JP4844769B2 - Drive device - Google Patents

Description

  The present invention relates to a drive device, and more particularly to a drive device using an electromechanical transducer such as a piezoelectric element.

  Conventionally, linear actuators using electromechanical transducers such as piezoelectric elements, electrostrictive elements, and magnetostrictive elements have been used as autofocus actuators and zoom actuators for cameras.

  Japanese Patent No. 3188851 (Patent Document 1) is coupled to an electromechanical conversion element (piezoelectric element) and the electromechanical conversion element (piezoelectric element) and extends in the expansion and contraction direction of the electromechanical conversion element (piezoelectric element). A driving device including a driving member (driving shaft, vibration friction portion) and a driven member (zoom lens barrel) frictionally coupled to the driving member (vibration friction portion) is disclosed. In Patent Document 1, a driven member (zoom lens barrel) is driven by devising a drive signal to be applied to an electromechanical transducer (piezoelectric element). In Patent Document 1, a driving member (vibration friction portion) is sandwiched between a driven member and a friction plate. In other words, the driving member (vibration friction portion) penetrates between the driven member and the friction plate. The friction plate is pressed by the pressure contact spring in the direction of sandwiching the driving member (vibration friction portion) with the driven member.

  Japanese Patent Laying-Open No. 2006-276741 (Patent Document 2) discloses an optical module that can be miniaturized, is easy to assemble, and is resistant to drop impact. The optical module disclosed in Patent Document 1 includes a lens holder (driven member), a lens holder support, a piezoelectric element (electromechanical conversion element), a guide plate (vibration friction portion), an urging spring, It has. The lens holder (driven member) holds the lens and is movable in the optical axis direction of the lens. The lens holder support supports the lens holder so as to be slidable in the optical axis direction of the lens. A voltage is applied to the piezoelectric element (electromechanical conversion element) so that the extending speed and the contracting speed are different, and the piezoelectric element expands and contracts in the optical axis direction of the lens, and one surface in the expanding and contracting direction is fixed to the lens holder support. Yes. The guide plate (vibration friction part) can be moved in the optical axis direction of the lens as the piezoelectric element (electromechanical conversion element) expands and contracts, with the other surface in the expansion direction of the piezoelectric element (electromechanical conversion element) fixed. It is. Further, the guide plate (vibration friction portion) is slidably in contact with the outer peripheral surface of the lens holder (driven member). The biasing spring presses at least one of the guide plate (vibration friction portion) and the outer peripheral surface of the lens holder (driven member) against the other.

  The optical module disclosed in Patent Document 2 includes first and second bearing members that slidably hold a piezoelectric element (electromechanical conversion element) and serve as a slide bearing. The first and second bearing materials surround the four side surfaces of the piezoelectric element (electromechanical conversion element). The guide plate (vibration friction portion) moves in the optical axis direction as the piezoelectric element (electromechanical conversion element) expands and contracts, and the lens holder (driven member) moves through the plane wall of the lens holder (driven member). Guides movement in the direction of the optical axis. The guide plate is made of an inverted L-shaped member. The guide plate (vibration friction portion) includes a first guide plate extending in the optical axis direction and a second guide plate provided orthogonal to the first guide plate. The subject side surface of the piezoelectric element (electromechanical conversion element) is bonded to the second guide plate. The first guide plate is sandwiched between the second bearing member and the planar wall of the lens holder (driven member), and the first guide plate is slidably in contact with the planar wall. The biasing spring moves the first guide plate of the guide plate (vibration friction portion) to the lens holder (driven member) side via the first bearing member, the piezoelectric element (electromechanical transducer) and the second bearing member. It is an elastic member that urges to. The biasing spring is configured by a leaf spring or the like. The biasing spring is fixed to the inner wall of the actuator housing portion of the lens barrel (lens holder support).

  Furthermore, Japanese Unexamined Patent Application Publication No. 2007-49879 (Patent Document 3) discloses an actuator that can perform stable drive control. The actuator disclosed in Patent Document 3 includes an electromechanical conversion element (piezoelectric element) and a drive friction member (drive shaft, vibration friction portion) attached to one side in the expansion / contraction direction of the electromechanical conversion element (piezoelectric element). And a driven member (connection piece) engaged with the driving friction member, and a sliding member supported by the driven member and sliding on the driving friction member. The sliding member and the drive friction member are in surface contact. The sliding member is formed integrally with an urging means that is attached to the driven member and urges the driven member and the driving friction member to engage with each other.

