Patent ID: 12191714

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a rotor, a motor, and a brushless motor according to an embodiment of the present invention are described with reference to the accompanying drawings.

(Brushless Motor)

FIG.1is a perspective view of a brushless motor1.FIG.2is a cross-sectional view taken along line A-A ofFIG.1.

As shown inFIG.1andFIG.2, the brushless motor1is, for example, a drive source for a sunroof mounted on a vehicle. The brushless motor1includes a motor unit (motor)2, a deceleration unit3for decelerating and outputting the rotation of the motor unit2, and a controller unit4for controlling the drive of the motor unit2. Moreover, the motor unit2in the embodiment is an example of a motor within the scope of claims. Moreover, in the following description, the term “axial direction” refers to the rotary axis direction of a shaft31of the motor unit2, the term “circumferential direction” refers to the circumferential direction of the shaft31, and the term “radial direction” refers to the radial direction of the shaft31.

(Motor Unit)

The motor unit2includes a motor case5, a substantially square tubular stator8housed in the motor case5, and a rotor9arranged on the radial inner side of the stator8and rotatable with respect to the stator8. The motor unit2is a so-called brushless motor that does not require a brush to supply electric power to the stator8.

(Motor Case)

The motor case5is made of, for example, a material such as aluminum die casting having excellent heat dissipation. The motor case5includes a first motor case6and a second motor case7that can be divided in the axial direction. The outer shapes of the first motor case6and the second motor case7are each formed in a bottomed tubular shape. The outer shape of the first motor case6is formed in, for example, a bottomed square tubular shape. The outer shape of the second motor case7is formed in, for example, a bottomed tubular shape having a substantially rounded regular hexagonal cross section. The outer peripheral surface of the second motor case7has six corner portions7A and six flat portions7B.

The first motor case6is integrally formed with a gear case40so that an end portion10is joined to the gear case40of the deceleration unit3. A through hole10athrough which the shaft31of the rotor9can be inserted is formed at substantially the center of the end portion10in the radial direction.

In addition, an edge portion16for joining the second motor case7is formed at an opening portion6aof the first motor case6, and an outer flange portion17protruding radially outward is formed at an opening portion7aof the second motor case7. The edge portion16and the outer flange portion17are butted against each other to form the motor case5having an internal space. Besides, the stator8is arranged in the internal space of the motor case5so that a part of coils24described later is accommodated inside the first motor case6, and a stator core20described later is fitted inside the second motor case7.

(Stator)

FIG.3is a plan view of the stator8and the rotor9as viewed from the axial direction. As shown inFIG.2andFIG.3, the stator8includes the stator core20in which a tubular core portion21is integrally formed with a plurality of (for example, in the present embodiment, six) teeth22protruding radially inward from the core portion21. The stator core20is formed by laminating a plurality of metal plates in the axial direction. Moreover, the stator core20can be formed not only by laminating a plurality of metal plates in the axial direction, but also by, for example, pressure molding soft magnetic powder.

The core portion21is formed in a square tubular shape having a substantially rounded regular hexagonal cross section so as to be fitted inside the second motor case7. Accordingly, the outer peripheral surface of the core portion21has six corner portions and six flat portions. The plurality of teeth22are arranged so as to protrude radially inward from the portions corresponding to each side of the regular hexagon in the cross section of the core portion21.

The teeth22include an integrally formed teeth body22aand a pair of flange portions22b. The teeth body22aprotrudes inward along the radial direction from an inner peripheral surface of the core portion21. The flange portion22bextends along the circumferential direction from the radial inner end of the teeth body22a. The pair of flange portions22bare formed so as to extend outward in the circumferential direction from the teeth body22a. Besides, a slot19is formed between the flange portions22bwhich are adjacent in the circumferential direction.

In addition, the inner peripheral surface of the core portion21and the teeth22are covered with a resin insulator23. The coil24is attached so as to be wound around each tooth22from the surface of the insulator23. Each coil24generates a magnetic field for rotating the rotor9by power fed from the controller unit4.

(Rotor)

The rotor9is rotatably arranged on the radial inner side of the stator8through a minute gap. The rotor9includes the shaft31, a rotor core32, and four permanent magnets33. Thus, in the motor unit2, for example, the ratio of the number of magnetic poles of the permanent magnets33to the number of the slots19(the teeth22) is 4:6.

The rotor9rotates with a rotary axis which is a center line (shaft center) C1of the shaft31as the radial center.

The shaft31is integrally formed with a worm shaft44(seeFIG.2) that constitutes the deceleration unit3. The shaft31rotates around the rotary axis.

