JP2019022431A - Motor and brushless wiper motor - Google Patents

Abstract

To effectively reduce ripple at a low cost.SOLUTION: A motor part 2 comprises: a stator 8 having an annular stator core 20 and a plurality of teeth 22; coils 24 wound round the teeth 22; a rotor core 32 fixed to a shaft 31 and using a rotation axis as a radial center; magnets 33 arranged on an outer peripheral surface 32b of the rotor core 32, the radial thickness of both circumferential ends 33s around the rotation axis being less than the radial thickness of a circumferential middle part; and salient poles 35 projecting radially outside from the circumferential ends 33s of the magnets 33 and between adjacent magnets 33 in a circumferential direction of the outer peripheral surface 32b of the rotor core 32. In each magnet 33, the curvature radius R1 of an outer peripheral surface 33a is set to 0.8 time or less of a distance from the shaft center C1 of a shaft 31, in a portion located furthest radially outside of the outer peripheral surface 33a of the magnet 33.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a motor and a brushless wiper motor.

  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. An interlinkage magnetic flux is formed in the stator by supplying power to the coil. The rotor includes a rotating shaft, a substantially cylindrical rotor core that is fitted and fixed to the rotating 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, the method of arranging the permanent magnet on the rotor is roughly divided into two. One is a permanent magnet embedded system (IPM) in which a plurality of slits are formed in a rotor core and permanent magnets are arranged in the slits.
Further, as another method of arranging 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) (see, for example, Patent Document 1).

By the way, when the motor as described above is used for a wiper motor for an automobile, for example, both high rotation and high torque may be required.
In the SPM motor, if the current supply is advanced and widened, the rotation speed can be increased. The widening of the current supply is to wrap the supply timings of the currents of the three phases alternately supplied to each other to widen the angle to 120 ° or more. In this way, by using the field weakening by the advance angle energization and the wide angle energization, it is possible to increase the rotation speed of the motor.
In such an SPM motor, the torque can be increased by increasing the amount of magnet used.

JP 2016-214081 A

However, when the rotation and torque of the SPM motor are increased, ripples that cause the torque to periodically increase and decrease may occur with the rotation of the motor.
In order to cancel such a ripple, it is necessary to superimpose higher-order harmonic components such as the fifth, seventh, and eleventh orders on the phase current applied to the coil. However, generating high-order harmonics by calculating with a microcomputer of the drive circuit that supplies current to the coil has a high processing load and leads to an increase in the cost of the microcomputer.

  Therefore, the present invention has been made in view of the above-described circumstances, and provides a motor and a brushless wiper motor that can effectively reduce ripples at low cost.

The present invention employs the following means in order to solve the above problems.
That is, the motor of the present invention includes an annular stator core, a stator having a plurality of teeth protruding radially inward from an inner peripheral surface of the stator core, a coil wound around the teeth, and a diameter of the stator core. A shaft that rotates around the rotation axis on the inner side in the direction, a rotor core that is fixed to the shaft and that has the rotation axis as the center in the radial direction, and that is disposed on the outer peripheral surface of the rotor core, and ends on both sides in the circumferential direction around the rotation axis In the circumferential direction of the magnet, the magnet has a radial thickness smaller than the radial thickness in the circumferential intermediate portion and the magnet adjacent in the circumferential direction of the outer circumferential surface of the rotor core. And a salient pole projecting outward in the radial direction from the end of the magnet, and the ratio of the number of magnetic poles of the magnet to the number of teeth is 2n: 3n (however, Is a natural number), and the radius of curvature of the outer periphery of the magnet is 0.8 times the distance from the axis of rotation at the portion of the outermost surface of the magnet that is located radially outward. It is set as follows.

  In this way, the salient poles are protruded radially outward from the circumferential end of the magnet, and the radius of curvature of the outer peripheral surface of the magnet is rotated at a portion located on the outermost radial direction of the magnet. It was smaller than the distance from the axis. Thereby, the edge part of the circumferential direction both sides of a magnet will be arrange | positioned radially inside rather than a salient pole. And magnetic flux concentrates on a salient pole and it becomes difficult for a demagnetizing field to act on the end of a magnet. Then, it is possible to suppress higher-order harmonic components contained in the induced voltage when a current is supplied to the coil, and torque ripple in the motor can be suppressed. As described above, if the radius of curvature of the outer peripheral surface of the magnet is reduced, the effect of suppressing torque ripple can be obtained. Therefore, it is necessary to generate high-order harmonics by calculating with a microcomputer of a drive circuit that supplies current to the coil. It can be suppressed. Therefore, the necessity for providing a microcomputer with a high processing load in the drive circuit unit is reduced, and an increase in cost can be suppressed.

  The motor of the present invention includes an annular stator core, a stator having a plurality of teeth protruding radially inward from an inner peripheral surface of the stator core, a coil wound around the teeth, and a diameter of the stator core. A shaft that rotates around the rotation axis on the inner side in the direction, a rotor core that is fixed to the shaft and that has the rotation axis as the center in the radial direction, and that is disposed on the outer peripheral surface of the rotor core, and ends on both sides in the circumferential direction around the rotation axis In the circumferential direction of the magnet, the magnet has a radial thickness smaller than the radial thickness in the circumferential intermediate portion and the magnet adjacent in the circumferential direction of the outer circumferential surface of the rotor core. And a ratio of the number of magnetic poles of the magnet to the number of teeth is 2n: 3n (where n is The radius of curvature of the outer peripheral surface of the magnet is 0.8 times the distance from the rotation axis at the portion located on the outermost radial direction of the outer peripheral surface of the magnet. Larger than and 0.9 times or less, and the outer peripheral surface of the magnet has a flat surface portion in a range of electrical angle of 10 ° or more and 18 ° or less at both ends of the outer peripheral surface in the circumferential direction. It is characterized by that.

  In this way, the salient poles are protruded radially outward from the circumferential end of the magnet. In addition, the radius of curvature of the outer peripheral surface of the magnet is made smaller than the distance from the rotation axis at the portion located on the outermost radial direction on the outer peripheral surface of the magnet, and flat portions are provided at both ends in the circumferential direction of the outer peripheral surface of the magnet. Form. In this way, the end portions on both sides in the circumferential direction of the magnet are arranged radially inward from the salient poles. Thereby, magnetic flux concentrates on a salient pole and it becomes difficult for a demagnetizing field to act on the edge part of a magnet. Then, it is possible to suppress higher-order harmonic components contained in the induced voltage when a current is supplied to the coil, and torque ripple in the motor can be suppressed. Thus, if the radius of curvature of the outer peripheral surface of the magnet is reduced and the salient pole protrudes radially outward from the circumferential end of the magnet, a torque ripple suppressing effect can be obtained, which is high. It is possible to suppress the generation of harmonics of the order by calculating with a microcomputer of a drive circuit that supplies current to the coil. Therefore, the necessity for providing a microcomputer with a high processing load in the drive circuit unit is reduced, and an increase in cost can be suppressed.

  In the motor of the present invention, it is preferable that a circumferential width dimension at the radially outer end of the salient pole is set to 40 ° or less in electrical angle.

  According to such a configuration, the inductance value in the q-axis direction can be reduced by setting the electrical angle of the salient pole to 40 ° or less and reducing the width dimension of the salient pole in the circumferential direction. For this reason, a demagnetizing field can be suppressed.

  In the motor of the present invention, the circumferential width dimension at the radially outer end of the salient pole may be set to an electrical angle of 20 ° or more.

  According to such a configuration, the electrical angle of the salient pole can be set to 20 ° or more, and the width dimension in the radial direction can be ensured. Thereby, the effect that the demagnetizing field hardly acts on the end portion of the ferrite magnet can be surely obtained by concentrating the magnetic flux on the salient pole.

  In the motor of the present invention, the magnet may be a ferrite magnet, and the magnetization orientation may be a parallel orientation.

  According to such a configuration, the cogging of the motor can be suppressed and a high magnetic flux density can be obtained. Further, by using a ferrite magnet instead of a rare earth magnet as the magnet, even if the radial dimension of the magnet is increased in order to obtain a high torque, an increase in cost due to an increase in the amount of magnet used can be suppressed.

  The motor of the present invention may further include a drive circuit unit that applies a drive current in which a fifth harmonic is superimposed on the coil.

  According to such a configuration, it is only necessary to apply a driving current superimposed with the fifth harmonic to the coil, and it is possible to suppress the necessity of calculating and generating a higher harmonic by the microcomputer of the driving circuit.

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

  According to such a configuration, the radius of curvature of the outer circumferential surface of the magnet is reduced, and the salient poles are projected outward in the radial direction from the circumferential end portion of the magnet, thereby obtaining a torque ripple suppressing effect. As a result, it is possible to suppress the need to generate and generate higher-order harmonics by the microcomputer of the drive circuit that supplies current to the coil. Therefore, the necessity for providing a microcomputer with a high processing load in the drive circuit unit is reduced, and an increase in cost can be suppressed.

  According to the present invention, it is possible to effectively reduce ripples at low cost.

