Magnetic flux generation member and actuator

Abstract

This magnetic flux generation member includes a first magnetic part and a second magnetic part arranged on a single plane. The magnetization directions of the first magnetic part and the second magnetic part oppose each other.

Description

Magnetic flux generating member and actuator

[0001] This invention relates to a magnetic flux generating member and an actuator.

[0002] Conventional lens actuators drive the lens unit by bonding a thin magnet to the inner surface of a fixed frame and using the magnetic interaction with coils positioned opposite it (see, for example, Patent Document 1). While this enables autofocus and image stabilization, the configuration, which individually fixes multiple magnets, is prone to assembly errors, and the need to provide magnets in each direction increases the number of parts and man-hours. Furthermore, there are limitations to thinning a block magnet by cutting it, and it is practically impossible to process it to less than about 0.5 mm, thus limiting miniaturization and weight reduction. Bonded magnets offer excellent shape flexibility, but the resin content reduces magnetic flux density, making them unsuitable for high-driving force applications. Moreover, thin magnets are heavy and are generally placed in fixed parts, in which case the leakage magnetic field to the outside is large and prone to interference with surrounding equipment. In addition, since the paired coils are placed on the movable part side, heat dissipation is insufficient, making it difficult to pass large currents and limiting the improvement of responsiveness.

[0003] Japanese Patent Publication No. 2010-224489

[0004] This invention has been made in view of the above-mentioned problems, and aims to provide a compact, lightweight, highly efficient, and reliable magnetic flux generating member and an actuator using the same, while eliminating constraints on assembly and processing.

[0005] The magnetic flux generating member of this disclosure comprises a first magnetic part and a second magnetic part arranged on the same plane, wherein the magnetization directions of the first magnetic part and the second magnetic part are opposite to each other.

[0006] The sensor of this disclosure comprises the magnetic flux generating member and a magnetic sensor positioned at a location where it can magnetically interact with the magnetic flux generating member.

[0007] The actuator of this disclosure comprises a fixed portion and a movable portion, wherein one of the fixed portion and the movable portion has the magnetic flux generating member, and the other of the fixed portion and the movable portion has a coil positioned to be magnetically interactable with the magnetic flux generating member.

[0008] According to the present invention, it is possible to provide a compact, lightweight, highly efficient, and reliable magnetic flux generating member and an actuator using the same, while eliminating constraints on assembly and processing.

[0009] This is a perspective view showing one embodiment of the magnetic flux generating member of the present disclosure. This is a cross-sectional view of the AA' section in Figure 1A. This is a perspective view showing another embodiment of the magnetic flux generating member of the present disclosure. This is a cross-sectional view of the BB' section in Figure 2A. This is a cross-sectional view showing another embodiment of the magnetic flux generating member of the present disclosure. This is a cross-sectional view showing another embodiment of the magnetic flux generating member of the present disclosure. This is a cross-sectional view showing another embodiment of the magnetic flux generating member of the present disclosure. This is a cross-sectional view showing one embodiment of the actuator for a miniature camera of the present disclosure. This is a perspective view showing one embodiment in which a movable part is housed within a fixed part. This is a perspective view showing one embodiment of the fixed part. This is a cross-sectional view showing one embodiment of the actuator for a miniature camera of the present disclosure. This is a cross-sectional view showing one embodiment of the actuator for a miniature camera of the present disclosure. This is a perspective view of a member in which magnetic parts are formed on the front and back surfaces of a cobalt disk constituting an intermediate part. This is a perspective view of a donut-shaped soft magnetic disk that becomes the first intermediate part in the magnetic film of Figure 7D. This is a perspective view of a member in which a magnetic part is formed on one surface of a cobalt disk that becomes an end yoke after lamination. This is a perspective view of a circular magnetic film formed by laminating Figures 7A to 7C in order.

[0010] The embodiments of the present invention (hereinafter referred to as "the present disclosure") will be described in detail below, but the present invention is not limited thereto, and various modifications are possible without departing from its essence. In addition, in the drawings attached to this specification, the scale and aspect ratios of the dimensions may be changed and exaggerated from those of the actual objects for the convenience of illustration and ease of understanding.

[0011] 1. Magnetic Flux Generating Member Figure 1A shows an example of a perspective view of the magnetic flux generating member 1 of the present disclosure, and Figure 1B shows an example of a cross-sectional view AA' of Figure 1A. As shown in Figures 1A and 1B, the magnetic flux generating member 1 of the present disclosure comprises a first magnetic part 11 and a second magnetic part 12 arranged on the same plane, and the magnetization direction of the first magnetic part 11 and the magnetization direction of the second magnetic part 12 are opposite to each other. Here, "the magnetization directions are opposite to each other" means that the N pole or S pole of the first magnetic part 11 and the second magnetic part 12 are facing each other in the same plane.

[0012] As shown in Figure 1B, when the first magnetic part 11 and the second magnetic part 12 are magnetized in a direction that generates a repulsive force against each other in the in-plane direction, the magnetic flux generated from each magnetic part repels each other on the opposing surface, and the magnetic flux lines curve outwards in a large, closed path to avoid each other. At this time, the magnetic flux generated from the first magnetic part 11 and the second magnetic part 12 concentrates between them, and a region of high magnetic flux density is formed almost perpendicular to the out-of-plane direction of the magnetic flux generating member 1. In this way, the magnetic flux density generated by the magnetic flux generating member 1 becomes greater than that of a conventional magnet magnetized in the thickness direction. As a result, by facing a drive coil or the like towards the location where the magnetic flux of the magnetic flux generating member 1 is concentrated, that is, between the first magnetic part 11 and the second magnetic part 12, a high driving force can be exerted.

[0013] The first magnetic part 11 and the second magnetic part 12 may be arranged in contact with each other on the same plane with their magnetization directions facing each other, or they may be arranged with other members or regions such as the first intermediate part 21 in between, as shown in Figures 1A and 1B, with their magnetization directions facing each other.

