JP5920274B2 - Piezoelectric drive device and lens drive device - Google Patents

Description

  The present invention relates to a piezoelectric driving device and a lens driving device that drives a camera lens of a camera mounted on a mobile phone or the like using the piezoelectric driving device.

  Patent Document 1 discloses a lens driving device. The lens driving device includes a piezoelectric driving device and a lens holder. The piezoelectric drive device includes a piezoelectric element, a weight fixed to one end side in the expansion / contraction direction of the piezoelectric element, and a drive member fixed to the other end side in the expansion / contraction direction of the piezoelectric element by an adhesive. The lens holder engages with the outer peripheral surface of the drive member. When the piezoelectric element repeatedly expands and contracts, the lens holder moves to one or the other in the expansion / contraction direction of the piezoelectric element by a frictional force generated between the lens holder and the outer peripheral surface of the driving member.

Japanese Patent No. 4898264

  Since a lens holder is attached to the other end side of the piezoelectric element in the expansion / contraction direction via a drive member, a large moment acts on the other end side of the piezoelectric element. Therefore, when an impact is applied from the outside, a large shear force is particularly likely to act on the other end side of the piezoelectric element. As a result, there is a possibility that problems such as destruction of the piezoelectric element or peeling of the adhesion between the piezoelectric element and the driving member may occur.

  In Patent Document 1, an attempt is made to suppress the inconvenience by setting the position of the center of gravity of the drive member in the vicinity of a plane including the contact surface on which the piezoelectric element and the drive member abut. However, when the lens driving device is used in a mobile device such as a mobile phone, it is often exposed to an environment that is susceptible to external impact force. Was desired.

  Therefore, an object of the present invention is to provide a piezoelectric driving device and a lens driving device capable of further improving impact resistance.

  A piezoelectric driving device according to one aspect of the present invention has a piezoelectric element, a weight connected to one end side in the expansion / contraction direction of the piezoelectric element, a bottomed cylindrical shape, and the other end side in the expansion / contraction direction of the piezoelectric element. A drive member housed inside and having the other end connected to the bottom is provided with a buffer member disposed between a side surface of the piezoelectric element and an inner wall surface of the drive member.

  In the piezoelectric driving device according to one aspect of the present invention, the buffer member is disposed between the side surface of the piezoelectric element and the inner wall surface of the driving member. Therefore, even if an impact force acts on the drive member from the outside, the impact force is absorbed by the buffer member. Accordingly, since the impact force applied to the piezoelectric element can be reduced, it is possible to further improve the impact resistance.

  The buffer member may be disposed between the side surface of the piezoelectric element and the inner wall surface of the drive member and near the open end of the drive member. When an impact force is applied in the absence of the buffer member, the open end of the drive member moves greatly, and a large shear force can act on the piezoelectric element. However, if the buffer member is arranged near the open end of the drive member, the movement of the drive member at the open end is limited. Therefore, it is possible to further improve the impact resistance.

  A through hole may be formed in the bottom of the drive member. In general, the bottom of the driving member and the other end in the expansion / contraction direction of the piezoelectric element are bonded together with a fluid adhesive. In this case, when connecting the bottom portion of the driving member and the other end side of the piezoelectric element with an adhesive, it is difficult for the surplus adhesive toward the through hole and around the side surface of the piezoelectric element. For this reason, it is possible to suppress the expansion and contraction of the piezoelectric element from being hindered by the surplus adhesive that wraps around the side surface of the piezoelectric element.

  The buffer member may be made of resin.

  The inner diameter of the driving member near the open end may be larger than the inner diameter of the driving member near the bottom. In this case, when the buffer member is formed by injecting resin between the driving member and the piezoelectric element, the resin is likely to stay near the open end of the driving member.

  A lens driving device according to another aspect of the present invention includes any one of the piezoelectric driving devices described above and a lens holder that engages with the outer peripheral surface of the driving member.

  The lens driving device according to another aspect of the present invention has the same effect as the above piezoelectric driving device.

