JP2018169468A - Actuator, lens unit having the same, and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator capable of changing a movable portion supporting an image shake correction lens from a locked state to a locked unlocked state at high speed. The present invention is an actuator (10) for moving a camera shake correction lens (16), in which a fixed portion (12) and a camera shake correction lens are attached, and in a plane orthogonal to an optical axis. A magnetic fluid provided on one of a fixed portion or a movable portion, which holds a magnetic fluid inside, a movable portion (14) movably supported by the movable portion (14), a driving means (20, 22) for driving the movable portion, and a fixed portion or the movable portion. The holding portion (46) and the extending portion (42) provided so as to extend into the magnetic fluid held by the magnetic fluid holding portion from the other of the fixed portion or the movable portion, and the driving means can be controlled and moved. A control device that changes the viscosity of the magnetic fluid and locks and unlocks the movable part by moving the part and executing the camera shake correction control that corrects the camera shake, and by applying magnetism to the magnetic fluid (36). It is characterized by having and. [Selection diagram] Fig. 2

Description

  The present invention relates to an actuator, and more particularly to an actuator for moving a camera shake correction lens, a lens unit including the actuator, and a camera.

  At present, cameras with an image stabilization function and interchangeable lenses are widely used. In these cameras and interchangeable lenses with a camera shake correction function, a camera shake correction lens is moved in a plane orthogonal to the optical axis to correct a shake of an image formed on an image sensor or a film. However, in such a camera with a camera shake correction function or an interchangeable lens, when the camera shake correction function is not used, the camera shake correction lens is locked at a predetermined position so as not to deteriorate the formed image. It is preferable to keep it. Also, even when the camera or interchangeable lens is turned off, the camera shake correction lens rattles during transportation, etc., to prevent the lens moving mechanism from being worn or damaged in the worst case. In addition, it is preferable to lock the camera shake correction lens.

  Japanese Patent Laid-Open No. 10-142647 (Patent Document 1) describes an image blur prevention mechanism. In this image blur prevention mechanism, a shift lens for camera shake correction is attached to a support frame, and a lock ring is disposed so as to surround the support frame. Here, when locking the shift lens, the support frame is locked by rotating the lock ring and fitting the protrusions provided on the support frame to the inner peripheral surface of the lock ring.

Japanese Patent Laid-Open No. 10-142647

  However, in the image blur prevention mechanism described in Patent Document 1, when the support frame is locked, it is necessary to rotate the lock ring disposed so as to surround the support frame, so that the lock can be released quickly. There is a problem that it is difficult to do. In other words, since the lock ring is provided so as to surround the support frame holding the shift lens, it becomes a part having a certain size and mass, and is mechanically driven to lock the lock position. To move to and from the release position, a time on the order of several hundred milliseconds is required. A photographer who uses a camera or an interchangeable lens is required to take a picture using the camera shake correction function immediately after starting the camera shake correction function in order to capture a momentary photo opportunity. Therefore, the time delay of the order of several hundred milliseconds required for releasing the support frame of the shift lens is not acceptable to the photographer and is not satisfactory. Also, if a powerful motor for driving the lock ring is provided to drive the lock ring at a high speed, there is a problem that the lens barrel containing the motor becomes large or the power consumption of the motor becomes unacceptably large. is there.

  Accordingly, an object of the present invention is to provide an actuator that can move the movable portion supporting the image blur correction lens from the locked state to the unlocked state at high speed, a lens unit including the actuator, and a camera. Yes.

  In order to solve the above-described problems, the present invention provides an actuator for moving a camera shake correction lens, which is a fixed portion and a movable portion to which the camera shake correction lens is attached, A movable part supported so as to be movable in a plane orthogonal to the optical axis of the camera shake correction lens, a driving means for driving the movable part, and one of the fixed part and the movable part, and a magnetic fluid inside A magnetic fluid holding portion that holds the fluid, an extending portion that is provided so as to extend from the other of the fixed portion or the movable portion into the magnetic fluid held by the magnetic fluid holding portion, and a movable portion that controls the driving means. And a control device for executing the shake correction control for correcting the shake and changing the viscosity of the magnetic fluid by applying magnetism to the magnetic fluid to lock and release the movable part. Specially It is set to.

  In the present invention configured as described above, the movable portion to which the camera shake correction lens is attached is supported so as to be movable with respect to the fixed portion in a plane orthogonal to the optical axis, and is driven by the driving means. A magnetic fluid holding part holding a magnetic fluid therein is provided in one of the fixed part and the movable part, and an extension part extends into the magnetic fluid held in the magnetic fluid holding part from the other of these. . The control device controls the driving means to move the movable part to execute the camera shake correction control for correcting the camera shake, and changes the viscosity of the magnetic fluid by applying magnetism to the magnetic fluid, thereby Stop and release.

  According to the present invention configured as described above, the locking and releasing of the movable portion is performed by applying magnetism to the magnetic fluid and changing its viscosity. The locked state can be released at a higher speed than in the case where the lock is released by driving. As a result, when the photographer wants to use the camera shake correction function, the photographer can start shooting immediately and can accurately capture the photo opportunity.

  According to the actuator of the present invention, and the lens unit and camera including the actuator, the movable portion supporting the image blur correcting lens can be brought into the unlocked state from the locked state at a high speed.

It is sectional drawing of the camera by 1st Embodiment of this invention. It is a disassembled perspective view of the actuator with which the camera by 1st Embodiment of this invention is equipped. It is a perspective view which expands and shows the latching mechanism of the actuator with which the camera by 1st Embodiment of this invention is equipped. In 1st Embodiment of this invention, it is a figure which shows the simulation result which shows an example of the magnetic force line produced | generated inside the latching mechanism. It is a disassembled perspective view of the actuator for camera shake correction in 2nd Embodiment of this invention. It is a perspective view which expands and shows the latching mechanism with which the actuator for camera shake correction in 2nd Embodiment of this invention is equipped. In 2nd Embodiment of this invention, it is a figure which shows the simulation result which shows an example of the magnetic force line produced | generated inside the latching mechanism.

<First Embodiment>
(Camera configuration)
Embodiments of the present invention will be described with reference to the accompanying drawings. First, a camera according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a camera according to a first embodiment of the present invention.

  As shown in FIG. 1, a camera 1 according to an embodiment of the present invention includes a lens unit 2 and a camera body 4. The lens unit 2 includes a lens barrel 6, a plurality of lenses 8 arranged in the lens barrel, a camera shake correction actuator 10 for moving the camera shake correction lens 16 within a predetermined plane, a lens mirror And a gyro 34 which is a vibration detecting means for detecting the vibration of the cylinder 6.

  The camera 1 according to the embodiment of the present invention detects vibration by the gyro 34, operates the actuator 10 based on the detected vibration to move the camera shake correction lens 16, and moves the image sensor surface 4 a in the camera body 4. It stabilizes the focused image. In the present embodiment, a piezoelectric vibration gyro is used as the gyro 34. In the present embodiment, the camera shake correction lens 16 is configured by a single lens, but the lens for stabilizing an image may be a plurality of lens groups. In this specification, the camera shake correction lens includes one lens and a lens group for stabilizing an image.

  The lens unit 2 is attached to the camera body 4 and configured to form incident light on the image sensor surface 4a. The generally cylindrical lens barrel 6 holds a plurality of lenses 8 therein, and the focus can be adjusted by moving some of the lenses 8.

(Configuration of actuator)
Next, with reference to FIG. 2 to FIG. 4, the actuator 10 for correcting camera shake according to the first embodiment of the present invention will be described. FIG. 2 is an exploded perspective view of the actuator 10. FIG. 3 is an enlarged perspective view showing the locking mechanism of the actuator 10.

  As shown in FIG. 2, the actuator 10 is a fixed plate 12 that is a fixed portion fixed in the lens barrel 6, and a movable portion that is supported so as to be able to translate and rotate with respect to the fixed plate 12. The movable frame 14 includes three steel balls 18 that are movable portion support mechanisms that support the movable frame 14 with respect to the fixed plate 12. The fixed plate 12 and the moving frame 14 are arranged in parallel to each other.

  Further, as shown in FIG. 2, the actuator 10 includes a first drive magnet 22a, a second drive magnet 22b, and a third drive magnet 22c attached to the fixed plate 12 so as to form a pair. The actuator 10 is disposed inside the first driving coil 20a, the second driving coil 20b, the third driving coil 20c, and the driving coils 20a, 20b, and 20c attached to the moving frame 14, respectively. The first magnetic sensor 24a, the second magnetic sensor 24b, and the third magnetic sensor 24c, which are the first, second, and third position detection elements.

  The first drive magnet 22a attached to the fixed plate 12 is disposed so as to face the first drive coil 20a attached to the moving frame 14. Similarly, the second drive magnet 22b is disposed to face the second drive coil 20b, and the third drive magnet 22c is disposed to face the third drive coil 20c. In the present embodiment, the pair of the first drive magnet 22a and the first drive coil 20a, the pair of the second drive magnet 22b and the second drive coil 20b, and the third drive magnet 22c and the third drive. The pair of working coils 20c function as first to third driving means, respectively.

  Further, as shown in FIG. 1, the actuator 10 is based on the vibration detected by the gyro 34 and the positional information of the moving frame 14 detected by the first, second, and third magnetic sensors 24a, 24b, and 24c. The controller 36 is a control device that controls the current flowing through the first, second, and third drive coils 20a, 20b, and 20c.

  The actuator 10 translates the moving frame 14 with respect to the fixed plate 12 fixed to the lens barrel 6 in a plane parallel to the imaging element surface 4 a, and thereby a camera shake correction lens attached to the moving frame 14. When the lens barrel 6 is vibrated by moving the lens 16, the image formed on the imaging element surface 4a is driven so as not to be disturbed.

  Next, as shown in FIG. 2, the fixed plate 12 has a generally donut plate shape, and drive magnets 22a, 22b, and 22c are embedded therein, respectively. The centers of these driving magnets are respectively arranged on the circumference of a circle centered on the optical axis A (FIG. 1) of the lens unit 2. In the present embodiment, the first, second, and third driving magnets 22a, 22b, and 22c are arranged on the circumference centered on the optical axis A at equal intervals with a central angle of 120 °. ing. The first drive magnet 22a is arranged vertically above the optical axis A.

  In the present embodiment, as shown in FIG. 2, the first drive magnet 22a is composed of two rectangular partial magnets. These partial magnets are arranged symmetrically with respect to the magnetic pole boundary line on both sides of the magnetic pole boundary line directed in the radial direction of the circle centered on the optical axis A. In other words, the straight line in the radial direction passing through the middle of the two partial magnets becomes the magnetic pole boundary line of the first driving magnet 22a. Similarly, the second drive magnet 22b and the third drive magnet 22c are each composed of two rectangular partial magnets, and a magnetic pole boundary is formed between these partial magnets.

  Next, as shown in FIG. 2, the moving frame 14 includes a ring-shaped ring portion 14a surrounding the camera-shake correction lens 16, and three coil attachments formed so as to protrude radially from the ring portion 14a. It has a portion 14b and is arranged so as to overlap the fixing plate 12 in parallel. A camera shake correction lens 16 is attached to the inside of the ring portion 14a.

