Motor and driving device

Abstract

A motor (1) comprises: a magnet (12); one or a plurality of coils (14) facing the magnet (12) in a rotational axis direction (A); and a magnetic fluid (16). The magnet (12) is rotatably supported by the magnetic fluid (16) with respect to the coil (14). The magnet (12) preferably has an average crystal grain size in the range of 0.05 μm to 1.0 μm. In the rotational axis direction (A), the thickness of the magnet (12) is preferably 1.0 mm or less.

Description

Motors and Drives

[0001] The present invention relates to a motor and a drive device.

[0002] Patent Document 1 describes a brushless motor that includes a stator substrate on which multiple stator coils are arranged in the circumferential direction, a ring-shaped first magnet that faces one surface of the stator substrate across a gap and is magnetized with alternating north and south poles in the circumferential direction, and a ring-shaped second magnet that faces the other surface of the stator substrate across a gap and is magnetized with alternating north and south poles in the circumferential direction and is connected to the first magnet via the stator substrate so that their opposite poles face each other.

[0003] Japanese Patent Application Publication No. 5-30722

[0004] However, the motor of Patent Document 1 has a low strength against a load from the direction of the rotation axis when the motor is in use.

[0005] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a motor that can improve the strength against a load from the direction of the rotation axis when the motor is in use.

[0006] In order to solve the above-mentioned problems and achieve the object, a motor according to one embodiment of the present invention comprises a magnet, one or more coils facing the magnet in the direction of the rotation axis, and a magnetic fluid, and the magnet is rotatably supported by the magnetic fluid relative to the coil.

[0007] FIG. 1-1 is an exploded perspective view of a motor according to an embodiment. FIG. 1-2 is a front view of the motor. FIG. 1-3 is a schematic diagram of the X-X cross section of FIG. 1-2. FIG. 2 is a diagram illustrating the magnet produced in Example 1, including a front view and a partially enlarged view. FIG. 3 is a graph showing measured values ​​of magnetic flux density versus the number of magnetic poles. FIG. 4 is a perspective view of a drive device according to Example 5. FIG. 5 is an exploded perspective view of the drive device shown in FIG. 4. FIG. 6 is a cross section taken along the arrows XX-XX in FIG. 4. FIG. 7 is a perspective view showing the magnet, magnetic fluid, and substrate of the drive device shown in FIG. 4. FIG. 8 is a cross section of the magnet, magnetic fluid, and substrate shown in FIG. 7. FIG. 9 is a plan view showing the magnet and substrate shown in FIG. 7. FIG. 10 is a plan view and a partially enlarged view of the magnet shown in FIG. 7. FIG. 11 is an enlarged plan view of a portion of the circuit unit of the substrate shown in FIG. 9. FIG. 12 is a plan view showing the first coil group and the second coil group of the circuit unit of the substrate shown in FIG. 9. Fig. 13 is a perspective view of the drive unit shown in Fig. 4 with the cover removed to expose the blades. Fig. 14 is a plan view of the drive unit shown in Fig. 4 with the cover removed to expose the blades. Fig. 15 is a plan view of the drive unit shown in Fig. 4 with the blades rotated to make the opening narrower than in Fig. 14. Fig. 16 is a perspective view of a drive unit according to a sixth embodiment. Fig. 17 is a perspective view of a drive unit according to a seventh embodiment.

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same.

[0009] <Motor of the embodiment> Fig. 1-1 is an exploded perspective view of a motor of the embodiment, Fig. 1-2 is a front view of the motor, and Fig. 1-3 is a schematic diagram of a cross section taken along line X-X of Fig. 1-2. The motor 1 includes a magnet 12, one or more coils 14 facing the magnet 12 in the direction of the rotation axis A, and a magnetic fluid 16. The magnet 12 is rotatably supported by the magnetic fluid 16 relative to the coil 14. In the motor 1, a magnetic gap is formed between the magnet 12 and the coil 14 via the magnetic fluid 16, and the motor 1 is an axial gap type motor.

[0010] Specifically, in FIGS. 1-1 and 1-2, two coils 14 are formed on a substrate 18, and each of the two coils 14 has two electrodes 20 (i.e., a total of four electrodes 20). The current flow in the two coils 14 is two-phase, shifted by 90 degrees from each other. Specifically, the outermost two of the four coils (20a, 20d) and the other two in the center (20b, 20c) are electrically connected to their respective coils 14. In other words, the coil 14 extending from 20a makes approximately one circumferential turn around any location on the substrate before being connected to 20d. Furthermore, the coil 14 extending from 20b makes approximately one circumferential turn around any location on the substrate before being connected to 20c. This allows the two coils to be formed without crossing each other on the substrate.

[0011] On the other hand, the two coils 14 can also be arranged separately on multiple layers that make up the substrate 18. In this case, for example, one coil 14 can be arranged on the first layer of the substrate 18, and the other coil 14 can be arranged on the second layer of the substrate 18. This is not limited to this, and it is also possible to increase the number of layers to three or four, and arrange a coil 14 on each layer. This can improve the torque of the motor 1.

[0012] The motor 1 has improved strength against loads from the direction of the rotation axis when in use because a magnetic gap is formed via the magnetic fluid 16. In contrast, the motor of Patent Document 1 has a gap formed by an air gap, so has weak strength against loads from the direction of the rotation axis when in use.

[0013] More specifically, the substrate 18 has a plane extending in a direction perpendicular to the rotational axis direction A of the motor 1. The coil 14 is formed on this plane, and the electrodes 20 are provided. The magnetic fluid 16 is in contact with the plane at a position corresponding to the position where the coil 14 is formed. The magnetic fluid 16 is magnetically held by the magnet 12.

[0014] 1-2, the radial width of the coil 14 is formed to be larger than the radial width of the magnet 12. This prevents the magnet 12 from protruding from the coil 14 even if it shifts radially while the motor 1 is running, thereby ensuring stable operation of the motor 1.

[0015] As shown in Figure 1-3, the motor 1 has a magnetic gap formed via the magnetic fluid 16, and the magnet 12 is rotatably supported by the magnetic fluid 16 relative to the coil 14. This improves the motor's strength against loads from the rotational axis direction A when the motor 1 is in use. Also, since the magnet 12 and the coil 14 face each other in the axial direction, making it a so-called axial gap motor, the thickness in the rotational axis direction A can be reduced. Furthermore, because the magnetic fluid 16 is magnetically held by the magnet 12, the magnet 12, magnetic fluid 16, and coil 14 are arranged in this order when viewed from the rotational axis direction A.

[0016] The magnet 12 is ring-shaped and preferably has an average crystal grain size in the range of 0.05 μm to 1.0 μm, more preferably 0.1 μm to 1.0 μm, and even more preferably 0.3 μm to 0.6 μm. Specifically, the magnet 12 includes a rare earth magnet, and the rare earth magnet preferably has an average crystal grain size in the range of 0.05 μm to 1.0 μm, more preferably 0.1 μm to 1.0 μm, and even more preferably 0.3 μm to 0.6 μm. Because the average crystal grain size is within the above range, the magnet 12 can exhibit a predetermined rigidity in the rotation axis direction. In other words, because the crystalline structure is fine, the magnet 12 has high hardness. If the average crystal grain size is smaller than 0.05 μm, the magnet may become amorphous, potentially resulting in a loss of anisotropy. On the other hand, if the average crystal grain size is larger than 1.0 μm, there is a concern that the magnetic properties may be degraded. Furthermore, if the average crystal grain size is larger than 1.0 μm, there is a concern that the impact of deterioration due to cutting during the production of magnet 12 will be significant. Furthermore, in the hot-processed magnet described below, if the average crystal grain size is within the above range (i.e., if it is relatively small), deterioration due to cutting during production will be limited to the surface. In contrast, if the average crystal grain size is larger than the above range, there is a concern that deterioration will reach deeper through the crystal grain boundaries, resulting in a decrease in magnetic properties.

