Internal-combustion engines – Charge forming device – With fuel pump
Patent
1988-12-15
1991-12-31
Miller, Carl Stuart
Internal-combustion engines
Charge forming device
With fuel pump
123447, F02M 3704
Patent
active
050762397
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to the injection of fuel in an internal combustion engine, and more specifically, to controlling fuel injection so as to reduce the fuel injection rate at the start of fuel injection, especially under low-speed or low-load conditions so as to reduce combustion noise.
It is well known that the combustion noise of a diesel engine can be reduced under low-speed or low-load conditions by reducing the fuel injection rate. This has been achieved by providing a valve that opens to bleed fuel from the working chamber of the pump under low-speed or low-load conditions. For example, British Patent No. 2048373 discloses a fuel injection pump having a solenoid-operated valve that controls connection of the pump working chamber to an accumulator via a flow restrictor. The valve is urged to a closed position by spring means and fuel pressure in the pump working chamber, and is opened by the solenoid when energised. However, there is a tendency for the valve to reciprocate in operation due to the force of the solenoid overcoming the dynamic throttling effect of the fuel flow through the valve. Further, the fuel flow through the valve is dependent upon the lift pressure of the injector valves and upon the temperature of the fuel. Therefore, the valve is subject to wear and is inconsistent in operation. British Patent No. 1261246 discloses a fuel injection pump having a valve that controls connection of the pump working chamber through a restrictor to a closed chamber. The valve is a spool valve or rotary valve that is held either open or closed and is moved between these positions in accordance with engine operating conditions, such as engine speed or load.
U.S. Pat. No. 4,449,504 discloses a fuel injection pump having an accumulator connected to the pump working chamber so that it is responsive to the fuel pressure therein and serves to increase the volume of the working chamber with increasing fuel pressure under low-speed or low-load conditions. The accumulator comprises a piston which is moveable in a bore connected to the pump working chamber and which is backed up by a spring in a spring chamber that is connected via a rotary valve to the pump fuel supply. Under low-speed or low-load conditions, the piston is free to move against the action of the spring, but above a predetermined threshold speed or load, the valve is closed to isolate the spring chamber and thereby substantially lock the piston against movement.
German Patent No. 883038 discloses a fuel injection device in which an accumulator connected with the fuel supply line via a flow restrictor is used to automatically advance the start of fuel injection with increasing engine speed. This patent is totally concerned with events occurring within the fuel supply line, accumulator and orifice prior to the commencement of fuel injection in each cycle of the engine and the flow restrictor is specified as being sufficiently wide so that across the entire speed range of the engine the peak pressure in accumulator remains substantially the same.
British Patent No. 1573981 discloses a fuel injection device in which a very small accumulator is connected with the fuel supply line via a flow restrictor in order to reduce variations in fuel pressure at the end of the fuel injection stage of each cycle of the engine so as to produce a sharp cut-off in injection.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an improved method and means of controlling fuel injection, in particular to reduce combustion noise by reducing the fuel injection rate at the start of fuel injection, especially under low-speed conditions.
According to one aspect of the invention, a method of controlling the injection of fuel from a pressurised fuel supply via an injector valve of a fuel injector is characterised in that a closed chamber is connected via a permanently open flow restriction to the pressurised fuel supply, the volume of the closed chamber and the cross-sectional flow area of the restriction being selected to allow
REFERENCES:
patent: 2810375 (1957-10-01), Froehlich
patent: 3416506 (1968-12-01), Steiger
patent: 3810453 (1974-05-01), Wolfe
patent: 4029071 (1977-06-01), Saito
patent: 4161161 (1979-07-01), Bastenhof
patent: 4421088 (1983-12-01), Seilly
Miller Carl Stuart
Perkins Engines Group Limited
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