Rotation device

Abstract

This rotation device (1) comprises: a permanent magnet (13) provided with an inner periphery (13i), an outer periphery (13o), and a plurality of different magnetic pole parts (13a) arranged in the circumferential direction; and a magnetic body (17) provided with magnetic poles facing the permanent magnet (13) in the radial direction. The permanent magnet (13) has a ring shape, the relative density of the permanent magnet (13) is 95% or more, and the magnetization waveform of the permanent magnet (13) has a sinusoidal waveform.

Description

Rotating device

[0001] This invention relates to a rotating device.

[0002] Rotating devices may include a permanent magnet having multiple different magnetic poles arranged in the circumferential direction, and a magnetic material having magnetic poles opposite to the permanent magnet. For example, Patent Document 1 discloses a motor equipped with a specific ring magnet.

[0003] Japanese Patent Publication No. 2011-030314

[0004] In such rotating devices, it is sometimes necessary to achieve high torque while simultaneously suppressing cogging torque. One example of an object of the present invention is to provide a rotating device that can suppress the increase in cogging torque.

[0005] A rotating device according to one aspect of the present invention comprises a permanent magnet having an inner circumference, an outer circumference, and a plurality of different magnetic pole portions arranged in the circumferential direction, and a magnetic body having magnetic poles facing the permanent magnet in the radial direction, wherein the permanent magnet is ring-shaped, the relative density of the permanent magnet is 95% or more, and the magnetization waveform of the permanent magnet is sinusoidal.

[0006] This is a cross-sectional view of a rotating device according to one embodiment, taken along the axis of rotation. This is a cross-sectional view of a rotating device according to one embodiment, taken perpendicular to the axis of rotation. This is a plan view showing an example of a permanent magnet. This is a plan view showing an example of a magnetic material. This is a plan view showing an enlarged portion of a magnetic material according to a modified example.

[0007] In describing each embodiment of the present invention, for convenience of explanation, the direction along the rotation axis X of the rotating device is simply referred to as the rotation axis direction or axial direction. In the axial direction, the direction of arrow a in the drawing is referred to as one side, and the direction of arrow b, which is the opposite direction, is referred to as the other side. In a plane perpendicular to the rotation axis X, the direction of approaching or moving away from the rotation axis X is referred to as the radial direction. In the radial direction, the direction of arrow c, moving away from the rotation axis X, is referred to as the outside or one side, and the direction of arrow d, moving towards the rotation axis X, is referred to as the inside or the other side. In a certain member or part, the outer surface in the radial direction (direction of arrow c) may be referred to as the outer circumferential surface, and the inner surface in the radial direction (direction of arrow d) may be referred to as the inner circumferential surface. In a certain member or part, the outer part in the radial direction (direction of arrow c) may be referred to as the outer circumferential part, and the inner part in the radial direction (direction of arrow d) may be referred to as the inner circumferential part. The direction of rotation around the rotation axis X is referred to as the circumferential direction.

[0008] The rotating device according to the present invention may be a motor, a generator, or any other rotating device. The rotating device according to the present invention may be an outer rotor type motor or an inner rotor type motor. The rotating device according to the present invention may be a brushless motor or a brushed motor. The rotating device according to the present invention may be a DC motor or an AC motor. The rotating device according to the present invention may be a three-phase motor or a single-phase motor. For convenience, the rotating device 1 described below has a configuration as an outer rotor type brushless motor, but the rotating device 1 is merely one embodiment of the present invention, and the configuration of the present invention is applicable regardless of the type of rotating device.

[0009] First, the overall configuration of the rotating device 1 according to one embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of the rotating device 1 along the rotation axis X. Figure 2 is a cross-sectional view of the rotating device 1 perpendicular to the rotation axis X (section A-A shown in Figure 1).

[0010] As shown in Figures 1 and 2, the rotating device 1 is an outer rotor type brushless motor. The rotating device 1 comprises a shaft S, a cover 11, a cylinder 12, a permanent magnet 13, bearings 14 (first bearing 141 and second bearing 142), a holder 15, and a stator 16.

[0011] The shaft S is a generally cylindrical member. The shaft S extends along the axis of rotation X. In the axial direction, the shaft S protrudes from the cover 11 to one side (in the direction of arrow a).

