Lens barrel

Abstract

To provide a lens barrel that is mounted with an actuator of larger size than a lens barrel of the same size, and can drive a lens of larger mass.SOLUTION: A lens barrel comprises an actuator which drives a lens forward and backward along the optical axis, and a lens frame which holds the lens and is driven forward and backward along the lens and the optical axis by the actuator. The actuator has two permanent magnets which are arranged more on an outer peripheral side than an outer peripheral surface of the lens frame at an interval substantially in parallel with same electrodes face to face, a yoke which has a center yoke part, a back yoke part, and a yoke part, and a coil wound encircling the center yoke part. An I type yoke included in the yoke has pluralities of I type iron plates and iron plates each in a shape, excluding a part of a center yoke part of an I type iron plate, stacked, so that the center yoke part is less in stacking-directional thickness than any other part.SELECTED DRAWING: Figure 14A

Description

[Technical Field]

[0001] The present disclosure relates to a lens barrel equipped with an actuator that drives a lens back and forth along an optical axis. [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 (for example, Patent Document 1). In recent years, image pickup devices 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] For example, Patent Document 1 discloses a configuration in which a plurality of field magnet portions are provided for one coil to improve thrust. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-248290 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology disclosed in Patent Document 1 has limitations on how much thrust can be improved. The present disclosure provides a lens barrel that can mount a larger actuator in a lens barrel of the same size and drive a lens with a larger mass. [Means for solving the problem]

[0006] The lens barrel according to the present disclosure includes an actuator that drives the lens back and forth along the optical axis, and a lens frame that holds the lens and is driven back and forth along the optical axis by the actuator together with the lens. The actuator is disposed on the outer periphery of the lens frame and includes a yoke having two permanent magnets arranged substantially parallel and spaced apart with the same poles facing each other, a center yoke portion disposed between the two opposing permanent magnets, a back yoke portion disposed in contact with the surface of the permanent magnet opposite the opposing poles, and a yoke portion that magnetically connects the center yoke portion and the back yoke portion, and a coil wound around the center yoke portion. The yoke is formed by stacking multiple thin iron plates, and the portions corresponding to the back yoke portion and the yoke portion are integrated into a rectangular yoke, and the portion corresponding to the center yoke portion is combined with the rectangular yoke as an I-shaped yoke. The I-shaped yoke is constructed by stacking multiple I-shaped steel plates and steel plates with the shape of the center yoke portion of the I-shaped steel plate removed, so that the thickness of the center yoke portion in the stacking direction is thinner than the thickness of the other portions in the stacking direction. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing a camera according to the first embodiment. [Figure 2] FIG. 2 is a perspective view showing the lens barrel according to the first embodiment. [Figure 3] FIG. 3 is an exploded perspective view of the lens barrel according to the first embodiment. [Figure 4] FIG. 4 is a perspective view of the third-fourth group unit according to the first embodiment. [Figure 5] FIG. 5 is an exploded perspective view of the third-fourth group unit according to the first embodiment. [Figure 6A] FIG. 6A is a perspective view showing the linear actuator according to the first embodiment. [Figure 6B] FIG. 6B is a four-view diagram showing the linear actuator according to the first embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing the linear actuator according to the first embodiment. [Figure 8] FIG. 8 is a schematic diagram showing the arrangement of linear actuators in the lens barrel according to the first embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the arrangement of linear actuators in a lens barrel of Comparative Example 1 in which the coil is not offset. [Figure 10] FIG. 10 is a schematic diagram showing the arrangement of linear actuators in a lens barrel of Comparative Example 2, in which the size of the linear actuators is reduced. [Figure 11] FIG. 11 is a diagram showing the relationship between the coil offset amount and the performance of the linear actuator. [Figure 12] FIG. 12 is a graph showing the relationship between the coil offset amount and the performance of the linear actuator. [Figure 13A] FIG. 13A is a perspective view showing another yoke configuration according to the first embodiment. [Figure 13B] FIG. 13B is a four-view diagram showing another yoke configuration according to the first embodiment. [Figure 14A] FIG. 14A is a perspective view showing another yoke configuration according to the first embodiment. [Figure 14B] FIG. 14B is a four-view diagram showing another yoke configuration according to the first embodiment. [Figure 15] FIG. 10 is a perspective view of an actuator of a comparative example. [Figure 16A] FIG. 10 is a top view showing the configuration of an actuator of a comparative example. [Figure 16B] FIG. 10 is a front view showing the configuration of an actuator of a comparative example. [Figure 16C] FIG. 10 is a bottom view showing the configuration of an actuator of a comparative example. [Figure 16D] FIG. 16C is a cross-sectional view taken along the line DD in FIG. 16B. [Figure 16E] FIG. 10 is a side view showing the configuration of an actuator of a comparative example. [Figure 17] FIG. 10 is a perspective view of an actuator according to a second embodiment. [Figure 18A] FIG. 10 is a top view showing the configuration of the actuator of the second embodiment. [Figure 18B] FIG. 10 is a front view showing the configuration of an actuator according to a second embodiment. [Figure 18C] FIG. 10 is a bottom view showing the configuration of the actuator of the second embodiment. [Figure 18D] FIG. 18C is a cross-sectional view taken along the line DD in FIG. 18B. [Figure 18E] FIG. 10 is a side view showing the configuration of the actuator of the second embodiment. [Figure 19A] FIG. 10 is a front view showing the shape of an E-shaped yoke according to a second embodiment. [Figure 19B] FIG. 10 is a side view showing the shape of an E-shaped yoke according to a second embodiment. [Figure 20A] FIG. 19C is a cross-sectional view of the E-shaped yoke of FIG. 19B taken along line AA. [Figure 20B] FIG. 19C is a cross-sectional view of the E-shaped yoke of FIG. 19B taken along the line BB. [Figure 20C] FIG. 19C is a cross-sectional view of the E-shaped yoke of FIG. 19B taken along the line CC. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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.

