Patent Application
20200063704
The present disclosure relates generally to a liquid fuel injector for a fuel system in an internal combustion engine and relates more particularly to a liquid fuel injector having dual outlet checks and dual nozzle outlets supplied by a common nozzle supply cavity.
Fuel systems used in state-of-the-art internal combustion engines are relatively complex and sophisticated electromechanical systems. The associated engines can be direct-injected where fuel injectors extend into the engine cylinders, port-injected where fuel is delivered into a port in communication with an engine cylinder, or structured according to yet another strategy. In the case of compression ignition diesel engines it is typical for liquid fuel injection pressures to be as high as several hundred megapascals (MPa). Injections can occur multiple times per second, necessitating rapid travel of moving parts within the fuel injector in response to electromagnetic actuation forces and/or rapid pressure changes, and resulting in relatively intense, repetitive impacts, and in some instances a tendency toward liquid cavitation. The timing and manner of injection of fuel is typically relatively tightly controlled, with opening and closing of valves desirably quite rapid to produce so-called “square” injection rate shapes, ramp shapes, and still others.
Pressurization of the fuel to be injected can take place within the fuel injector itself, such as by way of a hydraulically actuated or cam-actuated plunger, or externally such that pressurized fuel is stored in a common rail or the like and a reservoir of pressurized fuel maintained for multiple fuel injectors. Due to the foregoing and other factors, fuel injectors are often purpose-built for certain fuel injection strategies and combustion recipes. One example fuel injector for an internal combustion engine is known from U.S. Pat. No. 7,556,017 to Gibson et al.
In one aspect, a liquid fuel injector for an internal combustion engine includes an injector body defining an inlet passage, a first set of nozzle outlets, a second set of nozzle outlets, a first control chamber, and a second control chamber each in fluid communication with the inlet passage, and a low-pressure space. The liquid fuel injector further includes a first outlet check having a closing hydraulic surface exposed to a fluid pressure of the first control chamber and movable between a closed position blocking the first set of nozzle outlets, and an open position. The liquid fuel injector further includes a second outlet check having a closing hydraulic surface exposed to a fluid pressure of the second control chamber and movable between a closed position blocking the second set of nozzle outlets, and an open position. The liquid fuel injector still further includes a first injection control valve positioned fluidly between the first control chamber and the low-pressure space, and a second injection control valve positioned fluidly between the second control chamber and the low-pressure space. The first set of nozzle outlets form a narrower spray angle and have a first combination of outlet number and outlet size, such that the first set of nozzle outlets produces a relatively greater steady flow of fuel for injection. The second set of nozzle outlets form a wider spray angle and have a second combination of outlet number and outlet size, such that the second set of nozzle outlets produces a relatively lesser steady flow of fuel for injection. The injector body further defines a common nozzle supply cavity in fluid communication with the inlet passage, and the first set of nozzle outlets and the second set of nozzle outlets being in fluid communication with the common nozzle supply cavity at the open position of the first outlet check and the second outlet check, respectively.
In another aspect, a fuel system for an internal combustion engine includes a liquid fuel supply, and a plurality of liquid fuel injectors each defining an inlet passage, a first set of nozzle outlets, a second set of nozzle outlets, and a low-pressure space. The plurality of liquid fuel injectors each include a first direct-operated outlet check movable between a closed position blocking the first set of nozzle outlets, and an open position, and a second direct-operated outlet check movable between a closed position blocking the second set of nozzle outlets and an open position. The plurality of liquid fuel injectors each further include a first injection control valve coupled with the first direct-operated outlet check and a second injection control valve coupled with the second direct-operated outlet check. The first set of nozzle outlets in each one of the plurality of liquid fuel injectors form a narrower spray angle and have a first combination of outlet number and outlet size, such that the first set of nozzle outlets produces a greater steady flow of fuel for injection. The second set of nozzle outlets in each one of the plurality of liquid fuel injectors form a wider spray angle and have a second combination of outlet number and outlet size different from the first combination, such that the second set of nozzle outlets produces a lesser steady flow of fuel for injection.
In still another aspect, a method of operating an engine includes supplying liquid fuel to a liquid fuel injector positioned at least partially within a cylinder in the engine, and injecting a first charge of the liquid fuel into a cylinder in the engine using a first set of nozzle outlets in a fuel injector, such that spray jets of the first charge of the liquid fuel are oriented at a relatively narrower spray angle. The method further includes autoigniting the first charge of the liquid fuel such that the first charge of the liquid fuel combusts by diffusion burning within the cylinder in a first engine cycle. The method further includes injecting a second charge of the liquid fuel into the cylinder using a second set of nozzle outlets in the fuel injector, such that spray jets of the second charge of liquid fuel are oriented at a relatively wider spray angle, and autoigniting the second charge of the liquid fuel such that the second charge of liquid fuel combusts by diffusion burning within the cylinder in a second engine cycle. The method still further includes transitioning operation of the engine from a relatively higher engine load in the first engine cycle to a relatively lower engine load in the second engine cycle, and decreasing fueling of the engine based on the transitioning of the operation of the engine, such that an amount of the second charge of liquid fuel is smaller than an amount of the first charge of liquid fuel.