  Each coil attachment part 14b is provided on the circumference of the circle centering on the optical axis A of the ring part 14a, and the first, second, and third drive coils 20a, 20b, and 20c are attached thereto. These first, second, and third drive coils 20a, 20b, and 20c are attached at positions that oppose the first, second, and third drive magnets 22a, 22b, and 22c attached to the fixed plate 12, respectively. ing. That is, in the present embodiment, the first, second, and third drive coils 20a, 20b, and 20c are arranged at equal intervals on the circumference of a circle centered on the optical axis A, and the first drive coil 20a is arranged vertically above the optical axis A.

  The first, second, and third drive coils 20a, 20b, and 20c are flat coils in which the windings are wound in a rectangular shape with rounded corners. Each driving coil is arranged so that a center line crossing the short side thereof is directed in a radial direction of a circle having the optical axis A as a center. In other words, each driving coil is arranged such that its short side is directed in a tangential direction of a circle centered on the optical axis A.

  Next, as shown in FIG. 2, the three steel balls 18 are sandwiched between the fixed plate 12 and the moving frame 14, and each have a central angle of 120 ° on the circumference of a circle centered on the optical axis A. They are arranged at intervals. Each steel ball 18 is disposed in a recess 30 formed at a position corresponding to each steel ball 18 of the fixing plate 12, and is prevented from falling off. As a result, the moving frame 14 is supported on a plane parallel to the fixed plate 12, and each steel ball 18 is rolled while being held, so that translational movement and rotational movement of the moving frame 14 with respect to the fixed plate 12 are allowed. Is done.

  Further, in the present embodiment, a steel sphere is used as the steel ball 18, but the moving frame 14 can be supported with respect to the fixed plate 12 by a resin sphere, for example. Also, the moving frame can be supported by a sliding surface that can slide smoothly without using steel balls, and the moving frame is supported so as to be movable in a plane perpendicular to the optical axis with respect to the fixed plate. Any movable part support mechanism can be used.

  Further, the actuator 10 has three suction yokes 28 attached to the moving frame 14 for attracting the moving frame 14 to the fixed plate 12. As shown in FIG. 2, the adsorption yoke 28 is a rectangular plate-like magnetic body attached to the back side (opposite side of the driving coil) of the coil attachment portion 14 b of the moving frame 14 and attached to the fixed plate 12. The drive magnets are arranged so as to correspond to the respective drive magnets. The moving frame 14 is attracted to the fixed plate 12 by the magnetic force exerted by each driving magnet on these attracting yokes 28, and the steel balls 18 are sandwiched therebetween.

Next, the driving force generated by each driving magnet and driving coil will be described.
As shown in FIG. 2, the first drive magnet 22a attached to the fixed plate 12 is positioned so that its magnetic pole boundary passes through the middle of each partial magnet of the drive magnet. The polarity also changes in the thickness direction. In the present embodiment, the driving magnet 22a has the left partial magnet surface in FIG. 2 magnetized with the S pole and the right side with the N pole, and the magnetic poles on the back side of each partial magnet are opposite. In this specification, the magnetic pole boundary line refers to a line passing through the middle (center) of the region magnetized in the S pole and the region magnetized in the N pole.

  Due to this magnetization, magnetic lines of force are formed between the driving magnet 22a and the attracting yoke 28 disposed corresponding thereto, and magnetism is applied to the first driving coil 20a disposed therebetween. . The magnetism by the drive magnet 22a mainly acts on the long side portion of the rectangular first drive coil 20a. Thereby, when a current flows through the first driving coil 20a, a horizontal driving force is generated between the first driving coil 20a and the driving magnet 22a.

  The second drive magnet 22b and the third drive magnet 22c attached to the fixed plate 12 are also magnetized in the same manner as the first drive magnet 22a, and the attachment direction to the moving frame 14 is 120 degrees each. It has been rotated. As a result, when a current flows through the second and third driving coils 20b and 20c, a driving force in a tangential direction of a circle centered on the optical axis A between the second and third driving magnets 22b and 22c. Occur respectively.

  Next, as shown in FIG. 2, a first magnetic sensor 24a, a second magnetic sensor 24b, and a third magnetic sensor 24c are arranged inside each driving coil. The first, second, and third magnetic sensors 24a, 24b, and 24c are configured to measure the position of the moving frame 14. Each magnetic sensor detects the amount of movement of the moving frame 14 with respect to the fixed plate 12 in a direction parallel to the line of action of the driving force generated when a current flows through each driving coil (a direction perpendicular to the magnetic pole boundary). Each magnetic sensor has its sensitivity center point for each drive when the moving frame 14 is at the control center position (when the optical axis of the camera shake correction lens 16 coincides with the optical axis of the lens unit 2). It arrange | positions so that it may be located on the magnetic pole boundary line of a magnet. In the present embodiment, a Hall element is used as the magnetic sensor.

  The output signal from the magnetic sensor is approximately 0 when the sensitivity center point of the magnetic sensor is located on the magnetic pole boundary of the driving magnet, the moving frame 14 moves, and the sensitivity center point of the magnetic sensor is the driving magnet. When it deviates from the magnetic pole boundary line, the output signal of the magnetic sensor changes. During the normal operation of the actuator 10, since the moving amount of the driving magnet is very small, a signal substantially proportional to the moving distance in the direction orthogonal to the magnetic pole boundary of the driving magnet is output from each magnetic sensor.

  For this reason, the first magnetic sensor 24a outputs a signal substantially proportional to the amount of translational movement of the moving frame 14 in the horizontal direction. The second and third magnetic sensors 24b and 24c output a signal substantially proportional to the translational movement amount of the moving frame 14 in the direction inclined by about 120 ° with respect to the vertical axis. Based on the signals detected by the first, second, and third magnetic sensors 24a, 24b, and 24c, the position where the moving frame 14 is translated and rotated with respect to the fixed plate 12 can be specified.

(Configuration of locking mechanism)
Next, the locking mechanism provided in the actuator 10 will be described with reference to FIGS. FIG. 3 is an enlarged perspective view showing the locking mechanism. FIG. 4 is a diagram showing a simulation result showing an example of a magnetic force line generated inside the locking mechanism in the present embodiment. FIG. 4A shows a state where the locking control coil is not energized. b) shows a state in which the locking control coil is energized.

