JP2023091273A - motor - Google Patents

Abstract

To provide a motor having a physique and performance equal to those of a conventional product using a neodymium magnet while using a ferrite magnet.SOLUTION: A motor 1 is an IPM-type motor having a magnet 23 embedded in a magnet fitting hole 22 formed in a rotor core 15. The magnet fitting hole 22 has a first magnetic storage part 22a extending in a radial direction, and a second magnet storage part 22b extending in a peripheral direction. The first magnetic storage part 22a and the second magnet storage part 22b communicate with each other, and the magnet fitting hole 22 is formed into a U shape. First and second magnets 23a and 23b are arranged in tight contact respectively in the first and second magnet storage parts 22a and 22b. In a rotor 3, a magnetic pole 28 is formed by the two first magnets 22a and one second magnet 22b arranged in the U shape.SELECTED DRAWING: Figure 2

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic flux concentration type electric motor, and more particularly to a so-called IPM (Interior Permanent Magnet) type brushless motor in which a magnet is embedded in a rotor.

In recent years, in various in-vehicle electric systems that use a motor as a drive source, such as an electric power steering system (EPS), the replacement of brushed motors with brushless motors is progressing from the viewpoint of durability, controllability, and functional safety. . Furthermore, in brushless motors for vehicles such as EPS motors, rare earth magnets such as neodymium magnets are increasingly being used in place of ferrite magnets in response to demands for smaller size and higher performance of devices.

However, although rare earth magnets are compact and have a high magnetic flux density, they are more expensive than ferrite magnets, and their production and raw material mining have a high environmental impact. It has an aspect that cannot be said to be a conforming material. Therefore, in consideration of cost and environmental impact, SPM (Surface Permanent Magnet) type EPS motors using ferrite magnets have recently been put on the market. In such a motor, taking advantage of the fact that ferrite magnets have a lower density and are lighter than neodymium magnets, the outer diameter of the rotor is increased and a ferrite magnet with a D-shaped cross section is arranged on the outer peripheral surface of the rotor to improve the magnet torque. there is

JP 2016-82733 A JP 2015-133839 A

However, since ferrite magnets have weaker magnetic force than rare earth magnets such as neodymium magnets, a large amount of magnets is required to obtain performance equivalent to that of conventional products with ferrite magnets. Therefore, as described above, measures such as increasing the outer diameter of the rotor are required, resulting in the problem of increasing the size of the motor. In addition, for EPS motors, for example, low inertia is required in relation to steering performance, etc., and there is a limit to the structure of increasing the outer diameter of the rotor to improve torque, which has hindered the adoption of ferrite magnets. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a motor that uses ferrite magnets but has the same size and performance as conventional products using neodymium magnets.

A motor according to the present invention includes a stator and a rotor disposed radially inside the stator, the rotor including a rotor core fixed to a rotating shaft and a magnet accommodating portion formed in the rotor core. and a magnet mounted thereon, wherein the magnet accommodating portion comprises a first magnet accommodating portion formed radially and extending along a radial direction, and arranged radially inside the first magnet accommodating portion. and a second magnet housing portion extending along the circumferential direction, wherein the first magnet housing portion communicates with the second magnet housing portion on the center side of the rotor, and the second magnet housing portion extends circumferentially. The magnets are formed of ferrite magnets and communicate with the first magnet containing portion at both ends in the direction, and the first magnet portion within the first magnet containing portion and the second magnet portion within the second magnet containing portion , wherein the second magnet portion is disposed radially inward of the first magnet portion without any gap, and the rotor includes two first magnet portions and a first magnet portion radially inward of the first magnet portion. It is characterized in that one magnetic pole is formed by two magnet parts.

In the present invention, by arranging the second magnet portion on the rotor center side of the two first magnet portions, the three directions of one magnetic pole of the rotor are formed in a form completely closed by magnets. As a result, a magnetic flux concentration type configuration is obtained in which the open portion is only on the stator side in terms of the magnetic circuit. In addition, since the second magnet portion is arranged radially inward of the first magnet portion without gaps, the gap in the rotor can be further reduced, and the proportion of the core cross section occupied by the magnets is improved. As a result, the amount of magnetic flux is increased, and it is possible to provide a motor having the same size and performance as conventional products using neodymium magnets while using ferrite magnets.

In the motor, three directions of the magnetic poles, that is, the circumferential direction and the radial direction, are closed without gaps by the two first magnet portions and one second magnet portion, and the opposing surfaces of the first magnet portion and the The surface of the second magnet portion surrounding the magnetic poles may be formed to have the same polarity. As a result, the first magnet portion and the second magnet portion are arranged in a pseudo Halbach arrangement, thereby improving magnetic force and reducing air gaps in the rotor.

In addition, the first magnet portion and the second magnet portion are formed of separate magnets, and the second magnet portion is brought into close contact with the entire surface of the radial inner end surface of the first magnet portion. You can place it. Furthermore, the first magnet portion and the second magnet portion can be formed as an integral magnet, and in this case, the magnet as a whole may be formed in a U shape or a U shape.

In addition, the first magnet portion and the second magnet portion may be formed by attaching pre-magnetized magnets in the magnet accommodating portion. The motor uses ferrite magnets, which have a weaker magnetic force than neodymium magnets, so that the magnets can be assembled relatively easily after magnetization, which is not easy with neodymium magnet motors, and the number of assembly steps can be reduced. In addition, since it can be easily disassembled, it is possible to improve recyclability.

According to the motor of the present invention, by arranging the second magnet portion on the rotor center side of the two first magnet portions, the three directions of one magnetic pole of the rotor can be completely closed by the magnets. , it is possible to obtain a magnetic flux concentration type configuration in which the open portion is only on the stator side in terms of magnetic circuit. Further, by arranging the second magnet portion in close contact with the radially inner end face of the first magnet portion in a closed state, the gap in the rotor can be further reduced, and the proportion of the core cross section occupied by the magnets can be improved. can be done. As a result, in the motor of the present invention, the amount of magnetic flux is increased, and while inexpensive ferrite magnets are used, the motor has the same size and performance as conventional products using expensive neodymium magnets. can be provided.

1 is a cross-sectional view of a brushless motor that is an embodiment of the present invention; FIG. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1; FIG. 4 is an explanatory diagram showing a configuration near a magnet mounting hole;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a brushless motor 1 (hereinafter abbreviated as motor 1) that is an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line AA in FIG. As shown in FIGS. 1 and 2, the motor 1 is an inner rotor type brushless motor with a stator 2 on the outside and a rotor 3 on the inside. used.

In addition, the motor 1 is a magnetic flux concentration type IPM motor in which the magnets of the rotor are arranged radially. It is In addition, by adopting the IPM structure, the motor 1 does not require a magnet holder or a magnet cover for fixing the magnet, unlike the conventional SPM structure motor. planned.

The stator 2 is fixed inside a bottomed cylindrical motor case 4 (hereinafter abbreviated as case 4) by a fixing means such as press fitting. The stator 2 includes a stator core 5, a stator coil 7 (hereinafter abbreviated as coil 7) wound around teeth 6 of the stator core 5, and a busbar unit (terminal unit) attached to the stator core 5 and electrically connected to the coil 7. ) 8. The case 4 is made of iron or the like and formed into a cylindrical shape with a bottom, and a bracket 9 (made of die-cast aluminum, for example) is attached to the opening of the case 4 with a fixing screw (not shown).

The stator core 5 is formed by stacking steel plate materials (for example, electromagnetic steel sheets), and has a plurality of teeth 6 (12 in this embodiment) protruding radially inward. Slots 10 are formed between adjacent teeth 6, and coils 7 are accommodated therein. A synthetic resin insulator 11 is attached to the stator core 5 , and a coil 7 is wound around the insulator 11 . As a result, the stator 2 has a 12-slot configuration.

A busbar unit 8 is attached to one end of the stator core 5 on the opening side of the case 4 . The busbar unit 8 has a structure in which a copper busbar is insert-molded in a synthetic resin main body. Around the busbar unit 8, a plurality of power supply terminals 12 are radially projected. When the busbar unit 8 is attached, the end portion 7a of the coil 7 pulled out from the stator core 5 is welded to the power supply terminal 12 . In the busbar unit 8, the number of busbars corresponding to the number of phases of the motor 1 (here, three for the U-phase, V-phase, and W-phase and one for connecting each phase, total four) is provided. there is Each coil 7 is electrically connected to a power supply terminal 12 corresponding to its phase. The stator core 5 is press-fitted and fixed in the case 4 after the busbar unit 8 is attached.

