JP2008197476A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator providing stable frictional force. <P>SOLUTION: The linear actuator (20) has: a lens movable part (32) including a lens holder (321) movable in the direction of the optical axis (O) of the lens relative to a base part (21); and a lens driving section (34) for driving the lens movable part. In the linear actuator (20), the base part (21) has a pair of main shafts extending parallel to the direction of the optical axis of the lens. The lens driving section (34) has: a plurality of piezoelectric units (341); and vibrating frictional part (342) slidably disposed on the pair of main shafts and having an internal circumferential face (342a) accommodating the lens movable part. The lens movable part (32) is disposed between the lens holder and the internal circumferential face of the vibration frictional part and includes: a pair of pads (322) frictionally connected with the internal circumferential face of the vibration frictional part; and a spring (323) interposed between the pair of pads and the lens holder and pressing the pair of pads radially outward. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a linear actuator, and more particularly to a linear actuator using a piezoelectric element.

  Conventionally, linear actuators using piezoelectric elements have been used as camera autofocus actuators and zoom actuators.

  For example, in Patent Document 1, in order to move the lens holder, a guide bar is bonded to one end in the expansion / contraction direction of the piezoelectric element, the lens holder is movably supported by the guide bar, and the lens holder is moved between the guide bar and the lens holder. A drive device including a leaf spring that generates a frictional force is disclosed. In Patent Document 1, a voltage is applied to a piezoelectric element so that the speed of extension differs from the speed of contraction.

  Further, Patent Document 2 discloses a piezoelectric element, a drive shaft (abrasion-resistant vibration rod) that is coupled to the piezoelectric element and extends in the expansion / contraction direction of the piezoelectric element, and a driven member that is frictionally coupled to the drive shaft ( A lens holder) is disclosed. In Patent Document 2, the lens holder is driven by devising a drive signal applied to the piezoelectric element.

  Further, Patent Document 3 discloses an optical module that is miniaturized and can improve the positional accuracy of the lens holder. The optical module disclosed in Patent Document 3 includes a lens holder for holding a lens, a lens holder support, a plurality of piezoelectric elements provided at rotationally symmetric positions around the optical axis of the lens, and fixed to the piezoelectric element. In addition, a plurality of weights provided at rotationally symmetric positions around the optical axis of the lens are provided. The lens holder is movable in the direction of the optical axis of the lens. The lens holder support has a cylindrical portion inside, and supports the lens holder on the inner peripheral surface of the cylindrical portion so as to be slidable in the optical axis direction of the lens. The lens holder support portion holds the lens holder at an arbitrary position in the optical axis direction of the lens by a static frictional force generated between the inner peripheral surface of the cylindrical portion and the outer peripheral surface of the lens holder. A voltage is applied to the plurality of piezoelectric elements so that the extending speed and the contracting speed differ, and the piezoelectric elements expand and contract in the optical axis direction of the lens. One surface of the plurality of piezoelectric elements in the expansion / contraction direction is fixed to a surface on one end side in the optical axis direction of the lens of the lens holder. The plurality of weights are fixed to the other surface of the piezoelectric element in the expansion / contraction direction.

  Anyway, in the optical module disclosed in Patent Document 3, the lens holder is moved by the “inertial force” of the weight generated by the expansion and contraction of the piezoelectric element. As the piezoelectric element, a laminated piezoelectric element in which a plurality of piezoelectric layers (internal electrodes) are laminated is used. In Patent Document 3, one end of a piezoelectric element is fixed to a lens holder (moving unit), and the other end of the piezoelectric element is fixed to a weight. That is, the lens unit is configured by a combination of the piezoelectric element, the lens holder, and the weight, and the lens unit is supported so as to be slidable in the optical axis direction of the lens with respect to the lens holder support. In Patent Document 3, the other end of the weight is not fixed anywhere, and the piezoelectric element and the weight are hung from the lens holder (moving part).

Japanese Patent No. 2633066 Japanese Patent No. 3188851 JP 2006-184565 A

  Patent Documents 1 to 3 described above have problems as described below.

  In the driving device disclosed in Patent Document 1, since the lens holder is movably supported by the guide rod bonded to the piezoelectric element, the guide rod extends long in the expansion / contraction direction of the piezoelectric element, thereby reducing the height. It is disadvantageous.

  Also in the drive device disclosed in Patent Document 2, the drive shaft extends in the expansion / contraction direction of the piezoelectric element, which is disadvantageous in reducing the height. In addition, since the lens holder is cantilevered by the drive shaft, it is mechanically impossible to move a heavy object such as a lens.

  In the optical module as disclosed in Patent Document 3, the inner peripheral surface of the cylindrical portion of the lens holder support and the outer peripheral surface of the lens holder are in direct contact with each other. The holder support has a structure for holding the lens holder at an arbitrary position on the optical axis of the lens. That is, since the friction surface between the lens holder support and the lens holder is in contact with the cylindrical surface, there is a problem that the contact area becomes unstable and the frictional force varies. Further, there is a problem that the contact surfaces are worn away by long-term use, and a stable frictional force cannot be obtained.

  The subject of this invention is providing the linear actuator which can obtain the stable frictional force.

  Other objects of the invention will become apparent as the description proceeds.

  According to the first aspect of the present invention, the stationary member (21; 22), the lens holder (321; 22) that holds the lens and is movable in the optical axis (O) direction of the lens with respect to the stationary member. 421) and a lens driving unit (34; 44) for driving the lens moving unit while slidably supporting the lens moving unit in the optical axis direction of the lens. The stationary member (21; 22) is disposed at a rotationally symmetric position around the optical axis (O) of the lens and extends in parallel with the optical axis direction of the lens. Including N main shafts (28), and the lens driving unit (34; 44) is disposed at a rotationally symmetric position around the optical axis of the lens. The stationary part expands and contracts in the direction of the optical axis. N piezoelectric units (341; 441) having one end in the expansion / contraction direction fixed thereto and the other end of the N piezoelectric units in the expansion / contraction direction, and are slidably disposed on the N main shafts. A vibration friction portion (342; 442) having an inner peripheral surface (342a; 442a) for accommodating the lens movable portion, and the lens movable portion (32; 42) includes the lens holder and the vibration friction portion. A plurality of pads (322; 422) frictionally coupled to the inner peripheral surface of the vibration friction portion, and the N pads and the lens holder. And a biasing means (323; 423) for biasing the N pads outward in the radial direction.

