JP2012050292A - Permanent magnet embedded rotor - Google Patents

Abstract

A permanent magnet embedded rotor capable of realizing field-weakening control with a simple configuration is provided.
A magnetic piece is in contact with the inner surface of a bridge portion of a rotor when the rotational speed is high, while the magnetic piece is in non-contact with the bridge portion when the rotational speed is low. The contact / separation mechanism 30 is provided adjacent to the rotor circumferential end 24a of the permanent magnet 24 embedded in the rotor 14 of the motor.
[Selection] Figure 3

Description

  The present invention relates to a permanent magnet embedded rotor used in a motor.

  2. Description of the Related Art Conventionally, a permanent magnet embedded rotor in which a permanent magnet is embedded in a rotor of a motor (hereinafter, appropriately referred to as an IPM (Interior Permanent Magnet) rotor) is known. Such an IPM rotor is rotatably arranged in a cylindrical starter. A rotating field is formed in the stator by, for example, passing an alternating current through a stator coil wound around a tooth portion arranged in the circumferential direction on the inner peripheral portion of the starter, whereby the IPM rotor is driven to rotate. .

  In order to increase the maximum rotational speed of the permanent magnet type motor, it is necessary to reduce the induced voltage (back electromotive force) generated in the stator coil by the rotation of the rotor embedded with the permanent magnet. When the motor is rotating at a low speed, since the voltage induced in the stator coil by the field by the permanent magnet is small, there is almost no influence on the rotation of the motor. However, when the rotation of the motor increases and the induced voltage becomes equal to the maximum voltage that can be supplied to the motor, the current cannot be supplied to the motor, so the rotation speed cannot be increased, and the torque of the motor rotor is Drops to zero. That is, the rotation speed of the motor when the induced voltage (back electromotive force) becomes equal to the maximum motor supply voltage is the maximum rotation speed.

  In the permanent magnet type motor, even if the current flowing through the stator coil is low, the motor torque can be increased by increasing the magnet torque if the field by the permanent magnet provided on the rotor is increased. However, if the field is strengthened, there arises a problem that the maximum rotational speed of the motor is lowered. In recent years, rare earth magnets are often used in permanent magnet type motors due to high performance of rare earth magnets. However, when a high-performance rare earth magnet is used, a high torque can be obtained at a low speed range, but there arises a problem that the maximum rotational speed of the motor becomes extremely low.

  For this reason, field weakening control is performed in which the electric angle phase of the current flowing in the stator coil is adjusted to reduce the field formed in the stator. By this field weakening control, the maximum number of revolutions of the motor can be increased. In this field weakening control, although the magnet torque is reduced, the reactance torque is increased, so that the total motor torque can be increased.

  JP-A-2002-204541 (Patent Document 1) as a related art document related to this includes a rotor having a plurality of permanent magnets and a stator provided concentrically to surround the rotor. In the permanent magnet type rotary electric motor, the inner ring and the outer ring that are combined in a rotatable state with respect to each other constitute a rotor, and the inner ring and the outer ring are caused to rotate relative to each other by the centrifugal force acting at the time of rotation. It is described that field control by the permanent magnets of the rotor is weakened by shifting the positions of the permanent magnets embedded in each of them, and the field weakening control is performed without operating the current of the stator winding.

JP 2002-204541 A

  However, the permanent magnet type rotary electric motor disclosed in Patent Document 1 requires a mechanism in which the rotor is constituted by a double ring of an inner ring and an outer ring, and a relative rotational movement is generated between the inner ring and the outer ring, and thus the configuration is complicated. There is a problem. In addition, it is preferable to suppress the current flowing through the stator coil during field weakening control in order to suppress the coil and thus the heat generation of the motor.

  An object of the present invention is to provide an IPM rotor capable of realizing field-weakening control with a simpler configuration.

  In the rotor according to the present invention, the magnetic piece is in contact with the inner surface of the bridge portion of the rotor when the rotational speed is high, while the magnetic piece is not in contact with the bridge portion when the rotational speed is low. The contact / separation mechanism is provided adjacent to the rotor circumferential end of a permanent magnet embedded in the rotor of the motor.

  In the rotor according to the present invention, the magnetic piece contact / separation mechanism includes the magnetic piece arranged to be movable in a space formed inside the rotor adjacent to the rotor circumferential end of the permanent magnet, and the rotor rotation It may sometimes include an elastic body whose length is changed by a centrifugal force acting on the magnetic piece.

