Appeal No. 2003-0176
Application 08/909,590
THE INVENTION
The appellants claim an acceleration sensor which, the
appellants state (specification, page 1, lines 4-7), is useful
for an air bag installed in a vehicle. Claim 1 is illustrative:
1. An acceleration sensor comprising:
a piezoelectric element having at least three piezoelectric
layers, a plurality of first electrodes and a plurality of second
electrodes, said piezoelectric layers being stacked with each
other in a thickness direction thereof so as to form a laminate
having first and second opposed ends in a lengthwise direction
thereof, said first and second electrodes being provided
respectively and alternately at each interface between said
piezoelectric layers and on top and bottom surfaces of said
laminate such that said first electrodes extend from said second
end toward but not to said first end and said second electrodes
extend from said first end toward but not to said second end and
partially overlap with each other via said piezoelectric layers;
and
a support for holding said piezoelectric element at the
vicinity of the said first and second ends of said laminate,
wherein said piezoelectric layers are polarized in the
thickness direction thereof only at the region where the first
and second electrodes overlap such that charges having opposite
polarities are accumulated at said first and second electrodes,
respectively, and the same polarity of charge is accumulated on
at least one of said first and second electrodes by a pair of
said piezoelectric layers in contact with the at least one of
said first and second electrodes, when said piezoelectric element
receives an impact in the thickness direction caused by an
acceleration, said overlap area being selected to provide a
desired output voltage and static capacitance.
2
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