JP2008048481A - Permanent magnet type motor - Google Patents

Abstract

An object of the present invention is to reduce cogging torque of a permanent magnet motor to reduce vibration and noise.
A plurality of permanent magnets 5 provided in a rotor 3 are divided into two in the rotational axis direction, and the divided permanent magnets 5 are arranged so as to be shifted from each other in the circumferential position. Among the laminated plates, the portion where the divided permanent magnets have different polarities in the direction of the rotation axis, the portion where the projecting portion 17 has a different polarity from one of the laminated plates constituting the rotor core. The magnetic path of the leakage magnetic flux generated between the different poles was formed. The magnetic energy that contributes to the rotation of the rotor 3 is prevented from changing due to the rotation of the rotor, and the effect of preventing the generation of new cogging torque due to the formation of the step skew is achieved.
[Selection] Figure 1

Description

  The present invention relates to a permanent magnet type motor having a permanent magnet attached to a rotor, and more particularly to a motor with reduced cogging torque to reduce noise and vibration.

  FIG. 11 is a cross-sectional view of a general configuration of a permanent magnet motor 50 in which a field permanent magnet is attached to a rotor. The motor 50 includes a stator 51 and a rotor 52. The stator 51 includes a cylindrical stator core 53 and a stator winding 54. A plurality of magnetic pole teeth 56 are formed inward from the peripheral yoke portion 55 of the stator core 53, and a slot 57 for winding the stator winding 54 is formed between adjacent magnetic pole teeth 56. Yes. A gap 58 is formed between the tip protruding portions of adjacent magnetic pole teeth 56, and the slot 57 is an open slot opened to the rotor 52 side by the gap 58. The stator core 53 having such a shape is manufactured by, for example, stacking a plurality of stator core pieces obtained by punching magnetic steel sheets into a shape as shown in the cross section of the figure.

  The rotor 52 is obtained by attaching a plurality of permanent magnets 61 to a cylindrical rotor core 60, and is rotatably supported inside the stator 51. The illustrated rotor 52 has a surface magnet structure in which the permanent magnet 61 is attached to the surface of the rotor core 60. The plurality of permanent magnets 61 are alternately arranged with N and S poles in the circumferential direction. When the stator winding 54 is energized to form a rotating magnetic field, the rotor 52 rotates around the rotation axis.

In such a permanent magnet type motor 50, when an attempt is made to rotate the rotor 52 at a constant speed by applying a rotational torque from the outside in a non-energized state, uneven rotation occurs in the required torque. This torque unevenness is due to the fact that the static magnetic attractive force acting between the rotor 52 and the stator 51 varies depending on the rotational position, and is called cogging torque. The magnitude of the cogging torque is considered to be a value obtained by differentiating the total magnetic energy of the magnetic path of the magnetic flux created by the permanent magnet 61 with the rotation angle. When the opening (gap) 58 exists in the slot 57 of the rotor core 60 as in the motor 50 shown in FIG. 11, the magnetic resistance of the magnetic path changes with the rotation of the rotor 52, and the total magnetism of the magnetic path. Energy also changes. As a result, cogging torque is generated.
If the cogging torque is large, not only vibration and noise are generated, but also the motor efficiency may be lowered. For these reasons, reducing the cogging torque is a major issue for permanent magnet motors.

  As a conventional technique for reducing the cogging torque, for example, as shown in FIG. 12, the permanent magnet 61 attached to the rotor 52 is divided into a plurality of stages in the axial direction, and the circumferential direction is increased as the divided permanent magnet 61 advances in the axial direction. There is a proposal of forming a so-called step skew, which is attached by changing gradually in steps (see Patent Document 1). This is to try to cancel the cogging torque generated at each stage mutually. However, when the step skew is formed, portions where the permanent magnets having different polarities are close to each other in the axial direction are generated, and a leakage magnetic flux as indicated by an arrow 62 in the drawing is generated at these close portions. When such a leakage magnetic flux is generated, the effective rotational torque is reduced, and the magnetic flux distribution created by the permanent magnet 61 deviates from the sine wave, and the effect of canceling the cogging torque is reduced.