  Japanese Patent Laying-Open No. 2007-49880 (Patent Document 4) discloses an actuator that improves the degree of freedom of shape. The actuator disclosed in Patent Document 4 is an electromechanical conversion element (piezoelectric element), a connecting member fixed to one side in the expansion / contraction direction of the electromechanical conversion element (piezoelectric element), and fixed to the connecting member. A rod-like drive friction member (drive shaft, vibration friction portion) (attached) and a driven member (connection piece) frictionally engaged with the drive friction portion are provided. That is, in the actuator disclosed in Patent Document 4, the electromechanical conversion element (piezoelectric element) and the drive friction member (vibration friction part) are connected via the connection member. The drive friction member (vibration friction portion) is disposed in parallel to the expansion / contraction direction of the electromechanical transducer (piezoelectric element). The connecting member is supported so as to be swingable around an action point provided between the electromechanical conversion element (piezoelectric element) and the drive friction member (drive shaft). A sliding member is provided at a connecting portion between the driven member (connecting piece) and the driving friction member (driving shaft). A holding spring is attached to the driven member (connection piece).

  Japanese Patent Application Laid-Open No. 2007-74889 (Patent Document 5) discloses a driving device that can reduce and stabilize the friction between the driving member and the driven member, and can move the driven member accurately and quickly. is doing. The drive device disclosed in Patent Document 5 includes an electromechanical conversion element (piezoelectric element), a drive member (vibration friction portion) attached to one side of the electrostriction direction of the electromechanical conversion element, and the drive member (vibration). And a driven member that is frictionally engaged with the friction portion. The drive member (vibration friction portion) is formed of a graphite composite such as carbon graphite.

  In the driving device disclosed in Patent Document 5, the driven member has a V-shaped groove, and the driving member (vibration friction portion) is engaged with the groove. The driven member has a leaf spring, and the driving member (vibration friction portion) is urged toward the driven member by the leaf spring. Alternatively, the driving member (vibration friction portion) is sandwiched between sliding portions having a V-shaped cross section.

  Japanese Patent Laying-Open No. 2007-181261 (Patent Document 6) discloses a drive unit that can reduce the size of an electromechanical conversion element in the expansion and contraction direction. The drive unit disclosed in Patent Document 6 includes an electromechanical conversion element (electrostrictive element) that expands and contracts in a predetermined direction by electric input, and a friction fixed to one end of the electromechanical conversion element (electrostrictive element) in the expansion and contraction direction. An engagement member (vibration friction portion) and a driven member frictionally engaged with the friction engagement member (vibration friction portion) are provided. The friction engagement portion of the driven member has a columnar shape, and extends substantially parallel to the expansion / contraction direction at a position off the extension line in the expansion / contraction direction of the electromechanical transducer (electrostrictive element).

  In the drive unit disclosed in Patent Document 6, the friction engagement portion of the driven member and the sliding surface of the friction engagement member (vibration friction portion) are slidably biased by the elastic member. The friction engagement member (vibration friction portion) is formed so as to surround the periphery of the driven member. The elastic member is a U-shaped leaf spring arranged so as to surround the friction engagement member (vibration friction portion), and this leaf spring is used to drive the driven member from the outside of the friction engagement member (vibration friction portion). It is configured to give an urging force. Alternatively, the elastic member is formed of a spring, and the spring is disposed along a groove formed on the side surface of the friction engagement member (vibration friction portion).

  Japanese Patent Laying-Open No. 2007-306763 (Patent Document 7) discloses a piezoelectric actuator having excellent impact resistance at an engaging portion between a driving member and a moving member. The piezoelectric actuator disclosed in Patent Document 7 includes a piezoelectric element (electromechanical conversion element), a driving member (vibration friction portion) elongated in one direction connected to the piezoelectric element, and a longitudinal direction of the driving member. And a movable member (driven member) arranged to be slidable. In a cross section viewed from the direction perpendicular to the longitudinal direction of the driving member (vibration friction portion), the sliding surface of the moving member (driven member) with respect to the driving member (vibration friction portion) is adjacent to the sliding surface. The corner formed by the end face is curved.

  In the piezoelectric actuator disclosed in Patent Document 7, the moving member (driven member) includes first and second engaging portions. The first engaging portion has a substantially U-shaped recess, and the guide member is accommodated in the recess. The second engaging portion has a substantially V-shaped recess, and the drive member (vibration friction portion) is accommodated in the recess. An engagement assisting member having a substantially V-shaped depression is covered in a state where the driving member (vibration friction part) is accommodated in the depression of the second engagement part. The engagement assisting member is biased with a predetermined pressing force by an L-shaped leaf spring attached to the second engagement portion with a screw.

Japanese Patent No. 3188851 JP 2006-276741 A (paragraphs 0015 to 0017, FIGS. 1 and 2) Japanese Unexamined Patent Publication No. 2007-49879 (paragraphs 0027 to 0041, FIGS. 4 to 8) JP 2007-49880 (paragraphs 0018 to 0020, FIG. 2) Japanese Patent Laying-Open No. 2007-74889 (paragraphs 0055 and 0086, FIGS. 5 and 12) Japanese Patent Laying-Open No. 2007-181261 (paragraphs 0017 to 0019, FIGS. 3 and 4) JP 2007-306763 A (paragraphs 0028 to 0030, FIG. 2 and FIG. 3)

  The drive devices disclosed in Patent Documents 1 to 6 described above have problems as described below.