[0009] 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) (1) Lens barrel configuration overview The configuration of a lens barrel 100 according to an embodiment will be described below with reference to the drawings. Fig. 1 is a perspective view showing a camera 1 according to an embodiment. Fig. 2 is a perspective view showing the general configuration of lens barrel 100 according to an embodiment. Fig. 3 is an exploded perspective view of lens barrel 100 according to an embodiment.

[0010] 1 and 2, lens barrel 100 is a retractable lens barrel that is detachably attached to the body of camera 1. As shown in Fig. 2, lens barrel 100 includes first unit 101, second unit 102, third-fourth unit 103, fifth unit 104, fixed frame 105, cam frame 106, and exterior unit 107. Lens barrel 100 is completed by assembling the various parts in the following order: First, fixed frame 105, fifth group unit 104, third-fourth group unit 103, and second group unit 102 are assembled to cam frame 106, in that order. Then, cam frame 106 with the various parts assembled is assembled to first group unit 101. By assembling the various parts in this order, lens barrel 100 is completed.

[0011] Lens barrel 100 is attached to the body of camera 1 via lens mount 110 and light-shielding frame 111 in a state where it is assembled to rear frame unit 109 together with substrate unit 108 . Board unit 108 is a unit for driving lens barrel 100, and includes a printed circuit board on which electrical components, electrical contacts, etc. are mounted. Rear frame unit 109 is a member that covers the outer periphery of the end of exterior unit 107 that faces the body of camera 1. Lens mount 110 is a connecting component that connects and fixes lens barrel 100 and rear frame unit 109 to the body of camera 1. Light-shielding frame 111 is a member that is disposed between lens mount 110 and the body of camera 1 and blocks out unnecessary light.

[0012] Lens barrel 100 is configured so that when a zoom ring provided on exterior unit 107 is rotated, cam frame 106 rotates in accordance with the rotation of the zoom ring. When cam frame 106 rotates, lens barrel 100 drives first group unit 101, second group unit 102, third-fourth group unit 103, and fifth group unit 104 back and forth in the direction of optical axis L.

[0013] Each unit has a cam pin that engages with a cam groove formed in the cam frame 106. Each unit also has a linear key that engages with a groove formed in the fixed frame 105. This allows each unit to be driven back and forth in the direction of the optical axis L relative to the fixed frame 105 and cam frame 106. The third-fourth group unit 103 also includes a mechanism for focus adjustment, and during image capture, the focus lens is driven by these mechanisms.

[0014] (2) 3rd and 4th group units Next, third-fourth group unit 103 will be described in detail. (2-1) Overall structure First, the overall configuration of third-fourth group unit 103 according to the embodiment will be described. Figure 5 is an exploded perspective view of third-fourth group unit 103 according to the embodiment. As shown in Figure 5, third-fourth group unit 103 includes, from the subject side to the image plane side, base frame 280, third group lens unit 210, focus lens unit 220 (fourth group lens unit), main shaft holding frame 260, and sub shaft holding frame 270.

