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Title:
ROTARY ELECTRIC MACHINE
Document Type and Number:
WIPO Patent Application WO/2015/118400
Kind Code:
A2
Abstract:
A rotary electric machine includes a rotor, a stator, a bypass core, a flux regulation coil, and a controller. The bypass core is opposed to protruding portions, and the protruding portions are provided on opposite sides of magnets provided in a rotor core as viewed in a direction of magnetization of the magnets, and protrude toward the bypass core from a surface of the rotor to which the magnets are exposed. The flux regulation coil is configured to regulate the magnetic flux passing through the bypass core. The controller is configured to control a current applied to the flux regulation coil such that the magnetic flux passing through the bypass core when the current is applied to the flux regulation coil is smaller than the magnetic flux passing through the bypass core when the current is not applied to the flux regulation coil.

Inventors:
YAMADA, Eiji (of 1 Toyota-cho, Toyota-sh, Aichi-ken ., 471-8571, JP)
Application Number:
IB2015/000099
Publication Date:
August 13, 2015
Filing Date:
February 02, 2015
Export Citation:
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Assignee:
TOYOTA JIDOSHA KABUSHIKI KAISHA (1 Toyota-cho, Toyota-shi, Aichi-ken, 471-8571, JP)
International Classes:
H02K21/02
Foreign References:
JP2008043099A2008-02-21
Download PDF:
Claims:
CLAIMS:

1. A rotary electric machine comprising:

a rotor including a rotor core and magnets provided in the rotor core, the rotor core having protruding portions;

a stator opposed to the rotor, the stator including a stator coil;

a bypass core configured to permit magnetic flux of the magnets to pass through the bypass core without passing through the stator, the bypass core being opposed to the protruding portions, the protruding portions being provided on opposite sides of the magnets as viewed in a direction of magnetization of the magnets, and the protruding portions protruding toward the bypass core from a surface of the rotor to which the magnets are exposed;

a flux regulation coil configured to regulate the magnetic flux passing through the bypass core; and

a controller configured to control a current applied to the flux regulation coil such that the magnetic flux passing through the bypass core when the current is applied to the flux regulation coil is smaller than the magnetic flux passing through the bypass core when the current is not applied to the flux regulation coil. 2. The rotary electric machine according to claim 1, wherein

the magnets include:

a first magnet in which a magnetic pole located closer to the stator is a north pole; and

a second magnet in which a magnetic pole located closer to the stator is a south pole,

the protruding portions are provided on opposite sides of one of the first magnet as viewed in a direction of magnetization of the first magnet and the second magnet as viewed in a direction of magnetization of the second magnet. 3. The rotary electric machine according to claim 1 or 2, wherein

the protruding portions protrude axially outwards from the surface of the rotor including axial end faces of the magnets.

4. The rotary electric machine according to claim 1, wherein

the magnets include: a first magnet in which a magnetic pole located closer to the stator is a north pole; and

a second magnet in which a magnetic pole located closer to the stator is a south pole,

the bypass core includes:

a first bypass core configured to permit magnetic flux of the first magnet to pass through the first bypass core without passing through the stator; and

a second bypass core configured to permit magnetic flux of the second magnet to pass through the second bypass core without passing through the stator,

the flux regulation coil includes:

a first flux regulation coil configured to regulate the magnetic flux of the first magnet passing through the first bypass core; and

a second flux regulation coil configured to regulate the magnetic flux of the second magnet passing through the second bypass core,

the rotor core includes:

first protruding portions that protrude toward the first bypass core from a surface of the rotor to which the first magnet is exposed, the first protruding portions are provided on opposite sides of the first magnet as viewed in a direction of magnetization of the first magnet;

second protruding portions that protrude toward the second bypass core from a surface of the rotor to which the second magnet is exposed, the second protruding portions are provided on opposite sides of the second magnet as viewed in a direction of magnetization of the second magnet,

the first bypass core is opposed to the first protruding portions, and

the second bypass core is opposed to the second protruding portions.

5. The rotary electric machine according to claim 4, wherein

the first bypass core is opposed to one axial end face of the rotor core; and the second bypass core is opposed to the other axial end face of the rotor core.

Description:
ROTARY ELECTRIC MACHINE

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a variable field type rotary electric machine.

2. Description of Related Art

[0002] In a variable field type rotary electric machine as described in Japanese Patent Application Publication No. 2008-43099 (JP 2008-43099 A), a field coil is used so as to make field magnetic flux of rotor teeth variable.

[0003] In the rotary electric machine of JP 2008-43099 A, current needs to be applied to the field coil all the time, so as to strengthen the field and weaken the field. Consequently, a loss caused by a copper loss of the field coil is increased.

SUMMARY OF THE INVENTION

[0004] The invention is concerned with a technology of reducing a loss that would arise when the amount of field magnetic flux of a rotor acting on a stator is varied.

[0005] A rotary electric machine related to the present invention includes a rotor, a stator, a bypass core, a flux regulation coil and a controller. The rotor includes a rotor core and magnets provided in the rotor core. The rotor core has protruding portions. The stator is opposed to the rotor, and includes a stator coil. The bypass core is configured to permit magnetic flux of the magnets to pass through the bypass core without passing through the stator. The bypass core is opposed to the protruding portions. The protruding portions are provided on opposite sides of the magnets as viewed in a direction of magnetization of the magnets. The protruding portions are protrude toward the bypass core from a surface of the rotor to which the magnets are exposed. The flux regulation coil is configured to regulate the magnetic flux passing through the bypass core. The controller is configured to control a current applied to the flux regulation coil such that the magnetic flux passing through the bypass core when the current is applied to the flux regulation coil is smaller than the magnetic flux passing through the bypass core when the current is not applied to the flux regulation coil.

[0006] According to the invention, current is applied to the flux regulation coil so as to reduce magnetic flux of the magnets passing through the bypass core, as compared with the case where no current is applied to the flux regulation coil, so that the magnetic flux of the magnets acting on the stator is increased. Therefore, when field weakening is effected for reduction of the amount of field magnetic flux of the rotor acting on the stator, no current needs to be applied to the flux regulation coil. Consequently, a copper loss of the flux regulation coil can be reduced, and a loss that would arise when the amount of field magnetic flux of the rotor acting on the stator is varied can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a cross-sectional view schematically showing the configuration of a rotary electric machine according to one embodiment of the invention, when viewed in a direction perpendicular to the center axis of rotation of the machine;

FIG. 2 is a perspective view showing a configuration example of a rotor 28 and a bypass core 54;

FIG. 3 is a perspective view showing a configuration example of the rotor 28; FIG. 4 is a view useful for explaining flow of magnetic flux of a permanent magnet 48n when a current is applied to a flux regulation coil 58;

FIG. 5 is a view useful for explaining flow of magnetic flux of a permanent magnet 48n when no current is applied to the flux regulation coil 58;

FIG. 6 is a cross-sectional view schematically showing the configuration of a rotary electric machine according to another embodiment of the invention, when viewed in a direction perpendicular to the rotation center axis of the machine;

FIG. 7 is a perspective view showing a configuration example of a rotor 28 and a bypass core 64;

FIG. 8 is a view useful for explaining flow of magnetic flux of a permanent magnet 48s when a current is applied to a flux regulation coil 68;

FIG. 9 is a view useful for explaining flow of magnetic flux of the permanent magnet 48s when no current is applied to the flux regulation coil 68;

FIG. 10 is a view useful for explaining flow of magnetic flux of the permanent magnet 48s when a current is applied to the flux regulation coil 58;

FIG. 11 is a cross-sectional view schematically showing the configuration of a rotary electric machine according to a further embodiment of the invention, when viewed in a direction perpendicular to the rotation center axis of the machine;

FIG. 12 is a view useful for explaining flow of magnetic flux of a permanent magnet 48n when no current is applied to a flux regulation coil 58;

FIG. 13 is a view useful for explaining flow of magnetic flux of the permanent magnet 48n when a current is applied to the flux regulation coil 58;

FIG. 14 is a cross-sectional view schematically showing the configuration of a rotary electric machine according to a still another embodiment of the invention, when viewed in a direction perpendicular to the rotation center axis of the machine;

FIG. 15 is a view useful for explaining flow of magnetic flux of a permanent magnet 48s when no current is applied to a flux regulation coil 68;

FIG. 16 is a view useful for explaining flow of magnetic flux of the permanent magnet 48s when a current is applied to the flux regulation coil 68;

FIG. 17 is a cross-sectional view schematically showing the configuration of a rotary electric machine according to another embodiment of the invention, when viewed in a direction perpendicular to the rotation center axis of the machine; and

FIG. 18 is a cross-sectional view schematically showing the configuration of a rotary electric machine according to a still another embodiment of the invention, when viewed in a direction perpendicular to the rotation center axis of the machine.

DETAILED DESCRIPTION OF EMBODIMENTS

[0008] Some embodiments of the invention will be described with reference to the drawings.

[0009] FIG. 1 through FIG. 3 schematically show the configuration of a rotary electric machine according to one embodiment of the invention. FIG. 1 is a cross-sectional view as seen in a direction perpendicular to the center axis of rotation of a rotor 28, and FIG. 2 is a perspective view of the rotor 28 and a bypass core 54, while FIG. 3 is a perspective view of the rotor 28. While the configuration of a circumferential portion of the rotor 28 is illustrated in FIG. 2 and FIG. 3, the remaining portion of the rotor 28 which is not shown in these figures is configured similarly to the illustrated portion.

[0010] The rotary electric machine has a stator 24 fixed to a casing, and the rotor 28 that is opposed to the stator 24 with a given clearance (magnetic gap) formed therebetween in a given direction, such that the rotor 28 is rotatable relative to the stator 24. In the embodiment of FIG. 1, the stator 24 and the rotor 28 are opposed to each other in radial directions, and the stator 24 is located on the radially outer side of the rotor 28 so as to be opposed to an outer circumferential surface of the rotor 28.

[0011] The stator 24 includes a stator core 36, and three-phase stator coils 38 of U phase, V phase, and W phase as a plurality of phases, which are mounted on the stator core 36 in its circumferential direction. With three-phase alternating current flowing through the three-phase stator coils 38, a rotating magnetic field that rotates in the circumferential direction of the stator 24 is generated in the stator 24.

[0012] The rotor 28 includes a rotor core 46, and a plurality of permanent magnets 48n, 48s mounted (at equal intervals) in the rotor core 46 while being spaced from each other in its circumferential direction. Each of the permanent magnets 48n has a radially outer magnetic pole face (closer to the stator 24), which is the north (N) pole, and a radially inner magnetic pole face (remote from the stator 24), which is the south (S) pole. On the other hand, each of the permanent magnets 48s has a radially outer magnetic pole face (closer to the stator 24), which is the south (S) pole, and a radially inner magnetic pole (remote from the stator 24), which is the north (N) pole. The permanent magnets 48n and the permanent magnets 48s are alternately arranged in the circumferential direction, so that the polarity of the permanent magnets 48n, 48s varies alternately in the circumferential direction. In the embodiment of FIG. 3, a plurality of sets of the permanent magnets 48n, 48s, each of which consists of two permanent magnets 48n or 48s arranged in V-shape, are embedded at a plurality of circumferentially spaced positions of the rotor core 46. However, the permanent magnets 48n, 48s are not necessarily arranged in V-shape. In operation, field magnetic flux of the permanent magnets 48n, 48s crosses the stator coils 38, so that torque is produced in the rotor 28, due to electromagnetic interactions (attraction and repulsion) between the rotating magnetic field of the stator 24 and the field magnetic flux of the rotor 28.

[0013] In this embodiment, a bypass core 54 that permits magnetic flux of the permanent magnets 48n to pass therethrough without passing through the stator 24 (stator core 36) is opposed to the rotor core 46 with a given clearance (magnetic gap) formed in a direction perpendicular to a given direction (direction in which the stator 24 and the rotor 28 are opposed to each other). In the embodiment of FIG. 1 and FIG. 2, the bypass core 54 and the rotor core 46 are opposed to each other in the axial direction perpendicular to the radial direction; more specifically, the bypass core 54 is located on one side (the left-hand side in FIG. 1) of the rotor core 46 as viewed in the axial direction, such that the bypass core 54 is opposed to one axial end face of the rotor core 46. The rotor core 46 is provided with protruding portions 56-1, 56-2 that protrude toward the bypass core 54 from a surface (the above-indicated one axial end face) of the rotor core 46 to which the permanent magnets 48n are exposed. The protruding portions 56-1, 56-2 are provided on the opposite sides of the permanent magnets 48n as viewed in the direction of magnetization, and the bypass core 54 is opposed to the protruding portions 56-1, 56-2 with given clearances formed therebetween. In the embodiment of FIG. 1 and FIG. 3, the protruding portion 56-1 is provided on one axial end face of a rotor core portion 46-1 located on the radially outer side of the north poles of the permanent magnets 48n (on the side closer to the stator 24), and the protruding portion 56-2 is provided on one axial end face of a rotor core portion 46-2 located on the radially inner side of the south poles of the permanent magnets 48n (on the side opposite to the stator 24). Thus, the protruding portions 56-1, 56-2 protrude to the above-indicated one side in the axial direction (axially outwards) from the surface including one axial end face of each permanent magnet 48n. A magnetic path that magnetically connects the protruding portions 56-1, 56-2 is formed by the bypass core 54, and the protruding portion 56-1, bypass core 54, and the protruding portion 56-2 cooperate to form a bypass magnetic path. The axial magnetic gaps formed between the bypass core 54 and the protruding portions 56-1, 56-2 may be set to be smaller than a radial magnetic gap formed between the stator 24 and the rotor 28, for example. The bypass core 54 extends in the circumferential direction along the rotor core 46, and is fixed to the casing. A hollow portion 54a is formed in the circumferential direction, within the bypass core 54.

