JP2014010380A - Lens actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens actuator used mainly for a camera and a mobile phone, which can achieve the improvement in positional accuracy of a lens holder.SOLUTION: When being moved in a direction of an optical axis OA of a lens relative to a fixing unit 24, a lens holder 21 is moved in a state where guide balls 23A to 23D are in contact with the lens holder 21 by the tension of wires. As a result, the lens holder 21 is supported by the wires and the guide balls 23A to 23D, so that the positional accuracy of the lens holder 21 is improved.

Description

  The present invention relates to a lens actuator mainly used for cameras, mobile phones and the like.

  Lens actuators having an autofocus function are widely used in cameras and mobile phones.

  Such a conventional lens actuator will be described with reference to FIGS.

  FIG. 8 is a sectional view of a conventional lens actuator 20, and FIG. 9 is an exploded perspective view of the lens actuator 20. Here, the lens actuator 20 includes a lens unit 1, a fixed unit 2, an upper spring 3, a lower spring 4, an upper cover 5, and a lower cover 6.

  The lens unit 1 includes a lens holder 7 and an AF (Auto Focus) coil 8. The AF coil 8 is fixed to the lower surface of the upper plate portion 7A of the lens holder 7 made of an insulating resin and having a substantially cylindrical shape.

  The fixed unit 2 includes a plurality of electrodes 11, an inner yoke 12, an outer yoke 13, a plurality of magnets 14, and a holder 15. Here, the inner yoke 12 and the outer yoke 13 are made of iron or the like, and are both cylindrical, and are arranged with the inner yoke 12 on the inner side and the outer yoke 13 on the outer side. A plurality of magnets 14 are disposed between the inner yoke 12 and the outer yoke 13, and the inner yoke 12, the outer yoke 13, and the magnet 14 are fixed to the holder 15.

  Further, a plurality of electrodes 11 are fixed to the holder 15, and the lens unit 1 is disposed between the plurality of electrodes 11.

  The lens unit 1 and the fixed unit 2 are connected to each other, and an upper spring 3 and a lower spring 4 are arranged. The lens unit 1 can move up and down with respect to the fixed unit 2. Here, both ends of the AF coil 8 are connected to the electrode 11 via the upper spring 3, so that a current can flow through the electrode 11.

  The upper cover 5 is disposed above the upper spring 3 and the lower cover 6 is disposed below the lower spring 4.

  The lens actuator 20 configured as described above is disposed inside an electronic device such as a mobile phone, a digital camera, or a portable information device. An imaging element (not shown) such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor is disposed below the lens actuator 20. The image sensor is connected to an electronic circuit (not shown) inside the electronic device.

  The electronic circuit is also connected to the AF coil 8 via the electrode 11, and controls the current flowing through the AF coil 8 based on the signal from the image sensor at the time of imaging, moves the lens unit 1 relative to the fixed unit 2, and automatically Perform focus control.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2008-32768 A

  However, in the conventional lens actuator, for example, when an impact or acceleration is applied to the lens actuator from the outside, the lens unit easily vibrates between the upper spring and the lower spring, and it is difficult to maintain the positional accuracy of the lens unit. It was.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a lens actuator with improved positional accuracy of the lens holder.

  In order to achieve the above object, the present invention particularly includes a wire arranged by bending along a side surface of the lens holder, and a plurality of guide balls arranged between the lens holder and the base, and is generated by the wire. The lens holder is configured to move the lens holder in the direction of the optical axis while rotating the guide ball by pressing the lens holder diagonally.

  According to the present invention, it is provided with a wire that is bent along the side surface of the lens holder, and a plurality of guide balls that are disposed between the lens holder and the base, and the guide ball and the guide ball by tension generated by the wire. Since the lens holder is supported by the wire and the guide ball by moving the lens holder in the optical axis direction in a state where the lens holder is in contact, a lens actuator with improved positional accuracy of the lens holder is provided. Can be provided.

