Patent ID: 6167697
Filing Date: 2001-01-02
Classification: F02D

Abstract:
A device (1) for controlling the air/fuel ratio of the mixture supplied to an endothermal engine (2), in which a catalytic converter (8) is disposed along an exhaust duct (7) for the combusted gases from this engine, the device (1) comprising a first (11) and a second (12) oxygen sensor which are disposed along the exhaust duct (7) upstream and respectively downstream of the catalytic converter (8) and are adapted to generate as output a first (V1) and a second (V2) signal indicating the stoichiometric composition of the exhaust gases, this device (1) comprising: a first closed loop control circuit (13) which is adapted to receive as input this first signal (V1) and is adapted to calculate a correction parameter (KO2) adapted to be applied to a theoretical value (Qt) of a quantity of fuel calculated in an open loop in order to obtain a corrected quantity of petrol (Qeff) for a fuel injection unit (4) of the engine (2); and a second control circuit (14) which receives as input the second signal (V2) and is connected as output to the first control circuit (13) in order to supply a correction signal (KO22) adapted to modify the correction parameter (KO2); the device (1) being characterised in that the second control circuit (14) comprises a first control branch (30) comprising: first sampling means (37) adapted to sample the second signal (V2) at a predetermined first frequency (f2); first processing means (38, 40, 41) cooperating with the first sampling means (37) in order to generate a first parameter (Vd) that is a function of the difference between the sampled values of the second signal (V2) at successive sampling instants, these first processing means (38, 40, 41) being adapted to process (41) the first parameter (Vd) in order to supply a first contribution (Vu) to the correction signal (KO22) and to ensure that the second signal (V2) tends rapidly to be brought and to remain in an interval of values (BM) corresponding to a zone of maximum efficiency of the catalytic converter (8).