  In the rotor according to the present invention, the magnetic piece contacts the inner surface of the bridge portion of the rotor during high speed rotation to form a leakage magnetic flux path at the end of the permanent magnet. Thereby, since the leakage magnetic flux from a permanent magnet increases, the field by a permanent magnet is weakened. On the other hand, the leakage flux path is not formed by positioning the magnetic piece away from the inner surface of the bridge portion of the rotor during low-speed rotation. Therefore, the field by the permanent magnet is not weakened, and a magnet torque according to the magnetic force of the permanent magnet can be obtained.

  Thus, according to the rotor according to the present invention, the field-weakening control can be realized by a simple configuration in which a mechanism that allows the magnetic piece to contact and separate from the inner surface of the bridge portion by the centrifugal force during rotation is provided adjacent to the permanent magnet. Is possible.

  In addition, by performing field-weakening control during high-speed rotation as described above, an induced voltage generated in the stator coil can be suppressed. As a result, when the field weakening control is performed by adjusting the current flowing through the stator coil, the coil current can be reduced. As a result, the heat generation of the stator coil and the heat generation of the motor can be effectively suppressed.

It is a figure which shows the axial direction end surface of the motor containing the rotor which is one Embodiment of this invention. It is an enlarged view of the A section in FIG. 1 at the time of low speed rotation. It is an enlarged view of the A section in FIG. 1 at the time of high speed rotation. It is a figure similar to FIG. 2 which shows the rotor of a modification.

  Embodiments according to the present invention will be described below in detail with reference to the accompanying drawings. In this description, specific shapes, materials, numerical values, directions, and the like are examples for facilitating the understanding of the present invention, and can be appropriately changed according to the application, purpose, specification, and the like.

  In the following, “axial direction” refers to the direction along the rotation center axis of the rotor, “radial direction” refers to the direction perpendicular to the rotation center axis, and “circumferential direction” refers to the rotation center axis as the center. A direction along the circumferential direction of a circle drawn on an orthogonal plane.

  FIG. 1 shows an axial end surface of a motor 10 according to an embodiment of the present invention. The motor 10 includes a cylindrical stator 12 and a columnar rotor 14 provided inside the stator 12. The motor 10 is housed in a case or housing (not shown).

  The stator 12 is constituted by a stator core 13 formed by, for example, laminating a large number of silicon steel plates formed in an annular shape by punching in the axial direction and integrally connecting them. On the inner periphery of the stator core 13, a plurality (eight in this embodiment) of teeth portions 16 are arranged at equal intervals in the circumferential direction and protruded radially inward. A slot portion 18 is formed between two adjacent tooth portions 16. The teeth portion 16 and the slot portion 18 have the same axial length as the stator core 13 and extend in the axial direction. A narrow gap is formed between the distal end surface on the radially inner side of the tooth portion 16 and the outer peripheral surface of the rotor 14 so that they do not cushion when the rotor rotates.

  A stator coil 20 is wound around each tooth portion 16 of the stator core 13. The stator coil 20 may be configured such that coils adjacent in the circumferential direction are electrically connected to each other, or a plurality of coils are connected every predetermined number in the circumferential direction to form a multi-phase coil. Although not shown in FIG. 1, each stator coil 20 protrudes outward from both axial end surfaces of the stator core 13, and this protruding portion is also called a coil end portion.

  In the stator 12 having such a configuration, when a voltage is applied to the stator coil 20 from the outside of the motor, a rotating magnetic field is formed in the stator 12 by the teeth portion 16 excited by the stator coil 20. . An IPM rotor, which will be described later, is rotationally driven by being attracted to the rotating magnetic field.

  In addition, although the stator 12 is demonstrated as what is comprised from the integral stator core 13, it is not limited to this, You may be comprised by connecting the division | segmentation core divided | segmented into multiple in the circumferential direction in a ring shape. In this case, the split core can be formed by a dust core, for example. Further, the stator coil may be configured by winding a round conductive wire, or may be formed as an edgewise coil by winding a strip-shaped flat plate. Further, the winding method of the coil around the stator 12 is not limited to the so-called concentrated winding, but may be so-called distributed winding.

  Next, the rotor 14 which is another motor component will be described.

  The rotor 14 includes a rotor core 15 having a columnar shape or a cylindrical shape, and a rotor shaft 22 fixed to the center of the rotor core 15. The rotor core 15 can be configured similarly to the stator core 13 described above. That is, for example, a large number of silicon steel plates punched into a disk shape are stacked in the axial direction and integrally connected by a method such as caulking, bonding, or welding.

  Both ends in the axial direction of the rotor shaft 22 fixed through the central hole of the rotor core 15 are rotatably supported by bearing members attached to a motor case (not shown). In FIG. 1, the rotation center axis X of the rotor shaft 22 is shown as a point.

