Honda Motor Co., Ltd.

Ngk Spark Plug Company, Limited

Kazuo Yanada

Seiji Oya

Koji Shiotani

Tomonori Kondo

Tomohiro Wakazono

Mineji Nasu

Hiroshi Kubota

Koichi Awano

Yuji Yasui

An exhaust purification system is provided that can continuously maintain a NOx purification rate to be high while suppressing the occurrence of ammonia slip. The exhaust purification system includes a slip determination portionthat determines the occurrence of ammonia slip based on an output value NH3of an ammonia sensor. A reference injection amount calculating portioncalculates a reference injection amount Gbased on a parameter correlating to an operating state of an engine. A switching injection amount calculating portiondecreases in amount a urea injection amount Gby setting a switching injection amount Gto a negative value in response to having determined that ammonia slip has occurred, and increases in amount the injection amount Gby setting the switching injection amount Gto a positive value in response to a storage amount estimated value SThaving fallen below a predetermined switch storage amount ST.

Exhaust purification system for internal combustion engine

A gas sensor controllerstops an operation of pumping in or out oxygen that is being performed by a first pump cellin a state that the oxygen concentration (oxygen partial pressure) of a gas to be measured is equal to a status judgment reference value (20%). The gas sensor controllercalculates an oxygen pressure in a second measurement chamberon the basis of a second pump current Ip. If the oxygen pressure in the second measurement chamberis equal to a deterioration judgment reference value, the gas sensor controllerjudges that the second pump cellis in a normal state. If the oxygen pressure in the second measurement chamberis different from the deterioration judgment reference value, the gas sensor controllerjudges that the second pump cellis in a deteriorated state.

Sensor deterioration judging apparatus and sensor deterioration judging method

In a sensor diagnosis process, a controller for controlling an NOx gas sensor performs processing of changing the oxygen partial pressure in a second measurement chamber by changing the oxygen partial pressure in a first measurement chamber (S), processing of detecting a current flowing through a second pump cell before the change of the oxygen partial pressure (S), and processing of detecting a current flowing through the second pump cell after the change of the oxygen partial pressure (S). Furthermore, the controller performs processing of judging whether or not the ratio between the current values detected by the respective current detecting unit falls within an allowable range, judging that the second pump cellis in a normal state if the ratio between the current values falls within the allowable range, and judging that the second pump cellis in a deteriorated state if the ratio between the current values is out of the allowable range (Sand S).

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Wako, Japan

Kazuo Yanada