JP2007072271A - Lens driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens driving device which lessens the leakage of magnetic flux from a magnet for applying a magnetic field to a coil for driving, so that the driving efficiency of a lens holder is improved and also the adverse influence on other devices caused by the leakage of the magnetic flux is reduced. <P>SOLUTION: The yoke 16 of the magnet 15 is constituted of an upper yoke 16A and a lower yoke 16B equipped with: an annular horizontal piece surrounding a driving coil 13 and the magnet 15 from an upper surface side or a lower surface side; an internal barrel projecting between the lens holder 12 and the driving coil 13; and an external barrel the inner periphery side of which the magnet 15 is attached to, and provided with a notched part 16k in the internal barrel. The driving coil 13 attached and fixed on a coil supporting member 14 provided on the outer periphery side of the lens holder 12 holding the lens 11, and the magnet 15 applying radial magnetic field to the driving coil 13 are surrounded by the yokes 16A and 16B. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a drive device for an objective lens such as a camera, and more particularly to improvement of drive efficiency of a lens drive device using a voice coil motor.

In recent years, cameras mounted on mobile phones and the like have increased the number of pixels, and advanced functions such as zoom processing and macro processing have been advanced. Not only that, but those with movable focus have been introduced. As a driving system for the movable focus lens system, a piezoelectric element is used as a power source (for example, refer to Patent Document 1), a stepping motor is used as a power source (for example, refer to Patent Document 2), or A device using a voice coil motor as a power source has been proposed (see, for example, Patent Document 3).
FIG. 6A is a diagram showing a configuration example of a lens driving device using a voice coil motor. The lens driving device 50 includes a U-shaped cylindrical yoke 51 made of a magnetic material such as soft iron, and the above-described lens driving device 50. A ring-shaped magnet 52 attached to the outer wall of the yoke 51, a carrier (hereinafter referred to as a lens holder) 54 for holding the lens 53 at the center position, a drive coil 55 attached to the lens holder 54, and the yoke 51 A base 56 to be mounted, a frame 57 that supports the base 56, two springs 58A and 58B that support the lens holder 54 above and below, and two caps 59A and 58B that cover the top and bottom of the springs 58A and 58B. And.

Since the drive coil 55 is installed in a magnetic field that is applied by the yoke 51 and the magnet 52 and is distributed radially around the coil, when the drive coil 55 is energized, A Lorentz force toward the direction of the subject (upward) as shown by the arrow in the figure is generated, and the lens holder 54 can be moved to a position balanced with the restoring force of the springs 58A and 58B. Therefore, the position of the lens 53 can be controlled by controlling the amount of movement of the lens holder 54 by controlling the current value supplied to the drive coil 55.
JP 2002-189165 A JP 2004-258111 A JP 2004-280031 A

  However, in the lens driving device 50 as described above, since the yoke 51 is disposed only on the lens opening side (upper side in the figure) of the magnet 52, as shown in FIG. On the side, there is a problem that the magnetic resistance increases and the magnetic flux leaks outside the lens driving device 50. If the magnetic flux leakage to the outside is large, the magnetic efficiency of the magnetic field applied to the drive coil 55 is lowered, and not only the driving efficiency of the lens holder 54 is bad, but also the leaked magnetic flux may adversely affect other devices. there were.

  The present invention has been made in view of the conventional problems, and can reduce the leakage of magnetic flux from the magnet that applies a magnetic field to the driving coil, thereby improving the driving efficiency of the lens holder. An object of the present invention is to provide a lens driving device that can reduce adverse effects on other devices.

According to the first aspect of the present invention, there is provided a holder for holding a lens, an annular drive coil attached to the holder, a yoke provided on the fixed member side, and a magnet attached to the inner surface side of the yoke. And an upper spring member and a lower spring member that connect the holder and the fixing member respectively on the upper side that is the opening side of the lens and the lower side that is opposite to the opening side. In a lens driving device that controls the amount of movement of the lens by a current value energized to the coil and a restoring force of each spring member, an annular horizontal that surrounds the yoke and the driving coil and the permanent magnet from the upper surface side. An upper yoke having a U-shaped cross section including a piece and an inner cylinder protruding downward from the holder side of the horizontal piece, and a lower part having an annular horizontal piece protruding to the lower surface side of the permanent magnet yoke One in which was formed from.
According to a second aspect of the present invention, in the lens driving device according to the first aspect, a coil support member for fixing and supporting the inner peripheral side and the lower end of the drive coil is provided on the outer peripheral portion of the holder. The drive coil is mounted on the coil support member, and a notch is provided in the inner cylinder of the upper yoke, and the coil is arranged inside the inner cylinder of the upper yoke.
According to a third aspect of the present invention, in the lens driving device according to the second aspect, the horizontal piece of the lower yoke is projected inward from the inner peripheral side of the magnet.
According to a fourth aspect of the present invention, in the lens driving device according to the second aspect, the lower yoke, an annular horizontal piece surrounding the drive coil and the permanent magnet from the lower surface side, and the horizontal piece A yoke having a U-shaped cross section including an inner cylinder projecting upward from the holder side of the holder, and a notch is provided in the inner cylinder of the lower yoke so that the coil is connected to the upper and lower yokes. It is arranged inside the inner cylinder.
According to a fifth aspect of the present invention, in the lens driving device according to any one of the first to fourth aspects, a preload is applied to the holder at a lower portion of the fixing member toward an upper direction of the holder. It has been granted.

According to the present invention, the yoke provided on the fixed member side of the lens driving device, on which the magnet for applying a radial magnetic field to the annular driving coil attached to the holder for holding the lens is attached to the inner surface thereof, An upper yoke having a U-shaped cross section including an annular horizontal piece surrounding the drive coil and the permanent magnet from the upper surface side, and an inner cylinder protruding downward from the holder side of the horizontal piece, Since it is composed of a lower yoke having an annular horizontal piece projecting to the lower surface side of the permanent magnet, and the drive coil and the magnet are surrounded by the yoke from above and below, leakage of magnetic flux to the outside is reduced. Can do. Therefore, the magnetic efficiency can be increased, the driving efficiency of the lens holder can be improved, and adverse effects on other devices due to magnetic flux leakage can be reduced.
At this time, a coil support member that fixes and supports the inner peripheral side and the lower end of the drive coil is provided on the outer periphery of the holder, and the drive coil is mounted on the coil support member, and the upper yoke A notch is provided in the inner cylinder so that the coil is disposed inside the inner cylinder of the upper yoke, and the lower yoke is protruded inward from the inner peripheral side of the magnet. If the coil is arranged inside the inner cylinders of the upper and lower yokes with the same configuration as the upper yoke, the magnetic flux can be further prevented from leaking, so that the magnetic efficiency can be further increased.

Hereinafter, the best mode of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the configuration of a lens driving device 10 according to the best mode of the present invention. In FIG. 1, 11 is a lens, 12 is a holder (lens holder) for holding the lens 11, and 13 is the lens. An annular drive coil 14 disposed on the outer peripheral side of the holder 12 is a coil support member that supports the drive coil 13. In this example, the shaft of the lens holder 12 provided on the outer peripheral side of the lens holder 12. The inner peripheral side of the drive coil 13 is bonded and fixed to the first support member 14a extending in the direction, and the lower end of the first support member 14a (the end opposite to the opening side of the lens 11) The lower end portion of the drive coil 13 is bonded and fixed to the second support member 14b protruding outward in the radial direction.
A cylindrical magnet 15 is provided on the outer peripheral side of the drive coil 13 and applies a radial magnetic field to the drive coil 13. A cylindrical upper yoke 16 is a U-shaped cross section made of a magnetic material such as soft iron. 16A and a yoke having an L-shaped cylindrical lower yoke 16B, 17A and 17B are upper and lower fixing members for supporting the magnet 15 and the yokes 16A and 16B, and 18A is a lens of the lens holder 12. A first spring member 18B is connected to the upper side which is the opening side and the upper fixing member 16A, and 18B is a second spring member which connects the lower side of the lens holder 12 and the lower fixing member 16B.
The lower fixing member 17B is provided with an annular projecting portion 17m projecting toward the bottom of the lens holder 12 on the inner peripheral side thereof, and the projecting portion 17m causes the second spring member 18B to move upward. To push up. As a result, since a preload is applied to the lens holder 12 in the upward direction, even when a shake or impact is input to the lens driving device 10, the shake or impact generated in the lens holder 12 is reduced. Can do.

