Induction motor rotor and induction motor equipped with the same

Abstract

The present application provides an induction motor rotor including a rotor body (1), rotor teeth (2) and rotor slots (3) arranged alternately around the circumference of the rotor body (1), and a plurality of grooves (4) at the ends of the rotor teeth (2) or a plurality of gaps (5) within the ends of the rotor teeth (2), which are arranged symmetrically about a center line (10) of the rotor teeth (2). The rotor of the present application and an induction motor including the rotor can reduce NVH caused by the cogging effect by, for example, about 50%. This can significantly improve the comfort of use for users, improve the efficiency of the induction motor, and extend the life of the induction motor.

Description

[Technical field]

[0001] The present invention relates to a motor rotor and an induction motor including the same, and more particularly to a motor rotor capable of reducing NVH of an induction motor. [Background technology]

[0002] With the development of the automobile manufacturing industry, the NVH performance of automobiles has become one of the comprehensive technical indicators of modern automobile manufacturing quality. NVH is an English abbreviation of Noise, Vibration, and Harshness. NVH provides the most direct and important experience to automobile users. Vehicle NVH problems are one of the issues that major automobile manufacturers and parts companies in the international automobile industry pay attention to. According to statistics, about one-third of the overall vehicle failure problems are related to vehicle NVH problems. The main excitation sources that affect the magnitude of NVH in the vehicle are engines, motors, reduction gears, tires, and other components. For electric vehicles, the main excitation source is the motor. Due to the large number of motors used in automobiles, research on motor noise and vibration is becoming increasingly important.

[0003] In the NVH of motors, the biggest source of NVH is electromagnetic noise, which is mainly concentrated in the stator of the motor. The stator of the motor is subjected to the electromagnetic forces of two parts, one part is tangential force, which is mainly torque pulsation. The other part is radial force, which is larger than the tangential force and is the main source of vibration and noise of the stator of the motor. Electromagnetic noise is a magnetic attraction force that changes in time and space and is caused by the magnetic attraction force acting between each part of the motor. The causes of the electromagnetic noise of an asynchronous motor can be classified into several categories as follows. First, there is a rotational force wave in the magnetic field of the air gap space, and the radial force wave component of the rotational force wave causes radial deformation and periodic vibration in the stator and rotor, which causes electromagnetic noise. Second, in addition to the fundamental wave component of the power supply, the air gap magnetic field also contains harmonic components, and the radial force wave of the harmonic also acts on the stator core and rotor core, respectively, causing radial deformation and periodic vibration in both. Generally, for harmonics, the rigidity of the motor rotor is relatively strong, so the radial deformation of the stator core is the main factor, which may cause large vibrations and noise. Thirdly, the deformation of different orders of harmonics of the stator core has different natural frequencies, and when the frequency of the radial force wave is close to or equal to a certain natural frequency of the core, "resonance" is caused. In this case, even if the amplitude of the radial force wave is not large, it will cause deformation of the core, periodic vibration, and large noise. Fourthly, when the stator is deformed, it will cause vibration of the surrounding air, which will generate noise. Therefore, it can be said that the force received by the stator teeth, especially the radial force, is the main source of vibration and noise (NVH).

[0004] There are various improvements for reducing NVH, and one example is a skewed rotor for a motor, which effectively solves the technical problem that the NVH of the motor in the prior art is relatively high, as disclosed in China Utility Model Patent Publication No. 210404878. The skewed rotor for the motor includes a shaft, a core is provided on the shaft, the core includes N (N≧2) core segments, and a predetermined included angle θ is provided between the magnetic poles of the adjacent core segments, the shaft is provided with at least one keyway extending in the axial direction for mounting the core segments, the keyway includes a reference keyway, and one end of the shaft is provided with a resolver mounting groove, and the reference keyway and the resolver mounting groove have radial centerlines in the same direction. This skewed rotor effectively reduces cogging torque and torque fluctuations through the skewed design of the rotor's iron core, thereby reducing motor vibration and power consumption at motor startup, effectively reducing the motor's NVH.

