Patent Application
20070227984
The present invention relates to fuel injectors for internal combustion engines; more particularly, to a fuel injector with a built-in orifice for reducing pressure pulsations.
Fuel injectors for controllably metering fuel to the combustion cylinders of internal combustion engines are well known. For ease and reliability in manufacturing, the fuel injectors typically are mounted by their inlet ends at appropriate intervals into a rigid fuel supply line harness, appropriately configured to place the injection end of each fuel injector into its corresponding injection socket in the manifold runner. Such a harness is known as a fuel injector rail, or simply a fuel rail.
In a typical direct injector fuel injection system, each injector is programmed to pulse or open every other revolution of the engine crankshaft. During an injector opening event in a direct injector fuel injection system, the measured fuel pressure in the fuel rail can instantaneously drop by more than 30 kPa, then can increase by more than 50 kPa after the injector closes. Although such high and low pressures can vary widely depending on rail volume, injector open/close time, and inlet line inner diameter, for example, in a typical four cylinder engine operating at 2000 RPM, the combined injectors can pulse at a rate of 66 pulses per second. In such injector-based systems, these pulses cause high frequency pressure waves of significant amplitude to propagate through the fuel rail(s) potentially causing erratic delivery of fuel to the cylinders.
The fuel rails themselves are typically bolted to the cylinder head. In one prior art design, the fuel rail is laterally offset from the position of the bolts which are secured to the cylinder head through brackets. The fuel rail is offset so the bolts are accessible when attaching or removing the fuel rail from the cylinder head. In this design, the brackets extend around a respective fuel injector socket, into which the inlet ends of the injectors are placed. This prior art design requires a jump tube leading from the rail to the respective injector socket.
One known method for reducing injector pressure pulsations is to include a restriction orifice in the fuel line leading to the injector. Due to the narrowing of the flow area, the restriction orifice breaks up and thus reduces the pressure pulsations. The location of the restriction orifice should be somewhere between the fuel rail and injector. In one known design, the restriction orifice is placed inside the jump tube. While this method is effective at reducing pressure pulsations, it also adds cost and complexity to the fuel system.
It would therefore be desirable to have a design and method for reducing pressure pulsations in a fuel line that does not increase cost or complexity to the system.
The present invention addresses the above need by providing a design and method for reducing pressure pulsations in a fuel line caused by the opening and closing of the fuel injectors. In a preferred embodiment, a restriction orifice is provided in the fuel injector filter of a respective fuel injector. The restriction orifice acts to break up and thus reduce or eliminate pressure pulsations through the fuel injector.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Referring to
It is noted that fuel rail 10 and bracket 12 are shown for purposes of environment only, and the present invention may be used in any fuel delivery system having one or more fuel injectors.
Fuel injectors 18 each have a fuel inlet end 18a and fuel outlet end 18b. Fuel is thus directed through fuel outlet end 18b upon the opening of the injector. As stated above, fuel injectors open and close very rapidly in order to provide the correct amount of fuel to the engine depending on the engine load condition. Without corrective measures being taken, unacceptable amounts of noise and vibration are created due to the rapid opening and closing of the fuel injectors as they pass fuel into the engine.
Referring to
The fuel injector filter is positioned within the longitudinal passageway 18c of the injector 18 to intercept and filter the fuel flowing therethrough prior to the fuel exiting the injector at outlet end 18b. As seen best in
It is noted that fuel filter bodies are typically injection molded from a plastic such as Nylon 66, for example. In a preferred embodiment, the restriction orifice 20 is between about 0.75 to about 2 mm in diameter although the final size will depend on the particular injector design employed. This restriction orifice is sufficient to substantially reduce or eliminate pressure pulsations in the fuel lines occurring as a result of the opening and closing of the fuel injectors.
While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.
