Internal-combustion engines – Charge forming device – Combined liquid and gaseous fuel
Patent
1996-04-12
1997-05-13
Solis, Erick R.
Internal-combustion engines
Charge forming device
Combined liquid and gaseous fuel
123575, F02M 2102, F02D 1906, F02C 940, F23N 500
Patent
active
056282940
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a system and method for the metered supply of at least a first and a second type of fuel, in particular petrol and LPG (Liquid Petroleum Gas), to a combustion installation, such as an internal combustion engine.
Combustion installations, which operate on more than one type of fuel, such as internal combustion engines, whereby the fuel supply is controlled by means of an electrical/electronic control unit are known per se in practice. The differences in energy content of the fuels concerned, which necessitate adapted metering, constitute a problem to be solved with such installations.
Netherlands Patent Application 82.00993 describes a system for the metered supply of petrol and/or LPG to an internal combustion engine with the aid of time-controlled fuel injectors. A mutually correct mechanical calibration of the petrol and LPG injectors used enables both types of injectors to be controlled by the same electronic control unit, which controls the duration and frequency of opening of the injectors, over the entire power and speed range of the engine.
International Patent Application W0-A-9,208,888 likewise describes a system for electronically controlled metering of the supply of petrol and LPG to an internal combustion engine, with which system the differences in energy content of the different types of fuel are compensated for with the aid of an additional electronic unit instead of by mechanical calibration of the injectors concerned. With this system the original electronic control unit for the petrol injectors is then used to determine the frequency of opening of the LPG injectors, whilst the additional electronic unit converts the duration of opening of the petrol injectors into a corresponding value for LPG. This system can essentially be regarded as the electronic equivalent of the mechanically calibrated fuel supply system disclosed in the said Netherlands Patent Application 82.00993.
Both systems have a facility for adapting the duration of opening of the injectors to a changing composition of the fuel, in which context consideration can be given to, for example, winter and summer composition of LPG, as a consequence of which the calorific value and the required amount of air per unit volume of fuel injected are not constant.
It has been found that this method of metering of the types of fuel is not optimum, which can be appreciated as follows.
Present day control units used for internal combustion engines have adaptive control characteristics. That is to say, the control unit is configured in such a way that it adjusts automatically to a change in the demand for fuel owing to, for example, wear, play or other causes in the engine, so as to be able to deliver performances comparable to those obtained when the engine is without defect. If an engine is run for a prolonged period on a first type of fuel, for example petrol, the control strategy of the control unit will have been optimally adjusted for petrol metering.
In particular because of the differences in calorific value of the types of fuel used, it will be clear that when there is a changeover from petrol to, for example, LPG the control unit will, as a consequence of its adaptive mode of operation, in the course of time adjust its control strategy to the optimum for LPG. In order to compensate for the metering variations which occur in the engine as a consequence of wear, play and the like, these two control strategies will, in general, not be the same.
On switching back from LPG to petrol a situation can then also arise in which, as a consequence of the use of LPG, the control unit has been adjusted into a region completely outside the operating range for petrol. Consequently, before optimum metering for petrol is achieved again, the internal combustion engine is not adequately controlled, which gives rise to temporarily reduced performance, but also to incorrect combustion with emissions causing additional environmental pollution and, possibly, a higher fuel consumption as the major adverse characteristics. Damage to
REFERENCES:
patent: 5228423 (1993-07-01), Oikawa et al.
patent: 5531200 (1996-07-01), Hosoe et al.
De Laat-De Haas Petronella C.
Krieckaert Paul E. C.
Oerlemans Johannes G. W. M.
Gentec B.V.
Solis Erick R.
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