It is a perspective view of the wiper motor in the embodiment of the present invention. It is sectional drawing which follows the AA line of FIG. 1 of the wiper motor in embodiment of this invention. It is the top view which looked at the stator and rotor in embodiment of this invention from the axial direction. It is the figure which expanded the rotor in embodiment of this invention. It is the figure which expanded the magnet in embodiment of this invention. It is a graph which shows the q-axis and d-axis inductance of the rotor in the embodiment of the present invention. It is a graph which shows the relationship between a torque and rotation speed at the time of performing advance angle energization and wide angle energization to the rotor in the embodiment of the present invention. It is a graph which shows the torque which generate | occur | produces with a rotor when the width dimension of the salient pole in embodiment of this invention is varied. It is a graph which shows the ripple rate which generate | occur | produces in a rotor when the width dimension of a salient pole in embodiment of this invention is varied. It is a graph which shows the cogging which generate | occur | produces in a rotor when the width dimension of the salient pole in embodiment of this invention is varied. It is a graph which shows the magnetic flux density in the edge part of the circumferential direction of the magnet of the rotor in embodiment of this invention. It is a figure which shows the direction of the magnetic flux in the circumference | surroundings of a salient pole when the salient pole in embodiment of this invention is made to project to the radial direction outer side rather than the edge part of the circumferential direction of a magnet. It is a figure which shows the direction of the magnetic flux in the circumference | surroundings of a salient pole when not making the salient pole in embodiment of this invention project outside radial direction rather than the edge part of the circumferential direction of a magnet. It is a graph which shows cogging generate | occur | produced in a rotor when the orientation of the magnet in embodiment of this invention is made into parallel orientation and radial orientation. It is a graph which shows the effective magnetic flux which generate | occur | produces in a rotor when the orientation of the magnet in embodiment of this invention is made into parallel orientation and radial orientation. It is a graph which shows the magnetic flux density in the edge part of the circumferential direction of the magnet of the rotor in embodiment of this invention. It is a graph which shows the minimum value of the magnetic flux density when the orientation of the magnet in the embodiment of the present invention is a parallel orientation and a radial orientation. It is a graph which shows the content rate of the harmonic contained in an induced voltage at the time of changing the curvature radius of the outer peripheral surface of the magnet in embodiment of this invention. It is a graph which shows the content rate of the harmonic contained in an induced voltage when the orientation of the magnet in embodiment of this invention is made into parallel orientation and radial orientation. It is a figure which shows the waveform of the three-phase drive current which has not superimposed the 5th harmonic in the embodiment of this invention. It is a figure which shows the torque waveform at the time of applying the three-phase drive current which has not superimposed the 5th harmonic in the embodiment of this invention. It is a figure which shows the waveform of the three-phase drive current which superimposed the 5th harmonic in the embodiment of this invention. It is a figure which shows the torque waveform at the time of applying the three-phase drive current which superimposed the 5th harmonic in the embodiment of this invention. FIG. 24 is a graph for comparing the generated torque in each order by performing FFT analysis on the torque waveforms of FIGS. 21 and 23 in the embodiment of the present invention. FIG. It is a figure which shows the shape of the magnet in the modification of embodiment of this invention in embodiment of this invention. It is a graph which shows the content rate of the harmonic contained in an induced voltage at the time of changing the range (electrical angle) which forms the plane part of a magnet in embodiment of this invention.

  Next, a motor and a brushless wiper motor according to an embodiment of the present invention will be described with reference to the drawings.

(Wiper motor)
FIG. 1 is a perspective view of the wiper motor 1. 2 is a cross-sectional view taken along line AA in FIG.
As shown in FIGS. 1 and 2, a wiper motor (brushless 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 (motor) 2, a speed reduction 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 is a plan view of the stator 8 and the rotor 9 as 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 main core) projecting radially inward from the core portion 21. The stator core 20 is integrally formed with six teeth 22 in the first embodiment.
The stator core 20 is formed by laminating a plurality of metal plates in the axial direction. The stator core 20 is not limited to the case where a plurality of metal plates are laminated in the axial direction, and may be formed, for example, by 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.

  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.

(Rotor)
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. Rotor core 32, and four magnets 33 provided on the outer peripheral surface of the rotor core 32. Thus, in the motor unit 2, the ratio between the number of magnetic poles of the magnet 33 and the number of slots 19 (teeth 22) is 4: 6.

The rotor core 32 is formed by laminating a plurality of metal plates in the axial direction. The rotor core 32 is not limited to the case where a plurality of metal plates are laminated in the axial direction, and may be formed, for example, by press-molding soft magnetic powder.
In addition, a through hole 32 a penetrating in the axial direction is formed at a substantially central portion 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 at equal intervals in the circumferential direction on the outer peripheral surface 32 b of the rotor core 32. 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. Further, 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 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. The magnets 33 are respectively disposed in the magnet housing portions 36 and are fixed to the rotor core 32 by, for example, an adhesive.

FIG. 4 is an enlarged view of the rotor 9 of FIG.
As shown in the figure, the magnet 33 is configured such that the radial thickness at the end portions 33s on both sides in the circumferential direction around the axis C1 of the shaft 31 is smaller than the radial thickness at the circumferential intermediate portion 33c. It is formed. Here, the magnet 33 is a ferrite magnet.
For this reason, the minute gap between the outer circumferential surface 33a on the radially outer side of the magnet 33 and the inner circumferential surface of the teeth 22 is the smallest in the circumferential center of the magnet 33 and gradually increases as the distance from the circumferential center in the circumferential direction increases. Become bigger.

As shown in FIG. 3, the magnet 33 has a center C <b> 2 of the outer peripheral surface 33 a that is offset radially outward with respect to the axis C <b> 1 of the shaft 31. Further, the magnet 33 has a radius of curvature (distance) R2 from the axial center C1 of the shaft 31 in the circumferential intermediate portion 33c where the radius of curvature R1 of the outer circumferential surface 33a is located on the outermost radial surface 33a of the magnet 33. Is set too small.
More specifically, as shown in FIG. 5, the circular arc surface W passing through the circumferential intermediate portion 33 c located on the outermost radial direction of the outer circumferential surface 33 a of the magnet 33 around the axis C <b> 1 of the shaft 31 is A distance from the axis C1 of the shaft 31 in the circumferential intermediate portion 33c of the surface 33a is a radius R2. The radius of curvature R1 of the outer peripheral surface 33a of the magnet 33 is set to 0.8 times or less (R1 ≦ 0.8 × R2) with respect to the radius R2 of the circular arc surface W. As a result, as shown in FIG. 4, the end portions 33 s on both sides in the circumferential direction of the magnet 33 are disposed radially inward of the salient poles 35.