The perspective view which removed the cover of the lens actuator by Embodiment 1 of this invention Exploded perspective view of the lens actuator Top view with the lens actuator cover removed Sectional view with the lens actuator cover removed The perspective view which removed the cover of the lens actuator by Embodiment 2 of this invention Exploded perspective view of the lens actuator Cross section of the lens actuator Sectional view of a conventional lens actuator Exploded perspective view of the lens actuator

(Embodiment 1)
Hereinafter, the lens actuator 100 according to the first embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a perspective view of the lens actuator 100 according to Embodiment 1 of the present invention with the cover 25 removed, and FIG. 2 is an exploded perspective view of the lens actuator 100.

  The lens actuator 100 has, for example, a width in the left-right direction (Y-axis direction) of 5 mm to 20 mm, a depth in the front-rear direction (X-axis direction) of 5 mm to 20 mm, and a height in the vertical direction (Z-axis direction) of 2 mm to 10 mm. The width in the left-right direction and the depth in the front-rear direction are configured with substantially the same dimensions.

  Here, the lens actuator 100 includes a lens holder 21, wires 22 </ b> A and 22 </ b> B, guide balls 23 </ b> A to 23 </ b> D, a fixing unit 24, and a cover 25.

  The lens holder 21 includes a lens barrel having a plurality of lenses, and two guide portions 21A are provided at the corners of the side surface along the optical axis OA direction of the lens. In addition, a substantially rhombic columnar protrusion 21B is disposed at a corner of the lens holder 21 sandwiched between the two guide portions 21A.

  The fixed unit 24 includes a base 31 and terminals 32A, 32B, 33A, 33B. The base 31 includes a pedestal portion 34 and a wall portion 35.

  Here, the pedestal portion 34 includes a circular hole 34A in the center, and includes recesses 34B and 34C around the circular hole 34A.

  Further, the wall portion 35 includes side walls 35A and 35B, and the side walls 35A and 35B are disposed on the pedestal portion 34 along the adjacent sides of the pedestal portion 34. Here, one ends of the side walls 35A and 35B are connected to each other and are substantially L-shaped when viewed from above. Further, recessed end portions 351A and 351B are provided on the open end faces of the side walls 35A and 35B.

  The terminals 32A and 32B are made of conductive metal and are insert-molded in the pedestal portion 34. Here, the locking portion 321A is disposed at one end of the terminal 32A, and the external terminal portion 322A is disposed at the other end. Further, the locking portion 321B is disposed at one end of the terminal 32B, and the external terminal portion 322B is disposed at the other end. The locking portions 321A and 321B protrude into the recesses 34B and 34C, respectively, and the external terminal portions 322A and 322B are arranged along the side surface of the pedestal portion 34.

  The terminals 33A and 33B are made of a conductive metal and are disposed in contact with the upper surface and side surfaces of the wall portion 35. Here, the locking portion 331A is disposed at one end of the terminal 33A, and the external terminal portion 332A is disposed at the other end. Further, the locking portion 331B is disposed at one end of the terminal 33B, and the external terminal portion 332B is disposed at the other end. The locking portions 331A and 331B are disposed so as to protrude from the upper surface of the wall portion 35, and the external terminal portions 332A and 332B are disposed in contact with the side surface of the wall portion 35.

  The fixed unit 24 and the lens holder 21 are combined so that the side surface of the lens holder 21 faces the side walls 35A and 35B of the fixed unit 24 thus configured. Here, the lower surface of the lens holder 21 is disposed on the pedestal portion 34.

  The guide balls 23 </ b> A to 23 </ b> D are disposed between the guide portion 21 </ b> A of the lens holder 21 and the guide portions 351 </ b> A and 351 </ b> B of the fixed unit 24 and rotate when the position of the lens holder 21 changes with respect to the fixed unit 24. The diameter of the guide balls 23A to 23D is preferably 0.5 mm or more and 1.5 mm or less, and is made of metal such as stainless steel, resin, ceramic, or the like.

