fourth aspect, and further comprises other plurality of magnets (12g,12h;12g,12h;12g,12h) each having a pole face, disposed annularly from the other side of said axis with respect to said yoke (11;11;11) with polarities being symmetric around said axis. Said magnetic members (13g,13h;13g,13h;13g,13h) are also provided between said other magnets.

A sixth aspect of the rotor according to this invention (1G;1I;1K) is the rotor according to the fifth aspect, in which said magnets (12a,12b;12a,12b;12a,12b) and said other magnets (12g,12h;12g,12h;12g,12h) are disposed to be nearly directly opposed with said yoke interposed therebetween, and exhibit magnetic poles of opposite polarity to said yoke.

A seventh aspect of the rotor according to this invention (1B) is the rotor according to the fourth aspect, in which a bonded magnet (120) covering said one side of said magnetic members (130a,130b) and said yoke (110) is provided, and said magnets (120a,120b) are said bonded magnet as magnetized.

An eighth aspect of the rotor according to this invention (1B) is the rotor according to the seventh aspect, in which said bonded magnet (120) is obtained by mixing dust of a rare-earth magnet with a binder such as resin.

A ninth aspect of the rotor according to this invention (1B) is the rotor according to the seventh aspect, in which said bonded magnet (121a,121b) covering said one side of said magnetic members (130a,130b) is substantially unmagnetized.

A tenth aspect of the rotor according to this invention (1B) is the rotor according to the ninth aspect, in which said magnetic members (130a,130b) have their surfaces vary sinusoidally around said axis.

An eleventh aspect of the rotor according to this invention (1A;1C;1E;1G;1H;1I;1J;1K;1L) is the rotor according to any one of the second to fourth aspects, in which a magnetic barrier (G1) is provided in a direction perpendicular to said axis between said magnetic members (13a,13b;13a,13b;13a,13b;13a,13b,13g,13h;13a,13b;13a,13b,13g,13h;13a,13b;13a,13b,13g,13h;13a,13b) and said magnets (12a,12b;12a,12b;12a,12b;12a,12b,12g,12h;12a,12b;12a,12b,12g,12h;12a,12b;12a,12b,12g,12h;12a,12b) adjacent to each other.

A twelfth aspect of the rotor according to this invention (1A;1C;1E;1G;1H;1I;1J;1K;1L) is the rotor according to the eleventh aspect, in which the width of said magnetic barrier is chosen to be not less than twice a distance (δ) between a pole face of a stator opposed to said rotor to constitute a motor and a pole face of the rotor.

A thirteenth aspect of the rotor according to this invention (1C;1E;1I;1J;1K;1L) is the rotor according to the second aspect, and further comprises other magnetic members (14a,14b;54c,54e;14a,14b,14g,14h;14a,14b,14g,14h;542,544;542,544) provided to cover said pole face of said magnets (12a,12b;12a,12b;12a,12b,12g,12h;12a,12b;12a,12b,12g,12h;12a,12b) magnetically independently and individually on said one side.

A fourteenth aspect of the rotor according to this invention (1C;1E;1K;1L) is the rotor according to the thirteenth aspect, in which edges (14aE,14bE) of said other magnetic members (14a,14b;54c,54e;542,544;542,544) in a circumferential direction around said axis are thinner than a central portion.

A fifteenth aspect of the rotor according to this invention (1C;1E;1K;1L) is the rotor according to the fourteenth aspect, in which edges (14aE,14bE) of said other magnetic members (14a,14b;54c,54e;542,544;542,544) in the circumferential direction around said axis have side surfaces inclined to said one side in said circumferential direction.

A sixteenth aspect of the rotor according to this invention (1C;1E;1K;1L) is the rotor according to the thirteenth aspect, in which said other magnetic members (14a,14b;54c,54e;542,544;542,544) are provided with grooves (141) in a radial direction around said predetermined axis on said one side.

A seventeenth aspect of the rotor according to this invention (1E;1K;1L) is the rotor according to the thirteenth aspect, in which a magnetic plate (542;542,544;542,544) covering said pole face and said magnetic members (13a,13b;13a,13g,13h;13a,13b) on said one side is provided, said magnetic plate has opening slits (55cto55f;55cto55f;55cto55f) extending from positions close to said axis to farther positions between said magnetic members and said magnets as viewed along said axis, divisions of said magnetic plate divided by said slits in a circumferential direction around said axis that cover said pole face serve as said other magnetic members (54c,54e;54c,54e;54c,54e). Said other magnetic members are connected to divisions (54d,54f;54d,54f;54d,54f) of said magnetic plate divided by said slits in the circumferential direction around said axis that cover said magnetic members with thin portions (56eto56h/56ito56l) interposed therebetween at least on the side of one ends of said slits.

An eighteenth aspect of the rotor according to this invention (1E;1K;1L) is the rotor according to the seventeenth aspect, in which the width of said slits (55cto55f;55cto55f;55cto550in said circumferential direction is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor (1E;1K;1L) to constitute a motor and surfaces of said other magnetic members on the side of the stator.

A nineteenth aspect of the rotor according to this invention (1C;1D;1E;1F;1I;1J;1K;1L;1M) is the rotor according to the first aspect, in which said magnetic members (14a,14b;54a,54b;54c,54e;54g,54h,54i,54j;14a,14b,14g,14h;14a,14b,14g,14h;542,544;542,544;541,545) are provided to cover said pole face at least on said one side.

A twentieth aspect of the rotor according to this invention (1I;1J;1K;1L;1M) is the rotor according to the nineteenth aspect, in which said magnetic members (14g,14h;14g,14h;544;544;545) are mounted on said magnets also from the opposite side of said one side.

A twenty-first aspect of the rotor according to this invention (1C;1E;1K;1L) is the rotor according to the nineteenth aspect, in which edges (14aE,14bE) of said magnetic members (54a,54b;54g,54h,54i,54j;542,544;542,544;541,545) in the circumferential direction around said axis are thinner than a central portion.

A twenty-second aspect of the rotor according to this invention (1C;1E;1K;1L;1M) is the rotor according to the nineteenth aspect, in which edges (14aE,14bE) of said magnetic members (54a,54b;54g,54h,54i,54j;542,544;542,544;541,545) in said circumferential direction around said axis have side surfaces inclined to said one side in said circumferential direction.

A twenty-third aspect of the rotor according to this invention (1C;1E;1K;1L;1M) is the rotor according to the nineteenth aspect, in which said magnetic members (54a,54b;54g,54h,54i,54j;542,544;542,544;541,545) are provided with grooves (141) on said one side in a radial direction around said predetermined axis.

A twenty-fourth aspect of the rotor according to this invention (1D;1E;1F;1K;1L;1M) is the rotor according to the nineteenth aspect, in which a magnetic plate (541;542;543;542,544;542,544;541,545) covering said pole face on said one side is provided, said magnetic plate has opening slits (55a,55b;55cto55f;55gto55j;55cto55f;55cto55f;55a,55b) extending from positions close to said axis to farther positions between said magnetic members as viewed along said predetermined axis, said magnetic plate divided by said slits in the circumferential direction around said axis serves as said magnetic members (54a,54b;54c,54e;54g,54h,54i,54j;54c,54e;54c,54e;54a,54b). Said magnetic members are connected to each other with thin portions (56a,56b/56c,56d;56eto56h/56ito56l;56eto56h/56ito56l;56eto56h/56ito56l;56a,56b/56c,56d) interposed therebetween at least on the side of one ends of said slits.

A twenty-fifth aspect of the rotor according to this invention (1D;1F;1M) is the rotor according to the twenty-fourth aspect, in which the width of said slits (55a,55b;55gto55j;55a,55b) in said circumferential direction is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor to constitute a motor and a pole face of the rotor.

A twenty-sixth aspect of the rotor according to this invention (1D;1F;1M) is the rotor according to the twenty-fourth aspect, in which said first type of said magnets (12a;12a,12c;12a) and said second type of said magnets (12b;12b,12d;12b) are formed integrally by a ring-like magnet. The ring-like magnet is unmagnetized in positions where said slits (55a,55b;55gto55j;55a,55b) are provided in plan view as viewed along said axis.

A twenty-seventh aspect of the rotor according to this invention (1D;1M) is the rotor according to any one of the nineteenth to twenty-sixth aspects, in which the area of one of said magnetic members (54a,54b;54a,54b) covering one of said pole face (12a,12b;12a,12b) is larger than the area of said pole face.

A twenty-eighth aspect of the rotor according to this invention (1D;1F;1M) is the rotor according to any one of the twenty-fourth to twenty-seventh aspects, in which said slits (55a,55b;55gto55j;55a,55b) are provided in the vicinity of the border between said first type of said magnets (12a;12c,12e;12a) and said second type of said magnets (12b;12d,12f;12b).

A twenty-ninth aspect of the rotor according to this invention (1L;1M) is the rotor according to the twenty-fourth aspect, and further comprises a magnetic plate (545) covering a pole face further provided for said first type of said magnets (12a) exhibiting said second polarity and a pole face further provided for said second type of said magnets (12b) exhibiting said first polarity, on the other side of said axis, and being of almost the same type as said magnetic plate (541) covering said pole face on said one side.

A thirtieth aspect of the rotor according to this invention (1E;1L) is the rotor according to any one of the twenty-fourth to twenty-ninth aspects, and further comprises other magnetic members (13a,13b) provided between said first type of said magnets (12a) and said second type of said magnets (12b). The slits (55cto55f) are provided in the vicinity of the border between the other magnetic members and said magnets (12a,12b).

A thirty-first aspect of the rotor according to this invention (1F) is the rotor according to any one of the twenty-fourth to thirtieth aspects, in which said slits (55gto55j) are provided to be inclined relative to the axial direction around said axis.

A thirty-second aspect of the rotor according to this invention (1D) is the rotor according to any one of the nineteenth to twenty-eighth aspects, and further comprises a yoke (11) backing said magnets (12a,12b) from the other side of said axis.

A thirty-third aspect of the rotor according to this invention is the rotor according to the fourth aspect, in which, in said yoke, a region having a predetermined length from said one side in a position where said magnetic members are extended along said axis is made of dust core, and steel sheets perpendicular to said axis are stacked out of said region.

A thirty-fourth aspect of the rotor according to this invention is the rotor according to the fourth aspect, in which said yoke (11) has recesses or through holes (11a,11b) into which said magnetic members (13a,13b) fit in the direction along said axis.

A thirty-fifth aspect of the rotor according to this invention is the rotor according to the fourth aspect, in which said yoke (11) has recesses (12aQ,12bQ) into which said magnets (12a,12b) fit in the direction along said axis.

A thirty-sixth aspect of the rotor according to this invention according to any one of the thirty-third to thirty-fifth aspects, and further comprises a magnetic plate (542) covering said pole face and said magnetic members (13a,13b) on said one side. The magnetic plate has opening slits (55cto550extending from positions close to said axis to farther positions between said magnetic members and said magnets as viewed along said axis, and divisions (54d,54f) of said magnetic plate divided by said slits in the circumferential direction around said axis that cover said magnetic members are formed integrally with said magnetic members.

A thirty-seventh aspect of the rotor according to this invention is the rotor according to the fourth aspect, and further comprises ridges (111a,111b) provided on said yoke (11) and coming into contact with said magnets from their outer peripheral sides.

A thirty-eighth aspect of the rotor according to this invention is the rotor according to the fourth aspect, and further comprises ridges (112a.113a,112b.113b) provided on said yoke (11) and coming into contact with said magnets from the side of the circumferential direction around said axis.

A thirty-ninth aspect of the rotor according to this invention is the rotor according to the seventeenth aspect, in which said magnetic plate has recesses or through holes (57a,57b) into which said magnetic members (13a,13b) fit in the direction along said axis.

A fortieth aspect of the rotor according to this invention is the rotor according to the seventeenth aspect, in which said magnetic plate (542) has recesses (57c,57d) into which said magnets (12a,12b) fit in the direction along said axis.

A forty-first aspect of the rotor according to this invention is the rotor according to either the thirty-ninth or fortieth aspect, and further comprises a yoke (11) backing said magnets (12a,12b) from the other side of said axis. Said yoke and said magnetic members are formed integrally.

A forty-second aspect of the rotor according to this invention is the rotor according to the twenty-fourth aspect, in which said magnetic plate (542) has recesses (57c,57d) into which said magnets (12a,12b) fit in the direction along said axis.

A forty-third aspect of the rotor according to this invention is the rotor according to either the seventeenth or twenty-fourth aspect, and further comprises ridges (58a,58b) provided on said magnetic plate (542) and coming into contact with said magnets from their outer peripheral sides.

A forty-fourth aspect of the rotor according to this invention is the rotor according to either the seventeenth or twenty-fourth aspect, and further comprises ridges (59a,59b,59c,59d) provided on said magnetic plate (542) and coming into contact with said magnets from the side of the circumferential direction around said axis.

A forty-fifth aspect of the rotor according to this invention is the rotor according to either the seventeenth or twenty-fourth aspect, in which said magnetic plate (542) is composed of magnetic plate components (542a,542b) divided in a position where said pole face is disposed as viewed along said axis.

A forty-sixth aspect of the rotor according to this invention is the rotor according to the forty-fifth aspect, in which said magnetic plate components (542a,542b) are adjacent to each other leaving gaps.

A forty-seventh aspect of the rotor according to this invention is the rotor according to the forty-fifth aspect, in which edges of said magnetic plate components (542a,542b) in the circumferential direction have steps in the direction along said axis. The steps of said magnetic plate components adjacent to each other engage with each other to constitute said magnetic plate (542).

