Patent ID: 12261480

MODES OF THE INVENTION

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings in detail. Purposes, specific advantages, and novel features of the invention will be made clear from the exemplary embodiments and the following detailed description in connection with the accompanying drawings. In addition, in the description of the present invention, detailed descriptions of related well-known functions, which unnecessarily obscure the gist of the invention, will be omitted.

FIG.1is a view illustrating a motor according to an embodiment.

Referring toFIG.1, a motor1according to the embodiment may include a shaft100, a rotor200, a stator300, a housing400, a busbar500, a sensing unit600, and a substrate700. Hereinafter, the term “inside” is referred to as a direction from the housing400toward the shaft100which is located at a center of the motor, and the term “outside” is referred to as a direction from the shaft100toward the housing400which is opposite to the inside.

The shaft100may be coupled to the rotor200. When an electromagnetic interaction occurs between the rotor200and the stator300due to a current being supplied, the rotor200rotates, and the shaft100rotates in conjunction with the rotor200. The shaft100is rotatably supported by bearings10. The shaft100may be connected to a vehicle's steering system, and power may be transmitted to the vehicle's steering system through the shaft100.

The rotor200rotates through the electrical interaction with the stator300. The rotor200may be disposed inside the stator300. The rotor200may include a rotor core210(seeFIG.2) and magnets220(seeFIG.2) disposed on the rotor core210. In this case, the rotor200may be a surface permanent magnet (SPM) type rotor in which the magnets220are disposed on an outer circumferential surface of the rotor core210or an inner permanent magnet (IPM) type rotor in which the magnets220are buried inside the rotor core210.

The stator300is disposed outside the rotor200. The stator300may include a stator core300A, coils300B, and an insulator300C installed on the stator core300A. The coil300B may be wound around the insulator300C. The insulator300C is disposed between the coil300B and the stator core300A to serve to electrically insulate the stator core300A from the coil300B. The coil300B induces an electrical interaction with the magnets220(seeFIG.2).

The busbar500is disposed on the stator300. The busbar500includes a busbar holder (not shown) formed of an insulating material and a plurality of terminals (not shown) coupled to the busbar holder. In this case, the busbar holder is formed of an insulating material to prevent the plurality of terminals from being connected to each other. In addition, the plurality of terminals serve to connect the coils300B wound around the stator core300A to apply currents to the coils.

The sensing unit600may be coupled to the shaft100. The sensing unit600includes a sensing plate (not shown) and a sensing magnet (not shown) disposed on the sensing plate. A sensor, which detects a magnetic force of the sensing magnet (not shown), may be disposed on the substrate700. In this case, the sensor may be a Hall integrated circuit (IC) and serves to detect a magnetic flux of the sensing magnet of the sensing unit600coupled to the shaft100. The sensing unit600and the substrate700serve to detect a position of the rotor200by detecting the magnetic flux changed according to rotation.

FIG.2is an enlarged view illustrating a stator core including a first surface, a second surface, and a third surface.

Referring toFIG.2, the stator core300A may include a yoke310and a tooth320. The tooth320may protrude from an inner circumferential surface of the yoke310toward a center C of the stator300. The tooth320may include a plurality of teeth320. The number of the teeth320may be variously changed according to the number of magnets220. The stator core300A may be formed by combining a plurality of divided cores each including the yoke310and the teeth320.

A cogging torque is generated in the form of a wave having an amplitude and a frequency, and a cogging main degree means a number of vibration times of a cogging torque waveform per unit rotation (one rotation) of a motor. When the cogging main degree increases, since the number of the vibration times of the cogging torque waveform also increases, the cogging torque may be significantly reduced. The cogging main degree may be determined by the number of the magnets220and the number of the teeth320. When the cogging main degree increases, the cogging torque may be reduced, but since the number of the magnets220and the number of the teeth320are fixed, the cogging main degree is also fixed.

However, in the motor1according to the embodiment, the cogging torque may be reduced using two methods. In one method, a shape of the tooth320is changed (into a concave notch shape) to increase a cogging main degree so as to increase a frequency so that a magnitude of a cogging torque is reduced. In the other method, the shape of the tooth320is changed (into a convex notch shape) to change a phase of a cogging torque waveform in reverse so that a reversed cogging torque waveform interferes with the cogging torque waveform with the normal phase thereby decreasing a magnitude of a cogging torque.

