Abstract: A three-way catalyst (10) is provided in the exhaust passage (9) of an engine (1) which stores and releases oxygen according to the oxygen concentration in the exhaust gas. A controller (2) calculates an oxygen storage amount of the catalyst (10) by accumulating a variation rate of the oxygen storage amount of the catalyst (10) based on the oxygen amount in the exhaust gas (S3-S5). A target oxygen amount in the exhaust gas is calculated which reduces the difference of the oxygen storage amount from a target oxygen storage amount (S6). A target air/fuel ratio is calculated based on a catalyst deterioration coefficient, an exhaust gas flowrate and the target oxygen amount (S7). Due to this process, it is possible to increase the speed and accuracy of control of the oxygen storage amount of the catalyst (10) towards the target oxygen storage amount.

Abstract: Fuel vapor adsorbed by activated carbon 4a in a canister 4 is introduced to an engine 10 by a manifold vacuum in an intake air passage 8, and burnt. The controller 21 estimates the fuel amount desorbed from the canister 4 during purge, using a canister model (physical model) comprising an equation which computes the adsorption amount and an equation which computes the desorption amount from the adsorption amount and purge rate. An injection pulse width output to injectors 15 is corrected to reduce an air-fuel ratio fluctuation due to the supply of this desorbed fuel to the engine 10.

Abstract: An engine exhaust emission control arrangement has a catalytic converter including a three-way catalyst. A first oxygen sensor detects an oxygen concentration of exhaust gas upstream of the catalyst and a second oxygen sensor detects an oxygen concentration of exhaust gas downstream of the catalyst. A microprocessor calculates a specific period oxygen storage amount of a catalyst while the upstream oxygen concentration is higher than the stoichiometric concentration and the downstream oxygen concentration is in a predetermined concentration range which has a value approximately equal to the stoichiometric oxygen concentration. The microprocessor also calculates a specific period oxygen release amount of a catalyst while the upstream oxygen concentration is lower than the stoichiometric concentration and the downstream oxygen concentration produces an indication of a predetermined concentration range.

Abstract: A catalyst which has an oxygen storage function is provided in the exhaust gas pipe 2 of an engine 1. The oxygen storage amount is estimated based on the output of the air/fuel ratio sensor 4 upstream of the catalyst 3. The air/fuel ratio is controlled so that the oxygen storage amount coincides with the target value. When the output of the downstream air/fuel ratio sensor 5 continuously displays a rich or a lean value for more than a determination time which is varied continuously with respect to operating conditions, deterioration in the upstream air/fuel ratio sensor 4 is detected. Thus the output of the upstream air/fuel ratio sensor 4 is corrected based on the output of the downstream air/fuel ratio sensor 5. In this manner, output fluctuations are corrected based on the deterioration of the air/fuel ratio sensor 4 upstream of the catalyst.

Abstract: A controller (6) computes the oxygen storage amount of the catalyst (3) separately as a high-speed component and a low speed component in accordance with actual characteristic. A target air-fuel ratio of an engine (1) is computed so that the oxygen storage amount is a predetermined target amount, and air-fuel ratio control of the engine (1) is performed. The oxygen storage amount is computed using an storage/release rate set according to the exhaust air-fuel ratio and catalyst temperature, etc. In this way, the oxygen storage amount of the catalyst can be precisely computed regardless of the variation in the storage/release rate which accompanies a catalyst temperature variation, and the real oxygen storage amount can therefore be controlled with a higher level of precision.

Abstract: A microprocessor (6) computes an oxygen storage amount of a catalyst (3) separately for a high speed component and a low speed component in accordance with real characteristic. A target air-fuel ratio of an engine (1) is computed and air-fuel ratio control of the engine (1) it is performed so that the high speed component is constant. The deterioration of the catalyst (3) is determined by integrating the high speed component of the oxygen storage amount computed during the air-fuel ratio control process for a predetermined number of times, and comparing its average value with a determining value. The oxygen storage amount of the high speed component which is sensitive to catalyst deterioration is integrated so as to obtain a highly precise determining result to determine the deterioration.

