Lens drive unit and lens barrel equipped with same

Abstract

To provide a lens drive unit with which it is possible to further improve thrust in order to drive heavier lenses smoothly, and a lens barrel that is equipped with this lens drive unit.SOLUTION: A lens drive unit 10 comprises two-phase coils 212 and a field unit 205. The two-phase coils 212 are fixed to a focus lens frame 210 that is movable back and forth in the optical axis direction and holds a lens, have a winding axis in a direction approximately orthogonal to the optical axis of the lens, and are arranged in a row along the optical axis direction. The field unit 205 has an N pole and an S pole that are alternately arranged along the optical axis direction, and are arranged at positions facing the radial both sides of the two-phase coils 212 so as to sandwich the two-phase coils 212 in the radial direction around the optical axis. Two sets or more of the coils 212 are arranged in a row along the optical axis direction, one set consisting of two-phase coils 212 per field unit 205.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to, for example, a lens driving unit that drives a lens back and forth along an optical axis direction, and a lens barrel including the same. [Background technology]

[0002] Conventionally, a linear motor capable of high-speed response has been used to move a lens frame of a lens barrel in the optical axis direction. In recent years, image pickup elements used in image pickup apparatuses have become larger in size in order to achieve higher pixel counts, improved dynamic ranges, and the like. As image sensors become larger, the lenses used in the lens barrels also become larger and the mass of the lenses increases. Therefore, the actuators that drive the larger lenses require a higher thrust force than before.

[0003] Therefore, the present applicant has proposed a linear motor capable of generating a higher thrust (Patent Document 1). Patent Document 1 discloses a linear motor that can improve the thrust density of a linear motor by making the field magnet part of the linear motor multipolar and performing two-phase drive, and that can easily achieve a long stroke by solving the problem of magnetic saturation.

[0004] The publication also discloses a configuration that can further improve thrust by providing magnets arranged along the optical axis direction at positions facing each other on both sides of the coil so as to sandwich the coil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-213433 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-described conventional configuration has the following problems. In other words, although the linear motor disclosed in Patent Document 1 makes it possible to drive a lens that is heavier than conventional lenses, there is a limit to how much thrust can be improved with the above configuration alone, and further improvements were necessary to enable driving heavier lenses. The present disclosure provides a lens driving unit capable of increasing thrust force compared to conventional units in order to smoothly drive a heavier lens, and a lens barrel equipped with the same. [Means for solving the problem]

[0007] The lens driving unit according to the present disclosure includes an n-phase coil and a first field magnet portion. The n-phase coil is fixed to a moving frame that holds the lens and is movable back and forth in the optical axis direction, has a winding axis in a direction substantially perpendicular to the optical axis of the lens, and is arranged side by side along the optical axis direction. The first field magnet portion has N poles and S poles that are arranged alternately along the optical axis direction, and is arranged at positions facing both sides of the n-phase coil in the radial direction so as to sandwich the n-phase coil in the radial direction centered on the optical axis. Two or more sets of coils are arranged side by side in the optical axis direction for the first field magnet portion, each set consisting of an n-phase coil (n is an integer greater than or equal to 2). [Effects of the Invention]

[0008] The lens driving unit according to the present disclosure can provide a greater thrust force than conventional units, allowing a lens with a larger mass to be driven back and forth in the optical axis direction. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an overall perspective view showing a lens barrel equipped with a lens driving unit according to the present disclosure. [Figure 2] FIG. 2 is an exploded perspective view of the lens barrel of FIG. [Figure 3] FIG. 3 is an exploded perspective view of the second group unit included in the lens barrel of FIG. [Figure 4A] FIG. 4A is a front view showing the magnetic circuit configuration of the lens driving unit of the first embodiment as viewed from the optical axis direction. [Figure 4B] FIG. 4B is a plan view showing the magnetic circuit configuration of the lens driving unit of the first embodiment. [Figure 4C] FIG. 4C is a side view showing the magnetic circuit configuration of the lens driving unit of the first embodiment. [Figure 5] FIG. 5 is an enlarged view of the X portion of FIG. 4C. [Figure 6A] FIG. 6A is a front view showing the magnetic circuit configuration of the voice coil motor of Comparative Example 1 as viewed from the optical axis direction. [Figure 6B] FIG. 6B is a plan view showing the magnetic circuit configuration of the voice coil motor of Comparative Example 1. As shown in FIG. [Figure 6C] FIG. 6C is a side view showing the magnetic circuit configuration of the voice coil motor of Comparative Example 1. FIG. [Figure 7A] FIG. 7A is a front view seen from the optical axis direction, showing the magnetic circuit configuration of the lens driving unit of Comparative Example 2 (Prior Document 1). [Figure 7B] FIG. 7B is a plan view showing the magnetic circuit configuration of the lens driving unit of Comparative Example 2 (Prior Document 1). [Figure 7C] FIG. 7C is a side view showing the magnetic circuit configuration of the lens driving unit of Comparative Example 2 (Prior Document 1). [Figure 8] FIG. 8 is a diagram comparing the characteristics of lens driving units. [Figure 9] FIG. 9 is a diagram comparing the characteristics of lens driving units. [Figure 10] FIG. 10 is an explanatory view showing the dynamic balance of the second lens group unit of FIG. 3 as viewed from the optical axis direction. [Figure 11] FIG. 11 is a perspective view showing the configuration of the lens driving unit according to the second embodiment. [Figure 12] FIG. 12 is an exploded perspective view of the lens driving unit of FIG. [Figure 13] FIG. 13 is a cross-sectional view of the lens driving unit of FIG. [Figure 14] FIG. 14 is a perspective view illustrating a conventional voice coil motor using a plurality of coils. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed descriptions than necessary may be omitted. For example, detailed descriptions of already well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, in the following description of the embodiments, expressions indicating relative directions or attitudes, such as parallel, perpendicular, and orthogonal, are used, but these expressions also include cases where the direction or attitude is not strictly that. For example, "parallel" does not only mean completely parallel, but also means substantially parallel, i.e., including a difference of, for example, a few percent.

[0011] The inventors have provided the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and do not intend for them to limit the subject matter described in the claims. (Embodiment 1) A lens driving unit according to an embodiment of the present disclosure and a lens barrel 100 including the same will be described below with reference to FIGS. 1 to 9. FIG.

[0012] (1) Overview of the configuration of the lens barrel 100 The configuration of a lens barrel 100 according to this embodiment will be described below with reference to the drawings. Fig. 1 is a perspective view showing the outline of the configuration of the lens barrel 100 according to this embodiment. Fig. 2 is an exploded perspective view of the lens barrel 100 according to this embodiment. Lens barrel 100 is a lens barrel for an interchangeable lens camera, and is detachably attached to a camera body (not shown), as shown in Fig. 1. Lens barrel 100 includes exterior unit 101, first unit 102, second unit 103, aperture unit 104, third unit 105, fourth unit 106, circuit board unit 107, and lens mount unit 108, as shown in Fig. 2. Then, the lens barrel 100 is attached to the camera body via the lens mount unit 108 in a state where the lens mount unit 108 is assembled from the exterior unit 101.

[0013] Exterior unit 101 is a substantially cylindrical member that forms the outer shell of lens barrel 100, and is disposed on the outermost side. The first unit 102 is a substantially cylindrical member that contains a first lens and is disposed on the inner peripheral surface side of the exterior unit 101. Second unit 103 is a substantially cylindrical member that holds a focus lens, and includes lens drive unit 10 (see FIG. 3) for driving focus lens 209 (described later) back and forth in the optical axis direction. Second unit 103 is disposed on the inner peripheral surface side of exterior unit 101.

[0014] Aperture unit 104 is a roughly annular member that is provided between second unit 103 and third unit 105 in order to adjust the amount of light that passes through the lens portion of lens barrel 100 by driving movable blades to change the area of ​​the opening. Third unit 105 is a substantially cylindrical member that holds an image stabilization lens and drives the image stabilization lens in a plane perpendicular to the optical axis. Third unit 105 is disposed on the inner peripheral surface side of exterior unit 101.

[0015] Fourth group unit 106 is a substantially cylindrical member that holds a fixed lens, and is disposed on the inner peripheral surface side of exterior unit 101. Circuit board unit 107 is a unit for driving lens barrel 100, and includes a printed circuit board on which electrical components, electrical contacts, etc. are mounted. Circuit board unit 107 is housed in the space between the image plane side of third group unit 105, the outer periphery of fourth group unit 106, and the inner periphery of exterior unit 101.

[0016] Lens mount unit 108 is a connecting component for connecting and fixing lens barrel 100 to a camera body (not shown), and is fixed to the end face of exterior unit 101 on the image plane side. (2) Second group unit Next, the configuration of second group unit 103 will be described in detail.

[0017] (2-1) Overall structure First, the overall configuration of second group unit 103 according to this embodiment will be described. Fig. 3 is an exploded perspective view of second group unit 103. As shown in Fig. 3, second group unit 103 includes, from the subject side to the image plane side, fixed frame 201, main shaft 202, sub shaft 203, flexible printed circuit board 204, field unit 205, focus lens unit 206, and holding frame 207.

