Motor

Abstract

An embodiment of the present invention provides a motor comprising: a stator that includes a stator core, a plurality of teeth protruding inward in the radial direction of the stator core, and pole shoes formed at the front end of each of the plurality of teeth; and a rotor that is rotatably disposed spaced apart inside the stator and provided with a plurality of permanent magnet insertion holes into which a plurality of permanent magnets are inserted, respectively. Slots are formed in between each of the plurality of teeth, the ratio between the number of the plurality of permanent magnet insertion holes and the number of the plurality of slots is an integer ratio, and the outer circumferential surface of the rotor is composed of a plurality of curved parts having the same curvature.

Description

motor

[0001] The present invention relates to a motor, and more particularly, to a motor in which the ratio of the poles of a rotor to the slots of a stator is an integer ratio, thereby providing excellent power density, while reducing cogging torque and making the waveform of the counter electromotive force closer to a sine wave, thereby reducing vibration and noise during operation.

[0002] Brushless direct current (BLDC) motors are widely used because they can prevent friction and wear, which are disadvantages of conventional DC motors, and are relatively efficient.

[0003] These BLDC motors are DC motors that eliminate the brushes and commutators and instead install electronic commutation mechanisms. Among BLDC motors, the internal-rotor type has a rotor with a permanent magnet at its center that rotates, and a stator with a drive coil wound around it is fixed. In other words, the stator with the drive coil wound on the outside is fixed, and the rotor with permanent magnets rotates on the inside.

[0004] An example of a conventional BLDC motor is disclosed in Korean Patent Publication No. 2011-0132012. The conventional motor (200) includes a stator (210) in which a plurality of slots (212) are arranged and assembled in a ring shape, and a rotor (220) rotatably positioned on the inside of the stator (210) and in which a plurality of permanent magnets (222) are inserted and spaced apart along the circumferential periphery. At this time, the rotor (220) has eight permanent magnets (222) arranged with their N and S poles alternately spaced apart along the circumferential periphery of the rotor, and the stator (210) has an 8-pole-12-slot structure in which twelve slots (212) are arranged and assembled in a ring shape.

[0005] However, in the case of a motor with an 8-pole-12-slot structure, the power density is relatively low compared to a motor with an integer ratio of poles and slots.

[0006] To solve this problem, if a motor with an integer ratio of poles to slots, such as an 8-pole-24-slot motor, is applied, the power density increases, and a winding structure with a winding coefficient of 1 is possible, enabling automation of the winding process. However, in this case, the cogging torque is large, which causes vibration and noise during motor operation. In addition, there is a problem that the waveform of the back electromotive force approaches a square wave due to the harmonic component of the back electromotive force, which causes vibration and noise and also affects the efficiency of the motor.

[0007] The purpose of the present invention is to provide a motor in which the ratio of the poles of the rotor to the slots of the stator is an integer ratio, thereby providing excellent power density, while reducing cogging torque and making the waveform of the counter electromotive force close to a sine wave, thereby reducing vibration and noise during operation.

[0008] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0009] In order to solve the above problem, one embodiment of the present invention provides a motor including a stator including a stator core, a plurality of teeth protruding radially inwardly from the stator core, and a pole shoe formed at a tip of each of the plurality of teeth; and a rotor rotatably arranged spaced apart from each other inside the stator and having a plurality of permanent magnet insertion holes into which a plurality of permanent magnets are respectively inserted; wherein a slot is formed between each of the plurality of teeth, and a ratio of the number of the plurality of permanent magnet insertion holes to the number of the plurality of slots is an integer ratio, and an outer peripheral surface of the rotor is characterized by being formed of a plurality of curved portions having the same curvature.

[0010] According to an embodiment, the number of the plurality of permanent magnet insertion holes may be 8, and the number of the plurality of slots may be 24.

[0011] According to an embodiment, each of the plurality of curved portions is arranged to correspond to each of the plurality of permanent magnet insertion holes, and the center of curvature of each of the curved portions may be at the same distance from the center of the rotor.

[0012] According to an embodiment, the radius of curvature (R2) of each of the curved portions may be smaller than the radius (R1) of a circle connecting the vertices of the plurality of curved portions that are furthest from the center of the rotor.

