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US 7,596,941 B2Granted
Air-fuel ratio control device for internal combustion engine
AssigneeMitsubishi Electric Corporation
InventorHideki Takubo
Life of this patent
Estimating the term…
Abstract
An air-fuel ratio control device for an internal combustion engine can detect the deteriorated purification state of a catalyst without delay after completion of rich or lean control, and can rapidly restore the purification state. A filter process constant for a downstream O2 sensor output is set smaller when rich or lean control are performed, thus allowing detection of the deteriorated purification state of the catalyst without delay. After the rich or lean control is completed, a dual O2 control system is used to rapidly restore the purification state. Further, the impact of downstream O2 sensor output variation when the catalyst is deteriorated can be suppressed, and stability of the dual O2 control system can be maintained.
Claims13
An air-fuel ratio control device for an internal combustion engine, comprising:
- a catalyst, disposed in an exhaust system of the internal combustion engine, that purifies exhaust gas;
- an upstream and a downstream air-fuel ratio sensor respectively disposed at an upstream side and a downstream side of the catalyst, the upstream and the downstream air-fuel ratio sensors detecting the air-fuel ratio of the exhaust gas;
- a first air-fuel ratio feedback control unit that adjust the air-fuel ratio supplied to the internal combustion engine using an output value of the upstream air-fuel ratio sensor;
- a filter processing unit that performs filter processing such that variation in an output value of the downstream air-fuel ratio sensor is suppressed;
- a second air-fuel ratio feedback control unit that adjusts a control constant of the first air-fuel ratio feedback control unit using the filter processed value of the output value of the downstream air-fuel ratio sensor;
- and
- a filter constant change unit that changes a filter constant of the filter processing unit so as to reduce suppression of the filter processing and set a filter effect smaller, when the air-fuel ratio supplied to the internal combustion engine is being controlled to be rich or lean using rich or lean control, and not when the air-fuel ratio is being controlled such that the atmosphere of the catalyst is in the vicinity of the stoichiometric air-fuel ratio.
4 more elements
An air-fuel ratio control device for an internal combustion engine, comprising:
- a catalyst, disposed in an exhaust system of the internal combustion engine, that purifies exhaust gas;
- an upstream and a downstream air-fuel ratio sensor respectively disposed at an upstream side and a downstream side of the catalyst, the upstream and the downstream air-fuel ratio sensors detecting the air-fuel ratio of the exhaust gas;
- a first air-fuel ratio feedback control unit that adjust the air-fuel ratio supplied to the internal combustion engine using an output value of the upstream air-fuel ratio sensor;
- a filter processing unit that performs filter processing such that variation in an output value of the downstream air-fuel ratio sensor is suppressed;
- a second air-fuel ratio feedback control unit that adjusts a control constant of the first air-fuel ratio feedback control unit using the filter processed value of the output value of the downstream air-fuel ratio sensor;
- and
- a filter constant change unit that changes a filter constant of the filter processing unit so as to reduce suppression of the filter processing and set a filter effect smaller, when the air-fuel ratio supplied to the internal combustion engine is being controlled to be rich or lean using rich or lean control, and not when the air-fuel ratio is being controlled such that the atmosphere of the catalyst is in the vicinity of the stoichiometric air-fuel ratio,
- wherein a period for which the filter effect is set smaller is set as:
- a period for which the air-fuel ratio supplied to the internal combustion engine is being controlled to be rich or lean using the rich or the lean control, rather than being controlled such that the atmosphere of the catalyst is in the vicinity of the stoichiometric air-fuel ratio;
- or is set as a post-completion predetermined period following completion of the rich or the lean control.
7 more elements
An air-fuel ratio control device for an internal combustion engine, comprising:
- a catalyst, disposed in an exhaust system of the internal combustion engine, that purifies exhaust gas;
- an upstream and a downstream air-fuel ratio sensor respectively disposed at an upstream side and a downstream side of the catalyst, the upstream and the downstream air-fuel ratio sensors detecting the air-fuel ratio of the exhaust gas;
- a first air-fuel ratio feedback control unit that adjust the air-fuel ratio supplied to the internal combustion engine using an output value of the upstream air-fuel ratio sensor;
- a filter processing unit that performs filter processing such that variation in an output value of the downstream air-fuel ratio sensor is suppressed;
- a second air-fuel ratio feedback control unit that adjusts a control constant of the first air-fuel ratio feedback control unit using the filter processed value of the output value of the downstream air-fuel ratio sensor;
- and
- a filter constant change unit that changes a filter constant of the filter processing unit so as to reduce suppression of the filter processing and set a filter effect smaller, when the air-fuel ratio supplied to the internal combustion engine is being controlled to be rich or lean using rich or lean control, and not when the air-fuel ratio is being controlled such that the atmosphere of the catalyst is in the vicinity of the stoichiometric air-fuel ratio,
- wherein a period for which the filter effect is set smaller is set as any one of:
- a period for which the first air-fuel ratio feedback control unit is stopped and a predetermined period after re-starting of the stopped first air-fuel ratio feedback control unit;
- a period for which the second air-fuel ratio feedback control unit is stopped and a predetermined period after re-starting of the stopped second air-fuel ratio feedback control unit.
7 more elements
Dependencies are inferred from the claim text.