Abstract: A controller (6) computes an oxygen storage amount of a catalyst (3) separately as a high speed component/amount and a low speed component/amount according to predetermined release/adsorption characteristics. A target air-fuel ratio of an engine is computed and the air-fuel ratio of the engine is controlled so that the high speed component is maintained constant. The target air-fuel ratio of the engine (1) is limited by an upper limiter and lower limiter so that the high speed component converges to the target value, an excessively large variation of the air-fuel ratio is prevented, and impairment of drivability and fuel cost-performance is also prevented. Further, after lean running due to fuel cut, etc., the lower limiter is lowered to the rich side, and the oxygen storage amount is rapidly induced to converge on the target value.

Abstract: A three-way catalyst (10) is provided in the exhaust passage (9) of an engine (1) which stores and releases oxygen according to the oxygen concentration in the exhaust gas. A controller (2) calculates an oxygen storage amount of the catalyst (10) by accumulating a variation rate of the oxygen storage amount of the catalyst (10) based on the oxygen amount in the exhaust gas (S3-S5). A target oxygen amount in the exhaust gas is calculated which reduces the difference of the oxygen storage amount from a target oxygen storage amount (S6). A target air/fuel ratio is calculated based on a catalyst deterioration coefficient, an exhaust gas flowrate and the target oxygen amount (S7). Due to this process, it is possible to increase the speed and accuracy of control of the oxygen storage amount of the catalyst (10) towards the target oxygen storage amount.

Abstract: A catalyst which has an oxygen storage function is provided in the exhaust gas pipe 2 of an engine 1. The oxygen storage amount is estimated based on the output of the air/fuel ratio sensor 4 upstream of the catalyst 3. The air/fuel ratio is controlled so that the oxygen storage amount coincides with the target value. When the output of the downstream air/fuel ratio sensor 5 continuously displays a rich or a lean value for more than a determination time which is varied continuously with respect to operating conditions, deterioration in the upstream air/fuel ratio sensor 4 is detected. Thus the output of the upstream air/fuel ratio sensor 4 is corrected based on the output of the downstream air/fuel ratio sensor 5. In this manner, output fluctuations are corrected based on the deterioration of the air/fuel ratio sensor 4 upstream of the catalyst.

Abstract: A controller (6) controls an air-fuel ratio of an engine (1) so that an oxygen storage amount of a catalyst (3) provided in an exhaust passage (2) is maintained constant. At this time, the controller (6) computes or estimates the oxygen storage amount separately for a first amount and a second amount, where the first amount is estimated based on a relationship between the first and second amount. The controller (6) controls the air/fuel ratio based on the estimated first amount.

Abstract: A catalyst 3 which has oxygen storage performance is installed in an engine exhaust passage 2, an oxygen storage amount is estimated based on the output of an upstream air-fuel ratio sensor 4 installed in the upstream of the catalyst 3, and an air-fuel ratio is controlled so that this oxygen storage amount coincides with a target value. When the output of a downstream air-fuel ratio sensor 5 has become lean or rich for longer than a fixed time, the output of the upstream air-fuel ratio sensor 4 is corrected based on the output of the downstream air-fuel ratio sensor 5 placed in the downstream of the catalyst 3. In this way, the output fluctuation due to deterioration of the air-fuel ratio sensor 4 upstream of the catalyst is corrected, and the catalyst oxygen storage amount is always precisely controlled to the target value.

Abstract: An oxygen storage amount of the catalyst (3) is estimated using a detection result from a front A/F sensor (4). An HC storage amount is calculated as a time integral of the product of the storage rate by the catalyst (3), the air-fuel ratio and the intake air amount, and a target air-fuel ratio is corrected so that a deficiency relative to a target amount of the oxygen storage amount is compensated based on this computation result.

Abstract: An engine exhaust emission control arrangement has a catalytic converter including a three-way catalyst. A first oxygen sensor detects an oxygen concentration of exhaust gas upstream of the catalyst and a second oxygen sensor detects an oxygen concentration of exhaust gas downstream of the catalyst. A microprocessor calculates a specific period oxygen storage amount of a catalyst while the upstream oxygen concentration is higher than the stoichiometric concentration and the downstream oxygen concentration is in a predetermined concentration range which has a value approximately equal to the stoichiometric oxygen concentration. The microprocessor also calculates a specific period oxygen release amount of a catalyst while the upstream oxygen concentration is lower than the stoichiometric concentration and the downstream oxygen concentration produces an indication of a predetermined concentration range.

