JP2016178751A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a brushless motor capable of increasing a leakage flux amount of a rotor reaching a magnetic sensor and suppressing a detection delay of the magnetic sensor to improve the output efficiency by attaching a flux induction part protruding toward the magnetic sensor side on an end face of a rotor core.SOLUTION: The brushless motor includes a rotor core 3 protruding toward a hall element 12 side provided at an interval in the peripheral direction on an end face, and a plurality of flux induction parts 3c guiding a leakage flux of a rotor to the hall element 12.SELECTED DRAWING: Figure 1

Description

  The present invention detects a rotational position in the circumferential direction of a rotor based on a stator that generates a rotating magnetic field, a rotor having a plurality of magnets rotatably provided inside the stator, and leakage magnetic flux from the rotor. The present invention relates to a brushless motor including a magnetic sensor.

In a brushless motor that includes a magnetic sensor that detects the polarity of a leakage magnetic flux of a rotor having a magnet and detects the rotor position, and switches the motor coil appropriately to generate a rotating magnetic field to rotate the rotor. It is necessary to supply the magnetic sensor with a magnetic flux that exceeds the threshold value for the magnetic sensor to determine the polarity.
In this case, when the magnetic flux reaching the magnetic sensor is small, or when the polarity of the magnetic flux is slowly switched at the position of the magnetic sensor, it takes time for the magnetic flux to exceed the threshold value. Detection may be delayed.
As a result, a delay occurs with respect to the original timing at which the energized phase of the motor should be switched, and as a result, the performance of the motor may be reduced.

  On the other hand, for the purpose of improving the detection accuracy of the Hall element that is a magnetic sensor, by providing a gap by a hole in the magnetic path of the rotor core, a leakage magnetic flux is generated therefrom, and the magnetic flux supplied to the Hall element is A brushless motor to be increased is known (for example, see Patent Document 1).

Japanese Patent No. 4233950

However, although the brushless motor increases the leakage magnetic flux by forming a hole in the magnetic path of the rotor core, it is not configured to effectively guide the magnetic flux to the Hall element.
Moreover, although the said patent document 1 has shown the structure which added the magnet for sensing in order to further increase a leakage magnetic flux, there exists a problem of causing the increase in a number of parts and cost.

  An object of the present invention is to solve the above-described problems, and by providing a magnetic flux guiding portion projecting toward the magnetic sensor on the end surface of the rotor core, the amount of leakage magnetic flux of the rotor reaching the magnetic sensor. An object of the present invention is to obtain a brushless motor that can increase the output, reduce the detection delay of the magnetic sensor, and improve the output efficiency.

A brushless motor according to the present invention includes a rotor core configured by laminating thin steel plates in an axial direction and fixed to a shaft, and a rotatable rotor having a plurality of magnets fixed to the rotor core at intervals in the circumferential direction; ,
A stator core having a plurality of teeth provided so as to surround the rotor in the circumferential direction and having a tip portion extending radially inward and forming a plurality of slots at intervals in the circumferential direction, and a conductive wire wound around the teeth. A stator having a stator coil that generates a rotating magnetic field by energizing
A magnetic sensor that is provided facing the rotor in the axial direction and detects the rotational position of the rotor in the circumferential direction by detecting the polarity of the magnetic flux of the magnet;
The rotor core has a plurality of magnetic flux guide portions that are provided on the end surface so as to protrude toward the magnetic sensor at intervals in the circumferential direction and guide the magnetic flux to the magnetic sensor.

According to the brushless motor according to the present invention, by providing the magnetic flux guiding portion on the end face of the rotor core, the leakage magnetic flux of the rotor can be efficiently supplied to the magnetic sensor.
For this reason, in the magnetic flux detected by the magnetic sensor, the change in magnetic flux before and after the switching of the polarity with respect to the rotation angle of the rotor can be made steep, so that the detection delay based on the threshold value of the magnetic sensor is reduced. The delay in switching the energization of the coil is reduced and the output efficiency is improved.