[0014] In this embodiment, a flux regulation coil 58 is provided for regulating the magnetic flux of the permanent magnets 48n passing through the bypass core 54. The flux regulation coil 58, which is housed in the hollow portion 54a inside the bypass core 54, extends in the circumferential direction along the bypass core 54 (rotor core 46), and is fixed to the casing. A section of the bypass core 54 cut along a plane that passes the axis of rotation of the rotor is shaped so as to form a circulation magnetic path in a direction in the plane of the section, and the circulation magnetic path is formed by the bypass core 54 around the flux regulation coil 58. In the embodiment of FIG. 1 and FIG. 2, the shape of the bypass core 54 (the shape of the circulation magnetic path) is quadrangular (rectangular), but may be a shape other than quadrangles provided that a circulation magnetic path is formed around the flux regulation coil 58. The circulation magnetic path of the bypass core 54 includes a magnetic path portion 54b located on the axially other side (closer to the rotor core 46) of the flux regulation coil 58, and a magnetic path portion 54c located on the axially one side (remote from the rotor core 46) of the flux regulation coil 58. When a current is applied to the flux regulation coil 58 in a direction indicated by arrow Al in FIG. 2, magnetomotive force is generated around the flux regulation coil 58, so that magnetic flux that circulates in the circulation magnetic path is generated in the bypass core 54 (within the section along the plane that passes the axis of rotation of the rotor). The current of the flux regulation coil 58 is controlled by a controller 40, based on the rotational speed and torque of the rotor 28, for example.

[0015] In an axially other side portion (right side portion in FIG. 1) of the rotary electric machine, the magnetic flux of the permanent magnets 48n crosses the stator coil 38 as indicated by arrows CI in FIG. 5, to provide effective magnetic flux that contributes to torque. However, in an axially one side portion (left side portion in FIG. 1) of the rotary electric machine, when no current is applied to the flux regulation coil 58, the magnetic flux of the permanent magnets 48n does not cross the stator coil 38, but passes through the rotor core portion 46-1, protruding portion 56-1, bypass core 54, protruding portion 56-2, and the rotor core portion 46-2, to be thus short-circuited, as indicated by arrows Dl, El in FIG. 5. In this case, the magnetic flux of the permanent magnets 48n does not contribute to torque. As a result, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 is reduced for field weakening. At this time, the magnetic flux of the permanent magnets 48n flowing in the circulation magnetic path of the bypass core 54 is split into magnetic flux passing through the magnetic path portion 54b as indicated by arrow Dl in FIG. 1, and magnetic flux passing through the magnetic path portion 54c as indicated by arrow El in FIG. 1. When the rotational speed of the rotor 28 is higher than a set speed, no current is applied to the flux regulation coil 58, so as to effect field weakening. Through the field weakening, the back electromotive force of the stator coil 38 can be reduced, and the magnetic flux density of the stator core 36 can be reduced for reduction of an iron loss. At the time of field weakening, there is no need to apply current to the flux regulation coil 58, and a copper loss of the flux regulation coil 58 can be reduced.

[0016] On the other hand, when a current is applied to the flux regulation coil

58 in the direction indicated by arrow Al in FIG. 2, magnetic flux that circulates in the circulation magnetic path in the bypass core 54 in a direction indicated by arrow Bl in FIG. 4 is generated. The magnetic flux produced by the current of the flux regulation coil 58 and the magnetic flux produced by the permanent magnets 48n pass in the same direction in the magnetic path portion 54b so as to reinforce each other, and pass in the opposite directions in the magnetic path portion 54c so as to act repulsively against each other. If the current of the flux regulation coil 58 is increased to be equal to or larger than a give value, the magnetic flux that passes through the magnetic path portion 54b is saturated. In this case, the magnetic resistance of the magnetic path portion 54b is increased to provide magnetic permeability equivalent to that of air, and the magnetic flux of the permanent magnets 48n passing through the bypass core 54 is reduced. As a result, in the above-indicated axially one side portion, too, the magnetic flux of the permanent magnets 48n crosses the stator coil 38 as indicated by arrows Fl in FIG. 4, and contributes to torque. In this manner, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 is increased, resulting in increase in the strength of the magnetic field (field strengthening). When the torque of the rotor 28 is larger than a set torque, for example, a current equal to or larger than a given value is applied to the flux regulation coil 58 in the direction indicated by arrow Al in FIG. 2, so as to strengthen the field. Through the field strengthening, the maximum torque that can be produced by the rotor 28 can be increased.

