Linear motor and lens barrel

Abstract

This invention provides a compact linear motor that maintains a sufficient stroke while suppressing performance changes and preventing a decrease in thrust efficiency during operation. [Solution] The linear motor according to the present invention has a first coil and a second coil, and a magnet arranged opposite the first coil and the second coil, the poles of the magnet change periodically along the driving direction, the first coil and the second coil are arranged such that in the driving direction their phases are shifted by 90° in electrical angle, and a portion of the surfaces of the first coil and the second coil that face the magnet overlap.

Description

Technical Field

[0001] The present invention relates to a linear motor and a lens barrel provided with the same, and particularly to a technique for driving a lens group in a lens barrel.

Background Art

[0002] Conventionally, in order to move a lens frame of a lens barrel in the optical axis direction, a linear motor capable of high-speed response has been adopted.

[0003] In recent years, imaging elements used in imaging devices have been increasing in size for the purpose of increasing pixel count, improving dynamic range, etc.

[0004] When the imaging element increases in size, the lenses used in the lens barrel also inevitably increase in size, and the amount of movement of the lenses also increases. In order to drive the enlarged lenses, a driving device for driving the lenses is required to have a greater thrust and a longer stroke than before.

[0005] In Patent Document 1, a technique related to a linear motor capable of increasing thrust and lengthening stroke, a lens barrel provided with the same, and an imaging device is disclosed.

[0006] Also, the applicant has disclosed in Japanese Patent Application No. 2023-219350 a linear motor that is long-stroke and small-sized while being capable of improving thrust, and a lens barrel having the same.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The invention disclosed in Patent Document 1 has two-phase drive coils arranged in series, which means that the dimensions occupied by the coils in the direction of motor travel are large, thus limiting the amount of stroke and miniaturization of the motor.

[0009] The invention disclosed in Japanese Patent Application No. 2023-219350 involves arranging one coil in one unit and configuring a two-phase linear motor with two such units. This reduces the size occupied by the coil in the driving direction within a single unit, enabling the construction of a linear motor that is both high-thrust and has a long stroke. However, because the magnitude of the thrust in each unit changes depending on the position in the optical axis direction, when moving the lens frame in the optical axis direction, the frictional force around the axis guiding the movement tends to increase, or the frictional force changes, or the direction and magnitude of the tilt of the lens frame changes, which can lead to a decrease in thrust efficiency and changes in performance.

[0010] As disclosed in Figure 9 of Japanese Patent Application No. 2023-219350, the aforementioned problem can be solved by using two sets of units, but this requires securing a large space for component placement, resulting in constraints on placement space.

[0011] This invention has been made in view of these problems, and aims to provide a compact linear motor that maintains a sufficient stroke while suppressing performance changes and preventing a decrease in thrust efficiency during operation. [Means for solving the problem]

[0012] To solve the aforementioned problems, the linear motor according to the present invention has a first coil and a second coil, a magnet arranged opposite the first coil and the second coil, the magnet's poles change periodically along the driving direction, the first coil and the second coil are arranged such that in the driving direction their phases are shifted by 90° in electrical angle, and a portion of the surfaces of the first coil and the second coil that face the magnet overlap. [Effects of the Invention]

[0013] According to the linear motor according to the present invention, it is possible to provide a small-sized linear motor that secures a stroke amount while suppressing performance changes while preventing a decrease in thrust efficiency during driving.

Brief Description of the Drawings

[0014] [Figure 1] External perspective view of the focus unit 10 [Figure 2] Exploded perspective view of FIG. 1 [Figure 3] Cross-sectional view of the linear motor 20 [Figure 4] View showing magnets arranged in the gaps between the protrusions provided at regular intervals on the main yokes 25a and 25b [Figure 5] View showing the relationship of the angular arrangement of the coils and magnets included in the linear motor 20 [Figure 6] View comparing the widths of the magnet 23, the first coil 21, and the second coil 22 in a direction orthogonal to the driving direction [Figure 7] View of the focus unit 10 as seen from the side [Figure 8] External perspective view of the focus unit 90 when a plurality of linear motors 20 are used [Figure 9] Exploded perspective view of FIG. 8

Modes for Carrying Out the Invention

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In this embodiment, only the main parts according to the present invention will be described, but other parts can be configured by appropriately using well-known techniques related to linear motors and lens barrels.

