Patent Application
20140251277
The present disclosure relates generally to a quill connector for a fuel system in an internal combustion engine, and relates more particularly to interrupting a flow of pressurized fuel to a fuel injector via a flow limiter subassembly positioned at least partially within an accumulator in the quill connector.
Many modern internal combustion engine systems exploit the desirable combustion and emission properties attendant to high fuel injection pressures. It is well known that such high pressure fuel injection, often on the order of 200 megapascals (MPa) or more, promotes atomization and vaporization of injected fuel, having various desirable results. One strategy developed decades ago to enable the supplying of highly pressurized fuel to multiple fuel injectors in a multi-cylinder engine is known as a common rail. A common rail is essentially a long tube which serves to store a volume of highly pressurized fuel received from a fuel pump, and configured to feed the highly pressurized fuel simultaneously to a group of fuel injectors on the engine as needed. While common rail designs have worked very well over the years, and are still in widespread use, they present certain manufacturing, packaging, and pressure containment and sealing challenges. Some of these issues have been exacerbated by the drive towards ever higher fuel pressures.
Strategies have been proposed where a dedicated pressure accumulator is provided in direct connection with each fuel injector in an engine system. The dedicated pressure accumulators store a volume of fuel sufficient to enable stable provision of the fuel at design pressures for injection by the fuel injectors, and can in at least certain instances be easier to package and less expensive to manufacture and maintain than certain common rail designs. United States Patent Application Publication No. 2011/0315117 A1 to Gerstner et al. is directed to one such dedicated accumulator strategy. In Gerstner et al., a plurality of pressure accumulators are provided, each connected with one fuel injector, and a plurality of flow limiters are positioned fluidly between the pressure accumulators and the corresponding fuel injectors, apparently to limit fuel leakage during catastrophic failure and/or to dampen pressure oscillations caused by operation of the fuel injectors. While Gerstner et al. provides a viable strategy, there is always room for improvement.
In one aspect, a quill connector for a fuel system in an internal combustion engine includes an elongate quill body defining a longitudinal axis extending between a proximal body end having a fuel inlet formed therein, and a distal body end having a fuel outlet formed therein. The elongate quill body further defines a fuel conduit fluidly connecting the fuel inlet with the fuel outlet. The fuel conduit includes a proximal accumulator segment having a greater volume, for containing a reserve of a pressurized fuel, and a distal injector supply segment having a lesser volume, for supplying the pressurized fuel to a fuel injector. The quill connector further includes a flow limiter subassembly for limiting oversupplying of the pressurized fuel, and including a guide component positioned within the accumulator segment, a seat component attached to the elongate quill body and supporting the guide component, and a hydraulically actuated valve and a biaser each positioned within the guide component. The biaser is held in compression between the valve and the seat component. The valve is movable in opposition to a biasing force of the biaser from a first position to a closed position at which the valve contacts the seat component to interrupt a flow of the pressurized fuel from the accumulator segment to the injector supply segment.
In another aspect, a fuel system for an internal combustion engine includes a supply of pressurized fuel, a fuel feed line in fluid communication with the supply of pressurized fuel, and a fuel injector. The fuel injector defines a high pressure fuel inlet, and a nozzle outlet, and has an injection valve movable between a first position at which the injection valve blocks the nozzle outlet from the high pressure fuel inlet, and a second position at which the nozzle outlet is open. The fuel system further includes a quill connector including a proximal end having a quill inlet formed therein and in fluid communication with the fuel feed line, and a distal end having a quill outlet formed therein. The distal end is in sealing engagement with the fuel injector, such that the quill outlet is in fluid communication with the high pressure fuel inlet. The quill connector defines a fuel conduit fluidly connecting the quill inlet with the quill outlet, the fuel conduit including a proximal accumulator segment having a greater volume, and a distal injector supply segment having a lesser volume. The quill connector further includes a flow limiter subassembly including a guide component, a seat component supporting the guide component within the accumulator segment, and a hydraulically actuated valve and a biaser each positioned within the guide component. The biaser is held in compression between the valve and the seat component, and the valve is movable in opposition to a biasing force of the biaser from a first position to a closed position at which the valve contacts the seat component to interrupt a flow of the pressurized fuel from the quill connector to the fuel injector.