The tooth320may include a first surface321, a second surface322, and a third surface323. The first surface321, the second surface322, and the third surface323may be an inner circumferential surface of the tooth320disposed opposite to the magnet220. The first surface321may be disposed between two second surfaces322in a circumferential direction of the stator300. Two second surfaces322may be disposed between two third surfaces323. The third surfaces323may be disposed at both ends of the tooth320in the circumferential direction of the stator300.

The first surface321and the second surfaces322may be disposed to form gaps therebetween in a radial direction of the stator300. In addition, the third surfaces323and the second surfaces322may be disposed to form gaps therebetween in the radial direction of the stator300. That is, the first surface321, the second surface322, and the third surface323may be disposed to be separated from each other by predetermined distances in the radial direction of the stator300. In other words, steps may be formed between the first surface321and the second surfaces322and between the second surfaces322and the third surfaces323, and connecting portions, which connect the surfaces, may be formed therebetween. In addition, a shortest distance R1from a center of the shaft100to the first surface321may be shorter than a shortest distance R3to the third surface323therefrom. In addition, the shortest distance R3from the center of the shaft100to the third surface323may be shorter than a shortest distance R2to the second surface322therefrom.

In addition, the first surface321, the second surfaces322, and the third surfaces323may be disposed on virtual circumferences about the center of the shaft100, and in this case, the first surface321may be disposed on a first circumference O1, the plurality of second surfaces322may be disposed on a second circumference O2having a radius which is greater than a radius of the first circumference O1, and the plurality of third surfaces323may be disposed on a third circumference O3having a radius which is smaller than that of the second circumference O2and greater than that of the first circumference O1.

Thus, the first surface321may be disposed to protrude further inward than the third surface323in the radial direction of the stator300. The second surface322may be concavely disposed further outward than the third surface323. A shape of the tooth320is for decreasing a cogging torque by increasing the number of vibration times of a cogging torque waveform and realizing a reverse phase.

Meanwhile, lengths L1of a plurality of first surfaces321disposed on the stator core300A may be the same in the circumferential direction. In addition, the length L1of the first surface321in the circumferential direction may be shorter than a length L2of the second surface322in the circumferential direction. In addition, the length L1of the first surface321in the circumferential direction may be the same as a length L3of the third surface323in the circumferential direction.

FIG.3is an enlarged view illustrating the stator core including a first protrusion, a second protrusion, and a third protrusion.

Referring toFIG.3, the tooth320may include a first protrusion324, a second protrusion325, and a third protrusion326, which are opposite to the magnet220and the rotor200. The first protrusion324, the second protrusion325, and the third protrusion326may be disposed to be spaced apart from each other in the circumferential direction of the stator core300A. The first protrusion324may be disposed between the second protrusion325and the third protrusion326in the circumferential direction of the stator core300A. The first protrusion324, the second protrusion325, and the third protrusion326have shapes protruding from the second surfaces322toward the shaft100in the radial direction of the stator core300A. The first protrusion324, the second protrusion325, and the third protrusion326protrude further inward than the second circumference O2. In addition, the first protrusion324protrudes further inward than the third circumference O3on which inner circumferential surfaces of the second protrusion325and the third protrusion326are disposed.

The first protrusion324may be disposed closer to the shaft100than the second protrusion325and the third protrusion326.

The first protrusion324may include the first surface321. In addition, each of the second protrusion325and the third protrusion326may include the third surface323. In the circumferential direction of the stator core300A, the second surface322may be disposed between the first protrusion324and the second protrusion325, and the second surface322may also be disposed between the first protrusion324and the third protrusion326.

FIG.4is an enlarged view illustrating the stator core including a first notch and a second notch.

Referring toFIG.4, the tooth320may include a first notch327and a plurality of second notches328which are opposite to the magnets220of the rotor. The first notch327has a convexly embossed shape with respect to the third surface323. The plurality of second notches328have a concavely engraved shape with respect to the third surface323. In this case, the first notch327and the plurality of second notches328may be disposed at opposite positions with respect to the third circumference O3.

In the circumferential direction of the stator core300A, the first notch327may be disposed between two second notches328. The first notch327may be disposed to overlap a line passing through a center of both ends of the tooth320from the shaft100. A shortest distance R6from the outer circumferential surface of the rotor core210to the first notch327may be in the range of 23% to 24% of a radius of the rotor core210. A shortest distance R7from the outer circumferential surface of the rotor core210to the second notch328may be in the range of 27% to 28% of the radius of the rotor core.

FIGS.5and6are enlarged views illustrating a stator core including a first surface, a second surface, a third surface, and a fourth surface according to a modified embodiment.