[0017] The thickness of the magnet 12 is preferably 1.0 mm or less in the rotation axis direction A. This has the advantage of allowing the motor 1 to be made more compact. From the viewpoint of manufacturing the magnet 12, the thickness is preferably 0.07 mm or more. The inner diameter of the magnet 12 is preferably 1 mm or more and 50 mm or less. The outer diameter of the magnet 12 is preferably 3 mm or more and 60 mm or less.

[0018] The magnet 12 has a plurality of magnetic poles. Specifically, the magnet 12 is magnetized at a predetermined magnetic pole pitch in the circumferential direction. From the viewpoint of magnetic flux density, the pitch of the plurality of magnetic poles is preferably 2.0 mm or less. Here, the magnetic pole pitch is the length of the magnet 12 on the outer periphery. From the viewpoint of magnetic flux density, the number of poles is preferably 16 or more.

[0019] Here, we will describe a method for manufacturing magnet 12. First, we will describe in detail the rare earth magnet used for magnet 12. Specifically, we can use a rare earth magnet that is a hot-worked magnet. In other words, it is a rare earth magnet obtained by hot plastic working an R-Fe-B alloy containing R (R represents rare earth elements including Nd), Fe, and B. For example, the above rare earth magnet can be produced by the following method.

[0020] [Preparation of Rare Earth Magnet Powder] First, R—Fe—B magnet powder is prepared as the rare earth magnet powder. The R—Fe—B (boron) magnet that constitutes the R—Fe—B magnet powder is a ternary tetragonal compound, RFe 14 B phase (e.g. R2Fe 14 The R-Fe-B magnet contains a rare earth element (Fe-B type compound phase) as the main phase. Furthermore, R-Fe-B magnets usually further contain an R-rich phase. R represents rare earth elements, including Nd. That is, R contains Nd as an essential component. Examples of rare earth elements include neodymium (Nd) and praseodymium (Pr), as well as 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). One or more other rare earth elements may be used together with Nd, or two or more may be used in combination. It is sufficient that at least Nd is used as R. Fe may be partially substituted with Co. When a portion of Fe is substituted with Co, it is preferable that Fe is contained in an amount of 50 atomic % or more when the total amount of Fe and Co is taken as 100 atomic %.

[0021] R-Fe-B magnets may contain other elements. Examples of such elements include titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W). These other elements may be used singly or in combination. In R-Fe-B magnets, R is preferably contained in an amount of 12 atomic % to 16 atomic %. B is preferably contained in an amount of 6 atomic % to 8 atomic %. Furthermore, when the above-mentioned other elements are contained, the total amount of the other elements is preferably greater than 0 atomic % and less than 3 atomic %. Here, the remainder is the total amount of Fe and unavoidably contained elements.

[0022] Here, as the R—Fe—B based magnet, for example, NdFe 14 An Nd--Fe--B based magnet using an Nd--Fe--B based alloy with B as the main phase will be described as an example.

[0023] Nd—Fe—B magnet powder is produced, for example, by a rapid cooling method (melt-spun method). Specifically, an Nd—Fe—B alloy is melted by high-frequency induction heating under reduced pressure or in an argon atmosphere. The molten alloy is then sprayed onto a rotating copper roll and rapidly cooled (cooled at high speed) to produce ribbon-shaped thin strips. These thin strips are then pulverized. For example, the thin strips are preferably broken into pieces of several millimeters to several tens of millimeters, and then pulverized using a pulverizer or the like. These thin strips are then pulverized to obtain pulverized powder.

[0024] The ribbon-shaped thin strips are pulverized to obtain pulverized powder, which is then heat-treated to obtain magnet powder. At this stage, the magnet powder is magnetically isotropic because the easy axes of magnetization of the crystal grains are not aligned in one direction. Note that pre-manufactured magnet powder can be used instead of actually producing magnet powder. For example, Magnequench offers magnetically isotropic magnet powder, which is made by pulverizing Nd—Fe—B-based ribbons produced by the ultra-rapid cooling method and then densifying them by hot press molding.

[0025] [Hot-Pressing Process: Fabrication of Sintered Magnet Body] Next, a first mold is prepared. The first mold is composed of a hollow cylindrical die, hollow cylindrical upper and lower punches inserted inside the die, and a cylindrical core placed inside the upper and lower punches. The die, upper and lower punches, and core are made of a conductive material (e.g., graphite, cemented carbide, etc.).

[0026] Next, rare earth magnet powder (Nd—Fe—B magnet powder) is filled into the first mold, and the mold is set in a sintering apparatus (SPS apparatus: spark plasma sintering apparatus) for sintering, and the sintered magnet body (hot-pressed magnet body) is removed from the first mold.

[0027] The magnetic powder filled in the cavity of the first die is compressed by the upper and lower punches due to the pressure applied between the upper and lower electrodes. Furthermore, current flows from the upper electrode to the upper punch, then through the die, core, and magnetic powder, and then to the lower electrode via the lower punch, generating Joule heat and generating discharge plasma within the magnetic powder, which heats the magnetic powder. For example, the magnetic powder is heated to 600-700°C while being pressurized at 30-50 MPa (hot press). Furthermore, sintering is preferably performed under reduced pressure in an inert atmosphere, specifically, an argon or nitrogen atmosphere.

[0028] After heating, the current is cut off and the magnet is cooled. After cooling to a predetermined temperature, the first mold is removed from the sintering apparatus. Specifically, the ring-shaped sintered magnet body formed by sintering the magnetic powder is removed from the first mold. In this state, the ring-shaped sintered magnet body has, for example, a relative density of approximately 90%, and the orientation of the easy axes of magnetization of its crystal grains is random, making it magnetically isotropic.

[0029] [Hot plastic working process: production of hot-worked magnet] Next, a second mold is prepared. The preparation of the second mold may be performed in parallel with the preparation of the first mold, or may be performed before the preparation of the first mold.

[0030] The sintered magnet body produced in the above-mentioned hot pressing step is placed in the second die, and the second die is then placed in a sintering machine to carry out hot plastic working.

[0031] In the sintering apparatus, an upper electrode is disposed on the upper end of the punch, and a lower electrode is disposed on the lower end of the die. The upper and lower electrodes are formed of a conductive material (e.g., graphite, cemented carbide, etc.). The sintering apparatus is equipped with a power supply device and a control device that apply a predetermined voltage between the upper and lower electrodes to supply a predetermined current. The sintering apparatus may be the same as the sintering apparatus used in the hot pressing process described above, or may be a separate device.

[0032] The sintered magnet body, placed between the die and punch of the second mold, is pressed by the die and punch. It is also heated by discharge plasma and Joule heat generated by current flowing through the upper electrode → punch → sintered magnet body → die → lower electrode. Hot plastic working begins with the application of a pressure of 30 to 100 MPa, followed by heating. The sintered magnet body is pressurized while being heated, for example, to a temperature of 600°C to 700°C. During heating, an ON-OFF DC pulse current is applied to the sintered magnet body. During hot plastic working, it is desirable to adjust the pressure so that the working speed does not increase, preferably to maintain a constant working speed. Hot plastic working is preferably performed under reduced pressure or in an inert atmosphere, specifically, an argon or nitrogen atmosphere. Hot plastic working is preferably performed from the start of displacement to its completion while monitoring the displacement. Here, the displacement is typically monitored by monitoring the displacement of a servo motor controlling the pressure.

[0033] The crystal grains of hot-worked magnets produced by hot plastic working are flattened, with the easy axis of magnetization oriented perpendicular to the flat surface of the crystal grains. When ribbons are produced by the rapid cooling method, the crystal grains have an isotropic shape, but hot plastic working causes the crystal grains to grow into a flat shape, and the flat surface of the particles is mechanically aligned in the direction of pressure. This means that the easy axis of magnetization is aligned with the direction of pressure (the minor axis direction of the crystal grains). As a result, the easy axis of magnetization of the crystal grains within the magnet is aligned in the thickness direction of the hot-worked magnet (the sintered magnet body is transformed into a hot-worked magnet by hot plastic working). Hot-worked magnets are produced by applying the manufacturing method of anisotropic magnets, known as hot extrusion.

[0034] After heating, the current is cut off and the sintering machine is cooled. After cooling to a predetermined temperature, the second die is removed from the sintering machine, and the ring-shaped hot-worked magnet obtained from the sintered magnet body by hot plastic working is taken out from the second die.

[0035] The hot-worked magnet obtained by hot plastic working has magnetic anisotropy, for example, its relative density is nearly the true density, and it has high magnetic properties. The hot-worked magnet produced has, for example, an average crystal grain size within the above range and a Curie point of 250°C or higher and 400°C or lower.

[0036] [Grinding Process] The hot-worked magnet obtained by hot plastic processing is ground into a predetermined shape. Specifically, the hot-worked magnet (ring-shaped magnet) that has been hot-worked is removed from the device. Next, the ring-shaped magnet is ground using a surface grinder to obtain a magnet 12 with a thickness within the above-mentioned range. Specifically, the magnet is ground so that the thickness direction coincides with the direction of pressure applied during production of the hot-worked magnet, i.e., the axis of easy magnetization. In other words, grinding is performed only in the minor axis direction (i.e., the axis of easy magnetization) of the flattened crystal grains in the hot-worked magnet (ring-shaped magnet). Grinding is performed using a rotary grinding wheel, such as a diamond grinding wheel.

[0037] For example, since the hot-processed magnet (the ring-shaped magnet after grinding) is obtained as described above, it is RFe 14The hot-processed magnet has a main phase structure containing a B compound. Specifically, the average crystal grain size of the main phase is within the above range. Furthermore, the axis of easy magnetization of this hot-processed magnet is oriented in the minor axis direction of the crystal grains of the main phase.

[0038] In addition to the above-described hot-processed magnet, a sintered magnet may also be used as the rare earth magnet used for magnet 12. Hot-processed magnets are preferably used because they can suppress magnetic field degradation more effectively than sintered magnets, even when the thickness of magnet 12 is 1.0 mm or less.

[0039] As a magnetization method for obtaining the magnet 12, for example, UHM magnetization as disclosed in JP 2021-093521 A is preferably used. That is, the object to be magnetized (for example, a hot-worked magnet, i.e., a hot-worked magnet after grinding) is heated to above the Curie point of the magnet powder, and while it is cooled below the Curie point, a magnetizing magnetic field is continuously applied to the object to be magnetized by a permanent magnet, which serves as a field source. In this way, the magnet 12 magnetized at a predetermined magnetic pole pitch in the circumferential direction can be obtained.

[0040] The magnetic fluid 16 is a magnetic colloid solution containing ferromagnetic ultrafine particles such as magnetite and composite ferrite, a surfactant, and a base liquid such as water and oil. The ferromagnetic ultrafine particles usually have a size on the nano-order.

[0041] The magnetic fluid 16 supports the magnet 12 so that it can rotate relative to the coil 14. For this reason, the magnetic fluid 16 adheres to at least the surface of the magnet 12 that faces the coil 14. However, the magnetic fluid 16 may also adhere to a surface of the magnet 12 other than the surface that faces the coil 14. For example, the magnetic fluid 16 may also adhere to the entire surface of the magnet 12.

[0042] The motor 1 uses the magnet 12 to which the magnetic fluid 16 is attached, and other components can be manufactured by known methods.

[0043] For the motor 1 described above, it is preferable that the aspect ratio of the motor (motor thickness relative to the motor outer diameter (motor thickness / motor outer diameter)) is 0.05 or more and 0.2 or less. This is preferable because the torque is 20 μN or more when the drive current is 300 mA. The motor preferably has an outer diameter of 4 mm or more and 30 mm or less, and a thickness of 0.1 mm or more and 3 mm or less. Here, the outer diameter of the motor refers to the maximum diameter of the device consisting of the coil substrate, coil, magnetic fluid, and magnet. Furthermore, the thickness of the motor refers to the total thickness when the coil substrate, coil, magnetic fluid, and magnet are stacked together.

[0044] The motor 1 described above is suitable for use as an aperture drive motor in a camera, and more specifically, in small portable electronic devices such as smartphones.

[0045] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[0046] [Examples] [Example 1] Fig. 2 is a diagram for explaining the magnet produced in Example 1. As described above, the Nd-Fe-B magnet powder (R2Fe 14 A sintered magnet body was prepared using the R2Fe alloy, and hot-worked magnets (ring-shaped magnets) were fabricated by hot plastic working. The ring-shaped magnets were then ground using a surface grinder. Specifically, the magnets were ground so that the thickness direction coincided with the direction of pressure applied during fabrication of the hot-worked magnet, i.e., the direction of easy magnetization. In other words, grinding was performed only in the minor axis direction (i.e., the direction of easy magnetization) of the flattened crystal grains in the hot-worked magnet (ring-shaped magnet). The resulting hot-worked magnets (ring-shaped magnets after grinding) contained R2Fe 14The rare earth magnet had a main phase structure containing a B compound, with the easy axis of magnetization oriented in the minor axis direction of the main phase crystal grains. Next, as shown in Figures 1-1 to 1-3 and 2, multiple magnetic poles were formed on one axial end face of the ring-shaped magnet. Specifically, it was magnetized in the axial direction and circumferential direction. Magnetization was performed using UHM magnetization as disclosed in JP 2021-093521 A. That is, the object to be magnetized (the ring-shaped magnet after grinding) was heated to above the Curie point of the magnet powder, and while cooling to below the Curie point, a magnetizing magnetic field was continuously applied to the object to be magnetized using a permanent magnet as a field source. In this way, magnet (1-1) was obtained. The average crystal grain size of the main phase of the rare earth magnet contained in magnet (1-1) was in the range of 0.03 μm to 0.6 μm. The thickness of magnet (1-1) was 0.3 mm. The outer diameter was 9.6 mm, and the inner diameter was 7.0 mm. The magnetic pole pitch was approximately 0.37 mm, and the number of poles was 80. The average crystal grain size was confirmed using the following method. It was performed by observing and measuring the main phase crystal grains of each magnet using a scanning electron microscope (SEM). Specifically, the observation magnification was 1500 to 20,000 times, the observation conditions were secondary electron images, the observation direction was the direction of easy magnetization, and the grain size was confirmed using known image processing software. The SEM images measured under these conditions were loaded into the image processing software, and the particle area and perimeter were calculated, and the equivalent circle diameter was converted. Then, multiple magnets were measured, and the average of the equivalent circle diameters was taken as the average crystal grain size.

[0047] [Example 2] Magnet (2-1) was obtained in the same manner as Example 1, except that the grinding conditions were changed. The average crystal grain size of the main phase of the rare earth magnet contained in magnet (2-1) was in the range of 0.03 μm to 0.6 μm. The thickness of magnet (2-1) was 0.07 mm. The outer diameter was 9.6 mm, and the inner diameter was 7.0 mm. The magnetic pole pitch was approximately 0.37 mm, and the number of poles was 80.

[0048] [Evaluation] [Motor Fabrication] A motor 1 as shown in Figure 1-1 was fabricated using the magnets (1-1) and (2-1) obtained in Examples 1 and 2. In this case, a magnetic colloid solution containing ferromagnetic ultrafine particles (nano-order) of composite ferrite, a surfactant, and a base liquid containing water and oil was used as the magnetic fluid 16. Both could be driven satisfactorily, and because a magnetic gap was formed via the magnetic fluid, the strength against loads from the direction of the rotation axis when the motor was in use was improved.

[0049] Example 3: The correlation between surface magnetic flux and the number of pole pairs was calculated using electromagnetic field analysis. The calculation method used was to calculate the value of surface magnetic flux at a point 0.1 mm away from an ideally fully magnetized magnet arranged according to the number of pole pairs.

