Exhaust gas purification device for an internal combustion engine
First Claim
1. An exhaust gas purification device for an internal combustion engine comprising:
- a three-way catalyst disposed in the exhaust gas passage of an internal combustion engine;
a NOX occluding and reducing catalyst disposed in the exhaust gas passage downstream of the three-way catalyst and absorbing NOX in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the NOX occluding and reducing catalyst is at a lean air-fuel ratio and releasing and reducing the absorbed NOX when the air-fuel ratio of the exhaust gas flowing into the NOX occluding and reducing catalyst is at a stoichiometric or a rich air-fuel ratio;
a first air-fuel ratio sensor disposed in the exhaust gas passage at the position between the three-way catalyst and the NOX occluding and reducing catalyst;
a second air-fuel ratio sensor disposed in the exhaust gas passage downstream of the NOX occluding and reducing catalyst;
air-fuel ratio control means for switching the air-fuel ratio of the exhaust gas flowing into the three-way catalyst either from a rich air-fuel ratio to a lean air-fuel ratio or from a lean air-fuel ratio to a rich air-fuel ratio; and
evaluating means for evaluating the abilities of both of the three-way catalyst and the NOX occluding and reducing catalyst when the air-fuel ratio control means switches the air-fuel ratio of the exhaust gas either from a rich air-fuel ratio to a lean air-fuel ratio or from a lean air-fuel ratio to a rich air-fuel ratio, wherein the evaluating means evaluates the ability of the three-way catalyst based on the output signal of the first air-fuel ratio sensor and evaluates the ability of the NOX occluding and reducing catalyst based on the output signals of both the first and the second air-fuel ratio sensors.
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Accused Products
Abstract
In an exhaust gas purification device for an internal combustion engine, a three-way catalyst and a NOX occluding and reducing catalyst (a NORC) are disposed in the exhaust gas passage of an engine in this order from the upstream side. A first air-fuel ratio sensor is disposed in the exhaust gas passage between the three-way catalyst and the NORC, and a second air-fuel ratio sensor is disposed in the exhaust gas passage downstream of the NORC. An engine electronic control unit (ECU) changes the operating air-fuel ratio of the engine from a lean air-fuel ratio to a rich air-fuel ratio and a rich air-fuel ratio to a lean air-fuel ratio in order to evaluate the abilities of the three-way catalyst and the NORC. The ECU evaluates the catalytic abilities based on the output of the first air-fuel ratio sensor when the engine air-fuel ratio is changed. Further, the ECU evaluates the catalytic ability and the NOX absorbing capacity of the NORC based on the outputs of the first and the second air-fuel ratio sensor when the engine operating air-fuel ratio is changed. The evaluation of the abilities of both the three-way catalyst and the NORC in one successive changing operation of the engine operating air-fuel ratio is based on only the outputs of the first and the second air-fuel ratio sensor.
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Citations
6 Claims
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1. An exhaust gas purification device for an internal combustion engine comprising:
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a three-way catalyst disposed in the exhaust gas passage of an internal combustion engine; a NOX occluding and reducing catalyst disposed in the exhaust gas passage downstream of the three-way catalyst and absorbing NOX in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the NOX occluding and reducing catalyst is at a lean air-fuel ratio and releasing and reducing the absorbed NOX when the air-fuel ratio of the exhaust gas flowing into the NOX occluding and reducing catalyst is at a stoichiometric or a rich air-fuel ratio; a first air-fuel ratio sensor disposed in the exhaust gas passage at the position between the three-way catalyst and the NOX occluding and reducing catalyst; a second air-fuel ratio sensor disposed in the exhaust gas passage downstream of the NOX occluding and reducing catalyst; air-fuel ratio control means for switching the air-fuel ratio of the exhaust gas flowing into the three-way catalyst either from a rich air-fuel ratio to a lean air-fuel ratio or from a lean air-fuel ratio to a rich air-fuel ratio; and evaluating means for evaluating the abilities of both of the three-way catalyst and the NOX occluding and reducing catalyst when the air-fuel ratio control means switches the air-fuel ratio of the exhaust gas either from a rich air-fuel ratio to a lean air-fuel ratio or from a lean air-fuel ratio to a rich air-fuel ratio, wherein the evaluating means evaluates the ability of the three-way catalyst based on the output signal of the first air-fuel ratio sensor and evaluates the ability of the NOX occluding and reducing catalyst based on the output signals of both the first and the second air-fuel ratio sensors. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification