Linear motor and lens barrel having the same

Abstract

To provide a linear motor capable of improving thrust in spite of a long stroke and small size, and a lens barrel having the same.SOLUTION: A linear motor according to the present invention has a first unit and a second unit, wherein each of the first unit and the second unit has one coil and a magnet arranged to face the coil, the pole of the magnet periodically changes along a driving direction, a fixing member is included to fix the coil included in the first unit and the coil included in the second unit, and a phase of the first unit and a phase of the second unit are shifted by 90° of an electrical angle with respect to the driving direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a linear motor and a lens barrel equipped 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, image sensors used in imaging devices have been increasing in size for the purpose of increasing the number of pixels, improving the dynamic range, etc.

[0004] When the image sensor increases in size, the lenses used in the lens barrel 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] Patent Document 1 discloses a technique related to a linear motor capable of increasing the thrust and lengthening the stroke, a lens barrel equipped with the same, and an imaging device.

[0006] According to the technique disclosed in Patent Document 1, by making the magnetic field part of the linear motor multi-polar and performing two-phase drive, the thrust density of the linear motor can be improved, and further, by solving the problem of magnetic saturation, it is possible to achieve a configuration that facilitates long stroke.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in the invention disclosed in Patent Document 1, since the coils for two-phase drive are arranged in series, the dimension occupied by the coils in the traveling direction of the motor becomes large, so there are limitations in securing the stroke amount and miniaturizing the motor. Also, there are limitations in improving the thrust force.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a linear motor that can improve the thrust force while having a long stroke and being small in size, and a lens barrel having the same.

Means for Solving the Problems

[0010] In order to solve the above-described problems, a linear motor according to the present invention is a linear motor including a first unit and a second unit, wherein the first unit and the second unit each have one coil and a magnet arranged to face the coil, the magnet has poles that periodically change along the driving direction, and has a fixing member that fixes the coil of the first unit and the coil of the second unit, and the phases of the first unit and the second unit are shifted by 90° in terms of electrical angle with respect to the driving direction.

Effects of the Invention

[0011] According to the present invention, it becomes possible to provide a linear motor that can improve the thrust force while having a long stroke and being small in size, and a lens barrel having the same.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

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Figure 11

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] The “substantially **” described in the description means, taking “substantially oval” as an example, including the oval itself and those recognized as substantially oval.

[0015] <1. Configuration of the Linear Motor> FIG. 1 is a perspective view of the linear motor 1 according to the present embodiment, and FIG. 2 is an exploded perspective view of FIG. 1.

[0016] The linear motor 1 includes a first unit 11 and a second unit 21. The first unit 11 includes a first coil 12 and a first magnet 13. The second unit 21 includes a second coil 22 and a second magnet 23.

[0017] In this embodiment, the linear motor 1 is configured as a driving device for driving a focus lens group used in a lens barrel, and the coil fixing portions 61 and 62, which are fixed members, are formed as a part of the movable lens frame 70. By fixing the first coil 12 to the coil fixing portion 61 and the second coil 22 to the coil fixing portion 62, the linear motor 1 that generates a thrust with respect to the driving direction of the movable lens frame 70 is configured by two units.

[0018] <2. Configuration of the First Unit 11 and the Second Unit 21> FIG. 3 is a side view of the first unit 11 and the second unit 21. Note that FIG. 3 is simplified for simplicity of explanation.

[0019] The first coil 12 included in the first unit 11 has a winding axis in a direction substantially perpendicular to the driving direction. The first magnet 13 is arranged so as to be sandwiched with a gap provided between the first magnet 13 and the first coil 12. By arranging in this way, the movable lens frame 70 to which the first coil 12 is fixed is configured to be movable in the driving direction. A first yoke member 14 is formed around the first magnet 13, and the first magnet 13 and the first yoke member 14 constitute a field magnet portion. The first yoke member 14 may be configured by combining a plurality of yoke members as shown in FIG. 2, or may be configured as an integral body. Similarly to the first unit 11, the second unit 21 includes a second coil 22, a second magnet 23, and a second yoke member 24.

[0020] FIG. 4 is a view of the first coil 12 and the second coil 22 as seen from a direction perpendicular to the driving direction. The first coil 12 and the second coil 22 have the same shape.