[0050] [Example 4] Analysis was performed on motors (4-1) to (4-4) using the following magnets (4-1) to (4-4), respectively. For the analysis, magnets (4-1) to (4-4) were used that were obtained in the same manner as in Example 1, except that the magnet thickness, outer periphery, and inner periphery of the magnet were changed. For this reason, the average crystal grain size of the main phase of the rare earth magnets contained in magnets (4-1) to (4-4) was set to be in the range of 0.03 μm to 0.6 μm. Furthermore, the magnet (4-1) had a thickness of 0.6 mm, an outer diameter of 9.6 mm, and an inner diameter of 7 mm; the magnet (4-2) had a thickness of 0.4 mm, an outer diameter of 9.6 mm, and an inner diameter of 7 mm; the magnet (4-3) had a thickness of 0.3 mm, an outer diameter of 9.6 mm, and an inner diameter of 7 mm; and the magnet (4-4) had a thickness of 0.1 mm, an outer diameter of 9.6 mm, and an inner diameter of 7 mm. The magnets (4-1) to (4-4) had a magnetic pole pitch of approximately 0.37 mm and a number of poles of 80. Motors (4-1) to (4-4) containing these magnets (4-1) to (4-4), respectively, were used. Table 1 shows the outer diameter and thickness of the motor. Here, the outer diameter of the motor was adjusted from the coil substrate, and the thickness was adjusted from the coil substrate thickness and the magnet thickness. The drive torque of these motors (4-1) to (4-4) was calculated by analysis when a drive current of 300 mA was applied. Table 1 shows the torque along with the aspect ratio of these motors (motor thickness relative to the motor outer diameter (motor thickness / motor outer diameter)).

[0051]

[0052] Fifth Embodiment One of the objectives of this embodiment is to provide a compact driving device.

[0053] In order to solve the above-mentioned problems and achieve the object, the drive device of this embodiment comprises a housing having a cover and a base with an opening, a magnet having multiple magnetic poles arranged circumferentially, multiple magnetic pole portions provided on the base in the direction of the rotation axis, multiple blades provided on the magnet in the direction of the rotation axis, and a magnetic fluid having magnetism that rotatably supports the magnet with respect to the housing, wherein the magnetic fluid forms a magnetic circuit with the magnet and the multiple magnetic pole portions, the multiple blades displace relative to the cover as the magnet rotates to open and close the opening, the multiple magnetic pole portions face the multiple magnetic poles of the magnet in the direction of the rotation axis, and the magnet is arranged inside one or more walls provided on the base in the radial direction.

[0054] According to one aspect of the drive device according to this embodiment, a compact drive device can be provided.

[0055] Next, a fifth embodiment of the drive device 10 will be described in detail with reference to the drawings. Note that the dimensional relationships and ratios of elements in the drawings may differ from reality. The dimensional relationships and ratios may differ between the drawings. Furthermore, the configuration of the motor 1 described above and the configuration of the motor MO included in the drive device 10 are, for example, identical.

[0056] Fig. 4 is a perspective view of the drive device 10 according to the fifth embodiment. Fig. 5 is an exploded perspective view of the drive device 10 shown in Fig. 4. Fig. 6 is a cross-sectional view taken along the arrows XX-XX in Fig. 4.

[0057] In the description of the driving device 10 of Example 5, in order to make it easier to understand the directions, the direction perpendicular to the surface of the substrate 3 is referred to as the rotational axis direction A, the direction in which the multiple magnets 5 are arranged is referred to as the circumferential direction C, and the direction included in a plane perpendicular to the rotational axis direction A, passing through the axis 221o of the through-hole portion 211c in the base 21, and perpendicular to the circumferential direction C is referred to as the radial direction R.

[0058] 4, 5, and 6 is mounted on a thin electronic device such as a smartphone, a tablet terminal, a drive recorder, etc. The drive device 10 includes a housing 2, a substrate 3, a magnetic fluid 4, a magnet 5, a rotor 6, a shield 7, and a plurality of blades 8.

[0059] The housing 2 according to this embodiment has a base 21 and a cover 22, and the base 21, the cover 22, and the substrate 3 form an internal space 2s (see FIG. 6 ). The internal space 2s accommodates a magnetic fluid 4, a magnet 5, a rotor 6, a shield 7, and blades 8.

[0060] The base 21 includes a main body 211 that is substantially rectangular in top view when viewed from the rotation axis direction A. The main body 211 includes a first recess 211a, a second recess 211b, a through-hole 211c, and a notch 211d.

[0061] The first recess 211a is recessed from a surface located on one side of the main body 211 in the rotational axis direction A toward the substrate 3. The second recess 211b is recessed from a surface located on one side of the first recess 211a in the rotational axis direction A toward the substrate 3. The through-hole 211c penetrates the main body 211 in the rotational axis direction A. The notch 211d is recessed from the outer circumferential edge of the main body 211 toward the inside in the radial direction R when viewed from the rotational axis direction A.

[0062] The inner peripheral surface 21f of the through-hole portion 211c of the base 21 faces the outer peripheral edge of the magnetic fluid 4, the outer peripheral edge of the magnet 5, and the outer peripheral edge of the rotor 6 in the radial direction R. In other words, the base 21 has the function of surrounding the magnetic fluid 4, the magnet 5, and the rotor 6 in the radial direction R.

[0063] The first recess 211a is formed in a generally ring-shaped (substantially annular) shape when viewed from above in the rotation axis direction A. The second recess 211b is formed in a generally ring-shaped (substantially annular) shape when viewed from above from one side in the axial direction. The diameter of the second recess 211b is smaller than the diameter of the first recess 211a. Furthermore, the second recess 211b is formed with a plurality of first pins 211p (six in this embodiment) that protrude from the surface of the second recess 211b toward one side in the axial direction.

[0064] The through-hole portion 211c is formed in a substantially circular shape in a top view when viewed from the rotation axis direction A. An inner circumferential surface 21f of the through-hole portion 211c in the base 21 functions as a wall.

[0065] The cutout portion 211d is formed in a substantially rectangular shape when viewed from above in the rotation axis direction A. The cutout portion 211d exposes a copper foil portion (hereinafter referred to as a land 322) of the circuit portion 32 on the substrate 3 from one side in the rotation axis direction A.

[0066] Although the drive device 10 according to this embodiment has one base 21, the base 21 may be made up of multiple components. In other words, in this embodiment, one wall is formed by the inner circumferential surface 21f of the through-hole portion 211c of one base 21, but if the base 21 is made up of multiple components, multiple walls will be formed. Furthermore, multiple walls may be formed by forming notches extending outward in the radial direction R at equal intervals on the inner circumferential surface 21f of the base 21, for example.

[0067] The cover 22 is formed in a ring shape (annular shape) and is disposed so as to face one surface of the blade 8 in the rotation axis direction A. The cover 22 is further formed with a first through hole 22H1, a second through hole 22H2, and an opening 22H3 that penetrate the cover 22 in the rotation axis direction A.

[0068] The first through-hole 22H1 is formed, for example, in a circular shape when viewed from the rotation axis direction A. The cover 22 is fixed to the base 21 by inserting a first pin 211p into the first through-hole 22H1.

[0069] When viewed from the rotation axis direction A, the second through hole 22H2 is formed as an elongated hole extending, for example, in the circumferential direction C. The second pin 6p of the rotating body 6 is inserted into the second through hole 22H2, and the second through hole 22H2 guides the movement of the second pin 6p of the rotating body 6 along the circumferential direction C.

[0070] The opening 22H3 is formed, for example, in a circular shape when viewed from the rotation axis direction A. The opening 22H3 transmits light to the lens unit U1 (see FIG. 6) via the substrate 3. The lens unit U1 is mounted on a camera (not shown) and incorporates a lens and an image sensor (not shown). The camera can capture moving or still images using the lens, image sensor, etc.

