Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Patent
1996-09-30
1998-10-27
Dougherty, Thomas M.
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
310321, H01L 4108
Patent
active
058281576
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a pyroelectric type infrared ray sensor for detecting an infrared ray released from an object without making contact, and a piezoelectric actuator which is a vibrating mechanism used as a chopper of such pyroelectric infrared ray.
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
Recently, the pyroelectric type infrared ray sensor is used in wide fields including measurement of temperature of foods in microwave ovens, and detecting the position of human bodies in air-conditioned, and its demand seems to increase further henceforth. The pyroelectric type infrared ray sensor makes use of the pyroelectric effect by a pyroelectric element such as single crystal of LiTaO.sub.3. The pyroelectric element has a spontaneous polarization, and is always generating surface electric charge, but maintains an electrically neutral state in the atmospheric stationary state by bonding with the electric charge in the atmosphere. When an infrared ray enters this pyroelectric element, the temperature of the pyroelectric element is changed, and accordingly the surface electric charge state is broken and changed from the neutral state. It is the pyroelectric type infrared ray sensor that is a device for detecting the electric charge generated on the surface and measuring the infrared ray incident amount. An object radiates an infrared ray depending on its temperature, and the position or temperature of the object can be detected by using this sensor. The pyroelectric effect is derived from the change of incident amount of infrared ray, and when detecting the temperature of an object as pyroelectric type infrared ray sensor, it is required to vary the infrared ray incident amount. What is used as this means is called a chopper, and it interrupts the incident infrared ray by force, and detects the temperature of the detecting object. As a conventional chopper, for example, an electromagnetic motor or piezoelectric actuator was used.
FIG. 13 is a perspective view of a prior art of pyroelectric type infrared ray sensor using a piezoelectric actuator having a piezoelectric element adhered to an elastic flat plate as the chopper. Generally, the actuator composing an adhered element by adhering a piezoelectric element to an elastic flat plate of metal or the like, fixing one end of the adhered element, and generating a flexural motion on the entire surface by making use of distortion by the piezoelectric element. This use of distortion by piezoelectric element is called bimorph type if the piezoelectric element is adhered to both sides of the elastic flat plate, or unimorph type if adhered to one side only, and the elastic flat plate is known as shim, and hereinafter these members are called in this manner.
FIG. 13 represents a piezoelectric actuator using a bimorph type element as chopper for pyroelectric type infrared ray sensor, wherein reference numeral 201 is a shim, 202a, 202b are piezoelectric elements, 203 is a shield plate, 204 is a base, 205 is a fixing piece, 206 is a wiring for shim, 207a, 207b are wirings for piezoelectric elements, 208 is an infrared ray detecting unit, 209 is a slit, and 210 is an infrared ray. On both sides of the shim 201 of elastic metal, piezoelectric elements 202a, 202b are adhered, and these three pieces are combined into one body, and a bimorph type element is composed. Electrodes are printed on the surface of the piezoelectric elements 202a, 202b. The adhesive surface is polarized in the vertical direction. The individual polarizing directions of the piezoelectric elements 202a, 202b are set by the direction of electric field applied between the shim 201 and the piezoelectric elements 202a, 202b by the wiring 206 taken out from the shim and the wirings 207a, 207b taken out from the piezoelectric elements, and are determined so that the piezoelectric elements 202a, 202b may always generate distortion in mutually reverse directions. That is, the direction of applied electric field and polarizing direction are determined so that when on
REFERENCES:
patent: 4966032 (1990-10-01), Takeuchi
patent: 5216313 (1993-06-01), Ohnishi et al.
patent: 5561337 (1996-10-01), Toda
Masutani Takeshi
Miki Katsumasa
Nomura Koji
Dougherty Thomas M.
Matsushita Electric - Industrial Co., Ltd.
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