US Patent 7099763 Vehicle rapid deceleration detection device

A vehicle speed memory unit stores a vehicle speed at a prior predetermined time, the vehicle speed being calculated from an interval of the vehicle speed pulse. A first rapid deceleration detecting section compares an elapsed time from a time the vehicle speed pulse signal is inputted, measured by an elapsed time measuring unit, with a pulse interval corresponding to a predetermined deceleration relative to a vehicle speed stored by the vehicle speed memory unit, or a second rapid deceleration detecting section calculates an undetermined vehicle speed from the elapsed time measured by the elapsed time measuring unit, and calculates a deceleration from the undetermined vehicle speed and the vehicle speed at the prior predetermined time, and compares the calculated deceleration with a predetermined deceleration threshold value. Thus, rapid vehicle deceleration can immediately be determined at the present time without waiting for the determination of the vehicle speed after input of the next pulse signal.