Method and system for fuel injector control - Patents.com

Abstract

To provide methods and systems for detection of a closing time of a solenoid valve.SOLUTION: A method may include monitoring a current of the solenoid valve, filtering the current, and determining the closing time of the solenoid valve based on each of the current and the filtered current. In some examples, the solenoid valve may be an electrically actuated fuel injection valve. In some examples, determining the closing time may include using the filtered current to determine an inflection point of the current.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the subject matter disclosed herein relate to methods and systems for fuel injector control. [Background technology]

[0002] Vehicles, such as rail cars, include power sources, such as diesel internal combustion engines. The vehicles may include one or more injection pumps in fluid communication with one or more fuel injectors mounted to one or more engine cylinders. A given injection pump may pressurize fuel for delivery to at least one of the one or more fuel injectors. The fuel may then travel through a respective fuel injector to the at least one fuel injector and then to at least one corresponding engine cylinder of the power source, where the fuel is combusted to provide power to the vehicle.

[0003] In some examples, each of the one or more fuel injectors may be included in a respective unit pump fuel injector assembly, and each of the one or more engine cylinders may be configured with a respective one of the one or more injector pumps. This allows fuel injection for each of the one or more engine cylinders to be individually controlled by precisely adjusting the fuel injection timing, fuel injection advance angle, and amount of fuel to be injected. To achieve such precise adjustments, electrically-actuated solenoid valve fuel injectors may be used that may receive an electrical current in response to a command to open or close a solenoid valve. Note that the fuel injection timing, fuel injection advance angle, and amount of fuel to be injected may be appropriately adjusted by adjusting the opening and closing times of the solenoid valve. Once it is determined that the solenoid valve is closed, fuel injection may commence.

[0004] Therefore, by increasing the accuracy of the detection of the closing time of the solenoid valve, the efficiency of the power source can be increased. Therefore, various algorithms exist for converting the signature of the measured electric current of the solenoid valve to determine the closing time. As an example, the second derivative of the measured current may be determined. When the second derivative of the current increases beyond a threshold, the solenoid valve is determined to be closed and fuel injection may be initiated. However, the second derivative of the current may be particularly sensitive to low signal-to-noise ratios. As a result, spurious spikes of the second derivative may reach a threshold prior to the closing of the solenoid valve, resulting in reduced control of the fuel injection timing, fuel injection advance, and fuel injection amount, respectively. Therefore, it is desirable to implement a detection algorithm with higher accuracy and / or lower sensitivity to artifacts. Summary of the Invention

[0005] In one embodiment, the method may include monitoring a current of an electrically actuated solenoid valve, filtering the current, and determining a closing time of the electrically actuated solenoid valve based on each of the current and the filtered current. [Brief description of the drawings]

[0006] [Figure 1] 1 shows a schematic diagram of a vehicle equipped with one or more electrically actuated solenoid valve fuel injectors according to one embodiment of the present disclosure. [Diagram 2] 1 illustrates a flowchart of a method for detecting the closing time of one or more electrically actuated solenoid valve fuel injectors according to one embodiment of the disclosure. [Figure 3A] 1 shows plots of measured current and its second derivative for an exemplary solenoid valve illustrating the detection of abnormal closing times provided by several detection algorithms. [Figure 3B] 1 shows plots of measured current and its second derivative for an exemplary solenoid valve illustrating the detection of abnormal closing times provided by several detection algorithms. [Figure 4A] 1 illustrates a plot of measured current and filtered current of an exemplary solenoid valve, where the filtered current may be utilized to determine a closing time of the exemplary solenoid valve, in accordance with one embodiment of the present disclosure. [Figure 4B] 1 illustrates a plot of measured current and filtered current of an exemplary solenoid valve, where the filtered current may be utilized to determine a closing time of the exemplary solenoid valve, in accordance with one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Embodiments of the present invention are disclosed in the following description and relate to a system and method for detecting the closing time or closing point of a solenoid valve, which may be included in an electrically actuated solenoid valve fuel injector located in a vehicle system. Accurately detecting the closing time of the solenoid valve is desirable to increase the efficiency of the engine of the vehicle system. Thus, a method is provided for determining the closing time of the solenoid valve by determining an inflection point of the measured current with a filtered version of the measured current. The inflection point can be interpreted as a change in the inductance of the solenoid valve indicative of closure.

[0008] Method embodiments provided herein may be utilized prior to each fuel injection to provide a real-time update of the accuracy of the closing time. Thus, in some embodiments, the closing time may be further monitored for anomalies indicative of solenoid valve degradation. A technical effect of such embodiments is that the efficiency of fuel injection may be improved by accurately characterizing the closing time of the solenoid valve, thereby reducing undesirable fuel injection advance / retardation and problems resulting from solenoid valve degradation. Thus, vehicle operator frustration may be reduced, maintenance costs may be minimized, and consistent vehicle operation may be maintained as fewer components are replaced over time while maintaining emission standards and expected refueling.