  The rotor core 15 has a plurality of permanent magnets 24 embedded in the core. In the rotor 14 of the present embodiment, four permanent magnets 24 are fixed inside the rotor core 15 at a position in the vicinity of the outer peripheral surface and evenly arranged in the circumferential direction. The permanent magnet 24 is a flat plate having an elongated end in the axial direction. A magnet insertion hole 26 is formed in the rotor core 15 so as to extend in the axial direction, and a permanent magnet 24 inserted from the axial end surface of the rotor core 15 is bonded to the magnet insertion hole 26 by a resin or the like. It is fixed at a predetermined position.

  As described above, in the rotor 14, the permanent magnet 24 is embedded and fixed inside the rotor core 15, so that the permanent magnet 24 does not separate from the rotor 14 due to centrifugal force during high-speed rotation, and the magnet insertion hole 26 The permanent magnet 24 does not move in the axial direction in the rotor core 15 because it is fixed by bonding or the like.

  The magnet insertion hole 26 formed in the rotor core 15 has a longitudinal width (or radial length) corresponding to the thickness of the permanent magnet 24 that is slightly large enough to allow the permanent magnet 24 to be inserted. On the other hand, the lateral width of the magnet insertion hole 26 (or the length in the direction orthogonal to the radial direction) is longer than that of the permanent magnet 24. As a result, a space is formed adjacent to both ends in the radial direction of the permanent magnet 24 fixed inside the magnet insertion hole 26, and the magnetic piece separating / separating mechanism 30 is provided in the space.

  Next, the magnetic piece separating / separating mechanism 30 will be described with reference to FIGS. 2 is an enlarged view of portion A in FIG. 1 during low-speed rotation, and FIG. 3 is an enlarged view of portion A in FIG. 1 during high-speed rotation.

  Referring to FIG. 2, a space 32 is formed adjacent to the circumferential end 24a of the permanent magnet 24 fixed to the magnet insertion hole 26 of the rotor core 15 as described above. The space 32 is formed to extend over the entire axial length of the rotor core 15. A narrow portion between the radially inner wall surface 34 forming the space 32 and the outer peripheral surface 15 a of the rotor core 15 is a bridge portion 36 of the rotor 14.

  Thus, by providing the space 32 having low magnetic permeability and magnetic resistance adjacent to the circumferential end 24a of the permanent magnet 24, there is an effect of suppressing the leakage magnetic flux at the circumferential end 24a of the permanent magnet 24. In FIG. 2, lines of magnetic force 25a and 25b emerging from the permanent magnet 24 are schematically shown by dotted lines (the same applies to FIGS. 3 and 4). The magnetic lines of force 25a from the radially outer side surface (for example, the N pole surface) of the end 24a of the permanent magnet 24 extend to the outside of the rotor 14 without going around the back side surface (for example, the S pole surface) of the permanent magnet 24. The situation is shown.

  The magnetic piece contacting / separating mechanism 30 provided in the space 32 includes a magnetic piece 38 and an elastic body 40. For example, an iron piece can be suitably used as the magnetic piece 38, but a metal piece made of another magnetic material or the like may be used. The magnetic piece 38 has substantially the same axial length as the permanent magnet 24, and is arranged extending in the space 32.

  For example, a coil spring is preferably used as the elastic body 40. The radially outer end of the elastic body 40 is connected to the magnetic piece 38. On the other hand, the radially inner end of the elastic body 40 is fixed to the inner wall surface facing the bridge portion 36 with the space 32 interposed therebetween. Thus, the length of the elastic body 40 is changed by the centrifugal force acting on the magnetic piece 38 when the rotor 14 rotates. That is, the elastic body 40 is stretched by the centrifugal force acting on the magnetic piece 38 when the rotor 14 rotates at a high speed, and is contracted when the rotor 14 is stopped or rotated at a low speed. The elastic body 40 may be an elastic body other than a coil spring, such as a leaf spring or rubber.

  The magnetic piece 38 has, for example, a sharp apex 39 so as to form a substantially right angle. Accordingly, the inner wall surface 34 of the space 32 is also formed in a recessed shape. Thus, as shown in FIG. 3, when the elastic body 40 is extended during the high-speed rotation of the rotor 14, the top 39 of the magnetic piece 38 is substantially in contact with the inner wall surface 34 of the space 32, that is, the bridge portion 36. It comes to contact without. The shape of the contact surface between the magnetic piece 38 and the bridge portion 36 may be any surface shape, for example, a top portion that curves and protrudes in an arc shape and an inner wall surface that is recessed in an arc shape.