The rotor core32, which comprises a rotor core base32baand protrusions35, is fixed so as to be fitted to the outside of the shaft31. The outer shape of the rotor core32is formed in a columnar shape with the shaft31as a shaft center C1.

The rotor core32is formed by laminating a plurality of metal plates in the axial direction. Moreover, the rotor core32can be formed not only by laminating a plurality of metal plates in the axial direction, but also by, for example, pressure molding soft magnetic powder.

Besides, a through hole32apenetrating in the axial direction is formed at substantially the center of the rotor core32in the radial direction. The shaft31is pressed into the through hole32a. Moreover, the shaft31may be relatively inserted into the through hole32aso that the rotor core32is fitted to the outside of the shaft31, and the shaft31and the rotor core32may be fixed by an adhesive or the like.

In the rotor core32, the positions of the arc center of an inner peripheral surface on the radial inner side (that is, an inner peripheral surface of the through hole32a) and the arc center of an outer peripheral surface32bon the radial outer side coincide with the position of the shaft center C1of the shaft31.

Furthermore, four protrusions35are arranged on the outer peripheral surface32bof the rotor core base32baat equal intervals in the circumferential direction. The protrusions35are formed so as to protrude outward in the radial direction and extend over the entire rotor core32in the axial direction.

In addition, the protrusions35are formed in such a manner that two side faces35afacing each other in the circumferential direction are parallel to the protrusion direction. That is, the protrusions35are formed in such a manner that the width dimensions in the circumferential direction are uniform in the protrusion direction.

Furthermore, round chamfered portions35bare formed at the corner portions of the protrusions35on both sides in the circumferential direction which is outside in the protrusion direction.

On the outer peripheral surface32bof the rotor core32formed in this way, the spaces between two protrusions35which are adjacent in the circumferential direction are each configured as a magnet housing portion36.

On the outer peripheral surface32bof the rotor core32formed in this way, the spaces between two protrusions35which are adjacent in the circumferential direction are each configured as a magnet housing portion36.

That is, the rotor9is a surface magnet (SPM: Surface Permanent Magnet) type rotor having field permanent magnets33on the outer peripheral surface32bof the rotor core32, as well as an inset type rotor provided with the protrusion35protruding outward in the radial direction of the rotor core32between the permanent magnets33arranged in the circumferential direction.

The four permanent magnets33are arranged in the four magnet housing portions36arranged on the outer peripheral surface32bof the rotor core32. In the magnet housing portion36, each permanent magnet33is fixed to the rotor core32by, for example, an adhesive or the like.

The permanent magnet33is, for example, a ferrite magnet, a neodymium bond magnet, a neodymium sintered magnet, or the like.

The permanent magnets33are magnetized so that the orientation of the magnetism (magnetic field) is a parallel orientation along the thickness direction. That is, the orientation of the permanent magnets33is a parallel orientation in which the easy magnetization direction is a direction parallel to the radial direction in the center of the permanent magnets33.

Besides, the permanent magnets33which are adjacent in the circumferential direction are arranged in such a manner that the magnetization directions are opposite to each other. The four permanent magnets33are arranged in such a manner that the magnetic poles are different from each other in the circumferential direction. That is, the permanent magnet33having the N pole on the outer peripheral side and the permanent magnet33having the S pole on the outer peripheral side are arranged adjacent to each other in the circumferential direction. Accordingly, the protrusion35of the rotor core32which is arranged between the permanent magnets33adjacent to each other in the circumferential direction is located at the boundary (pole boundary) of the magnetic poles.

FIG.4is a plan view in which a part of the rotor9is shown in an enlarged manner, and is a diagram showing the dimensions of the rotor core32and the permanent magnets33.

In the permanent magnets33, the position of an arc center Ci of an inner peripheral surface33bon the radial inner side coincides with the position of the shaft center C1of the shaft31.

In the permanent magnets33, an arc center Co of an outer peripheral surface33aon the radial outer side is eccentric with respect to the shaft center C1of the shaft31. Specifically, the arc center Co of the outer peripheral surface33aof the permanent magnet33is set closer to the outer peripheral surface32bof the rotor core32than the shaft center C1in the radial direction passing through the center of the permanent magnet33. Accordingly, the permanent magnet33is formed in such a manner that the radial thickness at end portions33sof the shaft31on both sides in the circumferential direction around the shaft center C1is smaller than the radial thickness in a center33cof the circumferential direction. As a result, a gap between the outer peripheral surface33aof the permanent magnet33on the radial outer side and the inner peripheral surface of the teeth22is the smallest in the center33cof the permanent magnet33in the circumferential direction, and tends to be larger as separated in the circumferential direction from the center33cof the circumferential direction.

