Capacitance type accelerometer for air bag system

A capacitance-accelerometer, comprising:

• a fixed electrode;
• and
• a movable electrode being supported by a cantilever at a portion adjacent to said fixed electrode having a gap thereinbetween;
• wherein grooves having openings which are disposed of at at least one side of said electrodes and are inter-connected with each other, are provided on a surface of said movable electrode, and
• said grooves are so arranged that electrode surface areas divided by said grooves are symmetrical with respect to a symmetrical axis parallel to said cantilever.

A capacitance-accelerometer comprising:

• a fixed electrode;
• and
• a movable electrode being supported by an elastic body and facing said fixed electrode at a portion having a gap thereinbetween;
• wherein grooves are provided on a surface of said movable electrode to divide said surface into a plurality of electrode surface areas,
• said grooves are so arranged that said plurality of electrode surface areas divided by said grooves are uniformly balanced, and
• end portions of said grooves open to four sides of said movable electrode.

A capacitance-accelerometer, comprising:

• a movable electrode being supported by an elastic body;
• and
• fixed electrodes, said movable electrode being disposed thereinbetween said fixed electrodes and said fixed electrodes facing respective surfaces of said movable electrode at a portion having a gap thereinbetween;
• wherein a plurality of grooves crossing each other on the surface of said movable electrode,
• end portions of said grooves open to an outside portion at the portion between said fixed electrodes and said movable electrode through openings, and
• through-holes leading to both surfaces of said movable electrode are formed at crossing points of said grooves.