Patent Application
20190128228
The present disclosure relates generally to a fuel system for an internal combustion engine, and more particularly to a fuel injector having a check assembly with a purging check movable to control admission of a purging fluid to a fuel passage for purging the fuel passage of fuel.
A variety of different technologies are used in modern internal combustion engines to optimize efficiency and manage emissions. In many engines it is desirable to limit production or output of particulate matter, oxides of nitrogen or “NOx,” and other materials such as unburned hydrocarbons, and carbon monoxide. Engine operating strategies for limiting certain emissions, including variable valve actuation strategies, post injections, pre-injections, exhaust gas recirculation or “EGR,” exhaust back pressure control strategies, and a host of others have been proposed over the years, with varying degrees of success. It is also well-known to treat exhaust directly, by way of catalyst-based reduction of certain exhaust constituents, particulate traps, and still others. Despite many advances across a range of technologies, engineers continue to search for improved ways to operate engines and ancillary engine systems, and new or further refined component designs, with the goal of optimizing engine emissions without sacrificing performance, efficiency or other desirable factors.
In recent years, significant engineering effort has gone into the development of improved fuel injector designs and operating techniques, notably for compression ignition diesel engines. It has been observed that relatively high fuel pressure can promote fuel atomization, which in turn tends to be associated with more complete burning of injected fuel and reduced production of particulate matter. Other techniques seek to strictly control start of injection and end of injection so as to provide a desirable, typically square, injection rate shape that provides desirable combustion characteristics.
One particular fuel injector design is known from U.S. Pat. No. 6,601,566 to Gillis et al., including directly controlled dual concentric checks in a fuel injector for a dual fuel engine. In the dual fuel environment of Gillis et al. two separate fuel injection checks can be packaged in a relatively modest space, and enabling use of two distinct quantities of liquid fuel to various ends, including operating the engine relatively more efficiently and more completely burning the fuel to produce lowered emissions.
In one aspect, a fuel injector includes an injector body defining a longitudinal axis and having a nozzle, the injector body having formed therein a fuel passage extending between a fuel inlet and a set of nozzle outlets. The nozzle includes an outlet check seat, and the set of nozzle outlets being distributed circumferentially about the longitudinal axis at locations that are adjacent to the outlet check seat and radially inward of the outlet check seat. The nozzle further includes a nozzle tip inner surface that is adjacent to the set of nozzle outlets and located radially inward of the set of nozzle outlets. The nozzle tip inner surface has a continuous extent amongst the set of nozzle outlets, such that the nozzle tip inner surface defines a sac forming a blind end of the fuel passage. The fuel injector further includes a check assembly positioned within the injector body, and having formed therein a purging fluid passage extending between a purging fluid inlet and a purging fluid outlet that opens to the fuel passage. The check assembly further includes an outlet check movable within the injector body between a retracted position where the fuel passage is in fluid communication with the set of nozzle outlets, and an advanced position where the outlet check contacts the outlet check seat. The check assembly further includes a purging check movable within the injector body between an advanced position where the purging check blocks the purging fluid outlet, and a retracted position where the purging fluid passage is in fluid communication with the fuel passage to admit purging fluid to the fuel passage for purging the sac of fuel.
In another aspect, a fuel system includes a fuel supply, a purging fluid supply, and a fuel injector having each of a fuel passage and a purging fluid passage formed therein. The fuel passage extends between a fuel inlet connected with the fuel supply and a set of nozzle outlets. The purging fluid passage extends between a purging fluid inlet connected with the purging fluid supply and a purging fluid outlet that opens to the fuel passage. The fuel injector further includes a nozzle tip inner surface that is adjacent to the set of nozzle outlets and has a continuous extent amongst the set of nozzle outlets, such that the nozzle tip inner surface defines a sac forming a blind end of the fuel passage. The fuel injector further includes an outlet check movable to control opening and closing of the plurality of nozzle outlets, and a purging check. The purging check is movable between an advanced position where the purging check blocks the purging fluid outlet, and a retracted position where the purging fluid passage is in fluid communication with the fuel passage to admit purging fluid to the fuel passage for purging the sac of fuel.
In still another aspect, a method of operating a fuel system for an internal combustion engine includes adjusting an outlet check in a fuel injector from a closed position to an open position, and spraying fuel out of a set of nozzle outlets in response to the adjusting of the outlet check in a fuel injector from a closed position to an open position. The method further includes adjusting a purging check in the fuel injector from a closed position to an open position, and purging the fuel passage of fuel by way of purging fluid admitted to the fuel passage in response to the adjusting of the purging check in the fuel injector from the closed position to the open position. The method still further includes reducing fuel dribble out of the fuel injector by way of the purging of the fuel passage of fuel.
Referring to
Each fuel injector 30 can further include an electrical actuator 32 structured to control initiation of a fuel injection event, and termination of the fuel injection event. Each fuel injector 30 can further include a second electrical actuator 34 structured to control the initiation of a purging fluid delivery event and termination of the purging fluid delivery event. It has been observed that a phenomenon known as fuel “dribble” or “dribbling” from tip 40 can result in fuel being delivered into an engine cylinder after the time at which fuel injection is desirably terminated, and/or being delivered in a manner that is undesirable, such as not atomized or not substantially atomized. The dribbled fuel is further understood to burn incompletely, not burn at all, or otherwise produce undesired emissions that can make achieving performance and operating goals of an engine challenging. As will be further apparent from the following description, engine system 10 is uniquely structured to controllably inject fuel in a manner that eliminates or substantially reduces the fuel dribble phenomenon.