Referring to
Fuel system 44 includes a liquid fuel supply 46 such as a fuel tank, and can include at least one pump structured to convey the liquid fuel to engine 10. In the illustrated embodiment a low-pressure transfer pump 48 receives fuel from supply 46 and transitions the fuel to a high-pressure pump 50 that feeds a pressurized fuel reservoir 52 such as a common rail. Fuel reservoir and common rail are terms used interchangeably herein. For purposes of the present disclosure common rail 52 can be understood to itself be, or be a part of, a fuel supply. It should be appreciated that a single monolithic pressurized fuel reservoir could be used, as well as a plurality of separate pressure accumulators, or still another strategy such as a plurality of unit pumps. An electronic control unit 54 may be coupled with a plurality of liquid fuel injectors 56 of fuel system 44. A mass flow sensor 55 may be coupled with electronic control unit 54 to monitor incoming air flow for determining or estimating engine load indirectly, the significance of which will be further apparent from the following description. Liquid fuel injectors 56 may each be coupled with engine housing 12 and positioned so as to extend at least partially into each one of combustion cylinders 14. Each liquid fuel injector 56 can include twin or dual outlet checks, as further discussed herein, structured to inject liquid fuel in different quantities, at different spray angles or different spray patterns, for example, and for different purposes, including a first liquid fuel charge that serves as a main charge during operating engine 10 in a higher portion of its load range, and a second charge of liquid fuel that serves as a main charge during operating engine 10 in a lower portion of its load range. As will be further apparent from the following description, it is contemplated that separate control and separate design of the two outlet checks enables optimization for their different intended purposes.
Referring also now to
Fuel injector 56 further includes a first electrically actuated injection control valve 82 in a first control valve assembly 81. Injection control valve 82 can be a first two-way injection control valve and is positioned fluidly between first control chamber 68 and low-pressure space 72. A control passage 83 extends between control valve assembly 81 and first control chamber 68. Control valve 82 is movable between a closed position blocking fluid communication between control passage 83 and low-pressure space 72 and an open position at which control passage 83 is fluidly connected to low-pressure space 72. Control valve 82 is thus structured to connect or disconnect a total of two passages. Fuel injector 56 also includes a second electrically actuated injection control valve 85 in a control valve assembly 84. Injection control valve 85 can be a second two-way injection control valve and is positioned fluidly between second control chamber 70 and low-pressure space 72. Instead of two-way injection control valves, three-way injection control valves, or still another valve configuration could be used. A control passage 87 extends between second control chamber 70 and control valve assembly 84. Control valve assembly 84 can function analogously to control valve assembly 81. In the illustrated embodiment each of control valve assembly 81 and control valve assembly 84 is a solenoid actuated control valve assembly structured to vary between a deenergized state where the respective control valves 82 and 85 are at their closed positions, and an energized state where control valves 82 and 85 move in opposition to a spring biasing force to an open position. Certain components are shared among control valve assembly 81 and control valve assembly 84, however, the present disclosure is not thereby limited. It can also be seen from
Injector body 58 further includes a casing 92 and a stack 94 positioned within casing 92. Injector body 58 also defines a common nozzle supply cavity 90 in fluid communication with inlet passage 60. Common nozzle supply cavity 90 can be understood as part of inlet passage 60, which in turn can be understood to extend from inlet 62 to each of nozzle outlets 64 and nozzle outlets 66. First set of nozzle outlets 64 and second set of nozzle outlets 66 are fluidly connected to common nozzle supply cavity 90 at the open position of first outlet check 74 and second outlet check 78, respectively. Common nozzle supply cavity 90 may be formed within stack 94, and each of first outlet check 74 and second outlet check 78 extends through common nozzle supply cavity 90. Stack 94 also includes a tip piece 95, positioned within casing 92 and having first set of nozzle outlets 64 and second set of nozzle outlets 66 formed therein. Tip piece 95 has therein a first guide bore 102 that receives first outlet check 74 and forms a first nozzle supply passage 104 with first outlet check 74. Tip piece 95 also has therein a second guide bore 106 that receives second outlet check 78 and forms a second nozzle supply passage 108 with second outlet check 78. A first M-orifice 110 is formed within tip piece 95 to limit flow through first nozzle supply passage 104. A second M-orifice 112 is formed within tip piece 95 to limit flow through second nozzle supply passage 108. A spacer 96, which can be cylindrical in shape, is positioned to abut tip piece 95 and includes a wall 99 extending circumferentially around first outlet check 74 and second outlet check 78 so as to form common nozzle supply cavity 90. Yet another stack piece 98 is positioned at least partially within casing 92, and an orifice plate 100 is sandwiched between stack piece 98 and spacer 96. Each of first outlet check 74 and second outlet check 78 can include opening hydraulic surfaces (not numbered) exposed to a fluid pressure of common nozzle supply cavity 90. Each of first outlet check 74 and second outlet check 78 is further biased closed by way of spring biasing in a generally known manner.
