JP5478844B2 - Electric motor - Google Patents

Description

  The present invention relates to an electric motor used for, for example, a starter motor for starting an engine for a motorcycle.

  Generally, an electric motor with a brush is often used as a starter motor for starting an engine of a motorcycle. This type of electric motor has a configuration in which a plurality of magnets are disposed on the inner peripheral surface of a yoke having a cylindrical portion, and an armature around which an armature coil is wound is rotatably supported. . The armature has an armature core that is externally fixed to the rotating shaft. In the armature core, teeth for winding the winding are formed radially, and a long slot is formed between the teeth in the axial direction.

  A winding is wound around each tooth to form an armature coil. The armature coil is electrically connected to a plurality of segments of the commutator attached to the rotating shaft. Each segment can be slidably contacted with a brush, and a current is supplied to the armature coil by applying a voltage from the brush to the segment. At this time, a magnetic field is formed in the armature coil, and the rotating shaft is driven by a magnetic attractive force or repulsive force generated between the magnet and the yoke.

  Here, in the electric motor, cogging torque is generated in the armature by the magnetic force of the magnet disposed on the yoke, and magnetic noise (noise) is generated due to this. In addition, in response to the recent demand for higher performance of electric motors, when the number of electric motors is increased, the frequency of rotating sound is high, and when the electric motor is stopped, the rotating sound of the armature is between And the natural frequency of the yoke may overlap and resonate.

In particular, when the number of slots is an even number, the positional relationship between the magnets and the slots (teeth) is the same at the point-symmetrical positions around the rotation axis, so the timing of cogging torque generation for each slot is the same. It overlaps at several places. For this reason, when the number of slots is even, the cogging torque is increased and the cogging torque is regularly generated and the magnetic sound is increased as compared with the case where the number of slots is odd. Therefore, the angle extending around the rotation axis of the magnet, that is, the magnet angle, is set so that the number of occurrences of cogging is an integer multiple of 2 or more of the least common multiple of the number of slots and the number of magnetic poles, so Has been proposed (see, for example, Patent Document 1).
JP 2003-134772 A

  However, even if the magnet angle stretched around the rotation axis of the magnet is set to a desired angle, if the number of slots is an even number, the cogging torque generation timing for each slot will not overlap. . For this reason, there is a problem that it is difficult to be an effective means for reducing the cogging torque and reducing the magnetic sound.

  Therefore, the present invention has been made in view of the above-described circumstances, and is an electric motor that can effectively reduce cogging torque and magnetic noise even when the number of slots is an even number. A motor is provided.

In order to solve the above-mentioned problem, the invention described in claim 1 includes a yoke having a cylindrical portion, a plurality of magnets arranged in parallel along the circumferential direction on the inner peripheral surface of the yoke, and a rotating shaft. An even number of teeth arranged at equal intervals in the circumferential direction, and an even number of slots formed between the teeth and extending along the axial direction, and N is a natural number of 2 or more, When the number of magnets is P, the electric motor in which the number P of magnets is set so as to satisfy P = 2 × N includes (P / 2) magnets adjacent to each other in the circumferential direction. a reference magnet group constituted by said about the axis of rotation is opposed, and circumferentially adjacent to each other (P / 2) number of opposed magnet group consisting of the magnet to the reference magnet group, the reference the magnet The magnets of the group are arranged with an interval of (360 ° / P), while the magnets of the counter magnet group are point-symmetric about the rotation axis of the magnets of the reference magnet group. All of the magnets arranged at the same angle from the position are shifted in the circumferential direction, and the shift direction is shifted in the clockwise direction, and the magnet is shifted in the counterclockwise direction. It is characterized by being arranged in .

With this configuration, the positional relationship between each magnet of the reference magnet group and each slot (teeth) facing this, and the positional relationship between each magnet of the opposing magnet group and each slot (tooth) facing this And can be changed. For this reason, even when the number of slots is set to an even number, the generation timing of the cogging torque for each slot can be shifted between the reference magnet group side and the counter magnet group side around the rotation axis.
Further, for example, when a so-called disk type commutator formed in a disk shape is used as the commutator, the number of segments of the commutator can be set to an even number by setting the number of slots to an even number. For this reason, in the disk-type commutator, the slits formed between the segments also exist at point-symmetric positions with the rotation axis as the center. Can be easily formed (slit cut).
Further, the timing of generating the cogging torque for each magnet of the opposed magnet group and these magnets can be shifted.

In the second aspect of the invention, when α represents an angle at which each magnet of the counter magnet group deviates in the circumferential direction from the point symmetry position of each magnet of the reference magnet group, ((360 ° / S) × ( 1/4)) ≦ α ≦ ((360 ° / S) × (3/4)) is characterized in that the angle α is set.
With this configuration, the positional relationship between each magnet in the reference magnet group and each slot facing it, and the positional relationship between each magnet in the opposing magnet group and each slot facing this are optimal for suppressing cogging. Can be set to state.

According to the first aspect of the present invention, the positional relationship between each magnet of the reference magnet group and each slot (tooth) facing the magnet, each magnet of the counter magnet group, and each slot (tooth) facing the magnet. Can be changed. For this reason, even when the number of slots is set to an even number, the generation timing of the cogging torque for each slot can be shifted between the reference magnet group side and the counter magnet group side around the rotation axis. Therefore, it is possible to reduce the cogging torque or to reduce the magnetic sound by making the generation of the cogging torque irregular.
For example, when a so-called disk-type commutator formed in a disk shape is used as the commutator, the number of segments of the commutator can be set to an even number by setting the number of slots to an even number. For this reason, in the disk-type commutator, the slits formed between the segments also exist at point-symmetric positions with the rotation axis as the center. Can be easily formed (slit cut). Therefore, it becomes possible to reduce manufacturing cost as the whole electric motor.
Furthermore, the positional relationship between each magnet of the opposed magnet group and each slot facing the magnet can be changed. For this reason, it is possible to shift the generation timing of the cogging torque for each magnet of the opposing magnet group and these magnets. Therefore, the cogging torque can be further reduced and the magnetic sound can be reduced.

According to the second aspect of the present invention, the positional relationship between the magnets of the reference magnet group and the slots facing the magnets, and the positional relationship between the magnets of the counter magnet group and the slots facing the magnets are reduced. Can be set to the optimum state.
Here, if the magnets on the counter magnet group side are displaced by an angle α or more, the end portions of these magnets eventually approach the next adjacent slot. For this reason, when the effect on the reduction of the cogging torque is taken into consideration, the arrangement positions of the respective magnets vary more than necessary, and the reduction of the effective magnetic flux becomes large.
For this reason, by configuring as in the third aspect of the invention, it is possible to more effectively reduce the cogging torque and the magnetic sound.

Next, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 to 3, the electric motor 1 is used as, for example, a two-wheel starter motor, and includes a front bracket 2 (left side in FIG. 1) fixed to the vehicle body and a front bracket 2. A cylindrical stator 3 to which one end is fixed, a rear bracket 4 (right side in FIG. 1) that closes the other end of the stator 3, and disposed in the stator 3, rotate to the front bracket 2 and the rear bracket 4. And an armature 5 that is freely supported.

  The armature 5 has a rotating shaft 10 connected to the shaft of the engine, and an armature core 11 and a commutator 12 are fixed to the rotating shaft 10. The armature core 11 is manufactured by laminating iron core pieces, and has a plurality (32 in this embodiment) of teeth 50 extending radially about the rotation shaft 10 (see FIG. 3). The teeth 50 are formed in a substantially T shape in a plan view in the axial direction, and a dovetail slot 51 that is long in the axial direction is formed between the teeth 50. A coil 13 is wound around the tooth 50 via a slot 51.

  The commutator 12 is a so-called disk type commutator having a disk shape. The commutator 12 has a plurality of segments 14 (for example, 32 in this embodiment) arranged radially around the rotary shaft 10, and each segment 14 is provided with insulation between the segments 14. A slit (not shown) is formed. One end of a winding forming the coil 13 is fixed to the segments 14.

  The front bracket 2 is provided with a hole 15 through which the rotary shaft 10 penetrates in the center, and a bearing 16 that rotatably supports one end portion of the rotary shaft 10 is press-fitted and fixed in the hole 15. Furthermore, an oil seal 17 is disposed on the outer side in the radial direction than the bearing 16. Further, an O-ring 18 used for mounting on the engine case is attached to the outer periphery. The outer edge portion of the front bracket 2 is fixed to the stator 3 with bolts 19.

  The stator 3 includes a yoke 21 formed in a substantially cylindrical shape having a cylindrical portion 21A. A plurality (six in this embodiment) of magnets 22 formed in the shape of roof tiles for field magnets are fixed to the inner peripheral side of the yoke 21 along the circumferential direction. That is, in this embodiment, the electric motor 1 is a 6-pole 32-slot motor in which the number of slots 51 (tooth 50) is 32 and the six magnets 22 are provided. As the magnet 22, for example, a neodymium rare earth magnet can be used.

Here, as shown in FIG. 2, when the number of magnets 22 is P and N is a natural number of 2 or more,
P = 2 × N
The number P is set so as to satisfy. In this embodiment, since six magnets 22 are fixed to the inner peripheral side of the yoke 21,
2 × N = 2 × 3 = P
It turns out that. Therefore, P = 2 × N (N: a natural number of 2 or more) is satisfied.

The six magnets 22 are composed of a reference magnet group 61 and a counter magnet group 62 that are arranged to face each other about the rotating shaft 10. Each of the magnet groups 61 and 62 is composed of the magnets 22 adjacent to each other, and the same number of magnets 22 exists in both the magnets 61 and 62. That is, the reference magnet group 61 includes
P / 2 = 6/2 = 3 (pieces)
While the magnet 22 is present,
The counter magnet group 62 also has P / 2 = 6/2 = 3 (pieces)
The magnet 22 is present.

Each magnet 22 existing in the reference magnet group 61 is arranged at a reference position. The reference position is a position when all the magnets 22 are arranged on the inner peripheral side of the yoke 21 at equal intervals in the circumferential direction. That is, with respect to the arrangement interval of the magnets 22 existing in the reference magnet group 61, if the circumferential angle between the center positions of the adjacent magnets 22 and 22 is θ,
θ = 360 ° / P
The angle θ is determined so as to satisfy
In this embodiment, since the number (total number) P of the magnets 22 is “6”, the magnets 22 existing in the reference magnet group 61 are 360 ° / P = 360 ° / 6 = 60 ° in the circumferential direction.
It will be arrange | positioned at intervals of.

  On the other hand, the magnets 22 existing in the counter magnet group 62 are arranged so as to be shifted from the point symmetry positions of the magnets 22 existing in the reference magnet group 61 by an angle α in the circumferential direction. Further, the deviation directions of the respective magnets 22 existing in the opposed magnet group 62 from the respective point-symmetric positions are staggered in the circumferential direction.

The angle α is given by assuming that the number of slots 51 is S.
((360 ° / S) × (1/4)) ≦ α ≦ ((360 ° / S) × (3/4))
It is set to satisfy.
Furthermore, the angle α is
((360 ° / S) × (1/2)) = α
It is desirable that

That is, in this embodiment, since S = 32, the angle α is
((360 ° / S) × (1/2)) = ((360 ° / 32) × (1/2)) = 5.625 ° = α
It is desirable that This corresponds to an angle when the magnet 22 is displaced in the circumferential direction by a distance corresponding to half of the tooth 50 in the circumferential direction.

Here, if each magnet 22 of the opposing magnet group 62 is displaced by an angle α or more, the end portion of the magnet 22 will eventually approach the next tooth 50 (see the magnet 22 indicated by a two-dot chain line in FIG. 3). . This means that the positional relationship between the magnets 22 and the teeth 50 of the reference magnet group 61 and the positional relationship between the magnets 22 and the teeth 50 of the counter magnet group 62 are the same. Therefore, the angle α is set to ((360 ° / S) × (1/4)) ≦ α ≦ ((360 ° / S) × (3/4)).
By setting so as to satisfy, it is ensured that the positional relationship between each magnet 22 of the reference magnet group 61 and the tooth 50 (slot 51) and each magnet 22 of the counter magnet group 62 and the tooth 50 (slot 51). The positional relationship can be changed.

The angle α is ((360 ° / S) × (1/4)) ≦ α ≦ ((360 ° / S) × (3/4)).
If the above condition is not satisfied, the effective magnetic flux with respect to the teeth 50 is greatly reduced, and the motor efficiency is reduced.

Also, in particular, the angle α is ((360 ° / S) × (1/2)) = α
By setting so as to satisfy, the position of each magnet 22 of the opposed magnet group 62 can be shifted from the reference position by a distance corresponding to a half in the circumferential direction of the tooth 50 (see portion C in FIG. 3).
Therefore, as a result, the positional relationship between the magnets 22 and the teeth 50 of the reference magnet group 61 and the positional relationship between the magnets 22 and the teeth 50 of the opposing magnet group 62 are shifted to the maximum. Therefore, the timing of occurrence of cogging generated in the opposed magnet group 62 can be shifted to the maximum.

As shown in FIGS. 1 and 4, the rear bracket 4 is fixed with a bolt 23 at one end of the yoke 21 where the magnet 22 is disposed.
The rear bracket 4 has a bottomed cylindrical shape, and the other end portion of the rotary shaft 10 of the armature 5 is inserted into a boss portion 25 protruding from the center of the bottom portion 4A. The boss portion 25 is press-fitted with an oilless metal 26 as a bearing, and the armature 5 is rotatably supported via the oilless metal 26.
The rear bracket 4, the yoke 21, and the front bracket 2 are made of a conductive material, for example, aluminum die casting.

  A brush holder 30 is fixed inside the bottom portion 4A of the rear bracket 4. The brush holder 30 is a substantially annular resin molded product, and protrudes so that the central portion 30 </ b> A surrounds the boss portion 25. Further, four holder portions 31 are integrally provided so as to surround the boss portion 25. The holder portion 31 extends in the axial direction, and one conductive brush 32 slidably contacting the segment 14 of the commutator 12 of the armature 5 is slidably received in each holder portion 31.

The brush 32 is urged toward the commutator 12 by a spring 33 disposed in the holder portion 31. A pigtail 34 is attached to the brush 32 by integral molding. The pigtail 34 is pulled out from a slit formed in the side portion of the holder portion 31.
Pigtails 34 extending from two of the four brushes 32 (plus-side brush 32 </ b> A) are connected to a power supply terminal 36 via a power supply plate 35. Pigtails 34 extending from the remaining two brushes 32 (minus side brush 32B) are connected to the ground terminal 40.

  The power supply terminal 36 is formed of a bolt member in which the head 41 is disposed in the brush holder 30. Each of the brush holder 30 and the rear bracket 4 is provided with terminal insertion holes 42 and 43 through which the power supply terminal 36 is inserted. An O-ring 44 is inserted into the terminal insertion hole 43, and the power supply terminal 36 is inserted from the inside of the brush holder 30 toward the outside of the rear bracket 4. The head 41 of the power supply terminal 36 is electrically connected to a power supply plate 35 that is insert-molded in the brush holder 30. The power feeding plate 35 is bent in a substantially L shape, and two pigtails 34 from the brush 32A are fixed thereto by spot welding or the like.

  Outside the rear bracket 4, a nut 47 is tightened after passing the resin bush 45 and the stopper washer 46 through the power supply terminal 36, and the brush holder 30 and the rear bracket 4 are sandwiched between the power supply terminal 36 and the nut 47. Yes. A power supply wiring (not shown) is connected to the nut 47 and is electrically connected to the battery. An insulating cover 48 is attached to the outside of the rear bracket 4 so as to surround the nut 47.

  Under such a configuration, the electric motor 1 is fixed to a vehicle body of a motorcycle, such as an engine cover. At this time, the rotary shaft 10 extending from the front bracket 2 is connected to a one-way clutch attached to the crankshaft. The electric motor 1 is grounded by the vehicle body. When a voltage is applied to the power supply terminal 36, a current flows from the commutator 12 that is in sliding contact with the brush 32A to the coil 13, and the armature 5 rotates. The rotation of the armature 5 rotates the crankshaft via the one-way clutch and starts the engine.

Next, the generation process of the cogging torque of the electric motor 1 will be described with reference to FIG. Here, attention is focused on the positional relationship between the reference magnet group 61 and the teeth 50, and particularly attention is focused on the center magnet 22A (hereinafter referred to as the center magnet 22A) in FIG.
As shown in the drawing, four teeth 50 (hereinafter referred to as opposed teeth 50A) are opposed to the central magnet 22A of the reference magnet group 61, respectively. In this case, the counter teeth 50A are attracted by the central magnet 22A with the same magnetic attraction force. For this reason, even if the armature 5 is rotated clockwise (in the direction of arrow D in FIG. 5), for example, almost no cogging torque is generated.

  Subsequently, when the armature 5 is rotated clockwise, the opposing tooth 50A at the rotation direction side end of the four teeth 50 is attracted to the magnet 22B adjacent in the rotation direction. At the same time, the teeth 50B located on the opposite side to the rotation direction of the opposing teeth 50A are attracted to the central magnet 22A. For this reason, a force directed in the rotational direction (clockwise direction) acts on the armature 5 to generate cogging torque.

  Here, in the case where all of the six magnets 22 are arranged at equal intervals in the circumferential direction on the inner peripheral side of the yoke 21, the number S of slots 51 in the electric motor 1 is set to an even number (32). Therefore, the positional relationship between the magnets 22 and 22 arranged to face each other about the rotation shaft 10 and the corresponding teeth 50 is the same. For this reason, cogging torque is generated at the same time among the teeth 50 that exist at point-symmetrical positions around the rotation axis 10 among the plurality of teeth 50. That is, since the cogging torque is generated at the same timing, the cogging torque is increased.

  On the other hand, in the electric motor 1 of this embodiment, since the six magnets 22 are composed of the reference magnet group 61 and the counter magnet group 62, they exist at point-symmetrical positions around the rotating shaft 10. The cogging torque does not occur at the same timing even between the teeth 50 to be used. That is, the timing for generating the cogging torque can be shifted between the teeth 50 positioned on the reference magnet group 61 side and the teeth 50 positioned on the counter magnet group 62 side. For this reason, it is possible to reduce the cogging torque.

  Therefore, according to the above-described embodiment, the positional relationship between each magnet 22 of the reference magnet group 61 and each slot 51 (tooth 50) facing this, and each magnet 22 of the facing magnet group 62 and each facing this. The positional relationship with the slot 51 (tooth 50) can be changed. For this reason, even if the number S of slots 51 is set to an even number, the teeth 50 located on the reference magnet group 61 side and the opposing magnet group 62 side are located around the rotation shaft 10. The timing at which the cogging torque is generated can be shifted between the teeth 50 being connected. That is, the generation timing of cogging torque can be shifted. Therefore, it is possible to reduce the cogging torque or to reduce the magnetic sound by making the generation of the cogging torque irregular.

  Moreover, since the deviation directions from the respective reference positions of the magnets 22 existing in the counter magnet group 62 are staggered in the circumferential direction, each slot 51 is provided for each magnet 22 positioned on the counter magnet group 62 side. The positional relationship with (tooth 50) can be changed. For this reason, since the timing of generating the cogging torque for each slot 51 (tooth 50) can be shifted only within the range of the opposed magnet group 62, the cogging torque can be further reduced and the magnetic sound is reduced. It becomes possible.

Then, an angle α in which each magnet 22 of the opposed magnet group 62 is shifted in the circumferential direction from the point symmetrical position (reference position) of each magnet 22 of the reference magnet group 61 is set to ((360 ° / S) × (1/4)). ≦ α ≦ ((360 ° / S) × (3/4))
By setting so as to satisfy, the positional relationship between the magnets 22 and the teeth 50 of the reference magnet group 61 and the positional relationship between the magnets 22 and the teeth 50 of the opposing magnet group 62 can be changed reliably. For this reason, it becomes possible to reduce cogging torque and magnetic sound more effectively.

In particular, the angle α is ((360 ° / S) × (1/2)) = α
By setting so as to satisfy, the positional relationship between the magnets 22 and the teeth 50 of the reference magnet group 61 and the positional relationship between the magnets 22 and the teeth 50 of the counter magnet group 62 can be shifted to the maximum. . For this reason, it is possible to minimize cogging torque and magnetic sound.

