Source: http://www.google.com/patents/US5489959?ie=ISO-8859-1
Timestamp: 2014-10-25 00:53:50
Document Index: 115087574

Matched Legal Cases: ['arts 14', 'art 14', 'art 14', 'arts 14', 'art 14', 'art 14', 'art 28', 'art 28', 'art 31', 'art 31', 'art 31', 'art 31', 'art 31', 'art 31', 'art 106', 'arts 106', 'arts 106', 'art 106', 'art 106']

Patent US5489959 - Light quantity adjusting device - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA 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...http://www.google.com/patents/US5489959?utm_source=gb-gplus-sharePatent US5489959 - Light quantity adjusting deviceAdvanced Patent SearchPublication numberUS5489959 APublication typeGrantApplication numberUS 08/457,164Publication dateFeb 6, 1996Filing dateJun 1, 1995Priority dateDec 18, 1992Fee statusPaidPublication number08457164, 457164, US 5489959 A, US 5489959A, US-A-5489959, US5489959 A, US5489959AInventorsHiroshi AkadaOriginal AssigneeCanon Kabushiki KaishaExport CitationBiBTeX, EndNote, RefManPatent Citations (2), Referenced by (25), Classifications (7), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetLight quantity adjusting deviceUS 5489959 AAbstract 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.
What is claimed is: 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.
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.
SUMMARY OF THE INVENTION One aspect of this invention resides in the provision of a light quantity adjusting device, wherein the phase of a cogging torque and that of a coil torque generated by a coil deviate from each other in such a manner that the cogging torque works to cause a rotor to rotate in one direction over the whole rotation angle range of the rotor, the coil torque works to cause the rotor to rotate in the other direction, the peak of the coil torque arises within the rotation angle range, and a composite torque obtained by combining the cogging torque and the coil torque works to cause the rotor to rotate in the other direction over the whole rotation angle range.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded oblique view showing in outline the essential parts of a light quantity adjusting device arranged as a first embodiment thereof.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is an exploded oblique view showing in outline the arrangement of the essential parts of a light quantity adjusting device which is arranged according to this invention as a first embodiment thereof. The light quantity adjusting device includes a rotor 1, a stator yoke 2, a coil 3, a bobbin 4, a cap 5, an arm 6, a base plate 7, a diaphragm blade group 8, a lid 9, a magnetism detecting element (Hall element) 10 and a flexible circuit board 11.
The operation of the light quantity adjusting device which is arranged as the embodiment described above is described as follows with reference to FIG. 5 which schematically shows the magnetic circuit: In FIG. 5, reference numeral 12 denotes a rotor, which is carried by a shaft to be rotatable thereon. The rotor 12 is provided with an arm 13 which is arranged to be movable in association with the rotation of the rotor 12. Reference numeral 14 denotes a stator yoke. The stator yoke 14 has first and second opposed parts 14a and 14b which are opposed to the rotor 12 and are respectively provided with first and second grooves 14a-1 and 14b-1. Assuming that the opening angle of the first opposed part 14a is 170� and that of the second opposed part 14b also 170�, for example, the first groove 14a-1 is located at 47.5� from a datum angle and the second groove 14b-1 at 227.5� as shown in FIG. 5. Reference numeral 15 denotes a coil. The coil 15 is wound around a part of the stator yoke 14. Reference numeral 16 denotes a stopper. When the arm 13 comes into contact with the stopper 16, the swing of the arm 13 in one direction comes to a stop at the stopper 16.
(3) The rotation angle range of the rotor, from the full open position to the full closed position, must be from 50� to 60�.
FIG. 8 shows a magnetic circuit as a model in which no groove is provided in the stator yoke. In this case, with the positional relation between the stator yoke 20 and the rotor 12 set at its initial point of 0�, when the rotor 12 is caused to make one rotation in the "+" direction, the torque characteristic becomes as shown in FIG. 9. In FIG. 9, the illustration includes a cogging torque 21, a torque 22 generated by the coil and a torque 23 obtained by combining the cogging torque 21 with the coil-generated torque 22.