  The magnet 33 is magnetized so that the magnetic field orientation is parallel to the thickness direction. And the magnet 33 is arrange | positioned so that a magnetic pole may become alternate in the circumferential direction. Furthermore, the salient poles 35 of the rotor core 32 are located between the magnets 33 adjacent in the circumferential direction, that is, at the boundary (pole boundary) of the magnetic poles.

The salient pole 35 has a circumferential width dimension set at an electrical angle θ of 20 ° or more and 40 ° or less at the radially outer end.
The circumferential width dimension at the radially outer end of the salient pole 35 refers to the width dimension between the circumferential corners 35b when the salient pole 35 is not formed with a round chamfer 35a. . In the following description, the circumferential width dimension at the radially outer end of the salient pole 35 will be simply referred to as the radial dimension of the salient pole 35 in the radial direction.

Furthermore, it is preferable that the salient poles 35 are formed in parallel with each other on opposite surfaces 35s facing the end 33s in the circumferential direction of the magnet 33 on both sides in the circumferential direction.
In addition, by forming the magnet 33 as described above, the salient pole 35 has the circumferential end portion 33s of the magnet 33 while the maximum outer diameter of the magnet 33 and the maximum outer diameter of the salient pole 35 are the same size. It protrudes radially outward.

(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.

  Further, three fixing brackets 54a, 54b, 54c are integrally formed on the side wall 40b of the gear case 40. These fixing brackets 54a, 54b, 54c are for fixing the wiper motor 1 to a vehicle body (not shown) or the like. The three fixing brackets 54a, 54b, 54c are arranged at substantially equal intervals in the circumferential direction so as to avoid the motor unit 2. Anti-vibration rubber 55 is attached to each of the fixed brackets 54a, 54b, 54c. The anti-vibration rubber 55 is for preventing vibrations when the wiper motor 1 is driven from being transmitted to a vehicle body (not shown).

  Further, a substantially cylindrical bearing boss 49 projects from the bottom wall 40 c 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 housed in the gear housing portion 42 includes a worm shaft 44 and a worm wheel 45 that meshes 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. Note that the worm shaft 44 and the shaft 31 may be integrally formed by molding a worm shaft portion and a rotating 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 center in the radial direction of the worm wheel 45. The output shaft 48 is disposed coaxially with the rotation 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 protrudes. 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 performs drive control of the motor unit 2 includes a controller board (drive circuit unit) 62 on which the magnetic detection element 61 is mounted, and a cover 63 provided to close the opening 40a of the gear case 40. Have. 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 connector terminals (both not shown) provided on the cover 63. Yes. In addition to the magnetic detection element 61, a power module (not shown) including a switching element such as an FET (Field Effect Transistor) that controls a current supplied to the coil 24 is mounted on the controller board 62. ing. 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.
A connector (not shown) is integrally formed on the outer periphery of the cover 63. This connector is formed so that it can be fitted with a connector extending from an external power source (not shown). The controller board 62 is electrically connected to the terminal of a connector (not shown). As a result, the power of the external power supply is supplied to the controller board 62.

  Here, the controller board 62 performs advance angle energization and wide angle energization with an electrical angle θ of 121 ° to 180 ° to the coil 24. Further, the controller board 62 applies a drive current in which a fifth harmonic is superimposed on the coil 24.

  Further, a fitting portion 81 that is fitted to the end portion of the side wall 40 b of the gear case 40 protrudes from the opening edge of the cover 63. 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. As a result, 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 power supplied to the controller board 62 via a connector (not shown) is selectively supplied to each coil 24 of the motor unit 2 via a power module (not shown).
Then, a predetermined interlinkage magnetic flux is formed in the stator 8 (tooth 22), and a magnetic attractive force and a repulsive force are generated between the interlinkage magnetic flux and an effective magnetic flux formed by the 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 to drive a desired electrical component.

  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.

(Operation and effect of rotor)
Next, the operation and effect of the rotor 9 will be described with reference to FIGS.
The motor unit 2 is a so-called SPM (Surface Permanent Magnet) motor in which a 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. Here, in order to further reduce the inductance value in the d-axis direction in the rotor 9, it is necessary to increase the radial dimension of the magnet 33. In this embodiment, since the magnet 33 is made of a ferrite magnet, even if the radial size of the magnet 33 is increased to increase the amount of magnet usage, the cost increase can be significantly suppressed as compared with the rare earth magnet. .

  Here, the four salient poles 35 provided on the outer peripheral surface 32b of the rotor core 32 have a circumferential width dimension set to an electrical angle θ of 20 ° to 40 °. Thus, the inductance value in the q-axis direction can be reduced by setting the width dimension of the salient pole 35 in the circumferential direction to 40 ° or less in terms of the electrical angle θ. Thereby, while suppressing a demagnetizing field, a high reluctance torque can be obtained. More specific description will be given below.