Injector body 58 still further defines a first set of orifices 86 arranged in an A-F-Z pattern among inlet passage 60, low-pressure space 72, and first control chamber 68. An “A” orifice is positioned fluidly between a check control chamber and an outlet to low pressure, whereas a “Z” orifice is fluidly between incoming high pressure and a check control chamber, and an “F” orifice fluidly connects a high pressure supply for the Z-orifice to an outlet of the A-orifice. A second set of orifices 88 is arranged in an A-F-Z pattern among inlet passage 60, low-pressure space 72, and second control chamber 70. Referring also now to
Orifice plate body 120 also includes a first outlet passage 150 and a second outlet passage 152 extending between lower plate body side 126 and upper plate body side 124, for connecting first and second control chambers 68 and 70 to low-pressure space 72. First set of orifices 86 in orifice plate body 120 is also shown in
It can also be noted from
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Referring to the drawings generally, during operating engine system 8 outlet check 78 can be controlled by way of injection control valve assembly 84 to open and close to inject a first charge of liquid diesel fuel into cylinder 14 in an engine cycle, using nozzle outlets 66 such that spray jets of the first charge of liquid fuel are oriented at relatively narrower spray angle 116. The first charge can be autoignited within cylinder 14 such that the first charge combusts by diffusion burning within cylinder 14 in the first engine cycle. Embodiments are also contemplated wherein both of second outlet check 78 and first outlet check 74 are operated by way of control valve assembly 84 and control valve assembly 81, respectively, to cooperate in injection of a charge of liquid diesel fuel, provide successive injections within the same engine cycle, such as pilot injections, pre-injections, or post-injections. Injection control valve assembly 84 can be energized to lift injection control valve 85 from its seat to cause a drop in pressure in second control chamber 70, in turn enabling pressure acting on opening hydraulic surfaces of outlet check 78 in common nozzle supply cavity 90 to lift outlet check 78 to open nozzle outlets 66. When injection is to be ended, or just prior to when injection is to be ended, injection control valve assembly 84 is deenergized, to close injection control valve 85 and enable pressure to increase in second control chamber 70 and act upon closing hydraulic surface 80 to cause outlet check 78 to close. Piston 16 moves in a conventional four-phase cycle to intake, compress, combust, and exhaust the mixture of air and diesel fuel. As noted above, outlet check 74 can be operated generally analogously to operation of outlet check 78 so as to inject a second charge of liquid diesel fuel into cylinder 14 using nozzle outlets 66, such that spray jets of the second charge of liquid fuel are oriented at a relatively wider spray angle. The second charge is autoignited in a manner generally analogous to that of the first charge.
Operation of engine 10 may be transitioned from a relatively higher engine load in the first engine cycle to a relatively lower engine load in the second engine cycle. Operation of engine 10 can of course be transitioned in the reverse, from one engine cycle where engine load is relatively lower to another engine cycle where engine load is relatively higher. Data produced by sensor 55 enables electronic control unit 54 to determine or estimate a present engine load and changes in engine load. In one implementation, transitioning of the operation of engine 10 includes transitioning from greater than a 50% load to less than a 50% load, using nozzle outlets 66 when engine 10 is operated at greater than 50% load and using nozzle outlets 64 when engine 10 is operated at less than 50% load. Other operating strategies could transition between the use of the respective sets of nozzle outlets at load thresholds other than 50%. In still other instances, a threshold for transitioning between use of nozzle outlets 64 and nozzle outlets 66 could vary cycle to cycle based upon factors such as engine speed, boost pressure, or still others. Fueling of engine 10 may be decreased based on the transitioning of the operation of engine 10, such that an amount of the second charge of liquid fuel is smaller than an amount of the first charge of liquid fuel. Analogously, when operation of engine 10 is transitioned from a lower load to a higher load, fueling of engine 10 may be increased.
As noted above, employing dual outlet checks can enable separation of design of each outlet check for different purposes, namely, different injection characteristics at different parts of an engine load range. A liquid fuel charge during lower load operation may be injected at a relatively shallower angle, whereas a charge for higher load operation can be injected at a somewhat deeper angle into cylinder 14 as discussed herein. It is believed that the deeper/narrower angle during higher load operation enables spray jets to somewhat limit entrainment of air such that NOx production is limited, and also to reduce risk of the spray jets impinging upon a cylinder liner. At lower load operation some of the constraints as to NOx production and liner impingement are relaxed.
It will also be recalled that orifice sets 86 and 88 affect the nature of fuel injection, and can be sized to various ends. F-orifices can be employed to slow a rate of pressure drop in the control chambers when connected to low pressure, and can hasten the rate of pressure build at the end of injection. As a result, the F-orifices can assist in obtaining a relatively square rate shape to an end of injection, or tailored to obtain another rate shape. Z-orifices can analogously assist in obtaining a relatively square end of injection shape, for example. Varying a size of a Z-orifice within the present context tends to have a relatively larger effect on end-of-injection properties than varying the size of an F-orifice. The M-orifices are controlled clearances around the outlet checks that act to retard the start of injection. The A-orifices also tend to affect start of injection, assisting in controlling spilling of pressure from the associated control chamber.
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.