[0013] According to an embodiment, a value obtained by subtracting the radius of curvature (R2) of each curved portion from the radius (R1) of a circle connecting the vertices of the plurality of curved portions that are furthest from the center of the rotor may be within a range of 7 mm to 11 mm.

[0014] According to an embodiment, the radius of curvature (R2) of each of the above curved portions may be within a range of 19 mm to 23 mm.

[0015] According to an embodiment, a main slit hole and a pair of sub slit holes arranged on each side of the main slit hole may be provided on the radially outer side of each of the permanent magnet insertion holes.

[0016] In some embodiments, the diameter of the main slit hole may be larger than the diameter of the pair of sub slit holes.

[0017] In some embodiments, the diameter of the pair of sub-slit holes may be 1.5 mm or more.

[0018] According to an embodiment, the angle (θ) formed by the main line connecting the center of the rotor and the center of the main slit hole and the sub line connecting the center of the rotor and the center of each sub slit hole may be within a range of 6° to 12°.

[0019] According to an embodiment, a notch formed concavely may be provided on the opposite surface of the pole shoe facing the rotor.

[0020] According to an embodiment, the opposite surface of the pole shoe is formed as a curved surface having a constant curvature, and may have a curvature equal to the curvature of a circle connecting the vertices of the plurality of curved surfaces that are furthest from the center of the rotor.

[0021] Depending on the embodiment, the radius of curvature (R3) of the notch may be within a range of 1 mm to 2 mm.

[0022] Another embodiment of the present invention for solving the above problem provides a motor including a stator including a stator core, a plurality of teeth protruding radially inwardly from the stator core, and a pole shoe formed at a tip of each of the plurality of teeth; and a rotor rotatably arranged spaced apart from each other inside the stator and having a plurality of permanent magnet insertion holes into which a plurality of permanent magnets are each inserted; wherein a slot is formed between each of the plurality of teeth, and a ratio of the number of the plurality of permanent magnet insertion holes to the number of the plurality of slots is an integer ratio, and a main slit hole and a pair of sub slit holes arranged on each side of the main slit hole are provided on a radially outer side of each of the permanent magnet insertion holes.

[0023] Another embodiment of the present invention for solving the above problem provides a motor including a stator including a stator core, a plurality of teeth protruding radially inwardly of the stator core, and a pole shoe formed at a tip end of each of the plurality of teeth; and a rotor rotatably arranged spaced apart from each other inside the stator and having a plurality of permanent magnet insertion holes into which a plurality of permanent magnets are each inserted; wherein a slot is formed between each of the plurality of teeth, and a ratio of the number of the plurality of permanent magnet insertion holes to the number of the plurality of slots is an integer ratio, and a notch formed concavely is provided on an opposite surface of the pole shoe facing the rotor.

[0024] According to the present invention, in a motor in which the ratio of the rotor poles to the stator slots is an integer ratio, cogging torque can be reduced through the anisotropic structure of the rotor, the slit-hole structure of the rotor, and the notch structure of the stator. In addition, since the waveform of the counter electromotive force approaches a sine wave, torque ripple, which is the fluctuation range of the cogging torque, can also be minimized. Consequently, vibration and noise during motor operation can be significantly reduced.

[0025] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the detailed description of the present invention or the composition of the invention described in the claims.

[0026] Figure 1 is a cross-sectional view showing a motor according to one embodiment of the present invention;

[0027] Figure 2 is a cross-sectional view of Figure 1 with the coil omitted;

[0028] Figure 3 is a graph showing the cogging torque reduction effect according to the anisotropic structure of the rotor.

[0029] Fig. 4 is an enlarged cross-sectional view of a part of Fig. 2;

[0030] Figure 5 is a graph showing the cogging torque reduction effect according to the slit hole structure of the rotor.

[0031] Fig. 6 is an enlarged cross-sectional view of a part of Fig. 2;

[0032] Fig. 7 is a graph showing the cogging torque reduction effect according to the notch structure of the stator.

[0033] Hereinafter, a preferred embodiment of the motor of the present invention will be described with reference to the attached drawings.

[0034] In addition, the terms described below are terms defined in consideration of the functions in the present invention, and may vary depending on the intention or custom of the user or operator. The examples below do not limit the scope of the present invention, but are merely exemplary matters of the components presented in the claims of the present invention.