[0017] Thus, the rotary electric machine according to this embodiment functions as a variable field type rotary electric machine in which the amount of the field magnetic flux of the rotor 28 acting on the stator 24 is changed by regulating the magnetic flux of the permanent magnets 48n passing through the bypass core 54 through control of current applied to the flux regulation coil 58. In comparison with the case where no current is applied to the flux regulation coil 58, the magnetic flux of the permanent magnets 48n acting on the stator 24 can be increased by passing a current through the flux regulation coil 58 in such a direction (direction indicated by arrow Al in FIG. 2) as to reduce the magnetic flux of the permanent magnets 48n passing through the bypass core 54. Therefore, a variable field can be realized by applying current to the flux regulation coil 58 only when the field is to be strengthened, and no current need be applied to the flux regulation coil 58 when the field is to be weakened. Consequently, a copper loss of the flux regulation coil 58 can be reduced, and a loss that would arise when the amount of the field magnetic flux of the rotor 28 acting on the stator 24 is changed can be reduced. Also, the magnetic path for adjusting the amount of field magnetic flux of the permanent magnets 48n is only required to be provided on the axially one side of the rotor 28, and need not be provided at the outer periphery of the stator as in the known counterpart; therefore, the outside diameter of the rotary electric machine can be reduced, and the overall size of the machine can be reduced.

[0018] In the following, rotary electric machines according to other embodiments of the invention will be described. In an embodiment shown in FIG. 6 and FIG. 7, a bypass core 64 that permits magnetic flux of the permanent magnets 48s to pass therethrough without flowing through the stator 24 (stator core 36) is opposed to the rotor core 46 with a given clearance (magnetic gap) formed in a direction perpendicular to a given direction, as compared with the embodiment shown in FIG. 1 through FIG. 3. In the embodiment of FIG. 6 and FIG. 7, the bypass core 64 and the rotor core 46 are opposed to each other in the axial direction perpendicular to the radial direction; more specifically, the bypass core 64 is located on the other side (the right-hand side in FIG. 6) of the rotor core 46 as viewed in the axial direction, such that the bypass core 64 is opposed to the other axial end face of the rotor core 46. The rotor core 46 is provided with protruding portions 66-1, 66-2 that protrude toward the bypass core 64 from a surface (the other axial end face) of the rotor core 46 to which the permanent magnets 48s are exposed. The protruding portions 66-1, 66-2 are provided on the opposite sides of the permanent magnets 48s as viewed in the direction of magnetization, and the bypass core 64 is opposed to the protruding portions 66-1, 66-2 with given clearances formed therebetween. In the embodiment of FIG. 6, the protruding portion 66-1 is provided on the other axial end face of a rotor core portion 46-3 located on the radially outer side of the south poles of the permanent magnets 48s (on the side closer to the stator 24), and the protruding portion 66-2 is provided on the other axial end face of a rotor core portion 46-4 located on the radially inner side of the north poles of the permanent magnets 48s (on the side opposite to the stator 24). Thus, the protruding portions 66-1, 66-2 protrude to the above-indicated other side in the axial direction (axially outwards) from a surface including the other axial end faces of the permanent magnets 48s. A magnetic path that magnetically connects the protruding portions 66-1, 66-2 is formed by the bypass core 64, and the protruding portion 66-1, bypass core 64, and the protruding portion 66-2 cooperate to form a bypass magnetic path. The axial magnetic gaps formed between the bypass core 64 and the protruding portions 66-1, 66-2 may be set to be smaller than a radial magnetic gap formed between the stator 24 and the rotor 28, for example. The bypass core 64 extends in the circumferential direction along the rotor core 46, and is fixed to the casing. A hollow portion 64a is formed in the circumferential direction, within the bypass core 64.

[0019] In the embodiment of FIG. 6 and FIG. 7, a flux regulation coil 68 is provided for regulating the magnetic flux of the permanent magnets 48s passing through the bypass core 64. The flux regulation coil 68, which is housed in the hollow portion 64a inside the bypass core 64, extends in the circumferential direction along the bypass core 64 (rotor core 46), and is fixed to the casing. A section of the bypass core 64 cut along a plane that passes the axis of rotation of the rotor is shaped so as to form a circulation magnetic path in a certain direction in the plane of the section, and the circulation magnetic path is formed by the bypass core 64 around the flux regulation coil 68. In the embodiment of FIG. 6 and FIG. 7, the shape of the bypass core 64 (the shape of the circulation magnetic path) is quadrangular (rectangular), but may be a shape other than quadrangles provided that a circulation magnetic path is formed around the flux regulation coil 68. The circulation magnetic path of the bypass core 64 includes a magnetic path portion 64b located on the axially one side (closer to the rotor core 46) of the flux regulation coil 68, and a magnetic path portion 64c located on the axially other side (remote from the rotor core 46) of the flux regulation coil 68. When a current is applied to the flux regulation coil 68 in a direction indicated by arrow A2 in FIG. 7, magnetic flux that circulates in the circulation magnetic path is generated in the bypass core 64 (in a section along the plane that passes the axis of rotation of the rotor), as indicated by arrow B2 in FIG. 8. The current of the flux regulation coil 68 is also controlled by the controller 40, based on the rotational speed and torque of the rotor 28, for example.