The radial thickness of the permanent magnet33is formed to be larger than the radial thickness of the rotor core32. For example, a radial thickness Rm in the center33cof the permanent magnet33in the circumferential direction is formed to be larger than a radial thickness Re in a center32cof the rotor core32in the circumferential direction.

Almost the entire inner peripheral surface33bof the permanent magnet33is in contact with the outer peripheral surface32bof the rotor core32. In addition, each surface of the permanent magnet33on both sides in the circumferential direction includes a circumferential side face33din contact with the protrusion35, and a connection surface33econnected to the circumferential side face33dand to the outer peripheral surface33aon the radial outer side.

The circumferential side face33dis smoothly connected to the inner peripheral surface33bon the radial inner side via an arc surface33f. The circumferential side face33dis formed on, for example, a flat surface.

The connection surface33eis arranged closer to the radial outer side than the circumferential side face33d, and is connected to the circumferential side face33dand to the outer peripheral surface33a.

The connection surface33eis formed on, for example, a flat surface. The connection surface33eis formed so as to gradually approach the center33eof the permanent magnets33in the circumferential direction as the connection surface33eis directed outward in the protrusion direction of the protrusion35. For example, the connection surface33eis formed so as to gradually increase the radial thickness of the permanent magnet33as the connection surface33eis directed outward in the radial direction. That is, the pair of connection surfaces33eon both sides of the permanent magnet33in the circumferential direction are formed so as to gradually decrease the interval in the circumferential direction as the connection surfaces33eare directed outward in the radial direction.

Besides, the connection surfaces33eare arranged parallel to the easy magnetization direction of the permanent magnets33.

FIG.5is a plan view in which a part of the rotor9is shown in an enlarged manner, and is a diagram showing a length range of the protrusion35in the protrusion direction.

The position of a front end35tof the protrusion35in the protrusion direction is arranged within the area between a center33gof the circumferential side face33dof the permanent magnet33in the protrusion direction and a crossing ridge portion33hwhere the circumferential side face33dand the connection surface33ecross. That is, the position of the front end35tis arranged between a straight line L1connecting the centers33gof the adjacent peripheral side faces33dand a straight line L2connecting the adjacent crossing ridge portions33hin the two permanent magnets33adjacent to each other so as to sandwich the protrusion35from both sides in the circumferential direction.

For example, a radius R (outer diameter/2) of a circle centered on the shaft center C1of the shaft31and tangent to the front end35tof the protrusion35is equal to or greater than a radius (first radius) R1of a circle centered on the shaft center C1and tangent to a straight line L1, and is equal to or smaller than a radius (second radius) R2of a circle centered on the shaft center C1and tangent to a straight line L2.

FIG.6is a graph showing an example of the relationship between the length of the protrusion35of the rotor9and an effective magnetic flux of the permanent magnets33.FIG.7is a graph showing an example of the relationship between the length of the protrusion35of the rotor9and a distortion rate of an induced voltage waveform. Moreover, inFIG.6andFIG.7, the length of the protrusion35is, for example, the radius R (outer diameter/2) of the circle tangent to the front end35tof the protrusion35.

In the rotor9, the fixing stability of the permanent magnets33in contact with the protrusion35(for example, the seating property for the magnet housing portion36or the like) tends to be improved with an increase in the length of the protrusion35in the protrusion direction. On the other hand, the magnetic flux leaking from the permanent magnet33to the protrusion35and the distortion of the induced voltage waveform tend to be larger with the increase in the length of the protrusion35in the protrusion direction. Moreover, the induced voltage is a voltage induced in each coil24by the external drive of the rotor9when the power supply for each coil24of the stator8is de-energized. The distortion of the induced voltage waveform is caused by, for example, superimposing harmonics in a sinusoidal induced voltage waveform, and causes an increase in vibration and noise when the brushless motor1is driven. The distortion rate shown inFIG.7is zero when the induced voltage waveform is sinusoidal.

As shown inFIG.6andFIG.7, the distortion of the induced voltage waveform tends to be larger as the radius R corresponding to the front end35tof the protrusion35increases from the first radius R1, and in contrast, the effective magnetic flux for the teeth22of the permanent magnets33is maximized at the second radius R2.

That is, the lower limit of the range that defines the length of the protrusion35in the protrusion direction is set to, for example, ensure desired fixing stability by the protrusion35supporting at least half or more of the portion of the circumferential side face33dof the permanent magnet33in the protrusion direction. In addition, the upper limit of the range that defines the length of the protrusion35in the protrusion direction is set to, for example, maintain the effective magnetic flux of the permanent magnets33within a predetermined range including a maximum value Wm while suppressing the distortion of the induced voltage waveform as much as possible below a predetermined allowable level.

