JP2012112489A - Leaf spring and lens driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leaf spring and a lens driving device which are further improved in impact resistance.SOLUTION: The leaf spring (24) includes: an annular inner peripheral side end (241); an outer peripheral side end (242) provided apart from the inner peripheral side end in a radial direction; N arm parts (243) provided along a circumferential direction for connection between the inner peripheral side end and the outer peripheral side end; N inner peripheral side connections (244) protruding outward in the radial direction from the inner peripheral side end so as to connect the inner peripheral side end and the N arm parts; and N outer peripheral side connections (245) protruding inward in the radial direction from the outer peripheral side end so as to connect the outer peripheral side end and the N arm parts. The inner peripheral side end (241) includes a buffering displacement part (241a) in at least one place between adjacent inner peripheral side connections (244).

Description

  The present invention relates to a lens driving device, and in particular, is provided on both sides in the optical axis direction of a lens holder (columnar movable portion) that holds a lens assembly (lens barrel), and the lens holder has a diameter relative to a fixed portion including a base member. The present invention relates to a leaf spring (support member; elastic member) that is supported so as to be displaceable in the optical axis direction while being positioned in a direction.

  A portable small camera is mounted on a camera-equipped mobile phone. This portable small camera uses an autofocus lens driving device. Conventionally, various autofocus lens driving devices have been proposed.

  For example, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2009-210055) discloses a lens driving device with improved impact resistance.

  As a driving source (driving method) used in such a lens driving device, a VCM method using a voice coil motor (VCM) is generally adopted. In a VCM type lens driving device, a columnar movable part (lens + lens holder) including a lens is supported so as to be displaceable in the optical axis direction (center axis direction) in a state of being radially positioned with respect to the fixed part. A supporting member (elastic member) is used. As such a support member (elastic member), a pair of leaf springs provided on both sides in the optical axis direction of a lens holder (columnar movable portion) that holds a lens assembly (lens barrel) is generally used. . The pair of leaf springs support the lens holder (columnar movable portion) so as to be displaceable in the optical axis direction in a state where the lens holder (columnar movable portion) is positioned in a radial direction with respect to a housing (tubular fixed portion) arranged around the lens holder. Of the pair of leaf springs, one is called an upper leaf spring and the other is called a lower leaf spring.

  Various leaf springs with improved impact resistance have been proposed.

  For example, Patent Document 1 discloses an inexpensive leaf spring with improved impact resistance. Each of the leaf springs has an inner circumferential side end portion (inner ring portion) and an outer circumferential side end portion (outer ring portion) formed in an annular shape, and N pieces provided along the circumferential direction in order to connect between them. It consists of an arm part. Each arm portion extends along the circumferential direction. The inner peripheral side connecting portion between the inner peripheral end and each arm portion protrudes radially outward from the inner peripheral end. The outer peripheral side connection part between the outer peripheral side end part and each arm part protrudes radially inward from the outer peripheral side end part. At least one of the plate width of the inner peripheral side root portion and the plate width of the outer peripheral side root portion of the arm portion is wider than the plate width of the central portion in the longitudinal direction of the arm portion.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-322540) discloses a camera module that prevents stress concentration on the base portion (root portion) of the bridging portion (arm portion) of the leaf spring due to impact and has excellent impact resistance. Disclosure.

  The leaf spring disclosed in Patent Document 2 includes an outer ring portion, an inner ring portion that is displaced with respect to the outer ring portion, and three bridging portions that support the inner ring portion with respect to the outer ring portion ( Arm portion). The bridging portion extends along the inner peripheral edge of the outer ring portion and the outer peripheral edge of the inner ring portion in a ring-shaped gap formed between the outer ring portion and the inner ring portion. The bridging portion has a slit that is a means for preventing stress concentration.

  Further, Patent Document 3 (Japanese Patent Application Laid-Open No. 2008-116622) is designed to relieve stress at the time of impact acting on a leaf spring that elastically supports a holder that holds a lens, thereby preventing plastic deformation of the leaf spring. A lens driving device is disclosed.

  The lens driving device disclosed in Patent Document 3 is a pair of a holder that holds a lens, a fixing member that is disposed outside the holder, and a holder and a fixing member that are respectively connected on the upper side and the lower side. A spring member (plate spring). The leaf spring includes a holder-side arc part (inner peripheral side fixed ring part) whose one end is fixed to the holder side, a fixed member side arc part (outer peripheral side fixed ring part) whose one end is fixed to the fixing member, and the holder side It comprises a plurality of arm portions that connect the arc portion (inner peripheral side fixed ring portion) and the fixed member side arc portion (outer peripheral side fixed ring portion). Each arm part is comprised from the 1st circular arc part, the 2nd circular arc part, and the substantially U-shaped curved part. A 1st circular arc part is extended toward the outer peripheral side protrusion piece direction connected to an outer peripheral side fixed ring part along a substantially circumferential direction from the inner peripheral side protrusion piece connected to an inner peripheral side fixed ring part. The second arc portion extends from the outer peripheral side protruding piece toward the inner peripheral side protruding piece direction along the substantially circumferential direction. The bending portion connects the first arc portion and the second arc portion and protrudes outward in the holder radial direction. The bending portion is provided at a position where the bending moment with respect to the bending of the arm portion in the driving direction is substantially zero.