[0012] The cover 11 comprises a plate portion 111 and a wall 112. The plate portion 111 is a disc-shaped or substantially disc-shaped part. In the axial direction, the plate portion 111 covers part or all of one side (direction of arrow a) of the rotating device 1. The plate portion 111 is arranged coaxially with the shaft S. A hole 11h is formed in the plate portion 111 around the rotation axis X. The hole 11h penetrates the plate portion 111 in the axial direction. The shaft S is inserted into and fixed in the hole 11h of the cover 11. Therefore, the shaft S and the cover 11 rotate together. The wall 112 extends from the radially outer end (direction of arrow c) of the plate portion 111 to the other side in the axial direction (direction of arrow b). The wall 112 is formed in a cylindrical or substantially cylindrical shape coaxial with the shaft S.

[0013] In the axial direction, a cylinder 12 and a permanent magnet 13 are fixed to the other side (direction of arrow b) of the wall 112 of the cover 11. The cylinder 12 and the permanent magnet 13 constitute the rotor of the rotating device 1. In the illustrated embodiment, the cylinder 12 is formed in a cylindrical or substantially cylindrical shape coaxial with the shaft S. The cylinder 12 is made of, for example, metal or an alloy. However, the cylinder 12 may be made of other materials. The cylinder 12 is, for example, a yoke.

[0014] In the radial direction, the permanent magnet 13 is positioned inside the cylinder 12 (in the direction of arrow d). As shown in Figure 2, the permanent magnet 13 comprises an inner circumference 13i, an outer circumference 13o, and a plurality (14 in the illustrated configuration) of different magnetic pole portions 13a arranged in the circumferential direction. In the illustrated configuration, the permanent magnet 13 is formed in a cylindrical (ring) shape. In other words, the inner circumference 13i is formed continuously around the circumference, and the outer circumference 13o is formed continuously around the circumference. The outer circumference 13o of the permanent magnet 13 is fixed to the inner circumferential surface of the cylinder 12. The cylinder 12 and the permanent magnet 13 rotate together with the shaft S and the cover 11.

[0015] As shown in Figure 1, the bearing 14 is interposed radially between the shaft S and the holder 15. The bearing 14 includes a first bearing 141 and a second bearing 142. However, the bearing 14 may consist of one or more bearings. In the axial direction, the first bearing 141 is positioned on one side (in the direction of arrow a) of the second bearing 142. In the axial direction, the first bearing 141 and the second bearing 142 are positioned apart from each other.

[0016] In the illustrated configuration, both the first bearing 141 and the second bearing 142 are ball bearings. However, either one or both of the first bearing 141 and the second bearing 142 may be other types of bearings, such as sleeve bearings.

[0017] The holder 15 rotatably supports the shaft S via the bearing 14. The holder 15 comprises a cylindrical portion 151 and a bottom portion 152. The cylindrical portion 151 is formed coaxially with the shaft S. The cylindrical portion 151 holds the bearing 14 (first bearing 141 and second bearing 142) on its inner circumferential surface. In the axial direction, the bottom portion 152 is connected to the other end (direction of arrow b) of the cylindrical portion 151. The bottom portion 152 is formed in a disc shape and extends radially outward (direction of arrow c) from the cylindrical portion 151. The bottom portion 152 may be, for example, a part that fixes the rotating device 1 to an external device (not shown).

[0018] The stator 16 is fixed to the outer circumferential surface of the cylindrical portion 151 of the holder 15. In the radial direction, the stator 16 and the permanent magnet 13 are spaced apart from each other and face each other. As shown in Figure 2, the stator 16 comprises a stator core 161, a coil 162, and an insulator 163.

[0019] The stator core 161 is a laminate formed by stacking magnetic materials 17, described later, in the axial direction. The stator core 161 comprises an annular portion 161a arranged coaxially with the shaft S, a plurality of spokes 161b (12 in the illustrated configuration) formed to extend radially from the annular portion 161a toward the permanent magnet 13, and teeth 161c extending circumferentially from the tips of the spokes 161b. In the radial direction, the teeth 161c face the permanent magnet 13. The coil 162 is wound around each of the plurality of spokes 161b. The stator core 161 and the coil 162 are insulated by an insulator 163 made of an insulating material.

