Patent Application
20210164425
The present disclosure relates generally to a common rail fuel system in an internal combustion engine, and more particularly to single-fluid common rail fuel injector assembly having a fuel recovery fitting.
Modern fuel systems used in internal combustion engines are typically relatively complex and highly sophisticated apparatus having many moving parts, and are required to handle high absolute pressures, as well as rapid pressure swings during operation. Engineers have discovered that precise control over fuel injection characteristics, including injection pressure, injection timing, injection rate shape, and other factors can have beneficial impacts on engine emissions. For example, it has been observed that a small pilot injection followed by a subsequent main injection can assist in promoting relatively rapid and complete combustion of a fuel charge in an engine cycle. Post injections, where a small injection follows a larger main injection, can also have beneficial impacts in certain circumstances. Fuel injection rate shape, referring to the shape of a signal trace reflecting fuel injection rate, can also be varied amongst square, ramp, and other shapes, to varying effect.
The implementation and control of pilot injections, post injections, rate shapes, and other fuel injection properties can differ based upon the basic design of fuel injectors and fuel systems. Where mechanical actuation of a fuel injector is employed, spill valves that selectively open to spill pressure during a plunger pressurization event in a fuel injector are commonly used to provide desired fuel injection characteristics. In other fuel systems, for example, common rail fuel systems where pressurized fuel is continuously available within a fuel injector, different strategies are used to control or vary injection properties. In the context of common rail fuel systems, success in rate shaping has been elusive, required unduly complex fuel injector designs, an injector actuation fluid different from the fuel that is injected, or presented still other challenges. U.S. Pat. No. 7,111,614 to Coldren et al. is directed to a known single-fluid injector apparently having rate shaping capability.
In one aspect, an internal combustion engine system includes an engine head having formed therein a plurality of fuel injector bores, a fuel supply including a pressurized fuel supply conduit, and a fuel return conduit fluidly connected to the fuel supply. The engine system further includes a plurality of fuel injectors positioned in the plurality of fuel injector bores. Each of the plurality of fuel injectors has formed therein an actuation fuel supply passage fluidly connected to the pressurized fuel supply conduit, a pressure control passage, a plunger control passage, a nozzle fuel supply passage extending between a plunger cavity and a nozzle outlet, and at least one actuation fuel outlet. Each of the plurality of fuel injectors further includes an intensifier plunger, a nozzle check, an injection control valve, and an intensifier control valve. A plurality of fuel recovery fittings are coupled to the plurality of fuel injectors and each fluidly connects the at least one actuation fuel outlet in the respective fuel injector to the fuel return conduit.
In another aspect, a fuel injector assembly includes an injector housing having formed therein an actuation fuel supply passage, a pressure control passage, an intensifier passage, a nozzle fuel supply passage extending between a plunger cavity and a nozzle outlet, and at least one actuation fuel outlet. The fuel injector assembly further includes an intensifier plunger having an actuation surface exposed to the intensifier passage, and a pressurization surface exposed to the plunger cavity. The fuel injector assembly also includes a nozzle check movable between a closed check position blocking the nozzle outlet, and an open check position, and having a closing hydraulic surface exposed to a fluid pressure of the pressure control passage. An injection control valve is movable between a first control valve position, where the pressure control passage is fluidly connected to the actuation fuel supply passage, and a second control valve position, where the pressure control passage is blocked from the actuation fuel supply passage and fluidly connected to the at least one actuation fuel outlet. The fuel injector assembly further includes an intensifier control valve, and a fuel recovery fitting, having a recovered fuel outlet coupled to the injector housing and fluidly connecting the at least one actuation fuel outlet to the recovered fuel outlet.
In still another aspect, a method of operating a common rail fuel system in an internal combustion engine includes moving a control valve in a fuel injector between a first control valve position and a second control valve position to vary a pressure of fuel in a pressure control passage in the fuel injector. The method further includes opening a nozzle check in the fuel injector based on a reduction in the pressure of fuel in the pressure control passage caused by the moving of the control valve, and varying a flow of fuel to a spool valve in the fuel injector based on the varying of the pressure of fuel in the pressure control passage. The method still further includes varying a rate of advancement of an intensifier plunger through a plunger cavity in the fuel injector based on the varied flow of fuel through the spool valve, and injecting fuel from the plunger cavity through a nozzle outlet in the fuel injector opened by the opening of the nozzle check at a fuel injection rate having a rate shape that is based on the varied rate of advancement of the intensifier plunger. The method still further includes recovering fuel from at least one actuation fuel outlet of the fuel injector in a fuel recovery fitting coupled with the fuel injector.
Referring to
Fuel pressurization pump 36 could include an inlet-metered pump, an outlet-metered pump, or still another type of pump structured to pressurize fuel for actuating components in fuel system 21 and providing fuel for injection, as further discussed herein. In the illustrated embodiment fuel pressurization pump 36 includes a higher pressure outlet 38 and a lower pressure outlet 40 structured to feed fuel to fuel supply conduit 24 and fuel supply conduit 26, respectively. One or more additional fuel filters 42 may be positioned fluidly between fuel pressurization pump 38 and engine head 18, for example in fuel supply conduit 26. Also in the illustrated embodiment fuel supply conduit 24 and fuel supply conduit 26 feed fuel through cylinder block 14 by way of passages and/or connectors located in cylinder block 14 and/or engine head 18. Fuel supply conduit 24 can be understood as a common rail. Common rail is intended herein to refer to any of a number of different fuel containment and supply strategies where a single pressurized fuel reservoir is employed to maintain fuel at a desired pressure for supplying to multiple different fuel injectors. Fuel supply conduit 24 may be maintained at a lower pressure than in other common rail systems, as pressurization to an injection pressure takes place within fuel injectors as further discussed herein. Quill connectors, pressure sensors, relief valves, or other known pressurized fuel supply connections and monitoring or control hardware may be provided in engine system 10, as will be understood to those skilled in the art.
