Emission control apparatus for internal combustion engine
First Claim
1. An emission control apparatus for an internal combustion engine comprising:
- an NOx-lessening catalyst disposed in an exhaust passage of the internal combustion engine, the NOx-lessening catalyst lessening an amount of NOx in exhaust gas flowing therein in accordance with a condition of the exhaust gas;
an NOx sensor disposed in the exhaust passage downstream of the NOx-lessening catalyst, an output of the NOx sensor corresponding to an NOx concentration of exhaust gas flowing out of the NOx-lessening catalyst; and
a controller monitoring an operational condition of the internal combustion engine and determining a deviation of the output value of the NOx sensor from a predetermined reference value when the engine is being operated under a predetermined operational condition, the controller correcting the output value of the NOx sensor, based on the deviation of the output value from the predetermined reference value.
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Accused Products
Abstract
An NOx-absorbing and reducing catalyst device is disposed in an exhaust passage of an engine. The NOx concentration in exhaust gas flowing out of the catalyst device is detected by an NOx sensor. Every time the NOx concentration detected by the NOx sensor increases to a predetermined value, an electronic control unit (ECU) of the engine reactivates the NOx-absorbing and reducing catalyst device by operating the engine at a rich air fuel ratio for a short time. The ECU also detects a deviation of the output of the NOx sensor on the basis of a reference value (corresponding to zero NOx concentration) and an output of the NOx sensor produced when the engine is being operated in a condition where the amount of NOx discharged from the engine is small, for example, a condition where the air-fuel ratio is on the lean side and the load is low (that is, in a condition where the NOx concentration in exhaust gas reaching the NOx sensor becomes substantially zero). Based on the detected deviation, the ECU corrects the output of the NOx sensor.
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Citations
10 Claims
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1. An emission control apparatus for an internal combustion engine comprising:
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an NOx-lessening catalyst disposed in an exhaust passage of the internal combustion engine, the NOx-lessening catalyst lessening an amount of NOx in exhaust gas flowing therein in accordance with a condition of the exhaust gas;
an NOx sensor disposed in the exhaust passage downstream of the NOx-lessening catalyst, an output of the NOx sensor corresponding to an NOx concentration of exhaust gas flowing out of the NOx-lessening catalyst; and
a controller monitoring an operational condition of the internal combustion engine and determining a deviation of the output value of the NOx sensor from a predetermined reference value when the engine is being operated under a predetermined operational condition, the controller correcting the output value of the NOx sensor, based on the deviation of the output value from the predetermined reference value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification