CN102203654A - Drive device - Google Patents

Abstract

A drive device which can efficiently move a member to be driven and which is of low profile. A drive device (20) is provided with an electromechanical conversion element (441) having first and second end surfaces (441a, 441b) facing each other in the expanding and contracting direction of the element, a vibration and friction section (443) mounted to the second end surface (441b) of the electromechanical conversion element (441), a driven member frictionally joined to the vibration and friction section, and a frictional-force applying means (424) for generating frictional force between the vibration and friction section and the driven member. The driven member can move in the direction in which the electromechanical conversion element expands and contracts. The vibration and friction section (443) has, in the direction perpendicular to the expanding and contracting direction, a friction surface which is a first end surface (4431). The driven member includes a bar-like movement shaft (423) making sliding contact with the friction surface of the vibration and friction section. The frictional-force applying means (424) is mounted to a member (422) other than the vibration and friction section (443).

Description

drive unit

technical field

The present invention relates to a drive device, and more particularly to a drive device using electromechanical conversion elements such as piezoelectric elements.

Background technique

Conventionally, as an autofocus driver or a zoom driver of a video camera, a linear actuator is used. The linear actuator uses electromechanical conversion elements such as piezoelectric elements, electrostrictive elements, and magnetostrictive elements (drivers). device).

Japanese Patent No. 3218851 (Patent Document 1) discloses an electromechanical transducer element (piezoelectric element), which is combined with the electromechanical transducer element (piezoelectric element) and extends in the expansion and contraction direction of the electromechanical transducer element (piezoelectric element). A component (a drive shaft, a vibrating friction part), and a driven component (variable focus lens barrel) frictionally coupled to the driving component (vibrating friction part). In the drive device disclosed in this patent document 1, a drive signal applied to an electromechanical conversion element (piezoelectric element) is considered to drive a driven member (variable focus lens barrel). In the drive device of Patent Document 1, a drive 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 presses the driving member (oscillating friction portion) in a direction sandwiched between the driven member and the driven member by the pressure contact spring.

In addition, Japanese Patent Application Laid-Open No. 2006-276741 (Patent Document 2) discloses an optical module that can be miniaturized, is easy to assemble, and has strong drop impact resistance. The optical module disclosed in this patent document 1 includes a lens holder (driven member), a lens holder support body, a piezoelectric element (electromechanical conversion element), a guide plate (vibration friction part), and an urging spring. The lens holder (driven part) holds the lens and is movable in the optical axis direction of the lens. The lens holder supporting body 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 expansion and contraction speeds are different, and expands and contracts in the optical axis direction of the lens, and one surface in the expansion and contraction direction is fixed to the lens holder support. The guide plate (vibration friction part) fixes the other side of the piezoelectric element (electromechanical transducer) in the expansion and contraction direction, and is movable in the optical axis direction of the lens as the piezoelectric element (electromechanical transducer) expands and contracts. In addition, the guide plate (vibration friction part) is in slidable contact with the outer peripheral surface of the lens holder (driven member). The urging spring presses at least one of the guide plate (vibration friction part) and the outer peripheral surface of the lens holder (driven member) toward 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 function as sliding bearings. The first and second bearing members surround four sides of the piezoelectric element (electromechanical conversion element). The guide plate (vibration friction part) moves in the direction of the optical axis as the piezoelectric element (electromechanical conversion element) expands and contracts. The movement of the lens holder (driven member) in the direction of the optical axis is guided by the plane wall of the lens holder (driven member). The guide plate is composed of reverse L-shaped members. The guide plate (vibration friction portion) is composed of a first guide plate extending in the optical axis direction and a second guide plate provided perpendicularly to the first guide plate. The object-side surface of the piezoelectric element (electromechanical transducer) is bonded to the second guide plate. The first guide plate is sandwiched between the second bearing component and the plane wall of the lens holder (driven component), and the first guide plate is slidably abutted against the plane wall. The urging spring is an elastic force that urges the first guide plate (vibration friction part) of the guide plate (vibration friction part) to the side of the lens holder (driven part) through the first bearing member, the piezoelectric element (electromechanical conversion element) and the second bearing member. part. The biasing spring is composed of a leaf spring or the like. The urging spring is fixed to the inner wall of the driver accommodating part of the lens barrel (lens holder supporting body).

Furthermore, Japanese Patent Laid-Open No. 2007-49879 (Patent Document 3) discloses a driver capable of stable drive control. The actuator disclosed in Patent Document 3 includes: an electromechanical conversion element (piezoelectric element); a driving friction member (drive shaft, vibration friction part) mounted on one side of the electromechanical conversion element (piezoelectric element) in the expansion and contraction direction; The driven part (connecting the fixed block) that the driving friction part cooperates with; and the sliding part that is supported on the driven part and slides on the driving friction part. The sliding member is in surface contact with the driving friction member. The sliding part is integrally formed with the urging mechanism, which is installed on the driven part and energizes in the direction of making the driven part cooperate with the driving friction part.

