JP2010197690A - Lens drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens drive device with a leaf spring capable of suppressing damage and excessive deformation due to impact or the like even when the device is made small in size and thin in thickness. <P>SOLUTION: The lens drive device includes: a movable body, which holds a lens and is movable in the direction of the optical axis of the lens; a fixed body that holds the movable body so that it is movable in the direction of the optical axis; a movable-body fixed portion 5a that has a drive mechanism for driving the movable body in the direction of the optical axis and is fixed to the movable body; a fixed-body fixed portion 5b fixed to the fixed body; and the leaf spring 5 having a plurality of arms 5c connecting the movable-body fixed portion 5a and the fixed-body fixed portion 5b. Part of each arm 5c is a low spring constant part 5h whose spring constant is smaller than the spring constant of the other part of the arm 5c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lens driving device mounted on a relatively small camera used in a mobile phone or the like.

  Conventionally, as a lens driving device for driving a photographing lens of a camera mounted on a mobile phone or the like, a moving lens body that moves in the optical axis direction while holding a plurality of lenses, and a moving lens via two leaf springs 2. Description of the Related Art A lens driving device including a fixed body that holds a body in a movable manner is known (see, for example, Patent Document 1). In the lens driving device described in Patent Document 1, a driving coil is wound around the outer periphery of a cylindrical sleeve constituting a moving lens body, and four magnets are arranged so as to face the outer peripheral surface of the driving coil. Has been placed.

  In this lens driving device, the leaf spring connects the portion fixed to the fixed body, the portion fixed to the moving lens body, the portion fixed to the fixed body, and the portion fixed to the moving lens body. It consists of three arms. In general, the width and thickness of the arm portion of the leaf spring used in the lens driving device are constant.

JP 2008-58659 A

  In recent years, in the market of cameras used for mobile phones and the like, there has been a growing demand for smaller and thinner cameras, and there has been a further demand for smaller and thinner lens driving devices mounted on cameras. . In order to meet such demands, it is necessary to reduce the size and thickness of the leaf springs constituting the lens driving device. However, as the leaf spring is reduced in size and thickness, the strength of the leaf spring decreases. Therefore, damage or excessive deformation of the leaf spring when an impact caused by dropping of the lens driving device is applied to the lens driving device may be a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a lens driving device including a leaf spring that can suppress damage and excessive deformation caused by an impact or the like even if the size and thickness are reduced.

  In order to solve the above problems, a lens driving device of the present invention includes a movable body that holds a lens and is movable in the optical axis direction of the lens, a fixed body that holds the movable body so as to be movable in the optical axis direction, and a movable body. A driving mechanism for driving the body in the optical axis direction, a movable body fixing portion fixed to the movable body, a fixed body fixing portion fixed to the fixed body, a movable body fixing portion, and a fixed body fixing portion A plate spring having a plurality of arm portions that connect to each other, and a part of the arm portion is a low spring constant portion having a smaller spring constant than other portions of the arm portion.

  In the lens driving device of the present invention, the leaf spring includes a movable body fixing portion that is fixed to the movable body, a fixed body fixing portion that is fixed to the fixed body, and a plurality of members that connect the movable body fixing portion and the fixed body fixing portion. And a part of the arm part is a low spring constant part having a smaller spring constant than the other part of the arm part. For this reason, in the present invention, even if the leaf spring is reduced in size and thickness, it is possible to suppress damage and excessive deformation of the leaf spring due to an impact applied to the lens driving device.

  That is, according to the study of the present inventor, when an impact is applied to the lens driving device when the width and thickness of the entire arm portion are constant and the spring constant of the arm portion is constant, the leaf spring is generated upon impact. Since stress concentrates on the connection part between the movable body fixing part and the arm part and the connection part between the fixed body fixing part and the arm part, when the leaf spring is reduced in size and thickness, when an impact is applied, Damage and excessive deformation are likely to occur at the connecting portion between the movable body fixing portion and the arm portion and at the connecting portion between the fixed body fixing portion and the arm portion.

  On the other hand, in the present invention, since a part of the arm part is a low spring constant part, when an impact is applied to the lens driving device, the connecting part between the movable body fixing part and the arm part and the fixing body In addition to the connection portion between the fixed portion and the arm portion, stress can be concentrated on the low spring constant portion. That is, the stress generated in the leaf spring when an impact is applied to the lens driving device is applied to the connecting portion between the movable body fixing portion and the arm portion, the connecting portion between the fixed body fixing portion and the arm portion, and the low spring constant portion. It becomes possible to disperse. Therefore, in the present invention, it is possible to reduce the stress at the connection portion between the movable body fixing portion and the arm portion, which occurs at the time of impact, and the stress at the connection portion between the fixed body fixing portion and the arm portion. Even if the leaf spring is reduced in size and thickness, damage and excessive deformation of the leaf spring due to an impact applied to the lens driving device or the like can be suppressed.

  In the present invention, the arm portion is preferably formed in a substantially arc shape, and the low spring constant portion is preferably formed in an intermediate portion in the circumferential direction of the arm portion. In the present invention, it is preferable that the arm portions are formed in a substantially arc shape, and the low spring constant portions are formed at substantially equal intervals in the circumferential direction of the arm portion. If comprised in this way, it will become possible to reduce the stress of the connection part of the movable body fixing | fixed part and arm part which generate | occur | produces at the time of an impact, and the stress of the connection part of a fixed body fixing | fixed part and an arm part with sufficient balance.