  In the linear actuator according to the first aspect of the present invention, the biasing means may be constituted by, for example, a ring-shaped spring (323; 423) partially cut away. Each of the N pads (322; 422) protrudes radially outward at both circumferential end portions thereof, and comes into contact with the inner peripheral surface (342a; 442a) of the vibration friction portion (342; 442). It is preferable to have a pair of protrusions (322-1; 422-1) having contact surfaces. The linear actuator (20) preferably further includes position restricting means for restricting the position of the lens in the optical axis (O) direction and the circumferential direction in the N pads (322: 422). In the case where the optical axis (O) of the lens extends in the vertical direction (Z), the position restricting means may be, for example, N upper convex portions that protrude radially outward from the upper end surface of the lens holder ( 321-1; 421-1), 2N lower convex portions (321-2; 421-2) projecting radially outward from the lower end surface of the lens holder, and upper ends of the N pads. Each of the N upper concave portions (322-2; 422-2) fitted with the N upper convex portions and the lower end portions of the N pads are provided in pairs, and the 2N pieces are provided. And 2N lower concave portions (322-3; 422-3) fitted to the lower convex portions. Each of the N piezoelectric units (341; 441) includes a laminated piezoelectric element (341-1; 441-1) in which a plurality of internal electrodes are laminated in the optical axis direction of the lens, and one of the laminated piezoelectric elements. A piezoelectric element fixing portion (341-2; 441-2) having one end surface coupled to the end surface may be included. In this case, the piezoelectric element fixing portion is fixed to the stationary member (21; 22), and the other end surface of the laminated piezoelectric element is coupled to the vibration friction portion (342; 442).

  According to a second aspect of the present invention, there is provided a stationary member including first and second base portions (21, 22) disposed at a predetermined distance from each other in the optical axis (O) direction of the lens; The first base portion and the second base portion are interposed between the first base portion and the second base portion, respectively, to hold the lens and to light the lens with respect to the stationary member. First and second lens movable parts (32, 42) including first and second lens holders (321, 421) movable in the axial direction; and the first lens movable part as an optical axis of the lens. A first lens driving section (34) for driving the first lens movable section while slidably supporting in the direction; and slidable in the optical axis direction of the lens. A second lens driving unit for driving the second lens movable unit while supporting the second lens driving unit 44), wherein the stationary member is disposed at a rotationally symmetric position around the optical axis of the lens, and the first base portion (21) and the second N main shafts (28) extending in parallel with the optical axis direction of the lens between the base portion (22) and the first lens driving portion (34) are arranged around the optical axis of the lens. N first piezoelectric units (341), which are arranged at rotationally symmetric positions, expand and contract in the optical axis direction of the lens, and have one end in the expansion / contraction direction fixed to the first base portion, and the N A first inner peripheral surface (342a) that is coupled to the other end of the first piezoelectric unit in the expansion / contraction direction and is slidably disposed on the N main shafts and accommodates the first lens movable portion. A first vibration friction portion (342) having The lens movable portion (32) is disposed between the first lens holder and the first inner peripheral surface of the first vibration friction portion, and the first vibration friction portion includes the first movable portion (32). N number of first pads (322) frictionally coupled to the inner peripheral surface, and the N number of first pads interposed between the N number of first pads and the first lens holder. First urging means (323) for urging the lens outward in the radial direction, and the second lens driving section (44) is disposed at a rotationally symmetric position around the optical axis of the lens, N number of second piezoelectric units (441) that expand and contract in the optical axis direction of the lens, and one end in the direction of expansion and contraction is fixed to the second base portion, and the direction of expansion and contraction of the N number of second piezoelectric units And is slidably disposed on the N main shafts and accommodates the second lens movable part. A second vibration friction portion (442) having a second inner peripheral surface (442a), and the second lens movable portion (42) includes the second lens holder and the second vibration. N second pads (422) disposed between the second inner peripheral surface of the friction portion and frictionally coupled to the second inner peripheral surface of the second vibration friction portion; Second urging means (423) interposed between the second pads and the second lens holder and urging the N second pads radially outward. A linear actuator characterized by this can be obtained.

  In the linear actuator according to the second aspect of the present invention, the first urging means may be constituted by, for example, a first spring (323) having a partially cut ring shape, and the second urging means. For example, the ring-shaped second spring (423) partially cut out may be formed. Each of the N first pads (322) protrudes radially outward at both circumferential ends thereof, and the first inner peripheral surface (342a) of the first vibration friction portion (342). It is preferable to have a pair of first protrusions (322-1) having contact surfaces that come into contact with each other, and each of the N second pads (422) is radially outward at both circumferential ends. Preferably, the second vibration friction portion (442) has a pair of second protrusions (422-1) having a contact surface that contacts the second inner peripheral surface (442a) of the second vibration friction portion (442).

  The linear actuator (20) includes first position restricting means for restricting the position of the lens in the optical axis (O) direction and the circumferential direction of the N first pads (322), and the N number of first pads (322). It is desirable to further include second position restricting means for restricting the position of the lens in the optical axis (O) direction and the circumferential direction of the second pad (422). When the optical axis (O) of the lens extends in the up-down direction (Z), the first position restricting means, for example, N protrudes radially outward from the upper end surface of the first lens holder. First upper convex portions (321-1), 2N first lower convex portions (321-2) projecting radially outward from the lower end surface of the first lens holder, and the N N first upper recesses (322-2) that are respectively provided at upper ends of the first pads and are fitted to the N first upper protrusions, and the N first pads. 2N first lower concave portions (322-3) provided in pairs at the lower ends of the pads, and fitted with the 2N first lower convex portions, respectively, The second position restricting means may be, for example, N second upper protrusions protruding radially outward from the upper end surface of the second lens holder. (421-1), 2N second lower projections (421-2) projecting radially outward from the lower end surface of the second lens holder, and upper ends of the N second pads Each of the N second upper concave portions (422-2) fitted to the N second upper convex portions and the lower ends of the N second pads. And 2N second lower concave portions (422-3) fitted to the 2N second lower convex portions.

  Each of the N first piezoelectric units (341) includes a first laminated piezoelectric element (341-1) in which a plurality of piezoelectric layers are laminated in the optical axis direction of the lens, and the first laminated layer. Each of the N second piezoelectric units (441) may include a first piezoelectric element fixing portion (341-2) having one end face coupled to one end face of the piezoelectric element. A second laminated piezoelectric element (441-1) in which a plurality of piezoelectric layers are laminated in the optical axis direction, and a second piezoelectric element fixing portion (441) having one end face coupled to one end face of the second laminated piezoelectric element. -2). In this case, the first piezoelectric element fixing portion (341-2) is fixed to the first base portion (21), and the other end surface of the first laminated piezoelectric element (341-1) is the first base portion (211-1). Coupled to the vibration friction portion (342), the second piezoelectric element fixing portion (441-2) is fixed to the second base portion (22), and the second laminated piezoelectric element (441-1) The other end surface is coupled to the second vibration friction portion (442). The first inner peripheral surface (342a) of the first vibration friction portion (342) and the second inner peripheral surface (442a) of the second vibration friction portion (442) are the light of the lens. It is preferable that they overlap each other in the axis (O) direction. In this case, the first movable range of the first lens movable portion (32) and the second movable range of the second lens movable portion (42) are mutually in the optical axis (O) direction of the lens. Overlap.

  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, the lens movable portion includes N pads frictionally coupled to the inner peripheral surface of the vibration friction portion, and biasing means for biasing these N pads radially outward. The individual pads are pushed outward in the radial direction by the urging means, so that a stable frictional force can be obtained.

