JP2010004711A - Driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device capable of preventing deterioration in a conductive adhesive while permitting expansion and shrinkage of an electromechanical conversion element. <P>SOLUTION: The driving device 1 is provided with: a piezoelectric element 5; a drive shaft 6 attached on one end of a telescopic direction of the piezoelectric element 5; a lens frame frictionally engaging with the drive shaft 6; an FPC 7 for transmitting a driving signal to the piezoelectric element 5; and a conductive adhesive 8 for fixing and electrically connecting the piezoelectric element 5 to the FPC 7. In the driving device 1, since an insulating adhesive 9 is provided so as to cover the conductive adhesive 8, the conductive adhesive 8 can be prevented from deterioration due to ambient environment. Furthermore, although high conductivity of the adhesive causes a decrease in elasticity of the adhesive, since the conductivity of the insulating adhesive 9 is lower than that of the conductive adhesive 8, the elasticity thereof is high. Thus, even if an adhesive area of the piezoelectric element 5 is increased due to the insulating adhesive 9, the expansion/shrinkage of the piezoelectric element 5 is hardly inhibited. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a driving apparatus suitable for driving a lens or the like in, for example, a mobile phone with a camera or a small digital camera.

As a conventional drive device, an electromechanical conversion element that expands and contracts along a predetermined expansion / contraction direction, a drive member attached to one end of the electromechanical conversion element in the expansion / contraction direction, and a driven body frictionally engaged with the drive member Are known (for example, see Patent Document 1). In such a drive device, the printed circuit board is electrically connected to the electromechanical conversion element with a conductive adhesive, and a drive signal is transmitted to the electromechanical conversion element. The printed circuit board is disclosed in Patent Document 2, for example. Incidentally, the present applicant has already filed a patent application as Japanese Patent Application No. 2008-087136 for a drive device in which a printed circuit board is mounted in parallel to the expansion and contraction direction of the electromechanical transducer.
JP 2006-311794 A JP 2007-274777 A

  However, in the drive device as described above, there is a problem that the conductive adhesive is deteriorated by the surrounding environment and the conductivity is deteriorated. In particular, this problem is remarkable in a high temperature and high humidity environment. Here, it is also conceivable to reduce an adverse effect due to deterioration of the conductive adhesive by increasing the amount of the conductive adhesive applied. However, in this case, the adhesion region of the electromechanical conversion element increases, and the expansion and contraction of the electromechanical conversion element may be hindered.

  Then, this invention makes it a subject to provide the drive device which can reduce deterioration of a conductive adhesive, accept | permitting expansion-contraction of an electromechanical conversion element.

  In order to solve the above problems, a drive device according to the present invention includes an electromechanical conversion element that expands and contracts along a predetermined expansion / contraction direction, a drive member attached to one end of the electromechanical conversion element in the expansion / contraction direction, and a drive member A driven body frictionally engaged with the printed circuit board; a printed circuit board that transmits a drive signal to the electromechanical conversion element; a conductive adhesive that fixes and electrically connects the electromechanical conversion element and the printed circuit board; And a resin that is provided so as to cover at least a part of the conductive adhesive and has lower conductivity than the conductive adhesive.

  In this drive device, resin is provided so as to cover at least a part of the conductive adhesive. Therefore, the conductive adhesive is protected by the insulating resin with respect to the surrounding environment, and for example, the deterioration of the conductive adhesive due to the surrounding environment can be suppressed even in a high temperature and high humidity environment. Here, usually, when the conductivity of the adhesive is high, the elasticity of the adhesive becomes low. In this respect, the resin has high elasticity because the conductivity is lower than that of the conductive adhesive as described above. Therefore, even if the adhesion region of the electromechanical conversion element is increased by this resin, the expansion and contraction of the electromechanical conversion element is hardly hindered. Therefore, the expansion and contraction of the electromechanical conversion element can be allowed.

  The resin preferably has higher moisture resistance than the conductive adhesive. In this case, deterioration of the conductive adhesive can be further reduced.

  The printed board is preferably a flexible printed board. In this case, the printed circuit board can be handled easily and the printed circuit board can be easily handled.

  Moreover, it is preferable that resin fixes an electromechanical conversion element and a printed circuit board mutually. In this case, it is possible to prevent the printed circuit board from being peeled off from the electromechanical conversion element. Furthermore, when the printed circuit board is a flexible printed circuit board, the above effect of preventing the printed circuit board from being peeled off from the electromechanical conversion element is particularly effective. This is because the flexible printed circuit board is easily deformed and therefore easily peeled off from the electromechanical transducer by the deformation load.

  The resin is preferably an insulating resin. In addition, the driven body may be specifically configured to include a lens frame and a lens.

  According to the driving device of the present invention, it is possible to reduce deterioration of the conductive adhesive while allowing expansion and contraction of the electromechanical conversion element.

DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

  FIG. 1 is a cross-sectional view of an embodiment of a drive device according to the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 and 2, the driving device 1 is a device for driving the lens 3 held by the lens frame (driven body) 2 along the optical axis OA. It is suitable for a small digital camera or the like.

  The drive device 1 includes a piezoelectric element (electromechanical conversion element) 5, a drive shaft (drive member) 6, a flexible printed circuit board (printed circuit board) 7, and a weight 11 in a holder 4 that constitutes the outer periphery of the drive device 1. ing.

  The piezoelectric element 5 expands and contracts along a stretching direction (hereinafter simply referred to as “stretching direction”) parallel to the optical axis OA. Opposing side surfaces 5 a and 5 a of the piezoelectric element 5 are sandwiched and held by an elastic member 12 fixed to the holder 4. Thereby, the piezoelectric element 5 is elastically supported by the holder 4. The drive shaft 6 extends along the expansion / contraction direction, and is fixed to one end of the piezoelectric element 5 in the expansion / contraction direction with an adhesive. The drive shaft 6 is formed in a columnar shape from a graphite complex in which graphite crystals are firmly combined, such as carbon graphite.

  In addition, one end of the drive shaft 6 passes through a bearing hole 41 a formed in the partition portion 41 of the holder 4 with a gap fit. On the other hand, the other end portion of the drive shaft 6 penetrates through a bearing hole 42a formed in the partition portion 42 of the holder 4 with a clearance fit. Thereby, the drive shaft 6 can reciprocate along the expansion and contraction direction. The holder 4 is formed with an opening 4a, and the opening 4a is covered with a detachable holder cover 13.

  The drive shaft 6 is frictionally engaged with the engagement portion 21 of the lens frame 2 whose movement region is regulated between the partition portions 41 and 42. FIG. 3 is a cross-sectional view taken along line III-III in FIG. As shown in FIG. 3, the plate member 22 is attached to the plate member 22 side by a plate member 22 having a V-shaped cross section fixed in the V groove 21 a of the engagement portion 21 and a plate spring 23 locked to the engagement portion 21. A plate member 24 having a V-shaped cross section that is biased sandwiches the drive shaft 6. Thereby, the engaging part 21 produces a fixed friction force between the drive shaft 6 in the movement.

  Returning to FIGS. 1 and 2, a flexible printed circuit board (hereinafter referred to as “FPC”) 7 has a tape shape extending in a direction substantially orthogonal to the expansion and contraction direction. As for FPC7, the piezoelectric element 5 is arrange | positioned on the surface 7a. Specifically, the piezoelectric element 5 is disposed on the surface 7a so that the FPC 7 is parallel to the expansion / contraction direction. The FPC 7 is electrically connected to the piezoelectric element 5 by a conductive adhesive 8 and is also electrically connected to a drive circuit (not shown). As a result, the FPC 7 transmits a drive signal, which is an electrical signal for driving the piezoelectric element 5, from the drive circuit to the piezoelectric element 5.

  In addition, the length of the FPC 7 in the expansion / contraction direction is smaller than the length of the piezoelectric element 5 in the expansion / contraction direction. The both end portions of the FPC 7 are located inside the both end portions of the piezoelectric element 5 in the expansion / contraction direction.

  The weight 11 is attached to the other end of the piezoelectric element 5 in the expansion / contraction direction. The weight 11 applies a load to the other end side of the piezoelectric element 5 to prevent the other end side of the piezoelectric element 5 from being displaced more than the one end side. The weight 11 here is preferably heavier than the drive shaft 6 in order to efficiently transmit the expansion and contraction of the piezoelectric element 5 to the drive shaft 6 side. For example, if the piezoelectric element 5 is supported by fixing the other end side of the weight 11 to the holder 4 or the holder cover 13, the elastic member 12 becomes unnecessary.

  Here, the connection between the piezoelectric element 5 and the FPC 7 described above will be described in detail.

  4 is a perspective view showing the periphery of the piezoelectric element of the drive device of FIG. 1, and FIG. 5 is a cross-sectional view taken along the line V-V of FIG. As shown in FIGS. 4 and 5, the conductive adhesive 8 fixes and electrically connects the piezoelectric element 5 and the FPC 7 to each other. The conductive adhesive 8 is provided so as to close a corner portion constituted by the surface 7 a of the FPC 7 and the side surface 5 a of the piezoelectric element 5. That is, the conductive adhesive 8 is applied in an L-shaped cross section (fillet shape). Thereby, the piezoelectric element 5 and the FPC 7 are bonded to each other, and the wiring pattern 10 on the surface 7a side of the piezoelectric element 5 and the electrode of the piezoelectric element 5 are electrically connected to each other. Here, as the conductive adhesive 8, for example, a thermosetting adhesive containing 70 wt% silver particles and 20 wt% epoxy resin is used.

  An insulating adhesive (resin) 9 is provided on the conductive adhesive 8 so as to cover the conductive adhesive 8. The insulating adhesive 9 covers the conductive adhesive 8 so that the conductive adhesive 8 is not exposed, and bonds (fixes) the piezoelectric element 5 and the FPC 7 to each other. Here, as the insulating adhesive 9, for example, a thermosetting adhesive made of an epoxy resin is used.

  The insulating adhesive 9 has a lower concentration of conductive particles than the conductive adhesive 8. The conductive particles are particles for imparting conductivity to the conductive adhesive 8 and are formed of metal particles such as silver particles or carbon particles, for example. Here, “insulating” means that the conductivity is lower than that of the conductive adhesive 8, that is, the insulating property is higher than that of the conductive adhesive 8. That is, the insulating adhesive 9 is not limited to being completely insulating, and may be electrically conductive as long as the insulating property is higher than that of the conductive adhesive 8. “Contained concentration” means, for example, the concentration of any of weight (mass), volume, number, number of moles, and the like.

  Further, the insulating adhesive 9 has higher moisture resistance and heat resistance than the conductive adhesive 8, and is less likely to be deteriorated by moisture (humidity) and heat than the conductive adhesive 8. Further, the insulating adhesive 9 has higher adhesiveness than the conductive adhesive 8. Incidentally, high adhesion means that a higher tensile force can be applied before the bonded materials break each other.

  In this drive device 1, a drive signal is input to the piezoelectric element 5, and the piezoelectric element 5 repeats expansion and contraction by the input of the drive signal. The drive shaft 6 reciprocates in accordance with the expansion and contraction. At this time, the speed at which the drive shaft 6 moves in one direction is different from the speed at which it moves in the other direction by making the extension speed and contraction speed of the piezoelectric element 5 different. Thereby, the engaging part 21 and by extension the lens frame 2 are moved in a desired direction.

  As described above, according to the driving device 1, the insulating adhesive 9 is provided so as to cover the conductive adhesive 8. Therefore, the conductive adhesive 8 is protected with respect to the surrounding environment by the insulating adhesive 9, and the deterioration of the conductive adhesive 8 due to the surrounding environment is suppressed even in a high temperature and high humidity environment such as a durability test. be able to. And suppressing the deterioration of the conductive adhesive 8 has the following effects. That is, it is possible to suppress the occurrence of microcracks in the conductive adhesive 8, and it is possible to prevent an increase in resistance value and thus a drive deterioration. A decrease in adhesiveness can be suppressed, and deformation of the FPC 7 can be prevented. As a result, durability against physical addition such as bending can be improved. That is, it is possible to prevent the piezoelectric element 5 and the FPC 7 from being separated.

  In general, when the content of the conductive particles in the adhesive is high, the conductivity is increased, and the adhesive becomes harder and harder when cured. However, the insulating adhesive 9 has a high elasticity (soft) when cured because the conductive particle 8 has a low content of conductive particles and low conductivity as described above. It has become. Therefore, even if the piezoelectric element 5 is bonded by the insulating adhesive 9 and the adhesion area is increased, the expansion and contraction of the piezoelectric element 5 is hardly hindered. As a result, expansion and contraction of the piezoelectric element 5 can be allowed, and adverse effects due to resonance caused by the expansion and contraction of the piezoelectric element 5 can be suppressed.

  Further, in the driving device 1, as described above, the insulating adhesive 9 has higher moisture resistance than the conductive adhesive 8. In this case, the deterioration of the conductive adhesive 8 can be further reduced. Furthermore, since the insulating adhesive 9 has higher heat resistance than the conductive adhesive 8, it is possible to further reduce such deterioration.

  In the driving device 1, as described above, the FPC 7 is used as a printed board. Therefore, handling of the printed circuit board is improved and the printed circuit board can be easily handled.

  Moreover, in the drive device 1, as described above, the insulating adhesive 9 bonds the piezoelectric element 5 and the FPC 7 to each other. Therefore, it is possible to further prevent the FPC 7 from peeling from the piezoelectric element 5. Further, the FPC 7 is more easily deformed than the normal printed circuit board, and is easily peeled off from the piezoelectric element 5 by the deformation load. Therefore, the above effect of preventing the FPC 7 from peeling from the piezoelectric element 5 is particularly effective.

  The present invention is not limited to the embodiment described above.

  For example, in the above embodiment, the insulating adhesive 9 is provided so as to cover the conductive adhesive 8, but the insulating adhesive 9 may be provided so as to cover at least a part of the conductive adhesive 8. Moreover, in the said embodiment, although the insulating adhesive 9 of the thermosetting adhesive was used as resin, as long as electroconductivity is lower than the conductive adhesive 8, you may use another resin.

  In the above embodiment, the printed circuit board is the FPC 7, but the printed circuit board may be a so-called rigid board. In the above embodiment, the lens frame 2 is driven as a driven body. However, a driven body other than the lens frame 2 may be driven.

It is sectional drawing of one Embodiment of the drive device which concerns on this invention. It is sectional drawing along the II-II line of FIG. It is sectional drawing along the III-III line of FIG. It is a perspective view which shows the piezoelectric element periphery of the drive device of FIG. It is sectional drawing along the VV line of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Drive apparatus, 2 ... Lens frame (driven body), 5 ... Piezoelectric element (electromechanical conversion element), 6 ... Drive shaft (drive member), 7 ... Flexible printed circuit board (printed circuit board), 8 ... Conductive adhesion Agent, 9 ... Insulating adhesive (resin).

Claims (6)

An electromechanical transducer that expands and contracts along a predetermined expansion and contraction direction;
A drive member attached to one end of the electromechanical transducer in the expansion and contraction direction;
A driven body frictionally engaged with the driving member;
A printed circuit board for transmitting a drive signal to the electromechanical transducer;
A conductive adhesive that fixes and electrically connects the electromechanical transducer and the printed circuit board to each other;
A drive device comprising: a resin provided so as to cover at least a part of the conductive adhesive and having lower conductivity than the conductive adhesive.   The drive device according to claim 1, wherein the resin has higher moisture resistance than the conductive adhesive.   The drive device according to claim 1, wherein the printed circuit board is a flexible printed circuit board.   The drive device according to claim 1, wherein the resin fixes the electromechanical conversion element and the printed circuit board to each other.   The drive device according to claim 1, wherein the resin is an insulating resin.   The driving apparatus according to claim 1, wherein the driven body includes a lens frame and a lens.

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