  As shown in FIG. 2, the locking mechanism 40 includes an extending portion 42 extending from the moving frame 14 toward the fixed plate 12 and an extending portion receiving portion 44 provided on the fixed plate 12. In the present embodiment, three extending portion receiving portions 44 are provided adjacent to the respective concave portions 30 of the fixed plate 12, and the moving frame 14 extends to positions corresponding to these extending portion receiving portions 44. Each part 42 is provided (only one is shown in FIG. 2). In other words, in the present embodiment, the locking mechanisms 40 are arranged on the circumference centered on the optical axis A at equal intervals with a central angle of 120 °.

  As shown in FIG. 3, the extending portion 42 is formed in a rod shape with a circular cross section, and extends in a direction parallel to the optical axis A from the moving frame 14 toward the fixed plate 12. The leading end of the extending portion 42 is received by the extending portion receiving portion 44. In the present embodiment, the extension portion 42 is positioned substantially on the central axis of the extension portion receiving portion 44 in a state where the optical axis of the camera shake correction lens 16 and the optical axis A of the lens unit 2 coincide.

  The extending portion receiving portion 44 is disposed on both sides of the magnetic fluid holding portion 46 holding the magnetic fluid therein, the magnetic fluid 48 filled in the magnetic body holding portion 46, and the magnetic fluid holding portion 46. Holding magnets 50a and 50b. Further, locking control coils 52a and 52b are respectively arranged between the magnetic fluid holding portion 46 and the holding magnets, and the back yoke is arranged so as to sandwich the holding magnets on the opposite side of the locking control coils. 54a and 54b are arranged.

  The magnetic fluid holding part 46 is formed in a cup shape with a circular cross section, and is configured to hold the magnetic fluid 48 therein. In the magnetic fluid 48 filled in the magnetic fluid holding part 46, the tip of the extending part 42 extending from the moving frame 14 is inserted. Accordingly, the fluid resistance of the magnetic fluid 48 acts on the movement of the extending portion 42, and thereby a braking force is applied to the moving frame 14. The magnetic fluid holding part 46 is made of a nonmagnetic material so as to transmit the magnetism generated by each holding magnet.

  The magnetic fluid 48 is a magnetic colloid solution in which ferromagnetic fine particles whose surfaces are covered with a surfactant are suspended in a base solution, and is filled in a cup-shaped magnetic fluid holding unit 46.

  The holding magnets 50 a and 50 b are cube-shaped magnets arranged so as to face both side surfaces of the magnetic fluid holding unit 46. Each of the holding magnets 50a and 50b is magnetized so that the magnetic poles are reversed on the side facing the magnetic fluid holding unit 46 and on the opposite side. In the present embodiment, the holding magnet 50a is magnetized with an S pole on the side close to the magnetic fluid holding portion 46 and an N pole on the opposite side, and the holding magnet 50b arranged so as to face the holding magnet 50a. The side close to the magnetic fluid holding part 46 is magnetized to the N pole, and the opposite side is magnetized to the S pole. As described above, the holding magnets 50 a and 50 b are arranged so that different magnetic poles face each other on both sides of the extending portion 42 extending into the magnetic fluid 48. For this reason, the magnetic fluid holding part 46 disposed between the holding magnets 50a and 50b generally transmits the magnetic field lines in the direction of the axis B from the holding magnet 50b to 50a. As described above, the holding magnets 50 a and 50 b form magnetic lines of force in the magnetic fluid 48 in a direction orthogonal to the extending portion 42 extending from the moving frame 14 toward the fixed plate 12 (crossing at right angles).

  The locking control coils 52a and 52b are coils arranged so as to be sandwiched between the magnetic fluid holding part 46 and each holding magnet, and are wound in a generally rectangular flat form. That is, the locking control coils 52a and 52b are coils wound flatly around the axis B connecting the holding magnets 50a and 50b, and are respectively provided between the magnetic poles of the holding magnets and the extending portions 42. Has been placed. For this reason, when the controller 36 supplies a current to each locking control coil, a magnetic force line in the direction of the axis B is generated in the magnetic fluid holding portion 46. Further, in a state where no current flows, each of the locking control coils hardly affects the lines of magnetic force generated by the holding magnets 50a and 50b.

  The back yokes 54a and 54b are plates made of a magnetic material, and are arranged adjacent to the holding magnets 50a and 50b, respectively, on the opposite side of the locking control coil. By arranging these back yokes 54a and 54b, the magnetism generated by the holding magnets 50a and 50b is efficiently directed to the magnetic fluid holding part 46 and transmitted through the magnetic fluid holding part 46. One point in FIG. Magnetic field lines as shown by chain lines are generated.

  The magnetic fluid 48 has a very high viscosity when fine particles of the suspended ferromagnetic material are connected to each other in a state where the magnetic lines of force are transmitted through the magnetic fluid 48. That is, in a state where no current is passed through the locking control coils 52a and 52b, the viscosity of the magnetic fluid 48 becomes extremely high due to the lines of magnetic force generated by the holding magnets 50a and 50b. In this state, an extremely high fluid resistance acts on the extending portion 42 extending from the moving frame 14 into the magnetic fluid 48, so that the moving frame 14 is substantially locked. As described above, the controller 36 changes the viscosity of the magnetic fluid 48 by applying magnetism to the magnetic fluid 48 to lock or release the moving frame 14. The locking by the magnetic fluid 48 is extremely stable, and the position of the moving frame 14 that is locked hardly changes even if the moving frame 14 is left to stand for a very long time in a state where its own weight is applied.