  Here, in order for the lens holder 21 to suppress vibration in the front-rear and left-right directions with respect to the fixed unit 24, the contact points of the guide balls 23A to 23D with respect to the guide portion 21A and the guide portions 351A and 351B are one point or two points for each. It is preferable that Note that the guide balls 23A and 23B are in contact with each other at a total of four points on one side (for example, the right side) of the guide portions 21A and 351A, and the guide balls 23C and 23D are on the opposite side (for example, the left side) of the guide portions 21A and 351B, respectively. It is desirable to touch at a total of three points. This is because the contact position is stable even if dimensional variation in manufacturing occurs.

  3 is a top view of the lens actuator 100 with the cover 25 removed, and FIG. 4 is a cross-sectional view of the lens actuator 100 with the cover 25 removed.

  Here, two guide balls 23A to 23D are arranged for each of the guide portions 351A and 351B provided diagonally in a top view. Here, when the centers of the four guide balls 23 </ b> A to 23 </ b> D are connected and a virtual region S as shown in FIG. 4 is set, the larger the area of the virtual region S, the vibration of the lens holder 21 in the front / rear / right / left direction with respect to the fixed unit 24. Can be suppressed.

  Since the vibration of the lens holder 21 can be suppressed when the virtual region S is larger, it is desirable that the guide portions 351A and 351B are provided diagonally in the top view of the lens holder 21 and the fixed unit 24.

  The guide balls 23A to 23D can be arranged as long as at least the area of the virtual region S can be secured. That is, the number of guide balls 23A to 23D is three or more, and the virtual region S connecting the centers thereof may have an area, in other words, the virtual region S may be a polygonal arrangement.

  The wires 22A and 22B are made of a shape memory alloy whose shape and tension change due to Joule heat generated in the wires 22A and 22B when an electric current is passed. The wires 22A and 22B are made of, for example, NiTi or NiTiCu, and the elastic modulus can be made in the range of, for example, 20 GPa to 100 GPa.

  Further, the wires 22A and 22B are configured such that when an electric current is passed, the tension increases and the length decreases. The wire 22A is slanted on the lens holder 21 from below the protrusion 21B, and the wire 22B is slanted on the lens holder 21 from above the protrusion 21B. Then, both ends of the wire 22A are fixed to the locking portion 331A and the locking portion 331B, and both ends of the wire 22B are fixed to the locking portion 321B and the locking portion 321A.

  The lens actuator 100 configured as described above is disposed inside an electronic device such as a mobile phone, a digital camera, or a portable information device. An imaging element (not shown) such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor is disposed below the lens actuator 100. The image sensor is connected to an electronic circuit (not shown) inside the electronic device.

  The electronic circuit is connected to the wires 22A and 22B via the terminals 32A, 32B, 33A and 33B. At the time of imaging, the electronic circuit controls the current flowing through the wires 22A and 22B based on the signal from the image sensor, etc. The fixed unit 24 is moved in the direction of the optical axis OA of the lens to perform autofocus control.

  Here, when the lens holder 21 is moved upward along the optical axis OA direction of the lens with respect to the fixed unit 24, a current is passed through the wire 22A. At this time, the tension generated in the wire 22 </ b> A increases, and the lens holder 21 is moved upward with respect to the fixed unit 24. Here, the lens holder 21 is pulled obliquely upward with respect to the fixed unit 24, and the guide balls 23 </ b> A to 23 </ b> D rotate and serve as bearings, so that the lens holder 21 moves smoothly with respect to the fixed unit 24.

  On the other hand, when the lens holder 21 is moved downward with respect to the fixed unit 24, a current is passed through the wire 22B. At this time, the tension generated in the wire 22B increases, and the lens holder 21 is moved downward relative to the fixed unit 24. Here, the lens holder 21 is pulled obliquely downward with respect to the fixed unit 24, and the guide balls 23 </ b> A to 23 </ b> D rotate and serve as bearings, so that the lens holder 21 moves smoothly with respect to the fixed unit 24.