Abstract: A controller (6) computes an oxygen storage amount of a catalyst (3) separately as a high speed component/amount and a low speed component/amount according to predetermined release/adsorption characteristics. A target air-fuel ratio of an engine is computed and the air-fuel ratio of the engine is controlled so that the high speed component is maintained constant. The target air-fuel ratio of the engine (1) is limited by an upper limiter and lower limiter so that the high speed component converges to the target value, an excessively large variation of the air-fuel ratio is prevented, and impairment of drivability and fuel cost-performance is also prevented. Further, after lean running due to fuel cut, etc., the lower limiter is lowered to the rich side, and the oxygen storage amount is rapidly induced to converge on the target value.

Abstract: A controller (6) computes the oxygen storage amount of the catalyst (3) separately as a high-speed component and a low speed component in accordance with actual characteristic. A target air-fuel ratio of an engine (1) is computed so that the oxygen storage amount is a predetermined target amount, and air-fuel ratio control of the engine (1) is performed. The oxygen storage amount is computed using an storage/release rate set according to the exhaust air-fuel ratio and catalyst temperature, etc. In this way, the oxygen storage amount of the catalyst can be precisely computed regardless of the variation in the storage/release rate which accompanies a catalyst temperature variation, and the real oxygen storage amount can therefore be controlled with a higher level of precision.

Abstract: A microprocessor (6) computes an oxygen storage amount of a catalyst (3) separately for a high speed component and a low speed component in accordance with real characteristic. A target air-fuel ratio of an engine (1) is computed and air-fuel ratio control of the engine (1) it is performed so that the high speed component is constant. The deterioration of the catalyst (3) is determined by integrating the high speed component of the oxygen storage amount computed during the air-fuel ratio control process for a predetermined number of times, and comparing its average value with a determining value. The oxygen storage amount of the high speed component which is sensitive to catalyst deterioration is integrated so as to obtain a highly precise determining result to determine the deterioration.

Abstract: A fuel vapor emission control device of an engine 10 includes a canister 4 which adsorbs fuel vapor generated in a fuel tank 1, and a purge valve 11 which opens and closes a pipe 6 connecting the canister 4 and an intake passage 8 of the engine 10. A controller 21 sets a target purge rate according to a difference between a target air-fuel ratio feedback deviation and an actual air-fuel ratio feedback deviation during purge, and drives the purge valve 11 so that the target purge rate is achieved.

Abstract: A fuel vapor emission control device of an engine 10 includes a canister 4 which adsorbs fuel vapor generated in a fuel tank 1, and a purge valve 11 which opens and closes a pipe 6 connecting the canister 4 and an intake passage 8 of the engine 10. A controller 21 sets a target purge rate according to a difference between a target air-fuel ratio feedback deviation and an actual air-fuel ratio feedback deviation during purge, and drives the purge valve 11 so that the target purge rate is achieved.

Abstract: Fuel vapor adsorbed by activated carbon 4a in a canister 4 is introduced to an engine 10 by a manifold vacuum in an intake air passage 8, and burnt. The controller 21 estimates the fuel amount desorbed from the canister 4 during purge, using a canister model (physical model) comprising an equation which computes the adsorption amount and an equation which computes the desorption amount from the adsorption amount and purge rate. An injection pulse width output to injectors 15 is corrected to reduce an air-fuel ratio fluctuation due to the supply of this desorbed fuel to the engine 10.

Abstract: A fuel property detecting system comprises a control unit coupled to a fuel injector and an air-fuel ratio sensor. The control unit is arranged to sample data of a response wave-form of an exhaust air-fuel ratio in response to an injected fuel quantity at a transient period, to identify a plant model as to fuel in use by controlling a parameter of a previously constructed plant model on the basis of the input and output data so as to decrease a prediction error between the plant model and a norm model, to calculate a cutoff frequency of the identified plant model, and to estimate a fuel property of the fuel in use from the calculated cutoff frequency of the identified plant model and data previous stored in the control unit.