Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1998-10-19
2001-06-05
Dombroske, George (Department: 2855)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C073S115060, C073S117020, C123S436000
Reexamination Certificate
active
06243641
ABSTRACT:
TECHNICAL FIELD
This invention is generally directed to the field of internal combustion engines and more particularly to a system and method for detecting engine cylinder misfires in such internal combustion engines.
BACKGROUND
In order to meet the demand for increased internal combustion engine efficiency and improved emissions control, engine manufacturers have developed techniques for constantly monitoring the operational characteristics of the engine to determine when engine operation is abnormal or outside of prescribed tolerances. This is particularly true with advanced engines which are designed to meet or exceed state-of-the art fuel economy and emissions control. Even more importantly, an internal combustion engine can be damaged, requiring costly repairs or earlier than normal overhaul, if it is operated in a non-optimal or malfunctioning condition.
One such characteristic of engine operation is that of an engine cylinder misfire. An engine cylinder misfire can occur due to failed ignition of the fuel-air mixture within an engine cylinder (lack of combustion) or the incomplete ignition of the fuel-air mixture caused by too lean of a mixture (incomplete combustion). Each of these misfires affect engine performance and can result in increased emissions and reduced fuel economy.
Damage to a vehicle can occur if an engine misfire condition is not detected and corrected. For example, many internal combustion engine driven vehicles employ catalytic converters to reduce the amount of pollution generated by the vehicle exhaust. Due to the structure and operation of catalytic converters, a large amount of heat is usually present within the converter itself. Therefore, where there is a lack of combustion or incomplete combustion, fuel is passed through the exhaust to the catalytic converter where, as a result of the heat in the converter, it combusts. The additional heat generated from this direct combustion in the catalytic converter quickly destroys the converter.
Various approaches have been employed in the prior art to detect engine misfires. One such technique positions a pressure transducer within the exhaust path of an internal combustion engine. Generally, the pressure transducer converts exhaust gas pressure to an electrical signal that can be processed to detect engine cylinder misfire, but none of the prior art methods take into account a multitude of present operating conditions of an internal combustion engine including fuel rate, engine speed, and coolant temperature, in combination with the output of the pressure transducer to detect an engine misfire.
For example, U.S. Pat. No. 5,193,513 to Marko et al. discloses a misfire detection system for use in an internal combustion engine in which an exhaust pressure sensor, a position sensor for sensing the rotational position of the engine, and an analog-to-digital converter for digitizing an analog signal received from the pressure sensor are employed. The digitized pressure data is compared using a data classifier (i.e. pattern recognition system) that is trained to recognize data signatures of individually misfiring cylinders. To train the classifier, the engine is operated in a service bay and engine data is collected during both intentionally induced misfires and under normal conditions. This data is then presented to the data classifier in a training operation. Engine misfire detection systems such as the one disclosed in Marko, et al., however, fail to compare a multitude of engine operation characteristics to sensed engine cylinder peak pressures as a way of detecting partial or complete engine misfires.
Using sampled engine operation data retrieved from sensors located within or on the internal combustion engine to detect engine speed, coolant temperature and fuel rate, for example, would allow a user to monitor and detect possible engine misfires in real-time during the operation of the vehicle. This would be accomplished by comparing the engine operation characteristics with the sensed cylinder exhaust pressure for each combustion cycle of an internal combustion engine. The prior art provides a variety of methods for detecting engine cylinder misfire for a combustion cycle, but fails to rely on engine operation characteristics in calculating partial or complete engine cylinder misfires. For example, U.S. Pat. No. 3,965,677 to Goto et al. discloses a misfire detecting apparatus in which the suction pressure of an engine is detected and used to calculate a threshold level wherein a cylinder misfire is declared if the exhaust gas pressure exceeds this threshold level. U.S. Pat. No. 3,983,754 to Deguchi et al. likewise discloses an apparatus for detecting misfires in a multi-cylinder internal combustion engine in which pressure responsive devices are provided in the branches of the exhaust manifold or exhaust ports and the outputs of these devices are compared to detect an engine cylinder misfire. U.S. Pat. No. 4,567,755 to Ootsuka et al. discloses an ignition/misfire detector for an internal combustion engine in which a pressure detection unit is used to detect changes in combustion pressure in the engine and an ignition/misfire detection unit is used to determine the occurrence of an engine ignition misfire. Finally, U.S. Pat. No. 3,924,457 to Oshima et al. discloses a misfire detecting device for an internal combustion engine in which an exhaust gas introducing tube is provided adjacent to an exhaust port in an exhaust passage to provide exhaust gas to a pressure transducer disposed at one end of the exhaust gas introducing tube to determine pressure fluctuation which may indicate a possible engine cylinder misfire. All of these methods of detecting engine cylinder misfire fail to employ a multitude of present engine operating conditions to provide an efficient engine cylinder misfire detection system.
A novel engine cylinder misfire detection system and improvement over the prior art is disclosed in U.S. Pat. No. 5,392,642 to Tau, a patent which is assigned to Cummins Engine Company, Inc., the same assignee of the present invention. This patent discloses an engine cylinder misfire system that uses a sensor to monitor an engine cylinder for all engine cycles and to provide an average of the detected output for each cylinder. Furthermore, the engine speed and fuel rate of the internal combustion engine are used to provide a more effective engine cylinder misfire detection system. Nevertheless, the invention disclosed in the Tau patent is directed to a system for detecting low power in at least one cylinder of a multi-cylinder engine. Furthermore, this application discloses the use of multiple pressure sensors, specifically one sensor for each cylinder to provide engine misfire detection.
Upon sensing a multitude of engine operation characteristics in real time, including engine exhaust pressure, a suitable algorithm must be formulated to process the electrical signals generated by the sensors into a readable form and to perform a series of operations to determine a partial or complete misfire. For example, in computing when an engine cylinder misfire has occurred, the prior art suggests a method in which a peak value and an average value is used for a sensed condition to detect the malfunction of an engine cylinder. For example, U.S. Pat. No. 5,144,929 to Hosoya et al. discloses an apparatus which calculates a peak level of a sensed condition and an average level of the sensed condition and uses those values to generate a peak threshold level using a peak threshold calculator. The average level is amplified using the peak threshold calculator and an offset value is added to this value to provide the peak threshold level. A subtractor is then used for making a comparison between the peak level and the peak threshold to provide a derivation level which is used to determine whether a malfunction has occurred in the engine cylinder. Although Hosoya et al. appears to disclose a method for utilizing sensed operating data to determine whether a malfunction in an engine cylinder has occurred, it fails to provide an
Andrews Eric B.
Stepper Mark R.
zur Loye Axel O.
Cummins Engine Company, Inc.
Dombroske George
Leedom Jr. Charles M.
Nixon & Peabody LLP
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