Power plants – Internal combustion engine with treatment or handling of... – Having means analyzing composition of exhaust gas
Reexamination Certificate
1998-08-05
2001-05-29
Chapman, Jeanette (Department: 3711)
Power plants
Internal combustion engine with treatment or handling of...
Having means analyzing composition of exhaust gas
C060S284000, C060S285000
Reexamination Certificate
active
06237327
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an engine control system for controlling combustion of an internal combustion engine equipped with an exhaust gas purifying catalyst, and, more particularly, to a fuel combustion control system for accelerating a rise in temperature of an exhaust gas purifying catalyst installed in an exhaust line during a cold start of the engine.
2. Description of the Related Art
Typically, there have been known various types of catalytic converters for purifying exhaust gas from an engine. Such a catalytic converter incorporates a three way catalyst to purify or significantly lower emission levels of unburnt hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx) and the like which can pose a health problem for the nation if uncontrolled. The three way catalyst is hard to present desired catalytic conversion efficiency if it is at lower temperatures and is, however, activated to present catalytic conversion efficiency when heated higher than a specific temperature sufficiently.
In this type of engine control system, it has been known to accelerate a rise in catalyst temperature by greatly retarding an ignition timing after top dead center while the catalyst has not yet attained an activated condition necessary to present desired catalytic conversion efficiency which is dictated based on a temperature of engine cooling water. One of the engine control systems of this type is known from, for example, Japanese Unexamined Patent Publication No. 8-232645. The engine control system causes a large retard of an ignition timing to provide a large amount of exhaust heat loss with an effect of rising exhaust gas temperature, as a result of which, the catalyst is quickly heated and suitably activated. Further, in order to prevent fuel combustion from being made unstable due to retarded fuel ignition, the prior engine control system is designed and adapted to improve ignitability and combustibility of an air-fuel mixture by generating a swirl of intake air in a combustion chamber, increasing a speed of an intake air stream or rising ignition energy.
It has been known as an effective control for rising exhaust gas temperature to shift an air-fuel ratio to a lean side as well as to retard an ignition timing. However, there is a somewhat conflicting problem between these control that a rise in exhaust gas temperature and stabilization of combustion are contrary to each other. Specifically, retarding an ignition timing and shifting an air-fuel ratio to a lean side in order to rise exhaust gas temperature are apt to make combustion unstable. In particular, since fuels practically used differ in quality such as the degree of fuel heaviness from one another, there is a fear of unstable combustion beyond an allowable limit due to variations of ignitability and combustibility of the fuels, which always causes engine vibrations and a sharp increase of harmful emissions. Because, while the engine is not yet warmed up, the catalyst remains inactive, there is a demand for controlling the level of harmful emissions as low as possible.
SUMMARY OF THE INVENTION
It is an objective of the invention to provide an fuel combustion control system which feedback controls an engine speed to remain within a limit on stable combustion according to fuel combustion so as to accelerate a rise in catalyst temperature and control the level of harmful emissions as well as securing stable combustion during a cold engine start.
The foregoing object of the present invention is achieved by providing a fuel combustion control system for an internal combustion engine which controls fuel combustion on the basis of control parameters including an air/fuel ratio, an ignition timing and an intake air flow so as to cause a rise in exhaust gas temperature while an exhaust gas purifying catalyst installed in an exhaust line of the engine is insufficiently warmed or inactive, detects a fluctuation of engine speed, controls an air/fuel ratio to reach a target value close to a stoichiometric value, for example a value between 13 and 17, and controls the control parameter other than air/fuel ratio so as to bring the fluctuation of engine speed within limits on stable combustion while the exhaust gas purifying catalyst is insufficiently warmed. The air/fuel ratio feedback control may be commenced immediately after an engine start.
With the fuel combustion control system of the invention, in order to accelerate a rise in catalyst temperature by, for example, retarding an ignition timing while the exhaust gas purifying catalyst is still inactive, the engine speed feedback control is performed to maintain fluctuations of engine speed within limits on stable combustion. The state of fuel combustion is detected on the basis of fluctuations of engine speed which may be detected as fluctuations of crankangular velocity, the engine is controlled to operate with speed changes close to but not exceeding limits on stable combustion, so that the engine is controlled so as to enhance acceleration of a rise in catalyst temperature as well as securing fuel combustion while the engine is still cold. Even if there is a difference in fuel quality such as heaviness between fuels due to which ignitability and combustibility varies, the same effects are realized in its own quality.
The fuel combustion control system tries to maintain an air/fuel ratio close to a stoichiometric value, so that the level of harmful emissions, such as hydrocarbons (HC) and carbon monoxide (CO), is sufficiently lowered. Further, controlling an air/fuel ratio to remain on the richer side than the stoichiometric value provides a reduction in nitrogen oxide (NOx) emission level. That is, the fuel combustion control system accomplishes both acceleration of a rise in catalyst temperature and reduction in level of harmful emissions.
The exhaust gas purifying catalyst is determined to remain inactive or to be not yet warmed up while the temperature of engine cooling water is lower than a predetermined value for a predetermined period of time. The ignition timing is retarded so as to provide a rise in exhaust gas temperature while the exhaust gas purifying catalyst remains inactive, and is, however, corrected to advance so as to maintain fluctuations of engine speed within limits on stable fuel combustion. While a retard of ignition timing accelerates a rise in catalyst temperature, it also cause a fluctuation of engine speed, the fuel combustion control system controls the fluctuation of engine speed to remain within the limits by advancing the ignition timing, so as to stabilize fuel combustion.
The fuel combustion control system may incorporate variable air intake means such as an idle speed control valve for increasingly and decreasingly changing intake air quantity bypassing an engine throttle and admitted to the engine and an idle sensor for detecting engine idling. When the engine is idling, the fuel combustion control system controls the variable air intake means to provide an increase in intake air quantity. Specifically, while the engine idling with the engine throttle remaining fully closed, the variable air intake means is opened according to fluctuations of engine speed, so that air charging efficiency is increased to cause the engine to provide an increased output with an effect of enhancing fuel combustion stability. The fuel combustion control system may control the variable air intake means so as to cause the engine to provide an increase in engine speed while the engine is cold, which yields more enhanced stability of engine speed. Specifically, the fuel combustion control system feedback controls the variable air intake means so as to cause the engine to attain a predetermined idle speed. This control prevents the driver and passengers from loosing natural feeling. Further, the control system may control the variable air intake means so as to intensify an air flow in the combustion chamber with acceleration of mixing air and fuel while the engine is cold, which prevents aggravation of fuel vapor
Ishihara Takahisa
Nishimura Eiji
Nishimura Hirofumi
Taga Junichi
Abrams Hugh A.
Chapman Jeanette
Mazda Motor Corporation
Sidley & Austin
Varma Sneh
LandOfFree
Fuel combustion control system for engine does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fuel combustion control system for engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fuel combustion control system for engine will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2500915