Permanent magnet motor capable of reducing cogging torque ripple

Abstract

A permanent magnet motor capable of reducing cogging torque pulsation, comprising a stator part, a permanent magnet, and a rotor part, the rotor part is mounted at the center of the stator part, and an air gap is formed between the outer circumferential surface of the rotor part and the inner arc surface of the stator part, the cross section of the permanent magnet is an isosceles trapezoid, the permanent magnet is fixed in the rotor part, and the center line of the permanent magnet coincides with the radial line of the rotor part, the paths of the magnetic field lines of the permanent magnet are distributed symmetrically on both sides of the center line of the permanent magnet, and the left and right sides of the trapezoid of the permanent magnet form 90° included angles with the center line of the permanent magnet, respectively. The present invention can reduce the cogging torque pulsation of the permanent magnet motor, reduce vibration and noise caused by the cogging torque pulsation, reduce fluctuations in rotation speed, and make the operation of the permanent magnet motor smoother by changing the shape of the permanent magnet.

Description

Technical Field

[0001] The present invention relates to a permanent magnet motor, and more particularly to a permanent magnet motor capable of reducing cogging torque ripple.

Background Art

[0002] As shown in FIGS. 1 to 3, a conventional permanent magnet motor generally includes a stator component, a permanent magnet, and a rotor component. The cross section of the permanent magnet used therein is basically a rectangular structure. The permanent magnets are N-pole permanent magnets and S-pole permanent magnets. The N-pole permanent magnets and the S-pole permanent magnets are alternately fixed in the rotor component. There is a large cogging torque ripple in the permanent magnet motor. Due to the cogging torque ripple, the permanent magnet motor generates vibration and noise, and the rotational speed fluctuates, so that the permanent magnet motor cannot operate smoothly, which affects the performance of the permanent magnet motor. In particular, in variable speed drive, when the frequency of the cogging torque ripple coincides with the mechanical resonance frequency of the stator or the rotor, the vibration and noise generated by the cogging torque will be further amplified. Similarly, due to the presence of the cogging torque ripple, the low-speed performance of the permanent magnet motor in the speed control system and the high-precision positioning of the permanent magnet motor in the position control system are also affected.

Summary of the Invention

Problems to be Solved by the Invention

[0003] In view of the above-mentioned drawbacks of the prior art, the problem to be solved by the present invention is to provide a permanent magnet motor having smaller cogging torque ripple and vibration noise and capable of reducing the cogging torque ripple.

Means for Solving the Problems

[0004] As a technical means adopted by the present invention to solve the above problems, there is a permanent magnet motor capable of reducing cogging torque pulsation, including a stator component, a permanent magnet, and a rotor component. The rotor component is attached to the center of the stator component, and an air gap is formed by the outer peripheral surface of the rotor component and the inner arc surface of the stator component. In the permanent magnet motor, the cross section of the permanent magnet is an isosceles trapezoid. The permanent magnet is fixed within the rotor component, and the center line of the permanent magnet coincides with the radius line of the rotor component. The path of the magnetic force lines of the permanent magnet is symmetrically distributed on both sides of the center line with the center line of the permanent magnet as a reference, and forms an included angle of 90° with the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet respectively. The trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet each form an included angle with the center line of the permanent magnet. It is a permanent magnet motor capable of reducing cogging torque pulsation, characterized by the above.

[0005] Preferably, the included angle is 5 to 20°, and most preferably, it is 8°.

[0006] Preferably, the permanent magnet is fixed within the trapezoidal slot of the rotor component.

[0007] Preferably, at the top and bottom of the trapezoidal slot of the rotor component, in order to play a role in magnetic shielding and reduce magnetic flux leakage, a top window and a bottom window are respectively provided.

[0008] Preferably, the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet are closely fixed to the left side surface and the right side surface of the trapezoidal slot of the rotor component respectively.

[0009] Preferably, the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet are respectively pasted to the left side surface and the right side surface of the trapezoidal slot of the rotor component through an adhesive.