Japanese Unexamined Patent Application Publication No. 2007-49880 (Patent Document 4) discloses an actuator with increased degree of freedom in shape. The actuator disclosed in Patent Document 4 includes: an electromechanical conversion element (piezoelectric element); a connection member fastened to one side of the electromechanical conversion element (piezoelectric element) in the expansion and contraction direction; The rod-shaped driving friction member (drive shaft, vibrating friction part); and the driven part (connecting fixed block) frictionally combined with the vibrating friction part. That is, in the actuator disclosed in Patent Document 4, the electromechanical conversion element (piezoelectric element) and the driving friction member (vibration friction portion) are connected via a connection member. The drive friction part (vibration friction part) is arranged parallel to the expansion and contraction direction of the electromechanical conversion element (piezoelectric element). The connection member is supported swingably around an action point provided between the electromechanical conversion element (piezoelectric element) and the driving friction member (vibration friction portion). A sliding member is provided at the connecting portion of the driven member (connecting stop block) and the driving friction member (driving shaft). A pressing spring is installed on the driven part (connecting the fixed block).

In addition, Japanese Patent Application Laid-Open No. 2007-74889 (Patent Document 5) discloses a driving device that reduces friction between a driving member and a driven member, stabilizes it, and enables accurate and rapid movement of the driven member. The driving device disclosed in Patent Document 5 includes: an electromechanical conversion element (piezoelectric element); a driving member mounted on one side of the electromechanical conversion element in the expansion and contraction direction; part. The driving member (vibration friction part) is formed of a graphite composite such as graphite carbon, for example.

In the driving device disclosed in Patent Document 5, the driven member has a V-shaped groove, and the driving member (vibration friction portion) fits into the groove. The driven member has a leaf spring, and the driving member (oscillating friction portion) is biased toward the driven member by the leaf spring. Alternatively, the driving member (vibration friction part) is sandwiched by the sliding part having a V-shaped cross section.

Japanese Patent Application Laid-Open No. 2007-181261 (Patent Document 6) discloses a drive unit that can be downsized in the expansion-contraction direction of the electromechanical conversion element. The drive unit disclosed in Patent Document 6 includes: an electromechanical transducer element (piezoelectric element) that expands and contracts in a predetermined direction upon input of electric power; and a friction fit member fixed to one end of the electromechanical transducer element (piezoelectric element) in the stretching direction (vibration friction portion); and a driven member friction-fitted with the friction fit member (vibration friction portion). The friction fit portion of the driven member is configured in a columnar shape, is located at a position deviated from the extension line of the expansion and contraction direction of the electromechanical conversion element (piezoelectric element), and extends approximately parallel to the expansion and contraction direction.

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 fit portion of the friction fit member (vibration friction portion) is formed so as to surround the driven member. The elastic member is a U-shaped leaf spring disposed so as to surround the friction fit member (vibration friction portion), and is configured to apply force to the driven member from the outside of the friction fit member (vibration friction portion) through the leaf spring. Alternatively, the elastic member is formed of a spring, and the spring is arranged along a groove formed on a side surface of the friction fitting member (vibration friction portion).

Japanese Unexamined Patent Application Publication No. 2007-306763 (Patent Document 7) discloses a piezoelectric actuator having excellent shock resistance at a mating portion of a driving member and a moving member. The piezoelectric actuator disclosed in this patent document 7 includes: a piezoelectric element (electromechanical conversion element); a driving member (vibration friction part) that is connected to the piezoelectric element and is elongated in one direction; A moving member (driven member) that is slidably arranged in the longitudinal direction. In a cross-section viewed from a direction perpendicular to the longitudinal direction of the driving member (vibrating friction portion), the sliding surface of the moving member (driven member) facing the driving member (vibrating friction portion) and the sliding surface opposite to the sliding surface are The corner formed by the adjacent end faces 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 U-shaped recessed portion, and the driving member (vibration friction portion) is accommodated in the recessed portion. In the state where the drive member (vibration friction part) is accommodated in the recessed part of the second fitting part, the fitting auxiliary part having the substantially V-shaped recessed part is covered. The fitting assist member is biased with a predetermined pressing force by an L-shaped leaf spring screwed to the second fitting portion.

