System and method for detecting top dead center of a cylinder using a fuel injector as a pressure sensor

Abstract

A pressure-based piston top dead center ("TDC") position measurement system is disclosed that includes a fuel injector configured to inject fuel into a combustion chamber partially bounded by a piston, and a controller configured to control the fuel injector to cause fuel injection while the piston is in each of a plurality of different positions relative to TDC, while ensuring that fuel is provided to the fuel injector at a substantially constant pressure. The controller is further configured to estimate the pressure in the combustion chamber in response to each fuel injection, to fit a curve to the estimated pressures, and to determine a TDC position of the piston that is related to a maximum pressure on the curve.

Description

[0001] Cross-reference of related applications

[0002] Reference is made to Indian Patent Application No. 202111020242, filed on May 3, 2021, entitled “System and method for detecting cylinder TDC using a fuel injector as a pressure sensor”, which is incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] The disclosed embodiments generally relate to fuel injection control for internal combustion engines, and more specifically to improving injection initiation timing by using the fuel injector as a pressure sensor to detect the actual dead center (“TDC”) position of the piston. Background Technology

[0004] Internal combustion engines typically use fuel injectors to inject fuel into cylinders that house reciprocating pistons. For optimal combustion, which improves fuel efficiency and reduces emissions, precise timing of fuel injection relative to the piston position is crucial. This requires the controller that controls the injector's operation to know the piston's position as it travels between bottom dead center (“BDC”) and top dead center (“TDC”). In many engine systems, the piston position is indicated by output signals from one or more crankshaft sensors. Essentially, if the crankshaft's rotational position is known, the piston's position (attached to the crankshaft) is also known. However, as engines age, the crankshaft may shift, and the crank angle indicated by the crankshaft sensor may deviate by a few degrees from the actual crank angle. Therefore, a controller using an incorrect crank angle to determine the piston position may cause the injector to inject fuel too early or too late during the cycle (depending on the direction of the inaccuracy). This can lead to incomplete combustion, resulting in reduced fuel efficiency and increased emissions. Therefore, improvements are clearly needed in this area. Summary of the Invention

[0005] In one embodiment, this disclosure provides a system for determining the top dead center (“TDC”) position of a piston configured to reciprocate in an engine cylinder, comprising: a fuel injector fluidly coupled to a fuel accumulator and configured to inject fuel from the accumulator into the engine cylinder; a pressure sensor positioned to sense fuel pressure in the accumulator; and a controller in communication with the fuel injector and the pressure sensor, the controller being programmed to receive from the pressure sensor a signal indicating the sensed fuel pressure in the accumulator; to prevent fuel flow into the accumulator when the sensed pressure corresponds to a desired pressure; after preventing fuel flow into the accumulator, to cause the fuel injector to provide multiple fuel injections into the engine cylinder while the piston is in corresponding plurality of positions in the engine cylinder; to estimate corresponding plurality of cylinder pressures in response to the multiple fuel injections; to fit a curve to the plurality of estimated cylinder pressures; to determine a maximum pressure value on the curve; and to correlate the maximum pressure value with the true TDC position of the piston. In one aspect of this embodiment, the controller prevents fuel flow into the accumulator by cutting off operation of a fuel pump or closing at least one of an inlet metering valve. On the other hand, each of the multiple fuel injections lasts for a fixed period of time. In yet another aspect, the controller is programmed to estimate cylinder pressure by calculating the fuel flow rate through the fuel injector and using the calculated fuel flow rate to estimate cylinder pressure. In yet another aspect of this embodiment, the multiple fuel injections include a first fuel injection when the piston is in a first position in the engine cylinder, a second fuel injection when the piston is in a second position in the engine cylinder, and a third fuel injection when the piston is in a third position in the engine cylinder. In yet another aspect, the system determines the piston's TDC position during an engine maintenance event. In yet another aspect, the controller is programmed to provide multiple fuel injections to the engine cylinder during the non-ballistic region corresponding to the fuel injector's curve.

[0006] In another embodiment of this disclosure, a method is provided for determining the top dead center (“TDC”) position of a piston configured to reciprocate in an engine cylinder using a fuel injector, comprising: receiving a signal from a pressure sensor indicating fuel pressure sensed in an accumulator fluidly coupled to the fuel injector; responding to the sensed pressure corresponding to a desired pressure by preventing fuel flow into the accumulator; after preventing fuel flow into the accumulator, causing the fuel injector to provide multiple fuel injections to the engine cylinder while the piston is in corresponding multiple positions in the engine cylinder; estimating corresponding multiple cylinder pressures in response to the multiple fuel injections; fitting a curve to the multiple estimated cylinder pressures; determining a maximum pressure value on the curve; and associating the maximum pressure value with the true TDC position of the piston. In one aspect of this embodiment, preventing fuel flow into the accumulator includes at least one of cutting off operation of a fuel pump or closing an inlet metering valve. In another aspect, each of the multiple fuel injections lasts for a fixed period of time. In yet another aspect of this embodiment, estimating the corresponding multiple cylinder pressures includes calculating a fuel flow rate through the fuel injector and estimating the cylinder pressure using the calculated fuel flow rate. On the other hand, multiple fuel injections include a first fuel injection when the piston is in a first position in the engine cylinder, a second fuel injection when the piston is in a second position in the engine cylinder, and a third fuel injection when the piston is in a third position in the engine cylinder. In yet another aspect, the method is performed during engine maintenance events. In another aspect of this embodiment, causing the fuel injector to provide multiple fuel injections to the engine cylinder when the piston is in the corresponding multiple positions includes providing multiple fuel injections during the non-ballistic region corresponding to the fuel injector's curve.

[0007] In another embodiment of this disclosure, a pressure-based piston top dead center (“TDC”) position measurement system is provided, comprising: a fuel injector configured to inject fuel into a combustion chamber partially defined by a piston; and a controller configured to control the fuel injector to induce fuel injection at each of a plurality of different positions of the piston relative to the TDC, while ensuring fuel is supplied to the fuel injector at a substantially constant pressure; wherein the controller is further configured to estimate the pressure in the combustion chamber in response to each fuel injection, fit a curve to the estimated pressure, and determine the TDC position of the piston associated with the maximum pressure on the curve. In one aspect of this embodiment, fuel is supplied to the fuel injector at a substantially constant pressure via an accumulator, and the controller deactivates the input source of the accumulator before inducing fuel injection. In a variation of this aspect, the input source is either a fuel pump or an inlet metering valve. In another aspect, each fuel injection lasts for a fixed period of time. In yet another aspect of this embodiment, the controller is configured to estimate the pressure in the combustion chamber using a calculated fuel flow rate through the fuel injector. In yet another aspect, the plurality of different positions of the piston includes at least three different positions.

[0008] It should be understood that, in various embodiments, the foregoing concepts and the additional concepts discussed below can be arranged in any suitable combination. Furthermore, other advantages and novel features of this disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying drawings. Attached Figure Description

[0009] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in different figures may be indicated by similar reference numerals. For clarity, not every component in every figure is labeled. In the drawings:

[0010] Figure 1 This is a conceptual diagram of the fuel supply system for the engine cylinders;

[0011] Figure 2 It is a high-level concept diagram illustrating the forces applied to an object;

[0012] Figure 3A This is a conceptual perspective view of an internal combustion engine cylinder with the piston in the first position;

[0013] Figure 3B This is a conceptual perspective view of an internal combustion engine cylinder with the piston in the second position; and

[0014] Figure 4A This is a concept diagram of a fuel injector and cylinder with primary internal pressure.

[0015] Figure 4BThis is a concept diagram of a fuel injector and cylinder with a second internal pressure;

[0016] Figure 5 It is a flowchart depicting a method for determining the piston position according to the principles of this disclosure;

[0017] Figure 6 It is a diagram depicting the piston position measured during an engine cycle using the method according to this disclosure, and an accompanying conceptual cylinder diagram for each measurement;

[0018] Figure 7 It is a graph depicting actual pressure drop measurements at three different piston positions for three different types of fuel injectors according to this disclosure; and

[0019] Figure 8 It depicts the expected TDC position of the piston and its use. Figure 7 A chart comparing the actual TDC locations determined by pressure drop measurements. Detailed Implementation

