JP7287825B2 - motor and wiper motor - Google Patents

Description

The present invention relates to motors and wiper motors.

Among motors, there is a motor that utilizes the magnetic force (magnet torque) of a permanent magnet and reluctance torque. This type of motor includes a substantially annular stator around which a plurality of windings are wound, and a rotor provided radially inside the stator so as to be rotatable with respect to the stator.
The stator includes a substantially annular stator core, and a plurality of teeth radially extending from an inner peripheral surface of the stator core and arranged side by side in the circumferential direction. Slots are formed between teeth adjacent in the circumferential direction. A plurality of windings are wound around each tooth by passing the windings through the slots.

The rotor has a rotating shaft and a rotor core fixed to the rotating shaft. The rotor core has permanent magnets that are curved in a radially inwardly convex shape per pole, and that are formed in a plurality of layers per pole. By providing such permanent magnets, the rotor core is provided with a direction in which the interlinking magnetic flux of the stator easily flows and a direction in which it is difficult to flow. Since the reluctance torque generated by this can be used, a high-torque motor can be obtained.

Various techniques have been disclosed to improve the performance of the motor described above. For example, a technique for connecting the tips of teeth adjacent in the circumferential direction is disclosed (see Patent Document 1, for example). According to this, the torque ripple generated in the slot can be reduced.
Also, for example, a technique for defining the spacing between permanent magnets in each layer per pole has been disclosed (see, for example, Patent Document 2). According to this, the reluctance torque can be utilized to the maximum.

JP 2013-192359 A JP-A-8-331783

However, the above-described conventional techniques are techniques specialized for reducing torque ripple and increasing reluctance torque, respectively, so it is difficult to say that any technique has an excellent performance balance. For this reason, there is a problem that there is a limit to a high-performance motor.

Accordingly, the present invention provides a high-performance motor with excellent performance balance and a wiper motor.

In order to solve the above problems, a motor according to the present invention includes: an annular stator core; a plurality of teeth projecting radially inward from an inner surface of the stator core and arranged along the circumferential direction; and a rotor core provided radially inside the teeth so as to be rotatable about the rotation axis with respect to the teeth and having four magnetic poles along the circumferential direction, The rotor core has four layers of slits formed in each of the quarter angular regions, and has permanent magnets housed in each of the slits. The slit is curved so as to have a convex shape toward the rotor core, and the slit is arranged radially inward of the rotor core relative to the width in the lateral direction of the slit arranged near the outer peripheral surface of the rotor core. Both ends of each of the slits in the circumferential direction extend to the vicinity of the outer peripheral surface of the rotor core. The distance from the outer peripheral surface is the same, and when the number of poles of the rotor core is Jn and the number of teeth is Tn, the number of poles Jn and the number of teeth Tn are set so as to satisfy Jn:Tn=2:12. Each of the permanent magnets is curved so as to form a convex shape radially inward for each pole so as to correspond to the shape of the corresponding slit, and the permanent magnet is curved in the direction of the rotation axis. The width of the magnet in the lateral direction as viewed from above is uniform throughout the longitudinal direction as viewed from the direction of the rotation axis, and the width of the magnet is equal to the length of the outer peripheral surface of the rotor core per pole in the circumferential direction: It is set at a ratio of 35% to 55%, and is arranged radially inward of the rotor core relative to the magnet width of the permanent magnet arranged closer to the outer peripheral surface of the rotor core for each pole of the rotor core. The magnet width of the permanent magnet is large, and the distance between the slits adjacent in the radial direction among the four layers of slits in the rotor core is the distance from the radially inner side of the rotor core to the outer peripheral surface of the rotor core. It is characterized by becoming longer as it goes .

In the above configuration, the magnet width of the permanent magnet may be set at a rate of 45% of the circumferential length of the outer peripheral surface of the rotor core per pole .

In the above configuration, the permanent magnets may be radially oriented or polarly oriented.

In the above configuration, the permanent magnet may contain ferrite.

A wiper motor according to the present invention is characterized by using the motor described above in a wiper device mounted on a vehicle.

According to the present invention, reduction in torque ripple and improvement in torque can be achieved in a well-balanced manner, and a high-performance motor and wiper motor can be provided.

