JP6916133B2 - Brushless motor - Google Patents

Description

The present invention relates to a brushless motor, and more particularly to an electric motor provided with a transmission mechanism using a worm gear or the like.

Conventionally, as a means for reducing torque ripple and cogging of a brushless motor (hereinafter abbreviated as a motor), a so-called skew structure in which the position where the polarity of the magnetic pole is switched (magnetic pole boundary position) is shifted in the rotational direction along the axial direction. It has been known. However, in a motor having such a skew structure, as the magnetic pole boundary position is tilted, the rotational force due to magnetic attraction and repulsion and the thrust force (force along the extension direction of the rotation axis: thrust electromagnetic force) due to the axial component thereof. Occurs. Therefore, for example, as in Patent Document 1, a configuration has been proposed in which the tilt direction of the skew is switched along the axial direction, that is, the thrust force is canceled by so-called V-skew magnetism.

Japanese Unexamined Patent Publication No. 2014-107951

However, in the above-mentioned V-skew magnetism, although the force in the thrust direction can be canceled out, the thrust force of the rotor is almost nonexistent during the rotation of the motor. For this reason, the thrust position of the rotor becomes unstable, and in a motor having a V-skew structure, the meshing state of the gears in the reduction mechanism becomes discontinuous, and the lack of thrust force causes noise and vibration. There was a challenge. Further, although the thrust electromagnetic force is canceled out and almost disappears, as shown in FIG. 7, there is a problem that the rotor position becomes more unstable and the sound and vibration worsen due to the presence of ripples in the residual portion.

An object of the present invention is to stabilize the thrust position of a rotor and suppress sound and vibration in a brushless motor having a skew structure.

The brushless motor of the present invention has a stator having a stator core, a winding wound around the stator core, a rotating shaft arranged radially inside the stator, and a pole polarity fixed to the rotating shaft. A brushless motor having a rotor having a skew structure in which the magnetic pole boundary position at which the switch is switched is shifted in the rotation direction along the extension direction of the rotation axis, and the magnets are provided at both ends in the axial direction. The overhang portion has an overhang portion extending in the axial direction from each of the axial end portions of the stator core, and the overhang portion has different extension amounts with respect to the axial end portion of the stator core. The skew structure has a first skew portion and a second skew portion whose magnetic pole boundary positions deviate from each other in the rotation direction, and the connection point between the first skew portion and the second skew portion is the magnet. It is characterized in that it is arranged at a position offset in the axial direction from the axial center position of the overhang portion to the overhang portion side having a large extension amount.

The other brushless motor of the present invention includes a stator including a stator core, a winding wound around the stator core, a rotating shaft arranged radially inside the stator, and a magnetic pole fixed to the rotating shaft. A brushless motor including a rotor having a skew structure in which the magnetic pole boundary position at which the polarity of the above is switched is shifted in the rotation direction along the extension direction of the rotation axis, and the magnet is one end in the axial direction thereof. The portion has an overhang portion extending in the axial direction from the axial end portion of the stator core, and the skew structure has a first skew portion in which the direction in which the magnetic pole boundary position deviates in the rotational direction is different from each other. It has a second skew portion, and the connection point between the first skew portion and the second skew portion is arranged at a position axially offset from the axial center position of the magnet to the overhang portion side. It is characterized by.

In the present invention, a so-called V-skew structure is adopted in which the tilt direction of the magnetic pole boundary position in the rotor magnet (rotor magnet) is switched along the axial direction to balance the thrust electromagnetic force, while the end portion of the magnet is used. Is provided with an overhang portion that is asymmetric in the axial direction. That is, overhang portions having different extension amounts (overhang amounts) are provided at both ends of the magnet, or overhang portions are provided only at one end of the magnet. As a result, a constant thrust electromagnetic force is generated, and the thrust position of the rotor is stabilized while the motor is rotating. As a result, the generation of noise and vibration is suppressed, such as the meshing state of the gears in the reduction mechanism being stabilized. Further, regarding the refraction position of the magnetic pole boundary position in the V-skew structure, when there are overhang portions at both ends of the magnet, the side with the larger overhang amount, or when there is an overhang portion on only one side, the overhang portion is present. , Move to the side where the overhang part exists. As a result, the ripple of the thrust electromagnetic force can be reduced, the thrust position of the rotor is further stabilized, and sound and vibration are suppressed more effectively.

According to the brushless motor of the present invention, in a brushless motor having a skew structure in which the magnetic pole boundary position of the rotor magnet is displaced in the rotational direction along the extension direction of the rotation axis, the inclination direction of the magnetic pole boundary position is switched along the axial direction. By adopting a so-called V-skew structure and providing an overhang portion at at least one end of the magnet, the thrust position of the rotor during motor rotation is stabilized, and noise and vibration can be suppressed. Further, regarding the refraction position of the magnetic pole boundary position in the V-skew structure, when there are overhang portions at both ends of the magnet, the side with the larger overhang amount, or when there is an overhang portion on only one side, the overhang portion is present. By moving it closer to the side where the overhang portion exists, the ripple of the thrust electromagnetic force can be reduced, the thrust position of the rotor can be further stabilized, and sound and vibration can be suppressed more effectively.

It is sectional drawing which shows the structure of the motor unit which is one Embodiment of this invention. It is explanatory drawing which shows the relationship between the rotor and the stator in the motor unit of FIG. It is a graph which compared and showed the thrust electromagnetic force when the asymmetric overhang is provided and the thrust electromagnetic force when the overhang part is not provided. It is explanatory drawing which shows the skew structure of a magnet. It is a graph which shows the relationship between the refraction position in V-skew magnetism, and the 4th-order component and the 12th-order component of thrust electromagnetic force. It is a graph which compared the ripple of the thrust electromagnetic force for each refraction position. It is explanatory drawing which shows the ripple which occurs in the residual part of the thrust electromagnetic force in the conventional motor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a motor unit 1 using a brushless motor according to an embodiment of the present invention. The motor unit 1 of FIG. 1 is composed of a brushless motor 2 (hereinafter abbreviated as motor 2) and a reduction mechanism unit (transmission mechanism) 3. For example, a sunroof of an automobile, a wiper device, a power window, and a power. It is used as a drive source for seats and the like. In the motor unit 1, the rotation of the rotation shaft 4 of the motor 2 is changed in the speed reduction mechanism unit 3, and is output from the output shaft 5 to the outside of the unit.

The motor 2 is a brushless motor, and is composed of a stator 11 and a rotor 12 rotatably arranged in the stator 11. The stator 11 includes a bottomed tubular motor housing 13 and a stator core 14 fixed to the inner surface of the motor housing 13. The stator core 14 is formed by laminating a plurality of plates made of a magnetic material, and has a plurality of (here, 6) slots 15 extending in the axial direction. A coil 16 forming a multi-phase winding is wound in the slot 15. The rotor 12 includes a rotating shaft 4 and a magnet 17 fixed to the rotating shaft 4. One end side of the rotating shaft 4 is rotatably supported by bearings 18 arranged at the ends of the motor housing 13. The magnet 17 is a rare earth permanent magnet such as neodymium, dysprosium, and samarium, and a ring magnet (here, quadrupole magnetization) magnetized so as to have different polarities along the circumferential direction is used. ..

The reduction mechanism portion 3 is composed of a worm 6 formed on the rotating shaft 4 and a worm wheel (driven gear) 6 that meshes with the worm (drive gear) 5, and is formed of synthetic resin or aluminum die casting. It is arranged in the gear case 21. As shown in FIG. 1, one end opening side of the motor housing 13 is fixed to the gear case 21. The rotating shaft 4 of the motor 2 extends into the gear case 21, and the rotating shaft 4 is rotatably supported by bearings 22 and bearings 23 provided in the gear case 21. The worm wheel 7 is fixed to the output shaft 5, and the output shaft 5 rotates together with the worm wheel 7. In the worm 6 and the worm wheel 7, the tooth surfaces 6a and 7a are not parallel to the thrust direction X (extension direction of the rotation shaft 4), but are inclined with respect to the thrust direction.

FIG. 2 is an explanatory diagram showing the relationship between the rotor 12 and the stator 11. As shown in FIG. 2, in the motor 2, the axial length Lm of the magnet 17 on the rotor 12 side is longer than the axial length Lc of the stator core 14 on the stator 11 side. An overhang portion (first overhang portion 33, second overhang portion 34) extending in the axial direction without facing the stator core 14 is provided at both ends of the magnet 17 in the axial direction. .. Further, in the motor 2, the overhang amounts (extension amount) OH1 and OH2 of the first overhang portion 33 and the second overhang portion 34 are different, and the overhang amount OH2 of the second overhang portion 34 is larger. Is increasing (OH1 <OH2). That is, the first and second overhang portions 33 and 34 are provided asymmetrically in the axial direction.

By forming one of the first and second overhang portions 33 and 34 larger in this way, a thrust electromagnetic force is always generated in one direction in the rotor 12. FIG. 3 is a graph showing a comparison between the thrust electromagnetic force when the asymmetric overhang is provided and the thrust electromagnetic force when the overhang portion is not provided. The waveform of the conventional structure in FIG. 3 is scaled up in the Y-axis direction to be the waveform of FIG. 7. As shown in FIG. 3, the thrust electromagnetic force is almost 0 when there is no overhang portion, whereas in a motor provided with an asymmetric overhang portion such as the motor 2, the thrust electromagnetic force is always constant in a constant direction. Force is generated. Therefore, the thrust position of the rotor during the rotation of the motor is stable, and the meshing state of the gears in the reduction mechanism is stable. Therefore, it is possible to suppress noise and vibration generated by discontinuous gear meshing and the like.

Further, as shown in FIG. 2, in the motor 2, the magnetic pole boundary line P of the magnet 17 is skew-magnetized so as to be displaced in the radial direction along the axial direction. FIG. 4 is an explanatory diagram showing a skew structure of the magnet 17. As shown in FIGS. 2 and 4, in the magnet 17, the inclination direction of the magnetic pole boundary line P is switched along the axial direction, and the magnetic pole boundary line P is formed in a V shape. That is, the magnet 17 is so-called V-skew magnetized, and the first skew portion 31 and the second skew portion 32 having different inclination directions are provided along the axial direction. The start point Q1 and the end point Q2 of the magnetic pole boundary line P exist at the same position in the axial direction, and the angle θ in the circumferential direction between the start point Q1 / end point Q2 and the turning point M is a skew angle. Either the point Q1 or the point Q2 may be the start point or the end point.

The connection point between the first skew portion 31 and the second skew portion 32 is a folding point M of the magnetic pole boundary line P. The position of the folding point M (skew refraction position: hereinafter referred to as a refraction position) is a position deviated from the axial center position C of the magnet 17 by a deviation amount δ toward the second overhang portion 34. .. That is, the refraction position of the magnetic pole boundary line P is offset from the axial center position C of the magnet 17 toward the second overhang portion 34, and the first skew portion 31 and the second skew portion 32 are It is formed asymmetrically along the axial direction. Therefore, the axial length Ls1 of the first skew portion 31 and the axial length Ls2 of the second skew portion 32 are longer in the first skew portion 31 located on the side where the overhang amount OH is smaller (Ls1). > Ls2). Here, the ratio Ls1: Ls2 of the axial lengths of both is set to Ls1: Ls2 = 6.5: 3.5 because Ls1 is large.

FIG. 5 is a graph showing the relationship between the refraction position (Ls1: Ls2) of the magnetic pole boundary line P in the V-skew structure and the fourth-order and twelfth-order components of the thrust electromagnetic force, and FIG. 6 is the ripple (rotation) of the thrust electromagnetic force. It is a graph which compared the angle (electrical angle) and the thrust electromagnetic force) for each refraction position. In each case, the ratio of the overhang amounts OH1 and OH2 of the first and second overhang portions 33 and 34 is 1: 2 (OH1: OH2 = 1: 2) in the 4-pole 6-slot motor. ..

As shown in FIG. 5, the fourth-order component of the thrust electromagnetic force decreases in the range of Ls1: Ls2 = 6: 4 to 7: 3, and is the smallest in the case of 6.5: 3.5. Further, the 12th-order component of the thrust electromagnetic force also has a relatively low refraction position in the range of 6: 4 to 7: 3, and is the smallest in the case of 6.5: 3.5. On the other hand, as shown in FIG. 6, the ripple of the electromagnetic force is also suppressed to be smaller when the refraction positions are 6: 4, 6.5: 3.5, and 7: 3 than when the ratios are other. That is, in order to suppress the ripple of the thrust electromagnetic force, it is preferable to set the refraction position of the V skew in the range of 6: 4 to 7: 3, preferably 6.5: 3.5. In response to this, the motor 2 of the present embodiment is also set to Ls1: Ls2 = 6.5: 3.5 as described above.

In this way, while adopting the V-skew structure, the refraction position of the magnetic pole boundary line P is moved to the larger second overhang portion 34 side, and the position is set to Ls1: Ls2 = 6: 4 to 7: 3. By setting to, it is possible to reduce the ripple (thrust vibration) of the thrust electromagnetic force. As a result, it becomes possible to suppress noise and vibration caused by discontinuity of tooth meshing in a reduction mechanism such as a worm.

As described above, the motor 2 according to the present invention balances the thrust electromagnetic force by the V-skew structure, while always generating a constant thrust electromagnetic force by adopting the asymmetric overhang structure. As a result, the thrust position of the rotor during the rotation of the motor is stabilized, and noise and vibration can be suppressed. Further, by moving the refraction position of the magnetic pole boundary line P in the V-skew structure closer to the larger overhang portion side, the ripple of the thrust electromagnetic force can be reduced, and the thrust position of the rotor can be further stabilized. , Sound and vibration can be suppressed more effectively.