It is sectional drawing which shows the brushless motor of Embodiment 1 of this invention. It is a figure when the rotor of FIG. 1 is seen in the axial direction from the Hall sensor side. It is a figure when the magnetic flux guidance | induction part of FIG. 1 is seen to radial direction. It is a figure when the rotor which shows the modification of the brushless motor of FIG. 1 is seen to an axial direction from the Hall element side. FIG. 6 is a characteristic diagram showing a relationship between a rotor rotation angle and a leakage magnetic flux density of the rotor at the position of the Hall element according to the first embodiment. It is a figure when the rotor of the brushless motor of Embodiment 2 of this invention is seen in the axial direction from the Hall element side. It is a figure when the rotor of the brushless motor of Embodiment 3 of this invention is seen in the axial direction from the Hall element side.

  Hereinafter, the brushless motor of each embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding members and parts will be described with the same reference numerals.

Embodiment 1 FIG.
FIG. 1 is a sectional view showing a brushless motor 1 according to Embodiment 1 of the present invention.
The brushless motor 1 (hereinafter abbreviated as “motor”) according to the first embodiment includes a flat bracket 15, a bottomed cylindrical housing 14 covering the surface of the bracket 15, and a first provided on the bracket 15. A rotor 2 fixed to a shaft 5 rotatably supported at both ends by a second bearing 7 provided on the bearing 6 and the housing 14, and a rotor 2 fixed to the inner wall surface of the housing 14 and surrounding the rotor 2 along the circumferential direction. And a Hall element 12 which is a magnetic sensor provided on the substrate 13 attached to the bracket 15 and facing the end face of the rotor 2.

The rotor 2 includes a rotor core 3 configured by laminating thin steel plates 3d in the axial direction, and a plurality of magnets 4 fixed to the rotor core 3 at intervals in the circumferential direction.
The stator 8 has a stator core 9 having a plurality of teeth whose tip portions extend radially inward and form a plurality of slots at intervals in the circumferential direction, and a conducting wire is wound around the teeth via an insulator 10 to energize the conducting wire. And a stator coil 11 that generates a rotating magnetic field.
The rotor core 3 and the stator core 9 have the same height on the second bearing 7 side, and on the first bearing 6 side, the end face of the rotor core 3 protrudes toward the Hall element 12 side compared to the end face of the stator core 9.
Thus, the portion of the rotor 2 that faces the stator 8 in the radial direction contributes to the torque generation of the motor 1, and the portion of the rotor 2 that protrudes from the end face of the stator 8 toward the Hall element 12 side becomes the Hall element 12. Contributes to the generation of magnetic flux to be supplied.

FIG. 2 is a view of the rotor 2 of FIG. 1 when viewed in the axial direction from the Hall element 12 side.
The rotor core 3 is formed with a plurality of magnet embedding holes 3a arranged at equal intervals in the circumferential direction and penetrating in the axial direction, and constitutes an embedded magnet type rotor in which the magnets 4 are fixed to the magnet embedding holes 3a. To do.
The magnet 4 may be fixed to the rotor core 3 by pouring an adhesive into the magnet embedding hole 3a, or may be press-fitted and fixed to the magnet embedding hole 3a.
The magnet 4 is magnetized so that adjacent magnets have different poles, and a plurality of poles are formed in the circumferential direction on the outer periphery of the rotor core 3.
A circular hole 3b is formed at the center of the rotor core 3, and the rotor core 3 is fixed by, for example, a shaft 5 being press-fitted into the hole 3b.

  Here, one thin steel plate 3d on the Hall element 12 side of the rotor core 3 is formed on the outer peripheral edge portion on the outer side in the radial direction of the magnet 4 with a hole between the poles of adjacent magnets 4 as shown in FIG. A convex magnetic flux guiding portion 3c protruding to the element 12 side is formed. The magnetic flux guiding portion 3c formed by pressing the thin steel plate 3d, for example, has a function of guiding the leakage magnetic flux of the rotor 2 to the Hall element 12 side.

The motor 1 has a control circuit (not shown) having an arithmetic circuit for receiving a detection signal of leakage magnetic flux of the rotor 2 from the Hall element 12 and switching to energization to an appropriate phase.
Specifically, the Hall element 12 determines the polarity from the detected leakage magnetic flux of the rotor 2 and sends a signal to the control circuit. The control circuit determines an appropriate energized phase based on a signal from the Hall element 12 and sequentially switches the energized phase to the stator coil 11 to generate a rotating magnetic field in the stator 8. The rotating magnetic field pulls the magnetic pole of the rotor 2 so that the rotor 2 rotates about the shaft 5.