[0020] Now for reference Figure 1 This diagram shows a high-level concept of the engine's fuel supply system. Many components are omitted for clarity. Typically, a fuel pump system (not shown) supplies fuel to a fuel accumulator, hereinafter referred to as the common rail 10. Typically, high-pressure fuel in the common rail 10 is directed via conduit 12 (only one shown) to multiple fuel injectors 14 (only one shown), which inject fuel 16 in a controlled manner into the corresponding combustion chamber 18 (only one shown) of the corresponding engine cylinder 20 (only one shown). The timing of the fuel injection is controlled by a controller 21, which can also monitor the fuel pressure in the common rail 10 by receiving pressure signals from a pressure sensor 23. A piston 22, connected to a connecting rod 24, reciprocates within the cylinder 20 between bottom dead center (“BDC”) and top dead center (“TDC”) positions. Depending on the type of engine, when piston 22 approaches TDC, the fuel / air mixture in combustion chamber 18 is ignited (compression ignition or spark ignition), and the explosion forces piston 22 downward, thereby transmitting power through connecting rod 24 to rotate crankshaft (not shown).

[0021] Controller 21 may be part of an engine control module or ECM. Alternatively, controller 21 may be a separate fuel injector controller. Controller 21 may include processor 25 and memory storage device 27. Processor 25 may be any suitable processor, such as a central processing unit (CPU), state machine, system-on-a-chip (SoC), etc. Memory storage device 27 may be any suitable memory, such as random access memory (RAM), read-only memory (ROM), flash memory, etc.

[0022] In some examples, components electrically coupled to controller 21 have one or more sensors (not shown) coupled thereto, which perform measurements indicating the current state of the components, such as pressure in common rail 10. In some examples, this data is stored in memory storage device 27 of controller 21, allowing controller 21 to use the stored data at any time without having to perform new measurements when needed. In some examples, the data in memory storage device 27 is updated frequently at a constant rate, i.e., new measurements are performed at predetermined intervals, thus maintaining the "freshness" of the data. In some examples, controller 21 has instructions stored in memory storage device 27, such as computational algorithms, which processor 25 uses to execute processes as disclosed herein.

[0023] Controller 21 may form part of a processing subsystem that includes one or more computing devices, processors or processing circuitry, and communication hardware having a non-transitory computer-readable storage medium. Controller 21 may be a single device or a distributed device, and the functionality of the controller may be executed by hardware and / or by processing instructions stored on a non-transitory machine-readable storage medium. Exemplary processors include application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), and microprocessors including firmware. Exemplary non-transitory computer-readable storage media include random access memory (RAM), read-only memory (ROM), flash memory, hard disk storage devices, electrically erasable programmable ROM (EEPROM), electrically programmable ROM (EPROM), disk storage devices, and any other medium that can be used to carry or store processing instructions and data structures and can be accessed by a general-purpose or special-purpose computer or other processing device.

[0024] Some operations of the controller 21 described herein include operations for interpreting and / or determining one or more parameters. The interpretation or determination utilized herein includes receiving values ​​by any method known in the art, including receiving values ​​from a data link, network communication, or input device; receiving electronic signals (e.g., voltage, frequency, current, or pulse-width modulation signals) indicating said values ​​(e.g., common rail 10 pressure); receiving computer-generated parameters indicating said values; reading said values ​​from a memory location on a non-transitory machine-readable storage medium; receiving said values ​​as runtime parameters by any means known in the art and / or by receiving values ​​of parameters that can be interpreted from them and / or by referring to default values ​​interpreted as values ​​of said parameters.

[0025] As used herein, the term "logic" includes software and / or firmware that executes on one or more programmable processors, application-specific integrated circuits, field-programmable gate arrays, digital signal processors, hardwired logic, or combinations thereof. Therefore, various logics may be implemented in any suitable manner and will remain in accordance with the embodiments disclosed herein, depending on the implementation.

[0026] Implementations of the techniques described herein can be carried out in any of a variety of ways. For example, implementations can be carried out using hardware, software, or a combination thereof. When implemented in software, the software code can execute on any suitable processor or set of processors, whether provided in a single computing device or distributed across multiple computing devices. Such processors can be implemented as integrated circuits, wherein one or more processors reside within integrated circuit components, including commercially available integrated circuit components known in the art as, for example, CPU chips, GPU chips, microprocessors, microcontrollers, or coprocessors. Alternatively, the processor can be implemented in custom circuitry, such as ASICs, or in semi-custom circuitry resulting from configuring programmable logic devices. As yet another alternative, the processor can be part of a larger circuit or semiconductor device, whether commercially available, semi-custom, or custom. As a specific example, some commercially available microprocessors have multiple cores, such that one or a subset of these cores can constitute the processor. However, the processor can be implemented using circuitry of any suitable format.

[0027] Furthermore, the various methods or processes outlined in this paper can be encoded as software that can be executed on one or more processors employing any of a variety of operating systems or platforms. Additionally, this software can be written using any of a variety of suitable programming languages ​​and / or programming or scripting tools, and can also be compiled into executable machine language code or intermediate code that executes on a framework or virtual machine.

[0028] In this regard, the disclosed embodiments may be embodied in a computer-readable storage medium (or multiple computer-readable media) encoded with one or more programs (e.g., a computer memory, one or more floppy disks, compact discs (CDs), optical discs, digital video optical discs (DVDs), magnetic tape, flash memory, field-programmable gate arrays or other semiconductor devices, or other tangible computer storage media), which, when executed on one or more computers or other processors, performs methods implementing various embodiments of the disclosure discussed herein. It is apparent from the foregoing examples that a computer-readable storage medium can retain information for a sufficient time to provide computer-executable instructions in a non-transitory form. Such one or more computer-readable storage media may be transportable, such that one or more programs stored thereon can be loaded onto one or more different computers or other processors to implement the various aspects of this disclosure as discussed above. As used herein, the term "computer-readable storage medium" covers only non-transitory computer-readable media that can be considered an article of manufacture (i.e., an article of manufacture) or a machine. Alternatively or additionally, this disclosure may be embodied in computer-readable media other than computer-readable storage media, such as propagating signals.

[0029] The terms “program” or “software” are used herein in a general sense to refer to any type of computer code or set of computer-executable instructions that can be used to program a computing device or other processor to implement the various aspects of this disclosure as discussed above. Furthermore, it should be understood that, according to one aspect of this disclosure, one or more computer programs that perform the methods of this disclosure when executed do not need to reside on a single computer or processor, but can be distributed in a modular manner across multiple different computers or processors to implement the various aspects of this disclosure.

[0030] Computer-executable instructions can take many forms, such as program modules executed by one or more computers or other devices. Typically, program modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. The functionality of program modules can usually be combined or distributed in various implementation schemes as needed.

[0031] Furthermore, data structures can be stored in any suitable form on a computer-readable medium. For simplicity, a data structure can be shown as having fields related by their location within the data structure. This relationship can also be achieved by allocating the storage of fields to locations in the computer-readable medium that convey the relationship between the fields. However, any suitable mechanism can be used to establish relationships between the information in the fields of a data structure, including by using pointers, labels, or other mechanisms that establish relationships between data elements.

[0032] According to the principles of the present disclosure, the fuel injector 14 can be used as a pressure sensor to detect the actual TDC position of the piston 22 in the cylinder 20. As further described below, the controller 21 cuts off fuel supply to the common rail 10, so that the pressure in the common rail 10 remains constant. Then, as the piston 22 moves through a reciprocating cycle, the controller 21 causes the injector 14 to inject fuel for a constant duration at least three times. By monitoring the pressure drop in the common rail 10 using the pressure sensor 23, the controller 21 can estimate the fuel pressure in the combustion chamber 18 for each injection. A curve is fitted to these data points, and the maximum value of the curve is identified as corresponding to the actual TDC position of the piston 22.

[0033] Reference is now made to Figure 2 , which illustrates the basic concept of the present disclosure. It is known that at a constant common rail pressure (P r1 ), if the injector 14 performs fuel injection for a fixed period of time, the amount of injected fuel differs between the two cases shown in Figure 2 , because P r1 <<P r2 . In the above case, if f f >F1, the object 12 is displaced as indicated by S1. Similarly, if f f >F2, the object 12 is displaced as indicated by S2. Furthermore, if F2>>F1, then S2<<S1. In the two cases shown in Figure 2 , the force f f in this concept is the same as the force applied to the object 12 from the left, while F1 and F2 are applied reaction forces both smaller than f f . Applying these principles to Figure 1 , f f corresponds to the fuel pressure in the common rail 10, F1 corresponds to the pressure in the combustion chamber 18 when the piston 22 is at BDC, and F2 corresponds to the pressure in the combustion chamber 18 when the piston 22 is at TDC.

