Abstract: An air/fuel control system having a feedback variable generated by modulating fuel flow into the engine, generating an error signal from a difference between the average of an exhaust gas oxygen sensor output and a reference value correlated with a desired air/fuel ratio, and integrating the error signal. The reference value is periodically offset in both lean and rich air/fuel directions. A biasing signal is generated from an exhaust gas oxygen sensor position downstream of the converter in response to the air/fuel offset. After removing the offset from the reference value, the bias signal is applied thereto for centering engine air/fuel operation within the peak efficiency window of a catalytic converter.

Abstract: A system and method to control the ignition timing of engine (28) are used to rapidly warm a catalytic converter (52). A controller (8) calculates (402) hydrocarbon efficiency of the converter (52) from a ratio of the integrals of hydrocarbon sensors respectively positioned downstream (48) and upstream (46) of the converter (52). The controller retards ignition timing to a value retarded from nominal ignition timing (416, 426) when the calculated hydrocarbon efficiency is less than a desired efficiency (418).

Abstract: An air/fuel control system for an engine (10) provides an air/fuel indicating signal linearly related to average engine air/fuel operation from a two-state exhaust gas oxygen sensor (76). Fuel delivered to the engine is modulated with a periodic or modulation signal (244). The modulation signal is offset in either a fuel increasing or a fuel decreasing direction when the air/fuel indicating signal is respectively saturated at either a lean or a rich value (394-420).

Abstract: An air/fuel control system for an engine (28) provides an air/fuel indicating signal linearly related to average engine air/fuel operation from a two-state exhaust gas oxygen sensor (44). Fuel delivered to the engine is modulated with a periodic signal (144). A reference value corresponding to a desired air/fuel ratio is subtracted from a rolling average of the exhaust gas oxygen sensor output to provide an error signal (148-152). A feedback variable (FV) for adjusting the engine air/fuel ratio is generated from a proportional plus integral controller having the error signal as its input (156). In this manner, average engine air/fuel ratio is maintained at the desired air/fuel ratio and the rolling average of the exhaust gas oxygen sensor output provides an air/fuel indicating signal.

Abstract: An engine air/fuel control system and method is provided having feedback control responsive to an exhaust gas oxygen sensor. A fuel command responsive to the EGO sensor is modulated (312) and the modulation disabled in response to detection of an air/fuel transient period (502-510, 610). In addition, feedback control gain is increased (514, 614) and the modulation signal held at a value opposite the state of the EGO sensor occurring upon initiation of the air/fuel transient period (510, 610). An indication is provided that the air/fuel transient is terminated when the EGO sensor switching frequency resumes a normal condition (522-528, 622-628). Modulation is thereafter resumed and the feedback gain restored (532-538, 632-638).

Abstract: An engine air/fuel control system modulates the flow of fuel delivered to the engine with a modulation signal (100, 144) The feedback variable generated (210-228) from a two-state exhaust gas oxygen sensor (16) corrects the fuel flow (156). During each of a plurality of pre-determined intervals, the fuel flow is biased with a rich offset (342). Amplitude of the modulation signal is corrected by a difference between the feedback variable generated during two successive occurrences of the predetermined interval (346-378).

Abstract: An air/fuel control system for an engine (28) provides an air/fuel indicating signal linearly related to average engine air/fuel operation from a two-state exhaust gas oxygen sensor (44). Fuel delivered to the engine is modulated with a periodic signal (144). Adaptive feedback control (steps 200-280) adaptively learns a desired amplitude for the periodic signal to generate the air/fuel indicating signal with desired sensitivity and operating range.

Abstract: A fuel control system operates under closed-loop control to sense the oxygen content of the combustion products of an internal combustion engine along with the engine angular velocity and air flow through the intake manifold and to alter the composition of air and fuel combusted by the engine, such that under stable closed-loop control, the air/fuel composition generally oscillates about stoichiometry between a minimum and a maximum value. The rate of fluctuation of the oxygen content of the combustion products is monitored and if the oxygen content does not switch when expected, then a transient change in the exhaust content of the exhaust gas is assumed and a transient response is generated. The transient response comprises the generation of an air/fuel ratio substantially equal in magnitude and time but opposite in direction from the detected transient. After the transient response, periodic fluctuation of the air/fuel ratio between the minimum and maximum values is resumed.

Abstract: An engine air/fuel control system is shown (300-428) responsive to a feedback variable derived (410-428) from an exhaust gas oxygen sensor (16) positioned upstream of a catalytic converter (20). A non-catalytic exhaust gas oxygen sensor (24) having a non-catalytic electrode (490) positioned in the engine exhaust downstream of the converter (20) is coupled to a current pumping circuit (28). Current is pumped into an electrode of the downstream sensor (24) shifting its output step change towards richer air/fuel ratios. Pumping current is gradually increased in amplitude until the downstream sensor (24) incurs a change in its output state (602-634). The pumping current occurring at the time of such change in output states provides a measurement of catalyst efficiency.

Abstract: A control system and method maintains engine air/fuel operation near stoichiometry (104-178) in response to exhaust gas oxygen sensors (44,52) positioned both upstream and downstream of a catalytic converter (50). A non-catalytic exhaust gas oxygen sensor (54), having non-catalytic electrode, is positioned downstream of the converter (50) and its output voltage (Vo) monitored. Pumping current (Ip) is applied to an electrode of the non-catalytic sensor at a predetermined magnitude (IPREF) from a pumping current generator (56). When the output voltage (Vo) is detected at a predetermined high voltage range (302-318) an indication of degraded converter efficiency is provided (320).

Abstract: Air/fuel and ignition control of engine (28) are used to more rapidly heat-up a catalytic converter (52). A control system (8) generates a fuel command (100) for fuel delivery to the engine (28) based upon at least an amount of air inducted into the engine. The fuel command is offset by a predetermined amount in a lean direction during a period after engine start to shift the engine exhaust gas mixture towards a preselected air/fuel ratio lean of stoichiometry (106-122). In addition, the fuel command is corrected by a correction value so that the exhaust gas mixture is shifted ore closely to the preselected air/fuel ratio (126-140). Correction values are adaptively learned (300-324) during a portion of the warm-up period from a feedback signal derived from an exhaust gas oxygen sensor (44). Ignition timing and engine idle are also controlled (350-374) to further achieve more rapid warm-up of the catalytic converter (52).

Abstract: An air/fuel control system (8) generates a fuel command (100) for fuel delivery to the engine (28) based upon at least an amount of air inducted into the engine. This fuel command is trimmed by a feedback variable derived (240-282) from an exhaust gas oxygen sensor (44) when feedback control is initiated. Feedback control is commenced when the peak-to-peak output of the sensor is less than a threshold value (122-128) while pumping current applied to a sensor electrode is modulated (122-128). Modulation is then removed but the pumping current is maintained to shift the sensor output to a preselected lean air/fuel ratio (128). Lean air/fuel feedback control continues until the converter is warmed (130-140).

Abstract: An engine air/fuel control system (8) and method for controlling an engine (28) coupled to a catalytic converter (50) and for providing a measurement of engine emissions (202-296). Nitrogen oxides concentration, hydrocarbon concentration, and carbon monoxide concentration of exhaust gases downstream of the converter are measured (46, 54, and 52). Each concentration measurement is averaged for the speed load cell in which such measurement occurred (244-256). Each concentration average measurement is converted to a measurement of mass emissions emitted during a test cycle (268-284). Fuel delivered to the engine is corrected by a feedback variable (104-134, 158-178) derived from both an exhaust gas oxygen sensor (44) positioned upstream of the converter and the three sensors positioned downstream of the converter (46, 52, 54). A measurement of emissions in response to the averaged mass measurements of emission concentration downstream of the converter is also provided (278-296).

