Internal-combustion engines – Engine speed regulator – Having condition responsive means with engine being part of...
Patent
1996-01-29
1997-05-13
Moulis, Thomas N.
Internal-combustion engines
Engine speed regulator
Having condition responsive means with engine being part of...
123436, F02D 4134, G01P 1100
Patent
active
056282915
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a fuel system for an internal combustion engine, the system comprising a fuel pump, a controller for controlling the operation of the fuel pump so that fuel is delivered to the engine at the required time and in the desired quantity, means for supplying a demand signal to the controller, a wheel driven by the engine, a plurality of indicia on the wheel, and positioned about the axis of rotation thereof, transducer means responsive to the passage of said indicia as the wheel rotates, and means responsive to the signals generated by said transducer means for measuring the time intervals between the passage of the indicia past said transducer means.
In an example the indicia take the form of teeth which are formed in the periphery of the wheel and the transducer means is a variable reluctance probe. However, the indicia may have other forms such for example as a plurality of marks on the surface of the wheel and the transducer means in this case would comprise an optical sensor. The teeth or other indicia are equiangularly spaced about the axis of rotation of the wheel however, due to manufacturing difficulties the spacings may not be exactly equal and this means that for a given speed of rotation of the wheel, the time intervals between the passage of the teeth past the transducer means will not be equal and therefore the speed signal which is computed each time a tooth passes the transducer means will not be constant even through the rotational speed is constant.
In practice the speed of an engine fluctuates in a generally sinusoidal manner, as each engine cylinder partakes of its power stroke and this represents an additional problem when determining the engine speed.
W0-A-9307497 and U.S. Pat. No. 5,117,681 describe methods of correcting for tooth spacing errors but in each case the assumption is made that it is possible during operational use of the engine to arrange that the engine speed is either constant or there is a constant speed change. In W0-A-9307497 the constant speed change is said to take place when the engine is decelerating. U.S. Pat. No. 5,117,681 also refers to engine deceleration and advocates that this should be carried out with the fuel supply to the engine cut off and with the throttle closed. As an alternative it is stated that the engine speed can be regarded as constant when the engine is being cranked by the starter motor without fuel being supplied to the engine.
The engine in U.S. Pat. No. 5,117,681 is clearly a spark ignition engine having a much lower compression ratio than a diesel engine. It is not clear what sort of engine is envisaged in W0-A-9307497.
Applicant has found that with the much higher compression ratio of a diesel engine which of course does not have an air flow restricting throttle, there is still sufficient engine speed fluctuation on overrun or when the engine is decelerating, to make it necessary to take the speed fluctuation into account.
The object of the invention is to provide such a system in a simple and convenient form.
According to the invention a fuel system of the kind specified includes means for determining indicia spacing errors from the signals provided by the transducer means and further means responsive to the generally sinusoidal fluctuation of engine speed for correcting the determined indicia spacing errors, the corrected determined indicia spacing errors being utilised with the measured time intervals to provide an engine speed signal to the controller.
An example of a fuel system in accordance with the invention will now be described with reference to the accompanying drawings and diagrams in which:
FIG. 1 is a diagrammatic layout of the fuel system as applied to a compression ignition engine,
FIG. 2 is a graph showing a pseudo random sequence of tooth spacing errors for a 60 tooth wheel, the X axis showing the tooth number and the Y axis the error in degrees,
FIG. 3 is a graph showing the estimated tooth spacing errors as determined using a first processing step of the invention but showing in addition the eff
REFERENCES:
patent: 4553427 (1985-11-01), Kuraoka et al.
patent: 5117681 (1992-06-01), Dosdall et al.
patent: 5207199 (1993-05-01), Sekiguchi
patent: 5339781 (1994-08-01), Osawa
patent: 5385129 (1995-01-01), Eyberg
patent: 5495415 (1996-02-01), Ribbens et al.
Gravestock Robert E.
Wrobel Jeremy S.
Lucas Industries Public Limited Company
Moulis Thomas N.
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