  FIG. 2 is a diagram showing details of the upper yoke 16A and the lower yoke 16B. Each of the yokes 16A and 16B is an annular horizontal piece 16a surrounding the drive coil 13 and the magnet 15 from the upper surface side or the lower surface side. And an inner cylinder 16b projecting between the lens holder 12 and the drive coil 13, and an outer cylinder 16c having the magnet 15 attached to the inner periphery thereof. A notch 16k is provided. The notch portion 16k is provided to dispose the drive coil 13 that is bonded and fixed to the coil support member 14 between the inner cylinder 16b and the magnet 15. Even in the structure in which the drive coil 13 is bonded and fixed, the drive coil 13 and the magnet 15 can be surrounded by the yokes 16A and 16B. Therefore, as shown in FIG. 3, the magnetic flux from the inner peripheral side of the magnet 15 can penetrate the drive coil 13 almost vertically, and the magnetic flux that penetrates the drive coil 13 is Since the inner cylinder 16b, the horizontal piece 16a and the outer cylinder 16c of the upper yoke 16A and the inner cylinder 16b, the horizontal piece 16a and the outer cylinder 16c of the lower yoke 16B are guided to the outer peripheral side of the magnet 15, the magnetic flux is external. It becomes difficult to leak. Accordingly, it is possible to reduce adverse effects on other devices due to magnetic flux leakage, to greatly increase the magnetic efficiency, and to improve the driving efficiency of the lens holder.

Thus, according to this best mode, the yoke 16 of the magnet 15, the annular horizontal piece 16 a surrounding the drive coil 13 and the magnet 15 from the upper surface side or the lower surface side, the lens holder 12, and the above An upper cylinder 16A provided with an inner cylinder 16b projecting between the drive coil 13 and an outer cylinder 16c having the magnet 15 attached to the inner circumference thereof, and a notch 16k provided in the inner cylinder 16b. The drive coil 13 composed of a lower yoke 16B and bonded and fixed to a coil support member 14 provided on the outer peripheral side of the lens holder 12 holding the lens 11, and a magnet 15 for applying a radial magnetic field to the drive coil 13. Is surrounded by the yokes 16A and 16B, magnetic flux leakage from the magnet 15 can be greatly reduced. Accordingly, it is possible to reduce adverse effects on other devices due to magnetic flux leakage, and it is possible to greatly increase the magnetic efficiency, thereby improving the driving efficiency of the lens holder.
Further, an annular protrusion 17m is provided on the lower fixing member 17B, and the second spring member 18B supporting the lens holder 12 from the lower side is pushed upward, and the lens holder 12 is moved upward. Since the preload is applied to the lens holder 12, it is possible to reduce shaking and impact generated in the lens holder 12.