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

  FIG. 1 is an external perspective view showing a linear actuator 20 according to an embodiment of the present invention. Here, as shown in FIG. 1, an orthogonal coordinate system (X, Y, Z) is used. In the state shown in FIG. 1, in the Cartesian 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 FIG. 1, the vertical direction Z is the direction of the optical axis O of the lens.

  The illustrated linear actuator 20 includes a stationary member including a first base portion 21 and a second base portion 22. The first and second base portions 21 and 22 are arranged at a predetermined distance from each other in the direction of the optical axis O of the lens. In the illustrated example, the first base portion 21 is disposed above the vertical direction Z (the optical axis O direction of the lens), and the second base portion 22 is below the vertical direction Z (the optical axis O direction of the lens). Is arranged. Between the first base portion 21 and the second base portion 22, an outer cover 24 having a substantially rectangular tube shape is provided. An actuator body (described later) of the linear actuator 20 is mounted inside the outer cover 24.

  The first base 21 has a cylindrical portion 211 with the optical axis O of the lens as the central axis. The first group fixed lens FL is fixedly disposed on the cylindrical portion 211.

  Although not shown, an image sensor disposed on the substrate is mounted on the center of the second base 22. The imaging device captures a subject image formed by a first group fixed lens FL, a second group lens (described later), and a third group lens (described later) and converts it into an electrical signal. The imaging element is configured by, for example, a charge coupled device (CCD) type image sensor, a complementary metal oxide semiconductor (CMOS) type image sensor, or the like.

  FIG. 2 is a perspective view of the linear actuator 20 with the outer cover 24 removed from the linear actuator 20 of FIG. FIG. 3 is an exploded perspective view of the linear actuator 20 shown in FIG.

  As shown in FIGS. 2 and 3, the linear actuator 20 includes a zoom lens driving unit 30 and an autofocus lens driving unit 40. The zoom lens driving unit 30 is disposed on the first base portion 21 side, and the autofocus lens driving unit 40 is disposed on the second base portion 22 side. In other words, the zoom lens drive unit 30 is disposed above the vertical direction Z (the optical axis O direction of the lens), and the autofocus lens drive unit 40 is disposed below the vertical direction Z (the optical axis O direction of the lens). Has been.

  Here, the zoom lens drive unit 30 is also referred to as a first drive unit, and the autofocus lens drive unit 40 is also referred to as a second drive unit. As will be described later, each of the zoom lens drive unit (first drive unit) 30 and the autofocus lens drive unit (second drive unit) 40 substantially has the optical axis O of the lens as a rotation axis twice. It has a two-fold rotationally symmetric structure.

  The first base portion 21 has a pair of first protrusions 212 that protrude downward along the vertical direction Z at corners in a diagonal direction centered on the optical axis O of the lens. The second base portion 22 has a pair of second protrusions 222 that protrude downward along the vertical direction Z at corners in a diagonal direction centered on the optical axis O of the lens. As will be described later, the pair of first protrusions 212 is provided with a pair of first piezoelectric units 341, and the pair of second protrusions 222 is provided with a pair of second piezoelectric units 441.

  As shown in FIG. 3, the stationary member includes a pair of main shafts 28. The pair of main shafts 28 are disposed at rotationally symmetric positions around the optical axis O of the lens. The pair of main shafts 28 extend between the first base portion 21 and the second base 22 in parallel with the optical axis direction O of the lens. One end (upper end) of the pair of main shafts 28 is fixed to the first base portion 21, and the other end (lower end) is fixed to the second base portion 22.

  In this example, the zoom lens is called a second group movable lens (first lens), and the autofocus lens is called a third group movable lens (second lens). The combination of the zoom lens driving unit (first driving unit) 30 and the first base portion 21 is called a second group lens driving mechanism (first lens driving mechanism). The combination of the autofocus lens driving unit (second driving unit) 40 and the second base portion 22 is called a third group lens driving mechanism (second lens driving mechanism).

  The second group lens driving mechanism (first lens driving mechanism) will be described with reference to FIGS. 4 is a perspective view of the second lens drive mechanism (first lens drive mechanism), FIG. 5 is an exploded perspective view of the second lens drive mechanism (first lens drive mechanism), and FIG. It is a fragmentary sectional perspective view of the 2nd group lens drive mechanism (1st lens drive mechanism).

The zoom lens drive unit (first drive unit) 30 includes a first lens movable unit 32 and a first lens drive unit 34. The first lens movable unit 32 includes a first lens holder 321 that holds first to third zoom lenses (second group movable lenses) ZL ₁ , ZL ₂ , and ZL ₃ . The first lens holder 321 is movable in the direction of the optical axis O of the lens with respect to the stationary member (first base portion 21). The first lens driving unit 34 drives the first lens moving unit 32 as described later while supporting the first lens moving unit 32 slidably in the optical axis O direction of the lens.

  The first lens driving unit 34 includes a pair of first piezoelectric units 341 and a first vibration friction unit 342. The pair of first piezoelectric units 341 are arranged at rotationally symmetric positions around the optical axis O of the lens. The pair of first piezoelectric units 341 expands and contracts in the direction of the optical axis O of the lens. One end of the pair of piezoelectric units 341 in the expansion / contraction direction is fixed to the first base portion 21. The first vibration friction portion 342 is coupled to the other end of the pair of piezoelectric units 341 in the expansion / contraction direction. The first vibration friction portion 342 is slidably disposed on the pair of main shafts 28.

  The first vibration friction portions 342 are spaced apart from each other in the front-rear direction X, disposed at rotationally symmetric positions around the optical axis O of the lens, and a pair of first side wall portions 342 extending along the up-down direction Z. -1. The pair of first side wall portions 342-1 has a pair of first inner peripheral surfaces 342a that accommodate the first lens movable portion 32 as inner wall surfaces thereof.

  The first vibration friction portion 342 has a pair of first through holes 342b into which the pair of main shafts 28 are inserted. As a result, the first vibration friction portion 342 is restricted from rotating around the optical axis O of the lens and can vibrate only in the direction of the optical axis O of the lens.

  Each of the pair of first piezoelectric units 341 includes a first laminated piezoelectric element 341-1 in which a plurality of piezoelectric layers are laminated in the optical axis O direction of the lens, and one end face of the first laminated piezoelectric element 341-1. A first piezoelectric element fixing portion 341-2 having one end surface coupled to the (upper end surface). The first piezoelectric element fixing portion 341-2 functions as a weight. The first piezoelectric element fixing portion 341-2 is fixed to the first base portion 21. The other end face (lower end face) of the first laminated piezoelectric element 341-1 is coupled to the first vibration friction portion 342.

  More specifically, as shown in FIG. 6, the pair of first protrusions 212 of the first base portion 21 are the first piezoelectric element fixing portions (weights) 341-of the pair of first piezoelectric units 341. 2 has a pair of first cylindrical holes 212a. As a result, the first piezoelectric element fixing portion 341-2 is fixed to the first base portion 21. It should be noted that the bonding between one end face (upper end face) of the first multilayer piezoelectric element 341-1 and the first piezoelectric element fixing portion 341-2 and the other end face (lower side) of the first multilayer piezoelectric element 341-1. The joining between the end face) and the first vibration friction portion 342 will be described in detail later.