The perspective view of the wiper motor in embodiment of this invention. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1; FIG. 2 is a radial cross-sectional view of a stator and a rotor in an embodiment of the present invention; FIG. 4 is a developed view of teeth of the stator according to the embodiment of the present invention; The top view which looked at some rotors from the axial direction in embodiment of this invention. The orientation of the permanent magnet in the embodiment of the present invention is shown, (a) is radial orientation and (b) is polar orientation. 5 is a graph showing changes in the torque of the motor section according to the number of layers of permanent magnets in the embodiment of the present invention. 5 is a graph showing changes in torque ripple of the motor section according to the number of layers of permanent magnets in the embodiment of the present invention. 4 is a graph showing changes in the cogging torque of the motor section according to the number of layers of permanent magnets in the embodiment of the present invention . The graph which shows the change of the torque of a motor part in the magnet width of embodiment of this invention. 4 is a graph showing changes in torque ripple of the motor section with magnet widths according to the embodiment of the present invention. 4 is a graph showing changes in cogging torque of the motor section with magnet widths according to the embodiment of the present invention . 5 is a graph comparing the effective magnetic flux of a permanent magnet in an embodiment of the present invention between radial orientation and parallel orientation. A demagnetization curve of a permanent magnet in an embodiment of the present invention. The figure showing the demagnetization factor of the permanent magnet by the flux linkage of the stator in the embodiment of the present invention. The top view which looked at some rotors from the axial direction in the reference example of this invention.

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

[ Embodiment ]
<Wiper motor>
FIG. 1 is a perspective view of the wiper motor 1. FIG. FIG. 2 is a cross-sectional view along line AA in FIG.
As shown in FIGS. 1 and 2, a wiper motor 1 is mounted on a vehicle, for example, and serves as a drive source for a wiper device 100 for wiping a window glass (both not shown). The wiper motor 1 includes a motor section 2 (corresponding to the motor in the claims), a deceleration section 3 that decelerates and outputs the rotation of the motor section 2, and a controller section 4 that controls the drive of the motor section 2. .
In the following description, simply referring to the axial direction refers to the direction of the rotation axis C of the shaft 31 of the motor section 2, to simply refer to the circumferential direction of the shaft 31, and to simply refer to the radial direction to refer to the shaft 31. shall refer to the radial direction of

<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 provided radially inside the stator 8 and rotatable with respect to the stator 8 . 9 and . The motor unit 2 is a so-called brushless motor that does not require brushes when supplying power to the stator 8 .

<Motor case>
The motor case 5 is made of a material having excellent heat dissipation properties, such as die-cast aluminum. The motor case 5 is composed of a first motor case 6 and a second motor case 7 which are axially separable. 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 formed integrally with the gear case 40 of the reduction section 3 so that the bottom portion 10 is joined to the gear case 40 of the reduction section 3 . A through-hole 10 a through which the shaft 31 of the rotor 9 can be inserted is formed at substantially the center in the radial direction of the bottom portion 10 .

An outer flange portion 16 is formed in the opening portion 6 a of the first motor case 6 so as to protrude outward in the radial direction. An outer flange portion 17 is formed in the opening portion 7a of the second motor case 7 so as to protrude outward in the radial direction. A motor case 5 having an internal space is formed by abutting these outer flange portions 16 and 17 together. The outer peripheral surface of the stator 8 is fitted in the inner space of the motor case 5 and the inner peripheral surfaces of the first motor case 6 and the second motor case 7 . Note that the stator 8 may be fitted only to the first motor case 6 at the outer peripheral surface of the stator 8 .

<Stator>
FIG. 3 is a cross-sectional view along the radial direction of the stator 8 and the rotor 9. As shown in FIG.
As shown in FIGS. 2 and 3, the stator 8 includes a cylindrical stator core 21 having a substantially annular cross-sectional shape along the radial direction, and a stator core 21 integrated with the stator core 21 to protrude radially inward from the stator core 21 . A plurality of (for example, 24 in this embodiment ) teeth 22 are provided. The stator core 21 and teeth 22 are formed, for example, by laminating a plurality of metal plates in the axial direction. Note that the stator core 21 is not limited to being formed by laminating a plurality of metal plates in the axial direction, and may be formed, for example, by pressing soft magnetic powder.

The teeth 22 are formed by integrally molding a tooth body 91 radially protruding from the inner peripheral surface of the stator core 21 and a flange portion 93 formed at the radially inner end of the tooth body 91 and extending in the circumferential direction. It is a thing. The teeth 22 each have an insulator 23 that covers the periphery of the tooth body 91 and the radially outer side surface of the collar portion 93 . Slots 90 are formed between the teeth 22 adjacent in the circumferential direction. A plurality of windings 24 are inserted into each slot 90 . The windings 24 inserted into the slots 90 are insulated from the teeth 22 by the insulators 23 .

<Structure of Winding>
FIG. 4 is a developed view of the teeth 22 of the stator 8. As shown in FIG. In FIG. 4, the teeth 22 are numbered sequentially in the circumferential direction. In FIG. 4 , slots 90 correspond to spaces between teeth 22 adjacent in the circumferential direction. In FIG. 4, magnetic poles (N pole, S pole) are shown above the stator 8 . In this embodiment , the number of magnetic poles is four (details will be described later).