[0020] In the axially one side portion (left side portion in FIG. 6) of the rotary electric machine, the magnetic flux of the permanent magnets 48s crosses the stator coil 38 as indicated by arrows C2 in FIG. 9, to provide effective magnetic flux. However, when no current is passed through the flux regulation coil 68, the magnetic flux of the permanent magnets 48s does not cross the stator coil 38, in the axially other side portion (right side portion in FIG. 6), but passes through the rotor core portion 46-2, protruding portion 66-2, bypass core 64, protruding portion 66- 1, and the rotor core portion 46-1, to be thus short-circuited, as indicated by arrows D2, E2 in FIG. 9. As a result, the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 is reduced for field weakening. When the rotational speed of the rotor 28 is higher than a set speed, for example, no current is applied to the flux regulation coil 68, so as to effect field weakening, i.e., weaken the field.

[0021] On the other hand, when a current is applied to the flux regulation coil

68 in the direction indicated by arrow A2 in FIG. 7, magnetic flux that passes through the magnetic path portion 64b is saturated. In this case, the magnetic resistance of the magnetic path portion 64b is increased to provide magnetic permeability equivalent to that of air, and the magnetic flux of the permanent magnets 48s passing through the bypass core 64 is reduced. As a result, in the above-indicated axially other side portion of the rotary electric machine, too, the magnetic flux of the permanent magnets 48s crosses the stator coil 38 as indicated by arrows F2 in FIG. 8. In this manner, the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 is increased, resulting in increase in the strength of the magnetic field (field strengthening). When the torque of the rotor 28 is larger than a set torque, for example, a current equal to or larger than a given value is applied to the flux regulation coil 68 in the direction indicated by arrow A2 in FIG. 7, so as to strengthen the field. In comparison with the case where no current is applied to the flux regulation coil 68, the magnetic flux of the permanent magnets 48s acting on the stator 24 can be increased, by applying a current to the flux regulation coil 68 in such a direction (direction indicated by arrow A2 in FIG. 7) as to reduce the magnetic flux of the permanent magnets 48s passing through the bypass core 64. The amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 is changed through control of the current of the flux regulation coil 58, in substantially the same manner as in the embodiment shown in FIG. 1 through FIG. 3.

[0022] In the case where the protruding portions 56-1, 56-2 are provided on the opposite sides of the permanent magnets 48s as viewed in the direction of magnetization, as shown in FIG. 10, for example, as compared with the embodiment of FIGS. 1 - 3, the magnetic flux produced by current applied to the flux regulation coil 58 (in the direction indicated by arrow Al in FIG. 2) and the magnetic flux produced by the permanent magnets 48s flow in opposite directions and act repulsively against each other, in the magnetic path portion 54b of the bypass core 54, as indicated by arrows Bl, D2 in FIG. 10, and the magnetic flux passing through the magnetic path portion 54b is not saturated. In this case, even if a current is applied to the flux regulation coil 58 (in the direction indicated by arrow Al in FIG. 2), the magnetic flux of the permanent magnets 48s passing through the bypass core 54 is not reduced, and the amount of field magnetic flux of the permanent magnets 48s which crosses the stator coil 38 is not increased. Thus, in the embodiment of FIGS. 1 - 3, the amount of field magnetic flux acting on the stator 24 through control of current of the flux regulation coil 58 can be adjusted only with respect to the permanent magnets 48n of the rotor 28. On the other hand, in the embodiment of FIGS. 6, 7, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 can be changed by controlling the current of the flux regulation coil 58, and the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 can be changed by controlling the current of the flux regulation coil 68. Accordingly, the amount of field magnetic flux can be adjusted with respect to all of the permanent magnets 48n, 48s of the rotor 28, and the effect of changing the amount of field magnetic flux can be improved. Also, the magnetic paths for adjusting the amount of field magnetic flux of the permanent magnets 48n, 48s may be provided only on the axially opposite sides of the rotor 28, and need not be provided at the outer periphery of the stator; therefore, the outside diameter of the rotary electric machine can be reduced, and the overall size of the machine can be reduced.

[0023] In an embodiment shown in FIG. 11, a cutout (void) 54d is formed in the circumferential direction in a portion of the bypass core 54 which is located on the axially other side (closer to the rotor core 46) of the flux regulation coil 58, as compared with the embodiment shown in FIGS. 1 - 3. The cutout 54d is located on the radially inner side of the protruding portion 56-1 and the radially outer side of the protruding portion 56-2. Since the cutout (void) 54d is formed in the magnetic path of the bypass core 54 around the flux regulation coil 58, unlike the embodiment shown in FIGS. 1 - 3, no circulation magnetic path is formed around the flux regulation coil 58 in the bypass core 54.