  Further, by adjusting the tension of the wires 22A and 22B, it is possible to adjust the balance of forces such as frictional force, pressing force, wire tension, and gravity, and the balance of the rotational moment due to these forces. As a result, the lens holder 21 can stably move in the direction of the optical axis OA, and variations in the amount and speed of movement of the lens holder 21 in the direction of the optical axis OA can be suppressed.

  That is, when the lens holder 21 moves in the direction of the optical axis OA of the lens with respect to the fixed unit 24, the lens holder 21 is obliquely pressed against the fixed unit 24 by the tension of the wires 22A and 22B to rotate the guide balls 23A to 23D. At the same time, the lens holder 21 is moved stably and smoothly using the tension of the wires 22A and 22B.

  Since the rigidity of the wires 22A and 22B and the guide balls 23A to 23D is high, the position of the lens holder 21 is stably maintained even when an impact or acceleration is applied to the lens actuator 100 from the outside.

  Further, since the rigidity of the wires 22A and 22B and the guide balls 23A to 23D is high, the resonance frequency when the lens holder 21 moves in the optical axis direction can be increased. Thereby, the vibration when the lens holder 21 moves can be quickly attenuated, and the position control accuracy of the lens holder 21 can be improved.

  Note that current may flow through both the wires 22A and 22B, but when the lens holder 21 is moved upward with respect to the fixed unit 24, the current flowing through the wire 22A is made larger than the current flowing through the wire 22B. . Further, when the lens holder 21 is moved downward with respect to the fixed unit 24, the current flowing through the wire 22B is made larger than the current flowing through the wire 22B.

  When the lens holder 21 is stationary with respect to the fixed unit 24, the tension of the wire 22A or the wire 22B is controlled by an electric current to be stationary.

  The lens holder 21 does not need to have a lens barrel as long as the lens can be held. Even when the lens barrel is not provided, the optical axis OA direction and the moving direction of the lens holder 21 can be made to coincide with each other.

  Thus, according to the present embodiment, when the lens holder 21 moves relative to the fixed unit 24, the tension of the wires 22A and 22B presses the lens holder 21 against the fixed unit 24 and rotates the guide balls 23A to 23D. It is configured to make it. Thereby, since the lens holder 21 is supported by the wires 22A and 22B and the guide balls 23A to 23D, the positional accuracy of the lens holder 21 is improved.

  In addition, the wires 22A and 22B are made of a conductive shape memory alloy, and when a current is passed through the wires 22A and 22B, tension is generated in the wires 22A and 22B.

  Furthermore, two wires 22A and 22B are provided, and the wires 22A and 22B are arranged so that the tension generated in the direction of the optical axis OA is in the opposite direction, and the tension generated by the two wires 22A and 22B. When the difference occurs, the lens holder 21 moves, so that the responsiveness of movement in both the upper and lower directions is further improved.

  Further, the lens holder 21 includes a protrusion 21B, and the wires 22A and 22B are placed on the protrusion 21B and bent. Thereby, tension | tensile_strength can be generate | occur | produced by arrangement | positioning with which wire 22A, 22B was decided, and the variation in the movement amount and movement speed of the lens holder 21 to an optical axis OA direction can be suppressed.

(Embodiment 2)
Hereinafter, the lens actuator 400 according to Embodiment 2 of the present invention will be described with reference to FIGS.

  5 is a perspective view of the lens actuator 400 according to Embodiment 2 of the present invention with the cover 45 removed, FIG. 6 is an exploded perspective view of the lens actuator 400, and FIG. 7 is a cross-sectional view of the lens actuator 400.

  The lens actuator 400 includes a lens holder 41, a wire 42, guide balls 43 </ b> A to 43 </ b> D, a fixing unit 52, a cover 45, an upper biasing spring 46, a lower biasing spring 47, and a coil spring 48.

  The fixing unit 52 includes a base 51, terminals 50 </ b> A and 50 </ b> B, and a guide plate 49.

  The lens actuator 400 moves the lens holder 41 upward with respect to the fixed unit 52 by the tension due to the deformation of the wire 42, and when the tension generated by the wire 42 decreases, the lens holder 41 is moved to the fixed unit 52 by the restoring force of the coil spring 48. On the other hand, it is configured to move downward.