FIG. 6 is a graph showing the inductances Lq and Ld [mH] of the q-axis and d-axis of the rotor 9, and the rotor 9 of the present embodiment is compared with the rotor of the conventional structure. Here, the conventional structure is a structure of a rotor of a so-called IPM (Interior Permanent Magnet) motor in which permanent magnets are arranged in slits having a plurality of diameters in the rotor core.
As shown in the figure, it can be confirmed that the rotor 9 of this embodiment has a smaller inductance value for both the q-axis and the d-axis than the conventional structure.

FIG. 7 is a graph showing changes in the number of revolutions of the rotor 9 when the vertical axis is the rotational speed [rpm] of the rotor 9 and the horizontal axis is the torque [N · m] of the rotor 9. More specifically, FIG. 6 is a graph showing the relationship between the torque [N · m] and the rotation speed [rpm] when the rotor 9 is subjected to advance angle energization and wide angle energization. The rotor 9 of the form is compared with the rotor of the conventional IPM structure.
As shown in the figure, it can be confirmed that the rotor 9 of the present embodiment generates higher torque and rotational speed than the conventional structure.

FIG. 8 is a graph showing a change in torque of the rotor 9 when the vertical axis is the torque [N · m] of the rotor 9 and the horizontal axis is the salient pole width [mm] of the salient pole 35 provided on the rotor core 32. It is. More specifically, FIG. 7 is a graph showing the torque generated in the rotor 9 of the present embodiment when the width dimension (electrical angle θ) in the circumferential direction of the salient pole 35 is varied.
FIG. 9 is a graph showing changes in the ripple rate of the rotor 9 when the vertical axis is the ripple rate [%] of the rotor 9 and the horizontal axis is the salient pole width [mm] of the salient pole 35 of the rotor core 32. More specifically, FIG. 8 is a graph showing a ripple rate generated in the rotor 9 of this embodiment when the width dimension of the salient pole 35 is varied.
FIG. 10 is a graph showing the cogging change of the rotor 9 when the vertical axis is cogging [mN · m] of the rotor 9 and the horizontal axis is the salient pole width [mm] of the salient pole 35 of the rotor core 32. More specifically, FIG. 9 is a graph showing cogging generated in the rotor 9 of the present embodiment when the width dimension of the salient pole 35 is varied.

  As shown in FIGS. 8 to 10, in the rotor 9 of the present embodiment, the circumferential width of the salient pole 35 is 3 mm (electrical angle θ = 20 °) to 5 mm (electrical angle θ = 40 °). In addition, it can be confirmed that a high reluctance torque can be obtained and a ripple rate and cogging can be suppressed.

  Further, the magnetic flux is concentrated on the salient pole 35 by projecting the salient pole 35 radially outward from the circumferential end portion 33 s of the magnet 33. In this way, the demagnetizing field is less likely to act on the end 33 s of the magnet 33.

11, the vertical axis represents the magnetic flux density [T] at the circumferential end 33 s of the magnet 33 of the rotor 9, and the circumferential end of the magnet 33 when the horizontal axis represents the rotation angle [deg] of the rotor 9. It is a graph which shows the change of magnetic flux density in 33s. More specifically, FIG. 10 is a graph showing the magnetic flux density [T] at the circumferential end portion 33 s of the magnet 33 of the rotor 9, and the salient poles 35 are arranged more than the circumferential end portion 33 s of the magnet 33. When projecting radially outward (reference symbol E in FIG. 11) and when projecting poles 35 are not projected radially outward from the circumferential end 33s of the magnet 33 (reference symbol C in FIG. 11). Comparing.
As shown in the figure, compared to the case where the salient pole 35 is not projected radially outward from the circumferential end 33 s of the magnet 33, the salient pole 35 is more radial than the circumferential end 33 s of the magnet 33. When protruding outward, it can be confirmed that the magnetic flux density is high and demagnetization is difficult.

12 and 13 are diagrams showing the direction of the magnetic flux around the salient pole 35. When the salient pole 35 is projected radially outward from the circumferential end 33s of the magnet 33 (FIG. 12). And the case where the salient pole 35 is not projected radially outward from the circumferential end portion 33s of the magnet 33 (FIG. 13).
Compared to the case where the salient pole 35 is not projected radially outward from the circumferential end 33 s of the magnet 33 as shown in FIG. 13, the salient pole 35 is arranged around the magnet 33 as shown in FIG. 12. When protruding in the radial direction from the end portion 33 s in the direction, it can be confirmed that the magnetic flux is concentrated on the end portion 33 s of the magnet 33 and the magnetic flux is concentrated on the salient pole 35.

  In addition, the salient poles 35 are formed in parallel with each other on opposite surfaces 35 s facing the circumferential end 33 s of the magnet 33 on both sides in the circumferential direction. Here, if the base portion of the salient pole 35 has a large width at the root portion on the inner side in the radial direction and the width at the tip portion on the outer side in the radial direction is small, the trapezoidal shape is disposed between the salient poles 35 adjacent in the circumferential direction. The end portions 33s on both sides in the circumferential direction of the magnet 33 become thinner, and demagnetization is likely to occur. Further, if the base part of the salient pole 35 has a small width dimension and the tip part has a large width dimension, the salient pole 35 tends to saturate the magnetic flux density. On the other hand, by forming the salient poles 35 with the opposing surfaces 35s on both sides in the circumferential direction parallel to each other, demagnetization is less likely to occur and saturation of the magnetic flux density can be suppressed.

