System and method for fuel injection timing drift detection and compensation

Abstract

At least some embodiments of the present disclosure relate to a fuel injection timing drift detection and / or compensation system. In some cases, the system collects or receives a series of fuel pressure data measured by one or more fuel pressure sensors. The system is configured to receive an indication of a fuel flow cut-off and an injection start command signal. The system uses the series of fuel pressure data to calculate a set of pressure drops and identify a selected pressure drop that is greater than a predetermined threshold to determine a measured injection start timing based on the selected pressure drop. The system is also configured to evaluate whether a fuel injection drift occurred based on the received injection start command signal and the measured injection start timing. In some cases, the fuel injection drift is used to compensate for fuel injection timing or raise a flag indicating a drift.

Description

Technical Field

[0001] This disclosure generally relates to systems and methods for detecting and compensating for fuel injection timing drift. Background Technology

[0002] In an internal combustion engine, one or more fuel pumps deliver fuel to a common rail. The fuel is then delivered from the common rail to the engine cylinders via fuel injectors for combustion, powering the engine-driven system. Like all mechanical devices, fuel injectors have physical dimensions that cause differences between them. Furthermore, each fuel injector has a different wear rate and responds differently to temperature changes. Due to these physical differences, injectors may exhibit injection timing drift. Moreover, the timing of fuel injection affects the engine's combustion efficiency. Summary of the Invention

[0003] For a variety of reasons, it is desirable to detect and control fuel injection timing in internal combustion engines or other engines. In some cases, meeting the injection timing diagnostic requirements of on-board diagnostic rules is challenging. In some cases, engine position sensor (EPS) diagnostic systems provide timing drift detection but cannot detect phase shift errors at a finer resolution and compensate for phase shift errors for emissions benefits. Additionally, fuel injection timing drift is generally not actively monitored and corrected throughout the engine's lifespan. Furthermore, in some cases, precise control of fuel injection timing can optimize combustion and improve fuel efficiency. At least some embodiments of this disclosure use crankshaft synchronizing pressure data collected during fuel flow cutoff to measure the injection start (“SOI”) timing of each cylinder of the engine. In some cases, timing drift or timing offset is calculated by comparing the measured SOI timing with the commanded SOI timing. In some cases, timing drift or timing offset is used to generate a compensation scheme for fuel injection timing drift. In some cases, timing compensation or timing offset for one or more injectors is analyzed to flag fault codes.

[0004] One embodiment of this disclosure relates to a system comprising: one or more memories storing instructions and a series of fuel pressure data measured by a fuel pressure sensor; and one or more processors configured to execute the instructions to perform operations. The operations include: receiving an indication of fuel flow cutoff; and receiving an injection start command signal. The operations further include: in response to receiving the fuel flow cutoff indication, the one or more processors using the series of fuel pressure data to calculate a set of pressure drops; the one or more processors comparing the set of pressure drops to the predetermined threshold to identify selected pressure drops greater than the predetermined threshold; the one or more processors determining a measured injection start timing based on the selected pressure drops; and the one or more processors assessing whether fuel injection drift has occurred based on the received injection start command signal and the measured injection start timing.

[0005] Another embodiment of this disclosure relates to a method implemented by a computer system having one or more processors and memory. The method includes the steps of: collecting a series of fuel pressure data; receiving an indication of fuel flow cutoff; and receiving an injection start command signal. The method further includes: in response to receiving the fuel flow cutoff indication, the one or more processors using the series of fuel pressure data to calculate a set of pressure drops; the one or more processors comparing the set of pressure drops with the predetermined threshold to identify selected pressure drops greater than the predetermined threshold; the one or more processors determining a measured injection start timing based on the selected pressure drops; and the one or more processors assessing whether fuel injection drift has occurred based on the received injection start command signal and the determined injection start timing.

[0006] Another embodiment of this disclosure relates to a method implemented by a computer system having one or more processors and memory. The method includes the steps of: collecting a series of crank-synchronous fuel pressure data; receiving an injection start command signal; calculating a set of pressure drops by the one or more processors using the series of crank-synchronous fuel pressure data collected during a fuel flow cut-off period; comparing the set of pressure drops with a predetermined threshold by the one or more processors to identify selected pressure drops greater than the predetermined threshold; determining a measured injection start timing by the one or more processors based on the selected pressure drops; and evaluating whether fuel injection drift has occurred by the one or more processors based on the received injection start command signal and the measured injection start timing.

