KR20150044537A - Motor - Google Patents

Abstract

The present invention relates to a motor. According to an embodiment of the present invention, provided are effects of improving the efficiency of the motor by reducing demagnetization phenomenon, prolonging the lifespan of the motor, and simplifying a manufacturing process. The motor according to the present invention comprises: a stator; a rotor core; and a plurality of magnetic members.

Description

Motor {Motor}

More particularly, the present invention relates to a motor, and more particularly, to a motor in which a magnet member composed of two permanent magnets having different properties is coupled to a rotor core to prevent or reduce irreversible potato phenomenon, To a motor in which the manufacturing process is simplified.

1 is a cross-sectional view showing a conventional motor.

1, a conventional motor 100 includes a stator 120 having a circular yoke portion 120a and a tooth 120b around which a coil (not shown) is wound. And a plurality of permanent magnets 150 are arranged and fixed in the circumferential direction on the outer circumferential surface of the rotor core 130 so that the rotor core 130 is rotatable in the hollow.

A plurality of teeth 120b protrude from the stator 120 at equal intervals along the inner circumferential surface of the circular ring-shaped yoke portion 120a. A coil (not shown) is wound around the teeth 120b to rotate the motor 100 (Not shown).

The rotor core 130 is formed by stacking a plurality of silicon steel plates, and a shaft hole 130a through which the shaft 140 is fixed is formed at the center of the shaft hole 130. The groove 130b is recessed in the circumferential direction of the outer circumferential surface The permanent magnet 150 is press-fitted.

When the coil 100 is powered, a magnetic flux is generated in a direction perpendicular to the rotor core 130, and the motor 100 rotates. Particularly, the motor shown in FIG. 1 is a SPM (Surface Permanent Magnet) The permanent magnets 150 are attached to the outer circumferential surface of the rotor core 130.

On the other hand, a motor provided with a permanent magnet necessarily carries a large cogging torque, restricting smooth rotation due to the cogging torque, causing vibration, speed fluctuation, and vibration noise. Therefore, need. The cogging torque is a pulsation torque generated by the tendency of the permanent magnet 150, the rotor core 130, and the motor 100 to maintain the reluctance in the direction of minimum. Here, cogging refers to a case where the rotor core 130 is rotated smoothly without being smoothly rotated when the rotor core 130 is rotated at 1 to 4 rpm, and the cogging torque refers to a difference between the largest and smallest variation in torque. In order to reduce the cogging torque, there is a method of changing the shape of the stator or the permanent magnet. In order to reduce the cogging torque and the back electromotive force harmonic component of the motor 100, the thickness of both ends of the permanent magnet 150 is made thin .

On the other hand, periodic waveforms can be analyzed with several sinusoidal waves having different frequencies. Among them, the lowest frequency is the fundamental wave and the other frequency is higher than the fundamental frequency. Even when a back electromotive force is generated, there is a problem that harmonics are generated in the same manner. To prevent this, both ends of the permanent magnet 150 are formed thin.

However, since the conventional motor 100 according to the related art has a complicated manufacturing process because the permanent magnet 150 is inserted into the groove of the rotor core 130 by press-fitting, the thickness of both ends of the permanent magnet 150 is thin The demagnetization resistance of the permanent magnet 150 is greatly reduced, and there is a problem that a partially irreversible potato phenomenon occurs. Particularly, in the case of a motor used in an electric power assisted steering apparatus driven at a high temperature, the magnetic flux density of the bending point of the magnet is remarkably lower than the room temperature, so that potato phenomenon is likely to occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the background described above, and it is an object of the present invention to provide a magnet member having two or more permanent magnets having different properties, And a motor in which the manufacturing process is simplified by being slidably coupled.

The objects of the present invention are not limited thereto, and other objects not mentioned may be clearly understood by those skilled in the art from the following description.

According to an embodiment of the present invention, there is provided a stator comprising: a stator having a tooth whose inner surface is wound with a coil; A rotor core provided on an inner side of the stator and integrally formed on an outer circumferential surface thereof and having a plurality of protruding engaging portions formed at equal intervals in a circumferential direction; And a first permanent magnet which is coupled between a pair of adjacent projecting engaging portions of the outer circumferential surface of the rotor core and a second permanent magnet which is coupled to both sides of the first permanent magnet but is supported by the projecting engaging portion and has a coercive force larger than that of the first permanent magnet And a plurality of magnet members including two permanent magnets.

According to an embodiment of the present invention, a magnet member formed by coupling a second permanent magnet having a large coercive force to a first permanent magnet is coupled to the rotor core, thereby reducing a partial irreversible potato phenomenon that may occur in a conventional motor .