Japanese Patent Laying-Open No. 2009-210055 (FIG. 3) JP 2007-322540 A (FIG. 1) JP 2008-116622 A (FIG. 2)

  By the way, the lower leaf spring has an inner peripheral side end (inner ring part) fixed to the lower side of the resin lens holder, and an outer peripheral side end part (outer ring part) between the yoke and the base member (actuator base). It is sandwiched between and fixed. More specifically, the inner peripheral side end portion (inner ring portion) of the lower leaf spring is fixed (supported) to the lower end of the lens holder by thermally welding a support portion provided at the lower end of the resin lens holder. . Therefore, the lower leaf spring is fixed to the optical axis direction in which the lens holder moves up and down by this heat welding.

  However, in the lateral direction (radial direction), there is play in the lower leaf spring. Therefore, in the drop impact test of the portable small camera, the inner ring portion is distorted in the longitudinal direction between the support portions of the inner ring portion of the lower leaf spring. As a result, a part of the inner ring portion is deformed in the direction of rising from the lower end of the lens holder, and interferes with a base member (actuator base) disposed at a position facing the lower leaf spring. For this reason, there is a possibility that the lens holder is inclined with respect to the fixed portion including the base member (actuator base).

  Further, there is a possibility that a problem that the characteristics of the lens driving device deteriorate due to the inclination of the lens holder and a problem that dust occurs due to the lower leaf spring coming into contact with the base member may occur.

  The above-mentioned Patent Documents 1 to 3 have no recognition (description) about the above-mentioned problems, and the leaf springs disclosed in the above-mentioned Patent Documents 1 to 3 are not provided with any measures to prevent the above-mentioned problems. Not.

  The subject of this invention is providing the leaf | plate spring and lens drive device which improved the impact resistance more.

  Another object of the present invention is to provide a lens driving device capable of suppressing deterioration of characteristics.

  Still another object of the present invention is to provide a lens driving device capable of preventing dust generation.

  According to the first aspect of the present invention, the columnar movable portion (14, 16) disposed in the central portion is used as the fixed portion (12, 18, 20, 28) disposed in the outer periphery of the movable portion. On the other hand, the leaf spring (24) is supported so as to be displaceable in the central axis (O) direction in a state of being positioned in the radial direction, and the leaf spring (24) is formed with an annular inner peripheral side end portion (241). In order to connect between the outer peripheral side end (242) spaced apart radially outward from the inner peripheral side end and the inner peripheral end and the outer peripheral end along the circumferential direction. The provided N (N is an integer greater than or equal to 2) arm portions (243), projecting radially outward from the inner peripheral end, and connecting the inner peripheral end and the N arm portions. N inner peripheral side connecting portions (244) and N outer peripheral sides projecting radially inward from the outer peripheral end portion to connect the outer peripheral end portion and the N arm portions A connection portion (245), and the inner peripheral side end portion (241) has a buffer displacement portion (241a) at least at one position between the adjacent inner peripheral side connection portions (244). A leaf spring (24) is obtained.

  In the leaf spring (24) according to the first aspect of the present invention, the inner peripheral side connecting portion (244) has an opening (244a) for attaching the inner peripheral side end portion (241) to the movable portion (14, 16). May have. The buffer displacement portion (241a) may be selected from any one of a substantially U shape, Ω shape, and S shape, for example. The material of the leaf spring (24) is preferably made of high hardness stainless steel.

  According to the second aspect of the present invention, the lens holder (14) having the cylindrical portion (140) for holding the lens assembly, and the fixing portions (12, 18,. 20, 28), an upper leaf spring (22) for connecting the lens holder and the fixing portion on its upper side, and a lower leaf spring (24) for connecting the lens holder and the fixing portion on its lower side. In the lens driving device (10), the lower leaf spring (24) is fixed to the lower inner peripheral end (241) of the annular shape fixed to the lower end of the lens holder, and to the lower inner periphery. In order to connect the lower outer peripheral side end (242) spaced apart radially outward from the side end and the lower inner peripheral end and the lower outer peripheral end in the circumferential direction. N arms (243) provided along the lower arm portion (243), N lower inner peripheral side connecting portions (244) projecting radially outward from the inner peripheral end portion and connecting the lower inner peripheral end portion and the N lower arm portions; N lower outer peripheral connection portions (245) that project radially inward from the outer peripheral end portion and connect the lower outer peripheral end portion and the N lower arm portions. The lower inner peripheral end portion (241) has a buffer displacement portion (241a) at least at one position between the adjacent lower inner peripheral coupling portions.

