The present disclosure relates generally to a fuel system for an internal combustion engine, and more particularly to positioning an isolation valve assembly between each of a plurality of fuel injectors in a fuel system and a common drain conduit.
Internal combustion engines are well known and widely used in applications ranging from electrical power generation to providing torque for machinery propulsion, and powering pumps, compressors, and other equipment. In some internal combustion engines, such as compression ignition diesel engines, the subsystem for providing fuel is complex and has many rapidly moving parts, high fluid pressures, and otherwise harsh conditions. Service life of such fuel systems is typically desired to be in the tens of thousands of hours. In a typical fuel system for a compression ignition diesel engine, a plurality of fuel injectors are each associated with one of a plurality of cylinders and extend into the individual cylinders to directly inject metered amounts of pressurized fuel. Individual fuel injectors may be equipped with so-called unit pumps having a fuel pressurization plunger driven by an engine cam or hydraulic fluid, for example. In other systems a common reservoir of pressurized fuel known as a common rail serves as a reservoir for storing a volume of fuel at a suitable injection pressure.
In either of these systems, some of the hydraulically actuated and electrically actuated components can be sensitive to fluid pressure phenomena generated elsewhere in the system. One known common rail fuel system, for instance, is disclosed in United States Patent Application No. 2011/0297125 to Shafer et al.
In one aspect, a fuel system includes a plurality of fuel injectors, each of the plurality of fuel injectors including an injection control valve assembly and a direct operated nozzle check, and having a high pressure nozzle supply passage and a check control chamber formed therein. The fuel system further includes a common drain conduit fluidly connected to each of the plurality of fuel injectors to receive drained actuating fluid for each of the direct operated nozzle checks. The fuel system still further includes a plurality of isolation valve assemblies each positioned fluidly between the common drain conduit and one of the plurality of fuel injectors. Each of the plurality of isolation valve assemblies includes an isolation valve member movable between a closed position blocking the injection control valve assembly in the one of the plurality of fuel injectors from the common drain conduit, and an open position, and a biaser biasing the isolation valve member toward the closed position.
In another aspect, a fuel injector includes an injector body having a high pressure nozzle supply passage, a check control chamber, and a low pressure outlet formed therein. The fuel injector further includes a direct operated nozzle check, and an injection control valve assembly. The fuel injector still further includes an isolation valve assembly having an isolation valve member movable between a closed position blocking the injection control valve assembly in the one of the plurality of fuel injectors from the common drain conduit, and an open position, and a biaser biasing the isolation valve member toward the closed position.
In still another aspect, an isolation valve assembly for a fuel system includes a valve body positionable in a fuel injector, the valve body having formed therein a low pressure outlet, a drain path structured to fluidly connect to a check control chamber for an outlet check in the fuel injector, and a valve seat positioned fluidly between the drain path and the low pressure outlet. The isolation valve assembly further includes an injection control valve assembly having an injection control valve member movable between a closed control valve position blocking the valve seat, and an open control valve position, and an isolation valve member. The isolation valve member is positioned fluidly between the injection control valve assembly and the low pressure outlet and is movable between an open isolation valve position and a closed isolation valve position. The isolation valve assembly still further includes a biaser biasing the isolation valve member toward the closed isolation valve position, such that movement of the isolation valve member from the closed isolation valve position to the open isolation valve position in response to a pulse of fluid pressure through the valve seat is in opposition to a biasing force of the biaser.
Referring to
Fuel system 20 includes a fuel supply or fuel tank 22, and equipment for conveying fuel from fuel tank 22 to combustion cylinders 18, including a low pressure transfer pump 24, a high pressure pump 26, and a common rail 28 structured to receive pressurized fuel from high pressure pump 26 and store the pressurized fuel for delivery to a plurality of fuel injectors 32 by way of a plurality of fuel supply lines 44. Fuel supply lines 44 may be formed at least partially within engine head 16 and connected with each of fuel injectors 32 by way of so-called quill connectors or the like, or by way of any other suitable strategy. Fuel system 20 is a common rail fuel system in a practical implementation, however, the present disclosure is not thereby limited and could alternatively include a plurality of unit pumps driven by an engine cam, or by way of hydraulic actuation, and associated with or part of each one of fuel injectors 32. Still other possible configurations might include a number of unit pumps less than the number of fuel injectors, with each individual unit pump serving to pressurize fuel for more than one fuel injector and storing the pressurized fuel in a shared fuel pressure accumulator.
