Patent Application
20230184189
The present disclosure relates generally to energizing a solenoid actuator for a valve of a fuel injector, and more particularly to energizing a solenoid actuator by way of a reduced energy waveform.
Modern internal combustion engines utilize a range of operating and logic strategies for associated fuel systems. In a typical fuel system configuration a plurality of fuel injectors are each associated with one of a plurality of combustion cylinders in an engine. The fuel injectors are electronically controlled and receive electrical control current signals from an engine control system. The electrical control currents cause energizing of solenoids or other electrical actuators in or associated with the fuel injectors to adjust valves that determine the timing and manner of injection of fuel and sometimes fuel pressurization.
One known fuel system configuration applied extensively to compression-ignition diesel engines employs a direct operated nozzle check that can be opened and closed to start and end injection of fuel based on a closing hydraulic pressure that is applied to a surface of the check. A spill valve in the fuel injector controls fluid connection between a plunger cavity and a low pressure space. When the spill valve is open a plunger in the fuel injector can reciprocate passively to exchange fuel between the plunger cavity and low pressure space. When the spill valve is closed the plunger pressurizes fuel in the fuel injector to an injection pressure, with the timing of fuel injection controlled by way of the direct operated check as stated above.
Engineers have experimented for decades with the manner in which electrical actuators for such spill valves and direct operated checks can be energized and deenergized to various ends. In some instances the spill valve is closed to start building pressure in the fuel injector, the check operated to perform a single shot fuel injection, and the spill valve opened. In other instances the spill valve can be closed and opened multiple times during an engine cycle to enable multiple fuel pressurization events during a single plunger stroke, which are exploited to inject multiple shots of fuel. There can be advantages to employing multiple shots of fuel in certain instances. Certain engine operating conditions, however, can make injection of multiple shots of fuel in a single engine cycle challenging. United States Patent Application Publication No. US20210140386A1 shows a typical spill valve fuel injector arrangement.
In one aspect, a method of operating a fuel system for an engine system includes energizing a solenoid actuator for a valve of a fuel injector in a first engine cycle of an engine via a standard waveform, and injecting a shot of fuel in the first engine cycle based on the energizing a solenoid actuator via a standard waveform. The method further includes determining suitability for reduced energy operating of the fuel system, and energizing the solenoid actuator in a second engine cycle of the engine via a reduced energy waveform based on the determining suitability of the engine system for reduced energy operating of the fuel system. The method further includes injecting a shot of fuel in the second engine cycle based on the energizing a solenoid actuator via a reduced energy waveform.
In another aspect, a fuel system for an engine includes a fueling control unit having an energizing waveform controller structured to energize a solenoid actuator via a standard waveform to actuate a valve in a fuel injector in a first engine cycle. The energizing waveform controller is further structured to energize the solenoid actuator via a reduced energy waveform to actuate the valve in a second engine cycle, and to switch from a higher voltage power supply to a lower voltage power supply during the energizing of the solenoid actuator in a second engine cycle.
In still another aspect, a method of extending an engine speed range for multi-shot fuel injection in an engine includes actuating a valve of a fuel injector for the engine a plurality of times in an engine cycle, and injecting a plurality of shots of fuel into a combustion cylinder of the engine in the engine cycle based on the actuating a valve a plurality of times. The method further includes energizing a solenoid actuator of the valve via a reduced energy waveform to cause at least one of the actuations of the valve.
Referring to
Engine system 10 further includes a fuel system 20. Fuel system 20 will typically include a plurality of fuel injectors each positioned to extend partially into one of a plurality of combustion cylinders in engine 12. In
Fuel injector 22 also includes an injection control valve assembly 32. Injection control valve assembly 32 is operable to control a closing hydraulic pressure in pressure control chamber 38 to enable opening and closing of DOC 28. Injection control valve assembly 32 includes an injection control valve 34 movable to open and close a valve seat 36. When valve seat 36 is opened pressure control chamber 38 can fluidly connect to a low pressure space 54 defined by injector housing 24 enabling DOC 28 to open and permit spraying of fuel from nozzle outlets 30. When valve seat 36 is closed an increased hydraulic pressure is seen in pressure control chamber 38 and causes DOC 28 to close. An armature 40 is coupled with injection control valve 34. Armature 40 is associated with a solenoid actuator 42 that can be energized to magnetically attract armature 40 and open valve seat 36. When solenoid actuator 42 is deenergized a biasing spring 52 urges injection control valve 34 closed against valve seat 36.
