WO2019202915A1

WO2019202915A1 - Motor, brushless wiper motor, and method for driving motor

Info

Publication number: WO2019202915A1
Application number: PCT/JP2019/012371
Authority: WO
Inventors: 竜大堀; 直樹塩田
Original assignee: 株式会社ミツバ
Priority date: 2018-04-19
Filing date: 2019-03-25
Publication date: 2019-10-24
Also published as: JP7105598B2; JP2019193350A

Abstract

Provided are: a motor with which it is possible to obtain adequate motor characteristics while suppressing magnetic oscillation in the case where the ratio between the numbers of teeth and the number of magnetic poles of the permanent magnets is 2:3; a brushless wiper motor; and a method for driving the motor. This motor is provided with: a stator; a coil which is wound around teeth of the stator; a rotor core that is fixed to a shaft rotating on the radially inner side of a stator core of the stator and that has a radial-direction center that coincides with the rotational axis of the shaft; a plurality of permanent magnets which are disposed on an outer circumferential surface of the rotor core; and salient poles which are formed between the permanent magnets in the outer circumferential surface of the rotor core in such a manner as to protrude radially outward. The ratio between the number of teeth and the number of magnetic poles of the permanent magnets is 2:3. The coil has a three-phase structure and has a Y-connection. The waveform of the drive voltage to be applied to the coil is obtained by superimposing a fifth harmonic on a fundamental sinusoidal wave. The fifth harmonic is in the antiphase to the phase of the fundamental sinusoidal wave.

Description

Motor, brushless wiper motor, and motor driving method

The present invention relates to a motor, a brushless wiper motor, and a motor driving method.

A brushless motor (hereinafter sometimes simply referred to as a motor) includes a stator having teeth around which a coil is wound, and a rotor that is rotatably provided on the radial inner side of the stator. Slots are formed between adjacent teeth in the circumferential direction. A coil is wound around each tooth through this slot.
An interlinkage magnetic flux is formed in the stator by supplying power to the coil. The rotor includes a shaft, a substantially columnar rotor core that is fitted and fixed to the shaft, and a permanent magnet provided on the rotor core. Then, a magnetic attractive force or a repulsive force is generated between the interlinkage magnetic flux formed in the stator and the permanent magnet provided in the rotor core, and the rotor continuously rotates.

Here, as a method of arranging the permanent magnets on the rotor, there is a method of arranging permanent magnets on the outer peripheral surface of the rotor core (SPM: Surface Permanent Magnet). Various methods for increasing the torque in the SPM rotor have been proposed.

For example, a rotor having a salient pole protruding outward in the radial direction between permanent magnets adjacent in the circumferential direction on the outer peripheral surface of the rotor core has been proposed. By providing the salient poles, in the rotor core, a direction in which the interlinkage magnetic flux (q-axis magnetic flux) due to the stator coil easily flows and a direction in which the interlinkage magnetic flux hardly flows (d-axis direction) are formed. As a result, reluctance torque is generated in the rotor core, and this reluctance torque can also contribute to the rotational force of the rotor.

JP 2002-262533 A

By the way, the present inventors provide salient poles in the rotor core as in the above-mentioned prior art, and in a motor in which the ratio of the number of magnetic poles of the permanent magnet to the number of teeth is 2: 3, the coil connection method is Y connection. Furthermore, it has been found that magnetic vibration (electromagnetic vibration) can be greatly reduced by making the voltage waveform of the drive voltage applied to the coil a waveform in which the fifth harmonic is superimposed on the basic sine wave. In particular, it has been confirmed that twelfth-order magnetic vibration can be significantly reduced. However, when a drive voltage on which fifth harmonics are superimposed is applied, the output duty exceeds the duty upper limit value, so that there is a problem that the output duty must be reduced.

This will be described in more detail with reference to FIGS.
FIG. 9 is a graph showing a waveform of the drive voltage when the vertical axis is the duty [%] of the drive voltage and the horizontal axis is the phase [°] of the drive voltage, and (a) is a basic sine of the drive voltage. The waveform of a wave is shown, (b) shows the waveform which superimposed the 5th harmonic in the same phase as a fundamental sine wave, (c) shows the waveform which reduced the duty of the drive voltage of (b). Note that the scales of the vertical and horizontal axes in FIGS. 9 (a) to 9 (c) are the same. In FIG. 9, “+ 5th order” indicates that the 5th harmonic is superimposed on the basic sine wave.