Each of fuel injectors 32 includes an injection control valve assembly 34, and a direct operated nozzle check 36. Injection control valve assembly 34 is electrically actuated, and direct operated nozzle check is hydraulically actuated. An electronic control unit 30 may be in control communication with each injection control valve assembly 34 associated with each of fuel injectors 32.
Fuel system 20 also includes a common drain conduit 38 fluidly connected to each of fuel injectors 32 to receive drained actuating fluid for each of direct operated nozzle checks 36. A drain line 42 may extend between each fuel injector 32 and common drain conduit 38, and may be formed in engine head 16, for example. As shown in
Referring also now to
Also in the illustrated embodiment, an orifice plate 58, or potentially a plurality of orifice plates of generally known design, define check control chamber 66. Conveying of high pressure fuel through one or more orifice plates 58 and other internal components of injector body 46, as well as providing low pressure connections is generally performed by way of known configurations of fuel injector componentry. In general terms, actuating injection control valve assembly 34 open enables relieving of a closing hydraulic pressure on a back end of direct operated nozzle check 36, permitting direct operated nozzle check 36 to lift from its closed position to its open position and initiate spraying of pressurized fuel out of nozzle outlets 68. Actuating injection control valve assembly 34 closed enables returning of closing hydraulic pressure to the back end of direct operated nozzle check 36 to end spraying of fuel. Injector body 46 also includes a nozzle piece 48 wherein spray orifices 68 are formed, a casing 50, and a valve body 52. Valve body 52 is part of injector body 46 and can also be understood as part of isolation valve assembly 40.
Valve body 52 may have low pressure outlet 69 formed therein. Referring also now to
It has been observed that opening valve seat 75 to enable lifting of direct operated nozzle check 36 can produce a pulse of fluid pressure through valve seat 75. In earlier systems where low pressure outlets of individual fuel injectors could communicate with one another by way of a common drain conduit unobstructed, these pulses of fluid pressure were observed to potentially cause problematic cross-talk, such as by popping open an injection control valve in one fuel injector in response to a pulse of fluid pressure, or multiple pulses of fluid pressure, produced by one or more of the other fuel injectors. As will be further apparent by way of the following description, isolation valve assembly 40 is structured to reduce or eliminate such cross-talk or other phenomena leading to performance degradation in a fuel system.
It will be recalled that each of a plurality of isolation valve assemblies 40 in fuel system 20 includes an isolation valve member 56 movable between a closed isolation valve position blocking the corresponding injection control valve assembly 34 from common drain conduit 38, and an open isolation valve position. Isolation valve assembly 40 further includes a biaser 80 biasing isolation valve member 56 toward the closed position. Isolation valve member 156 may be associated similarly with a biaser (not numbered), and may otherwise be structured substantially identically to isolation valve member 56 and associated components. Referring also now to
As shown in
As discussed herein, isolation valve assembly 40 may be normally closed to block fluid communication between the associated fuel injector 32, and injection control valve assembly 34 in particular, and common drain conduit 38 and other fuel injections and thereby prevent fluid pressure pulses from being communicated between fuel injectors 32, and cause injection control valve assembly 34 to pop open or cause other problems potentially leading to performance degradation or requiring changes to control methodology or electronic trimming. In one implementation, it may be desirable for isolation valve assembly 40 to produce a back pressure of approximately 550 kiloPascals (kPa), although depending upon fuel system design a different back pressure might be desired.
As can be seen comparing
The present description is for illustrative purposes only, and should not be construed to narrow the breadth of the present disclosure in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the full and fair scope and spirit of the present disclosure. Other aspects, features and advantages will be apparent upon an examination of the attached drawings and appended claims. As used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.
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