[0014] In this case, it is preferable that the first intermediate portion 21 is made of a soft magnetic material. This allows the first intermediate portion 21 to function as a magnetic yoke, efficiently guiding the magnetic flux generated from the first magnetic portion 11 and the second magnetic portion 12 to the first intermediate portion 21. As a result, the magnetic flux tends to concentrate in the out-of-plane direction of the first intermediate portion 21. Therefore, by positioning a drive coil or the like between the first magnetic portion 11 and the second magnetic portion 12, that is, facing the first intermediate portion 21, a higher driving force can be achieved.

[0015] A soft magnetic material can be used as the constituent material for the first intermediate section 21. For example, a metal member made of cobalt (Co) or iron (Fe) or a soft magnetic alloy member may be used as the base material to construct the first intermediate section 21.

[0016] Further, the first intermediate portion 21 may include an adhesive layer. Specifically, an adhesive layer may be provided between the first magnetic portion 11 and the soft magnetic material, or between the second magnetic portion 12 and the soft magnetic material. Alternatively, the first magnetic portion 11 and the soft magnetic material, or the second magnetic portion 12 and the soft magnetic material may be directly joined without an adhesive layer. As a mode of forming the first magnetic portion 11 and the second magnetic portion 12 on the soft magnetic material without an adhesive layer, there is a case where a magnetic film is directly grown on the surface of the soft magnetic material used as a base material.

[0017] As shown in FIG. 1A, the magnetic flux generating member 1 of the present disclosure may be arranged such that the first magnetic portion 11, the first intermediate portion 21, and the second magnetic portion 12 are arranged as rows substantially parallel to each other in the same plane. At this time, either one or both of the extending directions D3 or D1 of each row may be substantially orthogonal to the magnetization direction D2 of the first magnetic portion 11. Thereby, a strong magnetic flux density distribution in the out-of-plane direction occurs near the boundary between the first magnetic portion 11 and the second magnetic portion 12. Furthermore, such an arrangement can be repeated to form a plurality of rows in which the first magnetic portion 11 and the second magnetic portion 12 are alternately arranged. In that case, since like poles face each other at each boundary, a strong magnetic flux density distribution in the out-of-plane direction can also be periodically configured. Also, the magnetic flux generating member 1 of the present disclosure may be formed in a cylindrical or prismatic shape.

[0018] Further, FIG. 2A shows a perspective view of the magnetic flux generating member 1 formed in an annular shape, and FIG. 2B shows an example of a cross-sectional view taken along the line BB' of FIG. 2A. Thus, the magnetic flux generating member 1 of the present disclosure may be formed in an annular shape. Here, "annular" means a shape having an opening in the center and continuously extending so as to surround the opening. The annular form is not limited to a circular ring shape, but widely includes continuous frame-like shapes such as a rectangular shape, an elliptical shape, a regular polygon, and an irregular polygon.

[0019] Furthermore, in this case, the circumferential direction D3' of the ring may be approximately perpendicular to the magnetization direction D2 of the first magnetic part 11. As a result, the magnetic flux generated from the first magnetic part 11 and the second magnetic part 12 is concentrated in the out-of-plane direction D1 on the inner surface 1a or outer surface 1b of the ring, and a strong magnetic field distribution is obtained. Here, "out-of-plane direction" means a direction perpendicular to the circumferential direction D3' of the ring, that is, it coincides with the outward or inward direction along the radial direction of the annular ring. Therefore, by using an annular magnetic flux generating member 1, a region with a high magnetic flux density can be formed directly above the inner or outer surface, and by placing a drive coil at that position, a large driving force can be efficiently obtained. In addition, the magnetic flux is efficiently concentrated near the surface of the entire ring, and leakage magnetic fields can be suppressed.

[0020] Next, Figure 3A shows a cross-sectional view of another embodiment of the magnetic flux generating member 1. As shown in Figure 3A, the magnetic flux generating member 1 of this disclosure may include a third magnetic part 13 arranged on the same plane as the first magnetic part 11, and a second intermediate part 22 located between the first magnetic part 11 and the third magnetic part 13. Here, the third magnetic part 13 may be a hard magnetic material, and the second intermediate part 22 may be a soft magnetic material. Also, as shown in Figure 3A, the first magnetic part 11 and the third magnetic part 13 may be magnetized in a direction that generates an attractive force between them in the in-plane direction.

[0021] As a result, for example, the magnetic flux generated from the third magnetic part 13 is efficiently guided toward the first magnetic part 11 via the second intermediate part 22. In particular, when the second intermediate part 22 is made of a soft magnetic material, it acts as a magnetic yoke, efficiently guiding the magnetic flux from the third magnetic part 13. Since the first magnetic part 11 and the second magnetic part 12 have the same poles facing each other, a strong magnetic flux distribution is formed in the out-of-plane direction near their boundary. However, by providing the third magnetic part 13, the magnetic flux guided toward the first magnetic part 11 increases, and as a result, the magnetic flux density formed between the first magnetic part 11 and the second magnetic part 12 is further improved. In this way, the third magnetic part 13 acts to supplementarily strengthen the magnetic flux of the first magnetic part 11, thereby increasing the magnetic flux density near the surface of the magnetic flux generating member 1. The same effect can be obtained even when the magnetic flux is guided toward the third magnetic part 13 in the magnetization direction from the first magnetic part 11.

[0022] Incidentally, in the above description, the third magnetic portion 13 has been described from the viewpoint of increasing the magnetic flux of the first magnetic portion 11. However, the present invention is not limited to this, and the third magnetic portion 13 may be used in a manner of increasing the magnetic flux of the second magnetic portion 12. That is, the second intermediate portion 22 is not limited to being located between the first magnetic portion 11 and the third magnetic portion 13, and may be located between the second magnetic portion 12 and the third magnetic portion 13. In this case, as shown in FIG. 3A, the second magnetic portion 12 and the third magnetic portion 13 may be magnetized in a direction in which an attractive force is generated between them in the in-plane direction.