  Here, the lens holder 41 is provided with a cylindrical circular hole 414 having the optical axis OA as a central axis, and a substantially cylindrical wall portion 415 is formed outside thereof. The lens holder 41 is a portion that holds the lens barrel in the circular hole 414 (the lens barrel is omitted in the drawing). A protrusion 412 is formed on the lower outer periphery of the wall 415 of the lens holder 41. Further, a coil spring receiving portion 416 protruding from the upper surface of the protrusion 412 is provided in a substantially cylindrical shape. In addition, ball receiving surfaces 413A and 413B that are recessed and come into contact with the guide balls 43A to 43D are formed at two positions on the side surface of the lens holder 41.

  In addition, spring receiving portions 411A and 411B are formed on the upper surface and the lower surface of the portion close to the protrusion 412 in the wall portion 415 of the lens holder 41, respectively. The upper urging spring 46 and the lower urging spring 47 are fixed so as to come into contact with the surfaces of the spring receiving portions 411A and 411B facing the optical axis OA, respectively. The upper urging spring 46 and the lower urging spring 47 are made by bending a metal wire, and have a restoring force to return to the original shape when deformed. The lens holder 41 is combined with an L-shaped guide plate 49 by an upper urging spring 46 and a lower urging spring 47.

  Furthermore, the coil spring 48 is fixed so that the lower end thereof is in contact with the upper plane of the protrusion 412. The coil spring receiving portion 416 is formed in a substantially cylindrical shape, and the lower portion of the coil spring 48 is disposed so as to surround the cylindrical shape of the coil spring receiving portion 416. The upper end portion of the coil spring 48 is fixed so as to contact the inner surface of the cover 45. The coil spring 48 is fixed in a contracted state from the natural length, and applies a downward force to the lens holder 41.

  Next, the configuration of the fixed unit 52, the wire 42, and the guide balls 43A to 43D will be described.

  The base 51 includes a bottom surface portion 511, side surface portions 512A and 512B, terminal receiving surfaces 513A and 513B, and a column portion 514. Terminals 50A and 50B are fixed to terminal receiving surfaces 513A and 513B. The guide plate 49 is fixed so as to be in contact with the side surfaces 512A and 512B, the terminal receiving surfaces 513A and 513B, and the inner surface of the pillar 514.

  The guide plate 49 is made of metal. The guide plate 49 is bent along the inner wall of the column portion 514, and spring receiving portions 491A and 491B are formed at the upper and lower portions of the curved surface, respectively. The upper biasing spring 46 and the lower biasing spring 47 are fixed to the inner side surfaces of the spring receiving portions 491A and 491B, respectively. Both ends of the guide plate 49 are bent along the intersecting line between the side surface portion 512A and the terminal receiving surface 513A and the intersecting line between the side surface portion 512B and the terminal receiving surface 513B, and a guide ball is placed inside the bent portion. Ball receiving surfaces 492A and 492B that come into contact with 43A to 43D are formed.

  The guide balls 43A and 43B are disposed between the ball receiving surface 413B and the ball receiving surface 492B, and the guide balls 43C and 43D are disposed between the ball receiving surface 413A and the ball receiving surface 492A. When the lens holder 41 moves up and down with respect to the guide plate 49, the ball receiving surfaces 413A and 413B are rotated so that the guide balls 43A to 43D rotate while contacting the ball receiving surfaces 413A and 491A or the ball receiving surfaces 413B and 491B. Retained.

  Both ends of the wire 42 are fixed to the conductive terminals 50 </ b> A and 50 </ b> B, and the central portion of the wire 42 is disposed to pass under the protrusion 412 of the lens holder 41. The wire 42 is formed of a shape memory alloy. The shape memory alloy is made of a material such as TiNi or TiNiCu, for example.