[0010] Preferably, the permanent magnet has a split structure, is split along the center line, and is composed of a left part of the permanent magnet and a right part of the permanent magnet. In this way, the manufacturing becomes easier.

[0011] More specifically, the permanent magnets are an N-pole permanent magnet and an S-pole permanent magnet, and the N-pole permanent magnet and the S-pole permanent magnet are alternately fixed within the rotor component.

Advantages of the Invention

[0012] Compared with the prior art, the advantages of the present invention are as follows. By changing the shape of the permanent magnet, the path of the magnetic force lines is symmetrically distributed on both sides of the center line with respect to the center line of the permanent magnet, and forms a 90° included angle with the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet respectively. Since the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet form an included angle with the center line of the permanent magnet, the cogging torque ripple of the permanent magnet motor can be reduced, the vibration and noise caused by the cogging torque ripple can be reduced, the fluctuation of the rotational speed can be reduced, the operation of the permanent magnet motor can be made smoother, and the low-speed performance of the permanent magnet motor in the speed control system and the high-precision positioning of the permanent magnet motor in the position control system can be improved.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5a

Figure 5b

Figure 6

Figure 7

Figure 8a

Figure 8b

Figure 9

Figure 10

Figure 11

Mode for Carrying Out the Invention

[0014] Hereinafter, the present invention will be further described in conjunction with the drawings and embodiments.

[0015] Embodiment 1 As shown in FIGS. 4 and 5, a permanent magnet motor capable of reducing cogging torque pulsation includes a stator component 10, an N-pole permanent magnet 20, an S-pole permanent magnet 30, and a rotor component 40.

[0016] The rotor component 40 is attached to the center of the stator component 10, and an air gap is formed by an outer peripheral surface 405 provided on the rotor component and an inner arc surface 101 provided on the stator component.

[0017] The N-pole permanent magnet 20 has an isosceles trapezoidal cross-section, and its left side surface 201 and right side surface 202 are respectively fixed in close contact with the left side surface and the right side surface of the trapezoidal slot provided on the rotor component. If an adhesive is used for close contact, the N-pole permanent magnet will be more firmly fixed in the trapezoidal slot of the rotor component.

[0018] The above-mentioned N-pole permanent magnet 20 is fixed in the trapezoidal slot of the rotor component, and the center line C of the N-pole permanent magnet coincides with the radius line R of the rotor component.

[0019] The path of the magnetic flux lines W of the above-mentioned N-pole permanent magnet is symmetrically distributed on both sides of the center line C with the center line C of the N-pole permanent magnet as the reference, and forms an included angle of 90° with the trapezoidal left side surface and the trapezoidal right side surface of the N-pole permanent magnet respectively. The direction of the path of the magnetic flux lines W is determined by the magnetization direction.

[0020] The included angle between each of the trapezoidal left side surface 201 and the trapezoidal right side surface 202 of the above-mentioned N-pole permanent magnet and the center line C of the permanent magnet is L, and the included angle L in this embodiment is 8°.

[0021] Similarly, except that the direction of the path of the magnetic flux lines W, that is, the magnetization direction, of the S-pole permanent magnet 30 is opposite to that of the N-pole permanent magnet, the remaining structures are all the same as those of the N-pole permanent magnet, and are fixed to the rotor component in the same manner.

[0022] The included angle between each of the trapezoidal left side surface 301 and the trapezoidal right side surface 302 of the above-mentioned S-pole permanent magnet and the center line C of the permanent magnet is L, and the included angle L in this embodiment is 8°.

[0023] As shown in FIG. 6, in the permanent magnet motor capable of reducing the cogging torque ripple described above, the magnetic flux lines W of the N-pole permanent magnet enter the rotor component from the trapezoidal left side surface, flow through the rotor component and then flow into the air gap, flow through the air gap and then enter the inner arc surface of the stator component, further flow through the stator component and then flow into the inner arc surface, flow through the air gap again and then enter the rotor component, and return to the trapezoidal right side surface of the N-pole permanent magnet, forming a complete distribution of the magnetic flux line loop.

