Lens drive device

1. A lens drive device whose shape is substantially rectangular when viewed in an optical axis direction of a lens, the lens drive device comprising:

a movable body which holds the lens and which is movable in the optical axis direction; and

a drive mechanism for driving the movable body in the optical axis direction;

wherein the drive mechanism further comprises:

a drive magnet part which is formed in a substantially triangular prism shape and which is disposed at least one of four corners of the lens drive device;

a drive coil which is wound around in a substantially triangular tube shape so that its inner peripheral face is oppositely disposed to an outer peripheral face of the drive magnet part through a gap space; and

a magnetic member which is disposed on an object to be photographed or imaged side with respect to the drive coil; and

wherein the drive magnet part is magnetized so that magnetic flux passing through the drive coil is generated at an opposite position to the drive coil; and

wherein the magnetic member is attracted toward an intermediate position of the drive magnet part in the optical axis direction.

2. The lens drive device according to claim 1 , further comprising a fixed body for movably holding the movable body,

wherein the drive coil and the magnetic member are attached to the movable body and the drive magnet part is attached to the fixed body.

3. The lens drive device according to claim 2 , wherein the magnetic member is disposed on an end face on the object to be photographed or imaged side of the drive coil.

4. The lens drive device according to claim 3 , wherein

the drive magnet part includes two drive magnet pieces which are formed in a substantially triangular prism shape and which are disposed so as to superpose on each other in the optical axis direction, and

opposite faces in the optical axis direction of the two drive magnet pieces are magnetized in same magnetic pole as each other, and

the magnetic member is attracted toward a portion between the two drive magnet pieces in the optical axis direction.

5. The lens drive device according to claim 4 , wherein

the two drive magnet pieces are a first magnet piece which is disposed on the object to be photographed or imaged side and a second magnet piece which is disposed on an opposite-to-object side,

a length in the optical axis direction of the first magnet piece is longer than a length of the second magnet piece in the optical axis direction, and

the magnetic member is disposed on the object to be photographed or imaged side with respect to an end face on the opposite-to-object side of the first magnet piece in the optical axis direction.

6. The lens drive device according to claim 4 , wherein

the drive magnet part is disposed at each of four corners of the lens drive device, and

the magnetic member is formed in a substantially ring shape and is disposed on an inner side in a radial direction of the lens drive device with respect to the drive magnet part.

7. The lens drive device according to claim 6 , further comprising an abutting member for abutting with the movable body which is urged in the optical axis direction by an attraction force generated between the drive magnet part and the magnetic member,

wherein the drive magnet part and the drive coil are disposed so that, when the movable body is located at a reference position where the movable body is abutted with the abutting member, a magnetic center position of the drive magnet part in the optical axis direction is displaced from a center position of the drive coil in the optical axis direction, and so that, when the movable body is located at a predetermined position in a moving range of the movable body, the magnetic center position of the drive magnet part in the optical axis direction and the center position of the drive coil in the optical axis direction are coincided with each other.

8. The lens drive device according to claim 4 , wherein a width of the drive coil in the optical axis direction is not less than a distance between the opposite faces of the two drive magnet pieces which are faced each other in the optical axis direction.

9. The lens drive device according to claim 1 , wherein

the drive magnet part includes two drive magnet pieces which are formed in a substantially triangular prism shape and which are disposed so as to superpose on each other in the optical axis direction, and

opposite faces in the optical axis direction of the two drive magnet pieces are magnetized in a same magnetic pole as each other, and

the magnetic member is attracted toward a portion between the two drive magnet pieces in the optical axis direction.

10. The lens drive device according to claim 9 , wherein

the two drive magnet pieces are a first magnet piece which is disposed on the object to be photographed or imaged side and a second magnet piece which is disposed on an opposite-to-object side,

a length in the optical axis direction of the first magnet piece is longer than a length of the second magnet piece in the optical axis direction, and

the magnetic member is disposed on the object to be photographed or imaged side with respect to an end face on the opposite-to-object side of the first magnet piece in the optical axis direction.

11. The lens drive device according to claim 9 , wherein

the drive magnet part is disposed at each of four corners of the lens drive device, and

the magnetic member is formed in a substantially ring shape and is disposed on an inner side in a radial direction of the lens drive device with respect to the drive magnet part.

