Abstract: A catalyst monitoring system is provided for monitoring catalyst efficiency in a catalytic converter of a motor vehicle. The catalyst monitoring system includes a catalyst monitor receiving electrical signals indicative of oxygen in the exhaust gas from a first oxygen sensor positioned between the vehicle's engine and the catalytic converter and a second oxygen sensor positioned downstream from the catalytic converter. Each of these input signals are filtered in the catalyst monitor such that a particular range of frequencies that encapsulate information regarding catalyst efficiency are passed. The filtered signals are then used to establish an amplitude ratio between the downstream oxygen signal and the upstream oxygen signal, such that the algorithm output linearly correlates to catalyst efficiency of the catalytic converter. Digital signal filtering is preferably implemented using a finite impulse response bandpass filter, a full-wave rectifier, a low pass filter, a sampler and a signal normalizer.

Abstract: The present invention overcomes these problems by providing an oxygen sensor located in the exhaust stream of an internal combustion engine, a load sensing device which generates a signal indicative of an internal combustion engine load, a central processing unit which calculates a running average of the oxygen content in the exhaust stream indicated by the oxygen sensor and a fuel injection device which supplies fuel to the combustion air in response to the central processing unit. The central processing unit uses the running average of the oxygen content in the exhaust stream, in lieu of the instantaneous oxygen content, to modify the fuel equation for determining the proper air fuel mix when transitioning from closed to open loop operation. The resulting air fuel mixture thus reflects the average oxygen value in the exhaust over a period of time. This average serves to cancel out the extreme surplus and deficiency of oxygen in the exhaust stream due to dithering.

Abstract: A system and method for monitoring efficiency of a catalytic converter count switches of at least one upstream sensor interposed the engine and the converter and count switches of a downstream sensor, interposed the converter and atmosphere, during a definite time period after a switch of the at least one upstream sensor to account for propagation delay of exhaust gases traveling between the at least one upstream and downstream sensor. Upstream sensor switches may optionally be counted only if predetermined entry conditions are satisfied while downstream switches occurring during respective definite time periods after an upstream switch are counted without regard to the entry conditions. A switch ratio based on the number of switches of the at least one upstream sensor and switches of the downstream sensor is used to monitor conversion efficiency of the catalyst.

Abstract: A method and apparatus converts time-resolved sensor signals into transfer functions and/or cumulative transfer function signals which can be attained by computation means such as by using Fast Fourier Transforms. A signal, as a means to assess catalyst performance such as a signal based on sensing oxygen concentration or air to fuel ratio or hydrocarbon concentration in motor vehicle exhaust in accordance with the present invention is in the time domain and has multiple components at different frequencies. The use of Fast Fourier Transforms isolates the various spectral densities which arise from different frequency components of the complex time domain signal. Cross spectral density function and power spectral density function are used to determine the transfer function. The analysis has been found to be substantially independent of operating conditions. The transfer function and cumulative transfer function have been found to be a precise indication of the catalyst performance.

Abstract: Process for the quantitative determination of gasoline film deposited on the intake manifold of an engine with controlled ignition, which comprises the following steps:a) feeding of a first set of injectors (I) with a first fuel selected from those which do not leave deposits in the feeding manifold;b) opening of the second set of injectors (II) fed with a second fuel to be tested, until an equilibrium stage of the air/fuel ratio equal to that of step (a) is reached;c) calculation of the mass of fuel film by integrating the difference in the flow-rate values measured in step (b).

Abstract: The invention relates to a process for monitoring the operativeness of a catalytic converter used to clean the exhaust gas in an internal combustion engine that is regulated by a lambda sensor through temperature measurement with a heat tone sensor exhibiting a catalytically active coating. The process provides information on both the percentage of individual, non-converted exhaust components and on the current thermal load on the catalytic converter. Readings are taken by the heat tone sensor at time intervals corresponding to the normal regulating frequency of the lambda sensor. This results in a quadratic function in which the height of the amplitude represents the percentage of non-converted individual exhaust components. The mean temperature of the catalytic converter can be inferred by rectifying the quadratic function.

Abstract: An engine control system includes an inverse model which includes a forward model and a feedback loop, wherein an actuating parameter, such as the quantity of fuel injected from a fuel injector, outputted from the forward model is used as a controlled variable, such as the air-fuel ratio in an exhaust system, inputted into the inverse model through the feedback loop. The forward model has preferably a learning function using condition-indicating factors such as engine speed and throttle angle. Accuracy of the inverse model is improved and appropriate engine control can be realized even during a transient state of the engine.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor for detecting the air-fuel ratio of exhaust gases from the engine. An ECU estimates the air-fuel ratio of a mixture supplied to each of the cylinders cylinder by cylinder in response to an output from the air-fuel ratio sensor, by using an observer based on a model representative of the behavior of the exhaust system. Cylinder-by-cylinder air-fuel ratio control amounts corresponding respectively to the cylinders are calculated for carrying out feedback control of the air-fuel ratio of the mixture such that each of the estimated air-fuel ratio is converged to a desired value.

Abstract: The device for determining deterioration of a catalytic converter includes a catalytic converter disposed in the exhaust gas passage of the engine and an air-fuel ratio sensor disposed on the exhaust gas passage downstream of the catalytic converter. The device performs two types of determining operations based on the length of the output response curve of the downstream air-fuel ratio sensor, one is a deterioration determining operation which determines whether the catalytic converter has deteriorated and the other is a normal determining operation which determines whether the catalytic converter is normal. The device also estimates the temperature of the catalytic converter based on the operating condition of the engine, and sets a deterioration diagnosis intake air flow range and a normal diagnosis intake air flow range in accordance with the estimated temperature of the catalytic converter.

Abstract: A method for monitoring the efficiency of a catalytic converter in a motor vehicle includes the steps of determining if at least one predetermined condition is met for monitoring the efficiency of the catalytic converter. The method includes biasing a fuel feedback multiplier of an internal combustion engine of the motor vehicle to run rich or lean if the at least one predetermined condition is met. The method includes counting a number of switches across a predetermined switch point from an upstream oxygen sensor and a downstream oxygen sensor. The method includes calculating a switching frequency ratio based on the count of the switches from the upstream oxygen sensor and downstream oxygen sensor and using the switching frequency ratio to establish the efficiency level of the catalytic converter.

Abstract: This invention pertains to a vehicular on-board diagnostic emission system in which the system determines whether the vehicle is continuously in compliance with regulatory emission standards by sensing only hydrocarbon and carbon monoxide emissions at a position downstream from the three way catalytic converter. All emission data sensed is correlated to a basic vehicle function, such as speed, and sorted into a number of histograms corresponding to vehicle operating conditions specified by emission regulations. The histograms are sampled in a statistically validated manner to determine if the vehicle complies with emission standards. If a failure has occurred, further histogram diagnostic routines are sequentially implemented to determine which emission system of the vehicle has failed.

Abstract: A system and method measures hydrocarbon conversion efficiency of a catalytic converter (501). Total-combustible sensors (511, 521) are positioned to measure exhaust gas on both sides of the catalytic converter (501). Signals from these sensors (511, 521) have a magnitude comprised of a first portion, dependent on a concentration of the hydrocarbon gas in the gas stream, and a second portion, dependent on a concentration of the other combustible gasses in the gas stream, where a magnitude relationship between the first portion and the second portion is variable when the gas stream transitions into a region on the rich side of stoichiometry. The signals from these sensors (511, 521) are filtered so that a magnitude relationship between a first and second portion of the filtered signals is constant when the gas stream (506) transitions into the region on the rich-side of stoichiometry. Hydrocarbon conversion efficiency (529) is computed dependent on the filtered signals (515, 525).

Abstract: A method for monitoring the conversion capacity of a catalytic converter assesses a conversion capacity of a preliminary catalytic converter by calculating thermal energy generated in a reference catalytic converter that is not catalytically coated in accordance with a temperature model and making a comparison with a measured thermal energy generated in the preliminary catalytic converter. A measure of the conversion capacity of the preliminary catalytic converter is ascertained from the difference, and it is compared with a comparison value. The preliminary catalytic converter has an adequate conversion capacity if the difference is above the comparison value.

