Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2000-07-07
2001-11-06
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...
C060S284000, C060S300000, C060S301000
Reexamination Certificate
active
06311482
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an air-fuel ratio control apparatus for internal combustion engines which uses catalyst for purifying exhaust gases at the upstream and downstream sides of the exhaust pipe of the internal combustion engine, to thereby control the air-fuel mixture ratio by regulating the amount of fuel injection to cylinders according to engine operating conditions.
As a conventional technology for warming up an exhaust gas purifying catalyst in a short period of time, injection dither is proposed to increase and decrease the amount of fuel injection for alternately leaning and enriching fuel in relation to the stoichiometric air-fuel ratio (&lgr;=1). The injection dither is performed to supply oxygen (O
2
) and unburned fuel (HC and CO) to the catalyst by increasing or decreasing the amount of fuel to be injected, for reaction and heating in the presence of the catalyst, thereby raising the catalyst temperature to accomplish early activation of the catalyst. Generally, when the injection dither is carried out, the target air-fuel ratio is changed over by leaning and enriching the fuel at intervals of 1 to 5 injections by fuel injectors.
However, the method of effecting catalyst activation by the injection dither is effective only for warming up one catalyst from a cold state. However, in a system in which catalysts are arranged in series in the exhaust pipe, the catalyst on the upstream side is early warmed up. If the injection dither is kept operated after the completion of the warm-up of the catalyst, the catalyst on the upstream side will be overheated, exceeding the permissible temperature. If, however, the injection dither is stopped upon the completion of the catalyst warm-up in an attempt to obviate this disadvantage, there will take place such a problem that the catalyst on the downstream side will not lower to a desired temperature.
In JP-A-8-158858, a front catalyst is mounted on the upstream side of the exhaust pipe, while a main catalyst is disposed on the downstream side. During the period of front catalyst activation after engine start-up, the exhaust gas temperature rises to positively activate the front and main catalysts. After the activation of the front catalyst, the exhaust gas temperature rise stops and the main catalyst is activated by the use of the injection dither which increases and decreases the air-fuel ratio. The front catalyst can be prevented from overheating.
In this apparatus, however, the injection dither is carried out after the activation of the front catalyst. The heating of the front catalyst can not be prevented, presenting a problem of catalyst overheat. Also if one tries to restrain the heating of the front catalyst, there will occur such a problem as a deteriorated activation effect of the main catalyst.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an air-fuel ratio control apparatus for internal combustion engines which is capable of proper temperature control of both catalysts provided in series in an engine exhaust pipe to thereby ensure more efficient purification of exhaust gases.
According to the present invention, an air-fuel ratio control apparatus for internal combustion engines comprises exhaust gas purifying catalysts mounted on the upstream and downstream sides of an exhaust passage of an internal combustion engine, a fuel injector for injection of a desired quantity of fuel into a cylinder of the internal combustion engine in accordance with an engine operating condition, and an electronic control unit. The control unit changes an air-fuel ratio to lean and rich magnitudes by alternately increasing and decreasing the quantity of fuel injection. The lean/rich changeover of the exhaust air-fuel ratio is performed at an interval including a period during which the lean and rich components in the exhaust gas react with the upstream catalyst and a period thereafter during which an unreacted exhaust gas passes through the upstream catalyst.
REFERENCES:
patent: 5462039 (1995-10-01), Mamiya et al.
patent: 5491975 (1996-02-01), Yamashita et al.
patent: 5537321 (1996-07-01), Yoshizaki et al.
patent: 5678402 (1997-10-01), Kitagawa et al.
patent: 5785138 (1998-07-01), Yoshida
patent: 5974788 (1999-11-01), Hepburn et al.
patent: 5979158 (1999-11-01), Kaiser et al.
patent: 5996337 (1999-12-01), Blosser et al.
patent: 0 312 835 (1989-04-01), None
patent: 5-272396 (1993-10-01), None
patent: 8-158858 (1996-06-01), None
Denion Thomas
Denso Corporation
Nguyen Tu M.
Nixon & Vanderhye P.C.
LandOfFree
Air-fuel ratio control apparatus for internal combustion... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Air-fuel ratio control apparatus for internal combustion..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Air-fuel ratio control apparatus for internal combustion... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2617438