Exhaust emission purifying device for internal combustion engine
AssigneeMitsubishi Jidosha Kogyo Kabushiki Kaisha
InventorsYasuki Tamura, Kazuhito Kawashima, Takuya Okamoto, Osamu Nakayama
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Abstract
When exhaust gases flowing into catalysts (e.g., a NOx catalyst and a three-way catalyst) continue to be in the fuel-rich atmosphere for a predetermined period of time or longer, an exhaust emission purifying device for an internal combustion engine leans an air-fuel mixture or supplies the secondary air to the exhaust gases in order to turn the exhaust gases flowing into catalysts into an oxygen-rich atmosphere. This enables the proper regeneration of the degraded catalysts, and thus improves an exhaust emission control performance.
Claims17
An exhaust emission purifying device for an internal combustion engine, comprising:
- an exhaust emission purifying catalyst for purifying toxic substances in exhaust gases, said exhaust emission purifying catalyst being disposed in an exhaust passage of the internal combustion engine;
- a control unit for temporarily switching the exhaust gases, flowing upstream of said exhaust emission purifying catalyst, into an oxygen-rich atmosphere when the exhaust gases flowing upstream of said exhaust emission purifying catalyst continue to be a fuel-rich atmosphere;
- and
- a reducing agent supply control device for controlling supply of a reducing agent to the exhaust gases,
- wherein said reducing agent supply control device controls supply of said reducing agent to the exhaust gases when said control unit switches the exhaust gases into the oxygen-rich atmosphere.
A method of recovering an exhaust emission purifying device for an internal combustion engine, comprising:
- performing fuel-rich atmosphere state in exhaust gases which flow into the exhaust emission purifying device;
- determining that the reaction of said exhaust emission purifying device has degraded by said performing step;
- switching said exhaust gases from fuel-rich atmosphere to oxygen-rich atmosphere;
- and
- increasing a reducing agent in said exhaust gases at least in said switching step.
An exhaust emission purifying device for an internal combustion engine, comprising:
- an exhaust emission purifying catalyst for purifying toxic substances in exhaust gases, said exhaust emission purifying catalyst being disposed in an exhaust passage of the internal combustion engine;
- a fuel-rich atmosphere continuation index detecting device that detects a fuel-rich atmosphere continuation index indicative of an inverse proportion to a total amount of oxygen which flows into the catalyst during an operation in at least one of a stoichiometric and rich air-fuel ratio;
- and
- an oxygen-rich atmosphere continuation index detecting device that detects an oxygen-rich atmosphere continuation index indicative of a total amount of oxygen flowing into the catalyst during an operation in a lean air-fuel ratio;
- a control unit for temporarily switching the exhaust gases, flowing upstream of said exhaust emission purifying catalyst, into an oxygen-rich atmosphere when said detected fuel-rich atmosphere continuation index exceeds a first value and said detected oxygen-rich atmosphere continuation index exceeds a second value such that said control unit controls frequency of switching to the oxygen-rich atmosphere as a function of the ability of the oxygen-rich atmosphere to regenerate said exhaust emission purifying catalyst.
A method of recovering an exhaust emission purifying device for an internal combustion engine, comprising:
- detecting a fuel-rich atmosphere continuation index indicative of an inverse proportion to a total amount of oxygen which flows into the catalyst during an operation in at least one of a stoichiometric and rich air-fuel ratio;
- comparing said detected fuel-rich atmosphere continuation index with a first value;
- detecting an oxygen-rich atmosphere continuation index indicative of a total amount of oxygen flowing into the catalyst during an operation in a lean air-fuel ratio;
- comparing the detected oxygen-rich atmosphere continuation index with a second value;
- and
- switching said exhaust gases from fuel-rich atmosphere to oxygen-rich atmosphere when said detected fuel-rich atmosphere continuation index exceeds the first value and said detected oxygen-rich atmosphere continuation index exceeds the second value to regenerate a catalyst of the exhaust emission purifying device.
Dependencies are inferred from the claim text.