As shown in FIG. 9B, in the waveform in which the fifth harmonic is superimposed in the same phase as the basic sine wave, the upper limit value (peak value) is the duty upper limit value of the output duty of the basic sine wave (FIG. 9A ), The peak value of the basic sine wave (hereinafter referred to as the upper limit of the duty of the basic sine wave). In this case, the waveform of the drive voltage is disturbed, and the motor operation becomes unstable. For this reason, as shown in FIG. 9C, in the waveform in which the fifth harmonic is superimposed in the same phase as the basic sine wave, the output duty is reduced and the upper limit value is the duty upper limit value of the output duty of the basic sine wave. It is necessary to adjust so as not to exceed. When the adjustment is made in this way, the output performance of the motor is reduced as much as the output duty is reduced.

In FIG. 10, the vertical axis represents the rotational speed [rpm] of the rotor and the current value [A] supplied to the motor, and the horizontal axis represents the motor torque [N. m] represents the change in the number of revolutions and the current value (hereinafter, these values may be referred to as motor characteristics as a whole), and the drive voltage with the fifth harmonic superimposed (with the fifth harmonic) 6 is a graph comparing a driving voltage of a basic sine wave that does not superimpose a fifth harmonic.
As shown in FIG. 10, it can be confirmed that the drive voltage in which the fifth-order harmonics are superimposed deteriorates the motor characteristics as much as the output duty is reduced.

Therefore, the present invention provides a motor, a brushless wiper motor, and a motor capable of obtaining sufficient motor characteristics while suppressing magnetic vibration when the ratio between the number of magnetic poles of the permanent magnet and the number of teeth is 2: 3. A driving method is provided.

In order to solve the above problems, a motor according to the present invention is wound around a tooth having an annular stator core, a stator having a plurality of teeth projecting radially inward from an inner peripheral surface of the stator core, and A coil that rotates on the radially inner side of the stator core, a rotor core that is fixed to the shaft and that has a rotational axis of the shaft as a center in the radial direction, and a plurality of permanent magnets disposed on the outer peripheral surface of the rotor core; A salient pole formed so as to protrude radially outward between the permanent magnets adjacent in the circumferential direction of the outer peripheral surface of the rotor core, and contacting the circumferential side surface of the permanent magnet, The ratio between the number of magnetic poles of the permanent magnet and the number of teeth is set to 2: 3, and the coil has a three-phase structure and is Y-connected, and is applied to the coil. The waveform of the driving voltage that is a waveform fifth harmonic to the fundamental sine wave is superimposed, the fifth-order harmonic, characterized in that to the fundamental sine wave of the phase is opposite phase.

With this configuration, in a motor having a ratio of the number of magnetic poles of the permanent magnet to the number of teeth of 2: 3, this drive voltage is reduced without reducing the output duty of the drive voltage superimposed with the fifth harmonic. It is possible to prevent the upper limit value from exceeding the duty upper limit value of the basic sine wave. For this reason, sufficient motor characteristics can be obtained while suppressing magnetic vibration.

A brushless wiper motor according to the present invention includes the motor described above.

With such a configuration, a brushless wiper motor capable of obtaining sufficient motor characteristics while suppressing magnetic vibration can be provided.

A motor driving method according to the present invention includes an annular stator core, a stator having a plurality of teeth projecting radially inward from an inner peripheral surface of the stator core, a coil wound around the teeth, and the stator core A shaft that rotates radially inward, a rotor core that is fixed to the shaft and that has a rotational axis of the shaft as a radial center, a plurality of permanent magnets disposed on an outer peripheral surface of the rotor core, and the outer periphery of the rotor core Between the permanent magnets that are adjacent in the circumferential direction of the surface, and projecting poles that are formed to protrude radially outward, and in contact with the circumferential side surface of the permanent magnet, and the number of magnetic poles of the permanent magnet The ratio of the teeth to the number of teeth is set to 2: 3, and the coil has a three-phase structure and is Y-connected. , By applying a driving voltage waveform fifth harmonic to the fundamental sine wave is superimposed, the fifth-order harmonic, characterized in that to the fundamental sine wave of the phase is opposite phase.

By adopting such a method, in a motor in which the ratio of the number of magnetic poles of the permanent magnet to the number of teeth is 2: 3, this drive voltage is reduced without reducing the output duty of the drive voltage superimposed with the fifth harmonic. Can be prevented from exceeding the duty upper limit value of the basic sine wave. For this reason, sufficient motor characteristics can be obtained while suppressing magnetic vibration.