As shown in FIG. 4, each slot 90 has a plurality of windings 24 (for example, 10 in this embodiment ) inserted therein. Among the plurality of windings 24, a predetermined number (for example, 5 in this embodiment ) of the windings 24 are arranged with a predetermined number (for example, 4 in this embodiment ) of slots 90 interposed therebetween. Those inserted into the slots 90 located on both sides are connected via end coils 94 . The number of end coils 94 is the same as the number of windings 24, and corresponding windings 24 between predetermined slots 90 are separately connected. In this embodiment , the number of magnetic poles is four, and among the total number of 24 slots 90, the winding wire 24 is wound between the slots 90 located on both sides of the four slots 90. , a winding 24 is wound around the stator 8 by a distributed winding method.

The windings 24 configured in this way are connected to the controller section 4 with the terminal portions drawn out from the stator 8 . The winding 24 generates a magnetic field for rotating the rotor 9 by power supply from the controller section 4 .

<Rotor>
FIG. 5 is a plan view of the rotor 9 as seen from the axial direction, and shows only a circumferential angular region of 1/2 circumference.
As shown in FIGS. 3 and 5, the rotor 9 includes a shaft 31 integrally formed with a worm shaft 44 (see FIG. 2) that constitutes the reduction section 3, and a shaft 31 that is fitted and fixed to the outer peripheral surface of the shaft 31. and a plurality of permanent magnets 33 a to 33 d arranged in the rotor core 32 .

The rotor core 32 is formed, for example, by laminating a plurality of metal plates in the axial direction. It should be noted that the rotor core 32 is not limited to being formed by laminating a plurality of metal plates in the axial direction, and may be formed by pressing soft magnetic powder, for example.
A through hole 32a is formed in the radial center of the rotor core 32 along the axial direction. A shaft 31 is fixed to the through hole 32a by press fitting or the like. As a result, the shaft 31 and the rotor core 32 rotate together. The rotor core 32 is held in a state in which the outer peripheral surface 32b faces the inner peripheral surface of the stator core 21 with a predetermined air gap G in the radial direction.

In the rotor core 32, four layers of slits 35a to 35d (first slit 35a, second slit 35b, third slit 35c, fourth slit 35d) are arranged in the radial direction in each of the quarter angular regions. is formed by The first slit 35a is arranged on the outermost radial direction, and the second slit 35b, the third slit 35c, and the fourth slit 35d are arranged in order toward the radially inner side. A fourth slit 35 d is arranged at the innermost radial position of the rotor core 32 .
It should be noted that the shape of the rotor core 32 in the circumferential angular region of 1/4 turn is the same shape as the rotor core 32 in the other circumferential angular region of 1/4 turn. Therefore, in the following description, only the rotor core 32 in one quarter of the circumferential angular region will be described, and the description of the rotor core 32 in the other quarter of the circumferential angular region will be omitted.

Each of the slits 35a to 35d is formed along the flow of interlinkage magnetic flux that is formed when the winding 24 is energized. In other words, each of the slits 35a to 35d is curved so that the center in the circumferential direction is positioned radially inward (to form a convex shape radially inward). As a result, the rotor core 32 is provided with a direction in which the magnetic flux easily flows and a direction in which the magnetic flux hardly flows.

Both ends of the slits 35 a to 35 d in the circumferential direction extend to the vicinity of the outer peripheral surface 32 b of the rotor core 32 . The distances Ka to Kd between both longitudinal ends of each of the slits 35a to 35d and the outer peripheral surface 32b of the rotor core 32 when viewed in the axial direction are all the same. That is, the longitudinal lengths L1a to L1d of each of the slits 35a to 35d seen from the axial direction are
L1a<L1b<L1c<L1d (1)
meet. In other words, the lengths L1a to L1d in the longitudinal direction viewed from the axial direction gradually increase in order from the first slit 35a to the fourth slit 35d.

Widths W1a to W1d in the lateral direction of each of the slits 35a to 35d viewed from the axial direction are uniform (the same width) throughout the longitudinal direction. In addition, the widths Wa to Wd of the slits 35a to 35d in the lateral direction are
W1a<W1b<W1c<W1d (2)
meet. In other words, the widths W1a to W1d in the lateral direction viewed from the axial direction gradually increase in order from the first slit 35a to the fourth slit 35d. The widths W1a to W1d of the slits 35a to 35d arranged radially inward of the rotor core 32 are larger than the widths W1a to W1d of the slits 35a to 35d arranged closer to the outer peripheral surface 32b of the rotor core 32 .