A forty-eighth aspect of the rotor according to this invention is the rotor according to the forty-fifth aspect, in which edges of said magnetic plate components (542a,542b) in the circumferential direction have steps in the direction along said axis.

The steps of said magnetic plate components adjacent to each other are adjacent to each other, and form recesses which open on said one side and are in contact with each other on the other side of said axis.

A forty-ninth aspect of the rotor according to this invention is the rotor according to the thirty-sixth aspect, in which a distance (t3) between the other side of said magnetic plate (542) relative to said axis and said one side of said yoke (11) is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor to constitute a motor and a surface of said magnetic plate on the side of the stator.

A fiftieth aspect of the rotor according to this invention is the rotor according to either the thirty-seventh or thirty-eighth aspect, in which a distance between the other side of said magnetic plate (542) relative to said axis and said one side of said ridges (111a,111b,112a,113a,112b,113b) is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor to constitute a motor and a surface of said magnetic plate on the side of the stator.

A fifty-first aspect of the rotor according to this invention is the rotor according to the forty-first aspect, in which a distance (t3) between the other side of said magnetic plate (542) relative to said axis and said one side of said yoke (11) is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor to constitute a motor and a surface of said magnetic plate on the side of the stator.

A fifty-second aspect of the rotor according to this invention is the rotor according to the forty-third aspect, in which a distance between the said one side of said yoke (11) and the other side of said ridges (58a,58b) relative to said axis is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor to constitute a motor and a surface of said magnetic plate on the side of the stator.

A fifty-third aspect of the rotor according to this invention is the rotor according to the forty-fourth aspect, in which a distance between the said one side of said yoke (11) and the other side of said ridges (59a,59b,59c,59d) relative to said axis is chosen to be not less than twice the distance between a pole face of a stator opposed to the rotor to constitute a motor and a surface of said magnetic plate on the side of the stator.

A first aspect of an axial gap type motor according to this invention comprises the rotor according to any one of the first to fifty-third aspects and a stator (2). Said stator includes: a plurality of magnetic cores (221to226) standing along said axis; windings (231to236) wound around said magnetic cores; and a magnetic plate (24) mounted on said magnetic cores and having opening slits (251to256) extending from positions close to said axis to farther positions.

A second aspect of the axial gap type motor according to this invention comprises the rotor according to any one of the first to fifty-third aspects and a stator (3). Said stator includes: a substrate (31) having a surface (310) perpendicular to said axis; a pair of first-stage spacers (311,313) separated from each other and each extending at an angle of about 180 degrees, on said surface in the circumferential direction of said axis; a pair of second-stage spacers (312,314) extending at ends of said first-stage spacers at an angle of about 120 degrees in said circumferential direction on said first-stage spacers, respectively; a pair of magnetic cores (321,324) provided on said first-stage spacers, respectively; two pairs of magnetic cores (322,323/325,326) provided on said second-stage spacers, respectively; a pair of first windings (33a,33b) provided on said substrate and winding three of said magnetic cores; a pair of second windings (34a,34b) provided on said first-stage spacers and said first windings and winding three of said magnetic cores; and a pair of third windings (35a,35b) provided on said second-stage spacers and said second windings and winding three of said magnetic cores. Said first windings, said second windings and said third windings are arranged to be shifted 120 degrees from one another in said circumferential direction.

A third aspect of the axial gap type motor according to this invention comprises the rotor (1G;1I;1J;1K;1L) according to any one of the fifth to twentieth aspects and a pair of stators interposing said rotor.

A first aspect of a method of driving a motor according to this invention drives an axial gap type motor comprising the rotor according to any one of the first to fifty-third aspects and a stator opposed to said rotor, by flowing a sinusoidal current to said stator.

A second aspect of the method of driving a motor according to this invention drives an axial gap type motor comprising the rotor according to any one of the first to fifty-third aspects and a stator opposed to said rotor, by flowing a leading current to said stator.

A first aspect (200) of a compressor according to this invention is equipped with an axial gap type motor (100) comprising the rotor according to any one of the first to fifty-third aspects and a stator opposed to said rotor.

A second aspect (200) of the compressor according to this invention is the compressor of the first aspect, and further comprises a compression element (205) driven by said motor (100), and said compression element is provided below said motor.

Effects of Invention

The first aspect of the rotor according to this invention serves as a rotor having anti-saliency and being rotatable about a predetermined axis in an axial gap type motor. That is, the reluctance torque is utilized effectively, which increases torque and efficiency. Further, the effect of flux-weakening control is increased to enlarge the operating range.

According to the second aspect of the rotor according to this invention, the magnetic path passing through the magnetic members bypassing the magnets has an inductance larger than the magnetic path passing through the magnets and is perpendicular thereto when viewed as an electric angle. Thus, the q-axis inductance is increased, and anti-saliency is improved. Further, size reduction in the axial direction is easy.

According to the third aspect of the rotor according to this invention, the distance between the rotor and stator is not increased unnecessarily while earning the q-axis inductance.

According to the fourth aspect of the rotor according to this invention, a magnetic flux is prevented from short circuiting between the magnetic pole and pole face in the same magnet on the other side of the axis. Therefore, the magnetic flux generated from the pole face is supplied efficiently to the one side of the axis. Further, the magnetic resistance between the magnetic poles between the first type of the magnets and second type of the magnets on the other side of the axis is reduced. Accordingly, the permeance coefficient is increased, so that the operating point of the magnets is raised. The torque is thereby improved.

According to the fifth aspect of the rotor according to this invention, forming the motor along with the stators interposing the rotor improves the torque.

According to the sixth aspect of the rotor according to this invention, a region where the magnetic flux of the yoke saturates by the magnetic fluxes generated from the magnets is extended, and variations in magnetic fluxes flowing from the stators to the substrate is reduced, so that eddy-current loss based on the variations in magnetic fluxes is reduced.

According to the seventh aspect of the rotor according to this invention, it is easy to fix the magnets to the yoke. Moreover, they can be formed with improved adhesion, so that the permeance coefficient can be made still higher. Moreover, the use of the bonded magnet increases the flexibility in shape, which facilitates control of the distribution of magnetic flux supplied from the rotor. Further, the eddy-current loss is extremely reduced as compared to the case of employing a sintered rare-earth magnet. Furthermore, magnetic field orientation may or may not be performed at the time of molding, and magnetization is easily performed anytime after molding. In the case of performing magnetic field orientation at the time of molding, it is also easy to give an optimized magnetized distribution in order to reduce vibrations and noise.

According to the eighth aspect of the rotor according to this invention, the density of the magnetic flux generated by the rotor is increased.

According to the ninth aspect of the rotor according to this invention, through the use of the bonded magnet having high magnetic resistance and low conductivity, that the magnetic flux flows between the pole face exhibiting the first polarity with respect to the one side of the axis and the pole face exhibiting the second polarity with respect to the one side of the axis with the bonded magnet interposed therebetween, that is, magnetic flux leakage inside the rotor is small. That is, the substantially unmagnetized bonded magnet covering the one side of the magnetic members serves as a magnetic barrier between the pole faces.

According to the tenth aspect of the rotor according to this invention, it is easy to control the magnetic flux supplied from the rotor sinusoidally around the axis, thus the cogging torque is reduced.

According to the eleventh aspect of the rotor according to this invention, that the magnetic flux flows between the pole face exhibiting the first polarity and the pole face exhibiting the second polarity with the magnetic members interposed therebetween, that is, magnetic flux leakage inside the rotor is small. Therefore, the magnetic fluxes generated from the pole faces of the rotor is supplied efficiently to the stators opposed to these pole faces.

According to the twelfth aspect of the rotor according to this invention, magnetic flux leakage is reduced by making the magnetic resistance between the pole face exhibiting the first polarity and the pole face exhibiting the second polarity higher than the magnetic resistance between the stator and rotor.

According to the thirteenth aspect of the rotor according to this invention, the inductance corresponding to the magnetic flux flowing from outside bypassing the magnets is increased further. Further, other magnetic members are provided closer to the stator than the magnets, allowing the magnetic field from the stator to be likely to pass through the other magnetic members and to be less likely to reach the magnets of the rotor. This not only suppresses demagnetization of the magnets, but also allows eddy current, if any, to be likely to occur in the other magnetic members, and suppresses the occurrence of the eddy current inside the magnets. This is particularly advantageous in the case of employing a material of low electric resistance, e.g., a sintered rare-earth magnet for the magnets. In other words, the rotor of high magnetic flux density is obtained employing a sintered rare-earth magnet for the magnets without concern about the occurrence of eddy current.

According to the fourteenth aspect of the rotor according to this invention, the cogging torque is reduced.

According to the fifteenth aspect of the rotor according to this invention, skews is further obtained.

According to the sixteenth aspect of the rotor according to this invention, the grooves are opposed to the side of the stator, and the grooves serve as so-called supplemental grooves for shortening the cycle of cogging torque, thereby reducing the cogging torque.

According to the seventeenth aspect of the rotor according to this invention, the number of components is less and the magnetic plate is stronger than in the case of forming the magnetic members individually and separately. Since the thin portions are easy to become magnetically saturated, a short circuit of magnetic fluxes inside the rotor is extremely small even when the magnetic members are connected through the thin portions to eachother.

According to the eighteenth aspect of the rotor according to this invention, magnetic flux leakage is reduced by making the magnetic resistance between the pole face exhibiting the first polarity and the pole face exhibiting the second polarity higher than the magnetic resistance between the stator and rotor.

According to the nineteenth aspect of the rotor according to this invention, the inductance corresponding to the magnetic flux flowing from outside bypassing the magnets is increased further. Further, the magnetic members are provided closer to the stator than the magnets, allowing the magnetic field from the stator to be likely to pass through the other magnetic members and to be less likely to reach the magnets of the rotor. This not only suppresses demagnetization of the magnets, but also allows eddy current, if any, to be likely to occur in the magnetic members, and suppresses the occurrence of the eddy current inside the magnets. This is particularly advantageous in the case of employing a material of low electric resistance, e.g., a sintered rare-earth magnet for the magnets. In other words, the rotor of high magnetic flux density is obtained employing a sintered rare-earth magnetfor the magnets without concern about the occurrence of eddy current.

According to the twentieth aspect of the rotor according to this invention, forming the motor along with the stators interposing the rotor improves the torque.

According to the twenty-first aspect of the rotor according to this invention, the cogging torque is reduced.

According to the twenty-second aspect of the rotor according to this invention, skews is further obtained.

According to the twenty-third aspect of the rotor according to this invention, the grooves are opposed to the side of the stator, and the grooves serve as so-called supplemental grooves for shortening the cycle of cogging torque, thereby reducing the cogging torque.

According to the twenty-fourth aspect of the rotor according to this invention, the number of components is less and the magnetic plate is stronger than in the case of forming the magnetic members individually and separately. Since the thin portions are easy to become magnetically saturated, a short circuit of magnetic fluxes inside the rotor is extremely small even when the magnetic members are connected through the thin portions to eachother.

According to the twenty-fifth aspect of the rotor according to this invention, magnetic flux leakage is reduced by making the magnetic resistance between the pole face exhibiting the first polarity and the pole face exhibiting the second polarity higher than the magnetic resistance between the stator and rotor.

The twenty-sixth aspect of the rotor according to this invention is easy to manufacture. Further, a substrate for connecting the first type of the magnets and second type of the magnets is not required.

According to the twenty-seventh aspect of the rotor according to this invention, a short circuit of magnetic fluxes inside the rotor is reduced.

According to the twenty-eighth aspect of the rotor according to this invention, short circuiting between the first type of the magnets and second type of the magnets through the magnetic members is prevented by the slits.

According to the twenty-ninth aspect of the rotor according to this invention, forming the motor along with the stators interposing the rotor improves the torque.

According to the thirtieth aspect of the rotor according to this invention, short circuiting between the first type of the magnets and second type of the magnets through the magnetic members and other magnetic members is prevented by the slits.

According to the thirty-first aspect of the rotor according to this invention, the substantial border of the pole faces is inclined relative to the radial direction to provide so-called skews, thereby reducing the cogging torque.

According to the thirty-second aspect of the rotor according to this invention, magnetic fluxes are prevented from short circuiting between the magnetic pole on the other side of the axis and pole face in the same magnet. Therefore, the magnetic flux generated from the pole face is supplied efficiently to the one side of the axis. Further, the magnetic resistance between the magnetic poles on the other side of the axis is reduced between the first type of the magnets and second type of the magnets. Accordingly, the permeance coefficient is increased, so that the operating point of the magnets is raised. The torque is thereby improved.

According to the thirty-third aspect of the rotor according to this invention, dust core is employed in that region since magnetic fluxes flow both in the direction parallel to the axis and in the direction inclined thereto, and stacked steel sheets are employed out of that region since most magnetic fluxes flow in the direction perpendicular to the axis. This optimizes the magnetic characteristics of the rotor.

According to the thirty-fourth aspect of the rotor according to this invention, the magnetic members and yoke are easily aligned, and both are easily coupled.

According to the thirty-fifth aspect of the rotor according to this invention, the magnets and yoke are easily aligned, and both are easily coupled.

According to the thirty-sixth aspect of the rotor according to this invention, the inductance corresponding to the magnetic flux flowing from outside bypassing the magnets be is increased further. Further, the magnetic plate is provided closer to the stator than the magnets, allowing the magnetic field from the stator to be likely to pass through them agnetic plate and to be less likely to reach the magnets of the rotor. This not only suppresses demagnetization of the magnets, but also allows eddy current, if any, to be likely to occur in the magnetic plate, and suppresses the occurrence of the eddy current inside the magnets. This is particularly advantageous in the case of employing a material of low electric resistance, e.g., a sintered rare-earth magnet for the magnets. In other words, the rotor of high magnetic flux density is obtained employing a sintered rare-earth magnet for the magnets without concern about the occurrence of eddy current. Further, making the magnetic plate and magnetic members integral facilitates assembly of the rotor using the magnetic plate, magnetic members, yoke and magnets.

