Combustion controller for lean burn engines

Details Combustion controller for lean burn engines Combustion controller for lean burn engines

1998-12-18

2001-05-29

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S274000, C060S278000, C060S295000, C123S406440, C123S184550

Reexamination Certificate

active

06237329

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a combustion controller for lean burn type internal combustion engines. More specifically, the present invention pertains to a combustion controller for lean burn engines having a nitrogen oxide storage-reduction catalyst in their exhaust passages.
Generally, in conventional engines, fuel is injected into an intake port located upstream of a combustion chamber. The injected fuel is mixed with air in the port. In this way, a homogeneous mixture of fuel and air is supplied to the combustion chamber. In this type of engine, a throttle valve adjusts the opening degree of the intake passage. The throttle valve moves by accelerator manipulation. Accordingly, the amount of the mixture supplied to the combustion chamber is adjusted, and this controls the engine output.
However, in such a homogeneous combustion engine, low negative pressure, or great vacuum, is generated in the intake passage when the throttle valve moves. This increases pumping losses and lowers intake efficiency. On the other hand, some engines also use stratified charge combustion. In this technology, fuel is directly supplied to the combustion chamber with the intake passage widely opened, which results in an easy-to-burn mixture in the vicinity of the ignition plug.
In stratified combustion, when the engine load is low, fuel is directly injected into the combustion chamber. More precisely, fuel is injected in the vicinity of the ignition plug. The injected fuel burns with the intake air delivered from a widely open throttle valve. This lowers pumping losses. Further, stratified combustion engines can be operated with a lean air-fuel ratio, improving combustion efficiency.
In lean air-fuel ratio combustion, nitrogen oxide (NOx) is likely to be produced. To purify NOx, a NOx storage-reduction catalyst (NOx absorbent) is used in stratified combustion engines. A main component of the NOx storage-reduction catalyst is zeolite, which carries platinum. The zeolite stores NOx from the exhaust gas during the normal exhaust gas state. On the other hand, when the density of unburned hydrocarbons (HC) in the exhaust is high, the NOx stored in the catalyst is reduced by the HC and emitted as nitrogen gas (N
2
).
Japanese Unexamined Publication No. 8-319862 describes an apparatus having a NOx storage-reduction catalyst. In this apparatus, so-called rich-spike control is performed. When the engine is continuously operated with a lean air-fuel ratio, the amount of NOx stored in the NOx catalyst reaches saturation, and extra NOx, not stored in the catalyst, is emitted in the exhaust gas. To prevent this, the air-fuel ratio is controlled to be temporarily rich, or “spiked”, during a predetermined time interval. Then, the amount of HC in the exhaust gas increases and the NOx stored in the catalyst is reduced and emitted as nitrogen gas (N
2
).
Furthermore, in the apparatus of the Japanese Publication, a fuel injection amount is controlled to prevent a sudden torque change caused by rich-spike control. That is, the fuel injection amount is set such that the output torque during rich-spike control, based on the injection amount, will be equal to the output torque before rich-spike control.
However, engines are subject to many control variables. Under normal operation, various kinds of engine control parameters such as the air intake amount, the exhaust gas recirculation (EGR) amount, the fuel injection amount, the ignition timing are frequently changed when torque fluctuation and knocking are controlled. When these parameters are changed, engine output (torque) is likely to change. In the prior art, when output torque changes based on various engine controls, rich-spike control may wrongly recognize a target torque state and set the fuel injection amount to a wrong value. As a result, a sudden torque change may occur.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a fuel injection controller to prevent sudden torque changes when rich-spike control is performed in lean burn type engines, the exhaust passages of which have a nitrogen oxide storage-reduction catalyst.
To achieve the above objective, the present invention provides an engine that includes a combustion chamber for burning air-fuel mixture and an exhaust passage for discharging the burned gases. The engine is operated under a primary control procedure, wherein the primary control procedure controls torque fluctuation or knocking. The engine further includes the following: a catalyst in the exhaust passage for storing nitrogen oxides contained in the exhaust gas and for reducing the level of emitted nitrogen oxides; a detector for detecting an engine operation state for the primary control procedure; a determiner for determining whether to change the air-fuel ratio of the air-fuel mixture based on the state of the catalyst; and a controller for temporarily changing the air-fuel ratio based on the decision of the determiner. The fuel supplied to the combustion chamber during the temporary change of the air-fuel ratio is based on the detected engine operation state, which is determined and used in the primary control procedure, so that the nitrogen oxides stored in the catalyst will be reduced.
The present invention also provides a method for controlling an engine that has a combustion chamber for burning air-fuel mixture, an exhaust passage for discharging the burned gases, and a catalyst provided in the exhaust passage for storing, reducing and emitting nitrogen oxides of the exhaust gas. The method includes the following steps: detecting the engine state under a primary control procedure; judging the state of the catalyst; determining whether to change the air-fuel ratio based on the state of the catalyst; controlling the air-fuel ratio according to the result of the determining step in a temporary control procedure, so that the nitrogen oxides stored in the catalyst will be reduced and emitted; and regulating the fuel supply to the combustion chamber during the temporary control procedure as a function of the engine state detected during the primary control procedure. Accordingly, an output characteristic of the engine during the temporary control procedure is substantially matched with that produced during the primary control procedure.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.


REFERENCES:
patent: 4106448 (1978-08-01), Noguchi et al.
patent: 4164207 (1979-08-01), Okitsu et al.
patent: 4693076 (1987-09-01), Chujo et al.
patent: 5279115 (1994-01-01), Inoue et al.
patent: 5448887 (1995-09-01), Takeshima
patent: 5570574 (1996-11-01), Yamashita et al.
patent: 5595060 (1997-01-01), Togai et al.
patent: 5848529 (1998-12-01), Katoh et al.
patent: 5894724 (1999-04-01), Minowa et al.
patent: 5909723 (1999-06-01), Ichimoto et al.
patent: 5964088 (1999-10-01), Kinugasa et al.
patent: 5996338 (1999-12-01), Hirota
patent: 0 752 521 A1 (1997-01-01), None
patent: 62186034 (1987-08-01), None
patent: 04307058 (1994-04-01), None
patent: 6193487 (1994-07-01), None
patent: 7332071 (1995-12-01), None
patent: 8218918 (1996-08-01), None
patent: 8200045 (1996-08-01), None
patent: 8319862 (1996-12-01), None
patent: 9158759 (1997-06-01), None

Affiliated with

Also associated with

Rating

Combustion controller for lean burn engines does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Combustion controller for lean burn engines, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Combustion controller for lean burn engines will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2555754