[0018] Fixed frame 201 is a substantially annular member arranged on the subject side of second group unit 103, and holds the subject side ends of main shaft 202, sub shaft 203, and field unit (first field magnet part, second field magnet part) 205. An MR (Magneto-Resistive) sensor 208 is connected to the flexible printed circuit board 204 and is fixed in a state where it is wrapped around the outer periphery of the fixed frame 201 .

[0019] The focus lens unit 206 includes a focus lens 209 , a focus lens frame (first moving frame) 210 , an MR (Magneto-Resistive) magnet 211 , and a coil 212 . The focus lens 209 is fixed to the inner periphery of a focus lens frame 210 . The MR magnet 211 is fixed to the outer periphery of the focus lens frame 210.

[0020] A total of four coils 212 are fixed to the outer periphery of the focus lens frame 210, with two sets of two phases (two coils) arranged side by side along the optical axis direction for one field unit 205. The two sets of four coils 212 are arranged at approximately equal angular intervals in the circumferential direction at three locations on the outer periphery of the focus lens frame 210. Therefore, in this embodiment, a total of 12 coils 212, with two sets of two phases arranged at three locations, are fixed to the outer periphery of the focus lens frame 210.

[0021] The two-phase coil 212 refers to a configuration in which two coils, each with an electric wire wound around it, are arranged opposite each other along the optical axis direction of the field unit 205, with the winding axis being arranged along a direction perpendicular to the optical axis of the focus lens 209. The main shaft 202 and the sub shaft 203 are inserted into insertion holes 210b and 210c of the focus lens unit 206, respectively, and are arranged along the direction of the optical axis L. The main shaft 202 and the sub shaft 203 guide the movement of the focus lens unit 206 in the direction of the optical axis L. The main shaft 202, the sub shaft 203, and the field unit 205 have their image plane side ends fixed to a holding frame 207.

[0022] The holding frame 207 is fixed to the fixed frame 201 using a plurality of screws 213 . As a result, the focus lens unit 206 is driven in the direction of the optical axis L along the main shaft 202 while its rotation about the main shaft 202 is restricted by the sub-shaft 203 . The MR magnet 211 is an example of a position detection member that detects the position of the focus lens unit 206.

[0023] The MR sensor 208 is an example of the position detection sensor. The MR magnet 211 is provided in the focus lens unit 206 so that, when assembled, it is disposed near the MR sensor 208. Therefore, when the focus lens unit 206 including the MR magnet 211 moves back and forth in the direction of the optical axis L, the MR sensor 208 detects a change in the magnetic field caused by a change in the relative position of the MR magnet 211 with respect to the MR sensor 208.

[0024] As a result, by detecting the output of the MR sensor 208, the position of the focus lens unit 206 relative to the fixed frame 201 can be detected. In the present embodiment, an MR sensor is used as an example of a position detection sensor, but other position detection sensors such as a photocoupler may also be used. Furthermore, in this embodiment, an MR magnet is used as an example of a position detection member, but other position detection members such as a reflecting mirror may also be used.

[0025] The coil 212 is a component of the lens driving unit 10, which will be described later, and is fixedly disposed on the focus lens frame 210, and is held in a state where it is inserted into a gap in the field unit 205 in the imaging state. (2-2) Configuration of the lens driving unit 10 The configuration of the lens driving unit 10 including the field unit 205 and the coil 212 will be described in detail below.

[0026] The lens driving unit 10 is a device that drives the focus lens unit 206 back and forth in the direction of the optical axis L. For ease of explanation, the following description will focus on only one field unit 205 and its corresponding coil 212 out of the three field units 205 and their corresponding coils 212 provided in the configuration of FIG.

[0027] 4A to 4C are three-sided views showing the configuration of the lens driving unit 10 according to this embodiment, and FIG. 5 is an enlarged view of the X portion of FIG. 4C. The yoke A 215 and the yoke B 216 are made by punching out an iron sheet metal by press working, and as shown in Figures 4A to 4C, the yoke A 215 and the yoke B 216 are flat plate-shaped members.

[0028] The main magnet 217 and the sub-magnet 218 are, for example, Nd-based sintered magnets, and are each magnetized with a single pole. The sub-magnet 218 has a width in the optical axis direction that is half that of the main magnet. As shown in Figures 4A to 5, the field unit 205 is configured by sub-magnets 218 at both ends in the optical axis direction, and nine main magnets 217 between them, which are fixed to yoke A 215 and yoke B 216 so that the magnetization of the surface facing the coil 212 is regularly arranged with alternating north and south poles.

[0029] 4C, the coils 212 are arranged in the order of phase A, phase B, phase -A, and phase -B from the top. The phase A and phase -A coils are connected in series, and the phase B and phase -B coils are also connected in series. Hereinafter, a configuration in which two or more sets of two-phase coils, A phase and B phase (or -A phase and -B phase), are arranged along the optical axis direction for one field unit 205 is referred to as a tandem configuration.

