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).

Abstract: An air fuel ratio control system for an internal combustion engine having an electronic engine control module and an upstream and downstream exhaust gas oxygen sensor positioned in the engine exhaust gas stream. A first feedback loop includes the upstream EGO sensor. A second feedback loop includes a downstream EGO sensor and a trim bias signal to bias stored values provided from an air/fuel bias table. Such a biased signal is applied to an air fuel feedback controller which provides a feedback air fuel control signal to be applied to an open loop fuel controller.

Abstract: An air/fuel control system which includes feedback control from an exhaust gas oxygen sensor positioned upstream of a catalytic converter. The exact air/fuel ratio required optimum converter efficiency is determined by generating an emissions signal from both a HC/CO sensor and a NO sensor each positioned downstream of the catalytic converter. The feedback variable is trimmed by a signal derived from the emissions signal to maintain air/fuel operation at a value corresponding to maximum converter efficiency.

Abstract: An air/fuel control system for internal combustion engines having three-way (NOx, CO, and HC) catalytic converters. A feedback variable is generated by subtracting the normalized output of a nitrogen oxide sensor from the normalized output of a combined HC/CO sensor. The zero crossing point of the feedback variable identifies the operating point for optimal conversion efficiency of the catalytic converter and is used to trim liquid fuel delivery for maintaining optimal conversion efficiency.

Abstract: Method, for controlling fuel supply to an internal combustion engine utilizing a modulated air-fuel signal having a modified square-wave waveform, of monitoring operation of an oxygen sensor for sensing engine exhaust gas oxygen level. The method includes generating the modulated air-fuel signal having the modified square-wave waveform designed to produce a particular engine exhaust response for interrogating the oxygen sensor, and operating the engine based on the modulated air-fuel signal. The oxygen sensor produces an associated output signal in response to sensed exhaust gas oxygen levels. The method also includes processing the output signal of the oxygen sensor associated with the particular engine response so as to determine the operating condition of the oxygen sensor and to verify acceptable test conditions.

Abstract: A method of detecting catalyst malfunction in a vehicle uses an exhaust gas oxygen sensor downstream of the catalyst. A feedback loop controls the air-fuel ratio as a function of the output signal from the exhaust gas oxygen sensor. The feedback gain is increased from low gain to high gain and then operational parameters are examined. In a first version the amplitude of the exhaust gas oxygen sensor is used as an indication. In a second version, the amplitude of the exhaust gas oxygen sensor reaches a predetermined limit and then the feedback gain is examined. In a third version, limit-cycle operation is reached and the frequency of the limit-cycle is examined with respect to a predetermined frequency.

Abstract: An exhaust gas sensor system for use with an internal combustion engine having an exhaust conduit and a catalytic converter. The system includes an exhaust gas oxygen sensor, temperature sensor, and signal conditioner. The exhaust gas oxygen sensor is positioned on the conduit, downstream of the catalytic converter, and provides an oxygen level signal. The temperature sensor is also downstream of the catalytic converter, sensing the temperature of the oxygen sensor. A signal conditioner receives outputs from both the exhaust gas oxygen sensor and the temperature sensor. The oxygen level signal from the oxygen sensor is adjusted, according to the temperature sensed by the temperature sensor, to provide a more accurate oxygen level signal to other components of the engine such as, for example, an air-fuel controller.

Abstract: An exhaust gas oxygen sensor is used to control the air/fuel ratio of an internal combustion engine in combination with an electronic engine control. The exhaust gas oxygen sensor is positioned in the exhaust stream flow from the engine. The electronic engine control utilizes different air/fuel ratio feedback strategies depending upon whether the signal output from the exhaust gas oxygen sensor is saturated indicating a rich air/fuel ratio, saturated indicating a lean air/fuel ratio or operating in a linear region.

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).

Abstract: Disclosed is a method and apparatus for determining the hydrocarbon conversion efficiency of a catalytic converter used in conjunction with an internal combustion (IC) engine to reduce the pollutants contained in the IC exhaust gas comprising the steps of: (a) determining the hydrocarbon content of the IC exhaust gas prior to its entry into the catalytic converter by sampling the exhaust and passing the sample to a catalytic differential calorimetric sensor; (b) contacting the catalyst in the converter with the IC exhaust; (c) determining the hydrocarbon content of the exhaust leaving the catalytic converter by sampling the exhaust and passing the sample to the catalytic differential calorimetric sensor; and (d) comparing the hydrocarbon contents of the exhaust samples from steps (a) and (c) and thereby determining the hydrocarbon conversion efficiency of the catalyst in the converter.

Abstract: Apparatus, method and system are provided for monitoring catalytic converter efficiency in treating exhaust gas from an internal combustion engine. The air/fuel ratio fed to the engine is perturbed on a cylinder-to-cylinder basis above and below a mean or average air/fuel ratio. The signal from an exhaust gas exposed to the exhaust gas sensor downstream of the converter for the perturbation interval is compared to the signal for a non-perturbation interval. A signal is generated when the comparison indicates catalytic converter efficiency below a minimum acceptable level. The comparison may be carried out by comparing the difference in the mean value of the EGO sensor output signal for the perturbation and non-perturbation intervals to a preselected and stored reference value corresponding to the minimum acceptable efficiency. The efficiency monitoring test system may be incorporated into fuel control means for controlling air/fuel ratio during normal engine operation.

