Light quantity adjusting device

• US 5,489,959 A
• Filed: 06/01/1995
• Issued: 02/06/1996
• Est. Priority Date: 12/18/1992
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Akada, Hiroshi
• Primary Examiner(s): BLANKENSHIP, HOWARD BENNETT
• Application Number:
  US08/457,164
• Time in Patent Office: 250 Days
• Field of Search: 354/234.1, 354/235.1, 354/270, 354/271.1, 348/362, 348/363, 359/227, 359/230, 359/234, 310/36, 310/37, 310/38, 310/39, 385/18
• US Class Current: 396/508
• CPC Class Codes: G03B 7/10 a servo-motor providing energy to move the setting member

Abstract

A light quantity adjusting device is provided with a light blocking member for adjusting a quantity of light by moving the light blocking member and a drive source for driving the light blocking member. The drive source includes at least a rotor having a plurality of poles, a stator, a coil and a limiting part arranged to limit the rotation angle range of the rotor to an angle not exceeding 180 degrees. The drive source is arranged such that a cogging torque existing when the coil is not energized works over the whole rotation angle range to cause the rotor to rotate in one direction and, a coil torque generated when the coil is energized works over the whole rotation angle range to cause the rotor to rotate in the other direction. The peak of the coil torque is set to be obtainable within the rotation angle range, and a torque which is obtained by combining the cogging torque and the coil torque works to cause the rotor to rotate in the other direction.

Claims

1. A light quantity adjusting device comprising:

a light blocking member arranged to move to adjust a quantity of light; and

a drive source for driving said light blocking member, said drive source including at least a rotor having a plurality of poles, a stator, a coil and limiting means for limiting a rotation angle range, wherein a first torque generating irrespective of energization of said coil works over the whole rotation angle range to cause said rotor to rotate in one direction and a second torque generated when said coil is energized works over the whole rotation angle range to cause said rotor to rotate in the other direction, the peak of the second torque being set to be obtainable within the rotation angle range, and a torque which is obtained by combining the first torque and the second torque working to cause said rotor to rotate in the other direction.

2. A device according to claim 1, wherein stator poles of said stator are set in such a way as to cause the phase of the first torque and that of the second torque to deviate from each other.

3. A device according to claim 1, wherein the rotation of an output shaft of said rotor is transmitted to a driving member, and wherein said light blocking member is caused to move by the rotation of said driving member.

4. A device according to claim 2, wherein cutout parts are formed at said stator poles.

5. A device according to claim 2, wherein protruding parts are formed at said stator poles.

6. A device according to claim 2, wherein interpoles are formed at said stator poles.

7. A device according to claim 1, wherein the torque obtained by combining the first torque and the second torque becomes nearly flat within the rotation angle range.

8. A device according to claim 1, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, said stator is divided at least into two stator members, and said stator members are joined together by recessed and protruding joining parts.

9. A device according to claim 1, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, said stator is divided at least into two stator members, and said stator members are joined together by being pinched by pinching members which have elasticity.

10. A device according to claim 1, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, and said stator is formed approximately in an arcuate shape around an optical axis.

11. An optical apparatus having a light quantity adjusting device, comprising:

a light blocking member arranged to move to adjust a quantity of light, said light blocking member being movably supported by a support member which has a hole formed therein for passing a light flux;

a lens barrel member; and

a drive source for driving said light blocking member, said drive source including at least a rotor having a plurality of poles, a stator, a coil and limiting means for limiting a rotation angle range, wherein a first torque generating irrespective of energization of said coil works over the whole rotation angle range to cause said rotor to rotate in one direction and a second torque generated when said coil is energized works over the whole rotation angle range to cause said rotor to rotate in the other direction, the peak of the second torque being set to be obtainable within the rotation angle range, and a torque which is obtained by combining the first torque and the second torque working to cause said rotor to rotate in the other direction.

12. An apparatus according to claim 11, wherein said rotor is disposed in a position which is eccentric in the direction of an optical axis of said lens barrel member.

13. An apparatus according to claim 11, wherein stator poles of said stator are set in such a way as to cause the phase of the first torque and that of the second torque to deviate from each other.

14. An apparatus according to claim 11, wherein the rotation of an output shaft of said rotor is transmitted to a driving member, and wherein said light blocking member is caused to move by the rotation of said driving member.

15. An apparatus according to claim 11, wherein cutout parts are formed at said stator poles.

16. An apparatus according to claim 11, wherein the torque obtained by combining the first torque and the second torque becomes nearly flat within the rotation angle range.

17. An apparatus according to claim 11, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, said stator is divided at least into two stator members, and said stator members are joined together by being pinched by pinching members which have elasticity.

18. An apparatus according to claim 11, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, and said stator is formed approximately in an arcuate shape around an optical axis.

19. An apparatus according to claim 11, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, and said stator is mounted directly on said lens barrel member.

20. An apparatus according to claim 11, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, said stator is supported by a second support member, and said second support member is mounted on said lens barrel member.

21. A driving device including at least a rotor having a plurality of poles, a stator, a coil and limiting means for limiting a rotation angle range, wherein a first torque generating irrespective of energization of said coil works over the whole rotation angle range to cause said rotor to rotate in one direction and a second torque generated when said coil is energized works over the whole rotation angle range to cause said rotor to rotate in the other direction, the peak of the second torque being set to be obtainable within the rotation angle range, and a torque which is obtained by combining the first torque and the second torque working to cause said rotor to rotate in the other direction.

22. A device according to claim 21, wherein stator poles of said stator are set in such a way as to cause the phase of the first torque and that of the second torque to deviate from each other.

23. A device according to claim 22, wherein cutout parts are formed at said stator poles.

24. A device according to claim 22, wherein protruding parts are formed at said stator poles.

25. A device according to claim 22, wherein interpoles are formed at said stator poles.

26. A device according to claim 21, wherein the torque obtained by combining the first torque and the second torque becomes nearly flat within the rotation angle range.

27. A device according to claim 21, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, said stator is divided at least into two stator members, and said stator members are joined together by recessed and protruding joining parts.

28. A device according to claim 21, wherein said stator is arranged to serve also as a yoke, said coil is wound around said stator, said stator is divided at least into two stator members, and said stator members are joined together by being pinched by pinching members which have elasticity.