[0005] However, although the skewed rotor can be used to reduce torque pulsation, as described above, there are various causes for the radial force of the stator teeth, which is the main source of motor NVH, and it may not be possible to effectively reduce the radial force of the stator teeth by simply reducing torque pulsation. In particular, in induction motors in which rotor bars are inserted into rotor slots, the skewed rotor may not be applicable due to manufacturing constraints. In addition, the skewed rotor of a motor has the problem of high costs due to the complicated machining of the rotor. Summary of the Invention [Problem to be solved by the invention]

[0006] In response to the above-mentioned problems existing in the prior art, an object of the present application is to provide an induction motor rotor that can more efficiently reduce NVH of induction motors, in particular induction motors in which rotor bars are inserted into rotor slots, and an induction motor including the induction motor rotor. [Means for solving the problem]

[0007] In order to achieve the above object, the technical solution of the present application is realized as follows.

[0008] According to one aspect of the present application, there is provided an induction motor rotor including a rotor body, alternating rotor teeth and rotor slots around a circumference of the rotor body, and grooves or gaps at or within the ends of the rotor teeth symmetrically arranged about a centerline of the rotor teeth.

[0009] Preferably, two of each of the plurality of grooves or the plurality of gaps are provided in two rotor teeth whose centerlines overlap.

[0010] Preferably, each rotor tooth is provided with said groove or said gap.

[0011] Preferably, the shape of the groove is one of a semicircle, a semiellipse, a triangle, a rectangle, and a trapezoid.

[0012] Preferably, the shape of the gap is one of a semicircle, a semiellipse, a triangle, a rectangle, and a trapezoid.

[0013] Preferably, at least a portion of the rotor teeth are interconnected.

[0014] Preferably, the rotor slots adopt an open slot geometry.

[0015] Also provided is an induction motor including the induction motor rotor described above.

[0016] Also provided is a rotor blank including a blank body, alternating rotor teeth and rotor slots disposed around a circumference of the blank body, and grooves at or gaps within the ends of the rotor teeth symmetrically disposed about a centerline of the rotor teeth. Effect of the Invention

[0017] The present invention has the following advantages and beneficial effects: The motor rotor and the induction motor equipped therewith solve the problems of the prior art by providing grooves (notches) on the surface of the rotor teeth or adding gaps close to the surface of the rotor teeth in the rotor teeth, thereby reducing the harmonic magnetic flux caused by the rotor slotting effect in the air gap, and thus reducing the NVH according to the number of rotor slots. [Brief description of the drawings]

[0018] [Figure 1a] FIG. 1a is a plan view of an induction motor rotor according to a first embodiment of the present invention. [Figure 1b] FIG. 1b is a schematic diagram of an induction motor rotor according to a first embodiment of the present invention, in which grooves are provided on the outer circumferential surface thereof. [Diagram 2] FIG. 2 is a diagram showing the shape of a groove provided in a rotor tooth of the present application. [Figure 3a] FIG. 3a is a plan view of an induction motor rotor according to a second embodiment of the present invention. [Figure 3b] FIG. 3b is a schematic diagram of an induction motor according to a second embodiment of the present invention in which gaps are provided between rotor teeth. [Figure 4] FIG. 4 is a diagram showing the shape of the gaps provided in the rotor teeth of the present application. [Figure 5a] FIG. 5a is a comparison diagram between the radial force received by the stator teeth of a conventional stator and the radial force received by the stator teeth when grooves are provided in the induction motor rotor of the present application. [Figure 5b] FIG. 5b is a comparison diagram between the radial force received by the stator teeth of a conventional stator and the radial force received by the stator teeth when a gap is provided in the induction motor rotor of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Traditional induction motors generally adopt a tooth-slot structure, where the teeth are used to guide the magnetic field lines and reduce the reluctance, and the slots are used to fit the windings to intersect the magnetic field lines in the teeth. Due to the different permeabilities of the teeth and slots, the rotor will have different numbers of magnetic field lines at different positions. When the magnetic poles are aligned with the stator teeth, the magnets will attract each other, which will hinder the rotation of the motor rotor, which is called the cogging effect of the motor.