FIG. 4 is a modification of the motor 1 according to the first embodiment, and is a view when the rotor 2 is viewed in the axial direction from the Hall element 12 side.
In this modification, the magnetic flux guiding portion 3c is formed on the outer side in the radial direction of each magnet 4 and in the intermediate portion in each circumferential direction. The magnetic flux guiding portion 3c is formed by pressing a single thin steel plate 3d as in the thin steel plate 3d of FIG.

FIG. 5 is a characteristic diagram showing the relationship between the rotation angle of the rotor 2 and the leakage magnetic flux density of the rotor 2 at the position of the Hall element 12 of the first embodiment.
In FIG. 5, the broken line is the rotor without the magnetic flux guiding portion 3 c, and the solid line is the rotor 2 shown in FIG. 2, in which the magnetic flux guiding portion 3 c is formed between the magnets 4 adjacent in the circumferential direction, that is, between the poles. Is the rotor 2 shown in FIG. 4 in which the magnetic flux guiding portion 3c is formed at the middle portion of the magnet 4, that is, at the pole center.
From FIG. 5, even if the magnetic flux guiding portion 3c is formed between the poles or in the middle of the magnetic pole, the magnetic flux density increases in the entire rotation region of the rotor 2 as compared with the rotor not having the magnetic flux guiding portion 3c. You can see that
Further, it can be seen that the value of the magnetic flux density is maximum when the magnetic flux guiding portion 3c is formed at the pole center at the pole center line C in FIG.
Further, even when the magnetic flux guiding portion 3c is formed between the poles or in the middle of the pole, the change in the magnetic flux density near the switching of the polarity, that is, the gradient may become steep as the magnetic flux density increases. Recognize.

  In FIG. 5, the threshold value when the Hall element 12 detects polarity reversal is indicated by a dotted line. According to this, both of the detection delay angle A1 when the magnetic flux guiding portion 3c is formed between the poles and the detection delay angle A2 when the magnetic flux guiding portion 3c is formed at the center of the pole do not have the magnetic flux guiding portion. It can be seen that the detection delay is reduced compared to the detection delay angle B of FIG.

As described above, according to the motor 1 of the first embodiment, the rotor core 3 has the plurality of magnetic flux guide portions 3c provided on the end face so as to protrude toward the hall element 12 with a circumferential interval. Therefore, the leakage magnetic flux of the rotor 2 can be efficiently supplied to the hall element 12. Therefore, the magnetic flux gradient near the polarity switching of the magnetic flux reaching the Hall element 12 becomes steep, and the detection delay of the Hall element 12 can be reduced.
Therefore, the delay in switching the energization of the motor 1 is reduced, and the output efficiency of the motor 1 can be increased.

Moreover, since the magnetic flux of the magnet 4 supplied to the Hall element 12 can be increased without extending the magnet 4 from the end face of the rotor core 3 to the Hall element 12 side, the cost of parts does not increase.
Further, since it is not necessary to install a sensor magnet for supplying magnetic flux to the Hall element 12 separately from the magnet 4, the overall length of the motor 1 is flattened without increasing the axial length of the motor 1. be able to.

Further, the magnetic flux guiding portion 3c is easily formed by extruding the thin steel plate 3d into a convex shape by pressing, and can be realized at low cost.
Furthermore, the length in the circumferential direction of the magnetic flux guiding portion 3c and the height protruding from the end face of the rotor 2 can be arbitrarily set.
Thereby, the magnetic flux guidance | induction part 3c can be optimized for the shape for obtaining a desired leakage magnetic flux according to the magnetic flux intensity of the magnet 4, and arrangement | positioning of the Hall element 12. FIG.

Further, the magnetic flux guiding portion 3c protrudes closer to the hall element 12 than the stator core 9 in the axial direction.
For this reason, it is reduced that the magnetic flux emitted from the magnetic flux guiding portion 3 c flows into the stator core 9, and a large amount of magnetic flux is induced in the Hall element 12.

