Patent Application
20220268234
The present disclosure relates generally to limiting errors in fuel injection quantity in a fuel system, and more particularly to retarding an armature in an injection control valve assembly to stabilize closing of an injection control valve.
Fuel systems employed in internal combustion engines, and notably compression-ignition engines, are typically complex apparatuses. Fuel system components can be subjected to harsh service conditions including high pressures, rapid pressure changes, and repeated impacts of valve elements and related parts over time. Fuel injectors are employed to inject pressurized fuel at pressures which can be in excess of 200 Megapascals (MPa), and can actuate a number of times ranging into the billions over the course of a typical service life. Engineers have discovered that reliable operation and optimized performance of a fuel system can be critical to achieving goals such as power density, emissions mitigation, and efficiency.
In view of the above goals, systems for monitoring, controlling, and electronically trimming fuel system components such as fuel injectors with great precision have been developed and are widespread throughout the world. It has also been observed that controlling fuel injector operation, for example, through the use of varied pulse width of fuel delivery command signals can be used to operate a fuel injector at different engine conditions as well as compensate for individual injector variation and changes to injector behavior over time. U.S. Pat. No. RE37807E1 to Shinogle is directed to a strategy for electronic trimming. The strategy set forth by Shinogle et al. apparently minimizes or eliminates performance variation of an apparatus such as a fuel injector by deriving trim signals from observed performance parameter values taken at a plurality of operating conditions. While electronic trimming strategies such as that proposed by Shinogle et al., and still others, can assist in optimizing performance, there remains ample room for improvement and development of alternative strategies. For instance, there are some scenarios where conventional electronic trimming and other control strategies are insufficient to account for certain mechanical and hydraulic phenomena that can be observed, at least at times, that cause errors in a quantity of injected fuel.
In one aspect, a fuel system for an engine includes a fuel injector having formed therein a high pressure fuel inlet and a control chamber, and defining a low pressure space. The fuel injector has an outlet check having a closing hydraulic surface exposed to a fluid pressure of the control chamber, a solenoid actuator, an armature movable in the fuel injector based on energizing and deenergizing the solenoid actuator, and an injection control valve movable in the fuel injector based on the moving of the armature to open and close a fluid connection between the control chamber and the low pressure space. A fueling control unit is electrically connected to the solenoid actuator and structured to energize the solenoid actuator to lift the armature from a stop position and open the injection control valve to start an injection of fuel from the fuel injector. The fueling control unit is further structured to deenergize the solenoid actuator to initiate returning the armature to the stop position, and reenergize the solenoid actuator with an armature retarding current while the armature is in flight toward the stop position. The fueling control unit is still further structured to stabilize, by way of the armature retarding current, closing of the injection control valve to end the injection of fuel from the fuel injector.
In another aspect, a fuel control system includes a fueling control unit having a data processor, and a computer readable memory. The computer readable memory stores fueling control instructions for actuating a fuel injector to inject fuel into a combustion cylinder in an engine, and a trim file for limiting an error in a quantity of the injected fuel. The data processor is structured by way of executing the fueling control instructions to energize a solenoid actuator in the fuel injector with a pull-in current to lift an armature from a stop position and open an injection control valve to start an injection of fuel from the fuel injector. The data processor is further structured to deenergize the solenoid actuator to initiate returning the armature to the stop position, and reenergize the solenoid actuator with an armature retarding current that is based on the trim file while the armature is in flight toward the stop position. The data processor is still further structured to stabilize, by way of the armature retarding current, closing of the injection control valve to end the injection of fuel from the fuel injector.
In still another aspect, a method of operating a fuel system for an engine includes energizing a solenoid actuator to lift an armature in a fuel injector from a stop position, and opening an injection control valve fluidly between a check control chamber and a low pressure space of the fuel injector, based on the lifting of the armature, to start an injection of fuel from the fuel injector. The method further includes deenergizing the solenoid actuator to initiate returning of the armature to the stop position, reenergizing the solenoid actuator to retard the armature while in flight toward the stop position, and stabilizing, based on the retarding of the armature, closing of the injection control valve to end the injection of fuel.