[0030] Here, when currents with a phase difference of 90° are passed through coils A and -A and coils B and -B according to the phase relationship between coil 212 and field unit 205, coil 212 is subjected to Lorentz force and driven in the optical axis direction. More specifically, a field unit 205 is fixed to the fixed frame 201 side, and a coil 212 is fixed to the focus lens unit 206 side. When current is applied to the coil 212, the focus lens unit 206 is driven in the optical axis direction relative to the fixed frame 201.

[0031] (2-3) Comparison of characteristics between the lens driving unit 10 and comparative examples 1 and 2 Here, in order to clarify the characteristics of the lens driving unit 10 of this embodiment shown in Figures 4A to 4C, the characteristics will be explained by comparison with a conventional voice coil motor (Comparative Example 1) shown in Figures 6A to 6C and a lens driving unit of a basic configuration using only two coils as disclosed in Patent Document 1 (Comparative Example 2) shown in Figures 7A to 7C.

[0032] FIG. 8 is a table comparing the characteristics of the lens driving unit 10 with those of comparative examples 1 and 2. In Figure 8, the voice coil motor of Comparative Example 1 shown in Figures 6A to 6C and the lens driving unit of Comparative Example 2 shown in Figures 7A to 7C show cases where the design is made to maximize the thrust force within the combined range of the size of the field magnet part excluding the protrusion and the coil resistance value. Here, the characteristics of the voice coil motor of Comparative Example 1 shown in FIGS. 6A to 6C will be compared with those of the lens driving unit of the basic configuration of Comparative Example 2 shown in FIGS. 7A to 7C.

[0033] First, comparing the sizes, as shown in Figure 8, the voice coil motor of Comparative Example 1 shown in Figures 6A to 6C and the lens driving unit of the basic configuration of Comparative Example 2 shown in Figures 7A to 7C have field magnet parts with approximately the same size (thickness 10 mm, width 24 mm, length 35 mm). The field magnet section refers to a section including a main yoke, a sub-yoke, and a magnet, and is a section that generates a fixed magnetic field (to generate a Lorentz force in the coil).

[0034] On the other hand, the voice coil motor of Comparative Example 1 has a coil protruding downward from the field magnet portion as shown in FIG. 6A, and is therefore substantially one size larger than the lens driving unit of Comparative Example 2 having the basic configuration. As for thrust, as shown in FIG. 8, the maximum thrust of the voice coil motor of Comparative Example 1 is 0.68 N, whereas the maximum thrust of the lens driving unit of the basic configuration of Comparative Example 2 is 1.10 N, which is approximately 62% greater.

[0035] This shows that the lens driving unit with the basic configuration of Comparative Example 2 has an overwhelmingly higher thrust force than the voice coil motor of Comparative Example 1. Furthermore, since the coil protrudes in the voice coil motor of Comparative Example 1, it is clear that this difference will become even greater if the lens driving unit with the basic configuration of Comparative Example 2 is made larger. Next, the characteristics of the lens driving unit of the basic configuration of Comparative Example 2 shown in FIGS. 7A to 7C will be compared with those of the lens driving unit 10 of this embodiment shown in FIGS. 4A to 4C.

[0036] First, comparing the sizes, as shown in Figure 8, the lens driving unit 10 of this embodiment shown in Figures 4A to 4C has a length in the optical axis direction (50 mm) that is 15 mm longer in the optical axis direction, equivalent to three main magnets (two coils), compared to the lens driving unit of the basic configuration of Comparative Example 2 (35 mm). Furthermore, as shown in FIG. 8, the thrust force of the lens driving unit of the basic configuration is 1.10 N, whereas the thrust force of the lens driving unit 10 of this embodiment is 1.55 N, which is approximately 41% higher.

[0037] This shows that in the lens driving unit 10 of this embodiment shown in Figures 4A to 4C, a tandem configuration is adopted in which two or more sets of two-phase coils are arranged in series for one field unit 205, and although the lens driving unit 10 is slightly longer in the optical axis direction, the other dimensions remain exactly the same, and the thrust can be increased. (2-4) Comparison of characteristics with a configuration in which multiple lens driving units 10 are provided The characteristics of a configuration using a single lens driving unit 10 have been described above, but the characteristics of a configuration using a plurality of lens driving units 10 will be described below.

[0038] FIG. 9 is a table comparing the characteristics when multiple lens drive units are used. Here, a brief description will be given of the characteristics when two lens driving units of the basic configuration of Comparative Example 2 are used ("x2 configuration" in FIG. 9). Normally, if two lens drive units are used, it would seem that the thrust would be doubled, but if two of the same lens drive units are used in parallel, the power consumption would also be doubled.

