JP2009130661A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide piezoelectric actuators which reduces a camera case in size and weight and effectively removes dust attached to an optical element by increasing vibration generating force. <P>SOLUTION: In the piezoelectric actuators 12 and 12b for vibrating an optical element 11 in a camera to remove dust attached to a lens or the like constituting the optical element, laminated piezoelectric elements 27 are respectively connected to both surfaces of an elastic conductive SIMM layer 25. In the laminated piezoelectric elements 27, a plurality of electrode layers and piezoelectric ceramic layers 24 are alternately laminated, electrodes facing each other are configured so as to be respectively connected to two different potentials to be driven, and a laminated piezoelectric bimorph structure is formed, which causes bending displacement by applying voltage so that the laminated piezoelectric elements 27 on both the surfaces of the SIMM layer 25 may be distorted in the opposite direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a piezoelectric actuator that is used in a camera having an imaging function, and in particular, removes dust adhering to the inside of the camera.

  Conventionally, since a relatively large pixel pitch of the image sensor has been used, it has not been a problem. However, when a recent small image sensor with more than 1 million pixels is used in a camera, an image is captured. The pixel pitch of the element becomes fine, and the shadow of dust adhering to the optical element surface near the imaging surface of the image sensor is reflected on the image sensor and greatly affects the image quality. It has become.

  One way to solve this problem is to have a structure that seals the image sensor as much as possible. Further, in a single-lens reflex camera with interchangeable lenses, the lens is removed from the camera body and a special operation mode is used. Then, a method of exposing the image sensor and blowing off dust on the image sensor with a blower or the like is employed.

  Conventionally, a method of removing dust from a lens with a piezoelectric actuator is also known. For example, Patent Document 1 describes this dust removing piezoelectric actuator.

  FIG. 5 shows a perspective view of a conventional piezoelectric actuator. A piezoelectric actuator 42a and a piezoelectric actuator 42b are fixed to the outside of the optical element 41. Further, each piezoelectric actuator has a weight 43a and a weight 43b made of a material having a relatively large specific gravity such as tungsten, copper, or iron. It is fixed.

  A periodic voltage from an oscillator is applied to the piezoelectric actuators 42a and 42b, and the weights 43a and 43b vibrate in the lens optical axis direction. The optical element 41 can be vibrated in the optical axis direction by the reaction of the weight. By this vibration, dust on the surface of the optical element can be pulled away from the surface, and dust can be removed in a direction in which gravity is applied. If vibration is applied in a state where gravity is applied in the in-plane direction of the optical element 41, dust on both sides can be removed.

JP 2002-204379 A

  Conventional piezoelectric actuators cannot remove dust sufficiently because the dust is pulled away by an indirectly generated vibration force of weight reaction. Further, in order to increase the vibration, the weight needs to be large enough, and the size of the camera body increases and the weight itself increases, which is an obstacle to downsizing the camera.

  Therefore, it has been difficult to provide a piezoelectric actuator that can reduce the size and weight of the camera housing and at the same time reliably remove dust attached to the optical element with a large vibration generating force.

  The technical problem of the present invention is a piezoelectric actuator that solves the above problems, realizes a reduction in size and weight of the camera housing, and can reliably remove dust adhering to the optical element by increasing vibration generation force. It is to provide.

  The present invention has been made to solve the above-described problems, and employs a piezoelectric actuator that does not rely on the weight for the vibration force for separating dust, making the weight unnecessary and hindering the reduction in size and weight of the camera housing. It is something that is not.

  As the piezoelectric actuator, in the present invention, a piezoelectric ceramic using a piezoelectric ceramic having a high energy conversion efficiency and utilizing a piezoelectric longitudinal effect (adding an electric signal in the polarization direction and generating distortion and stress in a direction parallel thereto) is used. .

  According to the present invention, a piezoelectric actuator that vibrates an optical element inside a camera and removes dust adhering to a lens or the like constituting the optical element, which is laminated on both sides of an elastic conductive shim layer. Bonding piezoelectric elements, the multilayer piezoelectric element is configured such that a plurality of electrode layers and piezoelectric ceramic layers are alternately stacked, and the opposing electrodes are driven to be connected to two different potentials, A piezoelectric actuator having a multilayer piezoelectric bimorph structure in which bending displacement is generated by applying a voltage to the multilayer piezoelectric elements on both sides of the shim layer so that the generated strains are opposite to each other is obtained. It is done.

  According to the present invention, since the weight that increases the vibration generating force and prevents the conventional downsizing is unnecessary, the camera housing can be reduced in size and weight, and dust attached to the optical element can be effectively removed. It has become possible to provide a piezoelectric actuator.

  A piezoelectric actuator according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a piezoelectric actuator of the present invention. The piezoelectric actuators 12a and 12b of the present invention are fixed to the outside of the optical element 11 inside the camera as in the conventional example.

  When a periodic voltage from an oscillator is applied to each of the piezoelectric actuators 12a and 12b, the piezoelectric actuators 12a and 12b are set to vibrate in the lens optical axis direction. Since the optical element 11 can be vibrated in the optical axis direction by this vibration, the dust on the surface of the optical element can be pulled away from the surface by the vibration, and the vibration is applied in a state where gravity is applied to the surface direction of the optical element 11. , It is possible to remove dust on both surfaces of the lens.

  FIG. 2 shows a structural diagram of a piezoelectric actuator according to the present invention. 2A is a cross-sectional view, and FIG. 2B is a plan view. In this piezoelectric actuator, laminated piezoelectric elements 27 are bonded to both surfaces of a conductive shim layer 25 having elasticity, and the laminated piezoelectric elements 27 have electrode layers (internal electrodes 22) and piezoelectric ceramic layers 24 alternately. A plurality of electrodes are stacked, and opposed electrodes are connected to two different potentials so as to be driven, and distortions generated in the stacked piezoelectric elements 27 on both sides of the shim layer 25 are opposite to each other. By adopting a laminated piezoelectric bimorph structure that causes bending displacement by applying a voltage so as to become smaller, the camera housing can be reduced in size and weight, and the vibration generating force increases, so that it adheres to the optical element Dust can be removed strongly.

  Hereinafter, the manufacturing method of the piezoelectric actuator of this invention is demonstrated.

  A slurry prepared with a powder of piezoelectric ceramic material, an organic binder, and an organic solvent is formed into a film by a doctor blade method or an extrusion molding method to obtain a green sheet (unsintered raw sheet). An electrode pattern is printed on both sides of the green sheet using an electrode paste mainly composed of silver. The green sheets on which the electrode patterns are formed are laminated and pressure-bonded while shifting the positions so that the opposing electrodes become portions corresponding to the end portions thereof. Then, it is separated and cut into a desired shape. At this time, the internal electrodes 22 are configured to be exposed to the opposing surface on each end surface.

  Next, the laminated body is fired at a temperature of 450 ° C. to 600 ° C. in the atmosphere for several hours to decompose all the organic substances contained therein (debinding treatment), and then at a temperature between 900 ° C. and 1200 ° C. Bake. Thereafter, the double-sided external electrode 21 and the side surface external electrodes 23a and 23b are applied to both surfaces and end surfaces of the laminate. With this process, the internal electrodes 22 of the respective layers of the piezoelectric element are alternately connected so that an electric field can be applied to each piezoelectric ceramic layer 24 when a voltage is applied to the electrodes at both ends, and the laminated piezoelectric element 27 is obtained.

  The double-sided external electrode 21 and side surface external electrodes 23a and 23b may be formed by any method such as printing and baking of electrode paste, vapor deposition or sputtering. Next, in order to form a bimorph, the conductive shim layer 25 and the multilayer piezoelectric element 27 are bonded to the front and back of the shim layer 25 via the adhesive layer 26, whereby the present invention is applied. A piezoelectric actuator having a laminated piezoelectric bimorph structure is completed.

  FIG. 1 shows the piezoelectric actuator of the present invention fixed to the optical element in the same manner as in the prior art. As is clear from comparison between FIGS. 1 and 5, the piezoelectric actuator according to the present invention is shown. The optical element unit using the is small and light and has a bimorph structure, so that the vibration generating force is increased.

  As an example according to the present invention, a laminated piezoelectric bimorph structure in which two laminated piezoelectric actuators having a length L25 mm, a width W5 mm, and a thickness t0.5 mm are attached to both surfaces of a 42 alloy shim material L28 mm × W5 mm × t0.2 mm. As an example of a laminated piezoelectric actuator, and a laminated piezoelectric actuator in which an L10 mm × W10 mm × t3 mm iron weight is attached to a laminated element of L10 mm × W10 mm × t18 mm, voltage-displacement amount and generated force-displacement amount Compared.

  FIG. 3 shows a measurement diagram of comparative measurement between the piezoelectric actuator prototype of the present invention and a conventional product. In the voltage-displacement measurement, a specified voltage is applied to the piezoelectric actuator 32 of the present invention and the conventional piezoelectric actuator 33 + weight 34 fixed to the measurement table 31, and the displacement amount in the center of each piezoelectric actuator displacement direction (displacement in the Z-axis direction). ) Was measured with a laser displacement meter. The generated force-displacement measurement is performed so that the set generated force (pressure) is obtained while measuring with the pressure sensor fixed to the piezoelectric actuator 32 of the present invention fixed on the measurement table 31 and the conventional piezoelectric actuator 33 + weight 34. A voltage was applied, and the displacement amount (Z-axis direction displacement) at the center of each piezoelectric actuator displacement direction at that time was measured with a laser displacement meter.

  FIG. 4 is a characteristic comparison diagram between a piezoelectric actuator prototype according to the present invention and a conventional product. FIG. 4A is a voltage-displacement characteristic comparison diagram. The prototype according to the present invention has a larger displacement with respect to voltage. FIG. 4B is a characteristic comparison diagram of the generated force-displacement amount. The prototype according to the present invention has a greater generated force with respect to the displacement amount. As shown in FIG. 3, the prototype according to the present invention is improved in both displacement and generating force as compared with the conventional product as shown in the characteristic comparison diagram of FIG. It was confirmed that

  As described above, it has become possible to provide a piezoelectric actuator that can reduce the size and weight of the camera housing and can strongly remove dust adhering to the optical element by increasing the vibration generating force.

  Although the present invention has been specifically described with reference to the embodiments, the present invention is not limited to these embodiments, and design changes within a range not departing from the gist of the present invention are included in the present invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

  According to the piezoelectric actuator using the laminated piezoelectric bimorph of the present invention, a piezoelectric actuator capable of reducing the size and weight of the camera housing and powerfully removing dust attached to the optical element by increasing the vibration generating force. Can be provided.

The perspective view of the piezoelectric actuator of this invention. FIG. 2A is a structural view showing a piezoelectric actuator according to an embodiment of the present invention, FIG. 2A is a cross-sectional view, and FIG. 2B is a plan view. The comparison measurement figure of the piezoelectric actuator prototype of this invention, and a conventional product. FIG. 4 (a) is a voltage-displacement characteristic comparison diagram, and FIG. 4 (b) is a generated force-displacement characteristic comparison chart. The perspective view of the conventional piezoelectric actuator.

Explanation of symbols

11 Optical Element 12a (Invention) Piezoelectric Actuator 12b (Invention) Piezoelectric Actuator 21 Double-sided External Electrode 22 Internal Electrode 23a Side External Electrode 23b Side External Electrode 24 Piezoelectric Ceramic Layer 25 Shim Layer 26 Adhesive Layer 27 Multilayer Piezoelectric Element 31 Measuring table 32 (conventional) piezoelectric actuator 33 (conventional) piezoelectric actuator 34 weight 41 optical element 42a (conventional) piezoelectric actuator 42b (conventional) piezoelectric actuator 43a weight 43b weight

Claims (1)

  A piezoelectric actuator that vibrates an optical element inside a camera and removes dust adhering to the optical element, wherein a laminated piezoelectric element is bonded to each of both surfaces of a conductive shim layer having elasticity, and the laminated piezoelectric element The element is configured such that a plurality of electrode layers and piezoelectric ceramic layers are alternately stacked, and the electrodes facing each other are driven by being connected to two different potentials, and the stacked piezoelectric elements on both sides of the shim layer A piezoelectric actuator having a laminated piezoelectric bimorph structure in which bending displacement is generated by applying a voltage so that the generated strains are opposite to each other.

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