[0021] The first coil 12 and the second coil 22 are substantially oval hollow coils and have a flat plate shape. In this embodiment, the first coil 12 and the second coil 22 have a flat plate shape, but may have a cylindrical shape as long as the movable lens frame 70 is movable in the driving direction.

[0022] The pitch between the hollow portion and the conductor portion of the first coil 12 and the second coil 22, that is, the distance between the central portions of the two substantially straight portions of the conductor portion of the coil, is set to 180° in electrical angle. Although details will be described later, by setting the pitch between the hollow portion and the conductor portion to 180° in electrical angle, a linear motor advantageous for improving thrust and achieving a long stroke can be configured. The conduction portion 50 is connected to a flexible printed circuit board (not shown) and is configured to be able to energize the coil.

[0023] The hollow portions of the first coil 12 and the second coil 22 are preferably made narrow within a range where no manufacturing inconvenience occurs. Although the pitch between the hollow portion and the conductor portion is set to 180° in electrical angle, by narrowing the hollow portion by increasing the number of turns of the coil or the like, the current flowing through the conductor portion can be increased, and an improvement in thrust can be expected. As a means of narrowing the hollow portion while setting the pitch between the hollow portion and the conductor portion to 180° in electrical angle, using a winding bobbin as thin as possible during coil manufacturing, or pressing a coil manufactured by winding it in a cylindrical shape to obtain a desired shape, etc.

[0024] Also, the arc portion of the coil may be bent in the vertical direction as needed. By bending the arc portion of the coil, it becomes possible to make the size in the longitudinal direction compact, contributing to the miniaturization of the unit.

[0025] The first magnet 13 is arranged to face the first coil 12. In FIG. 3, magnets are arranged above and below the coil, respectively, but in the case where there are size constraints or the like, a single-sided arrangement is also acceptable. Similarly, the second magnet 23 is arranged to face the second coil 22.

[0026] In the present embodiment, the first magnet 13 and the second magnet 23 are configured by arranging a plurality of magnets such that the S pole and the N pole periodically reverse along the driving direction. Note that one cycle of the S pole and the N pole is configured to be 360° in electrical angle.

[0027] Each magnet only needs to have poles that periodically change along the driving direction. It may be configured by arranging a plurality of magnets as in this embodiment so that the S poles and N poles are arranged to periodically reverse along the driving direction, or it may be configured by multi-pole magnetization of a single magnetic plate. When the first magnet 13 and the second magnet 23 are configured by performing multi-pole magnetization on a single magnetic plate, since the holding rigidity of the magnet can be borne by the magnetic plate itself as compared with the case of arranging a plurality of magnets, each yoke portion can be simplified, which is advantageous for miniaturization of the unit. Furthermore, when configured by performing multi-pole magnetization on a single magnetic plate, it contributes to reducing the variation error caused by the number of parts during manufacturing as compared with arranging a plurality of magnets.

[0028] Also, the first magnet 13 and the second magnet 23 may form poles of a Halbach array along the driving direction. By forming poles of a Halbach array, magnetic flux can be concentrated on the coil facing surface, which contributes to improving the thrust.

[0029] FIG. 5 is a diagram showing the arrangement of the first coil 12 provided in the first unit 11 and the second coil 22 provided in the second unit 21 in terms of the relationship of the electrical angle. The first coil 12 and the second coil 22 are arranged with a 90° shift in the electrical angle. By arranging the first coil 12 and the second coil 22 with a 90° shift in the electrical angle, it is possible to drive the member fixed to the coil in the driving direction by applying two-phase currents with a 90° phase shift to each coil.

[0030] As shown in FIG. 6, a configuration may be adopted in which the phases of the first unit 11 and the second unit 21 are shifted by 90° in the electrical angle by shifting the arrangement of the magnets instead of shifting the arrangement of the coils. Also in this case, by driving each coil in two phases, the member fixed to the coil can be driven in the driving direction.

[0031] By arranging one coil in one unit and configuring a two-phase linear motor with two units like the first unit 11 and the second unit 21 of the present embodiment, it is possible to reduce the dimension occupied by the coil in the driving direction within one unit, and it becomes possible to configure a linear motor that can achieve a long stroke while having a high thrust.

