Permanent magnet motor

Abstract

To increase an output torque of an electric motor by reducing a leakage of magnetic flux generated from a permanent magnet to increase magnetic flux linkage with a stator coil.SOLUTION: A permanent magnet electric motor 1 comprises: a rotor 3 provided with a plurality of permanent magnets 31; and a stator 5 provided with teeth 53 and stator-side slots 55 and disposed with coils 57. A relationship Pa=|Ns-Pr| is established where Pa is the number of pole pairs of the stator coils, Ns is the number of teeth of the stator, and Pr is the number of pole pairs of the rotor. The permanent magnets 31 are disposed on an outer circumferential surface of a rotor core 35 that configures the rotor 3. Polarities of magnetization of the permanent magnets 31 are identical on the outer circumferential side of the rotor core 35. Between the permanent magnets 31 adjacent to each other in the circumferential direction of the rotor core 35, magnetic members having a permeability higher than a vacuum permeability are disposed. A magnetization direction of an end portion of the permanent magnet 31 in the circumferential direction of the rotor core is inclined to a magnetic pole center direction of the permanent magnet 31.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to permanent magnet motors. [Background technology]

[0002] A conventional PM type vernier motor is disclosed in Patent Document 1. In the vernier motor disclosed in Patent Document 1, permanent magnets are arranged in slots formed at equal intervals on the outer peripheral surface of a rotor core, and soft magnetic material such as iron, which is the material of the rotor core, is arranged between the permanent magnets, forming a so-called consequent pole type rotor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-207857 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional vernier motor described above, the magnetic flux generated by the permanent magnet leaks through the stator teeth, which reduces the magnetic flux linkage with the stator coil, making it impossible to increase the output torque of the motor.

[0005] Therefore, the present invention has been proposed in consideration of the above-mentioned circumstances, and has as its object to provide a permanent magnet motor that can increase the flux linkage with the stator coil by reducing leakage of magnetic flux generated from the permanent magnets, thereby increasing the output torque of the motor. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a permanent magnet electric motor according to one aspect of the present invention has a relationship Pa = |Ns - Pr| where Pa is the number of pole pairs of the stator coil, Ns is the number of teeth of the stator, and Pr is the number of pole pairs of the rotor. Multiple permanent magnets are arranged on the outer peripheral surface of a rotor core that constitutes the rotor, and the magnetization polarities of the multiple permanent magnets are the same on the outer peripheral surface side of the rotor core. Magnetic members having a magnetic permeability higher than that of a vacuum are arranged between adjacent permanent magnets in the circumferential direction of the rotor core. The magnetization direction of the permanent magnets at the ends in the circumferential direction of the rotor core is inclined toward the magnetic pole centers of the permanent magnets. [Effects of the Invention]

[0007] According to the present invention, by reducing leakage of magnetic flux generated from the permanent magnets, it is possible to increase the flux linkage with the stator coil and increase the output torque of the electric motor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing the structure of a permanent magnet motor according to a first embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of a permanent magnet provided in the permanent magnet electric motor according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing the results of calculations of the flow of magnetic flux lines in a conventional electric motor by finite element analysis. [Figure 4] FIG. 4 is a diagram showing the results of calculations of the flow of magnetic flux lines in the permanent magnet electric motor according to the first embodiment by finite element analysis. [Figure 5] FIG. 5 is a diagram showing the relationship between the angle formed by the magnetization direction and the tangent direction of the rotor core and the output torque in the permanent magnet electric motor according to the first embodiment. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a permanent magnet provided in a permanent magnet electric motor according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] A first embodiment of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and detailed description will be omitted.

[0010] Fig. 1 is a cross-sectional view showing the structure of a permanent magnet motor according to this embodiment. As shown in Fig. 1, permanent magnet motor 1 includes rotor 3 and stator 5. Here, permanent magnet motor 1 is a vernier motor, where the relationship Pa = |Ns - Pr| holds when the number of pole pairs of the coil of stator 5 is Pa, the number of teeth of stator 5 is Ns, and the number of pole pairs of rotor 3 is Pr.

[0011] The rotor 3 is disposed inside the stator 5, and is composed of a cylindrical rotor core 35 equipped with a plurality of permanent magnets 31 and fixed to a rotating shaft 33. Rotor-side slots 37 are formed at regular intervals in the circumferential direction on the outer circumferential surface of the rotor core 35, and the permanent magnets 31 are fixed in the rotor-side slots 37 with an adhesive.

[0012] Furthermore, salient pole portions 39 are disposed between adjacent permanent magnets 31. The salient pole portions 39 are portions formed in a convex shape by forming recesses in the rotor-side slots 37. Therefore, the salient pole portions 39 are formed from the material of the rotor core 35, for example, iron, and are formed from a magnetic member having a magnetic permeability higher than that of a vacuum. In other words, they are formed from a soft magnetic material.