  In the present invention, it is preferable that the plurality of arm portions are arranged at a substantially equiangular pitch around the optical axis of the lens, and the low spring constant portions are arranged at a substantially equiangular pitch around the optical axis. . With this configuration, regardless of the direction of the force applied to the leaf spring at the time of impact, the stress generated in the leaf spring is reduced by connecting the movable body fixing portion and the arm portion, the fixed body fixing portion and the arm. It becomes possible to disperse in a well-balanced manner in the connecting portion with the portion and the low spring constant portion.

  In the present invention, the arm portion is formed in a substantially arc shape, and the width of the low spring constant portion in the radial direction of the arm portion is narrower than the radial width of other portions of the arm portion excluding the low spring constant portion. It is preferable that If comprised in this way, even if the thickness of the whole arm part in an optical axis direction is constant, it becomes possible to form a low spring constant part in an arm part. Therefore, even when a low spring constant portion is formed on the arm portion, it is possible to form a leaf spring by pressing, etching, or the like. That is, even when a low spring constant portion is formed on the arm portion, a small and thin leaf spring can be formed relatively easily.

  In the present invention, the drive mechanism includes a substantially columnar drive magnet portion fixed to the fixed body, a substantially cylindrical shape wound around and fixed to the movable body, and an inner peripheral surface of the drive magnet portion. And a driving coil disposed so as to face the outer peripheral surface of the arm portion with a predetermined gap, the arm portion is formed in a substantially arc shape, and the driving magnet portion is disposed outside the arm portion in the radial direction. In the low spring constant portion, the outer peripheral side of the arm portion is preferably recessed toward the inner peripheral side. If comprised in this way, it will become possible to enlarge the arrangement space of the drive magnet part, preventing interference with the drive magnet part arrange | positioned on the outer side of the radial direction of an arm part, and an arm part. Therefore, the driving magnet portion can be formed larger without increasing the outer shape of the lens driving device, and the driving force of the driving mechanism can be improved.

  In the present invention, a case body that is formed in a substantially rectangular tube shape that is substantially square when viewed from the optical axis direction and that forms the side surface of the lens driving device is provided, and the drive mechanism includes at least one of the four corners of the case body. A substantially triangular prism-shaped driving magnet portion disposed at a location and a substantially triangular cylindrical shape wound so that the inner peripheral surface thereof faces the outer peripheral surface of the driving magnet portion with a predetermined gap. The fixed body fixing portion is formed in a substantially rectangular frame shape and is disposed along the inner peripheral surface of the case body, and the movable body fixing portion is disposed inside the fixed body fixing portion. And it is preferable that the connection part of a fixed body fixing | fixed part and an arm part is formed in the substantially middle position of four linear side parts which comprise a fixed body fixing | fixed part. If comprised in this way, it will become possible to enlarge the arrangement space of a drive mechanism, preventing interference with the drive mechanism arrange | positioned at the four corners of a case body, and an arm part. Therefore, the driving mechanism can be enlarged without increasing the outer shape of the lens driving device, and the driving force of the driving mechanism can be improved.

  As described above, in the lens driving device of the present invention, even if the leaf spring is reduced in size and thickness, it is possible to suppress damage and excessive deformation of the leaf spring at the time of impact.

It is a perspective view of the lens drive device concerning an embodiment of the invention. It is sectional drawing of the EE cross section of FIG. It is a disassembled perspective view of the lens drive device shown in FIG. It is a perspective view for demonstrating the arrangement | positioning relationship of the drive magnet part and drive coil which are shown in FIG. It is a side view of the drive magnet part and drive coil which are shown in FIG. It is a figure for demonstrating the magnetization state of the magnet part for a drive arrange | positioned at the four corners of the lens drive device of FIG. It is a top view of the leaf | plate spring shown in FIG. It is an enlarged view of the G section of FIG. It is a figure of the leaf | plate spring used for the simulation for demonstrating the effect of the lens drive device concerning embodiment of this invention, (A) is a top view of the leaf | plate spring concerning an Example, (B) is a comparative example. It is a top view of this leaf | plate spring. (A) is a graph which shows the simulation result for demonstrating the effect of the lens drive device concerning embodiment of this invention, (B) is a table | surface list of the original data of the graph of (A).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Schematic configuration of lens driving device)
FIG. 1 is a perspective view of a lens driving device 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line EE of FIG. FIG. 3 is an exploded perspective view of the lens driving device 1 shown in FIG. FIG. 4 is a perspective view for explaining the positional relationship between the drive magnet unit 17 and the drive coil 18 shown in FIG. FIG. 5 is a side view of the drive magnet unit 17 and the drive coil 18 shown in FIG. FIG. 6 is a diagram for explaining a magnetized state of the driving magnet unit 17 disposed at the four corners of the lens driving device 1 of FIG.