As apparent from FIG. 9, the torque obtained with the cogging torque combined with, i.e., added to, the coil-generated torque fails to have such a characteristic that satisfies all the above-stated conditions which are (1) to have the torque act in the direction of closing over the whole range from the full open position to the full closed position at the time of nonenergization (when the coil is not energized) and to act in the direction of opening over the whole range at the time of energization; (2) to have a torque curve which either remains at about the same value or becomes slightly lower accordingly as the rotor rotates in the opening direction with the same current allowed to flow; and (3) the rotation angle range of the rotor from the full open position to the full closed position is from 50� to 60� or thereabout. The magnetic circuit having the stator yoke arranged in the shape as shown in FIG. 8 is, therefore, inapposite to the drive source of the light quantity adjusting device.
FIG. 10 schematically shows a magnetic circuit which serves as the drive source of the light quantity adjusting device arranged according to this invention as its first embodiment. The first and second opposed parts 14a and 14b of the stator yoke 14 are respectively provided with the first groove 14a-1 and the second groove 14b-1, which are located in the following positions: When the first opposed part 14a is, for example, at an opening angle of 170� and the second opposed part 14b also at the opening angle of 170�, the first groove 14a-1 is located for example, at an angle of 47.5� from a datum angle and the second groove 14b-1 at an angle of 227.5�.
With the magnetic circuit arranged in this manner, when a constant current is allowed to flow to the coil 15 to cause the rotor 12 to make one rotation in the "+" direction from an initial state of having the stator yoke 14 and the rotor 12 in a positional relation as shown in FIG. 10, the torque characteristic in relation to the rotation angle of the rotor 12 becomes as shown in FIG. 11. In FIG. 11, the illustration includes a cogging torque 24, a torque 25 which is generated by the coil and a torque 26 which is obtained by adding the cogging torque 24 to the coil-generated torque 25. As shown in FIG. 11, the phase of the cogging torque 24 and that of the coil-generated torque 25 deviate from each other, thereby giving a characteristic which satisfies the above conditions approximately within a range between 130� and 180�. Further, the cogging torque 24 is set in such a way as to have a peak P1 of its component in the "+" direction and the torque 25 generated by the coil to have a peak P2 of its component in the "-" direction, respectively, within the range of 130� to 180�.
The positional relations between the rotor 12 and the arm 13 and between the arm 13 and the stopper 16 are set, on the basis of the characteristic thus obtained, in such a way as to allow the use of the magnetic circuit, for example, within the range of the rotation angle of the rotor from 130� to 180�. Then the rotor 12 and the arm 13 can be rotated within such a range.
(Second Embodiment) In the case of the first embodiment of this invention described above, a desired torque characteristic is obtained by providing grooves in the stator yoke in such a way as to shift the phase relation between the cogging torque and the torque generated by the coil. The same advantage is, however, attainable also by arranging some magnetic pieces as interpoles.
FIG. 12 shows the magnetic circuit arrangement of a light quantity adjusting device arranged as a second embodiment of this invention. Referring to FIG. 12, interpoles 29a and 29b which are magnetic pieces are secured to a stator yoke 28 or a base plate by a known method such as press fitting. The interpoles 29a and 29b are arranged in the following positions: With the opening angle of a first opposed part 28a of the stator yoke 28 assumed to be 170� and that of a second opposed part 28b to be also 170� in the magnetic circuit which is schematically shown in FIG. 13, the first interpole 29a is disposed, for example, at 317.5� and the second interpole 29b at 137.5� with respect to a datum angle.
(Third Embodiment) While the desired torque characteristic is obtained by forming the grooves in the predetermined parts of the stator yoke to shift the phase relation between the cogging torque and the torque generated by the coil in the case of the first embodiment, the same advantageous effect is attainable by providing some protruding parts, instead of the grooves, in predetermined parts of the stator yoke.