Referring toFIGS.5and6, positions of a first surface321, second surfaces322, and third surfaces323in a radial direction are the same as the positions of the first surface321, the second surfaces322, and the third surfaces323of the stator core300A illustrated inFIG.2. A stator core300A according to the modified embodiment further includes fourth surfaces329. In a circumferential direction of a stator300, the fourth surfaces329may be disposed between the first surface321and the second surfaces322. The fourth surfaces329may be disposed between the first surface321and the second surfaces322in the circumferential direction around a center of a shaft100and may be disposed to have predetermined gaps from the first surface321and the second surfaces322in the radial direction from the center of the shaft100.

In other words, steps may be formed between the fourth surface329and the first surface321and between the fourth surface329and the second surface322, and connection portions, which connect the surfaces, may be formed between the surfaces. In addition, a shortest distance R1from the center of the shaft100to the first surface321may be shorter than a shortest distance R9to the fourth surface329therefrom. In addition, the third surface323and the fourth surface329may be disposed on one third circumference O3. Accordingly, a shortest distance R3from the center of the shaft100to the third surface323may be the same as the shortest distance R9from the center of the shaft100to the fourth surface329.

Referring toFIG.5, when compared to the stator core300A ofFIG.2, a length L1of the first surface in the circumferential direction and a length L2of the second surface in the circumferential direction are the same, and a length L3of the third surface of the stator core300A ofFIG.5in the circumferential direction may be shorter than the length L3of the stator core300A ofFIG.2.

Referring toFIG.6, when compared to the stator core300A ofFIG.2, a length L2of the second surface in the circumferential direction and a length L3of the third surface in the circumferential direction are the same, and a length L1of the first surface of a stator core300A ofFIG.6in the circumferential direction may be shorter than that of the stator core300A ofFIG.2.

FIG.7is a graph showing a cogging torque corresponding to a first ratio.

Referring toFIGS.2and7, a value A ofFIG.7corresponds to a reference value of a desired cogging torque. When a first ratio is in the range of 7.5% to 12.5%, a value of a cogging torque is less than or equal to the reference value. The first ratio is a ratio of the shortest distance R3(seeFIG.2) from the center C of the shaft100to the third surface323to the length L2(seeFIG.2) of the second surface322in the circumferential direction.

In this case, the shortest distance R3may correspond to an inner radius of the stator300. When the first ratio is less than or equal to 7.5% or greater than or equal to 12.5%, it may be seen that the value of the cogging torque is greater than 0.03 Nm which is the reference value of the cogging torque.

FIG.8is a graph showing a cogging torque corresponding to a second ratio.

Referring toFIGS.2and8, a value A ofFIG.8corresponds to a reference value of a desired cogging torque. When a second ratio is in the range of 2.0% to 4.0%, a value of a cogging torque is less than or equal to the reference value. The second ratio is a ratio of the shortest distance R3from the center C of the shaft100to the third surface323to a shortest distance R4from the third surface323to the second surface322. More precisely, the second ratio is a ratio of the shortest distance R3from the center C of the shaft100to the third surface323to the shortest distance R4from the third circumference O3, on which the third surface323is disposed, to the second surface322. When the second ratio is less than or equal to 2.0% or greater than or equal to 4.0%, it may be seen that the value of the cogging torque is greater than 0.03 Nm which is the reference value of the cogging torque.

FIG.9is a graph showing a cogging torque corresponding to a third ratio.

Referring toFIGS.2and9, a value A ofFIG.9corresponds to a reference value of a desired cogging torque. A third ratio may be less than or equal to 2.0%. The third ratio is a ratio of the shortest distance R3from the center C of the shaft100to the third surface323to a shortest distance R5from the third surface323to the first surface321. More precisely, the third ratio is a ratio of the shortest distance R3from the center C of the shaft100to the third surface323to the shortest distance R5from the third circumference O3, on which the third surface323is disposed, to the first surface321. When the third ratio is greater than or equal to 2.0, it may be seen that the value of the cogging torque is greater than 0.03 Nm which is the reference value of the cogging torque.

As described above, the motor according to one exemplary embodiment of the present invention has been specifically described with reference to the accompanying drawings.

The above description is only an example describing a technological scope of the present invention. Various changes, modifications, and replacements may be made by those skilled in the art without departing from the spirit and scope of the present invention. Therefore, the embodiments disclosed above and in the accompanying drawings should be considered in a descriptive sense only and not for limiting the technological scope. The technological scope of the present invention is not limited by the embodiments and the accompanying drawings. The scope of the present invention should be interpreted by the appended claims and encompass all equivalents falling within the scope of the appended claims.