  The lens driving device 1 of this embodiment is mounted on a relatively small camera used in a mobile phone or the like, and is formed in a substantially quadrangular prism shape as a whole as shown in FIG. That is, the lens driving device 1 is formed so that the shape of the lens for photographing when viewed from the direction of the optical axis L (optical axis direction) is a substantially square shape. In this embodiment, the lens driving device 1 is formed so that the shape when viewed from the optical axis direction is substantially square.

  In the camera in which the lens driving device 1 of this embodiment is mounted, an image sensor (not shown) is arranged on the lower side (that is, the Z2 direction side) of FIG. 2, and the upper side (that is, the Z1 direction side) of FIG. The subject placed in is photographed. Therefore, in the following description, the Z1 direction side is the subject side, and the Z2 direction side is the anti-subject side (imaging element side). In the following description, two directions orthogonal to the optical axis L and orthogonal to each other are defined as an X direction and a Y direction. In this embodiment, the four side surfaces of the lens driving device 1 are parallel to the X direction or the Y direction.

  As shown in FIGS. 1 and 2, the lens driving device 1 includes a movable body 2 that holds a photographing lens and is movable in the optical axis direction, and a fixed body that holds the movable body 2 so as to be movable in the optical axis direction. 3 and a drive mechanism 4 for driving the movable body 2 in the optical axis direction. The movable body 2 is movably held by the fixed body 3 via two types of plate springs 5 and 6 (see FIG. 3). In addition, illustration of the leaf | plate springs 5 and 6 is abbreviate | omitted in FIG.

  The movable body 2 is fixed by electrically connecting a sleeve 8 that holds a lens holder 7 to which a plurality of lenses are fixed and an end of a driving coil 18 that constitutes the driving mechanism 4 by soldering or the like. Coil end fixing members 9 and 10. 2, illustration of the coil end fixing members 9 and 10 is omitted, and illustration of the lens holder 7 is omitted in FIG.

  The lens holder 7 is formed in a substantially cylindrical shape, and a plurality of lenses are fixed on the inner peripheral side thereof. A male screw is formed on the outer peripheral surface of the lens holder 7 on the subject side. The sleeve 8 is formed in a substantially cylindrical shape as a whole. The subject side of the sleeve 8 is formed in a substantially cylindrical shape. The sleeve 8 holds the lens holder 7 on its inner peripheral side. That is, a female screw that engages with a male screw formed on the outer peripheral surface of the lens holder 7 is formed on the inner peripheral surface of the sleeve 8. In this embodiment, the outer diameter of the lens holder 7 on the subject side is smaller than the outer diameter on the opposite subject side, and the outer diameter on the subject side of the sleeve 8 is also smaller than the outer diameter on the opposite subject side. .

  The coil end fixing members 9 and 10 are made of a conductive metal material. The coil end fixing members 9 and 10 are fixed to the end surface of the sleeve 8 on the side opposite to the subject.

  The fixed body 3 includes a first case body 11 disposed on the subject side and a second case body 12 disposed on the opposite subject side.

  The first case body 11 is formed of a magnetic material, and is formed in a substantially square cylindrical shape with a bottom having a bottom portion 11a and a cylindrical portion 11b. Specifically, the 1st case body 11 is formed in the substantially square cylinder shape with a bottom which becomes a substantially square shape when seeing from an optical axis direction. A circular through hole 11c is formed at the center of the bottom 11a disposed on the subject side. The first case body 11 is disposed so as to surround the outer peripheral side of the movable body 2 and the drive mechanism 4, and constitutes a side surface of the lens driving device 1.

  For example, the second case body 12 is formed of a resin material and is formed in a substantially rectangular tube shape. The second case body 12 is attached to the anti-subject side of the first case body 11 so as to cover the outer peripheral side of the lens holder 7 on the anti-subject side.

  The leaf spring 5 is disposed on the subject side of the movable body 2. The detailed configuration of the leaf spring 5 will be described later.

  The leaf spring 6 is composed of a sleeve fixing portion fixed to the sleeve 8, a case body fixing portion fixed to the second case body 12, and an arm portion connecting the sleeve fixing portion and the case body fixing portion. Arranged on the opposite side of the body 2. The sleeve fixing portion is fixed to the end surface of the sleeve 8 on the side opposite to the subject via the coil end fixing members 9 and 10. That is, the sleeve fixing portion is fixed to the coil end fixing members 9 and 10. The case body fixing portion is fixed to a fixing surface formed on the subject side of the second case body 12.

  As shown in FIGS. 2 to 4, the driving mechanism 4 includes four substantially triangular prism-shaped driving elements disposed at four corners of the lens driving device 1 (specifically, four corners inside the first case body 11). The magnet unit 17 includes four drive coils 18 wound in a substantially triangular tube shape and arranged so that the inner peripheral side thereof faces the outer peripheral surface of the drive magnet unit 17 via a predetermined gap. ing. In addition, the drive mechanism 4 is fixed to the end face on the subject side of the drive coil 18 and is attracted toward the drive magnet pieces 23 and 24, which will be described later, constituting the drive magnet unit 17; Coil protection members 20 and 21 that are attached to the subject side and the opposite subject side of the drive coil 18 and protect the drive coil 18 are provided.