[0023] As a result, the magnetic flux from the third magnetic portion 13 is efficiently guided to the second magnetic portion 12, and the magnetic flux density of the second magnetic portion 12 is reinforced. Therefore, the magnetic flux density formed between the first magnetic portion 11 and the second magnetic portion 12 is further improved.

[0024] Further, FIGS. 3B and 3C show cross-sectional views of other embodiments of the magnetic flux generating member 1. As shown in FIGS. 3B and 3C, the magnetic flux generating member 1 of the present disclosure may have an outer edge portion 23 disposed on the same plane as the first magnetic portion 11. Here, the outer edge portion 23 is a soft magnetic material that constitutes the end face of the magnetic flux generating member 1. This outer edge portion 23 functions as a back yoke and serves to capture the magnetic flux that tends to leak to the back side of the first magnetic portion 11 and guide it inside. As a result, the magnetic flux path from the first magnetic portion 11 to the second magnetic portion 12 is reinforced, and the out-of-plane magnetic flux distribution formed near the boundary between the first magnetic portion 11 and the second magnetic portion 12 is further emphasized. Also, this is the same whether the outer edge portion 23 is provided outside the second magnetic portion 12 or outside the third magnetic portion 13.

[0025] The in-plane length L1 of the first magnetic portion 11 and the second magnetic portion 12 may be determined in consideration of the magnetic flux density required for functional expression and the constraints in film formation technology. In the present disclosure, the length L1 of the first magnetic portion 11 and the second magnetic portion 12 is preferably 10 to 300 μm, more preferably 100 to 300 μm, and still more preferably 150 to 300 μm. When the length L1 is within the above range, film formation is easy and sufficient magnetic force can be generated.

[0026] Also, the in-plane separation distance L2 between the first magnetic part 11 and the second magnetic part 12 is preferably 10 to 300 μm, 25 to 250 μm, 50 to 200 μm, or 75 to 150 μm. Here, the in-plane direction means, for example, the direction of D2 or D3 in FIG. 1A. The separation distance means, for example, the length of the intermediate part 21 located between the first magnetic part 11 and the second magnetic part 12 in FIG. 3A. Otherwise, it refers to the distance when the first magnetic part 11 and the second magnetic part 12 are separated even when there is no intermediate part between them. When the separation distance L2 is within the above range, the out-of-plane magnetic flux density tends to be further improved.

[0027] As the materials constituting the first magnetic part 11, the second magnetic part 12, and the third magnetic part 13, rare earth elements and transition metal elements may be used. In particular, a magnet material having a composition containing samarium (Sm) or neodymium (Nd) as the rare earth element and containing cobalt (Co) or iron (Fe) as the transition metal element is desirable. Each magnetic part composed of these is a typical rare earth-transition metal-based hard magnetic material, such as Sm-Co-based (SmCo alloy) or Nd-Fe-B-based (Nd １７ Fe １４ alloy with B as the main phase).

[0028] Specific magnet phases of the first magnetic part 11, the second magnetic part 12, and the third magnetic part 13 include a SmCo ５ type crystal phase represented by the composition formula RT ５ (R = rare earth element, T = transition metal element), a Sm ２ T １７ type, a Sm ２ Co １７ type, a Sm ２ Fe １７ type crystal phase, a Nd ２ Fe １７ type crystal phase, a NdFe １２ represented by the composition formula RT １２ , and further a crystal phase in which nitrogen is introduced as in R ２ T １７ N ３ to enhance the magnetic properties (e.g., Sm ２ Fe １７ N ３Examples include the following. Rare earth-transition metal magnet materials are suitable because they have strong uniaxial magnetic anisotropy, resulting in excellent demagnetization resistance, and they can maintain high coercivity even when made into thin or thick films.

[0029] Furthermore, each magnetic part containing rare earth elements and transition metal elements may have a concentration gradient (composition gradient) of transition metal elements in the magnetization direction. For example, in the in-plane direction of the first magnetic part 11, the first concentration of transition metal elements on the side of the second magnetic part 12 and the second concentration of transition metal elements on the opposite side of the second magnetic part 12 may differ by a predetermined ratio or more. In this case, the first concentration may be lower than the second concentration by a predetermined ratio or more, or the first concentration may be higher than the second concentration by a predetermined ratio or more. The first and second concentrations can be defined as the ratio of the number of transition metal elements to the total number of atoms (100%) of rare earth elements and transition metal elements.

[0030] Similarly, in the in-plane direction of the second magnetic portion 12, the first concentration of the transition metal element on the side of the first magnetic portion 11 and the second concentration of the transition metal element on the side opposite to the first magnetic portion 11 may differ by a predetermined proportion or more.

[0031] The above predetermined ratio, i.e., the absolute difference between the first concentration and the second concentration, may preferably be 0.01% or more, 0.05% or more, 0.07% or more, 0.09% or more, 0.10% or more, 0.12% or more, or 0.15% or more. Alternatively, the above predetermined ratio may preferably be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, 2% or less, 1% or less, 0.7% or less, 0.5% or less, or 0.3% or less.

[0032] Such compositional gradients can be achieved by methods such as changing the target composition over time during sputter deposition (described later) or by tilting the elemental distribution through diffusion treatment.

[0033] Furthermore, the first intermediate portion 21, the second intermediate portion 22, and the outer edge portion 23 are not particularly limited, but examples include those containing Co, Fe, Ni, Mo, Ta, Nb, FeCo, CoCr, CoCrMo, etc. Also, the first intermediate portion 21, the second intermediate portion 22, and the outer edge portion 23 may have the same transition metal elements as the transition metal elements contained in the first magnetic portion and the second magnetic portion.