[0007] While several embodiments have been disclosed, other embodiments of this disclosure will become apparent to those skilled in the art from the following detailed description, which illustrates and describes illustrative embodiments of this disclosure. Therefore, the accompanying drawings and the detailed description should be considered illustrative in nature and not restrictive. Attached Figure Description

[0008] The above and other features of this disclosure, and the ways in which they are obtained, will become more apparent from the following description of embodiments of this disclosure, taken in conjunction with the accompanying drawings, and the disclosure itself will be better understood, wherein:

[0009] Figure 1 This is a simplified schematic diagram of a portion of an exemplary internal combustion engine;

[0010] Figure 2 This is a conceptual block diagram of one embodiment of a fuel injection timing drift detection and compensation system;

[0011] Figure 3 This is an illustrative example of crankshaft synchronizing fuel pressure data;

[0012] Figure 4 These are illustrative examples of relevant representative signal waveforms;

[0013] Figure 5A This is a flowchart of an example of a fuel injection timing detection and compensation system;

[0014] Figure 5B This is a flowchart of an exemplary embodiment of a fuel injection timing detection and compensation system; and

[0015] Figure 6 It is an illustrative waveform representing fuel pressure data for an engine with multiple cylinders and injectors. Detailed Implementation

[0016] In some embodiments, the engine described below includes a control system configured to perform certain operations to control the fuel system and detect and control fuel injection timing. In some embodiments, the control system includes part of a processing subsystem having one or more computing devices, said computing devices having one or more memories, one or more processors, and various communication hardware components. The processing subsystem may be a single device or a distributed device, and the functionality of the subsystem's controller (described below) may be implemented by hardware and / or executing computer instructions stored on a non-transient computer-readable storage medium.

[0017] Reference Figure 1The diagram shows a simplified schematic of a portion of an exemplary internal combustion engine 10. The engine 10 includes an engine block 11, a fuel system 16, and a control system 18. The engine block 11 includes an engine cylinder block 12 and a cylinder head 14 connected to the engine cylinder block 12. The control system 18 receives signals from sensors located on the engine 10 and transmits control signals to devices located on the engine 10 to detect, analyze, and control the function of those devices (e.g., one or more fuel injectors).

[0018] Periodically, after receiving a fuel flow cut-off command to stop the fuel flow, fuel system 16 stops the fuel flow to the accumulator of fuel system 16. The term "cut-off" in this disclosure corresponds to shutting off, interrupting, or stopping the fuel flow to the fuel accumulator. When the fuel flow to the fuel accumulator stops (this forms a termination event), control system 18 receives a signal indicating the fuel pressure in the fuel accumulator from a pressure sensor associated with the fuel accumulator. In some embodiments, control system 18 may collect fuel pressure data during a fuel flow cut-off event and / or use the fuel pressure data collected during the fuel flow cut-off event, for example, to reduce noise and / or isolate fuel pressure variations attributable solely to fuel injection events. In some cases, control system 18 processes the fuel pressure data to identify timing of pressure drops greater than a predetermined threshold, thereby measuring the actual SOI timing. In some cases, the fuel pressure data is crank-synchronous fuel pressure data, referring to fuel pressure data in the crank angle domain. In some embodiments, the crank angle domain refers to data sampled at crank angles (e.g., 0°, 6°, 120°, etc.). In some cases, the control system 18 is also configured to receive an indication of an SOI command to determine the commanded SOI timing and to determine a timing offset or fuel injection drift offset trend based on the measured SOI timing and the commanded SOI timing. In some cases, SOI timing is measured and / or determined at the crank angle.

[0019] exist Figure 1 In the example shown, the engine block 12 includes a crankshaft 20, a plurality of pistons 22, and a plurality of connecting rods 34. The pistons 22 are positioned to reciprocate in a plurality of engine cylinders 36, with one piston positioned in each engine cylinder 36. The connecting rods 34 connect each piston to the crankshaft 20. The movement of the pistons in the engine 10 under the influence of the combustion process causes the connecting rods 34 to move the crankshaft 20.

[0020] In the example shown, multiple fuel injectors 38 are positioned within the cylinder head 14. Each fuel injector 38 is fluidly connected to the combustion chamber 40. The fuel system 16 supplies fuel to the injectors 38, which then inject the fuel into the combustion chamber 40 through the action of the fuel injectors 38, thus forming one or more injection events. The fuel system 16 includes a fuel circuit 42, a fuel tank 44 that contains fuel, a high-pressure fuel pump 46 positioned downstream of the fuel tank 44 along the fuel circuit 42, and a fuel accumulator or common rail 48 positioned downstream of the high-pressure fuel pump 46 along the fuel circuit 42. Although the fuel accumulator or common rail 48 is shown as a single unit or element in the exemplary embodiment, the accumulator 48 may be distributed across multiple elements that contain high-pressure fuel. These elements may include the fuel injectors 38, the high-pressure fuel pump 46, and any lines, channels, pipes, hoses, etc., connecting the high-pressure fuel to the multiple elements, thus eliminating the need for a separate fuel accumulator 48.

[0021] In the example shown, fuel system 16 also includes an inlet metering valve 52 positioned upstream of high-pressure fuel pump 46 along fuel circuit 42 and one or more outlet check valves 54 positioned downstream of high-pressure fuel pump 46 along fuel circuit 42 to allow unidirectional fuel flow from high-pressure fuel pump 46 to fuel accumulator 48. Inlet metering valve 52 has the capability to alter or shut off fuel flow to high-pressure fuel pump 46, thereby shutting off or stopping fuel flow to fuel accumulator 48. Although not shown, additional elements may be positioned along fuel circuit 42. For example, inlet check valves may be positioned downstream of inlet metering valve 52 and upstream of high-pressure fuel pump 46, or inlet check valves may be incorporated into high-pressure fuel pump 46. Fuel circuit 42 connects fuel accumulator 48 to fuel injector 38, which receives fuel from fuel circuit 42 and then supplies a controlled amount of fuel to combustion chamber 40. In some embodiments, fuel system 16 may also include a low-pressure fuel pump 50 positioned along fuel circuit 42 between fuel tank 44 and high-pressure fuel pump 46. The low-pressure fuel pump 50 increases the fuel pressure to a first pressure level before fuel flows into the high-pressure fuel pump 46, which increases the operating efficiency of the high-pressure fuel pump 46. In some embodiments, the fuel system 16 has a fuel pressure relief valve that can be mechanically or electronically actuated downstream of the fuel accumulator 48. This fuel pressure relief valve provides an alternative path to release excess fuel from the fuel accumulator to the fuel tank via the fuel discharge loop during high fuel pressure events caused by any changes or malfunctions in fuel system components.