[0016] The "substantially **" described in the description means, for example, in the case of "substantially oval", it is intended to include the oval itself and those recognized as substantially oval.

[0017] FIG. 1 is an external perspective view of the focus unit 10 according to the present invention, and FIG. 2 is an exploded perspective view of FIG. 1.

[0018] The focus unit 10 includes a linear motor 20 and a lens frame 11.

[0019] The linear motor 20 includes a first coil 21 and a second coil 22. Magnets 23 and 24 are arranged at positions facing the first coil 21 and the second coil 22. The magnets 23 and 24 are held by a yoke 25, and the magnets 23 and 24 and the yoke 25 constitute a field magnetic part.

[0020] The first coil 21 and the second coil 22 are substantially oval hollow coils and have a flat plate shape. The first coil 21 and the second coil 22 are configured to be movable in the optical axis direction between the magnets 23 and 24. Also, a winding axis in a direction substantially perpendicular to the driving direction of the first coil 21 and the second coil 22 forms the hollow of the hollow coil.

[0021] The first coil 21 and the second coil 22 are fixed to a coil fixing part 12 provided on the lens frame 11. The coil fixing part 12 is configured such that the arrangements of the first coil 21 and the second coil 22 are shifted in phase by 90° in the driving direction.

[0022] The yoke 25 is composed of main yokes 25a and 25b and yoke retainers 25c and 25d, and is fixed to a lens barrel (not shown). Since the main yokes 25a and 25b hold the magnets, they are likely to be deformed by the attractive force of the magnets 23 and 24. Therefore, the deformation of the main yokes 25a and 25b may be prevented by fixing the yoke retainers 25c and 25d to the main yokes 25a and 25b with screws. In addition, in order to prevent the deformation of the main yokes 25a and 25b, the ends along the longitudinal direction of the main yokes 25a and 25b may be bent, a beam structure may be provided at a position that does not prevent the movement of the coils of the main yokes 25a and 25b, or a reinforcing member may be provided along the longitudinal direction of the main yokes 25a and 25b.

[0023] The lens frame 11 holds the lens, and the first coil 21 and the second coil 22, fixed to the coil fixing part 12, are configured to move in the optical axis direction by moving through the gap between the magnets 23 and 24. By moving the lens frame 11 in the optical axis direction, the lens barrel, which includes the focus unit 10, can perform focusing. In this embodiment, the lens frame 11 is configured to be movable for focusing, but it is not limited to this, and the lens frame 11 may also be configured to be movable for zooming.

[0024] Figure 3 is a cross-sectional view of the linear motor 20. Note that Figure 3 has been simplified for the sake of clarity in the explanation.

[0025] As shown in Figure 3, the magnets 23 and 24 are arranged so that their poles periodically change along the driving direction. In this embodiment, multiple magnets 23 and 24 are arranged in a row such that the poles on the faces facing each coil periodically reverse along the driving direction. This generates thrust by alternately energizing the first coil 21 and the second coil 22 fixed to the coil fixing part 12, causing the lens frame 11 to move back and forth along the driving direction.

[0026] The magnets 23 and 24 may have a Halbach arrangement of poles that changes along the driving direction. By arranging the poles in a Halbach arrangement, the magnetic flux can be concentrated on the surface opposite the coil, which contributes to improving thrust.

[0027] Furthermore, magnets 23 and 24 may be constructed by applying multi-pole magnetization to a single magnetic plate. When multiple magnets are applied to a single magnetic plate, the holding rigidity of the magnets can be borne by the magnetic plate itself, compared to when multiple magnets are arranged side by side. This simplifies the yoke 25 and is advantageous for miniaturizing the unit. In addition, when multiple magnets are applied to a single magnetic plate, it contributes to reducing variations in manufacturing errors caused by the number of parts, compared to when multiple magnets are arranged side by side.