[0024] Similarly, except that the magnetic flux lines of the S-pole permanent magnet enter the rotor component from the trapezoidal right side surface of the S-pole permanent magnet and finally return to the trapezoidal left side surface of the S-pole permanent magnet, which is different from the distribution of the magnetic flux line loop of the N-pole permanent magnet, the remaining distributions of the magnetic flux lines are all the same as those of the N-pole permanent magnet.

[0025] As shown in FIGS. 10 and 11, in a conventional permanent magnet motor, the cross section of the permanent magnet is rectangular, and the maximum peak value Tmax = 2.954 N·m in the waveform of the cogging torque ripple of the motor. On the other hand, in a permanent magnet motor capable of reducing the cogging torque ripple according to Embodiment 1, the included angles between each of the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet and the center line C of the permanent magnet are 8°, and the maximum peak value Tmax = 0.545 N·m in the waveform of the cogging torque ripple of the motor. The reduction rate of the cogging torque ripple is: reduction rate of cogging torque ripple = (2.954 - 0.545) ÷ 2.954 × 100% = 81.55%. The reduction of the cogging torque ripple of the permanent magnet motor is realized, the vibration and noise caused by the cogging torque ripple are reduced, the fluctuation of the rotation speed is reduced, the operation of the motor becomes smooth, the low-speed performance of the motor in the speed control system and the high-precision positioning of the motor in the position control system are improved, and the usage requirements are satisfied.

[0026] The present invention also examines the included angle L between each of the trapezoidal left side surface and the trapezoidal right side surface of the permanent magnet and the center line C of the permanent magnet. Regarding the time change diagram of the motor cogging torque ripple in this embodiment, reference is made to FIG. 11. Regarding the relationship between the change of the included angle L and the motor cogging torque ripple, reference is made to Table 1. As can be seen from Table 1, the included angle is preferably 5 to 20°, and most preferably 8°.

[0027] Table 1 Relationship table between the included angle L between the trapezoidal left side surface / right side surface of the permanent magnet and the center line and the motor cogging torque ripple JPEG0007700380000001.jpg68170

[0028] Embodiment 2 As shown in FIGS. 7 to 9, another permanent magnet motor capable of reducing the cogging torque ripple has a split-type permanent magnet, and other structures are exactly the same as those of the permanent magnet motor of Embodiment 1.

[0029] More specifically, the permanent magnet is divided into an N - pole permanent magnet and an S - pole permanent magnet. The N - pole permanent magnet is composed of a left part 20A of the N - pole permanent magnet and a right part 20B of the N - pole permanent magnet. The S - pole permanent magnet is composed of a left part 30A of the S - pole permanent magnet and a right part 30B of the S - pole permanent magnet.

[0030] As shown in FIG. 8a, the above - mentioned split - type N - pole permanent magnet is split along its center line, and the left part 20A of the N - pole permanent magnet and the right part 20B of the N - pole permanent magnet are adhered. The magnetization direction of the left part of the N - pole permanent magnet is from the center line C towards the left trapezoidal side 20A1, forming a 90° angle with the left trapezoidal side 20A1. The left trapezoidal side 20A1 forms an angle L with the center line C. The magnetization direction of the right part of the N - pole permanent magnet is from the right trapezoidal side 20B1 towards the center line C, forming a 90° angle with the right trapezoidal side. The right trapezoidal side forms an angle L with the center line. According to such a structure, magnetization of the left part and the right part of the N - pole permanent magnet becomes easier.

[0031] Similarly, the above - mentioned split - type S - pole permanent magnet 30 is split along its center line, and the left part 30A of the S - pole permanent magnet and the right part 30B of the S - pole permanent magnet are adhered. Except that the magnetization direction is reversed, the remaining structure is exactly the same as that of the left part and the right part of the N - pole permanent magnet.

[0032] As shown in FIG. 8b, the magnetization direction of the left part of the above - mentioned split - type S - pole permanent magnet is from the left trapezoidal side 30A1 towards the center line C, forming a 90° angle with the left trapezoidal side 30A1. The left trapezoidal side 30A1 forms an angle L with the center line C. The magnetization direction of the right part of the S - pole permanent magnet is from the center line C towards the right trapezoidal side 30B1, forming a 90° angle with the right trapezoidal side 30B1. The right trapezoidal side forms an angle L with the center line C. According to such a structure, magnetization of the left part and the right part of the N - pole permanent magnet becomes easier.

[0033] Regarding the magnetic - force line distribution of the above - mentioned permanent - magnet motor, please refer to FIG. 9, which is exactly the same as that in Example 1.

[0034] The performance of the above permanent magnet motor is the same as that of Example 1.

[0035] It should be noted that the azimuth characters such as left and right indicating the directions referred to in this embodiment and the documents of this application, and the terms including such azimuth characters are used only for the convenience of explanation, and are related only to the specific azimuth determined during the description, and do not limit the content and protection scope of the present invention.

Claims

1. A permanent magnet motor capable of reducing cogging torque pulsation, comprising a stator component, a permanent magnet, and a rotor component, wherein the rotor component is attached to the center of the stator component, and an air gap is formed by the outer peripheral surface of the rotor component and the inner arc surface of the stator component. In the permanent magnet motor, the cross section of the permanent magnet is an isosceles trapezoid, the permanent magnet is fixed within the rotor component, and the center line of the permanent magnet coincides with the radius line of the rotor component. The path of the magnetic force lines of the permanent magnet is symmetrically distributed on both sides of the center line with respect to the center line of the permanent magnet, and forms an included angle of 90° with the left trapezoidal surface and the right trapezoidal surface of the permanent magnet respectively. The left trapezoidal surface and the right trapezoidal surface of the permanent magnet each form an included angle with the center line of the permanent magnet. A permanent magnet motor capable of reducing cogging torque pulsation, characterized by the above.

2. The included angle formed by the left trapezoidal surface and the right trapezoidal surface of the permanent magnet and the center line of the permanent magnet is 10 to 45°. A permanent magnet motor capable of reducing cogging torque pulsation according to Claim 1, characterized by the above.

3. The included angle formed by the left trapezoidal surface and the right trapezoidal surface of the permanent magnet and the center line of the permanent magnet is 18°. A permanent magnet motor capable of reducing cogging torque pulsation according to Claim 2, characterized by the above.

4. The permanent magnet is fixed within the trapezoidal slot of the rotor component. A permanent magnet motor capable of reducing cogging torque pulsation according to Claim 1, characterized by the above.

5. The left trapezoidal surface and the right trapezoidal surface of the permanent magnet are closely fixed to the left side surface and the right side surface of the trapezoidal slot of the rotor component respectively. A permanent magnet motor capable of reducing cogging torque pulsation according to Claim 4, characterized by the above.

6. The left trapezoidal surface and the right trapezoidal surface of the permanent magnet are attached to the left side surface and the right side surface of the trapezoidal slot of the rotor component respectively through an adhesive. A permanent magnet motor capable of reducing cogging torque pulsation according to Claim 5, characterized by the above.

7. A top window and a bottom window are respectively provided at the top and the bottom of the trapezoidal slot of the rotor component. A permanent magnet motor capable of reducing cogging torque pulsation according to Claim 4, characterized by the above.

8. The permanent magnet motor capable of reducing cogging torque pulsation according to claim 1, wherein a top window and a bottom window are respectively provided at the top and the bottom of the trapezoidal slot of the rotor component.

9. The permanent magnet motor capable of reducing cogging torque pulsation according to claim 1, wherein the permanent magnet has a split structure, is split along the center line, and is composed of a left part of the permanent magnet and a right part of the permanent magnet.

10. The permanent magnet motor capable of reducing cogging torque pulsation according to claim 1, wherein the permanent magnet is an N-pole permanent magnet and an S-pole permanent magnet, and the N-pole permanent magnet and the S-pole permanent magnet are alternately fixed in the rotor component.

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