[0022] Control system 18 may include control processor 56 and wiring harness 58. Many aspects of the invention are described from the perspective of operations to be performed by a computer system or other hardware capable of executing programmed instructions. It will be appreciated that, in each embodiment, various operations may be performed by dedicated circuitry (e.g., discrete logic gates interconnected to perform dedicated functions), by program instructions (software) (such as program modules) executed by one or more processors, or by a combination of these components. Furthermore, this disclosure may also be considered to be contained in non-transient computer-readable media, such as solid-state memory, magnetic disks, and optical disks, which contain a suitable set of computer instructions, such as program modules and data structures, that will cause a processor to perform the techniques and embodiments described herein. Computer-readable media may include: electrical connections having one or more wires, disk storage, magnetic tape cassettes, magnetic tape or other magnetic storage devices, portable computer disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), or any other medium capable of storing information.

[0023] It should be noted that the systems disclosed herein are shown and discussed as having various modules and units performing specific functions. It should be understood that, for clarity, these modules and units are shown schematically only based on their functionality and do not necessarily represent specific hardware or software. In this respect, these modules, units, and other components can be hardware and / or software implemented to substantially perform their specific functions as explained herein. The various functions of different components can be combined or separated in any way into hardware and / or software modules and can be used individually or in combination. Therefore, various aspects of this disclosure can be implemented in many different forms, and all such forms are considered to be within the scope of this disclosure.

[0024] The control system 18 also includes an accumulator pressure sensor 60 and a crank angle sensor. While sensor 60 is described as a pressure sensor, it can be other devices that can be calibrated to provide a pressure signal representing fuel pressure, such as a force sensor, strain gauge, or other device. The crank angle sensor can be a gear sensor 62, a rotary Hall sensor 64, or other types of devices capable of measuring the rotation angle of the crankshaft 20. In some cases, the control system 18 uses signals received from the accumulator pressure sensor 60 and the crank angle sensor to determine that the combustion chamber is receiving fuel, which is then used to analyze the signals received from the accumulator pressure sensor 60, as will be described in more detail below. In some cases, the control system 18 uses a crank sensor or a combination of a crank sensor and a camshaft sensor to estimate the current ignition of the combustion chamber, where the camshaft sensor is located near the camshaft controlling the intake / exhaust valves.

[0025] The control processor 56 may be an electronic control unit or an electronic control module (ECM) that monitors the condition of the engine 10 or a related vehicle in which the engine 10 may be located. The control processor 56 may be a single processor, a distributed processor, an electronic equivalent of a processor, or any combination of the foregoing elements, as well as software, electronic memory, etc. The control processor 56 may include digital or analog circuitry. The control processor 56 may be connected to certain components of the engine 10 via wiring harness 58, although such connection may be made in other ways, including wireless systems. For example, the control processor 56 may be connected to and provide control signals to the inlet metering valve 52 and the fuel injector 38. In another example, the control processor 56 may be connected to and provide control signals to the fuel pressure relief valve.

[0026] When engine 10 is running, combustion in combustion chamber 40 causes piston 22 to move. The movement of piston 22 causes movement of connecting rod 34, which is driven to crankshaft 20, and the movement of connecting rod 34 causes rotational movement of crankshaft 20. The rotation angle of crankshaft 20 is measured by engine 10 to aid in the timing of combustion events in engine 10 and for other purposes. The rotation angle of crankshaft 20 can be measured at multiple locations, including the main crankshaft pulley (not shown), engine flywheel (not shown), engine camshaft (not shown), or on the crankshaft itself. The measurement of crankshaft 20 rotation angle can be performed using gear sensor 62, rotary Hall sensor 64, and other techniques. A signal representing the rotation angle of crankshaft 20 (also called crank angle) is transmitted from gear sensor 62 (e.g., an inductive sensor or Hall sensor), rotary Hall sensor 64, or other means to control system 18.

[0027] In some embodiments, crankshaft 20 drives high-pressure fuel pump 46 and low-pressure fuel pump 50. The operation of low-pressure fuel pump 50 draws fuel from fuel tank 44 and moves it along fuel circuit 42 toward inlet metering valve 52. Fuel flows downstream from inlet metering valve 52 along fuel circuit 42 through inlet check valve (not shown) to high-pressure fuel pump 46. High-pressure fuel pump 46 moves fuel downstream along fuel circuit 42 through outlet check valve 54 toward fuel accumulator or common rail 48. Inlet metering valve 52 receives a control signal from control system 18 and is operable to block fuel flow to high-pressure fuel pump 46. Inlet metering valve 52 may be a proportional valve or an on / off valve capable of rapid adjustment between an open and closed position to regulate the amount of fluid flowing through the valve.

