KR102566475B1 - Motor - Google Patents

Abstract

The present invention is a shaft; A rotor including a hole in which the shaft is disposed; and a stator disposed outside the rotor, wherein the number of poles of the rotor and the number of slots of the stator are determined so that two counter electromotive force signals having a first phase difference are generated. To provide a motor including a first coil and a second coil wound around a stator, respectively supplied with separate currents, and a control unit supplying currents having different phase differences to the first coil and the second coil, respectively. can

Description

motor {Motor}

The embodiment relates to a motor.

An electric power steering system (EPS) is a device that enables a driver to drive safely by ensuring turning stability of a vehicle and providing a quick restoring force. Such an electric steering device controls driving of a steering shaft of a vehicle by driving a motor through an electronic control unit (ECU) according to driving conditions detected by a vehicle speed sensor, a torque angle sensor, and a torque sensor.

A motor includes a stator and a rotor. The stator may include teeth forming a plurality of slots, and the rotor may include a plurality of magnets facing the teeth. Adjacent teeth are spaced apart from each other to form a slot open. At this time, cogging torque may occur due to a difference in air permeability between the metal stator and the slot open, which is an empty space, during the rotation of the rotor. Since this cogging torque causes noise and vibration, reducing the cogging torque is of paramount importance in improving the quality of the motor. In particular, torque ripple may occur in a high-speed condition, and this torque ripple causes a vibration problem of the steering device.

Accordingly, embodiments are intended to solve the above problems, and an object thereof is to provide a motor capable of reducing cogging torque and torque ripple while securing torque. The problem to be solved by the present invention is not limited to the above-mentioned problems, and other problems not mentioned herein will be clearly understood by those skilled in the art from the following description.

The embodiment includes a shaft, a rotor including a hole in which the shaft is disposed, and a stator disposed outside the rotor, and the number of poles of the rotor and the stator so that two counter electromotive force signals having a first phase difference are generated. The number of slots is determined, the stator includes a first coil and a second coil separated by circuit, and a motor including a controller supplying currents having different phase differences to the first coil and the second coil, respectively. can

Preferably, the rotor includes a rotor core and a plurality of magnets disposed on an outer circumferential surface of the rotor core, and the plurality of magnets may have only one of an N pole and an S pole.

Preferably, the rotor core may include a concave-convex portion disposed between the magnets and protruding in a radial direction with respect to the center of the rotor core.

Preferably, the thickness of the concave-convex portion in a radial direction with respect to the center of the rotor core is equal to or smaller than the thickness of the magnet, and the thickness of the concave-convex portion in a circumferential direction with respect to the center of the rotor core is equal to a width of the magnet. or can be small.

Preferably, the number of the plurality of magnets is 7, the number of concave-convex portions is 7, the number of slots of the stator is 12 slots, the concave-convex portion is the S pole of the magnet when the pole of the magnet is the N pole, and the When the pole of is the S pole, the uneven portion may be the N pole of the magnet.

Preferably, the number of the plurality of magnets is 5, the number of concave-convex portions is 5, the number of slots of the stator is 12 slots, the concave-convex portion is the S pole of the magnet when the pole of the magnet is N pole, and the When the pole of is the S pole, the uneven portion may be the N pole of the magnet.

Preferably, the controller may supply current having the same phase difference as the first phase difference to the first coil and the second coil, respectively.

Preferably, the first phase difference may be 20° to 40°.

Preferably, the stator may include a plurality of teeth on which the first coil and the second coil are wound, and a plurality of grooves may be disposed on an end surface of a shoe disposed on the teeth.

Preferably, the plurality of grooves may be arranged symmetrically with respect to a reference line passing through the center of the width of the tooth and the center of the stator.

Preferably, the plurality of grooves may be formed extending from an upper end to a lower end of the stator.

According to the embodiment, an advantageous effect of reducing cogging torque and torque ripple while securing maximum torque is provided.

1 is a view showing a motor according to an embodiment;
2 is a view showing a stator and a rotor;
3 is a view showing the size of the magnet and the uneven portion of the rotor;
4 is a view showing the grooves of the teeth of the stator;
5 is a graph showing back EMF signals having different phase differences;
6 is a view showing a stator in which a first coil and a second coil are wound;
7 is a graph comparing the torque of the comparative example and the torque of the embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments taken in conjunction with the accompanying drawings. And, in describing the present invention, detailed descriptions of related known technologies that may unnecessarily obscure the subject matter of the present invention will be omitted.

Terms including ordinal numbers such as second and first may be used to describe various components, but the components are not limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a second element may be termed a first element, and similarly, a first element may be termed a second element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

1 is a view showing a motor according to an embodiment.

Referring to FIG. 1 , a motor according to an embodiment may include a shaft 100, a rotor 200, and a stator 300.