[0039] In the case of a lens barrel for an interchangeable lens camera, the power used within the lens barrel is supplied from the camera body, but there is a set upper limit to the power that can be supplied from the camera body to the lens barrel, and there is also a set upper limit to the power that can be used by the lens drive unit. For this reason, in a lens barrel containing two lens drive units, the power that can be supplied to each lens drive unit is halved, and the thrust force does not double. Therefore, when comparing characteristics, it is appropriate to compare under conditions that combine the overall power consumption.

[0040] FIG. 9 shows the results of comparing the characteristics when the coil winding specifications are adjusted so that the power consumed by the lens drive unit is constant. In the case of a configuration using two basic configurations of Comparative Example 2 (×2 configuration) (see the upper part of Figure 9), the maximum thrust is 1.55 N, which is approximately 41% higher than the maximum thrust of 1.10 N of the basic configuration of Comparative Example 2 (see the upper part of Figure 9).

[0041] Therefore, it is clear that the characteristics are equivalent to those of the single lens driving unit 10 in the tandem configuration of this embodiment shown in FIGS. 4A to 4C and described in (2-3) above. Here, when comparing a configuration using two basic configurations (x2 configuration) of Comparative Example 2 with the tandem configuration of the lens driving unit 10 of this embodiment, it can be seen that although the tandem configuration of this embodiment is 15 mm longer in the optical axis direction than Comparative Example 2, the projected area in the optical axis direction and the overall volume are significantly smaller.

[0042] In particular, the amount of permanent magnets used in the tandem configuration of this embodiment is significantly reduced to 71% of the amount used in the configuration of two basic configurations (x2 configuration) of Comparative Example 2. Nd-based sintered magnets use rare earth metals such as Nd (neodymium) and Dy (dysprosium). For this reason, the price per mass tends to be very high, but by reducing the amount of magnets used, it is possible to reduce costs even for a lens drive unit with the same output.

[0043] Furthermore, in the configuration of this embodiment, the amount of yoke and permanent magnets used, which have a large specific gravity, can be reduced, making it possible to reduce the weight. Furthermore, in Figure 9, when comparing the basic configuration as a comparative example with the configuration including three lens driving units 10 of this embodiment (tandem x 3), it can be seen that the maximum thrust of the basic configuration is 1.10 N, while the configuration including three lens driving units 10 of this embodiment (tandem x 3) can generate a thrust of 2.67 N, which is approximately 2.4 times greater.

[0044] This thrust is approximately 3.9 times the thrust of 0.68 N of the voice coil motor alone of Comparative Example 1 shown in FIGS. 6A to 6C and 8. In this way, by providing multiple lens driving units (i.e., using multiple field units), and by using a tandem configuration in which two or more sets of two-phase coils are arranged in series for one field unit, as in the lens driving unit 10 of this embodiment, it is possible to improve thrust compared to conventional configurations. As a result, it is possible to drive a lens with a large mass, which was difficult to drive with conventional configurations, back and forth in the optical axis direction.

[0045] The specific gravity of the glass material used in lenses is generally around 3 to 5. Therefore, a lens with a large mass is usually not a single lens with a large mass, but rather a lens made up of multiple lenses, such as the focus lens 209 shown in FIG. 3. For this reason, lenses with a large mass often necessarily have a certain length in the optical axis direction, so when driving a lens with a large mass, it is generally acceptable for the driving unit to have a certain length in the optical axis direction.

[0046] As described above, by configuring the lens driving units 10 in tandem and by combining multiple lens driving units 10 within the allowable range for the lens driving unit 10, it is possible to provide a lens driving unit 10 that can effectively utilize the space both circumferentially around the optical axis and in the optical axis direction within the limited size of the lens barrel, and can drive lenses with a larger mass.

[0047] In FIG. 9, a tandem configuration has been described in which four coils (two sets of two-phase coils) are used for one field unit, but a configuration in which six or more coils (three sets of two-phase coils) are used may also be used. In addition, in the above embodiment, a case has been described in which the focus lens unit 206 is driven back and forth in the optical axis direction using a two-phase coil 212, but a three- or more-phase coil may be used as long as it is driven using an n-phase coil (n is an integer greater than or equal to 2).

[0048] For example, in the case of three-phase drive, a set of three coils is used for one field unit, aligned in the optical axis direction. However, in order to achieve three-phase drive, it is necessary to use sets of three coils aligned in the optical axis direction, which means that the length of each set of coils in the optical axis direction tends to be longer than in the case of two-phase drive. Furthermore, when multiple sets of coils are arranged, there is a risk that the number of options for arranging the coils will be limited due to restrictions on the length in the optical axis direction.

[0049] Therefore, it can be said that two-phase drive, in which two coils are arranged along the optical axis direction for one field unit, offers greater design freedom. (2-5) Points to note when using a configuration with multiple lens driving units 10 As described above, it has been shown that combining and using multiple lens drive units 10 with a tandem configuration can improve thrust and thereby drive lenses with a larger mass. However, when the lens unit (movable part) including the lens becomes heavy, vibrations of the moving part, particularly vibrations caused by backlash due to the clearance between the outer circumferential surface of the main shaft 202 and the inner circumferential surface of the insertion hole 210b of the focus lens frame 210, tend to occur, and so some measure is needed to suppress the vibrations.

[0050] Hereinafter, a method for suppressing vibrations that tend to occur when a plurality of lens driving units 10 are used in combination will be described with reference to FIG. FIG. 10 is a diagram of the focus lens unit 206 of the first embodiment as viewed from the subject side in the optical axis direction. In FIG. 10, when the focus lens unit 206 moves at a constant speed or when it moves back and forth at a low frequency and small amplitude, the forces applied to the focus lens unit 206 are dominated by the thrust generated by the coils 212a, 212b, and 212c and the frictional force generated between the main shaft 202 and the focus lens frame 210.

[0051] 10, the coils 212a, 212b, and 212c are disposed at three equal positions around the optical axis center C1 of the lens, so that the centers of the thrust forces generated by the coils 212a, 212b, and 212c coincide with the optical axis center C1. Also, the frictional force generated between the main shaft 202 and the focus lens frame 210 is directed in the opposite direction to the thrust forces of the coils 212a, 212b, and 212c.

[0052] Therefore, when the focus lens unit 206 moves at a constant speed or moves back and forth at a low frequency and small amplitude, the focus lens frame 210 vibrates in a mode in which the center of thrust from the coils 212a, 212b, and 212c vibrates back and forth in the optical axis direction around the main shaft 202. 10, when focus lens unit 206 reciprocates at a high frequency and large amplitude, the inertial force that tends to keep focus lens unit 206 in the same position becomes dominant, causing focus lens unit 206 to vibrate loosely in a mode in which the thrust centers of coils 212a, 212b, and 212c vibrate back and forth with the vicinity of the center of gravity G1 of the movable part as a fulcrum.

[0053] The center of gravity G1 of the movable part refers to the position of the center of gravity of all components that constitute the movable part that can move relative to the fixed frame 201, such as the focus lens unit 206, including the focus lens frame 210 to which the focus lens 209 is fixed. In addition, in the case of the above-mentioned intermediate state (reciprocating motion at a medium frequency and medium amplitude), the vibration occurs with a fulcrum being any point between the center of gravity G1 of the movable part and the main shaft 202 on the plane passing through the center of gravity G1 of the movable part and the main shaft 202.

[0054] Here, by bringing the thrust centers of the coils 212a, 212b, and 212c closer to the fulcrum of vibration, the moment force applied to the focus lens unit 206 is reduced, thereby reducing backlash vibration. The thrust of the coils 212a, 212b, and 212c is greatest when they reciprocate at a high frequency and a large amplitude. Therefore, if the center of gravity G1 of the movable part is aligned with the center of thrust of the coils 212a, 212b, and 212c, vibration can be suppressed even when they reciprocate at a high frequency and a large amplitude, which tends to increase play vibration.

[0055] Therefore, when considering cases where the actuator is driven under various drive conditions, loose vibration can be suppressed by aligning the center of gravity G1 of the movable part with the center of thrust of the coils 212a, 212b, and 212c. However, in the case of lens barrel 100 of the first embodiment, as described above, the outer periphery is substantially cylindrical, the inner periphery has focus lens 209 at the center, and a plurality of parts are arranged in the circumferential direction, such as main shaft 202, sub shaft 203, MR sensor 208, and MR magnet 211. Therefore, the locations where field units 205a, 205b, and 205c and coils 212a, 212b, and 212c can be arranged are limited.

[0056] In this embodiment 1, as shown in FIG. 10, three field units 205a, 205b, and 205c are arranged at approximately equal angular intervals in the circumferential direction around the optical axis center C1 of the focus lens 209, and other components are arranged between them. In this way, when there are restrictions on the arrangement of field units 205a, 205b, and 205c, field units 205a and 205c are arranged on both sides of plane P1 that passes through center of gravity G1 of the movable part and main shaft 202. That is, as shown in Fig. 10, field unit 205a and field unit 205c are arranged on both sides of plane P1 that passes through center of gravity G1 of the movable part and main shaft 202.