[0028] In one embodiment, a fuel pressure sensor 60 is connected to a fuel accumulator 48 and is capable of detecting or measuring the fuel pressure in the fuel accumulator 48. The fuel pressure sensor 60 sends a signal indicating the fuel pressure in the fuel accumulator 48 to a control system 18. The fuel accumulator 48 is connected to each fuel injector 38. The control system 18 provides control signals to the fuel injectors 38, which determine operating parameters for each fuel injector 38, such as the duration of operation of the fuel injector 38, the start of injection, and the number of fuel supply pulses per ignition or injection event cycle, the number of fuel supply pulses determining the amount of fuel delivered by each fuel injector 38.

[0029] In some embodiments, the fuel system 16 may also include a fuel pressure relief valve that can be mechanically or electronically actuated downstream of the fuel accumulator. This provides an alternative path to release excess fuel from the fuel accumulator to the fuel tank via the fuel discharge circuit during high fuel pressure events caused by any variation or malfunction in the fuel system components. If an electronic pressure relief valve is used, it may receive a control signal from the control system 18 and be operable to release unwanted overflow to the fuel tank via the fuel discharge circuit. In some cases, the use of a mechanical or electronic fuel pressure relief valve depends on the overall engine configuration and application.

[0030] Control system 18 includes processes that control certain components of engine 10 to measure and / or compensate for fuel injection timing drift. Now turn to Figure 2 A fuel injection timing drift detection and compensation system 200 according to one embodiment of the present disclosure is shown. System 200 is part of control system 18. In the illustrated embodiment, fuel injection timing drift detection and compensation system 200 includes a fuel flow controller 210, a fuel injector controller 220, a data analyzer 230, and a fuel data storage library 240. One or more components of fuel injection timing drift detection and compensation system 200 are optional.

[0031] In some embodiments, the fuel injection timing drift detection and compensation system 200 receives fuel pressure data 201 and crank angle sensor data 202. In some cases, the fuel pressure data 201 and / or crank angle sensor data 202 are stored in a fuel data storage library 240. In some cases, the fuel pressure data 201 and / or crank angle sensor data 202 include an associated timestamp. In some cases, the fuel pressure data 201 and / or crank angle sensor data 202 are sampled by crank angle and imprinted with the crank angle. In some cases, the fuel flow controller 210 may generate a fuel flow cut-off signal and provide the fuel flow cut-off signal to the data analyzer 230. In some cases, in response to receiving the fuel flow cut-off signal, the data analyzer 230 begins analyzing the fuel pressure data 201. In some embodiments, the data analyzer 230 identifies fuel pressure drops greater than a predetermined pressure drop threshold to measure SOI timing. In some cases, the magnitude of the predetermined pressure drop threshold is selected based on the sampling frequency.

[0032] In some implementations, the data analyzer 230 is configured to group fuel pressure data into subsets of fuel pressure data, where the data variance in each subset is less than a predetermined fluctuation threshold, and is configured to determine the fuel pressure drop between two adjacent subsets of the fuel pressure data. In some examples, if a selected pressure drop greater than the predetermined pressure drop threshold is associated with a first subset of the pressure data and a second subset of the pressure data sampled after the first subset, the last pressure data in the first subset of the fuel pressure data is used to determine the measured SOI timing. In some cases, the measured SOI timing is determined based on the second subset of the fuel pressure data. In one example, consecutive fuel pressure data points are identified as having a pressure drop greater than a predetermined threshold. In this example, the first fuel pressure drop is used to determine the measured SOI timing. In some cases, the data analyzer 230 uses crank angle sensor data 202 when determining the measured SOI timing. In some embodiments, the fuel injector controller 220 provides an SOI command signal to the data analyzer 230. The data analyzer 230 determines the commanded SOI timing based on the received signal. In some cases, when determining the SOI timing of a command, the data analyzer 230 uses crank angle sensor data 202.

[0033] The fuel data store 240 can be implemented using any of the configurations described below. The data store may include random access memory, flat files, XML files, and / or one or more database management systems (DBMS) running on one or more database servers or data centers. The database management system may be a relational (RDBMS), hierarchical (HDBMS), multidimensional (MDBMS), object-oriented (ODBMS or OODBMS), or object-relational (ORDBMS) database management system, etc. The data store may be a single data store. In some cases, the data store may include multiple data stores.

[0034] In some embodiments, the data analyzer 230 uses the measured SOI timing and the commanded SOI timing to determine the fuel injection timing offset. In one example, equation (1) is used to calculate the timing offset.

[0035] TimeOffset=MeasuredSOI-CmdSOI (1),

[0036] Where MeasuredSOI is the measured SOI timing, and CmdSOI is the commanded SOI timing. In some cases, timing offset is used as an indication of timing trend, for example, indicating whether the measured SOI timing is before or after the commanded SOI timing. In some cases, timing offset and / or timing trend are used to determine compensation for fuel injection timing.