[0028] Furthermore, when multiple magnets 23 and 24 are arranged in a row such that the poles on the faces facing each coil periodically reverse along the driving direction, they may be placed in the gaps between protrusions provided at regular intervals on the main yoke 25a (25b), as shown in Figure 4. When multiple magnets are arranged in a row, the cumulative error in the magnet pitch increases due to the addition of manufacturing errors in the width of each magnet, resulting in a difference between the design thrust value and the actual thrust value, which can lead to a deterioration in stopping accuracy and a decrease in drive quality. By placing them in the gaps between protrusions provided on the main yoke 25a (25b), the cumulative error in the magnet pitch can be reduced, and position adjustment during assembly can be easily performed. In Figure 4, two protrusions p are placed between the magnets, but there may be only one, and they do not have to be round in shape.

[0029] As shown in Figures 1, 2, and 3, the first coil 21 and the second coil 22 are arranged with a portion of their components overlapping on the surfaces facing the magnets 23 and 24. By arranging the first coil 21 and the second coil 22 with a portion of their components overlapping on the surfaces facing the magnets 23 and 24, it becomes easier to secure space in the direction of drive compared to arranging the first coil 21 and the second coil 22 side by side along the direction of drive. This makes it possible to construct a linear motor with a long stroke and a compact size.

[0030] Figure 5 shows the relationship between the electrical angle arrangement of the coils and magnets included in the linear motor 20.

[0031] As described above, in this embodiment, magnets 23 and 24 are arranged in a row such that the poles on the faces facing each coil periodically reverse along the driving direction, but one period of the S pole and N pole is configured to be 360° in electrical angle. In other words, one of the arranged magnets corresponds to 180° in electrical angle.

[0032] In this embodiment, the pitch between the hollow portion and the wire portion of each coil, that is, the distance between the centers of the two substantially straight portions of the wire portion of the coil, is set to an electrical angle of 180°. As shown in Figure 5, by arranging the first coil 21 and the second coil 22 with an electrical angle offset of 90° in the driving direction, two-phase current can be supplied to each coil and driven. In this embodiment, the pitch between the hollow portion and the wire portion of each coil is set to 180°, but this is not limited to this. Each coil can be driven by arranging them with an electrical angle offset of 90° in the driving direction.

[0033] Figure 6 is a diagram comparing the widths of the magnet 23, the first coil 21, and the second coil 22 in the direction perpendicular to the driving direction. Here, we will explain the magnet 23, but the same applies to the magnet 24.

[0034] The width A in the direction perpendicular to the driving direction in the first coil 21 and the second coil 22 is set to be larger than the width B in the direction perpendicular to the driving direction in the magnet 23. By making width A larger than width B, the magnetic field generated from the magnet 23 can be fully utilized as thrust for the linear motor 20, contributing to an improvement in thrust.

[0035] Figure 7 is a side view of the focus unit 10. Note that, to make the arrangement easier to understand, a portion of the yoke 25 and the magnet 24 are removed from the diagram.

[0036] As shown in Figure 7, the coil fixing section 12 is configured to fix an area exceeding width B in a plane perpendicular to the driving direction of the first coil 21 and the second coil 22. By configuring the coil fixing section 12 in this way, it is possible to minimize the gap between the magnets 23 and 24 facing the first coil 21 and the second coil 22 by not placing any coil fixing members in the gap, thereby contributing to an improvement in thrust.

[0037] As shown in the figures, the first coil 21 and the second coil 22 are arranged so that the conductor portion of the other coil completely covers the air core portion of the other coil. By arranging them in this way, the structure makes it difficult for adhesive to leak when bonding and fixing each coil to the lens frame 11, thus contributing to improved ease of assembly.

[0038] The above describes the focus unit 10 using the linear motor 20, but it is also possible to configure a focus unit 90 using multiple linear motors according to the present invention. Figure 8 is an external perspective view of the focus unit 90 when multiple linear motors according to the present invention are used, and Figure 9 is an exploded perspective view of Figure 8. Hereafter, the explanation of the configuration which is common to the case when a single linear motor is used will be omitted.

