JP6364337B2 - Lens linear actuator - Google Patents

Description

  The present invention relates to a lens driving linear actuator that drives a lens in the optical axis direction of a lens barrel.

  Conventionally, as an actuator for driving a lens in the optical axis direction of a lens barrel, a lens frame holding a lens, a driving coil fixed to the lens frame, and a driving magnet provided on a fixed frame facing the driving coil There is known a linear actuator having (for example, Patent Document 1). The driving magnet has a structure in which two oppositely magnetized regions are alternately arranged along the moving direction of the lens frame.

  The position of the lens frame in the optical axis direction is detected by an MR magnet fixed to the lens frame and an MR (magnetoresistance effect) sensor provided on the fixed frame. Then, the controller detects the position of the lens frame from the output of the MR sensor, and controls the current that flows through the driving coil based on the detection result.

  However, for example, when a slight deviation occurs in the relative position between the driving coil due to a mounting magnet mounting error or the like, the detection result by the MR sensor and the actual position of the lens frame do not match, and the position by the MR sensor Detection accuracy is lowered, and precise drive control of the lens frame is not possible.

  On the other hand, a linear actuator is known in which a Hall element is fixed to a lens frame, the Hall element is opposed to a driving magnet, and a relative position between the driving magnet and the lens frame is directly detected. (For example, patent document 2).

JP 2004-191453 A JP 2013-222116 A

  However, the linear actuator disclosed in the cited document 2 has a hall element arranged in a driving coil provided in the lens frame, so that the noise included in the detection signal increases, and the position detection with high accuracy cannot be performed. As a result, precise drive control of the lens frame cannot be performed.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a lens driving linear actuator that can detect the position of the lens frame in the optical axis direction with high accuracy and can accurately drive and control the lens frame. .

  One aspect of the linear actuator for lens driving according to the present invention includes: a magnet unit arranged in a fixed portion and arranged in a row so that the magnetic poles of a plurality of magnets are switched; and at least two arranged to face the magnet unit A moving part having a coil part, a lens, and a magnetic flux detection part, and moving in the optical axis direction by the action of the at least two coil parts and the magnet part; opposite to the coil part across the magnet part And a yoke having a notch part for allowing a magnetic flux entering the magnetic flux detection part to pass when the moving part moves, and the notch part of the moving part. A first magnetic flux detection unit that is formed to be at least longer than the length of the magnet unit along the movement direction, and the magnetic flux detection unit is positioned opposite to one of the S pole and the N pole when the movement unit is stationary; Boundary between S pole and N pole And having a second magnetic flux detecting portion located.

  According to the present invention, it is possible to provide a lens driving linear actuator that can detect the position of the lens frame in the optical axis direction with high accuracy and can accurately drive and control the lens frame.

FIG. 1 is a cross-sectional view showing a lens barrel including a lens driving linear actuator according to an embodiment. FIG. 2 is a perspective view showing a lens driving linear actuator incorporated in the lens barrel of FIG. FIG. 3 is an exploded perspective view in which the actuator of FIG. 2 is disassembled. FIG. 4 is a front view of the actuator of FIG. 2 as viewed from the direction of arrow IV. FIG. 5 is a top view of the actuator of FIG. FIG. 6 is a cross-sectional view of the actuator shown in FIG. 2 taken along VI-VI. FIG. 7 is a partially enlarged cross-sectional view in which the region R in FIG. 6 is partially enlarged. FIG. 8 is a cross-sectional view of the actuator of FIG. 2 cut along VIII-VIII.

Hereinafter, a lens driving linear actuator 10 (hereinafter simply referred to as an actuator 10) according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a lens barrel 100 in which the actuator 10 of this embodiment is incorporated. The lens barrel 100 has a plurality of sets of lens groups coaxially along the optical axis. The lens barrel 100 is, for example, an interchangeable lens that can be attached to and detached from a camera body (not shown). The actuator 10 moves one lens 1 among a plurality of lenses arranged coaxially along the optical axis in the optical axis direction.