  The pair of first piezoelectric units 341 and the first vibration friction portion 342 are juxtaposed with respect to the optical axis O of the lens, as shown in FIG. Therefore, the zoom lens drive unit (first drive unit) 30 can be reduced in height. As a result, the second group lens driving mechanism (first lens driving mechanism) can also be reduced in height.

  Referring also to FIG. 7, the first lens movable portion 32 is a pair of first lenses disposed between the first lens holder 321 and the first inner peripheral surface 342 a of the first vibration friction portion 342. Of pads 322. The pair of first pads 322 are spaced apart from each other in the front-rear direction X and are disposed at rotationally symmetric positions around the optical axis O of the lens, and the pair of first inner peripheral surfaces 342a of the first vibration friction portion 342. Friction coupling with. More specifically, each of the pair of first pads 322 has a pair of first first protrusions 322-1 protruding outward in the radial direction at both ends in the left-right direction Y. The pair of first protrusions 322-1 has a contact surface that comes into contact with the first inner peripheral surface 342a of the first vibration friction portion 342. That is, the first inner peripheral surface 342a of the first vibration friction portion 342 acts as a friction drive surface, and the contact surfaces of the pair of first protrusions 322-1 act as friction driven surfaces.

  A first spring 323 is interposed between the pair of first pads 322 and the first lens holder 321. The first spring 323 has a ring shape with a part cut away. In other words, the pair of first protrusions 322-1 of the pair of first pads 322 is pressed against the first inner peripheral surface 342a of the first vibration friction portion 342 by the first spring 323. In any case, the first spring 323 functions as a first biasing unit that biases the pair of first pads 322 radially outward.

  Therefore, even if the friction-driven surface (the contact surface of the pair of first protrusions 322-1) is worn away, the pair of first pads 322 is radiused by the first spring (first biasing means) 323. Since it is pushed out in the direction, a stable frictional force can be obtained until the pair of first protrusions 322-1 disappears.

  The first lens holder 321 has a pair of first upper protrusions 321-1 projecting radially outward from the upper end surface along the front-rear direction X, and two projecting radially outward from the lower end surface. It has a pair of first lower convex parts 321-2. On the other hand, each of the pair of first pads 322 includes a first upper concave portion 322-2 into which the first upper convex portion 321-1 corresponding to the upper end portion is fitted, and a pair corresponding to the lower end portion. And a pair of first lower concave portions 322-3 to which the first lower convex portions 321-2 are fitted. Accordingly, the vertical direction Z (direction of the optical axis O of the lens) and the circumferential position of the pair of first pads 322 are restricted, and the pair of first pads 322 are radially outward by the first springs 323. Is only movable. At any rate, the pair of first upper convex portions 321-1 of the first lens holder 321, the two pairs of first lower convex portions 321-2, and the first upper concave portions 322 of the pair of first pads 322. 2 and the pair of first lower recesses 322-3 serve as first position regulating means for regulating the position of the lens in the optical axis O direction and the circumferential direction of the pair of first pads 322.

As described above, the first lens movable unit 32 receives the force in the optical axis (O) direction of the lens by the first lens driving unit 34 from the entire periphery of the first lens holder 321. For this reason, the second lens drive mechanism (first lens drive mechanism) makes sense to drive a heavy object such as the _{first to} third zoom lenses ZL ₁ , ZL ₂ , ZL ₃ . Has a structure. In addition, it is possible to reduce the inclinations of the first to third zoom lenses ZL ₁ , ZL ₂ , and ZL ₃ during driving of the first lens movable unit 32 (first lens holder 321).

  The third group lens driving mechanism (second lens driving mechanism) will be described with reference to FIGS. FIG. 8 is a perspective view of the third group lens driving mechanism (second lens driving mechanism), FIG. 9 is an exploded perspective view of the third group lens driving mechanism (second lens driving mechanism), and FIG. It is a fragmentary sectional perspective view of a 3rd group lens drive mechanism (2nd lens drive mechanism).

  The autofocus lens driving unit (second driving unit) 40 includes a second lens movable unit 42 and a second lens driving unit 44. The second lens movable unit 42 includes a second lens holder 421 that holds an autofocus lens (third movable group lens) AFL. The second lens holder 421 is movable in the optical axis O direction of the lens with respect to the stationary member (second base portion 22). The second lens driving unit 44 drives the second lens moving unit 42 as described later while supporting the second lens moving unit 42 slidably in the optical axis O direction of the lens.

  The second lens driving unit 44 includes a pair of second piezoelectric units 441 and a second vibration friction unit 442. The pair of second piezoelectric units 441 are arranged at rotationally symmetric positions around the optical axis O of the lens. The pair of second piezoelectric units 441 expands and contracts in the direction of the optical axis O of the lens. One end of the pair of piezoelectric units 441 in the expansion / contraction direction is fixed to the second base portion 22. The second vibration friction portion 442 is coupled to the other end of the pair of second piezoelectric units 441 in the expansion / contraction direction. The first vibration friction portion 442 is slidably disposed on the pair of main shafts 28.

  The second vibration friction portions 442 are spaced apart from each other in the front-rear direction Y, are disposed at rotationally symmetric positions around the optical axis O of the lens, and a pair of second side wall portions 442 extending along the up-down direction Z. -1. The pair of second side wall portions 442-1 has a pair of second inner peripheral surfaces 442a that house the second lens movable portion 42 as inner wall surfaces thereof.

  The second vibration friction portion 442 has a pair of second through holes 442b into which the pair of main shafts 28 are inserted. Thereby, the second vibration friction portion 442 is restricted from rotating around the optical axis O of the lens and can vibrate only in the direction of the optical axis O of the lens.

  Each of the pair of second piezoelectric units 441 includes a second laminated piezoelectric element 441-1 in which a plurality of piezoelectric layers are laminated in the optical axis O direction of the lens, and one end surface of the second laminated piezoelectric element 441-1. A second piezoelectric element fixing portion 441-2 having one end face coupled to the (lower end face). The second piezoelectric element fixing portion 441-2 serves as a weight. The second piezoelectric element fixing portion 441-2 is fixed to the second base portion 22. The other end face (upper end face) of the second multilayer piezoelectric element 441-1 is coupled to the second vibration friction portion 442.

  More specifically, as shown in FIG. 10, the pair of second protrusions 222 of the second base portion 22 are the second piezoelectric element fixing portions (weights) 441-of the pair of second piezoelectric units 441. 2 has a pair of second cylindrical holes 222a into which 2 is inserted. As a result, the second piezoelectric element fixing portion 441-2 is fixed to the second base portion 22. It should be noted that the bonding between one end surface (lower end surface) of the second multilayer piezoelectric element 441-1 and the second piezoelectric element fixing portion 441-2 and the other end surface (upper surface) of the second multilayer piezoelectric element 441-1. The joining between the end face) and the second vibration friction portion 442 will be described in detail later.

  The pair of second piezoelectric units 441 and the second vibration friction portion 442 are juxtaposed with respect to the optical axis O of the lens, as shown in FIG. Therefore, the focus lens drive unit (second drive unit) 40 can be reduced in height. As a result, the third group lens driving mechanism (second lens driving mechanism) can also be reduced in height.

