Importance

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Abstract

Fuel injection equipment for an internal combustion engine is modified by connecting a closed chamber (28) via a permanently open flow restriction (29) either to the working chamber (11) of a fuel pump (1), or to a high pressure fuel supply connection (36) between the output of the working chamber (11) and a fuel injector (39), or to a pressurized fuel supply passage (55) in the injector upstream of an injector valve (48). The volume of the closed chamber (28) and the cross sectional flow area of the restriction (29) are selected to allow a predetermined volume of pressurized fuel to flow into the closed chamber (28) when the equipment is operating, thereby reducing the flow of fuel through the injector valve (48) during the initial period of injection. To reduce combustion noise at and below a predetermined engine speed, the volume of the closed chamber (28) and the cross sectional flow area of the restriction (24) are selected to allow a predetermined volume of fuel to flow into the closed chamber (28) during the ignition delay period at said predetermined speed, said predetermined volume of fuel corresponding to the maximum compressiblity of the fuel in the closed chamber at said predetermined engine speed. A second flow restriction (40) is added in the flow path (41) to the fuel injector (39) downstream of the connection to the closed chamber (28). This second restriction (40) is located adjacent to the connection (29) to the closed chamber (28) and has a cross sectional flow area comparable to the minimum cross sectional flow area of the flow path downstream of the second restriction (40).

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First Claim