Internal-combustion engines – Charge forming device – Including means responsive to instantaneous change in engine...
Reexamination Certificate
2000-09-28
2002-03-12
Solis, Erick (Department: 3747)
Internal-combustion engines
Charge forming device
Including means responsive to instantaneous change in engine...
C123S568160, C060S285000, C060S276000, C073S117020, C701S114000
Reexamination Certificate
active
06354269
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a system for performing control of an engine and diagnosing the control of an engine.
DESCRIPTION OF RELATED ART
It has been known in the art to increase the amount of HC (hydrocarbon that is unburned fuel and reformed HC due to combustion) in exhaust gas by performing fuel injection divided into a plurality of parts through a fuel injector that sprays fuel directly into a combustion chamber. For example, fuel injection control is performed by spraying fuel through main fuel injection only at a point of time near a top dead center of a compression stroke while an engine operates in ordinary engine operating conditions. In order to increase the HC concentration of exhaust gas, the fuel injection control is performed by spraying fuel through post-fuel injection subsequently to the main fuel injection according to engine operating conditions when necessary. In the case where NOx trapping substance operative to absorb NOx in exhaust gas is provided in an exhaust gas passage, the amount of the HC concentration of exhaust gas is increased for the purpose of causing the NOx trapping substance to release NOx or supplying HC as a deoxidizing substance to a catalyst for purifying exhaust gas by deoxidizing NOx in the exhaust gas.
Japanese Unexamined Patent Publication No. 8-200045 discloses a system having a NOx trapping substance in an exhaust passage which performs fuel injection at a point of time near a top dad center in a compression stroke while an engine operates in ordinary engine operating conditions. The system performs post-fuel injection in either an expansion stroke or an exhaust stroke, additionally to the main fuel injection that is implemented at a point of time near the dead top center of the compression stroke, so as to decline an exhaust gas air-to-fuel ratio when releasing NOx from the NOx trapping substance. The term “exhaust gas air-to-fuel ratio” as used herein shall mean and refer to a ratio of the entire amount of air relative to the entire amount of fuel in exhaust gas. NOx released from the NOx trapping substance reacts on HC or CO on a noble metal catalyst such as platinum and the like and then is deoxidized. The system that Japanese Unexamined Patent Publication No. 8-200045 discloses is configured and adapted to close an exhaust gas recirculation passage so as to prevent recirculation of a large amount of unburned fuel from being admitted into an intake stream when implementing fuel injection for refreshing the NOx trapping substance while the engine operates in a region of lower and moderate engine loads where a large amount of exhaust gas is expected to be recirculated.
In the case of increasing the HC concentration of exhaust gas by means of altering the mode of fuel injection, it is definitely required that the mode of fuel injection is altered as previously scheduled. Therefore, it is preferred to ascertain whether a fuel injection mode is normally altered as scheduled. As a means for ascertainment of a normal alteration in fuel injection mode, an HC sensor may be disposed in the exhaust gas passage to detect the HC concentration of exhaust gas. A change in output from the HC sensor is checked at an occurrence of an alteration in fuel injection mode in order to make a decision as to whether or not the fuel injection mode alteration control is normal or should be corrected. However, because exhaust gas contains different kinds of HC, detection of HC concentrations of the exhaust gas by the HC sensor is hardly accurate.
In place of detecting the HC concentration of exhaust gas, it may be carried out to detect the concentration of oxygen (O2) or NOx of exhaust gas. That is, since a change in HC concentration of exhaust gas is revealed as a change in exhaust gas air-to-fuel ratio or oxygen concentration of exhaust gas, a change in HC concentration of exhaust gas is monitored indirectly by monitoring the oxygen concentration of exhaust gas. In the case where a NOx deoxidizing catalyst is provided in the exhaust gas passage, since an increase in HC concentration of exhaust gas quickens deoxidization of NOx, the NOx concentration of exhaust gas declines as the HC concentration of exhaust gas increases. On the grounds, a change in HC concentration of exhaust gas is monitored indirectly by monitoring the NOx concentration of exhaust gas.
However, though the oxygen sensor is suitable for detection as to whether an exhaust gas air-to-fuel ratio is near a specific ratio, nevertheless, the oxygen sensor is hard to detect a wide range of oxygen concentrations of exhaust gas even if it is of a linear type. There are less types of NOx sensors that are simple in construction and capable of accurately detecting NOx concentrations of exhaust gas. Further, because HC is low in reactivity on O2 or NOx while the exhaust gas is at low temperatures, so that it is hard to detect accurate HC concentrations of exhaust gases. In addition, processing an output from the sensor is apt to make control complicated.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an engine control system which is capable of diagnosing whether not only fuel injection mode alteration control but also a change in composition of exhaust gas are achieved as expected without using a sensor which detects a component concentration of exhaust gas.
It is another object of the present invention to provide an engine control system which is capable of correcting fuel injection mode alteration control without using a sensor which detects a component concentration of exhaust gas.
The foregoing objects of the present invention are accomplished by diagnosing normality or abnormality of the fuel injection mode alteration control or correcting the fuel injection mode alteration control on the basis of engine output which varies according to a HC content of recirculated exhaust gas.
According to an aspect of the present invention, the diagnostic system for diagnosing normality or abnormality of control of an engine which is equipped with a fuel injector for supplying fuel into the combustion chamber, exhaust gas control means for controlling a change in composition of exhaust gas from the engine so as to cause a change in HC concentration of the exhaust gas according to engine operating conditions and an exhaust gas recirculation system for recirculating partly exhaust gas into an intake system of the engine comprises output detecting means for detecting engine output of the engine and diagnostic means for making a diagnosis of normality or abnormality of the control of the change in composition of the exhaust gas when the engine output does not causes a predetermined change meeting to the change in HC concentration of the recirculated exhaust gas after the change in composition of the exhaust gas.
When the exhaust gas control means controls a change in composition of exhaust gas so as to causes a change in HC concentration, since exhaust gas is partly recirculated into an intake system of the engine, the HC content of burned gas in the combustion chamber of an engine varies with a time lag behind the change in composition of the exhaust gas as long as the control of a change in composition of exhaust gas is performed as expected. The change in HC content of exhaust gas appears as a change in engine output. When the engine output does not change correspondingly to a change in composition of exhaust gas, namely, a change in HC concentration of recirculated exhaust gas as expected, this indicates that the change in composition of exhaust gas fails to meet the expectation, then the control of a change in composition of exhaust gas is regarded as abnormal. The change in composition of exhaust gas such as to cause a change in HC concentration such as, for example, a change in fuel combustion in the combustion chamber, is achieved by an alteration of fuel injection mode such as a change in the amount of fuel injection, a change in the number of times of fuel injection or a change in fuel injection timing, or a change in ignition timing if the
Kobayashi Akihiro
Saito Tomoaki
Seino Yusuke
Yasutomi Katsuaki
Mazda Motor Corporation
Solis Erick
Studebaker Donald R.
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