[0013] With this configuration, when the outer peripheral surface of the permanent magnet 31 is the north pole, the salient pole portion 39 becomes the south pole, and the north and south poles are alternately formed on the outer peripheral surface of the rotor core 35, making the rotor 3 a consequent pole type rotor. However, the north and south poles may be of opposite polarity.

[0014] The stator 5 is composed of a cylindrical stator core 51 and is provided with teeth 53 and stator-side slots 55, with coils 57 arranged in the stator-side slots 55. A plurality of teeth 53 are formed at regular intervals on the inner peripheral surface of the stator core 51, with stator-side slots 55 arranged between adjacent teeth 53. A winding is wound around the teeth 53 in the circumferential direction, and the coils 57 are arranged in the stator-side slots 55.

[0015] Next, the detailed structure of the permanent magnet 31 will be described with reference to Fig. 2. Fig. 2 is an enlarged cross-sectional view of the permanent magnet 31. The permanent magnets 31 are arranged on the outer peripheral surface of the rotor core 35, and the magnetization polarity of the multiple permanent magnets 31 is the same on the outer peripheral surface side of the rotor core 35. In other words, the polarity on the outer peripheral surface side of the permanent magnets 31 is all either N pole or S pole.

[0016] Furthermore, the magnetization direction of the end of permanent magnet 31 in the circumferential direction of rotor core 35 is inclined toward the magnetic pole center of permanent magnet 31. As shown in Fig. 2, permanent magnet 31 is composed of multiple magnets 40, 42 divided in the circumferential direction of rotor core 35, and magnet 40 is fixed to the magnets 42 on both sides with an adhesive or the like. Of the multiple magnets, magnet 40 located at the circumferential center of rotor core 35 has a magnetization direction that is radial to rotor core 35 and faces outward, as indicated by arrow A1.

[0017] On the other hand, the magnetization direction of the magnets 42 located at the circumferential ends of the rotor core 35 is inclined toward the magnetic pole center of the permanent magnet 31, as shown by arrow A2. That is, the magnetization direction of the magnets 42 located at the ends is inclined at an angle θ toward the direction of the pole center axis 44. The pole center axis 44 is a line that passes through the magnetic pole center in the radial direction from the center of the rotation shaft 33, and the angle θ is the angle formed between the magnetization direction of the permanent magnet 31 at the end in the circumferential direction of the rotor core 35 and the tangent direction of the rotor core 35. A line 46 indicating the tangent direction of the rotor core 35 is obtained by moving a tangent to the outer peripheral surface of the rotor core 35, and is perpendicular to the pole center axis 44.

[0018] In this way, in this embodiment, the magnetization direction of the end of the permanent magnet 31 in the circumferential direction of the rotor core 35 is inclined toward the center of the magnetic pole, thereby reducing leakage of magnetic flux generated from the permanent magnet 31.

[0019] Here, the effect of reducing magnetic flux leakage by the permanent magnet motor 1 according to this embodiment will be described with reference to Figures 3 and 4. Figure 3 is a diagram showing the results of calculations using finite element analysis of the flow of magnetic flux lines within a conventional consequent-pole motor when no load is applied. The closed curves in the figure represent magnetic flux lines. Meanwhile, Figure 4 is a diagram showing the results of calculations using finite element analysis of the flow of magnetic flux lines within the permanent magnet motor 1 according to this embodiment when no load is applied.

[0020] As shown in FIG. 3, in a conventional consequent-pole motor, a rotor 60 includes permanent magnets 62, and salient pole portions 64 made of iron or the like are disposed between adjacent permanent magnets 62. In the conventional motor, as shown by the circled portions in FIG. 3, many of the magnetic flux lines passing through the salient pole portions 64 return to the rotor 60 at the teeth 66 and leak. This shows that the number of magnetic flux lines passing through the stator 68 is reduced. Therefore, in the conventional motor, the leakage flux reduces the magnetic flux flowing to the stator 68, reducing the magnetic flux linkage with the coils 70 provided in the stator 68, making it impossible to increase the motor's output torque.

[0021] In contrast, in the permanent magnet motor 1 according to this embodiment, as shown in the circled areas in Figure 4, most of the magnetic flux lines that pass through the salient pole portions 39 flow into the stator 5 without leaking back to the rotor 3 side. This shows that a large number of magnetic flux lines pass through the stator 5. Therefore, in the permanent magnet motor 1 according to this embodiment, leakage magnetic flux is reduced and the magnetic flux flowing into the stator 5 is increased, which increases the magnetic flux linkage with the coils 57 provided in the stator 5 and enables the output torque of the motor to be increased.

[0022] 2, the width L1 of the permanent magnet 31 in the circumferential direction of the rotor core 35 is larger than the width L2 of the salient pole portion 39 in the circumferential direction of the rotor core 35. The salient pole portion 39 is made of a magnetic material, and when made of an electromagnetic steel sheet generally used in motors, the saturation magnetic flux density of the salient pole portion 39 is high relative to the residual magnetization of the permanent magnet 31. Therefore, the width L2 of the salient pole portion 39 in the circumferential direction of the rotor core 35 can be made smaller than the width L1 of the permanent magnet 31 in the circumferential direction of the rotor core 35. This allows the width L1 of the permanent magnet 31 in the circumferential direction of the rotor core 35 to be larger, thereby increasing the surface area of ​​the permanent magnet 31 and increasing the magnetic flux linkage with the coil 57.

[0023] On the other hand, if the width L1 of the permanent magnet 31 in the circumferential direction of the rotor core 35 is made larger than the width L2 of the salient pole portion 39 in the circumferential direction of the rotor core 35, leakage magnetic flux would increase through the magnetic members, suppressing an increase in the number of flux linkages. However, in the permanent magnet electric motor 1 according to this embodiment, the magnetization direction of the end of the permanent magnet 31 in the circumferential direction of the rotor core 35 is inclined toward the center of the magnetic pole, thereby significantly reducing leakage magnetic flux. This effectively increases the surface area of ​​the permanent magnet 31 and increases the flux linkage with the coil 57. Note that the portion of the permanent magnet 31 where the magnetization direction is inclined is limited relative to the entire permanent magnet 31, so the impact of reducing the amount of magnetic flux in this portion is sufficiently small.

[0024] Next, with reference to Fig. 5, the relationship between the angle θ shown in Fig. 2 and the output torque of the permanent magnet motor 1 will be described. As shown in Fig. 2, the angle θ is the angle formed between the magnetization direction of the magnet 42 and the tangential direction of the rotor core 35. Therefore, when the angle θ is 90 degrees, the magnetization direction is perpendicular to the tangential direction, and, as with conventional motors, the magnetization direction of the magnet 42 is in the radial direction of the rotor core 35 without being inclined toward the magnetic pole center.

[0025] As shown in Figure 5, when the angle θ is 90 degrees, the magnetization direction of the magnet 42 is not tilted, so the output torque is minimum. Then, when the magnetization direction of the magnet 42 is gradually tilted and the angle θ is reduced from 90 degrees, the output torque of the permanent magnet motor 1 increases as the angle θ decreases. In other words, the output torque of the permanent magnet motor 1 increases as the magnetization direction of the magnet 42 is tilted more. As a result, it can be seen that the output torque of the permanent magnet motor 1 is maximum when the angle θ is 10 degrees, and the output torque increases sufficiently at angles θ of 30 degrees or more.

[0026] [Effects of the first embodiment] As described above in detail, in the permanent magnet electric motor 1 according to this embodiment, the magnetization direction of the end of the permanent magnet 31 in the circumferential direction of the rotor core 35 is inclined toward the magnetic pole center of the permanent magnet 31. This reduces leakage of magnetic flux generated from the permanent magnet 31, thereby increasing the flux linkage with the stator coil and increasing the output torque of the electric motor.

[0027] Furthermore, in the permanent magnet motor 1 according to this embodiment, the permanent magnet 31 is composed of a plurality of magnets 40, 42 divided in the circumferential direction of the rotor core 35. Of the plurality of magnets, the magnetization direction of the magnet 40 located at the circumferential center of the rotor core 35 is in the radial direction of the rotor core 35. Meanwhile, the magnetization direction of the magnet 42 located at the circumferential end of the rotor core 35 is inclined toward the magnetic pole center of the permanent magnet. This allows the magnetization direction of the end of the permanent magnet 31 in the circumferential direction of the rotor core 35 to be inclined toward the magnetic pole center of the permanent magnet 31 using a plurality of magnets. This reduces leakage of magnetic flux generated from the permanent magnet 31, thereby increasing the flux linkage with the stator coil and increasing the output torque of the motor.

[0028] Furthermore, in the permanent magnet motor 1 according to this embodiment, the angle formed between the magnetization direction of the end of the permanent magnet 31 in the circumferential direction of the rotor core 35 and the tangential direction of the rotor core 35 is set to 30 degrees or less. This maximizes the output torque of the motor.

[0029] Furthermore, in the permanent magnet motor 1 according to this embodiment, the width of the permanent magnets 31 in the circumferential direction of the rotor core 35 is made larger than the width of the magnetic members arranged between the permanent magnets 31 in the circumferential direction of the rotor core 35. This increases the surface area of ​​the permanent magnets 31, thereby increasing the magnetic flux linkage with the stator coil and increasing the output torque of the motor.

[0030] [Second embodiment] A second embodiment of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and detailed description will be omitted.

[0031] The permanent magnet motor 1 according to this embodiment differs from the first embodiment in that the permanent magnet 31 is not formed by combining a plurality of magnets, but is formed by a single magnet.

[0032] 6, the magnetization direction of permanent magnet 31, indicated by arrow A3, is inclined toward the magnetic pole center of permanent magnet 31. The angle θ that the magnetization direction indicated by arrow A3 forms with the tangent direction of rotor core 35 increases from the circumferential end of rotor core 35 of permanent magnet 31 toward the magnetic pole center. That is, the magnetization direction indicated by arrow A3 is inclined greatly at the circumferential end because the angle θ is small, but the angle θ increases toward the magnetic pole center, so that near the magnetic pole center, the magnetization direction is in the radial direction of rotor core 35 and faces outward.

[0033] By using a permanent magnet 31 as shown in Figure 6, with one magnet, the magnetization direction near the magnetic pole center of permanent magnet 31 can be oriented in the radial direction of rotor core 35, and the magnetization direction at the circumferential end of rotor core 35 can be inclined toward the magnetic pole center.

[0034] The permanent magnet 31 shown in FIG. 6 can be produced by magnetizing a magnet whose magnetic anisotropy can be controlled as desired and whose axis of easy magnetization is as shown by arrow A3 in FIG.

[0035] [Effects of the second embodiment] As described above in detail, in the permanent magnet electric motor 1 according to this embodiment, the angle formed between the magnetization direction of the permanent magnet 31 and the tangential direction of the rotor core 35 increases from the end of the permanent magnet 31 in the circumferential direction of the rotor core 35 toward the magnetic pole center. This makes it possible for a single magnet to have the magnetization direction of the permanent magnet 31 oriented in the radial direction of the rotor core 35 near the magnetic pole center of the permanent magnet 31, and to have the magnetization direction inclined toward the magnetic pole center at the end of the rotor core 35 in the circumferential direction. This reduces manufacturing costs and reduces leakage magnetic flux, thereby increasing the magnetic flux linkage with the stator coil and increasing the output torque of the electric motor.

[0036] The above-described embodiment is merely an example of the present invention, and therefore the present invention is not limited to the above-described embodiment, and various modifications can be made to the design and other aspects of the present invention without departing from the technical concept of the present invention. [Explanation of symbols]

[0037] 1 Permanent magnet electric motor 3.60 rotor 5, 68 Stator 31, 62 Permanent magnets 33 Rotation axis 35 rotor core 37 Rotor side slot 39, 64 salient pole part 40, 42 Magnets 44 Polar center axis 46 Tangent direction line 51 stator core 53, 66 teeth 55 Stator side slot 57, 70 coils

Claims

1. A permanent magnet motor comprising: a rotor provided with a plurality of permanent magnets; and a stator provided with teeth and slots in which coils are arranged, wherein when the number of pole pairs of the coils of the stator is Pa, the number of teeth of the stator is Ns, and the number of pole pairs of the rotor is Pr, the relationship Pa = |Ns - Pr| holds; the plurality of permanent magnets are arranged on an outer peripheral surface of a rotor core that constitutes the rotor, and the magnetization polarities of the plurality of permanent magnets are the same on the outer peripheral surface side of the rotor core; a magnetic member formed of a soft magnetic material and having a magnetic permeability higher than that of a vacuum is disposed between the permanent magnets adjacent to each other in the circumferential direction of the rotor core; A permanent magnet motor, wherein the magnetization direction of the end of the permanent magnet in the circumferential direction of the rotor core is inclined toward the magnetic pole center of the permanent magnet.

2. The permanent magnet is composed of a plurality of magnets divided in the circumferential direction of the rotor core, Among the plurality of magnets, the magnet located at the circumferential center of the rotor core has a magnetization direction that is a radial direction of the rotor core, 2. The permanent magnet motor according to claim 1, wherein the magnetization direction of the magnets located at the circumferential ends of the rotor core is inclined toward the magnetic pole center of the permanent magnet.

3. 2. The permanent magnet electric motor according to claim 1, wherein the magnetization direction of the permanent magnet is inclined toward a magnetic pole center of the permanent magnet, and the angle formed between the magnetization direction and a tangential direction of the rotor core increases from an end of the permanent magnet in the circumferential direction of the rotor core toward the magnetic pole center.

4. The permanent magnet electric motor according to any one of claims 1 to 3, wherein an angle formed between the magnetization direction of the end of the permanent magnet in the circumferential direction of the rotor core and the tangential direction of the rotor core is 30 degrees or less.

5. A permanent magnet motor according to any one of claims 1 to 4, wherein the width of the permanent magnets in the circumferential direction of the rotor core is larger than the width of the magnetic members arranged between the permanent magnets in the circumferential direction of the rotor core.

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