Rotor and permanent magnet type motor generator provided with the same

Abstract

To provide a rotor for use in a permanent magnet type motor generator in which a gap magnetic flux density is converted into a sine wave.SOLUTION: A rotor includes a shaft, a rotary member bonded to the shaft, and a magnet that has a curved shape and is disposed in an outer circumferential portion of the rotary member so as to project toward the shaft. The magnet has two side surfaces which are parallel with the center axis of the shaft, an inner circumferential surface, and an outer circumferential surface, and is oriented in such a way that the easy-magnetization axis forms an arc shape in a cross section F along a direction perpendicular to the center axis of the shaft, and the arc is a part of a concentric circle. When the center point of the concentric circle is defined as a point A, a point indicating the boundary between one of the side surfaces and the outer circumferential surface is defined as a point B, and a point indicating the boundary between one of the side surfaces and the inner circumferential surface is defined as a point C, an angle α formed between a straight line L1 that is a straight line connecting the point A and the point B and a straight line L2 that is a straight line connecting the point B and the point C ranges from 3 to 15 degrees.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rotor and a permanent magnet type motor generator having the rotor. [Background technology]

[0002] Conventionally, rotors, magnets used therein, and motors including the same have been proposed.

[0003] For example, Patent Document 1 describes a rotor comprising a rotor core rotatable about a central axis, and a rotor magnet fixed to the outer peripheral surface of the rotor core, the rotor magnet having a plurality of magnetized portions arranged circumferentially in a Halbach array, the plurality of magnetized portions including a plurality of radially magnetized portions whose magnetization direction is radial, and a plurality of non-radially magnetized portions whose magnetization direction is different from the radial direction, the rotor core having a hole portion recessed from a surface on one axial side of the rotor core to the other axial side, and being a non-magnetic member made of a non-magnetic material, the hole portion being located radially inside the radially magnetized portion.

[0004] Patent Document 2 describes a Halbach array rotor comprising a rotor having an annular permanent magnet and a support that supports the permanent magnet from the radially inner side, in which the permanent magnet is magnetized in a Halbach array along a plane perpendicular to the axial direction of the rotor, and the support has a plurality of air gaps formed therein that are aligned around the axis of the rotor.

[0005] Patent document 3 also describes a polar anisotropic magnet having the following configuration: (1) the polar anisotropic magnet is made of a solid magnet, (2) the polar anisotropic magnet has a magnetic pole boundary surface parallel to the z-axis, and (3) the polar anisotropic magnet has an orientation region in which the magnetization easy axis is oriented in an arc-like and concentric manner on the xy plane.

[0006] Patent Document 4 describes a permanent magnet motor comprising a rotor yoke rotatably provided on the outside of a stator and configured in an approximately cylindrical shape, and an anisotropic magnet arranged on the inner circumference of the rotor yoke so as to have multiple magnetic poles and formed so that the surface facing the stator is curved, wherein the portion constituting one magnetic pole of the anisotropic magnet is formed so that the radial thickness at both ends is 0.4 to 0.8 times the radial thickness at the center, and the center of orientation within the magnetic pole is shifted from the center of rotation toward the magnet. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2020 / 195006 [Patent Document 2] JP 2020-129888 A [Patent Document 3] JP 2018-38162 A [Patent Document 4] JP 2006-94604 A Summary of the Invention [Problem to be solved by the invention]

[0008] In a permanent magnet motor generator, it is preferable that the gap magnetic flux density between the stator and rotor be sinusoidal (close to a sine wave). This is expected to reduce iron loss and torque pulsation, which is the source of vibration and noise, by reducing cogging torque.

