JP2007300708A - Piezoelectric drive unit, image forming device, and portable terminal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive unit that achieves the improvement of shock resistance and size reduction and thinning. <P>SOLUTION: The drive unit comprises a piezoelectric element, a weight fixed to one end of the piezoelectric element in the elongation/contraction direction, and a drive member fixed to the other end of the piezoelectric element. The piezoelectric element and the weight abut on each other while being spatially overlapped with each other with respect to the elongation/contraction direction of the piezoelectric element. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 has a diameter Φ of 3 [mm], a length of 1 [mm], and is made of a metal such as tungsten having a high density. 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.

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. Accordingly, 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 apparatus using the piezoelectric element as shown in FIG. 6, the driving member, the piezoelectric element, and the weight are arranged in series in the expansion / contraction direction of the piezoelectric element. The driving member needs to secure the length of the engaging member that is frictionally held in addition to the distance necessary for movement, and the total length becomes long. Therefore, when the piezoelectric drive device is applied to an auto focus mechanism or a zoom mechanism by moving the lens, it moves in the direction of the optical axis as in the portion A of the imaging device 120 shown in FIG. Since a length obtained by adding the length of the engaging member to the necessary distance is necessary, this is an obstacle to downsizing and thinning of a device in which the piezoelectric driving device is mounted.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric drive device that realizes a reduction in size and thickness of a device in which the piezoelectric drive device is mounted.

  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 piezoelectric element and the weight are It is in contact with the piezoelectric element in the direction of expansion and contraction with a spatial overlap.

  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.

  According to another aspect of the present invention, there is provided a driving device comprising: a piezoelectric element having a recess; a weight having a flat portion fixed to one end in the expansion / contraction direction of the piezoelectric element; and a protrusion accommodated in the recess of the piezoelectric element; And a driving member fixed to the other end of the head.

  With this configuration, since the convex portion of the weight is accommodated in the concave portion of the piezoelectric element, the lengthwise dimension of the piezoelectric element and the weight added can be shortened, and the entire drive device can be reduced in size. .

  The drive device according to the present invention includes a piezoelectric element, a concave portion that accommodates a part of the piezoelectric element, a weight that is fixed to one end of the piezoelectric element in the expansion / contraction direction on the bottom surface of the concave portion, and a piezoelectric element And a driving member fixed to the other end.

  According to this configuration, since the weight is generally manufactured by die casting, machining by a lathe, etc., the difficulty in processing can be performed with almost no change, so that the piezoelectric element can be easily created. 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. Further, 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 apparatus of the present invention, 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 image pickup apparatus 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. A driving device that is in contact with the piezoelectric element in an expanding / contracting direction with a spatial overlap, an engaging member that engages the driving member and a lens barrel that holds the lens, and electrically emits light from the lens. An imaging element that changes to a signal, and the lens barrel moves in the optical axis direction of the lens in accordance with expansion and contraction of the piezoelectric element.

  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 to the above configuration, the imaging apparatus of the present invention is such that the imaging magnification of the imaging element with respect to the imaging surface changes when 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). In the piezoelectric element 3 according to the first embodiment, a portion 3a in which disk-shaped PZT is stacked and a portion 3b in which a central portion is stacked with a donut-shaped PZT having a hollow shape are integrally formed. That is, the piezoelectric element 3 has a shape having a cylindrical space 9 having a certain depth.

  The weight 2 provided on one end side of the piezoelectric element 3 is made of a metal having a high density such as tungsten, for example, has a stepped shape, and a portion having a small diameter is inserted corresponding to the space 9. is there. The weight 2 is bonded and fixed to the piezoelectric element 3 at a stepped portion 2b having a large diameter. At this time, it is necessary to provide a gap 10 between the distal end portion of the thin portion 2 a of the weight 2 and the piezoelectric element 3.

  This is because the weight 2 is arranged at the end of the piezoelectric element 3, and this can be equivalent to that in which the weight 2 is mechanically folded. The piezoelectric element 3 and the weight 2 are arranged so as to be coaxial. Specifically, for example, the diameter portion of the stepped portion 2b of the weight 2 is Φ3.5 [mm] and the length is 0.48 [mm], and the diameter portion of the thin portion 2a is Φ1.8 [mm]. The length was 0.98 [mm]. Further, the piezoelectric element 3 was molded so that the outer diameter was Φ3.2 [mm] and the length was 1.5 [mm], and the space 9 was Φ2 [mm] and the length was 1.0 [mm].

