JP4612851B2 - Lens drive device - Google Patents

Description

  The present invention relates to a lens driving device that moves a lens holding member holding a photographing lens for a camera or a video camera in the optical axis direction for focusing, zooming, or the like.

  Conventionally, as a lens driving device for a still camera or a video camera, for example, a small stepping motor as disclosed in Patent Document 1 is arranged in parallel with a lens, and the lens is driven by a lead screw or the like. There is.

  FIG. 9 shows the configuration. In FIG. 9, 201 is a lens, 202 is a lens holding frame for fixing the lens 201, 203 is a sleeve part integrally formed with the lens holding frame 202, 204 and 205 are guide shafts extending along the optical axis of the lens 201, 206 is a stepping motor having a lead screw.

  In the above configuration, when the sleeve portion 203 is fitted to the guide shaft 204, the lens holding frame 202 can be moved in the optical axis direction. When the lead screw is rotated by the rotation of the stepping motor 206, the lens holding frame 202 is moved. Can move in the optical axis direction.

  However, the lead screw provided in the stepping motor 206 used in the lens driving device disclosed in Patent Document 1 needs to be longer than the moving distance of the lens 201. For this reason, the stepping motor 206 is disposed behind or in front of the lens 201. Normally, components such as a shutter, an aperture device, and a CCD are arranged before and after the lens. However, in the above configuration, the stepping motor 206 and these components easily interfere with each other, and there is a problem that the degree of freedom in design is reduced. .

  Further, the stepping motor used in the above lens driving device or the like has a solid cylindrical shape having no opening (meaning that there is no opening penetrating in the center and there is a component in the center). Therefore, in order to avoid interference with the optical path, it is necessary to dispose the stepping motor outside the lens in parallel with the optical axis in the lens barrel of the camera. This is shown in FIG. When the diameter of the stepping motor M is D1, the diameter of the lens 301 is D2, and the diameter of the ground plane 300 is D3, the diameter D3 of the ground plane 300 is “2 × D1 + D2” at the minimum, and cannot be reduced.

In view of this point, Patent Document 2 discloses a lens driving device configured as shown in FIG. This lens driving device is formed in a hollow cylindrical shape, and at least an outer peripheral surface is divided in the circumferential direction and magnets 401 alternately magnetized with different poles, a first bobbin 402 around which a coil is wound, a coil Is excited by a coil wound around the first bobbin 403 and the first bobbin 402, and the first outer magnetic pole portion 404 facing the outer peripheral surface on one end side of the magnet 401 and the inner periphery of the magnet 401 A first inner magnetic pole portion 405 having a substantially hollow cylindrical shape facing the surface and a second outer magnetic pole portion facing the outer peripheral surface on the other end side of the magnet 401 by being excited by a coil wound around the second bobbin 403. 406, a stepping motor provided with a second inner magnetic pole portion 407 having a substantially hollow cylindrical shape facing the inner peripheral surface of the magnet 401, and a hollow portion of the first inner magnetic pole portion 405 or Includes a lens 408 having an optical axis at the inner diameter side opening of the second inner magnetic pole portion 407, and a lens moving member 409 that rotates in conjunction with the magnet 401 and moves the lens 408 in the optical axis direction by the rotation. The diameter of the lens driving device is “the diameter of the lens 408 + 2 × the thickness in the radial direction of the stepping motor”, which is a small-diameter and compact device that can improve the above-described problems.
Japanese Utility Model Publication No. 2-71155 JP 2002-051524 A

  However, the lens driving device disclosed in Patent Document 2 has the following problems. In other words, since the magnet 401 constituting the rotor is covered with the magnetic pole portions 405 to 407, it is necessary to move the lens 408 by projecting a pin from the magnet 401 in order to extract the output of the rotor to the outside. . For this reason, the configuration of the apparatus is complicated and it is difficult to reduce the diameter.

  In order to avoid this, if the stepping motor composed of the magnet 401 or the like and the lens moving member 409 are arranged in the optical axis direction, the lens driving device can be reduced in diameter, but the length in the optical axis direction is at least “lens Therefore, it is difficult to shorten the lens driving device.

(Object of invention)
An object of the present invention is to provide a lens driving device that can achieve a reduction in diameter and a reduction in axis.