An electronic control unit 42 may be in control communication with electrical actuators 32 and also with electrical actuators 34 for purposes consistent with the aims of controllably injecting fuel without fuel dribble. Engine system 10 also includes a purging fluid supply 44 having a purging fluid supply inlet 46 structured to feed purging fluid, such as air, to fuel injectors 30, in parallel with fuel fed from fuel tank 24 by way of common rail 28 or other fuel delivery means. A purging fluid filter 48 can be positioned fluidly between purging fluid supply inlet 46 and each of a plurality of purging fluid inlets 76 formed in each injector body 36 of the plurality of fuel injectors 30. Also formed in injector body 36 of each of the plurality of fuel injectors 30 is a fuel inlet 62.
Turning now to
Nozzle 38 further includes an outlet check seat 58, with nozzle outlets 56 being distributed circumferentially about longitudinal axis 50 at locations that are adjacent to outlet check seat 58 and radially inward of outlet check seat 58. A check assembly 70 is also positioned within injector body 36, check assembly 70 having formed therein a purging fluid passage 72 extending between a purging fluid inlet 79 formed in check assembly 70 and a purging fluid outlet 78 that opens to fuel passage 52. Purging fluid inlet 79 may fluidly connect to purging fluid inlet 76 in injector body 36. Check assembly 70 further includes an outlet check 74 movable within injector body 36 between a retracted position where fuel passage 52 is in fluid communication with the set of nozzle outlets 56, and an advanced position where outlet check 74 contacts outlet check seat 58. Check assembly 70 also includes a purging check 82 movable within injector body 36 between an advanced position where purging check 82 blocks purging fluid outlet 78, and a retracted position where purging fluid passage 72 is in fluid communication with fuel passage 52 to admit purging fluid to fuel passage 52.
In the illustrated embodiment, purging check 82 and outlet check 74 are concentric, and coaxially arranged with one another within injector body 36. Purging check 82 is shown positioned within outlet check 74, and outlet check 74 includes a distal tip 90 having purging fluid outlet 78 formed therein. It will be recalled that electrical actuator 32 can selectively connect internal plumbing of fuel injector 30 with low pressure outlet 60 to control injection of fuel. In a practical implementation, outlet check 74 can include a closing hydraulic surface 80 exposed to a fluid pressure of fuel inlet 62 or alternately a fluid pressure of low pressure outlet 60. Varying a fluid pressure acting upon closing hydraulic surface 80 in this general manner controls the opening and closing of nozzle outlets 56. As noted above, purging check 82 can be operated, such as by way of electrical actuator 34, to supply purging fluid such as pressurized air to the vicinity of nozzle outlets 56. In the illustrated embodiment, fuel injector 30 also includes a plunger 66 that can be used to pressurize purging fluid delivered by way of purging fluid inlet 76 for delivery to purging fluid passage 72. Plunger 66, or another fluid pressurization mechanism, could be cam actuated, hydraulically actuated, or actuated by another technique altogether. Moreover, rather than pressurizing the purging fluid within fuel injector 30, a compressor or other purging fluid pressurization device could be employed that feeds pressurized purging fluid to all of fuel injectors 30 in engine system 10. Electrical actuator 34 could be a solenoid actuator, as could electrical actuator 32, used in a generally conventional manner to lift purging check 82 to open purging fluid outlet 78. Alternatively or in addition, the pressure of purging fluid conveyed through purging fluid passage 72 could act on opening pneumatic or hydraulic surfaces of purging check 82 to achieve similar aims. It should be appreciated that no limitation as to any particular strategy for controlling the opening and closing of outlet check 74 and purging check 82 is intended by way of the present description, and a great many different possible configurations will be apparent to those skilled in the art.
Referring also now to
Outlet check 74 also includes purging check seat 88, which is contacted by purging check 82 at the advanced position. Purging check seat 88 extends circumferentially around purging fluid outlet 78, in the illustrated embodiment. It can still further be noted that purging fluid passage 72 is formed between outlet check 74 and purging check 82. In the embodiment shown in
Referring to
Referring to the drawings generally, but in particular now to
In an implementation, adjusting purging check 82 from its closed position to its open position can be commenced prior to completing returning of outlet check 74 from its open position to its closed position. Purging check 82 can be opened prior to, after, or at the same time as, closing of outlet check 74, however. At the appropriate timing, purging check 82 begins to lift from seat 88 to move toward its open position. It can be seen that at the state depicted in
Those skilled in the art will appreciate that sizing of hydraulic or pneumatic opening surfaces and/or closing surfaces, relative strength of electrical actuators, the timing of electrical actuator control signals and/or the strength of electrical actuator control signals, are all factors that could be varied to achieve a particular pattern of adjusting check assembly 70. It will generally be desirable to provide purging fluid at a pressure that is greater than fuel pressure. At minimum, purge pressure will typically be higher than cylinder pressure at end of injection. For these reasons, an internal pressurization mechanism within each fuel injector such as plunger 66 provides a practical implementation strategy. It will also be recalled that operating fuel system 22 in the manner discussed herein can reduce fuel dribble out of fuel injector 30, and other fuel injectors contemplated herein, by way of the purging of fuel passage 52, and in particular sac 86, of fuel. Referring now to
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.