[0015] The focus lens unit 220 is an autofocus lens unit that is driven back and forth in the direction of the optical axis L by a linear actuator (lens barrel actuator) 310 (described later), and holds a focus lens 221. The third lens unit 210 holds the zoom lens 211, and is fixed to the base frame 280 after its position relative to the base frame 280 has been adjusted.

[0016] A main shaft 261 is stretched between the base frame 280 and the main shaft holding frame 260. Furthermore, a counter shaft 271 is stretched between the base frame 280 and the counter shaft holding frame 270. As a result, the focus lens unit 220 is driven back and forth in the direction of the optical axis L while being guided by the main shaft 261 and the sub shaft 271. More specifically, the focus lens unit 220 is driven in the direction of the optical axis L along the main shaft 261 while its rotation around the main shaft 261 is restricted by the sub-shaft 271.

[0017] That is, the focus lens unit 220 is held in a state in which it can move along the direction of the optical axis L. The main shaft 261 and the sub-shaft 271 are each an example of a shaft that guides the movement of the focus lens unit 220 in the direction of the optical axis L. An MR (Magneto Resistive) element 281 (an example of a position detection sensor) is fixed to the base frame 280. Furthermore, an MR magnet 223 (an example of a position detection member) is fixed to the focus lens unit 220.

[0018] 5, the MR magnet 223 is provided in the focus lens unit 220 so as to be disposed in the vicinity of the MR element 281 when assembled. Therefore, when the focus lens unit 220 including the MR magnet 223 moves back and forth in the direction of the optical axis L, a change in the magnetic field caused by a change in the relative position of the MR magnet 223 with respect to the MR element 281 is detected by the MR element 281.

[0019] As a result, by detecting the output of the MR element 281, the shift position of the focus lens unit 220 relative to the base frame 280 can be detected. In the present embodiment, an MR element 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.

[0020] (2-2) Configuration of the Linear Actuator 310 Next, linear actuator (lens barrel actuator) 310 according to this embodiment will be described. The linear actuator 310 is a device that drives the focus lens unit 220 back and forth in the direction of the optical axis L.

[0021] As shown in Figure 5 etc., the linear actuator 310 has a substantially U-shaped yoke A (first yoke) 311, a yoke B (second yoke) 312 having a shape mirror-symmetrical to the yoke A311, a pair of permanent magnets 313 fixed to the inner periphery of the yoke A311 and the yoke B312, a sub-yoke (third yoke) 314 that covers the open portions of the yoke A311 and the yoke B312, and a coil 315.

[0022] 5, yoke A 311 and yoke B 312 are fixed to main shaft holding frame 260. Sub-yoke 314 is held on the base frame 280 side. Coil 315 is fixed to focus lens unit 220. In this embodiment, the focus lens unit 220 is driven by one linear actuator 310.

[0023] For the sake of convenience, only the configuration of the linear actuator 310 will be explained below from the configuration of FIG. Fig. 6A is a perspective view showing the configuration of linear actuator 310 according to this embodiment. Fig. 6B is a four-view diagram showing the configuration of linear actuator according to this embodiment. Fig. 7 is a cross-sectional view showing the configuration of linear actuator 310 according to this embodiment.

[0024] 6A, 6B and 7, the yoke A 311, the yoke B 312 and the sub-yoke 314 are made by pressing an iron plate. The permanent magnet 313 is a sintered Nd-based magnet, and is magnetized so that the surface in contact with the yoke is the south pole and the opposite surface is the north pole, and is fixed to the yoke A 311 and the yoke B 312. The yoke A311 and the yoke B312 are fixed so that the outer walls on the sides to which the permanent magnet 313 is not fixed come into contact with each other.

[0025] The coil 315 is wound around the portion where the yoke A 311 and the yoke B 312 are in contact with each other and where the permanent magnet 313 is not fixed. A sub-yoke 314 is fixed to the substantially U-shaped open portion of the yoke A 311 and the yoke B 312. The sub-yoke 314 closes the open portion of the yoke A 311 and the yoke B 312 and also serves to magnetically couple the yoke A 311 and the yoke B 312.