[0071] Next, the substrate 3, magnetic fluid 4, and magnet 5 in the drive device 10 will be described with reference to Figures 7, 8, 9, 10, 11, and 12. Figure 7 is a perspective view showing the magnet 5, magnetic fluid 4, and substrate 3 of the drive device 10 shown in Figure 4. Figure 8 is a cross-sectional view of the magnet 5, magnetic fluid 4, and substrate 3 shown in Figure 7. Figure 9 is a plan view showing the magnet 5 and substrate 3 shown in Figure 7. Figure 10 is a plan view and a partially enlarged view of the magnet 5 shown in Figure 7. Figure 11 is an enlarged plan view of a portion of the circuit unit 32 of the substrate 3 shown in Figure 9. Figure 12 is a plan view showing the first coil group 321A and the second coil group 321B of the circuit unit of the substrate 3 shown in Figure 9.

[0072] The substrate 3 is, for example, a circuit board, and a flexible printed circuit (FPC) can be used. The substrate 3 has an insulating base 31 and a conductive circuit portion 32 formed on one surface in the rotation axis direction A. The base 31 is formed, for example, from an optically transparent epoxy resin or PI (polyimide). The circuit portion 32 is a conductor formed, for example, from a copper alloy. The circuit portion 32 shown in FIG. 9 includes a coil 321, a land 322, and an electrical connection portion 323. The coil 321 is an example of a magnetic pole portion in the drive device 10 according to this embodiment.

[0073] More specifically, the circuit portion 32 includes a plurality of coils 321 (40 in this embodiment), a plurality of lands 322 (four in this embodiment), and a plurality of electrical connection portions 323 (four in this embodiment).

[0074] The coil 321 has, for example, a first portion 3211 , a second portion 3212 , a third portion 3213 , a fourth portion 3214 , a fifth portion 3215 , and a sixth portion 3216 .

[0075] The first portion 3211 extends linearly along the radial direction R. The second portion 3212 extends in an arc shape along the circumferential direction C from an inner end of the first portion 3211 in the radial direction R. The third portion 3213 extends linearly along the radial direction R from an end of the second portion 3212 on one side in the circumferential direction C.

[0076] The fourth portion 3214 extends in an arc shape along the circumferential direction C from an outer end of the third portion 3213 in the radial direction R. The fifth portion 3215 extends in a straight line along the radial direction R from an end of the fourth portion 3214 on one side in the circumferential direction C. The sixth portion 3216 extends in an arc shape along the circumferential direction C from an inner end of the fifth portion 3215 in the radial direction R.

[0077] The lands 322 are electrodes for applying a voltage to the coil 321. The lands 322 are arranged, for example, in a row in the horizontal direction. The electrical connection portions 323 electrically connect the lands 322 and the coil 321.

[0078] Of the four lands 322, a first land 322a and a second land 322b arranged on the outer sides in the horizontal direction are electrically connected to the AC power supply PS. A first coil group 321A in which a plurality of coils 321 (10 in this embodiment) are connected in series is configured between an electrical connection part 323 connected to the first land 322a and an electrical connection part 323 connected to the second land 322b.

[0079] In the first coil group 321A, the first land 322a is connected to the first coil 321Aa by an electrical connection portion 323, and the first coil 321Aa is connected to the second coil 321Ab that is adjacent to the first coil 321Aa in the counterclockwise direction in the circumferential direction C. Then, the third coil 321Ac to the tenth coil 321Aj are connected in series from the second coil Ab in counterclockwise order along the circumferential direction C. Furthermore, when the first land 322a is taken as the starting point, the last tenth coil 321Aj is connected to the second land 322b by the electrical connection portion 323.

[0080] Of the four lands 322, the third land 322c and the fourth land 322d, which are located on the inner side in the horizontal direction, are electrically connected to the AC power supply PS. A second coil group 321B in which a plurality of (10 in this embodiment) coils 321 are connected in series is configured between the electrical connection part 323 connected to the third land 322c and the electrical connection part 323 connected to the fourth land 322d.

[0081] In the second coil group 321B, the third land 322c is connected to the first coil 321Ba by the electrical connection portion 323, and the first coil 321Ba is connected to the second coil 321Bb that is adjacent to the first coil 321Ba in the counterclockwise direction in the circumferential direction C. Then, the third coil 321Bc to the tenth coil 321Bj are connected in series in counterclockwise order from the second coil Bb along the circumferential direction C. Furthermore, when the third land 322c is taken as the starting point, the last tenth coil 321Bj is connected to the fourth land 322d by the electrical connection portion 323.

[0082] In the drive device 10 according to this embodiment, each of the multiple coils 321 constituting the first coil group 321A is positioned further outward in the radial direction R than each of the multiple coils 321 constituting the second coil group 321B. Therefore, in the circuit section 32 according to this embodiment, it is possible to prevent the first coil group 321A and the second coil group 321B from intersecting on the substrate 3.

[0083] The plurality of coils 321 constituting the first coil group 321A and the plurality of coils 321 constituting the second coil group 321B will be described in more detail below.

[0084] In each of the odd-numbered coils 321, the first portion 3211, the second portion 3212, and the third portion 3213 are arranged in a U-shape that opens outward in the radial direction R when viewed from the rotation axis direction A.

[0085] In addition, in each of the odd-numbered coils 321, the third portion 3213, the fourth portion 3214, and the fifth portion 3215 are arranged in a U-shape that opens inward in the radial direction R when viewed from the rotation axis direction A.

[0086] Then, the first portion 3211, the second portion 3212, and the third portion 3213 of the first coil group 321A are arranged inside the first portion 3211, the second portion 3212, and the third portion 3213 of the second coil group 321B in the radial direction R. In addition, the third portion 3213, the fourth portion 3214, and the fifth portion 3215 constituting the second coil group 321B are arranged inside the third portion 3213, the fourth portion 3214, and the fifth portion 3215 of the first coil group 321A in the radial direction R.

[0087] In each of the even-numbered coils 321, the first portion 3211, the second portion 3212, and the third portion 3213 are arranged in a U-shape that opens inward in the radial direction R when viewed from the rotation axis direction A.

[0088] In addition, in each of the even-numbered coils 321, the third portion 3213, the fourth portion 3214, and the fifth portion 3215 are arranged in a U-shape that opens outward in the radial direction R when viewed from the rotation axis direction A.

[0089] Then, the first portion 3211, the second portion 3212, and the third portion 3213 of the second coil group 321B are arranged inside the first portion 3211, the second portion 3212, and the third portion 3213 of the first coil group 321A in the radial direction R. In addition, the third portion 3213, the fourth portion 3214, and the fifth portion 3215 constituting the first coil group 321A are arranged inside the third portion 3213, the fourth portion 3214, and the fifth portion 3215 of the second coil group 321B in the radial direction R.

[0090] Furthermore, the multiple coils 321 can be arranged separately on multiple layers that make up the substrate 3. In this case, for example, the first coil group 321A can be arranged on the first layer of the substrate 3, and the second coil group 321B can be arranged on the second layer of the substrate 3. This is not limited to this, and it is also possible to increase the number of layers to three or four, and arrange different coils on each layer. This can improve the torque of the drive unit 10.

[0091] The magnetic fluid 4 is formed in a ring shape (annular shape) and has an opening 4H. The magnetic fluid 4 is arranged so as to contact one surface of the substrate 3 in the rotation axis direction A. The opening 4H penetrates the magnetic fluid 4 in the rotation axis direction A. As shown in FIG. 6 , the opening 4H of the magnetic fluid 4 coincides with the opening 22H3 of the cover 22 in the rotation axis direction A.

[0092] The magnetic fluid 4 is a magnetic colloid solution containing ferromagnetic ultrafine particles such as magnetite and composite ferrite, a surfactant, and a base liquid such as water and oil. The ferromagnetic ultrafine particles are on the nanometer order.

[0093] The magnetic fluid 4 adheres to at least the surface of the magnet 5 facing the coil 321 in the rotation axis direction A. However, the magnetic fluid 4 may also adhere to a surface of the magnet 5 other than the surface facing the coil 321. For example, the magnetic fluid 4 may adhere to the entire surface of the magnet 5. Furthermore, the magnetic fluid 4 supports the magnet 5 rotatably relative to the coil 321.