  Subsequently, the operation of the magnetic piece contacting / separating mechanism 30 having the above configuration will be described.

  When the rotor 14 rotates at a low speed, the elastic body 40 remains in a contracted state as shown in FIG. 2, and the magnetic piece 38 is separated from the bridge portion 36 of the rotor 14. As a result, as described above, the magnetic lines of force 25a emitted from the circumferential end 24a of the permanent magnet 24 extend to the outside of the rotor 14 without going around the back surface. As a result, the field by the permanent magnet 24 is not weakened, and a magnet torque according to the magnetic force of the permanent magnet 24 can be obtained.

  On the other hand, when the rotor 14 rotates at a high speed, the elastic body 40 extends due to the centrifugal force acting on the magnetic piece 38 as shown in FIG. Then, the magnetic piece 38 moves in the direction of the arrow B in the space 32 and comes into contact with the bridge portion 36. Thereby, a leakage magnetic flux path passing through the magnetic piece 38 adjacent to the end 24a of the permanent magnet 24 is formed. As a result, a leakage magnetic flux is generated in which the magnetic line of force 25a emitted from the end 24a of the permanent magnet 24 goes around to the back side via the magnetic piece 38 at the position in contact with the bridge portion 36. The field formed outside is weakened. Thus, in the rotor 14 of the present embodiment, field weakening control is achieved by a simple configuration in which a mechanism for bringing the magnetic piece 38 into and out of contact with the inner surface 34 of the bridge portion 36 by a centrifugal force during rotation is provided adjacent to the permanent magnet 24. Can be realized.

  In addition, since the field weakening control can be performed when the rotor 14 rotates at high speed as described above, the induced voltage generated in the stator coil 20 can be suppressed. As a result, when the field weakening control is performed by adjusting the current flowing through the stator coil 20, the coil current can be reduced. As a result, the heat generation of the stator coil 20 and the heat generation of the motor 10 can be effectively suppressed.

  When the rotor 14 rotates at medium speed, the elastic body 40 is slightly extended by the centrifugal force acting on the magnetic piece 38, but the magnetic piece 38 maintains a non-contact state with respect to the bridge portion 36. Therefore, since the space 32 exhibits the leakage magnetic flux suppressing function, the magnet torque is not reduced.

  The rotor according to the present invention is not limited to that of the above-described embodiment, and various improvements or changes can be made.

  For example, as shown in FIG. 4, a partition wall 42 may be provided between the permanent magnet 24 and the magnetic piece 38. The partition wall 42 can be suitably configured by a resin layer or the like. By providing such a partition wall 42, it is possible to prevent the magnetic body piece 38 from coming into direct contact with the permanent magnet 24 to form a leakage magnetic flux path. In addition, by providing the partition wall 42, it is possible to prevent the magnetic piece 38 from vibrating and generating noise in the space 32 while ensuring the smooth mobility of the magnetic piece 38 in the arrow B direction. it can.

  In the above description, the magnetic piece 38 is described or illustrated as being located on the side of the permanent magnet 24 regardless of the rotor rotational speed. However, the present invention is not limited thereto, and the magnetic piece is not limited to the low-speed rotation of the rotor. A magnetic piece contacting / separating mechanism is configured so that it is located away from the permanent magnet radially inward and protrudes radially outward during high-speed rotation of the rotor to come into contact with the bridge portion shown in FIG. Also good.

  DESCRIPTION OF SYMBOLS 10 Motor, 12 Stator, 13 Stator core, 14 Rotor, 15 Rotor core, 15a Rotor outer peripheral surface, 16 teeth part, 18 slot part, 20 Stator coil, 22 Rotor shaft, 24 Permanent magnet, 24a Rotor circumferential direction end, 25a, 25b Magnetic field line, 26 Magnet insertion hole, 30 Magnetic body piece contact / separation mechanism, 32 Space, 34 Inner wall surface or inner surface, 36 Bridge part, 38 Magnetic body piece, 39 Top part, 40 Elastic body, 42 Partition wall, X Rotation center axis.

Claims (2)

  A magnetic piece contacting / separating mechanism in which the magnetic piece comes into contact with the inner surface of the bridge portion of the rotor when the rotational speed is high while the magnetic piece is not in contact with the bridge portion when the rotational speed is low. A rotor provided adjacent to a rotor circumferential end of a permanent magnet embedded in the rotor. The rotor according to claim 1,
The magnetic piece contact / separation mechanism acts on the magnetic piece movably disposed in a space formed inside the rotor adjacent to the rotor circumferential end of the permanent magnet and the magnetic piece when the rotor rotates. A rotor including an elastic body whose length is changed by centrifugal force.

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