Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1994-08-10
1996-07-30
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Fuel injection system
F02M 5100
Patent
active
055402054
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the controlling of the air fuel ratio of the combustion mixture for a fuel injected internal combustion engine. In the specification, the reference to air fuel ratio is in relation to the overall air fuel ratio for each engine cycle and does not refer to air fuel ratio at any particular location within the combustion chamber of the engine.
Conventional homogeneous charge internal combustion engines normally utilise an air-fuel delivery system in which the amount of air flowing to the engine is controlled by the operator and the amount of air-flow inturn determines the amount of fuel to be delivered to the engine. Thus the amount of air flowing to the engine directly determines the power output of the engine. This is true for both carburetted and fuel injected systems. For example, with a typical fuel injected system an air-flow meter is employed to determine the amount of air flowing to the engine. The fuel to be injected to the engine is then determined by reference to, inter alia, the measured air-flow.
However, with recent developments in internal combustion engine technology there is a tendency to stratify the air-fuel mixture within the combustion chamber. This is particularly true of some two-stroke cycle engines. When a stratified charge mixture is utilised there will be an excess of air within the combustion chamber which will not be involved in the combustion process. Thus the total amount of air flowing to the engine is, in general, not directly related to the engine power output as is the case for a homogeneous charge engine. In such a case it is desirable to de-couple the fuel flow to the engine from the air flow to the engine so that the air and fuel flows can be independently controlled. One such method of achieving this de-coupling is known as a Drive-By-Wire (DBW) system with engine fuel control.
In a conventional DBW system the operator does not directly control the air or the fuel but merely generates a signal ("demand" signal) which indicates the operators requirements (eg. increase or decrease in power output from the engine). This demand signal may then be processed by an Electronic Control Unit (ECU) which controls the air flow and which in turn determines the fuel flow requirements of the engine. By incorporating an engine fuel control function to the conventional DBW system the ECU controls the fuel flow which in turn determines the air flow requirements of the engine. Although such a system satisfies the required need for de-coupling it has certain disadvantages.
The applicants co-pending Australian Patent Application No. 51065/90, which is hereby incorporated by reference, describes a partial DBW system with engine fuel control or "hybrid" DBW system. In this system there is a direct mechanical linkage to a main air throttle and an ECU controlled by-pass of the main throttle. The by-pass is of such proportions that it can supply the entire air flow to the engine at low loads and speeds but cannot supply the entire air flow required at high loads and speeds. Thus, the sizing of the by-pass, which is not mechanically linked to the driver, is such that if some excursion in the normal control of the by-pass did occur it would not lead the engine to enter into a high power output operating region which could be dangerous. Furthermore, apart from the cost and weight advantages the hybrid system also provides increased accuracy since the resolution in the control function is increased as only a part of the total air flow area is being affected, and improved responsiveness due to the lower inertia of moving parts due to their smaller size.
With this hybrid system the ECU controlled by-pass can, in the low load region of engine operation, fully control the air flow to the engine. As the load demand on the engine is increased the mechanically operated main throttle will allow some air flow to the engine. When this occurs the by-pass can be used as a trimming device to provide the desired amount of air-flow to the engine. This facility is discussed more fully in our
REFERENCES:
patent: 4932371 (1990-06-01), Albertson et al.
patent: 4960097 (1990-10-01), Tachibana et al.
patent: 5339784 (1994-08-01), Fukui
patent: 5341786 (1994-08-01), Abe et al.
patent: 5349933 (1994-09-01), Hasegawa et al.
Davis Robert M.
Smith Darren A.
Thompson Ian R.
Nelli Raymond A.
Orbital Engine Company (Australia) Pty. Limited
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