[0009] FIG. 1 illustrates an embodiment of a system in which one or more electrically actuated fuel injectors may be installed. Specifically, FIG. 1 illustrates a block diagram of one embodiment of a vehicle system 100. In the illustrated example, an engine is coupled to a vehicle, shown as a rail car 106 (e.g., a locomotive). The vehicle may run on rails 102 via a number of wheels 112. As illustrated, the vehicle may include an engine 104. The engine may include a number of cylinders 101 (only representative cylinders shown in FIG. 1), each cylinder including at least one intake valve 103, exhaust valve 105, and fuel injector 107. Each intake valve 103, exhaust valve 105, and fuel injector 107 may include an actuator that may be actuated by a signal from an engine controller 110. In other non-limiting embodiments, the engine may be in a stationary platform. Suitable stationary platforms may include power-plant applications. Other suitable vehicles include marine, mining or industrial equipment, on-road vehicles, and off-highway vehicle propulsion systems.

[0010] In one embodiment, each fuel injector 107 may be an electrically actuated fuel injector fluidly coupled to a respective valve 109, such as a proportional solenoid valve or a proportional spool valve, the opening and closing of which may be regulated by a controller. Thus, the controller may command the valve to be fully closed, fully open, or to a position between fully closed and fully open in order to control the fuel flow to the fuel injector at a desired fuel flow rate (as dictated by the controller).

[0011] As shown, the valve 109 may further be fluidly coupled to a fuel pump 111 such that liquid fuel may be delivered by the fuel pump to the fuel injectors as regulated by the valve via the controller. Thus, with respect to the fuel flow, the fuel pump may be disposed upstream of the valve, which may be disposed upstream of the fuel injectors. In this manner, the fuel injectors, the valve, and the fuel pump may be included in a unit pump fuel injector assembly 113, which is one of one or more unit pump fuel injector assemblies each coupled to one of the plurality of cylinders. Thus, fuel injection into each of the one or more engine cylinders may be individually controlled by the controller. For example, the controller may control one or more engine actuators to adjust fuel injection timing, fuel injection advance, and / or the amount of fuel injected into a given cylinder based on monitoring of a corresponding unit pump fuel injector assembly.

[0012] Although proportional solenoid valves and proportional spool valves are exemplary embodiments of at least one valve, any suitable control element can be used. For example, the position or state of the valve can be controlled electrically by controlling the current through the valve. As another example, the position or state of the valve can be controlled mechanically, hydraulically, hydromechanically, electrically, electromechanically, magnetically, or electromagnetically by controlling a servo motor that regulates the valve.

[0013] The engine may receive intake air for combustion from an intake passage 114. The intake passage 114 may include an air filter 160 that filters air from outside the vehicle. Exhaust gases resulting from combustion within the engine may be provided to an exhaust passage 116. The exhaust gases may pass through the exhaust passage and exit an exhaust stack of the rail vehicle. The exhaust passage may include an exhaust gas sensor 162 that may monitor exhaust gas temperature and / or air-fuel ratio and may couple to a controller to provide monitoring data.

[0014] In one example, the engine may be a diesel engine that combusts air and diesel fuel via compression ignition. In another example, the engine may be a dual or multi-fuel engine that may combust a mixture of gaseous fuel and air when diesel fuel is injected during compression of the air-fuel mixture. In other non-limiting embodiments, the engine may further combust fuels including gasoline, kerosene, natural gas, biodiesel, or other petroleum distillates of similar density via compression ignition (and / or spark ignition).

[0015] A suitable rail vehicle may be a diesel electric locomotive. Suitable diesel electric locomotives may include mainline vehicles, heavy haul freight vehicles, passenger rail vehicles, shunters, switchers, and the like. Diesel electric locomotives may include other power sources, such as hybrid electric (battery) engines, fuel cell engines, hydrogen engines, and the like. Although diesel is used as an example fuel, other fuels may be used. Suitable other fuels may include gasoline, kerosene, ethanol, biodiesel, natural gas, and combinations thereof. As shown in FIG. 1 , the engine may be coupled to a power generation system, which includes an alternator / generator 122 and a number of electric traction motors 124. For example, the engine may be a diesel and / or natural gas engine that generates a torque output that may be transmitted to the alternator / generator, which is mechanically coupled to the engine. In one embodiment herein, the engine 104 may be a multi-fuel engine that runs on diesel fuel and natural gas.

[0016] The electrical power generated by the alternator / generator may be stored and applied for subsequent propagation to various downstream electrical components. As an example, the alternator / generator may be electrically coupled to a plurality of electric traction motors, and the alternator / generator may provide electrical power to the plurality of electric traction motors. As shown, each of the plurality of electric traction motors may be coupled to one of a plurality of wheels to provide traction power for propelling the railcar. An example configuration may include one electric traction motor per wheel set (e.g., a subset of the plurality of wheels). As shown here, six electric traction motors may correspond to each of six pairs of motive wheels of the railcar. In another example, the alternator / generator may be coupled to one or more resistive grids 126. The resistive grids may dissipate excess engine torque via heat generated by the grid from the electricity generated by the alternator / generator. Additionally or alternatively, the resistive grids may be used in a dynamic braking mode to dissipate electricity generated by the traction motors.

[0017] In some embodiments, the vehicle system may include a turbocharger 120 disposed between the intake passage 114 and the exhaust passage 116. The turbocharger may increase the air charge of the ambient air drawn into the intake passage to provide a greater charge density during combustion, increasing power output and / or engine operating efficiency. The turbocharger may include at least one compressor (not shown) that may be driven at least in part by at least one corresponding turbine (not shown). In some embodiments, the vehicle system may include an aftertreatment system coupled to the exhaust passage upstream and / or downstream of the turbocharger. In one embodiment, the aftertreatment system may include a diesel oxidation catalyst (DOC) and / or a diesel particulate filter (DPF). In other embodiments, the aftertreatment system may additionally or alternatively include one or more emission control devices. Such emission control devices may include a selective catalytic reduction (SCR) catalyst, a three-way catalyst, a NOx trap, or various other devices or exhaust aftertreatment systems.