(Deceleration Unit)

Returning toFIG.1andFIG.2, the deceleration unit3includes the gear case40to which the motor case5is attached, and a worm reduction mechanism41housed in the gear case40.

The gear case40is made of, for example, a material such as aluminum die casting having excellent heat dissipation. The outer shape of the gear case40is formed in, for example, a box shape. The gear case40has a gear accommodation portion42having the worm reduction mechanism41accommodated therein. In addition, an opening portion43that allows the through hole10aof the first motor case6to communicate with the gear accommodation portion42is formed at a place where the first motor case6is integrally formed at an end portion40aof the gear case40.

In addition, a guide plate49is arranged on the gear case40. The guide plate49is arranged to support an output shaft48of the worm reduction mechanism41to be rotatable.

The worm reduction mechanism41accommodated in the gear accommodation portion42is constituted of the worm shaft44and a worm wheel45meshed with the worm shaft44.

The worm shaft44is arranged coaxially with the shaft31of the motor unit2. Besides, the worm shaft44is rotatably supported by bearings46and47having both ends arranged on the gear case40. The end portion of the worm shaft44on the motor unit2side protrudes to the opening portion43of the gear case40via the bearing46. The protruding end portion of the worm shaft44is joined to the end portion of the shaft31of the motor unit2, and the worm shaft44is integrated with the shaft31. Moreover, the worm shaft44and the shaft31may be integrally formed by forming a worm shaft portion and a rotary shaft portion from one base material.

The worm wheel45meshed with the worm shaft44is provided with the output shaft48in the radial center of the worm wheel45. The output shaft48is arranged coaxially with the rotary shaft direction of the worm wheel45, and is connected to a gear unit50protruding to the outside of the gear case40via the guide plate49of the gear case40. The gear unit50is connected to an electrical component (not shown).

In addition, the worm shaft44is provided with a rotation position detection portion60for detecting the rotation position of the worm shaft44. The rotation position detection portion60is connected to the controller unit4.

(Controller Unit)

The controller unit4that controls the drive of the motor unit2has a controller board62on which a magnetic detection element or the like is mounted. Besides, the controller board62is arranged in the through hole10aof the first motor case6.

The controller board62is a so-called epoxy board in which a plurality of conductive patterns (not shown) are formed. The terminal portion of the coil24drawn from the stator core20of the motor unit2is connected to the controller board62, and a terminal11arranged in the gear case40is electrically connected to the controller board62. In addition, in addition to the magnetic detection element, a power module (not shown) including a switching element such as a field effect transistor (FET) that controls the current supplied to the coil24is also mounted on the controller board62. Furthermore, a capacitor (not shown) for smoothing the voltage applied to the controller board62or the like is mounted on the controller board62.

The terminal11is formed in a manner that the terminal11can be fitted with a connector extending from an external power supply (not shown). Besides, the controller board62is electrically connected to the terminal11. Accordingly, the electric power of the external power supply is supplied to the controller board62.

(Operation of Brushless Motor)

Next, the operation of the brushless motor1is described.

In the brushless motor1, the electric power supplied to the controller board62via the terminal11is selectively supplied to each coil24of the motor unit2via the power module (not shown).

Then, the current flowing through each coil24forms a predetermined interlinkage magnetic flux in the stator8(the teeth22). A magnetic attractive force or repulsive force (magnet torque) is generated between the interlinkage magnetic flux and the effective magnetic flux formed by the permanent magnets33of the rotor9.

Besides, the protrusion direction of the protrusion35of the rotor core32is set as a direction in which the interlinkage magnetic flux from the stator8(the teeth22) flows easily, and the protrusion35generates a reluctance torque that rotates the rotor core32so as to reduce the magnetic resistance (reluctance) of the magnetic path of the interlinkage magnetic flux.

The magnet torque and reluctance torque continuously rotate the rotor9.

The rotation of the rotor9is transmitted to the worm shaft44integrated with the shaft31and further transmitted to the worm wheel45meshed with the worm shaft44. Then, the rotation of the worm wheel45is transmitted to the output shaft48connected to the worm wheel45, and the output shaft48drives a desired electrical component.