  Further, since the number of segments 14 arranged in the disc-shaped commutator 12 is set to an even number as in the case of the slot 51 (for example, 32 in this embodiment), slits formed between the segments 14 ( (Not shown) also exist at point-symmetrical positions around the rotation axis 10. For this reason, it is possible to easily form a slit (slit cut) as compared with the case where the number of segments 14 is an odd number. Therefore, it is possible to reduce the manufacturing cost of the electric motor 1 as a whole.

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.
In the above-described embodiment, the case where the number S of the slots 51 (the teeth 50) is set to “32” has been described. However, the present invention is not limited to this, and the armature 5 includes a plurality of slots 51 (the teeth 50). ) May be provided.

  Furthermore, in the above-described embodiment, a case has been described in which the deviation directions from the reference positions of the magnets 22 present in the opposed magnet group 62 are staggered in the circumferential direction. However, the present invention is not limited to this, and it is only necessary that each magnet 22 existing in the opposed magnet group 62 be shifted from the reference position by the angle α, and the shift direction is not particularly limited.

  And in the above-mentioned embodiment, the case where the yoke 21 of the stator 3 was formed in the substantially cylindrical shape which has 21 A of cylinder parts was demonstrated. However, the invention is not limited to this, and the yoke 21 may be formed in a substantially bottomed cylindrical shape having the cylindrical portion 21A.

In the above embodiment, when the number of the magnets 22 is P and N is a natural number of 2 or more,
P = 2 × N
The number P is set so as to satisfy the condition, and specifically, the case where six magnets 22 are fixed to the inner peripheral side of the yoke 21 has been described. However, the present invention is not limited to this, and only two magnets 22 may be disposed on the inner peripheral side of the yoke 21.
In this case, one of the two magnets 22 may be disposed in a circumferential direction shifted from a point-symmetric position around the rotation axis 10 of the other magnet 22. In this way, even when the number S of slots 51 is set to an even number, the generation timing of the cogging torque generated between one magnet 22 and the slot 51 facing the other, and the other Since the generation timing of the cogging torque generated between the magnet 22 and the slot 51 opposed to the magnet 22 can be shifted, the same effect as that of the above-described embodiment can be obtained.

It is a partial cross section figure of the electric motor in the embodiment of the present invention. It is a top view of the stator in the embodiment of the present invention. It is sectional drawing which follows the BB line of FIG. It is sectional drawing which follows the AA line of FIG. It is explanatory drawing of the cogging torque generation | occurrence | production process in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 3 Stator 10 Rotating shaft 21 Yoke 21A Tube part 22 Magnet 50 Teeth 51 Slot 61 Reference magnet group 62 Opposing magnet group P Number of magnets S Number of slots

Claims (2)

A yoke having a cylindrical portion;
A plurality of magnets arranged side by side along the circumferential direction on the inner circumferential surface of the yoke;
An even number of teeth arranged at equal intervals in the circumferential direction around the rotation axis;
An even number of slots formed between the teeth and extending along the axial direction;
When N is a natural number of 2 or more and the number of magnets is P,
P = 2 × N
In the electric motor in which the number P of the magnets is set so as to satisfy
A reference magnet group composed of (P / 2) magnets adjacent to each other in the circumferential direction, and arranged to face the reference magnet group around the rotation axis and adjacent to each other in the circumferential direction (P / 2) Consists of a counter magnet group consisting of the magnets,
While the magnets of the reference magnet group are arranged at an interval of (360 ° / P),
Each of the magnets of the opposed magnet group is arranged by being shifted in the circumferential direction by the same angle from the point symmetry position around the rotation axis of each of the magnets of the reference magnet group,
In addition , the electric motor is characterized in that the magnets that are shifted in the clockwise direction and the magnets that are shifted in the counterclockwise direction are alternately arranged . The number of slots is S,
When the angle that each magnet of the opposed magnet group is shifted in the circumferential direction from the point symmetrical position of each magnet of the reference magnet group is α,
((360 ° / S) × (1/4)) ≦ α ≦ ((360 ° / S) × (3/4))
The electric motor according to claim 1, wherein the angle α is set so as to satisfy

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