Further, since the magnet member is slidably coupled to the protruding engaging portion formed integrally with the rotor core, the manufacturing process is simplified.

1 is a cross-sectional view of a motor according to the prior art;
2 is a sectional view of a motor according to an embodiment of the present invention;
3 is a sectional view of a motor according to another embodiment of the present invention;
4 is a cross-sectional view of a motor according to another embodiment of the present invention;
5 is a perspective view showing the motor of Fig. 2;
Fig. 6 is an exploded perspective view showing the motor of Fig. 2;

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings.

In describing the components of the present invention, the terms first, second, A, B, (a), (b), and the like can be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

Hereinafter, a case where the motor according to an embodiment of the present invention is a SPM (Surface Permenant Magnet) type motor will be described as an example.

2 is a cross-sectional view illustrating a motor according to an embodiment of the present invention. 3 is a cross-sectional view showing a motor according to another embodiment of the present invention. 4 is a cross-sectional view illustrating a motor according to another embodiment of the present invention. Fig. 5 is a perspective view showing the motor of Fig. 2; Fig. 6 is an exploded perspective view showing the motor of Fig. 2;

As shown in these figures, the motor 200 according to an embodiment of the present invention includes: a stator 210 having a tooth 212b on which an inductor (not shown) is wound; A rotor core 221 provided on the inner side of the stator 210 and integrally formed on the outer circumferential surface thereof and having a plurality of protruding engaging portions 226 formed at regular intervals in the circumferential direction; A first permanent magnet 222a coupled between a pair of adjacent protruding engaging portions 226 of the outer circumferential surface of the rotor core 221 and a second permanent magnet 222b coupled to both sides of the first permanent magnet 222a, And a plurality of magnet members 222 supported by the first permanent magnets 222a and including a second permanent magnet 222b having a larger coercive force than the first permanent magnets 222a.

The stator 210 has a structure in which a plurality of teeth 212b protrude at equal intervals along the inner circumferential surface of a circular ring-shaped yoke portion 212a and is inserted and fixed in a housing (not shown) of the motor 200 And the coil 212 is wound around the teeth 212b.

When a power is applied to the motor 200, a current flows through a coil (not shown) wound around the teeth 212b to generate a magnetic field (moving magnetic field) inside the stator 210. The magnetic field is applied to the first permanent magnets 222a And the second permanent magnets 222b to generate a magnetic force in a circumferential direction so that the rotor core 221 rotates. On the other hand, the rotor core 221 is made by stacking a plurality of silicon steel plates or by compressing a soft magnetic powder.

A hollow shaft hole 229 through which the shaft 230 passes is formed in the inside of the rotor core 221 and a plurality of protruding engagements 227 are formed on the outer circumferential surface of the rotor core 221 radially outwardly of the rotor core 221. A portion 226 is formed. An example of the structure of the projecting engagement portion 226 will be described in more detail. The projecting engagement portion 226 includes an insertion portion 227 protruding radially outwardly from the outer circumferential surface of the rotor core 221; And a fixing portion 228 extending from the upper end of the insertion portion 227 to both sides in the circumferential direction. Here, the inserting portion 227 supports the side surface of the second permanent magnet 222b, and the fixing portion 228 supports the upper end of the second permanent magnet so as to support the first permanent magnet 222a and the second permanent magnet 222b 222b of the magnet member. The material of the protrusion coupling portion 226 may be the same as that of the rotor core 221, or may be made of metal or synthetic resin which is nonconductive.

The magnet member 222 includes a first permanent magnet 222a and a second permanent magnet 222b. The first permanent magnet 222a is disposed between a pair of adjacent protruding engaging portions of the outer circumferential surface of the rotor core 221 Lt; / RTI > On the other hand, both side surfaces of the first permanent magnet 222a are attached to the second permanent magnet 222b.

The magnet member 222 can be slidably engaged with the protruding engaging portion 226 so that the magnet member 222 is slidably engaged with the protruding engaging portion 226 so that the permanent magnet 150 Is press-fitted into the groove of the rotor core 130, thereby complicating the manufacturing process.