  Referring also to FIG. 11, the second lens movable portion 42 is a pair of second lenses disposed between the second lens holder 421 and the second inner peripheral surface 442 a of the second vibration friction portion 442. The pad 422 is included. The pair of second pads 422 are spaced apart from each other in the left-right direction Y and are disposed at rotationally symmetric positions around the optical axis O of the lens, and the pair of second inner peripheral surfaces 442a of the second vibration friction portion 442. Friction coupling with. More specifically, each of the pair of second pads 422 has a pair of second projecting portions 422-1 projecting radially outward at both ends in the front-rear direction X. The pair of second protrusions 422-1 has a contact surface that comes into contact with the first inner peripheral surface 442a of the second vibration friction unit 442. That is, the second inner peripheral surface 442a of the second vibration friction portion 442 acts as a friction drive surface, and the contact surfaces of the pair of second protrusions 422-1 act as friction driven surfaces.

  12 and 13 in addition to FIG. 11, a second spring 423 is interposed between the pair of second pads 422 and the second lens holder 421. The second spring 423 has a ring shape with a part cut away. In other words, the pair of second protrusions 422-1 of the pair of second pads 422 are pressed against the second inner peripheral surface 442a of the second vibration friction part 442 by the second spring 423. In any case, the second spring 423 serves as a second urging unit that urges the pair of second pads 422 radially outward.

  Therefore, even if the friction-driven surface (the contact surface of the pair of second protrusions 422-1) wears down, the pair of second pads 422 are radiused by the second spring (second biasing means) 423. Since it is pushed out in the direction, a stable frictional force can be obtained until the pair of second protrusions 422-1 disappear.

  The second lens holder 421 has a pair of second upper projections 421-1 projecting radially outward from the upper end surface along the left-right direction Y, and two projecting radially outward from the lower end surface. It has a pair of second lower convex portions 421-2.

  On the other hand, referring also to FIG. 14, each of the pair of second pads 422 includes a second upper concave portion 422-2 into which the second upper convex portion 421-1 corresponding to the upper end portion is fitted. And a pair of second lower concave portions 422-3 into which a pair of second lower convex portions 421-2 corresponding to the lower ends thereof are fitted. As a result, the vertical direction Z (the direction of the optical axis O of the lens) and the circumferential position of the pair of second pads 422 are restricted, and the pair of second pads 422 are radially outward by the second springs 423. Is only movable. At any rate, the pair of second upper convex portions 421-1 of the second lens holder 421, the two pairs of second lower convex portions 421-2, and the second upper concave portions 422 of the pair of second pads 422. 2 and the pair of second lower recesses 422-3 serve as second position restricting means for restricting the position of the lens in the optical axis O direction and the circumferential direction of the pair of second pads 422.

  As described above, the second lens movable unit 42 receives a force in the optical axis (O) direction of the lens by the second lens driving unit 44 from the entire periphery of the second lens holder 421. For this reason, the third lens group driving mechanism (second lens driving mechanism) has a reasonable structure for driving a heavy object such as the autofocus lens AFL. In addition, the inclination of the autofocus lens AFL during the driving of the second lens movable unit 42 (second lens holder 421) can be reduced.

  As shown in FIG. 2, when these components are assembled, the first vibration friction portion 342 of the zoom lens drive unit (first drive unit) 30 and the autofocus lens drive unit (second drive unit) are assembled. The 40 second vibration friction portions 442 are combined together with a gap between them. Therefore, the first inner peripheral surface 342a of the first vibration friction portion 342 and the second inner peripheral surface 442a of the second vibration friction portion 442 overlap each other in the optical axis O direction of the lens. As a result, the first movable range of the first lens movable unit 32 and the second movable range of the second lens movable unit 42 overlap each other in the optical axis O direction of the lens. As a result, the linear actuator 20 can be reduced in height.

  Next, the current supplied to the laminated piezoelectric element and the displacement generated in the laminated piezoelectric element will be described with reference to FIG. FIG. 15 is the same as that shown in FIG. FIGS. 15A and 15B show the change in the current supplied to the laminated piezoelectric element by the drive circuit (not shown) and the displacement of the laminated piezoelectric element, respectively.

  As shown in FIG. 15A, a large current (positive direction) and a predetermined constant current (negative direction) are alternately passed through the laminated piezoelectric element. In such a situation, as shown in FIG. 15B, the laminated piezoelectric element has a sudden displacement (elongation) corresponding to a large current (positive direction) and a gentle displacement corresponding to a constant current (negative direction). (Shrinkage) occurs alternately.

  That is, a rectangular wave current is applied to the laminated piezoelectric element (FIG. 15A), and a sawtooth-like displacement (expansion / contraction) is generated with respect to the laminated piezoelectric element (FIG. 15B).

  The operation of the zoom lens driving mechanism (zoom lens driving unit 30) will be described with reference to FIGS. 5 and 6 in addition to FIG. First, an operation when the first lens movable portion 32 is moved upward along the vertical direction Z will be described.

  First, as shown in FIG. 15A, when a large current in the positive direction is passed through the pair of first laminated piezoelectric elements 341-1, as shown in FIG. 15B, the pair of first laminated piezoelectric elements. The element 341-1 rapidly undergoes an extensional displacement in the thickness direction. As a result, the first vibration friction portion 342 moves rapidly downward along the optical axis O direction (vertical direction Z) of the lens. At this time, the first lens movable portion 32 is caused by the inertial force between the first inner peripheral surface 342a of the first vibration friction portion 342 and the friction driven surface 322-1 of the pair of first pads 322. It won't move because it overcomes the frictional force and stays in that position.

  Next, as shown in FIG. 15A, when a constant current in the negative direction is passed through the pair of first laminated piezoelectric elements 341-1, as shown in FIG. The piezoelectric element 341-1 is gently contracted in the thickness direction. As a result, the first vibration friction portion 342 moves gently upward along the optical axis O direction (vertical direction Z) of the lens. At this time, the pair of first pads 322 are pressed in the radial direction by the first spring 323, and the first inner peripheral surface 342 a of the first vibration friction portion 342 and the pair of first pads 322 are rubbed. The first lens holder 32 and the first vibration friction portion 342 are substantially in the direction of the optical axis O of the lens (because the first lens holder 32 is in surface contact with the drive surface 322-1 and coupled by frictional force generated on the contact surface. It moves upward along the vertical direction Z).

  In this way, a large current in the positive direction and a predetermined constant current in the negative direction are alternately passed through the pair of first multilayer piezoelectric elements 341-1, and the pair of first multilayer piezoelectric elements 341-1 are expanded and displaced. By alternately generating the contraction displacement, the first lens holder 321 (first lens movable portion 32) can be continuously moved upward along the lens optical axis O direction (vertical direction Z). .

  In order to move the first lens movable portion 32 downward along the lens optical axis O direction (vertical direction Z), a large current in the negative direction is applied to the pair of first laminated piezoelectric elements 341-1 contrary to the above. And a predetermined constant current in the positive direction can be alternately flowed.