[0020] In the rotating device 1, when current flows through the coil 162, the permanent magnet 13 rotates due to the electromagnetic interaction between the permanent magnet 13 and the stator 16. As the permanent magnet 13 rotates, the cover 11 fixed to the permanent magnet 13 and the shaft S fixed to the cover 11 also rotate. In this way, the rotating device 1 is configured such that the cover 11 and the shaft S rotate relative to the holder 15.

[0021] The above describes the overall configuration of a rotating device 1, which is an example of the present invention. Below, the permanent magnet 13 and the magnetic material 17 provided on the stator core 161 of the stator 16 will be described in more detail.

[0022] Figure 3 is a plan view showing the permanent magnet 13. As shown in Figure 3, the permanent magnet 13 comprises an inner circumference 13i, an outer circumference 13o, and a plurality (14 in the illustrated embodiment) of different magnetic pole portions 13a. In the illustrated embodiment, the permanent magnet 13 is ring-shaped. In this embodiment, the permanent magnet 13 has a configuration in which the magnetic flux in the circumferential direction is greater than the magnetic flux in the radial direction at the plurality of different magnetic pole portions 13a. The radial thickness of the permanent magnet 13 is, for example, 1.0 mm or less.

[0023] Figure 3 schematically shows the flow of magnetic flux in the circumferential direction generated by the permanent magnet 13 using arrows. When a radially magnetized permanent magnet is used, the magnetic flux in the radial direction is dominant, but in the permanent magnet 13 of the rotating device 1, the magnetic flux in the circumferential direction is greater than the magnetic flux in the radial direction. In the permanent magnet 13, the magnetic flux in the circumferential direction may be greater (more) than the magnetic flux in the radial direction between adjacent magnetic pole portions 13a. The permanent magnet 13 may have portions that are magnetized in directions different from the radial and axial directions. The angle of the magnetization direction with respect to the radial direction of the permanent magnet 13 may change periodically as it moves toward the circumferential direction. Such a permanent magnet 13 may be polarly anisotropically magnetized, but it may not have complete anisotropy and may be a magnet that has partial isotropy.

[0024] The permanent magnet 13 may, for example, be configured such that, as shown in Figure 3, the magnetic flux lines within the magnet are mainly oriented in the circumferential direction (the circumferential component of the magnetic flux density vector is dominant over the radial component). The relative density of the permanent magnet 13 is 95% or more. The relative density of the permanent magnet 13 is the measured value ρ of the density of the permanent magnet 13 measured using the buoyancy method. １ And the theoretical density ρ obtained from the material of the permanent magnet 13 (the theoretical density when there are no voids, etc., and the entire occupied volume is filled with material) ０ Using (ρ １ / ρ ０ It can be calculated from ) × 100 (%). The permanent magnet 13 may have a surface magnetic flux density of 40.0 mT / g or more per unit mass.

[0025] The magnetization waveform of the permanent magnet 13 is sinusoidal. In other words, the permanent magnet 13 is sinusoidally magnetized. Specifically, the surface magnetic flux density on the surface of the permanent magnet 13, especially on the surface facing the stator 16 (magnetic material 17), changes sinusoidally along the circumferential direction. That is, in a graph with the mechanical angle on the horizontal axis and the surface magnetic flux density on the vertical axis, the waveform exhibits a sinusoidal shape. Therefore, the magnetization waveform of the permanent magnet 13 is distinguishable from rectangular wave, trapezoidal wave, and triangular wave shapes.

[0026] The permanent magnet 13 may be manufactured using rare-earth iron-based magnet powder. As the rare-earth iron-based magnet powder, for example, rare-earth iron-based magnet powder obtained by crushing magnetically isotropic rare-earth iron-based magnet strips produced by an ultra-rapid quenching method may be used. Rare-earth iron-based magnet powder produced by an ultra-rapid quenching method typically has a flattened shape. The rare-earth iron-based magnet powder obtained in this way is magnetically isotropic.