[0018] As shown in FIG. 1, the vehicle system may include a thermal management system 150 (e.g., an engine cooling system). The cooling system may circulate a coolant (e.g., water, glycol, etc.) through the engine to absorb engine waste heat and distribute the heated coolant to a heat exchanger such as a radiator 152 (e.g., a radiator heat exchanger). A suitable coolant may be water. A fan 154 may be coupled to the radiator to maintain airflow through the radiator when the vehicle is moving slowly or when the engine is stopped while running. In some examples, the speed of the fan may be controlled by a controller. The coolant cooled in the radiator may go into a tank (not shown). The coolant may then be returned to the engine or another component of the vehicle system by a water or coolant pump 156.

[0019] The controller may control various components associated with the vehicle. As an example, various components of the vehicle system may be coupled to the controller via a communication channel or data bus. In an example, the controller may include a computer control system. The controller may additionally or alternatively include a memory that holds a non-transitory computer readable storage medium (not shown) that includes code that enables on-board monitoring and control of the operation of the rail vehicle. In some examples, the controller may include multiple controllers in communication with each other, such as a first controller for controlling the engine and a second controller for controlling other operating parameters of the rail vehicle (traction motor load, blower speed, etc.). The first controller may control various actuators based on output received from the second controller and / or the second controller may control various actuators based on output received from the first controller.

[0020] The controller may receive information from a number of sensors and may send control signals to a number of actuators. The controller may receive signals from various engine sensors, described in further detail herein, to determine operating parameters and conditions while monitoring the control and management of the engine and / or railcar, and adjust various engine actuators accordingly to control the operation of the engine and / or railcar. For example, the controller may receive signals from various engine sensors, including, but not limited to, engine speed, engine load, intake manifold air pressure, boost pressure, exhaust pressure, ambient pressure, ambient temperature, exhaust gas temperature, exhaust gas air-fuel ratio, particulate filter temperature, particulate filter back pressure, engine coolant pressure, and the like. In some embodiments, the various engine sensors may include a current sensor 115 coupled to each fuel injector 109 to measure a current therethrough, which may be communicatively coupled to the controller and configured to transmit such current measurements to the controller. Additional sensors, such as a coolant temperature sensor, may be located within the cooling system. Correspondingly, the controller may control the engine and / or railcar by sending commands to various components, such as multiple electric traction motors, alternators / generators, fuel injectors, valves (e.g., valve 109), coolant pumps, etc. For example, the controller may control the operation of restrictive elements (e.g., valves) in the engine cooling system. Other actuators controllable by the controller may be coupled to various locations within the railcar.

[0021] In one example, a method is provided for determining a closing time of a fuel injector based on each of a measured current and a filtered current, as described in detail with reference to FIG. 2. In some examples, the closing time may be based on an inflection point of the measured current. An example of determining the inflection point is illustrated by the plots of FIG. 4A and FIG. 4B. In another example, the closing time may be based on a second derivative of the measured current, which may have a lower signal-to-noise ratio than the filtered current, as described below with reference to FIG. 3A and FIG. 3B.

[0022] Referring now to FIG. 2, a flow chart illustrating a method 200 for detecting a closing point of a fuel injector is shown. In some examples, the fuel injector may be an electrically actuated solenoid valve in a unit pump fuel injector assembly. As an example, the fuel injector may be valve 109 of FIG. 1. The fuel injector current may be measured and filtered (e.g., using a low pass filter) or otherwise mathematically attenuated. The measured current and the filtered current may be monitored to determine an inflection point in the measured current, which may indicate an inductance change corresponding to the closing point (e.g., a point at which the operation of the fuel injector substantially ceases). The closing point may then be used to ensure that the desired fuel injection timing, fuel injection advance, and fuel injection amount are achieved as expected.

[0023] Specifically, because the difference between the closing of the fuel injector and the start of fuel injection (e.g., the needle lift of the fuel injector) can be small and difficult to predict, the closing point of the fuel injector may be effectively substituted by the controller as the closest point to the start of fuel injection (as the closing point of the fuel injector may correspond to the point at which the fuel injector is most exposed to the upstream fuel pressure or fuel flow delivered by the fuel pump). A number of additional factors may determine the actual fuel delivery to the cylinder, including camshaft pressure, overall fuel pump pressure, fuel pressure at the inlet of the fuel pump, injection timing, the volume of fuel in the injection line of the unit pump fuel injector assembly (which in some instances corresponds to the fuel injection amount), the physical structure of the fuel injector, and combinations thereof. For example, depending on the engine application and mode of operation, the start of fuel injection may begin prior to the closing of the fuel injector (e.g., some fuel may enter the cylinder while the fuel injector is open), or fueling may be delayed until the fuel injector is determined to be closed.

[0024] In an additional or alternative example, the closing point may be updated periodically during engine operation to monitor and diagnose fuel injector degradation. In one example, the expected closing point may be determined by simulation and / or test (experimental) data (e.g., stored in a map or look-up table), whereby the detected closing point may be compared to the expected closing point to diagnose fuel injector degradation.