[0037] In one example, data analyzer 230 uses the timing trend to select fuel injection timing compensation with a predetermined compensation amount. For example, if the timing trend is backward, the predetermined compensation amount is 1 degree crank angle relative to TDC (“Top Dead Center”), and data analyzer 230 selects a fuel injection timing compensation of 1 degree relative to TDC. As another example, if the timing trend is forward, the predetermined compensation amount is 1 degree crank angle relative to TDC, and data analyzer 230 selects a fuel injection timing compensation of -1 degree relative to TDC. In another example, data analyzer 230 applies a filter to the timing offset and / or timing trend to determine the timing compensation. For example, data analyzer 230 applies a first-order filter to the timing offset and / or timing trend to determine the timing compensation. In one example, the determined timing compensation (f-SOI) is calculated as follows:

[0038] f-SOI current =α*f-SOI previous +(1-α)*SOI offset (2), where f-SOI current This is the timing compensation used in the current calculation, where α is a coefficient or filter constant / coefficient, f-SOIprevious This is used for the previously calculated timing compensation, and SOI offset The time offset is determined by the data analyzer 230. The coefficient α is chosen, for example, to be 0.9, as a smoothing filter for the calculated time offset.

[0039] In some cases, data analyzer 230 provides fuel injector controller 220 with determined timing compensations (e.g., calculated timing offset, predetermined timing compensation, filtered timing offset) to adjust the SOI timing for future commands. In some cases, data analyzer 230 is configured to use any of the embodiments described herein to determine timing compensation for each of these injectors. In some cases, data analyzer 230 is configured to flag a fault code if one or more fault criteria based on the determined injector timing compensation and / or timing offset are met. In some cases, the fault code is a standard engine fault code, such as those listed in an on-board diagnostic system (“OBD-II”).

[0040] In some implementations, various components of system 200 may execute software or firmware stored in a non-transitory computer-readable medium to perform various processing steps. The various components and processors of system 200 may be implemented by one or more computing devices, including but not limited to circuits, computers, processors, processing units, microprocessors, and / or mobile computing devices. In some implementations, the various components of system 200 may be implemented on a shared computing device. Alternatively, the components of system 200 may be implemented on multiple computing devices. In some implementations, the various modules and components of system 200 may be implemented as software, hardware, firmware, or a combination thereof. In some implementations, the various components of the fuel injection timing drift detection and compensation system 200 may be implemented in software or firmware executed by a computing device.

[0041] Figure 3 This is an illustrative example of crankshaft-synchronized fuel pressure data. In one embodiment, the fuel pressure data is synchronized with the crank angle via a reference tooth (e.g., a missing tooth). In one example, the crank angle is detected by a crank angle sensor, for example... Figure 1 The crank gear sensor 62 is shown. In one embodiment, the crank angle sensor detects the rising edge of the crank teeth. In one embodiment, the angle between adjacent crank teeth is a known degree T. In the example shown, the relative angle between adjacent crank teeth 305 is further divided into sampling angles R, where a fuel pressure sensor (e.g., 60) samples at a sampling resolution S and generates pressure data 301. In some cases, the resolution of the sampling rate R can be calculated using equation (3):

[0042] R=T*CN / (60*S) (3),

[0043] Where T is the angle between adjacent teeth, S is the sampling frequency, C is the number of teeth on the crankshaft wheel, and N is the engine speed in RPM (revolutions per minute). In one example, when T = 6°, C = 60°, and S = 10 kHz, the resolution R = 0.6 degrees / pressure sample. In some cases, the sampling frequency S for fuel pressure data is greater than 1 kHz. In some cases, the sampling frequency S is greater than 5 kHz.

[0044] In one embodiment, fuel pressure data 301 is sampled at a known constant frequency during a known time period with a known crank angle variation, such that fuel pressure data 301 is synchronized with crank angle sensor data 302. In another embodiment, fuel pressure data 301 is synchronized with crank angle by sampling the fuel pressure data at the crank angle. In yet another embodiment, a memory buffer storing the sampled fuel pressure data 301 is imprinted with the crank angle.

[0045] Figure 4 This is an illustrative example of a relevant representative signal waveform. Waveform 401 shows an actual piston (e.g., Figure 1 An example of position 22). Waveform 405 shows an exemplary crank pulse, while the dashed waveform 407 shows the waveform of a missing crank tooth. Waveform 410 shows an example of a cam pulse. Waveform 415 shows an example of an injector pulse representing injector current. Waveform 420 shows an example of a fuel consumption rate shape. Waveform 425 shows an example of fuel pressure data (e.g., Figure 2 (201). In the example shown, a fuel pressure drop greater than a predetermined threshold is detected at T2, where the commanded SOI timing is at T1. In some cases, the commanded SOI timing T1 and / or T2 is the timing relative to the TDC. The timing offset TO1 is expressed as the difference between T1 and T2.

[0046] Figure 5AA flowchart illustrating an example of a fuel injection timing detection and compensation system is shown. One or more steps in the flowchart are optional. In one example, the system collects a series of fuel pressure data (510A). The system is also configured to receive a fuel flow cutoff indication (515A). The fuel flow cutoff indication includes, for example, a command, a signal, or other indication indicating the start of a fuel flow cutoff cycle. In some cases, the fuel flow cutoff period ends after receiving an EOI (“End of Injection”) signal from the last of a plurality of cylinders in the engine. In an example with six cylinders (e.g., cylinders #1, #2, #3, #4, #5, #6) and the cylinders starting injection in the order of #1, #5, #3, #6, #2, and #4, the fuel flow cutoff period ends after receiving an EOI signal from cylinder #4. Furthermore, the system receives an injection start command indication (520A) and optionally determines the SOI timing of the command. In some cases, the system receives a series of crank sensor data (525A) and is configured to synchronize the series of fuel pressure data with the series of crank sensor data (530A). The system then uses the series of fuel pressure data to calculate a set of pressure drops (535A).

[0047] In some cases, the system uses the series of fuel pressure data collected after receiving a fuel flow cutoff indication to calculate the set of pressure drops. In some cases, the system uses the series of fuel pressure data collected during a fuel flow cutoff to calculate the set of pressure drops. In some cases, each of the set of pressure drops is the difference between the current sample of fuel pressure data and the fuel pressure data of a previous sample. In some cases, the previous sample is the sample immediately preceding the current sample. In some examples, consecutive fuel pressure data are identified as having a pressure drop greater than a predetermined threshold. In such examples, the first fuel pressure drop is used to determine the SOI timing of the measurement. In some cases, the system divides the series of fuel pressure data into subsets, where each subset of the fuel pressure data is consecutively sampled data and has a variance less than a predetermined fluctuation threshold. In one instance, the variance of a set of data is calculated using the following equation (1):

[0048]

[0049] Where N is the number of samples in the dataset, μ is the mean of the dataset, and σ 2 It is the variance of the dataset.

[0050] In some cases, the system determines a set of pressure drops based on two adjacent subsets of fuel pressure data. In one example, if a first subset of fuel pressure data has a first baseline value and a second subset of fuel pressure data has a second baseline value (where the second subset is sampled immediately after the first subset), then the pressure drop is the difference between the first and second baseline values. In some cases, the baseline value is the average of a set of data. In some cases, the baseline value is the median of a set of data.

[0051] In one example, the system compares the set of pressure drops to a predetermined threshold to identify selected pressure drops greater than the predetermined threshold (540A), and determines the measured injection start timing based on the selected pressure drops (545A). In some examples, where the selected pressure drops are associated with a first subset of pressure data and a second subset of pressure data sampled after the first subset, the last pressure data in the first subset of fuel pressure data is used to determine the measured SOI time. In some cases, the last pressure data is accompanied by the crank angle. Furthermore, the system assesses whether fuel injection timing drift has occurred based on the measured injection start timing and the received injection start command signal (550A).

[0052] In some cases, the system calculates the timing offset based on the measured injection start timing (555A) and the received SOI command signal. In some cases, the timing offset is calculated based on both the measured injection start timing and the commanded SOI timing. In some cases, both the commanded and measured injection start timings are expressed in crank angles. In some cases, the calculated timing offset is measured in crank angles. In one example, the calculated timing offset is a timing drift trend. For example, the calculated timing offset is an indication that the measured fuel injection precedes the commanded fuel injection or that the measured fuel injection follows the commanded fuel injection. In some embodiments, the system collects fuel pressure data at high resolution, for example, to improve timing offset accuracy. In some cases, fuel pressure data is collected at a sampling frequency greater than or equal to 1 kHz. In some cases, fuel pressure data is collected at a sampling frequency greater than or equal to 2 kHz. In some cases, fuel pressure data is collected at a sampling frequency greater than or equal to 5 kHz. In some cases, fuel pressure data is collected at a sampling frequency greater than or equal to 10 kHz.

[0053] Optionally, the system uses the timing offset to determine timing compensation (560A). In some cases, the system stores the determined timing offset in a data store (e.g., Figure 2In some cases, each timing offset record stored in the data store is associated with a timestamp / crank angle position and the injector. In some cases, the system applies a filter to the timing offset to determine timing compensation. In some cases, the system applies a filter to the timing offset to determine timing compensation using one or more timing offsets associated with the same injector stored in the data store. In some cases, the system applies a smoothing filter to the timing offset. In some cases, the system applies a low-pass filter to the timing offset. In some cases, the system applies a first-order filter to the timing offset. In some cases, the system applies a second-order filter to the timing offset.

[0054] Optionally, the system evaluates whether timing compensation and / or timing offset meet a fault criterion (565A). In one example, the fault criterion includes a predetermined offset threshold such that if the value of one or more timing offsets is greater than the predetermined offset threshold, the fault criterion is met. As used herein, "value" refers to the amplitude of a data or signal. In one example, the fault criterion includes a predetermined compensation threshold such that if the value of one or more timing compensations is greater than the compensation threshold, the fault criterion is met. In some cases, the fault criterion includes the timing conditions of all injectors of the engine (e.g., 6 injectors). In some cases, the fault criterion includes the timing conditions of a single injector. In some cases, the fault criterion includes the timing conditions of a minimum number of injectors (e.g., 3 out of a total of 6 injectors). In some embodiments, the fault criterion includes the timing conditions of the injectors over a period of time (e.g., 2 fuel flow cutoff cycles). For example, the fault criterion includes a fixed injector system having three or more injection timing offsets greater than a predetermined offset threshold during two consecutive fuel flow cutoff cycles. In some cases, the time period is multiple fuel flow cutoff cycles. In some embodiments, the failure criterion includes the injector timing condition for a single cycle (e.g., one fuel flow cutoff cycle). In some cases, the failure criterion includes a timing condition model (e.g., a failure count as a function of time). In one example, the timing condition model is a linear model over time. In another example, the timing condition model is a nonlinear model that varies over time.

