Anti-theft system for disabling a vehicle engine

Abstract

A vehicle anti-theft system that disables a vehicle engine upon detection of an unauthorized vehicle start-up, after the engine is running, by disconnecting the vehicle battery and draining the alternator voltage to ground through a resistor. A fob transmitter transmits a coded frequency signal that is received by a receiver associated with the anti-theft system to arm the system. When the system is armed, it monitors whether the engine is running and has been recently started using a combination of vibration detection, voltage fluctuations in the battery voltage and the actual battery voltage. If the system determines that the engine is running and has been recently started, the system will issue a first command that opens a relay switch to disconnect the battery and a second command that closes a switch to connect the alternator to ground through the resistor. In order to prevent a vehicle from being jump started by using a second battery, the system includes a reset clock and associated delay that resets the decision to connect the alternator to ground at periodic intervals so as to repeatedly test for the presence of the second battery and cause the engine to stall after the second battery is disconnected. A driver entry detection portion of the system determines whether someone has entered the vehicle, and issues a chirp signal to notify the occupant that the system is armed. A state of charge algorithm is also provided to determine whether the battery voltage has reached a minimum state of charge for reliably starting the vehicle, and also disconnect the battery once the minimum level has been reached.

Dependencies are inferred from the claim text.