[0025] The instructions for performing the method 200 may be executed by a controller, such as the controller 110 of FIG. 1, based on instructions stored in a memory of the controller and in conjunction with signals received from a sensor of the engine system, such as a current sensor coupled to a fuel injector. Additionally, the controller may use engine actuators of the engine system to adjust engine operation in accordance with the method 200 described below. The instructions for performing the method 200 and the commands to the engine actuators generated therefrom may be executed automatically by the controller and the engine system (after an operator command, at pre-set intervals, and / or under pre-set conditions). Additionally, although the method 200 is described below with reference to one fuel injector, the method 200 may be applied sequentially or in parallel to multiple similarly configured fuel injectors in a vehicle system. Thus, an exemplary embodiment of the method 200 may enable detection and monitoring of the closing point of one or more electrically actuated solenoid valves in a unit pump fuel injector assembly.

[0026] In step 205, method 200 may include detecting and / or estimating and / or measuring one or more engine operating conditions. By way of example, the one or more engine operating conditions may include engine speed, engine load, engine temperature, ambient conditions (e.g., ambient temperature, pressure, humidity, etc.), current operator torque demand, manifold pressure, manifold airflow, fuel temperature, exhaust gas air-fuel ratio, etc. The one or more engine operating conditions may be measured by one or more sensors communicatively coupled to the controller (e.g., exhaust gas air-fuel ratio may be measured directly via exhaust gas sensor 162) or may be inferred based on available data (e.g., engine temperature may be estimated from engine coolant temperature measured by an engine coolant temperature sensor).

[0027] The controller may use one or more engine operating conditions to infer a current state of engine operation and determine whether the current state of engine operation is suitable for performing closing point detection. Specifically, in step 210, the method 200 may include determining whether one or more closing point detection conditions are satisfied. For example, the one or more closing point detection conditions may include the start of a fuel delivery request received at the controller, a threshold time period elapsed since the last closing point determination, an engine temperature within a predetermined temperature range, etc. In one example, closing point detection may be initiated every time a given fuel injector (in a given unit pump fuel injector assembly associated with a given cylinder) is commanded to inject fuel. In another example, closing point detection may be initiated when the engine temperature is greater than a first threshold temperature and / or less than a second threshold temperature, and the first threshold temperature is less than the second threshold temperature. If the one or more closing point detection conditions are not satisfied, the method 200 may proceed to 215, where the method 200 may include maintaining the current engine operation. In such an instance, closure point detection may not be initiated.

[0028] If one or more closure point detection conditions are met, the method 200 may proceed to 220, where the method 200 may include performing closure point detection. Specifically, the controller may command the fuel injector to open by applying an actuation voltage. Concurrently, or during a predetermined window following the opening of the fuel injector, the controller may periodically or substantially continuously receive sampled data from a current sensor coupled to the fuel injector. Thus, in some examples, the sampled data may be a measured current of the fuel injector.

[0029] In some examples, the predetermined time period may be based on a maximum number of samples or a sampling threshold. Thus, the predetermined time period may be equal to or less than a sampling duration determined as a product of the sampling threshold and the sampling rate. The sampling period may be determined based on the length of time the fuel injector is expected to be open. For example, the sampling period may be staggered after the commanded opening of the fuel injector so that the closing time may be obtained within the sampling period (e.g., the sampling period may be selected to ensure that there is sufficient time for the fuel injector to open, remain open to deliver fuel to the fuel injector, and close). In some examples, the length of time the fuel injector is expected to be open may be determined based on at least the fuel pressure at the inlet of the fuel injector (which may further be a function of the low-side fuel system pressure and pump speed, respectively), and the fuel injection amount (which may further be a function of the torque / power demand).

[0030] As described above, once an inflection point in the measured current is identified, a closure point may be determined. In some examples, an inflection point may be identified when the measured current and the filtered current are within a threshold of each other. In one example, an inflection point may be identified when the measured current and the filtered current are substantially equal. Thus, closure point detection may be based on an iterative algorithm that iterates up to n sampling steps until convergence is reached.

[0031] Thus, closure point detection may begin with the initialization of one or more variables. Specifically, at 225, method 200 may include initializing n (e.g., to 0 or 1), i.e., indexing the first iteration. At 230, method 200 may include initializing buff(n) based on the sampled data. In some examples, buff(n) may be a first buffer stored in the controller's memory, where buff(n) may hold the measured current for the current iteration. At 235, method 200 may include initializing temp(n)=buff(n). In some examples, temp(n) may be a second buffer stored in the controller's memory, where, for iterations beyond the first iteration, temp(n) may hold the filtered current for the current iteration (see 250 below).

[0032] Once the one or more variables are initialized, an iterative algorithm may be started and the one or more variables may be iteratively updated until convergence is reached. At 240, the method 200 may include incrementing n by 1. At step 245, the method 200 may include updating buff(n) based on the sampling data. For example, buff(n) may be updated with the measured current of the current iteration. At 250, the method 200 may include updating temp(n) based on temp(n-1) and buff(n) (for example, the second buffer in the current iteration may be updated based on the second buffer in the most recent iteration before the current iteration and the first buffer in the current iteration). In some examples, a low pass filter may be applied to buff(n) to update temp(n). In such examples, temp(n) may be determined as follows: temp(n)=FF*temp(n-1)+(1-FF)*buff(n) (1) Here, FF is a calibratable filter coefficient that can be tuned for a given engine application (where "application" is used to mean how much power the engine is putting out under what conditions), the configuration of the valve assembly (where "configuration" is used to mean how the components of the valve assembly are assembled together and interact mechanically, electrically, fluidly, etc.), the configuration of the engine (where "configuration" is used to mean how the components of the engine are assembled together and interact mechanically, electrically, fluidly, etc.), etc. In one example, FF=0.5. In some examples, a delay inherent in the low pass filter may be utilized to account for the difference between the closing of the fuel injector and the start of fuel injection.

[0033] In some examples, the mathematical form and / or parameters (e.g., calibratable filter coefficients) of the low pass filter may be adjusted based on simulation and / or test (experimental) data. For example, the simulation and / or test data may be obtained based on each of idle and rated power (e.g., high power) conditions, from which other operating modes are extrapolated / approximated. The simulation and / or test data may additionally or alternatively be selected such that the low pass filter may account for outliers as well as common operating modes or situations of the fuel injector. In one example, the inductance / resistance (for both outliers and common operating modes or situations) may be used in addition to one or more of the spring constant, mass, and friction of the fuel injector to formulate the low pass filter and determine the electrical characteristics of the measured current signature.

[0034] In step 255, method 200 may include determining whether the absolute difference between buff(n) and temp(n) is less than a convergence threshold. The convergence threshold may be adjusted to any level of accuracy by an operator or manufacturer of the vehicle system. For example, the convergence threshold may be selected to balance any noise in the measured and filtered currents with the desired accuracy of the closure point. Although an absolute difference based convergence threshold is used in 255, in other examples additional or alternative convergence criteria (e.g., dynamically scalable coefficients, root mean square deviation, etc.) may be used.

[0035] If the absolute difference between buff(n) and temp(n) is greater than or equal to the convergence threshold, method 200 may proceed to 260, where method 200 may include determining whether n is greater than a sampling threshold. In some examples, the sampling threshold may correspond to a maximum number of samples obtained during a given window. The maximum number of samples may correspond to the sampling period divided by the sampling rate. In one example, the maximum number of samples may be 150. In an additional or alternative example, the sampling rate may be 100 kHz. If n is less than or equal to the sampling threshold, method 200 may return to 240 and continue the iterative algorithm by incrementing n by 1.

[0036] If n is greater than the sampling threshold, method 200 may proceed to 280, where method 200 may include terminating closure point detection, generating a first driver indication, storing a first diagnostic code, and / or modifying one or more engine operating conditions based on the first driver indication and / or the first diagnostic code. The first driver indication and / or the first diagnostic code may indicate to an operator, manufacturer, technician, etc. that a closure point was not detected during a predetermined time period and that the fuel injector may have deteriorated. In such an example, the closure point may not be updated.

[0037] In one example, the first driver instruction may include illuminating a malfunction indicator lamp (MIL), and the first diagnostic code may be set and stored in a memory of the controller. Illumination of the MIL may indicate a request that the vehicle system be serviced, and the first diagnostic code may indicate to a technician that the fuel injector is degraded. And, the MIL and the first diagnostic code may be reset after service of the vehicle system is completed (e.g., after replacing the fuel injector).

[0038] Returning to 255, if the absolute difference between buff(n) and temp(n) is less than the convergence threshold, an inductance change may be detected and the method 200 proceeds to 265, where the method 200 may include updating the closure point (e.g., stored in a memory of the controller) and modifying one or more engine operating conditions. As an example, the start of fuel injection may be advanced or delayed during a subsequent fuel injection event based on the updated closure point. As another example, the fuel injection advance may be increased or decreased during a subsequent fuel injection event based on the updated closure point. As yet another example, the fuel injection amount may be increased or decreased during a subsequent fuel injection event based on the updated closure point. Updating the closure point may further include incrementing an aging counter by one. Thus, in some examples, the aging counter may track the total number of fuel injection cycles of the fuel injector for determining or predicting degradation past its useful life.

[0039] In step 270, method 200 may include determining whether the fuel injector is degraded. In some examples, the closure point (as updated at 265) may be compared to an expected closure point (e.g., stored in a map or look-up table). For example, the fuel injector may be determined to be degraded if the difference between the (detected) closure point and the expected closure point is greater than a threshold difference. In additional or alternative examples, an aging counter (incremented at 265) may be compared to a threshold count. For example, the fuel injector may be determined to be degraded if the aging counter is greater than the threshold count. If the fuel injector is determined to be not degraded, method 200 may proceed to method 275, which may include terminating closure point detection and continuing engine operation (e.g., operating the engine without actively processing and filtering sampled data). In such examples, the fuel injector may be indicated as not degraded.

[0040] If the fuel injector is determined to be degraded, method 200 may proceed to 280, where method 200 may include terminating the closing point detection, generating a second driver instruction, storing a second diagnostic code, and / or modifying one or more engine operating conditions based on the second driver instruction and / or the second diagnostic code. The second driver instruction and / or the second diagnostic code may indicate to an operator, manufacturer, technician, etc. that the closing point detection indicates that the fuel injector may be degraded.

[0041] In one example, the second driver instruction may include illuminating the MIL, and a second diagnostic code may be set and stored in the memory of the controller. Illuminating the MIL may indicate a need for service of the vehicle system, and the second diagnostic code may indicate to a technician that the fuel injector is degraded. And, the MIL and second diagnostic code may be reset after service of the vehicle system is completed (e.g., after replacing the fuel injector).

[0042] Method 200 is not limited to fuel injectors and may be adapted for use with other solenoid valve implementations. Additionally, method 200 may be adapted to detect and monitor inductance changes in other electrically actuated components (e.g., other than solenoid valves).

[0043] 3A and 3B, plots of measured current and its second derivative versus time are shown for an exemplary solenoid valve included in a locomotive. FIG. 3A shows plots 300 and 325 illustrating the measured current and the second derivative of the measured current, respectively, for an exemplary solenoid valve at idle operation of the locomotive. FIG. 3B shows plots 350 and 375 illustrating the measured current and the second derivative of the measured current, respectively, for an exemplary solenoid valve at rated power operation of the locomotive (e.g., at notch N8). The measured current (mA) is represented on the vertical axis of each of plots 300 and 350, and the second derivative of the measured current (mA / s 2 ) is represented on the vertical axis of each of plots 325 and 375, and the number of samples is represented on the horizontal axis of each of plots 300, 325, 350, and 375. The samples may be collected at a predetermined sampling rate, such as 100 kHz. In plots 300 and 350, curves 301 and 351, respectively, show the measured current. In plots 325 and 375, curves 302 and 352, respectively, show the second derivative of the measured current. Additionally, in plots 325 and 375, curves 303 and 353, respectively, show a positive threshold that, if exceeded by the second derivative of the measured current, may indicate an exemplary solenoid valve closing point in some detection algorithms. The second derivative of the measured current may be determined during a predetermined window, as approximated by dashed boxes 304 and 354, respectively, in plots 325 and 375.

[0044] Plots 325 and 375 illustrate anomalous closure point detection provided by an exemplary detection algorithm. As shown, the second derivative of the measured current (curves 302 and 352) may have a relatively low signal-to-noise ratio, such that the second derivative of the measured current may anomalously and unexpectedly increase above the positive threshold (curves 303 and 353). In some examples, as shown in plots 325 and 375, respectively, the second derivative of the measured current may exceed the positive threshold multiple times during a given window (dashed boxes 304 and 354), resulting in premature detection of the closure point and obscuring the actual closure point.

[0045] 4A and 4B, plots of measured and filtered currents for an exemplary solenoid valve included in a locomotive are shown. FIG. 4A shows plot 400 illustrating measured and filtered currents for an exemplary solenoid valve at idle operation of the locomotive. Plot 425 further shown in FIG. 4A shows a close-up of insert 410 of plot 400. FIG. 4B shows plot 450 illustrating measured and filtered currents for an exemplary solenoid valve at rated power operation of the locomotive (e.g., at notch N8). Plot 475 further shown in FIG. 4B shows a close-up of insert 460 of plot 450. Measured current (mA) is represented on the vertical axis of each of plots 400, 425, 450, and 475, and sample number is represented on the horizontal axis of each of plots 400, 425, 450, and 475. The samples may be collected at a predetermined sampling rate, such as 100 kHz. In plots 400 and 450, curves 401 and 451 respectively indicate the measured current, curves 402 and 452 respectively indicate the filtered current, and curves 403 and 453 respectively indicate the inflection point of the measured current, which may indicate the closing point of the example solenoid valve in the detection algorithm provided by the embodiments described herein. Specifically, the inflection point of the measured current may be determined by the detection algorithm where the filtered current meets the measured current. The filtered current may be obtained by applying a low pass filter to the measured current, where the filter coefficient of the low pass filter is, for example, 0.5 (however, as described above with reference to FIG. 2, the filter coefficient may vary based on simulation and / or test data for a given engine application). The filtered current may be determined during a predetermined window, as approximated by dashed boxes 404 and 454 in plots 425 and 475, respectively.

[0046] As shown in Figures 4A and 4B, the detection algorithm can accurately and reproducibly detect the inflection point of the measured current without using a relatively low signal-to-noise ratio to which the second derivative of the measured current is susceptible. The inflection point may correspond to a local minimum that indicates an inductance change during closing of the exemplary solenoid valve. In addition, in order to more accurately detect the closing point, the fuel injection timing, the fuel injection advance angle, and the fuel injection amount may each be more accurately controlled.

[0047] A method may be provided for more accurately determining the closing time or closing point of a solenoid valve in an engine fuel injector. In some examples, during engine operation, the current of the solenoid valve may be measured and filtered (e.g., with a low pass filter), and the filtered current may have a relatively high signal-to-noise ratio. When the filtered current is substantially equal to the measured current, an inflection point of the measured current may be determined, the inflection point indicating an inductance change of the solenoid valve at closing. A technical effect of comparing the measured current to the filtered current to determine the inflection point, and thereby determining the closing time, is that the total number of false positives may be reduced compared to some closing time detection algorithms (e.g., closing time detection algorithms based on the second derivative of the measured current, etc.). Furthermore, by accurately monitoring the closing time over the life of the solenoid valve, degradation may be indicated in real time through abnormal closing time trends, and an operator may be notified and / or mitigating actions may be implemented.