  On the other hand, a magnetic field line in a direction to cancel the magnetic field lines formed by the holding magnets 50a and 50b by passing a current in a predetermined direction through the locking control coils 52a and 52b disposed adjacent to the magnetic fluid holding unit 46. Can be formed. As described above, when current is passed through the locking control coils 52a and 52b to cancel at least a part of the lines of magnetic force, the lines of magnetic force passing through the magnetic fluid 48 become very weak, and the magnetic fluid 48 is not magnetized. And the viscosity of the magnetic fluid 48 decreases. In this state, the fluid resistance acting on the extending portion 42 extending into the magnetic fluid 48 is equivalent to the fluid resistance due to a normal colloidal solution, and hardly affects the movement of the moving frame 14. The locking of the moving frame 14 is released.

  FIG. 4 is a simulation result showing an example of the state of the lines of magnetic force in the extending portion receiving portion 44. FIG. 4 (a) shows a state in which no current flows through the locking control coils 52a and 52b, and FIG. b) shows a state in which a current in a direction to cancel the lines of magnetic force generated by the holding magnets 50a and 50b is passed through the locking control coils 52a and 52b.

  In FIG. 4A, strong lines of magnetic force are generated between the holding magnets 50a and 50b, and the viscosity of the magnetic fluid 48 held by the magnetic fluid holding part 46 is extremely increased by the lines of magnetic force. On the other hand, in FIG. 4B, the magnetic lines of force generated by the holding magnets 50a and 50b are deflected or blocked by the locking control coils 52a and 52b disposed adjacent to them, thereby holding the magnetic fluid. Magnetic field lines passing through the inside of the portion 46 are extremely weak. In this state, the viscosity of the magnetic fluid 48 is low and hardly affects the movement of the moving frame 14.

  Further, in the state shown in FIG. 4A, the magnetic lines of force that pass through the magnetic fluid 48 are directed from the holding magnet 50b to 50a, and in this direction (direction parallel to the paper surface of FIG. 4) The fine particles in 48 are connected to each other. Therefore, the fluid resistance acting on the extending portion 42 inserted in the magnetic fluid 48 is in the direction of the axis B (FIG. 3) connecting the holding magnets 50a and 50b, parallel to the direction in which the fine particles are connected. Is relatively weak and relatively strong in the direction across the axis B. In the present embodiment, as shown in FIG. 2, the three extending portion receiving portions 44 are provided on the fixed plate 12 so that the directions of the axis B are different from each other. The moving frame 14 can be reliably locked.

(Image stabilization control)
Next, the operation of the camera 1 according to the first embodiment of the present invention will be described with reference to FIG. First, when the power of the camera 1 is turned off, no current flows through the locking control coils 52a and 52b. In this state, the magnetic fluid 48 is highly viscous, and the moving frame 14 has three engagements. It is locked by the stop mechanism 40. When the power source of the camera 1 is turned on and a start switch (not shown) for the camera shake correction function is turned on, the actuator 10 provided in the lens unit 2 is operated. When the actuator 10 is activated, the controller 36 causes a current to flow through the locking control coils 52a and 52b and cancels a part of the lines of magnetic force generated by the holding magnets 50a and 50b. Thereby, since the viscosity of the magnetic fluid 48 is lowered, the force with which the magnetic fluid 48 holds the extending portion 42 is weakened, the movable frame 14 becomes movable, and the locking is released. Here, since a decrease in the viscosity of the magnetic fluid 48 occurs instantaneously by passing a current through each of the locking control coils, after the camera shake correction function is activated, it takes several milliseconds to several tens of milliseconds. The locking of the moving frame 14 is released. For this reason, if the photographer activates the camera shake correction function, the photographer can immediately perform shooting using the camera shake correction, and can accurately capture the photo opportunity.

  Further, when the camera shake correction function is activated, the gyro 34 attached to the lens unit 2 detects vibration in a predetermined frequency band every moment and outputs it to the controller 36. A lens position command signal is generated based on the angular velocity signal detected by the gyro 34. By moving the camera shake correction lens 16 momentarily to the position commanded by the lens position command signal, the image focused on the image sensor surface 4a of the camera body 4 is stabilized. In this way, the controller 36 controls the driving means to move the moving frame 14 and execute camera shake correction control for correcting camera shake.

  When the camera shake correction function is turned off or when the power of the camera 1 is turned off, the actuator 10 moves the moving frame 14, and the optical axis of the camera shake correction lens 16 is the optical axis A of the lens unit 2. In this state, the current flowing through the locking control coils 52a and 52b is turned off. Thereby, since the viscosity of the magnetic fluid 48 increases instantaneously, the force with which the magnetic fluid 48 holds the extension 42 is increased, and the moving frame 14 is locked at that position. The locked state of the moving frame 14 is maintained even after the camera 1 is turned off.

  According to the actuator of the first embodiment of the present invention, the moving frame 14 is locked and released by applying magnetism to the magnetic fluid 48 and changing its viscosity. The locked state can be released at a higher speed than when mechanically driven to release the lock.

  In the actuator of this embodiment, the magnetic fluid 48 held by the magnetic fluid holding portion 46 is magnetized to increase the viscosity of the magnetic fluid 48 and the extending portion 42 is held by the magnetic fluid. The magnets generated by the holding magnets 50a and 50b are arranged so as to cancel each other so that the holding force of the extending part 42 is weakened by reducing the viscosity of the holding magnets 50a and 50b and the magnetic fluid 48. The controller 36 has a lock control coil 52a, 52b, and the controller 36 locks so that at least a part of the magnetism of the holding magnets 50a, 50b is canceled when the lock of the moving frame 14 is released. A current is passed through the control coils 52a and 52b.

  That is, according to the actuator of this embodiment, the extending portion 42 is held by increasing the viscosity of the magnetic fluid 48 by the holding magnets 50a and 50b, and the holding magnets 50a and 52b hold the holding magnets 50a and 52b. The lock is released by canceling the magnetism of 50b. For this reason, since the moving frame 14 is locked in a non-energized state to the locking control coils 52a and 52b, the locked state can be maintained without consuming electric power.