Referring to
Engine system 10 further includes a fuel system 18. Fuel system 18 includes a fuel tank 20, a transfer pump 22, a high pressure pump 24, and a pressurized fuel reservoir such as a common rail 26. A plurality of feed lines 28 extend from common rail 26 to a plurality of fuel injectors 30 each positioned for direct injection of a pressurized liquid fuel from common rail 26 into one of combustion cylinders 16. In other embodiments, fuel injectors 30 might each be associated with a unit pump, dedicated to that fuel injector or shared with one or more other fuel injectors. Each of fuel injectors 30 includes a directly controlled outlet check 32, and an injection control valve assembly 34 having a solenoid actuator 36 and an injection control valve 38, as well as other components and features further discussed herein.
Engine system 10 further includes a fuel control system 40 having a fueling control unit 42 electrically connected to each of solenoid actuators 36. Fueling control unit 42 includes a data processor 44, and a computer readable memory 46. Data processor 44 may be any suitable computerized processor having a central processing unit, such as a microprocessor or a microcontroller. Description and discussion herein of fueling control unit 42 or parts thereof should not be taken to require any number, type, arrangement, allocation of functions, or any other limitation in particular with respect to system components or architecture. Fueling control unit 42 could be a fuel system control unit dedicated for fuel system operation, or a part of a control unit having various other functions, for instance. Computer readable memory 46 could include any suitable computer readable memory such as RAM, ROM, EEPROM, DRAM, SDRAM, flash, a hard drive, or still another.
Computer readable memory 46 stores fueling control instructions 48 for actuating each of fuel injectors 30 to inject fuel into one of combustion cylinders 16 in engine 12, and a trim table 50 including a plurality of trim files for limiting an error in a quantity of injected fuel. Computer readable memory 46 may also store back electro-motive force (EMF) monitoring instructions 52. In some embodiments, fueling control unit 42 may be structured for in-chassis determining and populating of trim table 50, and in this regard can execute back EMF monitoring instructions 52 for purposes further discussed herein. In other instances, trim table 50 may be populated during fuel injector testing and calibration during engine manufacturing and build, or some combination of populating trim table 50 in-chassis and during manufacturing might be used. Trim table 50 might also include trim files downloaded from a server and potentially updated periodically, or read computer readable memory or otherwise machine readable codes resident on fuel injectors 30. Fuel control system 40 may further include a pressure sensor 58 structured to monitor a fuel pressure in common rail 26, an engine speed sensor 54 structured to monitor an engine speed, and a temperature sensor 56 structured to monitor a temperature such as a fuel temperature, an engine temperature, or any other temperature for control purposes that will be further apparent by way of the following description. Fueling control unit 42 is electrically connected to each solenoid actuator 36 as noted above and may also be electrically connected to, or otherwise in communication with, the various sensors in fuel control system 40, and to high pressure pump 24.
Referring also now to
As also noted above, fuel injector 30 includes an injection control valve assembly 34. Injection control valve assembly 34 includes a solenoid actuator 36 having a solenoid coil (not separately numbered), and an armature 70. Armature 70 is movable in fuel injector 30 based on energizing and deenergizing solenoid actuator 36. Injection control valve 38 is movable in fuel injector 30 based on the moving of armature 70 to open and close a fluid connection between control chamber 64 and low pressure space 66. In the illustrated embodiment injection control valve 38 includes a ball valve, which may be a flat-sided ball valve. Injection control valve 38 is movable between a closed position, as depicted in
In the illustrated embodiment, injection control valve assembly 34 further includes a valve rod 80 that is unattached to injection control valve 38 and coupled with armature 70. Injection control valve 38 is held captive between valve rod 80 and valve seat 78. When solenoid actuator 36 is energized with an electrical current, armature 70 is drawn magnetically toward solenoid actuator 36. When solenoid actuator 36 is deenergized, partly or totally deenergized, armature 70 may move away from solenoid actuator 36. As can be seen from
To this end, fueling control unit 42 is structured, by way of executing fueling control instructions 48, to energize solenoid actuator 36 with a pull-in current to lift armature 70 from its first stop position and open injection control valve 38 to start an injection of fuel from fuel injector 30. Fueling control unit 42 and data processor 44 are referred to herein interchangeably, at times, with regard to functionality and structure, and thus the description of logic functions and execution of instructions by fueling control unit 42 should be understood to refer also generally to data processor 44. Fueling control unit 42 is further structured, by way of executing fueling control instructions 48, to deenergize solenoid actuator 36 to initiate returning armature 70 to the first stop position. It will be recalled that armature 70 can be understood to have a first stop position in contact with stop 84, and a second stop position where valve rod 80 contacts stop 88. Accordingly, when solenoid actuator 36 is energized with a pull-in current armature 70 lifts from contact with stop 84 and travels, axially in fuel injector 30, until valve rod 80 contacts stop 88. In some embodiments energizing solenoid actuator 36 in the manner described includes energizing solenoid actuator 36 with a subsequent hold current to hold armature in a lifted position with valve rod 80 against stop 88, having a magnitude less than a magnitude of the pull-in current. Fueling control unit 42 is further structured to deenergize solenoid actuator 36 to initiate returning armature 70 to the first stop position. It will also be recalled that armature 70 returns towards the first stop position in contact with stop 84 under the influence of a bias of biasing spring 90. Fueling control unit 42 is further structured, by way of executing fueling control instructions 48, to reenergize solenoid actuator 36 with an armature retarding current, which may be based on a stored trim file in trim table 50, while armature 70 is in flight toward the first stop position. Fueling control unit 42 is further structured to stabilize, by way of the armature retarding current, closing of injection control valve 38 to end the injection of fuel from fuel injector 30.
Referring also now to
Electronic trimming may employ varied pulse width, or sometimes other pulse properties, in a fuel injector electrical actuator to vary operation of the fuel injector to achieve some desired aim, typically metering the fuel so as to provide a desired injection quantity. Fuel injectors can vary in performance one to another based on factors such as manufacturing tolerances. Fuel injectors can also vary in operation over time due to wear, deformation of components, or for other reasons. Fuel injectors can also vary in operation at different engine states, including different engine temperatures, different fuel temperatures, different cylinder pressures, or for various other reasons. The present disclosure contemplates receiving, with data processor 44, engine state data. The engine state data may be associated with a closing timing of injection control valve 38. For instance, fuel may have a varied viscosity at different temperatures, potentially affecting the tendency of armature 70 to bounce or the manner by which armature 70 bounces. At higher temperatures armature bouncing may be more pronounced, and at lower temperatures less pronounced or not observed at all. Accordingly, one example of engine state data that might be received by data processor 44 is fuel temperature data. Another example of engine state data includes engine or fuel injector aging state data, for instance service hours or some other direct or indirect measure of aging state. Based on the different armature bouncing likelihood, or properties of bouncing, injection control valve 38 can also vary with respect to valve bouncing or other forms of closing instability at different engine states. Another way to understand this relationship is that a valve closing timing, or an expected valve closing timing, of injection control valve, can vary based on engine state. The use of electronic trim files in trim table 50 can enable fueling control unit 42 to compensate for such variation, and in the example suggested above by varying at least one of dwell time 140 or duration 145 of armature retarding current 115 by way of electronic trimming.
Referring to the drawings generally, but also now to
Reenergizing solenoid actuator 36 can be based on a first trim file, and can occur in a first engine cycle or a prior or preceding engine cycle. A first trim file could be a trim file applied to determine a dwell time between a hold current and the armature retarding current, a duration of the armature retarding current, both dwell and duration, a magnitude of the armature retarding current, or still another property. Engine state data is received/inputted at a block 240. From block 230 the logic advances to a block 250 to reenergize solenoid actuator 36 with an armature retarding current that is based on a second trim file different from the first trim file. Block 250 represents a fuel injection event that occurs in a second, or subsequent engine cycle. In some engine states no armature retarding current may be used at all. Between blocks 230 and 250 fueling control unit 42 can be operating to energize and deenergize solenoid actuator 36, analogous to blocks 210-220, but these logic steps are omitted for clarity of illustration. It will thus be appreciated that based upon various changes to engine state different trim files can be applied to vary the armature retarding current in an engine cycle relative to a preceding armature current in a preceding engine cycle.
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.