It goes without saying that the present invention is not limited to the above-described embodiment and can be variously modified without departing from the gist thereof.
For example, in the above-described embodiment, the configuration in which the overhang portions 33 and 34 are provided at both ends in the axial direction of the magnet 17 is shown. It is also possible to apply the invention. In this case, the folding point M (refraction position) of the magnetic pole boundary line P is provided at a position offset to the side where the overhang portion exists, and overhangs the skew portion (first skew portion) on the side without the overhang portion. It is formed longer in the axial direction than the skew portion (second skew portion) on the side with the hang portion (Ls1> Ls2). Then, the ratio Ls1: Ls2 of the axial lengths of the first and second skew portions is set in the range of 6: 4 to 7: 3, preferably 6.5: 3.5.

Further, in FIG. 2, the N side of the magnetic pole boundary line P is convex and the S side is concave, but the inclination direction of the magnetic pole boundary line P may be the opposite. Further, in the above-described embodiment, the configuration in which the ring magnet is used for the magnet 17 is shown, but a segment magnet may be used. In that case, a plurality of magnets are arranged while being displaced in the radial direction along the axial direction. A so-called step skew structure may be used.

In addition, the motor 2 has an SPM (Surface Permanent Magnet) configuration in which the magnet 17 directly faces the stator core 14, but an IPM (Interior Permanent Magnet) in which a steel rotor core is provided on the rotor side and a magnet is embedded inside the rotor core. The present invention can also be applied to a motor having a configuration. In the present invention, the term "fixed to the rotating shaft" means not only the form in which the magnet is directly fixed to the rotating shaft, but also the inside or the outer periphery of the rotor core or the like attached to the rotating shaft. It also includes a form in which a magnet is fixed to a rotating shaft via a rotor core or the like.

The brushless motor according to the present invention can be widely applied not only to in-vehicle motors of automobiles but also to electric motors used in home appliances, industrial machines and the like.

1 Motor unit 2 Brushless motor 3 Reduction mechanism 4 Rotating shaft 5 Output shaft 6 Warm (drive gear)
6a Tooth surface 7 Worm wheel (driven gear)
7a Tooth surface 11 Stator 12 Rotor 13 Motor housing 14 Stator core 15 Slot 16 Coil 17 Magnet 18 Bearing 21 Gear case 22 Bearing 23 Bearing 31 1st skew part 32 2nd skew part 33 1st overhang part 34 2nd overhang part C magnet Axial center position Lm Magnet Axial length Lc Stator core Axial length Ls1 1st skew Axial length Ls2 2nd skew Axial length M Folding point of magnetic pole boundary line OH Magnet overhang amount OH1 1st overhang part overhang amount OH2 2nd overhang portion Overhang amount P Magnetic pole boundary line Q1 Start point of magnetic pole boundary line Q2 End point of magnetic pole boundary line X Thrust direction δ: Deviation amount

Claims (2)

A stator comprising a stator core and windings wound around the stator core,
A magnet having a skew structure in which a rotation shaft arranged inside the stator in the radial direction and a magnetic pole boundary position fixed to the rotation shaft and switching the polarity of the magnetic poles are displaced in the rotation direction along the extension direction of the rotation shaft. A rotor with, and a brushless motor with.
The magnet has overhangs extending axially from each of the axial ends of the stator core at both ends in the axial direction, and the overhangs extend with respect to the axial ends of the stator core, respectively. The amount of extension is different from each other,
The skew structure has a first skew portion and a second skew portion in which the directions in which the magnetic pole boundary positions deviate in the rotational direction are different from each other.
The connection point between the first skew portion and the second skew portion is located at a position offset in the axial direction from the axial center position of the magnet to the overhang portion having a large extension amount in the overhang portion. A brushless motor that is characterized by being used. A stator comprising a stator core and windings wound around the stator core,
A magnet having a skew structure in which a rotation shaft arranged inside the stator in the radial direction and a magnetic pole boundary position fixed to the rotation shaft and switching the polarity of the magnetic poles are displaced in the rotation direction along the extension direction of the rotation shaft. A rotor with, and a brushless motor with.
The magnet has an overhang portion extending axially from the axial end portion of the stator core at one end portion in the axial direction.
The skew structure has a first skew portion and a second skew portion in which the directions in which the magnetic pole boundary positions deviate in the rotational direction are different from each other.
A brushless motor characterized in that the connection point between the first skew portion and the second skew portion is arranged at a position offset in the axial direction from the axial center position of the magnet to the overhang portion side.

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