Prior art literature:

patent documents

Patent Document 1: Japanese Patent No. 3218851;

Patent Document 2: Japanese Patent Laid-Open No. 2006-276741 (paragraphs 0015-0017, Figure 1, Figure 2);

Patent Document 3: Japanese Patent Laid-Open No. 2007-49879 (paragraphs 0027-0041, Figures 4-8);

Patent Document 4: Japanese Patent Application Laid-Open No. 2007-49880 (paragraphs 0018-0020, Figure 2);

Patent Document 5: Japanese Patent Laid-Open No. 2007-74889 (paragraphs 0055, 0086, Figure 5, Figure 12);

Patent Document 6: Japanese Patent Laid-Open No. 2007-181261 (paragraphs 0017-0019, Fig. 3, Fig. 4);

Patent Document 7: Japanese Unexamined Patent Application Publication No. 2007-306763 (paragraphs 0028 to 0030, FIG. 2 and FIG. 3 ).

Contents of the invention

The problem to be solved by the invention

In the drive devices disclosed in the above-mentioned Patent Documents 1 to 7, there are problems described below.

In the driving device disclosed in Patent Document 1, since the driving member (drive shaft, vibration friction part) extends in the telescopic direction of the electromechanical conversion element, the driving part (drive shaft, vibration friction part) is larger than the driven part (variable focus lens). Lens barrel) is longer and prone to inclination due to the reciprocating motion of the driving parts (drive shaft, vibration friction part). In addition, the longer the moving distance of the driven member (variable focus lens barrel), the longer the driving member (drive shaft, vibration friction part), and unnecessary vibration modes tend to occur. In addition, there is a friction fit portion on the extension line of the joint portion between the electromechanical conversion element and the driving member (drive shaft, vibration friction portion), which is disadvantageous for height reduction.

In the optical module disclosed in Patent Document 2, it is necessary to include first and second bearing members that slidably hold a piezoelectric element (electromechanical conversion element) and function as sliding bearings. As a result, there is a problem that the number of parts increases and the structure becomes complicated.

In the actuator disclosed in Patent Document 3, as in the drive device disclosed in Patent Document 1, the drive friction member (oscillating friction portion) extends in the expansion-contraction direction of the electromechanical conversion element. As a result, the driving friction member (oscillating friction portion) is longer than the driven member, and the driving friction member (oscillating friction portion) reciprocates and tends to tilt easily. In addition, the longer the movement distance of the driven member, the longer the drive friction member (vibration friction portion) becomes, and an unnecessary vibration mode tends to occur. In addition, since the friction fit portion is provided in the extension of the joint portion between the electromechanical conversion element and the driving friction member (vibration friction portion), it is disadvantageous for height reduction.

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

In the drive device disclosed in Patent Document 5, as in the drive device disclosed in Patent Document 1, the drive member (vibration friction portion) extends in the direction of expansion and contraction of the electromechanical conversion element. As a result, the driving member (vibration friction part) is longer than the driven member, and the driving member (vibration friction part) reciprocates and tends to tilt easily. In addition, the longer the moving distance of the driven member, the longer the driving member (vibration friction part), and an unnecessary vibration mode tends to occur. In addition, since the friction fit portion is provided in an extension of the joint portion between the electromechanical conversion element and the driving member (vibration friction portion), it is disadvantageous for height reduction.

In the drive unit disclosed in Patent Document 6, an elastic member is mounted on a friction fit member (vibration friction portion). In such a configuration, when a high-frequency voltage is applied to the electromechanical transducer element, the elastic member resonates and becomes a frequency band that vibrates in a phase opposite to that of the friction fitting member (vibrating friction portion). The phase difference between the elastic member and the friction-fitting member (vibration friction part) becomes a main cause of a reduction in the moving speed of the frictionally coupled driven part (moving member) and a phenomenon of inversion of the moving direction.

In the piezoelectric actuator disclosed in Patent Document 7, as in the drive device disclosed in Patent Document 1, the drive friction member (oscillating friction portion) extends in the expansion-contraction direction of the piezoelectric element (electromechanical conversion element). As a result, the driving member (oscillating friction part) is longer than the moving member (driven member), and the driving member (vibrating friction part) tends to tilt due to the reciprocating motion. In addition, the longer the moving distance of the moving member (driven member), the longer the driving member (vibration friction part), and an unnecessary vibration mode tends to occur. In addition, since the friction fitting part is provided in the extension of the junction part of the piezoelectric element (electromechanical conversion element) and the driving member (vibration friction part), it is disadvantageous for height reduction.

Therefore, an object of the present invention is to provide a drive device capable of efficiently moving a driven member.

Another object of the present invention is to provide a driving device capable of reducing the height.

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

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

method used to solve the problem

If the gist of the exemplified form of the present invention is described, it can be understood that the drive device includes: an electromechanical conversion element having first and second end faces opposite to each other in the expansion and contraction direction; a vibrating friction part; a driven part frictionally coupled with the vibrating friction part; and a friction force applying mechanism that generates frictional force between the vibrating friction part and the driven part. The driven member can move in the expansion and contraction direction of the electromechanical conversion element. According to an exemplary aspect of the present invention, the vibration friction portion has a friction surface as a first end surface in a direction perpendicular 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 vibrating friction portion. The friction applying mechanism is attached to a member other than the vibrating friction part.