Abstract: A method is provided for determining wall wetting for an engine which includes running a multi-cylinder engine at a predetermined speed and load. The fuel delivery and spark to one of the cylinders is then interrupted. The hydrocarbon level exhausted from the cylinder is then measured for a predetermined number of engine cycles. The test results can then be curve fitted to the relationship HCPPM=(A+B* engine cycle).sup.(1/exp). In this relationship, HCPPM is the hydrocarbon count in parts per million, A and B are each constants, and the exponent exp is derived using an iterative process. The exponent which is derived is the main qualifier for wall wetting.

Abstract: In a heated type oxygen sensor having a sensing element responding to changes in the exhaust oxygen content and a heater inside, a diagnostic system for diagnosing deterioration of the heated type oxygen sensor comprises an electronic control unit being responsive to an engine temperature for discriminating whether the engine is in a cold-engine state or in a fully warmed-up state. The diagnostic system includes a first warm-up time setting circuit for setting a predetermined oxygen sensor's warm-up time at a first delay time which is preset to be suitable for the cold-engine state, during cold-engine operations, and a second warm-up time setting circuit for setting the predetermined oxygen sensor's warm-up time at a second delay time which is preprogrammed to be suitable for the fully warmed-up state, during fully warmed-up engine operations.

Abstract: In a method for checking the function of the electrical heater of a lambda probe in the exhaust line of an internal combustion engine, the electrical resistance of the heater is measured. Measurement of the electrical resistance of the heater is performed using a measuring current that is smaller than the heater current. During the measurement, the heater current switched off. The electrical resistance of the heater is preferably connected to a positive voltage to supply the (heating or measuring) current.

Abstract: An apparatus and a method for judging the deterioration state of a catalyst device and an oxygen content sensing device are disclosed, in which virtual signals are generated to accurately determine the deterioration state of the catalyst device and the oxygen content sensing device by utilizing theoretical oxygen content sensing signals which are calculated in accordance with the operation state of automobiles.

Abstract: An air/fuel ratio control apparatus for executing auxiliary control of an air/fuel ratio by compensating an injected fuel amount set by a control system for maintaining the air/fuel ratio at a preset value. The air/fuel ratio control apparatus includes a state detecting unit for detecting a plurality of physical values which can be measured at low temperature and which show a state of an engine, an air/fuel ratio estimating unit for receiving a plurality of physical values detected by the state detecting means as input parameters and for estimating the air/fuel ratio using a neural network, and a compensatory fuel amount calculating unit for calculating a compensatory fuel amount for the injected fuel amount from the estimated air/fuel ratio. Here, low temperature refers to a temperature at which an air/fuel sensor cannot operate.

Abstract: A system and method estimates tailpipe emissions by sensing (703) a catalyzed gas stream (506) and providing a total-combustible gas signal (511) dependent thereon. The total-combustible gas signal (511) has a magnitude comprised of a first portion, dependent on a concentration of the hydrocarbon gas in the catalyzed gas stream (506), and a second portion, dependent on a concentration of the other combustible gasses in the catalyzed gas stream (506). A magnitude relationship between the first portion and the second portion is variable when the catalyzed gas stream (506) transitions into a region on the rich side of stoichiometry. The variability the magnitude relationship of the first and second portions is filtered out so that the magnitude relationship is substantially constant when the catalyzed gas stream (506) transitions into the region on the rich side of stoichiometry.

Abstract: A catalytic reaction system for promoting hydrocarbon reduction during periods of fuel rich engine operation of a multicylinder internal combustion engine which operates from signals generated by a microprocessor based engine controller. Each cylinder is fueled by an injection means, signalled by the engine controller. The amount of fuel injected into each cylinder may be different, so that each cylinder can be operated at different fuel/air ratios. The microprocessor senses metered air intake, ambient temperatures, engine speed and exhaust gas oxygen content. The sensed information is used to calculate the amount of oxygen needed by the catalytic converter to efficiently remove hydrocarbons and by adjusting the fuel/air ratios in one or more cylinders, effects the quantity of oxygen fed to the exhaust gas.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system, for detecting the air-fuel ratio of exhaust gases from the engine. An ECU calculates an air-fuel ratio control amount, based on the output from the air-fuel ratio sensor, by using an adaptive controller having an adaptive parameter-adjusting mechanism for adjusting adaptive parameters, such that the air-fuel ratio of a mixture supplied to the engine is converged to a desired air-fuel ratio, and controls the air-fuel ratio of the mixture in a feedback manner, according to the calculated air-fuel ratio control amount. The adaptive parameter-adjusting mechanism calculates a parameter corresponding to an integral term of the air-fuel ratio control amount, and limit-checks a value of the parameter corresponding to the integral term so as to fall within a predetermined limit range.

