Fluid sprinkling – spraying – and diffusing – Injection nozzle opened by relieving supply
Reexamination Certificate
2001-03-02
2003-05-06
Ganey, Steven J. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Injection nozzle opened by relieving supply
C239S088000, C239S124000, C239S533400, C239S533900, C239S585100, C123S468000, C123S472000
Reexamination Certificate
active
06557779
ABSTRACT:
TECHNICAL FIELD
This invention relates to an improved fuel injector which effectively controls the flow rate of fuel injected into the combustion chamber of an engine.
BACKGROUND OF THE INVENTION
In most fuel supply systems applicable to internal combustion engines, fuel injectors are used to direct fuel pulses into the engine combustion chamber. A commonly used injector is a closed-needle injector which includes a needle assembly having a spring-biased needle valve element positioned adjacent the needle orifices for resisting blow back of exhaust gas into the pumping or metering chamber of the injector while allowing fuel to be injected into the cylinder. The needle valve element also functions to provide a deliberate, abrupt end to fuel injection thereby preventing a secondary injection which causes unburned hydrocarbons in the exhaust. The needle valve is positioned in a needle cavity and biased by a needle spring to block fuel flow through the needle orifices. In many fuel systems, when the pressure of the fuel within the needle cavity exceeds the biasing force of the needle spring, the needle valve element moves outwardly to allow fuel to pass through the needle orifices, thus marking the beginning of injection. In another type of system, such as disclosed in U.S. Pat. No. 5,676,114 to Tarr et al., the beginning of injection is controlled by a servo-controlled needle valve element. The assembly includes a control volume positioned adjacent an outer end of the needle valve element, a drain circuit for draining fuel from the control volume to a low pressure drain, and an injection control valve positioned along the drain circuit for controlling the flow of fuel through the drain circuit so as to cause the movement of the needle valve element between open and closed positions. Opening of the injection control valve causes a reduction in the fuel pressure in the control volume resulting in a pressure differential which forces the needle valve open, and closing of the injection control valve causes an increase in the control volume pressure and closing of the needle valve. U.S. Pat. No. 5,463,996 issued to Maley et al. discloses a similar servo-controlled needle valve injector.
Internal combustion engine designers have increasingly come to realize that substantially improved fuel supply systems are required in order to meet the ever increasing governmental and regulatory requirements of emissions abatement and increased fuel economy. It is well known that the level of emissions generated by the diesel fuel combustion process can be reduced by decreasing the volume of fuel injected during the initial stage of an injection event while permitting a subsequent unrestricted injection flow rate. As a result, many proposals have been made to provide injection rate control devices in closed needle fuel injector systems. One method of controlling the initial rate of fuel injection is to spill a portion of the fuel to be injected during the injection event. For example, U.S. Pat. No. 5,647,536 to Yen et al. discloses a closed needle injector which includes a spill circuit formed in the needle valve element for spilling injection fuel during the initial portion of an injection event to decrease the quantity of fuel injected during this initial period thus controlling the rate of fuel injection. A subsequent unrestricted injection flow rate is achieved when the needle valve moves into a position blocking the spill flow causing a dramatic increase in the fuel pressure in the needle cavity. However, the needle valve is not servo-controlled and, thus, this needle assembly does not include a control volume for controlling the opening and closing of the needle valve. Moreover, the rate shaping needle assembly does not permit the rate to be selectively varied.
Other rate shaping systems decrease rate of fuel flow during the initial portion of the injection event by, for example, throttling the fuel to the needle orifices. Although these systems create injection rate shaping, the spilling and throttling of fuel during the initial period of injection achieves a reduced injection flow rate by reducing the injection pressure adjacent the needle orifices. The decrease in injection pressure may disadvantageously result in decreased atomization of the fuel spray by the needle orifices, thus adversely affecting fuel economy and increasing emissions.
Another manner of optimizing combustion is to create pilot and/or post injection events. Most current diesel injectors include fixed needle orifice areas sized to provide optimum injection duration at rated speed and load with the highest allowable injection pressure. However, in order to optimize combustion, pilot and post injection events must include extremely small quantities of fuel at high injection pressures. With a fixed spray orifice size, this results in an extremely short event that is difficult to control. To compensate, the needle opening velocity may be reduced so that the fuel flow is throttled before the spray orifices during the pilot and post injection events. However, needle velocity is not easily controllable from injector to injector, while throttling wastes fuel energy and does not provide optimum combustion performance. At low speed and light load, it is also desirable to have small spray orifices to increase injection duration without lowering injection pressure.
Another fuel injector design providing some limited control over fuel injection rate and quantity includes two needle valve elements for controlling the flow of fuel through respective sets of injection orifices. For example, U.S. Pat. No. 5,458,292 to Hapeman discloses a fuel injector with inner and outer injector needle valves biased to close respective sets of spray holes and operable to open at different fuel pressures. The inner needle valve is reciprocally mounted in a central bore formed in the outer needle valve. However, the opening of each needle valve is controlled solely by injection fuel pressure acting on the needle valve in the opening direction such that the valves necessarily open when the injection fuel pressure reaches a predetermined level. Consequently, the overall and relative timing of opening of the valves, and the rate of opening of the valves, cannot be controlled independently. Moreover, the valve opening timing and rate is undesirably dependent on the injection fuel pressure.
U.K. Pat. Application No. 2266559 to Hlousek discloses a closed needle injector assembly including a hollow needle valve for cooperating with one valve seat formed on an injector body to provide a ma in injection through all the injector orifices and an inner valve needle reciprocally mounted in the hollow needle for creating a pre-injection through a few of the injector orifices. However, the valve seat allowing the inner valve needle to block the pre-injection flow is formed on the hollow valve member and the inner valve needle is biased outwardly away from the injector orifices. This arrangement requires a third valve seat for cooperation with the inner valve element when in a pre-injection open position to prevent flow through all of the injector orifices, resulting in an unnecessarily complex and expensive assembly. Also, this assembly is designed for use with two different sources of fuel requiring additional delivery passages in the injector. In addition, like Hapeman, this design requires the timing and rate of opening of at least one of the needle valves to be controlled by fuel injection pressure thereby limiting injection control.
U.S. Pat. No. 5,199,398 to Nylund discloses a fuel injection valve arrangement for injecting two different types of fuels into an engine which includes inner and outer poppet type needle valves. During each injection event, the inner needle valve opens a first set of orifices to provide a preinjection and the outer needle valve opens a second set of orifices to provide a subsequent main injection. The outer poppet valve is a cylindrical sleeve positioned around a stationary valve housing containing the inner poppet valve.
U.S. Pat. No. 5
Benson Donald J.
Carroll, III John T.
Perr J. Victor
Perr Julius P.
Peters Lester L.
Brackett, Jr. Tim L.
Cummins Engine Company, Inc.
Ganey Steven J.
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