JP7199287B2 - brushless motor - Google Patents

Description

The present invention relates to brushless motors.

As a brushless motor, for example, a rotor is known in which a cylindrical magnet (ring magnet) is externally fitted and fixed to a rotating shaft in which a rotor core is fixed to the motor shaft. Cylindrical magnets are pole-oriented magnets formed into a cylindrical shape by pole-oriented magnets such as polar anisotropic magnets.
The pole-oriented magnet is magnetized so that the N and S poles appear at equal intervals only on the outer peripheral surface, which is the surface facing the stator, and the magnetic pole center portion that contributes most to the generation of torque on the outer peripheral surface. has a high magnetic flux density.
Therefore, compared to, for example, a radially oriented magnet that is magnetized so that the N and S poles appear on both the outer and inner peripheral surfaces, the motor can be made to have a high torque, and the size of the magnet can be reduced to reduce the size of the motor. (see, for example, Patent Literature 1).

JP-A-11-146618

However, in the rotor of the brushless motor disclosed in Patent Document 1, the pole-oriented magnets are brought into contact with the rotor core, which is a magnetic member, by externally fitting and fixing the pole-oriented magnets to the rotor core of the rotating shaft. As a result, magnetic flux leakage may occur in the inner circumference of the pole-oriented magnet, reducing the effective magnetic flux.
As a countermeasure against this, it is conceivable to suppress magnetic flux leakage by using a non-magnetic member for the member that contacts the inner peripheral portion of the pole-oriented magnet. However, when the rotary shaft of the brushless motor is required to have functional strength, it is necessary to use an iron-based member for the rotary shaft. Thus, it has been considered difficult to suppress magnetic flux leakage in a rotor having pole-oriented magnets when an iron-based member is used for the rotating shaft.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a brushless motor capable of suppressing magnetic flux leakage from pole-oriented magnets.

In order to solve the above problems, a brushless motor according to the present invention includes a stator including a stator core having teeth formed along the radially inner side; windings wound around the stator core; and a support comprising a shaft arranged radially inward of the stator core and rotating with respect to the stator core, and a rotor core integrally fixed to the shaft , wherein the support comprises a front It is made of a magnetic material having a magnet that has a polar orientation that generates a magnetic pole on the surface facing the teeth and is provided in a circumferential shape, and the magnet is made of a bond magnet and is spaced apart in the circumferential direction of the magnet. a plurality of protrusions formed so as to be continuous in the axial direction of the support and projecting radially inward to contact the support; and a concave portion formed in each of the plurality of convex portions, wherein the width dimension of the plurality of convex portions is formed to be constant, tip surfaces of the plurality of convex portions are formed so as to follow the outer peripheral surface of the rotor core, and the plurality of convex portions is in contact with the outer peripheral surface of the rotor core, and has a space formed by the recess and the outer peripheral surface of the rotor core .

The brushless motor according to the present invention is characterized in that the number of the plurality of convex portions is three.

According to the present invention, a plurality of protrusions are formed at intervals in the circumferential direction of the magnet. Thereby, magnetic flux leakage of the pole-oriented magnet can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the motor with a reduction gear in 1st Embodiment which concerns on this invention. Sectional drawing which follows the II-II line of FIG. Sectional drawing which expanded the III section of FIG. FIG. 4 is a conceptual diagram for explaining the flow of magnetic flux in the rotor in the first embodiment; 4 is a graph for explaining the effective magnetic flux of the magnet in the first embodiment; (a) is a side view for explaining an example of fitting the magnet in the first embodiment into the rotor core, and (b) is a side view for explaining a state in which the magnet in the first embodiment is partially fitted into the rotor core. (a) is a side view for explaining a state in which the magnet in the first embodiment is externally fitted and fixed to the rotor core, and (b) is a front view for explaining the state in which the magnet in the first embodiment is externally fitted and fixed to the rotor core. Sectional drawing which shows the motor part in 2nd Embodiment which concerns on this invention.

Next, brushless motors according to embodiments of the present invention will be described with reference to the drawings. In the embodiments, an example in which a brushless motor is used as a motor unit and applied to a motor with a speed reducer will be described, but the brushless motor can also be applied to other motors.
(First embodiment)
(motor with reducer)
FIG. 1 is a cross-sectional view showing a motor 1 with a speed reducer according to the first embodiment.
As shown in FIG. 1, the motor 1 with a speed reducer includes a motor section 2 and a reduction section 3 that reduces the rotation of the motor section 2 and outputs the reduced speed.
In the following description, the term "axial direction" refers to the rotation axis direction of the shaft 21 of the motor unit 2, the term "circumferential direction" refers to the circumferential direction of the shaft 21, and the term "radial direction" refers to the shaft direction. 21 radial direction.

The motor unit 2 includes a motor case 5 , a substantially cylindrical stator 6 housed in the motor case 5 , and a rotor 8 provided radially inside the stator 6 and rotatable with respect to the stator 6 . and have. The motor unit 2 is a so-called brushless motor that does not require brushes when supplying power to the stator 6 .

(stator)
FIG. 2 is a cross-sectional view taken along line II--II of FIG.
As shown in FIG. 2 , the stator 6 includes a stator core 10 and coils (windings) 14 . The stator core 10 includes a tubular core portion 11 having a substantially circular cross-sectional shape along the radial direction, and a plurality of (for example, nine in the first embodiment) teeth formed radially inward from the core portion 11. 12 and are integrally molded.
Stator core 10 is formed by laminating a plurality of metal plates in the axial direction. Note that the stator core 10 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.

The teeth 12 each include a tooth main body 12a protruding inward along the radial direction from an inner peripheral surface 11a of the core portion 11, and a flange portion 12b formed along the circumferential direction from the radial inner end of the tooth main body 12a. It is integrally molded. The flange portion 12b is formed along both sides in the circumferential direction from the tooth main body 12a. A slot 16 is formed between the collar portions 12b adjacent in the circumferential direction.

Moreover, the inner peripheral surface 11 a of the core portion 11 and the teeth 12 are covered with a resin insulator 17 . A coil 14 is wound (wound) around each tooth 12 from above the insulator 17 . Each coil 14 generates a magnetic field for rotating the rotor 8 by power supply from the power supply.

(rotor)
The rotor 8 is rotatably provided inside the stator 6 in the radial direction with a minute gap therebetween. The rotor 8 includes a shaft 21 integrally formed with a worm shaft 33 (see FIG. 1) that constitutes the reduction section 3, a cylindrical rotor core (support) 22 externally fitted and fixed to the shaft 21, and an outer circumference of the rotor core 22. and a magnet 23 provided on the surface.
The rotor core 22 is arranged radially inside the teeth 12 . The rotor core 22 is a cylindrical member having the shaft 21 as an axis C1 when it is externally fitted and fixed to the shaft 21 . The rotor core 22 is a magnetic member formed by laminating a plurality of metal plates in the axial direction. It should be noted that the rotor core 22 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. The rotor core 22 is made of a material with magnetism and thus has functional strength.

A mounting portion 22a having a through hole penetrating in the axial direction is provided at substantially the center of the rotor core 22 in the radial direction. The shaft 21 is press-fitted into the mounting portion 22a. Alternatively, the shaft 21 may be inserted into the mounting portion 22a, and the rotor core 22 may be externally fixed to the shaft 21 using an adhesive or the like. The shaft 21 is functionally strong because it is made of an iron-based magnetic material.

Furthermore, a magnet 23 is externally fitted and fixed to the outer peripheral surface 22 b of the rotor core 22 . That is, the magnet 23 is circumferentially formed over the entire circumference of the outer peripheral surface 22 b of the rotor core 22 . The magnet 23 is a polar-oriented magnet such as a polar-anisotropic magnet formed in a cylindrical shape (ring shape). The magnet 23 is arranged radially inward of the teeth 12 , so that a magnetic pole is generated on the surface facing the teeth 12 and magnetic flux flows in the arrow A direction.