[0094] The magnet 5 is formed in a ring shape (annular shape) and has an opening 5H. The magnet 5 is arranged so as to contact one surface of the magnetic fluid 4 in the rotation axis direction A. The opening 5H passes through the magnet 5 in the rotation axis direction A. As shown in FIG. 6 , the opening 5H of the magnet 5 coincides with the opening 22H3 of the cover 22 in the rotation axis direction A.

[0095] The magnet 5 is rotatably supported by the magnetic fluid 4 relative to the coil 321. In the rotation axis direction A of the drive device 10, a magnetic gap is formed between the magnet 5 and the coil 321 via the magnetic fluid 4.

[0096] Furthermore, in the driving device 10 according to this embodiment, the motor MO is formed by the substrate 3, the magnetic fluid 4, and the magnet 5. More specifically, in the driving device 10, the axial gap type motor MO is formed by the substrate 3, the magnetic fluid 4, and the magnet 5. For example, as shown in Fig. 8 , in the rotation axis direction A perpendicular to the surface of the substrate 3, the magnetic fluid 4 is arranged so as to be in contact with the surface of the substrate 3, and the magnet 5 is arranged so as to be in contact with the surface of the magnetic fluid 4.

[0097] In the drive unit 10, a magnetic gap is formed between the coil 321 of the substrate 3 and the magnet 5 via the magnetic fluid 4 in the direction of the rotation axis A, and therefore the strength against the load from the direction of the rotation axis A during driving can be improved. In contrast, for example, the motor described in JP-A-5-30722 has a gap formed by an air gap, and therefore has weak strength against the load from the direction of the rotation axis A during driving.

[0098] On the other hand, in the driving device 10 according to this embodiment, the substrate 3 has a plane extending in a direction perpendicular to the rotation axis direction A. A coil 321 and a land 322 are formed on this plane of the substrate 3. The magnetic fluid 4 is in contact with the plane at a position corresponding to the position where the coil 321 is formed. The magnetic fluid 4 is magnetically held by the magnet 5.

[0099] 9, width 321W of coil 321 in the radial direction R is larger than width 5W of magnet 5 in the radial direction R. This prevents magnet 5 from protruding from coil 321 even if magnet 5 shifts in the radial direction R while drive device 10 is in operation, thereby ensuring stable operation of drive device 10.

[0100] As shown in Figure 8, in the drive unit 10, a magnetic gap is formed via the magnetic fluid 4, and the magnet 5 is rotatably supported by the magnetic fluid 4 relative to the coil 321. This improves the strength against loads from the rotational axis direction A when the drive unit 10 is in operation. Also, since the magnet 5 and the coil 321 face each other in the axial direction (rotational axis direction A), which is a so-called axial gap motor, the thickness in the rotational axis direction A can be reduced. Furthermore, because the magnetic fluid 4 is magnetically held by the magnet 5, the magnet 5, magnetic fluid 4, and coil 321 are arranged in this order when viewed from the rotational axis direction A.

[0101] The magnet 5 is ring-shaped and has an average crystal grain size preferably in the range of 0.05 μm to 1.0 μm, more preferably in the range of 0.1 μm to 1.0 μm, and even more preferably in the range of 0.3 μm to 0.6 μm. Specifically, the magnet 5 includes a rare earth magnet, and the rare earth magnet has an average crystal grain size preferably in the range of 0.05 μm to 1.0 μm, more preferably in the range of 0.1 μm to 1.0 μm, and even more preferably in the range of 0.3 μm to 0.6 μm. Because the average crystal grain size is within the above range, the magnet 51 can exhibit a predetermined rigidity in the rotation axis direction A. In other words, because the crystalline structure is fine, the magnet 51 has high hardness. If the average crystal grain size is smaller than 0.05 μm, the magnet may become amorphous, potentially resulting in a loss of anisotropy. On the other hand, if the average crystal grain size is larger than 1.0 μm, there is a concern that the magnetic properties may be degraded. Furthermore, if the average crystal grain size is larger than 1.0 μm, there is a concern that the impact of deterioration due to cutting during the production of magnet 5 will be significant. Furthermore, in the hot-worked magnet described below, if the average crystal grain size is within the above range (i.e., if it is relatively small), deterioration due to cutting during production will be limited to the surface. In contrast, if the average crystal grain size is larger than the above range, there is a concern that deterioration will reach deeper through the crystal grain boundaries, resulting in a decrease in magnetic properties.

[0102] The thickness of the magnet 5 is preferably 1.0 mm or less in the rotation axis direction A. This has the advantage of allowing the drive device 10 to be made more compact. From the viewpoint of manufacturing the magnet 5, the thickness is preferably 0.07 mm or more. The inner diameter of the magnet 5 is preferably 1 mm or more and 50 mm or less. The outer diameter of the magnet 5 is preferably 3 mm or more and 60 mm or less.

[0103] The magnet 5 has multiple magnetic poles (80 in this embodiment). Specifically, the magnetic poles are formed at a predetermined pitch in the circumferential direction C of the magnet 5. As shown in FIG. 10 , the magnet 5 according to this embodiment has N poles (one magnetic pole) and S poles (the other magnetic pole) arranged alternately in the circumferential direction C. From the viewpoint of magnetic flux density, the pitch of the multiple magnetic poles is preferably 2.0 mm or less. Here, the magnetic pole pitch is the length on the outer periphery of the magnet 5. Furthermore, from the viewpoint of magnetic flux density, the number of poles is preferably 16 or more. In the drive device 10 according to this embodiment, the number of pole pairs each consisting of one N pole and one S pole and the number of the multiple coils 321 are both the same, for example, 40.

[0104] Next, the motor MO when the drive device 10 having the above configuration is driven will be described. When the motor MO is driven, an AC voltage is applied between the first land 322a and the second land 322b by the AC power supply PS, and a current flows from the first land 322a to the second land 322b. In the rotation axis direction A, an S pole is formed in each portion of the coil 321 facing the S pole of the magnet 5, and an N pole is formed in each portion of the coil 321 facing the N pole of the magnet 5. The repulsive force of the magnetic poles then causes the magnet 5 to rotate in the circumferential direction C, and the magnetic pole of the magnet 5 and the magnetic pole of each portion of the coil 321 become opposite, forming a magnetic circuit MC (see FIG. 7 ) by the magnetic fluid 4, the magnet 5, and the coil 321.

[0105] Furthermore, an AC voltage is applied between the third land 322c and the fourth land 322d from the AC power supply PS so that the phase difference is 90 degrees with respect to the phase between the first land 322a and the second land 322b, causing the magnetic poles of the magnet 5 and the magnetic poles of each part of the coil 321 to match, and the repulsive force of the magnetic poles causes the magnet 5 to rotate in the circumferential direction C. Thereafter, the magnetic poles of the magnet 5 and the magnetic poles of each part of the coil 321 become opposite, and a magnetic circuit MC (see FIG. 7) is formed by the magnetic fluid 4, the magnet 5, and the coil 321.

[0106] Thereafter, in the same manner as described above, an AC voltage is applied to the circuit portion 32 from the AC power supply PS, causing the magnet 5 to rotate in the circumferential direction C relative to the housing 2 and the substrate 3 .

[0107] Next, the rotor 6 and the shield 7 will be described again with reference to FIGS.

[0108] The rotating body 6 is formed in a ring shape (annular shape) and has an opening 6H. The rotating body 6 is disposed so as to contact one surface of the magnet 5 in the rotational axis direction A. The opening 6H penetrates the rotating body 6 in the rotational axis direction A. As shown in FIG. 6 , the opening 6H of the rotating body 6 coincides with the opening 22H3 of the cover 22 in the rotational axis direction A. Furthermore, the rotating body 6 is formed with a plurality of second pins 6p (six in this embodiment) that protrude from the surface of the rotating body 6 toward one side in the rotational axis direction A. Because the rotating body 6 is fixed to the magnet 5 by, for example, an adhesive, the rotating body 6 rotates relative to the housing 2 and the substrate 3 along with the rotation of the magnet 5 in the circumferential direction C when the drive device 10 is driven.