12. The lens drive device according to claim 11 , further comprising an abutting member for abutting with the movable body which is urged in the optical axis direction by an attraction force generated between the drive magnet part and the magnetic member,

wherein the drive magnet part and the drive coil are disposed so that, when the movable body is located at a reference position where the movable body is abutted with the abutting member, a magnetic center position of the drive magnet part in the optical axis direction is displaced from a center position of the drive coil in the optical axis direction, and so that, when the movable body is located at a predetermined position in a moving range of the movable body, the magnetic center position of the drive magnet part in the optical axis direction and the center position of the drive coil in the optical axis direction are coincided with each other.

13. The lens drive device according to claim 11 , wherein the magnetic member is disposed on an end face on the object to be photographed or imaged side of the drive coil.

14. The lens drive device according to claim 1 , wherein

the drive magnet part includes two drive magnet pieces which are formed in a substantially triangular prism shape and which are disposed so as to superpose on each other in the optical axis direction, and

opposite faces in the optical axis direction of the two drive magnet pieces are magnetized in a same magnetic pole as each other, and

the drive magnet part is disposed at each of four corners of the lens drive device.

15. The lens drive device according to claim 14 , wherein

the two drive magnet pieces are a first magnet piece which is disposed on the object to be photographed or imaged side and a second magnet piece which is disposed on an opposite-to-object side, and

the magnetic member is disposed on the object to be photographed or imaged side with respect to an end face on the opposite-to-object side of the first magnet piece in the optical axis direction.

16. The lens drive device according to claim 15 , wherein the magnetic member is disposed on an end face on the object to be photographed or imaged side of the drive coil.

17. The lens drive device according to claim 16 ,

wherein the movable body comprises:

a lens holder which is provided with a small diameter part on which a small diameter lens is mounted and a large diameter part on which a large diameter lens is mounted; and

a sleeve which holds the lens holder on its inner peripheral side;

wherein the sleeve is formed with a placing face on which the drive coil is placed at a boundary portion between the small diameter part and the large diameter part of the lens holder, and a placing face for disposing the magnetic member on the end face on the object to be photographed or imaged side of the drive coil.

18. The lens drive device according to claim 14 , wherein a width of the drive coil in the optical axis direction is not less than a distance between the opposite faces of the two drive magnet pieces which are faced each other in the optical axis direction.

19. The lens drive device according to claim 1 , further comprising an abutting member for abutting with the movable body which is urged in the optical axis direction by an attraction force generated between the drive magnet part and the magnetic member,

wherein the drive magnet part and the drive coil are disposed so that, when the movable body is located at a reference position where the movable body is abutted with the abutting member, a magnetic center position of the drive magnet part in the optical axis direction is displaced from a center position of the drive coil in the optical axis direction, and so that, when the movable body is located at a predetermined position in a moving range of the movable body, the magnetic center position of the drive magnet part in the optical axis direction and the center position of the drive coil in the optical axis direction are coincided with each other.

20. The lens drive device according to claim 19 , wherein

when the movable body is located at the reference position, the center position of the drive coil in the optical axis direction is located on the opposite-to-object side with respect to the magnetic center position of the drive magnet part in the optical axis direction, and

when the movable body is located at a position nearest to the object to be photographed or imaged side, the center position of the drive coil is located on the object to be photographed or imaged side with respect to the magnetic center position of the drive magnet part.

21. The lens drive device according to claim 20 , wherein

a magnetic pole different from magnetic poles of both ends in the optical axis direction of the drive magnet part is formed at an intermediate position in the optical axis direction of the drive magnet part, and

the magnetic member is attracted toward the magnetic pole formed at the intermediate position.

22. The lens drive device according to claim 21 , wherein

the drive magnet part is provided with a first magnet piece which is disposed on the object to be photographed or imaged side, a second magnet piece which is disposed on an opposite-to-object side, and a magnetic plate which is sandwiched between the first magnet piece and the second magnet piece so that the first magnet piece, the magnetic plate and the second magnet piece are superposed on each other, and

opposite faces in the optical axis direction of the first drive magnet piece and the second magnet piece are magnetized in a same magnetic pole as each other, and

when the movable body is located at the reference position, the magnetic member is disposed in the optical axis direction on the object to be photographed or imaged side with respect to an end face on the opposite-to-object side of the first magnet piece and the magnetic member is attracted toward the magnetic plate.