  In the drive device disclosed in Patent Document 1, since the drive member (drive shaft, vibration friction portion) extends in the expansion / contraction direction of the electromechanical transducer, the drive member (drive shaft, vibration friction portion) is driven. It is longer than the member (zoom lens barrel), and the drive member (drive shaft, vibration friction portion) is reciprocated and easily tilted. Further, the longer the moving distance of the driven member (zoom lens barrel), the longer the driving member (drive shaft, vibration friction portion), and it is easy to generate an unnecessary vibration mode. Furthermore, since there is a friction engagement portion on the extension of the coupling portion between the electromechanical conversion element and the drive member (drive shaft, vibration friction portion), it is disadvantageous for low profile.

  In the optical module disclosed in Patent Document 2, it is necessary to include first and second bearing members that hold a piezoelectric element (electromechanical conversion element) in a slidable manner and serve as a slide bearing. As a result, there are problems that the number of parts increases and the structure becomes complicated.

  In the actuator disclosed in Patent Document 3, the drive friction member (vibration friction part) extends in the expansion / contraction direction of the electromechanical conversion element, similarly to the drive device disclosed in Patent Document 1. As a result, the drive friction member (vibration friction portion) is longer than the driven member, and the drive friction member (vibration friction portion) reciprocates and tends to be inclined. Further, as the movement distance of the driven member is increased, the driving friction member (vibration friction portion) is also increased, and an unnecessary vibration mode is easily generated. Furthermore, since there is a friction engagement portion on the extension of the coupling portion between the electromechanical conversion element and the drive friction member (vibration friction portion), it is disadvantageous for a reduction in height.

  In the actuator disclosed in Patent Document 4, the electromechanical conversion element and the drive friction member (vibration friction portion) are connected via a connection member. As a result, there are problems that the number of parts increases and the structure becomes complicated.

  In the drive device disclosed in Patent Document 5, like the drive device disclosed in Patent Document 1, the drive member (vibration friction portion) extends in the expansion / contraction direction of the electromechanical transducer. As a result, the drive member (vibration friction portion) is longer than the driven member, and the drive member (vibration friction portion) reciprocates, so that inclination is likely to occur. Further, the longer the movement distance of the driven member, the longer the driving member (vibration friction portion), and it is easy to generate an unnecessary vibration mode. Furthermore, since there is a friction engagement portion on the extension of the coupling portion between the electromechanical conversion element and the drive member (vibration friction portion), it is disadvantageous for a reduction in height.

  In the drive unit disclosed in Patent Document 6, an elastic member is attached to a friction engagement member (vibration friction portion). In such a structure, when a high frequency voltage is applied to the electromechanical transducer, the elastic member resonates, and a frequency band that vibrates in an opposite phase to the friction engagement member (vibration friction portion) appears. The phase difference between the elastic member and the friction engagement member (vibration friction portion) causes a decrease in the movement speed of the driven portion (moving member) that is frictionally coupled and a reverse phenomenon of the movement direction.

  In the piezoelectric actuator disclosed in Patent Document 7, the driving member (vibration friction portion) extends in the expansion / contraction direction of the piezoelectric element (electromechanical conversion element), as in the driving device disclosed in Patent Document 1. . As a result, the drive member (vibration friction portion) is longer than the moving member (driven member), and the drive member (vibration friction portion) is likely to be inclined due to reciprocating motion. Further, as the moving distance of the moving member (driven member) is increased, the driving member (vibration friction portion) is also increased, and an unnecessary vibration mode is easily generated. Furthermore, since there is a friction engagement portion on the extension of the coupling portion between the piezoelectric element (electromechanical conversion element) and the drive member (vibration friction portion), it is disadvantageous for a reduction in height.

  Therefore, the subject of this invention is providing the drive device which can move a to-be-driven member efficiently.

  The other subject of this invention is providing the drive device which can aim at height reduction.

  Another object of the present invention is to provide a drive device having a simple structure.

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

According to the present invention, the electromechanical transducer element (441) having a pair of end faces (441a, 441b) facing each other in the expansion / contraction direction (Z) and one of the pair of end faces (441b) of the electromechanical transducer element are attached. The generated vibration friction portion (443), a driven member (423) frictionally coupled to the vibration friction portion, and a friction force adding means (424; for generating a friction force between the vibration friction portion and the driven member). 444), and in the drive device (20; 20A; 20B) in which the driven member (423) can move in the expansion / contraction direction (Z) of the electromechanical transducer, the vibration friction portion (443) is orthogonal to the expansion / contraction direction The driven member has a friction surface as a first end surface (4431) in the direction to be driven, and the driven member includes a rod-shaped moving shaft (423) that is in sliding contact with the friction surface of the vibration friction portion, and the driving device (20; 20A; 20B). Is the moving axis (4 3) the fixed or mobile axis (423) comprises a lens holder which is integrally formed (422), the frictional force adding means (424; 444) is a member other than the vibration friction portion (443) (422; 30) The drive device is characterized by comprising a spring attached along the outer peripheral wall of the lens holder (422) .