  In addition, the magnetization orientation of the magnet 33 is parallel orientation. Thereby, while suppressing cogging, a high magnetic flux density can be obtained.

FIG. 14 is a graph showing cogging [mN · m] generated in the rotor 9 of the present embodiment when the orientation of the magnet 33 is parallel orientation or radial orientation. FIG. 15 is a graph showing the effective magnetic flux [μWb] generated in the rotor 9 of this embodiment when the orientation of the magnet 33 is parallel orientation or radial orientation.
As shown in FIGS. 14 and 15, it can be confirmed that the cogging is suppressed and the effective magnetic flux is increased by setting the magnetization orientation of the magnet 33 to the parallel orientation.

Further, in FIG. 16, the vertical axis represents the magnetic flux density [T] at the circumferential end 33s of the magnet 33 of the rotor 9, and the horizontal axis represents the circumferential direction of the magnet 33 when the rotational angle [deg] of the rotor 9 is defined. It is a graph which shows the change of magnetic flux density in end 33s. More specifically, FIG. 15 is a graph showing the magnetic flux density [T] at the circumferential end portion 33 s of the magnet 33 of the rotor 9, and the salient pole 35 is positioned more than the circumferential end portion 33 s of the magnet 33. When projecting radially outward (symbol E in FIG. 16), when salient poles 35 are not projected radially outward from the circumferential end 33s of the magnet 33 (symbol C in FIG. 16), In each of the above, a comparison is made between the case where the magnet 33 has a parallel orientation and a radial orientation.
FIG. 17 shows a case where the salient pole 35 protrudes radially outward from the circumferential end portion 33 s of the magnet 33 (reference numeral E in FIG. 17), and the salient pole 35 extends to the circumferential end portion 33 s of the magnet 33. The minimum value of the magnetic flux density when the magnet 33 is magnetized in the parallel orientation and in the radial orientation (C in FIG. 17) in the case where the magnet 33 is not projected outward in the radial direction. MIN).

  As shown in FIGS. 16 and 17, the salient pole 35 protrudes radially outward from the circumferential end 33 s of the magnet 33, and the magnetization orientation of the magnet 33 is set to a parallel orientation, thereby reducing the magnetic field. Can be effectively suppressed.

  Further, the magnet 33 has a curvature radius R1 of the outer peripheral surface 33a of 0 relative to a radius R2 from the axis C1 of the shaft 31 in the circumferential intermediate portion 33c located most radially outward of the outer peripheral surface 33a of the magnet 33. It was set to be 8 times or less. As a result, the end portions 33 s on both sides in the circumferential direction of the magnet 33 are disposed radially inward of the salient poles 35. Thereby, the magnetic flux is concentrated on the salient pole 35, and the demagnetizing field is less likely to act on the end 33 s of the magnet 33. Then, higher harmonic components contained in the induced voltage when the current is supplied to the coil 24 can be suppressed, and the torque ripple in the motor unit 2 can be suppressed.

FIG. 18 is a graph showing the content of harmonics included in the induced voltage when the radius of curvature R1 of the outer peripheral surface 33a of the magnet 33 is changed to vary the ratio to the radius R2.
As shown in the figure, the eleventh-order harmonic component is less than 1% by setting the curvature radius R1 of the outer peripheral surface 33a of the magnet 33 to 0.8 or less with respect to the radius R2 of the circumferential intermediate portion 33c. It can be confirmed that it is reduced.
Further, FIG. 19 is a graph showing the content of harmonics included in the induced voltage when the orientation of the magnet 33 is parallel orientation or radial orientation.
As shown in the figure, it can be confirmed that the 11th-order harmonic component is reduced when the magnet 33 is in parallel orientation.

  In addition, the controller board 62 is configured to apply a drive current in which the fifth harmonic is superimposed on the coil 24. Thereby, the torque ripple in the motor part 2 can be suppressed.

  FIG. 20 is a diagram showing three-phase drive current waveforms in which the fifth harmonic is not superimposed when the vertical axis is the drive current [A] and the horizontal axis is the angle [θ]. In FIG. 21, a three-phase drive current without superimposing fifth-order harmonics is applied when the vertical axis is the torque [N · m] of the rotor 9 and the horizontal axis is the rotation angle [deg] of the rotor 9. It is a figure which shows the torque waveform in a case. FIG. 22 is a diagram illustrating a waveform of a three-phase driving current in which a fifth harmonic is superimposed with the driving current [A] on the vertical axis and the angle [θ] on the horizontal axis. FIG. 23 shows a case where a three-phase driving current superimposed with fifth harmonics is applied when the vertical axis is the torque [N · m] of the rotor 9 and the horizontal axis is the rotation angle [deg] of the rotor 9. It is a figure which shows a torque waveform. FIG. 24 is a graph in which the torque waveforms in FIGS.