  As shown in the cross-sectional view of FIG. 7, the lens actuator 400 is square when viewed from above, and the terminals 50 </ b> A and 50 </ b> B, the protrusion 412, and the column part 514 are arranged at different corners. As schematically shown in FIG. 7, in a plane perpendicular to the optical axis, the force Fw applied by the wire 42 to the lens holder 41 is approximately in the direction from the corner at which the protrusion 412 is disposed toward the corner at which the column portion 514 is disposed. is there. The upper urging spring 46 and the lower urging spring 47 are fixed in a state of being deformed in a direction in which the upper urging spring 46 and the lower urging spring 47 are compressed along a straight line connecting the corner at which the protrusion 412 is disposed. For this reason, in the plane perpendicular to the optical axis, the upper biasing spring 46 and the lower biasing spring 47 are about the angle at which the protrusion 412 is disposed with respect to the lens holder 41 from the corner at which the column portion 514 is disposed. A force Fs in the direction of the direction is applied. The shape and arrangement of the upper biasing spring 46 and the lower biasing spring 47 are designed so that the size of Fs is larger than the size of Fw. Since the size of Fs is larger than the size of Fw, the lens holder 41 is pressed against the guide balls 43A to 43D in the same direction as Fs by the resultant force. Therefore, the guide balls 43A to 43D are moved between the ball receiving surfaces 413A and 413B of the lens holder 41 and the ball receiving surfaces 492A and 492B of the guide plate 49 by the force of the upper biasing spring 46 and the lower biasing spring 47. Is pressed and held. If the guide plate 49 is made of, for example, stainless steel (SUS), it is desirable from the viewpoint of strength, processing accuracy, and cost. It is possible to process the guide plate 49 with high accuracy by forming the guide plate 49 using a method such as bending or forging.

  When operating the lens actuator 400 configured as described above, a voltage is applied between the terminals 50A and 50B to pass a current. When the current flowing through the wire 42 is increased, the Joule heat generated in the wire 42 is increased, whereby the temperature of the wire 42 is increased and the length of the wire 42 is shortened. Further, when the current flowing through the wire 42 is reduced, the Joule heat generated in the wire 42 is reduced, whereby the temperature of the wire 42 is reduced and the length of the wire 42 is extended.

  When the wire 42 expands and contracts, the guide balls 43A and 43B keep contact with the ball receiving surface 413B and the ball receiving surface 492B, and the guide balls 43C and 43D keep contact with the ball receiving surface 413A and the ball receiving surface 492A. For this reason, the lens holder 41 moves in the vertical direction along the optical axis OA.

  The coil spring 48 serving as a driving member has a function of moving the lens holder 41 downward when the current flowing through the wire 42 is reduced. However, as long as it has a function of moving the lens holder 41 downward, a spring having another shape such as a leaf spring can be used in addition to the coil spring. In addition to the spring, for example, the lens actuator 400 can be configured by a structure in which the lens holder 41 is moved downward by a magnetic force generated between a magnet and a magnetic body.

  The upper biasing spring 46 and the lower biasing spring 47 are taken as an example of the pressing member that presses the lens holder 41, and the case where the ball is formed of a metal wire has been described. However, the guide balls 43A to 43D are formed of the ball receiving surface 413A and the ball receiving surface 413A. Any material may be used as long as it has a function capable of being pressed and held between 413B and the ball receiving surfaces 492A and 492B. For example, in addition to a spring formed of a metal wire, it may be configured by a spring of another shape such as a leaf spring or a coil spring, or rubber may be used. The pressing member may have a structure that performs the same function by, for example, a magnetic force between a magnet and a magnetic body.

  As described above, when the lens holder 41 is operated by passing a current through the wire 42, the force Fw exerted on the lens holder 41 by the wire 42 increases. For this reason, when the lens holder 41 is operated by passing a current through the wire 42, the guide balls 43A and 43B are pressed against the ball receiving surface 413B and the ball receiving surface 492B, and the guide balls 43C and 43D are The force pressed against the receiving surface 413A and the ball receiving surface 492A is reduced.