[0034] 2. Sensor Using a Magnetic Flux Generating Member The sensor of this disclosure comprises the magnetic flux generating member 1 and a magnetic sensor 124 positioned to be magnetically interactable with the magnetic flux generating member 1. Specifically, when the magnetic flux generating member 1 receives an external magnetic field and undergoes a change in position or angle, its magnetic flux distribution changes the amount of magnetic flux passing through the magnetic sensor. This causes an induced electromotive force and inductance change in the magnetic sensor, and by detecting this electrical signal, the position and displacement of the magnetic flux generating member 1 can be measured non-contact. For example, a method can be employed in which an alternating current is applied to the magnetic sensor to detect the change in impedance, or a method can be employed in which the magnetic sensor is arranged as a passive element to detect the induced voltage accompanying the movement of the magnetic flux generating member 1.

[0035] Furthermore, if the magnetic flux generating member 1 is multi-pole magnetized, the magnetic sensor can sequentially detect multiple magnetic poles in response to movement and rotation, enabling measurement of not only linear displacement but also rotation angle and velocity. Thus, the sensor of this disclosure can realize multi-degree-of-freedom detection functions in a compact configuration, going beyond simple position detection.

[0036] 3. Actuator Using a Magnetic Flux Generating Member The actuator of this disclosure comprises a fixed part and a movable part, one of the fixed part and the movable part having the magnetic flux generating member, and the other fixed part and the movable part having a coil positioned to be magnetically interactable with the magnetic flux generating member. Here, the magnetic flux generating member may be formed directly on the surface of the fixed part or the movable part. This makes it possible to provide a small, lightweight, highly efficient and reliable actuator while eliminating constraints on assembly and processing.

[0037] In the following, we will describe a configuration in which the movable part has a lens and the fixed part has an image sensor, and a configuration in which the fixed part has a lens and the movable part has an image sensor.

[0038] 3.1. Figure 4A shows a cross-sectional view illustrating one embodiment of the actuator for a miniature camera of the present disclosure, with a lens on the movable part side and an image sensor on the fixed part side. As shown in Figure 4A, in the actuator for a miniature camera 100, the movable part 110 is equipped with a lens unit 111, and the fixed part 120 is equipped with an image sensor 121, with the image sensor 121 and the lens unit 111 arranged on the same optical axis.

[0039] The movable part 110 has an annular magnetic flux generating member 1 and a lens unit 111 fitted inside it. The fixed part 120 has drive coils 122 positioned opposite the movable part 110, in particular, at positions corresponding to the out-of-plane direction between the first magnetic part 11 and the second magnetic part 12. That is, each drive coil 122 is positioned corresponding to the direction of the magnetic flux generated by the magnetic flux generating member 1.

[0040] Next, Figures 4B to 4C show other drawings illustrating actuators for small cameras.

[0041] Figure 4B shows a perspective view of the small camera actuator shown in Figure 4A. As shown in Figure 4B, the movable part 110 is housed within the fixed part 120, and the movable part 110 is driven within the fixed part 120 by a magnetic flux generating member 1 installed on the movable part 110 and a drive coil 122 installed on the fixed part 120. A lens unit 111 is provided on the front side, and an image sensor 121 is positioned on the bottom side.

[0042] Figure 4B is a perspective view of the actuator in Figure 4A with the lens unit 111 removed from the movable part 110. In Figure 4B, the movable part 110 has an annular magnetic flux generating member 1, and the magnetization directions of the first magnetic part 11 and the second magnetic part 12 are substantially perpendicular to the circumferential direction of the ring. That is, the magnetic flux generated from the first magnetic part 11 and the second magnetic part 12 is concentrated out of plane on the inner surface 1a or outer surface 1b of the ring, resulting in a strong magnetic field distribution in the X and Y directions. In addition, the second magnetic part 12 also provides a magnetic flux generating function in the Z axis direction.

[0043] Therefore, the movable part 110 (lens unit 111) can be driven in the X / Y and Z directions by interaction (attraction and repulsion) with the magnetic field generated by energizing the opposing drive coil 122. This optimizes the relative positional relationship between the lens unit 111 and the fixed image sensor 121, enabling autofocus drive in the Z direction and image stabilization in the X / Y directions. The movable part 110 may be supported by the fixed part 120 by an elastic body 123 such as a spring, and a passive positional restoring force may be applied to ensure that the optical axis is always aligned.

[0044] The magnetic flux generating member 1 of this disclosure can form a region of high magnetic flux density substantially perpendicular to the out-of-plane direction by means of a first magnetic part 11 and a second magnetic part 12 that are magnetized in opposing directions. Therefore, even if the magnetic flux generating member 1 is thin and lightweight, a high driving force can be exerted. Furthermore, by providing the magnetic flux generating member 1 on the movable part 110 side, the drive coil 122 that generates heat can be placed on the fixed part 120 side, and the fixed part 120 can act as a heat sink to dissipate the heat from the coil, making it possible to flow a larger current and drive at high speed.

[0045] Figure 4C is a perspective view of the fixed part 120 of the actuator in Figure 4A, before the movable part 110 is installed, as seen from the lens unit 111 side. The fixed part 120 is a frame that encloses the actuator, and various components such as a drive coil 122, an image sensor 121, and a magnetic sensor 124 may be mounted inside it. Spaces may be provided on the inner wall surface of the fixed part 120 for mounting the drive coils 122 in the X, Y, and Z directions, and these are arranged to surround the lens opening.

[0046] Furthermore, as shown in Figure 4A, the third magnetic part 13 may be magnetized so that multiple different polarities (N poles and S poles) appear (hereinafter also referred to as "multi-pole magnetization"). By having multiple N poles and S poles in the third magnetic part 13 through multi-pole magnetization, it is possible to design a complex magnetic circuit or create a magnetic field distribution tailored to a specific application. By creating a structure in which N poles and S poles are adjacent in the Z plane by the third magnetic part 13, the magnetoresistance of the magnetic circuit around the magnet can be reduced, and the magnetic path becomes relatively closed, thereby reducing the leakage magnetic field of the actuator. In addition, since the magnetic flux is concentrated in the coil / magnetic sensor 124, the driving force of the actuator can be increased. Also, if a magnetic sensor 124 is provided, the position detection accuracy is improved, allowing for more precise feedback control.