  In order to reduce the leakage magnetic flux when the step skew is formed, a gap 63 is provided between adjacent steps as shown in FIG. 13 (see Patent Document 2), or a nonmagnetic material is interposed in the gap 63. There is a proposal (see Patent Document 3).

Furthermore, there is also a proposal (see Patent Document 4) in which a magnetic insulating layer made of a nonmagnetic material is provided on the stator core portion facing the boundary between adjacent steps in the step skew.
Japanese Utility Model Publication No. 61-17876 JP-A-8-251847 JP 2000-308287 A JP 2003-284276 A

  The stator core is generally manufactured on one production line while being “automatically caulked” by pressing. In order to laminate two kinds of materials, a magnetic material and a non-magnetic material, separate production lines are required, and a caulking process is also required separately. For this reason, using a non-magnetic material for a part of the stator core leads to an increase in manufacturing man-hours, and causes problems such as an increase in parts procurement and mixing of materials.

  The present invention was made to solve such problems of the prior art, and its purpose is to effectively reduce the cogging torque without increasing the number of manufacturing steps, and to reduce the vibration and noise. It is to provide a mold motor.

  A permanent magnet type motor according to a first aspect of the present invention for solving the above-described problems includes a stator having a stator core provided with a plurality of magnetic pole teeth and a stator winding slot, and a plurality of stator magnets on the outer periphery of the rotor core. A permanent magnet motor comprising a rotor configured to be fixed to the stator and rotatably disposed inside the stator, wherein the plurality of permanent magnets are divided into a plurality in the direction of the rotation axis. The divided permanent magnets are arranged so as to be shifted from each other in the circumferential position, and at least a portion of the divided permanent magnets in which the divided permanent magnets have different polarities in the direction of the rotation axis is magnetized. A magnetic layer made of a material is provided.

  In this way, if the permanent magnet attached to the rotor is divided into a plurality of parts in the axial direction and shifted in the circumferential direction, so-called step skew is formed, the cogging torque generated in each divided part cancels each other and is synthesized. The cogging torque is reduced. Further, in the present invention, a magnetic layer made of a magnetic material is disposed at a portion where at least the divided permanent magnets have different polarities in the rotation axis direction among the divided permanent magnets. For this reason, in the part where the different pole magnets generated by the step skew formation are adjacent to each other in the rotation axis direction, the magnetic flux generated between the different pole magnets passes through the magnetic layer. The generated magnetic flux can be prevented from reaching the stator.

  According to the present invention, it is possible to prevent the magnetic flux traveling between the different pole magnets from reaching the stator, so that the magnetic energy contributing to the rotation of the rotor is prevented from changing due to the rotation of the rotor. There is an effect that the generation of new cogging torque due to the formation of the step skew is prevented. Further, since it is not necessary to use two kinds of materials, a magnetic material and a non-magnetic material, for the stator core, the man-hour for manufacturing the stator core is not increased.

  Hereinafter, an embodiment of a permanent magnet type motor according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing the configuration of the stator 2 and the rotor 3 and the arrangement relationship thereof in the permanent magnet type motor 1. Is shown. The rotating shaft necessary for the motor, its support mechanism, stator winding, and motor case are omitted.

  The rotor 3 has a surface magnet structure in which a permanent magnet 5 is attached to the outer surface of a cylindrical rotor core 4, and a center hole 6 for fitting a rotating shaft (not shown) is formed at the center. . The permanent magnet 5 is divided into two in the rotational axis direction and arranged in two stages. The permanent magnet 5 is formed in a substantially arc shape in cross section, and is magnetized so that an N pole and an S pole exist in the thickness (radial direction) direction. The permanent magnet 5 includes a magnet that is magnetized so that the surface side is an N pole, and a magnet that is magnetized so that the surface side is an S pole. Are alternately arranged with a predetermined circumferential gap 7 therebetween. Each of the divided permanent magnets 5 is arranged at a divided portion (step-to-step boundary) 8 with its circumferential position shifted from each other, so that a so-called step skew is formed.