Abstract: An air fuel ratio control system for an internal combustion engine having an electronic engine control module and an upstream and a downstream exhaust gas oxygen sensor positioned in the engine exhaust gas stream. A first feedback loop includes the upstream EGO sensor and an air fuel bias table. A second feedback loop includes a downstream EGO sensor and a trim signal to change the stored values in the air fuel bias table.

Abstract: An on-board monitoring system for an automotive emission catalyst has (i) a test chamber remote from the automobile's engine exhaust gas stream; (ii) apparatus for supplying the chamber with sampled exhaust gases sequestered from the 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) apparatus for comparing the sensed signal with a reference signal, and, if a predetermined difference is exceeded, the catalyst is indicated as faulty. 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 apparatus for permitting flow-through of no more than one channel to the chamber at any one moment, preferably cycled at a certain frequency.

Abstract: An engine air/fuel control and catalyst monitoring means includes a first EGO sensor positioned upstream of a catalyst and a second EGO sensor positioned downstream of the catalyst. Outputs from both EGO sensors are applied to a complementary filter set. The output from the upstream EGO sensor is applied to a high pass filter section and the output from the downstream EGO sensor is applied to a low pass filter section. The summer receives inputs from each of the high pass and low pass filter sections and provides an output to a feedback controller which in turn controls a fuel metering system applying fuel to the engine. The downstream EGO sensor also provides a signal indicative of the efficiency of the catalyst.

Abstract: A system and method for controlling operation of an engine wherein a fuel vapor recovery system is coupled between an air/fuel intake and a fuel supply system. An air/fuel ratio indication is provided by a proportional plus integral feedback controller coupled to a two-state exhaust gas oxygen sensor. In response to the air/fuel ratio indication and a measurement of inducted air flow, a base fuel command is generated. To compensate for purging of fuel vapors, a reference air/fuel ratio is subtracted from the air/fuel ratio indication and the resulting error signal generated. This compensation factor represents a learned value which is directly related to fuel vapor concentration, and it is subtracted from the base fuel command to correct for induction of fuel vapors.

Abstract: A control system for an engine having both a fuel vapor recovery system and air/fuel ratio feedback control. The engine is equipped with a venturi in its intake passage. A vapor reservoir is coupled between the fuel vapor recovery system and a nozzle orifice positioned in the venturi throat. Vapor flow into the reservoir is regulated by a solenoid valve responsive to a pressure switch which is referenced to the venturi inlet pressure. Action of the pressure switch maintains reservoir pressure at the venturi inlet pressure such that vapor flow is linearly proportional to inducted air flow regardless of engine manifold pressure. In an alternate embodiment, the fuel tank is coupled to the venturi through a pressure regulating system as described above. The vapor recovery canister is independently coupled to the venturi through a similar pressure control system.

Abstract: A method of on-board detection of the degradation of an automotive catalyst which receives the emissions from an engine placed in a closed-loop feedback control with an A/F characteristic sensor immersed in the emissions. The method comprises: (a) artificially modulating the frequency and/or amplitude of the control for a predetermined burst period; (b) sensing an A/F characteristic by an independent sensor substantially immediately downstream of the catalyst at events prior to and during the burst period; and (c) determining if there is an absence of a substantial change between events in the independently sensed A/F characteristic, thus indicating a degraded catalyst. The artificial modulation changes the oxygen exposure of the catalyst during a short catalyst interrogation period in a manner to magnify the oxygen absorption characteristic of the noble metals within the catalyst.

Abstract: An internal combustion engine includes an air/fuel ratio control system for providing a desired fuel charge to the engine in relation to a measurement of inducted airflow. The mixture of inducted air and fuel is trimmed in response to an exhaust gas oxygen sensor for maintaining a desired air/fuel ratio. A fuel vapor recovery system is also included for inducting fuel vapors from the fuel system into the engine in proportion to inducted airflow. The desired fuel charge is corrected by a factor approximating response time of a change in vapor flow rate caused by a change in inducted airflow.

Abstract: A control system for engines equipped with both a fuel vapor recovery system and an air/fuel ratio feedback control system. The air/fuel ratio feedback control system regulates delivery of fuel in response to an exhaust gas oxygen sensor such that the mixture of air, fuel, and recovered fuel vapor approximates a desired air/fuel ratio. The fuel vapor recovery system includes two parallel solenoid valves which are phased controlled by a phase controller responsive to a measurement of inducted airflow such that total purge flow through both valves is proportional to inducted airflow.

Abstract: A control system and method for an internal combustion engine and receiving inducted fuel vapors from a fuel vapor recovery system. An electronically actuated solenoid valve coupled to the fuel vapor recovery system regulates rate of vapor flow in response to the duty cycle of a desired rate of vapor flow command. The pressure differential across the valve is regulated to achieve substantially sonic vapor flow such that vapor flow is independent of engine manifold pressure fluctuations and linearly proportional to the duty cycle of the desired vapor flow command. An air/fuel ratio feedback control system is thereby able to maintain a desired air/fuel ratio during changes in inducted airflow.