According to the thirty-seventh aspect of the rotor according to this invention, the magnets can easily be aligned, and the magnets are stopped against the centrifugal force produced in the magnets by rotation of the rotor.

According to the thirty-eighth aspect of the rotor according to this invention, the magnets are easily aligned.

According to the thirty-ninth aspect of the rotor according to this invention, the magnetic members and magnetic plate are easily be-aligned, and both are easily becoupled.

According to the fortieth aspect of the rotor according to this invention, the magnets and magnetic members can easily be aligned, and both can easily be coupled.

According to the forty-first aspect of the rotor according to this invention, magnetic fluxes are prevented from short circuiting between the magnetic pole on the other side of the axis and pole face in the same magnet. Therefore, the magnetic flux generated from the pole face is supplied efficiently to the one side of the axis. Further, the magnetic resistance between the magnetic poles on the other side of the axis is reduced between the first type of the magnets and second type of the magnets. Accordingly, the permeance coefficient is increased, so that the operating point of the magnets is raised. The torque is thereby improved. Further, making the yoke and magnetic members integral facilitates assembly of the rotor using the magnetic plate, magnetic members, yoke and magnets.

According to the forty-second aspect of the rotor according to this invention, the magnets and magnetic members are easily aligned, and both are easily coupled.

According to the forty-third aspect of the rotor according to this invention, the magnets are easily aligned, and the magnets are stopped against the centrifugal force produced in the magnets by rotation of the rotor.

According to the forty-fourth aspect of the rotor according to this invention, the magnets are easily aligned.

According to the forty-fifth aspect of the rotor according to this invention, the magnetic plate are divided and formed in small size, facilitating manufacture with iron dust core.

According to the forty-sixth aspect of the rotor according to this invention, the gaps are opposed to the side of the stator, and the gaps serve as so-called supplemental grooves for shortening the cycle of cogging torque, thereby reducing the cogging torque.

According to the forty-seventh aspect of the rotor according to this invention, the structure of the magnetic plate composed of magnetic plate components are made strong.

According to the forty-eighth aspect of the rotor according to this invention, the recesses are opposed to the side of the stator, and the recesses serve as so-called supplemental grooves for shortening the cycle of cogging torque, thereby reducing the cogging torque. Further, the magnetic fluxes of the magnets are utilized effectively.

According to the forty-ninth aspect of the rotor according to this invention, the magnetic flux is likely to flow from the pole face to the stator even when the magnets are embedded to fit into the yoke.

According to the fiftieth aspect of the rotor according to this invention, the magnetic flux is likely to flow from the pole face to the stator even when the yoke is provided with ridges.

According to the fifty-first aspect of the rotor according to this invention, the magnetic flux is likely to flow from the pole face to the stator even when the magnets are embedded to fit into the magnetic plate.

According to the fifty-second aspect of the rotor according to this invention, the magnetic flux is likely to flow from the pole face to the stator even when the magnetic plate is provided with ridges.

According to the first aspect of the axial gap type motor according to this invention, the pole faces of the magnetic cores are extended substantially, making it easier to make the magnetic flux density between the rotor and stator uniform. Further, the windings are protected by the magnetic plate.

According to the second aspect of the axial gap type motor according to this invention, the three pairs of windings are easily disposed stably.

According to the third aspect of the axial gap type motor according to this invention, the presence of mechanisms for generating torque on both sides of the rotor improves the torque.

According to the first aspect of the method of driving the motor according to this invention, the cogging torque is suppressed.

According to the second aspect of the method of driving the motor according to this invention, the reluctance torque is utilized effectively, which increases torque and efficiency. Further, the effect of flux-weakening control is increased to enlarge the operating range.

According to the first aspect of the compressor according to this invention, high efficiency is obtained.

According to the second aspect of the compressor according to this invention, an axial gap type motor having a large diameter is prevented from stirring oil.

DETAILED DESCRIPTION OF THEINVENTION

Basic Idea of this Invention

Before starting detailed description of embodiments, the basic idea of this invention will be described. Of course, this basic idea is included in the present invention.

Similarly to a radial gap type motor, in an axial gap type motor, improved so-called saliency does for making effective use of reluctance torque, thus increasing the torque and efficiency and to increase the effect of flux-weakening control, thereby enlarging the operating range. In other words, an inductance (d-axis inductance) Ld corresponding to a magnetic flux flowing from outside through between magnetic poles of a rotor having different polarities needs to be smaller than an inductance (q-axis inductance) Lq corresponding to a magnetic flux flowing from outside bypassing the magnet.

Incidentally, in a radial gap type motor, a so-called embedded magnet type rotor with magnets embedded in a rotor iron core has been presented.FIG. 65is a perspective view illustrating the structure of such embedded magnet type rotor900. A rotor iron core91is provided with embedding trenches92, in each of which a permanent magnet93is embedded. A mode is illustrated here in which four magnets93are embedded around a shaft hole94through which a rotation shaft is inserted. Adjacent permanent magnets93have magnetic poles different in polarity from each other being directed toward the outer surface of the rotor900.

One of the causes of increased q-axis inductance Lq in the rotor900is the presence of a magnetic path95passing through a portion of the rotor iron core91appearing as a projection91cpresent between edges of adjacent magnets93and interposed between the trenches92and a portion appearing as an inner portion91aaround the shaft hole94surrounded by the magnets93from outside. The magnetic path95is to be a path along which a magnetic flux supplied from a stator (not shown) passing through the outer surface of the rotor900flows bypassing the magnets93. The magnetic path which bypasses magnets between the magnets in this manner will hereinafter be called a first type magnetic path.

Further, another one of the causes of increased q-axis inductance Lq is the presence of a magnetic path96passing through a portion of the rotor iron core91appearing as an outer portion91boutside a magnet93. The magnetic path96is also to be a path along which a magnetic flux supplied from the stator flows bypassing the magnets93. The magnetic path which bypasses magnets closer to the stator than the magnets as viewed from the stator in this manner will hereinafter be called a second type magnetic path.

Therefore, providing the first type magnetic path and second type magnetic path in the rotor of an axial gap type motor can make the q-axis inductance larger than the d-axis inductance and increase anti-saliency.

To provide the first type magnetic path in the rotor of the axial gap type motor, it is useful that a magnetic member is disposed on almost the same plane as the magnets. At this time, the magnetic member may cover the shaft hole, but in that case, it is desirable to use devices such that the rotation shaft to be inserted into the shaft hole does not serve as a magnetic path, similarly to the rotor of a typical radial gap type motor.

To provide the second type magnetic path in the rotor of the axial gap type motor, it is useful that the magnetic poles directed toward the rotor are each covered with a magnetically independent magnetic member. This case is inferior to the case of providing the first type magnetic path in terms of increased axial gaps, but facilitates reduction of demagnetized fields in the magnets and suppression of the occurrence of eddy current within the magnets, as will be described later, by thinking out its configuration.

Employment of such rotor having anti-saliency for the motor permits effective use of the reluctance torque, which increases torque and efficiency. Further, the effect of flux-weakening control is increased to enlarge the operating range.

To utilize the reluctance torque, it is desirable that the stator employed for the motor along with the rotor have salient poles made of magnetic member, e.g., teeth.

Providing the first type magnetic path and second type magnetic path in the rotor of the axial gap type motor offers an advantage in that the magnet torque and reluctance torque can both be designed larger than in the rotor of the radial gap type motor. The reason will be described below.

In the rotor of the radial gap type motor, the first type magnetic path95and second type magnetic path96are disposed alternately on its cylindrical surface. And the first type magnetic path95is present between embedded magnets93bypassing the magnets93.

Therefore, as the position where the magnets93are embedded is made closer to the center of rotation in order to increase the cross-sectional area of the second type magnetic path96, the cross-sectional area of the first type magnetic path95decreases. Conversely, to increase the cross-sectional area of the second type magnetic path96without losing the cross-sectional area of the first type magnetic path95, the magnetic pole width (a dimension of the magnetic pole in cross section perpendicular to the rotation shaft, rather than the thickness of the magnet) of the magnets93must be narrowed while making the position where the magnets93are embedded closer to the center of rotation. This also applies similarly when the cylindrical surface of the rotor of the radial gap type motor increases in external shape. This is because the minimum value of the magnetic path width of the first type magnetic path95is almost determined in the positions where the magnets93are embedded. And, narrowing the magnetic pole width of the magnets93in this manner results in reduction of magnet torque.

In contrast, in the rotor of the axial gap type motor, the second type magnetic path is achieved by magnetic members covering the magnetic poles directed toward the stator, and its cross-sectional area is grasped in cross section along the circumferential direction. The thickness of this magnetic member can thus be increased irrespective of the size of magnets, and there is no need to vary the size and position of magnets in design for increasing the cross-sectional area of the second type magnetic path. Therefore, the cross-sectional area of the first type magnetic path (which is grasped in cross section perpendicular to the rotation shaft) achieved by magnetic members disposed on almost the same plane as the magnets is not decreased. It is therefore possible to increase the cross-sectional area of the second type magnetic path without reducing the magnet torque or losing the cross-sectional area of the first type magnetic path.

Further, even when reduced in thickness in the direction of the rotation shaft, the rotor of the axial gap type motor can be increased in outer shape to increase the area of magnetic poles, so that the magnet torque and reluctance torque can both be increased.

Furthermore, in the rotor of the axial gap type motor, the surface opposed to the gaps is a plane, which makes it easy to increase the processing accuracy and assembling accuracy. In addition, even when the second type magnetic path cannot be provided or the magnetic materials achieving this path have a small thickness, the magnets can easily be processed and have high dimensional accuracy since the pole face of a magnet is a plane.

First Embodiment

FIG. 1is a diagram illustrating the structure of a rotor1A according to a first embodiment of the present invention, which is a plan view as viewed from the side of a stator (not shown) in the case of constituting a motor along with the stator.FIGS. 2 and 3are sectional arrowed views in positions II-II and respectively.

The rotor1A includes magnets12aand12b, magnetic members13aand13band a substrate11on which they are mounted. That is, the rotor1A can be employed as a rotor with one pole pair (the number of poles: 2). The substrate11is also provided with a shaft hole10at its center.

The plurality of magnets12aand12bare disposed annularly around the shaft hole10with their polarities being symmetric, and their pole faces are perpendicular to the direction of the rotation shaft (this is the direction in which the rotation shaft to be inserted into the shaft hole10extends and parallel to the direction perpendicular to the sheet of drawing ofFIG. 1). The magnet12ahas a pole face exhibiting a first polarity on one side of the rotation shaft (on this side of the sheet of drawing ofFIG. 1), and the magnet12bhas a pole face exhibiting a second polarity on the one side of the rotation shaft. Herein, the magnets12aand12bare assumed, for example, to exhibit N and S poles, respectively, on the side of the stator (on this side of the sheet of drawing ofFIG. 1). The magnets12aand12bare made of rare-earth sintered magnets, for example.

The plurality of magnetic members13aand13bare disposed perpendicularly to the direction of the rotation shaft, more specifically, extending between the magnets12aand12b. The magnetic members13aand13bare made of, for example, a high permeable magnetic material such as iron, dust core, or the like. However, it is desirable to employ iron dust core in terms of reducing iron loss.

In the rotor1A, the d-axis direction is the direction connecting the magnets12aand12b, and almost in parallel to a phantom line showing the position (FIG. 3). On the other hand, the q-axis direction is the direction connecting the magnetic members13aand13b, and almost in parallel to a phantom line showing the position II-II (FIG. 2).

In such structure, the magnetic path bypassing the magnets12aand12band passing through the magnetic members13aand13bis a magnetic path in the q-axis direction, and the magnetic path passing through the magnets12aand12bis a magnetic path in the d-axis direction. And, these magnetic paths are perpendicular to each other when viewed as electric angles. Accordingly, in the present embodiment, the first type magnetic path is achieved by the magnetic members13aand13b. Therefore, the q-axis inductance can be increased, and anti-saliency can be improved. Further, size reduction in the axial direction is easy.

It is desirable that surfaces of the magnets12aand12band magnetic members13aand13bon the side of the stator be positioned on the same plane. This is because, when the magnetic members13aand13bhave small thickness, the q-axis inductance cannot be increased, and on the other hand, when the surfaces of the magnetic members13aand13bon the side of the stator extend farther to the side of the stator than the pole faces of the magnets12aand12b, the distance between the pole face of the rotor and pole face of the stator (hereinafter this will be provisionally called “interposed distance to armature”) increases.

In the present embodiment, it is desirable that gaps G1serving as magnetic barriers for blocking the flow of magnetic fluxes be provided between the magnets12a,12band the magnetic members13a,13b. It is to prevent magnetic fluxes from flowing between the pole faces of the magnets12aand12bthrough the magnetic members13aand13b. This reduces short circuit leakage of magnetic flux inside the rotor which is grasped as magnetic flux leakage with respect to the magnetic flux flowing between the stator and rotor. This allows the magnetic fluxes generated from the pole faces of the rotor to be supplied efficiently to the stator opposed to these pole faces.