[0009] An object of the present invention is to provide a permanent magnet type motor generator in which the gap magnetic flux density is made sinusoidal, and a rotor that can be used therefor. [Means for solving the problem]

[0010] The present invention relates to the following (1) to (5). (1) a shaft; A rotating member joined to the shaft; a magnet arranged within the outer periphery of the rotating member so as to be curved and convex toward the shaft; A rotor having The magnet is The shaft has two side surfaces parallel to a central axis thereof, and an inner peripheral surface and an outer peripheral surface, In a cross section F perpendicular to the central axis of the shaft, the axis of easy magnetization is oriented to form an arc, the arc being a part of a concentric circle, and the center point of the concentric circle is point A; In the cross section F, when a point indicating a boundary between one of the side surfaces and the outer peripheral surface is defined as point B, and a point indicating a boundary between one of the side surfaces and the inner peripheral surface is defined as point C, a straight line L which is a straight line connecting point A and point B is defined as point B. 1 and the line L that connects points B and C. 2 A rotor having an angle α of 3 to 15 degrees. (2) The rotor according to (1) above, wherein in the cross section F, the side surface of the magnet forms an outwardly convex curve. (3) At the cross section F, the curve is a straight line L 1 and the line L 2 The rotor according to (2) above, which is located between (4) The rotor according to (1) or (2) above is used as an inner rotor, The permanent magnet motor generator further comprises an outer stator having a central through hole into which the inner rotor is inserted. (5) The outer stator is A permanent magnet type motor generator as described in (4) above, in which a plurality of teeth that form the iron core of the armature coil are arranged radially, and a coil is wound around the teeth. Effect of the Invention

[0011] According to the present invention, it is possible to provide a permanent magnet type motor generator in which the gap magnetic flux density is made sinusoidal, and a rotor that can be used therefor. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram (schematic diagram) showing a cross section (defined as cross section F) of a rotor of the present invention cut in a direction perpendicular to the central axis of a shaft. [Diagram 2] FIG. 2 is an enlarged (schematic) view of one of the magnets 10 of the present invention shown in FIG. [Diagram 3] FIG. 3 is an enlarged (schematic) view showing a preferred embodiment of magnet 10 of the present invention. [Figure 4] FIG. 4 shows a cross section (schematic diagram) of the motor generator of the present invention taken in a direction perpendicular to the central axis of the shaft of the rotor of the present invention. [Diagram 5] 1 is a diagram (graph) showing the relationship between mechanical angle (deg) and magnetic flux density (T) measured in an example. [Figure 6] 1 is a diagram (graph) showing the relationship between the mechanical angle (deg) and the line-to-line induced voltage (V) measured in an example. [Figure 7] 1 is a diagram (graph) showing the relationship between angle α and induced voltage waveform THD (%) measured in an example. [Figure 8] 1 is a diagram (graph) showing the relationship between angle α and cogging torque (mNm) measured in an example. [Figure 9] FIG. 2 is a diagram (schematic diagram) showing a side view of a motor measurement device used in the examples, in which a dynamo motor and a test motor are connected on one axis with a torque meter sandwiched between them. [Figure 10] Fig. 10(a) is a graph showing the relationship between the angle α and the induced voltage or torque reduction rate when the distance R is changed. Fig. 10(b) is a graph showing the relationship between the angle α and the induced voltage or torque reduction rate when the distance DR is changed. [Figure 11]Fig. 11(a) is a graph showing the relationship between the angle α and the cogging torque when the distance DR is changed. Fig. 11(b) is a graph showing the relationship between the angle α and the cogging torque when the distance R is changed. Note that the cogging torque on the vertical axis in Figs. 8 and 11 corresponds to the result of calculating the difference between the maximum and minimum of the cogging torque waveform. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will now be described. The present invention relates to a rotor having a shaft, a rotating member joined to the shaft, and a magnet arranged in an outer periphery of the rotating member so as to be curved and convex toward the shaft, the magnet has two side surfaces parallel to the central axis of the shaft, as well as an inner circumferential surface and an outer circumferential surface, the magnet has an easy axis of magnetization oriented to form an arc in a cross section F perpendicular to the central axis of the shaft, the arc being a part of a concentric circle, the center point of the concentric circle being point A, a point indicating the boundary between one of the side surfaces and the outer circumferential surface in the cross section F being point B, and a point indicating the boundary between one of the side surfaces and the inner circumferential surface being point C, the straight line L connecting point A and point B being a straight line L. 1 and the line L that connects points B and C. 2 The rotor has an angle α of 3 to 15 degrees. Such a rotor will hereinafter be referred to as the "rotor of the present invention."

