Patent ID: 6978200

Claim:
An activation device for a passenger protection apparatus which is made to activate said passenger protection apparatus in accordance with a behavior of a vehicle, comprising: an angular velocity sensor for detecting a roll angular velocity of said vehicle; relative angle calculating means for calculating a roll relative angle of said vehicle on the basis of the roll angular velocity detected by said angular velocity sensor; roll judging means for making a judgment indicating the occurrence of a roll of said vehicle when the roll angular velocity detected by said angular velocity sensor and the vehicle roll relative angle calculated by said relative angle calculating means satisfy a predetermined threshold condition; drive control means for activating said passenger protection apparatus when said roll judging means makes the vehicle roll judgment; a plurality of acceleration sensors for detecting accelerations of said vehicle in lateral directions; collision state discriminating means for making a discrimination of a collision state of said vehicle on the basis of the accelerations detected by said plurality of acceleration sensors; and threshold switching means for setting said predetermined threshold condition for the vehicle roll judgment in accordance with the collision state discriminated by said collision state discriminating means wherein said roll judging means sets a threshold line on a two-dimensional map using a roll angular velocity and a roll relative angle as parameters and makes a judgment indicating the occurrence of a roll of said vehicle when a history line drawn on the basis of the roll angular velocity detected by said angular velocity sensor and the roll relative angle calculated by said relative angle calculating means runs from a non-roll area lying on a side of an origin with respect to said threshold line to a roll area lying on a side opposite to said origin with respect to said threshold line, and said threshold switching means sets said threshold line in accordance with the collision state discriminated by said collision state discriminating means.