A magnetic flux flows back and forth between the rotor and stator. And, a magnetic flux flows between the magnets12aand12bthrough two gaps G1on the both edges of the magnetic member13aor magnetic member13b. Therefore, it is desirable that the width of gap G1be chosen to be greater than the interposed distance to armature. This is to reduce a magnetic flux short circuit within the rotor by making the magnetic resistance between the magnets12aand12bthrough the magnetic member13a(or magnetic member13b) higher than the magnetic resistance between the stator and rotor.

Further, it is desirable that a gap G2serving as a magnetic barrier for blocking the flow of magnetic flux be provided between the magnets12a,12b, magnetic members13a,13band shaft hole10. This is to prevent a short circuit from occurring in the magnetic flux between the magnets12aand12beven when the rotation shaft to be inserted into the shaft hole10is made of a magnetic material such as iron. Of course, there is no need to provide the gap G2if the rotation shaft is non-magnetic steel.

It is desirable that the width of gap G2be also chosen to be greater than the interposed distance to armature. This is because the magnetic flux passing through the rotation shaft between the magnets12aand12bcrosses the gap G2twice.

The substrate11may be a magnetic member. In this case, the substrate11serves as a yoke for backing the magnets12aand12b, a so-called back yoke. The provision of the back yoke avoids the magnetic flux from short circuiting between the pole face on the side of the stator and the magnetic pole on the opposite side in the magnet12a(or magnet12b) itself. The magnetic flux generated from the pole face on the side of the stator can thereby be supplied to the stator efficiently.

In the case where the substrate11is a magnetic member, the magnetic flux flows between the magnets12aand12bpassing through the magnetic member13aor magnetic member13b, one gap G1and substrate11, so that it is desirable that the gap G1be chosen to be not less than twice the interposed distance to armature. Similarly, it is desirable that the width of gap G2be chosen to be not less than twice the interposed distance to armature.

Further, the magnetic resistance between the magnetic poles of the magnets12aand12bon the opposite side of the stator can be reduced. Accordingly, the permeance coefficient can be increased, which raises the operating point of the magnets12aand12b. This results in improved torque.

FIG. 4is a perspective view illustrating a method of manufacturing the rotor1A. The substrate11with the magnetic member13aand magnetic member13bmounted in predetermined positions is prepared. Then, the magnets12aand12bare mounted respectively in predetermined positions12aP,12bP between the magnetic member13aand magnetic member13bon the substrate11. In the case where the substrate11also serves as a back yoke, the substrate11, magnetic member13aand magnetic member13bmay be formed integrally.

The magnets12aand12bmay be fixed to the substrate11by an adhesive or the like, but may previously be formed integrally on the substrate11on the side where the magnetic members13aand13bare provided in the case of using a bonded magnet. In this case, the magnets12aand12band magnetic members13aand13bcome into intimate contact, so that the gaps G1cannot be provided.

However, magnetizing with distribution of the magnetic flux density so as to be extremely low at the edges of the magnets12aand12bin the circumferential direction around the rotation shaft can provide a structure magnetically equivalent substantially to providing the gaps G1.

It is possible to previously form the substrate11and magnets12aand12bintegrally by a bonded magnet. In this case, so-called polar anisotropic orientation may be employed.

Second Embodiment

FIG. 5is a diagram illustrating the structure of a rotor1B according to a second embodiment of the present invention, which is a plan view as viewed from the side of a stator (not shown) in the case of constituting a motor along with the stator.FIGS. 6 and 7are sectional arrowed views in positions VI-VI and VII-VII, respectively.

The rotor1B includes magnets120a,120b, magnetic members130a,130band a substrate110on which they are mounted. That is, the rotor1B can also be employed as a rotor with one pole pair (the number of poles: 2). The substrate110is also provided with the shaft hole10at its center.

The substrate110and magnetic members13aand13bare formed integrally employing, for example, a high permeable magnetic material such as iron, iron dust core, or the like. That is, the substrate110also serves as a back yoke. It is desirable to employ iron dust core for the substrate110and magnetic members130aand130bboth in terms of forming integrally and in terms of reducing iron loss.

The substrate110and magnetic members130aand130bare provided with a bonded magnet120from the side where the magnetic members130aand130bare provided, and the stator (not shown) is to be disposed on this side.

The bonded magnet120is formed to cover not only the portions interposed between the magnetic members130aand130bbut also the magnetic members130aand130b. The bonded magnet120may be formed without covering these portions, but even if there exist portions121a,121bwhich cover the magnetic members130aand130b, respectively, these portions substantially serve as magnetic barriers having high magnetic resistance since they are thin.

The magnets120aand120bcan be achieved by magnetizing the bonded magnet120. Specifically, the portions interposed between the magnetic members130aand130bare magnetized, and the portions121a,121bare not magnetized substantially. The magnets120aand120badjacent with the magnetic members130aand130binterposed therebetween are magnetized with different polarities.

Accordingly, the first type magnetic path is also achieved by the magnetic members130aand130bin the rotor1B, similarly to the rotor1A. Therefore, the q-axis inductance can be increased, and anti-saliency can be improved.

FIG. 8is a developed view in which the structure of the rotor1B is developed in the circumferential direction. In the drawing, the upper side is the side of the stator, and symbols “N” and “S” respectively indicate polarities exhibited by the pole faces of the magnets120aand120bon the side of the stator.

Magnetization with such polarities prevents the bonded magnet120positioned at the border between the magnets120aand120b, i.e., the portions121aand121bcovering the magnetic members130a,130bfrom being magnetized substantially, which serve as magnetic barriers between the magnets120aand120b. This is because the material for bonded magnet generally has a low permeability, and the portions121aand121bcan be formed thin.

The permeance coefficient can further be increased since the employment of such structure increases the degree of contact between the magnets120aand120band substrate110serving as a yoke in the rotor1B. Further, the rotor1B can be formed with improved adhesion between magnets and substrate without separately bonding the magnets to the substrate.

The bonded magnet is a mixture of a binder such as resin and magnet dust, and thus has a high electric resistance, which can extremely reduce the eddy-current loss as compared to the case of employing a sintered rare-earth magnet. Of course, a rare-earth magnet may be employed as the magnet dust, and in that case, the magnetic flux density generated by the rotor can be increased.

FIG. 9is a developed view showing a modification of the present embodiment in which a modified structure of the rotor1B is developed in the circumferential direction. In this structure, the magnetic members130aand130bhave their surfaces vary sinusoidally in the circumferential direction. More specifically, a sine wave appears at the same frequency as the number of poles (1, here) of the rotor per cycle.

Forming the bonded magnet120on such substrate110and magnetic members130aand130bfacilitates control of the magnetic flux supplied from the rotor1B sinusoidally around the rotation shaft, thus allowing the cogging torque to be reduced.

The use of the bonded magnet120increases the flexibility in shape of the magnets120aand120b, which facilitates control of the distribution of magnetic flux supplied from the rotor1B as in the modification shown inFIG. 9.

FIGS. 10 and 11are perspective views illustrating a method of manufacturing the rotor1B. The substrate110with the magnetic members130aand130bmounted in predetermined positions is prepared (FIG. 10). Then, the bonded magnet120is formed on top of these members (FIG. 11). To optimize the interposed distance to armature, it is desirable to planarize the surface of the bonded magnet120on the side of the stator. The bonded magnet120may or may not be subjected to magnetic field orientation at the time of molding, and is easily magnetized anytime after molding to obtain the magnets120aand120b. When performing magnetic field orientation at the time of molding, it is also easy to give an optimized magnetic distribution in order to reduce vibrations and noise.

Further, by providing wedge-like projections or recesses in the substrate and applying the bonded magnet to cover or fill the portions, the bonded magnet and substrate are less likely to be separated.

If the bonded magnet120is present outside the magnets130aand130b, the bonded magnet120is formed thick on the substrate110at that portion. Therefore, to make an unmagnetized portion thin, it is desirable to coincide the outer edges of the magnetic members130aand130bwith the outer edge of the bonded magnet120. To achieve this simply, it is desirable to coincide the outer edges of the magnetic members130aand130bwith the outer edge of the substrate110.FIG. 10illustrates the case where the outer edges of the magnetic members130aand130bcoincide with the outer edge of the substrate110.

In the rotor1B, it is desirable that the gap2G be provided around the shaft hole10adjacent to the magnets120a,120band magnetic members130a,130b, similarly to the rotor1A.

Third Embodiment

FIG. 12is a diagram illustrating the structure of a rotor1C according to a third embodiment of the present invention, which is a plan view as viewed from the side of a stator (not shown) in the case of constituting a motor along with the stator.FIGS. 13and14are sectional arrowed views in positions XIII-XIII and XIV-XIV, respectively. The rotor1C has a structure in which magnetic members14aand14bprovided magnetically independently are individually mounted on the pole faces of the magnets12aand12bfor coverage in the rotor1A (FIGS. 1 to 3) shown in the first embodiment. Illustrated here is the case where the magnetic members14aand14bare of the same type as the magnets12aand12b. SinceFIG. 12is a plan view as viewed from the side of the stator, the symbols14a(12a) and14b(12b) indicate that the magnets12aand12bare hidden by the magnetic members14a,14b. The pole face of the rotor1C serves as the surfaces of the magnetic members14aand14bon the side of the stator.

In the rotor1C, the first type magnetic path is formed by the magnetic members13aand13bsimilarly to the rotor1A, and in addition, the second type magnetic path is formed by the magnetic members14aand14bprovided closer to the side of the stator than the magnets12aand12b. That is, the presence of the magnetic members14aand14bin the d-axis direction as shown inFIG. 14can further increase the q-axis inductance as compared to the rotor1A.

The rotor1C can be manufactured similarly to the rotor1A, and the magnetic members14aand14bare mounted on the magnets12aand12b, respectively.FIG. 15is a perspective view illustrating a method of manufacturing the rotor1C to be manufactured in this manner. While the shape of the magnetic members13aand13bshown inFIG. 15is slightly different from the magnetic members13aand13bshown inFIG. 12, no particular description for distinction is not made here. This also applies to other embodiments.

The substrate11may be made of a magnetic member, and may be provided with the function as a back yoke for the magnets12aand12b.

Here, the thickness of magnetic member13a, the thickness of magnetic member13b, the sum of thicknesses of magnetic member14aand magnet12a, and the sum of thicknesses of magnetic member14band magnet12bare chosen to be equal to one another. Provision of the magnetic members14aand14bin the rotor1C on the side of the stator in this manner has the disadvantage of difficulty in reducing the size of the motor in the axial direction, but facilitates device for reducing the cogging torque and device for obtaining skews, as will be described below.

Further, the arrangement of the magnetic members14aand14bcloser to the side of the stator than the magnets12aand12bmakes an eddy current, if occurred, to be more likely to occur in the magnetic members14aand14b, and prevents the occurrence of eddy current inside the magnets12aand12b. This is particularly advantageous in the case of employing a material of low electric resistance, e.g., a sintered rare-earth magnet for the magnets12aand12b. This is because it is possible to suppress reduction in efficiency due to heat generation of magnets and increase in iron loss. In other words, the rotor of high magnetic flux density can be obtained employing a sintered rare-earth magnet for the magnets12aand12bwithout concern about the occurrence of eddy current.

Of course, employing a material of low iron loss, e.g., iron, for the magnetic members14aand14bpresent in positions where eddy current is likely to occur permits reduction in eddy-current loss.

Such advantage is particularly suitable for the case of employing the rotor1C in a motor driven by a PWM inverter. This is because current flown into the motor by the PWM inverter has a high frequency, and an eddy current is likely to occur near the surface of magnetic members because of the skin effect.

FIGS. 16 to 19are all developed views in which various modifications of the rotor1C are developed in the circumferential direction. In the drawing, the upper side is the side of the stator. In the first modification shown inFIG. 16, the magnetic members14aand14bhave a drum shape that projects toward the stator, and an edge14aE of the magnetic member14ain the circumferential direction and an edge14bE of the magnetic member14bin the circumferential direction are thinner than the central portions of the magnetic members14aand14b. The cogging torque can thereby be reduced, similarly to the device that the tip of the teeth of the stator retracts from the rotor in a radial gap type motor.

Further, as in the second modification shown inFIG. 17, the edges14aE and14bE may be beveled to be thinner than the central portions of the magnetic members14aand14b.

Alternatively, as in the third modification shown inFIG. 18, inclining the side faces of the edges14aE and14bE toward the direction of thickness (direction of rotation shaft) in the circumferential direction with respect to the axial direction further allows skews to be obtained.

In the fourth modification shown inFIG. 19, so-called supplemental grooves141are provided on the surfaces of the magnetic members14aand14bon the side of the stator in the radial direction. The supplemental grooves141can shorten and reduce the cycle of cogging torque, similarly to supplemental grooves provided in the axial direction on the teeth surface of a stator in a radial gap type motor.

In the rotor1C and the above-described modifications, it is desirable to provide the gaps G1and G2, similarly to the rotor1A. While the magnetic members14aand14bdo not always need to be of the same type as the magnets12aand12b, the dimensional relationship between magnets and magnetic members forming the second type magnetic path will be described in a subsequent embodiment.

Fourth Embodiment

While the third embodiment has described the case where both the first type magnetic path and second type magnetic path are present, it is possible to form the second type magnetic path only. When such mode is to be achieved by an embedded magnet type rotor of a radial gap type motor, the structure will rather become complicated.

FIG. 20is a diagram illustrating the structure of a rotor1D according to a fourth embodiment of the present invention, which is a plan view as viewed from the side of a stator (not shown) in the case of constituting a motor along with the stator.FIGS. 21 and 22are sectional arrowed views in positions XXI-XXI and XXII-XXII, respectively. The rotor1D has a structure in which the magnetic members13aand13bare omitted from the rotor1A (FIGS. 1 to 3) shown in the first embodiment, and a magnetic plate541mounted on the pole faces of the magnets12aand12bfrom the side of the stator to cover them is added.

The magnetic plate541has opening through slits55a,55bextending from positions close to the shaft hole10to farther positions. And, the magnetic plate541divided by the slits55aand55bin the circumferential direction around the shaft hole10serves as magnetic members54aand54b, respectively. The magnetic members54aand54bare connected to each other at the ends of the slits55aand55bon the outer peripheral side with thin portions56aand56binterposed therebetween and at the ends on the side of the shaft hole10with thin portions56cand56dinterposed therebetween. The slits55aand55bare positioned between the magnets12aand12bin plan view, and prevent the magnetic flux from short circuiting. The pole face of the rotor1D serves as the surfaces of the magnetic members54aand54bon the side of the stator.

With such structure, the magnetic members54aand54bcan be obtained with less number of components than in the case of forming individually and separately like the magnetic members14aand14bof the rotor1C (FIGS. 12 to 19) shown in the third embodiment, and the magnetic plate541can be increased in strength. Since the thin portions56ato56dare easy to become magnetically saturated, a short circuit of magnetic flux inside the rotor1D is extremely small even when the magnetic members54aand54bare connected with these portions interposed therebetween.

And, the magnetic members54aand54bsuppress the occurrence of eddy current inside the magnets12aand12b, similarly to the magnetic members14aand14b. Of course, employing a material of low iron loss, e.g., iron dust core, electromagnetic steel sheets stacked in a suitable direction or the like, for the magnetic plate541present in positions where eddy current is likely to occur permits reduction in eddy-current loss.

Further, the area of the magnetic members54aand54bcovering the pole faces of the magnets12aand12bcan easily be made larger than the area of the pole faces. Since the area of the pole faces is increased while reducing a short circuit of magnetic flux inside the rotor by the presence of the slits55aand55b, magnetic saturation inside the magnetic plate541can be reduced.

It is desirable that the width of the slits55aand55bin the circumferential direction be chosen to be not less than twice the interposed distance to armature. This is to make the magnetic resistance of the magnetic path passing between the magnets12aand12bthrough the magnetic members54aand54bhigher than the magnetic resistance between the stator and rotor, thereby reducing the magnetic flux short circuit within the rotor.

FIG. 23is a perspective view illustrating a method of manufacturing the rotor1D. The rotor1D can be manufactured similarly to the rotor1C. That is, the magnets12aand12bare mounted in the predetermined positions12aP and12bP on the substrate11, respectively, and the magnetic plate541instead of the magnetic members14aand14b(FIG. 15) is mounted on the magnets12aand12b. The positions of the slits55aand55bat this time are as described above.

Of course, shape modifications as shown inFIGS. 16 to 19in the third embodiment may be made in the magnetic members54aand54b.

Further, the magnets12aand12bmay be formed integrally by a ring-like magnet. In that case, it is desirable to substantially unmagnetize in the vicinity of the positions where the slits55aand55bare provided in plan view. This mode also has advantages of easy manufacture and that the substrate11on which the magnets12aand12bare mounted can be omitted.

Unmagnetization substantially involves the case of being simply not magnetized, and in addition, also involves the case of being magnetized perpendicularly to the axial direction and not containing a magnetized component in the axial direction.

Further, the substrate11may be made of a magnetic member, and may be provided with the function as a back yoke for the magnets12aand12b. It is possible to previously form the substrate11and magnets12aand12bintegrally by a bonded magnet. In this case, so-called polar anisotropic orientation may be employed.

In the case where the substrate11is made of a magnetic member, the magnetic field from the stator is likely to flow from the magnetic members54aand54bcovering the pole face to the substrate11bypassing the magnets12aand12b, so that the magnets12aand12bare less likely to become demagnetized.

Fifth Embodiment

FIG. 24is a diagram illustrating the structure of a rotor1E according to a fifth embodiment of the present invention, which is a plan view as viewed from the side of a stator (not shown) in the case of constituting a motor along with the stator.FIGS. 25,26and27are sectional arrowed views in positions XXV-XXV, XXVI-XXVI and XXVII-XXVII, respectively. The rotor1E has a structure in which other magnetic members54c,54e,54dand54frespectively mounted on the magnets12aand12band magnetic members13aand13bfrom the side of the stator to cover them are added to the rotor1A (FIGS. 1 to 3) shown in the first embodiment.

Specifically, a magnetic plate542mounted from the side of the stator on the magnets12aand12band magnetic members13aand13bto cover them is provided. The magnetic plate542has a hole540larger than the shaft hole10. And, the magnetic plate542has opening through slits55cto55fextending from positions close to the shaft hole10to farther positions, and the magnetic plate542divided by these slits in the circumferential direction serves as magnetic members54cto54f.

More specifically, in plan view, the slit55cis positioned between the magnet12aand magnetic member13a, the slit55dis positioned between the magnet12band magnetic member13a, the slit55eis positioned between the magnet12band magnetic member13b, and the slit55fis positioned between the magnet12aand magnetic member13b.

And, the magnetic plate542positioned between the slits55cand55dserves as the magnetic member54d, the magnetic plate542positioned between the slits55dand55eserves as the magnetic member54e, the magnetic plate542positioned between the slits55eand55fserves as the magnetic member54f, and the magnetic plate542positioned between the slits55fand55cserves as the magnetic member54c.

The magnetic members54cand54dare connected to each other at the end of the slit55con the outer peripheral side with a thin portion56einterposed there between and at the end on the side of the shaft hole10with a thin portion56iinterposed therebetween, the magnetic members54d,54eare connected to each other at the end of the slit55don the outer peripheral side with a thin portion56finterposed therebetween and at the end on the side of the shaft hole10with a thin portion56jinterposed therebetween, the magnetic members54e,54fare connected to each other at the end of the slit55eon the outer peripheral side with a thin portion56ginterposed therebetween and at the end on the side of the shaft hole10with a thin portion56kinterposed therebetween, and the magnetic members54fand54care connected to each other at the end of the slit55con the outer peripheral side with a thin portion56hinterposed therebetween and at the end on the side of the shaft hole10with a thin portion56linterposed therebetween. The pole face of the rotor1E serves as the surfaces of the magnetic members54cand54eon the side of the stator.

In another point of view, the magnetic members54cand54ecovering the magnets12aand12bare connected to the magnetic members54dand54fcovering the magnetic members13aand13bwith the aforementioned thin portions interposed therebetween.

The slits55cto55fprevent the magnetic flux from flowing between the magnets12aand12band magnetic members13aand13bin the magnetic plate542. Since the thin portions56eto56lare easy to become magnetically saturated, a short circuit of magnetic flux inside the rotor1E is extremely small even when the magnetic members54cto54fare connected to one another with these portions interposed therebetween.

It is desirable that the width of the slits55cto55fin the circumferential direction be chosen to be greater than the interposed distance to armature, unlike the case described in the fourth embodiment. This is because the magnetic path passing through the magnetic members54c,54dand54ebetween the magnets12aand12bhas two slits55cand55d.

WhileFIG. 24illustrates the case of employing the width of the slits55cto55fin the circumferential direction equal to the gaps G1in the circumferential direction positioned at the border between the magnets12aand12band magnetic members13aand13b, both do not always need to be in agreement. The width of the slits55cto55fin the circumferential direction can be set larger when designing with a view to reducing the leakage flux within the rotor1E, and smaller when designing with a view to obtaining the substantial pole faces of the magnets12aand12bwidely.

With such structure, the magnetic inductance of the second type magnetic path can be made still larger, and anti-saliency can be improved. Further, the number of components can be less, and the magnetic plate542can be made stronger than in the case of forming the magnetic members54cto54findividually and separately. Of course, employing a material of low iron loss, e.g., iron dust core, electromagnetic steel sheets stacked in a suitable direction or the like, for the magnetic plate542present in the position where eddy current is likely to occur permits reduction in eddy-current loss.

FIG. 28is a perspective view illustrating a method of manufacturing the rotor1E. The rotor1E can be manufactured similarly to the rotor1D. That is, the magnets12aand12bare mounted in the predetermined positions12aP and12bP on the substrate11, respectively, and the magnetic plate542is mounted on the magnets12aand12band magnetic members13aand13b. The positions of the slits55cto55fat this time are as described above.

Of course, shape modifications as shown inFIGS. 16 to 19in the third embodiment may be made in the magnetic members54cto54f.

Further, the substrate11may be made of a magnetic member, and may be provided with the function as a back yoke for the magnets12aand12b. It is possible to previously form the substrate11and magnets12aand12bintegrally by a bonded magnet. In this case, so-called polar anisotropic orientation may be employed.

In the case where the substrate11is a magnetic member, the magnetic flux flows between the magnets12aand12bpassing through the magnetic member13aor magnetic member13b, one slit and substrate11, so that it is desirable that the width of slit be chosen to be not less than twice the interposed distance to armature.

Sixth Embodiment

FIG. 29is a diagram illustrating the structure of a rotor1F according to a sixth embodiment of the present invention, which is a plan view as viewed from the side of a stator (not shown) in the case of constituting a motor along with the stator. The substrate11is provided with the shaft hole10at its center. Four magnets12c,12d,12eand12fare provided on the substrate11, and the magnets12cand12epresents a first polarity (e.g., N pole), and the magnets12dand12fpresents a second polarity (e.g., S pole), respectively, with respect to the stator (this side of the sheet of drawing). Accordingly, the rotor1F can be employed as a rotor with two pole pairs (the number of poles: 4).

The rotor1F does not have magnetic members between the magnets, similarly to the rotor1D (FIGS. 20 to 22) shown in the fourth embodiment, and a magnetic plate543is mounted instead of the magnetic plate541. The magnetic plate543has the hole540larger than the shaft hole10. The magnetic plate542has opening through slits55gto55jextending from positions close to the shaft hole10to farther positions, and the magnetic plate543divided by these slits in the circumferential direction serves as magnetic members54gto54j.

More specifically, in plan view, the slit55gis positioned between the magnets12cand12d, the slit55his positioned between the magnets12dand12e, the slit55iis positioned between the magnets12eand12f, and the slit55jis positioned between the magnets12fand12c.

And, the magnetic plate543positioned between the slits55jand55gserves as the magnetic member54g, the magnetic plate543positioned between the slits55gand55hserves as the magnetic member54h, the magnetic plate543positioned between the slits55hand55iserves as the magnetic member54i, and the magnetic plate543positioned between the slits55iand55jserves as the magnetic member54j.

Similarly to the rotor1D (FIGS. 20 to 23) shown in the fourth embodiment and rotor1E (FIGS. 24 to 28) shown in the fifth embodiment, adjacent ones of the magnetic members54gto54jare connected to each other at the ends of the slits55gto55jon the outer peripheral side and on the side of the shaft hole10with thin portions interposed therebetween. The pole face of the rotor1F serves as the surfaces of the magnetic members54gto54jon the side of the stator.

Similarly to the slits55ato55fdescribed in the fourth embodiment and fifth embodiment, the slits55gto55jblocks the magnetic flux from flowing between the magnets12cand12din the magnetic plate543. Further, since the thin portions in the rotor1F are also easy to become magnetically saturated similarly to the already-mentioned thin portions56ato56l, a short circuit of magnetic flux inside the rotor1F is extremely small even when the magnetic members54gto54jare connected to each other with these portions interposed therebetween.

With such structure, effects similar to the fourth embodiment and fifth embodiment can be obtained. Further, in the rotor1F according to the present embodiment, the slits55gto55jare inclined with respect to the radial direction, so that the borders of pole faces of the rotor1F are inclined with respect to the radial direction. Thus, so-called skews are provided, which can reduce the cogging torque.

InFIG. 29, the line connecting the end of each of the slits55gto55jon the outer peripheral side and the center Z of the rotor1F is shown as an skew angle relative to the line connecting the end on the side of the shaft hole10and the center Z of the rotor1F, and the case of 15 degrees is illustrated. Further, the case in which the slits55gto55jextend linearly is shown, but they may extend in curve.

Further, the magnets12cto12dmay be formed integrally by a ring-like magnet. In that case, it is desirable to substantially unmagnetize in the positions where the slits55gto55jare provided in plan view. This mode also has advantages of easy manufacture and that the substrate11on which the magnets12aand12bare mounted can be omitted. In the case of omitting the substrate11, it is desirable to subject the magnets to polar anisotropic orientation.

It is desirable that the width of the slits55gto55jin the circumferential direction be chosen to be not less than twice the interposed distance to armature, similarly to the case described in the fourth embodiment. This is because the magnetic path through which the magnetic flux short circuits between adjacent magnets flows corresponds to one slit.

Of course, shape modifications as shown inFIGS. 16 to 19in the third embodiment may be made in the magnetic members54gto54j.

Further, the substrate11may be made of a magnetic member, and may be provided with the function as a back yoke for the magnets12cand12d. It is possible to previously form the substrate11and magnets12cand12dintegrally by a bonded magnet. In this case, so-called polar anisotropic orientation may be employed.

FIG. 30is a plan view showing a rotor1F1according to a modification of the sixth embodiment of the present invention. The rotor1F1has a configuration that the slits55g,55h,55iand55jof the rotor1F are extended in width. Specifically, both ends of one slit in the circumferential direction are inclined with respect to the radial direction. And, the case in which the angle formed by lines respectively dividing the skew angles is 30 degrees isillustrated.

By extending the slits in this manner, the magnetic flux concentrates on the center of each of the magnetic members54gto54jin plan view, which may increase the torque.