[0032] <3. Comparison of Thrust> FIG. 7 is a thrust simulation diagram when the pitch of the hollow portion and the conductor portion of the first coil 12 and the second coil 22 is set to 150°. The first magnet 12 and the second magnet 22 are each configured such that one cycle of the S pole and the N pole is 360° in electrical angle, and a thrust is generated by applying a two-phase current to each coil arranged with a 90° shift.

[0033] The broken line in FIG. 7 is the thrust borne by the first coil 12, the dashed-dotted line is the thrust borne by the second coil 22, and the solid line is the synthesis of the thrusts borne by the first coil 12 and the second coil 22. Each thrust is calculated as the value generated when the magnetic force generated at the electrical angle of 0° and the electrical angle of 360° is set to 1 and the magnetic force generated at the electrical angle of 180° is set to -1 in the first magnet 13 and the second magnet 23 in which one cycle of the S pole and the N pole is 360° in electrical angle. When the pitch of the hollow portion and the conductor portion of the first coil 12 and the second coil 22 was set to 150°, the maximum thrust was 2.73 and the average thrust was 2.44.

[0034] FIG. 8 is a thrust simulation diagram when the pitch of the hollow portion and the conductor portion of the first coil 12 and the second coil 22 is set to 180°. Except for the coil pitch, the configuration is the same as in the simulation diagram of FIG. 7. The first magnet 13 and the second magnet 23 are each configured such that one cycle of the S pole and the N pole is 360° in electrical angle, and a thrust is generated by applying a two-phase current to each coil arranged with a 90° shift.

[0035] The dashed line in Fig. 8 is the thrust borne by the first coil 12, the chain line is the thrust borne by the second coil 22, and the solid line is the synthesis of the thrusts borne by the first coil 12 and the second coil 22. Each thrust is calculated as a value generated when the magnetic force generated at the electrical angle of 0° and the electrical angle of 360° is set to 1, and the magnetic force generated at the electrical angle of 180° is set to -1 in the first magnet 13 and the second magnet 23 in which one cycle of the S pole and the N pole is configured as 360° in electrical angle. When the pitch between the hollow part and the conductor part is set to 180°, the maximum thrust is 2.83 and the average thrust is 2.51, resulting in a higher thrust compared to the case where the pitch between the hollow part and the conductor part is set to 150°.

[0036] The closer the pitch between the hollow part and the conductor part is to 180°, the greater the resulting thrust. Also, when the pitch between the hollow part and the conductor part is set to 180° or more, depending on the narrowness of the hollow part, it is possible to obtain a thrust equivalent to that when the pitch between the hollow part and the conductor part is set to about 180°. However, since the dimension occupied by the coil in the driving direction becomes large, it is disadvantageous for increasing the stroke length or miniaturizing the unit. Therefore, in order to satisfy each of the requirements of increasing the stroke length, miniaturizing the unit, and increasing the thrust, it is preferable to set the pitch between the hollow part and the conductor part near 180°.

[0037] <4. Application to the lens barrel> As described with reference to Figs. 1 and 2, the linear motor of the present embodiment is configured as a driving device for driving the focus lens group used in the lens barrel. When the linear motor of the present embodiment is used in the lens barrel, a configuration for obtaining a higher thrust is considered. Fig. 9 is a perspective view of the linear motor 2 including four units, and Fig. 10 is an exploded perspective view of the linear motor 2. Note that the same reference numerals are used to describe the components common to the linear motor 1.

[0038] The linear motor 2 includes a first unit 11, a second unit 21, a third unit 31, and a fourth unit 41. The first unit 11 includes a first coil 12, a first magnet 13, and a first yoke member 14. The second unit 21 includes a second coil 22, a second magnet 23, and a second yoke member 24. The third unit 31 includes a third coil 32, a third magnet 33, and a third yoke member 34. The fourth unit 41 includes a fourth coil 42, a fourth magnet 43, and a fourth yoke member 44.

[0039] Coil fixing parts 61, 62, 63, 64 which are fixing members are formed on a part of the movable lens frame 80, and are provided so as to be able to fix the four coils included in the four units. By fixing the first coil 12 to the coil fixing part 61, the second coil 22 to the coil fixing part 62, the third coil 32 to the coil fixing part 63, and the fourth coil 42 to the coil fixing part 64, the linear motor 2 that generates thrust by the four units is configured.