  The drive magnet unit 17 includes two substantially triangular prism-shaped drive magnet pieces 23 and 24 arranged so as to overlap in the optical axis direction, and a magnetic plate 25 arranged between the drive magnet pieces 23 and 24. It has. The object side surface of the magnetic plate 25 is fixed to the end surface of the driving magnet piece 23 on the side opposite to the subject, and the surface of the magnetic plate 25 opposite to the object side is fixed to the end surface on the subject side of the driving magnet piece 24. Has been.

  The drive magnet pieces 23 and 24 are formed so that the shape when viewed from the optical axis direction is a substantially right-angled isosceles triangle, and is substantially parallel to the optical axis L and orthogonal to each other as shown in FIG. And two rectangular flat surface portions 23a and 24a and one rectangular inclined surface portion 23b and 24b that are substantially parallel to the optical axis L and connect the two flat surface portions 23a and 24a.

  The driving magnet pieces 23 and 24 are arranged so that the inner peripheral surface of the cylindrical portion 11b of the first case body 11 and the flat portions 23a and 24a are substantially parallel to each other. That is, the two drive magnet pieces 23 and 24 arranged at diagonal positions inside the first case body 11 are arranged such that the slope portions 23b and 24b face each other. The driving magnet piece 23 is fixed to the bottom 11 a of the first case body 11. Specifically, the subject-side end surface of the driving magnet piece 23 is fixed to the surface of the bottom portion 11a opposite to the subject. Further, the end surface on the subject side of the driving magnet piece 23 is in contact with the surface on the side opposite to the subject of the bottom portion 11a.

  The magnetic plate 25 is made of a magnetic material. The magnetic plate 25 is formed in a flat plate shape having a substantially right-angled isosceles triangle shape similar to that of the drive magnet pieces 23 and 24 when viewed from the optical axis direction.

  A flat magnetic plate 26 made of a magnetic material is fixed to the end surface of the driving magnet piece 24 on the side opposite to the subject. The magnetic plate 26 is formed so that the shape when viewed from the optical axis direction is a substantially right-angled isosceles triangle. Further, the magnetic plate 26 is in contact with the inner peripheral surface of the cylindrical portion 11 b of the first case body 11.

  The driving coil 18 is formed by being wound so that the shape when viewed from the optical axis direction is a substantially right-angled isosceles triangle, and is substantially parallel to the optical axis L as shown in FIG. Two rectangular surface portions 18a that are orthogonal to each other and one rectangular inclined surface portion 18b that is substantially parallel to the optical axis L and that connects the two orthogonal surface portions 18a are provided.

  The four drive coils 18 are fixed to the outer peripheral surface of the sleeve 8. Specifically, the four driving coils 18 are arranged at a pitch of about 90 ° so that the inner circumferential surface of the driving coil 18 and the outer circumferential surface of the driving magnet portion 17 are substantially parallel with a predetermined gap. The drive coil 18 is fixed to the outer peripheral surface of the sleeve 8, and is disposed at the four corners inside the first case body 11. The drive coil 18 is disposed at four corners inside the first case body 11 with predetermined gaps between the drive coil 18 and the inner peripheral surface of the first case body 11, and together with the sleeve 8, the optical axis. It can move in the direction.

  As shown in FIGS. 5 and 6, the two drive magnet pieces 23 and 24 constituting the drive magnet unit 17 have the same magnetic poles (S pole and S pole, or N pole) in the optical axis direction. N poles) are arranged to face each other. Therefore, a magnetic flux F that passes through the orthogonal surface portion 18a and the inclined surface portion 18b of the driving coil 18 is generated between the driving magnet pieces 23 and 24.

  Further, as shown in FIG. 6, the magnetic poles formed on the opposing surfaces of the two driving magnet pieces 23 and 24 constituting the driving magnet unit 17 are adjacent to each other in the circumferential direction of the lens driving device 1. This is different from the magnetic poles formed on the opposing surfaces of the two driving magnet pieces 23 and 24. For example, the magnetic poles formed on the opposing surfaces of the driving magnet pieces 23 and 24 arranged on the right and left sides in FIG. 6 are S poles, and the driving magnet pieces 23 arranged on the upper and lower sides in FIG. , 24 are N poles. Therefore, a magnetic flux F is generated between the driving magnet pieces 23 and 24 arranged on the upper and lower sides in FIG. 6 and between the driving magnet pieces 23 and 24 arranged on the right and left sides in FIG. Yes.

(Configuration of leaf spring)
FIG. 7 is a plan view of the leaf spring 5 shown in FIG. FIG. 8 is an enlarged view of a portion G in FIG.

  The leaf spring 5 includes four movable body fixing portions 5a fixed to the movable body 2, a fixed body fixing portion 5b fixed to the fixed body 3, and four connecting the movable body fixing portion 5a and the fixed body fixing portion 5b. Arm portion 5c. The leaf spring 5 of this embodiment is formed by etching, pressing, or the like, and the entire thickness of the leaf spring 5 is substantially constant.