The magnet 23 is a plastic bond type bonded magnet in which magnetic powder and resin are bonded. Bonded magnets are flexible magnets made by crushing magnets such as ferrite magnets and kneading them into rubber or plastic. For example, bonded magnets using neodymium magnets or samarium iron-nitrogen magnets have stronger magnetic force than ordinary sintered ferrite magnets, can be processed into complicated shapes, and are particularly applied to small motors and the like.

FIG. 3 is a cross-sectional view enlarging the III section of FIG.
As shown in FIG. 3 , the magnet 23 has a plurality of convex portions (bridge portions) 25 formed on the inner peripheral surface 23 a and concave portions 26 formed between adjacent convex portions 25 . The plurality of protrusions 25 are arranged at equal intervals in the circumferential direction on the inner peripheral surface 23a of the magnet 23 . The plurality of protrusions 25 are formed so as to extend axially along the outer peripheral surface 22b of the rotor core 22 when in contact with the outer peripheral surface 22b. In the embodiment, the number of the plurality of protrusions 25 is three, but it is also possible to select a different number of the plurality of protrusions 25 .
Moreover, although an example in which the plurality of protrusions 25 are arranged at equal intervals in the circumferential direction on the inner peripheral surface 23a of the magnet 23 will be described, it is also possible to arrange the plurality of protrusions 25 at non-equidistant intervals.

The convex portion 25 protrudes radially inward from the inner peripheral surface 23 a of the magnet 23 toward the outer peripheral surface 22 b of the rotor core 22 . The convex portion 25 is formed to have a constant width, and the tip surface 25 a is formed so as to follow the outer peripheral surface 22 b of the rotor core 22 .
In the first embodiment, an example in which the width dimension of the convex portion 25 is formed to be constant will be described, but the shape of the convex portion 25 is not limited to this. As another shape of the convex portion 25, for example, the convex portion 25 can be tapered from the proximal end to the distal end.

A concave portion 26 is formed between the adjacent convex portions 25 by the inner peripheral surface 23 a of the magnet 23 and the adjacent convex portions 25 . That is, the bottom of the recess 26 is formed by the inner peripheral surface 23 a of the magnet 23 . The bottom of the recess 26 (that is, the inner peripheral surface 23a of the magnet 23) is formed in a concave curve along the outer peripheral surface 22b of the rotor core 22 at a constant distance radially outward from the outer peripheral surface 22b. .

A plurality of projecting portions 25 of the magnet 23 are fitted into the rotor core 22 , and tip end surfaces 25 a of the plurality of projecting portions 25 come into contact with the outer peripheral surface 22 b of the rotor core 22 . A plurality of protrusions 25 are fixed to the outer peripheral surface 22b of the rotor core 22 with an adhesive 41 (see FIG. 7B) or the like. Thereby, the plurality of protrusions 25 and the rotor core 22 are integrated (contacted).
In this state, the concave portion 26 of the magnet 23 is arranged without contact with the outer peripheral surface 22 b of the rotor core 22 . A curved space 28 is formed between the recess 26 and the outer peripheral surface 22 b of the rotor core 22 .

(Reduction part)
Returning to FIG. 1 , the reduction section 3 includes a gear case 31 to which the motor case 5 is attached, and a worm reduction mechanism 32 housed in the gear case 31 . The worm reduction mechanism 32 is composed of a worm shaft 33 and a worm wheel 34 meshed with the worm shaft 33 . The worm shaft 33 is arranged coaxially with the shaft 21 of the motor section 2 . Both ends of the worm shaft 33 are rotatably supported through bearings 36 and 37 provided in the gear case 31 .

The end of the worm shaft 33 on the side of the motor unit 2 protrudes through the bearing 36 to reach the opening of the gear case 31 . The protruding end of the worm shaft 33 and the end of the shaft 21 of the motor section 2 are joined together to integrate the worm shaft 33 and the shaft 21 . The worm shaft 33 and the shaft 21 may be integrally formed by molding the worm shaft portion and the rotary shaft portion from one base material.