When a three-phase drive current without superimposing fifth-order harmonics as shown in FIG. 20 is applied, a torque ripple having periodic torque fluctuation is generated in the motor unit 2 as shown in FIG. . On the other hand, when a three-phase driving current superimposed with fifth harmonics as shown in FIG. 22 is applied, torque ripple can be significantly reduced in the motor unit 2 as shown in FIG. I can confirm.
And as shown in FIG. 24, it can confirm that a 6th-order torque ripple is significantly reduced by an electrical angle by superimposing a 5th-order harmonic on a drive current.

  As described above, the motor unit 2 and the wiper motor 1 described above are wound around the stator 22 having the annular stator core 20 and the plurality of teeth 22 projecting radially inward from the inner peripheral surface of the stator core 20. The coil 24 to be rotated, the shaft 31 rotating around the axis C1 on the radial inner side of the stator core 20, the rotor core 32 fixed to the shaft 31 and having the axis C1 as the radial center, and the outer peripheral surface 32b of the rotor core 32 In the circumferential direction of the magnet 33 and the outer circumferential surface 32b of the rotor core 32, the radial thickness at the end portions 33s on both sides in the circumferential direction around the axis C1 is smaller than the radial thickness at the circumferential intermediate portion. Between the adjacent magnets 33, the salient poles 35 formed to protrude radially outward from the circumferential end 33 s of the magnet 33, The ratio of the number of poles to the number of teeth 22 is 2n: 3n (where n is a natural number), and the magnet 33 has the radius of curvature R1 of the outer peripheral surface 33a located on the outermost radial direction of the outer peripheral surface 33a of the magnet 33. In the circumferential intermediate portion 33c, the radius R2 from the axis C1 of the shaft 31 is set to be 0.8 times or less.

  As described above, the salient pole 35 is projected radially outward from the circumferential end 33 s of the magnet 33, and the curvature radius R 1 of the outer circumferential surface 33 a of the magnet 33 is set to the circumferential direction of the outer circumferential surface 33 a of the magnet 33. It was made smaller than the radius R2 in the intermediate part 33c. As a result, the end portions 33 s on both sides in the circumferential direction of the magnet 33 are disposed radially inward of the salient poles 35. Therefore, the magnetic flux is concentrated on the salient pole 35, and the demagnetizing field is less likely to act on the end 33 s of the magnet 33. Then, higher harmonic components contained in the induced voltage when the current is supplied to the coil 24 can be suppressed, and the torque ripple in the motor unit 2 can be suppressed. Thus, if the radius of curvature of the outer peripheral surface 33a of the magnet 33 is reduced, the effect of suppressing torque ripple can be obtained. Therefore, the higher-order harmonics are calculated by the microcomputer of the controller board 62 that supplies current to the coil 24. The need to generate is reduced. Therefore, the necessity for providing the controller board 62 with a microcomputer having a high processing load is reduced, and an increase in cost can be suppressed. As a result, the ripple can be effectively reduced at a low cost.

  Further, with the configuration as described above, it is possible to increase the torque of the motor unit 2 and to suppress cogging. Furthermore, in such a motor part 2, high rotation can be achieved by performing advance angle energization and wide angle energization. Therefore, it is possible to increase the rotation speed and torque while suppressing an increase in cost.

  Moreover, the width dimension in the radial direction of the salient pole 35 was set to be an electrical angle of 40 ° or less. According to such a configuration, the inductance value in the q-axis direction can be reduced by setting the electrical angle of the salient pole 35 to 40 ° or less and reducing the width dimension of the salient pole 35 in the circumferential direction. . For this reason, a demagnetizing field can be suppressed.

  Further, the width dimension of the salient pole 35 in the radial direction was set to be an electrical angle of 20 ° or more. According to such a configuration, the electrical angle of the salient pole 35 is set to 20 ° or more, and the width dimension in the radial direction can be ensured. Therefore, the magnetic flux concentrates on the salient pole 35, so that the effect that the demagnetizing field is less likely to act on the end portion 33s of the magnet 33 can be obtained with certainty. Moreover, a high reluctance torque can be obtained by setting the electrical angle θ of the salient pole 35 to 20 ° or more and 40 ° or less.

  The magnet 33 is a ferrite magnet, and the magnetization orientation is parallel. According to such a configuration, cogging of the motor unit 2 can be suppressed and a high magnetic flux density can be obtained. Further, by using a ferrite magnet instead of a rare earth magnet for the magnet 33, even if the radial dimension of the magnet 33 is increased, an increase in cost due to an increase in the amount of use of the magnet 33 can be suppressed.

  In addition, the controller board 62 is configured to apply a drive current in which the fifth harmonic is superimposed on the coil 24. According to such a configuration, torque ripple in the motor unit 2 can be suppressed.

(Modification of the embodiment)
The magnet 33 shown in the above embodiment has a shape in which the outer peripheral surface 33a has a constant radius of curvature R1, but is not limited thereto.
FIG. 25 is a diagram showing the shape of a magnet in a modification of the embodiment of the present invention.
As shown in the figure, the magnet 33B has a flat portion 37 in an end portion 33s on both sides in the circumferential direction of the outer peripheral surface 33a in a range where the electrical angle θ2 is 10 ° or more and 18 ° or less. The flat surface portion 37 is formed by flatly forming the outer peripheral surface 33a of the magnet 33B.