Abstract: An on-board monitoring system for an automotive emission catalyst [having] has (i) a test chamber remote from the automobile's engine exhaust gas stream; (ii) [means] apparatus for supplying the chamber with sampled exhaust gases sequestered from said stream; (iii) a single hydrocarbon sensor exposed to the exhaust gas in the chamber to render a signal responsive to the concentration of hydrocarbon in the chamber; and (iv) [means] apparatus for comparing the sensed signal with a reference signal, and, if a predetermined difference is exceeded, the catalyst is indicated as faulty. [Means (ii) may have] Apparatus (ii) has a supply channel interconnected between the chamber and the gas stream upstream of the catalytic converter, a supply channel independently interconnected between the chamber and the gas stream downstream of the catalytic converter, and valve [means] apparatus for permitting flow-through of no more than one channel to said chamber at any one moment, preferably cycled at a certain frequency.

Abstract: Engine air/fuel ratio is controlled in response to a comparison of an exhaust gas oxygen sensor output with a reference value. A correction voltage is generated which is related to a change in the midpoint between saturated output states of the sensor during a test period in which engine air/fuel operation is first forced rich and then forced lean of a preselected air/fuel ratio. The sensor output amplitude is shifted with the correction voltage to reduce variations between the reference value and the midpoint.

Abstract: A system for maintaining engine air/fuel operation within the efficiency window of a catalytic converter. Fuel delivered to the engine is adjusted in response to a step change in an output of an exhaust gas oxygen sensor positioned upstream of the converter. The step change is shifted in response to an error signal derived from a downstream emissions sensor.

Abstract: A control system for maintaining engine air/fuel operation within the efficiency window of a catalytic converter. An exhaust gas oxygen sensor having a step change between first and second output states and positioned downstream of the converter. A step change in the downstream sensor output is initialized to an initial air/fuel ratio by pumping current through one of the sensing electrodes of the downstream sensor. An emission control signal is derived from the initialized downstream sensor output to bias an air/fuel feedback loop.

Abstract: An engine air/fuel feedback control system adjusts the engine air/fuel ratio in response to a modified output of an exhaust gas oxygen sensor. A sensor output is compared to a reference at its nominal midpoint to develop a two-state signal indicating operation rich or lean of stoichiometry. This two-state or step output is shifted towards the peak efficiency window of a catalytic converter by pumping current through a sensor electrode in response to an error signal derived from a downstream sensor. Shifts in the upstream sensor amplitude caused by current pumping are corrected by a correction factor which is adaptively learned during a test cycle.

Abstract: A fuel control system operating under closed-loop control senses the oxygen content of the combustion products of an internal combustion engine along with the engine angular velocity and air flow through the intake manifold. The fuel control system supplies an air/fuel modulation signal to modify a fueling value which is calculated as a function of the engine angular velocity and air flow. An oxygen sensor monitoring test is performed periodically to determine the efficacy of the oxygen sensor. The total switching time of the oxygen sensor, comprising the lean-to-rich and rich-to-lean switching times, is determined and checked against a range. If the total switching time is within the range then the difference between the lean-to-rich and rich-to-lean switching times, is determined and checked against a second range. If the difference is within the second range the oxygen sensor is determined to be operating effectively and the test is terminated.

Abstract: A method of monitoring, while on board an automotive vehicle, one or more of catalyst performance, engine misfire, and combustion quality, the vehicle having an internal combustion engine equipped with a catalyst for converting noxious emissions of the engine, comprising: (i) exposing at least one pair of EGO sensors to substantially the same emissions either exiting from the engine or from the catalyst, one of the EGO sensors having its electrode highly catalytic, and the other sensor having its electrode low-to-noncatalytic; (ii) comparing the outputs of the sensor electrodes (amplitude, frequency, or phase shift) to determine if there is a sufficient differential to indicate a misfire or poor combustion in the case of the sensors being located downstream of the engine exhaust but upstream of the catalyst, or indicating poor catalyst efficiency in the case of the sensors being placed substantially immediately downstream of the catalyst. The catalyst may be a three-way catalyst (or an oxidation catalyst).