  In the driving device (20; 20A; 20B) according to the present invention, the vibration friction portion (443) preferably has a groove (4431a) having a V-shaped cross section on the friction surface (4431). The angle of the V-shaped groove (4431a) is preferably in the range of 30 degrees to less than 180 degrees.

According to a first aspect of the present invention, the upper Symbol frictional force adding means (424) is attached to the lens holder (422). The frictional force adding means may be constituted by, for example, an urging member (424) attached to the lens holder (422). In this case, the urging member (424) has a first end portion (424a) attached to the lens holder (422) and a first end surface (4431) of the vibration friction portion (443) in the expansion / contraction direction (Z). And a second end portion (424b) that abuts on a second end face (4432) facing each other in a direction orthogonal to the direction. For example, the urging member may include a spring (424) in which the first end (424a) is bonded to the lens holder (422). Alternatively, the biasing member may comprise a spring (424) having a first end (434a) screwed to the lens holder (422).

According to a second aspect of the present invention, the driving device (20B) includes a housing (30) for accommodating the Les Nzuhoruda, the frictional force adding means (444) is attached to the housing (30). The frictional force adding means may be constituted by, for example, an urging member (444) attached to the inner wall surface (34a) of the housing (30). In this case, the urging member (444) includes the vibration friction portion (443) with the first end (444a) attached to the inner wall surface (34a) of the housing (30) and the moving shaft (423) interposed therebetween. ) And a second end (444b) facing the friction surface (4431). For example, the urging member may include a spring (444) in which the first end (444a) is bonded to the inner wall surface (34a) of the housing.

  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 vibration friction portion has a friction surface as a first end surface in a direction orthogonal to the expansion and contraction direction, the driven member includes a rod-shaped moving shaft that is in sliding contact with the friction surface of the vibration friction portion, and a frictional force adding means Is attached to a member other than the vibration friction portion, so that the driven member can be moved efficiently.

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

  A driving apparatus 20 according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing the driving device 20. FIG. 2 is a perspective view of the autofocus lens driving unit 40 of the driving apparatus 20 shown in FIG. FIG. 3 is a perspective view of the autofocus lens driving unit 40 as viewed from the upper right and obliquely upward. FIG. 4 is a perspective view of the autofocus lens driving unit 40 as viewed from the upper right side. FIG. 5 is a side view of the autofocus lens driving unit 40. FIG. 6 is a perspective view showing the lens driving unit 44 of the autofocus lens driving unit 40 together with the driven member 423 and the spring 424.

  Here, as shown in FIGS. 1 to 6, an orthogonal coordinate system (X, Y, Z) is used. 1 to 6, in the orthogonal coordinate system (X, Y, Z), the X axis is the front-rear direction (depth direction), the Y axis is the left-right direction (width direction), and the Z axis is The vertical direction (height direction).

The illustrated driving device 20 is used as, for example, the lens driving unit 44 of the autofocus lens driving unit 40. In that case, in the example shown in FIGS. 1 to 4, the vertical direction Z is the direction of the optical axis O of the lens.

  As shown in FIG. 1, the driving device 20 includes a substantially rectangular parallelepiped housing (housing) 30 that covers an autofocus lens driving device 40 described later. In other words, the autofocus lens driving device 40 is disposed in the housing (housing) 30. The housing (housing) 30 includes an upper frame 32, a lower frame 34, an actuator base 36, and an upper cover 38. The actuator base 36 is attached to the lower frame 34. A stationary member (weight) 442 described later is mounted on the actuator base 36. The upper cover 38 has a circular opening 38a with the optical axis O of the lens as the central axis.

  On the other hand, although not shown, an image sensor disposed on the substrate is mounted at the center of the lower frame 34. This imaging device captures a subject image formed by a movable lens (described later) and converts it into an electrical signal. The imaging device is configured by, for example, a CCD (charge coupled device) type image sensor, a CMOS (complementary metal oxide semiconductor) type image sensor, or the like.

  2 to 4, a guide shaft 39 (see FIG. 9) is provided in the housing (housing) 30 on the left front side. The guide shaft 39 extends in parallel with the optical axis O. The guide shaft 39 stands on the lower frame 34 of the housing (housing) 30. A driven member 423, which will be described later, is provided on the right rear side opposite to the guide shaft 39 with the optical axis O interposed therebetween. In the illustrated example, the driven member 423 includes a rod-shaped moving shaft. The movement axis 423 also extends in parallel with the optical axis O. That is, the guide shaft 39 and the moving shaft 423 are disposed at rotationally symmetric positions around the optical axis O.