In the best mode, the upper yoke 16A and the lower yoke 16B have substantially the same configuration. However, instead of the lower yoke 16B, the cross-sectional shape as shown in FIG. If the lower yoke 16C is used and the front end side of the horizontal piece 16a of the lower yoke 16C protrudes from the inner peripheral side of the magnet 15, as shown in FIG. Since the magnetic flux can be sufficiently guided to the outer peripheral side of the magnet 15, the magnetic efficiency can be greatly increased, and the driving efficiency of the lens holder can be improved.
Further, as shown in FIG. 5A, even if the tip of the horizontal piece 16a is the lower yoke 16D extending to the lower surface of the magnet 15, the upper and lower sides of the magnet 15 are connected to the upper yoke 16A and the lower yoke 16D. Therefore, the leakage of magnetic flux can be reduced as compared with the conventional example shown in FIG. As shown in FIG. 5 (b), even if a yoke 16D having an L-shaped cross section is added to the lower portion of the conventional yoke 51, the leakage of magnetic flux can be reduced and the magnetic efficiency can be reduced. Can be increased. In this case, the yoke 51 does not need to be provided with the notch portion 16k like the upper yoke 16A, but the inner peripheral side of the drive coil 13 cannot be firmly bonded and fixed as in this example. The drive coil 13 is preferably configured to be bonded and fixed to the coil support member 14.

  As described above, according to the present invention, leakage of magnetic flux from a magnet that applies a magnetic field to the driving coil can be reduced, and the driving efficiency of the lens holder can be improved. It can be improved, and adverse effects on other devices due to magnetic flux leakage can be reduced.

It is a schematic diagram which shows the structure of the lens drive device which concerns on the best form of this invention. It is a figure which shows the structure of the yoke which concerns on this best form. It is a schematic diagram which shows the flow of the magnetic flux at the time of using the yoke by this invention. It is a schematic diagram which shows the other structure of the lens drive device by this invention. It is a schematic diagram which shows the other structure of the lens drive device by this invention. It is a schematic diagram which shows the structure of the conventional lens drive device, and the flow of magnetic flux.

Explanation of symbols

10 lens drive device, 11 lens, 12 lens holder, 13 drive coil,
14 coil support member, 14a first support member, 14b second support member,
15 magnet, 16 yoke, 16A upper yoke, 16B lower yoke,
16a horizontal piece, 16b inner cylinder, 16c outer cylinder, 16k notch,
17A Upper fixing member, 17B Lower fixing member, 17m protrusion,
18A 1st spring member, 18B 2nd spring member.

Claims (5)

  A holder for holding a lens, an annular drive coil mounted on the holder, a yoke provided on the fixing member side, a magnet attached to the inner surface side of the yoke, the holder and the fixing member An upper spring member and a lower spring member that are connected to each other on the upper side that is the opening side of the lens and the lower side that is opposite to the opening side, respectively, and a current value for energizing the drive coil and each spring member In the lens driving device for controlling the moving amount of the lens by the restoring force of the lens, the yoke, the annular horizontal piece surrounding the driving coil and the permanent magnet from the upper surface side, and the lower part from the holder side of the horizontal piece A cross-sectional shape including an inner cylinder projecting in the direction is formed by a U-shaped upper yoke and a lower yoke having an annular horizontal piece projecting on the lower surface side of the permanent magnet. Lens driving device.   A coil support member for fixing and supporting the inner peripheral side and the lower end of the drive coil is provided on the outer peripheral portion of the holder, and the drive coil is mounted on the coil support member and the inner portion of the upper yoke is mounted. 2. The lens driving device according to claim 1, wherein a notch portion is provided in the cylinder, and the coil is disposed inside the inner cylinder of the upper yoke.   3. The lens driving device according to claim 2, wherein the horizontal piece of the lower yoke protrudes inward from the inner peripheral side of the magnet.   A cross-sectional shape having an U-shaped cross section including an annular horizontal piece surrounding the lower yoke, the drive coil and the permanent magnet from the lower surface side, and an inner cylinder protruding upward from the holder side of the horizontal piece 3. The lens driving device according to claim 2, wherein a notch portion is provided in the inner cylinder of the lower yoke, and the coil is disposed inside the inner cylinders of the upper and lower yokes. . The lens driving device according to any one of claims 1 to 4, wherein a preload is applied to the holder at a lower portion of the fixing member toward an upper portion of the holder.

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