[0024] When no current is applied to the flux regulation coil 58, the magnetic flux of the permanent magnets 48n do not cross the stator coil 38, in an axially one side portion (left side portion in FIG. 11) of the rotary electric machine, but passes through the rotor core portion 46-1, protruding portion 56-1, bypass core 54, protruding portion 56-2, and the rotor core portion 46-2, as indicated by arrow El in FIG. 12, to be thus short-circuited. As a result, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 is reduced, and the field can be weakened. When the rotational speed of the rotor 28 is higher than a set speed, for example, no current is applied to the flux regulation coil 58, so that the field is weakened.

[0025] On the other hand, if a current is applied to the flux regulation coil 58 in the same direction as the direction indicated by arrow Al in FIG. 2, magnetomotive force is generated in a direction indicated by arrow Gl in FIG. 13, in the bypass core 54 around the flux regulation coil 58. The magnetomotive force produced by the current of the flux regulation coil 58 is applied in a direction opposite to the direction in which the magnetic flux of the permanent magnets 48n passes through the bypass core 54. Accordingly, the magnetic flux of the permanent magnets 48n passing through the bypass core 54 is pushed back by the magnetomotive force produced by the current of the flux regulation coil 58, and crosses the stator coil 38 as indicated by arrow Fl in FIG. 13 in the axially one side portion, too. Thus, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 is increased, and the field can be strengthened. When the torque of the rotor 28 is larger than a set torque, for example, a current is applied to the flux regulation coil 58 in the same direction as that indicated by arrow Al in FIG. 2, so that the field is strengthened. Thus, in comparison with the case where no current is applied to the flux regulation coil 58, the magnetic flux of the permanent magnets 48n acting on the stator 24 can be increased, by applying current to the flux regulation coil 58 in such a direction (the same direction as that indicated by arrow Al in FIG. 2) as to reduce the magnetic flux of the permanent magnets 48n passing through the bypass core 54. Further, by controlling the current that flows through the flux regulation coil 58 (in the same direction as that indicated by arrow Al in FIG. 2), the amount of magnetic flux of the permanent magnets 48n passing through the bypass core 54 can be controlled, and the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 can be controlled.

[0026] Further, in an embodiment shown in FIG. 14, a cutout (void) 64d is formed in the circumferential direction in a portion of the bypass core 64 on the axially one side (closer to the rotor core 46) of the flux regulation coil 68, as compared with the embodiments shown in FIGS. 6, 7 and 11. The cutout 64d is located on the radially inner side of the protruding portion 66-1, and on the radially outer side of the protruding portion 66-2.

[0027] When no current is applied to the flux regulation coil 68, the magnetic flux of the permanent magnets 48s do not cross the stator coil 38 in the axially other side portion (right side portion in FIG. 14) of the rotary electric machine, but passes through the rotor core portion 46-2, protruding portion 66-2, bypass core 64, protruding portion 66-1, and the rotor core portion 46-1, as indicated by arrow E2 in FIG. 15, to be short-circuited. Thus, the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 is reduced, and the field can be weakened. When the rotational speed of the rotor 28 is higher than a set speed, for example, no current is applied to the flux regulation coil 68, so that the field is weakened.

[0028] On the other hand, when a current is applied to the flux regulation coil 68 in the same direction as that indicated by arrow A2 in FIG. 7, magnetomotive force is generated in a direction indicated by arrow G2 in FIG. 16, in the bypass core 64 around the flux regulation coil 68. The magnetomotive force produced by the current of the flux regulation coil 68 is applied in the direction opposite to that of the magnetic flux of the permanent magnets 48s which passes through the bypass core 64. Accordingly, the magnetic flux of the permanent magnets 48n passing through the bypass core 64 is pushed back by the magnetomotive force produced by the current of the flux regulation coil 68, and crosses the stator coil 38 as indicated by arrow F2 in FIG. 16 in the axially other side portion, too. Thus, the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 is increased, and the field can be strengthened. When the torque of the rotor 28 is larger than a set torque, for example, a current is applied to the flux regulation coil 68 in the same direction as that indicated by arrow A2 in FIG. 7, so that the field can be strengthened. Thus, in comparison with the case where no current is applied to the flux regulation coil 68, the magnetic flux of the permanent magnets 48s acting on the stator 24 can be increased, by applying current to the flux regulation coil 68 in such a direction (the same direction as that indicated by arrow A2 in FIG. 7) as to reduce the magnetic flux of the permanent magnets 48s passing through the bypass core 64. Further, by controlling the current that flows through the flux regulation coil 68 (in the same direction as that indicated by arrow A2 in FIG. 7), the amount of magnetic flux of the permanent magnets 48s passing through the bypass core 64 can be controlled, and the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 can be controlled. In this connection, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 is changed by controlling the current of the flux regulation coil 58, in substantially the same manner as that of the embodiment shown in FIG. 1 through FIG. 3.