  The operation of the autofocus drive mechanism (autofocus lens drive unit 40) will be described with reference to FIGS. 9 and 10 in addition to FIG. First, an operation when the second lens movable portion 42 is moved downward along the vertical direction Z will be described.

  First, as shown in FIG. 15A, when a large current in the positive direction is passed through the pair of second laminated piezoelectric elements 441-1, as shown in FIG. 15B, a pair of second laminated piezoelectric elements. The element 441-1 rapidly undergoes displacement in the thickness direction. As a result, the second vibration friction portion 442 rapidly moves upward along the optical axis O direction (vertical direction Z) of the lens. At this time, the second lens movable portion 42 is caused by the inertia force between the second inner peripheral surface 442a of the second vibration friction portion 442 and the friction driven surface 422-1 of the pair of second pads 422. It won't move because it overcomes the frictional force and stays in that position.

  Next, as shown in FIG. 15A, when a constant current in the negative direction is passed through the pair of second laminated piezoelectric elements 441-1, the pair of second laminated piezoelectric elements 441-1 gradually increases in the thickness direction. This produces a contraction displacement. As a result, the second vibration friction portion 442 gently moves downward along the optical axis O direction (vertical direction Z) of the lens. At this time, the pair of second pads 422 are pressed in the radial direction by the second spring 423, and the second inner peripheral surface 442 a of the second vibration friction portion 442 and the pair of second pads 422 are rubbed. The second lens holder 42 is substantially in the direction of the optical axis O of the lens along with the first vibration friction portion 442 (being in surface contact with the drive surface 422-1 and coupled by frictional force generated on the contact surface). It moves downward along the vertical direction Z).

  In this way, a large positive current and a predetermined constant current in the negative direction are alternately passed through the pair of second multilayer piezoelectric elements 441-1 to cause the pair of second multilayer piezoelectric elements 441-1 to expand and displace. By alternately generating the contraction displacement, the second lens holder 421 (second lens movable portion 42) can be continuously moved downward along the lens optical axis O direction (vertical direction Z). .

  In order to move the second lens movable portion 42 upward along the lens optical axis O direction (vertical direction Z), a large current in the negative direction is applied to the pair of second laminated piezoelectric elements 441-1 contrary to the above. And a predetermined constant current in the positive direction can be alternately flowed.

  Next, the first laminated piezoelectric element 341-1 used for the first piezoelectric unit 341 and the second laminated piezoelectric element 441-1 used for the second piezoelectric unit 441 will be described.

  The laminated piezoelectric element has a rectangular parallelepiped shape, and the element size is 0.9 [mm] × 0.9 [mm] × 1.5 [mm]. A low Qm material such as PZT is used as the piezoelectric material. A laminated piezoelectric element is manufactured by alternately stacking 50 layers of piezoelectric material having a thickness of 20 [μm] and internal electrodes having a thickness of 2 [μm] in a comb shape. The effective internal electrode size of the laminated piezoelectric element is 0.6 [mm] × 0.6 [mm]. In other words, a ring-shaped dead zone portion (clearance) having a width of 0.15 [mm] exists in the peripheral portion located outside the effective internal electrode of the multilayer piezoelectric element.

  As will be described in detail below, in the present invention, the end face of the laminated piezoelectric element is bonded to an object to be bonded with an adhesive while avoiding the dead zone.

  Next, referring to FIG. 16 in addition to FIG. 6, a joining method between the one end surface 341-1 a of the first multilayer piezoelectric element 341-1 and the first piezoelectric element fixing portion 341-2, A joining method between the other end face 341-1b of the first laminated piezoelectric element 341-1 and the first vibration friction portion 342 will be described.

  The first piezoelectric element fixing portion 341-2 has a first adhesive drum 341-2a corresponding to the size of the internal electrode of the first multilayered piezoelectric element 341-1. As a result, one end face (upper end face) 341-1a of the first laminated piezoelectric element 341-1 is made to be the first piezoelectric element fixing portion 341- by the adhesive accumulated in the first adhesive dip 341-2a. 2 is joined. In other words, when the one end face (upper end face) 341-1a of the first multilayer piezoelectric element 341-1 is bonded (bonded) to the first piezoelectric element fixing portion 341-2, the first multilayer piezoelectric element 341 is bonded. The adhesive was applied avoiding the -1 dead zone.

  On the other hand, the first vibration friction portion 342 includes a first positioning guide hole 342c for guiding the position of the other end of the first multilayer piezoelectric element 341-1 and the first multilayer piezoelectric element 341-1. And a second adhesive dummy 342d corresponding to the size of the internal electrode. As a result, the other end face (lower end face) of the first multilayer piezoelectric element 341-1 in a state where the other end portion of the first multilayer piezoelectric element 341-1 is positioned and guided along the first positioning guide hole 342a. 341-1b is joined to the first vibration friction portion 342. In other words, when the other end face (lower end face) 341-1b of the first multilayer piezoelectric element 341-1 is bonded (bonded) to the first vibration friction portion 342, the first multilayer piezoelectric element 341-1 has the first multilayer piezoelectric element 341-1. The adhesive is applied to avoid the dead zone.

  Next, referring to FIG. 17 in addition to FIG. 10, a joining method between the one end surface 441-1a of the second multilayer piezoelectric element 441-1 and the second piezoelectric element fixing portion 441-2, A joining method between the other end face 441-1b of the second multilayer piezoelectric element 441-1 and the second vibration friction portion 442 will be described.

  The second piezoelectric element fixing portion 441-2 has a third adhesive drum 441-2a corresponding to the size of the internal electrode of the second multilayer piezoelectric element 441-1. As a result, one end surface (lower end surface) 441-1a of the second laminated piezoelectric element 441-1 is made to be the second piezoelectric element fixing portion 441- by the adhesive accumulated in the third adhesive drum 441-1a. 2 is joined. In other words, when the one end surface (lower end surface) 441-1a of the second multilayer piezoelectric element 441-1 is bonded (bonded) to the second piezoelectric element fixing portion 441-2, the second multilayer piezoelectric element 441 is provided. The adhesive was applied avoiding the -1 dead zone.

  On the other hand, the second vibration friction portion 442 includes a second positioning guide hole 442c for guiding the position of the other end of the second multilayer piezoelectric element 441-1, and the second multilayer piezoelectric element 441-1. And a fourth adhesive dummy 442d corresponding to the size of the internal electrode. As a result, the other end face (upper end face) of the first multilayer piezoelectric element 441-1 in a state where the other end part of the second multilayer piezoelectric element 441-1 is positioned and guided along the second positioning guide hole 442a. 441-1b is joined to the second vibration friction portion 442. In other words, when the other end face (upper end face) 441-1b of the second multilayer piezoelectric element 441-1 is bonded (bonded) to the second vibration friction portion 442, the second multilayer piezoelectric element 441-1 has the second multilayer piezoelectric element 441-1. The adhesive is applied to avoid the dead zone.