[0034] In Figure 3A , Figure 3B , Figure 4A and Figure 4B , P r1 is the pressure inside the combustion chamber 18 of the cylinder 20 when the piston 22 is at BDC, and P r2 is the pressure inside the combustion chamber 18 of the cylinder 20 when the piston 22 is at TDC. Figure 4A and Figure 4B are simplified diagrams of Figure 3A and Figure 3B respectively. As shown in Figure 4A , when the piston 22 is at BDC, the pressure difference across the injector 14 is the rail pressure P r minus Pr1 Similarly, when piston 22 is at TDC, the pressure difference across injector 14 is equal to the orbital pressure P. r Subtract P r2 . Figure 4A The black shading in jet 14 indicates P r With P r1 The large pressure difference between them. Figure 4B The pressure difference is smaller (and therefore lighter) because, due to piston 22 being at TDC, P r2 higher.

[0035] According to this disclosure, by cutting off the fuel pump (not shown), the rail pressure can be kept substantially constant, thereby allowing the use of a crankshaft synchronization pressure signal to determine the pressure drop (ΔP) across the injector 14 for the corresponding fuel quantity injected. Therefore, ΔP1 and ΔP2 can be obtained for injections performed at different piston positions because different fuel injection quantities exist. In this way, the injector 14 can be used as a pressure sensor to obtain information about the actual TDC position of the piston 22, as further described below.

[0036] The flow rate of a known fluid through an orifice can be expressed as: (Equation 1), where A is the orifice area and V is the fluid velocity. Furthermore, according to Bernoulli's principle that the increase in fluid velocity and the decrease in static pressure occur simultaneously, it is known that... (Equation 2), where P is pressure, ρ is density, v is flow velocity, g is gravitational acceleration, and h is head. Since the coefficient ρgh is essentially the same on both sides of the ejector's pilot valve, therefore... Therefore, The variable with subscript 1 is on the common rail 10 side of injector 14, and the variable with subscript 2 is on the cylinder 20 side of injector 14. When the common rail 10 pressure P1 is much greater than the combustion chamber 18 pressure P2 (i.e., P1 >> P2), v2 is greater than v1. Therefore, when (P1 – P2) changes, (v2 – v1) also changes. Using the above understanding and Equation 1, it can be determined that as (P1 – P2) changes, the flow rate through the orifice of injector 14 changes, and therefore the amount of fuel injected changes.

[0037] By keeping the common rail 10 pressure (P1) constant (i.e., during pump shut-off), multiple measurements can be taken by setting P2 to different values. P2 is at different values ​​depending on the position of piston 22 during its cycle between BDC and TDC. The corresponding pressure drop measurement of the injection can then be correlated with P2, and therefore with the injection timing (i.e., the position of piston 22). As can be seen from the foregoing, when piston 22 is in TDC, pressure P2 is at its highest value during the cycle, and therefore the injection quantity and associated ΔP are lowest. Therefore, using three or more readings as described above, a curve can be fitted to the data to correlate ΔP with the injection timing.

[0038] Figure 5 The process for determining the TDC position of the piston according to the principles of the present invention is described. At step 30, fuel is pumped to the common rail 10 until the pressure (as sensed by the common rail pressure sensor 23) reaches the desired test pressure (“P”). 输入 When the common rail 10 reaches the desired test pressure, controller 21 shuts off the fuel pump and / or closes the inlet metering valve (not shown) at step 32 to prevent further fuel from entering the common rail 10. In this way, the rail pressure will remain substantially constant for each subsequent fuel injection, as described below. At step 34, controller 21 causes fuel injector 14 to inject fuel into combustion chamber 18 for a specific time period. As further described below, the fuel injection time at step 34 is the same for all fuel injection events at step 34, such that the area of ​​the orifice (“A”) of injector 14 is constant.

[0039] As described above, by maintaining the common rail 10 pressure (i.e., the input pressure P) 输入 With the orifice area A constant, the flow rate through the orifice of injector 14 will be proportional to the pressure at the orifice outlet, which corresponds to the pressure in combustion chamber 18 or cylinder pressure. Cylinder pressure is determined at step 36. At step 38, it is determined whether three or more cylinder pressure measurements have been performed for the current test cycle in the manner described above. If not, the process returns to step 34 for another fuel injection and returns to step 36 for another cylinder pressure determination. This process is repeated until at least three cylinder pressure measurements have been performed, at which point the process continues to step 40.