  FIG. 2 is a top view of the stator 2 and the rotor 3 shown in FIG. Only the stator core 9 is shown as the stator 2. A plurality of magnetic pole teeth 11 projecting radially toward the center are formed from the peripheral yoke portion 10 of the stator core 9. The fixed iron core 9 is manufactured by laminating a required number of magnetic steel plates such as silicon steel plates punched into shapes as shown in FIG. 2 and caulking them in the axial direction.

  At the tip end portion of the magnetic pole tooth 11, an overhanging portion 12 that protrudes on both sides in the circumferential direction is provided. A slot 13 is formed between the adjacent magnetic pole teeth 11 for passing the stator winding. A gap 14 is formed between the tip protruding portions 12 of the adjacent magnetic pole teeth 11, and the slot 13 is opened to the rotor 3 side by the gap 14. That is, the slot 13 in this case is an open slot.

  On the other hand, the rotor core 4 of the rotor 3 is laminated in the axial direction by laminating a necessary number of magnetic materials, such as magnetic steel plates such as silicon steel plates, which are each punched into an outer circular shape as shown in FIG. It was made by caulking. The permanent magnets 5 are arranged in two stages on the outer periphery of the rotor core 4. At the boundary of the two-stage permanent magnets 5, as shown in FIG. A considerable gap 15 is formed. Of the laminated plates constituting the rotor core 4, the outer periphery of one laminated plate (magnetic plate) 16 facing the gap 15 at the boundary between the two-stage permanent magnets 5 is shown in FIGS. As shown to a), the protrusion part (magnetic layer) 17 of the rectangular shape corresponding to the number of the permanent magnets 5 of each step is protrudingly provided.

  In the case where a step skew is formed by dividing the permanent magnet 5 in two and shifting it in the circumferential direction, as shown in FIG. 3, the two-stage permanent magnets 5 are arranged in the rotation axis direction (vertical direction in FIG. 3). The part 18 which becomes a different pole arises by the number of the permanent magnets 5 of each step. The plurality of projecting portions 17 projecting from the outer periphery of the laminated plate 16 are between the two-stage permanent magnets 5, and the portions where the permanent magnets 5 have different polarities in the rotational axis direction ( Hereinafter, it is located at the opposite pole portion 18).

  In the present embodiment, the positioning in the circumferential direction is performed as follows in order to correctly position the projecting portion 17 projecting from the outer periphery of the single laminated plate 16 at the opposite pole facing portion 18. That is, a caulking projection 19 as shown in FIG. 5 is formed on the laminating plate constituting the rotor core 4 including the laminating plate 16, and the formation of the caulking projection 19 is convex on one side of the laminating plate, on the opposite side. A recess is formed on one side. And the laminated board laminated | stacked mutually is crimped | bonded by this convex being fitted by a concave (uneven fitting means).

  The laminated plate 16 in which the protrusions 17 are formed is positioned in the circumferential direction with respect to the upper rotor core portion and the lower rotor core portion by this concave-convex fitting. When a permanent magnet is attached to the outer peripheral surface of the rotor core 4, the rotor core 4 is positioned in the circumferential direction on the basis of the unevenness present in the uppermost and lowermost laminated plates, and this positioning state Below, the permanent magnet 5 is stuck. For this reason, the protrusion part 17 comes to be correctly located in the different pole opposing part 18 between the permanent magnets 5 of 2 steps | paragraphs.

  By the way, the cogging torque is caused by a difference in static magnetic attractive force between the stator 2 and the rotor 3 depending on the rotor position, as described in “Background Art”. The magnitude is considered to be a change (differential value depending on the rotation angle) of the total magnetic energy of the magnetic path of the magnetic flux created by the permanent magnet 5 with respect to the rotor rotation angle. The change in the total magnetic energy is caused by the change in the magnetic resistance of the magnetic path due to the rotation of the rotor 3.