[0040] The phase of the first unit 11 and the phase of the second unit 21 are shifted by 90° in electrical angle with respect to the driving direction. Similarly, the phase of the third unit 31 and the phase of the fourth unit 41 are shifted by 90° in electrical angle with respect to the driving direction. The phase shift is configured by shifting the arrangement of the coils or the arrangement of the magnets. Thrust is generated by passing a two-phase current through each pair of units.

[0041] The first unit 11 and the third unit 31 have the same configuration, and the second unit 21 and the fourth unit 41 have the same configuration. That is, the thrust is improved by combining a plurality of sets of units used in the linear motor 1. In addition, since the units have the same configuration, the mass productivity of the parts is also excellent.

[0042] FIG. 11 is a view of the linear motor 2 seen from the front. Since the first unit 11 and the third unit 31 have the same configuration, and the second unit 21 and the fourth unit 41 have the same configuration, each pair has the same phase.

[0043] The first unit 11 and the third unit 31 are arranged to face each other and are arranged at a substantially equal distance around the optical axis 90. Similarly, the second unit 21 and the fourth unit 41 are also arranged to face each other and are arranged at a substantially equal distance around the optical axis 90. By arranging in this way, when generating thrust by energizing two-phase current to the four units, since two units having the same phase are driven simultaneously, no unnecessary moment is generated, which is advantageous for improving the thrust efficiency.

[0044] The above is the description of this embodiment. In the description of this embodiment, only the main parts related to the present invention are described, but the other parts can be appropriately configured by well-known techniques of linear motors and lens barrels.

[0045] Also, the description of the above embodiment is an example of the linear motor and lens barrel of the present invention, and the present invention is not limited to this embodiment within the scope not departing from the gist thereof. Various design changes, modified implementations, combinations, and sub-combinations are possible, and all are included in the equivalent scope of the present invention.

Description of Reference Numerals

[0046] 1, 2 Linear motor 11 First unit 12 First coil 13 First magnet 14 First yoke member 21 Second unit 22 Second coil 23 Second magnet 24 Second yoke member 31 Third unit 32 Third coil 33 Third magnet 34 Third yoke member 41 Fourth unit 42 Fourth coil 43 Fourth magnet 44 Fourth yoke member 50 Conductive part 61, 62, 63, 64 Coil fixing parts 70, 80 Movable lens frames 90 Optical axis

Claims

1. A linear motor comprising a first unit and a second unit, wherein the first unit and the second unit each have one coil and a magnet arranged to face the coil, the poles of the magnet periodically change along the driving direction, having a fixing member for fixing the coil of the first unit and the coil of the second unit, and a linear motor, characterized in that the phase of the first unit and the phase of the second unit are shifted by 90° in electrical angle with respect to the driving direction.

2. The linear motor according to claim 1, wherein the pitch of the hollow portion and the conductor portion on the facing surface of the coil with the magnet is 180° in electrical angle.

3. The linear motor according to claim 1, wherein the magnet is a magnet array arranged such that the poles periodically reverse along the driving direction.

4. The linear motor according to claim 1, wherein the arrangement of the poles that periodically change along the driving direction of the magnet is a Halbach array.

5. The linear motor according to claim 1, wherein the poles that periodically change along the driving direction of the magnet are formed by multi-pole magnetization of one magnet.

6. Comprising a third unit and a fourth unit, the third unit has the same configuration as the first unit, the fourth unit has the same configuration as the second unit, the fixing member can fix the coil of the third unit and the coil of the fourth unit, the phase of the third unit and the phase of the fourth unit are shifted by 90° in electrical angle with respect to the driving direction, the phases of the set of the first unit and the third unit are the same, and the phases of the set of the second unit and the fourth unit are the same, the first unit and the third unit are arranged to face each other, the second unit and the fourth unit are arranged to face each other, and the linear motor according to claim 1, characterized in that the arrangement intervals of the first unit and the third unit are substantially equidistant around the axis in the driving direction, and the arrangement intervals of the second unit and the fourth unit are substantially equidistant around the axis in the driving direction.

7. A lens barrel comprising the linear motor according to claims 1 to 6.

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