[0047] In this disclosure, the magnetic flux generating member 1 of the movable part 110 may also function as a sensor. That is, a magnetic sensor 124 (e.g., a Hall element) for detecting the magnetic flux generated by the magnetic flux generating member 1, for example, the third magnetic part 13, may be provided on the fixed part 120, thereby enabling non-contact detection of the position and orientation of the movable part 110. When the magnetic sensor 124, such as a Hall element, is positioned opposite the third magnetic part 13, the output of the detector changes according to the magnetic field strength from the magnetic flux generating member 1. By calculating the relative distance between the movable part 110 equipped with the magnetic flux generating member 1 and the magnetic sensor 124 from this output change, it is possible to detect the position of the lens unit 111 (movable part 110) with high accuracy.

[0048] For example, the displacement in the Z-axis direction (optical axis direction) can be calculated from the magnetic field strength, allowing the distance (focus position) between the lens and the image sensor 121 to be determined in real time. Furthermore, by arranging multiple magnetic sensors 124 in the X and Y axis directions and detecting changes in magnetic flux in each direction, the two-dimensional displacement of the movable part 110 can be measured.

[0049] The position detection signal obtained by the magnetic sensor 124 is fed back to the control circuit, which adjusts the current to each drive coil 122 according to the deviation from the target position to control the position of the movable part 110. This constitutes a feedback control system that positions the lens to the desired focus position or correction position while maintaining high precision alignment between the lens optical axis and the center of the image sensor 121 (optical axis alignment). For example, in response to a small lateral displacement of the lens unit 111 detected during image stabilization, the control circuit sends a correction current to the coil, moving the lens unit 111 in the opposite direction to cancel out the optical axis misalignment. The combination of detection by the magnetic sensor 124 and magnetic flux generation by the magnetic flux generating member 1 improves the positioning accuracy and responsiveness of the movable part 110, enabling precise feedback control.

[0050] Furthermore, the sensor function of the magnetic flux generating member 1 may be not only for position detection but also for angle detection (tilt detection). For example, if the movable part 110 equipped with the magnetic flux generating member 1 rotates (tilts) slightly around a certain axis, the magnetic flux distribution also changes accordingly. In this disclosure, for example, a plurality of magnetic sensors 124 arranged on the fixed part 120 may detect the difference in magnetic field strength in response to the tilt of the movable part 110 around the X or Y axis. This makes it possible to calculate the tilt angle of the lens unit 111 and reflect it in the correction control. That is, the magnetic flux generating member 1 can generate magnetic flux for detecting parallel movement and magnetic flux for detecting rotational movement in cooperation with the magnetic sensors 124. By using such angle detection functions in combination, even slight tilts of the optical axis can be detected and compensated for, enabling more advanced image stabilization and correction.

[0051] As described above, in this configuration, the magnetic flux generating member 1 of the movable part 110 functions not only as a driving magnet but also as a sensor for detecting position and attitude. This reduces the number of parts and simplifies the structure, and has the advantage of eliminating the position sensor that was previously implemented separately. In addition, because the magnetic flux generating member 1 can generate a high magnetic flux density, it is possible to miniaturize and lighten the device, and as a result, the high-speed response of the actuator can be improved. With the above configuration, a compact camera module that can control the lens position at high speed and with high precision has been realized.

[0052] As a modified example, Figure 5 shows a configuration in which the magnetic flux generating member 1 is formed on the inner surface of the fixed part 120 instead of the movable part 110. When the fixed part 120 itself functions as a soft magnetic yoke, the magnetic flux generated from the magnetic flux generating member 1 passes through the fixed part 120, forming a closed magnetic circuit. This suppresses leakage of the magnetic field to the outside of the actuator, and has the effect of reducing magnetic interference with surrounding electronic equipment.

[0053] 3.2. Figure 6 shows a cross-sectional view illustrating another embodiment of the actuator for a miniature camera of the present disclosure, in which the fixed part has a lens and the movable part has an image sensor. Figure 6 is a cross-sectional view showing an embodiment in which the arrangement relationship between the lens unit 221 and the image sensor 211 is reversed, as a modified example of the actuator configuration shown in Figure 4. In the actuator for a miniature camera 200, the movable part 210 is equipped with the image sensor 211 and the fixed part 220 is equipped with the lens unit 221, and the image sensor 211 and the lens unit 221 are arranged on the same optical axis.

[0054] The movable part 210 has an annular magnetic flux generating member 1 and an image sensor 211 fitted inside it. The movable part 210 and the fixed part 220 are connected by an elastic body 223, and drive coils 222 are arranged on the fixed part 220 at a position facing the magnetic flux generating member 1 of the movable part 210, with each drive coil being positioned corresponding to the direction of the magnetic flux generated by the magnetic flux generating member 1.

[0055] In this configuration, when current flows through the drive coil, its magnetic flux interacts with the magnetic flux generated from the magnetic flux generating member 1 on the inner surface of the fixed part 220, becoming the driving force for the movable part 210 in the X, Y, and Z directions. That is, parallel movement for image stabilization in the X and Y axes and movement for focus adjustment in the Z axis direction are possible, and the relative position of the image sensor 211 with respect to the fixed lens can be adjusted by moving the movable part 210. Since the lens unit 221 itself is held by the fixed part 220 and the optical system is stable, the positional relationship between the sensor surface and the lens optical axis is optimized by controlling the position of the movable part 210, thereby performing focusing and image stabilization.

