Internal-combustion engines – Charge forming device – Air/fuel ratio prior to combustion responsive means
Reexamination Certificate
2002-08-30
2004-04-13
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Air/fuel ratio prior to combustion responsive means
C123S549000, C123S478000, C123S590000
Reexamination Certificate
active
06718960
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a diagnostic apparatus for a gas mixture supply apparatus and diagnostic method thereof. More particularly, it relates to a trouble diagnostic apparatus of the gas mixture supply apparatus of an internal combustion engine equipped with gas mixture supply means for supplying gas mixture from upstream of the main fuel injection valve, a diagnostic method thereof and improvement of fail-safe measures.
In the prior art proposal, fuel injected by a fuel injection valve is heated and evaporated by a heater provided on an intake passage, thereby reducing the amount of fuel deposited on the intake passage and intake valve, and improving combustion at the time of starting a freezer, in particular. It also proposes a method for reducing the emission volume of hazardous hydrocarbon. For example, U.S. Pat. No. 5,894,832 proposes that a fuel injection valve (upstream fuel injection valve) and a heater are installed in an auxiliary air passage for bypassing an upstream throttle valve in addition to a fuel injection valve main fuel injection valve) provided close to the intake port of each cylinder. This configuration allows fuel to be injected from the upstream fuel injection valve to the heater in the warm-up process after starting the freezer, and prevents fuel from depositing on the intake passage by fuel evaporation promoted by the heater, thereby improving combustion.
According to the aforementioned known example, furthermore, gas mixture formation is improved by supply of evaporated fuel into the cylinder, with the result that combustion is improved. Accordingly, stable combustion can be ensured even if the delay angle for ignition timing in the idling operation after startup is made greater than the conventional engine without heater. This provides an advantage of reducing the amount of emitted hazardous hydrocarbon (HC) after startup of the freezer, by heating and evaporating fuel through a heater and increasing the delay angle for ignition timing so that exhaust temperature is raised to promote the activity of catalyst. The aforementioned known example also discloses a method for evaluating an error by heater current value when the data current detecting means is provided.
Japanese Application Patent Laid-Open Publication Nos. 2000-213398 and 2000-274296 disclose a method for improving combustion in the area of high speed and high load especially through homogenous air intake in a direct injection spark ignition type internal combustion engine, alternating current they are not directly intended to improve of combustion at the time of freezer startup. Namely, they disclose a fuel injection control apparatus provided with switching control means to ensure that fuel supply function is shared between the main fuel injection valve for direction injection of fuel into a combustion chamber and an auxiliary fuel injection valve capable of supplying fuel in the intake passage, wherein they propose means for diagnosing a trouble of the auxiliary fuel injection valve based on a predetermined operation condition—an air-fuel ratio detected in the area of high speed and high load, according to disclosed embodiments.
The prior art gas mixture supply apparatus, however, has the following problems.
According the aforementioned patent, when fuel is supplied from the upstream fuel injection valve, combustion is improved by allowing fuel to be deposited on the heater and to be evaporated therefrom. Accordingly, injection on the side of the main fuel injection valve is almost completely stopped during the use. Further, detection of heater current makes it possible to detect clearly a detectable phenomenon such as a heater current error, for example, when the heater has been extremely deteriorated or a cable of the power supply system for the heater has been disconnected. Even if there is an error as a gas mixture, however, an error of gas mixture cannot be detected when a not very conspicuous deterioration of heater performance has occurred or when an error of the upstream fuel injection valve has occurred even if there is no error as a heater performance—for example, when there is a decrease in the area pf flow path, hence decrease in the amount of fuel injection, for example, due to blocking of a passage for supplying fuel to the upstream fuel injection valve and mixture of foreign substances into the fuel injection valve or their deposition therein. Thus, supply of a sufficient amount of evaporation fuel is stopped without an error being identified as such, so the effect of combustion improvement cannot be ensured. This may lead to increase in the amount of emitted hydrocarbon, stalling of an engine or complete combustion failure in the worst case, according to the prior art.
In the operation mode where independent injection of a gas mixture supply apparatus with upstream fuel injection valve is performed after startup by the main fuel injection valve especially during the period of operation period including startup cranking, stalling of the engine occurs almost at the same time as it has started to rotate under its own power if there is an error in the gas mixture supply apparatus, for example, in the aforementioned heater or upstream fuel injection valve. Traveling cannot be performed in the worst case. Such a problem is found out in the prior art.
The art disclosed in Japanese Application Patent Laid-Open Publication Nos. 2000-213398 and 2000-274296 are intended to improve combustion in the area of high speed and high load especially though homogenous air intake in a direct injection spark ignition type internal combustion engine. So switch control means for sharing control with the main fuel injection valve by operating the auxiliary fuel injection valve is set in the area of high speed and high load, and setting is made in advance to ensure that the air-fuel ratio in concurrent use of the auxiliary fuel injection valve and main fuel injection valve denotes a rich mixture, while the air-fuel ratio when fuel is injected only from the main fuel injection valve shows a lean mixture. Accordingly, if air-fuel ratio in the case of the main fuel injection valve alone is set to a weakly lean level, there is no conspicuous change in combustion. So there is no deterioration in maneuverability which may be felt as a shock by an operator, and detection is possible in terms of changes of air-fuel ratio. From the viewpoint of the gas mixture supply apparatus alone, however, when an error has occurred to the gas mixture supply apparatus, deterioration in maneuverability is easily recognized. This requires deterioration of the state of combustion to be quickly detected. In the detection by an air-fuel ratio sensor, mainly the O2 concentration is detected, so output on the side of lean mixture may be produced even in the case of characteristic misfiring of the engine. Even if mixture is inadequate as a gas mixture, air-fuel ratio error is not detected when the ratio between air and fuel is not incorrect. Such a problem is found in the prior art. Further, the engine starts to rotate under its own power during the period of operation including startup cranking. This corresponds to the transient area characterized by a big change in combustion. Early detection of deterioration of the state of combustion is difficult, and diagnosis based on the air-fuel ratio may contain incorrect detection. Such problem is found out in the prior art.
SUMMARY OF THE INVENTION
The present invention has been made to solve the aforementioned problems. The object of the invention is to provide a diagnostic apparatus for gas mixture supply apparatus and diagnostic method thereof, capable of,
finding out an error in gas mixture by the gas mixture supply apparatus if there is any,
ensuring at least the engine startup,
permitting continued operation of the engine without a problem which may cause stalling of the engine, and
preventing deterioration of exhaust gas.
To achieve the above object, a diagnostic apparatus for the aforementioned gas mixture supply apparatus according to
Amou Kiyoshi
Ichihara Takanobu
Someno Tadashi
Crowell & Moring LLP
Hoang Johnny H.
Wolfe Willis R.
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