[0035] To clearly explain the present invention, irrelevant parts have been omitted, and the same reference numerals are used throughout the specification to refer to identical or similar components. Throughout the specification, when a part is said to "include" a certain component, unless specifically stated otherwise, this does not mean that other components may be included, but rather that other components may be included.

[0036]

[0037] First, with reference to FIG. 1, let us look at the overall structure of a motor according to one embodiment of the present invention, for example, a motor for an electric compressor.

[0038] The motor of the present invention is an internal rotation motor having a cylindrical shape, a stator (100) provided on the outside, and a rotor (300) provided on the inside.

[0039] The stator (100) includes a stator core (110), a plurality of teeth (120) protruding radially inwardly from the stator core (110), and a pole shoe (130) formed at the tip of each of the plurality of teeth (120). The plurality of teeth (120) are preferably arranged at equal intervals along the circumferential direction, and a coil (200) to which a current is applied can be wound around each tooth (120). A slot (150), which is an empty space, is formed between adjacent teeth (120), so that a plurality of slots (150) are formed in the same number as the plurality of teeth (120). The pole shoe (130) can be formed to extend a predetermined distance from the tip of each tooth (120) to each of both sides in the circumferential direction. In the present embodiment, the plurality of slots (150) are formed in 24 numbers.

[0040] The rotor (300) is rotatably arranged spaced apart from the interior of the stator (100), and a shaft can be coupled to the center of the rotor (300). The rotor (300) is provided with a plurality of permanent magnet insertion holes (310) into which a plurality of permanent magnets (400) are each inserted. In the present embodiment, the plurality of permanent magnets (400) are formed in a straight line shape and are radially arranged close to the outer circumference of the rotor (300). At this time, the plurality of permanent magnets (400) are formed in eight pieces, and the N poles and S poles are alternately arranged along the circumferential direction of the rotor (300).

[0041] As such, the motor of the present invention corresponds to an 8-pole-24-slot structure. That is, the ratio of the number of permanent magnet insertion holes (310) to the number of slots (150) is an integer ratio (1:3 in the present embodiment), and thus, the power density is excellent. In addition, the weight of the motor is reduced and its performance is improved compared to the conventional 8-pole-12-slot structure.

[0042] In the present invention, as illustrated in FIG. 2, the rotor (300) has an anisotropic structure that is not a perfect circle. Cogging torque is generated by the difference in magnetic resistance between the permanent magnet and the stator slot structure when there is no load, and has periodicity due to the relationship between the slot and the magnet. In order to reduce the cogging torque, the shape of the rotor and stator must be changed to change the air gap and thus the air gap magnetic flux density. In the present invention, an anisotropic rotor structure is applied as a method for reducing the air gap magnetic flux density. The central part of the rotor magnetic pole is made to have the same existing air gap, and an anisotropic structure is applied to both edges to increase the air gap length, thereby changing the shape of the air gap magnetic flux density into a sinusoidal flux distribution.

[0043] Specifically, the outer surface of the rotor (300) is formed of a plurality of curved portions (302) having the same curvature. Each of the plurality of curved portions (302) is arranged to correspond to each of the plurality of permanent magnet insertion holes (310), and the center of curvature of each curved portion (302) is at the same distance from the center of the rotor (300). That is, eight curved portions (302) are arranged to correspond to eight permanent magnet insertion holes (310) on the radially outer side of each permanent magnet insertion hole (310), and when a virtual circle corresponding to one curved portion is drawn and moved in the circumferential direction while maintaining the distance from the center of the rotor (300), all of the curved portions can overlap.

[0044] At this time, the radius of curvature (R2) of each curved portion (302) is smaller than the radius (R1) of a circle (C1) connecting the vertices of multiple curved portions (302) furthest from the center of the rotor (300). In Fig. 2, the radius (R2) of an imaginary circle (C2) corresponding to one curved portion (302) located on the farthest right is shown as the radius of curvature of the curved portion.