  That is, when the lens holder 41 is operated by passing an electric current through the wire 42, the friction force received by the guide balls 43A and 43B from the ball receiving surface 413B and the ball receiving surface 492B, and the guide balls 43C and 43D and the ball receiving surface 413A. The frictional force received from the ball receiving surface 492A is reduced. From this, it is possible to operate the lens holder 41 smoothly and with high accuracy.

  In addition, since the loss due to the frictional force is small, it is possible to efficiently operate the lens holder 41 by the wire 42, and even when the rigidity of the coil spring 48 is increased, the lens holder 41 can be smoothly operated. it can.

  When the rigidity of the wire 42, the guide balls 43A to 43D, and the coil spring 48 increases, the resonance frequency when the lens holder 41 moves in the optical axis direction and when the lens holder 41 is held at a fixed position increases. As a result, vibration when the lens holder 41 is moved and when the lens holder 41 is held at a fixed position can be reduced, and vibration can be quickly attenuated. Accuracy can be improved.

  Further, the flatness of the ball receiving surface can be improved by forming the ball receiving surfaces 492A and 492B in contact with the guide balls 43A to 43D from metal. Thus, the frictional force between the guide balls 43A to 43D and the ball receiving surfaces 492A and 492B can be further reduced, and the lens holder 41 can be operated more smoothly and with high accuracy.

  In addition, forming the ball receiving surfaces 492A and 492B in contact with the guide balls 43A to 43D from metal has an effect of improving the strength of the ball receiving surfaces. The ball receiving surface can be prevented from being deformed by the force with which the guide balls 43 </ b> A to 43 </ b> D are pressed against the ball receiving surface, and the lens holder 41 can be moved with a large tension of the wire 42. For this reason, the position control of the lens holder 41 can be performed more accurately and at higher speed.

  Further, since the lens holder 41 is operated using the wire 42 made of a shape memory alloy, the generation of electromagnetics can be reduced as compared with the case where the lens holder is moved by a motor or the like. In addition, it is possible to reduce the influence of electromagnetic noise on an image sensor (not shown) disposed under the lens actuator and other peripheral electronic components.

  Furthermore, when the lens holder is moved by a motor or the like, a magnetic force is generated between the motor and the magnetic body, which causes a problem of hindering the movement of the lens holder. According to the configuration of the present embodiment, No magnetic force is generated between them.

  For this reason, for example, the guide balls 43A to 43D can be formed of a magnetic material using stainless steel or the like as a material. Compared with the case where the guide balls are formed of a material such as ceramic, the size and strength of the guide balls The degree of freedom in designing the characteristics can be increased and the cost can be reduced.

  According to the configuration of the present embodiment, since the lens holder 41 is operated by one wire 42, the lens actuator can be configured to be small and light.

  According to the configuration of the present embodiment, since the ball receiving surfaces 492A and 492B are configured by the integral guide plate 49, the relative positions of the ball receiving surfaces 492A and 492B can be arranged with high accuracy. For this reason, the accuracy of the position control of the lens holder 41 can be increased. In particular, by increasing the flatness of the surface that contacts the guide balls 43A to 43D on the ball receiving surface and increasing the parallelism with the optical axis OA of the same plane, the lens tilt when the lens holder 41 moves is prevented. be able to. This can improve the optical characteristics when the lens is moved for focusing.

  Further, since the guide plate 49 has a function of holding the guide balls 43A to 43D and a function of fixing the upper urging spring 46 and the lower urging spring 47, it is possible to reduce the number of parts. For this reason, the cost can be reduced, and further, the position accuracy can be prevented from being lowered due to the variation in assembly, and the position control accuracy of the lens holder 41 can be improved.

  In the above description, the case where the portion where the fixed unit 52 contacts the guide balls 43A to 43D is formed of metal is described. However, the portion where the lens holder 41 contacts the guide balls 43A to 43D can also be formed of metal. Thus, the same effect can be obtained. In addition, it is possible to form a portion where the fixed unit 52 or the lens holder 41 is in contact with the guide balls 43A to 43D using a semiconductor such as silicon. In this case, the strength and flatness of the ball receiving surfaces 413A and 413B. Can be further improved.

