Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1991-01-29
1993-10-26
Argenbright, Tony M.
Internal-combustion engines
Charge forming device
Fuel injection system
123492, 123493, F02D 4110, F02D 4112, F02D 4122
Patent
active
052556557
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a fuel injection system for an internal combustion engine.
BACKGROUND OF THE INVENTION
In an internal combustion engine having a fuel injection system, it is necessary to inject the correct amount of fuel into the engine to produce a stoichiometric fuel/air mixture to produce satisfactory operation of the engine. In stationary conditions this is the state of the art. However, as the load on the engine increases, the amount of air drawn into each cylinder increases accordingly, and it is necessary to increase the amount of fuel injected. Conversely, as the load on the engine decreases it is necessary to reduce the amount of fuel injected. The correct matching of the air/fuel ratio even in these dynamic conditions is still a problem.
In present systems it is usual to provide a sensor in the air inlet system of the engine to give a measure of the engine load in the form of an electrical signal as a basis for calculating the amount of fuel which needs to be injected. Examples of such sensors are a pressure sensor, a hot film or hot wire air mass meter and a flap-type meter. The signals obtained from such sensors follow the load very accurately during constant load conditions and even during slowly-changing load conditions. However, under rapidly-changing load conditions, the signals obtained are inaccurate and lead to mismatching of the injected fuel. For example, the signals evaluated from a pressure sensor can only follow the true change in the load slowly with a certain delay, and thus signals obtained from it for the amount of fuel calculated therefrom to be injected produces a lean mixture. Signals from the other types of sensors mentioned overshoot considerably the value corresponding to the true load during rapidly-changing load conditions due to the fact that they measure the air drawn into the manifold which must first be filled with air, before the actual cylinder charge is increased. In some cases, after a first overshoot of the signal an undershoot occurs, especially in the case of a flap-type meter. The result is a fuel/air mixture which can excessively be rich or lean. A further reason for mismatching of the air/fuel ratio during load changes is the resulting variation of the fuel wall film which needs to be compensated for by special algorithms.
It is an object of the present invention to provide a fuel injection system for an internal combustion engine which is able to follow a rapidly-changing load more closely, and to maintain the desired air/fuel ratio.
SUMMARY OF THE INVENTION
The present invention is a fuel injection system for an internal combustion engine that calculates the pulse width of an angle-synchronous fuel injection pulses based on a main engine load sensor signal and a throttle valve angle sensor signal. The main engine load sensor signal is generated from a sensor, for example, that measures the pressure in an engine air inlet system. The throttle valve engine sensor signal is a measurement of the degree of opening of an engine throttle. The throttle valve angle sensor signal is used to change the calculation of the basic angle-synchronous fuel injection signal when the measured rate of change of the throttle valve angle is at or above a predetermined value which enables the fuel/air mixture to more closely follow any rapid change in engine load.
The present invention also changes calculation of the basic angle-synchronous fuel injection signal by altering filtering characteristic of a filter function normally applied to the basic angle-synchronous fuel injection signal, by altering sampling of the signal from the main engine load sensor, or by deriving the basic angle-synchronous fuel injection signal from the throttle valve angle signal instead of from the main load sensor signal. In addition, the system of the present invention discloses injecting one or more intermediate synchronous fuel injection pulses between the normal angle-synchronous fuel injection pulses to further enable the fuel/air mixture to more cl
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patent: 4817572 (1989-04-01), Nakaniwa et al.
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Patent Abstracts of Japan vol. 10, No. 234 (M-507) (2290) Aug. 14, 1986, JP-A-61 66825 (Japan Electronic Control Syst Co Ltd) Apr. 5, 1986.
Patent Abstracts of Japan vol. 7, No. 265 (M-258) (1410) Nov. 25, 1983, JP-A-58 144635 (Toyota Jidosha Kogyo K.K.) Aug. 29, 1983.
Denz Helmut
Roth Andreas
Wild Ernst
Argenbright Tony M.
Robert & Bosch GmbH
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