In still another aspect, a method of limiting oversupplying a pressurized fuel from a quill connector to a fuel injector in an internal combustion engine includes conveying a pressurized fuel from a greater volume accumulator segment to a lesser volume injector supply segment of a fuel conduit in the quill connector. The method further includes supplying the pressurized fuel from the injector supply segment to the fuel injector, and hydraulically actuating a valve in a flow limiter subassembly of the quill connector during the supplying of the pressurized fuel, such that the valve moves toward a closed position contacting a seat component of the flow limiter subassembly. The method further includes guiding the valve during the actuation within a guide component of the flow limiter subassembly supported within the accumulator segment via the seat component, and blocking fluid communication between the accumulator segment and the injector supply segment via contacting the valve with the seat component at the closed position, such that the supplying of the pressurized fuel to the fuel injector is interrupted.
Referring to
Each of fuel injectors 32 may further include a high pressure fuel inlet 34 in fluid communication with the corresponding quill connector, and a nozzle 36 receiving the pressurized fuel from the corresponding quill connector 30. Each fuel injector 32 may further include a nozzle outlet 37, and an injection valve 38 positioned at least partially within nozzle 36 and movable between a first position at which injection valve 38 blocks nozzle outlet 37 from high pressure fuel inlet 34, and a second position at which nozzle outlet 37 is open and not blocked by injection valve 38. It will be appreciated that reference numerals identifying features on one of fuel injectors 32 in
Referring also now to
Quill connector 30 may further include a clamp 60 positioned upon outer surface 49 and defining a plurality of bores 62 each configured to receive a bolt for clamping quill connector 30 to cylinder head 18, and further being configured to clamp distal tip 74 against fuel injector 32 such that sealing surface 76 forms a fluid seal therewith. An inlet body 64 is also coupled to proximal end 44, and in a practical implementation strategy includes a plurality of bolts 72 extending through bores in inlet body 64 to clamp inlet body into engagement with quill body 40. In the
As noted above, fuel conduit 52 may fluidly connect quill inlet 46 with quill outlet 50. Fuel conduit 52 may further include a proximal accumulator segment 54 having a greater volume, for containing a reserve of a pressurized fuel, and a distal injector supply segment having a lesser volume, for supplying the pressurized fuel to a fuel injector. Accumulator segment 54 may be configured to store a reserve of pressurized fuel received from high pressure pump 26 via one of feed lines 31 which is many times a volume of the largest fuel injection which is expected to be performed by fuel injector 32. In certain embodiments, a volume of proximal accumulator segment 54 may be about thirty times a volume of the largest expected fuel injection. Providing an accumulation volume in this general manner enables sufficient pressurized fuel to be consistently available for fuel injection, and can serve to attenuate or negate pressure waves, pulses, and other hydraulic phenomena arising out of the actuation of multiple additional fuel injectors and other components in fuel system 20 affecting fuel supply pressure. An inner diameter dimension of accumulator segment 54 may be greater than an inner diameter dimension of segment 56, for instance about two, three, four, or more times greater. An inner diameter dimension of fuel feed lines 31 may be less than the inner diameter dimension of segment 54.
Referring also now to
In a practical implementation strategy, guide component 82 may have the form of a guide sleeve coaxial with quill body 40. A clearance 78 may extend radially between guide component 82 and quill body 40, in particular between guide component 84 and inner surface 51. Guide component 54 may further define a reset orifice 94 in fluid communication with clearance 78, and reset orifice 94 may have a flow area less than a minimum flow area of clearance 78. Subassembly 80 may define a cavity 96 which refills with pressurized fuel supplied via clearance 78 and orifice 94 in a manner discussed further herein.
Valve 86 may be movable in a distal direction from its open position to its closed position. Subassembly 80 may further include a stop component 110 coupled to a proximal guide end 90 of guide component 82 and limiting travel of valve 86 in a proximal direction past its first position. In a practical implementation strategy, stop component 110 may include a nut threadedly engaged with guide component 82. It may further be noted from
As noted above, seat component 84 may be attached to quill body 40 and supports guide component 82. In a practical implementation strategy, seat component 84 includes a head 102, which may be generally cup-shaped and positioned in opposition to valve 86, such that the cup-shapes of the respective components open toward one another. Seat component 84 may further include a hollow neck 104 extending in an distal direction from head 102 into injector supply segment 56 and interference fitted with quill body 40 therein. In other words, neck 104 may be interference fitted with inner surface 51 of quill body 40 to form a press fit attachment 106 therewith. As noted above, seat component 84 may be understood to support guide component 82, within accumulator segment 54, and in particular may support guide component 82 against axial displacement. Seat component 84 may further support guide component 82 via holding it in abutment against quill body 40 such that tilting out of desired coaxial alignment is prevented. Head 102 may further include a valve seating surface 108, which includes an annular seating surface, contacted by valve 86 at its closed position. An edge filter 58 may be positioned within injector supply segment 56 between neck 104 and quill outlet 50 as shown in
Referring now to
In contrast to certain known flow limiter designs, flow limiter subassembly 80 is positioned directly within an accumulated volume, and can be manufactured and assembled as a separate component, which can then be installed within quill body 40. In a practical implementation strategy, one technique for installing subassembly 80 includes sliding subassembly 80 in a distal direction through quill body 40, up to a point at which neck 104 begins to be received within injector supply segment 56. At this point, an elongate tool can be passed through stop component 110, and into engagement with valve 86. Valve 86 is then pushed in opposition to a biasing force of biaser 88, until skirt 100 contacts seating surface 108. Valve 86 can then be used to transmit a press fit force from the elongate tool to seat component 84, and press neck 104 into injector supply segment 56 to form press fit attachment 106. It is contemplated that press fit attachment 106 will form a sufficiently fluidly tight seal to prevent any substantial leakage of pressurized fuel from accumulator segment 54 into injector supply segment 56 when valve 86 is in its closed position, with skirt 100 sealing against valve seating surface 108. A generally unobstructed flow of highly pressurized fuel into accumulator segment 54 can hold valve 86 in sealing engagement against seat portion 84 where downstream fluid pressure remains low, such as might occur in the case of fuel injector performance degradation or failure.
Referring to the drawings generally, during operation of fuel system 20, high pressure pump 26 will continuously or at regular pumping strokes supply pressurized fuel to quill connectors 30, which in turn convey the pressurized fuel from accumulator segment 54 to injector supply segment 56 within each quill connector 30, depending upon a pressure drop from segment 54 to segment 56, in turn induced by actuation of injection valve 38 in the corresponding fuel injector 32. The pressurized fuel can thus be supplied on an as-needed basis from segment 56 to the fuel injector 32.
During the flow of pressurized fuel from segment 54 to segment 56, valve 86 may be hydraulically actuated such that valve 86 moves from its first, retracted position toward its closed advanced position contacting seat component 84. Valve 86 may be guided during the actuation within guide component 82. During normal, non-problematic operation of fuel system 20, a fuel injection will typically terminate via closing of injection valve 38 prior to a time at which valve 86 contacts seat component 84. As a result, a pressure of fuel in segment 54 and segment 56 may begin to equalize. Clearance 78 and reset orifice 94 provide a flow path for pressurized fuel to refill cavity 96, such that hydraulic pressure and hydraulic force on a distal side of valve 86 versus a proximal side of valve 86 are substantially equal. With the hydraulic pressures equalized, a biasing force of biaser 88 can act to return valve 86 to its first position, abutting stop component 110. In a practical implementation strategy, sizing of surfaces of valve 86 exposed to pressurized fuel, as well as a spring force of biaser 88, may be tailored to enable this general functionality. It should be appreciated, however, that hydraulic surfaces on valve 86 might be sized such that valve 86 is hydraulically biased one direction or the other, depending upon the particular application. Likewise, a stiffness or relative compression of biaser 88 might be tailored for various purposes. It should be appreciated that if biaser 88 has too weak a biasing force exerted on valve 86, then valve 86 could be expected in some instances to “rachet” towards a closed position in response to repeated fuel injection cycles. If the biasing force is too strong, valve 86 might not be capable of moving to its fully closed position contacting seat component 84 when needed. Still other factors such as travel distance of valve 86, axial length of skirt 100, and even depth of axial penetration of stop component 110 into guide component 82 can all bear on proper operation of subassembly 80.
In a further practical implementation strategy, subassembly 80 may be configured such that valve 86 moves to its closed position and blocks fluid communication between segment 54 and segment 56, thus interrupting fuel injection, when a quantity of pressurized fuel has been supplied to the corresponding fuel injector 32 which is equal to about 1.5 times a maximum fuel injection amount fuel injector 32 is designed to deliver. As discussed above, subassembly 80, and valve 86, may be reset via conveying pressurized fuel to a distal side of valve 86 via reset orifice 94. In the case of catastrophic fuel injector failure, it is contemplated that valve 86 may remain held in its closed position, and no such resetting would occur, at least in some instances. Where the fuel injector is merely degraded in performance, and still capable of injecting fuel, at least partial resetting may occur to enable continued operation, with enough pressurized fuel making its way to a distal side of valve 86 to allow biaser 88 to move valve 86 off seat component 84 and continue operating until servicing, but providing protection against the oversupplying of fuel that might otherwise occur.
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.