Abstract: There is provided an air-fuel ratio control system for an internal combustion. An air-fuel ratio sensor arranged in the exhaust system detects an air-fuel ratio of exhaust gases emitted from the engine. An amount of fuel to be supplied to the engine is controlled in response to the output from the air-fuel ratio sensor by using a controller of a recurrence formula type, such that an air-fuel ratio of a mixture supplied to the engine is converged to a desired air-fuel ratio, to thereby effect feedback control of the air-fuel ratio of the mixture. The desired air-fuel ratio is determined based on operating conditions of the engine. The desired air-fuel ratio is smoothed when the engine is in a predetermined operating condition. The feedback control of the air-fuel ratio is carried out by the use of the smoothed desired air-fuel ratio.

Abstract: A catalyst system employed in the exhaust stream of an internal combustion engine (10) wherein the catalyst deterioration is monitored by an engine controller (26) connected to a first oxygen sensor (22) mounted upstream of a catalyst (18) and a second oxygen sensor (24) mounted downstream. After a cold start of the engine (10) a calibration of the first and second sensors is conducted, to assure accuracy between the two sensors and determine if one of the sensors has failed, and also a light-off time for the catalyst (18) is determined as one way to measure the deterioration of the catalyst.

Abstract: Control of operation of an internal combustion engine is responsive to an estimate of catalyst deterioration in an engine exhaust gas catalytic treatment device, including ignition timing control, intake air control, and supplemental catalyst heating control. The deterioration estimate is responsive to a catalyst temperature estimate which may be corrected in accord with the estimated deterioration.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter, a first exhaust gas sensor, and a second exhaust gas sensor. A sliding mode controller determines a correction quantity to equalize the concentration of the component downstream of the catalytic converter to a predetermined appropriate value based on the output from the second exhaust gas sensor. A feedback controller determines a correction quantity to converge the concentration of the component downstream of the catalytic converter toward the predetermined appropriate value, and feed-back controls the rate at which fuel is supplied to the engine with the determined correction quantity.

Abstract: An air-fuel control system for use with an internal combustion engine has a catalytic converter in an exhaust system of the engine, for purifying an exhaust gas emitted from the engine, a first exhaust gas sensor in the exhaust system for detecting an air-fuel ratio of the exhaust gas upstream of the catalytic converter, and a second exhaust gas sensor in the exhaust system for detecting the concentration of a component of the exhaust gas which has passed through the catalytic converter, downstream of the catalytic converter. A sliding mode controller determines a correction quantity at a first period to correct the air-fuel ratio of the engine so as to equalize the concentration of the component downstream of the catalytic converter to a predetermined appropriate value, according to a sliding mode control process based on the output from the second exhaust gas sensor.

Abstract: A method of measuring temperature of a catalytic converter in a motor vehicle includes the step of determining a first oxygen sensing mechanism output, determining if it is time to determine a second oxygen sensing mechanism output, and determining the second oxygen sensing mechanism output if it is time to determine the second oxygen sensing mechanism output. The method also includes the step of determining a change in oxygen sensing mechanism output by taking a difference between the first oxygen sensing mechanism output and the second oxygen sensing mechanism output. The method further includes the step of finding a catalytic converter temperature in a look-up table using the change in oxygen sensing mechanism output, and using the catalytic converter temperature as needed by an electronic control mechanism to operate an engine of the motor vehicle.

Abstract: A cylinder-by-cylinder air-fuel ratio-estimating system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine, at a confluent portion of the exhaust system. The air-fuel ratio of a mixture supplied to each of the cylinders of the engine is estimated based on an output from the air-fuel ratio sensor, by using an observer for observing the internal operative state of the exhaust system based on a model representative of the behavior of the exhaust system. A gain for use in the estimation of the air-fuel ratio of the mixture supplied to each of the cylinders is estimated by the observer according to operating conditions of the engine.