A rotor 3 is inserted inside the stator 2 . The rotor 3 has a rotor shaft 13, and the rotor shaft 13 is rotatably supported by bearings 14a and 14b. The bearing 14a is fixed to the center of the bottom of the case 4, and the bearing 14b is fixed to the center of the bracket 9, respectively. A cylindrical rotor core 15 and a rotor (resolver rotor) 17 of a resolver 16 that is rotation angle detection means are attached to the rotor shaft 13 . A stator (resolver stator) 18 of the resolver 16 is housed in a resolver bracket 19 made of synthetic resin and fixed inside the bracket 9 with mounting screws 20 .

The rotor core 15 is configured by laminating a plurality of circular thin core plates (steel plates) made of a magnetic material. The rotor core 15 is provided with a shaft hole 21 and a plurality of magnet mounting holes (magnet housing portions) 22 . A shaft hole 21 is formed in the center of the rotor core 15, and the rotor shaft 13 is press-fitted therein. The magnet mounting holes 22 are formed in a substantially U-shape, and are provided in plural along the circumferential direction on the outer peripheral side of the shaft hole 21 .

FIG. 3 is an explanatory diagram showing the configuration near the magnet mounting hole 22. As shown in FIG. As shown in FIG. 3, the magnet mounting hole (magnet housing portion) 22 includes a first magnet mounting hole (first magnet housing portion) 22a extending along the radial direction and a magnet mounting hole (first magnet housing portion) 22a extending radially inside the first magnet mounting hole 22a. and a second magnet mounting hole (second magnet accommodating portion) 22b arranged and extending along the circumferential direction. The first magnet mounting hole 22a communicates with the second magnet mounting hole 22b on the side of the rotor center O, and the magnet mounting hole 22 as a whole has a substantially U shape that is open on the outer diameter side. A magnet 23 using a solid ferrite magnet is accommodated in the magnet mounting hole 22 .

The first magnet attachment holes 22a are formed to have a rectangular cross section, and a plurality of (here, 20) are radially arranged along the circumferential direction. As shown in FIG. 2, the first magnet mounting holes 22a are arranged so that two of each are adjacent to each other in the circumferential direction. The first magnet mounting hole 22a is closed at its radially outer side by a bridge portion 24, while being open at its inner diameter side end, and communicates with a second magnet mounting hole 22b having a substantially rectangular cross section. ing. That is, the second magnet mounting hole 22b communicates with the first magnet mounting hole 22a at both ends in the circumferential direction. One U-shaped magnet mounting hole 22 is formed by two first magnet mounting holes 22a and one second magnet mounting hole 22b which are spaced apart.

The magnet 23 includes a flat plate-like first magnet (first magnet portion) 23a housed in the first magnet mounting hole 22a, and a radially inner end face of the first magnet 23a housed in the second magnet mounting hole 22b. and a second magnet (second magnet portion) 23b disposed so as to close the entire surface of the magnet. The first magnet 23a has a cuboid shape with a rectangular cross section, and is fixed in the first magnet mounting hole 22a with an adhesive. A gap portion 25 in which the first magnet 23a does not exist is formed facing the bridge portion 24 at the radially outer end portion of the first magnet mounting hole 22a. In the motor 1, the air gap 25 prevents demagnetization of the first magnet due to the influence of the field magnetic field of the stator 2, and also prevents short-circuiting of the north and south poles at the outer end of the first magnet 23a. ing.

The second magnet 23b has a polygonal cross section (here, a hexagon) in which both corners of one opposite side of a trapezoid are chamfered wide, and is fixed in the second magnet mounting hole 22b with an adhesive. . At both ends of one side of the second magnet 23b in the circumferential direction, sloped portions 26 are formed by obliquely wide chamfering the corner portions. When the magnet 23 is attached in the magnet attachment hole 22, the slope portion 26 is brought into close contact with the radially inner end surface 27 of the first magnet 23a. That is, the first magnets 23a are arranged in close contact with the radially outer end portions of the second magnets 23b. At this time, the entire surface of the end surface 27 is covered with the slope portion 26 , and the U-shaped magnet 23 without a gap is formed in the magnet mounting hole 22 .