Furthermore, the outer peripheral surface 33a of the magnet 33B is a curved surface 38 having a constant radius of curvature R3 between the flat portions 37 on both sides in the circumferential direction (the range indicated by the arrow in FIG. 25).
The curvature radius R3 of the curved surface 38 is 0. 0 with respect to the radius R2 (see FIG. 5) from the axis C1 of the shaft 31 in the circumferential intermediate portion 33c located on the outermost radial surface 33a of the magnet 33B. It is larger than 8 times and 0.9 times or less (0.8 × R2 <R3 ≦ 0.9 × R2).

Also in the motor unit 2 and the wiper motor 1 having such a magnet 33B, it is possible to suppress higher-order harmonic components contained in the induced voltage when a current is supplied to the coil 24. As a result, torque ripple in the motor unit 2 can be suppressed.
In this way, by reducing the radius of curvature of the outer peripheral surface 33a of the magnet 33B and forming the flat portion 37 at the end portions 33s on both sides in the circumferential direction, the salient pole 35 is made to be more than the end portion 33s in the circumferential direction of the magnet 33B. If it projects outward in the radial direction, the effect of suppressing torque ripple can be obtained. Therefore, it is possible to suppress the generation of higher-order harmonics by calculation with the microcomputer of the controller board 62 that supplies current to the coil 24. For this reason, the necessity for providing the controller board 62 with a microcomputer having a high processing load is reduced, and an increase in cost can be suppressed. Therefore, ripple can be effectively reduced at low cost.

FIG. 26 is a graph showing the content rate of harmonics included in the induced voltage when the range (electrical angle θ2) for forming the flat portion 37 of the magnet 33B is changed.
As shown in the figure, the radius of curvature R3 of the outer circumferential surface 33a (curved surface 38) of the magnet 33 is larger than 0.8 times and smaller than 0.9 times the radius R2 of the circumferential intermediate portion 33c. It can be confirmed that the eleventh-order harmonic component is reduced to less than 1% by setting and setting the flat portion 37 to 10 ° or more and 18 ° or less in electrical angle θ2.

(Other embodiments)
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.
In addition to this, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate without departing from the gist of the present invention.

1. Wiper motor (brushless wiper motor)
2 ... Motor part (motor)
DESCRIPTION OF SYMBOLS 8 ... Stator 9 ... Rotor 20 ... Stator core 22 ... Teeth 24 ... Coil 31 ... Shaft 32 ... Rotor core 33, 33B ... Magnet 33a ... Outer peripheral surface 33c ... Circumferential intermediate part (circumferential intermediate part)
33 s ... end 35 ... salient pole 37 ... plane 38 ... curved surface 62 ... controller board (drive circuit part)
C1 axis (rotation axis)
C2 ... Center R1, R3 ... Radius of curvature R2 ... Radius (distance)

Claims (7)

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 about the rotation axis on the radially inner side of the stator core;
A rotor core fixed to the shaft and having the rotational axis as a radial center;
A magnet disposed on an outer peripheral surface of the rotor core, wherein the radial thickness at both ends in the circumferential direction around the rotation axis is smaller than the radial thickness at the intermediate portion in the circumferential direction;
Between the magnets adjacent in the circumferential direction of the outer peripheral surface of the rotor core, salient poles formed to protrude radially outward from the circumferential end of the magnet;
With
The ratio between the number of magnetic poles of the magnet and the number of teeth is set to 2n: 3n (where n is a natural number),
In the magnet, the radius of curvature of the outer peripheral surface is set to be 0.8 times or less with respect to the distance from the rotation axis at the portion located radially outermost on the outer peripheral surface of the magnet. Motor. 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 about the rotation axis on the radially inner side of the stator core;
A rotor core fixed to the shaft and having the rotational axis as a radial center;
A magnet disposed on an outer peripheral surface of the rotor core, wherein the radial thickness at both ends in the circumferential direction around the rotation axis is smaller than the radial thickness at the intermediate portion in the circumferential direction;
Between the magnets adjacent in the circumferential direction of the outer peripheral surface of the rotor core, salient poles formed to protrude radially outward from the circumferential end of the magnet;
With
The ratio between the number of magnetic poles of the magnet and the number of teeth is set to 2n: 3n (where n is a natural number),
In the magnet, the radius of curvature of the outer peripheral surface is greater than 0.8 times and 0.9 times the distance from the rotation axis at the portion located radially outermost on the outer peripheral surface of the magnet. The motor is characterized in that the outer peripheral surface of the magnet has a flat surface portion in an electric angle range of 10 ° to 18 ° at both ends in the circumferential direction of the outer peripheral surface. 3. The motor according to claim 1, wherein a circumferential width dimension at the radially outer end of the salient pole is set to 40 ° or less in electrical angle. The motor according to claim 3, wherein a circumferential width dimension at the radially outer end of the salient pole is set to an electrical angle of 20 ° or more. The motor according to any one of claims 1 to 4, wherein the magnet is a ferrite magnet, and the orientation of magnetization is parallel orientation. The motor according to claim 1, further comprising a drive circuit unit that applies a drive current in which a fifth harmonic is superimposed on the coil. A brushless wiper motor comprising the motor according to any one of claims 1 to 6.

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