Seventh Embodiment

The first to sixth embodiments have specifically described the structures of the rotors1A to1F. Either of the rotors according to the present invention as illustrated in these embodiments may be combined with a conventional axial gap type stator to constitute an axial gap type motor. Of course, in either of the rotors obtained by the present invention, the structure of the stator is not limited to the stator2or a stator3which will be described later.

In the present embodiment and an eighth embodiment, the structure of a stator that can be employed with the rotors according to the present invention and the structure of a motor obtained by combination with the rotors will be illustrated.

FIG. 31is a perspective view illustrating the structure of the rotor1F and stator2that can be employed for the motor according to the present invention. While being disassembled along a rotation axis center90inFIG. 31, the rotor1F and stator2are each practically stacked along the rotation axis center90.

For simplicity, the case in which skews are not provided for the slits55gto55jof the rotor1F is illustrated here.

A substrate21in the stator2has a surface210perpendicular to the rotation axis center90, and magnetic cores221to226standing almost in parallel to the rotation axis center90and disposed annularly around the rotation axis center90are provided on the surface210. The magnetic cores221to226are provided closer to the rotor than the substrate21.

A high permeable magnetic material such as iron may be employed for the magnetic cores221to226. While the case in which the magnetic cores221to226show rounded triangle poles is illustrated here, another configuration may be employed.

The substrate21and magnetic cores221to226may be formed integrally by, for example, iron dust core.

The substrate21may be either a magnetic member or a non-magnetic member, but it is desirable to employ a magnetic member in order to make it serve as a back yoke for the magnetic cores221to226.

Windings231to236are wound around the magnetic cores221to226, respectively. That is, the windings231to236are directly wound around the magnetic cores221to226by concentrated winding absolutely independently in different phases. Since the windings are in one layer in the direction of the rotation axis center90without overlapping, the amount of copper is small, and the dimension in the direction of the rotation axis center90can be reduced. InFIG. 31, conductors of each of the windings231to236are not minutely shown but shown collectively per winding.

The windings231to236are wound as three-phase windings, and form pairs in each phase. And, the pairs of windings are disposed in positions shifted 180° from each other in the circumferential direction. And, by flowing current to the windings231to236, a magnetic flux is generated from each of the windings231to236.

In the case where the stator2constitutes a motor along with a rotor with one pole pair, magnetic fluxes of opposite phases to each other are generated by this one pair of windings. In the case where the stator2constitutes a motor along with a rotor with two pole pairs, magnetic fluxes of the same phase to each other are generated by this one pair of windings. Since the rotor1F illustrated inFIG. 31has two pole pairs, magnetic fluxes of the same phase to each other are generated by the aforementioned one pair of windings.

WhileFIG. 31illustrates the case in which a magnetic plate24is mounted on the magnet cores221to226in the stator2, this may be omitted. The magnetic plate24is provided with a central hole250and slits251to256, all extending therethrough. The slits251to256are provided to extend through from the inner peripheral side (the side of the central hole250) to the outer peripheral side of the magnetic plate24while leaving thin portions.

In plan view along the rotation axis center90, the central hole250is surrounded by the magnetic cores221to226, and the slit251is interposed between the magnetic cores221and222, the slit252between the magnetic cores222and223, the slit253between the magnetic cores223and224, the slit254between the magnetic cores224and225, the slit255between the magnetic cores225and226, and the slit256between the magnetic cores226and221.

Even with such magnetic plate24provided, the likelihood that the thin portions become magnetically saturated and the presence of the slits251to256prevent the magnetic fluxes generated from the magnetic cores221to226from short circuiting due to the magnetic plate24. In other words, the magnetic plate24serves as six magnetic members261to266each interposed between a pair of slits, and the magnetic members261to266may have the function of substantially widening the pole faces of the magnetic cores221to226.

Since the windings231to236are enclosed in the border areas between each of the magnetic cores221to226in the circumferential direction, the border areas cannot be reduced. However, the pole face of the stator2can be grasped as the surface of the magnetic plate24on the side of the rotor. Therefore, the substantial widening of the pole face by the magnetic cores221to226than the magnetic members261to266makes it easier to make the magnetic flux density between the rotor and stator uniform.

It is desirable that a suitable value for a width G3of the slits251to256in the circumferential direction be set not less than twice the interposed distance to armature. This is because a magnetic barrier corresponding to one slit exists on the magnetic path leaking between two of the magnetic members261to266within the stator, and on the other hand, the magnetic path flowing through the rotor goes and returns between the stator and rotor.

The magnetic plate24and magnetic plate543are desirable in terms of allowing magnetic fluxes to be exchanged efficiently between the rotor and stator, provided that they are almost equal in inside diameter and outside diameter. The magnetic plate24also serves to protect the windings231to236.

FIG. 32is a side view of a motor100constructed by combining the structure shown inFIG. 31along the rotation axis center90, and the interposed distance to armature δ is illustrated.

FIG. 33is a sectional view illustrating a compressor200to which the above-mentioned motor100is applied. The motor100is shown by using a side view.

A coolant is supplied from an inlet pipe206, and the coolant is compressed by a compression element205driven by the motor100, and the compressed high-pressure coolant is discharged from a discharge pipe207. The use of a radial gap type motor causes a problem in that even ice machine oil goes out from the discharge pipe since an air gap communicates with the discharge pipe without its top shielded.

However, when employing the axial gap type motor100as in the present invention, ice machine oil can be dropped by centrifugal force from the lower surface of the rotor1F disposed on the upper side toward the sidewall of the compressor200, which is desirable in terms of reduction in oil coming-up.

Further, a balance weight208attached to the rotor1F on the opposite side of the stator2can be increased in diameter, and thus can be reduced in length in the direction of rotation axis.

The compression element205is more suitable when disposed below the motor100. This is not to stir the ice machine oil since the rotor1F has a large diameter. When disposed horizontally, the rotor is immersed in the ice machine oil, so that it is desirable to dispose the compressor200vertically.

The driving circuit may be driven by a three-phase inverter. In a single phase, the direction of rotation is difficult to be fixed, and the circuit will become complicated in four or more phases. In terms of control of torque ripple, the driving current waveform should be a sine wave.

Since the compressor200is thus driven by the motor which employs the rotor according to the present invention, the compressor efficiency is high. It is needless to say that application to such compressor is possible even when employing the rotor other than that of the present embodiment.

Eighth Embodiment

FIG. 34is a perspective view illustrating the structure of the rotor1F and stator3that can be employed for a motor according to the present invention. While being disassembled along the rotation axis center90, the rotor1F and stator3are each practically stacked along the rotation axis center90.FIG. 35is a perspective view of a magnetic member30provided for the stator3.

The magnetic members13aand13b(FIGS. 1 to 4) provided on the substrate11are hidden by the substrate11, and thus do not appear inFIG. 34. Conductors of each of windings33a,33b,34a,34b,35aand35bare not minutely shown but shown collectively per winding.

In the magnetic member30, a substrate31has a surface310perpendicular to the rotation axis center90, and first-stage spacers311,313and second-stage spacers312,314are provided on the surface310. Magnetic cores321and324stand respectively on the first-stage spacers311and313, and magnetic cores322,323and magnetic cores325,326stand respectively on the second-stage spacers312and314, all almost in parallel to the rotation axis center90. The magnetic cores321to326are disposed annularly in this order around the rotation axis center90. The magnetic cores321to326are provided closer to the rotor than the substrate31.

The first-stage spacers311and313are both provided on the surface310, and extend with an angle of 180 degrees in the circumferential direction, but are separated from each other. The second-stage spacers312and314are respectively provided on the ends of the first-stage spacers311and313in the circumferential direction, and extend with an angle of 120 degrees, but are separated from each other.

Provided on the surface310are the magnetic members311to316standing almost in parallel to the rotation axis center90and disposed annularly with an angle of 60 degrees around the rotation axis center90. The magnetic members311to316are provided closer to the rotor than the substrate31.

The stator3has the three pairs of windings33a,33b,34a,34b,35aand35b, each of which is wound around three magnetic members by so-called distributed winding. For instance, as shown inFIG. 34, the windings33a,33b,34a,34b,35aand35bpreviously wound into a predetermined shape are prepared, and they are embedded into the magnetic member30along the rotation axis center90in the order to be described below.

Specifically, first, the winding33ais provided to surround the magnetic cores321,322and323, and the winding33bis provided to surround the magnetic cores324,325and326. At this time, the windings33aand33bare provided around the first-stage spacers311and313, respectively.

By making the height of the first-stage spacers311and313coincide with the width of the windings33aand33bin the direction of rotation shaft, the first-stage spacers311,313and windings33aand33bfit into a first layer L1.

Next, the winding34ais provided to surround the magnetic cores322,323and324, and the winding34bis provided to surround the magnetic cores325,326and321. At this time, the windings34aand34bare both mounted on the first-stage spacers311,313, windings33aand33b. As described above, by making the first-stage spacers311,313, windings33aand33bfit into the first layer L1, the windings34aand34bcan be disposed stably.

By making the height of the second-stage spacers312and314coincide with the width of the windings34aand34bin the direction of rotation shaft, the second-stage spacers312,314, windings34aand34bfit into a second layer L2.

Further, the winding35ais provided to surround the magnetic cores323,324and325, and the winding35bis provided to surround the magnetic cores326,321and322. At this time, the windings35aand35bare both mounted on the second-stage spacers312,314, windings34aand34b. As described above, by making the second-stage spacers312,314, windings34aand34bfit into the second layer L2, the windings35aand35bcan be disposed stably.

By making the height of the magnetic cores323and326coincide with the width of the windings35aand35bin the direction of rotation shaft, the magnetic cores323,326, windings35aand35bfit into a third layer L3. Of course, in order to reduce the interposed distance to armature, the top surfaces of the magnetic cores321to326on the side of the rotor1A may extend off the windings35aand35bto the side of the stator1A.

The state where the magnetic member30is provided with the windings33a,33b,34a,34b,35aand35bas described above is shown inFIG. 36as a perspective view.

Next, current to be flown to the windings33a,33b,34a,34b,35aand35bin order to rotate the rotor1A will be described. Here, the case of rotating the rotor1A counterclockwise in the direction of looking at the stator3from the rotor1A is illustrated as an example.

Since the windings33aand33bare directly opposed to the magnets12aand12bin the state shown inFIG. 34, current to be flown is zero. This is because a torque caused by current, if flowing, is zero.

On the other hand, current to be flown to the winding34aexcites the magnetic cores322,323and324to the N pole in order to attract the magnet12bexhibiting the S pole on the side of the stator3. That is, the current is flown in the counterclockwise direction. Conversely, current is flown to the winding34bin the clockwise direction, to excite the magnetic cores326,321and322to the S pole, thereby attracting the magnet12aexhibiting the N pole to the side of the stator3.

Similarly, current to be flown to the winding35aneeds to be excited to the N pole in order to attract the magnet12b. Therefore, the current is flown in the counterclockwise direction. Current to be flown to the winding35bneeds to be excited to the S pole in order to attract the magnet12a. Therefore, the current is flown in the clockwise direction.

Since the magnet12aexhibiting the N pole approaches the winding33awhen the rotor1A starts to rotate in the counterclockwise direction, the magnetic cores321,322and323are excited to the S pole. Specifically, a U-phase current is flown in the clockwise direction. On the other hand, since the magnets12aand12bapproaches the winding34aand34b, respectively, the current value is made close to zero. Since the magnet12bapproaches the winding35ain a position where the mutual positional relationship with the magnet12bmaximizes the torque, the current value is increased. This is similar to the winding35b.

That is, using the positional relationship between the rotor1A and stator3in the circumferential direction at a point of time as a reference as inFIG. 34, current phases of the windings33a,33b,34a,34b,35aand35bare 180°, 0°, 120°, 300°, 60° and 240°, respectively, which are not phase lead or phase lag.

A pair of windings in each of the layers L1, L2and L3is disposed in a position shifted 180 degrees from each other in the circumferential direction. Further, the respective pairs of windings are disposed in a position shifted 120 degrees from each other. Flowing a U-phase current to the windings33aand33bin opposite phases to each other (i.e., with a difference of 180 degrees in electric angle), flowing a V-phase current to the windings34aand34bin opposite phases to each other, and flowing a W-phase current to the windings35aand35bin opposite phases to each other achieves operation as a three-phase axial gap type stator. It is desirable that exciting currents flown to these windings be sine-wave currents. It is to suppress the torque ripple.

Three-phase currents shifted 120° from one another can be employed as currents to be flown to the windings33b,34band35b, when wound in the opposite direction to the windings33a,34aand35a, respectively.

These currents are obtained by an inverter, for example, and the frequency and current value are varied according to necessity to drive the motor.

The rotor1A has anti-saliency, and the q-axis inductance Lq is larger than the d-axis inductance Ld. Therefore, advancing the current phase allows an effective use of the reluctance torque. By advancing the current phase at an angle exceeding 0° and less than 45° from the above-mentioned current phase, the reluctance torque can be used in combination. While depending on the design of the q-axis inductance Lq and d-axis inductance Ld and loading point, the torque can be generally maximized by advancing at 15 to 30°, approximately.

Since magnetic fluxes flow to the magnetic member30and magnetic members13aand13b(cf.FIGS. 1 to 4) also in the axial direction, iron loss increases in steel sheets stacked in the axial direction. Therefore, it is desirable to use iron dust core.

Further, to the substrate11, when serving as a back yoke, magnetic fluxes of the surfaces opposed to the pole faces of the magnets12aand12bflow constantly, and in addition, a magnetic flux that varies by the exciting current of the stator3also flows through the magnetic members13aand13b. Therefore, it is also desirable to employ iron dust core to form the substrate11.