  When the rotor 3 is rotated inside the stator core 9 having the open slots as shown in FIG. 2, the gaps 14 of the open slots are scattered in the circumferential direction, so that the magnetic force depends on the rotation angle of the rotor 3. The resistance changes and the total magnetic energy of the magnetic path changes. The open slot gaps 14 exist at equal intervals, and the permanent magnets 5 of the rotor 3 are also mounted at equal intervals. Therefore, the cogging torque is repeatedly generated by the least common multiple of the number of poles of the rotor 3 and the number of slots of the stator 2 while the rotor 3 makes one rotation. One cycle of the cogging torque is equal to the time for which the rotor 3 rotates by dividing the mechanical angle obtained by dividing 360 ° by the least common multiple. In the case of the 8-pole 12-slot configuration as shown in FIG. The time for 15 ° rotation is one cycle of cogging torque.

  The magnitude of the cogging torque changes with a waveform that is almost similar to a sine wave during one period. A curve (1) in FIG. 6 is a waveform example of cogging torque generated in the upper half portion (upper portion) of the rotor 3 in the permanent magnet type motor 1 in FIG. Since the cogging torque changes in such a waveform, it can be expected that if the waveforms are shifted by a half period and added together, the two cogging torques cancel each other and the combined cogging torque can be reduced.

  Curve (2) in FIG. 6 shows that the permanent magnet 5 in the lower half (lower part) of the rotor 3 in the permanent magnet type motor 1 in FIG. This is the magnitude of the cogging torque generated in the lower part of the rotor 3 when the rotor 3 is mounted shifted in the circumferential direction by an amount corresponding to 1/2 of the rotation angle 15 ° of the rotor 3 corresponding to one period waveform of the cogging torque. . The combined cogging torque obtained by synthesizing the upper curve (1) and the lower curve (2) is ideally very small because the waveforms cancel each other as shown by the curve (3) in FIG. Value. However, the cogging torque that is actually generated is not as small as the curve (3) in FIG. 4, but is large as the curve (4) in FIG.

  By the way, the cogging torque can be canceled out by forming the step skew as described above, among the magnetic flux components produced by the permanent magnet 5, the change in magnetic energy due to the component on the plane perpendicular to the rotation axis. Only. Magnetic energy changes due to axial components do not cancel each other.

  When the step skew is formed by dividing the permanent magnet 5 in two and shifting in the circumferential direction, the different-polarity facing portions 18 are formed at several positions as described above. In that part, when it is assumed that there is no protrusion 17, a leakage magnetic flux as indicated by an arrow K in FIG. FIG. 8 schematically shows the magnetic path through which the leakage magnetic flux passes by enlarging the opposite pole facing portion 18. As shown in the figure, the magnetic path of the leakage magnetic flux enters the stator core 9 through the air gap 20 between the rotor 3 and the stator 2 and the air gap 20 and enters the stator core 9 again. 20 and a magnetic path 22 entering the different pole magnet.

  Among these, the magnetic path 22 of the leakage magnetic flux that also passes through the stator core 9 is a magnetic path that is formed when the tip of the magnetic pole teeth 11 of the stator core 9 exists in the opposite pole facing portion 18. In the case where the stator core 9 is formed in an open slot, when the different pole facing portion 18 comes to a position facing the open slot, only the portion corresponding to the open slot is the tip of the magnetic pole teeth 11 (tip overhang portion 14). Will not exist). Therefore, the magnetic path (the magnetic path 22 in FIG. 8) of the leakage magnetic flux that also passes through the stator core 9 is not formed at that position.

  Thus, depending on the presence or absence of the open slot of the stator core 9, the magnetic path is changed by the rotation of the rotor 3, and the magnetic energy due to the magnetic flux component in the rotation axis direction is changed. This change causes cogging torque. That is, when the step skew is formed, a new factor for generating the cogging torque is generated near the boundary.