[0020] More specifically, the core's inner circular surface is undulating due to the presence of the core slots, and the magnetic resistance of the air gap actually changes for the magnetic poles. When the magnetic poles face the teeth, the magnetic resistance is small, and when the magnetic poles face the core slots, the magnetic resistance of the air gap is large. As the magnetic poles rotate, the magnetic resistance of the air gap changes, and an electromotive force is induced in the stator winding. The electromotive force induced in the winding by this cogging effect is called tooth harmonic electromotive force.

[0021] These radial force waves due to the tooth harmonic electromotive forces act on the iron cores of the stator and rotor, respectively, causing radial deformation and periodic vibrations in them. In general, the harmonics cause radial deformation in the stator iron core, resulting in large vibrations and noise.

[0022] In this situation, one possible method to reduce the radial deformation occurring in the stator core is rotor skew. However, rotor skew may not be able to effectively reduce the radial force of the stator teeth. Also, due to manufacturing constraints, skewed rotors may not be applicable, especially in induction motors where rotor bars are inserted into rotor slots.

[0023] In order to solve the above problems and more efficiently reduce the NVH of induction motors, the present application proposes a solution of providing grooves on the outer circumferential surface of the rotor or adding gaps to the rotor teeth close to the rotor surface. Specifically, grooves are provided symmetrically on the rotor surface around the centerline of the rotor teeth, or gaps are provided symmetrically inside the rotor teeth around the centerline of the rotor teeth. In the case of rotor blanking, grooves are provided symmetrically on the outer circumferential surface of the blank around the centerline of the rotor teeth, or gaps are provided symmetrically inside the rotor teeth around the centerline of the rotor teeth, along the circumferential direction of the blanking, thereby reducing the main harmonic components.

[0024] More specifically, harmonics are generated from the grooves or gaps themselves, and when the harmonics generated from the grooves or gaps and the harmonics generated from the stator change in phase, the cogging torque ripple increases, and conversely, when the harmonics generated from the grooves or gaps and the harmonics generated from the stator change in different phases, the cogging torque ripple is reduced. When an included angle occurs between the center line of the rotor teeth of the rotor and the center line of the stator teeth of the stator during rotation, the cogging torque ripple is reduced. In addition, the harmonics generated from the grooves or gaps cancel out the harmonics of the original harmful harmonic components. Furthermore, the waveform of the harmonics of the original harmful harmonic components is smoothed, eliminating harmful oscillations.

[0025] Specifically, referring to Fig. 5a and Fig. 5b, Fig. 5a and Fig. 5b show a comparison of the radial force of the stator teeth between an induction motor with a groove or gap in the rotor and an induction motor without a groove or gap in the rotor, in which "baseline" means that no groove or gap is applied. As can be seen from Fig. 5a and Fig. 5b, when the rotor does not have a groove or gap, as shown in the baseline, a radial force of about 25 to 26 N is generated on the stator teeth due to the influence of harmonics generated from the harmonic magnetic flux due to the cogging effect of the rotor in the air gap. In contrast, when grooves or gaps are provided symmetrically around the center line of the rotor teeth, the grooves or gaps reduce the harmonic components, so that the radial force of the stator teeth is reduced to about 12 to 14 N. From this, it can be seen that by providing grooves or gaps symmetrically around the center line of the rotor teeth, the radial force of the stator teeth can be significantly reduced. As described above, since the force received by the stator teeth, especially the radial force, is the main source of vibration and noise (NVH), the NVH of the induction motor is significantly reduced. In particular, in the case of an induction motor in which rotor bars are inserted into rotor slots, when a skewed rotor cannot be applied due to manufacturing constraints, the problem of high NVH of such an induction motor can be solved.

[0026] In order to more clearly explain the objectives, technical solutions and advantages of the present application, the embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Of course, these embodiments are only some of the embodiments of the present invention, and are not all of the embodiments. Other embodiments that a person skilled in the art can obtain based on these embodiments without requiring creative labor are also included in the protection scope of the present invention.

[0027] Example 1 Fig. 1a is a plan view of an induction motor rotor core of the present application. As shown in Fig. 1a and Fig. 1b, the present application provides an induction motor rotor including a rotor body 1, rotor teeth 2 and rotor slots 3 alternately arranged along the circumference of the rotor body 1, and grooves 4 symmetrically arranged around a center line 10 of the rotor teeth 2. Among them, the grooves 4 are arranged on the outer surface of the rotor teeth 2, and the rotor slots 3 are used for inserting bars.