  Further, in the actuator of the present embodiment, the holding magnets 50 a and 50 b have magnetic force lines in the magnetic fluid 48 in a direction substantially perpendicular to the extending portion 42 extending from the moving frame 14 into the magnetic fluid 48. It is arranged to form.

  For this reason, according to the actuator of the present embodiment, the holding magnets 50a and 50b generate magnetic lines of force in the direction substantially perpendicular to the extending portion 42 extending from the moving frame 14 into the magnetic fluid 48. Therefore, the holding magnets 50a and 50b can efficiently increase the viscosity of the magnetic fluid 48 and hold the extending portion 42.

  Further, according to the actuator of the present embodiment, the holding magnets 50a and 50b are arranged so that different magnetic poles are opposed to both sides of the extending portion 42 extending into the magnetic fluid 48, and the locking control coil 52a. , 52b are disposed between the magnetic poles of the holding magnets 50a, 50b and the extending portion 42, respectively. For this reason, the magnetic force lines generated by the holding magnets 50a and 50b can be canceled efficiently, and the locking of the extending portion 42 can be released with a small current consumption flowing in the locking control coil.

Second Embodiment
Next, an actuator according to a second embodiment of the present invention will be described with reference to FIGS. The actuator of the second embodiment of the present invention differs from the first embodiment described above in the configuration of the locking mechanism. Accordingly, only the points of the present embodiment that are different from the first embodiment will be described here, the same reference numerals are given to the same components, the description thereof will be omitted, and the description of the same operation and effect will also be omitted. .

  FIG. 5 is an exploded perspective view of an actuator for camera shake correction according to the second embodiment of the present invention. FIG. 6 is an enlarged perspective view showing a locking mechanism provided in the actuator of the present embodiment. FIG. 7 is a diagram showing a simulation result showing an example of a magnetic force line generated inside the locking mechanism in the present embodiment. FIG. 7A shows a state in which the locking control coil is not energized. b) shows a state in which the locking control coil is energized.

(Configuration of actuator)
As shown in FIG. 5, the actuator 100 of the present embodiment is different from the first embodiment in that a second fixing plate 102 that is a fixing portion is provided in addition to the fixing plate 12. The second fixed plate 102 is a generally donut-shaped thin plate, and is disposed in parallel to the fixed plate 12 on the side opposite to the fixed plate 12 with respect to the moving frame 14.

  In the present embodiment, the extension plate receiving portion 44 is not provided on the fixed plate 12, and the extension portion receiving portion 108 is provided on the second fixed plate 102. On the other hand, the moving frame 14 is provided with an extending portion 106 extending toward the second fixed plate 102, and the extending portion 106 and the extending portion receiving portion 108 constitute a locking mechanism 104. Furthermore, as shown in FIG. 5, the locking mechanisms 104 are arranged at two locations on the circumference with the optical axis A as the center.

(Configuration of locking mechanism)
As shown in FIG. 6, the extending portion 106 is formed in a rod shape having a circular cross section, and extends in a direction parallel to the optical axis A from the moving frame 14 toward the second fixed plate 102. The leading end of the extension part 106 is received by the extension part receiving part 108. In the present embodiment, the extension portion 106 is positioned substantially on the central axis of the extension portion receiving portion 108 in a state where the optical axis of the camera shake correction lens 16 and the optical axis A of the lens unit 2 coincide.

  The extending portion receiving portion 108 is disposed under the magnetic fluid holding portion 110 holding the magnetic fluid therein, the magnetic fluid 112 filled in the magnetic body holding portion 110, and the magnetic fluid holding portion 110. Holding magnet 114. Furthermore, a locking control coil 116 is disposed along the inner wall surface of the magnetic fluid holding unit 110.

  The magnetic fluid holding unit 110 is formed in a cup shape with a circular cross section, and is configured to hold the magnetic fluid 112 therein. In the magnetic fluid 112 filled in the magnetic fluid holding part 110, the tip of the extending part 106 extending from the moving frame 14 is inserted. Accordingly, the fluid resistance of the magnetic fluid 112 acts on the movement of the extending portion 106, and thereby a braking force is applied to the moving frame 14. The magnetic fluid holding unit 110 is made of a nonmagnetic material so as to transmit the magnetism generated by the holding magnet 114. The magnetic fluid 112 is a colloid solution similar to the magnetic fluid 48 in the first embodiment.

  The holding magnet 114 is a disk-shaped magnet disposed below the magnetic fluid holding part 110, that is, on the extension line of the extension part 106. The holding magnet 114 is magnetized so that the magnetic poles are reversed between the surface adjacent to the magnetic fluid holding unit 110 and the opposite surface. In the present embodiment, the holding magnet 114 is magnetized with an N pole on the side adjacent to the magnetic fluid holding unit 110 and an S pole on the opposite side. As described above, the holding magnet 114 is disposed on the extension line of the extending portion 106 extending into the magnetic fluid 112, and is magnetized so that one of the magnetic poles faces the extending portion 106.

  For this reason, the magnetic fluid holding part 110 disposed above the holding magnet 114 extends upward along the central axis of the magnetic fluid holding part 110 as shown by a one-dot chain line in FIG. (As viewed in the direction in which the extending portion 106 extends), a magnetic force line extending in the radial direction from the central axis and descending downward around the magnetic fluid holding portion 110 is formed. As described above, the holding magnet 114 forms magnetic field lines in the magnetic fluid 48 in a generally radial direction around the extending portion 106 extending from the moving frame 14 toward the second fixed plate 102.