[0029] In the embodiment of FIG. 11, the amount of field magnetic flux acting on the stator 24 can be adjusted through control of the current of the flux regulation coil 58, only with respect to the permanent magnets 48n of the rotor 28. According to the embodiment of FIG. 14, on the other hand, the amount of field magnetic flux can be adjusted with respect to all of the permanent magnets 48n, 48s of the rotor 28, and the effect of changing the amount of field magnetic flux can be improved.

[0030] In an embodiment shown in FIG. 17, the bypass core 54 is located between the protruding portions 56-1, 56-2 as viewed in the radial direction, and the bypass core 54 is opposed to the protruding portions 56-1, 56-2 with given clearances (magnetic gaps) formed therebetween in the radial direction, as compared with the embodiment shown in FIG. 11. In the embodiment shown in FIG. 17, the amount of field magnetic flux of the permanent magnets 48n acting on the stator 24 is changed through control of current of the flux regulation coil 58, in substantially the same manner as that of the embodiment shown in FIG. 11. While the magnetic gaps are provided in the axial direction between the bypass core 54 and the protruding portions 56-1, 56-2 in the embodiments shown in FIGS. 1 - 3 and 11, the magnetic gaps are provided in the radial direction between the bypass core 54 and the protruding portions 56-1, 56-2 in the embodiment shown in FIG. 17, so that changes in the magnetic resistance in the magnetic gaps in response to axial displacement of the rotor 28 can be curbed or reduced. Further, the protruding portions 56-1, 56-2 and the bypass core 54 are arranged side by side in the radial direction, so that the axial length of the rotary electric machine can be shortened, and the overall size of the machine can be reduced.

[0031] Further, in an embodiment as shown in FIG. 18, the bypass core 64 is located between the protruding portions 66-1, 66-2 as viewed in the radial direction, and the bypass core 64 is opposed to the protruding portions 66-1, 66-2 with given clearances (magnetic gaps) formed therebetween in the radial direction, as compared with the embodiments shown in FIG. 14 and FIG. 17. In the embodiment shown in FIG. 18, the amount of field magnetic flux of the permanent magnets 48s acting on the stator 24 is changed through control of current of the flux regulation coil 68, in substantially the same manner as that of the embodiment shown in FIG. 14. While the magnetic gaps are provided in the axial direction between the bypass core 64 and the protruding portions 66-1, 66-2, in the embodiments shown in FIGS. 6, 7 and 14, the magnetic gaps are provided in the radial direction between the bypass core 64 and the protruding portions 66-1, 66-2 in the embodiment shown in FIG. 18, so that changes in the magnetic resistance in the magnetic gaps in response to axial displacement of the rotor 28 can be curbed or reduced. Further, the protruding portions 66-1, 66-2 and the bypass core 64 are arranged side by side in the radial direction, so that the axial length of the rotary electric machine can be shortened, and the overall size of the machine can be reduced.

[0032J In one form of the invention, the magnets may include a first set of magnets in which magnetic poles located closer to the stator are north poles, and a second set of magnets in which magnetic poles located closer to the stator are south poles, and the protruding portions may be provided on the opposite sides of one of the first set of magnets and the second set of magnets as viewed in a direction of magnetization thereof.

[0033] In one form of the invention, the protruding portions may protrude axially outwards from the surface of the rotor including axial end faces of the magnets.

[0034] In one form of the invention, the magnets may include a first set of magnets in which magnetic poles located closer to the stator are north poles, and a second set of magnets in which magnetic poles located closer to the stator are south poles, and the bypass core may include a first bypass core configured to permit magnetic flux of the first set of magnets to pass therethrough without passing through the stator, and a second bypass core configured to permit magnetic flux of the second set of magnets to pass therethrough without passing through the stator. The flux regulation coil may include a first flux regulation coil configured to regulate the magnetic flux of the first set of magnets passing through the first bypass core, and a second flux regulation coil configured to regulate the magnetic flux of the second set of magnets passing through the second bypass core. The rotor core may include first protruding portions that protrude toward the first bypass core from a surface of the rotor to which the first set of magnets are exposed, and the first protruding portions may be provided on opposite sides of the first set of magnets as viewed in a direction of magnetization thereof. The rotor core may further include second protruding portions that protrude toward the second bypass core from a surface of the rotor to which the second set of magnets are exposed, and the second protruding portions may be provided on opposite sides of the second set of magnets as viewed in a direction of magnetization thereof. The first bypass core may be opposed to the first protruding portions, and the second bypass core may be opposed to the second protruding portions.

[0035] In one form of the invention, the first bypass core may be opposed to one axial end face of the rotor core, and the second bypass core may be opposed to the other axial end face of the rotor core.

[0036] While some embodiments of the invention have been described, the invention is by no means limited to these embodiments, but may be embodied in various forms, without departing from the principle of the invention. Also, parts of the illustrated embodiments may be combined as appropriate, without departing from the principle of the invention.