A worm wheel 34 that meshes with the worm shaft 33 is provided with an output shaft 38 at the radial center of the worm wheel 34 . The output shaft 38 is arranged coaxially with the rotation axis direction of the worm wheel 34 and protrudes outside the gear case 31 via a bearing boss (not shown) of the gear case 31 . A spline that can be connected to an electrical component (not shown) is formed at the projecting tip of the output shaft 38 .

Examples of electrical equipment include sunroofs, power windows, and power seats. That is, the motor 1 with a speed reducer of the first embodiment can be applied to brushless sunroof motors, brushless power window motors, and brushless power seat motors, and can also be applied to other general brushless motors.
Here, the rotor core 22 and the shaft 21 are made of a material with magnetism, so that they have the functional strength necessary for driving the electrical equipment.

(Rotor magnetic flux)
FIG. 4 is a conceptual diagram illustrating the flow of magnetic flux in the rotor 8 in the first embodiment. In FIG. 4, an arrow A indicates the flow of the magnetic flux of the magnet 23. As shown in FIG.
As shown in FIG. 4, the magnet 23 has a plurality of protrusions 25 formed on the inner peripheral surface 23a. Therefore, a curved space 28 is formed between the concave portion 26 of the magnet 23 and the outer peripheral surface 22 b of the rotor core 22 . Thereby, the magnetic flux flow of the magnet 23 magnetized in the polar orientation can be interrupted by the space 28 . Therefore, the magnetic flux leakage of the magnet 23 magnetized in the polar orientation can be suppressed to be reduced, and the amount of magnetic flux can be increased with respect to the amount of magnet usage.

FIG. 5 is a graph for explaining the effective magnetic flux per 1g of the magnet 23 in the first embodiment. In FIG. 5, the vertical axis indicates the effective magnetic flux μwb/g per gram.
As shown in FIG. 5, the magnet of the comparative example has a small effective magnetic flux per 1 g of magnet. The magnet of the comparative example is different from the magnet of the embodiment in that the inner peripheral surface of the magnet is not formed with a convex portion and a concave portion. That is, the magnet of the comparative example is in contact with the entire outer peripheral surface 22 b of the rotor core 22 over the entire inner peripheral surface. Therefore, the magnetic flux of the magnet 23 leaks to the rotor core 22 side, and the effective magnetic flux per 1 g of magnet becomes small.

In contrast, the magnet 23 of the embodiment has a plurality of protrusions 25 and a plurality of recesses 26 formed on the inner peripheral surface 23a. A space 28 is formed between the concave portion 26 of the magnet 23 and the outer peripheral surface 22b of the rotor core 22, and the space 28 blocks the flow of magnetic flux. As a result, the magnet 23 of the embodiment can secure a larger effective magnetic flux per 1 g of magnet than the comparative example by suppressing magnetic flux leakage so as to reduce it.

Returning to FIG. 3, it is desirable that the area where the magnet 23 contacts the outer peripheral surface 22b of the rotor core 22 is as small as possible from the viewpoint of suppressing magnetic flux leakage of the magnet 23. FIG. On the other hand, when the magnets 23 are attached to the rotor core 22, it is necessary to ensure coaxiality between the outer peripheral surface 23b (see FIG. 2) of the magnets 23 and the shaft 21. FIG.
From this point of view, it is preferable to set the number of protrusions 25 provided on the magnet 23 to, for example, three. By setting the number of protrusions 25 to three, the magnetic flux leakage of the magnet 23 can be suitably suppressed while coaxiality between the outer peripheral surface 23b of the magnet 23 and the shaft 21 is ensured. Note that the number of protrusions 25 is not limited to three.

As described above, according to the motor section 2 of the first embodiment, the rotor core 22 and the shaft 21 are made of a material having magnetism. can be provided. In addition, by providing a plurality of protrusions 25 on the inner peripheral surface 23a of the magnet 23, it is possible to suppress magnetic flux leakage and increase the amount of magnetic flux with respect to the amount of magnet usage.

