Collision detection apparatus and collision detection method

A collision detection method employed in a collision detection apparatus installed in a vehicle in order to detect a collision between the vehicle and an external object, the collision detection apparatus including:

• an energy absorption member that possesses conductivity and absorbs impact energy by being crushed in a predetermined crushing direction;
• two contact members that possess conductivity and are disposed in contact with front and rear end surfaces in a direction of a vehicle length of the energy absorption member in the crushing direction in order to press and crush the energy absorption member in the crushing direction;
• and
• an electric resistance detector that is electrically connected to both of the two contact members,
• the collision detection method comprising:
• an electric resistance detection step in which variation in an electric resistance value between the contact members accompanying crushing of the energy absorption member is detected by the electric resistance detector;
• and
• a displacement calculation step in which a displacement amount of the energy absorption member between the contact members in the crushing direction is calculated on the basis of the variation in the electric resistance value detected in the electric resistance detection step.