To provide a collision detecting apparatus for a vehicle, including an
integrating member for cumulatively integrating an output from an
acceleration sensor when the output exceeds a specific calculation start
level, and a collision detecting member for outputting a collision signal
when a cumulative integral value calculated by the integrating member
exceeds a threshold value, wherein the collision detecting apparatus is
intended to accurately perform a collision decision by preventing the
occurrence of an erroneous detection based on a vibration waveform of
acceleration of the vehicle as a result of, for example, riding past a
stepped portion. The collision detecting apparatus includes a vibration
waveform detecting means W for detecting that an output waveform from the
acceleration sensor S is a specific periodical vibration waveform. When
the vibration waveform detecting member W detects the vibration waveform,
the integrating member does not stop the cumulative integration even if
the output G returns to a specific calculation end level G.sub.0 and
continues the cumulative integration for the output G that contains not
only an output component corresponding to a negative acceleration but also
an output component corresponding to a positive acceleration.