[0055] Optionally, if the fault criteria are met, the system flags a fault code (570A). In some cases, a fault code is selected from a predetermined code set. In one example, the fault code is selected from the OBD-II code. In some embodiments, the system uses timing compensation to adjust the timing of the next or future injection start command (575A). For example, a timing compensation of 1° for the injector is applied to the timing of the next injection start command for the injector.

[0056] Figure 5BA flowchart illustrating an exemplary embodiment of a fuel injection timing drift detection and compensation system is shown. One or more steps in the flowchart are optional. The system first checks activation conditions (510B). In some embodiments, activation conditions include fuel supply logic, common rail pressure signals, engine speed and position signals, etc. The system searches for fuel flow cut-off events (515B). In some cases, fuel flow cut-off events are indicated by commands sent to the engine. In some cases, fuel flow cut-off events occur periodically (e.g., every 36 seconds). During a cut-off event (or cut-off cycle), the system records, for example, SOI commands for multiple injectors (517B). During a cut-off event, the system analyzes fuel pressure data to determine whether injection has occurred (520B). In one example, the system evaluates whether the difference in fuel pressure data is greater than a predetermined threshold. In some cases, the predetermined threshold is a threshold based on fuel pressure (522B).

[0057] The system assesses whether cylinder injection occurred during the cut-off event (525B). If no cylinder injection occurred, the system returns to step 515B. If cylinder injection did occur, the system determines the timing of the measured SOI (also known as the actual SOI) (530B). In one embodiment, the measured SOI timing is represented by a buffer index starting at a differential pressure greater than a predetermined threshold. In some cases, the storage buffers for fuel pressure data and the corresponding fuel pressure drop data are indexed by crank angle (532B). In some cases, the same index for the corresponding fuel pressure data is used to record the differential pressure. In some cases, the measured SOI timing is represented or converted to crank angle. The system uses any of the embodiments described herein, employing both the actual SOI and the commanded SOI information, to determine the timing offset (535B).

[0058] The system checks whether compensation is enabled (540B). If compensation is not enabled, optionally, the system records fault information (542B) if fault criteria are met. In one example, fault criteria include an offset threshold for a calibrable number of instances. If the timing offset is greater than the offset threshold for a calibrable number of instances, fault information is recorded. Fault information includes, for example, a fault code, fault condition, fault criteria used, etc. If compensation is enabled, the system applies a compensation algorithm using any of the embodiments described herein (545B). When compensation exceeds a compensation threshold, fault information is recorded (547B), including, for example, a fault code, fault condition, fault criteria used, etc. In some cases, the system records or outputs the timing offset, applied compensation, and / or fault information for each injector (550B).

[0059] Figure 6This is an illustrative waveform representing fuel pressure data for an engine with multiple cylinders and injectors. In the example shown, waveform 600 represents a portion of the fuel pressure data for a six-cylinder engine during a fuel flow cutoff cycle. 601 shows the fuel pressure drop caused by injection from cylinder #1, 610 shows the fuel pressure drop caused by injection from cylinder #5, and 620 shows the fuel pressure drop caused by injection from cylinder #3. The SOI times of commands for cylinders #1, #5, #3, and #6 are recorded online at 602, 612, 622, and 632, respectively, and the corresponding TDCs are recorded at 601, 611, 621, and 631. The pressure drop start times (603, 613, and 623) represent the measured SOI times for cylinders #1, #5, and #3, respectively. In one example, the timing offsets for cylinders #1, #5, and #3 are represented as 605, 615, and 625, respectively. In some embodiments, the timing data is used to determine whether timing drift and / or timing compensation has occurred for each injector in the cylinder.

[0060] While various embodiments of this disclosure have been shown and described, it should be understood that these embodiments are not limited thereto. Those skilled in the art can change, modify, and further apply these embodiments. Therefore, these embodiments are not limited to the details previously shown and described, but also include all such changes and modifications.

Claims

1. A system, comprising: one or more memories having stored thereon instructions and a series of fuel pressure data measured by a fuel pressure sensor; one or more processors configured to execute the instructions to perform operations comprising: receiving an indication of a fuel flow cutoff; receiving an injection start command signal; in response to receiving the indication of a fuel flow cutoff, computing, by the one or more processors, a set of pressure drops using the series of fuel pressure data; comparing, by the one or more processors, the set of pressure drops to a predetermined threshold to identify a selected pressure drop that is greater than the predetermined threshold; determining, by the one or more processors, a measured injection start timing based on the selected pressure drop; and evaluating, by the one or more processors, whether a fuel injection drift occurred based on the received injection start command signal and the measured injection start timing.