[0045] In particular, it is preferable that the value obtained by subtracting the radius of curvature (R2) of each curved portion (302) from the radius (R1) of the circle (C1) connecting the vertices of the plurality of curved portions (302) furthest from the center of the rotor (300) be within the range of 7 mm to 11 mm, and it can be seen from the graph of Fig. 3 that the cogging torque is significantly reduced in that range. The graph of Fig. 3 is derived by changing the radius of curvature (R2) of the curved portion (302) while keeping the remaining conditions constant. At this time, the radius (R1) of the circle (C1) is set to 30 mm.

[0046] Additionally, the radius of curvature (R2) of each curved portion (302) is effective in reducing cogging torque when it is within the range of 19 mm to 23 mm.

[0047] As illustrated in FIG. 4, according to an embodiment, a main slit hole (320) and a pair of sub slit holes (330a, 330b) arranged on both sides of the main slit hole (320) may be provided on the radially outer side of each permanent magnet insertion hole (310). That is, eight main slit holes (320) and eight pairs of sub slit holes (330a, 330b) may be provided corresponding to eight permanent magnet insertion holes (310). As the slit holes are formed in this manner, the inter-pole leakage flux within the rotor can be reduced, thereby concentrating the no-load flux linkage toward the stator.

[0048] Due to the anisotropic structure of the rotor (300) and the linear permanent magnet (400), the diameter of the main slit hole (320) can be formed to be larger than the diameters of the pair of sub-slit holes (330a, 330b). At this time, for effective reduction of cogging torque, the diameter of the pair of sub-slit holes (330a, 330b) is preferably 1.5 mm or more.

[0049] In addition, it is preferable that the angle (θ) formed by the main line (ML) connecting the center of the rotor (300) and the center of the main slit hole (320) and the sub-line (SL) connecting the center of the rotor (300) and the center of each sub-slit hole (330a, 330b) be within the range of 6° to 12°, and it can be seen from the graph of FIG. 5 that the cogging torque is significantly reduced in that range. The graph of FIG. 5 is derived by changing the value of the angle (θ) while keeping the remaining conditions constant. In the present embodiment, each of a pair of sub-slit holes (330a, 330b) is formed symmetrically with respect to the main line (ML).

[0050] As illustrated in FIG. 6, according to an embodiment, a notch (132) formed concavely may be provided on the opposite surface of the pole shoe (130) facing the rotor (300). In this embodiment, the opposite surface of the pole shoe (130) is formed as a curved surface having a constant curvature, but has the same curvature as the curvature of a circle (C1) connecting the vertices of a plurality of curved portions (302) furthest from the center of the rotor (300).

[0051] In this embodiment, the notch (132) has a semicircular shape and is located at the center of the pole shoe (130). That is, the center of curvature of the notch (132) is located on the same line as the center line in the width direction of the tooth (120). At this time, when the inner diameter position of the stator (100) is fixed, the radius of curvature (R3) of the notch (132) is preferably within the range of 1 mm to 2 mm, and it can be seen from the graph of Fig. 7 that the cogging torque is significantly reduced in that range. The graph of Fig. 7 is derived by changing the value of the radius of curvature (R3) of the notch (132) while keeping the remaining conditions constant.

[0052] In the above embodiment, it is explained based on the application of the anisotropic structure of the rotor, the slit hole structure of the rotor, and the notch structure of the stator, but it is of course possible to apply only one of these.

[0053] As described above, the motor of the present invention can reduce cogging torque through the anisotropic structure of the rotor, the slit-hole structure of the rotor, and the notched structure of the stator. Furthermore, since the waveform of the counter electromotive force approaches a sine wave, torque ripple, which is the fluctuation range of cogging torque, can also be minimized. Consequently, vibration and noise during motor operation can be significantly reduced.

[0054] That is, compared to a motor with a basic 8-pole-24-slot structure to which the anisotropic structure of the rotor, the slit hole structure of the rotor, and the notch structure of the stator are not applied, the motor of the present invention not only increases efficiency, but also reduces the weight of the rotor (300) and greatly reduces cogging torque.

[0055] The present invention is not limited to the specific embodiments and descriptions described above, and anyone with ordinary skill in the art to which the present invention pertains can make various modifications without departing from the gist of the present invention as claimed in the claims, and such modifications are within the protection scope of the present invention.