[0028] The groove 4 can be designed in various shapes, and may be a semicircle or semi-ellipse as shown in FIG. 1b, or may be a triangle, rectangle, trapezoid, or other irregular shape as shown in FIG. 2. However, the shape of the groove 4 is symmetrical about the center line 10 of the rotor tooth 2. For example, in the case of a circle, the diameter line of the circle overlaps with the center line 10 of the rotor tooth 2, that is, the center line 10 of the rotor tooth 2 passes through the center of the circle. In the case of an ellipse, the major axis or minor axis of the ellipse overlaps with the center line 10 of the rotor tooth 2. In the case of a triangle, it should be an isosceles triangle or an equilateral triangle, among which, for example, when an inverted triangle is formed so that the apex angle faces the center of the rotor body 1, the apex angle bisector of the isosceles triangle overlaps with the center line 10 of the rotor tooth 2, or the center line of the equilateral triangle overlaps with the center line 10 of the rotor tooth 2.

[0029] During operation of the induction motor, for example in the motor operation mode, when power is applied to the stator of the induction motor (not shown) around the rotor, a rotating magnetic field is generated in the air gap between the stator and the rotor. Electromagnetic torque generated by electromagnetic induction acts on the rotor, causing the rotor to rotate under the action of the electromagnetic torque, thereby outputting mechanical power to the outside. At this time, the induction motor is configured so that electrical energy is input from the stator and mechanical energy is output from the rotor, and the motor is in an operating state.

[0030] However, when the rotor teeth 2 face the stator poles (stator windings) (not shown), the air gap becomes relatively small and the magnetic resistance becomes small, and when the rotor slots 3 face the stator poles, the air gap becomes relatively large and the magnetic resistance becomes large, which is called the cogging effect. The cogging effect induces harmonic electromotive forces in the stator bars. When radial forces due to the harmonic electromotive forces act on the stator and rotor, vibrations and noise are generated.

[0031] For example, when the rotor tooth 2 faces the stator pole (not shown), a radial force F1 toward the center of the rotor is generated in the stator due to the cogging effect as described above. However, in the case of a rotor provided with the groove 4 of the present application as described above, the groove 4 is provided in the rotor tooth 2, so that the air gap becomes relatively large, and as a result, a radial force F2 (not shown) in the opposite direction to the radial force F1 is generated. Since the direction of the radial force F2 is opposite to the direction of the radial force F1, a part of the radial force F1 is offset, that is, the radial force F1 is reduced. Therefore, the vibration and noise caused by the radial force F1 are also reduced. Similarly, the groove 4 can also reduce the radial force acting on the rotor tooth 2, so that the vibration and noise caused by this are reduced.

[0032] In the generator operation mode of the induction motor, the rotor rotates in the opposite direction to the motor operation mode, so that mechanical energy is input from the rotor and electrical energy is output from the stator. As in the motor operation mode, a radial force F2 in the opposite direction to the radial force F1 is generated in the groove 4, which is offset by the radial force F1 generated in the stator, and the radial force received by the stator is similarly reduced.

[0033] Similarly, the grooves 4 also act to reduce harmonic electromotive forces caused by the cogging effect, thereby reducing vibrations and noise associated with the output of electrical energy.

[0034] Furthermore, in the electromagnetic braking operation mode of the induction motor, the same action as that of the groove 4 in the above process occurs, so the description thereof will be omitted here.

[0035] According to the research and experiments of the present inventor, as shown in Figures 5a and 5b, for example, the radial force of the stator can be reduced by about 50%. Since the radial force of the stator teeth is the main source of vibration and noise (NVH), the NVH caused by the cogging effect can be relatively reduced by about 50%. In an induction motor equipped with the rotor of the present application and an electric vehicle equipped with the induction motor, the user's comfort can be significantly improved, and the efficiency of the induction motor can be improved and the life of the induction motor can be extended.