  In order to achieve the above object, an invention according to claim 1 includes a stator including a coil and a magnet, and a rotor including a magnetic pole portion excited by the coil and rotatably supported by the stator. And a lens driving device having a hollow cylindrical motor substantially coaxial with the optical axis, a lens holding member that holds a lens, and a guide member that holds the lens holding member so as to be movable in the optical axis direction. A first screw portion provided in the circumferential direction on the outer peripheral portion of the rotor, and extending in the optical axis direction with a predetermined width, integrally formed with the lens holding member, and the diameter of the first screw portion and the motor A second screw portion that meshes in the direction, and the lens holding member is moved in the optical axis direction by the action of the meshed first screw portion and the second screw portion as the motor rotates. In In which a lens driving device for moving.

  Similarly, in order to achieve the above object, an invention according to claim 2 includes a stator including a coil and a magnet, and a rotor including a magnetic pole portion excited by the coil and rotatably supported by the stator. A hollow cylindrical motor substantially coaxial with the optical axis, a lens holding member that holds the lens and supports the stator, and a guide member that holds the lens holding member movably in the optical axis direction. A first screw portion provided in a circumferential direction on an outer peripheral portion of the rotor; and a first screw portion that extends in the optical axis direction with a predetermined width and is integrally formed with a base plate. And a second threaded portion that meshes in the radial direction of the motor, and the lens is held by the action of the meshed first threaded portion and the second threaded portion as the motor rotates. In which a lens driving device for moving the timber in the optical axis direction.

  According to the present invention, it is possible to provide a lens driving device capable of achieving a small diameter and a short axis.

  The best mode for carrying out the present invention is as shown in Example 1 and Example 2 described below.

  FIG. 1 is a cross-sectional view showing the overall configuration of a lens driving apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a ground plane and 2 is a lens. Reference numerals 3 and 4 are guide shafts fixed to the base plate 1 and arranged in parallel with the lens optical axis. Reference numeral 5 denotes a lens holding frame for holding the lens 2, and the detailed shape will be described later. A motor support plate 6 is fixed to the main plate 1. Reference numeral 7 denotes a cylindrical stepping motor, which will be described in detail later. In FIG. 1, a part of the ground plane 1 and the lens holding frame 5 are shown in cross section.

  FIG. 2 is an exploded perspective view showing components of the lens driving device of FIG. 1, and the base plate 1 and the lens 2 are not shown for the sake of simplicity. FIG. 3 is a cross-sectional view showing the structure of the lens driving device after assembly.

  As shown in FIGS. 2 and 3, the lens holding frame 5 has a substantially disk shape, and the lens 2 is fixed at the center. Further, a sleeve portion 51 extending in the optical axis direction is integrally provided, and a U-shaped guide portion 5 a is provided at a symmetrical position with respect to the sleeve 51 and the center point of the lens 2. The lens holding frame 5 is fitted to the guide shaft 4 in a hole 51 b provided in the sleeve portion 51, and the U-shaped guide portion 5 a is fitted to the guide shaft 3. As a result, the lens holding frame 5 can move in the optical axis direction along the guide shafts 3 and 4 while being restricted in rotation.

  The sleeve portion 51 has a screw portion 51a on the surface on the optical axis side. The screw portion 51 a has a spiral shape centered on the virtual rotation axis of the stepping motor 7, has a length equal to or longer than the movement amount of the lens 2 in the optical axis direction, and is a component of the later-described rotor that is a component of the stepping motor 7. It is formed so as to be able to mesh with the screw portion 23a of the rotating member 23 forming a part. The longer the length of the sleeve portion 51 in the optical axis direction, the less the lens 2 is inclined with respect to the optical axis, which is advantageous in terms of optical performance. Therefore, by providing the screw portion 51a in the sleeve portion 51, the only member that is long in the optical axis direction is the sleeve portion 51, which is advantageous in constructing a compact lens driving device. Further, in this configuration, since the screw portion 51a meshes with a screw portion 23a described later at a part of the circumference in the circumferential direction, the frictional force generated between the screws can be reduced and efficient lens driving can be achieved. A device can be configured.

  The motor support plate 6 has a disk shape, has an opening for allowing a light beam to pass through the center, and is fixed to the ground plate 1. Moreover, it has the notch parts 6a and 6b for avoiding interference with the sleeve part 51 on either side. When the lens driving device of the first embodiment is used for a camera equipped with a shutter, the motor support plate 6 can also serve as a shutter base plate.

  The stepping motor 7 includes the following hollow cylindrical stator and hollow cylindrical rotor.

  The hollow cylindrical stator includes a fixed yoke 11, a first coil 12, a second coil 13, and a magnet 14. The fixed yoke 11 is made of a soft magnetic material, forms a magnetic pole part, has a hollow cylindrical shape with the lens optical axis as a central axis, and is provided with a disk-shaped bearing part 11a at one end. Similarly, the magnet 14 has a hollow cylindrical shape, and the magnet 14 is divided into n pieces (10 pieces in the first embodiment) in the circumferential direction and the S pole and the N pole are alternately magnetized. It has a magnetic part, is sandwiched between the first coil 12 and the second coil 13 from the axial direction, and is arranged concentrically with the fixed yoke 11 on the outer peripheral part of the fixed yoke 11.

  The hollow cylindrical rotor includes a first rotating yoke 21, a second rotating yoke 22, and a rotating member 23.

  The first rotating yoke 21 is made of a soft magnetic material and includes a substantially hollow cylindrical outer cylinder 21a and a disk-shaped bearing portion 21b. As shown in FIG. 4, the outer cylinder 21 a has first magnetic pole portions 21-1, 21-2,..., 21-5 (21 -n / 2) at its tip portion. These first magnetic pole portions 21-1, 21-2,..., 21-5 are partly cut out of a cylindrical shape and extend in the direction of the central axis in parallel to the magnetized surface of the magnet 14. Further, it is formed in a so-called comb-teeth shape. The number of comb teeth is 1 to n / 2, and 5 in this embodiment. Therefore, the first magnetic pole portions 21-1, 21-2,..., 21-5 are formed with a predetermined tooth width at an interval of 720 / n ° in the circumferential direction.

  The second rotating yoke 22 is made of a soft magnetic material, and is constituted by a substantially hollow cylindrical outer cylinder. The outer cylinder of the second rotating yoke 22 has second magnetic pole portions 22-1, 22-2,..., 22-5 (22-n / 2) at the tip thereof. These second magnetic pole portions 22-1, 22-2,..., 22-5 are cut out of a part of the cylindrical shape and extend in the direction of the central axis in parallel to the magnetized surface of the magnet 14. Further, it is formed in a so-called comb-teeth shape. The number of comb teeth is 1 to n / 2, and 5 in this embodiment. Therefore, the second magnetic pole portions 22-1, 22-2,..., 22-5 are formed with a predetermined tooth width at an interval of 720 / n ° in the circumferential direction.

  The rotating member 23 is made of a nonmagnetic material and has a hollow cylindrical shape with the optical axis as the central axis. A first rotary yoke positioning portion 23b and a second rotary yoke positioning portion 23c are provided on the inner peripheral portion. The first rotary yoke positioning portion 23b is formed of a groove having substantially the same width as that of the first magnetic pole portion 21-1 and the like of the first rotary yoke 21, and allows the first rotary yoke 21 to be fitted. The second rotary yoke positioning portion 23 c is formed of a groove portion having substantially the same width as the second magnetic pole portion 22-1 and the like of the second rotary yoke 22, and the second rotary yoke 22 is connected to the first rotary yoke 21. The fitting is possible while maintaining a predetermined positional relationship. Further, the rotating member 23 has a screw portion 23 a that meshes with the screw portion 51 a of the sleeve portion 51 on the outer peripheral portion. The number of turns of the screw portion 23a is preferably less than or equal to 1 rotation and less than or equal to 3 rotations with less friction. The screw portion 23a meshes with the screw portion 51a, and the lens holding frame 5 can be moved in the optical axis direction as the stepping motor 7 rotates. At this time, the rotor is rotatably supported with respect to the stator while the optical axis is the central axis.

  Next, the operation of the lens driving device configured as described above will be described. 4, 5, 6, and 7 are diagrams illustrating the polarities and rotation positions of the magnetic pole portions of the first rotating yoke 21 and the second rotating yoke 22 when the stepping motor 7 rotates. FIG. 4A is a diagram viewed from the AA line direction of FIG. 3, and FIG. 5B is a diagram viewed from the BB direction of FIG. For the sake of simplicity, only the motor portion is shown.

  In the state of FIG. 4, the first coil 12 is positively energized to excite the first rotating yoke 21 to the N pole, and the second coil 13 is reversely energized to connect the second rotating yoke 22 to S. It is a figure when exciting to the pole. When such energization is performed, the state shown in FIG. 4 is a stable rotational position of the rotor due to the magnetic attractive force between the excited first rotating yoke 21 and second rotating yoke 22 and the magnet 14. It becomes.

  Similarly, FIG. 5 shows a stable position when the first coil 12 is reversely energized and the second coil 13 is reversely energized. Similarly, FIG. 6 shows a stable position when the first coil 12 is reversely energized and the second coil 13 is positively energized. Similarly, FIG. 7 shows a stable position when the first coil 12 is positively energized and the second coil 13 is positively energized.

  In this way, the stable position of the rotor is sequentially switched by 180 / n degrees (18 degrees in this embodiment) by switching the direction of energization to the first coil 12 and the second coil 13 in the forward and reverse directions. Can continue. Accordingly, the rotor can be rotated.

  When the rotor is rotated once, the lens holding frame 5 is moved in the optical axis direction by the action of the screw portion 23a provided on the rotating member 23 and the screw portion 51a provided on the sleeve portion 51 of the lens holding frame 5. It can be moved by one pitch, and the position of the lens 2 in the optical axis direction can be freely determined.

  By using the lens driving device having the configuration of the first embodiment, the following effects can be obtained.

  The combined thickness of the stepping motor 7 and the screw parts 23a and 51a can be reduced. Since the rotor is exposed to the outside as described above, the screw portion 23a can be provided directly on the rotating member 23. Compared to the case where the screw portion is rotated by using the conventional hollow cylindrical stepping motor disclosed in Patent Document 2, this eliminates the need for the output pin, so that a simpler configuration can be achieved. Therefore, the diameter can be reduced and the cost can be reduced.

  Further, the diameter of the lens driving device is at least “the diameter of the lens 2 + the thickness in the radial direction of the stepping motor 7 × 2 + the thickness of the sleeve portion 51 × 2”. Here, the thickness of the stepping motor 7 used in the first embodiment means “radius of the outer peripheral portion of the first and second rotating yokes 21 and 22−radius of the inner peripheral portion of the fixed yoke 11”. It is. The size is about half of the diameter of the solid cylindrical motor used in Patent Document 1 (D1 in FIG. 10). This is because the diameter of the solid cylindrical stepping motor is equal to or larger than the thickness of the magnet used therein × 2 whereas the thickness of the stepping motor 7 used in the first embodiment is “ This is because the magnet 14 can be configured to have a thickness of 1 × 1 or more. Therefore, the diameter of the lens driving device can be reduced by the thickness of the stepping motor as compared with the conventional lens driving device disclosed in Patent Document 1 or the like.

  Further, the thickness of the rotor is equal to or less than “the thickness of the rotating member 23 + the thickness of the first and second rotating yokes 21 and 22”, and can be made thinner than the above-described conventional example.

  In addition, since the magnet 14 is directly attached to the fixed yoke 11, the diameter of the stepping motor can be reduced by an amount corresponding to the gap between the magnet 14 and the fixed yoke 11 as compared with the conventional example.

  In the conventional example using the lead screw disclosed in Patent Document 1 and the conventional example in which the stepping motor and the screw portion disclosed in Patent Document 2 are arranged in the axial direction, the length of the lens driving device in the optical axis direction is At a minimum, only “lens movement amount + motor length + screw engagement” is required. On the other hand, in the lens driving device according to the first embodiment, the stepping motor 7 and the engagement portions of the screw portions 23a and 51a are arranged in the radial direction. Accordingly, the length of the lens driving device in the optical axis direction can be set to “lens movement amount + length of the stepping motor 7”, and can be shortened by the amount of engagement between the screw portions 23a and 51a. That is, the lens driving device can be shortened.

  Further, the hollow cylindrical stepping motor 7 is arranged on the outer periphery of the lens 2, and only the guide shafts 3 and 4 and the sleeve portion 51 of the lens holding frame 5 are arranged behind the motor support plate 6. This is because the motor is not arranged behind the motor support plate as in the case where a lead screw as disclosed in Patent Document 1 is used, so components such as a shutter mechanism, a diaphragm mechanism, and a CCD that come behind the motor support plate 6 are used. Does not cause any interference. For this reason, it is possible to increase the degree of freedom in arranging other components. It is easy to use the guide shaft as a guide rail.

  Furthermore, by providing the screw part 51a in the sleeve part 51, the screw part 23a and the screw part 51a mesh with each other at a part of the circumference. As a result, the frictional force generated between the screw portions can be reduced, and the efficiency of the lens driving device can be increased.

  FIG. 8 is a cross-sectional view showing the main configuration of the lens driving apparatus according to the second embodiment of the present invention, and the same components as those in the first embodiment are denoted by the same reference numerals.

  In FIG. 8, 101 is a ground plane, and 102 is a lens. Reference numerals 103 and 104 denote guide shafts fixed to the base plate 101 and arranged in parallel with the lens optical axis. A lens holding frame 105 holds the lens 102. Reference numeral 106 denotes a fixed yoke constituting the magnetic pole portion, which has the same shape as the fixed yoke 11 used in the first embodiment, but is fixed to the lens holding frame 105 instead of the base plate 101. Reference numeral 107 denotes a rotating plate.