  In order to prevent the occurrence of cogging torque due to this new factor, the state of the magnetic flux passing between the two permanent magnets 5 in the opposite pole facing portion 18 should always be the same regardless of the rotational position. Then, even if the rotor 3 rotates, the magnetic energy does not change, so that cogging torque is not generated.

  Therefore, in the permanent magnet type motor 1 of the present embodiment, as shown in FIGS. 1, 3, and 4, the protruding portion of the laminated plate 16 is disposed on the opposite-polarity facing portion 18 among the two stages of permanent magnets 5. 17 is interposed. Then, as shown in FIG. 8A, most of the magnetic flux emitted from the N pole among the opposite-polar magnets facing each other passes through the protrusion 17 to the S pole using the protrusion 17 as a magnetic path. Since it comes in, the influence on the torque by the magnetic flux generated between the different pole magnets can be eliminated. Accordingly, it is possible to prevent the generation of new cogging torque due to the leakage magnetic flux newly generated in the opposite pole facing portion 18.

  FIG. 7 compares the magnitude of the cogging torque with and without the measure for reducing the cogging torque according to the present embodiment. The curve of (5) is the measured value when no countermeasure is taken (same as (4) of FIG. 6), and the curve of (6) is the cogging torque of the permanent magnet type motor 1 of this embodiment. The permanent magnet type motor 1 of this embodiment in which measures are taken shows that the cogging torque is greatly reduced.

  In such a permanent magnet type motor 1 of this embodiment, the stator core 9 is entirely made of only a magnetic material, and no nonmagnetic material as described in Patent Document 4 is used. Therefore, the stator core 9 can be manufactured on the same manufacturing line.

  Similarly, the rotor core 4 is also made of a magnetic material and can be manufactured on the same line. Here, the laminated plate provided with the projecting portion 17 and the laminated plate not provided with the projecting portion 17 are the outer shape in a shape that does not form the projecting portion 17 in the outer shape punching station of the progressive press line for punching the laminated plate from the silicon steel plate. The laminate having the projecting portion 17 by selecting only the case of operating the punching die and the case of simultaneously operating the attached die for punching in the shape of the projecting portion 17 projecting from the die, It can be manufactured in the same line as a laminated board that does not have the protrusion 17.

  In the above embodiment, a permanent magnet type motor having 8 poles and 12 slots and permanent magnets attached to the surface of the rotor core is described as an example. However, the same idea applies to motors having different numbers of poles and slots. It can be applied and has the same effect. Furthermore, a magnet-embedded motor in which a permanent magnet is embedded in the stator core, an abduction type (outer rotor type) motor in which a cylindrical rotor with a permanent magnet is rotated outside the stator, and on the stator side The present invention can be similarly applied to a commutator motor in which a rotor core having a permanent magnet and a winding is rotated.

  9 and 10 show another embodiment of the present invention. This embodiment is different from the above-described embodiment in that the laminated plate 23 corresponding to the opposite pole facing portion 18 has a circular shape whose outer diameter is substantially equal to the outer diameter of the rotor 3 including the permanent magnet 5. It is in place. In this laminated plate 23, the outer peripheral portion (magnetic layer) 23 a fills the gap 15 between the two-stage permanent magnets 5, and not only the opposite-pole facing portion 18 of the two-stage permanent magnet 5 but also the same-pole facing portion. 24 is also located.

In this case, as shown in FIG. 10 (a), the outer peripheral portion 23a of the laminated plate 23 located in the same-pole facing portion 24 is magnetized from the N pole of each permanent magnet 5 itself and into its S pole. Compared to FIG. 10B showing the case where the outer peripheral portion 23a is not provided to form the path, the rotational torque of the rotor 3 is slightly reduced, but the function of reducing the cogging torque is one implementation described above. It can be obtained in the same manner as in the case of the form.
(Modified embodiment)
The permanent magnet motor 1 may be modified as follows.