  In the lens driving device (10) according to the second aspect of the present invention, the lens holder (14) has N support portions (144) for supporting the lower inner peripheral end portion of the lower spring at the lower end thereof. ). In this case, the N lower inner peripheral side coupling portions (244) have openings (244a) for attaching the lower inner peripheral end portions with the N support portions of the lens holder. The buffer displacement portion (241a) may be selected from any one of a substantially U shape, Ω shape, and S shape, for example. The upper leaf spring (22) is an annular upper inner peripheral end (221) fixed to the upper end of the lens holder (14), fixed to the fixed portion, and radially outward from the upper inner peripheral end. N pieces (N is 2) provided along the circumferential direction in order to connect the upper outer peripheral end (222) provided at a distance from the upper inner peripheral end and the upper outer peripheral end. (The above integer) upper arm portion (223) and N upper sides that project radially outward from the upper inner peripheral end and connect the upper inner peripheral end and the N upper arm portions. An inner peripheral side connection portion (224) and N upper outer peripheral side connection portions that project radially inward from the upper outer peripheral end portion and connect the upper outer peripheral end portion and the N upper arm portions ( 225), and the N upper outer peripheral side coupling portions (225) are connected to the N upper arm portions (223) from the upper outer peripheral end portion (222). Preferably it has a curved shape to the base portion. The material of the lower leaf spring (24) and the upper leaf spring (22) is preferably made of high hardness stainless steel.

  The reference numerals in the parentheses are given for ease of understanding, and are merely examples, and of course are not limited thereto.

  In the present invention, since the buffer displacement portion is provided at at least one position between the adjacent inner peripheral side connecting portions at the inner peripheral end portion of the leaf spring, the inner peripheral end portion and the arm portion are prevented from being deformed. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the lens drive device by one embodiment of this invention, (A) is a top view of a lens drive device, (B) is a front view of a lens drive device, (C) is a lens drive device. It is a right view. It is a disassembled perspective view of the lens drive device shown in FIG. It is a top view of the lower leaf | plate spring which concerns on one embodiment of this invention. FIG. 4 is a partially enlarged plan view showing an enlarged main part of a lower leaf spring shown in FIG. 3. It is a perspective view which shows the state which attached the lower inner peripheral side edge part of the related lower leaf | plate spring to the lower end side of a lens holder. It is a figure which shows the modification of the buffer displacement part shown in FIG. It is a top view of the upper side leaf | plate spring which concerns on one embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  A lens driving device 10 according to an embodiment of the present invention will be described with reference to FIGS. 1A is a plan view of the lens driving device 10, FIG. 1B is a front view of the lens driving device 10, and FIG. 1C is a right side view of the lens driving device 10. FIG. 2 is an exploded perspective view of the lens driving device 10.

  Here, as shown in FIGS. 1 and 2, an orthogonal coordinate system (X, Y, Z) is used. In the state shown in FIGS. 1 and 2, in the orthogonal coordinate system (X, Y, Z), the X axis is the front-rear direction (depth direction), the Y axis is the left-right direction (width direction), and the Z axis is The vertical direction (height direction). In the example shown in FIGS. 1 and 2, the vertical direction Z is the optical axis O direction of the lens.

  However, in the actual use situation, the optical axis O direction, that is, the Z-axis direction is the front-rear direction. In other words, the upward direction of the Z axis is the forward direction, and the downward direction of the Z axis is the backward direction.

  The illustrated lens driving device 10 is a VCM type lens driving device using a voice coil motor (VCM) as a driving source (driving method).

  The illustrated lens driving device 10 is provided in a camera-equipped mobile phone capable of autofocusing. The lens driving device 10 is for moving a lens assembly (lens barrel) (not shown) in the direction of the optical axis O. Therefore, the optical axis O is a drive axis (center axis). The lens driving device 10 is also called an actuator. The lens driving device 10 includes a base member (actuator base) 12 disposed on the lower side (rear side) in the Z-axis direction (optical axis O direction). A sensor substrate (not shown) is disposed under the base member (actuator base) 12 (rear part). The sensor board mounts electronic components such as an image sensor and a clock generation source. The lens driving device 10 and the sensor substrate are covered with a shield case (not shown). The shield case is for shielding electromagnetic noise generated from the sensor substrate.

  A camera module is configured by a combination of the lens driving device 10, the sensor substrate, the image sensor, and the shield case.

  The imaging element captures a subject image formed by the lens assembly and converts it into an electrical signal. The imaging device is configured by, for example, a CCD (charge coupled device) type image sensor, a CMOS (complementary metal oxide semiconductor) type image sensor, or the like.

  The lens driving device 10 includes a lens holder 14 having a cylindrical portion 140 for holding a lens assembly (lens barrel), and a driving coil 16 fixed to the lens holder 14 so as to be positioned around the cylindrical portion 140. And a pair of plates provided on both sides of the cylindrical portion 140 of the lens holder 14 in the optical axis O direction, the permanent magnet 18 disposed opposite to the drive coil 16, the yoke 20 holding the permanent magnet 18, and the cylindrical portion 140 of the lens holder 14. Springs 22 and 24. The pair of leaf springs 22 and 24 support the lens holder 14 so as to be displaceable in the optical axis O direction with the lens holder 14 positioned in the radial direction. Of the pair of leaf springs 22, 24, one leaf spring 22 is called an upper leaf spring, and the other leaf spring 24 is called a lower leaf spring.

  Further, as described above, in the actual use situation, the upward direction in the Z-axis direction (optical axis O direction) is the forward direction, and the downward direction in the Z-axis direction (optical axis O direction) is the backward direction. Therefore, the upper leaf spring 22 is also called a front spring, and the lower leaf spring 24 is also called a rear spring.

