Patent Application
20210140386
The present disclosure relates generally to systems for internal combustion engines, and more particularly, to methods and systems for valve movement detection in a fuel injector of an internal combustion engine.
Many internal combustion engines include electronic control units that monitor and operate aspects of the operation of the engine, including the timing and quantity of fuel injection. Engine control units perform these operations with the use of a series of maps, or other programming, stored in memory of the control unit. In conjunction with these maps or programs, control units receive and calculate various items of feedback representative of the operation of the engine. Some engines employ fuel injectors that each have multiple electronically-controlled valves. These valves transition between closed and open positions by selectively energizing actuators, such as solenoids, within each injector. These fuel injector solenoids may be connected to a power supply controlled by the control unit. Some control units may be programmed to detect movement of the valves. For example, when solenoids are deactivated, the control unit may detect movement of a valve member based on free-wheeling current generated in the solenoid (e.g., current induced by movement of a valve member returning to a resting position). The solenoids may be positioned in close proximity to each other to satisfy size constraints of the injector. However, drive currents of such closely-positioned solenoids in a fuel injector may introduce noise or cross-talk. This cross-talk may impair the ability of the control unit to accurately detect aspects of the fuel injector, such as movement of one or more valves.
A method of detecting a valve opening or closing event is disclosed in International Publication No. WO 2018/185314 A1 (the '314 publication) to Sykes. The method described in the '314 publication involves applying a voltage to a solenoid and sampling the current through the solenoid to determine the start of injection. The method of the '314 publication involves applying a continuously-chopped current so that a system for injecting reductant can be used in conjunction with a high voltage power supply. While the method of the '314 publication may be useful in some circumstances, it may not be useful in systems in which two or more solenoids are disposed in close proximity to each other and subject to cross-talk.
The disclosed method and system may solve one or more of the problems set forth above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.
In one aspect, a fuel injection method may include applying a first method current to close a spill valve according to a first method, applying a control valve current to open a control valve, and discontinuing the application of the control valve current to thereby cause the control valve to close. The method may also include applying a second method current to maintain the spill valve closed according to a second method, and detecting a timing of a closing of the control valve while applying the second method current according to the second method, the second method being different than the first method.
In another aspect, a fuel injection method for a mechanically-actuated electronically-controlled fuel injector having a spill valve and a control valve may include applying a chopped spill valve current to close the spill valve according to a first method, applying a control valve current to cause a control valve member of the control valve to move from a first position to a second position, and stopping the application of the control valve current to cause the control valve member to return to the first position from the second position. The method may also include switching the chopped spill valve current to a non-chopped spill valve current to maintain the spill valve closed, according to a second method, and detecting a timing of the return of the control valve member to the first position while applying the non-chopped spill valve current.
In yet another aspect, a fuel injection control system may include at least one power source, a fuel injector including a spill valve including a spill valve solenoid and a control valve including a control valve solenoid, and a controller. The controller may be configured to apply a first method current to the spill valve solenoid according to a first method, apply a control valve current to open a control valve, and discontinue the application of the control valve current to the control valve solenoid to cause the control valve to close. The controller may also be configured to apply a second method current to hold the spill valve closed according to a second method, and detect a timing of a closing of the control valve while applying the second method current, wherein the second method has a lower cross-talk potential than the first method.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and together with the description, serve to explain the principles of the disclosed embodiments.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “having,” including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. Moreover, in this disclosure, relative terms, such as, for example, “about,” “substantially,” “generally,” and “approximately” are used to indicate a possible variation of ±10% in the stated value.
Spill valve 20 may be a normally-open, two-way, two-position valve. When spill valve 20 is open, a spill valve member 22 may be positioned to permit communication between high-pressure fuel channel 18 and low-pressure fuel channel 50. Spill valve member 22 may be biased toward an open position by a spring member, for example. A position of spill valve 20 may be controlled by energizing an actuator, such as spill valve solenoid 24, to generate a magnetic field that controls a motion of spill valve member 22. For example, spill valve 20 may be closed when spill valve solenoid 24 is energized by either battery 60 or HVPS 66.
DOC valve 30 may be a normally-closed, three-way, two-position valve. In a first position of DOC valve 30 illustrated in
Check valve 40 may be a one-way needle valve including a needle valve member 42 configured to block or allow communication between a check valve chamber 46 and injection orifices 48. A spring member 45 may bias needle valve member 42 toward the closed position illustrated in
ECM 80 may be configured to receive various sensed inputs and generate commands or control signals to control the operation of a plurality of fuel injectors 28. ECM 80 may embody a single microprocessor or multiple microprocessors that receive inputs and issue control signals, including commands for circuitry of battery 60 and commands 68 for controlling circuitry of HVPS 66. These commands may allow ECM 80 to selectively energize solenoids 24, 34 with electrical power from battery 60, HVPS 66, or both. ECM 80 may include a memory, a secondary storage device, a processor, such as a central processing unit or any other means for accomplishing a task consistent with the present disclosure. The memory or secondary storage device associated with ECM 80 may store data and software to allow ECM 80 to perform its functions, including the functions described below with respect to method 200 (
Fuel injection system 10 may be used in conjunction with any appropriate machine or vehicle that includes an internal combustion engine. In particular, fuel injection system 10 may be used in any internal combustion engine in which two or more solenoids, such as a spill valve solenoid and a control valve solenoid of a fuel injector, could be subject to cross-talk (e.g., due to being placed in proximity to each other). Moreover, fuel injection system 10 may be used in any internal combustion engine in which it may be desirable to determine a timing at which a valve changes state (e.g., to a closed position) based on free-wheeling current generated by a solenoid for a control valve.
