Page 81 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Chapter 1.3

Ford Motor Co. - Ford France SA - Ford Werke AG - Ford

Motor Co. Canada - Ford Motor Co. Ltd.

Ford has presented since 1992 a significant number of methods concerning diagnostic methods
of deterioration of catalytic converters. Most of these methods, except otherwise mentioned,
have been applied for the engine layout of fig. 29 (see EP0619420 (1994)).

The controller is shown in the b!ock diagram of fig. 29 as a conventional microcomputer
including: microprocessor unit, input ports, output ports, read-only memory (ROM) for
storing the control program, random access memory (RAM) for temporary data storage which
may also be used for counters or timers, keep-alive memory for storing learned values and a
conventional data bus.

The controller is shown receiving various signals from sensors coupled to the engine including:
measurement of inducted mass airflow from a mass airflow sensor, engine coolant temperature
!?om a temperature sensor, and indication of engine speed (rpm) from a tachometer.

The output signal VI from a conventional exhaust gas oxygen sensor 1, positioned upstream
of catalytic converter, is compared to a reference value associated with stoichiometry in a
comparator for providing a compared output signal VI. Compared signal VI is a two-state
signal which is a predetermined high voltage when exhaust gases are rich of stoichiometry and

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