  The upper leaf spring (front spring) 22 and the lower leaf spring (rear spring) 24 are made of a metal such as stainless steel or beryllium copper, for example. The upper leaf spring (front spring) 22 and the lower leaf spring (rear spring) 24 are manufactured by pressing a predetermined thin plate or etching using a photolithography technique. Note that the etching process is more preferable than the press process. This is because residual stress does not remain in the leaf spring in the etching process.

  Further, as the material of the leaf spring, it is preferable to use stainless steel, particularly high hardness stainless steel, rather than beryllium copper. The reason is that beryllium compounds are known to be highly toxic, and from the environmental point of view, it is desired to use materials other than beryllium copper (beryllium-free) as the material of the leaf spring. . In addition, as high hardness stainless steel, NTK S-4 by Nippon Metal Industry Co., Ltd. or NTK 301 (SUS301) can be used, for example.

  The yoke 20 has a substantially square cylindrical shape. That is, the yoke 20 includes a substantially square cylindrical outer cylinder portion 202, a rectangular ring-shaped end portion 204 that extends to the inside of the outer cylindrical portion 202 at the upper end (front end) of the outer cylindrical portion 202, and the ring. And two inner vertical extending portions 206 extending vertically downward in parallel with the optical axis O at both ends opposed to each other in the front-rear direction X inside the end portion 204. The outer cylindrical portion 202 is called a shield yoke, and each of the two inner vertical extending portions 206 is called a back yoke. In the outer cylinder portion (shield yoke) 202, a central portion 202-1 of a pair of sides facing each other in the left-right direction Y projects outward in the radial direction.

  Therefore, the drive coil 16 also has a substantially square tube shape that matches the shape of the square tube-shaped yoke 20. The cylindrical portion 140 of the lens holder 14 has two contact portions 140-1 that protrude outward in the radial direction at positions corresponding to the left-right direction Y of the drive coil 16. The two flat portions 162 of the drive coil 16 are bonded to the two contact portions 140-1. That is, the drive coil 16 is bonded to the two contact portions 140-1 of the cylindrical portion 140.

  On the other hand, the permanent magnet 18 is composed of four permanent magnet pieces 182 having a triangular cross section disposed at the four corners of the yoke 20 and two permanent magnet pieces 184 having a rectangular cross section facing the two flat portions 162 of the drive coil 16. Composed. Specifically, the two permanent magnet pieces 184 having a rectangular cross section are attached to the inner wall of the central portion 202-1 of the pair of sides of the outer cylindrical portion 202 of the yoke 20. That is, the permanent magnet 18 is composed of a total of six permanent magnet pieces 182 and 184 arranged at the four corners and the two sides of the rectangular cylindrical outer cylinder portion 202 of the yoke 20.

  A permanent magnet 18 is disposed on the inner peripheral surface of the outer cylindrical portion (shield yoke) 202 of the yoke 20 at a distance from the drive coil 16.

  The upper leaf spring (front spring) 22 is disposed on the upper side (front side) of the lens holder 14 in the optical axis O direction, and the lower leaf spring (rear side spring) 24 is disposed on the lower side (rear side) of the lens holder 14 in the optical axis O direction. Be placed. The upper leaf spring (front spring) 22 and the lower leaf spring (rear spring) 24 have substantially the same configuration.

  The upper leaf spring (front spring) 22 includes an upper inner peripheral end 221 attached to the upper end of the lens holder 14 as described later, and an upper outer periphery attached to the ring-shaped end 204 of the yoke 20 as described later. Side end portion 222. Four upper arm portions 223 are provided between the upper inner peripheral end 221 and the upper outer peripheral end 222. Each upper arm portion 223 connects the upper inner peripheral end 221 and the upper outer peripheral end 222.

  Similarly, the lower leaf spring (rear spring) 24 is attached to the lower inner peripheral end 241 attached to the lower end of the lens holder 14 as will be described later, and to the actuator base (base member) 12 as described later. And a lower outer peripheral end 242 to be attached. Four lower arm portions 243 are provided between the lower inner end portion 241 and the lower outer end portion 242. Each lower arm portion 243 connects the lower inner peripheral end 241 and the lower outer peripheral end 242.

  The inner peripheral side end (222; 242) is also called an inner ring part (inner ring part), and the outer peripheral side end part (224; 244) is also called an outer ring part (outer ring part).

  Further, a more detailed configuration (structure) of the upper leaf spring (front spring) 22 will be described later with reference to FIG. 7, and a more detailed configuration (structure) of the lower leaf spring (rear spring) 24 will be described. Will be described later with reference to FIGS.

  Next, a method for attaching the upper leaf spring (front spring) 22 will be described.

  The upper inner peripheral end 221 of the upper leaf spring (front spring) 22 is sandwiched and fixed between the lens holder 14 and the stopper 26. In other words, the stopper 26 is fitted to the lens holder 14 so as to sandwich the upper inner end 221 of the upper leaf spring (front spring) 22 between the upper end of the lens holder 14.