[0027] Rare earth iron-based magnet powder preferably contains at least Nd as a rare earth element, for example, an Nd-Fe-B magnet. Nd-Fe-B magnets are ternary tetragonal compounds. ２ Fe １４ It contains a type B compound phase as the main phase. In addition, Nd-Fe-B magnets usually further contain a rare earth-rich phase (Nd-rich phase), etc. Nd-Fe-B magnets may be used individually or in combination of two or more types.

[0028] Rare earth iron-based magnet powder may contain rare earth elements other than Nd. Examples of such rare earth elements include praseodymium (Pr), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Rare earth elements other than Nd may be used individually or in combination of two or more.

[0029] In Nd-Fe-B magnets, Fe may be partially (usually less than 50 atomic percent) substituted with Co. Furthermore, Nd-Fe-B magnets may contain other elements. Examples of these other elements include titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), copper (Cu), and gallium (Ga). These elements may be used individually or in combination of two or more.

[0030] The permanent magnet 13 may be manufactured, for example, by mixing the rare earth iron-based magnet powder mentioned above with a polymer such as polystyrene to make a compound, subjecting the resulting compound to hot densification and, if necessary, hot plastic deformation, and then magnetizing the resulting sintered magnet body.

[0031] Next, the magnetic material 17 will be described using Figure 4. The magnetic material 17 is a flat plate-shaped member. As shown in Figure 4, the magnetic material 17 comprises an annular portion 171, a plurality of spokes 172 (12 in the illustrated form) extending in the radial direction, and teeth 173 extending in the circumferential direction.

[0032] Multiple spokes 172 extend radially outward from the annular portion 171 (in the direction of arrow c). Teeth 173 are portions that spread out circumferentially from the tip (radially outer end) of each spoke 172. Teeth 173 become magnetic poles facing the permanent magnet 13 in the radial direction.

[0033] The magnetic material 17 is stacked in the axial direction to form the stator core 161. The annular portion 171, spokes 172, and teeth 173 of the magnetic material 17 are stacked in the axial direction to form the annular portion 161a, spokes 161b, and teeth 161c of the stator core 161, respectively.

[0034] The thickness (plate thickness) of the magnetic material 17 is not particularly limited, but may be, for example, 0.2 mm or less, or 0.1 mm or less. The magnetic material 17 is, for example, a silicon steel sheet. However, the magnetic material 17 may contain amorphous materials, and may be an amorphous metal or amorphous alloy that does not have a crystalline structure. If the magnetic material 17 is formed from a material containing amorphous materials, it becomes easier to achieve a very thin plate thickness, such as 0.1 mm or less. If the thickness of the magnetic material 17 is thin, it becomes easier to suppress eddy current losses even when using a permanent magnet 13 with a large surface magnetic flux density per unit mass.

[0035] In the circumferential direction, the width of one magnetic pole portion 13a of the permanent magnet 13 may be greater than the width of one magnetic pole of the magnetic material 17 (the maximum width of the teeth 173 in the circumferential direction). In other words, the angle θ shown in Figure 3. １The magnitude of is the angle θ shown in FIG. 4 ２ may be larger than the magnitude of. By doing this, the cogging torque generated in the rotating device 1 can be reduced. Note that "the width of one magnetic pole portion 13a of the permanent magnet 13" refers to the width when the permanent magnet 13 is divided by the number of magnetic poles in the circumferential direction. Therefore, the angle θ １ is a value obtained by dividing 360° by the number of magnetic poles of the permanent magnet 13.

[0036] The configuration of the rotating device 1 according to the present embodiment is as described above. The magnetization waveform of the permanent magnet 13 included in the rotating device 1 has a sinusoidal shape. Therefore, even when a high relative density and high-strength permanent magnet 13 is used, an increase in cogging torque can be suppressed.

[0037] Further, in the permanent magnet 13 included in the rotating device 1 according to the present embodiment, in each of the plurality of different magnetic pole portions 13a, the magnetic flux directed in the circumferential direction is larger than the magnetic flux directed in the radial direction. Therefore, even when a high relative density and high-strength permanent magnet 13 is used, an increase in cogging torque can be further suppressed.