[0109] The shield 7 has a function of preventing the magnetic fluid 4 from drying, for example. The shield 7 is formed in a ring shape (annular). The shield 7 is disposed so as to contact one surface of the rotor 6 in the rotation axis direction A. The shield 7 is further formed with a first through hole 7H1, a second through hole 7H2, and an opening 7H3 penetrating the shield 7 in the rotation axis direction A. The first through hole 7H1 is formed, for example, in a circular shape when viewed from the rotation axis direction A. The shield 7 is fixed to the base 21 by inserting a first pin 211p into the first through hole 7H1. The second through hole 7H2 is formed as an elongated hole extending in the circumferential direction C when viewed from the rotation axis direction A. The second pin 6p of the rotor 6 is inserted into the second through hole 7H2, and the second through hole 7H2 guides movement of the second pin 6p of the rotor 6 along the circumferential direction C. The opening 7H3 penetrates the shield 7 in the rotation axis direction A. As shown in FIG. 6, the opening 7H of the shield 7 coincides with the opening 22H3 of the cover 22 in the rotation axis direction A.

[0110] Next, blades 8 will be described with reference to Figures 13 and 14. Figure 13 is a perspective view of drive unit 10 shown in Figure 4 with cover 22 removed to expose blades 8. Figure 14 is a plan view of drive unit 10 shown in Figure 4 with cover 22 removed to expose blades 8.

[0111] Each of the plurality of (six in this embodiment) blades 8 is arranged so as to contact one surface of the rotor 6 in the rotation axis direction A. Each blade 8 is formed so as to extend along the circumferential direction C, and has a first end 8e1 located on one side in the circumferential direction C, a second end 8e2 located on the other side in the circumferential direction C, and an inner peripheral edge 8e3 located on the inside in the radial direction R.

[0112] The plurality of blades 8 are arranged in a ring shape (annular shape) along the circumferential direction C, and therefore the inner peripheral edges 8e3 of the plurality of blades 8 form an opening 8H3.

[0113] Furthermore, each of the blades 8 is formed with a first through hole 8H1 and a second through hole 8H2 that penetrate the blade 8 in the rotation axis direction A.

[0114] The first through-holes 8H1 are formed, for example, in a circular shape when viewed from the rotation axis direction A, and are arranged so as to be closer to the first end 8e1 than to the second end 8e2. Each of the blades 8 is supported by the base 21 so as to be rotatable about the axis of the first pin 211p by inserting a first pin 211p into the first through-hole 8H1.

[0115] The second through-hole 8H2 is formed as an elongated hole extending in the circumferential direction C so that the distance from the axis 211o to the first end 8e1 side is different from the distance from the axis 211o to the second end 8e2 side when viewed from the rotation axis direction A. More specifically, as shown in FIG. 14 , the second through-hole 8H2 is formed so that the distance from the axis 211o to the first end 8e1 side is greater than the distance from the axis 211o to the second end 8e2 side when viewed from the rotation axis direction A. Therefore, when the magnet 5 and the rotor 6 move in the circumferential direction C, each of the blades 8 rotates around the axis of the first pin 211p, and the size of the opening 8H3 formed by the multiple inner peripheral edges 8e3 increases or decreases when viewed from the rotation axis direction A. In other words, the multiple blades 8 have an aperture function that adjusts the amount of light incident on the lens unit U1 through the opening 22H3 of the cover 22 and the substrate 3 by opening and closing the opening 8H3.

[0116] Next, the driving of the drive unit 10 will be described with reference to Figures 13 to 15. Figure 14 is a plan view of the drive unit 10 shown in Figure 4 in a state where the blade 8 has been rotated to make the opening 8H3 narrower than that shown in Figure 15.

[0117] When the drive device 10 is driven, AC voltages are applied from the AC power supply PS to the first coil group 321A and the second coil group 321B so that the coils are out of phase with each other by 90 degrees. In other words, among the multiple coils 321, the current flow in the coils 321 constituting the first coil group 321A and the coils 321 constituting the second coil group 321B is two-phase.

[0118] As a result, the magnet 5 and the rotor 6 rotate to one side in the circumferential direction C (for example, counterclockwise in the circumferential direction C in FIG. 14 ), and the second pin 6p moves toward the second end 8e2 in the circumferential direction C. More specifically, the second pin 6p moves from the first end 8e1 side to the second end 8e2 side inside each second through hole 8H2 of the blade 8, and each blade 8 rotates around the axis of the first pin 211p, and the area of ​​the opening 8H3 formed by the multiple blades 8 increases.

[0119] On the other hand, if an AC voltage is applied from the AC power supply PS so that the current flowing from the AC power supply PS is reversed, the magnet 5 and the rotor 6 rotate to the other side in the circumferential direction C (for example, clockwise in FIG. 15 ), and the second pin 6p moves toward the first end 8e1 in the circumferential direction C. More specifically, the second pin 6p moves from the second end 8e2 side to the first end 8e1 side inside each second through hole 8H2 of the blade 8, and therefore each blade 8 rotates around the axis of the first pin 211p, and the area of ​​the opening 8H3 formed by the multiple blades 8 decreases.

[0120] That is, when the drive device 10 according to this embodiment is driven, an AC voltage is applied from the AC power supply PS to the circuit unit 32, causing the magnet 5 and the rotating body 6 to rotate in the circumferential direction C relative to, for example, the housing 2, the substrate 3, the magnetic fluid 4, and the shield 7. Then, the second pin 6p of the rotating body 6 moves inside the second through-hole 8H2, thereby increasing or decreasing the area of ​​the opening 8H3 formed by the plurality of blades 8, and adjusting the amount of light incident on the lens unit U1 through the opening 22H3 of the cover 22 and the substrate 3.

[0121] As described above, the driving device 10 according to this embodiment includes the housing 2 having the cover 22 with the opening 22H3 and the base 21, the magnet 5 having multiple magnetic poles aligned in the circumferential direction C, multiple coils (magnetic pole portions) 321 provided on the base 21, multiple vanes 8 provided on the magnet 5 in the rotational axis direction A, and a magnetic fluid 4 rotatably supporting the magnet 5 relative to the housing 2. The magnetic fluid 4 forms a magnetic circuit MC with the magnet 5 and the multiple coils (magnetic pole portions) 321. The multiple vanes 8 are displaced relative to the cover 22 as the magnet 5 rotates, opening and closing the through-hole 211c. In the rotational axis direction A, the multiple coils (magnetic pole portions) 321 face the multiple magnetic poles of the magnet 5. In the radial direction R, the magnet 5 is disposed inside one or more walls (the inner peripheral surface 21f of the base 21) provided on the base 21. Therefore, the driving device 10 according to this embodiment can be thin in thickness in the rotational axis direction A, thereby providing a compact driving device 10. Therefore, drive unit 10 according to this embodiment can provide an electronic device with a reduced thickness in the rotation axis direction A. Furthermore, drive unit 10 mounted on an electronic device has an aperture function that adjusts the amount of light incident on the camera lens, allowing the camera to capture high-quality video or still images.

[0122] In the driving device 10 according to this embodiment, the through-hole portion 211c of the base 21 faces the outer circumferential edge of the magnetic fluid 4, the outer circumferential edge of the magnet 5, and the outer circumferential edge of the rotating body 6 in the radial direction R, and the base 21 has the function of surrounding the magnetic fluid 4, the magnet 5, and the rotating body 6 in the radial direction R. Therefore, in the rotation axis direction A when the driving device 10 according to this embodiment is not being driven, the inner circumferential surface 21f of the base 21 acts as a wall, preventing the magnetic fluid 4 and the magnet 5 from moving out of position with the circuit section 32.