  The stopper 26 has the following functions. That is, the stopper 26 has a function of bringing the upper inner peripheral end 221 of the upper leaf spring (front spring) 22 into close contact with the lens holder 14 with high accuracy. As a result, variations in VCM (voice coil motor) characteristics can be improved. The stopper 26 has a function of improving the adhesive strength of the upper leaf spring (front spring) 22. Thereby, the impact resistance of the lens driving device 10 is improved. Further, the stopper 26 has a function of preventing deformation of the upper leaf spring (front spring) 22 when the lens driving device 10 is dropped. This also improves the impact resistance of the lens driving device 10. The stopper 26 has a function of determining the mechanical stroke of the lens driving device 10.

  On the other hand, an upper outer peripheral end 222 of the upper leaf spring (front spring) 22 is sandwiched and fixed between the ring-shaped end 204 of the yoke 20 and the cover 28. More specifically, the cover 28 has a square ring shape with a circular opening 28a at the center. The cover 28 has four protrusions 282 that protrude downward at its four corners. The upper outer peripheral side end 222 of the upper leaf spring 22 has four through holes 222a through which the four protrusions 282 pass. The ring-shaped end portion 204 of the yoke 20 has four insertion holes 204a into which the four protrusions 282 are inserted at the four corners. Accordingly, the four protrusions 282 of the cover 28 are fitted into the four fitting holes 204 a of the ring-shaped end portion 204 of the yoke 20 through the four through holes 222 a of the upper outer peripheral side end portion 222 of the upper leaf spring 22. .

  A ring-shaped plate 34 for adjusting the spring constant is disposed between the upper outer peripheral end 222 of the upper leaf spring 22 and the cover 28.

  Next, a method for attaching the lower leaf spring (rear spring) 24 will be described.

  A lower outer peripheral end 242 of the lower leaf spring (rear spring) 24 is fixed to the yoke 20 via an annular spacer 30. In other words, the spacer 30 and the lower outer peripheral end 242 of the lower leaf spring (rear spring) 24 are sandwiched and fixed between the yoke 20 and the base member (actuator base) 12. More specifically, the base member (actuator base) 12 has a square ring shape with a circular opening 12a at the center. The base member (actuator base) 12 has four protrusions 122 protruding upward at the four corners. The lower outer peripheral end 242 of the lower leaf spring 24 has four through holes 242a through which the four protrusions 122 pass. The spacer 30 has an insertion hole 30a into which these four protrusions 122 are inserted. Accordingly, the four protrusions 122 of the base member (actuator base) 12 are fitted into the four fitting holes 30 a of the spacer 30 through the four through holes 242 a of the lower outer peripheral end 242 of the lower leaf spring 24. The

  As will be described later with reference to FIG. 5, the lower inner peripheral end 241 of the lower leaf spring (rear spring) 24 is fixed (supported) to the lower end (rear end) side of the lens holder 14. The

  The lower end of the lens holder 14 is loosely fitted in the circular opening 12 a of the base member (actuator base) 12. In other words, the lower end of the lens holder 14 is opposed to the base member (actuator base) 12 with its circular opening 12a with a clearance.

  The base member (actuator base) 12 is equipped with an IR cut filter (not shown). The base member (actuator base) 12 is manufactured by injection molding. The material of the base member (actuator base) 12 is made of an engineering plastic such as a liquid crystal polymer (LCP). As is well known, LCP is a relatively inelastic resin.

  The base member (actuator base) 12 is opposed to each other at the four corners in the left-right direction Y so as to sandwich the ring-shaped base portion 120 and the central portion 202-1 of the pair of sides of the outer cylindrical portion 202 of the yoke 20. And four projecting portions 124 projecting upward in the vertical direction Z from the base portion 120.

  The four protrusions 124 have protrusions 124-1 formed at the four corners of the base member (actuator base) 12. Each protrusion 124-1 has a substantially cylindrical shape extending in the vertical direction Z. In the illustrated example, the diameter of each protrusion 124-1 is about 0.1 mm. Each projecting portion 124-1 has a substantially conical tip portion 124-1 a at the top thereof. Further, the lower end 124-1 b of each protrusion 124-1 is located above the substrate contact surface of the base member (actuator base) 12.

  A female screw 142 is cut on the inner peripheral wall of the cylindrical portion 140 of the lens holder 14. On the other hand, although not shown, a male screw that is screwed into the female screw 142 is cut on the outer peripheral wall of the lens assembly (lens barrel). Therefore, in order to attach the lens assembly (lens barrel) to the lens holder 14, the lens assembly (lens barrel) is rotated around the optical axis O with respect to the cylindrical portion 140 of the lens holder 14 and along the optical axis O direction. By screwing together, the lens assembly (lens barrel) is accommodated in the lens holder 14 and joined together by an adhesive or the like.

  The lens driving device 10 includes a power supply member 32 disposed between a lower leaf spring (rear spring) 24 and a base member (actuator base) 12. The power supply member 32 is for supplying power to the drive coil 16.

  The power supply member 32 is sandwiched between the lower leaf spring 24 and the base member (actuator base) 12 and is electrically connected to a pair of lead wires (not shown) of the drive coil 16. 322 and a pair of sheet metal terminals 324 having springiness extending downward from the flexible printed circuit board 322 to the sensor board.

