Measuring and testing – Vehicle chassis – Steering
Reexamination Certificate
1998-12-09
2001-06-05
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Vehicle chassis
Steering
Reexamination Certificate
active
06240772
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a system and method for detecting an engine malfunction in an internal combustion engine using crankcase pressure.
BACKGROUND ART
In the control of internal combustion engines, the conventional practice utilizes electronic control units having volatile and non-volatile memory, input and output driver circuitry, and a processor capable of executing a stored instruction set, to control the various functions of the engine and its associated systems. A particular electronic control unit communicates with numerous sensors, actuators, and other electronic control units necessary to control various functions, which may include various aspects of engine malfunction diagnostics, fuel delivery, transmission control, or many others.
Malfunction diagnosis in internal combustion engines is commonplace. This is due to the desire to detect engine failures or malfunctions before they occur, or as soon as possible after they occur, to provide an opportunity for remedial measures to avert severe engine damage. Crankcase pressure has been used to detect various piston-related engine malfunctions. One method is to use a pressure limit switch which provides a signal when crankcase pressure exceeds a predetermined threshold. This approach requires a pressure limit switch selected based on a particular application or an engine family which exhibits similar crankcase pressures during operation. A crankcase pressure exceeding the predetermined threshold results in the limit switch generating a signal which is used by the electronic control unit to indicate a fault. The electronic control unit may then take appropriate action depending upon the particular application, which may include generating a warning message or indicator light, or shutting down the engine, for example.
Another method of detecting an engine malfunction based on crankcase pressure uses a pressure sensor which provides a continuously variable signal representing current crankcase pressure. The electronic control unit periodically samples the signal generated by the pressure sensor and compares it to a predetermined crankcase pressure limit. The pressure limit is generally a value which is determined based on expected crankcase pressure at the maximum rated engine speed and load (or power). This method allows the use of a single crankcase pressure sensor for a variety of applications since the limit value may be calibrated for each engine or engine family and stored in the electronic control unit. While this strategy is capable of detecting various piston or cylinder-related malfunctions at maximum speed and load, it is insufficient to detect impending failures at lower speeds and loads. In addition, it is desirable to detect failures or impending failures as quickly as possible to provide the electronic control unit or the vehicle operator sufficient time to take remedial actions to avoid a catastrophic failure.
DISCLOSURE OF INVENTION
It is therefore an object of the present invention to provide a method and system for enhanced engine malfunction detection based on engine crankcase pressure.
Another object of the present invention is to provide a system and method for detecting an engine malfunction having a selectable or tunable sensitivity for various applications.
A further object of the present invention is to provide a system and method for detecting piston/cylinder related engine malfunctions at low engine speeds and loads.
Another object of the present invention is to provide a system and method for detecting an engine fault having equal detectability of excessive crankcase pressure at all speeds and loads.
A still further object of the present invention is to provide a system and method for engine protection which function while the engine is operating at less than maximum power.
Yet another object of the present invention is to provide a system and method for engine protection capable of detecting a failed piston condition immediately after the engine is started.
In carrying out the above object and other objects and features of the present invention, a method for detecting engine malfunctions is provided. The method includes sensing crankcase pressure, determining a current value for at least one engine operating parameter and comparing the crankcase pressure to a limit which varies as a function of the at least one engine operating parameter. The method further comprises providing an indication that crankcase pressure has exceeded the crankcase pressure limit and may also include controlling the engine based on the indication. In one embodiment, an indexing value is determined based on the engine operating parameter(s) and used to access a look-up table containing crankcase pressure limit values. Preferably, the index value is a function of engine speed and requested torque. Of course, the at least one engine operating parameter may be any one or more of a variety of engine operating parameters which are measured, sensed, calculated, or inferred, including engine speed, actual or requested torque, oil temperature, oil pressure, fuel temperature, coolant temperature, and the like.
In further carrying out the above objects, and other objects, features, and advantages of the invention, a computer readable storage medium is provided. The computer readable storage medium has information stored thereon representing instructions executable by a computer to enhance engine malfunction detection. The computer readable storage medium includes instructions for determining a crankcase pressure limit based on at least one engine operating parameter. The computer readable storage medium also includes instructions for comparing a sensed crankcase pressure to the determined limit and generating a signal when the sensed crankcase pressure exceeds the limit.
A system for providing enhanced fault detection based on engine crankcase pressure includes a crankcase pressure sensor for providing a continuously variable signal indicative of crankcase pressure in communication with an electronic control unit for controlling an internal combustion engine. The system also includes at least one additional sensor which provides a signal indicative of an engine operating parameter. The electronic control unit includes control logic for determining a value indicative of crankcase pressure based on a signal provided by the crankcase pressure sensor. The electronic control unit also includes control logic for determining a reference value indicative of engine operating conditions based on signals provided by the at least one additional sensor. The electronic control unit uses the reference value to determine a current limit for the crankcase pressure and compares the crankcase pressure value to the limit. If the crankcase pressure value exceeds the limit value, the control logic generates a corresponding fault signal or code. The fault code may be logged for future reference by service personnel and used by the electronic control unit for subsequent processing which may include illumination of a service indicator, reduction of available engine power, and/or shutdown of the engine.
The advantages accruing to the present invention are numerous. For example, the present invention facilitates detection of faults while the engine is operating at less than maximum power. The present invention will redetect a failed piston condition almost immediately after the engine is restarted. The present invention provides a tunable fault detection strategy which can be adjusted or calibrated to change its sensitivity based on the particular application.
The above object and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.
REFERENCES:
patent: 4223654 (1980-09-01), Wessel et al.
patent: 4424709 (1984-01-01), Meier, Jr. et al.
patent: 5131371 (1992-07-01), Wahl et al.
patent: 5165373 (1992-11-01), Cheng
patent: 5165579 (1992-11-01), Lund
patent:
Brooks & Kushman PC
Detroit Diesel Corporation
Fuller Benjamin R.
Stevens Maurice
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