Vibration-type actuator, interchangeable lens, image pickup apparatus, and automatic stage

Abstract

The present invention provides a vibration-type actuator that makes it possible to improve and stabilize yields. A vibration-type actuator includes a vibrator including an elastic body with a protrusion having a contact portion, and an electromechanical transducer attached to a surface of the elastic body; and a flexible printed circuit board having an electrode portion and attached to the electromechanical transducer. There is a space between the contact portion and the electromechanical transducer. No end portion of the electrode portion of the flexible printed circuit board is overlapped with the space in a direction perpendicular to the surface of the elastic body.

Claims

1. A vibration-type actuator comprising: a vibrator including an elastic body and an electromechanical transducer attached to a surface of the elastic body; and a flexible printed circuit board having an electrode portion and attached to the electromechanical transducer, wherein the elastic body has an attached portion to which the electromechanical transducer is attached and a protrusion having a contact portion and a standing portion between the contact portion and the attached portion, wherein there is a space surrounded by the contact portion, the standing portion, and the electromechanical transducer, and wherein no end portion of the electrode portion of the flexible printed circuit board is overlapped with the space in a direction perpendicular to the surface of the elastic body.

2. The vibration-type actuator according to claim 1, wherein the electrode portion of the flexible printed circuit board is not overlapped with the space in the direction perpendicular to the surface of the elastic body.

3. The vibration-type actuator according to claim 1, wherein the elastic body has a spring portion between the standing portion and the contact portion.

4. The vibration-type actuator according to claim 1, wherein the protrusion is disposed at a node portion of vibration in a long-side direction of the vibrator.

5. The vibration-type actuator according to claim 1, wherein the protrusion is disposed at an antinode portion of vibration in a short-side direction of the vibrator.

6. The vibration-type actuator according to claim 1, wherein the standing portion has a gap around the contact portion.

7. An interchangeable lens comprising: a lens; and the vibration-type actuator according to claim 1, the vibration-type actuator being configured to drive a lens holding member that holds the lens.

8. An image pickup apparatus comprising: an image pickup element; a lens; and the vibration-type actuator according to claim 1, the vibration-type actuator being configured to drive a lens holding member that holds the lens.

9. An image pickup apparatus comprising: a lens; an image pickup element; and the vibration-type actuator according to claim 1, the vibration-type actuator being configured to drive the image pickup element.

10. An automatic stage comprising: a stage; and the vibration-type actuator according to claim 1, the vibration-type actuator being configured to drive the stage.

11. The vibration-type actuator according to claim 1, wherein the flexible printed circuit board has a base portion, wherein the electrode portion is disposed on the base portion, and wherein no end portion of the base portion of the flexible printed circuit board is overlapped with the space in the direction perpendicular to the surface of the elastic body.

12. A vibration-type actuator comprising: a vibrator including an elastic body and an electromechanical transducer attached to a surface of the elastic body; and a flexible printed circuit board having an electrode portion and attached to the electromechanical transducer, wherein the elastic body has an attached portion to which the electromechanical transducer is attached and a protrusion having a contact portion and a standing portion between the contact portion and the attached portion, wherein there is a space surrounded by the contact portion, the standing portion, and the electromechanical transducer, and wherein the electrode portion of the flexible printed circuit board is not overlapped with the space in a direction perpendicular to the surface of the elastic body.

13. The vibration-type actuator according to claim 12, wherein no flexible printed circuit board is overlapped with the space in the direction perpendicular to the surface of the elastic body.

14. The vibration-type actuator according to claim 12, wherein the flexible printed circuit board has a base portion, wherein the electrode portion is disposed on the base portion, and wherein the base portion of the flexible printed circuit board is not overlapped with the space in the direction perpendicular to the surface of the elastic body.

15. A vibration-type actuator comprising: a vibrator including an elastic body and an electromechanical transducer attached to a surface of the elastic body and having an electrode layer; and a flexible printed circuit board attached to the electromechanical transducer, wherein the elastic body has an attached portion to which the electromechanical transducer is attached and a protrusion having a contact portion and a standing portion between the contact portion and the attached portion, wherein there is a space surrounded by the contact portion, the standing portion, and the electromechanical transducer, and wherein the electrode layer of the electromechanical transducer is not overlapped with the space in a direction perpendicular to the surface of the elastic body.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a perspective view illustrating a configuration of a vibration-type actuator according to a first embodiment of the present invention.

(2) FIG. 2A is a top view illustrating the configuration of the vibration-type actuator according to the first embodiment of the present invention.

(3) FIG. 2B is a cross-sectional view taken along line IIB-IIB in FIG. 2A.

(4) FIG. 3 is a top view illustrating a configuration of a vibration-type actuator according to a second embodiment of the present invention.

(5) FIG. 4A is a top view illustrating a configuration of a vibration-type actuator according to a third embodiment of the present invention.

(6) FIG. 4B is a bottom view illustrating the configuration of the vibration-type actuator according to the third embodiment of the present invention.

(7) FIG. 5 illustrates a configuration of a vibration-type actuator of related art.

(8) FIG. 6A illustrates a bending vibration mode of the vibration-type actuator illustrated in FIG. 5.

(9) FIG. 6B illustrates another bending vibration mode of the vibration-type actuator illustrated in FIG. 5.

(10) FIG. 7A is a top view illustrating another configuration of the vibration-type actuator of the related art.

(11) FIG. 7B is a cross-sectional view taken along line VIIB-VIIB in FIG. 7A.

(12) FIG. 8 illustrates an application of a vibration-type actuator.

(13) FIG. 9 illustrates another application of a vibration-type actuator.

DESCRIPTION OF EMBODIMENTS

(14) First Embodiment

(15) A first embodiment will be described with reference to FIG. 1. FIG. 1 is a general perspective view of a linear vibration-type actuator. Referring to FIG. 1, the linear vibration-type actuator includes a vibrator 1 and a slider 5 serving as a driven member.

(16) The vibrator 1 includes a piezoelectric element 3 which is a thin plate-like electromechanical transducer, and an elastic body 2 which is attached to one surface of the piezoelectric element 3. The elastic body 2 has an attached portion 22 having a surface to which the piezoelectric element 3 is attached, and protrusions 21. The protrusions 21 each have a contact portion 21a to be in contact with the slider (driven member) 5 when the vibrator 1 is driven, a standing portion 21b between the contact portion 21a and the attached portion 22, and a spring portion 21c between the contact portion 21a and the standing portion 21b. Therefore, the protrusions 21 each have an internal space. In FIG. 1, the standing portion 21b is continuous throughout the periphery of the protrusion 21. Alternatively, for example, the standing portion 21b may have some side faces with a gap, such as an opening, between them. That is, the standing portion 21bmay have a gap around the contact portion 21a. Although the elastic body 2 has two protrusions 21 in this example, the elastic body 2 may have only one protrusion 21 or three or more protrusions 21. For example, the two protrusions 21 are disposed at node portions of vibration in a long-side direction of the vibrator 1 (i.e., in the driving direction of the vibrator 1). The closer the protrusions 21 are to nodes, the larger the amount of driving in the long-side direction. The protrusions 21 may be disposed at antinode portions of vibration in a short-side direction of the vibrator 1 (i.e., in the direction intersecting the driving direction of the vibrator 1). The closer the protrusions 21 are to antinodes, the larger the amount of driving in a thickness direction of the vibrator 1 (i.e., in the thrust direction). Note that a node portion of vibration refers to a location closer to a node than to an antinode of vibration, and an antinode portion of vibration refers to a location closer to an antinode than to a node of vibration.

(17) A flexible printed circuit board 4 for feeding power to the piezoelectric element 3 is attached to a surface of the piezoelectric element 3, the surface being opposite the surface to which the elastic body 2 is attached.

(18) The elastic body 2 may be made of a material having a low vibration damping property, such as metal or ceramic. In manufacture of the elastic body 2, the protrusions 21 may be formed integrally with the elastic body 2 by press molding or cutting, or may be formed separately and attached later on to the elastic body 2 by welding or bonding. There may be a plurality of protrusions 21 as in the present embodiment, or may be only one protrusion 21.

(19) Lead zirconate titanate is used to form the piezoelectric element 3. A lead-free piezoelectric material, such as bismuth sodium titanate, may be used to form the piezoelectric element 3. The piezoelectric element 3 is provided with an electrode pattern made of silver or the like on a surface thereof. The surface provided with the electrode pattern is opposite the surface to which the elastic body 2 is attached. For simplicity, the electrode pattern is not shown in the present embodiment.

(20) Polyimide or polyethylene terephthalate may be used to form a base portion 41 of the flexible printed circuit board 4. Copper, silver, or carbon may be used to form the electrode pattern. The base portion 41 is disposed so as not to overlap with the internal spaces of the protrusions 21 in a direction perpendicular to a surface of the elastic body 2, the surface being a surface to which the piezoelectric element 3 is attached (i.e., in the thickness direction of the vibrator 1 or the direction perpendicular to the plane of FIG. 2A). Specifically, the flexible printed circuit board 4 is formed so as not to overlap with the internal spaces of the protrusions 21. The idea that the flexible printed circuit board 4 is not overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1 means that the image of the flexible printed circuit board 4 when the vibrator 1 is viewed in the thickness direction of the vibrator 1 does not overlap with the internal spaces of the protrusions 21.

(21) A method for manufacturing the vibration-type actuator will now be described. First, the elastic body 2 and the piezoelectric element 3 are bonded to each other using an adhesive. Next, the piezoelectric element 3 and the flexible printed circuit board 4 are bonded to each other, for example, with an adhesive, an anisotropic conductive film, or an anisotropic paste.

(22) To achieve a desired bonding strength or thickness in bonding, it is necessary to apply a predetermined surface pressure at about room temperature to about 180 degrees (Celsius). In the case of using an anisotropic conductive film or an anisotropic paste, a pressure needs to be applied at 180 degrees (Celsius) to 200 degrees (Celsius) to achieve conduction.

(23) An electrode portion 42 made of a conductive material is formed on the base portion 41. The electrode portion 42 is 17.5 micrometers to 35 micrometers thick, and the base portion 41 is 12.5 micrometers to 25 micrometers thick. When a pressure is applied to the flexible printed circuit board 4 via a component made of a relatively soft material, such as rubber or resin, a stress is produced not only in the electrode portion 42, but also in the entire base portion 41 of the flexible printed circuit board 4.

(24) In the present embodiment, the base portion 41 is disposed so as not to overlap with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1. Therefore, the vibrator 1 is subjected to pressure in an area not overlapping with the internal spaces of the protrusions 21 of the elastic body 2. If the flexible printed circuit board 4 is disposed over the entire piezoelectric element 3, an excessive stress is concentrated on parts of the piezoelectric element 3 facing the internal spaces of the protrusions 21 due to lack of stiffness.

(25) However, in the present embodiment, the base portion 41 of the flexible printed circuit board 4 is disposed so as to avoid regions overlapping with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1. Therefore, the concentration of stress on the piezoelectric element 3 can be reduced. It is thus possible to achieve stable manufacture which does not cause breakage of the piezoelectric element 3.

(26) In this example, the base portion 41 of the flexible printed circuit board 4 is disposed so as not to overlap with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1. However, when the base portion 41 of the flexible printed circuit board 4 is disposed such that at least an end of the base portion 41 is not overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1, the concentration of stress on the piezoelectric element 3 can be reduced. By disposing the base portion 41 of the flexible printed circuit board 4 such that no end portion of the base portion 41 is overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1, the concentration of stress on the piezoelectric element 3 can be more efficiently reduced.

(27) The driving principle of the vibration-type actuator will not be described here, as it is the same as that in the related art.

(28) Note, however, that the method for producing elliptical motion on a contact surface in the linear vibration-type actuator of the present invention is not limited to that described above. For example, vibrations in bending vibration modes different from those described above may be combined together, or a vibration in a bending vibration mode may be combined with a vibration in a vertical vibration mode where an elastic body expands and contracts in the long-side direction.

(29) Any driving method may be used as long as it is a method that produces elliptical motion on the contact surface by combining a vibration primarily in a vibration mode where the contact surface is displaced in a feed direction and a vibration in a vibration mode where the contact surface is displaced in a thrust direction.

(30) Although the piezoelectric element 3 has a thin rectangular plate-like shape in the present embodiment, the shape of the piezoelectric element 3 is not limited to this. For example, the piezoelectric element 3 may have a rectangular shape with rounded corners. The piezoelectric element 3 may be of any shape, as long as any of the driving methods described above enables relative movement of the vibrator 1 and the slider (driven member) 5.

(31) Second Embodiment

(32) A second embodiment will be described with reference to FIG. 3. The driving principle and the configuration of components except the flexible printed circuit board 4 are the same as those in the first embodiment. In the present embodiment, a pressure is applied to the flexible printed circuit board 4 by a member made of a material of high stiffness.

(33) The electrode portion 42 is 17.5 micrometers to 35 micrometers thick, and the base portion 41 is 12.5 micrometers to 25 micrometers thick. In bonding of the flexible printed circuit board 4 and the piezoelectric element 3, when a pressure is directly applied to the flexible printed circuit board 4 by a member made of a material of high stiffness, such as metal, the resulting stress is concentrated on the electrode portion 42 because of the electrode thickness.

(34) Therefore, when the electrode portion 42 is disposed so as not to overlap with the internal spaces of the protrusions 21, the concentration of stress on the piezoelectric element 3 can be reduced.

(35) In this case, since the base portion 41 can be freely disposed regardless of the locations of the protrusions 21, the bonding strength can be adjusted by extending the base portion 41.

(36) In this example, the electrode portion 42 of the flexible printed circuit board 4 is disposed so as not to overlap with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1. However, when the electrode portion 42 of the flexible printed circuit board 4 is disposed such that at least an end of the electrode portion 42 is not overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1, the concentration of stress on the piezoelectric element 3 can be reduced. Thus, it is possible to reduce uneven application of pressure to the vibrator 1 from uneven portions created by the electrode portion 42 and the base portion 41, and reduce concentration of stress on parts of the piezoelectric element 3 overlapping with the uneven portions in the thickness direction of the vibrator 1. Therefore, by disposing the electrode portion 42 of the flexible printed circuit board 4 such that no end portion of the electrode portion 42 is overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1, the concentration of stress on the piezoelectric element 3 can be more effectively reduced.

(37) Third Embodiment

(38) A third embodiment concerns a method in which the stress concentration is reduced by a configuration of an electrode layer (electrode pattern) 31 of the piezoelectric element 3. The driving principle and the configuration of other components are the same as those in the first embodiment.

(39) In the present embodiment, as illustrated in FIG. 4A and 4B, the base portion 41 is disposed to overlap with the internal spaces of the protrusions 21, whereas the electrode layer 31 of the piezoelectric element 3 is disposed so as not to overlap with the internal spaces of the protrusions 21. For simplicity, the electrode portion 42 is not shown in FIGS. 4A and 4B. The electrode layer 31 is about 2 micrometers to 10 micrometers thick. Since uneven portions created by the electrode layer 31 are not overlapped with the internal spaces of the protrusions 21 in the direction of pressure application, the concentration of stress on the piezoelectric element 3 can be reduced. In this example, the electrode layer 31 of the piezoelectric element 3 is disposed so as not to overlap with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1. However, when the electrode layer 31 of the piezoelectric element 3 is disposed such that at least an end of the electrode layer 31 is not overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1, the concentration of stress on the piezoelectric element 3 can be reduced. By disposing the electrode layer 31 of the piezoelectric element 3 such that no end portion of the electrode layer 31 is overlapped with the internal spaces of the protrusions 21 in the thickness direction of the vibrator 1, the concentration of stress on the piezoelectric element 3 can be more effectively reduced.

(40) Fourth Embodiment

(41) An application of a vibration-type actuator according to the present invention will be described with reference to FIG. 8. In this example, a vibration-type actuator that drives a lens for automatic focusing is included in a lens barrel of an image pickup apparatus (optical device), such as a camera.

(42) FIG. 8 illustrates a driving mechanism for driving a lens in a lens barrel. A driving mechanism according to a fourth embodiment includes the vibration-type actuator according to any of the first to third embodiments, a driven member, and a first guide bar and a second guide bar arranged in parallel to each other and configured to slidably retain the driven member.

(43) By elliptical motion of protrusions of the vibrator produced by applying a driving voltage to the electromechanical transducer, a relative moving force is generated between the vibrator and the second guide bar in contact with the protrusions of the elastic body. This makes the driven member movable along the first and second guide bars.

(44) Specifically, as illustrated in FIG. 8, a driving mechanism 100 of the present embodiment primarily includes a lens holder 52 serving as a lens holding member, a lens 57, the vibrator 1 to which a flexible printed circuit board is joined, a pressure magnet 55, two guide bars 53 and 54, and a base member (not shown).

(45) The two guide bars, the first guide bar 53 and the second guide bar 54, are each retained and secured at both ends thereof by the base member (not shown) such that they are arranged in parallel to each other.

(46) The lens holder 52 includes a cylindrical holder portion 52a, a retaining portion 52b that retains and secures the vibrator 1 and the pressure magnet 55, and a first guide portion 52c that is fitted to the first guide bar 53 and serves as a guide.

(47) The pressure magnet 55 that forms a pressurizing unit includes a permanent magnet and two yokes disposed on both sides of the permanent magnet. A magnetic circuit is formed between the pressure magnet 55 and the second guide bar 54, so that an attractive force is generated between them. The pressure magnet 55 is spaced from the second guide bar 54, which is disposed to be in contact with the vibrator 1. A pressure is applied between the second guide bar 54 and the vibrator 1 by the attractive force described above.

(48) The two protrusions 21 of the elastic body are brought into pressure contact with the second guide bar 54 to form a second guide portion. The second guide portion forms a guide mechanism using a magnetic attractive force. The vibrator 1 and the second guide bar 54 are pulled apart from each other, for example, by being subjected to an external force. In this case, the lens holder 52 is returned to a desired position when a fall preventing portion 52d of the lens holder 52 hits the second guide bar 54.

(49) Feeding a desired electric signal to the vibrator 1 generates a driving force between the vibrator 1 and the second guide bar 54. The lens holder 52 is driven by this driving force. The vibration-type actuator according to any of the first to third embodiments can be used here.

(50) In the present embodiment, the vibration-type actuator is used to drive a lens for automatic focusing in the image pickup apparatus. However, the application of the present invention is not limited to this. For example, the vibration-type actuator may be used to drive a lens holder for moving a zoom lens. Therefore, the vibration-type actuator according to the present invention can be mounted not only in an image pickup apparatus, but also in an interchangeable lens, to drive a lens. The vibration-type actuator may be used to drive an image pickup element, or to drive a lens and an image pickup element for correction of motion blur caused by hand shake

(51) Fifth Embodiment

(52) FIG. 8 illustrates an example where a vibration-type actuator of the present invention is used in an image pickup apparatus, but the application is not limited to this. A vibration-type actuator of the present invention may also be used to drive various stages of microscopes and the like. In an example illustrated in FIG. 9, a vibration-type actuator is used to drive a stage of a microscope.

(53) FIG. 9 is a perspective view of a microscope serving as an image pickup apparatus according to a fifth embodiment of the present invention. The microscope illustrated in FIG. 9 includes an image pickup unit 60 having an image pickup element and an optical system therein, and an automatic stage 61 having an automatic stage 61 disposed on a base and moved by a vibration-type actuator. An object to be observed is placed on the stage 62 and an enlarged image of the object is captured by the image pickup unit 60. When the range of observation is wide, the object is moved in the X or Y direction in FIG. 9 by causing the vibration-type actuator to move the stage 62, so that many captured images are acquired. Then, a computer (not shown) combines the captured images together to generate a high-resolution image of a wide observation range.

(54) The vibration-type actuator according to any of the first to third embodiments can be used here.

(55) While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

(56) This application claims the benefit of Japanese Patent Application No. 2013-129223, filed Jun. 20, 2013, which is hereby incorporated by reference herein in its entirety.

REFERENCE SIGNS LIST

(57) 1 vibrator

(58) 2 elastic body

(59) 21 protrusion

(60) 3 piezoelectric element

(61) 31 electrode layer

(62) 4 flexible printed circuit board

(63) 41 base portion

(64) 42 electrode portion

(65) 106 elastic body

(66) 107 electromechanical transducer

(67) 108 protrusion

(68) 109 flexible printed circuit board

(69) 116 slider