(Magnet assembly procedure)
FIG. 6A is a side view illustrating an example of fitting the magnet 23 into the rotor core 22 in the first embodiment. FIG. 6(b) is a side view illustrating a state in which the magnet 23 according to the first embodiment is inserted halfway into the rotor core 22. FIG.
As shown in FIG. 6A, an adhesive 41 is applied to the outer peripheral surface 22b of the rotor core 22. As shown in FIG. In this state, a plurality of protrusions 25 (see FIG. 3) of the magnet 23 are fitted onto the outer peripheral surface 22b of the rotor core 22 as indicated by arrows B. As shown in FIG.

As shown in FIG. 6B, the end surface 23c of the magnet 23 contacts the adhesive 41 by fitting the plurality of projections 25 of the magnet 23 onto the outer peripheral surface 22b of the rotor core 22 as indicated by arrow B. As shown in FIG. In this state, the magnet 23 is continuously inserted further in the arrow B direction.
Here, a plurality of spaces 28 (see FIG. 3) are formed by the concave portion 26 of the magnet 23 and the outer peripheral surface 22b of the rotor core 22. As shown in FIG. Therefore, the adhesive 41 can be received in multiple spaces 28 . As a result, scraping off the adhesive 41 applied to the outer peripheral surface 22 b of the rotor core 22 by the end surface 23 c of the magnet 23 can be suppressed.

FIG. 7(a) is a side view illustrating a state in which the magnet 23 according to the first embodiment is externally fitted and fixed to the rotor core 22. FIG. FIG. 7(b) is a front view illustrating a state in which the magnet 23 in the first embodiment is externally fitted and fixed to the rotor core 22. FIG.
As shown in FIG. 7(a), the magnet 23 is fitted on the outer peripheral surface 22b of the rotor core 22 to the assembly position.

As shown in FIG. 7B, the magnet 23 is fitted into the outer peripheral surface 22b of the rotor core 22 up to the assembly position. In this state, the adhesive 41 applied to the outer peripheral surface 22b of the rotor core 22 is received in the plurality of spaces 28. As shown in FIG. The tip surfaces 25 a of the plurality of protrusions 25 of the magnet 23 are fixed with an adhesive 41 while being in contact with the outer peripheral surface 22 b of the rotor core 22 . The plurality of recesses 26 are fixed to the outer peripheral surface 22 b of the rotor core 22 by the adhesive 41 received in the plurality of recesses 26 of the magnet 23 .

Therefore, the magnet 23 is externally fitted and fixed to the outer peripheral surface 22b of the rotor core 22 with the adhesive 41 with high adhesive strength. As a result, the magnets 23 can be easily assembled to the outer peripheral surface 22b of the rotor core 22 while the adhesion strength of the magnets 23 to the outer peripheral surface 22b of the rotor core 22 is increased.

Also, the adhesive 41 applied to the outer peripheral surface 22b of the rotor core 22 can be prevented from being scraped off by the end surface 23c of the magnet 23. FIG. Therefore, there is no possibility that the scraped off adhesive will protrude. As a result, the step of wiping off the protruding adhesive can be eliminated. Furthermore, it is possible to avoid risks such as foreign matter and facility malfunction due to dripping of the adhesive 41 .

Here, as a comparative example, for example, a magnet that does not have a plurality of protrusions 25 will be described. If the magnet does not have a plurality of protrusions 25 as in the comparative example, a clearance is required to allow an adhesive to intervene between the inner peripheral surface of the magnet and the outer peripheral surface 22 b of the rotor core 22 . Therefore, in the comparative example, it is difficult to ensure coaxiality of the magnets with respect to the rotor core 22 .
On the other hand, the magnet 23 of the first embodiment can receive the adhesive 41 in the plurality of concave portions 26 by providing the plurality of convex portions 25 . Therefore, it is possible to suitably bring the plurality of projections 25 into contact with the outer peripheral surface 22 b of the rotor core 22 . Thereby, the motor section 2 of the first embodiment can ensure coaxiality of the magnet 23 with respect to the rotor core 22 .