During an operation of an internal combustion engine, fuel injection system 10 may direct fuel, such as diesel fuel, into a combustion chamber of the engine. Each fuel injector 28 may inject fuel during one or more injection events of a cycle of engine 10. For example, fuel injection system 10 may be configured to inject fuel once, twice, or three times during a single cycle of the engine. A largest amount of fuel, as measured in fuel mass, may be injected during a main injection. One or more smaller injection events may occur before or after the main injection. An injection that occurs before the main injection may form a pilot injection, while an injection that occurs after the main injection may form a post injection. A pilot injection that occurs shortly before the main injection may be referred to as a close-coupled pilot injection, while a post injection that occurs shortly after the main injection may be referred to as a close-coupled post injection. Fuel injection system 10 may, while the internal combustion engine is operating, continuously monitor the operation of fuel injector 28 and adjust the timing of the pilot, main, and/or post injections based on feedback or sensed information and operator commands.
With reference to the spill current waveform 130 illustrated in
With continued reference to the spill valve current waveform of
As shown in the second waveform 132 of
In order to ensure detection of free-wheeling current 140, ECM 80 may be configured to adjust first timing 152 and second timing 154 during which the second program of the control strategy is performed. In one aspect, first timing 152 may be approximately the same timing as the beginning of window 144. However, the exact timing 152 may be earlier than window 144, if desired. ECM 80 may adjust timings 152, 154, and the amount of time between timings 152, 154. For example, when timing 152 is later than the beginning of the rise of free-wheeling current 140, a beginning of free-wheeling current 140 may be truncated (not detected). Thus, ECM 80 may adjust first timing 152 to an earlier timing in a subsequent injection. If timing 154 occurs prior to the end of free-wheeling current 140, timing 154 may be advanced in a subsequent injection. Moreover, if ECM 80 determined that the amount of time between timings 152, 154 is too short (free-wheeling current is truncated) or too long, timings 152, 154 may be performed closer together or farther apart, respectively. Thus, timings 152, 154 may be dynamic, and may be based on one or more previous detections of free-wheeling current 140 to minimize delays between timings 152, 154 and window 144.
As can be seen in
In injection patterns where pilot, main, and post injections are all applied in a single combustion cycle, ECM 80 may be configured to apply the second program between the pilot and main injections for a first combustion cycle, and between the main and post injections for a second combustion cycle. Thus, the timing of the second program may change, or alternate, between different injection cycles. Alternatively, the second program may be applied twice during a single combustion cycle, once between the pilot and main injections, and again between main and post injections, if desired. A similar process may be employed when injection events vary over time. For example, a first injection event may include close-coupled pilot and main injections, while a second injection event may include main and close-coupled post injections. ECM 80 may detect valve closure timing 160 between each of these events in each injection cycle.
ECM 80 may be configured to adjust the timings of pilot, main, and/or post injections based on the detected valve closure timing 160. For example, ECM 80 may be configured to adjust a dwell time or a duration of time between a pilot injection and a main injection, or between the main injection and the post injection. Additionally or alternatively, ECM 80 may adjust a duration of an injection for one or more of the pilot injection, main injection or post injection. In particular, the duration and/or dwell may be adjusted based on a difference between the detected valve closure timing 160 and an expected valve closure timing. Thus, adaptive trim may be performed continuously (or intermittently at predetermined intervals) to monitor and adjust the precise timings and injection strategy for operating injectors 28.
While the second program may include the application of battery 60, the use of battery 60 during the second program may be avoided by instead increasing a level of chopped current 100 above that of the initial level 102 at a timing immediately prior to first timing 152. Then, at timing 152, the second program may de-energize solenoid 24. In this exemplary alternative second method, due to the increased amount of current applied immediately prior to first timing 152, the current may decay relatively slowly, maintaining spill valve member 22 in the closed position until second timing 154 at which chopped current 100 may again be applied (as minimum current 106). Regardless of the action taken to execute the second method, chopped current is not applied for at least a portion of the period of time extending from first timing 152 to second timing 154. Additionally, while intermediate 104 and minimum 106 current levels are illustrated are shown as being separate, the application of minimum current level 106 may occur earlier (e.g., at least partially prior to first timing 152).
In some fuel injectors, the proximity between two or more solenoids may interfere with or prevent current sensing when chopped current is employed. For example, detection of a return timing of a control valve member may be challenging when a close-coupled pilot or a close-coupled post injection is performed, particularly when free-wheel measurements are employed. For example, noise may be introduced by the current chopping. This noise may cause false detection signals. By transitioning to a second program, which may include switching from a chopped current to a non-chopped current, it may be possible to detect a timing of an opening or closing of a valve with increased accuracy. This information may allow for precise control over valve trim, allowing ECM 80 to modify injection timings with increased precision. In one aspect, accurate valve return information may allow for improved injection size and dwell control. This improved control may improve engine performance, reduce emissions of pollutants, reduce noise, and improve the durability of the engine.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed method and system without departing from the scope of the disclosure. Other embodiments of the method and system will be apparent to those skilled in the art from consideration of the specification and practice of the apparatus and system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