Of course, iron may be employed for the magnetic cores321to326. Further, While the case in which the magnetic cores321to326show rounded triangle poles is illustrated, another configuration may be employed.

The substrate31of the magnetic member30may be a non-magnetic member, however, it is desirable to be a magnetic member in order to serve as a back yoke for the magnetic cores321to326.

Further, a non-magnetic member may be employed for the first-stage spacers311,313, second-stage spacers312and314. However, making these spacers of iron dust core similarly to the magnetic cores321to326achieves the advantage of being able to be formed integrally.

Of course, the substrate31may be made of iron dust core integrally with the first-stages pacers311,313, second-stage spacers312,314, and magnetic cores321to326.

Ninth Embodiment

The rotors and motors described in the previous embodiments are provided with one stator. However, the present invention may also be applied to the case where a pair of stators interposing a rotor therebetween are provided as illustrated in Patent documents 1 to 4.

FIG. 37is a perspective view illustrating the structure of a rotor1G according to a ninth embodiment of the present invention. While being disassembled along a rotation axis center90inFIG. 37, the rotor1G is practically stacked along the rotation axis center90.

The rotor1G has a structure in which magnets12g,12hand magnetic members13gand13hare provided for the rotor1A (FIGS. 1 to 4) shown in the first embodiment on the opposite side of the magnets12a,12b, magnetic members13aand13b(not appearing inFIG. 37). The positional relationship between the magnets12g,12h, magnetic members13gand13hon one side surface of the substrate11is the same as the positional relationship between the magnets12a,12b, magnetic members13aand13bon the other side surface of the substrate11.

For instance, the magnets12a,12b, magnetic members13aand13bare equal in thickness to one another, and the magnets12g,12h, magnetic members13gand13hare equal in thickness to one another. Alternatively, they may all be equal in thickness to one another.

By providing such rotor1G with stators respectively on the side of the magnets12aand12band the side of the magnets12gand12hto constitute a motor, mechanisms for generating torque are generated on both sides of the substrate11. Thus, the motor is easy to increase the torque, or easy to obtain a necessary torque with less current.

While the case where the magnets12a,12band magnetic members13a,13bare opposite to the magnets12g,12hand magnetic members13g,13h, respectively, with the substrate11interposed therebetween is illustrated here, such opposition is not necessarily required. However, this opposition makes it easier to design the arrangement of the stators.

Of course, it is also desirable in terms of obtaining skews that the opposing relationship be slightly displaced from the directly-opposed position. Alternatively, it is not necessary to make the magnets12a,12b, magnetic members13a,13band the magnets12g,12h, magnetic members13gand13hdirectly opposite to each other in the case where rotating fields generated by the pair of stators provided with the rotor1G interposed therebetween are not directly opposite to each other with the rotor1G interposed therebetween.

Further, in the case where the substrate11is made of a magnetic member to serve as a back yoke, it is desirable that the magnets12gand12hpresent the same polarities as the magnets12aand12b, respectively, on the opposite side of the substrate11. That is, when the magnets12aand12bexhibit the N pole and S pole, respectively, on the opposite side of the substrate11, it is desirable that the magnets12gand12hexhibit the N pole and S pole, respectively, on the opposite side of the substrate11.

Such opposition of magnetic poles of opposite polarities with the substrate11interposed therebetween makes a magnetic flux less likely to flow between the magnets12a,12band magnets12g,12hthrough the substrate11, so that the substrate11is improved in function as a back yoke for the magnets12a,12band for the magnets12g,12h. This extends a region in the substrate11where the magnetic flux saturates by means of magnetic fluxes of the magnets12a,12b,12gand12h, and reduces variations in magnetic fluxes flowing from the stators to the substrate11, so that eddy-current loss based on the aforementioned variations in magnetic fluxes can be reduced.

FIG. 38is a perspective view illustrating the structure of another rotor1H according to the present embodiment. The rotor1H has a structure in which the substrate11is omitted from the rotor1A (FIGS. 1 to 4) shown in the first embodiment. Since the magnets12aand12bhave magnetic poles on their both surfaces, providing the rotor1H with stators on its both sides allows mechanisms for generating torque to be formed on the both sides.

It is desirable that the structure shown inFIG. 38have gaps between the magnets12a,12band magnetic members13a,13b(depicted as the gaps G1inFIG. 1) as described with respect to the rotor1A. Therefore, when forming the rotor1H, it is desirable that a non-magnetic filling material be employed for the gaps and that the magnets12a,12band magnetic members13a,13bbe bonded to one another with this filling material interposed therebetween.

FIG. 39is a perspective view illustrating another preferable mode of the rotor114. In a rotor4, the magnets12a,12band magnetic members13a,13bshown inFIG. 38are molded by resin or the like while keeping this positional relationship. The rotor4has a cylinder40at its center, and a rotation shaft (not shown) is inserted here. The cylinder40corresponds to the gap G2shown inFIG. 1, and prevents the magnets12a,12band magnetic members13a,13bfrom magnetically short circuiting even when the rotation shaft is a magnetic member.

The mode in which the cylinder40has a thickness in the radial direction larger than the thickness of most part of the rotor4in the radial direction and has a shape projecting from the surface is illustrated here. However, the size relationship between these thicknesses can be designed depending on various conditions.

FIG. 40is a perspective view illustrating the structure of a motor including the rotor1H and stators3A and3B interposing the rotor from its both sides, which is shown disassembled in the direction of thickness. Practically, the rotor1H is molded as the rotor4, for example, and the stators3A and3B are each stacked and held keeping the interposed distance to armature between the rotor1H and stators3A,3B.

As the stators3A and3B, the stator3(FIGS. 34 to 36) described in the eighth embodiment may be employed. That is, the stator3A has a magnetic member30A in correspondence to the magnetic member30, a winding33A in correspondence to the windings33aand33b, a winding34A in correspondence to the windings34aand34b, and a winding35A in correspondence to the windings35aand35b. Similarly, the stator3B has a magnetic member30B in correspondence to the magnetic member30, a winding33B in correspondence to the windings33aand33b, a winding34B in correspondence to the windings34aand34b, and a winding35B in correspondence to the windings35aand35b.

In the rotor1H, the magnets12a,12band magnetic members13aand13bconstitute a mechanism in which the stators3A and3B each generate torque, so that it is desirable that the structures of the stators3A and3B, particularly, the windings33A and33B, windings34A and34B, and windings35A and35B be in mirror image relation, with the substrate interposed therebetween. Since the magnets12aand12bshow different magnetic poles on the both sides, respectively, it is also desirable that the direction of current to be flown in the windings33A and33B, the windings34A and34B, and the windings35A and35B be in mirror image relation.

Of course, their displacements from the mirror image relation is also a desirable design matter in terms of obtaining skews.

FIG. 41is a perspective view illustrating the structure of another rotor1I according to the preset embodiment. While being disassembled along the rotation axis center90, the rotor1I is practically stacked along the rotation axis center90.

The rotor1I has a structure in which the rotor1C (FIGS. 12 to 14) shown in the third embodiment is provided with the magnets12g,12h, magnetic members13g,13h,14gand14hon the substrate11on the opposite side of the magnets12a,12b, magnetic members13a,13b,14aand14b(magnetic member13adoes not appear inFIG. 41). The positional relationship between the magnets12g,12h, magnetic members13g,13h,14gand14hon one side surface of the substrate11is the same as the positional relationship between the magnets12a,12b, magnetic members13a,13b,14aand14bon the other side surface of the substrate11.

For instance, the thickness of magnetic member13a, the thickness of magnetic member13b, the sum of thicknesses of magnetic member14aand magnet12a, and the sum of thicknesses of magnetic member14band magnet12bare chosen to be equal to one another. Similarly, the thickness of magnetic member13g, the thickness of magnetic member13h, the sum of thicknesses of magnetic member14gand magnet12g, and the sum of thicknesses of magnetic member14hand magnet12hare chosen to be equal to one another. They may all be equal in thickness to one another.

By interposing such rotor1I between stators from the both sides to constitute a motor, similarly to the rotor1G,1H or the like, the motor which is easy to increase the torque can be obtained.

In the rotor I1, similarly to the rotor1G, the case where the magnets12a,12b, magnetic members13a,13b,14aand14bare opposed to the magnets12g,12hand magnetic members13g,13h,14gand14h, respectively, is illustrated, however, such opposition is not necessarily required.

FIG. 42is a perspective view illustrating the structure of another rotor1J according to the present embodiment. While being disassembled along the rotation axis center90, the rotor1J is practically stacked along the rotation axis center90.

The rotor1J has a structure in which the substrate11is omitted from the rotor1C (FIGS. 12 to 14) shown in the third embodiment, and the magnetic members14gand14hare added. The magnetic members14gand14hare opposed to the magnetic members14aand14bwith the magnets12aand12binterposed therebetween, respectively. It is also desirable to form the rotor1J by molding by resin or the like, similarly to the rotor4.

For instance, the sum of thicknesses of magnetic members14a,14gand magnet12a, the sum of thicknesses of magnetic members14b,14hand magnet12b, the thickness of magnetic member13a, and the thickness of magnetic member13bare chosen to be equal to one another.

Since the magnets12aand12bhave magnetic poles on their both surfaces, providing the rotor1J with stators on its opposite sides allows mechanisms for generating torque to be formed on the both sides.

FIG. 43is a perspective view illustrating the structure of another rotor1K according to the present embodiment. While being disassembled along the rotation axis center90, the rotor1K is practically stacked along the rotation axis center90.

The rotor1K has a structure in which the rotor1E (FIGS. 24 to 28) shown in the fifth embodiment is provided with the magnets12g,12h, magnetic members13g,13h, and magnetic plate544on the substrate11on the opposite side of the magnets12a,12b, magnetic members13a,13band magnetic plate542(magnetic members13aand13bdo not appear inFIG. 43). The positional relationship between the magnets12g,12h, magnetic members13g,13h, and magnetic plate542on one side surface of the substrate11is the same as the positional relationship between the magnets12a,12b, magnetic members13a,13band magnetic plate544on the other side surface of the substrate11.

For instance, the thicknesses of magnets12a,12b, magnetic members13aand13bare equal to one another, and the thicknesses of magnets12g,12h, magnetic members13gand13hare equal to one another. Alternatively, they may all be equal in thickness to one another.

The magnetic plate544also has a similar structure to the magnetic plate542, has the hole540and opening slits extending through in the vicinity of the border between each of the magnets12g,12h, magnetic members13gand13h, and is mounted on them from the opposite side of the substrate11.

By interposing such rotor1K between stators from the both sides to constitute a motor, the motor which is easy to increase the torque can be obtained.

In the rotor1K, similarly to the rotor1G, the case where the magnets12a,12b, magnetic members13aand13bare opposed to the magnets12g,12hand magnetic members13gand13h, respectively, is illustrated, however, such opposition is not necessarily required.

FIG. 44is a perspective view illustrating the structure of another rotor1L according to the present embodiment. While being disassembled along the rotation axis center90inFIG. 44, the rotor1L is practically stacked along the rotation axis center90.

The rotor1L has a structure in which the substrate11is omitted from the rotor1E (FIGS. 24 to 28) shown in the fifth embodiment, and the magnetic plate544is added. It is desirable to form the rotor1L by molding by resin or the like, similarly to the rotor4.

The magnets12aand12bhave magnetic poles on their both surfaces. That is, in the case where the magnets12aand12bhave pole faces exhibiting the N pole and S pole, respectively, on the side of the magnetic plate542, the magnets12aand12bhave pole faces exhibiting the S pole and N pole, respectively, on the side of the magnetic plate544. Therefore, providing the rotor1L with stators on its opposite sides allows mechanisms for generating torque to be formed on the both sides.

Of course, shape modifications as shown inFIGS. 16 to 19in the third embodiment may be made in the magnetic plates542and544.

FIG. 45is a perspective view illustrating the structure of another rotor1M according to the present embodiment. While being disassembled along the rotation axis center90inFIG. 45, the rotor1M is practically stacked along the rotation axis center90.

The rotor1M has a structure in which the substrate11is omitted from the rotor1D (FIGS. 20 to 23) shown in the fourth embodiment, and a magnetic plate545is added. The magnetic plate545has a structure of almost the same type as the magnetic plate541.

Slits provided for the magnetic plate545are disposed to oppose to the slits55aand55bof the magnetic plate541. However, they may be displaced from the directly-opposed position in terms of reducing the cogging torque, or the like.

Since the magnets12aand12bhave magnetic poles on their both surfaces, providing the rotor1M with stators on its opposite sides allows mechanisms for generating torque to be formed on the both sides.

Of course, shape modifications as shown inFIGS. 16 to 19in the third embodiment may be made in the magnetic plates541and545. Further, the magnets12aand12bmay be formed integrally by a ring-like magnet, as described in the fourth embodiment.

The magnetic plates541and545are not necessarily required to be of completely the same type to each other, but may be of almost the same type and different from each other for the purpose of distinguishing front and rear of the rotor1M, or the like. Further, they may be of almost the same type to a degree that similar effects can be obtained even with slight differences in shape.

Tenth Embodiment

FIG. 46is a perspective view illustrating a method of manufacturing a rotor according to a tenth embodiment of the present invention. This can be employed as a method of manufacturing the rotor1E shown inFIG. 24.FIG. 47is a sectional view of the rotor1E when manufactured according to the present embodiment, and shows a cross section in the same position as the sectional view shown inFIG. 25.