FIG. 14 shows a third embodiment of this invention which is arranged in the above-stated manner. In FIG. 14, reference numeral 31 denotes a stator yoke which is provided with the protruding parts, including a first protruding part 31a-1 and a second protruding part 31b-1. The positions of these protruding parts in the magnetic circuit which is schematically shown in FIG. 15 are as follows: Assuming that the opening angle of a first opposite part 31a of the stator yoke 31 is, for example, 170� and that of a second opposite part 31b also 170�, the first protruding part 31a-1 is, for example, located at 317.5� and the second protruding part 31b-1 at 137.5� with respect to a datum angle.
(Fourth Embodiment) In the case of the first embodiment described in the foregoing, the base plate is provided for fixing the magnetic circuit of the driving part in place. However, this arrangement may be changed to use a lens tube for this purpose instead of using the base plate.
(Fifth Embodiment) The following describes a fifth embodiment of this invention: FIG. 19 best shows a feature of the magnetic circuit of a light quantity adjusting device of the fifth embodiment. The magnetic circuit is shown as viewed in the direction of an optical axis. In FIG. 19, the illustration includes a rotor 1, a stator yoke 45 which is in an approximately arcuate shape and is made of a soft magnetic material, a coil 3 and a base plate 46. The stator yoke 45 which is approximately in an arcuate shape is provided with grooves in its parts opposed to the rotor 1. These grooves are located, for example, in the same positions as in the case of the first embodiment. The fifth embodiment operates in the same manner as the first embodiment. Therefore, the operating principle of the fifth embodiment is omitted from description.
(Sixth Embodiment) FIG. 22 shows the arrangement of a stator yoke of a sixth embodiment of this invention as in a state of being joined. In FIG. 22, parts which are the same as or similar to the parts shown in FIG. 2 are indicated by the same reference numerals and the details of them are omitted from description.
(Seventh Embodiment) FIG. 23 is an oblique view showing a stator yoke of a seventh embodiment of this invention in a state of being joined. In joining stator yoke pieces together, an angular member 61 of a C shape may be used as shown in FIG. 23. The C shaped angular member 61 has locking claws 61a-1 and 61b-1. The stator yoke pieces 2a"-1 and 2b"-1 are provided with locking claw engaging grooves 60a and 60b for engaging each other. Like the sixth embodiment, the protruding pieces 61a and 61b of the angular member 61 which serve as pinching pieces are arranged to be slanting inward and toward each other before insertion of the stator yoke in between them. After insertion, the protruding pieces 61a and 61b exert their resilient forces to push the joining faces of the stator yoke pieces 2a'-1 and 2b"-1 against each other in such a way as to fix the stator yoke. This arrangement thus gives the same advantage as that of the sixth embodiment. Further, the use of the angular member 61 for this purpose separately from the base plate effectively prevents the base plate from such a damage as having locking claws broken.
(Eighth Embodiment) Next, a light quantity adjusting device which is arranged as an eighth embodiment of this invention is described as follows: Referring to FIG. 25, a rotor 101 is magnetized to have two poles and is magnetized mainly perpendicular to a rotor shaft. A stator 102 is made of a magnetic material such as a silicon steel plate and is composed of two stator pieces 102-1 and 102-2. The pole position of one stator piece 102-1 is shifted toward the optical axis of a lens barrel (see FIG. 1). Therefore, the rotor 101 can be set in a position which is virtually shifted toward the optical axis to permit reduction in size. The stator 102 is provided with positioning holes 102a and 102b. A bobbin 103 which is formed by molding a resin material is provided with a hole 103a for inserting the stator 102 and has a conducting wire wound around it on the outer side of the hole 103a. An arm 104 is formed by molding a resin material and serves also as the shaft of the rotor 101. A cap 105 is formed by molding a resin material. The cap 105 is provided with a bearing 105a and engaging holes 105b and 105c for engaging a case 106. The case 106 is formed by molding a resin material and is provided with a pinching part 106e for pinching the stator 102, protruding parts 106aand 106b for positioning the stator 102 and the cap 105, pinching parts 106c and 106d for pinching the cap 105, a pinching part 106f for pinching a magnetism detecting element 107 and a bearing part 106g (shown in FIG. 26(a)) for receiving the shaft part of the arm 104.
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