  The locking control coil 116 is a cylindrical coil wound along the inner wall surface of the magnetic fluid holding part 110 having a circular cross section, and the magnetic fluid 112 is filled inside the locking control coil 116. . That is, the locking control coil 116 is wound in a cylindrical shape around the central axis of the magnetic fluid holding part 110 and surrounds the extending part 106 inserted inside thereof. For this reason, when the controller 36 supplies a current in a predetermined direction to the locking control coil 116, a magnetic force line is generated in the magnetic fluid holding unit 110 that is substantially opposite to the magnetic force line generated by the holding magnet 114. Further, in a state where no current flows, the locking control coil 116 hardly affects the lines of magnetic force generated by the holding magnet 114.

  The magnetic fluid 112 has a very high viscosity when fine particles of the suspended ferromagnetic material are connected to each other in a state where the magnetic lines of force are transmitted inside. That is, in a state where no current is passed through the locking control coil 116, the magnetic fluid 112 becomes extremely viscous due to the lines of magnetic force generated by the holding magnet 114. In this state, an extremely high fluid resistance acts on the extending portion 106 extending from the moving frame 14 into the magnetic fluid 112, and the moving frame 14 is substantially locked. As described above, the controller 36 changes the viscosity of the magnetic fluid 112 by applying magnetism to the magnetic fluid 112, and locks or releases the moving frame 14. The locking by the magnetic fluid 112 is extremely stable, and the position of the moving frame 14 that is locked hardly changes even if the moving frame 14 is left to stand for a very long time in a state where its own weight is applied.

  On the other hand, by passing a current in a predetermined direction through the locking control coil 116 disposed inside the magnetic fluid holding unit 110, a magnetic force line in a direction to cancel the magnetic force line formed by the holding magnet 114 can be formed. it can. In this way, by passing an electric current through the locking control coil 116 and canceling at least part of the lines of magnetic force, the lines of magnetic force passing through the magnetic fluid 112 become very weak, and the magnetic fluid 112 is similar to the state where no magnetism is applied. In this state, the viscosity of the magnetic fluid 112 decreases. In this state, the fluid resistance acting on the extension 106 extending into the magnetic fluid 112 is equivalent to the fluid resistance due to a normal colloidal solution, and hardly affects the movement of the moving frame 14. The locking of the moving frame 14 is released.

  FIG. 7 is a simulation result showing an example of the state of the lines of magnetic force in the extending portion receiving portion 108. FIG. 7 (a) shows a state in which no current flows through the locking control coil 116, and FIG. FIG. 6 shows a state in which a current in a direction to cancel the lines of magnetic force generated by the holding magnet 114 is passed through the locking control coil 116.

  In FIG. 7A, strong magnetic lines of force are generated by the holding magnet 114, and the viscosity of the magnetic fluid 112 held in the magnetic fluid holding unit 110 is extremely increased by the magnetic lines of force. On the other hand, in FIG. 7B, a part of the lines of magnetic force generated by the holding magnet 114 is canceled out by the locking control coil 116 disposed inside the magnetic fluid holding unit 110, and the magnetic fluid holding unit 110. The lines of magnetic force that pass through the inside are extremely weak. In this state, the viscosity of the magnetic fluid 112 is low and hardly affects the movement of the moving frame 14.

  Further, in the state shown in FIG. 7A, the magnetic lines of force that pass through the magnetic fluid 112 spread radially around the extending portion 106 (the central axis of the magnetic fluid holding portion 110). The fine particles in the magnetic fluid 112 are bound to each other. For this reason, the fluid resistance acting on the extending portion 106 inserted in the magnetic fluid 112 acts substantially uniformly in any direction. In the present embodiment, as shown in FIG. 5, by providing two extending portion receiving portions 108 on the second fixed plate 102, the moving frame 14 is reliably locked.

  Furthermore, the locking mechanism 104 provided in the present embodiment can also be used as a damper for the movement of the moving frame 14. That is, the locking mechanism 104 moderately weakens the lines of magnetic force generated by the holding magnet 114 by adjusting the current that the controller 36 passes through the locking control coil 116, and gives the magnetic fluid 112 a desired viscosity. Can do. In this way, during the execution of the camera shake correction control, damping can be given to the movement of the moving frame 14 by weakening the magnetism generated by the holding magnet 114 by passing an appropriate current through the locking control coil 116. . Accordingly, the locking mechanism 104 can be used as a damper to suppress overshoot of the moving frame 14 in the camera shake correction control and to improve the accuracy of the camera shake correction control. The locking mechanism 40 in the first embodiment can also be used as a damper.

  According to the actuator of the second embodiment of the present invention, the holding magnet 114 has substantially radial magnetic lines of force around the extending portion 106 extending from the moving frame 14 into the magnetic fluid 112. It is arranged to be formed inside. Therefore, magnetic lines of force generated by the holding magnet 114 are isotropically generated around the extending portion 106, and the viscous resistance of the magnetic fluid 112 acting on the extending portion 106 acts substantially uniformly in each direction. Thereby, the extension part 106 can be strongly held in any direction by the magnetic fluid 112, and the moving frame 14 can be held by a small number of locking mechanisms.

  Further, according to the actuator of the present embodiment, the holding magnet 114 is disposed on the extension line of the extending portion 106 that extends from the moving frame 14 into the magnetic fluid 112, and the locking control coil 116 includes the extending portion. It arrange | positions so that the circumference | surroundings of 106 may be surrounded. Therefore, the extension portion 106 can be held and released by the single holding magnet 114 and the single locking control coil 116.

  Furthermore, according to the actuator of the present embodiment, the controller 36 applies a current to the locking control coil 116 and weakens the magnetism generated by the holding magnet 114 during execution of camera shake correction, thereby reducing the moving frame 14. It is configured to provide damping for movement. Therefore, the locking mechanism 104 can be used as a damper mechanism simply by adjusting the current flowing through the locking control coil 116, and overshoot of the moving frame 14 or the like in the camera shake correction control is suppressed, and the camera shake correction control is performed. Can improve the accuracy.