[0026] When a current is applied to the coil 315, the coil 315 is subjected to a Lorentz force and is driven in the direction of the optical axis L. More specifically, a permanent magnet 313 is fixed to the base frame 280 side, and a coil 315 is fixed to the focus lens unit 220 side, so that by passing current through the coil 315, the focus lens unit 220 is driven in the direction of the optical axis L relative to the base frame 280.

[0027] In the linear actuator 310 of this embodiment, the center Oc of the coil 315 is offset from the centers Om of the two permanent magnets 313, as shown in FIG. That is, the linear actuator 310 of this embodiment includes two permanent magnets 313, yokes A311 and B312, a sub-yoke 314, and a coil 315, as shown in FIGS. 6A, 6B, and 7.

[0028] The two permanent magnets 313 are arranged substantially parallel to each other with a gap between them, with the same poles facing each other. Note that the two permanent magnets 313 do not necessarily have to be arranged substantially parallel to each other. The yokes A311, B312 and sub-yoke 314 each have a center yoke portion 316 arranged between two opposing permanent magnets 313, a back yoke portion 317 arranged in contact with the surface of the permanent magnet 313 opposite the opposing poles, and a yoke portion 318 that magnetically joins the center yoke portion 316 and the back yoke portion 317.

[0029] The coil 315 is wound around the center yoke portion 316 , and its center is provided at a position offset from the center of the two permanent magnets 313 toward the outer periphery of the optical axis of the focus lens 221 . The reason why the center Oc of the coil 315 is offset from the centers Om of the two permanent magnets 313 as described above will be explained in detail below.

[0030] 8, 9, and 10 are schematic diagrams showing the arrangement of linear actuator 310 within lens barrel 100. FIG. FIG. 8 shows a linear actuator 310 of this embodiment. In FIG. 8, the dashed line indicates the range within lens barrel 100 where linear actuator 310 can be installed.

[0031] The circle on the inner periphery of the dashed line indicates the range within which the lens restricts the placement of the linear actuator 310. Since the outer shape of a lens is usually circular, the linear actuator 310 needs to be placed further outward than the circle on the inner periphery of the dashed line. In this embodiment, the dashed line on the inner periphery shown in FIG. 8 corresponds to the contour line of the outer periphery of the substantially cylindrical portion of the focus lens unit 220.

[0032] On the other hand, the circle on the outer periphery of the dashed line indicates the range in which the installation of linear actuator 310 is restricted by the mechanism and exterior of lens barrel 100. In the present embodiment, the cam mechanism is disposed on the outer periphery of third-fourth group unit 103 within lens barrel 100, and therefore the placement of actuator 310 is limited by the inner diameter of fixed frame 105. For this reason, hereinafter, the dashed line on the outer periphery shown in FIG. 8 corresponds to the contour line of the inner periphery of fixed frame 105.

[0033] However, in a lens barrel that does not have a cam mechanism, or that has a cam mechanism but that is located in a range that does not overlap with third-fourth group unit 103, the movement is limited by the inner peripheral surface of exterior unit 107. Therefore, the dashed line on the outer periphery shown in Figure 8 is not limited to the contour line of the inner peripheral surface of fixed frame 105 as in this embodiment. Lens barrel 100 generally includes a cam mechanism for zooming, or an operation ring for operating lens barrel 100. The cam mechanism or operation ring has a generally cylindrical shape.

[0034] Therefore, the linear actuator 310 is arranged on the inner periphery of these members, and therefore needs to be arranged on the inner periphery of the circle on the outer periphery of the dashed line portion. In other words, the linear actuator 310 must be arranged so as to fit within the cylindrical space formed between the two concentric circles indicated by the dashed lines in FIG. In the configuration of this embodiment, as shown in Figure 8, a linear actuator 310 of maximum size is placed within the range of a donut-shaped cylinder of width r1 formed between two circles indicated by dashed lines.

[0035] As described above, in the linear actuator 310 of this embodiment, the center Oc of the coil 315 is offset from the center Om of the two permanent magnets 313, and the coil 315 is installed so as to be offset toward the outer periphery of a circle centered on the optical axis L of the lens. Here, in the linear actuator 310 shown in FIG. 8, the width (height direction in the drawing) of the yokes A311 and B312 and the permanent magnet 313 is set to d1.

[0036] FIG. 9 shows the configuration of Comparative Example 1, in which the sizes of yokes A311 and B312, coil 315, and permanent magnets 313 are the same, and the center Oc of coil 315 is designed to coincide with the center Om of the two permanent magnets 313. In the configuration of Comparative Example 1, as is clear from FIG. 9, when the width d2 of yoke A311, yoke B312, and permanent magnet 313 is equivalent to the width d1 of yokes A311, B312, and permanent magnet 313 in FIG. 8, it can be seen that they extend outward from the cylindrical range of width r2 (= r1) formed between the two circles indicated by the dashed lines.

[0037] Figure 10 shows the configuration of Comparative Example 2, in which the width of permanent magnet 313 and the radial width of coil 315 are reduced compared to the configuration of Comparative Example 1 shown in Figure 9 so that linear actuator 310 does not protrude from the cylindrical range indicated by the dashed line. That is, in Comparative Example 2 of FIG. 10, the width d3 of the yoke A311, yoke B312 and permanent magnet 313 is configured to be smaller than the widths d1 and d2 of the yokes A311, B312 and permanent magnet 313 of FIGS.

[0038] FIG. 10 shows a configuration in which the center Oc of the coil 315 is designed to coincide with the center Om of the two permanent magnets 313, and the width (vertical dimension in the figure) of the permanent magnets 313 and the radial width d3 of the coil 315 are reduced so that the linear actuator 310 does not extend beyond the cylindrical range of width r3 (= r1, r2) formed between the two circles indicated by dashed lines.

[0039] Comparing the configuration of this embodiment (FIG. 8) with Comparative Example 2 (FIG. 10), it can be seen that by offsetting the center Oc of the coil 315 from the center Om of the two permanent magnets 313 as shown in FIG. 8, it is possible to use permanent magnets 313 and coils 315 that are one size larger than those in the configuration of Comparative Example 2. In other words, as a result of comparing the configurations shown in Figures 8 to 10, by arranging the center Oc of the coil 315 on the outer periphery of a circle centered on the optical axis L of the lens with respect to the center Om of the two permanent magnets 313 as shown in Figure 8, it is possible to use a permanent magnet 313 and a coil 315 that are larger than those in Comparative Example 2, in which the width (the dimension in the vertical direction in the figure) of the permanent magnet 313 and the width in the radial direction of the coil 315 are reduced, as shown in Figure 10.

[0040] Therefore, for the same size linear actuator 310, a larger size permanent magnet 313 and coil 315 can be used, and therefore sufficient thrust can be obtained to drive a larger lens. 11 and 12 show an example obtained by simulating using magnetic field analysis how the performance of the linear actuator 310 changes when the center Oc of the coil 315 is offset from the center Om of the permanent magnet 313. FIG.

[0041] 11 and 12, the offset amount X of the center Oc of the coil 315 indicates how much the center Oc of the coil 315 is offset from the center Om of the permanent magnet 313 when the width Wm of the magnet is 100%. 11, the performance degradation (thrust reduction) of the linear actuator when the coil 315 is offset is 0.7% when the coil offset amount is 10%, 3.0% when the coil offset amount is 20%, and 4.8% when the coil offset amount is 25%. Therefore, it was found that if the coil offset amount is kept below 20%, the reduction in thrust can be made very small, at 3% or less.

[0042] From the above, it is preferable that the coil offset amount X (%) satisfies the following relational expression (1). 0 <X≦20(%)·····(1) In the configuration of this embodiment shown in Figure 8, the coil offset amount is 10%, and the thrust reduction is only 0.7% compared to Comparative Example 1 shown in Figure 9, in which the center Oc of the coil 315 is not offset from the center Om of the permanent magnet 313.

[0043] On the other hand, although not shown, when a similar simulation using magnetic field analysis was performed on Comparative Example 2 shown in Figure 10 in which the size of the linear actuator 310 was reduced, the thrust was 0.288 N, which was a 7.9% decrease in thrust compared to Comparative Example 1 shown in Figure 9 in which the center Oc of the coil 315 was not offset from the center Om of the permanent magnet 313. Here, when comparing the configuration of this embodiment shown in Figure 8 with Comparative Example 2 shown in Figure 10, in which the size of the linear actuator 310 is reduced, it was found that the configuration of this embodiment has a 7.2% higher thrust.

[0044] As described above, in the linear actuator 310 of this embodiment, the center Oc of the coil 315 is positioned so as to be offset from the center Om of the two permanent magnets, and the coil 315 is installed so as to be offset from the optical axis center of the lens toward the outer periphery. This allows a larger sized linear actuator 310 to be arranged, thereby improving the performance, such as increasing the driving force of the linear actuator 310.

