JP4898264B2 - Piezoelectric driving device, imaging device, and portable terminal device - Google Patents

Description

  The present invention relates to a driving device using an electromechanical transducer such as a piezoelectric element, and more particularly to an imaging device such as a camera provided with the driving device, and a portable terminal provided with the imaging device.

  Conventionally, a drive device using a piezoelectric element is described in Patent Document 1, for example. The driving device described in Patent Document 1 is provided with two lens groups and driving means for driving the respective lens groups in a zoom lens, and has not been used in an area required for movement of each other lens group. The area is used effectively.

  With this configuration, the size of the lens driving mechanism in the optical axis direction can be reduced. In other words, the lens driving mechanism can be further reduced in size by disposing the driving means of the two lens groups in opposite directions and overlapping in the optical axis direction (see Patent Document 1).

Japanese Patent Application Laid-Open No. 2005-228561 describes a drive device that rapidly expands and contracts a piezoelectric element by applying a sawtooth drive voltage to the piezoelectric element.
FIG. 6 shows a schematic configuration diagram of an example of a driving device using a piezoelectric element. A drive device 100 shown in FIG. 6 includes a piezoelectric element 103, a weight 102 provided on one end side of the piezoelectric element 103, and a drive shaft 104 provided on the other end side of the piezoelectric element 103, each of which is made of an adhesive or the like. Bonded and fixed.

  The drive shaft 104 is provided with an engaging member (moving body) so as to grasp the shaft from both sides of the shaft. Here, the engaging member includes a slider 107 and a holder 105 and a spring 106 as a biasing means for frictionally engaging the slider 107 and the holder 105 with the drive shaft.

  The piezoelectric element 103 is configured by stacking (depositing) piezoelectric elements made of lead zirconate titanate (hereinafter PZT). For example, PZT has a sheet-like shape having a thickness of about 50 [μm] and a diameter Φ of 1.8 [mm]. Electrodes for applying an electric field to both surfaces are provided with silver, palladium or the like. When about 60 layers of this sheet are stacked, the total thickness becomes about 3.5 [mm].

  The weight 102 is made of a metal such as tungsten having a high density and a diameter Φ of 3 [mm] and a length of 1 [mm]. The drive shaft 104 is obtained by aligning carbon long fibers having a diameter Φ of 1 [mm] and a length of 4 [mm] in the axial direction and hardened with an epoxy resin as a binder.

  As shown in FIG. 6, the weight 2 configured in this manner has a substantially bilaterally symmetric shape, and the center of gravity G2 is located at the center. The drive shaft 104 also has a substantially bilaterally symmetric shape, and the center of gravity G1 is located at the center.

By applying a sawtooth drive voltage to the piezoelectric element 103, the drive shaft attached to the piezoelectric element is rapidly expanded and contracted, and the moving body frictionally held on the drive shaft can repeatedly move “sliding” and “non-sliding”. (See Patent Document 2).
JP 2002-131611 (Page 3-4, FIG. 6) JP 2002-218773 A (page 3-4, FIG. 1 and FIG. 3)

  As an application example of the driving device 100, FIG. 7 shows a schematic configuration diagram of an imaging device 120 using the driving device 100. As illustrated in FIG. 7, the imaging device 120 includes an aspheric lens 121, an optical filter 123, and a semiconductor imaging element 124 that are disposed in a housing 125 along the optical axis. The lens 121 is held by a lens barrel 122, and an engagement member 127 that engages with the drive shaft 104 of the drive device 100 is provided in a part of the lens barrel 122.

  The lens barrel 122 can be moved in the optical axis direction by the driving device 100 in which the driving shaft 104 is arranged in parallel with the optical axis. Thus, the lens barrel 122 can be moved in the optical axis direction in order to form an image of the subject exactly on the imaging surface of the imaging device 124 with respect to the distance of the subject.

  However, in the driving device using the piezoelectric element as shown in FIG. 6, when an impact force due to dropping or the like is applied from the outside of the driving device, the force acts on the center of gravity G1 of the driving shaft 104, and the piezoelectric element A moment is generated between the bonding surface on one end side of 103. Since this moment acts as a shearing force on the bonding surface, when the impact force is large or the distance between the center of gravity and the bonding is large, the shearing force increases and the adhesive part peels off. May cause failure or noise.