[0014] Moreover, the magnet possessed by the rotor of the present invention will hereinafter be referred to as the "magnet of the present invention."

[0015] The present invention also provides a permanent magnet type motor generator having the rotor of the present invention as an inner rotor, and further having an outer stator with the inner rotor inserted into a central through hole. Such a permanent magnet type motor generator will hereinafter be referred to as the "motor generator of the present invention."

[0016] The rotor of the present invention will be described with reference to the drawings. FIG. 1 shows a cross section (defined as cross section F) of a rotor of the present invention cut in a direction perpendicular to the central axis of a shaft. Note that the figures used below, including FIG. 1, show examples of the rotor of the present invention or the motor-generator of the present invention including the rotor of the present invention, and the rotor of the present invention and the motor-generator of the present invention are not limited to the aspects shown in the figures.

[0017] The rotor 1 of the present invention comprises a shaft 2, a rotating member 4, and a magnet 10 of the present invention.

[0018] The shaft 2 is a rotating shaft located at the center of the rotor 1 of the present invention.

[0019] The rotating member 4 is joined to the shaft 2 . The rotating member 4 can be made of a non-magnetic material. Examples of non-magnetic materials that form the rotating member 4 include titanium, aluminum, resin, ceramics, and CFRP. In the present invention, the rotating member is preferably made of a non-magnetic material from the viewpoint of effectively utilizing the GAP magnetic flux, but may be made of a material with weak magnetic properties, such as ceramics having weak magnetism.

[0020] 1, magnet 10 of the present invention has a curved shape at cross section F. And, it is arranged inside the outer periphery of rotating member 4 so as to be convex toward shaft 2. In other words, magnet 10 of the present invention is on the outer periphery of rotating member 4 and embedded within rotating member 4, and is not in contact with the outer periphery surface of rotor 1 of the present invention, nor is it exposed.

[0021] When the rotor 1 of the present invention includes n magnets 10 of the present invention, the rotor 1 of the present invention has n magnetic poles (n: an even number of 2 or more). Fig. 1 shows an example in which there are eight magnets 10 of the present invention and the rotor 1 of the present invention has eight magnetic poles. The number of magnetic poles provided in the rotor 1 of the present invention is not particularly limited. In general, the greater the number of magnetic poles, the greater the number of times the magnetic flux linking the coil is switched. Even taking into account the reduction in the amount of magnet in each pole, at the same rotation speed, the greater the number of magnetic poles, the greater the torque and power generation. To obtain such an effect, the number of magnetic poles is preferably four or more, and more preferably eight or more. On the other hand, if the number of magnetic poles is too large, the stator shape and windings become complicated, causing the motor size to become larger, which is particularly noticeable in small motors. Therefore, the number of magnetic poles is preferably 16 poles or less, and more preferably 12 poles or less.

[0022] The magnet 10 of the present invention will be described in detail with reference to FIG. Figure 2 is an enlarged (schematic) view of one of the magnets 10 of the present invention in Figure 1. Thus, Figure 2 shows the magnet 10 of the present invention at cross section F.

[0023] The magnet 10 of the present invention has two side surfaces 11 and 12 parallel to the central axis of the shaft. Similarly, it has an inner peripheral surface 13 and an outer peripheral surface 14 parallel to the central axis of the shaft. In other words, magnet 10 of the present invention has a shape obtained by cutting a hollow cylinder in two places along its length, or a shape similar thereto. When magnet 10 of the present invention is obtained by cutting a hollow cylinder in two places along its length, the surface that was the inner surface of the hollow cylinder is inner circumferential surface 13, the surface that was the outer surface of the hollow cylinder is outer circumferential surface 14, and the surfaces that appear by cutting in two places are side surfaces 11 and 12. In addition, the inner circumferential surface 13 is a surface that forms a line close to point A on cross section F, which will be described later, the outer circumferential surface 14 is a surface that faces the inner circumferential surface 13, and the side surfaces 11 and 12 are surfaces that connect the inner circumferential surface 13 and the outer circumferential surface 14. In addition, it is preferable that the curve formed by inner surface 13 and outer surface 14 at cross section F forms part of a circular arc, and that the arc is preferably a concentric circle, and the center of the concentric circle is preferably point A, which will be described later.