Thus, the rotor core 32 is configured with four poles. That is, the q-axis hits the pole boundary. The q-axis is the direction in which interlinkage magnetic flux tends to flow. A direction along the radial direction that is electrically and magnetically orthogonal to the q-axis is referred to as the d-axis.
In the rotor core 32, four layers of slits 35a to 35d are formed per pole (circumferential angular region of 1/4 circumference of the rotor core 32).
Here, when the number of poles of the rotor core 32 is Jn and the number of teeth 22 of the stator 8 is Tn, the number of poles Jn and the number of teeth Tn are:
Jn:Tn=2:12 (3)
is set to meet In the present embodiment, the number of poles Jn of the rotor core 32 is 4, and the number of teeth 22 of the stator 8 Tn is 24, which satisfies the above equation (3).

The widths W1a to W1d of the slits 35a to 35d in the lateral direction are the circumferential length Lc of the outer circumferential surface 32b of the rotor core 32 per pole (the circumferential length Lc between the q axes of the outer circumferential surface 32b of the rotor core 32). The ratio to the length Lc) (hereinafter referred to as the slit width ratio) is set at a ratio of 35% to 55%. In other words, the slit width ratio is
35≦{(W1a+W1b+W1c+W1d)/Lc}×100≦55 (4)
is set to meet Further, widths W1a to W1d in the lateral direction of the slits 35a to 35d are preferably 45% of the circumferential length Lc of the outer peripheral surface 32b of the rotor core 32 per pole. Details of this will be described later.

Permanent magnets 33a-33d (a first permanent magnet 33a, a second permanent magnet 33b, a third permanent magnet 33c, a third 4 permanent magnets 33d) are provided. Between the slits 35a-35d and the corresponding permanent magnets 33a-33d, slight gaps 34a-34d are formed only at both longitudinal ends of the permanent magnets 33a-33d when viewed in the axial direction. Therefore, the magnet widths W2a to W2d in the lateral direction of the permanent magnets 33a to 33d when viewed from the axial direction are
W2a<W2b<W2c<W2d (5)
meet. In other words, the magnet widths W2a to W2d in the lateral direction viewed from the axial direction gradually increase in order from the first permanent magnet 33a to the fourth permanent magnet 33d. Permanent magnets 33a to 33d arranged radially inward of rotor core 32 have magnet widths W2a to W2d larger than permanent magnets 33a to 33d arranged closer to outer peripheral surface 32b of rotor core 32 .

The magnet widths W2a to W2d in the lateral direction of the permanent magnets 33a to 33d are ratios to the circumferential length Lc of the outer peripheral surface 32b of the rotor core 32 per pole (this ratio is hereinafter referred to as the magnet width ratio). ) is set at a rate of 35% to 55%. In other words, the ratio of the magnet width is
35≦{(W2a+W2b+W2c+W2d)/Lc}×100≦55 (6)
is set to meet Further, the magnet widths W2a to W2d in the lateral direction of the permanent magnets 33a to 33d are preferably 45% of the circumferential length Lc of the outer peripheral surface 32b of the rotor core 32 per pole. Details of this will be described later.

Each of the permanent magnets 33a-33d is a permanent magnet containing ferrite. The permanent magnets 33a to 33d may contain ferrite, and may be so-called sintered ferrite magnets or bonded ferrite magnets, or may be permanent magnets obtained by mixing ferrite and rare earth (for example, samarium).

FIG. 6 shows the orientation of the permanent magnets 33a-33d, where (a) is the radial orientation and (b) is the polar orientation.
The permanent magnets 33a to 33d may be oriented radially as shown in FIG. 6(a) or polarly oriented as shown in FIG. 6(b).

Also, the permanent magnets 33a to 33d are formed to have different polarities in the radial direction. The permanent magnets 33a to 33d arranged in the slits 35a to 35d with the same magnetic pole are arranged so that the magnetic poles are oriented in the same direction. The permanent magnets 33a to 33d arranged in the slits 35a to 35d of each pole are arranged so that the magnetic poles are arranged in order in the circumferential direction.
Each air gap 34a-34d functions as a flux barrier to prevent the magnetic flux of each permanent magnet 33a-33d from leaking in a predetermined direction.

<Deceleration part>
Returning to FIGS. 1 and 2 , the reduction section 3 includes a gear case 40 to which the motor case 5 is attached, and a worm reduction mechanism 41 housed in the gear case 40 . The gear case 40 is made of a material having excellent heat dissipation properties, such as die-cast aluminum. The gear case 40 is formed in a box shape having an opening 40a on one side, and has a gear housing portion 42 for housing a worm reduction mechanism 41 therein. In the side wall 40b of the gear case 40, an opening 43 is formed at a portion where the first motor case 6 is integrally molded, which communicates the through hole 10a of the first motor case 6 with the gear housing portion 42. .