According to the present invention, in a motor in which the ratio of the number of magnetic poles of the permanent magnet to the number of teeth is 2: 3, the upper limit value of the driving voltage is reduced without reducing the output duty of the driving voltage superimposed with the fifth harmonic. Can be prevented from exceeding the duty upper limit value of the basic sine wave. For this reason, sufficient motor characteristics can be obtained while suppressing magnetic vibration.

It is a perspective view of the wiper motor in the embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. It is a block diagram of the stator and rotor in embodiment of this invention. It is the connection diagram of the coil in embodiment of this invention, (a) shows the case where each phase is connected in series, (b) shows the case where each phase is connected in parallel. It is the A section enlarged view of FIG. It is a graph at the time of showing each voltage waveform in embodiment of this invention, and making the connection system of a coil the Y connection system. It is a graph at the time of showing each voltage waveform in embodiment of this invention, and making the connection system of a coil the delta connection system. It is the graph which compared the motor characteristic in embodiment of this invention, and the motor characteristic in a delta connection. It is a graph which shows the waveform of the conventional drive voltage, (a) shows the waveform of the fundamental sine wave of a drive voltage, (b) shows the waveform which superimposed the 5th harmonic in the same phase as the fundamental sine wave. , (C) shows a waveform in which the duty of the drive voltage in (b) is reduced. It is the graph which showed the conventional motor characteristic, and compared the drive voltage which superimposed the 5th harmonic, and the drive voltage of the fundamental sine wave which does not superimpose the 5th harmonic.

Next, an embodiment of the present invention will be described based on the drawings.

(Wiper motor)
FIG. 1 is a perspective view of the wiper motor 1. FIG. 2 is a cross-sectional view taken along line AA in FIG.
As shown in FIGS. 1 and 2, the wiper motor 1 serves as a drive source for a wiper mounted on a vehicle, for example. The wiper motor 1 includes a motor unit 2, a deceleration unit 3 that decelerates and outputs the rotation of the motor unit 2, and a controller unit 4 that performs drive control of the motor unit 2.
In the following description, the axial direction simply refers to the rotational axis direction of the shaft 31 of the motor unit 2, the simple circumferential direction refers to the circumferential direction of the shaft 31, and the simple radial direction refers to the shaft. The radial direction of 31 shall be said.

(Motor part)
The motor unit 2 includes a motor case 5, a substantially cylindrical stator 8 housed in the motor case 5, and a rotor 9 provided on the radially inner side of the stator 8 and rotatable with respect to the stator 8. And. The motor unit 2 is a so-called brushless motor that does not require a brush when supplying power to the stator 8.

(Motor case)
The motor case 5 is formed of a material having excellent heat dissipation, such as aluminum die casting. The motor case 5 includes a first motor case 6 and a second motor case 7 that are configured to be separable in the axial direction. The first motor case 6 and the second motor case 7 are each formed in a bottomed cylindrical shape.
The first motor case 6 is integrally formed with the gear case 40 so that the bottom 10 is joined to the gear case 40 of the speed reduction unit 3. A through-hole 10a through which the shaft 31 of the rotor 9 can be inserted is formed at a substantially central portion of the bottom portion 10 in the radial direction.

In addition, an outer flange portion 16 that projects outward in the radial direction is formed in the opening 6 a of the first motor case 6, and is stretched outward in the radial direction in the opening 7 a of the second motor case 7. An outer flange portion 17 is formed. A motor case 5 having an internal space is formed by abutting these

outer flange portions

16 and 17 together. A stator 8 is disposed in the internal space of the motor case 5 so as to be fitted into the first motor case 6 and the second motor case 7.

(Stator)
FIG. 3 shows the configuration of the stator 8 and the rotor 9 and corresponds to a view seen from the axial direction.
As shown in FIGS. 2 and 3, the stator 8 includes a cylindrical core portion 21 whose cross-sectional shape along the radial direction is a substantially circular shape, and a plurality of (for example, a book) In the embodiment, 6) teeth 22 and a stator core 20 are integrally formed. The stator core 20 is formed by laminating a plurality of electromagnetic steel plates in the axial direction or press-molding soft magnetic powder.

The teeth 22 are formed by integrally forming a teeth main body 101 projecting along the radial direction from the inner peripheral surface of the core portion 21 and a flange 102 extending along the circumferential direction from the radial inner end of the teeth main body 101. It is. The flange portion 102 is formed so as to extend from the teeth body 101 to both sides in the circumferential direction. And the slot 19 is formed between the collar parts 102 adjacent in the circumferential direction.

Further, the inner peripheral surface of the core portion 21 and the teeth 22 are covered with a resin insulator 23. A coil 24 is wound around each of the teeth 22 from above the insulator 23. Each coil 24 generates a magnetic field for rotating the rotor 9 by power feeding from the controller unit 4.

4A and 4B are connection diagrams of the coil 24. FIG. 4A shows a case where the phases are connected in series, and FIG. 4B shows a case where the phases are connected in parallel.
As shown in FIGS. 4A and 4B, the coil 24 has a three-phase structure of a U phase, a V phase, and a W phase. Moreover, the connection system of the coil 24 is a Y connection (star connection) system.
As shown in FIG. 4 (a), the connection structure of the coil 24 may be a Y-connection structure in which the coils 24 of the same phase are connected in series. As shown in FIG. Alternatively, a Y-connection structure in which in-phase coils 24 are connected in parallel may be used.

(Rotor)
FIG. 5 is an enlarged view of a portion A in FIG.
As shown in FIGS. 3 and 5, the rotor 9 is rotatably provided on the radially inner side of the stator 8 through a minute gap. The rotor 9 has a substantially cylindrical shape with a shaft 31 integrally formed with a worm shaft 44 (see FIG. 2) constituting the speed reduction portion 3 and an outer fitting and fixing to the shaft 31 and having the shaft 31 as an axis (rotation axis) C1. The rotor core 32 and four permanent magnets 33 provided on the outer peripheral surface 32b of the rotor core 32 are provided.
Thus, in the motor unit 2, the ratio between the number of magnetic poles of the permanent magnet 33 and the number of slots 19 (teeth 22) is 2: 3. For example, a ferrite magnet is used as the permanent magnet 33. However, the present invention is not limited to this, and a neodymium bonded magnet or a neodymium sintered magnet can be used as the permanent magnet 33 instead of the ferrite magnet.

The rotor core 32 is formed by laminating a plurality of electromagnetic steel plates in the axial direction or press-molding soft magnetic powder. A through hole 32 a penetrating in the axial direction is formed at the substantially center in the radial direction of the rotor core 32. The shaft 31 is press-fitted into the through hole 32a. The shaft 31 may be inserted into the through hole 32a, and the rotor core 32 may be externally fixed to the shaft 31 using an adhesive or the like.

Furthermore, four salient poles 35 are provided on the outer peripheral surface 32b of the rotor core 32 at equal intervals in the circumferential direction. The salient poles 35 are formed so as to protrude outward in the radial direction and extend in the entire axial direction of the rotor core 32. Round chamfered portions 35 a are formed at the corners on the radially outer side of the salient poles 35 and on both sides in the circumferential direction.

The salient pole 35 desirably has a circumferential width dimension at the radially outer end portion 35t of 20 ° or more and 40 ° or less in electrical angle θ. Note that the circumferential width dimension at the radially outer end 35t of the salient pole 35 is the circumferential corner 35b (hereinafter referred to as the salient pole 35) when the round pole chamfer 35a is not formed on the salient pole 35. (Referred to as a radial corner 35b). In the following description, the circumferential width dimension at the radially outer end 35t of the salient pole 35 will be simply referred to as the circumferential width dimension of the salient pole 35.

The salient pole 35 is formed so that both side surfaces 35c opposed in the circumferential direction are parallel to each other. That is, the salient pole 35 is formed so that the circumferential width dimension is uniform in the radial direction.
Further, one groove portion 91 is formed in the radially outer end portion 35t of the salient pole 35 at the substantially central portion in the circumferential direction over the entire axial direction. The groove portion 91 is formed in a substantially V-groove shape so that the groove width in the circumferential direction gradually narrows toward the inner side in the radial direction.

The outer peripheral surface 32b of the rotor core 32 formed in this way is configured as a magnet storage portion 36 between two salient poles 35 adjacent in the circumferential direction. Permanent magnets 33 are disposed in these magnet storage portions 36 and are fixed to the rotor core 32 by, for example, an adhesive.
In the permanent magnet 33, the arc center Co of the outer circumferential surface 33a on the radially outer side and the arc center Ci of the inner circumferential surface 33b on the radially inner side coincide with the position of the axis C1 of the shaft 31. Further, the diameter of the circle passing through the radially outer end 35t of the salient pole 35 and the diameter of the outer peripheral surface 33a of the permanent magnet 33 are the same.

The entire inner peripheral surface 33 b of the permanent magnet 33 is in contact with the outer peripheral surface 32 b of the rotor core 32. Further, both side surfaces in the circumferential direction of the permanent magnet 33 are located on the radially inner side, a salient pole contact surface 33d that is in contact with the side surface 35c of the salient pole 35, and a radially outer side than the salient pole contact surface 33d. The inclined surface 33e located is smoothly connected. The salient pole contact surface 33d is smoothly connected to the inner peripheral surface 33b via the arc surface 33g.

The inclined surface 33e is formed to be inclined and flat so as to gradually move away from the salient pole 35 as it goes from the radial outer end of the salient pole contact surface 33d toward the outer peripheral surface 33a of the permanent magnet 33. In one permanent magnet 33, inclined surfaces 33 e on both sides in the circumferential direction are parallel to a straight line L connecting the circumferential intermediate portion 33 c of the permanent magnet 33 and the axis C <b> 1 of the shaft 31. For this reason, the two inclined surfaces 33e are also parallel to each other.

Further, the permanent magnet 33 is magnetized so that the magnetization (magnetic field) is oriented in parallel along the thickness direction. And the permanent magnet 33 is arrange | positioned so that a magnetic pole may become alternate in the circumferential direction. For this reason, the salient poles 35 of the rotor core 32 are located between the permanent magnets 33 adjacent in the circumferential direction, that is, at the boundary (pole boundary) of the magnetic poles. The orientation of magnetization of the permanent magnet 33 is not limited to parallel orientation, and may be radial orientation.

(Decelerator)
Returning to FIGS. 1 and 2, the speed reduction unit 3 includes a gear case 40 to which the motor case 5 is attached, and a worm speed reduction mechanism 41 accommodated in the gear case 40. The gear case 40 is made of a material with excellent heat dissipation, such as aluminum die cast. The gear case 40 is formed in a box shape having an opening 40a on one surface, and has a gear housing portion 42 for housing the worm reduction mechanism 41 therein. The side wall 40b of the gear case 40 is formed with an opening 43 that communicates the through hole 10a of the first motor case 6 and the gear housing portion 42 at a location where the first motor case 6 is integrally formed. Yes.

Also, a substantially cylindrical bearing boss 49 projects from the bottom wall 40c of the gear case 40. The bearing boss 49 is for rotatably supporting the output shaft 48 of the worm reduction mechanism 41, and a sliding bearing (not shown) is provided on the inner peripheral surface. Further, an O-ring (not shown) is mounted on the inner peripheral edge of the bearing boss 49. This prevents dust and water from entering from the outside to the inside via the bearing boss 49. A plurality of ribs 52 are provided on the outer peripheral surface of the bearing boss 49. Thereby, the rigidity of the bearing boss 49 is ensured.

The worm speed reduction mechanism 41 accommodated in the gear accommodating portion 42 includes a worm shaft 44 and a worm wheel 45 engaged with the worm shaft 44. The worm shaft 44 is disposed coaxially with the shaft 31 of the motor unit 2. The worm shaft 44 is rotatably supported by

bearings

46 and 47 provided on the gear case 40 at both ends. The end of the worm shaft 44 on the motor unit 2 side protrudes to the opening 43 of the gear case 40 through the bearing 46. The protruding end portion of the worm shaft 44 and the end portion of the shaft 31 of the motor unit 2 are joined, and the worm shaft 44 and the shaft 31 are integrated. The worm shaft 44 and the shaft 31 may be integrally formed by molding a worm shaft portion and a shaft portion from one base material.

The worm wheel 45 meshed with the worm shaft 44 is provided with an output shaft 48 at the radial center of the worm wheel 45. The output shaft 48 is arranged coaxially with the rotational axis direction of the worm wheel 45, and protrudes to the outside of the gear case 40 via the bearing boss 49 of the gear case 40. A spline 48 a that can be connected to an electrical component (not shown) is formed at the protruding tip of the output shaft 48.

Further, a sensor magnet (not shown) is provided at the radial center of the worm wheel 45 on the side opposite to the side from which the output shaft 48 is projected. This sensor magnet constitutes one of the rotational position detector 60 that detects the rotational position of the worm wheel 45. The magnetic detection element 61 that constitutes the other of the rotational position detection unit 60 is provided in the controller unit 4 that is disposed facing the worm wheel 45 on the sensor magnet side of the worm wheel 45 (on the opening 40a side of the gear case 40). Yes.

(Controller part)
The controller unit 4 that controls the drive of the motor unit 2 includes a controller board 62 on which the magnetic detection element 61 is mounted, and a cover 63 provided so as to close the opening 40a of the gear case 40. The controller board 62 is disposed opposite to the sensor magnet side of the worm wheel 45 (opening 40a side of the gear case 40).

The controller board 62 is obtained by forming a plurality of conductive patterns (not shown) on a so-called epoxy board. The controller board 62 is connected to a terminal portion of the coil 24 drawn from the stator core 20 of the motor unit 2 and is electrically connected to terminals (not shown) of the connector 11 provided on the cover 63. . In addition to the magnetic detection element 61, a power module (not shown) composed of a switching element such as an FET (Field Effect Transistor) that controls the drive voltage supplied to the coil 24 is mounted on the controller board 62. Has been. Further, a capacitor (not shown) for smoothing the voltage applied to the controller board 62 is mounted on the controller board 62.

The cover 63 covering the controller board 62 configured in this manner is formed of resin. The cover 63 is formed so as to bulge slightly outward. The inner surface side of the cover 63 is a controller housing portion 56 that houses the controller board 62 and the like.
The connector 11 is integrally formed on the outer periphery of the cover 63. This connector 11 is formed so as to be able to be fitted with a connector 11 extending from an external power source (not shown). The controller board 62 is electrically connected to the terminals of the connector 11. As a result, the power of the external power supply is supplied to the controller board 62.

Furthermore, a fitting portion 81 is formed on the opening edge of the cover 63 so as to be fitted with the end portion of the side wall 40 b of the gear case 40. The fitting portion 81 is configured by two

walls

81 a and 81 b along the opening edge of the cover 63. And the edge part of the side wall 40b of the gear case 40 is inserted (fitted) between these two

walls

81a and 81b. Thereby, a labyrinth portion 83 is formed between the gear case 40 and the cover 63. The labyrinth 83 prevents dust and water from entering between the gear case 40 and the cover 63. The gear case 40 and the cover 63 are fixed by fastening a bolt (not shown).

(Wiper motor operation)
Next, the operation of the wiper motor 1 will be described.
In the wiper motor 1, the voltage supplied to the controller board 62 via the connector 11 is selectively applied to each coil 24 of the motor unit 2 as a drive voltage via a power module (not shown). Then, a predetermined flux linkage is formed in the stator 8 (tooth 22), and a magnetic attractive force or repulsive force is generated between the flux linkage and an effective magnetic flux formed by the permanent magnet 33 of the rotor 9. Thereby, the rotor 9 rotates continuously.

When the rotor 9 rotates, the worm shaft 44 integrated with the shaft 31 rotates, and further the worm wheel 45 meshed with the worm shaft 44 rotates. Then, the output shaft 48 connected to the worm wheel 45 rotates, and a desired electrical component (for example, a wiper driving device mounted on a vehicle) is driven.

The rotation position detection result of the worm wheel 45 detected by the magnetic detection element 61 mounted on the controller board 62 is output as a signal to an external device (not shown). The external device (not shown) controls the switching timing of the switching elements and the like of the power module (not shown) based on the rotational position detection signal of the worm wheel 45, and the drive control of the motor unit 2 is performed. The output of the drive signal of the power module and the drive control of the motor unit 2 may be performed by the controller unit 4.

(Rotor action)
Next, the operation of the rotor 9 will be described.
Here, the rotor 9 is a so-called SPM (Surface Permanent Magnet) type rotor in which a permanent magnet 33 is disposed on the outer peripheral surface 32 b of the rotor core 32. For this reason, the inductance value in the d-axis direction can be reduced. In addition, the rotor 9 is provided with salient poles 35 between the permanent magnets 33 adjacent in the circumferential direction. As a result, the inductance value in the q-axis direction due to the interlinkage magnetic flux of the stator 8 can be increased as compared with the case where the salient pole 35 is not provided. Therefore, the rotor 9 is rotated using the difference in reluctance torque between the d-axis direction and the q-axis direction.

(Drive voltage to coil)
Next, the driving voltage applied to the coil 24 will be described with reference to FIG.
FIG. 6 is a graph showing voltage waveforms when the vertical axis is duty [%] and the horizontal axis is phase [°]. In FIG. 6, waveforms of all three phases (U phase, V phase, W phase) are shown. In FIG. 6, the waveforms indicated by broken lines are the waveforms of the basic sine waves (fundamental waves) Us1, Vs1, and Ws1. The waveform indicated by the two-dot chain line is the waveform of the fifth harmonic (fifth) Uh1, Vh1, Wh1. The waveform shown by the solid line is the waveform (synthesis) Uc1, Vc1, Wc1 of the drive voltage applied to the coil 24 in which the fifth harmonic is superimposed on the basic sine wave.

As shown in FIG. 6, the waveforms Uc1, Vc1, Wc1 of the driving voltage applied to the coil 24 are obtained by changing the fifth-order harmonics Uh1, Vh1, Wh1 to the basic sine waves Us1, Vs1, Ws1, respectively. It becomes a superimposed waveform. At this time, the phases of the fifth harmonics Uh1, Vh1, and Wh1 of the respective phases are opposite to those of the basic sine waves Us1, Vs1, and Ws1.
As shown in FIG. 6, the upper limit values (peak values) of the waveforms Uc1, Vc1, and Wc1 of the drive voltage are equivalent to the upper limit values (peak values) of the waveforms of the basic sine waves Us1, Vs1, and Ws1. That is, it is not necessary to reduce the output duty of the drive voltage as in the prior art.

Here, the connection method of the coil 24 is the Y connection (star connection) method (see FIGS. 4A and 4B) as described above, but the connection method of the coil 24 is assumed to be the delta connection method. A case is compared with the case where the coil 24 is a Y-connection system.
FIG. 7 is a graph showing each voltage waveform when the vertical axis is duty [%] and the horizontal axis is phase [°], and the connection method of the coil 24 is a delta connection method. FIG. 7 shows the waveforms of all three phases (U phase, V phase, W phase) as in FIG. In FIG. 7, the waveform indicated by the broken line is the waveform of the fundamental sine wave (fundamental wave) Us2, Vs2, and Ws2. A waveform indicated by a two-dot chain line is a waveform of fifth-order harmonics (fifth-order) Uh2, Vh2, and Wh2. The waveform shown by the solid line is the waveform (synthesis) Uc2, Vc2, Wc2 of the drive voltage applied to the coil 24 in which the fifth harmonic is superimposed on the basic sine wave. Moreover, the scale of the vertical axis | shaft of FIG. 7 and a horizontal axis shall be the same as the scale of the vertical axis | shaft of FIG.

As shown in FIG. 7, when the connection method of the coil 24 is a delta connection method, the phases of the fifth harmonics Uh2, Vh2, Wh2 superimposed on the basic sine waves Us2, Vs2, Ws2 are the same as the basic sine wave. It is necessary to. In this case, the upper limit values (peak values) of the drive voltage waveforms Uc2, Vc2, and Wc2 are equivalent to the drive voltage waveforms Uc1, Vc1, and Wc1 shown in FIG. 6, but the waveforms of the basic sine waves Us2, Vs2, and Ws2. Exceeds the upper limit (peak value). For this reason, it is necessary to reduce the output duty of the drive voltage. As described above, when the connection method of the coil 24 is the delta connection method, even if the fifth harmonics Uh2, Vh2, and Wh2 are superimposed on the basic sine waves Us2, Vs2, and Ws2 as drive voltages, no effect is obtained. Can be confirmed.

In FIG. 8, the vertical axis represents the rotor speed [rpm] and the current value [A] supplied to the motor, and the horizontal axis represents the motor torque [N. m] is a graph showing the number of revolutions and the change of the current value (motor characteristics), in the case of the drive voltage of the present embodiment (Y connection) (hereinafter simply referred to as the case of the present embodiment), and the delta In the connection, the case of the drive voltage in which the fifth harmonics Uh2, Vh2, and Wh2 are superimposed on the basic sine waves Us2, Vs2, and Ws2 (hereinafter simply referred to as the delta connection) is compared.
As shown in FIG. 8, it can be confirmed that the motor characteristics in this embodiment are improved as compared with the case of delta connection.

Thus, in the motor unit 2 in which the ratio between the number of magnetic poles of the permanent magnet 33 and the number of slots 19 (teeth 22) is 2: 3 and the connection method of the coil 24 is the Y connection method, it is applied to the coil 24. As a driving voltage, the fifth harmonic is superimposed on the basic sine wave. The fifth harmonic is in antiphase with the fundamental sine wave. Therefore, it is possible to prevent the upper limit value of the drive voltage from exceeding the duty upper limit value of the basic sine wave without reducing the output duty of the drive voltage on which the fifth harmonic is superimposed. Therefore, sufficient motor characteristics can be obtained while suppressing the magnetic vibration of the motor unit 2.

