Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1995-01-04
1996-03-05
Argenbright, Tony M.
Internal-combustion engines
Charge forming device
Fuel injection system
123480, F02D 4124, F02D 4130
Patent
active
054958415
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a device and method for correcting the fuel amount in an internal combustion engine.
Because of the growing demand for minimising emissions from Otto engines an increasing amount of interest bas been shown in sequential computer controlled injection of fuel to the inlet valves. Sequential injection, where the fuel is injected individually for each cylinder to the inlet valve, where the cylinder is already in or at the beginning of the intake stroke, provides more precise dosing of the fuel before each combustion than if the fuel were to be injected simultaneously as soon as a cylinder is in the intake stroke. There are a number of patents on computer controlled sequential injection. In U.S. Pat. No. 4,785,784 and U.S. Pat. No. 4,961,411 two computer controlled injection systems are described in which two injections per cylinder take place for each intake stroke, and in which the second injection provides a correcting quantity if the fuel requirement has been changed since the first injection was initiated. The purpose of this is to ensure a faster response in transient load cases. The two-stage injection in these patents generally takes place as a split injection, and also mainly whilst the inlet valve is open.
SUMMARY OF THE INVENTION
The invention is applied advantageously to Otto engines with electronic, computerised control of preferably sequential fuel injection. The object of this invention is to provide a fast response and optimum performances by simple means in transient load cases, with the smallest possible number of fuel flow calculations. A further object is to obtain a single, coherent injection based on the most instantaneous engine parameters possible, without the need for a continuously repeated calculation of the fuel demand. A single injection, with only one mechanical opening and one mechanical closing of the injector, favours more precise dosing of the fuel quantity since the fuel flow is irregular and difficult to define both during the opening and closing phases, whilst the flow with a fully open valve is relatively regular and well defined. To achieve these advantages the device according to the invention for correcting the fuel flow includes means for determining the stroke position of the engine, fuel injection means selectively activatable during respective cycles of the engine for injecting fuel towards the inlet valve, and control means for controlling the activation and deactivation of the fuel injection means in accordance with a fuel amount demand. The control means includes a memory for storing the fuel amount demand during one cycle of operation as a base value, interrupt means for storing a preliminary value of a time period during which the injection means is to remain activated, the preliminary value being determined in accordance with the base value means for determining the instantaneous fuel demand, and means for comparing the instantaneous fuel demand with the base value and, if the instantaneous fuel demand differs from the base value by a predetermined amount, changing the preliminary value to a corrected value corresponding to the instantaneous fuel demand. The injection means remains activated for a time period equal to the preliminary value or, if the preliminary has been changed, the corrected value.
A method in accordance with the invention includes activating the fuel injection means for a first predetermined time interval based upon an activation time period for the injection means during a preceding cycle of operation, determining at the time of activation or deactivation of the injection means the instantaneous fuel demand of the cylinder and, in the event of a difference exceeding a predetermined amount of the instantaneous fuel demand from the fuel demand corresponding to the first predetermined time interval, correcting the activation time of the injection means to a second time interval corresponding to the instantaneous fuel demand.
A further object, of an embodiment of the invention is to use
REFERENCES:
patent: 4646698 (1987-03-01), Inoue et al.
patent: 4785784 (1988-11-01), Nanyoshi et al.
patent: 4911131 (1990-03-01), Nakaniwa et al.
patent: 4961411 (1990-10-01), Oshiage et al.
patent: 4987544 (1991-01-01), Honda et al.
patent: 5003953 (1991-04-01), Welgarz et al.
patent: 5050084 (1991-09-01), Nakaniwa
Gillbrand Peter
Tegnelius Lars
Argenbright Tony M.
Saab Automobile Aktiebolag
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