A valve cover 44 is also attached to engine head 18, such that a space 46 is formed between valve cover 44 and engine head 18. Engine system 10, and fuel system 21, also includes a plurality of fuel injectors 50 in a plurality of fuel injector assemblies 52 positioned in the plurality of fuel injector bores 20. Fuel injector assemblies 52 each also include a fuel recovery fitting 54 coupled to the corresponding one of the plurality of fuel injectors 50. A plurality of fuel seals 142 are formed between the plurality of fuel recovery fittings 54 and the respective fuel injectors 50, and also potentially between fuel recovery fittings 54 and engine head 18 as further discussed herein. Each of the plurality of fuel recovery fittings 54 may be positioned at least partially within space 46. Engine oil supplied directly or incidentally into space 46 could contact fuel recovery fittings 54 to assist in cooling.
Referring also now to
Injection control valve 82 may be part of a control valve subassembly 118 including a valve body 120 and a valve member, such as a poppet valve member 122, movable relative to valve body 120 to contact a lower seat 124 or an upper seat 126 at the first control valve position and the second control valve position, respectively. A biaser 128, such as a conventional biasing spring, biases valve member 122 toward the second control valve position. An electrical actuator 130, such as a solenoid electrical actuator, is provided and can be varied in electrical energy state to move valve member 122 in opposition to a bias of biaser 128 from the first control valve position to the second control valve position.
Fuel injector 50 also includes an intensifier control valve 86. In a practical implementation strategy, intensifier control valve 86 includes a spool valve having a first end surface 88 and a second end surface 90. First end surface 88 can be exposed to a fluid pressure of pressure control passage 60, and second end surface 90 can be exposed to a fluid pressure of actuation fuel supply passage 58. By varying a position of injection control valve 82, fluid connections amongst pressure control passage 60, actuation fuel supply passage 58, and drain port 68 can be varied. Lower seat 124 may be a three-way valve seat formed in injector housing 56 and positioned fluidly amongst pressure control passage 60, actuation fuel supply passage 58, and drain port 68. Thus, injection control valve 82, namely, valve member 122, blocks three-way valve seat 124 at the first control valve position, and does not block valve seat 124 at the second control valve position.
Those skilled in the art will be familiar with certain related aspects of functionality of a pilot control valve, such as injection control valve 82, and a slide-type hydraulic valve, such as intensifier control valve 86. During, or in preparation for, a fuel injection event, injection control valve 82 can be opened and closed multiple times to vary a pressure acting upon first end surface 88 by way of varied pressure in pressure control passage 60. When a fuel pressure of actuation fuel supply passage 58 is acting on both end surface 88 and end surface 90 of intensifier control valve 86, intensifier control valve 86 may be balanced, and positioned such that intensifier control passage 62 is at a lower pressure, such as a drain pressure, and such that intensifier plunger 72 is retracted, approximately as shown in
It will be recalled that injection control valve 82 may be part of a control valve subassembly 118. Control valve subassembly 118 may have an outside surface 119, and a fuel collection cavity 121 extends between inside surface 108 of sleeve portion 106 and outside surface 119 of control valve subassembly 118. It will also be recalled the at least one actuation fuel outlet can include drain port 68 and also leakage path 70. During moving valve member 122 some pressurized fuel can be expected to leak through a clearance between valve body 120 and valve member 122, and find its way outside of injector housing 56. Fuel collection cavity 121 is simultaneously fluidly connected with leakage path 70 and drain port 68. Continued expelling of pressurized fuel into fuel collection cavity 121 can be expected to assist in maintaining a flow of fuel from the respective fuel recovery fitting 54 of each fuel injector 50 to fuel return conduit 28. The flow of fuel can also assist in cooling control valve subassembly 118. Fuel seal 142 may fluidly seal amongst engine head 18, fuel injector 50, and fuel recovery fitting 54. In the illustrated embodiment, injector body 57 has plunger cavity 65 formed therein, and fuel seal 142 fluidly seals between fuel recovery fitting 54 and injector body 57. In particular, fuel recovery fitting 54 includes a radially projecting flange 140, and fuel seal 142 may seal with flange 140 and with fuel injector 50, including injector body 57, and with engine head 18.
Referring also now to
Referring to the drawings generally, operating fuel system 31 in engine system 10 can include moving control valve 82 between its first control valve position and second control valve position, to vary a pressure of fuel in pressure control passage 60 as discussed herein. Nozzle check 78 is opened based on a reduction in the pressure of fuel in pressure control passage 60 caused by the moving of control valve 82. As discussed above, intensifier control valve 86 is adjusted to vary a flow of fuel therethrough based on the varying of the pressure of fuel in pressure control passage 60. As also discussed herein, a rate of advancement of intensifier plunger 72 through plunger cavity 63 is varied based on the varied flow of fuel through intensifier control valve 86. With nozzle check 78 opened, fuel from plunger cavity 65 is injected through nozzle outlet 66 at a fuel injection rate having a rate shape that is based on the varied rate of advancement of intensifier plunger 72.
Embodiments are contemplated where injection control valve 82 is moved multiple times to open and close seat 124, with intensifier control valve 86 correspondingly accelerated, decelerated, reversed, stopped, or fully opened and then fully closed, all during, or in anticipation of, a single injection cycle. Accordingly, pressure and flow of fuel in intensifier passage 62 can be varied in a manner that produces numerous different fuel injection rate shapes. The fuel leaked through leakage path 70, and fuel expelled through drain port 68, is recovered by way of fuel recovery fitting 54 in fuel collection cavity 108, and returned to fuel supply 22 as discussed herein.
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.