[0045] In the present embodiment, as described above, the size of the linear actuator 310 is increased by prioritizing performance improvements such as improvement of the driving force of the linear actuator 310. However, according to the configuration of the present disclosure, when a linear actuator 310 is configured with performance equivalent to that of the conventional configuration, that is, with permanent magnets 313 and coils 315 of approximately the same size, the center Oc of coil 315 is positioned so as to be offset from the center Om of the two permanent magnets.

[0046] This makes it easier for linear actuator 310 to fit inside lens barrel 100, allowing the outer diameter of lens barrel 100 to be reduced. In addition, in the present embodiment, a configuration in which one linear actuator 310 is provided for one lens unit has been described. However, in the configuration of the present disclosure, a configuration in which multiple linear actuators are provided for one lens unit may also be used. With this configuration, it is possible to drive a lens with a larger mass.

[0047] When constructing a lens barrel 100 including two linear actuators 310, it is desirable that the linear actuators 310 are respectively arranged in the upper and lower spaces formed above and below the cylindrical housing portion (fixed frame 105) of the lens barrel 100 when the camera 1 is in the position when taking a landscape photograph. When linear actuator 310 is disposed inside lens barrel 100, light reflected by linear actuator 310 may appear in a photograph. Here, the imaging element provided on the main body side of camera 1 typically has a horizontally long shape. For this reason, when linear actuator 310 is disposed in the upper and lower spaces inside the housing, it is disposed farther from the optical path than in a configuration in which linear actuator 310 is disposed in the left and right spaces or diagonal parts, which has the advantage that reflected light is less likely to appear in a photograph.

[0048] Furthermore, in the above embodiment, the yoke portion of the linear actuator is configured by combining two press-molded U-shaped yokes (yoke A 311 and yoke B 312) with a flat sub-yoke 314. However, the linear actuator of the present disclosure may also be configured by combining one E-shaped yoke (fourth yoke) 321 with a flat sub-yoke (fifth yoke) 322, as shown in Figures 13A and 13B.

[0049] Alternatively, the linear actuator of the present disclosure may be configured by fixing an I-shaped center yoke (seventh yoke) 324 that forms a center yoke portion to the center of a square yoke (sixth yoke) 323, as shown in Figures 14A and 14B. In either case, the yoke is shaped to have a center yoke portion located between two permanent magnets arranged facing each other, a back yoke portion that contacts the surface opposite the facing surfaces of the permanent magnets, and a yoke portion that magnetically joins the center yoke portion and the back yoke portion, thereby achieving the same effects as the above embodiment.

[0050] In the first embodiment, as described above, the actuator is devised so that it can be easily accommodated in the substantially cylindrical space inside lens barrel 100, and a larger actuator than conventional can be installed in the same space. (Comparison with comparative examples) Here, as an actuator having a configuration that can be easily accommodated within the substantially cylindrical space of the lens barrel, for example, actuators such as those shown in FIG. 15 and FIGS. 16A to 16E can be considered as other configurations.

[0051] Fig. 15 shows a perspective view of an actuator of a comparative example, and Figs. 16A to 16E show the configuration of the actuator of a comparative example. 15 and 16A to 16E, in the configuration of the actuator of the comparative example, center yoke 401, which is located at a substantially central position, has a cylindrical shape. Two permanent magnets 402 are arranged so that their respective magnetic poles directly face center yoke 401. Back yoke 403 is arranged on the surface of permanent magnet 402 opposite the surface facing center yoke 401.

[0052] As shown in FIG. 16B, both ends of back yoke 403 and center yoke 401 are joined by yoke portion 404. Here, in the actuator of this comparative example, in order to make it easier to fit into the approximately cylindrical space of the lens barrel, two permanent magnets 402 are arranged along an approximately arc-shaped position centered on the central axis of center yoke 401, as shown in Figure 16D.

[0053] This configuration allows the actuator to be stored along the inner surface that forms the approximately cylindrical space of the lens barrel, making it possible to install a larger-sized actuator within the same lens barrel and improve the performance of the actuator. Comparing the actuator of the first embodiment with the actuator of the comparative example shown in Figure 15 and Figures 16A to 16E, the difference is that in the actuator of the first embodiment, the two permanent magnets 313 are arranged approximately parallel to each other, whereas in the comparative example, the two permanent magnets 402 are not parallel to each other but are arranged in a direction that intersects each other, as shown in Figure 16D.

[0054] That is, in the yokes fixed to these permanent magnets 313, 402, in the first embodiment, the center yoke portion 316 and the back yoke portion 317 are configured with surfaces that are substantially parallel to each other. In contrast, in the comparative example, as shown in Fig. 16D, the surfaces of the two back yokes 403 are not substantially parallel to each other but are arranged in directions that intersect each other, or are configured with curved surfaces.

[0055] In the actuator of the first embodiment, the yoke portion is configured as three separate parts (one center yoke portion 316 and two back yoke portions 317). On the other hand, in the actuator of the comparative example, the yoke shape is configured as five separate parts (a center yoke 401, two back yokes 403, and two yoke portions 404) because dividing the yoke into three parts would result in the shapes of the parts becoming too complicated.

[0056] As described above, the configuration of the first embodiment has the advantage that the shape of the yoke can be easily created and the number of divisions of the yoke can be reduced compared to the comparative example. Furthermore, if the yoke is divided into multiple parts, it is necessary to ensure that the parts can be assembled even if there are dimensional variations among them. This requires gaps at the joints between the parts, which can lead to a risk of a decrease in actuator performance due to magnetic resistance at the joints. In contrast, the configuration of the first embodiment allows the number of divisions of the yoke to be reduced, minimizing performance degradation due to magnetic resistance at the joints of the yoke.

[0057] (Embodiment 2) Hereinafter, in the second embodiment, the method of configuring the yoke will be described in more detail. Fig. 17 shows a perspective view of the actuator according to embodiment 2. Figs. 18A to 18E show the configuration of the actuator according to embodiment 2. 17 and 18A to 18E, the center yoke portion, back yoke portion, and portions corresponding to the lower yoke portion are integrated into E-shaped yoke 406. Two flat yoke members 407 are attached to the end portion (upper end portion in the figure) of E-shaped yoke 406, forming the upper yoke portion.

[0058] 19A and 19B are diagrams showing the shape of an E-yoke 406 included in the actuator according to the second embodiment. The E-shaped yoke 406 shown in FIGS. 19A and 19B is made up of a plurality of thin iron plates stacked together, as shown in FIG. 19B. Half-punched dowel portions 410 are formed on the multiple iron plates that make up the E-shaped yoke 406. The convex side of each dowel portion 410 is press-fitted into the concave side of the dowel portion 410 of the adjacent iron plate that is placed on top of the other iron plate, thereby integrating the multiple iron plates.

[0059] This type of processing method is called the laminate press method, and by stacking multiple iron plates each having a half-punched dowel portion 410 to form the E-shaped yoke 406, it is possible to improve productivity and dimensional accuracy. 20A to 20C show cross-sectional shapes at three locations of an E-shaped yoke 406 included in the actuator according to the second embodiment.

[0060] 20A is a cross-sectional view taken along line AA of the E-shaped yoke 406 shown in FIG. 19B, FIG. 20B is a cross-sectional view taken along line BB, and FIG. 20C is a cross-sectional view taken along line CC. The shape of the E-shaped yoke 406 shown in Figure 20B is obtained by removing four protrusion shapes 411 from the shape of the E-shaped yoke 406 in Figure 20A, and the shape of the E-shaped yoke 406 shown in Figure 20C is obtained by further removing the center yoke portion 412 from the shape of the E-shaped yoke 406 in Figure 20B.

[0061] Each steel plate, which has a different shape depending on the cross section, is not made using separate dies, but rather using a single progressive die. For example, in the progressive die and press machine used in the lamination press method, the stage of the press machine is partially moved and stopped, and the movement of the stage portion is controlled. Specifically, a stage is operated to cut out the four protrusion shapes 411 and the shape of center yoke portion 412 shown in FIG. 20A, thereby forming the cross-sectional shape of E-shaped yoke 406 shown in FIG. 20B.

[0062] This allows for the use of a single progressive die to punch out different shapes, and by regularly repeating this operation, it is possible to mass-produce E-shaped yokes 406 with different cross-sectional shapes depending on the position, continuously and with high precision at high speed. 15 and 16A to 16E, even if you try to integrate the yoke shapes of the comparative examples into an E-shaped yoke, each surface faces at an angle, making it difficult to integrate them using the lamination press method. For this reason, it is necessary to create each part separately and combine them to form the structure.