A substantially cylindrical bearing boss 49 protrudes from the bottom wall 40 c of the gear case 40 . The bearing boss 49 rotatably supports the output shaft 48 of the worm speed reduction mechanism 41 . A sliding bearing (not shown) is provided on the inner peripheral surface of the bearing boss 49 . An O-ring (not shown) is attached to the inner peripheral edge of the tip of the bearing boss 49 . This prevents dust and water from entering from the outside through 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 reduction mechanism 41 housed in the gear housing portion 42 is composed of a worm shaft 44 and a worm wheel 45 meshed with the worm shaft 44 . The worm shaft 44 is arranged coaxially with the shaft 31 of the motor section 2 . Both ends of the worm shaft 44 are rotatably supported by bearings 46 and 47 provided in the gear case 40 . The end of the worm shaft 44 on the side of the motor unit 2 protrudes through the bearing 46 to reach the opening 43 of the gear case 40 . The protruding end of the worm shaft 44 and the end of the shaft 31 of the motor section 2 are joined together to integrate the worm shaft 44 and the shaft 31 . The worm shaft 44 and the shaft 31 may be integrally formed by molding the worm shaft portion and the rotating shaft portion from one base material.

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

A sensor magnet (not shown) is provided at the center of the worm wheel 45 in the radial direction on the side opposite to the side where the output shaft 48 protrudes. This sensor magnet constitutes one of the rotational position detectors 60 that detect the rotational position of the worm wheel 45 . The magnetic detection element 61, which constitutes the other side of the rotational position detection section 60, is provided in the controller section 4 arranged to face the worm wheel 45 on the sensor magnet side of the worm wheel 45 (on the side of the opening 40a of the gear case 40). there is

<Controller part>
The controller section 4 that controls the drive of the motor section 2 includes a controller board 62 on which a magnetic detection element 61 is mounted, and a cover 63 that closes the opening 40 a of the gear case 40 . The controller board 62 is arranged to face the sensor magnet side of the worm wheel 45 (the side of the opening 40a of the gear case 40).

The controller board 62 is a so-called epoxy board on which a plurality of conductive patterns (not shown) are formed. The windings 24 of the motor section 2 are connected to the controller board 62, and terminals of a connector provided on the cover 63 (both not shown) are electrically connected. In addition to the magnetic detection element 61 , the controller board 62 is mounted with a power module (not shown) comprising switching elements such as FETs (Field Effect Transistors) for controlling the current supplied to the winding 24 . The controller board 62 is mounted with a capacitor (not shown) for smoothing the voltage applied to the controller board 62 .

A cover 63 that covers the controller board 62 configured in this way is made of resin. The cover 63 is formed to protrude slightly outward. The inner surface side of the cover 63 serves as a controller accommodating portion 56 that accommodates the controller board 62 and the like.
A connector (not shown) is integrally formed on the outer peripheral portion of the cover 63 . This connector is formed so as to be fittable with a connector extending from an external power source (not shown). A controller board 62 is electrically connected to terminals of this connector. As a result, power from the external power supply is supplied to the controller board 62 .

Here, the controller board 62 performs lead-angle energization and wide-angle energization with an electrical angle θ of 121° to 180° to the windings 24 . The controller board 62 applies to the winding 24 a drive current on which the fifth harmonic is superimposed.

An opening edge of the cover 63 is formed with a protruding fitting portion 81 that is fitted with an end portion of the side wall 40 b of the gear case 40 . The fitting portion 81 is composed of two walls 81 a and 81 b along the opening edge of the cover 63 . The end 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 portion 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 bolts (not shown).

<Operation of wiper motor>
Next, operation of the wiper motor 1 will be described.
In the wiper motor 1, power supplied to the controller board 62 via the connector 11 is selectively supplied to each winding 24 of the motor section 2 via a power module (not shown). Then, the current flowing through each winding 24 forms a predetermined magnetic flux linkage in the stator 8 (teeth 22). This interlinking magnetic flux generates magnetic attraction or repulsion (magnet torque) with the effective magnetic flux formed by the permanent magnets 33 of the rotor 9 . The interlinking magnetic flux also causes the rotor 9 to generate reluctance torque. Thereby, the rotor 9 is continuously rotated.

Rotation of the rotor 9 is transmitted to a worm shaft 44 integrated with the shaft 31 and further transmitted to a worm wheel 45 meshing with the worm shaft 44 . Rotation of the worm wheel 45 is transmitted to an output shaft 48 connected to the worm wheel 45 . A wiper device 100 is driven by the output shaft 48 .

A detection signal of the rotational position of the worm wheel 45 detected by the magnetic detection element 61 mounted on the controller board 62 is output to an external device (not shown). The external device (not shown) is, for example, a software functional unit that functions when a predetermined program is executed by a processor such as a CPU (Central Processing Unit). The software function unit is an ECU (Electronic Control Unit) comprising a processor such as a CPU, a ROM (Read Only Memory) for storing programs, a RAM (Random Access Memory) for temporarily storing data, and an electronic circuit such as a timer. . At least part of the external device (not shown) may be an integrated circuit such as an LSI (Large Scale Integration).

An external device (not shown) controls switching timing of a switching element of a power module (not shown) based on the rotational position detection signal of the worm wheel 45 to drive and control the motor section 2 . The output of the drive signal of the power module and the drive control of the motor section 2 may be executed by the controller section 4 instead of an external device (not shown).

<Motor Characteristics of Motor Unit and Method for Determining Shape of Rotor in this Embodiment >
Next, the motor characteristics of the motor unit 2 and the method of determining the shape of the rotor 9 of the present embodiment will be described with reference to FIGS. 7 to 15. FIG.
FIG. 7 is a graph showing changes in torque when the vertical axis is the torque [N·m] of the motor unit 2 and the horizontal axis is the number of permanent magnet layers per pole.
As shown in FIG. 7, it can be confirmed that the torque can be improved as the number of permanent magnet layers increases.

FIG. 8 is a graph showing changes in torque ripple when the vertical axis is the torque ripple [mN·m] of the motor section 2 and the horizontal axis is the number of permanent magnet layers per pole.
As shown in FIG. 8, it can be confirmed that when the number of layers of the permanent magnets is three or more, the torque ripple becomes extremely small compared to when the number of layers of the permanent magnets is two or less.

FIG. 9 is a graph showing changes in cogging torque when the vertical axis is the cogging torque [mN·m] of the motor unit 2 and the horizontal axis is the number of permanent magnet layers per pole.
As shown in FIG. 9, it can be confirmed that the cogging torque can be reduced particularly when the number of permanent magnet layers is four or more.

Here, in FIGS. 8 and 9, numerical values of torque ripple [mN・m] and cogging torque [mN・m] are not shown. mN·m] is extremely small. Therefore, the magnitude of the cogging torque [mN·m] is negligible with respect to the magnitude of the torque ripple [mN·m]. Therefore, based on FIGS. 7 to 9, in this embodiment , the number of layers of permanent magnets per pole is three or more.

FIG. 10 is a graph showing changes in torque when the vertical axis is the torque [N·m] of the motor section 2 and the horizontal axis is the ratio of the width of the magnet.
As shown in FIG. 10, it can be confirmed that good torque can be obtained when the ratio of the magnet width is in the range of 35% to 55%.

FIG. 11 is a graph showing changes in torque when the vertical axis is the torque ripple [mN·m] of the motor section 2 and the horizontal axis is the ratio of the width of the magnet.
As shown in FIG. 11, it can be confirmed that the torque ripple can be reduced when the ratio of the magnet width is from 35% to 55%.

FIG. 12 is a graph showing changes in torque when the vertical axis is the cogging torque [mN·m] of the motor section 2 and the horizontal axis is the ratio of the magnet width.
As shown in FIG. 12, it can be confirmed that the cogging torque can be reduced when the ratio of the magnet width is from 35% to 55%.
Therefore, based on FIGS. 10 to 12, the ratio of the magnet width is set at a ratio of 35% to 55% in this embodiment .

Here, as shown in FIG. 10, it can be confirmed that the torque becomes maximum when the ratio of the magnet width is 45%. Also, as shown in FIGS. 11 and 12, it can be confirmed that the torque ripple and the cogging torque are minimized when the ratio of the magnet width is 45%.

FIG. 13 is a graph comparing the effective magnetic flux [μWb] of the permanent magnets 33a to 33d between the radial orientation and the parallel orientation.
As shown in FIG. 13, it can be confirmed that the effective magnetic flux is larger when the permanent magnets 33a to 33d are oriented radially than when the permanent magnets 33a to 33d are oriented parallel. Incidentally, even when the permanent magnets 33a to 33d are polar-oriented, it can be said that the orientation is the same as the radial orientation.
Therefore, based on FIG. 13, in this embodiment , the orientation of the permanent magnets 33a to 33d is set to radial orientation or polar orientation.