  The fixed body fixing | fixed part 5b is formed in the substantially square frame shape. Specifically, the fixed body fixing | fixed part 5b is formed in the substantially square frame shape, and is comprised by the four linear side parts 5d. The fixed body fixing portion 5b is fixed to the surface on the side opposite to the subject of the bottom portion 11a of the first case body 11 via a spacer 14 (see FIG. 3) formed in a substantially square frame shape. That is, the fixed body fixing portion 5b is fixed to the spacer 14 fixed to the surface of the bottom portion 11a on the side opposite to the subject. The fixed body fixing portion 5b is fixed to the first case body 11 so that the straight side portion 5d is substantially parallel to the X direction or the Y direction, and the inner periphery of the cylindrical portion 11b of the first case body 11 is fixed. It is arranged along the surface.

  A first connection portion 5e serving as a connection portion between the fixed body fixing portion 5b and the arm portion 5c is formed at a substantially intermediate position of the straight side portion 5d. The first connecting portion 5e is formed from an approximately middle position of the straight side portion 5d toward the inside in the X direction or the inside in the Y direction. The first connection portion 5e is formed in a substantially ¼ arc shape with a small curvature radius.

  The movable body fixing | fixed part 5a is formed in a substantially annular shape (substantially circular frame shape), and is arrange | positioned inside the fixed body fixing | fixed part 5b. The movable body fixing portion 5a is fixed to the end surface of the sleeve 8 on the subject side. Specifically, as shown in FIG. 7, sleeve fixing portions 5f are formed at both ends in the X direction and both ends in the Y direction of the movable body fixing portion 5a. It is fixed to the end face. The sleeve fixing portion 5f is formed in a substantially semicircular shape and is formed so as to protrude toward the inner peripheral side of the movable body fixing portion 5a.

  Moreover, the 2nd connection part 5g used as the connection part of the movable body fixing | fixed part 5a and the arm part 5c is formed in the both ends of the X direction and the both ends of the Y direction of the movable body fixing | fixed part 5a. The second connecting portion 5g is formed from the X direction ends or the Y direction ends of the movable body fixing portion 5a toward the X direction outside or the Y direction outside. The second connection portion 5g is formed in a substantially ¼ arc shape with a small curvature radius.

  The arm part 5c is formed in a substantially arc shape. Specifically, the arm portion 5c is formed in a substantially ¼ arc shape with the optical axis L as the center. The four arm portions 5c are arranged with a substantially equiangular pitch around the optical axis L. That is, the four arm portions 5c are arranged at a substantially 90 ° pitch with the optical axis L as the center. For example, between the first connection portion 5e disposed on the left end side in FIG. 7 and the second connection portion 5g disposed on the upper end side in FIG. 7, the first connection portion 5e disposed on the upper end side in FIG. Between the second connection portion 5g disposed on the right end side in FIG. 7 and between the first connection portion 5e disposed on the right end side in FIG. 7 and the second connection portion 5g disposed on the lower end side in FIG. And the arm part 5c is arrange | positioned between each of the 1st connection part 5e arrange | positioned at the lower end side of FIG. 7, and the 2nd connection part 5g arrange | positioned at the left end side of FIG. The arm portion 5c is formed along the outer peripheral surface on the subject side of the sleeve 8 formed in a substantially cylindrical shape.

  The width of the arm portion 5c in the radial direction is substantially constant as a whole. However, the radial width of the intermediate portion (substantially central portion) in the circumferential direction of the arm portion 5c is narrower than other portions of the arm portion 5c. Specifically, as shown in FIG. 8, the intermediate portion in the circumferential direction of the arm portion 5 c is recessed from the outer peripheral side to the inner peripheral side of the arm portion 5 c, and the width of the recessed portion is the arm width. It is narrower than the radial width of the other part of the part 5c. In this embodiment, the intermediate portion in the circumferential direction of the arm portion 5c whose width in the radial direction is narrower than the other portion is a low spring constant portion 5h having a smaller spring constant than the other portion of the arm portion 5c. ing. That is, in this embodiment, the low spring constant portion 5h is formed at one place in the middle portion of the arm portion 5c in the circumferential direction.

  As described above, the four arm portions 5c are arranged at substantially equal angular pitches around the optical axis L. Therefore, the four low spring constant portions 5h are also arranged at substantially equal angular pitches around the optical axis L. That is, the four low spring constant portions 5h are arranged at a substantially 90 ° pitch with the optical axis L as the center. Further, the low spring constant portion 5h is disposed on a substantially diagonal line of the lens driving device 1 formed in a substantially quadrangular prism shape.

  As shown in FIG. 7, the driving magnet portion 17 is disposed inside the fixed body fixing portion 5b. Moreover, the drive magnet part 17 is arrange | positioned in the radial direction outer side of the arm part 5c. Specifically, when viewed from the optical axis direction, the perpendicular bisectors of the slope portions 23b, 24b of the drive magnet pieces 23, 24 pass through substantially the center position of the low spring constant portion 5h in the circumferential direction. In addition, the drive magnet portion 17 is disposed outside the arm portion 5c in the radial direction.

  In addition, in order to suppress the inclination of the movable body 2 with respect to the fixed body 3, the width of the first connection portion 5e and the width of the second connection portion 5g are wider than the width of the arm portion 5c. Further, in this embodiment, the leaf spring 5 is fixed to the movable body 2 and the fixed body 3 so that the urging force toward the opposite object side is generated in the movable body 2 when no current is supplied to the drive coil 18. Has been.

(Main effects of this form)
As described above, in this embodiment, the middle portion in the circumferential direction of the arm portion 5c constituting the leaf spring 5 is the low spring constant portion 5h having a smaller spring constant than the other portions of the arm portion 5c. . Therefore, in this embodiment, even if the leaf spring 5 is reduced in size and thickness, it is possible to suppress damage and excessive deformation of the leaf spring 5 due to an impact applied to the lens driving device 1 or the like.

  That is, according to the study of the present inventor, when the entire width of the arm portion 5c is constant and the spring constant of the arm portion 5c is constant, the stress generated in the leaf spring 5 at the time of impact is the first connection portion 5e. If the leaf spring 5 is reduced in size and thickness in order to concentrate on the second connection portion 5g, damage to the first connection portion 5e and the second connection portion 5g may occur when an impact is applied to the lens driving device 1. Excessive deformation tends to occur.

  On the other hand, in the present embodiment, since the middle portion of the arm portion 5c in the circumferential direction is the low spring constant portion 5h, when an impact is applied to the lens driving device 1, the first connection portion 5e and the second connection are provided. In addition to the portion 5g, stress is concentrated on the low spring constant portion 5h. That is, the stress generated in the leaf spring 5 when an impact is applied to the lens driving device 1 can be distributed to the first connection portion 5e, the second connection portion 5g, and the low spring constant portion 5h. Therefore, in this embodiment, the stress of the first connection portion 5e and the stress of the second connection portion 5g generated at the time of impact can be reduced. As a result, even if the leaf spring 5 is reduced in size and thickness, the lens driving device 1 It is possible to suppress the damage and excessive deformation of the leaf spring 5 due to an impact or the like at the time of falling.

  In particular, in this embodiment, the low spring constant portion 5h is formed at an intermediate portion in the circumferential direction of the arm portion 5c, so that the stress of the first connection portion 5e and the stress of the second connection portion 5g generated at the time of impact are balanced. Can be reduced.

  Hereinafter, the effect of this embodiment will be described more specifically based on simulation results. Using two types of leaf springs 5 and 105 shown in FIG. 9, the stresses generated in the first connection portion 5e, the second connection portion 5g, and the arm portion 5c when the arm portion 5c is deformed in the radial direction were calculated by simulation. . A leaf spring 5 shown in FIG. 9A is a leaf spring of this embodiment (a leaf spring of an example), and a leaf spring 105 shown in FIG. 9B is a leaf spring according to a comparative example. The leaf spring 105 is formed in the same way as the leaf spring 5 except that the low radial constant portion 5h is not formed in the arm portion 5c and the entire radial width of the arm portion 5c is substantially constant. Yes. For this reason, in FIG. 9B, the same reference numerals as the respective configurations of the leaf spring 5 are attached to the same configurations of the leaf spring 105 as the respective configurations of the leaf spring 5.

  In addition, the material of the leaf | plate springs 5 and 105 used by simulation is a nickel copper alloy, and thickness is 0.06 mm. Further, the width of the arm portion 5c excluding the low spring constant portion 5h of the leaf spring 5 and the width of the arm portion 5c of the leaf spring 105 used in the simulation are 0.13 mm, and the minimum width of the low spring constant portion 5h is 0. 093 mm. Further, the radius of curvature of the arm portion 5c of the leaf springs 5 and 105 used in the simulation is 3.87 mm.

  In the simulation, the right end side of the inner periphery of the movable body fixing portion 5a is pushed rightward (that is, pushed outward in the radial direction), and the right end side of the movable body fixing portion 5a is forced to the right by 0.1 mm. When deformed, the stresses generated at the five calculation points P1 to P5 were calculated. As shown in FIG. 9, the calculation location P5 is a location where the first connection portion 5e is formed, and the calculation location P1 is a location where the second connection portion 5g is formed. The calculation location P3 is an intermediate position of the arm portion 5c in the circumferential direction (a position where the low spring constant portion 5h is formed in the leaf spring 5). Furthermore, the calculation location P2 is an intermediate position between the calculation location P1 and the calculation location P3 of the arm portion 5c in the circumferential direction, and the calculation location P4 is the calculation location P3 and the calculation location of the arm portion 5c in the circumferential direction. Intermediate position with P5. In the simulation, the maximum value of Mises stress at each of the calculation points P1 to P5 was calculated.

  FIG. 10 shows the simulation result. As shown in FIG. 10, in the leaf spring 5 of the example, compared with the leaf spring 105 of the comparative example, the stress at the calculation points P1 and P5 decreased and the stress at the calculation point P3 increased. That is, in the leaf spring 105, the stress generated in the leaf spring 105 is concentrated in the first connection portion 5e and the second connection portion 5g, whereas in the leaf spring 5, the stress generated in the leaf spring 5 is the first connection. Dispersed in the portion 5e, the second connection portion 5g, and the low spring constant portion 5h. Further, the maximum value of stress generated in the leaf spring 5 is smaller than the maximum value of stress generated in the leaf spring 105. Thus, in this embodiment, the stress generated in the leaf spring 5 is distributed to the first connection portion 5e, the second connection portion 5g, and the low spring constant portion 5h, and the stress of the first connection portion 5e generated at the time of impact and the second The stress of the connection part 5g can be reduced. As a result, even if the leaf spring 5 is reduced in size and thickness, damage or excessive deformation of the leaf spring 5 due to an impact applied to the lens driving device 1 can be suppressed.

  Further, as shown in FIG. 10, the stresses at the calculation points P1 and P5 of the leaf spring 5 of the embodiment are reduced almost evenly with respect to the stresses at the calculation points P1 and P5 of the leaf spring 105 of the comparative example. Yes. Thus, in this embodiment, since the low spring constant portion 5h is formed in the middle portion in the circumferential direction of the arm portion 5c, the stress of the first connection portion 5e and the stress of the second connection portion 5g generated at the time of impact are reduced. It can be reduced with good balance.

  In addition, the average value of the stress of the calculation locations P1 to P5 calculated by the simulation was 451 (MPa) for the leaf spring 5 and 481 (MPa) for the leaf spring 105. Further, the difference between the maximum value and the minimum value of the stress at the calculation points P1 to P5 calculated by the simulation was 788 (MPa) for the leaf spring 5 and 809 (MPa) for the leaf spring 105.

  In this embodiment, the four arm portions 5c are arranged at a substantially equiangular pitch around the optical axis L, and the low spring constant portions 5h are arranged at a substantially equiangular pitch around the optical axis L. . Therefore, no matter what direction the force is applied to the leaf spring 5 at the time of impact, the stress generated in the leaf spring 5 is balanced in the first connection portion 5e, the second connection portion 5g and the low spring constant portion 5h. It becomes possible to disperse.

  In this embodiment, the radial width of the low spring constant portion 5h is narrower in the radial direction of the other portions of the arm portion 5c excluding the low spring constant portion 5h. Therefore, even if the overall thickness of the leaf spring 5 is constant, the low spring constant portion 5h can be formed in the arm portion 5c. Therefore, even when the low spring constant portion 5h is formed on the arm portion 5c, the leaf spring 5 can be formed by etching, pressing, or the like as described above. That is, even when the low spring constant portion 5h is formed on the arm portion 5c, the small and thin leaf spring 5 can be formed relatively easily.

  In this embodiment, the drive magnet portion 17 is configured so that the perpendicular bisectors of the slope portions 23b and 24b of the drive magnet pieces 23 and 24 when viewed from the optical axis direction pass through the approximate center position of the low spring constant portion 5h. As described above, the arm portion 5c is disposed outside in the radial direction. In the low spring constant portion 5h, the outer peripheral side of the arm portion 5c is recessed toward the inner peripheral side. Therefore, it is possible to increase the arrangement space of the driving magnet unit 17 while preventing interference between the driving magnet unit 17 and the arm portion 5c. Therefore, in this embodiment, the driving magnet portion 17 can be formed larger without increasing the outer shape of the lens driving device 1, and the driving force of the driving mechanism 4 can be improved.

  In particular, in the present embodiment, the first connection portion 5e is formed at a substantially intermediate position of the straight side portion 5d constituting the fixed body fixing portion 5b. Therefore, the arrangement space of the driving magnet unit 17 and the driving coil 18 is increased while preventing interference between the driving magnet unit 17 and the driving coil 18 disposed at the four corners of the lens driving device 1 and the arm unit 5c. It becomes possible. Therefore, in this embodiment, the driving magnet portion 17 and the driving coil 18 can be formed larger without increasing the outer shape of the lens driving device 1, and the driving force of the driving mechanism 4 can be improved. It becomes possible.

(Other embodiments)
The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention.

  In the embodiment described above, the low spring constant portion 5h is formed at one place in the middle portion of the arm portion 5c in the circumferential direction. In addition, for example, the low spring constant portions 5h may be formed at a plurality of locations (for example, 2 locations or 3 locations) of the arm portion 5c. That is, the radial width may be narrow at a plurality of locations of the arm portion 5c. In this case, the low spring constant portions 5h are preferably formed at substantially equal intervals in the circumferential direction of the arm portion 5c. If comprised in this way, the stress which arises in the leaf | plate spring 5 at the time of impact will be disperse | distributed with sufficient balance to the 1st connection part 5e, the 2nd connection part 5g, and the several low spring constant part 5h, and the 1st connection part 5e produced at the time of an impact will be carried out. And the stress of the second connection portion 5g can be reduced in a well-balanced manner.

  In the embodiment described above, the radial width of the low spring constant portion 5h is narrower than the radial width of the other portion of the arm portion 5c. In addition to this, for example, the radial width of the low spring constant portion 5h is the same as the radial width of the other portion of the arm portion 5c, and the thickness of the low spring constant portion 5h is other than that of the arm portion 5c. It may be thinner than the thickness of the part. That is, the low spring constant portion 5h may be formed in the arm portion 5c by making the thickness of a part of the arm portion 5c thinner than the thickness of the other portions of the arm portion 5c. Even in this case, as in the above-described embodiment, the stress generated in the leaf spring 5 when an impact is applied to the lens driving device 1, the first connection portion 5e, the second connection portion 5g, and the low spring constant portion 5h. Can be dispersed.