Further, the end surface of the rotor core 3 protrudes closer to the Hall element 12 than the end surface of the stator core 9.
Therefore, more magnetic flux from the end of the rotor 2 protruding toward the hall element 12 than the end face of the stator core 9 is supplied to the hall element 12 through the magnetic flux guiding portion 3c.

Further, as can be seen from FIG. 5, since the same effect can be obtained regardless of whether the magnetic flux guiding portion 3c is formed between the poles or in the center of the pole, the position at which the magnetic flux guiding portion 3c is to be formed is What is necessary is just to select suitably by the magnitude | size of 4.
For example, when the length of the magnet 4 along the circumferential direction is short, that is, when the distance between the magnets 4 adjacent in the circumferential direction is long, the length in the circumferential direction of the magnetic flux guiding portion 3c becomes long. It may be easier. In that case, in order to avoid deformation of the magnetic flux guiding portion 3c, the magnetic flux guiding portion 3c may be formed at the center of the pole so that the magnetic flux guiding portion 3c can be configured.

Embodiment 2. FIG.
FIG. 6 is a view of the rotor 2 of the motor 1 according to the second embodiment of the present invention as viewed in the axial direction from the Hall element 12 side.
In the motor 1 of the second embodiment, the magnetic flux guiding portion 3 c is provided on the radially inner side of the magnet 4.
Other configurations are the same as those of the motor 1 of the first embodiment.

In the motor 1 of the second embodiment, the magnetic flux guiding part 3c is formed in a magnetic path through which most of the magnetic flux between the magnets 4 adjacent in the circumferential direction flows.
For this reason, since the magnetic flux equivalent to or higher than that of the first embodiment passes through the magnetic flux guiding section 3c, the amount of leakage magnetic flux guided to the Hall element 12 can be further increased.
Further, since the magnetic flux guiding portion 3c is formed at a position away from the stator core 9, the amount of leakage magnetic flux from the stator core 9 superimposed on the magnetic flux guiding portion 3c is reduced.
As a result, the Hall element 12 can detect the magnetic poles of the rotor 2 more accurately, the energization switching delay due to the detection delay can be reduced, and the output efficiency of the motor 1 can be improved.
In addition, the magnetic flux guidance | induction part 3c may be formed in the pole center which is the center part of the circumferential direction of the magnet 4, and the same effect can be acquired also in this case.

Embodiment 3 FIG.
FIG. 7 is a view of the rotor 2 of the motor 1 according to the third embodiment of the present invention when viewed in the axial direction from the Hall element 12 side.
In the motor 1 of the third embodiment, the rotor 2 includes a rotor core 3 in which a plurality of thin steel plates 3d are stacked, a shaft 5 fixed by press-fitting into a hole 3b in the center of the rotor core 3, and the outer periphery of the rotor core 3. And a ring-shaped magnet 40 in which a plurality of provided magnetic poles are magnetized. The ring-shaped magnet 40 is fixed to the outer peripheral surface of the rotor core 3 using a method such as adhesion.
The magnetic flux guiding portion 3c is formed on the inner diameter side of the ring-shaped magnet 40 and between the poles.
Other configurations are the same as those of the motor 1 of the first embodiment.

According to the motor 1 of the third embodiment, the magnetic flux guiding portion 3c is formed in the magnetic path between the poles of the ring-shaped magnet 40, similarly to the motor 1 of the second embodiment.
For this reason, even in the case of the surface magnet type rotor using the ring-shaped magnet 40, most of the magnetic flux flowing through the magnetic path between the poles passes through the magnetic flux guiding portion 3c, so that the magnetic flux guiding portion 3c is transferred to the Hall element 12. The induced leakage magnetic flux can be increased, and the same effect as that of the motor 1 of the first embodiment can be obtained.

In the motor 1 of the third embodiment, the case of the ring-shaped magnet 40 has been described. However, the motor 1 is a surface magnet type rotor in which a plurality of tile-shaped or arc-shaped magnets are arranged on the outer peripheral surface of the rotor core 3. May be.
Further, similar to the motor 1 of the first and second embodiments, the same effect can be obtained even when the magnetic flux guiding portion 3c is formed at the pole center.