  The autofocus lens drive unit 40 includes a lens movable unit 42 and a lens drive unit 44. The lens driving unit 44 drives the lens moving unit 42 as described later while supporting the lens moving unit 42 slidably in the optical axis O direction.

  The lens movable portion 42 includes a lens barrel (lens assembly) 421 that holds an autofocus lens AFL that is a movable lens. The lens barrel 421 is held and fixed in a substantially cylindrical movable lens barrel (lens holder) 422. A female screw (not shown) is cut on the inner peripheral wall of the lens holder 422. On the other hand, a male screw (not shown) that is screwed into the female screw is cut on the outer peripheral wall of the lens barrel 421. Therefore, in order to attach the lens barrel 421 to the lens holder 422, the lens barrel 421 is rotated around the optical axis O with respect to the lens holder 422 and screwed along the direction of the optical axis O. It is accommodated in the lens holder 422 and joined together by an adhesive or the like.

  The lens holder 422 includes a first extending portion (first engaging portion) 4221 that extends radially outward at the upper end on the left front side. The first extending portion (first engaging portion) 4221 has a substantially U-shaped recess 4221u opened on the left side, and the guide shaft is accommodated in the recess 4221u. The lens holder 422 has a pair of second extending portions (second engaging portions) 4222 extending radially outward on the right back side. The pair of first extending portions (first engaging portions) 4222 have substantially U-shaped dents 4222u opened on the right side, and the moving shaft 423 is accommodated and fitted in the dents 4222u. . With such a configuration, the lens movable portion 42 can move only in the direction of the optical axis O with respect to the housing (housing) 30.

  The lens holder 422 has a third extending portion 4223 that extends radially outward on the left back side. The first end portion 424a of the spring 424 is bonded to the third extending portion 4223 with an adhesive. The spring 424 extends from the first end 424a to the right side in the left-right direction Y to the second end 424b. A projection 424 c that protrudes forward in the front-rear direction X is provided at the second end 424 b of the spring 424.

  The protrusion 424 c is biased by a spring 424 in a direction approaching the moving shaft 423 (front direction in the front-rear direction X). A vibration friction portion 443 described later is sandwiched between the first and second end surfaces 4431 and 4432 between the moving shaft 323 and the protrusion 424c. The first and second end faces 4431 and 4432 face each other in a direction orthogonal to the optical axis O direction. In other words, the first and second end faces 4431 and 4432 are opposed to each other in a direction orthogonal to the expansion / contraction direction of a laminated piezoelectric element 441 described later. The first end surface 4431 functions as a friction surface, as will be described later.

  The lens movable part 42 of the autofocus lens driving unit 40 is configured by a combination of the lens holder 422, the lens barrel (lens assembly) 421, the spring 424, and the moving shaft 423. As will be described later, a groove 4431 a having a V-shaped cross section is formed on the friction surface 4431 of the vibration friction portion 443.

  Next, the lens driving unit 44 of the autofocus lens driving unit 40 will be described. The lens driving unit 44 includes a laminated piezoelectric element 441 that functions as an electromechanical conversion element, the stationary member (weight) 442, and the vibration friction unit 443.

  The laminated piezoelectric element 441 expands and contracts in the optical axis O direction (vertical direction Z). The laminated piezoelectric element 441 has a structure in which a plurality of piezoelectric layers are laminated in the optical axis O direction. As shown in FIG. 5, the laminated piezoelectric element 441 has a first end face (lower end face) 441a and a second end face (upper end face) 441b that face each other in the expansion / contraction direction. The stationary member (weight) 442 is coupled to the first end face (lower end face) 441a of the laminated piezoelectric element 441 with an adhesive or the like. A combination of the laminated piezoelectric element 441 and the stationary member 442 is called a piezoelectric unit.

  The vibration friction portion 443 is attached to the second end surface (upper end surface) 441b of the multilayer piezoelectric element 441 with an adhesive or the like. In the illustrated example, the vibration friction portion 443 is directly coupled to the second end portion 441b of the multilayer piezoelectric element 441, but there is some kind of gap between the vibration friction portion 443 and the second end portion 441b of the multilayer piezoelectric element 441. A member may be interposed.

  The rod-shaped moving shaft 423 is frictionally coupled to the vibration friction portion 443. In the vibration friction portion 443, a groove 4431a having a V-shaped cross section is formed in a friction coupling portion (friction surface) 4431 between the vibration friction portion 443 and the rod-shaped moving shaft 423 at the front end in the front-rear direction X. .