FIG. 14 is a graph (demagnetization curve) showing changes in magnetic flux when the vertical axis is the magnetic flux [T] of the permanent magnet and the horizontal axis is the coercive force [kA/m] of the permanent magnet. A comparison was made between a neodymium magnet and a ferrite magnet.
As shown in FIG. 14, a neodymium magnet is less likely to be magnetized unless a larger magnetic field is applied than a ferrite magnet. For this reason, it can be confirmed that the neodymium magnet is less likely to be magnetized as it is positioned radially inward of the rotor core 32 compared to the ferrite magnet. Therefore, based on FIG. 14, the permanent magnets 33a to 33d in this embodiment are permanent magnets containing ferrite.

FIG. 15 is a plan view of the rotor 9 viewed from the axial direction, showing the demagnetization factors of the permanent magnets 33a to 33d due to the flux linkage of the stator 8. FIG.
Here, the q-axis of the rotor core 32 is the location of the switching timing of the flux linkage of the stator 8 . Therefore, as shown by dot hatching in FIG. 15, among the permanent magnets 33a to 33d, the third permanent magnet 33c and the fourth permanent magnet 33d located near the q-axis are demagnetized under the influence of the interlinkage magnetic flux. You can confirm that it is easy. Therefore, in this embodiment , the magnet widths W2a to W2d are gradually increased in order from the first permanent magnet 33a to the fourth permanent magnet 33d, based on FIG. That is, the magnet widths W2a to W2d of the permanent magnets 33a to 33d arranged radially inward of the rotor core 32 are larger than those of the permanent magnets 33a to 33d arranged closer to the outer peripheral surface 32b of the rotor core 32.

As described above, in the above- described embodiment, each pole of the rotor core 32 is curved so as to protrude radially inward, and three or more layers of permanent magnets 33a to 33d are provided for each pole. rice field. Also, the number of poles Jn of the rotor 9 and the number of teeth 22 of the stator 8 Tn are set so as to satisfy the above formula (3). Furthermore, the ratio of the magnet width of the permanent magnets 33a to 33d is set at a ratio of 35% to 55%. Therefore, the motor unit 2 can realize a reduction in torque ripple and an improvement in torque in a well-balanced manner.

Further, by setting the ratio of the magnet width of the permanent magnets 33a to 33d to 45%, it is possible to provide an excellent motor section 2 capable of minimizing torque ripple and maximizing torque.
Further, by setting the orientation of the permanent magnets 33a to 33d to radial orientation or polar orientation, the effective magnetic flux of the rotor 9 can be reliably increased.
By using the permanent magnets 33a-33d as permanent magnets containing ferrite, the permanent magnets 33a-33d can be reliably and sufficiently magnetized.
By making the magnet widths W2a to W2d of the permanent magnets 33a to 33d arranged radially inward of the rotor core 32 larger than those of the permanent magnets 33a to 33d arranged closer to the outer peripheral surface 32b of the rotor core 32, The influence of the interlinking magnetic flux of the stator 8 can be minimized, and the motor section 2 can have high performance.

[ Reference example ]
Next, a reference example will be described based on FIG. In addition, the same code|symbol is attached|subjected to the same aspect as above-mentioned embodiment, and description is abbreviate|omitted.
FIG. 16 is a plan view of the rotor 209 in the reference example as seen from the axial direction, and shows only a circumferential angular region of 1/2 circumference. FIG. 16 corresponds to FIG. 5 described above.
As shown in FIG. 16, the differences between the embodiment and the reference example are the shapes of the permanent magnets 33a to 33d and the slits 35a to 35d of the rotor 9 of the embodiment , and the permanent magnets 233a to 233d of the rotor 209 of the reference example . 233d and the slits 235a to 235d are different in shape.

That is, the permanent magnets 233a to 233d and the slits 235a to 235d of the rotor 209 of the reference example all have the same width in the lateral direction when viewed from the axial direction. No gap is formed between each of the slits 235a-235d and the corresponding permanent magnets 233a-233d, and the entire slits 235a-235d are filled with the corresponding permanent magnets 233a-233d. The distance between each of the slits 35a-35d (each of the permanent magnets 33a-33d) and the outer peripheral surface 232b of the rotor core 232 is preferably a distance at which the magnetic flux is saturated.
As a result, magnetic flux leakage from the permanent magnets 33a to 33d can be suppressed.
Even with such a configuration, the same effect as the above-described embodiment can be obtained.

It should be noted that the present invention is not limited to the above-described embodiments, and includes various modifications of the above-described embodiments within the scope of the present invention.
For example, in the above-described embodiment, the wiper motor 1 serves as a drive source for the wiper device 100 for wiping the window glass of the vehicle. However, it is not limited to this, and the above wiper motor 1 can be used as a drive source for electrical equipment mounted on a vehicle (for example, power windows, sunroofs, electric seats, etc.) and various other uses. can be adopted.