  In the above-described embodiment, the configuration has been described in which the permanent magnet attached to the rotor is divided into two in the direction of the rotation axis and the two-stage skew is provided, but the number of stages may be further increased. In this case, the circumferential shift angle of the permanent magnet between the stages is an angle obtained by dividing the rotation angle (mechanical angle) corresponding to one cycle of the cogging torque generated at each stage by the number of stages. In this way, the combined cogging torque obtained by synthesizing the cogging torque generated at each stage can be canceled more effectively.

  The magnetic layer may be separate from the laminated plates 16 and 24.

The block diagram of the permanent magnet type motor which concerns on one Embodiment of this invention Top view of the rotor and stator of the permanent magnet motor shown in FIG. Development view showing the arrangement of two-stage permanent magnets The perspective view which shows the position of the protrusion part formed in the laminated board in relation to a permanent magnet (A) is a perspective view of a laminated board, (b) is sectional drawing which shows the caulking | bonding state of a laminated board The figure explaining the reduction effect of the cogging torque by the formation of the step skew The figure explaining the reduction of cogging torque when the magnetic layer is provided in the part opposite to the opposite pole (A) is a figure explaining the magnetic path of the leakage magnetic flux when a magnetic layer is provided in the opposite pole opposing part, (b) is a figure explaining the magnetic path of the leakage magnetic flux when there is no magnetic layer in the different pole opposing part. The perspective view which shows other embodiment of this invention. (A) is a figure explaining a magnetic path when a magnetic layer is provided in the same-pole facing part, (b) is a figure explaining a magnetic path when there is no magnetic layer in the same-pole facing part. Sectional view of one configuration of a conventional permanent magnet type motor The perspective view which shows an example of the conventional rotor which formed the step skew The perspective view which shows the other example of the conventional rotor which formed the step skew

Explanation of symbols

  In the drawings, 1 is a permanent magnet motor, 2 is a stator, 3 is a rotor, 4 is a rotor core, 5 is a permanent magnet, 9 is a stator core, 10 is a stator core, 16 is a laminated plate (magnetic plate) ), 17 is a protrusion (magnetic layer), 23 is a laminated plate (magnetic plate), and 23a is an outer peripheral portion (magnetic layer) of the laminated plate.

Claims (4)

A stator having a stator core provided with a plurality of magnetic pole teeth and a stator winding slot, and a plurality of permanent magnets fixed to the outer periphery of the rotor core, and arranged rotatably inside the stator. In a permanent magnet type motor comprising a rotor made of
The plurality of permanent magnets are divided into a plurality in the direction of the rotation axis, and the divided permanent magnets are arranged shifted from each other in the circumferential direction,
A permanent magnet type motor, wherein a magnetic layer made of a magnetic material is provided at least in a portion where the divided permanent magnets have different polarities in the rotational axis direction among the divided permanent magnets. . The permanent magnet type motor according to claim 1,
The rotor iron core has a circular magnetic plate located at a boundary of the permanent magnet divided in the direction of the rotation axis,
The magnetic layer has a diameter larger than that of the rotor core by making the magnetic plate larger in diameter than the rotor core, thereby projecting outward from the rotor core and surrounding the entire circumference of the permanent magnets divided in the rotation axis direction. A permanent magnet type motor characterized in that it is formed so as to intervene in the motor. The permanent magnet type motor according to claim 1,
The rotor iron core has a circular magnetic plate located at a boundary of the permanent magnet divided in the direction of the rotation axis,
The magnetic layer protrudes from an outer periphery of the magnetic plate and is a protrusion that is located at a portion having a different polarity in the rotation axis direction among the permanent magnets divided in the rotation axis direction. A permanent magnet type motor characterized by comprising: In the permanent magnet type motor according to claim 3,
The magnetic plate was positioned in the circumferential direction by means of concave and convex fitting means with the rotor core existing on both sides of the magnetic plate in the direction of the rotation axis, and the protruding portion was divided in the direction of the rotation axis. A permanent magnet type motor configured to be located in a portion having a different polarity in the direction of the rotation axis among the permanent magnets.

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