  As described above, the lens movable portion 44 includes the spring 424 for pressing (biasing) the vibration friction portion 443 against the rod-shaped moving shaft 423. That is, the first end portion 424a of the spring 424 is fixed to the third extending portion 4223, and the vibration friction portion 443 is attached to the moving shaft 423 by the protrusion 424c attached to the second end portion 424b. Generates a pressing force to press. In other words, the spring 424 biases the protrusion 424c (second end 424b) to the vibration friction part 443, and clamps the vibration friction part 443 between the moving shaft 423 and the protrusion 424c, thereby causing the vibration friction part. It acts as a frictional force adding means (biasing means) for applying a frictional force between the friction surface 4431 of 443 and the moving shaft 423.

  In the vibration friction portion 443, a groove 4431 a having a V-shaped cross section is formed in a friction coupling portion (friction surface 4431) between the vibration friction portion 443 and the moving shaft 423. Due to the bilinear contact with the moving shaft 423 by the groove 4431a having a V-shaped cross section of the vibration friction portion 443, the contact state of the friction coupling portion (friction surface 4431) is stabilized, friction drive with good reproducibility is obtained, and movement There is an effect that the straight movement as the uniaxial moving body of the shaft 423 is improved. The angle of the groove 4431a having a V-shaped cross section is desirably in the range of 30 degrees to less than 180 degrees.

The effective length Ls of the spring 424 will be described with reference to FIG. As shown in FIG. 6, the driving device 20 can design the effective length Ls of the spring 424 to be long. Therefore, even if the dimensions and assembly dimensions of the spring 424 vary, the influence on the load can be reduced. As a result, it is possible to manufacture the drive device 20 with less performance variation for each product.

  In this way, since the effective length Ls of the spring 424 can be designed to be long, even if the material of the spring 424 is not only a metal but also a resin molded product, a sufficient elastic effect can be exhibited.

In the present embodiment, the spring 424 is attached not to the vibration friction portion 443 but to the lens movable portion 42 side. Thus, by separating the vibration friction portion 443 and the spring 424, it is possible to prevent the resonance phenomenon of the spring 424 from occurring. Therefore, the vibration friction portion 443 and the spring 424 are not reversed in phase, and the lens movable portion 42 can be moved efficiently. Further, the traveling direction of the lens movable unit 42 can be controlled to proceed in the intended direction.

The lens driving unit 44 and the lens movable unit 42 are juxtaposed with respect to the optical axis O as shown in FIGS. Therefore, the focus lens drive unit 40 can be reduced in height. As a result, the drive device 20 can also be reduced in height.

  Next, the current supplied to the laminated piezoelectric element 441 and the displacement generated in the laminated piezoelectric element 441 will be described with reference to FIG. FIG. 7 is the same as that shown in FIG. 7A and 7B show a change in current supplied to the laminated piezoelectric element 441 by a drive circuit (not shown) and a displacement of the laminated piezoelectric element 441, respectively.

  As shown in FIG. 7A, a large current (positive direction) and a predetermined constant current (negative direction) are alternately passed through the laminated piezoelectric element 441. In such a situation, as shown in FIG. 7B, the laminated piezoelectric element 441 has a sudden displacement (elongation) corresponding to a large current (positive direction) and a gentle corresponding to a constant current (negative direction). Displacement (shrinkage) occurs alternately.

  That is, a rectangular wave current is applied to the laminated piezoelectric element 441 (FIG. 7A), and a sawtooth wave-like displacement (expansion / contraction) is caused to the laminated piezoelectric element 441 (FIG. 7B).

  The operation of the autofocus lens drive unit 40 (drive device 10) will be described with reference to FIG. 2 in addition to FIG. First, an operation when the lens movable portion 42 is moved downward along the vertical direction Z will be described.

  First, as shown in FIG. 7A, when a large positive current is passed through the multilayer piezoelectric element 441, the multilayer piezoelectric element 441 rapidly undergoes an elongation displacement in the thickness direction as shown in FIG. 7B. . As a result, the vibration friction portion 443 rapidly moves upward along the optical axis O direction (vertical direction Z). At this time, the lens movable portion 42 overcomes the friction force between the vibration friction portion 443 and the rod-shaped moving shaft 423 by the inertial force, and remains substantially in that position, so it does not move.

  Next, as shown in FIG. 7A, when a constant current in the negative direction is passed through the multilayer piezoelectric element 441, the multilayer piezoelectric element 441 gradually contracts in the thickness direction. As a result, the vibration friction portion 443 moves gently downward along the optical axis O direction (vertical direction Z). At this time, since the vibration friction portion 443 and the rod-shaped moving shaft 423 are coupled by the friction force generated on the contact surface (friction surface 4431) between them, the lens movable portion 42 is substantially combined with the vibration friction portion 443. And move downward along the optical axis O direction (vertical direction Z).

