Acceleration sensor and triaxial acceleration sensor

A triaxial acceleration sensor comprising:

• a piezoelectric ceramic substrate;
• a surface electrode pattern formed on a front surface of said piezoelectric ceramic substrate and including one or more X-axis direction acceleration detecting electrodes for detecting acceleration in an X-axis direction, one or more Y-axis direction acceleration detecting electrodes for detecting acceleration in a Y-axis direction, one or more Z-axis direction acceleration detecting electrodes for detecting acceleration in a Z-axis direction, one or more X-axis direction acceleration output electrodes, one or more Y-axis direction acceleration output electrodes, one or more Z-axis direction acceleration output electrodes, a first wiring pattern for connecting said X-axis direction acceleration detecting electrodes and X-axis direction acceleration output electrodes to each other, a second wiring pattern for connecting said Y-axis direction acceleration detecting electrodes and Y-axis direction acceleration output electrodes to each other, and a third wiring pattern for connecting said Z-axis direction acceleration detecting electrodes and Z-axis direction acceleration output electrodes to each other;
• a counter electrode pattern formed on a rear surface of said piezoelectric ceramic substrate and arranged opposite to at least said X-axis direction acceleration electrodes, Y-axis direction acceleration detecting electrodes and Z-axis direction acceleration detecting electrodes;
• a weight of a cylindrical or hollow-cylindrical shape arranged in a manner to be fixed with respect to said piezoelectric ceramic substrate to generate stress depending on said acceleration in a region in which said X-axis direction acceleration detecting electrodes, Y-axis direction acceleration detecting electrodes and Z-axis direction acceleration detecting electrodes each are arranged;
• and
• low-dielectric layers arranged between all of at least said first to third wiring patterns or an essential part thereof and said piezoelectric ceramic substrate;
• said low-dielectric layers being substantially reduced in relative dielectric constant and being of sufficient thickness, as compared with that of said piezoelectric ceramic substrate so that any loss in the acceleration signal outputted from each of said output electrodes due to an electrostatic capacity formed between said wiring patterns, and output electrodes and said counter electrode pattern is minimized;
• said piezoelectric ceramic substrate being polarized at a portion thereof between each of said X-axis direction acceleration detecting electrodes, Y-axis direction acceleration detecting electrodes and Z-axis direction acceleration detecting electrodes and said counter electrode pattern.