Fuel injector 22 also includes a spill valve assembly 44. Spill valve assembly 44 includes a spill valve 46 coupled with an armature 48 and a solenoid actuator 50. When solenoid actuator 50 is energized armature 48 is magnetically attracted toward solenoid actuator 50. When solenoid actuator 50 is deenergized biasing spring 52 urges armature 48 and spill valve 46 away from solenoid actuator 50. Fuel injector 22 also includes a plunger 46 movable in a plunger cavity 58. In an implementation plunger 56 is mechanically cam-actuated by way of rotation of camshaft 16, in a generally known manner. When spill valve 46 is open, upward movement of plunger 56 causes fuel to be drawn into plunger cavity 58 such as by way of a spill passage 64 from low pressure space 54. Downward movement of plunger 56 causes the fuel to be discharged from plunger cavity 58 through spill passage 64 and back to low pressure space 54. When spill valve 46 is closed fluid communication between plunger cavity 58 and low pressure space 54 is blocked and advancement of plunger 56 causes fuel pressure in plunger cavity 58 to increase. The increased fuel pressure is communicated by way of a nozzle supply passage 60 to the vicinity of nozzle outlets 30. When DOC 28 is lifted, at a desirable timing, fuel sprays from nozzle supply passage 60 out of nozzle outlets 30. Another fluid passage 62 fluidly connects between nozzle supply passage 60 and injection control valve 34. In the illustrated embodiment spill valve assembly 44 is resident in fuel injector 22. In other embodiments a spill valve assembly could be positioned externally to fuel injector 22. Also in the illustrated embodiment the hydraulic control fluid used for direct control of DOC 28 is fuel. In other instances a different fluid, such as engine oil, could be used for direct control of a nozzle outlet check. Plunger 56 may be equipped with a tappet contacted by cam lobe 18. In other instances, a rocker arm actuation assembly could be interposed plunger 56 and camshaft 16.
Fuel system 20 also includes a fuel control system 70. Fuel control system 70 includes an electronic control module or ECM 72 having thereon an electronic control unit or ECU 74. ECU 74 can be, or can include, a programmable logic controller such as a microprocessor or microcontroller and suitable computer readable memory storing program control instructions which, when executed by a processor, cause fuel injector 22 to operate according to the present disclosure. Any suitable computer readable memory such as RAM, ROM, EPROM, DRAM, SDRAM, FLASH, or still another could be used. Fuel control system 70 also includes a lower voltage power supply such as a battery 78, and a boosted, higher voltage power supply 80. Battery 78 is shown as part of ECM 72 but could be a separate apparatus in other embodiments. Higher voltage power supply or HVPS 80 is shown physically separated from ECM 72 but could also be a part of ECM 72 in some embodiments. Fuel control system 70 also includes an engine speed sensor 82 and a fuel temperature sensor 84. As will be further apparent from the following description, fuel control system 70 is uniquely configured to operate fuel injector 22, and other such fuel injectors as might be included in fuel system 20, in a multi-shot fuel injection mode under different or broader engine operating conditions than is the case with certain other known control system arrangements. Moreover, as also further discussed herein, fuel control system 70 is capable of operating fuel injector 22, and other such fuel injectors as might be included in fuel system 20, in a relatively reduced energy or reduced power consumption mode.
In certain instances, a higher voltage power supply of or controlled by an ECM has a maximum power output that cannot be exceeded. As engine speed of an engine increases it is commonly necessary to increase an amount of fuel injected in a given engine cycle and potentially increase an amount of fuel injected per unit time. While an engine can be operated with various combinations and/or patterns of shot number, timing, and shot amount over part of an operating range, such as at lower engine speeds, it can desirable but challenging to utilize multi-shot injections or other variations in other parts of an engine operating range, such as at higher engine speeds. Put differently, at higher engine speeds it can be desirable to use multiple shots of fuel to deliver a desired fueling amount, but the capability to deliver multiple shots of fuel can be limited based on the power supply capabilities of the ECM. A pressure rise rate of fuel will typically also need to be relatively higher if all fuel needs to go in to a combustion cylinder in a single shot. A lack of multi-shot injection capabilities can have a detrimental effect respecting increased noise, vibration, harshness, smoke opacity, cold mode or cold start conditions, transient operating conditions of the engine, or other operating characteristics or states. The present disclosure provides solutions to these and other challenges.
To this end, fueling control unit or ECU 74 may include an energizing waveform controller 76. Energizing waveform controller 76 can include any combination of software, firmware, or hardware including circuitry, of electronic control unit 74, and is structured to energize a solenoid actuator of a fuel injector according to multiple different waveforms. In particular, energizing waveform controller 76 is structured to energize a solenoid actuator, such as one or both of solenoid actuators 50 and 42, via standard waveforms to actuate a valve such as injection control valve 34 or spill valve 46, in fuel injector 22. Energizing waveform controller 86 may be further structured to energize one or both of the subject solenoid actuators via a reduced energy waveform to actuate the subject valves.
Energizing waveform controller 76 is also structured to switch from a higher voltage power supply such as HVPS 80 to a lower voltage power supply such as battery 78, during the energizing of the subject solenoid actuator. In some embodiments, energizing waveform controller 76 energizes solenoid actuator 50 via a standard waveform to actuate spill valve 46 one or more times in a first engine cycle, and energizes solenoid actuator 50 via a reduced energy waveform to actuate spill valve 46 one or more times in a second engine cycle. Within a given engine cycle energizing waveform controller 76 may energize solenoid actuator 50 multiple times, potentially using a standard waveform for one or more of the energizations and a reduced energy waveform for one or more of the energizations. Part of the reduced energy waveform can be produced by power from HVPS 80 and part produced by power from battery 78, as further discussed herein.
Referring also now to
Decision block 110 performs a decision to use or not use a reduced energy waveform as noted above. In some instances, energizing waveform controller 76 is understood to determine suitability of engine system 10 for reduced energy operating of fuel system 22. This means that, at times, engine system 10 may not be suited or appropriate for multi-shot injection or another scenario where a reduced energy waveform might be used. In other instances, engine system 10 can be suited or appropriate for using the reduced energy waveform. For example, a fuel temperature that is relatively low could be associated with a higher fuel viscosity that makes injecting sufficient fuel in several smaller shots versus one larger shot impracticable. Engine speed could also exceed a speed at which there is sufficient time to inject several smaller shots versus one larger shot. Various other combinations of parameters listed, or still other parameters, might justify selection of a standard energy waveform, a reduced energy waveform, or combinations thereof. In any instance, solenoid actuators in fuel injector 22 may be operated with a reduced energy waveform to inject at least one shot of fuel where suitability of engine system 10 for reduced energy operating of fuel system 20 is determined.
Referring also now to
In the illustrated example, each of the standard waveform and the reduced energy waveform are defined by a pull-in current having a greater amplitude, a keep-in current of a medium amplitude, and a hold-in current having a lesser amplitude. The pull-in current of the reduced energy waveform is produced using a higher voltage power supply, however, in contrast to the standard waveform the keep-in current of the reduced energy waveform is produced using the lower voltage power supply. The pull-in current of the standard waveform has a relatively longer duration and the pull-in current of the reduced energy waveform has a relatively shorter duration. This strategy enables energy savings employing the reduced energy waveform. Also shown in
Referring now to
It should be appreciated, however, that various modifications and extensions to the scenario depicted in
Referring to the drawings generally, but focusing now on
From the foregoing description it will be appreciated that a valve in a fuel injector may be actuated a plurality of times in an engine cycle, and a plurality of shots of fuel injected into a combustion cylinder in the engine based on the plurality of actuations of the valve. The solenoid actuator for the valve can be energized using a reduced energy waveform to cause at least one of the plurality of actuations of the valve. By using the reduced energy waveform the power output capabilities of an ECM are not exceeded or otherwise limited. As noted above it can be challenging or impossible to employ multiple shot operation above a certain engine speed in certain known systems. Accordingly, by using a reduced energy waveform as described herein the engine speed range in which multi-shot fuel injection can be used can be extended.
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 fall 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.