Further, the salient poles 35 provided on the rotor core 32 are formed such that both side surfaces 35c facing each other in the circumferential direction are parallel to each other. That is, the salient pole 35 is formed so that the circumferential width dimension is uniform in the radial direction. For this reason, for example, the saturation of the magnetic flux flowing through the salient poles 35 can be suppressed as compared with the case where the salient poles 35 are trapezoidal when viewed from the rotation axis direction. Therefore, the rotor 9 can be efficiently rotated using the difference in reluctance torque between the d-axis direction and the q-axis direction with certainty.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention.
For example, in the above-described embodiment, the wiper motor 1 is taken as an example of the motor. However, the motor according to the present invention is not limited to the wiper motor 1, and other electrical components (for example, a power window, a sunroof, It can be used as a driving source for an electric seat or the like, and for various other purposes.

Further, in the above-described embodiment, the stator 8 has six teeth 22, and the rotor 9 has four permanent magnets 33, and thereby, the number of magnetic poles of the permanent magnet 33 and the slot 19 (tooth 22). The case where the ratio to the number is 2: 3 has been described. However, the present invention is not limited to this, and the ratio between the number of magnetic poles of the permanent magnet 33 and the number of slots 19 (teeth 22) may be 2: 3. That is, the number of permanent magnets 33 is not limited to four, and the number of slots 19 (teeth 22) is not limited to six.

Further, in the above-described embodiment, a case has been described in which one groove portion 91 is formed in the radial direction outer end portion 35t of the salient pole 35 at substantially the center in the circumferential direction over the entire axial direction. However, the present invention is not limited to this, and two or more groove portions 91 may be formed in the radially outer end portion 35 t of the salient pole 35.
Moreover, the groove part 91 demonstrated the case where it formed in the substantially V-groove shape so that the groove width of the circumferential direction may become narrow gradually as it goes to radial inside. However, the present invention is not limited to this, and the groove portion 91 only needs to be formed so that the circumferential groove width gradually decreases toward the radially inner side. For example, the groove portion 91 is formed in a substantially U shape. May be.

DESCRIPTION OF SYMBOLS 1 ... Wiper motor (brushless wiper motor), 2 ... Motor part (motor), 8 ... Stator, 20 ... Stator core, 22 ... Teeth, 24 ... Coil, 31 ... Shaft, 32 ... Rotor core, 33 ... Permanent magnet, 35 ... Projection Pole, Uc1, Vc1, Wc1 ... Drive voltage waveform, Uh1, Vh1, Wh1 ... Fifth harmonic, Us1, Vs1, Ws1 ... Basic sine wave

Claims

An annular stator core, and a stator having a plurality of teeth projecting radially inward from the inner peripheral surface of the stator core;
A coil wound around the teeth;
A shaft that rotates radially inside the stator core;
A rotor core fixed to the shaft and having a rotation axis of the shaft as a radial center;
A plurality of permanent magnets disposed on the outer peripheral surface of the rotor core;
Between the permanent magnets adjacent to each other in the circumferential direction of the outer peripheral surface of the rotor core, a salient pole formed to protrude outward in the radial direction, and a circumferential side surface of the permanent magnet is in contact,
With
The ratio between the number of magnetic poles of the permanent magnet and the number of teeth is set to 2: 3,
The coil has a three-phase structure and is Y-connected,
The waveform of the drive voltage applied to the coil is a waveform in which the fifth harmonic is superimposed on the basic sine wave,
5. The motor according to claim 5, wherein the fifth harmonic is in an opposite phase to the phase of the basic sine wave.
A brushless wiper motor comprising the motor according to claim 1.
An annular stator core, and a stator having a plurality of teeth projecting radially inward from the inner peripheral surface of the stator core;
A coil wound around the teeth;
A shaft that rotates radially inside the stator core;
A rotor core fixed to the shaft and having a rotation axis of the shaft as a radial center;
A plurality of permanent magnets disposed on the outer peripheral surface of the rotor core;
Between the permanent magnets adjacent to each other in the circumferential direction of the outer peripheral surface of the rotor core, a salient pole formed to protrude outward in the radial direction, and a circumferential side surface of the permanent magnet is in contact,
With
The ratio between the number of magnetic poles of the permanent magnet and the number of teeth is set to 2: 3,
The coil is a method of driving a motor having a three-phase structure and Y-connected,
A drive voltage having a waveform in which a fifth harmonic is superimposed on a basic sine wave is applied to the coil,
5. The motor driving method according to claim 5, wherein the fifth harmonic is in an opposite phase to the phase of the fundamental sine wave.