JP2017158241A - Single-phase brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single-phase brushless motor capable of reducing electromagnetic vibrations with a lower-order harmonic component of an electromagnetic force defined as an excitation force and noise with the electromagnetic vibrations.SOLUTION: A single-phase brushless motor comprises a stator 10 and a rotor 20. The stator 10 includes a stator core 11 including multiple salient poles 14, and a coil. The salient pole 14 includes a proximal portion 15 around which the coil is wound, and a distal end portion 16 that is spread in a circumferential direction rather than the proximal portion 15. A radial clearance between the distal end portion 16 and the rotor 20 is different between a first end E1 and a second end E2. On a cross section vertical to a rotation axis R of the rotor 20, an angle θ1 formed from a first straight line L1 passing the rotation axis R practically in parallel with a first side face 15c positioned at a front side in a rotation direction of the rotor 20 between both side faces of the proximal portion 15 and a second straight line L2 passing the rotation axis R and the first end E1 is larger than an angle θ2 formed from the first straight line L1 and a third straight line L3 passing the rotation axis R and the second end E2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a single-phase brushless motor.

  There is known a single-phase brushless motor in which a coil is composed of a single phase. In a single-phase brushless motor, in order to realize stable start-up, a gap in the radial direction between the salient pole of the stator core and the rotor may be made different at both ends in the circumferential direction of the salient pole. Conventionally, in order to reduce cogging torque in addition to realizing stable start-up, a single-phase brushless motor configured so that a gap in the radial direction between both ends of the salient pole in the circumferential direction and the rotor satisfies a predetermined relationship has been proposed. It has been proposed (Patent Document 1).

JP 2013-236464 A

  The conventional single-phase brushless motor described above can reduce cogging torque, and thus vibration and accompanying noise.

  However, the demand for reducing the vibration and noise of the single-phase brushless motor does not cease, and it is required to further reduce the vibration and noise. One of the causes of vibration and noise of a single-phase brushless motor is an electromagnetic force generated between the salient poles of the stator core and the magnet, particularly an electromagnetic vibration having a harmonic component as an excitation force. As a result of intensive studies, the present inventors have found that harmonic components of electromagnetic force, and hence electromagnetic vibration can be reduced.

  The present invention has been made in view of such a situation, and an object of the present invention is to reduce electromagnetic vibration using a harmonic component of electromagnetic force as an exciting force, and thus to reduce vibration and noise, and to reduce cogging. The object is to provide a single-phase brushless motor capable of reducing torque.

  In order to solve the above problems, a single-phase brushless motor according to an aspect of the present invention includes a stator and a rotor that rotates with respect to the stator. The stator includes a core having a plurality of salient poles and a coil formed by being wound around the salient poles. The rotor includes a magnet facing the salient pole in the radial direction and having a plurality of magnetic poles in the circumferential direction on the surface on the salient pole side. The salient pole includes a base around which the coil is wound, and a tip that is provided on the magnet side of the base and extends in the circumferential direction from the base. The radial clearance between the tip portion and the rotor is different between the first end portion on the front side in the rotational direction of the rotor and the second end portion on the rear side in the circumferential end portions of the tip portion. In a cross section perpendicular to the rotation axis, a first straight line that passes through the rotation axis and is substantially parallel to a side surface of the both sides of the base located on the front side in the rotation direction of the rotor, and passes through the rotation axis and the first end. The angle formed by the second straight line is larger than the angle formed by the first straight line and the third straight line passing through the rotation axis and the second end.

  According to this aspect, the harmonic component of the electromagnetic force is reduced.

  Note that any combination of the above-described constituent elements, and those obtained by replacing the constituent elements and expressions of the present invention with each other among methods, apparatuses, systems, etc. are also effective as an aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the electromagnetic vibration which makes a harmonic component of an electromagnetic force an excitation force, and the noise accompanying it can be reduced.

It is sectional drawing which shows the single phase brushless motor which concerns on embodiment. FIG. 2 is an enlarged cross-sectional view showing one of salient poles of the stator core of FIG. 1 and its periphery in an enlarged manner. FIG. 3A shows a harmonic component that is a multiple of 4 of the radial electromagnetic force generated between the stator core and the magnet, and FIG. 3B shows the rotational electromagnetic force generated between the stator core and the magnet. It is a figure which shows the harmonic component of the multiple of 4. It is a figure which shows a cogging torque.

  Hereinafter, the same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. In addition, the dimensions of the members in each drawing are appropriately enlarged or reduced for easy understanding. Also, in the drawings, some of the members that are not important for describing the embodiment are omitted.

  FIG. 1 is a cross-sectional view showing a single-phase brushless motor 100 according to an embodiment. FIG. 1 shows a cross section perpendicular to the rotation axis R of the rotor 20. Single-phase brushless motor 100 includes a stator 10 and a rotor 20 that rotates relative to stator 10. In the present embodiment, the rotor 20 rotates in the D direction indicated by the arrow (that is, the clockwise direction in FIG. 1). Stator 10 includes a stator core 11 and a coil 12. The rotor 20 includes a rotor yoke 21 and a magnet 22.

  Hereinafter, a direction parallel to the rotation axis R of the rotor 20 is defined as an axial direction, an arbitrary direction passing through the rotation axis R on a plane perpendicular to the rotation axis R is defined as a radial direction, and a direction closer to the rotation axis R in the radial direction. In the following description, the inner circumferential side, the far side from the rotation axis R is defined as the outer circumferential side, and the direction along the circumference of the circle centering on the rotation axis R on the plane perpendicular to the rotation axis R is defined as the circumferential direction.

  The stator core 11 has an annular portion 13 and four salient poles 14 extending from the annular portion 13 to the outer peripheral side. The stator core 11 is formed by, for example, laminating a plurality of thin electromagnetic steel plates and integrating them by caulking. Each salient pole 14 of the stator core 11 includes a base portion 15 extending from the annular portion 13 to the outer peripheral side, and a tip portion provided on the magnet 22 side of the base portion 15, that is, on the outer peripheral side of the base portion 15, and extending in the circumferential direction of the base portion 15. 16 is included. A coil 12 is wound around each base 15 via an insulator (not shown). When a drive current flows through the coil 12, a drive magnetic flux is generated along the salient pole 14.

  The rotor yoke 21 is formed in a predetermined substantially cup shape using a soft magnetic material. The magnet 22 is formed in a cylindrical shape, and is bonded and fixed to the cylindrical inner peripheral surface 21 a of the rotor yoke 21. The magnet 22 is formed of, for example, a rare earth magnet material or a ferrite magnet material. The magnet 22 is magnetized for driving with four poles in the circumferential direction. The magnet 22 faces the four salient poles 14 of the stator core 11 in the radial direction via a predetermined gap. Therefore, single-phase brushless motor 100 according to the embodiment has a 4-pole 4-slot structure.

  FIG. 2 is an enlarged cross-sectional view showing one of the salient poles 14 of the stator core 11 and its periphery. In FIG. 2, the display of the coil 12 is omitted. In FIG. 2, the first straight line L1 is parallel to the first side surface 15c located on the front side in the rotational direction (that is, the D direction) of the rotor 20 on both side surfaces (that is, the first side surface 15c and the second side surface 15d) of the base portion 15. Is a straight line passing through the rotation axis R. The second straight line L2 is the rotation axis R and the end portion located on the front side in the rotation direction of the rotor 20 among both ends in the circumferential direction of the tip portion 16 (particularly the first end in the circumferential direction of the outer peripheral surface 16c of the tip portion 16). Part E1). The third straight line L3 is a rotation axis R and an end portion located on the rear side in the rotation direction of the rotor 20 among both ends in the circumferential direction of the tip portion 16 (particularly the second end in the circumferential direction of the outer peripheral surface 16c of the tip portion 16). Part E2).

  The base 15 is formed in a substantially rectangular shape when viewed from the axial direction. Specifically, the base 15 is formed such that the width in the circumferential direction becomes wider toward the outer peripheral side. In particular, in the cross section perpendicular to the rotation axis R, the base portion 15 has a substantially constant width in the circumferential direction regardless of the radial position of the first portion 15a on the front side in the rotational direction of the rotor 20 relative to the first straight line L1. Thus, the second portion 15b on the rear side in the rotational direction of the rotor 20 with respect to the first straight line L1 is wider in the circumferential direction toward the outer peripheral side (in other words, the second side surface 15d of the base 15 and the first straight line L1 is formed so as to be separated from the outer peripheral side. Particularly in the present embodiment, the second portion 15b has a circumferential width W2 of the end portion on the inner circumferential side thereof that is narrower than a circumferential width W1 of the first portion 15a, and the circumferential length of the end portion on the outer circumferential side. The width W3 is formed to be wider than the circumferential width W1 of the first portion 15a.

  The tip portion 16 has an umbrella shape when viewed from the axial direction. The distal end portion 16 has a radial gap with the rotor 20 at the second end E2 on the rear side in the rotation direction of the rotor 20 and a radial direction with the rotor 20 at the first end E1 on the front side in the rotation direction of the rotor 20. The gaps are different from each other. In the present embodiment, the tip end portion 16 is formed such that the radial gap with the rotor 20 at the second end E2 is wider than the radial gap with the rotor 20 at the first end E1. More specifically, in the present embodiment, the distal end portion 16 is formed such that a radial gap with the rotor 20 becomes wider as it goes from the first end portion E1 to the second end portion E2. For example, the inner peripheral surface 22a of the magnet 22 is formed in an arc shape centered on the rotation axis R, and the outer peripheral surface 16c of the tip portion 16 is formed in an arc shape centered on a point different from the rotation axis R. This is realized.

  Further, the front end portion 16 has a circumferential width of the first portion 16a on the front side in the rotational direction of the rotor 20 relative to the first straight line L1, and a second portion on the rear side in the rotational direction of the rotor 20 relative to the first straight line L1. It is formed to be wider than the circumferential width of 16b. In other words, the distal end portion 16 is formed such that the angle θ1 formed by the first straight line L1 and the second straight line L2 is larger than the angle θ2 formed by the first straight line L1 and the third straight line L3.

  The operation of the single-phase brushless motor 100 configured as described above will be described. A drive current is supplied to the coil 12. When the drive current flows through the coil 12, magnetic flux is generated along the four salient poles 14, and the rotor 20 rotates.

  According to the single-phase brushless motor 100 according to the present embodiment described above, the tip portion 16 is formed such that the circumferential width of the first portion 16a is larger than the circumferential width of the second portion 16b. In other words, the tip end portion 16 is formed such that the angle θ1 is larger than the angle θ2. Thereby, compared with the case where angle (theta) 1 and angle (theta) 2 are equal, electromagnetic vibration can be reduced.

  In addition, according to single-phase brushless motor 100 according to the present embodiment, base 15 is formed so that the width in the circumferential direction becomes wider toward the outer peripheral side. Further, in the base portion 15, the circumferential width W2 of the inner circumferential end of the second portion 15b is narrower than the circumferential width W1 of the inner circumferential end of the first portion 15a, and the second portion 15b The circumferential width W3 of the outer peripheral end is formed to be wider than the circumferential width W1 of the first portion 15a on the outer circumferential side. Thereby, electromagnetic vibration can be further reduced.

In order to confirm the electromagnetic vibration reduction effect of the single-phase brushless motor 100 according to the present embodiment, the present inventors have compared the single-phase brushless motor 100 and a four-pole 4 having the same structure as the present embodiment as a comparative example. A single phase brushless motor with a slot structure was simulated. The difference between the single-phase brushless motor 100 and the single-phase brushless motor according to the comparative example is the configuration of the stator core. The configuration of each stator core is as follows.
<Stator core 11 of single-phase brushless motor 100 according to the present embodiment>
θ1 = 43 °
θ2 = 39 °
D1 / D2 = 1.36
W1 / D1 = 0.13
W2 / D1 = 0.11
W3 / D1 = 0.16
Here, D1 is the outer diameter of the annular portion 13, and D2 is the inner diameter of the annular portion 13.
<Stator core of single-phase brushless motor according to comparative example>
θ1 = θ2 = 40 °
D1 / D2 = 1.36
W1 / D1 = 0.15
W2 / D1 = 0.12
W3 / D1 = 0.15

  3 and 4 are graphs showing simulation results. FIG. 3A shows a harmonic component that is a multiple of 4 of the radial electromagnetic force generated between the stator core and the magnet, and FIG. 3B shows the rotational electromagnetic force generated between the stator core and the magnet. A harmonic component of a multiple of 4 is shown. 3A and 3B, the vertical axis represents the amplitude of the electromagnetic force. In particular, as shown in FIG. 3B, in the single-phase brushless motor 100 according to the present embodiment, in comparison with the single-phase brushless motor according to the comparative example, electromagnetic waves in the rotational direction generated between the stator core and the magnet. Among the harmonic components that are multiples of 4 times the force, the electromagnetic forces in the 8th, 12th, 16th, and 20th harmonic components having a large amplitude of the electromagnetic force are reduced.

  Further, the present inventors can calculate the electromagnetic force while changing the shape of the stator core 11 variously, and when θ2 / θ1 is in the range of 0.81 to 0.99, the torque comparable to the conventional one can be obtained, And it was confirmed that electromagnetic vibration can be reduced. In addition, the inventors have confirmed that particularly when θ2 / θ1 = 0.9, it is possible to obtain the same level of torque as in the prior art and to reduce the electromagnetic vibration most.

  FIG. 4 shows the cogging torque. In FIG. 4, the horizontal axis indicates the rotation angle, and the vertical axis indicates the cogging torque. As shown in FIG. 4, according to the single-phase brushless motor 100 according to the present embodiment, not only the electromagnetic force but also the cogging torque is reduced as compared with the single-phase brushless motor according to the comparative example (24 in the example of FIG. 4). % Reduction).

The single-phase brushless motor according to the embodiment has been described above. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are also within the scope of the present invention. is there. A modification is shown below.
(Modification 1)
In the embodiment, the case where the number of salient poles 14 of the stator core 11 is four has been described, but the present invention is not limited to this. For example, the number of salient poles 14 of the stator core 11 may be six. In this case as well, if θ2 / θ1 is in the range of 0.81 to 0.99, it is possible to obtain the same level of torque as in the prior art and reduce electromagnetic vibration.

(Modification 2)
In the embodiment, a so-called outer rotor type single-phase brushless motor in which the magnet 22 is located outside the stator core 11 has been described. However, the present invention is not limited to this. For example, a so-called inner rotor type single-phase brushless motor in which a magnet is positioned inside a stator core may be used.

(Modification 3)
Although the case where the stator core 11 is a laminated core has been described in the embodiment, the present invention is not limited to this. For example, the stator core 11 may be a solid core.

  Any combination of the above-described embodiments and modifications is also useful as an embodiment of the present invention. The new embodiment generated by the combination has the effects of the combined embodiment and the modified examples.

  10 stator, 11 stator core, 12 coil, 13 annular part, 14 salient pole, 15 base, 16 tip, 20 rotor, 22 magnet, 100 single-phase brushless motor, R rotating shaft.

Claims (4)

A stator,
A rotor that rotates relative to the stator,
The stator is
A core having a plurality of salient poles;
A coil formed by being wound around the plurality of salient poles,
The rotor includes a magnet facing the salient pole in the radial direction and having a plurality of magnetic poles in a circumferential direction on a surface on the salient pole side,
The salient pole includes a base on which a coil is wound, and a tip provided on the magnet side from the base and extending in the circumferential direction from the base,
The radial clearance between the tip portion and the rotor differs between the first end portion on the front side and the second end portion on the rear side in the rotational direction of the rotor among the circumferential end portions of the tip portion. And
In a cross section perpendicular to the rotation axis of the rotor,
A first straight line that passes through the rotation axis and is substantially parallel to a side surface of the both sides of the base that is located on the front side in the rotational direction of the rotor, and a second straight line that passes through the rotation shaft and the first end. The single-phase brushless motor is characterized in that an angle between the first straight line and a third straight line passing through the rotating shaft and the second end is larger.   The ratio of the angle formed by the first straight line and the third straight line to the angle formed by the first straight line and the second straight line is 0.81 to 0.99. Single phase brushless motor.   2. The single-phase brushless motor according to claim 1, wherein a ratio of an angle formed by the first straight line and the third straight line to an angle formed by the first straight line and the second straight line is 0.9. . In a cross section perpendicular to the rotation axis of the rotor,
The said base part is comprised so that the radial direction outer side may leave | separate the said 1st straight line and the back side surface of the rotation direction of the said rotor of the both sides | surfaces of the said base part. A single-phase brushless motor according to claim 1.

Images