  In this way, a large positive current and a predetermined constant current in the negative direction are alternately supplied to the laminated piezoelectric element 441 to cause the laminated piezoelectric element 441 to alternately generate an expansion displacement and a contraction displacement, whereby the lens holder 442 ( The lens barrel 421) can be continuously moved downward along the optical axis O direction (vertical direction Z).

  In order to move the lens movable portion 42 upward along the optical axis O direction (vertical direction Z), a large negative current and a predetermined constant current in the positive direction are applied to the laminated piezoelectric element 441 contrary to the above. This can be achieved by alternating flow.

  Next, the laminated piezoelectric element 441 will be described. The laminated piezoelectric element 441 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 441 is manufactured by alternately laminating 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 multilayer piezoelectric element 441 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 441.

  In the driving device 20 shown in FIGS. 1 to 5, the moving shaft 423 and the lens holder (lens support) 422 are separate and fixed to each other, but the moving shaft 423 and the lens holder (lens support) 422 are fixed. And may be configured integrally. In this case, the lens holder (lens support) 422 and the moving shaft 423 are made of the same material.

  With reference to FIG. 8, a driving apparatus 20A (autofocus lens driving unit 40A) according to a second embodiment of the present invention will be described. FIG. 8 is a perspective view of the autofocus lens driving unit 40A as viewed from the right rear and obliquely upward. The illustrated autofocus lens drive unit 40A has the same configuration as the autofocus lens drive unit 40 shown in FIG. 3 except that the method of attaching the spring 424, which is a biasing member, to the lens holder 422 is different. And work. Therefore, components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and only differences will be described below for the sake of simplification of description.

  In the autofocus lens driving unit 40 shown in FIG. 3, the first end 424a of the spring 424 is fixed to the third extending portion 4223 of the lens holder 422 with an adhesive.

  On the other hand, in the autofocus lens driving unit 40A shown in FIG. 8, the first end portion 424a of the spring 424 is screwed to the third extending portion 4223 of the lens holder 422 by a screw 425. .

  It is obvious that the autofocus lens drive unit 40A shown in FIG. 8 also has the same effect as the autofocus lens drive unit 40 according to the first embodiment described above.

  A driving device 20B (autofocus lens driving unit 40B) according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a perspective view of the autofocus lens driving unit 40B as seen from the diagonally upper front. FIG. 10 is a perspective view of the autofocus lens driving unit 40B as viewed from the right rear obliquely upward. FIG. 11 is a perspective view of the autofocus lens driving unit 40B as viewed from the upper right side. The illustrated autofocus lens driving unit 40B has the same configuration as that of the autofocus lens driving unit 40 shown in FIGS. 2 to 4 except that the mounting position of the spring as a biasing member is different. do. Therefore, the reference numeral 444 is attached to the spring. Accordingly, components having the same functions as those shown in FIGS. 1 to 5 are denoted by the same reference numerals, and only differences will be described below for the sake of simplicity. Reference numeral 39 indicates the above-described guide shaft.

  In the autofocus lens driving unit 40 shown in FIGS. 2 to 4, a spring 424 is attached to the lens holder 422. That is, the first end 424a of the spring 424 is fixed to the third extension 4223 of the lens holder 422 with an adhesive. Therefore, the spring 424 is a component of the lens moving unit 42.

  On the other hand, in the autofocus lens driving unit 40B shown in FIGS. 9 to 11, a spring 444 is attached to the housing 30. Therefore, the spring 444 is a component of the lens driving unit 44.

  Detailed description. The first end portion 444a of the spring 444 is attached to the inner wall surface 34a of the lower frame 34 of the housing 30 with an adhesive. On the other hand, the second end portion 444b of the spring 444 faces the friction surface 4431 of the vibration friction portion 443 with the moving shaft 423 interposed therebetween. A protrusion 444 c that protrudes rearward in the front-rear direction X is provided at the second end 444 b of the spring 444. The protrusion 444 c is biased by a spring 444 in a direction approaching the friction surface 4431 of the vibration friction portion 443 (rearward direction in the front-rear direction X). A moving shaft 423 is sandwiched between the friction surface 4431 and the protrusion 444c of the vibration friction portion 443.

  As described above, the lens driving unit 44 includes the spring 444 for pressing (urging) the rod-shaped moving shaft 423 against the vibration friction unit 443. That is, the first end 444a of the spring 444 is fixed to the inner wall surface 34a of the lower frame 34, and the protrusion 444c attached to the second end 444b causes the moving shaft 423 to move the vibration friction portion 443. Generates a pressing force that presses against. In other words, the spring 444 biases the protrusion 444c (second end 444b) to the moving shaft 423, and clamps the moving shaft 423 between the vibration friction portion 443 and the protrusion 444c, thereby causing the vibration friction portion 443. It acts as a friction force adding means (biasing means) for applying a friction force between the friction surface 4431 and the moving shaft 423.