  By energizing the drive coil 16 via the power supply member 32, the lens holder 14 (lens assembly) is positioned in the direction of the optical axis O by the interaction between the magnetic field of the permanent magnet 18 and the magnetic field generated by the current flowing through the drive coil 16. It is possible to adjust.

  In the lens driving device 10, the combination of the lens holder 14 that holds the lens assembly and the driving coil 16 functions as a columnar movable portion (14, 16) disposed in the center portion. Further, the combination of the base member (actuator base) 12, the permanent magnet 18, the yoke 20, and the cover 28 is a fixed portion (12, 18, 20, 28) disposed on the outer periphery of the movable portion (14, 16). Work as.

  Next, with reference to FIG. 3 and FIG. 4, the structure of the lower leaf | plate spring 24 which concerns on one embodiment of this invention is demonstrated in detail. FIG. 3 is a plan view of the lower leaf spring 24, and FIG. 4 is a partially enlarged plan view showing an enlarged main part of the lower leaf spring 24.

  As described above, the lower leaf spring (rear spring) 24 is fixed to the lower inner peripheral end 241 fixed to the lower end of the lens holder 14 and the base member (actuator base) 12 serving as a fixed portion. Four lower sides provided along the circumferential direction to connect the lower outer peripheral end 242 fixed to the lower outer peripheral end 241 and the lower outer peripheral end 242 Arm portion 243. The lower inner peripheral side end 241 has a substantially annular shape. The lower outer peripheral end 242 is provided away from the lower inner peripheral end 241 radially outward. In other words, the lower outer peripheral end 242 has a larger radius than the lower inner peripheral end 241. Each lower arm portion 243 extends along the circumferential direction. The four lower inner peripheral side connecting portions 244 that connect the lower inner peripheral end portion 241 and the four lower arm portions 243 project radially outward from the lower inner peripheral end portion 241. ing. Four lower outer peripheral side connecting portions 245 that connect the lower outer peripheral end portion 242 and the four lower arm portions 243 project radially inward from the lower outer peripheral end portion 242.

  As shown in FIG. 5, the lens holder 14 has four support portions 144 for supporting the lower inner peripheral end portion 241 of the lower spring 24 at the lower end thereof.

  The four lower inner peripheral side connecting portions 244 have openings 244 a for attaching the lower inner peripheral end portions 241 with the four support portions 144 of the lens holder 14.

  In the lower leaf spring 24 according to the present embodiment, the lower inner peripheral end 241 has a buffer displacement portion 241a at one location between the adjacent lower inner peripheral connecting portions 244.

  As shown in FIG. 4, the illustrated buffer displacement portion 241 a has an Ω shape.

  In contrast, the associated lower leaf spring 24 '(see FIG. 5) does not have the buffer displacement portion 241a. Therefore, in the related lower leaf spring 24 ′, the lower inner peripheral end 241 and the lower arm 243 are deformed in the drop test of the portable small camera. Since the lower leaf spring 24 according to the present embodiment has four buffer displacement portions 241a, the lower inner peripheral end portion 241 and the lower arm portion 243 are removed in a drop test of the portable small camera. It is possible to prevent deformation.

  Next, in order to better understand the effect of the lower leaf spring 24 according to the first embodiment of the present invention, a problem of the related lower leaf spring 24 'will be described with reference to FIG. FIG. 3 is a perspective view illustrating a state in which the lower inner peripheral end 242 of the related lower leaf spring 24 ′ is attached to the lower end side of the lens holder 13.

  The related lower leaf spring 24 ′ has the same configuration as the lower leaf spring 24 shown in FIG. 3 except that the buffer displacement portion 241 a is not provided.

  The lower inner peripheral end 241 of the related lower leaf spring 24 ′ is fixed to the lower end of the lens holder 14 as follows. First, the four support portions 144 provided at the lower end of the lens holder 14 are fitted into the openings 244 a provided in the four lower inner peripheral side connection portions 244. Then, the four support parts 144 are heat-welded. As a result, the lower inner peripheral end 241 of the related lower leaf spring 24 ′ is fixed to the lower end of the lens holder 14.

  Therefore, by this thermal welding, the related lower leaf spring 24 ′ is fixed with respect to the optical axis O direction in which the lens holder 14 moves up and down.

  However, in the lateral direction (radial direction), there is play in the associated lower leaf spring 24 '. Assume that an impact in a direction indicated by an arrow A in FIG. 5 is applied to the lens holder 14 by a drop impact test of the portable small camera. In response to this impact, the lower arm portion 243 is pulled in the direction indicated by the arrow B in FIG. 5 at the support portion 144 of the lower inner peripheral end (inner ring portion) 241 of the associated lower leaf spring 24 ′. . Therefore, distortion occurs in the longitudinal direction of the lower inner peripheral side end portion (inner ring portion) 241. As a result, a part of the lower inner peripheral side end (inner ring portion) 241 is deformed in the direction of rising from the lower end of the lens holder 14 as shown by an arrow C in FIG. 5, and faces the lower leaf spring 24 ′. It interferes with the base member (actuator base) 12 arranged at the position to be. As a result, there is a risk that the lens holder 14 may be tilted with respect to the fixed portion including the base member (actuator base) 12.