  FIG. 2 is a perspective view of the actuator 10 incorporated in the lens barrel 100, and FIG. 3 is an exploded perspective view of the actuator 10. 4 is a front view of the actuator 10 of FIG. 2 as viewed from the direction of the arrow IV, and FIG. 5 is a top view of the actuator 10 of FIG. 6 is a cross-sectional view of the actuator 10 of FIG. 2 cut along VI-VI, and FIG. 8 is a cross-sectional view of the actuator 10 of FIG. 2 cut along VIII-VIII. 7 is a partially enlarged cross-sectional view in which the region R in FIG. 6 is partially enlarged.

  The actuator 10 has a block-shaped base 11 that functions as a fixed portion. The base 11 is incorporated and fixed in the lens barrel 100. Both ends of two axes (that is, the main shaft 13 and the sub shaft 14) that support the lens frame 12 so as to be movable in the optical axis direction are fixed to the base 11. The main shaft 13 and the sub shaft 14 are each extended in the optical axis direction and extend in parallel to each other. The lens frame 12 holds the lens 1 described above, and is attached to a position where the optical axis passes through the center of the lens 1. In this state, the lens frame 12 can move in the optical axis direction with respect to the base 11.

  2 and 3, two sets of driving units 20 and 20 for moving the lens frame 12 along the axes 13 and 14 are provided above and below the lens frame 12. Since these two sets of drive units 20 and 20 have a symmetric structure around the optical axis, the same reference numerals are given to components that function in the same manner, and the drive unit 20 in the upper part of the figure is representative. A description of the drive unit 20 in the lower part of the figure will be omitted.

  The drive unit 20 includes two yokes 21 and 22 fixed to the base 11, a magnet unit 24 attached to one yoke 21, and two spacers 25 and 26 disposed between the yokes 21 and 22. Have. The yokes 21 and 22, the magnet portion 24, and the spacers 25 and 26 are disposed in the fixing system of the lens barrel 100 together with the base 11. The two spacers 25, 26 form a gap between the two yokes 21, 22, and secure a moving space for the coil portion 27 described later.

  The driving unit 20 includes a coil unit 27 fixed to the lens frame 12. The lens frame 12 and the coil unit 27 are disposed in the moving system of the lens barrel 100. The coil unit 27 includes a coil holder 28 fixed to the lens frame 12 and two coils 29 attached to the coil holder 28. The coil portion 27 is disposed on the opposite side of the lens frame 12 with the yoke 21 interposed therebetween.

  In FIG. 3, two Hall elements 31 and 32 (a magnetic flux detection unit, a first magnetic flux detection unit, and a second magnetic flux detection unit) are attached to the upper portion of the lens frame 12 side by side in the optical axis direction. Yes. The coil unit 27, the lens 1, and the two Hall elements 31 and 32 function as a moving unit that moves in the optical axis direction together with the lens frame 12.

  A GMR scale 33 is fixed near the main shaft 13 of the lens frame 12. The GMR scale 33 has a plurality of magnet portions (not shown) in which the magnetization directions are alternately reversed, arranged in the optical axis direction. A GMR sensor 34 is attached to a fixed frame (not shown) of the lens barrel 100 facing the GMR scale 33. The GMR sensor 34 detects a change in the magnetic flux of the GMR scale 33 that moves as the lens frame 12 moves, and detects the position of the lens frame 12 in the optical axis direction.

  When assembling the actuator 10 described above, the lens frame 12 holding the lens 1 is slidably attached to the main shaft 13 and the sub shaft 14, and both ends of the main shaft 13 and the sub shaft 14 are fixed to the base 11. In this state, the lens frame 12 is movable along the main shaft 13 and the sub shaft 14 in the optical axis direction. Two Hall elements 31 and 32 and a GMR scale 33 are attached to predetermined positions of the lens frame 12.

  Thereafter, one yoke 21 having a notch hole 21 a (notch portion, through hole) is attached to the base 11. With the yoke 21 attached to the base 11, the yoke 21 is not in contact with the lens frame 12. The yoke 21 is formed in a rectangular plate shape having a length that exceeds the entire length of the moving path of the lens frame 12. The yoke 21 has a notch hole 21a elongated in the longitudinal direction at the center thereof. The cutout hole 21 a passes through the yoke 21 and faces the two Hall elements 31 and 32 attached to the moving lens frame 12. The length of the cutout hole 21a in the optical axis direction is longer than the entire length of the movement path of the Hall elements 31 and 32.

  And the magnet part 24 and the spacers 25 and 26 are attached to the surface opposite to the lens frame 12 of the yoke 21. The spacers 25 and 26 are positioned and attached to the yoke 21 by fitting the bosses 25 a and 26 a into the holes 21 b and 21 c of the yoke 21. The spacers 25 and 26 are attached near both ends of the yoke 21 in the optical axis direction. The thickness of the spacers 25 and 26 in the stacking direction is larger than the thickness of the magnet portion 24.

  The magnet portion 24 has a structure in which the S pole and the N pole are alternately arranged with respect to the moving direction of the lens frame 12, that is, the optical axis direction, and the cutout hole 21a of the yoke 21 is partially provided. It sticks to the yoke 21 between the two spacers 25 and 26 so that it may block. In other words, the cutout hole 21 a of the yoke 21 has a length that exceeds the length of the magnet portion 24 along the optical axis direction. Thereby, the two Hall elements 31 and 32 can detect the magnetic flux of the magnet portion 24 over the entire length of the movement path. That is, the notch 21 a functions as an opening for allowing the magnetic flux detected by the Hall elements 31 and 32 to pass therethrough.

  Further, a coil part 27 is attached so as to sandwich the magnet part 24 between the yoke 21 and the yoke 21. At this time, first, two coils 29 are fixed to the coil holder 28, and the coil portion 27 is fixed to the lens frame 12. In this state, the coil holder 28 is in a non-contact state with the yoke 21 and the magnet portion 24 and can move in the optical axis direction together with the lens frame 12. That is, the coil holder 28 has a length that exceeds the width in the direction orthogonal to the optical axis direction of the magnet portion 24, and has two leg portions 28 a that face the lens frame 12 at both ends in the longitudinal direction. A fitting hole 28b for fitting the boss 12a of the lens frame 12 is provided at the distal end of the leg portion 28a in the extending direction.

  Finally, the other yoke 22 is fixed to the spacers 25 and 26. At this time, the yoke 22 is positioned and attached by fitting the bosses 25 b and 26 b of the spacers 25 and 26 into the holes 22 a and 22 b at both ends in the longitudinal direction of the yoke 22. In this state, the coil portion 27 is disposed in the gap between the magnet portion 24 and the yoke 22 and is not in contact with the yoke 22. In other words, the thickness of the two spacers 25 and 26 in the stacking direction is designed so that the coil portion 27 does not come into contact with the magnet portion 24 or the yoke 22 during the movement.

  A control unit (not shown) of the lens barrel 100 detects the position of the lens frame 12 in the optical axis direction based on the output of the GMR sensor 34, and controls the current flowing through the coil 29 of the coil unit 27 based on the detection result. . However, since the GMR sensor 34 detects the magnetic flux of the GMR scale 22 provided on the lens frame 12 separately from the drive unit 20, if there is an attachment error or the like in the magnet unit 24 or the coil unit 27, In some cases, the actual relative position between the coil unit 27 and the coil unit 27 cannot be accurately detected. In such a case, even if the current flowing through the coil 29 is controlled based on the output of the GMR sensor 34, the lens frame 12 cannot be precisely driven and the drive characteristics deteriorate.

  For this reason, in the present embodiment, Hall elements 31 and 32 for directly detecting the magnetic flux of the magnet unit 24 of the drive unit 20 are provided in the lens frame 12. Then, the detection results by the Hall elements 31 and 32 are fed back to the control unit, and the current flowing through the coil 29 is corrected based on the correction value calculated by the control unit.

  As shown in FIG. 7, the two Hall elements 31 and 32 are fixed to the lens frame 12 so as to be separated from each other along the moving direction of the lens frame 12 (that is, the optical axis direction). More specifically, the two Hall elements 31 and 32 are arranged at positions facing the windings of the two coils 29, respectively. That is, the pitch of the two coils 29 and the pitch of the two Hall elements 31 and 32 are the same. The winding width Wc of each coil 29 is smaller than the width Wm along the optical axis direction of each magnetic pole of the magnet portion 24.

  In addition, when one Hall element 31 is arranged at a position facing one magnetic pole as shown in the drawing, the two Hall elements are arranged so that the other Hall element 32 is arranged at a position facing the boundary of the magnetic pole. The distance between 31 and 32 and the distance between the magnetic poles of the magnet part 24 are set. Thereby, the lens frame 12 can be smoothly moved in the optical axis direction by causing a current having a frequency corresponding to the pitch of the magnetic poles of the magnet portion 24 to flow through the two coils with a phase shifted by 90 °.

  On the other hand, in order to increase the driving force of the lens frame 12 by the driving unit 20, it is desirable to provide yokes 21 and 22 on both sides of the magnet unit 24 and the coil unit 27, respectively. However, when the Hall elements 31 and 32 for directly detecting the magnetic flux of the magnet unit 24 are attached to the lens frame 12 as in the present embodiment, a conventional general configuration is provided between the lens frame 12 and the magnet unit 24. If a yoke having a shape (a yoke not having a notch hole) is provided, the magnetic flux of the magnet portion 24 is closed, and the magnetic flux cannot be detected by the Hall elements 31 and 32.

  For this reason, in the present embodiment, the cutout hole 21a having the shape described above is formed in the yoke 21 provided on the opposite side of the coil portion 27 with respect to the magnet portion 24 so that the magnetic flux of the magnet portion 24 passes through the Hall elements 31 and 32. Was provided. In the present embodiment, the example in which the Hall elements 31 and 32 are attached at positions that do not protrude into the notch 21a has been described. However, since the Hall elements 31 and 32 are brought closer to the magnet portion 24, the Hall element 31 is disposed. , 32 can also be arranged in the notch hole 21a. When the Hall elements 31 and 32 are arranged close to the magnet portion 24, the magnetic flux detection accuracy can be further increased.

  As described above, according to the present embodiment, since the hall elements 31 and 32 are provided on the opposite side of the coil part 27 with the magnet part 24 interposed therebetween, the hall elements 31 and 32 detect signal noise caused by flowing through the coil 29. Therefore, the position of the lens frame 12 with respect to the magnet portion 24 in the optical axis direction can be detected with high accuracy, and the lens frame 12 can be driven and controlled accurately along the optical axis direction.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications and applications are possible within the scope of the gist of the present invention. is there.

  DESCRIPTION OF SYMBOLS 1 ... Lens, 10 ... Actuator, 11 ... Base, 12 ... Lens frame, 13 ... Main shaft, 14 ... Sub shaft, 20 ... Drive part, 21, 22 ... Yoke, 21a ... Notch hole, 24 ... Magnet part, 25, 26 ... Spacer, 27 ... Coil section, 28 ... Coil holder, 29 ... Coil, 31, 32 ... Hall element, 33 ... GMR scale, 34 ... GMR sensor, 100 ... Lens barrel.

Claims (3)

A magnet portion arranged in a fixed portion and arranged in a row so that the magnetic poles of a plurality of magnets are switched;
A moving unit that has at least two coil units disposed opposite to the magnet unit, a lens, and a magnetic flux detection unit and moves in the optical axis direction by the action of the at least two coil units and the magnet unit; ,
A yoke that is disposed on the fixed portion on the opposite side of the coil portion with the magnet portion interposed therebetween, and has a notch portion for allowing a magnetic flux entering the magnetic flux detection portion to pass when the moving portion moves. And
The notch is formed longer than the length of the magnet part at least along the moving direction of the moving part,
The magnetic flux detection unit includes a first magnetic flux detection unit located opposite to one of the S pole and the N pole when the moving unit is stationary, and a second magnetic flux detection unit located at the boundary between the S pole and the N pole. A linear actuator for driving a lens.   The coil portion has a width smaller than the width of the magnetic pole of the magnet in the moving direction of the moving portion, and has a length dimension equal to or larger than the width of the magnet in a direction perpendicular to the moving direction of the moving portion, 2. The linear actuator for driving a lens according to claim 1, wherein two are arranged side by side in the moving direction of the moving part. A magnet portion arranged in a fixed portion and arranged in a row so that the magnetic poles of a plurality of magnets are switched;
A moving unit that has a coil unit disposed opposite to the magnet unit, a lens, and a magnetic flux detection unit and moves in the optical axis direction by the action of the coil unit and the magnet unit;
A yoke that is disposed in the fixed part opposite to the coil part across the magnet part, and has a through-hole through which the magnetic flux entering the magnetic flux detection part passes when the moving part moves;
A linear actuator for driving a lens.