Shaft 100 may be coupled to rotor 200 . When electromagnetic interaction occurs between the rotor 200 and the stator 300 through the supply of current, the rotor 200 rotates and the shaft 100 rotates in conjunction therewith. The shaft 100 may be connected to a steering shaft of a vehicle to transmit power to the steering shaft. Shaft 100 may be supported by bearings.

The rotor 200 rotates through electrical interaction with the stator 300. The rotor 200 is disposed inside the stator 300. The rotor 200 may include a rotor core and a magnet coupled to the rotor core. The rotor 200 may be classified into the following types according to the coupling method between the rotor core and the magnet.

The rotor 200 may be implemented in a type in which a magnet is coupled to an outer circumferential surface of a rotor core. In this type of rotor, a separate can member may be coupled to the rotor core in order to prevent separation of the magnet and increase coupling force. Alternatively, the magnet and the rotor core may be integrally formed by double injection.

Meanwhile, the rotor core may be formed by mutually stacking a plurality of plates in the form of thin steel plates. Alternatively, the rotor core may be implemented in a tubular shape so as not to form a skew angle, and the magnet may also be attached to the rotor core so as not to form a skew angle. Meanwhile, the rotor core may also be formed in a form in which a plurality of pucks (unit cores) forming a skew angle are stacked.

The stator 300 may be disposed outside the rotor 200 . The stator 300 causes an electrical interaction with the rotor 200 to induce rotation of the rotor 200 .

The bus bar 400 may be disposed above the stator 300 . The bus bar 400 may include a terminal inside the bus bar body. Also, the terminals of the bus bar 400 may include phase terminals connected to power sources of phases U, V, and W, and neutral terminals electrically connecting the phase terminals. Terminals of the bus bar 400 are connected to coils wound around the stator 300 .

The housing 500 may accommodate the rotor 200 and the stator 300 therein.

The rotor position detection device 600 is a device for detecting the position of the rotor 200 by being coupled to the shaft 100 to interlock with the rotor 200 . The rotor position sensing device 600 may include a sensing magnet and a sensing plate. The sensing magnet and the sensing plate may be coaxially coupled. The sensing magnet may include a main magnet disposed in a circumferential direction adjacent to a hole forming an inner circumferential surface and a sub magnet formed at an edge. The main magnets may be equally arranged in the circumferential direction so as to correspond in the rotation axis direction to the poles of the magnets inserted into the rotor of the motor. The sub-magnet is more subdivided than the main magnet and consists of many poles. Accordingly, it is possible to divide and measure the rotation angle more minutely, and the driving of the motor can be smoother. The sensing plate may be formed of a disc-shaped metal material. A sensing magnet may be coupled to an upper surface of the sensing plate. Also, the sensing plate may be coupled to the shaft 100 . A hole through which the shaft 100 passes is formed in the sensing plate.

A sensor for sensing the magnetic force of the sensing magnet may be disposed on the printed circuit board 700 . In this case, the sensor may be a Hall IC. The sensor generates a sensing signal by detecting a change in the N pole and S pole of the main magnet or sub magnet. The printed circuit board 700 may be coupled to the lower surface of the cover of the housing 500 and installed on the sensing magnet so that the sensor faces the sensing magnet.

2 is a view showing a stator and a rotor of 14 poles and 12 slots as a motor according to the first embodiment, and FIG. 3 is a view showing a stator and a rotor of 10 poles and 12 slots as a motor according to the second embodiment. am.

Referring to FIGS. 2 and 3 , the rotor 200 may include a rotor core 210 and a plurality of magnets 220 attached to the outer circumferential surface of the rotor core 210 . The plurality of magnets 220 may be spaced apart from each other at regular intervals in the circumferential direction based on the center C of the rotor core 210 . At this time, the plurality of magnets 220 may have one polarity of the N pole and the S pole. For example, all of the plurality of magnets 220 may have N-pole magnetism.

An uneven portion 211 may be disposed on an outer circumferential surface of the rotor core 210 . The uneven portion 211 is disposed between the magnets 220 and serves as an S pole. The uneven portion 211 may protrude from the outer circumferential surface of the rotor core 210 in a radial direction with respect to the center C of the rotor core 210 .

As the motor according to the first embodiment, a total of 7 magnets 220 may be disposed. Correspondingly, seven uneven portions 211 may also be disposed. Thus, the motor according to the embodiment may be a motor having 14 poles. Also, 12 slots may be provided between the teeth 320 and the teeth 320 .

As a motor according to the second embodiment, a total of five magnets 220 may be disposed. Correspondingly, five uneven portions 211 may also be disposed. Thus, the motor according to the embodiment may be a motor having 10 poles. Also, 12 slots may be provided between the teeth 320 and the teeth 320 .

3 is a view showing the size of the magnet and the uneven portion of the rotor.

Referring to FIG. 3 , the uneven portion 211 may correspond to or be smaller than the size of the magnet 220 .

For example, the width W1 of the uneven portion 211 may be equal to or smaller than the width W2 of the magnet 220 . The width W1 of the concave-convex portion 211 corresponds to the shortest straight line distance or arc length between both inner ends P1 and P2 of the concave-convex portion 211 in the circumferential direction from the center C of the rotor core 210. can do. In addition, the width W2 of the magnet 220 corresponds to the shortest straight line distance or arc length between both inner ends P3 and P4 of the magnet 220 in the circumferential direction from the center C of the rotor core 210. can

Also, the thickness t1 of the uneven portion 211 may be equal to or smaller than the thickness t2 of the magnet 220 . The thickness t1 of the concave-convex portion 211 refers to the width from the center C1 of the concave-convex portion 211 in the radial direction from the center C of the rotor core 210 to the inner side of the concave-convex portion 211 to the outer side. It may correspond to a straight line distance. The thickness (t2) of the magnet 220 is the straight line distance from the center (C) of the rotor core 210 to the center (C2) of the width of the magnet 220 in the radial direction from the inside to the outside of the magnet 220. may apply.

The size of the concave-convex portion 211 is based on a space between the magnets 220 and a distance between the outside of the concave-convex portion 211 and the stator.

When the unipolar magnet 220 is applied in this way, there is an advantage in greatly reducing the manufacturing cost of the motor. However, since the characteristics of the cogging torque and the characteristics of the torque ripple may be deteriorated due to the energy difference between the polarities, it is necessary to supplement them.

4 is a view showing the grooves of the teeth of the stator.

In order to complement the characteristics of cogging torque and torque ripple, it is intended to form a groove 322 in the stator 300 .

The stator 300 may be provided with an annular yoke 310 and a tooth 320 protruding from the yoke toward the center. A coil is wound around the teeth 320 . A plurality of teeth 320 may be disposed at regular intervals along the inner circumferential surface of the annular yoke. The number of teeth 320 corresponds to the number of slots of the motor. For example, as shown in the drawing, when the number of teeth 320 is 12, the number of slots is 12. A shoe 321 is disposed at an end of the tooth 320 . The shoe 321 is disposed so that its end face faces the magnet 220 .

Between adjacent teeth 320 and teeth 320 is formed as a winding space (P) of the coil. The shoes 321 of adjacent teeth 320 and the shoes 321 are spaced apart from each other to form a slot open (S). Slot open (S) is the entrance of the winding space (P), where the nozzle winding the coil is inserted.

An inner circumferential surface of the shoe 321 may include a groove 322 . The groove 322 may be concavely formed on the inner circumferential surface of the shoe 321 . Although the shape of the groove 322 is shown as an angular shape, the present invention is not limited thereto. Also, the groove 322 may be disposed along the axial direction of the stator 300 . In other words, the groove 322 may be disposed along the height direction of the stator 300 from the upper end to the lower end of the stator 300 . Two grooves 322 may be disposed. Based on the reference line L passing through the center of the width of the body 321 of the tooth 320 and the center of the stator 300, the two grooves 322 may be symmetrically disposed. The groove 322 serves to greatly reduce the cogging torque by increasing the frequency of the cogging torque waveform per unit period by playing a role corresponding to the slot opening S that causes a change in magnetic flux density.

5 is a graph showing back EMF signals having different phase differences.

Referring to FIG. 5 , in the motor according to the embodiment, the number of poles of the rotor 200 and the number of slots of the stator 300 may be determined so that two back EMF signals A and B having a first phase difference are output. For example, the motor according to the embodiment may be 14 poles and 12 slots. In the case of a 14-pole 12-slot motor, as shown in FIG. 5 , two back EMF signals having a phase difference of 30° are generated. The torque value of the motor is the value obtained by multiplying the back EMF by the current. Therefore, in order to obtain the maximum torque value, the current must be supplied so that the phase of the counter electromotive force and the phase of the current are the same. However, as shown in E of FIG. 5 , when currents of the same phase are supplied to two back EMF signals, torque is lost.

In this way, in a motor generating counter electromotive force having a phase difference, two coils through which separate current flows are wound around the stator 300 in order to reduce cogging torque and torque ripple while maximizing torque.

6 is a view showing a stator in which a first coil and a second coil are wound.

Referring to FIG. 6 , a first coil 330 and a second coil 340 separated by circuit may be wound around the teeth 320 of the stator 300 . The controller 800 may supply currents having different phase differences to the first coil 330 and the second coil 340 . The controller 800 may be an electronic device mounted on the printed circuit board 700 .

Based on the circumferential direction of the stator 300, the first coil 330 and the second coil 340 may be alternately disposed. Specifically, the first coil 330 may be wound around any one tooth 320 of the plurality of teeth 320, and the second coil 340 may be wound around the tooth 320 adjacent to the corresponding tooth 320.

If the first phase difference between the two back EMF signals is 30°, the controller 800 can secure the maximum torque by supplying current having a phase difference of 30° to the first coil 330 and the second coil 340. .

7 is a graph comparing the torque of Comparative Example 1 and the torque of the first embodiment, and FIG. 2 is a graph comparing the torque of Comparative Example 2 and the torque of the second embodiment.

Comparative Example 1 is a 14-pole, 12-slot motor in which a single coil is wound circuitwise. Comparative Example 2 is a 10-pole, 12-slot motor in which a single coil is wound circuitwise.

Referring to FIGS. 7 and 8 , in Comparative Example 1 and Comparative Example 2, two counter electromotive force signals having different phases in two coils having different electrical angles in the same phase (U phase, V phase, W phase) occurs, but since the current of the same phase is supplied to the corresponding coil, a loss occurs in torque. As a result, Comparative Example 1 and Comparative Example 2 show a relatively lower torque than Example. On the other hand, in the case of the first and second embodiments, it is possible to secure maximum torque without loss of torque by supplying current having a phase difference equal to the phase difference between the two back EMF signals to two coils separated circuitically. there is. As a result, the first and second embodiments exhibit higher torque than Comparative Examples 1 and 1 and Comparative Example 2, respectively.

In addition, the torque ripple M1 of the first embodiment and the torque ripple M3 of the second embodiment appear lower than the torque ripple M2 of Comparative Example 1 and the torque ripple M4 of Comparative Example 2. This is because the torque ripple is canceled when two torques having different phase differences are synthesized. As a result, it is possible to secure an effect of reducing torque ripple while securing maximum torque.

As we have seen before, if a unipolar magnet is applied to the motor, the manufacturing cost can be greatly reduced. There were problems of power drop, cogging torque and torque ripple increase. In the case of the motor according to the embodiment, the maximum torque is secured by reducing the cogging torque through the groove 322 disposed on the shoe 321 and supplying current having a phase difference equal to the phase difference of the counter electromotive force signal to the two coils. At the same time, it has the advantage of reducing torque ripple.

In the above, the motor according to one preferred embodiment of the present invention has been examined in detail with reference to the accompanying drawings.

One embodiment of the present invention described above should be understood as illustrative in all respects and not limiting, and the scope of the present invention will be indicated by the claims to be described later rather than the detailed description above. And it should be construed that all changes or transformable forms derived from the meaning and scope of the claims as well as their equivalent concepts are included in the scope of the present invention.

100: shaft
200: rotor
210: rotor core
211: uneven portion
220: magnet
300: stator
310: yoke
320: teeth
321: shoe
322 Home
400: bus bar
500: housing
600: Rotor position detection device
700: printed circuit board
800: control unit

Claims (11)

shaft;
A rotor including a hole in which the shaft is disposed; And
Including a stator disposed outside the rotor,
The number of poles of the rotor and the number of slots of the stator are determined so that two back EMF signals having a first phase difference are generated;
The stator includes a first coil and a second coil that are circuitically separated,
A controller supplying currents having different phase differences to the first coil and the second coil,
The rotor includes a rotor core and a plurality of magnets disposed on an outer circumferential surface of the rotor core, the plurality of magnets have only one of an N pole and an S pole, and the rotor core is disposed between the magnets and the magnets. and a concave-convex portion protruding in a radial direction with respect to the center of the rotor core, wherein a thickness of the concave-convex portion in a radial direction with respect to the center of the rotor core is equal to or smaller than a thickness of the magnet, and the rotor core The width of the uneven portion in the circumferential direction based on the center of is equal to or smaller than the width of the magnet, includes a groove formed concavely on the inner circumferential surface of the shoe of the stator, and generates a current to have the same phase difference as the first phase difference. A motor that supplies each of the first coil and the second coil. delete delete delete According to claim 1,
The number of the plurality of magnets is 7, the number of the concave-convex parts is 7,
The number of slots of the stator is 12 slots,
When the pole of the magnet is the N pole, the uneven portion is the S pole of the magnet,
When the pole of the magnet is the S pole, the uneven portion is the N pole of the motor. According to claim 1,
The number of the plurality of magnets is 5, the number of convex and convex portions is 5,
The number of slots of the stator is 12 slots,
When the pole of the magnet is the N pole, the uneven portion is the S pole of the magnet,
When the pole of the magnet is the S pole, the uneven portion is the N pole of the motor. delete According to claim 1,
The first phase difference is 20 ° to 40 ° motor. delete According to claim 1,
A motor in which the plurality of grooves are arranged symmetrically with respect to a reference line passing through the center of the width of the teeth and the center of the stator. According to claim 10,
A plurality of the grooves are formed extending from the upper end to the lower end of the stator.

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