Abstract: An air-fuel ratio sensing element comprises a pump cell having at least one pair of pump electrodes thereon, a sensor cell having at least one pair of sensor electrodes thereon, and a gas chamber having two surfaces defined by the pump cell and the sensor cell. Two to five gas holes, each having approximately the same diameter and communicating with the gas chamber, are provided for introducing sensed gas into the gas chamber. The gas holes form their projection images on the surface of the sensor cell which has a sensor electrode thereon and faces the gas chamber. The sensor electrode is shaped such that it is dividable into a plurality of similar subsections defined by virtual lines connecting the geometric centroid of the sensor electrode and the center of the projection image of each gas hole.

Abstract: A cylinder-by-cylinder air-fuel ratio-estimating system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine, at a confluent portion of the exhaust system. The air-fuel ratio of a mixture supplied to each of the cylinders is estimated based the output from the air-fuel ratio sensor, by using an observer for observing the internal operative state of the exhaust system based on a model representative of the behavior of the exhaust system. The air-fuel ratio at the confluent portion is estimated by using a delay parameter representative of the response delay of the air-fuel ratio sensor, and the air-fuel ratio of the mixture supplied to each of the cylinders is estimated by using the estimated air-fuel ratio at the confluent portion. The estimated air-fuel ratio of the mixture supplied to each of the cylinders is subsequently used for estimating a value of the air-fuel ratio at the confluent portion of the exhaust system.

Abstract: A managed fuel air mode control system is provided which operates in an open loop lean mode of operation whenever open loop enable criteria is met. During the open loop lean mode of operation, a rich A/F purge mode of operation is dictated when a NO.sub.x trap is determined to be full. After purging the trap, engine operation returns to stoichiometric and either enters a closed loop learning operation or returns to lean operation depending upon the time that has passed since the last learning operation. During the learning operation, an adaptive control algorithm learns or updates a long term correction factor that is used during the open loop lean A/F mode of operation. Also during open loop operation, the amount of SO.sub.x accumulated in the trap is calculated and the open loop mode is terminated when the amount of SO.sub.x exceed a threshold.

Abstract: An oxygen sensor has a detecting device unit for outputting a sensor current such as a limiting current of which a value is constant even though a sensing voltage applied to the oxygen sensor changes in a limiting current generating region and corresponds to an air-fuel ratio of a combustion gas and a heater for heating the detecting device unit to keep a resistance of the detecting device unit even though the oxygen sensor is degraded. When the sensing voltage is changed to a second sensing voltage of a resistance governing region, a current peak occurs in the sensor current, and a peak current value is detected. Because the peak current value decreases as the oxygen sensor is gradually degraded, when the peak current value is lower than a degradation judging value, it is judged that the oxygen sensor is degraded. Therefore, the diagnosis of the degradation of the oxygen sensor can be performed with a high accuracy.

Abstract: In an internal combustion engine equipped with electronically controlled fuel injection valves, there is provided an air-fuel ratio detecting system. The system comprises a wide range type air-fuel ratio sensor disposed in an exhaust pipe of the engine. The sensor issues an output voltage that varies continuously in accordance with an exhaust gas air-fuel ratio possessed by an exhaust gas in the exhaust pipe. The output voltage of the sensor is translated to an air-fuel ratio of air-fuel mixture with reference to a reference table. A variation characteristic of the output voltage of the sensor is decided relative to variation of the air-fuel ratio of air-fuel mixture. A correction data of the translated air-fuel ratio is formed with reference to the variation characteristic. The translated air-fuel ration is corrected with reference to the correction data.

Abstract: An apparatus for determining whether or not an air-fuel ratio sensor, which is arranged in an exhaust system of an internal combustion engine to detect the air-fuel ratio of exhaust gas, is activated. The apparatus has a heater for heating the air-fuel ratio sensor, a detector for detecting whether or not the air-fuel ratio sensor has reached a half-activated state to start changing the output thereof after the start of the engine, a unit for integrating power supplied to the heater from the start of the engine until the air-fuel ratio sensor reaches the half-activated state, a unit for estimating, according to the integrated power, the power to be supplied to the heater to bring the air-fuel ratio sensor to a full-activated state, and a unit for determining that the air-fuel ratio sensor is in the full-activated state once the estimated power has completely been supplied to the heater.