(Second embodiment)
Next, the motor section 50 of the second embodiment will be described. In the second embodiment, the same or similar members as those of the motor portion 2 of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.
FIG. 8 is a cross-sectional view showing the motor section 50 in the second embodiment.
As shown in FIG. 8, the motor section 50 replaces the rotor 8 of the first embodiment with a rotor 51, and is otherwise a brushless motor similar to the motor section 2 of the first embodiment.

The rotor 51 includes a shaft (support) 52 that is integrally formed with the worm shaft 33 (see FIG. 1) that constitutes the reduction section 3, and a magnet 54 that is externally fitted and fixed to the outer peripheral surface 52a of the shaft 52. there is The shaft 52 is arranged radially inside the teeth 12 . The shaft 52 is functionally strong because it is made of an iron-based magnetic material.
The magnet 54 is formed in a circumferential shape (ring shape) over the entire circumference of the outer peripheral surface 52a of the shaft 52, and a plurality of convex portions (bridge portions) 55 are formed on the inner peripheral surface 54a. The plurality of protrusions 55 protrude so as to come into contact with the outer peripheral surface 52a of the shaft 52, and are fixed (integrated) with an adhesive 41 (see FIG. 7B) while being in contact with the outer peripheral surface 52a.

In this state, the concave portion 56 of the magnet 54 is arranged without contact with the outer peripheral surface 52 a of the shaft 52 . A curved space 58 is formed between the recess 56 and the outer peripheral surface 52 a of the shaft 52 . That is, the motor portion 50 of the second embodiment has a shaft 52 made of a magnetic material, and a plurality of projecting portions 55 of the magnet 54 are fitted and fixed to the outer peripheral surface 52a of the shaft 52. Other configurations are similar to those of the first embodiment. It is the same as the motor part 2 of the form.

Also in the motor section 50 of the second embodiment, the same effects as those of the motor section 2 of the first embodiment can be obtained. That is, according to the motor section 50 of the second embodiment, the shaft 52 is made of a material having magnetism, so that the functional strength necessary for driving the electrical equipment can be provided. In addition, by providing a plurality of protrusions 55 on the inner peripheral surface 54a of the magnet 54, it is possible to suppress magnetic flux leakage and increase the amount of magnetic flux with respect to the amount of magnet usage.

It should be noted that the present invention is not limited to the above-described embodiments, but includes various modifications of the above-described embodiments within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Motor with reduction gear 2, 50... Motor part (brushless motor) 6... Stator 10... Stator core 12... Teeth 14... Coil 21... Shaft 22... Rotor core (support) 23, 54... Magnet, 25, 55... Convex part, 26, 56... Concave part, 52... Shaft (support body)

Claims (2)

a stator comprising a stator core having teeth formed along the radially inner side, and a winding wound around the stator core;
a support that is disposed radially inside the teeth and that includes a shaft that rotates with respect to the stator core; and a rotor core that is integrally fixed to the shaft ;
A brushless motor having
The support is made of a magnetic material having a polar orientation that generates magnetic poles on the surface facing the teeth and provided with magnets provided in a circumferential shape,
The magnet comprises a bond magnet, and has a plurality of protrusions formed so as to be continuous in the axial direction of the support at intervals in the circumferential direction of the magnet, protrude radially inward, and abut against the support. , recesses formed between the adjacent protrusions in a non-contact manner with respect to the outer peripheral surface of the rotor core,
The width dimensions of the plurality of protrusions are formed to be constant, the tip surfaces of the plurality of protrusions are formed so as to follow the outer peripheral surface of the rotor core, and the tip surfaces of the plurality of protrusions conform to the outer peripheral surface of the rotor core. abutting and having a space formed by the recess and the outer peripheral surface of the rotor core ;
A brushless motor characterized by: The brushless motor according to claim 1,
The brushless motor, wherein the plurality of convex portions is three.

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