[0048] In one example, the method includes monitoring a current of the electrically actuated solenoid valve, filtering the current, and determining a closing time of the electrically actuated solenoid valve based on each of the current and the filtered current. In one embodiment of the method, monitoring the current of the electrically actuated solenoid valve includes monitoring the current within a predetermined window following an opening of the electrically actuated solenoid valve. In one embodiment of the method, the electrically actuated solenoid valve is included in an engine. In one embodiment of the method, the method further includes updating a predetermined closing time based on the determined closing time, and adjusting one or more operating conditions of the engine based on the determined closing time. In one embodiment of the method, the current is filtered in response to one or more of a fuel request being initiated, an engine temperature being within a predetermined temperature range, and a threshold time period having elapsed since a last closing time determination. In one embodiment of the method, the method further includes generating an indication of degradation of the electrically actuated solenoid valve in response to a difference between the determined closing time and an expected closing time being greater than a threshold difference. In one embodiment of the method, the filtered current has a higher signal-to-noise ratio than a second derivative of the current. In one embodiment of the method, determining the closure time based on each of the current and the filtered current includes determining the closure time at the inflection point of the current in response to the filtered current being within a threshold difference of the current at the inflection point.

[0049] In another example, a method for an engine includes opening a solenoid valve coupled to a current sensor, measuring a current with the current sensor, filtering the current with a low pass filter, comparing the measured current to the filtered current to determine an inflection point of the measured current, and adjusting one or more engine operating conditions based on the inflection point. In one embodiment of the method, opening the solenoid valve includes applying an actuation voltage to the solenoid valve. In one embodiment of the method, the inflection point is indicative of an inductance change upon closing of the solenoid valve. In one embodiment of the method, the inflection point is a local minimum. In one embodiment of the method, the solenoid valve is a fuel injector in a unit pump fuel injector assembly of the engine. In one embodiment of the method, the one or more engine operating conditions include one or more of a fuel injection timing, a fuel injection advance, and an amount of fuel injected. In one embodiment of the method, a filter coefficient of the low pass filter is adjusted based on one or more of an application of the engine, a configuration of the engine, and a configuration of the unit pump fuel injector assembly.

[0050] In yet another example, a vehicle system includes a fuel injection pump in fluid communication with a fuel injector through a fuel injection valve, a sensor coupled to the fuel injection valve, and a controller communicatively coupled to each of the fuel injection pump, the fuel injector, the fuel injection valve, and the sensor, the controller executing instructions stored in a non-transitory memory to receive sampling data from the sensor, process the sampling data with a low pass filter, determine a closure point of the fuel injection valve based on the processed sampling data, and adjust operation of one or more of the fuel injection pump, the fuel injector, and the fuel injection valve based on the closure point. In one embodiment of the vehicle system, the sensor is a current sensor, the sampling data includes a plurality of current measurements, and processing the sampling data includes inputting each of the current measurements for an nth iteration in a predetermined window and the filtered current measurements for a (n-1)th iteration in the predetermined window to a low pass filter to obtain a filtered current measurement for the nth iteration. In one embodiment of the vehicle system, determining the closure point includes determining an absolute difference between the current measurement and the filtered current measurement for the nth iteration that is less than a convergence threshold. In one embodiment of the vehicle system, the fuel injector, the fuel injection pump, and the fuel injection valve are included in a diesel internal combustion engine, and the fuel injector is fluidly coupled to a cylinder of the diesel internal combustion engine. In one embodiment of the vehicle system, the vehicle system is a rail vehicle.

[0051] In another expression, the method includes iteratively performing a current sampling of the proportional solenoid valve for a first iteration and a second iteration, the first iteration including sampling a first current of the proportional solenoid valve, flowing the first current of the proportional solenoid valve to a first buffer, and initializing a second buffer based on the first buffer, the second iteration including sampling a second current of the proportional solenoid valve, sampling the second current after sampling the first current, updating the first buffer based on the second current, updating the second buffer by inputting the second buffer and the updated first buffer to a low pass filter, and indicating a closure of the proportional solenoid valve in response to an absolute difference between the updated first buffer and the updated second buffer being less than a convergence threshold. In one embodiment of the method, the method further includes terminating the current sampling of the proportional solenoid valve in response to an absolute difference between the updated first buffer and the updated second buffer being less than a convergence threshold. In one embodiment of the method, the method further includes continuing current sampling of the proportional solenoid valve in response to an absolute difference between the updated first buffer and the updated second buffer being greater than or equal to a convergence threshold. In one embodiment of the method, the method further includes generating an indication of degradation of the proportional solenoid valve in response to a total number of iterations of current sampling being greater than a sampling threshold. In one embodiment of the method, the proportional solenoid valve is configured to deliver fuel to a fuel injector of a diesel engine. In one embodiment of the method, the diesel engine is a power source for a locomotive. In one embodiment of the method, the method further includes incrementing an aging counter in response to an absolute difference between the updated first buffer and the updated second buffer being less than a convergence threshold, and generating an indication of degradation of the proportional solenoid valve in response to the aging counter exceeding a threshold count.

[0052] As used herein, an element or step described in the singular and proceeded with the word "a" or "an" should be understood as not excluding a plurality of said elements or steps, unless such exclusion is expressly stated. Moreover, reference to "one embodiment" of the invention does not exclude the existence of additional embodiments that also incorporate the described features. Furthermore, unless expressly stated to the contrary, an embodiment that "comprises," "includes," or "has" an element or elements having a particular characteristic may include additional such elements that do not have that characteristic. The terms "including" and "in which" are used as the plain language equivalents of the respective terms "comprising" and "wherein." Furthermore, terms such as "first," "second," and "third" are used merely as labels and are not intended to impose numerical requirements or a particular positional order on their objects.