  The drive shaft 4 is formed by aligning carbon long fibers having a diameter of Φ1.0 [mm] and a length of 4.0 [mm] in the axial direction and hardening with epoxy resin as a binder to improve wear resistance. .

  With this configuration, as shown in FIG. 1, the center of gravity G of the weight 2 is located in the vicinity of the intersection between the contact plane where the piezoelectric element 3 and the weight 2 adhere and the coaxial D.

  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. In addition, since the piezoelectric element 3 and the weight 2 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 generation of vibration and noise can be prevented.

  Further, in the driving device 1 of the first embodiment, the driving shaft 4 has the same shape, but a portion with a thin diameter of the weight 2 is inserted corresponding to the space 9 of the piezoelectric element 3. The dimension in the length direction including the piezoelectric element 3 and the weight 2 can be shortened. Specifically, the dimension in the length direction including the piezoelectric element 3 and the weight 2 can be changed from 3 [mm] to about 2 [mm], and can be shortened by 1 [mm]. Thereby, the whole drive device 1 can also be reduced in size, and the imaging device etc. to which the drive device 1 is applied 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 piezoelectric element 23 of the second embodiment has a cylindrical shape similar to the conventional example. On the other hand, the weight 22 is formed so that a cylindrical space is provided in the center portion and the piezoelectric element 23 can be accommodated therein. The piezoelectric element 23 and the weight 22 are bonded and fixed to the cylindrical bottom surface portion of the weight 22.

  With this configuration, the piezoelectric element 23 is formed so as to be accommodated in a cylindrical space provided in the central portion of the weight 22, so that the lengthwise dimension of the piezoelectric element 23 and the weight 22 is increased. It can be shortened, and the drive device 21 as a whole can be reduced in size.

  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. Therefore, compared to the first embodiment in which two types of piezoelectric elements are prepared and stacked, it becomes easier to create the piezoelectric elements.

  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, as shown in FIG. 2B, Embodiments 1 and 2 can be used in combination. That is, a structure in which a convex portion is provided so as not to contact the piezoelectric element 23 inside the concave portion provided in the weight 22 may be adopted. As a result, the degree of freedom in design can be improved. Moreover, since the shape of the weight can be made relatively large, an expensive material such as tungsten can be changed to an inexpensive material such as brass.

(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 4 of the drive device 31 is provided on 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 the driving shaft 4 is arranged in parallel with the optical axis. The lens 38 is an aspherical lens (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 or more 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, for example, a ¼ inch CCD having about 1.3 million pixels and 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, and the driving device 31 includes a piezoelectric element 33 and a weight 32 of the driving shaft 4. Since it is configured to overlap with the axial direction, the overall length is shortened even when the same drive shaft 4 is used.

  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.

  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 be made thin.

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 main parts of a modification of the drive 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
7 Slider 9 Space 10 Gap 30 Imaging device 31 Drive device 38 Aspherical lens 37 Lens tube 34 Optical filter 36 Semiconductor imaging device 35 Housing 27 Engaging member 40 Mobile phone device 41 Upper housing 42 Lower housing 43 Speaker 44 Display Screen 45 Hinge 46 Antenna 47 Input key

Claims (7)

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;
A driving device in which a piezoelectric element and a weight are in contact with each other in a spatially overlapping manner with respect to the expansion / contraction direction of the piezoelectric element. A piezoelectric element having a recess;
A weight having a flat portion fixed to one end in the expansion / contraction direction of the piezoelectric element and a convex portion accommodated in the concave portion of the piezoelectric element;
And a driving member fixed to the other end of the piezoelectric element. A piezoelectric element;
A weight housing at least a part of the piezoelectric element, and a weight fixed to one end of the piezoelectric element in a stretching direction at a bottom surface of the concave portion;
And a driving member fixed to the other end of the piezoelectric element.   The drive device according to any one of claims 1 to 3, wherein the piezoelectric element and the weight are 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 contact with each other in an 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 imaging apparatus according to claim 5, wherein an imaging magnification with respect to an imaging surface of the imaging 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 5.

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