[0036] Furthermore, since the radial force F2 generated in each groove 4 and directed in the opposite direction to the radial force F1 of the stator cancels the force of the corresponding stator tooth, it is preferable that each rotor tooth 2 is provided with the groove 4. This makes it possible to reduce the radial force of the stator in accordance with the number of grooves 4 provided (i.e., the number of rotor teeth), and thus to reduce NVH accordingly. However, the number of grooves 4 may be less than the number of rotor teeth 2, and in this case, the grooves 4 may be arranged so that the forces of the stator teeth are cancelled out, i.e., the grooves 4 may be provided symmetrically about the center line 10 of the rotor tooth 2.

[0037] Example 2 In this embodiment, the difference from embodiment 1 is that a gap 5 having the same function as the groove 4 is provided inside the rotor tooth 2, i.e., the gap 5 is provided inside the rotor tooth 2 and its position is close to the surface of the rotor tooth 2.

[0038] As shown in FIG. 3a, the gap 5 is provided inside the tip of the rotor tooth 2 so as to penetrate the rotor tooth 2. In this case, the gap 5 can change the size of the air gap, as described above. Specifically, when the rotor tooth 2 faces the stator pole (not shown), the air gap between the stator and the rotor becomes relatively small and the magnetic resistance becomes small, but due to the presence of the gap 5, an air gap corresponding to the air gap is generated inside the rotor tooth 2, so that the overall air gap becomes large and the overall change in the air gap is reduced. That is, contrary to the radial force F1 of the stator due to the facing of the rotor tooth 2 and the stator pole, a radial force F2 opposite to the radial force F1 of the stator tooth is generated due to the increase in the air gap caused by the gap 5, and the radial force acting on the stator tooth is reduced as described above, and as a result, the NVH can be reduced in the same manner.

[0039] The shape of the gap 5 may be, for example, a semi-ellipse (or semi-ring), a triangle, a rectangle, a trapezoid, an ellipse (or ring), or an irregular shape as shown in Fig. 4, in addition to the semi-circle as shown in Fig. 3b. The roles played by various shapes are similar.

[0040] For the rotor with the gap 5, according to the comparative diagram of the radial force of the stator without the gap and the radial force of the stator teeth with the gap shown in FIG. 5b, the radial force of the stator teeth is reduced from about 26-27N at the baseline to 17-18N on the right side, and the radial force is reduced by about 1 / 3. Since the radial force of the stator teeth is the main source of vibration and noise (NVH), it is possible to relatively reduce about 1 / 3 of the NVH caused by the cogging effect. Similarly, it is possible to improve the comfort of the user, improve the efficiency of the induction motor, and extend the life of the induction motor.

[0041] The number of gaps 5 is the same as that of the grooves 4 described above.

[0042] Modified Example Although the structure and advantages of the rotor and induction motor of the present application have been briefly described above, the rotor and induction motor of the present application are not limited to the above-mentioned embodiments, and various modified embodiments are possible. For example, as shown in Figs. 1a and 3a, the rotor slot 3 of the rotor of the present application is a closed slot (i.e., the rotor teeth 2 are connected to each other). The closed rotor slot 3 has a large leakage reactance and a small stray loss, which is advantageous for reducing vibration and noise, reducing the starting current, and reducing the cogging torque. However, the starting torque is reduced, and the power factor is reduced, and the starting performance is significantly affected by the shape of the rotor slot in particular. Therefore, the rotor of the present application can also be applied to a rotor in the form of an open slot, that is, the rotor teeth 2 are not connected to each other, and an opening is formed in the rotor slot 3. In this case, it is possible to provide a groove 4 in the rotor teeth 2 or a gap 5 inside the rotor teeth 2 as described above, and the same effects as those described above can be obtained.

[0043] Furthermore, the structure of the rotor provided with the grooves 4 or gaps 5 of the present application has been described above, but in addition to cast integral rotors, existing rotors are generally formed by stacking blanks manufactured from, for example, silicon steel plates. That is, the rotor of the present application can also be formed by stacking a plurality of rotor blanks. Therefore, the rotor blanks may also be provided with the grooves 4 or gaps 5 as described above, and when the rotor blanks are stacked to form the rotor of the present application, the provided grooves 4 or gaps 5 may be aligned. When the grooves 4 or gaps 5 are provided in each rotor tooth 2, the rotor teeth 2 may be aligned.

[0044] A rotor provided with the grooves 4 or gaps 5 of the present application, and an induction motor equipped with the rotor, can reduce the radial force of the stator due to the cogging effect, for example, by approximately 50%. Since the radial force of the stator teeth is the main source of vibration and noise (NVH), the NVH caused by the cogging effect can be relatively reduced by approximately 50%. In an induction motor equipped with the rotor of the present application, and in products such as electric vehicles equipped with the induction motor, the comfort for users can be significantly improved, the efficiency of the induction motor can be increased, and the life of the induction motor can be extended.

[0045] The above is merely an embodiment of the present application, and according to the above description, those skilled in the art can obtain various improvements or modifications based on the above embodiment. Those skilled in the art should understand that the above description is merely for better describing the present invention, and the protection scope of the present invention should be consistent with the protection scope of the claims. [Explanation of symbols]

[0046] 1 rotor body, 2 rotor teeth, 3 rotor slots, 4 grooves, 5 gaps, 10 rotor tooth centreline.

Claims

1. 1. An induction motor rotor comprising: a rotor body (1); rotor teeth (2) and rotor slots (3) arranged alternately around the circumference of the rotor body (1); and a plurality of grooves (4) at the ends of the rotor teeth (2) or a plurality of gaps (5) within the ends of the rotor teeth (2), the grooves (4) being arranged symmetrically about a centerline (10) of the rotor teeth (2).

2. 2. The induction motor rotor according to claim 1, characterized in that the number of grooves (4) or gaps (5) is less than the number of rotor teeth (2).

3. 2. An induction motor rotor according to claim 1, characterized in that each rotor tooth (2) is provided with said grooves (4) or said gaps (5).

4. 2. The induction motor rotor according to claim 1, characterized in that the shape of the grooves (4) is semicircular, semi-elliptical, triangular, rectangular, trapezoidal or other irregular shape.

5. 2. The induction motor rotor of claim 1, wherein the shape of the gap (5) is semicircular, semi-elliptical, triangular, rectangular, trapezoidal or other irregular shape.

6. 5. The induction motor rotor of claim 4, wherein at least some of the rotor teeth (2) are interconnected.

7. 6. An induction motor rotor as claimed in claim 5, characterized in that at least some of the rotor teeth (2) are interconnected.

8. 2. The induction motor rotor of claim 1, wherein the rotor slots (3) are open slots.

9. 1. An induction motor comprising an induction motor rotor, the induction motor rotor comprising a rotor body (1), rotor teeth (2) and rotor slots (3) arranged alternately around the circumference of the rotor body (1), and a number of grooves (4) at or within the ends of the rotor teeth (2) arranged symmetrically about a centerline (10) of the rotor teeth (2).

10. 10. The induction motor rotor according to claim 9, characterized in that the number of grooves (4) or gaps (5) is less than the number of rotor teeth (2).

11. 10. An induction motor rotor as claimed in claim 9, characterized in that each rotor tooth (2) is provided with said grooves (4) or said gaps (5).

12. 10. The induction motor rotor according to claim 9, characterized in that the shape of the grooves (4) is semicircular, semi-elliptical, triangular, rectangular, trapezoidal or other irregular shape.

13. 10. The induction motor rotor of claim 9, characterized in that the shape of the gap (5) is semicircular, semi-elliptical, triangular, rectangular, trapezoidal or other irregular shape.

14. 13. The induction motor rotor according to claim 12, characterized in that at least some of the rotor teeth (2) are interconnected.

15. 14. The induction motor rotor according to claim 13, characterized in that at least some of the rotor teeth (2) are interconnected.

16. An induction motor rotor as claimed in claim 9, characterized in that the rotor slots (3) are open slots.

17. 1. A rotor blank comprising: a blank body (1); rotor teeth (2) and rotor slots (3) arranged alternately around the circumference of the blank body (1); and a plurality of grooves (4) at the ends of the rotor teeth (2) or a plurality of gaps (5) within the ends of the rotor teeth (2), the grooves (4) being arranged symmetrically around a centerline (10) of the rotor teeth (2).

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