In the third embodiment, the spring 444 is attached not to the vibration friction portion 443 but on the housing 30 side. Thus, by separating the vibration friction portion 443 and the spring 444, the resonance phenomenon of the spring 444 can be prevented from occurring. Accordingly, the vibration friction portion 443 and the spring 444 are not reversed in phase, and the lens movable portion 42 can be moved efficiently. Further, the traveling direction of the lens movable unit 42 can be controlled to proceed in the intended direction.

  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, the movement axis has a cylindrical shape, but it is needless to say that the shape of the movement axis is not limited to this.

It is a perspective view which shows the drive device by the 1st Embodiment of this invention. It is the perspective view which looked at the autofocus lens drive unit of the drive device shown in FIG. FIG. 3 is a perspective view of the autofocus lens driving unit of FIG. FIG. 3 is a perspective view of the autofocus lens driving unit of FIG. FIG. 3 is a side view of the autofocus lens driving unit of FIG. 2. It is a perspective view which shows the lens drive part of the autofocus lens drive unit of FIG. 2 with a driven member and a spring. 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. It is the perspective view which looked at the drive device (autofocus lens drive unit) by the 2nd Embodiment of this invention from diagonally upper right back. It is the perspective view which looked at the drive device (autofocus lens drive unit) by the 3rd Embodiment of this invention from right front diagonally upward. FIG. 10 is a perspective view of the autofocus lens driving unit of FIG. It is the perspective view which looked at the autofocus lens drive unit of Drawing 9 from the diagonally upper right.

Explanation of symbols

20, 20A, 20B Drive device 30 Housing (housing)
32 Upper frame 34 Lower frame 34a Inner wall surface 36 Actuator base 38 Upper cover 39 Guide shaft 40, 40A, 40B Autofocus lens drive unit 42 Lens movable part 421 Lens barrel (lens assembly)
422 Movable lens barrel (lens holder, lens support)
4221 1st extension part (1st engaging part)
4221u hollow 4222 2nd extension part (2nd engaging part)
4222u hollow 4223 3rd extension part 423 driven member (moving axis)
424 Spring (biasing member)
424a First end portion 424b Second end portion 424c Projection 425 Screw 44 Lens drive portion 441 Multilayer piezoelectric element (electromechanical conversion element)
441a First end face (lower end face)
441b Second end surface 442 Stationary member (weight)
443 Vibration friction portion 4431 First end face (friction surface)
4431a V-shaped groove 4432 Second end surface 444 Spring (biasing member)
444a First end 444b Second end 444c Projection O Lens optical axis AFL Autofocus lens

Claims (10)

An electromechanical conversion element having a pair of end faces facing each other in the expansion and contraction direction, a vibration friction portion attached to one of the pair of end faces of the electromechanical conversion element, and a driven member frictionally coupled to the vibration friction portion And a frictional force adding means for generating a frictional force between the vibration frictional part and the driven member, wherein the driven member is movable in the expansion / contraction direction of the electromechanical transducer,
The vibration friction portion has a friction surface as a first end surface in a direction orthogonal to the expansion and contraction direction,
The driven member includes a rod-shaped moving shaft that is in sliding contact with the friction surface of the vibration friction portion;
The driving device includes a lens holder fixed to the moving shaft or configured integrally with the moving shaft,
The driving device according to claim 1, wherein the frictional force adding means includes a spring attached to a member other than the vibration friction portion along the outer peripheral wall of the lens holder .   The drive device according to claim 1, wherein the vibration friction portion has a groove having a V-shaped cross section on the friction surface.   3. The driving device according to claim 2, wherein an angle of the groove having the V-shaped cross section is in a range of 30 degrees to less than 180 degrees. The drive device according to claim 1, wherein the frictional force adding unit is attached to the lens holder. The frictional force adding means is composed of an urging member attached to the lens holder,
The urging member is in contact with a first end attached to the lens holder and a second end face facing the first end face of the vibration friction part in a direction perpendicular to the expansion / contraction direction. The driving device according to claim 4, wherein the driving device has an end of   The driving device according to claim 5, wherein the biasing member is configured by a spring having the first end bonded to the lens holder.   The drive device according to claim 5, wherein the biasing member includes a spring having the first end screwed to the lens holder. The driving device includes:
Comprising a Haujin grayed accommodating the lens holder,
The drive unit according to any one of claims 1 to 3, wherein the frictional force adding means is attached to the housing. The frictional force adding means is composed of an urging member attached to the inner wall surface of the housing,
The biasing member has a first end attached to the inner wall surface of the housing, and a second end facing the friction surface of the vibration friction portion with the moving shaft interposed therebetween. The drive device according to claim 8.   The drive device according to claim 9, wherein the biasing member includes a spring having the first end bonded to the inner wall surface of the housing.

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