The effects of the present invention are as follows.

In the present invention, since the vibrating friction part has a friction surface as a first end face in a direction perpendicular to the telescopic direction, the driven member includes a rod-shaped moving shaft slidingly contacting the friction surface of the vibrating friction part, and the frictional force applying mechanism Since it is attached to a member other than the vibration friction part, the driven member can be efficiently moved.

Description of drawings

FIG. 1 is a perspective view showing a drive device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of an auto-focus lens driving unit of the driving device shown in FIG. 1 viewed obliquely from the upper right front.

FIG. 3 is a perspective view of the auto-focus lens drive unit in FIG. 2 viewed obliquely from the upper right rear.

FIG. 4 is a perspective view of the auto-focus lens drive unit in FIG. 2 viewed obliquely from the upper right.

FIG. 5 is a side view of the autofocus lens driving unit of FIG. 2 .

FIG. 6 is a perspective view showing a lens driving unit of the autofocus lens driving unit in FIG. 2 together with a driven member and a spring.

Fig. 7 is a waveform diagram for explaining the current supplied to the laminated piezoelectric element and the displacement occurring in the laminated element.

8 is a perspective view of a driving device (autofocus lens driving unit) according to a second embodiment of the present invention viewed obliquely from the upper right rear.

9 is a perspective view of a driving device (autofocus lens driving unit) according to a third embodiment of the present invention viewed obliquely from above right front.

FIG. 10 is a perspective view of the auto-focus lens drive unit in FIG. 9 viewed obliquely from the upper right rear.

FIG. 11 is a perspective view of the auto-focus lens driving unit of FIG. 9 viewed obliquely from the upper right.

Detailed ways

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

A drive device 20 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 6 . FIG. 1 is a perspective view showing a driving device 20 . FIG. 2 is a perspective view of the auto-focus lens driving unit 40 of the driving device 20 shown in FIG. 1 viewed obliquely from the upper right front. FIG. 3 is a perspective view of the auto-focus lens drive unit 40 in FIG. 2 viewed obliquely from the upper right rear. FIG. 4 is a perspective view of the autofocus lens drive unit 40 as viewed obliquely from the upper right. 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. In the state shown in Figures 1 to 6, in the orthogonal coordinate system (X, Y, Z), the X-axis direction represents the front-to-back direction (depth direction), the Y-axis direction represents the left-right direction (width direction), and the Z-axis direction The direction indicates an up-down direction (height direction).

The illustrated driving device 10 is used, for example, as the lens driving unit 44 of the autofocus lens driving unit 40 . In this case, in the examples shown in FIGS. 1 to 6 , 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 box (housing) 30 that covers an autofocus lens driving device 40 described later. In other words, the autofocus lens driving device 40 is arranged inside the housing (casing) 30 . The case (casing) 30 includes an upper frame 32 , a lower frame 34 , a driver base 36 , and an upper cover 38 . The driver base 36 is mounted on the lower frame 34 . A stationary member (hammer) 442 to be described later is mounted on the driver base 36 . The upper cover 38 has a circular opening 38a whose central axis is the optical axis O of the lens.

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

Referring to FIGS. 2 to 4 , inside the case (casing) 30 , a guide shaft 39 is provided on the left-hand front side (see FIG. 9 ). The guide shaft 39 extends parallel to the optical axis O. As shown in FIG. The guide shaft 39 is erected on the lower frame 34 of the case (casing) 30 . A driven member 423 , which will be described later, is provided on the opposite side to the guide shaft 39 with the optical axis O interposed therebetween, that is, on the right rear side. In the illustrated example, the driven member 423 is constituted by a rod-shaped moving shaft. The movement axis 423 also extends parallel to the optical axis O. As shown in FIG. That is, the guide shaft 39 and the moving shaft 423 are arranged at rotationally symmetrical positions around the optical axis.

The autofocus lens driving device 40 is composed of a lens movable unit 42 and a lens driving unit 44 . The lens driving section 44 slidably supports the lens movable section 42 in the optical axis O direction and drives the lens movable section 42 as described later.

The lens movable section 42 includes a lens barrel (lens unit) 421 holding an auto focus lens AFL as a movable lens. A lens barrel (lens assembly) 421 is held fixed within a substantially cylindrical movable lens barrel (lens holder) 422 . Internal threads (not shown) are cut on the inner peripheral wall of the lens holder 422 . On the other hand, an external thread (shown) screwed to the above-mentioned internal thread is cut on the outer peripheral wall of the lens barrel 422 . Therefore, if the lens barrel 421 is to be installed on the lens frame 422, the lens barrel 421 is rotated around the optical axis O relative to the lens frame 422 and screwed along the optical axis O direction, so that the lens barrel 421 is accommodated in the lens frame 422. inside, and then bonded to each other by adhesives, etc.