2. The system of claim 1, wherein, each pressure drop in the set of pressure drops is computed based on a first sample of fuel pressure data and a second sample of fuel pressure data, wherein the first sample of fuel pressure data is measured at a first time, and wherein the second sample of fuel pressure data is measured at a second time different than the first time.

3. The system of claim 1, wherein, the operations further comprise: grouping the series of fuel pressure data into a plurality of subsets of fuel pressure data, wherein each subset of fuel pressure data is a contiguous sample of fuel pressure data and has a variance that is less than a predetermined fluctuation threshold, and wherein each pressure drop in the set of pressure drops is computed based on two adjacent subsets of fuel pressure data.

4. The system of claim 1, wherein, evaluating whether a fuel injection drift occurred includes: determining a timing offset based on the received injection start command signal and the measured injection start timing.

5. The system of claim 1, wherein, the operations further comprise: receiving a series of crank sensor data; and synchronizing, by the one or more processors, the series of fuel pressure data with the series of crank sensor data such that the series of fuel pressure data is synchronized with a crank angle.

6. The system of claim 4, wherein, the operations further comprise: evaluating whether a first fault criterion of the timing offset is satisfied; and in response to the first fault criterion being satisfied, generating a fault code.

7. The system of claim 4, wherein, the operations further comprise: determining a timing compensation based on the timing offset.

8. The system of claim 7, wherein, the operations further comprise: adjusting a timing of a next injection start command based on the timing compensation.

9. The system of claim 7, wherein, the operations further comprise: evaluating whether a second fault criterion of the timing compensation is satisfied; and in response to the second fault criterion being satisfied, generating a fault code.

10. A method implemented by a computer system having one or more processors and memory, the method comprising: collecting a series of fuel pressure data; receiving an indication of a fuel flow cutoff; receiving an injection start command signal; in response to receiving the indication of a fuel flow cutoff, computing, by the one or more processors, a set of pressure drops using the series of fuel pressure data; comparing, by the one or more processors, the set of pressure drops to a predetermined threshold to identify a selected pressure drop that is greater than the predetermined threshold; determining, by the one or more processors, a measured injection start timing based on the selected pressure drop; and evaluating, by the one or more processors, whether fuel injection drift occurred based on the received injection start command signal and the determined injection start timing.

11. The method of claim 10, further comprising: receiving a series of crank sensor data; and synchronizing, by the one or more processors, the series of fuel pressure data with the series of crank sensor data such that the series of fuel pressure data is synchronized with crank angle.

12. The method of claim 10, wherein, each pressure drop of the set of pressure drops is calculated based on a first sample of fuel pressure data and a second sample of fuel pressure data, wherein the first sample of fuel pressure data is measured at a first time, and wherein the second sample of fuel pressure data is measured at a second time different than the first time.

13. The method of claim 10, further comprising: grouping the series of fuel pressure data into a plurality of fuel pressure data subsets, wherein each fuel pressure data subset is a contiguous sample of fuel pressure data and has a variance less than a predetermined fluctuation threshold, and wherein each pressure drop of the set of pressure drops is calculated based on two adjacent fuel pressure data subsets.

14. The method of claim 10, wherein, the series of fuel pressure data is sampled at a predetermined sampling frequency.

15. The method of claim 10, wherein, evaluating whether fuel injection drift occurred includes: determining a timing offset based on the received injection start command signal and the determined injection start timing.

16. The method of claim 15, further comprising: evaluating, by the one or more processors, whether a first fault criterion of the timing offset is satisfied; and in response to the first fault criterion being satisfied, flagging a fault code.

17. The method of claim 15, further comprising: determining a timing compensation using the timing offset.

18. The method of claim 17, further comprising: adjusting a timing of a next injection start command based on the timing compensation.

19. The method of claim 17, further comprising: evaluating, by the one or more processors, whether a second fault criterion of the timing compensation is satisfied; and in response to the second fault criterion being satisfied, flagging a fault code.

20. A method implemented by a computer system having one or more processors and memory, the method comprising: collecting a series of crank synchronized fuel pressure data; receiving an injection start command signal; calculating, by the one or more processors, a set of pressure drops using the series of crank synchronized fuel pressure data collected during a fuel flow cutoff period; comparing, by the one or more processors, the set of pressure drops to a predetermined threshold to identify a selected pressure drop that is greater than the predetermined threshold; determining, by the one or more processors, a measured injection start timing based on the selected pressure drop; and evaluating, by the one or more processors, whether fuel injection drift occurred based on the received injection start command signal and the measured injection start timing.

21. The method of claim 20, wherein, Each pressure drop in the set of pressure drops is calculated based on a first sample of crank synchronous fuel pressure data and a second sample of crank synchronous fuel pressure data, wherein the first sample of crank synchronous fuel pressure data is measured at a first time, and wherein the second sample of crank synchronous fuel pressure data is measured at a second time different from the first time.

22. The method of claim 20, further comprising: grouping the series of crank synchronous fuel pressure data into a plurality of subsets of fuel pressure data, wherein each subset of fuel pressure data is a continuous sampling of fuel pressure data and has a variance less than a predetermined fluctuation threshold, and wherein each pressure drop in the set of pressure drops is calculated based on two adjacent subsets of fuel pressure data.

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