[0056] The detection mechanism using the magnetic flux generating member 1 and magnetic sensor 224 in this configuration is basically the same as that described above. In this configuration, the image sensor 211 shifts laterally (X / Y direction) relative to the optical axis to perform image stabilization. Therefore, a Hall IC capable of detecting two axes may be used as the magnetic sensor 224, or multiple single-axis magnetic sensors may be arranged to independently detect positional displacement in the X-axis and Y-axis directions. The detection signal is fed back to the control system, and feedback control is realized to keep the position of the movable part 210 (image sensor 211) constantly following the target by controlling the coil current according to the deviation from a predetermined target position. For example, if a tendency for the sensor to deviate laterally from the lens optical axis is detected due to device vibration, the control system immediately performs a corrective operation and drives the movable part 210 in the reverse direction to maintain optical axis alignment.

[0057] As a variation, it is also possible to adopt a configuration in which the magnetic flux generating member 1 is provided on the inner surface of the fixed part 220 and the drive coil is arranged on the outer circumference of the movable part 210. In either case, the principle of detecting the position and orientation of the movable part 210 from the change in the relative positional relationship between the magnetic flux generating member 1 and the magnetic sensor 224 is the same, and there is no change in the fact that the magnetic flux generating member 1 functions as a magnetic flux source for the sensor.

[0058] 4. Manufacturing Method The method for manufacturing the annular magnetic flux generating member 1 will be described below with reference to Figures 7A to 7D.

[0059] The magnetic flux generating member 1 of this disclosure can be manufactured by constructing the member shown in Figure 7A, or by stacking the members shown in Figures 7B to 7C on the member shown in Figure 7A. After magnetizing the member shown in Figure 7A, the members may be stacked so that the magnetization directions are opposite to each other, resulting in the magnetization directions of the first magnetic part and the second magnetic part being opposite to each other.

[0060] Figures 7A to 7C are perspective views showing examples of components used when manufacturing the magnetic flux generating member 1 of this disclosure, and Figure 7D is a perspective view of a circular magnetic film formed by stacking Figures 7A to 7C in that order.

[0061] Figure 7A shows a cobalt disk, which is a soft magnetic material, with magnetic portions formed on both its front and back surfaces. Here, the cobalt disk 22a may be considered the second intermediate portion 22, and the magnetic portions located on its front and back surfaces may be considered the first magnetic portion 11a and the third magnetic portion 13a, respectively.

[0062] Figure 7B shows a perspective view of a donut-shaped soft magnetic disk 21a, which becomes the first intermediate portion 21 in the magnetic film shown in Figure 7D. Figure 7C shows a cobalt disk 23a, which becomes an end yoke after lamination, with a second magnetic portion 12a formed on one side.

[0063] Figure 7D is a perspective view of a circular magnetic film formed by stacking Figures 7A to 7C in that order. In this magnetic film, the soft magnetic disk 21a in Figure 7B becomes the first intermediate portion 21, and the magnetic parts in contact with the front and back surfaces of the soft magnetic disk in Figure 7B (the first magnetic part 11a in Figure 7A and the second magnetic part 12a in Figure 7C) become the first magnetic part 11 and the second magnetic part 12, respectively. Furthermore, in the magnetic film of Figure 7D, the cobalt disk 22a in Figure 7A becomes the second intermediate portion 22, and the magnetic parts located on the front and back surfaces of the second intermediate portion 22 become the first magnetic part 11 and the third magnetic part 13. Also, in the magnetic film of Figure 7D, the cobalt disk 23a in Figure 7C becomes the end yoke (outer edge portion 23), and the magnetic part of the cobalt disk 23a becomes the second magnetic part 12.

[0064] Finally, the thickness and shape of the magnetic film may be adjusted by arbitrarily cutting the laminate using an end mill or the like.

[0065] Next, we will explain a method for forming a magnetic portion on the surface of a substrate such as a cobalt disk, as shown in Figures 7A and 7C.

[0066] First, a substrate is prepared as the base member. The substrate is not particularly limited, but in order to form a magnetic film on the surface of the substrate, it is preferable that at least the surface of the substrate has the same transition metal element as the transition metal element contained in the main magnetic layer. Examples of substrate materials include Co, Fe, Ni, Mo, Ta, Nb, FeCo, CoCr, CoCrMo, etc. For example, if the transition metal element contained in the main magnetic layer is Co or Fe, it is preferable that the surface of the substrate has a Co layer or an Fe layer. Alternatively, the substrate may be a Co substrate or an Fe substrate.

[0067] When using a Co substrate as the base material, it is preferable to use a metal Co plate or a metal Co block, and the purity of Co in the Co substrate may be 99% by mass or more, or 99.998% by mass or more. Another base material may be placed beneath the Co substrate. The thickness of the Co substrate is not particularly limited and can be appropriately selected depending on the application, but for example, it can be 0.01 to 2 mm.

[0068] The surface of the substrate is preferably roughened. For example, the arithmetic mean surface roughness Ra (e.g., JIS B 0601:2013) of the substrate surface is preferably 0.5 μm or more, and more preferably 5.1 μm or more. There is no particular upper limit to the arithmetic mean surface roughness Ra of the substrate, but it may be, for example, 50 μm or less, or 29 μm or less. Surface roughness can be measured by known methods. Furthermore, the surface roughness of the substrate can be controlled by known methods, such as sanding, sandblasting, barrel polishing, electrolytic polishing, and surface processing methods such as forming desired patterns (checkerboard patterns, etc.) by combining photolithography and etching (wet etching, dry etching, microblasting, etc.). In this case, when processing with sandpaper, it is preferable to perform the polishing in a random direction.

[0069] Next, SmCo is applied to the surface of the substrate. ２ A magnetic film, such as a membrane, is formed. The magnetic film is preferably manufactured by, for example, the molten salt immersion method or a method that applies the molten salt immersion method. Hereinafter, SmCo will be used as the magnetic film. ２ Let's explain an example of membrane formation.

[0070] First, a base material, an Sm source, and a reaction solution containing a molten salt are prepared. When preparing the reaction solution, a predetermined inorganic salt is first dehydrated by drying. Examples of inorganic salts include KCl (potassium chloride), LiCl (lithium chloride), and NaCl (sodium chloride). One type of inorganic salt may be used, or two or more inorganic salts may be used in combination. The dehydrated inorganic salt is heated to a predetermined temperature to melt it (molten salt). The temperature at which the inorganic salt is melted can be appropriately determined depending on the type of inorganic salt used, but it is preferably 400°C or higher, 500°C or higher, or 600°C or higher.