  In this manner, in the present embodiment, when the upper and lower end surfaces of the multilayer piezoelectric element in the expansion / contraction direction are bonded to the object to be bonded, the adhesive is applied while avoiding the dead zone portion of the multilayer piezoelectric element.

  FIG. 18 shows the amount of displacement of the laminated piezoelectric element by the conventional bonding method and the bonding method of the present invention. In FIG. 18, (A) shows the amount of displacement by the conventional bonding method, and (B) shows the amount of displacement by the bonding method of the present invention.

  Comparing FIG. 18 (A) and FIG. 18 (B), compared with the case of the conventional bonding method (FIG. 18 (A)) in which an adhesive is uniformly applied to the end face of the laminated piezoelectric element, It can be seen that the displacement amount of the laminated piezoelectric element can be efficiently secured in the case of the bonding method of the present invention (FIG. 18B) in which an adhesive is applied to the end face of the piezoelectric element while avoiding the dead zone. . In other words, when the voltage applied to the laminated piezoelectric element is the same, the bonding method of the present invention can obtain a larger displacement than the conventional bonding method. Specifically, when the displacement amount in the bonding method of the present invention is about 90 nm, the displacement amount in the conventional bonding method is about 50 nm.

  As a result, when the movable part is moved by the same distance, the actuator using the bonding method of the present invention can reduce the power consumption compared to the actuator using the conventional bonding method. Furthermore, since the bonding method of the present invention can reduce the stress applied to the bonded portion compared to the conventional bonding method, peeling can be prevented.

  Since the gist of the bonding method of the present invention is a method of applying an adhesive to the end face of the multilayer piezoelectric element while avoiding the dead zone, it is needless to say that the bonding method is not limited to the above-described embodiment.

  For example, as shown in FIG. 19, the contact surface of the object to be bonded is made to correspond to the size of the internal electrode of the multilayer piezoelectric element so that the dead zone is avoided and the adhesive is applied to the end face of the multilayer piezoelectric element. Anyway.

  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 above-described embodiment, each of the zoom lens driving unit (first driving unit) 30 and the autofocus lens driving unit (second driving unit) 40 uses the optical axis O of the lens as a rotation axis twice. In general, each of the zoom lens driving unit (first driving unit) and the autofocus lens driving unit (second driving unit) has a lens structure that is rotationally symmetrical twice. The optical axis O may be substantially n-fold rotationally symmetric with the rotation axis being N (N is an integer of 2 or more).

It is an external appearance perspective view which shows the linear actuator by carrying of one implementation of this invention. FIG. 2 is a perspective view of a linear actuator with an outer cover removed from the linear actuator illustrated in FIG. 1. FIG. 3 is an exploded perspective view of the linear actuator illustrated in FIG. 2. It is a perspective view of the 2nd group lens drive mechanism (1st lens drive mechanism) used for the linear actuator shown in FIG. FIG. 5 is an exploded perspective view of a second group lens driving mechanism (first lens driving mechanism) illustrated in FIG. 4. FIG. 5 is a partial cross-sectional perspective view of a second group lens driving mechanism (first lens driving mechanism) illustrated in FIG. 4. FIG. 5 is a perspective view of a first lens movable unit used in the second group lens driving mechanism (first lens driving mechanism) illustrated in FIG. 4. It is a perspective view of the 3rd group lens drive mechanism (2nd lens drive mechanism) used for the linear actuator shown in FIG. FIG. 9 is an exploded perspective view of a third group lens driving mechanism (second lens driving mechanism) illustrated in FIG. 8. FIG. 9 is a partial cross-sectional perspective view of a third group lens driving mechanism (second lens driving mechanism) illustrated in FIG. 8. It is a perspective view of the 2nd lens movable part used for the 3rd group lens drive mechanism (2nd lens drive mechanism) shown in FIG. FIG. 12 is an exploded perspective view of a second lens movable unit illustrated in FIG. 11. It is a perspective view which shows the 2nd spring used for the 2nd lens movable part shown in FIG. It is a perspective view which shows the 2nd pad used for the 2nd lens movable part shown in FIG. It is a wave form diagram for demonstrating the electric current supplied to a laminated piezoelectric element, and the displacement which generate | occur | produces in a laminated piezoelectric element. Description will be given of a joining method between one end face of the first laminated piezoelectric element and the first piezoelectric element fixing portion and a joining method between the other end face of the first laminated piezoelectric element and the first vibration friction portion. It is a figure for doing. Explained are a joining method between one end face of the second laminated piezoelectric element and the second piezoelectric element fixing portion, and a joining method between the other end face of the second laminated piezoelectric element and the second vibration friction portion. It is a figure for doing. It is a figure for demonstrating the displacement amount of the laminated piezoelectric element by the conventional adhesion | attachment method and the adhesion | attachment method of this invention. It is a figure for demonstrating the other adhesion | attachment method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Linear actuator 21 1st base part 211 Cylindrical part 212 1st protrusion part 212a 1st columnar hole 22 2nd base part 222 2nd protrusion part 222a 2nd columnar hole 24 Outer cover 28 Main shaft 30 Zoom lens drive unit (first drive unit)
32 1st lens movable part 321 1st lens holder 321-1 1st upper side convex part 321-2 1st lower side convex part 322 1st pad 322-1 1st protrusion part 322-2 1st Upper recess 322-3 first lower recess 323 first spring 34 first lens driving unit 341 first piezoelectric unit 341-1 first laminated piezoelectric element 341-1a one end surface (upper end surface)
341-1b The other end surface (lower end surface)
341-2 First piezoelectric element fixing portion (weight)
341-2a First adhesive drum 342 First vibration friction portion 342a First inner peripheral surface 342b First through hole 342c First positioning guide hole 342d First adhesive drum 342-1 First side wall 40 Autofocus lens drive unit (second drive unit)
42 2nd lens movable part 421 2nd lens holder 421-1 2nd upper side convex part 421-2 2nd lower side convex part 422 2nd pad 422-1 2nd protrusion part 422-2 2nd Upper concave portion 422-3 Second lower concave portion 423 Second spring 44 Second lens driving portion 441 Second piezoelectric unit 441-1 Second laminated piezoelectric element 441-1a One end surface (lower end surface)
441-2 Second piezoelectric element fixing portion (weight)
441-2a Third adhesive drum 442 Second vibration friction portion 442a Second inner peripheral surface 442b Second through hole 442c Second positioning guide hole 442d Fourth adhesive drum 442-1 Second side wall Part O Optical axis of lens FL First group fixed lens ZL ₁ , ZL ₂ , ZL ₃ Second group movable lens (zoom lens)
AFL 3rd group movable lens (autofocus lens)

Claims (13)