  Further, when the posture of the lens holder 14 is tilted, the characteristics of the lens driving device having the associated lower leaf spring 24 ′ are deteriorated, and the lower leaf spring 24 ′ is in contact with the base member 12, thereby generating dust. There is also a risk of malfunction.

  On the other hand, in the lower leaf spring 24 according to the present embodiment, a buffer displacement is provided at one location between the adjacent lower inner peripheral side connecting portion 244 adjacent to the lower inner peripheral end (inner ring portion) 241. The portion 241a (therefore, a total of four buffer displacement portions 241a) is provided. The present inventors have confirmed that the lower inner peripheral side end (inner ring portion) 241 is not deformed in the drop impact test of the portable small camera. Therefore, it is possible to prevent the lower inner peripheral side end portion (inner ring portion) 241 from coming into contact with the base member (actuator base) 12. As a result, the characteristic deterioration of the lens driving device is improved and dust generation can be prevented.

  In addition, the lower leaf | plate spring 24 which concerns on embodiment mentioned above is one between the lower inner peripheral side connection parts 244 adjacent to the lower inner peripheral side edge part (inner ring part) 241 as FIG. 3 shows. Although the buffer displacement portions 241a (four buffer displacement portions 241a in this example) are provided only at the locations, the buffer displacement portions 241a may be provided at a plurality of locations between the adjacent lower inner peripheral side connection portions 244. Good. For example, when the buffer displacement portions 241a are provided at two positions between the adjacent lower inner peripheral side connecting portions 244, the total number of the buffer displacement portions 241a is eight.

  Needless to say, the shape of the buffer displacement portion 241a is not limited to the Ω shape as shown in FIG. That is, any shape that does not deform the buffer displacement portion itself may be used.

  6A to 6L show modified examples of the buffer displacement portion 241a. For example, the buffer displacement portion 241a shown in FIGS. 6A, 6E, and 6I has a substantially U shape. Further, the buffer displacement portion 241a shown in FIGS. 6C and 6D has an S-shape. The buffer displacement portion 241a shown in FIG. 6 (H) has a V shape, and the buffer displacement portion 241a shown in FIG. 6 (K) has a W shape. The buffer displacement portion 241a shown in FIG. 6B has a meander shape. The buffer displacement portion 241a shown in FIG. 6 (F) has a rhombus shape, and the buffer displacement portion 241a shown in FIG. 6 (G) has a triangular shape. The buffer displacement portion 241a shown in () has a ring shape. The buffer displacement portion 241a shown in FIG. 6 (L) has a white V-shape.

  Next, with reference to FIG. 7, the structure of the upper leaf | plate spring 22 which concerns on one embodiment of this invention is demonstrated in detail. FIG. 7 is a plan view of the upper leaf spring 22.

  The upper leaf spring (front spring) 22 includes an upper inner peripheral end 221 fixed to the upper end of the lens holder 14 as described above, and an upper outer peripheral side fixed to the fixed portion that is the yoke 20 as described above. An end 222 and four upper arm portions 223 provided along the circumferential direction to connect the upper inner peripheral end 221 and the upper outer peripheral end 222 are provided. The upper inner peripheral side end 221 has a substantially annular shape. The upper outer peripheral end 222 is spaced apart from the upper inner peripheral end 221 radially outward. That is, the upper outer peripheral end 222 has a larger radius than the upper inner peripheral end 221. Each arm part 223 protrudes along the circumferential direction. The four upper inner peripheral side connecting portions 224 that connect the upper inner peripheral end portion 221 and the four upper arm portions 223 protrude radially outward from the upper inner peripheral end portion 221. The four upper outer peripheral side connecting portions 225 that connect the upper outer peripheral end portion 222 and the four upper arm portions 223 protrude from the upper outer peripheral end portion 222 inward in the radial direction.

  In the upper leaf spring 22 according to the present embodiment, the four upper outer peripheral side connecting portions 225 have a shape curved from the upper outer peripheral side end portion 222 to the root portions of the four upper arm portions 223. .

  Since the upper leaf spring 22 according to the present embodiment has the upper outer peripheral side connecting portion 225 having a curved shape, it is possible to release the stress generated in the drop impact test of the portable small camera. More specifically, the stress concentrated on the base portion of the upper arm portion 223 can be dispersed. In other words, the concentration of bending stress at the base portion of the upper arm portion 223 can be reduced.

  As described above, according to the present embodiment, the impact resistance of the upper leaf spring 22 and the lower leaf spring 24 and the lens driving device 10 can be further improved.

  Although the present invention has been described with reference to preferred embodiments, it is obvious that various modifications can be made by those skilled in the art without departing from the spirit of the present invention. For example, in the embodiment described above, the inner peripheral side end (221; 241) and the outer peripheral side end (222; 242) are connected by four arm portions (223; 243). In general, it is also applicable to leaf springs that connect N (N is an integer of 2 or more) arm portions between the inner peripheral end (221; 241) and the outer peripheral end (222; 242). Is possible.