In the above-described embodiment, the case where the windings 24 are wound around the stator 8 by the distributed winding method has been described. However, the windings 24 are not limited to this, and the windings 24 may be wound around the stator 8 by a lap winding method or a concentrated winding method.

In the above-described embodiment, the rotor core 32 is provided with four layers of permanent magnets 33a to 33d (first permanent magnet 33a, second permanent magnet 33b, third permanent magnet 33c, fourth permanent magnet 33d) for each pole. I explained the case where However, the present invention is not limited to this, and the rotor core 32 may be provided with three or more layers of permanent magnets per pole.

In the above-described embodiment, the number of poles Jn of the rotor core 32 is 4, and the number of teeth 22 of the stator 8 is 24 Tn. However, the present invention is not limited to this, and the number of poles Jn of the rotor core 32 and the number of teeth Tn of the teeth 22 may satisfy the above formula (3). By configuring in this way, the motor section 2 can be properly driven.

In the above- described embodiment, a case has been described in which the magnet widths W2a to W2d in the lateral direction viewed from the axial direction gradually increase in order from the first permanent magnet 33a to the fourth permanent magnet 33d.
Further, in the above-described embodiment , a slight air gap 34a is provided between each of the slits 35a to 35d and the corresponding permanent magnets 33a to 33d and at both longitudinal ends of each of the permanent magnets 33a to 33d when viewed from the axial direction. The case where ~34d is formed has been described. Further, in the reference example described above, the permanent magnets 233a to 233d and the slits 235a to 235d have all the same width in the lateral direction when viewed from the axial direction. Furthermore, when no gap is formed between each of the slits 235a to 235d and each of the corresponding permanent magnets 233a to 233d, and each of the slits 235a to 235d is entirely filled with the corresponding permanent magnets 233a to 233d. explained. However, the invention is not limited to this, and the embodiment and the reference example may be combined. For example, gaps 34a-34d may be formed at both longitudinal ends of the permanent magnets 233a-233d.

DESCRIPTION OF SYMBOLS 1... Wiper motor 2... Motor part (motor) 5... Motor case 6... 1st motor case 7... 2nd motor case 8... Stator 9, 209... Rotor 21... Stator core 22... Teeth 24 Winding 32, 232 Rotor core 32b, 232b Peripheral surface 33a to 33d, 233a to 233d Permanent magnet C Rotational axis Lc Circumferential length W2a to W2d Magnet width 100 Wiper device

Claims (5)

an annular stator core;
a plurality of teeth projecting radially inward from the inner surface of the stator core and arranged along the circumferential direction;
a plurality of windings wound around the teeth;
a rotor core provided radially inside the teeth so as to be rotatable about the rotation axis with respect to the teeth and having four magnetic poles along the circumferential direction;
The rotor core has four layers of slits formed in each of the quarter angular regions of the circumference, and has permanent magnets housed in each of the slits,
Each of the slits is curved to form a convex shape radially inward per pole,
The width in the transverse direction of the slits arranged radially inward of the rotor core is larger than the width in the transverse direction of the slits arranged near the outer peripheral surface of the rotor core,
Both ends of each of the slits in the circumferential direction extend to the vicinity of the outer peripheral surface of the rotor core. can be,
When the number of poles of the rotor core is Jn and the number of teeth is Tn, the number of poles Jn and the number of teeth Tn are:
Jn:Tn=2:12
is set to satisfy
Each of the permanent magnets is curved to form a convex shape radially inward for each pole so as to correspond to the shape of the corresponding slit,
The permanent magnet has a uniform magnet width in a lateral direction viewed from the rotation axis direction over the entire longitudinal direction viewed from the rotation axis direction, and the magnet width is uniform on the outer peripheral surface of the rotor core per pole. is set at a rate of 35% to 55% of the circumferential length of
For each pole of the rotor core, the magnet width of the permanent magnets arranged radially inward of the rotor core is larger than the magnet width of the permanent magnets arranged closer to the outer peripheral surface of the rotor core. nine,
Among the four layers of slits of the rotor core, the distance between the slits adjacent in the radial direction increases from the radially inner side of the rotor core toward the outer peripheral surface of the rotor core.
A motor characterized by: 2. The motor according to claim 1, wherein the magnet width of the permanent magnet is set at a rate of 45% of the circumferential length of the outer peripheral surface of the rotor core per pole. 3. The motor according to claim 1, wherein the permanent magnets are radially or polarly oriented. 4. The motor according to any one of claims 1 to 3, wherein the permanent magnet contains ferrite. A wiper motor, wherein the motor according to any one of claims 1 to 4 is used in a wiper device mounted on a vehicle.

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