Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2002-01-02
2004-03-30
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S367000
Reexamination Certificate
active
06713944
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuator using a strain element having such a property that it is deformed when voltage is applied, the so-called piezoelectric inverse effect, and a method of manufacturing the strain element.
2. Description of the Related Art
Conventionally, there has been an actuator using a piezoelectric element having such a property that a strain occurs and a deformation is caused when voltage is applied, the so-called piezoelectric inverse effect. In the actuator using the piezoelectric element, since an amount of deformation (amount of displacement) of the piezoelectric element is small, a mechanism portion (displacement enlargement mechanism portion) for enlarging the amount of displacement must be provided, and there has been a problem that its main body becomes large, and a problem that it takes labor to assemble the displacement enlargement mechanism portion.
Incidentally, the displacement enlargement mechanism portion is, as disclosed in Japanese Patent Unexamined Publication No. Hei. 4-25640, a mechanical enlargement mechanism portion employing the principle of leverage, a liquid type enlargement mechanism portion employing Pascal's principle, or the like.
Recently, an actuator in which the displacement enlargement mechanism portion is constructed by an actuator itself is proposed (Japanese Patent Unexamined Publication No. Hei. 6-216424). This actuator is constructed such that a belt-shaped piezoelectric element is helically wound over the full length of a hollow coil spring. According to this actuator, when voltage is applied to the piezoelectric element, a torsion moment by the deformation of the piezoelectric element acts on the full length of the coil spring, so that the coil spring is displaced in the axial direction. The amount of displacement of the coil spring in the axial direction can be made large if the number of turns of the coil spring is increased.
However, the actuator is assembled by helically winding the belt-shaped piezoelectric element over the full length of the hollow coil spring, and the step of helically winding the belt-shaped piezoelectric element is a very troublesome step, so that manufacturing costs are raised and the actuator is expensive.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a small and inexpensive actuator which has a simple structure and can obtain a large displacement, and a method of manufacturing a strain element applied to the actuator.
The actuator of the present invention has the following structure to solve the above problem.
(1) An actuator comprises a strain element having a property of a piezoelectric inverse effect, in which the strain element is wound like a coil, and electrodes are formed on an inner circumferential surface and an outer circumferential surface.
According to this structure, when voltage is applied between the electrodes formed on the inner circumferential surface and the outer circumferential surface, the strain element wound like the coil is displaced in a direction to contract or expand the diameter of the coil. At this time, if one end portion of the strain element wound like the coil is fixed, the other end portion, which is not fixed, is rotated in accordance with the contraction or expansion of the diameter. The rotation direction at this time is determined by the winding direction of the strain element, and the rotation amount of the other end portion is determined by the number of turns of the strain element or the like.
Accordingly, since the displacement of sufficient magnitude can be easily obtained by adjusting the number of turns or the like, a displacement enlargement mechanism portion is also not required.
Besides, the strain element having the shape wound like the coil can be easily formed by extrusion molding or the like, and formation of the electrodes on the inner circumferential surface and the outer circumferential surface of the strain element can be easily carried out by a well-known processing method such as a printing or plating method. Accordingly, the actuator of this invention does not require a troublesome step in its manufacturing process and can be formed inexpensively.
(2) An actuator comprises a strain element having a property of a piezoelectric inverse effect, in which a metal coil wound like a coil is provided, the strain element is formed on at least one of an inner circumferential surface and an outer circumferential surface of the metal coil, and an electrode is formed on a surface of the strain element.
According to this structure, the strain element is formed on one of or both of the inner circumferential surface and the outer circumferential surface of the metal coil wound like the coil. The electrode is formed on the surface of the strain element. When voltage is applied between the electrode and the metal coil, in accordance with the displacement of the strain element, the metal coil is deformed in a direction to contract or expand the diameter of the coil. Accordingly, similarly to the above structure (1), if one end portion of the metal coil is fixed, the other end portion which is not fixed is rotated.
Besides, when well-known hydrothermal synthesis is used, the strain element can be easily formed on the outer circumferential surface or the inner circumferential surface of the metal coil wound like the coil. Besides, formation of the electrode on the surface of the strain element (the surface here is a surface at a side opposite to a contact surface to the metal coil) can also be easily performed by a well-known method such as a printing or plating method.
Incidentally, as compared with a case where the strain element is formed on only one of the inner circumferential surface and the outer circumferential surface of the metal coil wound like the coil, when the strain element is formed on both the inner circumferential surface and the outer circumferential surface, the displacement of the metal coil becomes large, so that further miniaturization can be realized.
(3) An actuator provided with a strain element having a property of a piezoelectric inverse effect, in which the strain element is wound like a coil, an electrode having a width narrower than a width of the strain element is formed on an upper surface of the strain element along a side portion of one of an inner circumferential side and an outer circumferential side, and an electrode having a width narrower than the width of the strain element is formed on a lower surface of the strain element along a side portion of an opposite side of that of the upper surface.
According to this structure, the electrode having the width narrower than the strain element is formed on the upper surface of the strain element wound like the coil along the side portion of one of the inner circumferential side and the outer circumferential side, and the electrode having the width narrower than the strain element is formed on the lower surface of the strain element along the side portion of the opposite side of that of the upper surface. With respect to two electrodes arranged side by side, since a desirable shape is such that all of them are formed on the strain element, it is appropriate that the width of the electrode is made not larger than half of the width of the strain element. However, even if the electrode has a size exceeding the half so that it protrudes to the outside or inside of the strain element, there does not especially arise a problem.
When voltage is applied between the electrodes formed on the upper surface and the lower surface of the strain element, distortion is generated over the full length of the strain element wound like the coil, and displacement occurs in the axial direction. Since the displacement amount in the axial direction at this time can be adjusted by the number of turns of the strain element or the like, the displacement amount of sufficient magnitude can be easily obtained.
Besides, as described above, the strain element wound like the coil can be easily formed by the
Irie Atsushi
Omata Nobuaki
Dickstein Shapiro Morin & Oshinksy LLP
Dougherty Thomas M.
Omron Corporation
LandOfFree
Actuator and method of manufacturing a strain element does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Actuator and method of manufacturing a strain element, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Actuator and method of manufacturing a strain element will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3242455