[0063] When combining multiple parts in this way, it is necessary to ensure that assembly can be performed even if there are dimensional variations among the parts. For this reason, gaps are required at the joints between the parts, and there is a risk that the magnetic resistance at the joints will degrade the actuator's performance. On the other hand, in the configuration of the second embodiment, the yoke is simply divided into two parts: E-shaped yoke 406 and yoke member 407. This makes it possible to minimize the deterioration of the actuator characteristics due to the magnetic resistance of the joint.

[0064] To apply the lamination press method, the yoke must be configured to include surfaces that are approximately parallel to each other, i.e., the two permanent magnets fixed to the yoke must be disposed approximately parallel to each other. The above example shows how the laminate press method is used to improve the productivity of the yoke. However, the fact that the two permanent magnets fixed to the yoke are arranged approximately parallel to each other is particularly advantageous in that it makes it easier to integrate the yoke when the yoke is produced by other methods such as sintering or cutting, thereby improving the productivity of the yoke and minimizing the deterioration of characteristics due to magnetic resistance at the yoke joints.

[0065] For example, when producing a yoke by cutting, the comparative yoke shapes shown in Figures 15 and 16A to 16E require machining of surfaces that are oblique to each other. This requires inserting tools into the workpiece from multiple directions. In contrast, the E-shaped yoke of this second embodiment can be machined from only one direction, making it easier to machine. In the second embodiment, the yoke is divided into an E-shaped yoke 406 and a flat yoke member 407. However, a configuration in which the rectangular yoke and the I-shaped yoke shown in FIG. 14 are combined may also be used. In this case, the same effect can be obtained. [Industrial Applicability]

[0066] The present disclosure is widely applicable to linear actuators mounted on the lens barrel of an imaging device that captures an image of a subject. [Explanation of symbols]

[0067] 1 camera 100 Lens barrel 101 1st group unit 102 2nd group unit 103 3rd and 4th group unit 104 5-group unit 105 Fixed frame (housing part) 106 Cam frame 107 Exterior unit 108 Circuit Board Unit 109 Rear frame unit 110 lens mount 111 Blackout frame 210 3-group lens unit 211 Zoom Lens 220 Focus lens unit (4-group lens unit) 221 Focus Lens 223 MR magnet (position detection component) 260 Spindle holder frame 261 Main axis 270 Sub-shaft holding frame 271 Secondary shaft 280 base frame 281 MR element (position detection sensor) 310 Linear actuator (lens barrel actuator) 311 York A (1st York) 312 York B (Second York) 313 Permanent Magnets 314 Sub-York (Third York) 315 Coil 316 Center York 317 Back yoke 318 Yoke section 321 E-type yoke (4th yoke) 322 Sub-York (5th York) 323 Square yoke (6th yoke) 324 Center York (7th York) 401 Center York 402 Permanent Magnets 403 Back Yoke 404 Yoke section 405 coil 406 E-type yoke 407 Yoke member 408 Permanent Magnet 409 Coil 410 Dowel part 411 Protrusion shape 412 Center Yoke L optical axis Oc center Om heart r1,r2,r3 width X coil offset amount

Claims

1. an actuator that drives the lens back and forth along the optical axis; a lens frame that holds the lens and is driven back and forth along the optical axis by the actuator together with the lens; Equipped with The actuator is The lens frame is disposed on the outer periphery side of the outer periphery surface of the lens frame, Two permanent magnets arranged approximately parallel to each other with the same poles facing each other and spaced apart; a yoke having a center yoke portion provided between the two permanent magnets arranged opposite to each other, a back yoke portion provided in a position in contact with a surface of the permanent magnet opposite to the facing poles, and a yoke portion that magnetically joins the center yoke portion and the back yoke portion; a coil wound around the center yoke portion; It has The yoke is constructed by stacking a plurality of thin iron plates, and the portions corresponding to the back yoke and the yoke are integrated into a rectangular yoke, and the portion corresponding to the center yoke is combined with the rectangular yoke as an I-shaped yoke. The I-shaped yoke is constructed by stacking a plurality of I-shaped steel plates and steel plates with the shape of the center yoke portion of the I-shaped steel plates removed, so that the thickness of the center yoke portion in the stacking direction is thinner than the thickness of the other portions in the stacking direction. Lens barrel.

2. The I-shaped yoke is formed by stacking a plurality of thin iron plates in a radial direction around the optical axis of the lens. The lens barrel according to claim 1 .

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