  ADVANTAGE OF THE INVENTION According to this invention, the piezoelectric drive device and lens drive device which can aim at the further improvement of impact resistance can be provided.

FIG. 1 is a perspective view showing a lens driving device according to this embodiment. FIG. 2 is a top view showing the lens driving device according to the present embodiment. FIG. 3 is a side view showing the lens driving device according to the present embodiment. FIG. 4 is a cross-sectional view showing the piezoelectric driving device. FIG. 5 is a perspective view showing a multilayer piezoelectric element. FIG. 6 is a cross-sectional view showing a multilayer piezoelectric element. FIG. 7 is a diagram for explaining a voltage applied to the multilayer piezoelectric element.

  Embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are exemplifications for explaining the present invention and are not intended to limit the present invention to the following contents. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  As shown in FIGS. 1 to 4, the lens driving device 100 includes a lens holder 102, a biasing member 104, and the piezoelectric driving device 1. The lens driving device 100 is a device that drives a camera lens mounted on, for example, a mobile phone. When viewed from above (Z direction), the lens driving device 100 is disposed in a housing (not shown), and the size of the housing can be set to, for example, about 8.5 mm × 8.5 mm.

  The lens holder 102 includes a cylindrical tube portion 106 and a protruding portion 108. The lens holder 102 may be formed of, for example, a liquid crystal polymer containing carbon fiber or nylon.

  The inner peripheral surface of the cylindrical portion 106 has a perfect circle shape. A lens barrel (not shown) in which a lens is accommodated is attached to the inside of the cylindrical portion 106. When the lens barrel is attached to the cylindrical portion 106, the lens holder 102 holds the lens. The lens held in the lens barrel is exposed through an opening formed in a housing (not shown).

  The protruding portion 108 is an X direction orthogonal to the optical axis direction OA (Z direction) of the lens, and protrudes outward from the outer peripheral surface of the cylindrical portion 106. In the present embodiment, the X direction in which the protruding portion 108 protrudes coincides with the radial direction of the cylindrical portion 106. The protruding portion 108 extends along the optical axis direction OA (Z direction) of the lens and the Y direction (tangential direction of the cylindrical portion 106 when viewed from the optical axis direction OA of the lens) that is orthogonal to the X direction. The width of the protruding portion 108 in the Y direction can be set to be approximately the same as or smaller than the outer diameter (diameter) of the cylindrical portion 106, for example.

  The protrusion 108 has a side wall surface 108a that intersects the X direction and extends along the Y direction. Grooves 108b extending along the optical axis direction OA of the lens are formed on the side wall surface 108a. The groove portion 108b has a V-shape that becomes narrower toward the back side (the tube portion 106 side) when viewed from the optical axis direction OA of the lens.

  The biasing member 104 is a metal plate member, for example. The urging member 104 extends in the Y direction along the side wall surface 108a. One end of the biasing member 104 on the side facing the groove 108 b is a free end, and the other end of the biasing member 104 is fixed to the protruding portion 108. Therefore, one end of the urging member 104 is movable in a direction (X direction) that approaches or separates from the groove 108b.

  When the piezoelectric driving device 1 having an outer shape larger than the space is disposed in a space between one end of the urging member 104 and the groove portion 108b, the urging member 104 is pushed away from the groove portion 108b. However, since a restoring force is generated on the urging member 104 so as to return to the original shape, the urging force acts on the piezoelectric driving device 1 from the urging member 104. As a result, the piezoelectric driving device 1 is pressed against the groove 108 b (projecting portion 108) by the biasing member 104.

  The piezoelectric driving device 1 is a so-called SIDM (Smooth Impact Drive Mechanism) type piezoelectric actuator that can reciprocate the lens holder 102 in the order of nanometers by applying a voltage. As shown in FIG. 4, the piezoelectric driving device 1 includes a multilayer piezoelectric element 10, a weight 20, a driving member 22, a buffer member 24, and a pair of wirings 26.

  The laminated piezoelectric element 10 will be described with reference to FIGS. The multilayer piezoelectric element 10 includes a multilayer body 12 having a polygonal column shape (in this embodiment, a quadrangular column shape). The multilayer body 12 is configured by laminating a plurality of piezoelectric bodies 13 and a plurality of internal electrodes 14A and 14B in a predetermined order. The stacked body 12 has side surfaces 12a and 12b that are parallel to the stacking direction and face each other. For example, the laminated body 12 can be set to have a width of about 10 mm, a depth of about 10 mm, and a height of about 35 mm.

The piezoelectric body 13 is made of, for example, a piezoelectric ceramic material mainly composed of PZT (lead zirconate titanate). The thickness of the piezoelectric body 13 can be set to about 80 μm to 100 μm per layer, for example. Examples of the composition of PZT include the following.
Pb0.999 [(Zn _1/3 Nb _2/3 ) 0.11Ti0.425Zr0.465] O ₃ + 0.2wt% Fe ₂ O ₃ + 0.2wt% Sb ₂ O ₃

As the powder characteristics of PZT, for example, those having a BET specific surface area of about 2.5 m ² / g and an average particle diameter of about 0.6 μm are used. The sintering temperature of PZT is about 950 ° C. The melting point of the PZT material is about 1300 ° C.

  The internal electrodes 14A and 14B are made of a conductive material containing Ag and Pd as main components, for example. The thickness of the internal electrodes 14A and 14B can be set to about 2 μm, for example. The internal electrodes 14A and 14B are alternately stacked with the piezoelectric body 13 interposed therebetween. One end of the internal electrode 14 </ b> A is exposed on the side surface 12 a of the multilayer body 12. The other end of the internal electrode 14 </ b> A is located inside the side surface 12 b of the multilayer body 12. One end of the internal electrode 14 </ b> B is exposed on the side surface 12 b of the multilayer body 12. The other end of the internal electrode 14 </ b> B is located inside the side surface 12 a of the multilayer body 12. Thereby, a part of the internal electrodes 14 </ b> A and 14 </ b> B overlaps in the stacking direction of the stacked body 12.

  In the laminated body 12, the portion where the internal electrodes 14A and 14B overlap in the laminating direction is an active portion P where the piezoelectric body 13 is displaced when a voltage is applied to the internal electrodes 14A and 14B. The active part P (laminated piezoelectric element 10) expands and contracts in the stacking direction of the stacked body 12. In the multilayer body 12, the portions where the internal electrodes 14 </ b> A and 14 </ b> B do not overlap in the stacking direction (ends on both sides of the multilayer body 12) are inactive portions where the piezoelectric body 13 is not displaced when a voltage is applied to the internal electrodes 14 </ b> A and 14 </ b> B. Q.

  An external electrode 16 </ b> A is provided on the side surface 12 a of the multilayer body 12. The external electrode 16A is attached to the side surface 12a so as to cover the entire side surface 12a. Therefore, the external electrode 16A is electrically connected to each internal electrode 14A exposed on the side surface 12a on the side surface 12a. The external electrode 16A is made of, for example, a conductive material whose main component is Ag, Au, or Cu. The thickness of the external electrode 16A can be set to, for example, about 1 μm to 20 μm.

  An external electrode 16B is provided on the side surface 12b of the laminate 12. The external electrode 16B is a substantially rectangular strip and is attached to the side surface 12b so as to cover the entire side surface 12b. Therefore, the external electrode 16B is electrically connected to each internal electrode 14B exposed on the side surface 12b on the side surface 12b. The external electrode 16B is made of, for example, a conductive material whose main component is Ag, Au, or Cu. The thickness of the external electrode 16B can be set to about 1 μm to 20 μm, for example.

  Returning to FIG. 4, the weight 20 is fixed to one end side in the expansion / contraction direction of the multilayer piezoelectric element 10 via an adhesive 20 a. The adhesive 20a exhibits fluidity before bonding, but solidifies after bonding. The weight 20 has a substantially cross shape when viewed from the Z direction. Therefore, as will be described later, when the buffer member 24 is injected into the drive member 14 using a nozzle, the weight 20 does not prevent the tip of the nozzle from going into the drive member 22.

  The drive member 22 is a bottomed cylindrical body having a disc-shaped bottom portion and a cylindrical side wall provided integrally with the periphery of the bottom portion. The outer peripheral surface of the side wall of the driving member 22 is urged to the groove 108b by the urging member 104, and the engaged state with the groove 108b is maintained. That is, the lens holder 102 is engaged with the outer peripheral surface of the side wall of the drive member 22.

  A through hole 22 a is formed at the bottom of the drive member 22. The inner surface of the bottom of the driving member 22 and the end surface on the other end side in the expansion / contraction direction of the multilayer piezoelectric element 10 are fixed via an adhesive 22b. The adhesive 22a exhibits fluidity before bonding, but solidifies after bonding. The drive member 22 accommodates the other end side in the expansion / contraction direction of the multilayer piezoelectric element 10 therein. The inner peripheral surface of the side wall of the drive member 22 and the side surface of the multilayer piezoelectric element 10 are separated from each other. In the present embodiment, the inner diameter of the driving member 22 near the open end is set to be larger than the inner diameter of the driving member 22 near the bottom.

  The buffer member 24 is disposed between the side surface of the multilayer piezoelectric element 10 and the inner peripheral surface of the side wall of the drive member 22. In the present embodiment, the buffer member 24 is disposed near the open end of the drive member 22. The buffer member 24 can be formed of resin, for example. A silicon-based ultraviolet curing agent can be used as the resin. The buffer member 24 may have a hardness of about 30 Shore A hardness, for example.

  One end of the pair of wirings 26 is electrically connected to the external electrodes 16A and 16B, respectively. The other ends of the pair of wirings 26 are electrically connected to a power source (not shown). Therefore, a predetermined voltage is applied to the multilayer piezoelectric element 10 via the wiring 26.

  Next, the operation of the lens driving device 100 will be described. A sawtooth drive voltage as shown in FIG. 7 is applied to the laminated piezoelectric element 10 from a power source via a wiring 26.

  First, as shown in FIG. 7A, a case where the voltage drops rapidly after the voltage gradually increases will be described. In this case, as the voltage gradually increases, the stacked piezoelectric element 10 gradually extends in the stacking direction. At this time, the lens holder 102 also moves upward in FIG. 3 due to the frictional force generated between the outer peripheral surface of the side wall of the drive member 22 and the groove 108b and the biasing member 104. Thereafter, when the voltage suddenly drops, the laminated piezoelectric element 10 also shrinks rapidly. At this time, the lens holder 102 overcomes the friction generated between the lens holder 102 and the drive member 22 according to the law of inertia and stays there. By repeating this, the lens holder 102 gradually moves upward in FIG.

  On the other hand, as shown in FIG. 7B, a case where the voltage suddenly rises after the voltage gradually decreases will be described. In this case, as the voltage gradually decreases, the stacked piezoelectric element 10 gradually contracts in the stacking direction. At this time, the lens holder 102 also moves downward in FIG. 3 due to the frictional force generated between the outer peripheral surface of the side wall of the drive member 22 and the groove 108b and the biasing member 104. Thereafter, when the voltage suddenly rises, the laminated piezoelectric element 10 also grows rapidly. At this time, the lens holder 102 overcomes the friction generated between the lens holder 102 and the drive member 22 according to the law of inertia and stays there. By repeating this, the lens holder 102 gradually moves downward in FIG.

  In the present embodiment as described above, the buffer member 24 is disposed between the side surface of the multilayer piezoelectric element 10 and the inner peripheral surface of the side wall of the drive member 22. Therefore, even if an impact force acts on the drive member 22 from the outside, the impact force is absorbed by the buffer member 14. Therefore, since the impact force applied to the multilayer piezoelectric element 10 can be relaxed, it is possible to further improve the impact resistance.

  In the present embodiment, the buffer member 24 is disposed between the side surface of the multilayer piezoelectric element 10 and the inner peripheral surface of the side wall of the drive member 22 and closer to the open end of the drive member 22. If an impact force is applied when there is no buffer member 24, the open end of the drive member 24 moves greatly, and a large shearing force can act on the laminated piezoelectric element 10. However, if the buffer member 24 is disposed near the open end of the drive member 22, such movement of the drive member 24 at the open end is limited. Therefore, it is possible to further improve the impact resistance.

  In the present embodiment, a through hole 22 a is formed at the bottom of the drive member 22. Therefore, when connecting the bottom of the drive member 22 and the other end side of the multilayer piezoelectric element 10 with an adhesive, it is difficult for the excess adhesive to go to the through-hole 22a and wrap around the side surface of the multilayer piezoelectric element 10. Become. Therefore, it is possible to prevent the expansion and contraction of the multilayer piezoelectric element 10 from being hindered due to the surplus adhesive agent wrapping around the side surface of the multilayer piezoelectric element 10.

  In the present embodiment, the inner diameter of the driving member 22 near the open end is larger than the inner diameter of the driving member 22 near the bottom. Therefore, when the buffer member 24 is formed by injecting a resin between the driving member 22 and the laminated piezoelectric element 10, the resin tends to stay near the open end of the driving member 22.

  As mentioned above, although embodiment of this invention was described in detail, this invention is not limited to above-described embodiment. For example, as the buffer member 24, various materials and members capable of reducing the impact force can be used. Specifically, an O-ring may be used as the buffer member 24.

  The buffer member 24 may not be disposed near the open end of the drive member 22 as long as it is between the side surface of the multilayer piezoelectric element 10 and the inner peripheral surface of the side wall of the drive member 22.

  The drive member 22 may be completely filled with the buffer member 24. However, in this case, since expansion and contraction of the multilayer piezoelectric element 10 can be hindered, the buffer member 24 is partially disposed between the side surface of the multilayer piezoelectric element 10 and the inner peripheral surface of the side wall of the drive member 22. It is more preferable.

  The inner diameter of the drive member 22 may gradually decrease from the open end side to the bottom side. The inner diameter of the drive member 22 may be substantially the same from the open end side to the bottom side. The inner diameter of the drive member 22 may be smaller on the bottom side than on the open end side.

  There may be at least one through hole 22a, and there may be a plurality of through holes 22a. The through hole 22 a may not be formed in the bottom of the drive member 22.

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric drive device, 10 ... Multilayer piezoelectric element, 20 ... Weight, 22 ... Drive member, 22a ... Through-hole, 24 ... Buffer member, 100 ... Lens drive device, 102 ... Lens holder.

Claims (6)

A piezoelectric element;
A weight connected to one end side of the piezoelectric element in the expansion and contraction direction;
A driving member that has a bottomed cylindrical shape and that accommodates the other end side in the expansion / contraction direction of the piezoelectric element while the other end side is connected to the bottom,
A buffer member disposed between a side surface of the piezoelectric element and an inner wall surface of the driving member facing the side surface ;
The piezoelectric element is a stacked piezoelectric element that expands and contracts in the stacking direction,
A through hole is formed in the bottom of the drive member,
The piezoelectric drive device that is connected in a state in which the adhesive material is interposed between the bottom of the drive member and the other end of said piezoelectric element and said through hole is.   2. The piezoelectric driving device according to claim 1, wherein the one end side and the weight of the piezoelectric element are located outside an open end of the driving member.   3. The piezoelectric drive device according to claim 1, wherein the buffer member is disposed between a side surface of the piezoelectric element and an inner wall surface of the drive member and close to an open end of the drive member. The cushioning member is made of resin, the piezoelectric drive device according to any one of claims 1-3. The piezoelectric driving device according to claim 4 , wherein an inner diameter of the driving member near the open end is larger than an inner diameter of the driving member near the bottom. A piezoelectric driving device according to any one of claims 1 to 5 ;
A lens driving device comprising: a lens holder that engages with an outer peripheral surface of the driving member.

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