In the motor 1, ten magnetic poles 28 are formed on the rotor 3 side by the first magnets 23a arranged radially and extending in the axial direction, and the second magnets 23b arranged on the back side (inside in the radial direction) of the first magnets 23a. be done. As a result, the motor 1 of this embodiment has a 10-pole, 12-slot configuration. As described above, the magnets 23 are formed in a U-shape with no gaps, and the magnetic poles 28 have a shape in which the three magnets 23 are closed without gaps in the three directions of the circumferential direction and the radially inner side. . In this case, the first and second magnets 23a and 23b are arranged so that the surfaces surrounded by the three magnets forming the magnetic pole 28 (hereinafter referred to as inner surfaces) have the same polarity.

That is, in the magnetic poles 28, the opposing inner side surfaces 31 of the two first magnets 23a and the inner side surface 32 of the second magnet 23b facing the inner side surface 31 side are of the same polarity. As described above, in the motor 1, by arranging the rear magnet (the second magnet 23b) on the rotor center side of the two first magnets 23a, one pole is formed in a completely closed form with the magnet, thereby forming a magnetic circuit. As a matter of fact, a magnetic flux concentration type configuration is obtained in which the open portion is only on the stator side. As a result, the magnetic poles 28 can generate a magnetic flux equivalent to two magnets or more on the outer circumference of the rotor.

Further, the second magnet 23b is arranged in close contact with the end surface 27, which is a non-magnetic pole portion in a direction perpendicular to the magnetization direction of the first magnet 23a, and the magnetization direction of the second magnet 23b is substantially perpendicular to the magnetization direction of the first magnet 23a. becomes. For this reason, the first magnet 23a and the second magnet 23b form a shape close to a so-called Halbach arrangement, and at the magnetic pole 28, the flow of magnetic flux concentrates inside the magnet 23. The magnetic force can be improved more than when a gap is provided between the second magnets 23a and 23b. According to the inventor's analysis, by adopting the configuration of FIG. 3, the induced voltage is increased by 1.4 times or more compared to the case where the second magnet mounting hole 22b is used as a gap without inserting the second magnet 23b. bottom.

Further, in a conventional IPM motor, a gap is provided between the poles to prevent loss due to short-circuiting of the magnetic flux in the rotor core. In this regard, in the motor 1 according to the present invention, the pseudo-Halbach arrangement makes it difficult for the magnetic flux to leak outside the magnetic poles 28, that is, outside the first and second magnets 23a and 23b. Therefore, the gap for preventing magnetic flux leakage can be kept to a minimum, and the magnets can be arranged on the cross section of the rotor without waste, and NS short-circuiting can be prevented, thereby improving the effect of magnetic flux concentration. As a result, it is possible to reduce the air gap in the rotor, increase the proportion of the core cross section occupied by the magnet, and provide a more efficient motor.

On the other hand, in motors using neodymium magnets, the magnetic force of the magnets is extremely strong, making it difficult to assemble the magnets into the rotor after magnetization. It is carried out. At this time, if a magnet is arranged on the center side like the second magnet 23b, it is difficult to sufficiently magnetize it, and the magnetic force inevitably decreases, so that the advantage of the neodymium magnet cannot be utilized. Also, in the case of a configuration in which the bond magnet is injected toward the center side, the center side portion cannot be fully magnetized, and a satisfactory amount of magnetic flux cannot be obtained.

On the other hand, in the motor 1, since the magnet 23 is a ferrite magnet, the magnetized magnet 23 can be assembled in the rotor 3 in the same manner as in the conventional ferrite magnet motor. Therefore, the magnet 23 in a fully magnetized state can be mounted in the rotor 3, and a sufficient amount of magnetic flux can be obtained from the magnet (second magnet 23b) on the inner diameter side, realizing characteristics comparable to those of the conventional neodymium magnet motor. becomes possible. In addition, since the ferrite magnet itself has a weak magnetic attraction force, it is easy to assemble, improving the productivity of the process, and is easy to disassemble, thereby improving recyclability.

In addition, since the motor 1 uses ferrite magnets as the magnets 23, the cost of the magnets is lower than that of rare earth magnets, making it possible to significantly reduce costs compared to conventional motors using neodymium magnets. In addition, since it does not contain rare earth substances, the environmental load is small, and it is possible to realize products that meet the European LCA regulations and the concept of SDGs, and that it is less susceptible to market fluctuations. Furthermore, since the ferrite magnet has a high electrical resistance, the eddy current loss is small, and the heat generation of the magnet itself is small, so the change in the amount of magnetic flux with temperature is relatively small. In addition, since the ferrite magnet has a higher Curie point than the neodymium magnet, irreversible demagnetization of the magnet is less likely to occur in a high-temperature atmosphere. In other words, the motor 1 draws out performance equivalent to that of a neodymium magnet motor while taking advantage of ferrite magnets that have been used for a long time. It becomes possible to

It goes without saying that the present invention is not limited to the embodiments described above, and that various modifications can be made without departing from the scope of the present invention.
For example, in the motor 1, the magnet 23 is formed by three pieces of magnets (two first magnets 23a and one second magnet 23b). It is also possible to use magnets. In this way, by using a magnet integrally molded in a U-shape, it is possible to reduce the manufacturing cost and assembly cost of the magnet. Further, in the above-described embodiment, the magnet 23 has a U shape, but it may be formed in a U shape or a trapezoid shape without a base.

The present invention is applicable not only to motors for electric power steering devices, but also to oil pumps, electric brake systems, hybrid vehicles, electric vehicles, and the like. In addition, the motor of the present invention is applicable not only to automobiles, but also to other electric machines and devices such as household appliances and industrial machines.

1 Brushless Motor 2 Stator 3 Rotor 4 Motor Case 5 Stator Core 6 Teeth 7 Stator Coil 7a End 8 Busbar Unit 9 Bracket 10 Slot 11 Insulator 12 Power Supply Terminal 13 Rotor Shafts 14a, 14b Bearing 15 Rotor Core 16 Resolver 17 Resolver Rotor 18 Resolver Stator 19 resolver bracket 20 mounting screw 21 shaft hole 22 magnet mounting hole (magnet housing portion)
22a First magnet mounting hole (first magnet housing portion)
22b Second magnet mounting hole (second magnet housing)
23 magnet 23a first magnet (first magnet section)
23b second magnet (second magnet section)
24 Bridge portion 25 Gap portion 26 Slope portion 27 End surface 28 Magnetic pole 31 First magnet inner surface 32 Second magnet inner surface O Center of rotor

Claims (5)

a stator and a rotor disposed radially inward of the stator;
The rotor is a motor comprising a rotor core fixed to a rotating shaft and a magnet mounted in a magnet accommodating portion formed in the rotor core,
The magnet housing portion includes a first magnet housing portion formed radially and extending in a radial direction, and a second magnet housing portion disposed radially inside the first magnet housing portion and extending in a circumferential direction. the first magnet housing portion communicates with the second magnet housing portion on the center side of the rotor, and the second magnet housing portion communicates with the first magnet housing portion at both ends in the circumferential direction;
The magnet is formed of a ferrite magnet, and includes a first magnet portion in the first magnet housing portion and a second magnet portion in the second magnet housing portion, and the second magnet portion is the first magnet. are arranged radially inward of the
The motor of the rotor, wherein one magnetic pole is formed by two of the first magnet portions and a second magnet portion radially inside the first magnet portions. 2. The motor of claim 1, wherein
The magnetic poles are closed by two first magnet portions and one second magnet portion without gaps in three directions, ie, the circumferential direction and the radial direction inner side. 2. A motor according to claim 1, wherein a surface of a magnet portion surrounding said magnetic pole is formed to have the same polarity. 3. The motor according to claim 1 or 2,
The first magnet portion and the second magnet portion are formed of separate magnets,
The motor according to claim 1, wherein the second magnet portion is arranged in close contact with the first magnet portion so as to cover the entire radially inner end surface of the first magnet portion. 3. The motor according to claim 1 or 2,
The motor, wherein the first magnet part and the second magnet part are formed of an integrated magnet. In the motor according to any one of claims 1 to 4,
The motor, wherein the first magnet portion and the second magnet portion are formed by mounting pre-magnetized magnets in the magnet accommodating portion.

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