Internal-combustion engines – Charge forming device – Exhaust gas used with the combustible mixture
Reexamination Certificate
2000-03-23
2001-09-25
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Charge forming device
Exhaust gas used with the combustible mixture
C701S108000
Reexamination Certificate
active
06293267
ABSTRACT:
TECHNICAL FIELD
This invention relates to the control of an engine control valve such as an exhaust gas recirculation (EGR) valve, and more particularly to a control based on a commanded flow rate.
BACKGROUND OF THE INVENTION
An important aspect of motor vehicle engine control concerns proper positioning of a number of valves which control or regulate the passage of a compressible medium. For example, an exhaust gas recirculation valve is controlled to return a desired amount of exhaust gas to the intake air stream for emission control purposes.
A common approach utilized to control such valves is to specify a valve position in terms of various input parameters, based on extensive empirical testing and calibration. However, this approach is very time consuming and inefficient, and needs to be repeated or revised for each new powertrain configuration, or each change in an existing powertrain configuration. Furthermore, the trend in engine control is to develop model-based commands that take engine and vehicle dynamics into account, and the control methodology described above is not well suited to a model-based approach. Accordingly, what is needed is an improved control methodology that requires less calibration effort, that is less sensitive to changes in powertrain configuration, and that is more amenable to a model-based control approach.
SUMMARY OF THE INVENTION
The present invention is directed to an improved control methodology for an engine control valve, in which the valve is positioned in response to a commanded flow rate of a controlled medium. The method involves a valve characterization procedure in which the actual flow rate is measured for various combinations of valve position and pressure ratio across the valve, subject to a standard set of upstream pressure and temperature values. This results in a table of valve position in terms of pressure ratio and standard flow rate—that is, flow rate under the standard upstream pressure and temperature values. In operation, a controller addresses the table to obtain the desired valve position as a function of a determined pressure ratio across the valve, and a desired standard flow rate determined based on the commanded flow rate and the pressure and temperature of the controlled medium upstream of the valve, relative to the standard pressure and temperature values.
The calibration effort required for the control of this invention is significantly reduced compared to the conventional approach, and the control is based on the physical characteristics of the valve so that the flow rate can be scheduled based on engine control considerations. Additionally, the control is modular in nature, which minimizes the re-design and re-calibration efforts required due to changes in system design.
REFERENCES:
patent: 4750352 (1988-06-01), Kolhoff
patent: 5107724 (1992-04-01), Takizawa
patent: 5465617 (1995-11-01), Dudek et al.
patent: 5845627 (1998-12-01), Olin et al.
patent: 5974870 (1999-11-01), Treninies et al.
patent: 6178373 (2001-01-01), Davis et al.
Maloney Peter James
Smith James Craig
Castro Arnold
Cichosz Vincent A.
Delphi Technologies Inc.
Wolfe Willis R.
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