[0040] Based on the cylinder pressure, the pressure drop across the injector 14 (i.e., P) is used. 输入The fuel flow rate through injector 14 is estimated by the difference between the cylinder pressure and the pressure. It is known that the cylinder pressure is a function of piston movement and remains relatively constant for a mechanically sound cylinder 20. Therefore, the shape of the P-θ curve (i.e., the curve of cylinder pressure relative to piston position) also remains unchanged. Given the above cylinder pressure measurement or estimation, the P-θ curve can be fitted to the data by adjusting θ (i.e., the P-θ curve can be shifted along the x-axis to fit the pressure data). This process is performed at step 40. Finally, at step 42, the peak cylinder pressure is determined based on the fitted curve, and the corresponding piston position θ is determined as the true TDC position of piston 22.

[0041] As should be understood from the foregoing, the resolution of the described process for determining the true TDC position of piston 22 can be improved by using more than three fuel injections. Furthermore, the resolution can be improved by using lower speeds, lower track pressures (i.e., lower desired test pressures), and / or longer fuel injector 14 on-time. Additionally, higher resolution can be obtained by performing fuel injections during the non-ballistic region of the fuel injector profile. Finally, the above process can be repeated for multiple cylinders 20, and the results can be averaged to improve resolution.

[0042] Figure 6 The above is for reference. Figure 5 The process is described conceptually. Image A shows piston 22 at displacement position θ1, image B shows piston 22 at displacement position θ2, and image C shows piston 22 at displacement position θ3. As shown, when the first cylinder pressure measurement (“P”) is performed as described above... TP1 At the time of ( ), piston 22 approaches BDC in image A. More specifically, as piston 26 travels from BDC to TDC, it cuts off fuel to common rail 10, causing common rail pressure P r At the desired test pressure. Fuel is injected by injector 14 for a fixed period of time when piston 22 is in the position shown in image A. The track pressure drop caused by the injection allows for adjustments to the fuel flow rate (“Q”). TP1 The pressure P in the cylinder is then estimated as described above. The flow rate is then used to approximate the pressure P. TP1 This will generate test point 1 (“TP1”), as shown in the figure.

[0043] In the current cycle, corresponding to a later time in image B, when piston 22 is at position θ2, fuel is injected again within the same fixed time interval. As shown in the figure, the closer piston 22 is to TDC, the higher the cylinder pressure P. TP2 The higher the value, the better. This measurement corresponds to TP2. Similarly, when piston 22 is at position θ3, another fixed injection is performed, and the cylinder pressure P is increased. TP3 The measurement was TP3.

[0044] When calculating each of TP1, TP2, and TP3, a curve is fitted to the data points using any of a variety of curve fitting techniques. The curve is... Figure 6 The value is 50. Finally, the peak value of curve 50 is determined and can be calculated as the value corresponding to θ. TDC Or the true TDC of piston 22.

[0045] Now for reference Figure 7 The diagram shows the actual pressure drop data for three cylinders measured separately using three different sets of injection parameters. The first pressure drop bar, labeled 60A to 60C, corresponds to a common rail 10 pressure of 20 mg fuel injection and 500 bar. Pressure drop bar 60A is the first of the three injections, where the injection start (“SOI”) is at -5 degrees. Pressure drop bar 60B corresponds to an SOI of 0 degrees. Pressure drop bar 60C corresponds to an SOI of +5 degrees. It can be seen that the pressure drop represented by bars 60A to 60C is slightly different for each of the three injections.

[0046] Pressure drop bars 62A to 62C also correspond to 20mg fuel injection and a common rail 10 pressure of 500 bar. However, these measurements correspond to SOI at -25°C, 0°C, and +25°C, respectively. Pressure drop bars 64A to 64C correspond to higher levels of fuel injection and provide a larger pressure drop differential for the three measurements. More specifically, pressure drop bars 64A to 64C correspond to 40mg fuel injection, a common rail 10 pressure of 500 bar, and SOI at -20°C, 0°C, and +20°C.

[0047] Figure 8 Pressure drop bars 64A to 64C are reproduced to depict the operation of this disclosure. As shown, curve 66 is fitted to the pressure drop data represented by bars 64A to 64C. The peak of curve 66 corresponds to the actual TDC position of piston 22. Also as shown, in this example, curve 68 corresponds to expected data for cylinder 20 based on signals from, for example, one or more crankshaft sensors. In this example, the expected TDC position, marked 70, differs by several degrees from the actual or true TDC position determined using the principles of this disclosure.

[0048] In some embodiments, the methods and systems described above are performed as tests during planned maintenance events. Data obtained during this test can then be used in subsequent operations to improve fuel injection timing, thereby improving fuel efficiency and emissions. However, it should be understood that in other embodiments, measurements can be taken during runtime. Furthermore, while the principles of this disclosure are described in the context of providing a true TDC estimate, it should be understood that the same principles can be used to detect mechanical degradation (e.g., compression loss). Reference data can be collected at the end of the production line. Degradation of injector opening time is then corrected for based on non-mechanical data. Cylinder pressure can be estimated using the same non-ballistic region on-time. Mechanical degradation can be detected by comparing the calculated peak pressure with the reference data at the end of the production line.

[0049] 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 the described embodiments. Therefore, these embodiments are not limited to the details previously shown and described, but also include all such changes and modifications.

[0050] Furthermore, the connecting lines shown in the various figures included herein are intended to represent exemplary functional relationships and / or physical connections between various elements. It should be noted that many alternative or additional functional relationships or physical connections may exist in a real system. However, the benefits, advantages, problem solutions, and any elements that make any benefit, advantage, or solution appear or become more significant should not be construed as critical, essential, or necessary features or elements. Therefore, the scope is limited only by the appended claims, where references to singular elements are not intended to mean "one and only one," but rather "one or more," unless explicitly stated otherwise. Furthermore, where phrases like "at least one of A, B, or C" are used in the claims, it is contemplated that such phrases mean that A may exist alone in an embodiment, B may exist alone in an embodiment, C may exist alone in an embodiment, or any combination of elements A, B, or C may exist in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

[0051] In the detailed description herein, references such as "an embodiment," "an embodiment," and "an exemplary embodiment" indicate that the described embodiment may include a particular feature, structure, or characteristic; however, each embodiment may not necessarily include the stated particular feature, structure, or characteristic. Furthermore, such wording does not necessarily refer to the same embodiment. Moreover, when a particular feature, structure, or characteristic is described in connection with an embodiment, it should be assumed that, whether explicitly described or not, causing such feature, structure, or characteristic to work in combination with other embodiments is within the knowledge of one skilled in the art who benefits from this disclosure. After reading this specification, those skilled in the art will understand how to implement this disclosure in alternative embodiments.

[0052] Furthermore, none of the elements, components, or method steps in this disclosure are intended to be exclusive to the public, regardless of whether they are expressly recited in the claims. No element of any claim herein shall be construed under the provisions of 35 U.S.SC §112(f) unless the element is expressly recited using the phrase “means for…”. As used herein, the terms “comprising,” “including,” or any other variation thereof are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but may also include other elements not expressly listed or inherent to such a process, method, article, or apparatus.

[0053] While this teaching has been described in conjunction with various embodiments and examples, it is not intended to limit this teaching to such embodiments or examples. Rather, as those skilled in the art will understand, this teaching encompasses various alternatives, modifications, and equivalents. Therefore, the foregoing description and figures are by way of example only.

Claims

1. A system for determining the top dead center ("TDC") position of a piston configured to reciprocate in an engine cylinder, comprising: A fuel injector fluidly connected to a fuel accumulator and configured to inject fuel from the fuel accumulator into the engine cylinder; A pressure sensor, the pressure sensor being positioned to sense the fuel pressure in the fuel accumulator; as well as A controller, which communicates with the fuel injector and the pressure sensor, is programmed to receive from the pressure sensor a signal indicating the sensed fuel pressure in the fuel accumulator. When the sensed pressure corresponds to the desired pressure, fuel flow into the fuel accumulator is prevented. After preventing fuel from flowing into the fuel accumulator, the fuel injector delivers multiple fuel injections to the engine cylinder when the piston is in corresponding positions in the engine cylinder. In response to the multiple fuel injections, the corresponding cylinder pressures are estimated. The curve is fitted to the previously estimated corresponding cylinder pressures. Determine the maximum pressure value on the curve, and The maximum pressure value is correlated with the actual TDC position of the piston.