  The base plate 101 is provided with a screw portion 101 a and can be engaged with the screw portion 107 a provided on the outer peripheral portion of the rotating plate 107. As in the first embodiment, the screw portion 101a is provided on a part of the cylindrical side surface of the base plate 101, thereby reducing the meshing portion with the screw portion 107a and reducing the frictional force generated between the screws.

  The stepping motor according to the second embodiment includes a hollow cylindrical stator including a fixed yoke 106, a first coil 108, a second coil 109, and a magnet 110, a first rotating yoke 111, and a second rotating yoke. 112 and a rotor constituted by the rotating member 107.

  With the above-described configuration, the lens 102 can be driven in the optical axis direction as in the first embodiment. That is, by rotating the rotor, it is possible to change the relative position between the lens holding member 105 that is integral with the stator and the base plate 101 (screw portion 101a). The second embodiment is a so-called motor self-propelled drive system.

  By using the lens driving device having the configuration of the second embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.

  When the moving distance of the lens 102 becomes long, in the first embodiment, the screw part 51a provided on the sleeve part 51 of the lens holding frame 5 must be lengthened accordingly, and the moving distance depends on the lens moving distance. The lens holding frame 5 had to be enlarged. On the other hand, in the second embodiment, the size of the lens holding frame 105 can be made constant regardless of the lens moving distance. For this reason, this configuration is advantageous when the movement distance must be increased.

  In the second embodiment, since the stator is fixed to the lens holding frame 105, a motor support plate is not necessary, and the number of parts can be reduced.

It is a block diagram which shows the lens drive device concerning Example 1 of this invention. It is a disassembled perspective view which shows the component (a part of component is omitted) of the lens drive device of FIG. It is sectional drawing of the lens drive device of FIG. It is a figure which shows the polarity and rotation position of the 1st rotation yoke 21 and the 2nd rotation yoke 22 at the time of rotation of a stepping motor in Example 1 of this invention. It is a figure which shows the polarity and rotation position of the 1st rotation yoke 21 and the 2nd rotation yoke 22 at the time of rotation of a stepping motor in Example 1 of this invention. It is a figure which shows the polarity and rotation position of the 1st rotation yoke 21 and the 2nd rotation yoke 22 at the time of rotation of a stepping motor in Example 1 of this invention. It is a figure which shows the polarity and rotation position of the 1st rotation yoke 21 and the 2nd rotation yoke 22 at the time of rotation of a stepping motor in Example 1 of this invention. It is sectional drawing of the lens drive device concerning Example 2 of this invention. It is a disassembled perspective view which shows the component of the conventional lens drive device. It is a figure which shows the diameter of the lens drive device in the radial direction, a lens diameter, and the direct relationship of a motor conventionally. It is sectional drawing which shows the structure of the lens drive device using the stepping motor of the conventional hollow cylinder shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground plate 2 Lens 3, 4 Guide shaft 5 Lens holding frame 7 Stepping motor 23 Rotating plate 23a Screw part 51 Sleeve part 51a Screw part 101 Ground plate 101a Screw part 102 Lens 103,104 Guide shaft 105 Lens holding frame 107 Rotating plate 107a Screw part

Claims (2)

A stator including a coil and a magnet, a magnetic pole portion excited by the coil, and a rotor rotatably supported by the stator; a hollow cylindrical motor substantially coaxial with the optical axis;
A lens holding member for holding the lens;
A guide member that holds the lens holding member movably in the optical axis direction;
In a lens driving device having
A first screw portion provided in a circumferential direction on the outer peripheral portion of the rotor;
A second screw portion that extends in the optical axis direction with a predetermined width, is integrally formed with the lens holding member, and meshes with the first screw portion in the radial direction of the motor;
A lens driving mechanism that moves the lens holding member in the optical axis direction by the action of the meshed first and second screw portions as the motor rotates. apparatus. A stator having a coil and a magnet, a magnetic pole portion excited by the coil, and a rotor rotatably supported by the stator; a hollow cylindrical motor substantially coaxial with the optical axis;
A lens holding member that holds the lens and supports the stator;
A guide member that holds the lens holding member movably in the optical axis direction;
In a lens driving device having
A first screw portion provided in a circumferential direction on the outer peripheral portion of the rotor;
A second threaded portion that extends in the optical axis direction with a predetermined width, is integrally formed with the base plate, and meshes with the first threaded portion in the radial direction of the motor;
And the lens holding member is moved in the optical axis direction by the action of the meshed first screw portion and the second screw portion as the motor rotates. apparatus.

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