[0057] This allows the thrust centers of the coils 212a, 212b, and 212c to be brought closer to the plane P1 passing through the center of gravity G1 of the movable part, which serves as the fulcrum for backlash vibration, and the main shaft 202. Therefore, the thrust centers of the coils 212a, 212b, and 212c can be brought closer to the fulcrum of the rattle vibration, so that the rattle vibration can be effectively suppressed. Furthermore, in the lens driving unit 10 of this embodiment, as described above, n-phase (two-phase) coils are arranged for one field unit 205 so as to be sandwiched between the field unit 205 from both sides in the radial direction.

[0058] This prevents unnecessary force from being applied to the focus lens frame 210 in a direction intersecting the optical axis direction, thereby suppressing the occurrence of image blur when an image is captured by a camera equipped with the lens barrel 100. (Embodiment 2) In the above embodiment 1, an example was given in which the technology of the present disclosure was applied to drive a lens with a large mass, but the technology of the present disclosure is effective not only for driving a lens with a large mass, but also when used for other purposes.

[0059] In the second embodiment, an example in which the technology of the present disclosure is applied to drive a plurality of lens frames will be described below. FIG. 11 is a perspective view of the lens driving unit of the second embodiment. FIG. 12 is an exploded perspective view of the lens driving unit of the second embodiment. FIG. 13 is a perspective view of the lens driving unit of the second embodiment.

[0060] FIG. 14 is an explanatory diagram of a comparative example in which a plurality of coils are driven in a conventional voice coil motor. 11 to 13, the lens driving unit of the second embodiment is similar to the first embodiment in that two sets of coils are used for one field unit. However, the second embodiment differs in that two sets of coils, 212A and 212B, each consisting of two coils, are fixed to separate lens frames (first moving frame) 210A and lens frames (second moving frame) 210B, respectively, and are driven and controlled independently, as shown in FIG.

[0061] The configuration of the second embodiment shown in FIGS. 11 to 13 will be described in detail below. In FIG. 12, the A group lens unit 206A includes an A group lens 209A, an A group lens frame (first moving frame) 210A, and an A group coil 212A. The A group lens 209A is fixed to a lens frame 210A as shown in Fig. 13. An A group coil 212A is fixed to the outer peripheral surface of the lens frame 210A.

[0062] Similarly, the B group lens unit 206B includes a B group lens 209B, a B group lens frame (second moving frame) 210B, and a B group coil 212B. The B group lens 209B is fixed to a lens frame 210B as shown in Fig. 13. A B group coil 212B is fixed to the outer peripheral surface of the lens frame 210B. The main shaft 202A and the sub-shaft 203B are arranged along the direction of the optical axis L while being inserted into the insertion holes of the A group lens unit 206A and the B group lens unit 206B, respectively. The main shaft 202A and the sub-shaft 203B guide the movement of the A group lens unit 206A and the B group lens unit 206B in the direction of the optical axis L.

[0063] As described above, in the lens barrel of this embodiment, two axes (main axis 202A and sub-axis axis 203B) are shared by two lens units (A group lens unit 206A and B group lens unit 206B). This simplifies the configuration compared to a configuration in which two lens units are guided by separate axes, and also reduces variations in the relative accuracy (eccentricity, tilt) between the A group lens 209A and the B group lens 209B due to axis installation errors.

[0064] (3) Comparison of the Configuration of the Second Embodiment with the Comparative Example (Conventional Voice Coil Motor) Here, the advantages of the configuration of this embodiment will be explained in comparison with a configuration in which two coils are provided in one field portion in a conventional voice coil motor. Fig. 14 is an explanatory diagram of a conventional voice coil motor using two coils. In Fig. 14, the configuration is the same as that of the voice coil motor shown in Figs. 6A to 6C, except that two coils 312A and 312B are provided on main yoke 315.

[0065] When two coils are used in the conventional voice coil motor shown in FIG. 14, if one tries to ensure a range of motion for each of the two coils 312A and 312B, the permanent magnet 317 and main yoke 315 will inevitably become longer in the optical axis direction. If the permanent magnet 317 and main yoke 315 are lengthened in the optical axis direction, the main yoke 315 and sub-yoke 316 are more likely to become magnetically saturated. Therefore, simply lengthening them in the optical axis direction prevents the permanent magnet 317 from achieving its full potential, resulting in a decrease in thrust.