[0056] The present invention relates to a motor, and more particularly, to a motor in which the ratio of the poles of a rotor to the slots of a stator is an integer ratio, thereby providing excellent power density, while reducing cogging torque and making the waveform of the counter electromotive force closer to a sine wave, thereby reducing vibration and noise during operation.

Claims

1. A stator including a stator core, a plurality of teeth protruding radially inwardly from the stator core, and a pole shoe formed at the tip of each of the plurality of teeth; and A rotor is provided with a plurality of permanent magnet insertion holes, each of which is spaced apart and rotatably arranged inside the stator, into which a plurality of permanent magnets are inserted; A slot is formed between each of the plurality of teeth, and the ratio of the number of the plurality of permanent magnet insertion holes to the number of the plurality of slots is an integer ratio. A motor characterized in that the outer surface of the rotor is formed of a plurality of curved surfaces having the same curvature.

2. In paragraph 1, A motor characterized in that the number of the plurality of permanent magnet insertion holes is 8 and the number of the plurality of slots is 24.

3. In paragraph 1, A motor characterized in that each of the plurality of curved portions is arranged to correspond to each of the plurality of permanent magnet insertion holes, and the center of curvature of each of the curved portions is at the same distance from the center of the rotor.

4. In paragraph 3, A motor characterized in that the radius of curvature (R2) of each of the above curved portions is smaller than the radius (R1) of a circle connecting the vertices of the plurality of curved portions that are furthest from the center of the rotor.

5. In paragraph 4, A motor characterized in that the value obtained by subtracting the radius of curvature (R2) of each curved portion from the radius (R1) of a circle connecting the vertices of the plurality of curved portions furthest from the center of the rotor is within a range of 7 mm to 11 mm.

6. In paragraph 4, A motor characterized in that the radius of curvature (R2) of each of the above curved portions is within a range of 19 mm to 23 mm.

7. In paragraph 1, A motor characterized in that a main slit hole and a pair of sub slit holes arranged on each side of the main slit hole are provided on the radially outer side of each of the permanent magnet insertion holes.

8. In paragraph 7, A motor characterized in that the diameter of the main slit hole is larger than the diameter of the pair of sub slit holes.

9. In paragraph 8, A motor characterized in that the diameter of the pair of sub-slit holes is 1.5 mm or more.

10. In paragraph 7, A motor characterized in that the angle (θ) formed by the main line connecting the center of the rotor and the center of the main slit hole and the sub line connecting the center of the rotor and the center of each sub slit hole is within a range of 6° to 12°.

11. In paragraph 3, A motor characterized in that a notch is formed concavely on the opposite surface of the above-mentioned pole facing the rotor.

12. In paragraph 11, A motor characterized in that the opposing surface of the above-mentioned pole is formed as a curved surface having a constant curvature, and has a curvature identical to the curvature of a circle connecting the vertices of the plurality of curved surfaces that are furthest from the center of the rotor.

13. In paragraph 11, A motor characterized in that the radius of curvature (R3) of the above notch is within the range of 1 mm to 2 mm.

14. A stator including a stator core, a plurality of teeth protruding radially inwardly from the stator core, and a pole shoe formed at the tip of each of the plurality of teeth; and A rotor is provided with a plurality of permanent magnet insertion holes, each of which is spaced apart and rotatably arranged inside the stator, into which a plurality of permanent magnets are inserted; A slot is formed between each of the plurality of teeth, and the ratio of the number of the plurality of permanent magnet insertion holes to the number of the plurality of slots is an integer ratio. A motor characterized in that a main slit hole and a pair of sub slit holes arranged on each side of the main slit hole are provided on the radially outer side of each of the permanent magnet insertion holes.

15. A stator including a stator core, a plurality of teeth protruding radially inwardly from the stator core, and a pole shoe formed at the tip of each of the plurality of teeth; and A rotor is provided with a plurality of permanent magnet insertion holes, each of which is spaced apart and rotatably arranged inside the stator, into which a plurality of permanent magnets are inserted; A slot is formed between each of the plurality of teeth, and the ratio of the number of the plurality of permanent magnet insertion holes to the number of the plurality of slots is an integer ratio. A motor characterized in that a notch is formed concavely on the opposite surface of the above-mentioned pole facing the rotor.

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