In addition, the detection signal of the rotation position of the worm wheel45detected by the magnetic detection element mounted on the controller board62and the rotation position detection portion60is output to an external device (not shown). The external device (not shown) is, for example, a software function unit that functions by executing a predetermined program by a processor such as a central processing unit (CPU). The software function unit is an electronic control unit (ECU) equipped with a processor such as a CPU, a read only memory (ROM) for storing programs, a random access memory (RAM) for temporarily storing data, an electronic circuit such as a timer, and the like. In addition, at least a part of the external device (not shown) may be an integrated circuit such as a large scale integration (LSI). The external device (not shown) controls the switching timing of the switching element or the like of the power module (not shown) based on the detection signal of the rotation position of the worm wheel45and controls the drive of the motor unit2. Moreover, the output of the drive signal of the power module and the drive control of the motor unit2may be executed by the controller unit4instead of the external device (not shown).

As described above, according to the rotor9of the present embodiment, the protrusion35of the rotor core32can support more than half of the region on the circumferential side faces33dof the permanent magnets33in the protrusion direction. Accordingly, desired fixing stability (for example, seating property or the like) of the permanent magnets33on the outer peripheral surface32bof the rotor core32can be ensured.

For example, the desired fixing stability of the permanent magnets33can be ensured by the protrusion35even when the radial thickness of the permanent magnets33is formed to be relatively larger than the radial thickness of the rotor core32.

In addition, the protrusion35is formed so as not to protrude closer to the outside than the crossing ridge portion33hwhere the circumferential side face33dand the connection surface33eof the permanent magnets33cross in the protrusion direction. Accordingly, the magnetic flux leaking from the permanent magnet33to the protrusion35and the distortion of the induced voltage waveform can be suppressed as much as possible below a predetermined allowable level, and the effective magnetic flux of the permanent magnets33can be maintained within a predetermined range including a maximum value.

Besides, the orientation of the permanent magnets33is a parallel orientation, and the easy magnetization direction in the vicinity of the end portions33son both sides in the circumferential direction of the permanent magnets33adjacent to the protrusion35intersects with the protrusion direction of the protrusion35. Accordingly, formation of a magnetic path by the magnetic flux leaking from the permanent magnet33to the protrusion35is suppressed, and thus an increase in the leakage flux can be suppressed.

FIG.8is a plan view showing an example of the flow of magnetic flux to the protrusion35of the rotor9in the embodiment.FIG.9is a plan view showing an example of the flow of magnetic flux to the protrusion35of the rotor9in a comparative example of the embodiment.

In the comparative example shown inFIG.9, the orientation of the permanent magnets33is a radial orientation in which an easy magnetization direction D is radial along the radial direction of the permanent magnets33. In addition, the position of the front end35tof the protrusion35in the protrusion direction is arranged closer to the outside than the crossing ridge portion33hof the permanent magnets33. Accordingly, a magnetic path generated by the magnetic flux leaking from the permanent magnet33to the protrusion35is easily formed between the end portions33sof the permanent magnets33on both sides in the circumferential direction and the protrusion35.

On the other hand, in the embodiment shown inFIG.8, the orientation of the permanent magnets33is a parallel orientation. In addition, the position of the front end35tof the protrusion35in the protrusion direction is arranged within the area between the center33gof the circumferential side face33dof the permanent magnet33and the crossing ridge portion33h. Accordingly, the formation of the magnetic path by the magnetic flux leaking from the permanent magnet33to the protrusion35is suppressed as compared with the comparative example.

Besides, the connection surface33eof the permanent magnet33is parallel to the easy magnetization direction of the permanent magnet33which is a parallel orientation. Accordingly, the distortion of the induced voltage waveform can be suppressed.

In addition, the brushless motor1of the present embodiment includes the rotor9that ensures the desired effective magnetic flux of the permanent magnets33and suppresses the magnetic flux leaking from the permanent magnet33to the protrusion35and the distortion of the induced voltage waveform. Accordingly, it is possible to ensure a desired output while suppressing an increase in cogging torque and torque ripple due to the magnetic field distortion and an increase in vibration and noise when the brushless motor1is driven.

Variation Example

Hereinafter, a variation example of the embodiment is described.

In the embodiment described above, the arc center Co of the outer peripheral surface33aof the permanent magnets33on the radial outer side is eccentric with respect to the shaft center C1of the shaft31, but the present invention is not limited thereto. Similar to the arc center Ci of the inner peripheral surface33bon the radial inner side, the arc center Co of the outer peripheral surface33aof the permanent magnets33may coincide with the position of the shaft center C1of the shaft31.

Moreover, in the embodiment described above, the brushless motor1is a drive source for a sunroof mounted on a vehicle, but the present invention is not limited thereto. For example, the brushless motor1may be a drive source for various electrical components (for example, a power window, an electric seat, a wiper, and the like) mounted on a vehicle or a drive source mounted on various devices other than the vehicle.

The embodiments of the present invention are illustrative and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention as well as in the scope equivalent to that of the invention set forth in the claims.