  As mentioned above, although preferable embodiment of this invention was described, a various change can be added to embodiment mentioned above. In particular, in the above-described embodiment, the actuator of the present invention is applied to a digital camera. However, the actuator of the present invention can also be applied to a film camera or a camera for moving image shooting. In the above-described embodiment, the moving frame is provided with the extending portion, and the fixed plate (second fixed plate) is provided with the extending portion receiving portion. However, the moving frame is provided with the extending portion receiving portion. The extending portion can be provided on the fixing plate (second fixing plate).

  Further, in the above-described embodiment, the holding magnet is provided in the extension portion receiving portion, and the magnetic force lines due to the holding magnet are canceled by the locking control coil, but locking is not required when de-energized. Alternatively, the holding magnet can be omitted. In the configuration in which the holding magnet is omitted, a current is supplied to the locking control coil at the time of locking to increase the viscosity of the magnetic fluid, and the current flowing to the locking control coil is stopped when the locking is released. Reduce viscosity.

  Furthermore, in the above-described embodiment, the locking mechanism is also used as a damper. However, the locking mechanism in the above-described embodiment can be used only as a damper without being used for locking. When the locking mechanism is used only as a damper, the controller controls the driving means to move the movable part, and executes the shake correction control for correcting the shake, and by applying magnetism to the magnetic fluid, It functions as a control device that changes the viscosity of the magnetic fluid and adjusts the damping applied to the movable part. The holding magnet functions as a viscous resistance magnet that increases the viscosity of the magnetic fluid by applying magnetism to the magnetic fluid held by the magnetic fluid holding portion. Furthermore, the locking control coil is arranged so as to cancel the magnetism generated by the viscous resistance magnet so that the viscous resistance acting on the extension portion is weakened by reducing the viscosity of the magnetic fluid. Function as a coil.

  Also, when the locking mechanism is used only as a damper, the holding magnet can be omitted. In this case, the locking control coil functions as a damping adjustment coil arranged so that the viscous resistance acting on the extending portion can be adjusted by changing the viscosity of the magnetic fluid.

DESCRIPTION OF SYMBOLS 1 Camera 2 Lens unit 4 Camera main body 4a Image pick-up element surface 6 Lens barrel 8 Lens 10 Actuator 12 Fixed plate (fixed part)
14 Moving frame (movable part)
14a Ring portion 14b Coil mounting portion 16 Camera shake correction lens 18 Steel ball 20a First drive coil 20b Second drive coil 20c Third drive coil 22a First drive magnet 22b Second drive magnet 22c Third drive Magnet 30 Recess 28 Adsorption yoke 34 Gyro 36 Controller (control device)
40 Locking mechanism 42 Extending part 44 Extending part receiving part 46 Magnetic fluid holding part 48 Magnetic fluid 50a, 50b Holding magnets 52a, 52b Locking control coils 54a, 54b Back yoke 100 Actuator 102 Second fixing plate (fixing) Part)
104 Locking mechanism 106 Extension portion 108 Extension portion receiving portion 110 Magnetic fluid holding portion 112 Magnetic fluid 114 Holding magnet 116 Locking control coil

Claims (9)

An actuator for moving the camera shake correction lens,
A fixed part;
A movable part to which the camera shake correction lens is attached, and a movable part supported to be movable in a plane perpendicular to the optical axis of the camera shake correction lens with respect to the fixed part;
Driving means for driving the movable part;
A magnetic fluid holding part provided on one of the fixed part or the movable part and holding a magnetic fluid inside;
An extending portion provided so as to extend from the other of the fixed portion or the movable portion into the magnetic fluid held by the magnetic fluid holding portion;
By controlling the driving means to move the movable part to perform camera shake correction control for correcting camera shake, and by applying magnetism to the magnetic fluid, the viscosity of the magnetic fluid is changed, and A control device for performing locking and releasing; and
An actuator comprising:   Further, the magnet for holding is arranged so that the magnetic fluid is held by the magnetic fluid by increasing the viscosity of the magnetic fluid by magnetizing the magnetic fluid held by the magnetic fluid holding portion. And a locking control coil arranged so as to cancel the magnetism generated by the holding magnet so that the force for holding the extending portion is weakened by reducing the viscosity of the magnetic fluid. 2. The actuator according to claim 1, wherein when the lock of the movable portion is released, the control device causes a current to flow through the lock control coil so that at least a part of the magnetism of the holding magnet is canceled. .   The holding magnet is disposed so as to form a magnetic force line in the magnetic fluid in a direction substantially perpendicular to the extending portion extending from the fixed portion or the movable portion into the magnetic fluid. The actuator according to claim 2.   The holding magnet is arranged so that different magnetic poles are opposed to both sides of the extending portion extending into the magnetic fluid, and the locking control coil is connected to the magnetic pole of the holding magnet and the extending portion. The actuator according to claim 3, wherein the actuator is disposed between the first and second portions.   The holding magnet is disposed around the extending portion extending into the magnetic fluid from the fixed portion or the movable portion so that a substantially radial magnetic field line is formed in the magnetic fluid. The actuator according to claim 2.   The holding magnet is disposed on an extension line of the extension part extending from the fixed part or the movable part into the magnetic fluid, and the locking control coil surrounds the extension part. The actuator according to claim 5, which is arranged.   The control device is configured to give a damping to the movement of the movable part by passing a current through the locking control coil and weakening the magnetism generated by the holding magnet during the execution of the camera shake correction control. The actuator according to any one of claims 2 to 6. A lens unit with a camera shake correction function,
A lens barrel;
A lens arranged inside the lens barrel;
The actuator according to any one of claims 1 to 7,
A lens unit comprising: A camera with a camera shake prevention function,
The camera body,
The lens unit according to claim 8,
A camera characterized by comprising: