Patent Application
20140361096
This disclosure relates to a fuel injector that delivers fuel at different pressures and a constant fuel flow rate to a combustion chamber.
A variety of techniques exist to control fuel flow into a combustion chamber of an internal combustion engine. These techniques are often described as rate-shaping techniques, which provide varying methods of controlling rates of fuel flow into a combustion chamber. By reducing the rate of fuel flow during an initial portion of an injection event, NOx formation is reduced. The fuel flow rate is then increased or unrestricted during the latter portion of the injection event. However, dividing an injection event into a first portion with a first fuel flow rate and a second portion with a higher fuel flow rate increases the total length of an injection event, which increases fuel consumption and decreases engine efficiency.
This disclosure provides a fuel system for injecting fuel into a combustion chamber of an internal combustion engine. The fuel system comprises a variable pressure fuel supply, a fuel injector, and a controller. The variable pressure fuel supply is configured to selectively supply fuel at different pressure levels. The fuel injector includes an injector body, a first needle valve element, a second needle valve element, and an actuator. The injector body contains an injector cavity and a plurality of injector orifices communicating with a first end of the injector cavity to discharge fuel into the combustion chamber. The plurality of injector orifices includes a first set of injector orifices and a second set of injector orifices. The injector body includes a fuel transfer circuit for transferring fuel to the plurality of injector orifices. The first needle valve element is positioned in the injector cavity for controlling fuel flow through the first set of injector orifices and a first valve seat formed on the injector body. The first needle valve element is movable from a closed position against the first valve seat blocking flow through the first set of injector orifices to an open position permitting flow through the first set of injector orifices. The second needle valve element is positioned in the injector cavity for controlling fuel flow through the second set of injector orifices and a second valve seat formed on the injector body. The second needle valve element is movable from a closed position against the second valve seat blocking flow through the second set of injector orifices to an open position permitting flow through the second set of injector orifices. The actuator is movable to permit movement of the first and the second needle valve elements between the open and closed positions to define an injection event. The controller is connected to the actuator and to the variable pressure fuel supply. The controller is configured to generate a control signal to cause the variable pressure fuel supply to supply fuel to the injector cavity at a first pressure level during an initial portion of the injection event and at a second pressure level, higher than the first pressure level, during a subsequent portion of the injection event occurring after the initial portion.
This disclosure also provides a fuel system for injecting fuel into a combustion chamber of an internal combustion engine. The fuel system comprises a variable pressure fuel supply and a fuel injector. The variable pressure fuel supply is configured to selectively supply fuel at a first pressure level and a second pressure level higher than the first pressure level. The fuel injector includes an injector body, a first needle valve element, and a second needle valve element. The injector body contains an injector cavity and a plurality of injector orifices communicating with a first end of the injector cavity to discharge fuel into the combustion chamber. The plurality of injector orifices includes a first set of injector orifices and a second set of injector orifices. The injector body includes a fuel transfer circuit for transferring fuel to the plurality of injector orifices. The first needle valve element is positioned in the injector cavity for controlling fuel flow through the first set of injector orifices and a first valve seat formed on the injector body. The first needle valve element is movable from a closed position against the first valve seat blocking flow through the first set of injector orifices to an open position permitting flow through the first set of injector orifices. The second needle valve element is positioned in the injector cavity for controlling fuel flow through the second set of injector orifices and a second valve seat formed on the injector body. The second needle valve element is movable from a closed position against the second valve seat blocking flow through the second set of injector orifices to an open position permitting flow through the second set of injector orifices. The first and the second set of injector orifices are sized to provide a fuel flow rate at the first pressure level and the second set of injector orifices sized to provide substantially the fuel flow rate at the second pressure level.
This disclosure also provides a method of providing fuel to a combustion chamber from a fuel injector of an internal combustion engine. The method comprises providing fuel at a first fuel pressure level and a fuel flow rate through a first set of injector orifices and a second set of injector orifices into the combustion chamber during a first portion of an injection event, and providing fuel at a second fuel pressure level higher than the first fuel pressure level through the second set of injector orifices to cause fuel flow into the combustion chamber at substantially the same fuel flow rate during a second portion of the injection event.
Advantages and features of the embodiments of this disclosure will become more apparent from the following detailed description of exemplary embodiments when viewed in conjunction with the accompanying drawings.
Referring to
Engine body 12 includes at least one piston 22, and a connecting rod 24. Piston 22 is positioned for reciprocal movement in an engine cylinder 26. Connecting rod 24 connects piston 22 to a crank shaft (not shown). The movement of piston 22 under the action of a combustion process in engine 10 causes connecting rod(s) 24 to move the crankshaft. At least one fuel injector 28 is positioned within cylinder head 16. Each fuel injector 28 is fluidly connected to a combustion chamber 30, each of which is formed by one piston 22, cylinder head 16, and the portion of engine cylinder 26 that extends between piston 22 and cylinder head 16. While
Fuel system 18 provides fuel to injector(s) 28, which is then injected into combustion chamber(s) 30 by the action of fuel injector(s) 28, forming one or more injection events. Fuel system 18 includes a fuel circuit 32, a fuel tank 34, which contains a fuel, a fuel pump 36 positioned along fuel circuit 32 downstream from fuel tank 34, and a fuel accumulator or rail 38 positioned along fuel circuit 32 downstream from fuel pump 36. While fuel accumulator or rail 38 is shown as a single unit or element, accumulator 38 may be distributed over a plurality of elements that transmit or receive high-pressure fuel, such as fuel injector(s) 28, fuel pump 36, and any lines, passages, tubes, hoses and the like that connect high-pressure fuel to the plurality of elements. Fuel system 18 may further include an inlet metering valve 40 positioned along fuel circuit 32 upstream from fuel pump 36 and one or more outlet check valves 42 positioned along fuel circuit 32 downstream from fuel pump 36 to permit one-way fuel flow from fuel pump 36 to fuel accumulator 38. A pressure relief valve 44 may also be positioned along fuel circuit 32 to limit the fuel pressure in fuel circuit 32. Though not shown, additional elements may be positioned along fuel circuit 32. For example, inlet check valves may be positioned downstream from inlet metering valve 40 and upstream from fuel pump 36, or inlet check valves may be incorporated in fuel pump 36. A low-pressure fuel pump may also be positioned upstream from fuel pump 36, which may be described as a high-pressure fuel pump, to provide low-pressure fuel to fuel pump 36 to increase the efficiency of fuel pump 36. Inlet metering valve 40 has the ability to vary or shut off fuel flow to fuel pump 36, which thus varies or shuts off fuel flow to fuel accumulator 38. Fuel circuit 32 connects fuel accumulator 38 to fuel injector(s) 28, which then provide controlled amounts of fuel to combustion chamber(s) 30.
Control system 20 may include a controller, i.e., a control module, 46 and a wire harness 48. Many aspects of the disclosure are described in terms of sequences of actions to be performed by elements of a computer system or other hardware capable of executing programmed instructions, for example, a general purpose computer, special purpose computer, workstation, or other programmable data processing apparatus. It will be recognized that in each of the embodiments, the various actions could be performed by specialized circuits (e.g., discrete logic gates interconnected to perform a specialized function), by program instructions (software), such as logical blocks, program modules etc. being executed by one or more processors (e.g., one or more microprocessor, a central processing unit (CPU), and/or application specific integrated circuit), or by a combination of both. For example, embodiments can be implemented in hardware, software, firmware, middleware, microcode, or any combination thereof. The instructions can be program code or code segments that perform necessary tasks and can be stored in a non-transitory machine-readable medium such as a storage medium or other storage(s). A code segment may represent a procedure, a function, a subprogram, a program, a routine, a subroutine, a module, a software package, a class, or any combination of instructions, data structures, or program statements. A code segment may be coupled to another code segment or a hardware circuit by passing and/or receiving information, data, arguments, parameters, or memory contents.
The non-transitory machine-readable medium can additionally be considered to be embodied within any tangible form of computer readable carrier, such as solid-state memory, magnetic disk, and optical disk containing an appropriate set of computer instructions, such as program modules, and data structures that would cause a processor to carry out the techniques described herein. A computer-readable medium may include the following: an electrical connection having one or more wires, magnetic disk storage, magnetic cassettes, magnetic tape or other magnetic storage devices, a portable computer diskette, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (e.g., EPROM, EEPROM, or Flash memory), or any other tangible medium capable of storing information.
It should be noted that the system of the present disclosure is illustrated and discussed herein as having various modules and units which perform particular functions. It should be understood that these modules and units are merely schematically illustrated based on their function for clarity purposes, and do not necessarily represent specific hardware or software. In this regard, these modules, units and other components may be hardware and/or software implemented to substantially perform their particular functions explained herein. The various functions of the different components can be combined or segregated as hardware and/or software modules in any manner, and can be useful separately or in combination. Input/output or I/O devices or user interfaces including but not limited to keyboards, displays, pointing devices, and the like can be coupled to the system either directly or through intervening I/O controllers. Thus, the various aspects of the disclosure may be embodied in many different forms, and all such forms are contemplated to be within the scope of the disclosure.
Control module 46 may be an electronic control unit or electronic control module (ECM) that may monitor conditions of engine 10 or an associated vehicle in which engine 10 may be located. Control module 46 may be a single processor, a distributed processor, an electronic equivalent of a processor, or any combination of the aforementioned elements, as well as software, electronic storage, fixed lookup tables and the like. Control module 46 may include a digital or analog circuit. Controller 46 may connect to certain components of engine 10 by wire harness 48, though such connection may be by other means, including a wireless system. For example, controller 46 may connect to, generate, and provide control signals to inlet metering valve 40, to fuel injector(s) 28, and to a variable pressure fuel supply.
When engine 10 is operating, combustion in combustion chambers 30 causes the movement of piston(s) 22. The movement of piston(s) 22 causes movement of connecting rod(s) 24, which are drivingly connected to a crankshaft (not shown), and movement of connecting rod(s) 24 causes rotary movement of the crankshaft. The angle of rotation of the crankshaft is measured by engine 10 to aid in timing of combustion events in engine 10 and for other purposes. The angle of rotation of the crankshaft may be measured in a plurality of locations, including a main crank pulley (not shown), an engine flywheel (not shown), an engine camshaft (not shown), or on the camshaft itself.
The action of the crankshaft drives fuel pump 36, which pulls fuel from fuel tank 34 and moves the fuel along fuel circuit 32 toward inlet metering valve 40. From inlet metering valve 40, fuel flows downstream along fuel circuit 32 through inlet check valves (not shown) to fuel pump 36. Fuel pump 36 moves the fuel downstream along fuel circuit 32 through outlet check valves 42 toward fuel accumulator or rail 38. Inlet metering valve 40 receives control signals from control system 20 and is operable to control or block fuel flow to fuel pump 36. Inlet metering valve 40 may be a proportional valve or may be an on-off valve that is capable of being rapidly modulated between an open and a closed position to adjust the amount of fuel flowing through the valve. Pressure relief valve 44 connects a high-pressure portion of fuel circuit 42 to fuel tank 34, and limits the pressure in the high-pressure portion of fuel circuit 42. Controller 46 determines the timing of injection events in fuel injector 28, along with the duration of such events, to control the combustion process in combustion chambers 30.
Referring to
Injector body 50 includes an injector cavity 56 and a plurality of injector orifices 58 communicating with a distal or first end 60 of injector cavity 56 to permit discharge of fuel from injector cavity 56 into combustion chamber 30. Injector body 50 further includes a fuel transfer circuit 69. Injector orifices 58 includes a first set of injector orifices 70 located at a first radial distance 72 from longitudinal axis 68 and a second set of injector orifices 74 located at a second radial distance 76 from longitudinal axis 68. A first valve seat 82 is formed on an interior portion of injector body 50 in a location between first radial distance 72 and second radial distance 76. A second valve seat 84 is formed on an interior portion of injector body 50 in a location that is at a third radial distance 77 that is greater than second radial distance 76. Injector body 50 may also include an injector barrel 62, a nozzle housing 64, and a coupler 66 for attaching nozzle housing 64 to injector barrel 62. Injector barrel 62 includes an inlet passage 71 for connecting fuel from the variable pressure fuel supply to injector cavity 56. Needle valve assembly 52 includes a first needle valve element 78 positioned in injector cavity 56 for controlling fuel flow through first set of injector orifices 70 and a second needle valve element 80 positioned in injector cavity 56 for controlling fuel flow through second set of injector orifices 74. First needle valve element 78 is movable along longitudinal axis 68 from a closed position against first valve seat 82, which blocks fuel flow through first set of injector orifices 70, to an open position that permits fuel flow through first set of injector orifices 70. Second needle valve element 80 is movable along longitudinal axis 68 from a closed position against second valve seat 84, which blocks fuel flow through second set of injector orifices 74, to an open position that permits fuel flow through second set of injector orifices 74.
First needle valve element 78 includes a first needle distal end 97 that is adapted or configured to contact first valve seat 82 to block fuel flow to first set of injector orifices 70. First needle valve element 78 also includes a radially extending portion 99. Second needle valve element 80 includes a needle element cavity 86, formed by an interior surface 87, a transverse interior surface 93, a needle stop 88, and one or more needle passages 73. Needle stop 88 is fixedly formed on or attached to second needle valve element 80, such as by press fitting, in needle element cavity 86. Needle stop 88 includes a terminal or distal end portion 89, a proximate end surface 95, and a stop cavity 91. Needle stop 88 further includes one or more radially extending stop passages 90 that connect stop cavity 91 to the exterior of needle stop 88 to permit fuel flow in and out of stop cavity 91. First needle valve element 78 is telescopically received in needle element cavity 86 and stop cavity 91 to be slidably movable with respect to interior surface 87 along longitudinal axis 68. Fuel injector 28 further includes a first bias spring 100 positioned in stop cavity 91 between proximate end surface 95 and radially extending portion 99. In the exemplary embodiment, first bias spring 100 is in abutment with proximate end surface 95 and with radially extending portion 99 of first needle valve element 78. Radially extending portion 99 of first needle valve element 78 includes a first needle shoulder 96 on a distal side of radially extending portion 99. First bias spring 100 functions to bias or move first needle valve element 78 toward the distal end of fuel injector 28. When first needle valve element 78 is able to contact first valve seat 82 because of the position of second needle valve element 80, first bias spring 100 provides a bias force on first needle valve element 78 to be in a closed position in contact with first valve seat 82.
Fuel injector 28 further includes a plunger assembly 92, which movably connects actuator 54 with second needle valve element 80. In the exemplary embodiment, plunger assembly 92 includes a plunger bias spring 102, a plunger adapter 104, a first plunger 106, a hydraulic link 108, which includes a hydraulic link housing 110, and a second plunger 112. Hydraulic link housing 110 abuts injector barrel 62 and nozzle housing 64, preventing movement of hydraulic link housing 110. Hydraulic link housing 110 further includes a first longitudinal passage 120 and a second longitudinal passage 122. Plunger adapter 104 is configured to provide an interface between actuator 54 and first plunger 106. First plunger 106 extends along longitudinal axis 68 and slidably extends into first longitudinal passage 120 of hydraulic link housing 110 at a first, proximate end 116 in a substantially sealing manner that limits fluid flow along a first radial interface 114 between first plunger 106 and hydraulic link housing 110. Second plunger 112 extends along longitudinal axis 68 and slidably extends into second longitudinal passage 122 of hydraulic link housing 110 at a second, distal end 118 in a substantially sealing manner that limits fluid flow along a second radial interface 124 between second plunger 112 and hydraulic link housing 110. Second plunger 112 extends into and fixedly engages second needle valve element 80 so that movement of second plunger 112 causes movement of second needle valve element 80. Plunger bias spring 102 is positioned longitudinally between second needle valve element 80 and hydraulic link housing 110 and serves to assist in the movement of second needle valve element 80 into the closed position in conjunction with the movement of actuator 54.
Fuel transfer circuit 69 includes injector cavity 56 and inlet passage 71. As described further hereinbelow, during an injection event, fuel transfer circuit 69 transports or transfers fuel from fuel system 18 to first set of injection orifices 70 and second set of injector orifices 74. More specifically, inlet passage 71 accepts fuel at a plurality of pressure levels and transfers the fuel to injector cavity 56. The fuel flows along injector cavity 56 to the distal end of fuel injector 28. When controller 46 generates and transmits a control signal to de-energize actuator 54 to move second needle valve element 80 outwardly, first needle valve element 78 initially remains stationary with respect to nozzle housing 64 because of the force from bias spring 100. As second needle valve element 80 moves further outward, first needle shoulder 96 of first needle valve element 78 contacts transverse interior surface 93 of second needle valve element 80, which causes first needle valve element 78 to move with second needle valve element 80. Because actuator 54 moves at a high rate of speed, the movement of second needle valve element 80 and first needle valve element 78 from second valve seat 84 and first valve seat 82, respectively, at the beginning of an injection event is nearly instantaneous. Once first needle valve element 78 and second needle valve element 80 have moved away from first valve seat 82 and second valve seat 84, fuel is able to flow from fuel transfer circuit 69 through one or more sets of fuel injector orifices into combustion chamber 30.
Engine 10 further includes a variable pressure fuel supply 94 configured to selectively supply fuel at different pressure levels to fuel transfer circuit 69 of fuel injector 28. In the exemplary embodiment, variable pressure fuel supply 94 provides fuel to fuel transfer circuit 69 at two pressure levels. In the embodiment of
The operation of fuel injector 28 and engine 10 centers on a fuel injection event, which occurs from the time at least one needle valve element moves from first valve seat 82 or second valve seat 84 to permit fuel flow from fuel transfer circuit 69 through one or more sets of injector orifices into combustion chamber 30 until a subsequent time when both needle valve elements are positioned in contact with first valve seat 82 and second valve seat 84 to stop fuel flow from fuel transfer circuit 69 through all injector orifices into combustion chamber 30. When controller 46 determines it is time for an injection event, at time T1 shown in
Fuel is always present in fuel transfer circuit 69 at fuel pressure P1, and after time T1 the fuel flows through first set of injector orifices 70 and second set of injector orifices 74 at a rate R, as shown in
The fuel flow rate R at pressure P1 provides relatively large fuel droplets in combustion chamber 30 that reduce the effective diffusion combustion area around the fuel droplets. The large fuel droplets reduce NOx formation while maintaining a high rate of combustion. The fuel flow rate R at pressure P2 forms relatively small fuel droplets that increase the effective diffusion combustion area around the fuel droplets. The smaller fuel droplets function to burn particulate matter, but due to reduced oxygen and the presence of combustion products such as CO2 formed during combustion of the larger droplets, NOx production is minimized. As described hereinabove, the benefit to varying the pressure while maintaining a constant fuel flow rate is that the width of the fuel injection event is the same as for a fuel injector without rate shaping while attaining benefits similar to a rate-shaping fuel injector.
It should be understood from the foregoing description that variable pressure fuel supply 94 may take many different forms, as long as variable pressure fuel supply 94 is configured to receive control signals from control system 20 and to provide the pressure levels needed to maintain the constant fuel flow rate into combustion chamber 30 shown in
While various embodiments of the disclosure have been shown and described, it is understood that these embodiments are not limited thereto. The embodiments may be changed, modified and further applied by those skilled in the art. Therefore, these embodiments are not limited to the detail shown and described previously, but also include all such changes and modifications.