[0039] In Figures 8 and 9, the linear motors 20 and 30 are positioned opposite each other on the outer diameter of the lens frame 91. By positioning the linear motors 20 and 30 opposite each other, the midpoint of the thrust generation point of the coils of each linear motor can be brought close to the center of gravity of the movable part of the focus unit 90. This makes it less likely for the lens frame 91 to tilt relative to the axis that guides its movement, contributing to improved thrust efficiency and suppression of performance changes. Although two motors are shown in Figures 8 and 9, the number of motors may be increased to the extent that it does not cause space inconvenience if the lens frame 91 including the lens is heavy or if higher speed movement is desired.

[0040] The above describes embodiments of the present invention. According to the linear motor of the present invention, by arranging the first coil 21 and the second coil 22 on top of each other, space can be secured in the driving direction, making it possible to construct a motor that is compact in the driving direction while allowing for a long stroke.

[0041] Furthermore, compared to the technology disclosed in Japanese Patent Application No. 2023-219350 which configures a two-phase linear motor using two units, this method allows for the configuration of a linear motor without performance changes.

[0042] Furthermore, thrust efficiency can be increased by configuring the first coil 21 and the second coil 22 to have a width in the direction perpendicular to the driving direction on the surfaces facing the magnets 23 and 24 that are larger than the width of the magnets 23 and 24 in the direction perpendicular to the driving direction on the surfaces facing the first coil 21 and the second coil 22.

[0043] Furthermore, by using the linear motor according to the present invention in the lens barrel, it becomes possible to prevent a decrease in thrust efficiency when driving the movable lens frame inside the lens barrel, suppress changes in performance during driving, and secure the stroke amount.

[0044] The above describes embodiments of the present invention. However, the shapes of the parts shown in the embodiments are merely examples for carrying out this technology. Furthermore, the technology disclosed in the embodiments is not limited to the description of the embodiments and can be modified in various ways, all of which fall within the scope of equivalence of the present invention. [Explanation of Symbols]

[0045] 10.90 Focus Unit 20,30 Linear motor 21. First coil 22 Second Coil 23,24 Magnets 25 York 25a, 25b Main York 25c, 25d Yoke retainer 11.91 Lens frame 12,13 Coil fixing part

Claims

1. It has a first coil and a second coil, The first coil and the second coil have magnets arranged opposite each other, The aforementioned magnet has a periodic change of poles along the driving direction. In the driving direction arrangement, the phase of the first coil and the phase of the second coil are shifted by 90° in electrical angle. A linear motor characterized in that the first coil and the second coil are arranged so that a portion of the surface facing the magnet overlaps.

2. The linear motor according to claim 1, characterized in that the width of the first coil and the second coil in the direction perpendicular to the driving direction on the surfaces facing the magnet is greater than the width of the magnet in the direction perpendicular to the driving direction on the surfaces facing the first coil and the second coil.

3. The linear motor according to claim 1, characterized in that the first coil and the second coil are arranged to overlap so that the air core portion of one coil completely covers the wire portion of the other coil.

4. The linear motor according to claim 1, characterized in that the magnets are a series of magnets arranged so that their poles periodically reverse along the driving direction.

5. The linear motor according to claim 1, characterized in that the arrangement of poles that periodically changes along the driving direction of the magnet is a Halbach arrangement.

6. The linear motor according to claim 1, characterized in that the poles that periodically change along the driving direction of the magnet are magnetized with multiple poles on a single magnet.

7. A lens barrel comprising a linear motor according to any one of claims 1 to 6.

8. A lens barrel comprising a linear motor as described in claim 2, The lens barrel comprises a lens frame that can be moved in the optical axis direction by the linear motor, The lens frame includes a coil fixing portion capable of fixing the first coil and the second coil, The lens barrel is characterized in that the coil fixing portion is configured to fix a region in the first coil and the second coil that exceeds the width in the direction perpendicular to the driving direction on the surfaces of the magnet facing the first coil and the second coil.

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