A lens movable portion including a stationary member, a lens holder that holds the lens and is movable with respect to the stationary member in the optical axis direction of the lens, and the lens movable portion can slide in the optical axis direction of the lens A linear actuator including a lens driving unit that drives the lens movable unit while supporting the lens,
The stationary member includes N main shafts (N is an integer of 2 or more) arranged in a rotationally symmetrical position around the optical axis of the lens and extending in parallel with the optical axis direction of the lens,
The lens driving unit is
N piezoelectric units that are arranged at rotationally symmetric positions around the optical axis of the lens, expand and contract in the optical axis direction of the lens, and have one end in the expansion and contraction direction fixed to the stationary member;
A vibration friction portion coupled to the other end of the plurality of piezoelectric units in the expansion / contraction direction, slidably disposed on the N main shafts, and having an inner peripheral surface that accommodates the lens movable portion;
The lens movable part is
N pads disposed between the lens holder and the inner peripheral surface of the vibration friction portion, and frictionally coupled to the inner peripheral surface of the vibration friction portion;
Urging means interposed between the plurality of pads and the lens holder and urging the N pads radially outward;
A linear actuator characterized by that.   The linear actuator according to claim 1, wherein the urging means is formed of a ring-shaped spring partially cut away.   Each of the N pads has a pair of projecting portions that project radially outward at both circumferential end portions thereof and have contact surfaces that come into contact with the inner circumferential surface of the vibration friction portion. 2. The linear actuator according to 2.   4. The linear actuator according to claim 1, further comprising position restricting means for restricting positions of the lens in the optical axis direction and the circumferential direction in the N pads. 5. The optical axis of the lens extends in the vertical direction,
The position regulating means is
N upper convex portions projecting radially outward from the upper end surface of the lens holder;
2N lower convex portions projecting radially outward from the lower end surface of the lens holder;
N upper recesses that are respectively provided at upper ends of the N pads and are fitted with the N upper protrusions;
2N lower concave portions provided in pairs at the lower ends of the N pads, and fitted with the 2N lower convex portions,
The linear actuator according to claim 4, comprising: Each of the N piezoelectric units includes a laminated piezoelectric element in which a plurality of internal electrodes are laminated in the optical axis direction of the lens, and a piezoelectric element fixing portion having one end surface coupled to one end face of the laminated piezoelectric element. Have
The linear actuator according to claim 1, wherein the piezoelectric element fixing portion is fixed to the stationary member, and the other end surface of the laminated piezoelectric element is coupled to the vibration friction portion. A stationary member including first and second base portions arranged at a predetermined distance from each other in the optical axis direction of the lens; and interposed between the first base portion and the second base portion; First and second lenses each including first and second lens holders disposed on the first and second base portions to hold the lens and move in the optical axis direction of the lens with respect to the stationary member. A second lens movable portion; a first lens drive portion that drives the first lens movable portion while supporting the first lens movable portion slidably in the optical axis direction of the lens; A second lens driving unit that drives the second lens moving unit while supporting the second lens moving unit so as to be slidable in the optical axis direction of the lens,
The stationary member is disposed at a rotationally symmetric position around the optical axis of the lens, and extends between the first base portion and the second base portion in parallel with the optical axis direction of the lens. Including the main shaft (N is an integer of 2 or more),
The first lens driving unit includes:
N first piezoelectric units disposed at rotationally symmetric positions around the optical axis of the lens, expanding and contracting in the optical axis direction of the lens, and having one end in the expansion and contraction direction fixed to the first base portion; ,
The N first piezoelectric units are coupled to the other end in the expansion / contraction direction, are slidably disposed on the N main shafts, and have a first inner peripheral surface that accommodates the first lens movable portion. A first vibration friction part,
The first lens movable part is:
N pieces arranged between the first lens holder and the first inner peripheral surface of the first vibration friction portion and frictionally coupled to the first inner peripheral surface of the first vibration friction portion. A first pad of
First biasing means that is interposed between the N first pads and the first lens holder and biases the N first pads radially outward;
The second lens driving unit is
N second piezoelectric units disposed at rotationally symmetric positions around the optical axis of the lens, expanding and contracting in the optical axis direction of the lens, and having one end in the expansion and contraction direction fixed to the second base portion; ,
Coupled to the other end of the N second piezoelectric units in the expansion / contraction direction, is slidably disposed on the N main shafts, and has a second inner peripheral surface that accommodates the second lens movable portion. A second vibration friction part,
The second lens movable part is
N pieces arranged between the second lens holder and the second inner peripheral surface of the second vibration friction portion and frictionally coupled to the second inner peripheral surface of the second vibration friction portion A second pad of
Second biasing means interposed between the N second pads and the second lens holder and biasing the N second pads radially outward;
A linear actuator characterized by that. The first urging means comprises a ring-shaped first spring partly cut away,
The second urging means comprises a ring-shaped second spring partially cut away.
The linear actuator according to claim 7. Each of the N first pads protrudes radially outward at both circumferential end portions thereof and has a pair of contact surfaces that come into contact with the first inner peripheral surface of the first vibration friction portion. Having a first protrusion,
Each of the N second pads protrudes radially outward at both circumferential end portions thereof and has a pair of contact surfaces that come into contact with the second inner peripheral surface of the second vibration friction portion. Having a second protrusion,
The linear actuator according to claim 7 or 8. First position restricting means for restricting positions of the lens in the optical axis direction and the circumferential direction in the N first pads;
Second position restricting means for restricting positions of the lens in the optical axis direction and the circumferential direction in the N second pads;
The linear actuator according to any one of claims 7 to 9, further comprising: The optical axis of the lens extends in the vertical direction,
The first position restricting means includes
N first upper protrusions projecting radially outward from the upper end surface of the first lens holder;
2N first lower convex portions projecting radially outward from the lower end surface of the first lens holder;
N first upper recesses respectively provided at upper ends of the N first pads and fitted with the N first upper protrusions;
2N first lower recesses provided in pairs at the lower ends of the N first pads and fitted with the 2N first lower projections,
Consisting of
The second position restricting means includes
N second upper protrusions projecting radially outward from the upper end surface of the second lens holder;
2N second lower convex portions projecting radially outward from the lower end surface of the second lens holder;
N second upper recesses respectively provided at upper ends of the N second pads and fitted with the N second upper protrusions;
2N second lower concave portions provided in pairs at the lower ends of the N second pads, respectively, and fitted with the 2N second lower convex portions,
The linear actuator according to claim 10, comprising: Each of the N first piezoelectric units has a first laminated piezoelectric element in which a plurality of internal electrodes are laminated in the optical axis direction of the lens, and one end face on one end face of the first laminated piezoelectric element. A first piezoelectric element fixing portion coupled,
The first piezoelectric element fixing portion is fixed to the first base portion, and the other end surface of the first laminated piezoelectric element is coupled to the first vibration friction portion;
Each of the plurality of second piezoelectric units has a second laminated piezoelectric element in which a plurality of internal electrodes are laminated in the optical axis direction of the lens, and one end face coupled to one end face of the second laminated piezoelectric element. A second piezoelectric element fixing portion formed,
The second piezoelectric element fixing portion is fixed to the second base portion, and the other end surface of the second multilayer piezoelectric element is coupled to the second vibration friction portion. The linear actuator as described in any one. The first inner peripheral surface of the first vibration friction portion and the second inner peripheral surface of the second vibration friction portion overlap each other in the optical axis direction of the lens,
The first movable range of the first lens movable unit and the second movable range of the second lens movable unit overlap each other in the optical axis direction of the lens. The linear actuator as described in any one.

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