Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2000-02-03
2001-08-07
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...
C060S278000, C060S277000, C060S285000, C123S300000, C123S443000
Reexamination Certificate
active
06269634
ABSTRACT:
This application is based on patent application No. 11-29219 filed in Japan, the contents of which are hereby incorporated by references.
BACKGROUND OF THE INVENTION
This invention relates to an engine control device capable of reducing the sulfur content in exhaust gases from an engine.
One of well-known techniques for reducing nitrogen oxides (NOx) contained in engine exhaust gases is exhaust gas recirculation (EGR), in which part of the exhaust gas is returned to an intake air line as described in Japanese Unexamined Patent Publication No. 6-229322, for instance.
In an engine in which the air-fuel ratio is increased to produce a lean air-fuel mixture in a particular operating range, it is a common practice to provide an NOx-absorbing material which absorbs NOx contained in exhaust gas emissions when the air-fuel ratio is high and releases the NOx when the concentration of oxygen in the exhaust gas has dropped so that the released NOx is converted through a reduction reaction. As an example, this approach is used in a direct injection engine whose injector injects fuel directly into a combustion chamber during a compression stroke to produce stratified charge combustion in a low-load range. The NOx-absorbing material of the aforementioned type has such properties that it absorbs sulfur oxides (SOx) more easily than the NOx in the exhaust gas emissions when fuel or engine oil containing sulfur constituents produced in particular areas is used. The NOx-absorbing ability of the NOx-absorbing material is considerably degraded once it has been poisoned by absorbing the SOx.
Japanese Unexamined Patent Publication No. 6-066129 discloses a technique for overcoming such poisoning of an NOx-absorbing catalyst by SOx by increasing catalyst temperature when the concentration of sulfur in the NOx-absorbing catalyst is high. This technique uses an electric heater for increasing the catalyst temperature.
Another approach to the solution of the SOx poisoning problem is disclosed in Japanese Unexamined Patent Publication No. 11-107740, in which an NOx-absorbing catalyst is provided in an exhaust passage of a direct injection lean-burn gasoline engine, and the fuel is injected twice during a period from an intake stroke to a succeeding compression stroke to produce exhaust gas which is rich in carbon monoxide (CO) to thereby eliminate sulfur deposited in the NOx-absorbing catalyst.
As stated above, the technique disclosed in Japanese Unexamined Patent Publication No. 6-066129 requires the electric heater for increasing the catalyst temperature. This approach is not desirable from the viewpoint of space and cost savings. On the other hand, the approach of Japanese Unexamined Patent Publication No. 11-107740 makes it necessary to increase the catalyst temperature even more effectively, which is not desirable either.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an engine control device which has overcome the problems residing in the prior art.
It is another object of the invention to provide an engine control device which makes it possible to achieve space savings without causing cost increase.
In one aspect of the invention, an engine control device is adapted for controlling an engine provided with a fuel injection valve for supplying fuel to the engine, an EGR regulator for recirculating part of exhaust gas to an intake air line of the engine, an NOx-absorbing material arranged in an exhaust passage for discharging the exhaust gas from a combustion chamber of the engine for absorbing NOx in an oxygen-rich atmosphere while releasing NOx and absorbing sulfur content when the oxygen concentration drops. The engine control device includes a discriminator for judging whether the a mount of sulfur absorbed by the NOx-absorbing material has reached a prescribed quantity, and a desulfurization controller for causing the EGR regulator to decrease the EGR ratio to increase the temperature of the NOx-absorbing material and thereby desulfurizes the NOx-absorbing material when the amount of sulfur absorbed by the NOx-absorbing material is judged to have reached or exceeded the prescribed quantity based on the result of judgment made by the discriminator.
Other features of the present invention will be more readily understood from the following detailed description when read in conjunction with accompanying drawings.
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patent: 5974788 (1999-11-01), Hepburn et al.
patent: 5975046 (1999-11-01), Kaneko et al.
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patent: 6014859 (2000-01-01), Yoshizaki et al.
patent: 6058700 (2000-05-01), Yamashita et al.
patent: 06066129 (1994-03-01), None
patent: 06229322 (1994-08-01), None
patent: 10151353 (1998-06-01), None
patent: 11107740 (1999-04-01), None
Kuji Youichi
Kuroki Masayuki
Kyougoku Makoto
Miyoshi Seiji
Okamoto Kenji
Brooks & Kushman P.C.
Denion Thomas
Mazda Motor Corporation
Tran Binh
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