  Similarly, when an impact force due to dropping or the like is applied from the outside of the driving device, a force acts on the center of gravity G2 of the weight 102, and a moment is generated between the piezoelectric element 103 and the adhesive surface on one end side. Will occur. Since this moment acts as a shearing force on the bonding surface, when the impact force is large or the distance between the center of gravity and the bonding is large, the shearing force increases and the adhesive part peels off. May cause failure or noise.

  In the above-described drive device, the drive shaft, the piezoelectric element, and the weight are arranged in series in the expansion / contraction direction of the piezoelectric element, and the drive shaft is an engagement member that is frictionally held in addition to the distance necessary for movement. A distance plus the length is required. Therefore, when the conventional driving device is used for an auto focus mechanism or a zoom mechanism for moving the lens of the image pickup device, the entire length of the drive device becomes long, and the A portion of the image pickup device 120 shown in FIG. Thus, in order to secure the moving distance, it may be necessary to form a convex portion in a part of the housing, which is an obstacle to thinning the device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a driving device that realizes improvement in impact resistance and downsizing / thinning of the device.

Therefore, the drive device of the present invention includes a piezoelectric element, a weight fixed to one end of the piezoelectric element in the expansion / contraction direction, and a drive member fixed to the other end of the piezoelectric element, and the drive member and the piezoelectric element are The driving member is in contact with the expansion and contraction direction of the piezoelectric element in a spatially overlapping manner, and the center of gravity of the driving member is located in the vicinity of a plane including the contact surface on which the piezoelectric element and the driving member come into contact. is there.

With this configuration, since the piezoelectric element and the driving member overlap each other, the lengthwise dimension including the piezoelectric element and the driving member can be shortened, and the entire driving device can be reduced in size.
In addition, since the center of gravity of the driving member is located in the vicinity of the connection surface with the piezoelectric element, even when an impact force is applied from the outside to the driving device, almost no moment is generated, and the piezoelectric element And the shearing force on the bonding surface between the driving member and the driving member can be reduced. Therefore, even when a large impact force is applied to the driving device, it is possible to prevent peeling at the end portions of the driving member and the piezoelectric element.

The driving device of the present invention includes a piezoelectric element, a weight secured to one end stretching direction of the piezoelectric element, and a drive member fixed to the other end of the piezoelectric element, the driving member, the expansion and contraction of the piezoelectric element to the direction, it has a recess for accommodating at least a portion of the piezoelectric element, in which the center of gravity of the drive member in the vicinity of the plane in which the piezoelectric element and the drive member comprises abutting abutment surface is located is there.

With this configuration, a part of the piezoelectric element is accommodated in the concave portion of the driving member, so that the dimension in the length direction including the piezoelectric element and the driving member can be shortened, and the entire driving device is reduced in size. be able to.
In addition, since the center of gravity of the driving member is located in the vicinity of the connection surface with the piezoelectric element, even when an impact force is applied from the outside to the driving device, almost no moment is generated, and the piezoelectric element And the shearing force on the bonding surface between the driving member and the driving member can be reduced. Therefore, even when a large impact force is applied to the driving device, it is possible to prevent peeling at the end portions of the driving member and the piezoelectric element.

  In the driving device of the present invention, the piezoelectric element and the weight are in contact with each other with a spatial overlap with respect to the expansion / contraction direction of the piezoelectric element.

  With this configuration, since the piezoelectric element and the weight overlap, the dimension in the length direction including the piezoelectric element and the weight can be shortened, and the entire driving device can be reduced in size.

  In the driving device of the present invention, the weight has a recess that accommodates at least a part of the piezoelectric element with respect to the expansion / contraction direction of the piezoelectric element.

  With this configuration, since a part of the piezoelectric element is accommodated in the weight, the dimension in the length direction including the piezoelectric element and the weight can be shortened, and the entire driving device can be reduced in size. Further, since the weight is generally manufactured by die casting or machining by a lathe, the difficulty in processing can be performed with almost no change. Further, since the weight covers the outer shape of the piezoelectric element, the piezoelectric element can be protected. That is, for example, there is an advantage that the piezoelectric element can be prevented from being damaged by handling or the like.

  In the drive device of the present invention, the center of gravity of the weight is located in the vicinity of a plane including a contact surface on which the piezoelectric element and the weight contact.

  With this configuration, since the center of gravity of the weight is located near the connection surface with the piezoelectric element, even when an impact force is applied from the outside to the driving device, almost no moment is generated, and the piezoelectric The shearing force on the bonding surface between the element and the weight can be reduced. Therefore, even when a large impact force is applied to the drive device, it is possible to prevent the separation between the ends of the weight and the piezoelectric element.

  In the driving apparatus of the present invention, the driving member, the piezoelectric element, and the weight are arranged substantially coaxially.

  With this configuration, it is possible to reduce the moment generated in the weight due to expansion and contraction of the piezoelectric element, and it is difficult for a rotational movement having a component orthogonal to the expansion and contraction direction of the piezoelectric element to occur, so noise is generated without reducing efficiency. Can be prevented.

The imaging device of the present invention includes a piezoelectric element, a weight fixed to one end of the piezoelectric element in the expansion / contraction direction, and a driving member fixed to the other end of the piezoelectric element. Driving in which the center of gravity of the driving member is located in the vicinity of a plane including an abutting surface where the piezoelectric element and the driving member are in contact with each other in a spatially overlapping manner with respect to the expansion / contraction direction of the piezoelectric element An engagement member that engages the driving member and a lens barrel that holds the lens, and an image sensor that changes light from the lens into an electrical signal. It moves in the direction of the optical axis of the lens .

  With this configuration, in an imaging apparatus having a part that moves to the optical system in general, the thickness of the imaging apparatus is greatly influenced by the part that moves the optical system in the optical axis direction, not the optical path length of the optical system, The length of this part can be shortened, and the imaging apparatus can be made thinner. In addition, since the position of the center of gravity of the weight is substantially the same as the surface for fixing the driving member of the piezoelectric element, the generation of moment can be reduced with respect to the impact force applied from the outside, so that the impact resistance can be improved. .

  In the image pickup apparatus of the present invention, the imaging magnification of the image pickup element with respect to the image pickup surface changes as the lens barrel holding the lens moves in the optical axis direction.

  With this configuration, the size of the zooming mechanism can be shortened, so that the image pickup apparatus having the zoom lens can be downsized. In addition, since it is necessary to move a plurality of groups of lenses in a zoom lens, the degree of freedom of design tends to decrease.However, since the size of the zoom mechanism can be shortened, It becomes possible to increase the degree of freedom.

  Moreover, the portable terminal device of this invention is provided with said imaging device.

  With this configuration, the impact resistance of the mobile terminal device is improved. That is, since the length of the lens moving part of the imaging device can be shortened, the piezoelectric element and the weight overlap with each other in the expansion / contraction direction of the piezoelectric element even when a drop impact is applied to the mobile terminal device. Therefore, the moment due to the impact force applied to each interface is reduced by shortening the length. Thereby, the impact resistance characteristics of the mobile terminal device can be improved, and the reliability is improved.

  According to the drive device of the present invention, it is possible to improve the impact resistance and reduce the size and thickness of the device.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
Hereinafter, a driving apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a driving apparatus 1 showing a first embodiment of the present invention.

  A driving apparatus 1 according to the first embodiment shown in FIG. 1 includes a piezoelectric element 3, a weight 2 provided on one end side of the piezoelectric element 3, and a driving shaft 4 as a driving member provided on the other side of the piezoelectric element 3. Each of which is bonded and fixed by an adhesive (not shown).

  The piezoelectric element 3 is configured by stacking (depositing) piezoelectric elements made of, for example, lead zirconate titanate (hereinafter, PZT). The piezoelectric element 3 of the present embodiment is the same as the conventional one.

  The weight 2 that is bonded and fixed to one end side of the piezoelectric element 3 is made of a metal having a high density, such as tungsten, and has the same mass as that of the conventional one. The length is long.

  On the other hand, the drive shaft 4 has a bottomed cylindrical shape with an increased outer diameter, and can accommodate the piezoelectric element 3 and the weight 2 in the cylindrical shape so that they can be accommodated with spatial overlap. It is formed as follows. The drive shaft 4 is adhesively fixed to an end surface opposite to the end surface where the piezoelectric element 3 is bonded and fixed to the weight 2, and is mechanically folded back.

  The drive shaft 4, the piezoelectric element 3, and the weight 2 are arranged so as to be coaxial. Specifically, for example, the outer diameter of the weight 2 is Φ2 [mm] and the length is 2.25 [mm], the outer diameter of the piezoelectric element 3 is Φ1.8 [mm] and the length is 3.5 [mm], The drive shaft 4 is formed with an outer diameter of Φ3.2 [mm] and a length of 7 [mm]. The tip end portion of the drive shaft 4 is formed with an increased thickness, and the center of gravity G1 of the drive shaft 4 is located at a position that substantially coincides with the contact surface with the piezoelectric element 3 as shown in FIG. Further, the center of gravity G2 of the weight 2 is located near the center as in the conventional case.

  The drive shaft 4 is provided with an engaging member so as to grasp the shaft from both sides of the shaft. Here, the engaging member includes a slider 7 and a holder 5 and a spring 6 as a biasing means for frictionally engaging the slider 7 and the holder 5 with the drive shaft.

  Next, the operation of the drive device 1 will be described. A driving voltage such as a sawtooth wave is applied to the piezoelectric element 3 of the driving device 1 by a driving circuit constituted by an H bridge or the like (not shown). When the drive voltage is increased, the piezoelectric element 3 in FIG. 1 is deformed in the extending direction (the left direction in the figure). When the drive voltage is gradually increased, the piezoelectric element 3 extends slowly, and the drive shaft 4 is slowly displaced leftward along with this.

  The drive shaft 4 and the engaging member are displaced in the same positional relationship while being engaged by static friction. That is, when the voltage is gradually increased, the engaging member is displaced to the left in the figure.

  Next, when the driving voltage is suddenly changed in the reverse direction, the piezoelectric element 3 is rapidly contracted, and accordingly, the driving shaft 4 is rapidly displaced rightward. At this time, the engaging member overcomes the friction with the drive shaft 4 and stays there, and does not move (according to the law of inertia). As a result, the engagement member moves to the left with respect to the drive shaft 4. By repeating this, the engaging portion can be moved continuously.

  Also, changing the moving direction can be realized by reversing the voltage application or inverting the drive waveform. In this embodiment, since the drive circuit is an H bridge as described above, the polarity of the applied voltage can be easily reversed, which is convenient. The voltage waveform of the applied voltage, the application method, and the time interval can be changed in various ways, but it is important to optimize from the characteristics such as efficiency, moving speed, and noise depending on the actual system.

  Thus, the drive device 1 according to the first embodiment can move the engaging member. Further, since the center of gravity G1 of the drive shaft 4 is provided in the vicinity of one end side of the piezoelectric element 3, even when an external impact force is applied to the drive device 1, almost no moment is generated, and the piezoelectric element The shearing force on the bonding surface between the element 3 and the drive shaft 4 can be reduced. Therefore, even when a large impact force is applied to the drive device 1, it is possible to prevent the peeling between the end portions of the drive shaft 4 and the piezoelectric element 3. In addition, since the piezoelectric element 3, the weight 2, and the drive shaft 4 are arranged so as to be coaxial, an unnecessary moment generated in the weight 2 due to expansion and contraction of the piezoelectric element 3 can be reduced, and vibration and noise can be reduced. Generation can be prevented.

  Further, in the driving device 1 of the first embodiment, the piezoelectric element 3 has substantially the same shape as the conventional one, but the piezoelectric element 3 and the weight 2 are accommodated inside the driving shaft 4. The dimension in the length direction including the element 3, the weight 2, and the drive shaft 4 can be shortened. Specifically, the length of the entire driving device 1 in the length direction of 8.5 [mm] can be reduced to about 7.0 [mm] and can be reduced by 1.5 [mm]. It was. Thereby, the imaging device etc. which apply the drive device 1 can also be reduced in size and thickness.

  The specific dimensions can be changed as appropriate by changing the shape of the piezoelectric element and the weight, but in order to obtain the same characteristics, the piezoelectric element and the weight have the same volume before and after the change. It is desirable.

(Embodiment 2)
FIG. 2A is a cross-sectional view of a main part of a driving device 21 showing a second embodiment of the present invention.
In the following description, the same components as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  The drive device 21 according to Embodiment 2 of the present invention will be described. The weight 22 has a concave portion large enough to accommodate the piezoelectric element 23. That is, a hole is provided in the inner diameter portion of the weight 22 and the piezoelectric element 23 is inserted therein. Further, the weight 23 and the piezoelectric element 23 have a hole and an outer diameter that are coaxial D. The hole diameter of the weight 22 is slightly larger than the outer shape of the piezoelectric element 23. The piezoelectric element 23 is bonded and fixed at the bottom surface of the concave portion of the weight 22 and is formed so that the outer peripheral portion does not contact.

  The drive shaft 24 has a bottomed cylindrical shape with a large outer diameter, and the piezoelectric element 23 and the weight 22 can be accommodated in the cylindrical shape with spatial overlap, that is, can be built in. Is formed. The drive shaft 24 is adhesively fixed to an end surface opposite to the end surface to which the piezoelectric element 23 is bonded and fixed to the weight 22, and is mechanically folded back.

  The center of gravity G1 of the drive shaft 24 is near the center of the drive shaft 24 as shown in FIG. 2A. The center of gravity G2 of the weight 22 is located in the vicinity of the intersection between the plane including the contact end face with the piezoelectric element 23 and the simultaneous axis D.

  With this configuration, the center of gravity G <b> 2 of the weight 22 is positioned near one end side of the piezoelectric element 23. Therefore, even when an impact force is applied to the driving device 21 from the outside, almost no moment is generated, and the shearing force at the bonding surface between the piezoelectric element 23 and the weight 22 can be reduced. Therefore, even when a large impact force is applied to the driving device 21, it is possible to prevent peeling at the end portions of the weight 22 and the piezoelectric element 23.

  Further, since the piezoelectric element 23 is formed so as to be accommodated in a cylindrical space provided in the central portion of the weight 22, the lengthwise dimension including the piezoelectric element 23 and the weight 22 is shortened. Therefore, the drive device 21 as a whole can be downsized.

  Further, the drive device 21 of the second embodiment is slightly complicated in the shape of the weight as compared with the drive device 1 of the first embodiment, but the weight is generally manufactured by die casting, a lathe or the like. Due to machining, the difficulty in machining can be done with little change.

  Further, according to the configuration of the driving device 21 of the second embodiment, the weight 22 covers the outer shape of the piezoelectric element 23, so that the piezoelectric element can be protected. That is, for example, the piezoelectric element 23 can be prevented from being damaged by handling or the like.

  Further, since the weight 22 and the piezoelectric element 23 are accommodated in the drive shaft 24, the overall length of the drive device 24 can be shortened, and the piezoelectric element 23 is damaged by handling or the like. It has the advantage that can be prevented.

  Further, as shown in FIG. 2B, the bottom surface portion of the drive shaft 24 can be thick, and the center of gravity G1 of the drive shaft 24 can be located near the contact end surface of the drive shaft 24 and the piezoelectric element 23. By arranging the centers of gravity G1 and G2 at the corresponding end face positions of the piezoelectric elements 23 in this way, even when an impact force is applied to the driving device 21 from the outside, almost no moment is generated, The shearing force on the bonding surface can be reduced. Therefore, even when a large impact force is applied to the drive device 21, peeling occurs at the end portion between the drive shaft 24 and the piezoelectric element and at the end portion between the weight 22 and the piezoelectric element 23. Can be prevented, and the impact resistance of the apparatus can be improved.

(Embodiment 3)
The imaging device 30 according to the third embodiment will be described. FIG. 3 is a cross-sectional view of a main part of the imaging device 30 according to the third embodiment. In the following description, the same components as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  As illustrated in FIG. 3, the imaging device 30 includes an aspheric lens 38, an optical filter 34, and a semiconductor imaging element 36 that are disposed in the housing 35 along the optical axis. The lens 38 is held by a lens barrel 37, and an engaging member 27 that engages with the drive shaft 39 of the drive device 31 is provided in a part of the lens barrel 37.

  The lens barrel 37 can be moved in the optical axis direction by a driving device 31 in which a driving shaft 39 is arranged in parallel with the optical axis. The lens 38 is a lens having an aspherical shape (hereinafter referred to as “lens”), and only one lens is shown for the sake of simplicity. However, the lens 38 is actually composed of two lenses. A so-called auto focus function for moving the lens barrel 37 in the direction of the optical axis in order to form an exact object (not shown) on the imaging surface of the image sensor 36 with respect to the distance of the subject is provided. Yes.

  The autofocus method uses a known technique of reading an image and obtaining a point where the harmonic component of the read signal is maximized.

  The drive device 31 uses the drive device of the first or second embodiment described above, and the operation is the same as that described above. Thus, the so-called back focus position from the lens 38 to the imaging surface is adjusted by the driving device 31.

  The optical filter 34 is a reflection type configured by stacking dielectric films having different refractive indexes and suppresses transmission of light outside the visible light region. The semiconductor image sensor 36 is a 1/4 inch CCD having about 1.3 million pixels, and has a pixel size of about 2.8 [μm].

  The imaging device 30 of the third embodiment configured as described above uses the driving device 31 of the first or second embodiment described above. The driving device 31 includes a driving shaft 39, a piezoelectric element 33, a weight 32, and the like. Is configured so as to overlap with the axial direction of the drive shaft 39, the overall length is shortened.

  Therefore, the thickness of the entire imaging apparatus can be reduced even if the driving apparatus is installed parallel to the optical axis. In addition, it is clear that the total length can be reduced even when the drive device 31 does not protrude from the imaging device 30. Further, in such an imaging apparatus, it is advantageous in terms of efficiency to arrange a driving device that moves the optical system in the optical axis direction in parallel with the optical axis direction when performing autofocusing. However, the present invention can be applied to a device in which a drive device is arranged in a direction orthogonal to the optical axis and a conversion mechanism such as a cam is provided.

  Further, when the aspherical lens 38 arranged along the optical axis is a plurality of lens groups, the relationship between the lens groups in the optical axis direction and the relationship with the image sensor 36 can be changed. In this case, it is possible to change the imaging magnification with respect to the image plane. An imaging apparatus using a so-called zoom lens can be realized.

  When the aspherical lens 38 is composed of a plurality of lens groups, it is necessary to move each lens group, so that a plurality of driving devices are required, and the size in the axial direction becomes large, making it difficult to reduce the thickness. However, according to the present embodiment using the driving device 31, the driving device for the lens having a long moving distance in the lens group is made thinner by increasing the overlap between the piezoelectric element and the weight in the optical axis direction than the others. Can be realized. It is obvious to those skilled in the art that these dimensions and shapes can be changed as appropriate.

(Embodiment 4)
A mobile terminal device 40 according to the fourth embodiment will be described. FIG. 4 is a front view of the mobile terminal device 40 of the fourth embodiment. FIG. 5A is a side view of the mobile terminal device 40 of the fourth embodiment. FIG. 5B is a side view of the conventional portable terminal device 50.
In the following description, the same components as those described above are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 4, the mobile terminal device 40 according to the fourth embodiment is a foldable mobile phone. The mobile terminal device 40 is configured such that the upper housing 41 and the lower housing 42 can be folded via a hinge 45. The upper housing 41 includes a display screen 44 using liquid crystal, a speaker 43, an antenna 46 for transmitting and receiving, the imaging device 30, and the like. The lower housing 42 includes an input key 47, a microphone 44, and the like.

  The imaging device 30 uses the imaging device with an autofocus function in the third embodiment. A drive device 31 is disposed in a part of the imaging device 30. The imaging direction of the imaging device 30 is perpendicular to the plane including the display screen 44 in FIG. 4, that is, the optical axis is the front direction in FIG. The moving direction of the optical system by autofocus is also the front direction.

  The portable terminal device 40 is configured to be used by opening the upper housing 41 and the lower housing 42 when in use, and being folded when not in use.

  As described above, the portable terminal device 40 is mounted with the imaging device 30 shown in the third embodiment, and realizes improvement in thickness reduction. In the case of a folded mobile terminal, the imaging device mounted on the upper housing predominantly determines the thickness of the upper housing, but as shown in FIG. 5A, the mobile terminal device 40 of the fourth embodiment. While the thickness of the upper casing 41 is T1, the conventional portable terminal device 50 is equipped with the imaging device 120 including the conventional driving device 100, and as shown in FIG. The thickness of the body 51 is T3.

  In other words, T1 and T3 are obtained due to the difference in thickness of the imaging device 30 with respect to the optical axis direction of the driving device 41, and the relationship of T1 <T3 is established. Even if the imaging device does not dominately determine the thickness of the upper housing, it is possible to arrange other components, etc. It becomes possible to improve the degree of freedom of design such as adding parts.

  In addition, mobile phones are required to have improved impact resistance against dropping. By using the imaging device 30 according to the third embodiment, the center of gravity of the weight of the driving device 31 is arranged near the end face to which the piezoelectric element adheres as described above, so that it can be applied to a larger impact force than before. Peeling is difficult to occur. That is, since the moment due to the impact force is reduced with respect to the drop impact of the mobile terminal device, the impact resistance characteristics can be improved and the reliability is improved.

  Note that the driving device or the imaging device of this embodiment is not limited to this structure, and can be applied to various forms of portable information devices. For example, it can be clearly applied to PDAs (Personal Digital Assistants), personal computers, and portable information devices such as personal computer external devices.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

  The drive device of the present invention can be applied to a portable information device such as a camera, a mobile phone, a PDA (Personal Digital Assistant), a personal computer, an external device of the personal computer, and the like. It is useful as a drive device that can improve the performance and further reduce the size and thickness of the device.

Sectional drawing of the principal part of the drive device 1 of 1st Embodiment Sectional drawing of the principal part of the drive device 21 of 2nd Embodiment Cross-sectional view of the main part of a modified example of the drive device Sectional drawing of the principal part of the imaging device 30 of 3rd Embodiment Front view of the mobile terminal device 40 of the fourth embodiment (A) Side view of portable terminal device 40 of 4th Embodiment (b) Side view of conventional portable terminal device 50 Schematic configuration diagram of a driving device using a conventional piezoelectric element Schematic configuration diagram of an imaging device equipped with a conventional drive device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive device 2 Weight 3 Piezoelectric element 4 Drive shaft 5 Holder 6 Spring
DESCRIPTION OF SYMBOLS 7 Slider 30 Image pick-up device 31 Drive device 38 Aspherical lens 37 Lens tube 34 Optical filter 36 Semiconductor image pick-up element 35 Case 27 Engagement member 40 Cell-phone device 41 Upper case 42 Lower case 43 Speaker 44 Display screen 45 Hinge 46 Antenna 47 input key

Claims (9)

A piezoelectric element;
A weight fixed to one end of the expansion and contraction direction of the piezoelectric element;
A driving member fixed to the other end of the piezoelectric element;
The driving member and the piezoelectric element abut on the expansion / contraction direction of the piezoelectric element with a spatial overlap ,
A driving apparatus in which the center of gravity of the driving member is located near a plane including a contact surface on which the piezoelectric element and the driving member abut . A piezoelectric element;
A weight fixed to one end of the expansion and contraction direction of the piezoelectric element;
A driving member fixed to the other end of the piezoelectric element;
Drive member relative to the expansion and contraction direction of the piezoelectric element, it has a recess for accommodating at least a part of the piezoelectric element,
A driving apparatus in which the center of gravity of the driving member is located near a plane including a contact surface on which the piezoelectric element and the driving member abut . 3. The drive device according to claim 1, wherein the piezoelectric element and the weight are in contact with each other in a spatially overlapping manner with respect to the expansion / contraction direction of the piezoelectric element. 3. The driving device according to claim 1, wherein the weight has a concave portion that accommodates at least a part of the piezoelectric element with respect to a direction in which the piezoelectric element expands and contracts. 5. The drive device according to claim 3 , wherein the center of gravity of the weight is located near a plane including a contact surface on which the piezoelectric element and the weight contact. And the drive member and the piezoelectric element and the weight is, the driving device according to any one of claims 1 to 5 is arranged substantially coaxially. A piezoelectric element; a weight fixed to one end of the piezoelectric element in a direction of expansion and contraction; and a driving member fixed to the other end of the piezoelectric element. A driving device in which the center of gravity of the driving member is positioned in the vicinity of a plane that includes a contact surface that contacts the piezoelectric element and the driving member in contact with each other in a spatially overlapping manner;
An engaging member that engages the driving member and a lens barrel that holds the lens;
An image sensor that changes light from the lens into an electrical signal,
An imaging apparatus in which a lens barrel moves in the optical axis direction of a lens according to expansion and contraction of a piezoelectric element. The image pickup apparatus according to claim 7 , wherein an imaging magnification with respect to an image pickup surface of the image pickup element changes as a lens barrel holding a lens moves in an optical axis direction. A portable terminal device comprising the imaging device according to claim 7 .

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