  In the embodiment described above, the low spring constant portion 5h is formed by the outer peripheral side of the arm portion 5c formed in a substantially arc shape being recessed toward the inner peripheral side. That is, in the embodiment described above, the low spring constant portion 5h is formed in a substantially arc shape. In addition, for example, the low spring constant portion 5h may be formed in a substantially linear shape having a narrower width than other portions of the arm portion 5c. Further, the low spring constant portion 5h may be formed by meandering a band-like portion having a narrower width than other portions of the arm portion 5c. Further, the low spring constant portion 5h may be formed by recessing the inner peripheral side of the arm portion 5c formed in a substantially arc shape toward the outer peripheral side.

  In the embodiment described above, the driving magnet unit 17 and the driving coil 18 are disposed at the four corners of the lens driving device 1. In addition to this, for example, if the driving force of the movable body 2 can be obtained, the driving magnet portion 17 and the driving coil 18 are arranged only at three, two, or one corner of the lens driving device 1. May be. In this case, a guide shaft for guiding the movable body 2 in the optical axis direction is arranged at the corner of the lens driving device 1 where the driving magnet portion 17 and the driving coil 18 are not arranged, and is engaged with this guide shaft. An engaging recess may be formed in the sleeve 8. In the embodiment described above, the drive coil 18 is fixed to the movable body 2 side and the drive magnet portion 17 is fixed to the fixed body 3 side. However, the drive magnet portion 17 is fixed to the movable body 2 side. The driving coil 18 may be fixed to the fixed body 3 side.

  In the embodiment described above, the plate spring 5 is formed with four arm portions 5c. In addition, for example, the number of arm portions 5c formed on the leaf spring 5 may be three, or may be five or more. In the above-described embodiment, the plate spring 5 is used in the lens driving device 1 in which the driving magnet portion 17 and the driving coil 18 are arranged at the four corners of the lens driving device 1. Any lens driving device may be used as long as the movable body is a lens driving device held by a fixed body via a leaf spring. For example, the leaf spring of the present invention may be used in the lens driving device described in Patent Document 1 described above.

DESCRIPTION OF SYMBOLS 1 Lens drive device 2 Movable body 3 Fixed body 4 Drive mechanism 5 Leaf spring 5a Movable body fixing | fixed part 5b Fixed body fixing | fixed part 5c Arm part 5d Linear side part 5e 1st connection part (connection part of a fixed body fixing | fixed part and an arm part) )
5h Low spring constant part 11 First case body (case body)
17 Driving magnet 18 Driving coil L Optical axis

Claims (7)

A movable body that holds a lens and is movable in the optical axis direction of the lens, a fixed body that holds the movable body so as to be movable in the optical axis direction, and a drive for driving the movable body in the optical axis direction With a mechanism,
A leaf spring having a movable body fixing portion fixed to the movable body, a fixed body fixing portion fixed to the fixed body, and a plurality of arm portions connecting the movable body fixing portion and the fixed body fixing portion. Prepared,
A part of the arm part is a low spring constant part having a smaller spring constant than the other part of the arm part. The arm portion is formed in a substantially arc shape,
The lens driving device according to claim 1, wherein the low spring constant portion is formed at an intermediate portion in a circumferential direction of the arm portion. The arm portion is formed in a substantially arc shape,
The lens driving device according to claim 1, wherein the low spring constant portions are formed at substantially equal intervals in a circumferential direction of the arm portion. The plurality of arms are arranged at substantially equal angular pitches around the optical axis of the lens,
4. The lens driving device according to claim 1, wherein the low spring constant portions are arranged at substantially equal angular pitches around the optical axis. 5. The arm portion is formed in a substantially arc shape,
The width of the low spring constant portion in the radial direction of the arm portion is narrower than the radial width of other portions of the arm portion excluding the low spring constant portion. 5. The lens driving device according to any one of 4 to 4. The drive mechanism includes a substantially columnar drive magnet portion that is fixed to the fixed body, a substantially cylindrical winding and is fixed to the movable body, and an inner peripheral surface thereof is the drive magnet portion. A driving coil disposed so as to be opposed to the outer peripheral surface with a predetermined gap,
The arm portion is formed in a substantially arc shape,
The driving magnet portion is disposed on the outer side in the radial direction of the arm portion,
The lens driving device according to claim 5, wherein an outer peripheral side of the arm portion is recessed toward an inner peripheral side in the low spring constant portion. A case body that is formed in a substantially rectangular tube shape that is substantially quadrangular when viewed from the optical axis direction and that forms the side surface of the lens driving device,
The driving mechanism is wound in a substantially triangular cylindrical driving magnet portion disposed in at least one of the four corners of the case body and a substantially triangular cylindrical shape, and an inner peripheral surface thereof is an outer peripheral surface of the driving magnet portion. And a driving coil arranged to face each other with a predetermined gap therebetween,
The fixed body fixing portion is formed in a substantially rectangular frame shape, and is disposed along the inner peripheral surface of the case body,
The movable body fixing portion is disposed inside the fixed body fixing portion,
The connection part of the said fixed body fixing | fixed part and the said arm part is formed in the substantially intermediate position of the four linear side parts which comprise the said fixed body fixing | fixed part, The any one of Claim 1 to 6 characterized by the above-mentioned. A lens driving device according to claim 1.

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