[0123] In the drive device 10 according to this embodiment, the substrate 3 has a circuit section 32 formed of a conductor, and the circuit section 32 has a first coil group 321A configured by connecting a plurality of coils 321 in series, and a second coil group 321B configured by connecting a plurality of coils 321 in series, and each of the plurality of coils 321 configuring the first coil group 321A is located outside each of the plurality of coils 321 configuring the second coil group 321B in the radial direction R. Therefore, the circuit section 32 according to this embodiment can prevent the first coil group 321A and the second coil group 321B from crossing each other on the substrate 3, and the density of the circuit section 32 can be increased.

[0124] In the driving device 10 according to this embodiment, the outer circumferential portion 5o of the magnet 5 can come into contact with one or more walls (the inner circumferential surface 21f of the base 21) in the radial direction R. Therefore, in the rotation axis direction A when the driving device 10 according to this embodiment is not being driven, the inner circumferential surface 21f of the base 21 acts as a wall, preventing the magnetic fluid 4 from moving out of position from the coil (magnetic pole portion) 321 and the magnet 5.

[0125] In the driving device 10 according to this embodiment, the number of the magnetic poles of the magnet 5 is greater than the number of the coils 321 (magnetic pole portions).

[0126] In the driving device 10 according to this embodiment, the plurality of coils 321 (magnetic pole portions) are made of a conductor.

[0127] In the driving device 10 according to this embodiment, the plurality of magnetic pole portions are a plurality of coils 321 .

[0128] In the driving device 10 according to this embodiment, the thickness of the magnet 5 in the rotation axis direction A is 1.0 mm or less. Therefore, the thickness of the driving device 10 according to this embodiment in the rotation axis direction A can be made thin.

[0129] In the driving device 10 according to this embodiment, the pitch of the coils 321 (magnetic pole portions) is 2.0 mm or less.

[0130] In the driving device 10 according to this embodiment, the magnet 5 includes magnetic powder having a particle size ranging from 0.3 μm to 0.6 μm, and the magnet 5 has a predetermined rigidity in the direction A of the rotation axis.

[0131] The drive unit 10 according to the present embodiment has been described above as having six blades 8. However, the number of blades of the drive unit 10 according to the present embodiment is not limited to six and can be increased or decreased as appropriate.

[0132] 16 and 17, in the driving device 10 according to the fifth embodiment, a weight 9 may be fixed on the magnet 5. FIG. 16 is a perspective view of a driving device 10A according to the sixth embodiment. FIG. 17 is a perspective view of a driving device 10B according to the seventh embodiment. In the driving devices 10A and 10B shown in FIGS. 16 and 17, the weight 9 may rotate or be displaced in position in accordance with the rotation of the magnet 5.

[0133] Also, as shown in Figure 16, in the rotation axis direction A, there is a non-magnetic plate 43 between the magnetic fluid 4 and the coil 321, and the magnetic fluid 4 and the coil 321 may face each other via the non-magnetic plate 43.

[0134] 16 , the non-magnetic plate 43 may include an annular wall 435 extending in the rotation axis direction A. The annular wall 435 faces the magnetic fluid 4 in the radial direction, thereby preventing the magnetic fluid 4 from leaking outward in the radial direction.

[0135] 17 , a non-magnetic plate 45 may be provided between the magnet 5 and the magnetic fluid 4 in the rotation axis direction A, and the magnet 5 and the magnetic fluid 4 may face each other via the non-magnetic plate 45. In this case, the magnetic force of the magnet 5 acts on the magnetic fluid 4 beyond the non-magnetic plate 45. In such a configuration, the non-magnetic plate 45 is also rotatably supported by the magnetic fluid 4.

[0136] The non-magnetic plate 45 may also include an annular wall 453 extending in the rotation axis direction A. In this case, as shown in Fig. 17 , the annular wall 453 extends in the rotation axis direction A in the opposite direction to the direction in which the annular wall 435 extends. In this case, too, the annular wall 453 faces the magnetic fluid 4 in the radial direction, thereby suppressing leakage of the magnetic fluid 4.

[0137] The drive unit 10 may be configured to include both the annular walls 45 and 43. Also, in the motor 1 according to the embodiment, a non-magnetic plate may be provided between the magnetic fluid 16 and the coil 14, or between the magnet 12 and the magnetic fluid 16, or both, in the rotation axis direction A.

[0138] The above has been a description of the motor 1, and the drive unit 10, drive unit 10A, and drive unit 10B according to the embodiments and examples. However, the present invention is not limited to the embodiments and examples, and various modifications are possible without departing from the spirit of the present invention. The present invention also includes configurations in which the components of the above-described embodiments and examples are appropriately combined. Such modifications without departing from the spirit of the present invention are also included within the technical scope of the present invention, and this will be clear to those skilled in the art from the claims.

[0139] REFERENCE SIGNS LIST 1 motor, 12 magnet, 14 coil, 16 magnetic fluid, 18 substrate, 20 electrode, 10, 10A, 10B drive device, 2 housing, 21 base, 21f inner peripheral surface (wall), 22 cover, 22H3 opening, 3 substrate, 321 coil (magnetic pole portion), 4 magnetic fluid, 43, 45 non-magnetic plate, 435, 453 annular wall, 5, 51 magnet, 8 blade, 9 weight, MC magnetic circuit, A rotation axis direction, C circumferential direction, R radial direction

Claims

1. A motor comprising: a magnet; one or more coils facing the magnet in the direction of a rotation axis; and a magnetic fluid, wherein the magnet is rotatably supported by the magnetic fluid relative to the coil.

2. The motor according to claim 1, wherein the magnet has an average crystal grain size in the range of 0.05 μm to 1.0 μm.

3. The motor according to claim 1 or 2, wherein the thickness of the magnet in the direction of the rotation axis is 1.0 mm or less.

4. The motor according to claim 1 or 2, wherein the magnet has a plurality of magnetic poles, and the pitch of the plurality of magnetic poles is 2.0 mm or less.

5. The motor according to claim 1 or 2, wherein a magnetic gap is formed between the magnet and the coil via the magnetic fluid.

6. The motor according to claim 1 or 2, wherein the ratio of the thickness of the motor to the outer diameter of the motor (thickness of the motor / outer diameter of the motor) is 0.05 or more and 0.2 or less, and the torque is 20 μN or more.

7. A drive device comprising: a housing having a cover and a base with an opening; a magnet having a plurality of magnetic poles arranged in a circumferential direction; a plurality of magnetic pole portions provided on the base; a plurality of vanes provided on the magnet in the direction of the rotation axis; and a magnetic fluid having magnetism that rotatably supports the magnet relative to the housing, wherein the magnetic fluid forms a magnetic circuit with the magnet and the plurality of magnetic pole portions; the plurality of vanes are displaced relative to the cover as the magnet rotates to open and close the opening; in the direction of the rotation axis, the plurality of magnetic pole portions face the plurality of magnetic poles of the magnet; and in the radial direction, the magnet is disposed inside one or more walls provided on the base.

8. The drive device according to claim 7, wherein an outer periphery of the magnet is capable of contacting the one or more walls in the radial direction.

9. The drive device according to claim 7 or 8, wherein the number of the plurality of magnetic poles of the magnet is greater than the number of the plurality of magnetic pole portions.

10. The drive unit according to claim 7 or 8, wherein the plurality of magnetic pole portions are formed of a conductor.

11. The drive device according to claim 7 or 8, wherein the plurality of magnetic pole portions are a plurality of coils.

12. The drive unit according to claim 7 or 8, wherein the thickness of the magnet in the direction of the rotation axis is 1.0 mm or less.

13. The drive unit according to claim 7 or 8, wherein the pitch of the magnetic pole portions is 2.0 mm or less.

14. The drive unit according to claim 7 or 8, wherein the magnet comprises magnetic powder having a grain size in the range of 0.3 μm to 0.6 μm, and the magnet has a predetermined rigidity in the direction of the rotation axis.

Images