The radius of curvature of the outer side surface 223a of the first permanent magnet 222a is smaller than the radius of curvature of the inner side surface 223b while the radius of curvature gradually decreases toward both sides where the second permanent magnet 222b is coupled at the center . This is a structure for reducing the cogging torque which is inevitably generated in the motor 200. [

The cogging torque is a pulsation torque generated by the tendency of the first permanent magnet 222a, the second permanent magnet 222b, the rotor core 221, and the motor 200 to maintain the reluctance in the direction of minimum. Here, cogging means that when the rotor core 221 of the motor 200 rotates at 1 to 4 rpm, the rotor rotates non-uniformly without being smoothly rotated. The cogging torque is the difference between the largest and smallest variation in torque It says. According to an embodiment of the present invention, the curvature radius of the outer surface 223a of the first permanent magnet 222a is formed to be smaller than the curvature radius of the inner surface 223b, thereby reducing the cogging torque .

Further, since the radius of curvature of the outer surface 223a of the first permanent magnet 222a is formed to be smaller than the radius of curvature of the inner surface 223b, the back electromotive force harmonic component is also reduced. When an electromotive force is generated, counter-electromotive force is generated due to the inverse effect thereof, and a harmonic component is generated, which causes a problem of lowering the efficiency of the motor. However, the efficiency reduction is slowed due to the difference in radius of curvature.

The second permanent magnet 222b has one side attached to the first permanent magnet 222a and the other side supported on the insertion portion 227 of the protruding engagement portion 226. [ The radius of curvature of the outer surface 225a of the second permanent magnet 222b is smaller than the radius of curvature of the inner surface 225b but is connected to the protruding engagement portion 226 from the portion coupled with the first permanent magnet 222a And gradually decreases in the direction of the arrow. This is to match the structure with the first permanent magnet 222a and to reduce the cogging torque and the back electromotive force harmonic component.

Meanwhile, the second permanent magnets 222b may be formed of a material having a higher coercive force than the first permanent magnets 222a. Here, the coercive force refers to the intensity of a magnetic field which makes the residual magnetization zero when the magnetic field is increased in the opposite direction to the residual magnetization remaining when the magnetic field is zero in the magnetic saturation state of the ferromagnetic body. The order of magnitude of coercivity is in order of neodymium (Nd) magnets, samarium, cobalt, ferrite, and AlNiCo magnets. Therefore, it is most advantageous to use a neodymium magnet as the second permanent magnet 222b.

Neodymium magnets are made from NdFeB alloys of a certain composition into powders through a specific process, then mixed with a binder such as epoxy, compressed or molded into a certain shape using a method such as injection molding. It is necessary to add a binder which is nonmagnetic and thus magnetic properties are reduced by the proportion of the binder. However, it is easy to manufacture a permanent magnet having a complicated shape, less eddy current loss, and can be mass produced.

If the thickness of the permanent magnet is reduced, the potato resistance of the magnet is greatly decreased, so that a partially irreversible potato phenomenon may occur. The potato size is determined by the magnitude of the coercive force and the magnitude of the anti-magnetic field at the use temperature of the permanent magnet. The smaller the coercive force of the permanent magnet and the larger the magnitude of the semi-magnetic field, the thinner the permanent magnet is. An irreversible potato phenomenon may also occur. The antiferromagnetic field is the sum of the magnetic antiferromagnetic field generated by the magnetization of the permanent magnet and the field antiferromagnetic field generated from the outside, and the magnetic antiferromagnetic field increases as the thickness of the permanent magnet in the magnetization direction becomes thinner. Therefore, if the second permanent magnet 222b is formed of a material having a large coercive force, demagnetization phenomenon is reduced.

Permanent magnets are sensitive to temperature. Especially for ferrite magnets, when the temperature rises by 1 ℃, the magnetic flux density decreases by 0.18% and the coercive force increases by 0.35 ~ 0.55%. Conversely, as the temperature decreases, the magnetic flux density increases and the coercive force decreases. Potato phenomenon occurs mainly when the temperature goes down and comes back. When the Curie temperature is exceeded, a demagnetization phenomenon occurs in which the magnetic flux density inside the magnet becomes zero. Another example of potato phenomenon is an external magnetic field. When a current flows through a coil wound around the tooth 212b, a magnetic force line comes out from the coil. When the magnetic flux line is opposite to the magnetic force line of the permanent magnet, .

If a potato phenomenon occurs, the temperature of the motor may be increased, or the battery may be consumed in the case of an automobile, and a side effect may be caused to lower the rotational force.

Therefore, if permanent magnets having a large coercive force are used, the potato phenomenon due to temperature and external magnetic field is reduced, and consequently, the efficiency of the motor 200 is increased and the service life is prolonged. As the permanent magnet having a large coercive force according to the hysteresis loop, the residual magnetic flux density in the permanent magnet becomes larger, and if the residual magnetic flux density is large, the potato phenomenon can be reduced.