The lens holder 422 has a first extension portion (first fitting portion) 4221 extending outward in the radial direction at the upper end on the left-hand front side. The first extension portion (first engaging portion) 4221 has a substantially U-shaped recessed portion 4221U opened on the left side, and the guide shaft 39 is accommodated in the recessed portion 4221U. The lens holder 422 has a pair of second extending portions (second matching portions) 4222 extending radially outward on the inner right side. The pair of first extension parts (first fitting parts) 4222 has substantially U-shaped recessed parts 4222U opened on the right side, and the movement shaft 423 is housed and fitted in these recessed parts 4222U. With this structure, the lens movable part 42 can move only in the direction of the optical axis O with respect to the case (casing) 30 .

The lens holder 422 has a third extending portion 4223 extending outward in the radial direction on the inner left side. The first end portion 424a of the spring 424 is bonded to the third extension portion 4223 with an adhesive. The spring 424 extends from the first end portion 424a to the right side in the left-right direction Y to the second end portion 424b. On the second end portion 424b of the spring 424, a protrusion 424c protruding forward in the forward-backward direction X is provided.

The protrusion 424c is biased by the spring 424 in a direction approaching the moving shaft 423 (forward in the front-rear direction X). The vibrating friction part 443 to be described later is sandwiched between the moving shaft 323 and each protrusion 424 c by its first and second end surfaces 4431 , 4432 . The first and second end faces 4431 and 4432 face each other in a direction perpendicular to the optical axis O direction. In other words, the first and second end surfaces 4431 and 4432 face each other in a direction perpendicular to the expansion and contraction direction of the laminated piezoelectric element 441 described later. Furthermore, the first end surface 4331 functions as a friction surface as will be described later.

The lens movable part 42 of the autofocus lens driving unit 40 is constituted 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 drive unit 44 of the autofocus lens drive unit 40 will be described. The lens drive unit 44 is composed of a laminated piezoelectric element 441 operating as an electromechanical conversion element, the above-mentioned stationary member (weight) 442 , and the above-mentioned vibration friction unit 443 .

The laminated piezoelectric element 441 expands and contracts in the direction of the optical axis O (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 surface (lower end surface) 441 a and a second end surface (upper end surface) 441 b facing each other in the expansion and contraction direction. The stationary member (hammer) 442 is bonded to the first end surface (lower end surface) 441a of the laminated piezoelectric element 441 with an adhesive or the like. The combination of the laminated piezoelectric element 441 and the stationary part 442 is called a piezoelectric unit.

The vibrating friction part 443 is attached to the second end surface (upper end surface) 441b of the laminated piezoelectric element 441 with an adhesive or the like. In the illustrated example, the vibrating friction part 443 is directly connected to the second end 441b of the laminated piezoelectric element 441, but it is also possible to insert something between the vibrating friction part 443 and the second end 441b of the laminated piezoelectric element 441 part.

The rod-shaped moving shaft 423 is frictionally coupled with the vibration friction part 443 . In the vibration friction part 443 , a groove 4431 a having a V-shaped cross section is formed in a friction coupling part (friction surface) 4431 between the vibration friction part 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 vibrating friction portion 443 against the rod-shaped moving shaft 423 . That is, the first end portion 424a of the spring 424 is fastened to the third extension portion 4223, and the protrusion 424c attached to the second end portion 424b generates a pressing force for pressing the vibrating friction portion 443 against the moving shaft 423. In other words, the spring 424 urges the protrusion 424c (second end portion 424b) to the vibration friction part 443, and the vibration friction part 443 is clamped by the moving shaft 423 and the protrusion 424c, thereby acting as a frictional surface 4431 between the vibration friction part 443 and the movement. The frictional force application mechanism (biasing mechanism) that applies frictional force between the shafts 423 functions.

In the vibration friction part 443 , a groove 4431 a having a V-shaped cross section is formed in the friction coupling part (the friction surface 4431 ) between the vibration friction part 443 and the moving shaft 423 . By vibrating the two straight lines of the V-shaped groove 4431a in the cross-section of the friction part 443 and the moving shaft 423, the contact state of the friction coupling part (friction surface 4431) is stable and the reproducibility of the friction drive is obtained, and the movement is improved. The effect of the linear mobility of the shaft 423 as a single-axis movement. Furthermore, it is desirable that the angle of the groove 4431a having a V-shaped cross section be 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. 6 . As shown in FIG. 6 , the driving device 10 can design the effective length Ls of the spring 424 to be longer. Therefore, even if the size of the spring 424 deviates from the assembly size, the influence on the load can be reduced. As a result, the drive device 10 can be manufactured with reduced performance variation among products.

