Internal-combustion engines – Charge forming device – Fuel injection system
Reexamination Certificate
1999-07-20
2001-09-25
Miller, Carl S. (Department: 3747)
Internal-combustion engines
Charge forming device
Fuel injection system
C123S357000, C073S114220
Reexamination Certificate
active
06293251
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fuel system control techniques, and more specifically to techniques for diagnosing failures and fault conditions in a fuel system.
BACKGROUND OF THE INVENTION
Electronically controlled high pressure fuel systems are known and commonly used in the automotive and heavy duty truck industries. Such systems may include a fuel pump operable to provide high pressure fuel to a collection unit that supplies the pressurized fuel to one or more fuel injectors. One or more pressure sensors are typically provided for monitoring and controlling the fuel pressure throughout the system.
An example of one such system is described in U.S. Pat. No. 5,678,521 to Thompson et al., which is assigned to the assignee of the present invention. The Thompson et al. fuel system includes a pair of cam driven high pressure fuel pumps operable to pump fuel from a low pressure fuel source to an accumulator. The accumulator passes the high pressure fuel to a single injection control valve which is electronically controllable to supply the fuel to a distributor unit. The distributor, in turn, distributes the fuel to any of a number of fuel injectors. The accumulator includes a pressure sensor for monitoring accumulator pressure. An electronic control unit monitors accumulator pressure, throttle position and engine speed, and is operable to control the operation of the fuel system in accordance therewith.
High pressure fuel systems of the type just described, while having many advantages over prior mechanical systems, have certain drawbacks associated therewith. For example, failure of electrical and/or mechanical components of the system may result in total system failure, in which case the engine is often shut down leaving the vehicle and occupant stranded. In severe cases, failure of such components can lead to catastrophic destruction of fuel system components.
What is therefore needed is a system for diagnosing faults and failures in an electronically controlled fuel system of the type just described. Such a system should ideally log fault codes indicative of fuel system related failures, and pressure sensor failures in particular, to assist in repair efforts, and should additionally provide for a limp home fueling operational mode so that the vehicle can be driven out of danger and/or to a repair facility.
SUMMARY OF THE INVENTION
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, apparatus for diagnosing a fuel system of an internal combustion engine comprises an accumulator receiving pressurized fuel from a source of pressurized fuel, means for sensing fuel pressure within the accumulator and producing a pressure signal corresponding thereto, the pressure signal having peak values corresponding to peak pressures of fuel supplied thereto by the source of pressurized fuel, and a control computer sampling a number of first pressure values each near a separate one of the peak values and determining a number of pressure error values each between a separate one of the number of first pressure values and a corresponding reference pressure, the control computer determining a variance of at least some of the number of pressure error values and incrementing an error counter if the variance exceeds a variance threshold.
In accordance with another aspect of the present invention, a method of diagnosing a fuel system of an internal combustion engine comprises the steps of supplying fuel from a source of pressurized fuel to an accumulator based on a target fuel pressure value, measuring a number of peak pressure values within the accumulator each near corresponding actual peak pressures therein resulting from the supplying step, determining a number of error pressure values each between a separate one of the peak pressure values and the target fuel pressure value, determining a variance of at least some of the number of error pressure values, and incrementing an error counter if the variance exceeds a variance threshold.
In accordance with either of the foregoing aspects, the error counter is decremented, preferably not below a predefined count value, if the variance is less than the variance threshold. If the error counter exceeds a predefined count value, a fault code is logged and a limp home fueling algorithm is preferably executed.
One object of the present invention is to provide an apparatus and method for diagnosing erratic pressure sensor related failures in an electronically controlled fuel system of an internal combustion engine.
Another object of the present invention is to provide such an apparatus and method that logs a fault code and executed a limp home fueling algorithm upon detection of erratic pressure sensor behavior.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.
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Hemmerlein Rodney J.
West Stephen
Barnes & Thornburg
Cummins Engine, Inc.
Miller Carl S.
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