On the other hand, the maximum residual magnetic flux density of the first permanent magnet 222a may be larger than the maximum residual magnetic flux density of the second permanent magnet 222b. The maximum residual magnetic flux density means the maximum magnetic flux density remaining in the magnetic body when the magnetic field is reduced by decreasing the magnetization in the magnetic saturation state. The higher the magnetic flux density, the better the performance of the motor. According to the magnetic hysteresis curve, the greater the maximum residual magnetic flux density, the greater the possibility that the potato phenomenon is reduced. The ferrite magnets are not suitable for the first permanent magnet 222a because the ferrite magnets have a low magnetic flux density and a high coercive force, while the ferrite magnets have characteristics of low coercive force while obtaining high magnetic flux density. On the other hand, the samarium-cobalt magnet and the neodymium magnet are both suitable as the first permanent magnet 222a because of high magnetic flux density and coercive force.

The structure and effects of the motor 200 according to the above embodiment have been described. 3 and 4, motors 300 and 400 according to another embodiment and another embodiment will be described.

3, the first permanent magnet 322a of the motor 300 according to another embodiment of the present invention includes a rotor core 321 and a rotor core 321. The rotor core 321 includes a rotor core 321, (Not shown). The second permanent magnet 322b may be slidably coupled between the first permanent magnet 322a and the protruding engagement portion 336. [ However, the coupling method of the second permanent magnet 322b is not limited to the sliding coupling.

4, the motor 400 according to another embodiment does not include the protruding engaging portion 226, unlike the motor 200 according to the embodiment, The permanent magnets 422a and the second permanent magnets 422b may include the same number of magnet members 422. [

The radius of curvature of the outer surface 425a of the second permanent magnet 422b is formed to be larger than the radius of curvature of the inner surface 425b.

Since the second permanent magnets 422b are integrally formed between the first permanent magnets 422a unlike the first embodiment, the shape of the outer surface 425a is the same as that of the second permanent magnets 422b Of the first permanent magnets 422a. However, the shape of the second permanent magnet 422b is not limited to the shape shown in Fig. 4, and may have various shapes.

On the other hand, since the coercive force of the second permanent magnets 422b is set to be larger than the coercive force of the first permanent magnets 422a, the potato phenomenon is reduced and the efficiency of the motor 400 is increased .

5 and 6 illustrate a rotor 220 of the motor 200 according to the embodiment shown in FIG. 2 except for the stator 210. The rotor 220 has a first permanent magnet 222a and a second permanent magnet 222b. And the second permanent magnets 222b are coupled to each other. The magnet member 222 with the first permanent magnet 222a and the second permanent magnet 222b attached thereto can be slidably engaged with the protruding engagement portion 226 of the rotor core 221. [

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

210: stator 212a: yoke
212b: tooth 220: rotor
221: rotor core 222: magnet member
222a: first permanent magnet 222b: second permanent magnet
226: projecting engaging portion 227:
228: fixing part 229: shaft hole
334: groove

Claims (6)

A stator having teeth on which a coil is wound on an inner side;
A rotor core provided on the inner side of the stator and integrally formed on the outer circumferential surface thereof, the rotor core having a plurality of protruding engaging portions formed at regular intervals in the circumferential direction; And
A first permanent magnet coupled between a pair of adjacent protruding engaging portions of the outer circumferential surface of the rotor core; and a second permanent magnet coupled to both sides of the first permanent magnet, the first permanent magnet being supported by the protruding engaging portion, A plurality of magnet members including a second permanent magnet having a coercive force;
≪ / RTI > The method according to claim 1,
The projection-
An insertion portion protruding radially outwardly from an outer circumferential surface of the rotor core; And
A fixing unit extending from both ends of the insertion unit in the circumferential direction;
≪ / RTI > The method according to claim 1,
Wherein a groove recessed radially inward is formed on an outer circumferential surface of the rotor core so that a lower end of the first permanent magnet is inserted and fixed. The method according to claim 1,
Wherein the maximum residual magnetic flux density of the first permanent magnets is greater than the maximum residual magnetic flux density of the second permanent magnets. The method according to claim 1,
Wherein the radius of curvature of the outer surface of the first permanent magnet is smaller than the radius of curvature of the inner surface, and the radius of curvature gradually decreases from the center toward both sides of the second permanent magnet to which the second permanent magnet is coupled. The method according to claim 1,
Wherein a radius of curvature of an outer surface of the second permanent magnet is smaller than a radius of curvature of an inner surface but gradually decreases from a portion coupled with the first permanent magnet to a direction coupled with the projecting engagement portion.

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