In addition, this invention is not limited to the thing of Embodiment 1-3 mentioned above, In the range which does not deviate from the summary, it can change suitably and can be abbreviate | omitted.
For example, in each embodiment, the magnetic flux guiding portion 3c is formed by one thin steel plate 3d at the end of the rotor 2. However, the present invention is not limited to this, and each of the plurality of thin steel plates 3d has uneven portions. The magnetic flux guiding part 3c may be formed by forming and fitting and stacking them in the axial direction.
In the case of the magnetic flux guiding portion 3c, the strength increases and it is difficult to deform, and the magnetic resistance at the magnetic flux guiding portion 3c is reduced, so that more leakage magnetic flux is supplied to the Hall element 12.
Alternatively, a protrusion may be separately manufactured, and the protrusion may be welded onto the thin steel plate 3d of the rotor core 3 so that the protrusion is used as a magnetic flux guiding portion.
Further, although the Hall element 12 has been described as the magnetic sensor, it is of course not limited to this, and for example, a magnetoresistive element may be used.

  DESCRIPTION OF SYMBOLS 1 Brushless motor, 2 rotor, 3 rotor core, 3a Magnet embedding hole, 3b hole, 3c Magnetic flux guide part, 3d Thin steel plate, 4 Magnet, 5 Shaft, 6 1st bearing, 7 2nd bearing, 8 Stator, 9 Stator core, 10 insulator, 11 stator coil, 12 hall element (magnetic sensor), 13 substrate, 14 housing, 15 bracket, 40 ring magnet.

A brushless motor according to the present invention includes a rotor core configured by laminating thin steel plates in an axial direction and fixed to a shaft, and a rotatable rotor having a plurality of magnets fixed to the rotor core at intervals in the circumferential direction; ,
A stator core having a plurality of teeth provided so as to surround the rotor in the circumferential direction and having a tip portion extending radially inward and forming a plurality of slots at intervals in the circumferential direction, and a conductive wire wound around the teeth. A stator having a stator coil that generates a rotating magnetic field by energizing
A magnetic sensor that is provided facing the rotor in the axial direction and detects the rotational position of the rotor in the circumferential direction by detecting the polarity of the magnetic flux of the magnet;
The rotor core has a plurality of magnetic flux guide portions provided on the end face so as to protrude toward the magnetic sensor with a circumferential interval, and guides the magnetic flux to the magnetic sensor .
Each of the magnetic flux induction portions is provided between the adjacent magnets .

Claims (9)

A rotor core configured by laminating thin steel plates in the axial direction and fixed to the shaft, and a rotatable rotor having a plurality of magnets fixed to the rotor core at intervals in the circumferential direction;
A stator core having a plurality of teeth provided so as to surround the rotor in the circumferential direction and having a tip portion extending radially inward and forming a plurality of slots at intervals in the circumferential direction, and a conductive wire wound around the teeth. A stator having a stator coil that generates a rotating magnetic field by energizing
A magnetic sensor that is provided facing the rotor in the axial direction and detects the rotational position of the rotor in the circumferential direction by detecting the polarity of the magnetic flux of the magnet;
The rotor core is a brushless motor that has a plurality of magnetic flux guiding portions that are provided on the end face so as to protrude toward the magnetic sensor at intervals in the circumferential direction and guide the magnetic flux to the magnetic sensor.   The brushless motor according to claim 1, wherein each of the magnetic flux guiding portions is provided between the adjacent magnets.   2. The brushless motor according to claim 1, wherein each of the magnetic flux guiding portions is provided in an intermediate portion of each of the magnets.   The brushless motor according to any one of claims 1 to 3, wherein each of the magnetic flux guide portions is formed of one or a plurality of the thin steel plates.   The brushless motor according to any one of claims 1 to 4, wherein the end surface of the rotor core protrudes toward the magnetic sensor with respect to an end surface of the stator core.   The brushless motor according to any one of claims 1 to 5, wherein each of the magnetic flux guiding portions is provided on an outer side in a radial direction of the magnet.   The brushless motor according to any one of claims 1 to 5, wherein each of the magnetic flux guide portions is provided on an inner side in a radial direction of the magnet.   The brushless motor according to claim 1, wherein each of the magnets is provided in a plurality of holes formed in the rotor core.   The brushless motor according to claim 1, wherein each of the magnets is provided on an outer peripheral surface of the rotor core.

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