[0024] The easy axis and orientation direction are indicated by dotted lines in Figure 2. As shown in Figure 2, magnet 10 of the present invention is oriented so that the easy axis forms an arc at cross section F, and the arc is part of a concentric circle. The center point of the concentric circle is point A. Also, in cross section F, point B denotes the boundary between side surface 12, which is one of the two side surfaces, and outer circumferential surface . Moreover, a point indicating the boundary between the side surface 12 and the inner peripheral surface 13 is defined as point C. And the line connecting point A and point B is line L 1 Let the line connecting points B and C be line L. 2 Let us assume that.

[0025] In the magnet 10 of the present invention, the straight line L 1 and the line L 2 The angle α between the two is 3 to 15 degrees. The present inventors have discovered that in a motor generator of the present invention equipped with a rotor including such magnet 10 of the present invention, the gap magnetic flux density is made sinusoidal.

[0026] Next, a preferred embodiment of the magnet of the present invention will be described in detail with reference to FIG. FIG. 3, like FIG. 2, shows an embodiment of a magnet 10' of the present invention at cross section F. The only difference between the magnet 10' of the present invention shown in FIG. 3 and the magnet 10 of the present invention shown in FIG. 2 is the side surface 12'. As shown in FIG. 3, in cross section F, side surface 12' of magnet 10' of the present invention forms an outwardly convex curve. 1 and the line L 2 It exists between. The present inventors have discovered that in a motor generator of the present invention equipped with a rotor including such magnet 10' of the present invention, the gap magnetic flux density becomes more sinusoidal.

[0027] Next, the motor generator of the present invention will be described with reference to FIG. FIG. 4 shows a cross section (schematic diagram) of the motor generator of the present invention taken in a direction perpendicular to the central axis of the shaft of the rotor of the present invention.

[0028] As shown in FIG. 4, a motor generator 20 of the present invention has a rotor 1 of the present invention and an outer stator 3. A through hole is formed in the center of the outer stator 3, and the rotor 1 of the present invention is inserted into this through hole.

[0029] The outer stator 3 has a plurality of teeth 32. In the embodiment shown in FIG.

[0030] The teeth 32 form the iron core of the armature coil. Further, in the outer stator 3, a plurality of teeth 32 are arranged radially.

[0031] Coils (not shown) are wound around the teeth 32. The coils can be wound using distributed winding or concentrated winding, but in the case of the combination of the number of poles and the number of slots shown in the figure, concentrated winding is used. By passing an alternating current through the coil, a rotating magnetic field can be applied to the rotor 1 of the present invention. Furthermore, when the rotor 1 of the present invention is rotated from the outside, a voltage is induced across the coil due to the change in magnetic flux that accompanies the rotation, and a current can be extracted from the coil.

[0032] The motor generator of the present invention can be used as any of the following: an electric power device (a "motor" in the narrow sense) that converts electrical energy into mechanical energy, an electric power device (generator) that converts mechanical energy into electrical energy, and an electric power device that has the functions of both a motor and a generator (motor generator).

[0033] The rotor of the present invention is preferably used as an inner rotor in the motor generator of the present invention, but can also be used as a drive motor. EXAMPLES

[0034] The present invention will now be described with reference to examples.

[0035] <Experiment 1> Regarding the magnet shape, the correlation with the angle α was examined by electromagnetic field analysis using the finite element method (FEM), and the appropriate angle α was obtained from the gap magnetic flux density waveform. Furthermore, the optimum angle α was determined from the correlation with the total harmonic distortion (THD) of the line-to-line induced voltage waveform and the correlation with the cogging torque related to motor loss and vibration. Table 1 shows the specifications of the motor generator analyzed. Table 2 shows the analysis conditions related to the motor drive, and Figures 5 to 8 show the analysis results. In the experimental verification, measurements were performed using a motor generator using magnets with angles α of 0, 3, 6, ..., 18 deg, and the results are shown in Figure 5. The mechanical angle indicates the rotation angle of the motor shaft. The line-to-line induced voltage (V) indicates the induced voltage generated in the stator coil by the rotation of the rotor. The THD (%) of the line-to-line induced voltage waveform indicates the content ratio of 3rd, 5th, 7th to 127th order harmonics to the 1st order component obtained by FFT (Fast Fourier Transform) of one electrical angle period of the induced voltage waveform, and the smaller the content ratio, the closer the waveform is to a sine wave. As a supplementary note, since the induced voltage waveform has half-wave symmetry, the 2nd, 4th, 6th, and even-numbered harmonic components are zero. Finally, cogging torque (Nm) refers to the torque pulsation that appears when rotated externally under no load, and the quality of the cogging torque is evaluated based on the peak-to-peak value (the difference between maximum and minimum).

[0036] [Table 1]

[0037] [Table 2]

[0038] From the analysis results in Figure 5, it can be confirmed that the motor generator of the present invention including a rotor of the present invention equipped with a magnet of the present invention with an angle α of 3 to 15 degrees has a sinusoidal gap magnetic flux density compared to a magnet with an angle α of 0 degrees. It can also be seen that the gap magnetic flux density when the angle α is 15 degrees is closer to a sine wave than the waveform when the angle α is 18 degrees.

[0039] Furthermore, from the analysis results in Figure 6, it can be confirmed that the induced voltage waveform of the motor-generator of the present invention including a rotor of the present invention equipped with a magnet of the present invention having an angle α of 3 to 15 degrees is sinusoidal (has a shape closer to a sine wave) compared to a magnet with an angle α of 0 degrees.

[0040] From the analysis results in Fig. 7, it was confirmed that, when the angle α is increased, the torque decreases slightly, but when the angle α is between 15° and 18°, the THD of the induced voltage waveform remains almost unchanged, and there is no improvement when the angle α exceeds 15°. From these results, it is believed that the motor generator of the present invention including the rotor of the present invention equipped with the magnet of the present invention with an angle α of 3 to 15 degrees can achieve high torque with little iron loss.

[0041] From the analysis results in Figure 8, it is believed that the motor generator of the present invention including a rotor of the present invention equipped with a magnet of the present invention with an angle α of 3 to 15 degrees can achieve high torque with small torque pulsation compared to when the angle α is 0 degrees. Therefore, a motor generator of the present invention including a rotor of the present invention equipped with a magnet of the present invention with an angle α of 3 to 15 degrees can realize a motor generator with lower vibration and noise, and higher torque, compared to one with an angle α of 0 degrees.

[0042] <Experiment 2> First, several types of magnets were created in the configuration shown in Figure 2, with various changes in angle α, distance DR from the central axis of the shaft to point B, and distance R from point A to the inner surface 13, and several permanent magnet type motor generators of the configuration shown in Figure 4 were created equipped with each of these magnets. Here, the angle α is an integer between 1 degree and 20 degrees. However, the angle α for which the shape was not valid due to the values ​​of the distance DR and the distance R was not included in the manufacturing process. The distance DR was set to one of three values: 58 mm, 57.5 mm, and 57 mm. The distance R was set to one of three values: 7 mm, 8 mm, and 9 mm. Then, the induced voltage, torque reduction rate, and cogging torque were measured for each permanent magnet type motor generator. The respective measurement methods are as follows.

[0043] <Induced voltage> The permanent magnet type motor generator of the present invention was measured using the motor measuring device shown in Fig. 9. The motor measuring device is arranged so that a dynamo motor and a permanent magnet type motor generator as a test motor are connected on one axis with a torque meter (maximum measurement range: 700 Nm) in between. The test motor was rotated under no load using a dynamo motor as the drive source, and the induced voltage waveform was measured with a voltmeter. The measured waveform was then subjected to waveform analysis using FFT to calculate the THD of the induced voltage waveform. Table 3 shows the measurement conditions during the experiment.