[0071] An Sm source is added to the molten salt (molten inorganic salt) to obtain a reaction solution. Examples of Sm sources include metallic Sm and Sm alloys, and one type of Sm source may be used, or two or more types of Sm sources may be used. If the total number of moles of Sm source and inorganic salt in the reaction solution is 100 mol%, the proportion of Sm source in the reaction solution is preferably, for example, 0.2 mol% or more and 6 mol% or less.

[0072] Next, the above reaction solution is brought into contact with the surface of the substrate, and the Sm source in the molten salt is reacted and diffused onto the surface of the substrate to form a magnetic film containing Sm on the surface of the substrate. This step will be referred to as the reaction diffusion step.

[0073] In the reaction-diffusion step, the Co substrate (base material) is immersed in the reaction solution at a predetermined temperature for a predetermined time to form a magnetic coating containing Sm on both sides of the base material. However, if the base material is immersed in the reaction solution as is, a magnetic coating containing Sm will form even in areas where a magnetic coating is not desired, resulting in a decrease in yield. Therefore, areas where a magnetic coating is not desired may be covered with an inert film to suppress reaction-diffusion.

[0074] For example, it is preferable to form a mask of a high-melting-point material in areas where it is not needed. Examples of high-melting-point materials include W, Ta, Nb, Mo, or alloys containing at least one of these elements. The mask of the high-melting-point material can be formed, for example, by vapor deposition. After forming a mask of the high-melting-point material on the outer surface and end surface, the substrate is immersed in the reaction solution, allowing the Sm source to react and diffuse only in the necessary areas of the substrate, thereby forming a magnetic coating containing Sm.

[0075] In the reaction-diffusion step, the temperature of the reaction solution is maintained at a temperature that allows the inorganic salt to remain molten. From the viewpoint of efficiently forming a magnetic film, the temperature of the reaction solution is preferably 500°C to 900°C, and 650°C to 800°C. The reaction time can be appropriately set according to the reaction temperature and the proportion of Sm source in the reaction solution so that a magnetic film of the desired thickness can be formed. For example, the reaction time may be 1 hour to 60 hours.

[0076] In this embodiment, during the reaction time of the reaction-diffusion step, the concentration of Sm (an example of a rare earth element) in the reaction solution is not constant between the start and end of the reaction. Instead, the concentration of Sm at the end of the reaction is controlled to be at least 0.5 mol / L higher than at the start of the reaction. Specifically, the concentration of Sm at the start of the reaction may be 0.5 mol / L, and the concentration of Sm at the end may be 1.5 mol / L. For example, the concentration of Sm in the reaction solution is increased by gradually adding an Sm source to the reaction solution, thereby adjusting the concentration distribution of the transition metal element T in the magnetic film. The method of adding the Sm source may be continuous, intermittent, or all at once.

[0077] The magnetic coating formed on the surface of the substrate in the reaction diffusion process is Sm ２ Co １７ Layer and SmCo ５ It is a precursor of the layer. Specifically, the magnetic coating after the reaction diffusion process is Sm ２ Co ７ SmCo ３ SmCo ２ Sm ５ Co ２ Sm ３It is preferable that it contains Co and Sm as the main phases, and SmCo ２ It is particularly preferable to include as the main phase. SmCo ２ MgCu ２ It is an alloy of Sm and Co having a crystal structure of type . The main phase is SmCo ２ MgCu ２ If it has a crystal structure of the type, SmCo ２ The ratio of Sm atoms to Co atoms in a given material may deviate slightly from the stoichiometric ratio. For example, when additive elements are added to improve magnetic properties, the ratio of Sm atoms to Co atoms may deviate slightly from the stoichiometric ratio.

[0078] The magnetic coating consists of a main phase as well as SmCo ２ It may also contain different phases such as an Sm-rich phase with a higher Sm ratio, and grain boundary phases. The SmCo2 content in the magnetic coating is preferably 50 wt% or more, 70 wt% or more, and 90 wt% or more.

[0079] Furthermore, after the reaction diffusion step, the substrate on which the magnetic coating has been formed may be washed with an organic solvent such as ethanol or pure water.

[0080] Next, SmCo ２ A substrate on which a magnetic coating containing is formed is heated at a predetermined temperature for a predetermined time (heating step). In this heating step, SmCo ２ The reaction between the substrate and the Co on the substrate surface proceeds further, and the Co on the substrate surface and SmCo ２ From a magnetic coating consisting of layers, Sm ２ Co １７ Submagnetic layer consisting of layers and SmCo ５ A main magnetic layer consisting of layers may be formed. Alternatively, a secondary magnetic layer may be formed on the surface of the main magnetic layer.

[0081] The heating rate in the heating process is not particularly limited, but is preferably, for example, 1°C / min or more and 20°C / min or less. The holding temperature (target temperature) is preferably 800°C or more and 1200°C or less, 850°C or more and 1150°C or less, and 900°C or more and 1100°C or less. The holding time at the above holding temperature is preferably, for example, 2 hours or more and 48 hours or less. Furthermore, the cooling rate during cooling after heating is preferably 5°C / min or more, 10°C / min or more, and 20°C / min or more.

[0082] The atmosphere during the heating process is not particularly restricted, but SmCo ５ From the viewpoint of suppressing oxidation of the layer, an inert gas atmosphere is preferred. Examples of inert gases include Ar gas and N ２ Using gas or similar methods would suffice.

[0083] In this embodiment, after the heating step, the temperature may be lowered to a predetermined temperature and then maintained at that predetermined temperature for a predetermined time (low-temperature annealing step). This low-temperature annealing step converts the Co of the base material to SmCo. ５ Co elements diffuse into the grain boundaries through the crystal grain boundaries, forming SmCo. ５ The two-particle grain boundaries between crystalline particles may be modulated. In other words, it is thought that an amorphous phase richer in transition metals (Co) than the main phase crystalline particles, or a mixed phase of amorphous and microcrystalline phases, is more likely to form at the two-particle grain boundaries.

[0084] The holding temperature in the low-temperature annealing process is preferably 550°C to 700°C, and 550°C to 600°C. The holding time in the low-temperature annealing process is preferably, for example, 2 hours to 8 hours. In particular, in annealing at 600°C or below, SmCo ５ It is believed that, without the coarsening of the crystal grains of the main phase or decomposition of the main phase, the diffusion of elements (Co) from the substrate through the two-particle grain boundaries occurs, resulting in the formation of amorphous two-particle grain boundaries with a thickness of several nanometers. Furthermore, two-particle grain boundaries are formed even without low-temperature annealing.

[0085] A multilayer magnetic film can be manufactured through the above-described process (reaction-diffusion process, heating process, and low-temperature annealing process). In the magnetic film, Sm ２ Co １７ Layer and SmCo ５ The layers are formed in that order on the surface of the substrate, resulting in a multilayer structure. If a mask of high-melting-point material is formed on the surface of the substrate, the mask of high-melting-point material may be removed after the heating process, or it may be left in place.

[0086] The above-described method for manufacturing a magnetic film can be applied not only to flat substrates but also to forming a magnetic film on the surface of base members having various curved surfaces. In addition, it can be applied to forming a magnetic film on the inner surface of a cylindrical base member.

[0087] 1 Magnetic flux generating member 11 First magnetic part 12 Second magnetic part 13 Third magnetic part 21 First intermediate part 22 Second intermediate part 23 Outer edge part 100 Actuator for miniature camera 110 Movable part 111 Lens unit 120 Fixed part 121 Image sensor 122 Drive coil 123 Elastic body 124 Magnetic sensor 200 Actuator for miniature camera 210 Movable part 211 Image sensor 220 Fixed part 221 Lens unit 222 Drive coil 223 Elastic body 224 Magnetic sensor

Claims

1. A magnetic flux generating member comprising a first magnetic part and a second magnetic part arranged on the same plane, wherein the magnetization directions of the first magnetic part and the second magnetic part are opposite to each other.

2. The magnetic flux generating member according to claim 1, wherein the first magnetic part and the second magnetic part are magnetized in a direction that generates a repulsive force between them in the in-plane direction.

3. The magnetic flux generating member according to claim 1, further comprising a first intermediate portion located between the first magnetic portion and the second magnetic portion, wherein the first intermediate portion includes a soft magnetic material.

4. The magnetic flux generating member according to claim 3, wherein the first intermediate portion includes an adhesive layer.

5. The magnetic flux generating member according to claim 3, wherein the first magnetic portion, the first intermediate portion, and the second magnetic portion are arranged in substantially parallel rows in the same plane, and the extension direction of each row is substantially perpendicular to the magnetization direction of the first magnetic portion.

6. The magnetic flux generating member according to claim 1, wherein the magnetic flux generating member is formed in an annular shape, and the circumferential direction of the ring is substantially perpendicular to the magnetization direction of the first magnetic part.

7. A magnetic flux generating member according to claim 1, comprising: a third magnetic portion arranged in the same plane as the first magnetic portion and the second magnetic portion; and a second intermediate portion located between the first magnetic portion and the third magnetic portion, or between the second magnetic portion and the third magnetic portion, wherein the third magnetic portion is a hard magnetic material, and the first magnetic portion and the third magnetic portion, or the second magnetic portion and the third magnetic portion, are magnetized in a direction in which an attractive force is generated between them in the in-plane direction.

8. The magnetic flux generating member according to claim 7, wherein the second intermediate portion includes a soft magnetic material.

9. The magnetic flux generating member according to any one of claims 1, wherein the separation distance between the first magnetic portion and the second magnetic portion in the in-plane direction is 10 to 300 μm.

10. The magnetic flux generating member according to claim 1, having an outer edge portion arranged on the same plane as the first magnetic portion, wherein the outer edge portion constitutes the end face of the magnetic flux generating member, and the outer edge portion includes a soft magnetic material.

11. The magnetic flux generating member according to claim 1, wherein the first magnetic part and the second magnetic part each comprise a rare earth element and a transition metal element, the rare earth element comprising Sm and / or Nd, and the transition metal element comprising Co and / or Fe.

12. The magnetic flux generating member according to claim 1, wherein the first magnetic part and the second magnetic part contain a rare earth element and a transition metal element, and the first magnetic part and the second magnetic part have a concentration gradient of the transition metal element in the magnetization direction.

13. When the rare earth element is represented as R and the transition metal element as T, the first magnetic part and the second magnetic part are RT ５ , R ２ T １７ , RT １２ , R ２ T １７ N ３ A magnetic flux generating member according to claim 12, having any of the above.

14. A sensor comprising a magnetic flux generating member according to any one of claims 1 to 13, and a magnetic sensor disposed at a position where it can magnetically interact with the magnetic flux generating member.

15. An actuator comprising a fixed part and a movable part, wherein one of the fixed part and the movable part has a magnetic flux generating member according to any one of claims 1 to 13, and the other of the fixed part and the movable part has a coil positioned to be magnetically interactable with the magnetic flux generating member.

16. The actuator according to claim 15, wherein an annular magnetic flux generating member is disposed on one of the fixed portion and the movable portion, and the magnetization directions of the first magnetic portion and the second magnetic portion are substantially perpendicular to the circumferential direction of the ring.

17. The actuator according to claim 15, wherein the movable part has a lens unit, the fixed part has an image sensor, and the image sensor and the lens unit are arranged on the same optical axis.

18. The actuator according to claim 15, wherein the fixed portion has a lens unit, the movable portion has an image sensor, and the image sensor and the lens unit are arranged on the same optical axis.

Images