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

In addition, in this embodiment, the spring 424 is not attached to the vibration friction part 443 but is attached to the lens movable part 42 side. In this way, by separating the vibration friction part 443 and the spring 424 , it is possible to prevent the resonance phenomenon of the spring 424 from being caused. Therefore, the phases of the vibration friction part 443 and the spring 424 are not reversed, and the lens movable part 42 can be moved efficiently. Moreover, the advancing direction of the lens movable part 42 can also be controlled so that it may advance in a desired direction.

As shown in FIGS. 2 to 5 , the lens drive unit 44 and the lens movable unit 42 are arranged side by side with respect to the optical axis O. As shown in FIG. Therefore, it is possible to reduce the height of the autofocus lens driving unit 40 . 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 occurring in the laminated piezoelectric element 441 will be described with reference to FIG. 7 . In addition, FIG. 7 is the same member as the structure shown in FIG. 5 of the said patent document No. 3218851 (patent document 1). 7(A) is a diagram showing changes in current supplied to the multilayer piezoelectric element 441 by a drive circuit (not shown), and FIG. 7(B) is a diagram showing displacement of the multilayer piezoelectric element 441 .

As shown in FIG. 7(A), a large current (positive direction, that is, forward direction) and a predetermined constant current (negative direction, that is, reverse direction) alternately flow through the laminated piezoelectric element 441 . In this situation, as shown in FIG. 7(B), the laminated piezoelectric element 441 alternately produces a sharp displacement (stretch) corresponding to a large current (positive direction, that is, forward direction) and a constant current (negative direction, that is, reverse direction). Direction) corresponds to a smooth displacement (shrinkage).

That is, a rectangular wave current is applied to the laminated piezoelectric element 441 ( FIG. 7(A) ), and sawtooth-shaped displacement (expansion and contraction) occurs with respect to the laminated piezoelectric element 441 ( FIG. 7(B )).

Referring to FIG. 2 in addition to FIG. 7 , the operation of the autofocus lens drive unit 40 (drive device 10 ) will be described. First, the operation in the case of moving the lens movable portion 42 downward in the vertical direction Z will be described.

First, as shown in FIG. 7(A), a large current in the forward direction, that is, in the forward direction, flows through the laminated piezoelectric element 441 . In this case, as shown in FIG. 7(B), the laminated piezoelectric element 441 rapidly undergoes a stretching displacement in the thickness direction. As a result, the vibrating friction part 443 rapidly moves upward along the optical axis O direction (vertical direction Z). At this time, the lens movable part 42 does not move. The reason for this is that, due to its inertial force, the lens movable portion actually stays at its position against the frictional force between the vibrating friction portion 443 and the rod-shaped moving shaft 423 .

Next, as shown in FIG. 7(A), a constant current in the negative direction, that is, in the opposite direction, flows through the laminated piezoelectric element 441 . In this case, the laminated piezoelectric element 441 smoothly generates contraction displacement in the thickness direction. As a result, the vibrating friction part 443 slowly moves downward along the optical axis O direction (vertical direction Z). At this time, the lens movable part 42 actually moves downward along the optical axis O direction (vertical direction Z) together with the vibrating friction part 443 . The reason for this is that the vibration friction portion 443 and the rod-shaped moving shaft 423 are coupled together by the frictional force generated on the contact surface (friction surface 4431 ) therebetween.

In this way, a large current (positive direction, that is, the forward direction) and a certain current (negative direction, that is, the reverse direction) are alternately applied to the laminated piezoelectric element 441, so that the laminated piezoelectric element 441 alternately produces stretching displacement and contraction displacement, thereby enabling The lens holder 442 (lens barrel 421 ) continuously moves downward along the optical axis O direction (vertical direction Z).

The lens movable part 42 is moved upward along the optical axis O direction (vertical direction Z). Conversely, it can be realized by alternately flowing a large current (negative direction, that is, reverse direction) and a constant current (positive direction, that is, forward direction) through the laminated piezoelectric element 441 .

Hereinafter, the laminated piezoelectric element 441 will be described. The laminated piezoelectric element 441 is formed in 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. The laminated piezoelectric element 441 is manufactured by alternately stacking 50 layers of a piezoelectric material with a thickness of 20 [μm] and an internal electrode with a thickness of 2 [μm] in a comb shape. In addition, the effective internal electrode size of the laminated piezoelectric element 441 is 0.6 [mm]×0.6 [mm]. In other words, a ring-shaped dead zone portion (gap) with a width of 0.15 [mm] exists in the peripheral portion located outside the effective internal electrodes of the multilayer piezoelectric element 441 .

In the driving device 20 shown in Fig. 1 and Fig. 5, the moving shaft 423 and the lens holder (lens supporting body) 422 are separated and fastened to each other, but the moving shaft 423 and the lens holder (lens supporting body) may also be separated. Body) 422 is integrally formed. In this case, the lens holder (lens support) 422 and the moving shaft 423 are made of the same material.

A drive device 20A (autofocus lens drive unit 40A) according to a second embodiment of the present invention will be described with reference to FIG. 8 . FIG. 8 is a perspective view of the autofocus lens drive unit 40A viewed obliquely from the upper right rear. The illustrated autofocus lens drive unit 40A has the same structure as the autofocus lens drive unit 40 shown in FIG. same action. Therefore, parts having the same functions as those shown in FIG. 3 are attached with the same reference numerals, and only the differences will be described below for simplification of description.

In the auto-focus lens driving unit 40 shown in FIG. 3 , the first end 424 a of the spring 424 is fastened to the third extension 4223 of the lens holder 422 with an adhesive.

In contrast, in the autofocus lens driving unit 40A shown in FIG. 8 , the first end portion 424 a of the spring 424 is fixed on the third extension portion 4223 of the lens holder 422 with a screw 425 .

Obviously, the autofocus lens driving unit 40A shown in FIG. 8 also has the same effect as the autofocus lens driving unit 40 of the above-mentioned first embodiment.

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. 9 to 11 . FIG. 9 is a perspective view of the auto-focus lens drive unit 40B viewed obliquely from the upper right front. FIG. 10 is a perspective view of the auto-focus lens drive unit 40B viewed obliquely from the upper right rear. FIG. 11 is a perspective view of the autofocus lens drive unit 40B as viewed obliquely from the upper right. The illustrated autofocus lens drive unit 40B has the same structure as the autofocus lens drive unit 40 shown in FIGS. action. Therefore, reference numeral 444 is attached to the spring. Therefore, parts having the same functions as those shown in FIGS. 1 to 5 are given the same reference numerals, and only the differences will be described below for simplification of description. In addition, reference numeral 39 denotes the aforementioned guide shaft.

In the autofocus lens driving unit 40 shown in FIGS. 2 to 4 , the spring 424 is mounted on the lens holder 422 . That is, the first end portion 424a of the spring 424 is fastened to the third extension portion 4223 of the lens holder 422 with an adhesive. Therefore, the spring 424 is a constituent element of the lens moving unit 42 .

In contrast, in the autofocus lens drive unit 40B shown in FIGS. 9 to 11 , the spring 444 is mounted on the housing 30 . Therefore, the spring 444 is a constituent element of the lens driving unit 44 .

To describe in detail, the first end portion 444a of the spring 444 is attached to the inner wall surface 34a of the lower frame 34 of the case 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. On the second end portion 444b of the spring 444, a protrusion 444c protruding in the rear direction in the front-rear direction X is provided. The protrusion 444c is biased by the spring 444 in a direction approaching the friction surface 4431 of the vibration friction part 443 (rear direction in the front-rear direction X). The moving shaft 423 is held between the friction surface 4431 of the vibration friction part 443 and the protrusion 444c.

In this way, the lens drive unit 44 includes the spring 444 for pressing (biasing) the rod-shaped moving shaft 423 against the vibration friction unit 443 . That is, the first end portion 444a of the spring 444 is fastened to the inner wall surface 34a of the lower frame 34, and the protrusion 444c mounted on the second end portion 444b generates a pressing force for pressing the moving shaft 423 against the vibration friction portion 443. In other words, the spring 444 urges the protrusion 444c (second end portion 444b) to the moving shaft 423, and clamps the moving shaft 423 between the vibration friction part 443 and the protrusion 444c, thereby acting as a frictional surface 4431 between the vibration friction part 443 and the moving shaft. 423 to apply the friction applying mechanism (force applying mechanism) of frictional force and function.

In the third embodiment, the spring 444 is not attached to the vibration friction part 443 but is attached to the case 30 side. In this way, by separating the vibration friction part 443 and the spring 444 , it is possible to prevent the resonance phenomenon of the spring 444 from being caused. Therefore, the phases of the vibration friction part 443 and the spring 444 are not reversed, and the lens moving part 42 can be moved efficiently. In addition, the advancing direction of the lens moving part 42 can also be controlled so that it may advance in a desired direction.

In the driving device of the exemplary embodiment of the present invention described above, it is preferable that the vibrating friction portion has a groove having a V-shaped cross section on the friction surface. The angle of the V-shaped groove is preferably in the range of 30 degrees to less than 180 degrees.

According to a first aspect of the present invention, the drive device includes a lens holder fastened to or integrally formed with the movement shaft, and the friction force applying mechanism is mounted on the lens holder. The friction force applying mechanism may also be constituted by, for example, a force applying member mounted on the lens holder. In this case, the biasing member may also have: a first end installed on the lens holder; The first end surface faces in a direction perpendicular to the expansion and contraction direction. The biasing member can also be formed by, for example, a spring whose first end is bonded to the lens holder. It is also possible to replace the above structure, and the biasing member is composed of a spring whose first end is fixed on the lens holder by screws.

According to a second aspect of the present invention, the driving device includes a lens holder fastened to or integrally formed with the moving shaft; and a housing for accommodating the lens holder, and the friction applying mechanism is mounted on the housing. The friction applying mechanism may also be constituted by, for example, a biasing member mounted on the inner wall surface of the casing. In this case, the urging member may also have a first end installed on the inner wall of the casing; and a second end opposite to the friction surface of the vibration friction part with the moving shaft interposed therebetween. The biasing member may also be constituted by, for example, a spring whose first end is adhered to the inner wall surface of the casing.

As mentioned above, although this invention was especially shown and demonstrated with reference to the embodiment, this invention is not limited to these embodiment. It will be understood by those skilled in the art that various changes can be made in form and details without departing from the spirit and scope of the present invention defined by the technical solutions of the present invention. For example, in the above-mentioned embodiments, the movement shaft is formed in a cylindrical shape, but of course, the shape of the movement shaft is not limited to this.

This application claims the right of priority based on Japanese Patent Application No. 2008-284984 filed on November 6, 2008, the disclosure of which is incorporated herein as a reference in its entirety.

Claims (10)

1. A driving device (20, 20A, 20B), comprising: An electromechanical conversion element (441) having first and second end surfaces (441a, 441b) opposite to each other in the telescopic direction (Z); The vibration friction part (443) installed on the above-mentioned second end surface (441b) of the electromechanical conversion element; A driven part (423) frictionally combined with the vibration friction part, the driven part (423) can move in the telescopic direction (Z) of the above-mentioned electromechanical conversion element (441); and A frictional force applying mechanism (424, 444) that generates a frictional force between the vibrating friction portion and the driven member, wherein the driving device is characterized in that The vibration friction part (443) has a friction surface as a first end surface (4431) in a direction perpendicular to the expansion and contraction direction (Z), The driven member includes a rod-shaped moving shaft (423) that is in sliding contact with the friction surface of the vibration friction part, The friction applying mechanism (424, 444) is attached to a member (422, 30) other than the vibration friction part (443). 2. The driving device according to claim 1, characterized in that, The vibration friction part (443) has a groove (4431a) having a V-shaped cross section on the friction surface (4431). 3. The driving device according to claim 2, characterized in that, The angle (4431a) of the V-shaped groove is in the range of 30 degrees to less than 180 degrees. 4. The driving device according to any one of claims 1 to 3, characterized in that, The driving device (10, 10A) is provided with a lens holder (422) fastened to the moving shaft (423) or integrally formed with the moving shaft (423), The above-mentioned friction force applying mechanism (424) is installed on the above-mentioned lens holder (422). 5. The driving device according to claim 4, characterized in that, The above-mentioned frictional force applying mechanism is composed of a force applying member (424) installed on the above-mentioned lens holder (422), The above-mentioned biasing member (424) has: a first end portion (424a) installed on the above-mentioned lens holder (422); 443) is in contact with the second end surface (4432), and the second end surface (4432) is opposed to the first end surface (4431) in a direction perpendicular to the expansion and contraction direction (Z). 6. The driving device according to claim 5, characterized in that, The biasing member is composed of a spring (424) whose first end portion (424a) is bonded to the lens holder (422). 7. The driving device according to claim 5, characterized in that The biasing member is composed of a spring (424) whose first end portion (424a) is fixed to the lens holder (422) by a screw (425). 8. The driving device according to any one of claims 1 to 3, characterized in that The above-mentioned driving device (10B) has: A lens holder (422) fastened on the above-mentioned moving shaft (423) or integrally formed with the above-mentioned moving shaft (423); and Housing (30) for accommodating the lens holder, The above-mentioned friction applying mechanism (444) is installed on the above-mentioned casing (30). 9. The driving device according to claim 8, characterized in that The above-mentioned frictional force applying mechanism is composed of a biasing member (444) installed on the inner wall surface (34a) of the above-mentioned housing (30), The above-mentioned biasing member (444) has a first end portion (444a) installed on the inner wall surface (34a) of the above-mentioned housing (30); the above-mentioned moving shaft (423) and the above-mentioned vibration friction part (443) The second end portion (444b) opposite to the above friction surface (4431). 10. The driving device according to claim 9, characterized in that The urging member is composed of a spring (444) whose first end portion (444a) is bonded to the inner wall surface (34a) of the housing.

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