2. The system of claim 1, wherein the controller prevents fuel from flowing into the fuel accumulator by cutting off operation of the fuel pump or closing at least one of the inlet metering valves.

3. The system of claim 1, wherein each of the multiple fuel injections lasts for a fixed period of time.

4. The system of claim 1, wherein the controller is programmed to estimate the cylinder pressure by calculating the fuel flow rate through the fuel injector and using the calculated fuel flow rate to estimate the cylinder pressure.

5. The system of claim 1, wherein the multiple fuel injections include a first fuel injection when the piston is in a first position in the engine cylinder, a second fuel injection when the piston is in a second position in the engine cylinder, and a third fuel injection when the piston is in a third position in the engine cylinder.

6. The system of claim 1, wherein the system determines the TDC position of the piston during an engine maintenance event.

7. The system of any one of claims 1 to 6, wherein the controller is programmed to provide the multiple fuel injections to the engine cylinder during a non-ballistic region corresponding to the curve of the fuel injector.

8. A method for determining the top dead center ("TDC") position of a piston configured to reciprocate in an engine cylinder using a fuel injector, comprising: A signal is received from a pressure sensor, the signal indicating the fuel pressure sensed in an accumulator fluidly connected to the fuel injector; The sensed pressure corresponding to the desired pressure is responded to by preventing fuel from flowing into the accumulator; After preventing fuel from flowing into the accumulator, when the piston is in one of the corresponding multiple positions in the engine cylinder, the fuel injector provides multiple fuel injections to the engine cylinder. In response to the multiple fuel injections, estimate the corresponding cylinder pressures; Estimate the multiple accumulator pressure drop measurements corresponding to the corresponding multiple cylinder pressures; The curve is fitted to the previously estimated values ​​of the multiple accumulator voltage drop measurements; Determine the maximum pressure value on the curve; as well as The maximum pressure value is correlated with the actual TDC position of the piston.

9. The method of claim 8, wherein preventing fuel from flowing into the accumulator comprises at least one of shutting off the operation of the fuel pump or closing the inlet metering valve.

10. The method of claim 8, wherein each of the multiple fuel injections lasts for a fixed period of time.

11. The method of claim 8, wherein estimating the corresponding plurality of cylinder pressures includes calculating the fuel flow rate through the fuel injector and using the calculated fuel flow rate to estimate the cylinder pressure.

12. The method of claim 8, wherein the multiple fuel injections include a first fuel injection when the piston is in a first position in the engine cylinder, a second fuel injection when the piston is in a second position in the engine cylinder, and a third fuel injection when the piston is in a third position in the engine cylinder.

13. The method of claim 8, wherein the method is performed during an engine maintenance event.

14. The method of any one of claims 8 to 13, wherein when the piston is in corresponding plurality of positions in the engine cylinder, the fuel injector provides multiple fuel injections to the engine cylinder, including providing the multiple fuel injections during a non-ballistic region corresponding to the curve of the fuel injector.

15. A pressure-based piston top dead center ("TDC") position measurement system, comprising: A fuel injector configured to inject fuel into a combustion chamber partially defined by a piston; as well as A controller configured to control the fuel injector to induce fuel injection when the piston is in each of a plurality of different positions relative to the TDC, while ensuring that fuel is supplied to the fuel injector at a substantially constant pressure; The controller is further configured to estimate the pressure in the combustion chamber for each fuel injection, fit a curve to the already estimated pressure, and determine the TDC position of the piston associated with the maximum pressure on the curve.

16. The system of claim 15, wherein the fuel is supplied to the fuel injector at a substantially constant pressure via an accumulator, and the controller deactivates the input source of the accumulator before inducing the fuel injection.

17. The system of claim 16, wherein the input source is either a fuel pump or an inlet metering valve.

18. The system of any one of claims 15 to 17, wherein each fuel injection lasts for a fixed period of time.

19. The system of any one of claims 15 to 17, wherein the controller is configured to estimate the pressure in the combustion chamber using a calculated fuel flow rate through the fuel injector.

20. The system of any one of claims 15 to 17, wherein the plurality of different positions of the piston includes at least three different positions.

Images