[0053] The control methods and routines disclosed herein may be stored as executable instructions in a non-transitory memory and executed by a control system including a controller in combination with various sensors, actuators, and other engine hardware. The particular routines described herein may represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, etc. As such, the various actions, operations, and / or functions illustrated may be performed in the order illustrated, in parallel, or in some cases omitted. Similarly, the order of processing is not necessarily required to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated actions, operations, and / or functions may be performed repeatedly depending on the particular strategy used. Further, the described actions, operations, and / or functions may graphically represent code programmed into a non-transitory memory of a computer-readable storage medium within the engine control system, where the described actions are performed by executing instructions within a system that includes various engine hardware components in combination with an electronic controller.

[0054] This written description uses examples to disclose the invention, including the best mode, and also enables one of ordinary skill in the relevant art to practice the invention, including making or using any devices or systems and practicing any methods incorporated therein. The patentable scope of the invention is defined by the claims, and may include other embodiments that occur to those skilled in the art. Such other embodiments are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that do not differ substantially from the literal language of the claims.

[0055] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 045,006, entitled "METHODS AND SYSTEMS FOR FUEL INJECTOR CONTROL," filed June 26, 2020, the entire contents of which are incorporated herein by reference for all purposes.

Claims

1. Monitoring, via one or more controllers, a measured current of an electrically actuated solenoid valve included in an engine; filtering the measured current through a low pass filter in response to a fuel request being initiated, an engine temperature being within a predetermined temperature range, and a threshold time period having elapsed since the last determined closing time of the electrically actuated solenoid valve; determining, via the one or more controllers, the closing time of the electrically operated solenoid valve based on a comparison of the measured current to the filtered measured current, the comparison including determining an absolute difference between the measured current and the filtered measured current; The method includes:

2. 2. The method of claim 1, wherein monitoring the measured current of the electrically actuated solenoid valve comprises monitoring the measured current for a predetermined period of time following opening of the electrically actuated solenoid valve.

3. Furthermore, updating a previously determined closure time based on the determined closure time; and adjusting one or more operating conditions of the engine based on the determined closing time; The method of claim 1 , comprising:

4. generating an indication of deterioration of the electrically actuated solenoid valve in response to a difference between the determined closing time and the expected closing time being greater than a threshold difference; The method of claim 1 further comprising:

5. The method of claim 1 , wherein the filtered measured current has a higher signal-to-noise ratio than a second derivative of the measured current.

6. determining the closure time based on a comparison of the measured current and the filtered measured current; 2. The method of claim 1, comprising determining the closure time at an inflection point in response to the filtered measured current being within a threshold difference of the measured current at the inflection point of the measured current.

7. A method for an engine, comprising: Opening a solenoid valve connected to the current sensor; measuring a current with the current sensor; filtering the measured current with a low pass filter in response to a fuel request being initiated, the engine temperature being within a predetermined temperature range, and a threshold time period having elapsed since a last determined inflection point in the measured current; determining the inflection point of the measured current by comparing the measured current with the filtered current, the comparison including determining an absolute difference between the measured current and the filtered current; adjusting one or more engine operating conditions based on the inflection point; The method includes:

8. The method of claim 7, wherein opening the solenoid valve includes applying an operating voltage to the solenoid valve.

9. The method of claim 7, wherein the inflection point indicates an inductance change when the solenoid valve is closed.

10. The method of claim 7, wherein the inflection point is a local minimum.

11. The method of claim 7, wherein the solenoid valve is a fuel injector in a unit pump fuel injector assembly of the engine.

12. The method of claim 11, wherein the one or more engine operating conditions include one or more of fuel injection timing, fuel injection advance, and amount of fuel injected.

13. The method of claim 11, wherein the filter coefficients of the low pass filter are adjusted based on the application of the engine, the configuration of the engine, and the configuration of the unit pump fuel injector assembly.

14. a fuel injection pump in fluid communication with the fuel injector through a fuel injection valve; A sensor connected to the fuel injector; a controller communicatively coupled to each of the fuel injection pump, the fuel injector, the fuel injection valve, and the sensor, the controller executing instructions contained in a non-transitory memory to: receiving measured sampling data from the sensor; processing the measured sampled data with a low pass filter to obtain filtered sampled data responsive to a fuel request being initiated, the engine temperature being within a predetermined temperature range, and a threshold time period having elapsed since the last determined closing point of the fuel injector; determining the closing point of the fuel injector based on a comparison of the measured sampling data and the filtered sampling data, the comparison including determining an absolute difference between the measured sampling data and the filtered sampling data; adjusting operation of one or more of the fuel injection pump, the fuel injector, and the fuel injection valve based on the closing point; A controller; A vehicle system comprising:

15. the sensor is a current sensor; Processing the measured sampling data, inputting the current measurement for the nth iteration of the predetermined time period and the filtered current measurement for the (n-1)th iteration of the predetermined time period into the low pass filter to obtain a filtered current measurement for the nth iteration; The vehicle system of claim 14 , comprising:

16. The method of claim 15, wherein determining the closure point comprises: determining whether an absolute difference between the current measurement and the filtered current measurement for the nth iteration is less than a convergence threshold; 16. The vehicle system of claim 15, comprising:

17. the fuel injector, the fuel injection pump, and the fuel injection valve are included in a diesel internal combustion engine, 15. The vehicle system of claim 14, wherein the fuel injector is fluidly coupled to a cylinder of the diesel internal combustion engine.

18. A vehicle system as described in claim 14, which is a railway vehicle.

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