  In the above description, the configuration in which the lens holder 41 is moved using the force of the shape memory alloy has been described. However, the guide balls 43A to 43D are disposed between the fixed unit 52 and the lens holder 41, and the fixed unit. 52 or the surface where the lens holder 41 contacts the guide balls 43A to 43D is formed of a metal or a semiconductor, and other forces other than the generation force of the shape memory alloy such as electromagnetic force, electrostatic force and generation force of the piezoelectric body are applied. Even in the configuration in which the lens holder 41 is moved, the position control accuracy of the lens holder 41 can be improved.

  In the above description, the configuration has been described in which the guide balls 43A to 43D rotate when the lens holder 41 moves, but a configuration in which the guide balls 43A to 43D do not rotate when the lens holder 41 moves can also be considered. Even in this case, since the contact area between the fixed unit 52 and the lens holder 41 and the guide balls 43 </ b> A to 43 </ b> D is small, the friction can be reduced and the position control accuracy of the lens holder 41 can be improved. Even in this case, if the contact surface between the fixed unit 52 or the lens holder 41 and the guide balls 43A to 43D is made of metal, an effect of improving the accuracy of the position control of the lens holder 41 by reducing the frictional force can be obtained.

  A configuration in which grease is applied around the guide balls 43A to 43D in order to reduce the frictional force between the fixed unit 52 and the lens holder 41 and the guide balls 43A to 43D is also conceivable.

  The lens actuator according to the present invention can improve the positional accuracy of the lens holder, and is useful mainly for lens operation of a camera, a mobile phone, or the like.

21 Lens holder 21A Guide part 21B Protrusion 22A, 22B Wire 23A-23D, 43A-43D Guide ball 24 Fixing unit 25 Cover 31 Base 32A, 32B, 33A, 33B Terminal 34 Base part 34A Circular hole 34B, 34C Depression 35 Wall part 35A , 35B Side wall 41 Lens holder 42 Wire 45 Cover 46 Upper bias spring 47 Lower bias spring 48 Coil spring 49 Guide plate 50A, 50B Terminal 51 Base 52 Fixing unit 100 Lens actuator 321A, 321B, 331A, 331B Locking portion 322A, 322B, 332A, 332B External terminal portion 351A, 351B Guide portion 400 Lens actuator 411A, 411B, 491A, 491B Spring receiving portion 412 Protrusion 413A, 413 Ball receiving surface 414 a circular hole 415 wall 416 spring receiving portion 492A, 492B ball receiving surface 511 bottom portion 512A, 512B side portions 513A, 513B terminal receiving surface 514 column portion

Claims (7)

A lens holder on which a lens can be placed, a wire arranged by bending along a side surface of the lens holder, a plurality of terminals for fixing both ends of the wire, a base for fixing the plurality of terminals, and the lens A lens actuator comprising a plurality of guide balls arranged between a holder and the base, and configured to move the lens holder while the guide ball and the lens holder are in contact with each other by tension generated by the wire. . The lens actuator according to claim 1, wherein the wire is made of a conductive shape memory alloy, and the tension of the wire increases when a current is passed through the wire. The said wire is provided with two, It arrange | positions so that the direction in which each said wire bends may become an upside down direction, The said lens holder will move, if the tension | tensile_strength which generate | occur | produces in the said two said wires arises. Lens actuator. The lens actuator according to claim 1, wherein the lens holder includes a protrusion, and the wire is bent over the protrusion. The lens actuator according to claim 1, wherein the tension generated by the wire causes the lens holder to move obliquely pressing the lens holder against the base. And a pressing member that presses the lens holder against the base, wherein the force of the pressing member presses the lens holder against the base and reduces the force with which the lens holder is pressed against the base. The lens actuator according to claim 1, wherein a tension generated in the lens is applied to the lens holder. The lens actuator according to claim 1, wherein a contact surface between the base and the guide ball is made of metal.

Images