10 Lens drive device 12 Base member (actuator base)
12a Circular opening 120 Base part 122 Projection 124 Projection part 124-1 Projection part 124-1a Tip part 124-1b Lower end 14 Lens holder 140 Cylindrical part 140-1 Contact part 142 Female screw 144 Support part 16 Drive coil 162 Flat part 18 Permanent magnet 182 Permanent magnet piece with triangular cross section 184 Permanent magnet piece with rectangular cross section 20 Yoke 202 Outer cylinder (shield yoke)
202-1 center portion 204 ring-shaped end portion 204a fitting hole 206 inner vertical extending portion (back yoke)
22 Upper leaf spring (front spring)
221 Upper inner peripheral side end (inner ring)
222 Upper outer peripheral end (outer ring)
222a Through-hole 223 Upper arm portion 224 Upper inner circumferential side coupling portion 225 Upper outer circumferential side coupling portion 24 Lower leaf spring (rear spring)
241 Lower inner circumference end (inner ring)
241a Buffer displacement part 242 Lower outer peripheral side end (outer ring part)
242a Through-hole 243 Lower arm portion 244 Lower inner periphery connection portion 244a Opening 245 Lower outer periphery connection portion 26 Stopper 28 Cover 28a Circular opening 282 Protrusion 30 Spacer 30a Insertion hole 32 Power supply member 322 Flexible printed circuit board 324 Sheet metal Terminal 34 Ring-shaped plate O Optical axis (center axis)

Claims (9)

A plate spring that supports a columnar movable part arranged in the center part so as to be displaceable in the central axis direction in a state of being positioned in a radial direction with respect to a fixed part arranged in the outer periphery of the movable part, The leaf spring is
An annular inner peripheral end,
An outer peripheral side end provided spaced apart radially outward from the inner peripheral end,
N arm portions (N is an integer of 2 or more) provided along the circumferential direction in order to connect the inner peripheral end portion and the outer peripheral end portion;
N inner peripheral side connecting portions that project radially outward from the inner peripheral end portion and connect the inner peripheral end portion and the N arm portions;
N outer peripheral side connection portions that project radially inward from the outer peripheral side end portions and connect the outer peripheral side end portions and the N arm portions;
Have
The leaf spring, wherein the inner peripheral side end portion has a buffer displacement portion at at least one position between the adjacent inner peripheral side connecting portions.   2. The leaf spring according to claim 1, wherein the inner peripheral side connecting portion has an opening for attaching the inner peripheral end portion to the movable portion.   The leaf spring according to claim 1, wherein the buffer displacement portion is selected from any one of a substantially U shape, Ω shape, and S shape.   The leaf spring according to any one of claims 1 to 3, wherein the material of the leaf spring is made of high hardness stainless steel. A lens holder having a cylindrical portion for holding the lens assembly, a fixing portion disposed on the outer periphery of the lens holder, an upper leaf spring for connecting the lens holder and the fixing portion on the upper side thereof, In a lens driving device comprising: a lower leaf spring that connects the lens holder and the fixed portion on the lower side thereof;
The lower leaf spring is
An annular lower inner peripheral end fixed to the lower end of the lens holder;
A lower outer peripheral end fixed to the fixing portion and spaced apart radially outward from the lower inner peripheral end; and
N (N is an integer of 2 or more) lower arm portions provided along the circumferential direction to connect between the lower inner peripheral end and the lower outer peripheral end,
N lower inner peripheral side connection portions that project radially outward from the lower inner peripheral end portion and connect the lower inner peripheral end portion and the N lower arm portions; ,
N lower outer peripheral connection portions that project radially inward from the lower outer peripheral end portion and connect the lower outer peripheral end portion and the N lower arm portions;
Have
The lens driving device according to claim 1, wherein the lower inner peripheral end has a buffer displacement portion at least at one location between the adjacent lower inner peripheral connecting portions. The lens holder has N support portions for supporting a lower inner peripheral end portion of the lower spring at a lower end thereof,
6. The N lower inner peripheral side connecting portions have openings for attaching the lower inner peripheral end portions with the N support portions of the lens holder. Lens drive device.   The lens driving device according to claim 5, wherein the buffer displacement portion is selected from any one of a substantially U shape, Ω shape, and S shape. The upper leaf spring is
An annular upper inner peripheral end fixed to the upper end of the lens holder;
An upper outer peripheral end fixed to the fixing portion and spaced apart radially outward from the upper inner peripheral end; and
N (N is an integer of 2 or more) upper arm portions provided along the circumferential direction in order to connect between the upper inner peripheral end and the upper outer peripheral end,
N upper inner peripheral side connecting portions that project radially outward from the upper inner peripheral end portion and connect the upper inner peripheral end portion and the N upper arm portions;
N upper outer peripheral side connecting portions that project radially inward from the upper outer peripheral end portion and connect the upper outer peripheral end portion and the N upper arm portions;
Have
8. The N upper outer peripheral side connecting portions have a shape curved from the upper outer peripheral end portion to a root portion of the N upper arm portions. The lens drive device described in 1.   The lens driving device according to any one of claims 5 to 8, wherein a material of the lower leaf spring and the upper leaf spring is made of high hardness stainless steel.

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