Loading patent…
AssigneeHitachi, Ltd.
InventorsMinoru Ohsuga, Mamoru Fujieda, Nobuo Kurihara
Estimating the term…
In order to prevent a catalyst for an internal combustion engine from experiencing decreased efficiency by deterioration after long time use of the catalyst, the decreased efficiency of the catalyst is determined, and the internal engine is controlled based on results of the determination so as to maintain high efficiency of the catalyst. The catalyst is installed in an exhaust pipe of the engine. Sensors for detecting conditions of exhaust gas both at a upstream side and a downstream side of the catalyst are provided, respectively. As for the sensor, for example, an oxygen sensor whose output varies stepwise at .lambda.=1, or a sensor whose output varies in proportion to air-fuel ratio can be used. Detected values of the sensors are taken into a control unit, catalyst efficiency and deteriorating degree of the catalyst are estimated by comparison of the detected values, and the engine is controlled so that the catalyst efficiency is maximized. A preferable exhaust gas cleaning characteristics of the catalyst can be maintained because the decreased efficiency of the catalyst is determined exactly and the engine is controlled so as to prevent the catalyst from experiencing decrease efficiency.
An evaluating method for determining deterioration of a lean NO.sub.x catalyst installed in an exhaust gas system of an internal combustion engine for reducing NO.sub.x under a lean air-to-fuel ratio condition, comprising the steps of determining oxygen concentration upstream and downstream of the catalyst with a sensor when the engine is operated under the lean air-to-fuel ratio condition, and
An evaluating method for determining deterioration of a lean NO.sub.x catalyst installed in an exhaust gas system of an internal combustion engine for reducing NO.sub.x under a lean air-to-fuel ratio condition, comprising the steps of determining concentration of at least one engine exhaust gas component upstream and downstream of the catalyst with a sensor when the engine is operated under the lean air-to-fuel ratio condition, and
An evaluating method for determining deterioration of a lean NO.sub.x catalyst installed in an exhaust gas system of an internal combustion engine for reducing NO.sub.x under a lean air-to-fuel ratio condition, comprising the steps of determining oxygen concentration upstream and downstream of the catalyst with a sensor when the engine is operated under the lean air-to-fuel ratio condition,
An evaluating method for determining deterioration of a lean NO.sub.x catalyst installed in an exhaust gas system of an internal combustion engine for reducing NO.sub.x under a lean air-to-fuel ratio condition, comprising the steps of determining concentration of at least one exhaust gas component upstream and downstream of the catalyst with a sensor when the engine is operated under the lean air-to-fuel ratio condition in a steady state, and
An evaluating method for determining deterioration of a lean NO.sub.x catalyst installed in an exhaust gas system of an internal combustion engine for reducing NO.sub.x under a lean air-to-fuel ratio condition, comprising the steps of determining oxygen concentration upstream and downstream of the catalyst with a sensor when the engine is operated under the lean air-to-fuel ratio condition, and
An evaluating method for determining deterioration of a lean NO.sub.x catalyst installed in an exhaust gas system of an internal combustion engine for reducing NO.sub.x under a lean air-to-fuel ratio condition, comprising the steps of determining oxygen concentration upstream and downstream of the catalyst with a sensor when the engine is operated under the lean air-to-fuel ratio condition, and
Dependencies are inferred from the claim text.