[0066] On the other hand, according to the configuration of this embodiment 2 shown in FIGS. 11 to 13, when the field unit 205 is lengthened in the optical axis direction, the number of poles of the magnet can be increased, thereby making it possible to lengthen the field unit 205 without affecting magnetic saturation at all, and without reducing the thrust. Furthermore, when two coils are used in the conventional voice coil motor shown in Fig. 14, two coils 312A and 312B are wound around main yoke 315. Therefore, similar to a transformer, when current is applied to coil 312A, an induced voltage is generated in coil 312B. Therefore, even if an attempt is made to separately control the currents flowing through coils 312A and 312B, accurate control becomes difficult due to the interaction between coils 312A and 312B.

[0067] On the other hand, according to the configuration of the present embodiment 2 shown in FIGS. 11 to 13, the coils 212A and 212B are each air-core coils, and each of the coils 212A and 212B hardly affects the other coils, making it possible to easily control the current flowing through each of the coils 212A and 212B. As described above, according to the configuration of the second embodiment, even if the field unit 205 is lengthened in the optical axis direction, it is not affected by magnetic saturation, and therefore it is possible to avoid a decrease in the thrust of the coils 212A, 212B. Furthermore, even when a plurality of sets of coils 212A, 212B are combined with one field unit 205, there is almost no interaction between the coils 212A, 212B, which provides the useful effect of facilitating control.

[0068] In the above-described second embodiment, a configuration in which two lens units (A group and B group lens units 206A and 206B) are combined with one field unit has been described as an example, but a configuration in which three or more lens units are combined may also be used. Furthermore, the lens unit to be driven is not limited to a focus lens unit including a focus lens, but may be another moving frame such as a zoom lens unit, an image stabilization unit, or an aperture unit. [Industrial Applicability]

[0069] The lens driving unit of the present disclosure has the effect of being compact and capable of driving a lens to the end of the lens driving range by obtaining the necessary thrust, and therefore can be widely applied as an actuator for driving a lens. [Explanation of symbols]

[0070] 1 camera body 10 Lens drive unit 100 Lens barrel 101 Exterior unit 102 1st group unit 103 2nd group unit 104 Aperture unit 105 3rd group unit 106 4th group unit 107 Circuit Board Unit 108 Lens mount unit 201 Fixed Frame 202, 202A main shaft 203, 203B subshaft 204 Flexible Printed Circuit Board 205 Field magnet unit (first and second field magnet parts) 205A field magnet unit (first field magnet part) 205B Field unit (third field unit) 205C field magnet unit (second field magnet part) 206, 206A, 206B Focus Lens Unit 207 Retaining Frame 208 MR sensor 209 Focus Lens 209A A-group lens 209B B group lens 210 Focus lens frame (first moving frame) 210A A group lens frame (first moving frame) 210B B group lens frame (second moving frame) 211 MR Magnet 212, 212a, 212b coils 212A A group coil 212B B group coil 213 Screw 215 Main York 216 Sub York 217 Main Magnet 218 Sub Magnet C1 optical axis center G1 Center of gravity of moving part L optical axis P1 plane

Claims

1. A lens drive unit that is movable back and forth in the optical axis direction of a lens, and drives a first moving frame and a second moving frame that respectively hold the lens back and forth in the optical axis direction, n-phase coils each having an air core, each fixed to the first moving frame and the second moving frame, arranged side by side along the optical axis direction, and having a winding axis in a direction substantially perpendicular to the optical axis direction; a first field portion having north poles and south poles alternately arranged along the optical axis direction; Equipped with the coils are arranged in two or more sets, each set including a coil fixed to the first moving frame and a coil fixed to the second moving frame, with the n-phase coil being one set, in a state where the coils are combined into one first field magnet portion, and are aligned in the optical axis direction; the first moving frame and the second moving frame are driven separately; Lens drive unit. (n is an integer of 2 or more.)

2. the first field magnet portions are arranged at positions facing both sides of the n-phase coil in the radial direction so as to sandwich the n-phase coil in the radial direction centered on the optical axis of the lens, 2. The lens driving unit according to claim 1.

3. The n-phase coil is a two-phase coil.

2. The lens driving unit according to claim 1.

4. Further provided is a second field magnet portion arranged so as to surround the optical axis of the lens together with the first field magnet portion. The lens driving unit according to claim 1 .

5. a main shaft that supports the first moving frame in a state where the first moving frame can move back and forth in the optical axis direction, the first field magnet portion and the second field magnet portion are disposed on both sides of a plane passing through the center of gravity of the first moving frame that holds the lens and the main axis, 5. The lens driving unit according to claim 4.

6. a third field magnet portion disposed together with the first field magnet portion and the second field magnet portion so as to surround the optical axis; 6. The lens driving unit according to claim 4.

7. The lens driving unit according to any one of claims 1 to 6, the first moving frame and the second moving frame that are driven back and forth in the optical axis direction by the lens driving unit; A lens barrel comprising:

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