[0044] [Table 3]

[0045] <Torque reduction rate> Using the motor measuring device shown in Figure 9, the test motor was subjected to current control by an inverter, a load was applied to the test motor by a dynamo motor, and the torque generated in the test motor was measured by a torque meter. The measurement conditions are shown in Table 4.

[0046] [Table 4]

[0047] <Cogging torque> Using the motor measuring device shown in Figure 9, the test motor was rotated at 1 rpm using a dynamo motor as the driving source. In this state, the generated torque was measured with a torque meter. Here, the sampling period was set to 1000 Hz. The measurement conditions are shown in Table 5.

[0048] [Table 5]

[0049] <Measurement results> The measurement results of the induced voltage, torque and cogging torque are shown in Fig. 10 and Fig. 11. Here, Fig. 10(a) shows the relationship between the angle α and the induced voltage or torque reduction rate when the distance R is changed. In Fig. 10(a), "large R" means that R is 9 mm, "medium R" means that R is 8 mm, and "small R" means that R is 7 mm. Moreover, Fig. 10(b) shows the relationship between the angle α and the induced voltage or torque reduction rate when the distance DR is changed. In Fig. 10(b), "large DR" means when the DR is 58 mm, "medium DR" means when the DR is 57.5 mm, and "small DR" means when the DR is 57 mm. The torque reduction rate refers to the reduction rate based on the torque when the α angle is 0 degrees. The torque when the α angle is 0 degrees is calculated by polynomial approximation from the measured values ​​of a motor using a magnet shape that satisfies α angles of 1 to 20 degrees.

[0050] Moreover, Fig. 11(a) shows the relationship between the angle α and the cogging torque when the distance DR is changed. In Fig. 11(a), "large DR" means that the DR is 58 mm, "medium DR" means that the DR is 57.5 mm, and "small DR" means that the DR is 57 mm. Figure 11(b) shows the relationship between the angle α and the cogging torque when the distance R is changed. In Figure 11(b), "large R" means that R is 9 mm, "medium R" means that R is 8 mm, and "small R" means that R is 7 mm.

[0051] As shown in FIG. 10, it was confirmed that a motor generator equipped with a rotor with an angle α of 3 to 15 degrees has a THD of induced voltage of 6% or less and a torque reduction rate of 20% or less. Also, as shown in FIG. 11, it was confirmed that a motor generator equipped with a rotor with an angle α of 3 to 15 degrees had a cogging torque of 6 Nm or less. [Explanation of symbols]

[0052] 1. The rotor of the present invention 2 Shaft 3 Outer stator 4 Rotating members 10, 10' Magnet of the present invention 11 Side 12, 12´ Side 13 Inner surface 14 Outer surface 20 Permanent magnet motor generator of the present invention 32 Teeth

Claims

1. A shaft, A rotating member joined to the shaft; a magnet arranged within the outer periphery of the rotating member so as to be curved and convex toward the shaft; A rotor having The magnet is The shaft has two side surfaces parallel to a central axis thereof, and an inner peripheral surface and an outer peripheral surface, In a cross section F perpendicular to the central axis of the shaft, the axis of easy magnetization is oriented to form an arc, the arc being a part of a concentric circle, and the center point of the concentric circle is point A; In the cross section F, when a point indicating a boundary between one of the side surfaces and the outer peripheral surface is defined as point B, and a point indicating a boundary between one of the side surfaces and the inner peripheral surface is defined as point C, a straight line L connecting point A and point B is defined as 1 and a straight line L connecting points B and C. 2 A rotor having an angle α of 3 to 15 degrees.

2. 2. The rotor according to claim 1, wherein in said cross section F, said side surface of said magnet forms an outwardly convex curve.

3. In the cross section F, the curve is a straight line L 1 and the line L 2 The rotor of claim 2 , wherein the rotor is disposed between

4. The rotor according to claim 1 or 2 is used as an inner rotor, The permanent magnet motor generator further comprises an outer stator having a central through hole into which the inner rotor is inserted.

5. The outer stator includes:

5. The permanent magnet type motor generator according to claim 4, wherein a plurality of teeth that form an iron core of an armature coil are arranged radially, and a coil is wound around the teeth.

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