EP0594331A1
Expired / Lapsed
EP
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Piezoelectric sensor
Assignee: Oki Ceramic Industry Co Ltd
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Filing: 1993-10-07
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Granted: —
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Expires: 2013-10-07
Abstract
Abstract A piezoelectric sensor for detecting vibrations is disclosed, the sensitivity of which is less temperature dependent than that in the prior art even when it is used in a broad temperature range. A lower member (33) made of alumina is secured by an epoxy type adhesive (15) to the inner bottom surface of a vessel (31) made of an iron-nickel alloy containing 42% by weight of nickel. A piezoelectric element (13) using a PZT piezoelectric body (13a) is secured by an adhesive (15) to the lower member. An upper member (35) made of alumina having electrodes is secured to the piezoelectric element with the electrodes (35b,35c) of the upper member and those (13b,13d) of the piezoelectric element soldered to one another. The plan dimensions of the upper and lower members are slightly greater than those of the piezoelectric element. On the lamination including the piezoelectric element and lower and upper members, a thermally shrinkable tube is fitted, thus forming spaces (39,45) adjacent the top surface and periphery of the piezoelectric element. In this state, the piezoelectric element and so forth are sealed with a resin.
Inventors
- 👤 Toshihiko c/o Oki Ceramic Ind. Co. Ltd. Sato
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-04 14:21
CPC Classifications
H; H10; H10N; H10N30/00; H10N30/30; H10N30/302; G; G01; G01L; G01L23/00; G01L23/22; G01L23/221; G01L23/222; H10N30/80; H10N30/88
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
71 words
A piezoelectric sensor comprising a piezoelectric element (13) and a support (31,33) with said piezoelectric element secured to the support (31,33) to obtain a measurement signal from an object under measurement through the support, wherein, the support is entirely or partly made of a material having a coefficient of thermal expansion equal to or near the coefficient of thermal expansion of a piezoelectric body (13a) used for the piezoelectric element (13).
Claim 2
Dependent Claim
71 words
A piezoelectric sensor comprising a piezoelectric element (13) and a support (31,33) with said piezoelectric element secured to the support (31,33) to obtain a measurement signal from an object under measurement through the support, wherein, the support is entirely or partly made of a material having a coefficient of thermal expansion equal to or near the coefficient of thermal expansion of a piezoelectric body (13a) used for the piezoelectric element (13).
Claim 3
Dependent Claim
31 words
A piezoelectric sensor according to claim 1, wherein the support is a vessel (31) accommodating the piezoelectric element, the vessel being made of a material having said coefficient of thermal expansion.
Claim 4
Dependent Claim
47 words
A piezoelectric sensor according to claim 1, wherein the support includes a vessel (31) accommodating the piezoelectric element and a lower member (33) interposed between the vessel and the piezoelectric element, at least the lower member being made of a material having said coefficient of thermal expansion.
Claim 5
Dependent Claim
98 words
A piezoelectric sensor according to claim 1, wherein said piezoelectric sensor further comprises an upper member (35) provided on the surface of the piezoelectric sensor on the side thereof opposite the support, the upper member being made of a material having a coefficient of thermal expansion equal to or near the coefficient of thermal expansion used for the piezoelectric element and having electrodes (35b,35c) connected to electrodes (13b,13d) of the piezoelectric element, the piezoelectric element and the upper member being spaced apart and facing each other, outer lead (37) being connected to the electrodes of the upper member.
Claim 6
Dependent Claim
37 words
A piezoelectric sensor according to claim 4, wherein the electric connection between the piezoelectric element and the upper member is effected by connection between the electrodes of the piezoelectric element and the electrodes of the upper member.
Claim 7
Dependent Claim
148 words
A piezoelectric sensor according to claim 3, including an upper member (35) provided on the surface of the piezoelectric sensor on the side thereof opposite the support, the upper member being made of a material having a coefficient of thermal expansion equal to or near the coefficient of thermal expansion used for the piezoelectric element and having electrodes (35b,35c) connected to electrodes (13b,13d) of the piezoelectric element, the piezoelectric element and the upper member being spaced apart and facing each other, outer leads (37) being connected to electrodes (35b,35c) of the upper member; and wherein the piezoelectric sensor further comprises a cover member (43) covering the periphery of a lamination including the lower member, the piezoelectric element and the upper member such that a space (45) is secured around the periphery of the piezoelectric element, the lamination covered by the cover member being sealed by a sealing material.
Claim 8
Dependent Claim
43 words
A piezoelectric sensor according to claim 6, wherein the lower and upper members have plan dimensions greater than the plan dimensions of the piezoelectric element, the space around the periphery of the piezoelectric element making use of the difference of said plan dimensions.
Claim 9
Dependent Claim
28 words
A piezoelectric sensor according to claim 1, wherein the support is made of one or more members of the group consisting of iron-nickel alloys, bronze, "kovar" and aluminium.
Claim 10
Dependent Claim
29 words
A piezoelectric sensor according to claim 3, wherein the lower member is made of one of more members of the group consisting of aluminium, steatite and PZT type ceramics.
Claim 11
Dependent Claim
18 words
A piezoelectric sensor according to claim 3, wherein the lower member is secured by adhesive to the support.
Claim 12
Dependent Claim
74 words
A piezoelectric sensor according to claim 3, wherein the lower member is made up of two or more sub-members individually made of different materials with different respective coefficients of thermal expansion, the coefficients of thermal expansion being different stepwise such that those of sub-members closer to the object under measurement are closer to that of the object and those of sub-members close to the piezoelectric element are closer to that of the piezoelectric element.
Claim 13
Dependent Claim
38 words
A piezoelectric sensor according to claim 2 or claim 3, wherein the vessel is made of a material with a coefficient of thermal expansion equal to or near the coefficient of thermal expansion of the object under measurement.
Claim 14
Dependent Claim
47 words
A piezoelectric sensor according to claim 2 or claim 3, wherein at least a portion (31a) of the vessel facing the piezoelectric body is made of a material with a coefficient of thermal expansion equal to or near the coefficient of thermal expansion of the piezoelectric body.
Claim 15
Dependent Claim
20 words
A piezoelectric sensor according to claim 4, wherein the upper member faces (39) the piezoelectric element via an intervening space.
Claim 16
Dependent Claim
20 words
A piezoelectric sensor according to claim 4, wherein the upper member faces the piezoelectric element via an intervening insulator (41).
Claim 17
Dependent Claim
26 words
A piezoelectric sensor according to claim 4, wherein the periphery of the piezoelectric element and the lower and upper members is covered by an insulator (41).
Claim 18
Dependent Claim
18 words
A piezoelectric sensor according to claim 15 or claim 16, wherein the insulator is silicon rubber type resin.
References Cited (Backward Citations)
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