[0038] Further, in the rotating device 1 according to the present embodiment, in the circumferential direction, the angle θ formed by the width of one magnetic pole portion 13a of the permanent magnet 13 １ is larger than the angle θ formed by the width of one magnetic pole of the magnetic body 17 ２ . Therefore, even when a high relative density and high-strength permanent magnet 13 is used, an increase in cogging torque can be further suppressed.

[0039] While an example of the embodiment of the rotating device of the present invention has been described above, the rotating device of the present invention is not limited to the configuration of the above-described embodiment.

[0040] The rotating device of the present invention may include a magnetic body 27, a partially enlarged view of which is shown in FIG. 5, instead of the magnetic body 17 shown in FIG. The magnetic body 27 has the same configuration as the magnetic body 17, except that it includes spokes 272 instead of the spokes 172.

[0041] The spoke 272 extends from the annular portion 171 outward in the radial direction (in the direction of arrow c). The spoke 272 includes a first portion 272d and a second portion 272c that is closer to the permanent magnet 13 than the first portion 272d, and in the circumferential direction, the width W of the second portion 272c ２ is the width W of the first portion 272d １ is larger. That is, the dimension of the spoke 272 in the circumferential direction increases as it goes outward in the radial direction (in the direction of arrow c). Such a magnetic body 27 is more susceptible to the influence of the radial component of the magnetic flux from the permanent magnet 13. Therefore, the cogging torque in the rotating electric machine can be further reduced.

[0042] In the rotating electric machine of the present invention, the permanent magnet may be a component on the stator side, and the magnetic body may be a component on the rotor side. In the radial direction, the permanent magnet may be arranged inside the magnetic body. In the magnetic body, the spokes and teeth may extend inward in the radial direction from the annular portion.

[0043] The combination of the number of magnetic poles of the permanent magnet and the magnetic body can be arbitrarily changed. Further, in the circumferential direction, the width of one magnetic pole portion of the permanent magnet may be smaller than the width of one magnetic pole of the magnetic body.

[0044] The number of magnetic poles of the magnetic body (the number of spokes and teeth) affects the width (dimension in the circumferential direction) of the space in which the coil can be wound. In the rotating electric machine 1 described above, the number of magnetic poles of the permanent magnet 13 is 14, and the number of magnetic poles of the magnetic body is 12, so the angle formed by the space in which the coil 162 can be wound is the angle θ formed by one magnetic pole portion 13a of the permanent magnet 13 １ (see FIG. 3) is larger. However, in the rotating electric machine of the present invention, the angle formed by the space in which the coil can be wound may be smaller than the angle formed by one magnetic pole portion of the permanent magnet.

[0045] In addition, those skilled in the art can appropriately modify the rotating electric machine of the present invention and change the shapes, dimensions and combinations of various configurations in accordance with conventionally known knowledge. If such modifications still have the configuration of the present invention, the modified rotating electric machine is also included in the scope of the present invention.

[0046] 1...Rotating device, 13...Permanent magnet, 13a...Magnetic pole part, 13i...Inner circumference, 13o...Outer circumference, 17, 27...Magnetic material, 172, 272...Spokes, 173...Teeth, 272d...First part, 272c...Second part, X...Rotation axis.

Claims

1. A rotating device comprising: a permanent magnet having an inner circumference, an outer circumference, and a plurality of different magnetic pole portions arranged in the circumferential direction; and a magnetic material having magnetic poles facing the permanent magnet in the radial direction, wherein the permanent magnet is ring-shaped, the relative density of the permanent magnet is 95% or more, and the magnetization waveform of the permanent magnet is sinusoidal.

2. The rotating device according to claim 1, wherein in the circumferential direction, the width of one magnetic pole portion of the permanent magnet is greater than the width of one magnetic pole of the magnetic material.

3. The rotating device according to claim 1 or 2, wherein the magnetic material comprises spokes extending in the radial direction and teeth extending in the circumferential direction, and the spokes of the magnetic material comprises a first portion and a second portion closer to the permanent magnet than the first portion, and in the circumferential direction, the width of the second portion is greater than the width of the first portion.

4. The rotating device according to any one of claims 1 to 3, wherein the magnetic material includes an amorphous material.

5. The rotating device according to any one of claims 1 to 4, wherein the permanent magnet has a radial thickness of 1.0 mm or less.

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