In the present embodiment, the substrate11is provided with recesses11aand11b, within which the magnetic members13aand13bfit in the direction along the rotation axis. Then, the magnetic members13a,13band substrate11can easily be aligned, and both can easily be coupled.

Such structure, when viewed on the basis of the sectional view shown inFIG. 25, can be grasped that the substrate11is made of the same material as the magnetic members13aand13bin a position where the magnetic members13aand13bare extended along the rotation axis in a region having a predetermined length from the side of the magnetic plate542. When the magnetic members13aand13bare made of dust core, the recesses11aand11bwill be filled with iron dust core.

The substrate11other than the above-mentioned region may also be made of dust core. However, it is desirable that the substrate11other than the above-mentioned region be formed by stacking steel sheets perpendicular to the rotation axis. It is desirable to employ dust core in the above-mentioned region since the magnetic fluxes flow both in the direction parallel to the rotation axis and in the direction inclined thereto, and on the other hand, it is desirable to employ stacked steel sheets in terms of optimizing the magnetic characteristics of the rotor since most magnetic fluxes flow in the direction perpendicular to the rotation axis out of the above-mentioned region.

The structure in which stacked steel sheets, particularly, electromagnetic steel sheets are stacked is superior in magnetic characteristics in the direction perpendicular to the rotation axis, e.g., saturation magnetic flux density, permeability and iron loss. And, many magnetic fluxes in which the magnetic flux based on the current flown in the stator is superimposed on the magnetic fluxes of the permanent magnets need to flow in the substrate11. Therefore, the substrate11can be reduced in thickness by employing stacked steel sheets for the substrate11.

Further, it is also desirable to employ stacked steel sheets in terms of strength since there are many cases where the substrate11fits to the rotation shaft.

On the other hand, in the case where the rotor is a permanent magnet, variations in magnetic fluxes of permanent magnets result in many harmonics particularly by means of rotation of the rotor. Dust core having a low eddy-current loss is therefore desirable for the material of the magnetic plate542.

FIG. 48is a sectional view showing another modification of the present embodiment, and shows a cross section in the position corresponding toFIGS. 25 and 47. In the substrate11, the recesses11aand11bare both through holes, and the magnetic members13aand13bextend through the substrate11at the through holes in the direction along the rotation axis. At this time, it is desirable to employ dust core for the magnetic plate542and stacked steel sheets for the substrate11for similar reasons as described above. It is desirable that the magnetic members13aand13bbe integral with magnetic members54dand54fof the magnetic plate542which cover the magnetic members13aand13b. This is because press fitting of the magnetic members13aand13binto the recesses (or through holes)11aand11bfacilitates assembly of the rotor using the magnetic plate542, magnetic members13a,13b, substrate11, and magnets12aand12b.

The technique according to the present embodiment may be applied not only to the rotor1E but also the rotors1A (FIG. 1),1C (FIG. 12),1G (FIG. 37),1I (FIG. 41) and 1K(FIG. 43).

Eleventh Embodiment

FIG. 49is a perspective view illustrating a method of manufacturing a rotor according to an eleventh embodiment of the present invention. This can be employed as a method of manufacturing the rotor1E shown inFIG. 24.FIG. 50is a sectional view of the rotor1E when manufactured according to the present embodiment, and shows a cross section in the same position as the sectional view shown inFIG. 25.

In the present embodiment, the magnetic members54dand54fof the magnetic plate542which cover the magnetic members13aand13bare provided with recesses57aand57bon the side of the magnetic members13aand13b, within which the magnetic members13aand13bfit in the direction along the rotation axis. Then, the magnetic members13a,13band magnetic plate542can easily be aligned, and both can easily be coupled.

The magnetic plate542may be made of dust core along with the magnetic members13aand13b. In that case, the border between the magnetic members13a,13band magnetic plate542arises no problem, provided that they fit ideally.

FIG. 51is a sectional view showing a modification of this embodiment, and shows a cross section in the position corresponding toFIGS. 25 and 50. In the magnetic plate542, the recesses57aand57bare both through holes, and the magnetic members13aand13bextend through the magnetic plate542at the through holes in the direction along the rotation axis.

It is desirable that the magnetic members13aand13bbe integral with the substrate11. This is because it facilitates assembly of the rotor using the substrate11, magnetic members13a,13b, magnetic plate542, and magnets12aand12b.

The technique according to the present embodiment may be applied not only to the rotor1E but also to the rotors1K (FIG. 43) and 1L(FIG. 44).

Twelfth Embodiment

FIG. 52is a perspective view illustrating a method of manufacturing a rotor according to a twelfth embodiment of the present invention. This can be employed as a method of manufacturing the rotor1E shown inFIG. 24.FIG. 53is a sectional view of the rotor1E when manufactured according to the present embodiment, and shows a cross section in the same position as the sectional view shown inFIG. 26.

In the present embodiment, the magnetic members54dand54fof the magnetic plate542which cover the magnets12aand12bare provided with recesses57cand57don the side of the magnets12aand12b, within which the magnets12aand12bfit in the direction along the rotation axis. Then, the magnets12a,12band magnetic plate542can easily be aligned, and both can easily be coupled.

The technique of embedding the magnets in the magnetic plate in this manner may be applied not only to the rotor1E but also to the rotors1F (FIG. 29),1F1(FIG. 30),1K (FIG. 43),1L (FIG. 44) and 1M(FIG. 45).

FIG. 54is a perspective view illustrating another method of manufacturing the rotor according to this embodiment.FIG. 55is a sectional view of the rotor1E when manufactured according to this modification, and shows a cross section in the same position as the sectional view shown inFIG. 26.

In this modification, the substrate11is provided with recesses12aQ and12bQ, within which the magnets12aand12bfit in the direction along the rotation axis. Then, the magnets12a,12band substrate11can easily be aligned, and both can easily be coupled.

The technique of embedding the magnets in the magnetic plate in this manner may be applied not only to the rotor1E but also to the rotors1A (FIG. 1),1C (FIG. 12),1F (FIG. 29),1F1(FIG. 30),1G (FIG. 37),1I (FIG. 41) and 1K(FIG. 43).

FIG. 56is a sectional view showing another modification of the present embodiment, and shows a cross section in the same position as the sectional view shown inFIG. 26. A structure in which the recesses57c,57d, recesses12aQ and12bQ are all provided is shown, and the magnets12aand12bare embedded in the magnetic plate542and substrate11with thicknesses t1and t2, respectively. Introducing distance t3between the yoke side of the magnetic plate542and the magnetic plate542side of the substrate11, the thickness of the magnets12aand12bis the sum of the thicknesses t1, t2and distance t3.

When the distance t3is small, the magnetic flux generated by each of the magnets12aand12bflows between the substrate11and magnetic plate542in a short circuiting manner without interlinking with the stator. In other words, in order to flow the magnetic flux effectively to the stator, it is desirable to design the thickness of the magnets12aand12bto not less than the sum of twice the interposed distance to armature and thicknesses t1, t2.

Of course, the desirableness that the distance between the substrate11and magnetic plate542be not less than twice the interposed distance to armature is not limited to the present embodiment, but applies similarly to the other embodiments. Additionally saying, it is desirable that the distance between the magnetic plates542and544(or magnetic plates541and545) interposing the magnets12aand12bbe not less than twice the interposed distance to armature, like the rotors1L (FIGS. 44) and 1M(FIG. 45).

Thirteenth Embodiment

FIG. 57is a perspective view illustrating a method of manufacturing a rotor according to a thirteenth embodiment of the present invention.FIG. 58is a sectional view of the rotor1E manufactured according to the present embodiment corresponding to the position ofFIG. 26. While description will be made here taking the rotor1E shown inFIG. 24as an example, it may be applied to other rotors1A (FIG. 1),1C (FIG. 12),1F (FIG. 29),1F1(FIG. 30),1G (FIG. 37),1I (FIG. 41) and 1K(FIG. 43).

Ridges111aand111bcoming into contact with the magnets12aand12bfrom their outer peripheral side are provided on the substrate11. The ridges111aand111bfacilitates alignment of the magnets12aand12b, and stop the magnets12aand12bagainst the centrifugal force produced in the magnets12aand12bby rotation of the rotor.

Ridges112a,112b,113aand113bcoming into contact with the magnets12aand12bin the circumferential direction may be provided on the substrate11. They also facilitate alignment of the magnets12aand12b.

FIG. 59is a perspective view illustrating another method of manufacturing the rotor according to this embodiment.FIG. 60is a sectional view corresponding to the position ofFIG. 26. While description will be made here taking the rotor1E shown inFIG. 24as an example, it may be applied to other rotors1F (FIG. 29),1F1(FIG. 30),1K (FIG. 43),1L (FIG. 44) and 1M(FIG. 45).

Ridges58aand58bcoming into contact with the magnets12aand12bfrom their outer peripheral side are provided on the magnetic plate542. The ridges58aand58bfacilitate alignment of the magnets12aand12b, and stop the magnets12aand12bagainst the centrifugal force produced in the magnets12aand12bby rotation of the rotor.

Ridges59ato59dcoming into contact with the magnets12aand12bin the circumferential direction may be provided on the magnetic plate542. They also facilitate alignment of the magnets12aand12b.

It is desirable that the distance between the ridges111a,111b,112a,112b,113a,113band magnetic plate542, and the distance between the ridges58a,58b,59ato59dand substrate11not less than twice the interposed distance to armature, similarly to the aforementioned distance t3. This is to make the magnetic fluxes generated from the magnets12aand12beasier to flow into the stator.

However, the above-mentioned distances may be less than twice the interposed distance to armature, provided that width and length in which these ridges are provided are short. This is because these ridges are easy to become magnetically saturated, and have degraded function as the paths of magnetic fluxes.

The presence of the magnetic members13aand13bis not indispensable in the present embodiment. However, when they are provided, making them integral with the substrate11is desirable in terms of easier assembly of the rotor. Further, when a magnetic plate covering the magnets12aand12bis provided along with the magnetic members13aand13b, it is desirable that the magnetic plate be formed integrally with the magnetic members13aand13bfrom a similar point of view.

Fourteenth Embodiment

FIG. 61is a perspective view illustrating the structure of the magnetic plate542to be employed for a rotor according to a fourteenth embodiment of the present invention. While description will be made here taking the rotor1E shown inFIG. 24as an example, it may be applied to other rotors1D (FIG. 20),1F (FIG. 29),1F1(FIG. 30),1K (FIG. 43),1L (FIG. 44) and 1M(FIG. 45).

The magnetic plate542is composed of magnetic plate components542aand542bdivided in a position where the pole faces of the magnets12aand12b(cf.FIG. 24, for example) are provided as viewed along the rotation axis (i.e., in plan view). For instance, the position of division is the position XXVI-XXVI shown inFIG. 24.

Dust core is generally formed, but press pressure can be made lower as a compressed portion decreases in area. Therefore, dividing the magnetic plate542into small-size magnetic plate components542aand542bfacilitates manufacture by dust core.

The presence of the magnetic members13aand13bis not indispensable in the present embodiment. However, when they are provided, making them integral with the magnetic plate542is desirable in terms of facilitating alignment of the magnetic plate components542aand542band assembly of the rotor.

As shown inFIG. 62, the magnetic plate components542aand542bmay be adjacent to each other leaving gaps. The gaps are to be opposed to the stator side. Since the cogging torque is generally generated by variations in magnetic resistance of the gaps between the stator and rotor, the gaps serve as so-called supplemental grooves for shortening the cycle of cogging torque. The cogging torque is thereby reduced.

Further, the magnetic plate components542aand542bmay have steps on their edges in the circumferential direction with respect to the direction along the rotation axis.FIG. 63is a perspective view showing the state where the magnetic plate components542aand542bhaving the steps are adjacent to each other. The steps of the adjacent magnetic plate components542aand542bare adjacent to each other. And, these steps form recesses which come into contact on the side where the magnetic members13aand13bare provided and open on the opposite side (the stator side). In this mode, the cogging torque can also be reduced as described above. Further, the magnetic plate components542aand542bare in contact on the side where the magnets12aand12bare provided, which permits effective use of the magnetic fluxes form the magnets12aand12b.

Of course, the magnetic plate542may be formed with steps engaging with each other as shown inFIG. 64without forming such recesses. Such engagement of steps is desirable in terms of making the structure of the magnetic plate composed of magnetic plate components strong.

Various Modifications

It is known that it is desirable that the angle at which a magnet extends to be widened in the circumferential direction fall within the range of {(120±20)/P} degrees, assuming the pole pair number to be P. It is therefore desirable in the rotors1A to1E, for example, that the angle at which the magnets12aand12bare widened in the circumferential direction fall within the range of (120±20) degrees. Further, in the rotors1F and1F1, it is desirable that the angle at which the magnets12cto12fare widened in the circumferential direction fall within the range of (60±10) degrees.

To prevent the magnetic fluxes from short circuiting through the rotation shaft in the rotor, it is desirable to provide the gap G2(FIGS. 1,5,12, etc.), provide the cylinder40(FIG. 39) or employ non-magnetic steel for the rotation shaft, as described above.

To earn the distance corresponding to the gap G2, non-magnetic bosses may be provided on the inner periphery of the shaft hole10of the substrate11(FIGS. 1,5,12, etc.), the rotation shaft may be inserted into the shaft hole10with the bosses interposed therebetween.

It is not always required to provide the shaft hole10in the rotor. For instance, the rotation shaft may only be strongly coupled in the position of the shaft hole without coming into contact with the magnets and magnetic members. Further, the rotation shaft may be omitted like a magnetic bearing.

While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and the present invention is not limited thereto. It is therefore understood that numerous modifications not illustrated can be devised without departing from the scope of the invention.