Method and system for regulating fuel supply to an engine cylinder

Abstract

The present application relates to methods and systems for regulating fuel supply to engine cylinders. Methods and systems are provided for enabling transfer functions of direct injectors and port injectors, both supplying fuel to an engine cylinder, to be accurately learned. During selected conditions, the fraction of fuel injected directly can be actively changed from a target fraction to one of an upper and lower limit of the direct injectors to provide a measurable air-fuel ratio error. Fuel supply errors of the different fuel injectors are then learned based on the measured air-fuel ratio error relative to the actively changed fuel fraction.

Description

Technical Field

[0001] This invention relates to a system and method for supplying fuel to the cylinders of an internal combustion engine. Background Technology

[0002] Port fuel direct injection (PFDI) engines can advantageously utilize both port fuel injection and direct injection. For example, under higher engine loads, direct fuel injection can be used to inject fuel into the engine, thereby improving engine performance (e.g., increasing available torque and fuel economy). Under lower engine loads, port fuel injection can be used to inject fuel into the engine, thereby reducing vehicle emissions, noise, vibration, and discomfort (NVH), as well as wear on direct injection system components (e.g., injectors, DI pump solenoids, etc.).

[0003] Furthermore, to provide the desired catalytic converter performance and reduced emissions, the air-fuel ratio in a PFDI engine can be maintained at a desired level (e.g., stoichiometry). Conventional feedback air-fuel ratio control may involve monitoring exhaust oxygen concentration via one or more exhaust sensors and providing feedback on air-fuel ratio errors in the engine, allowing continuous calibration of the delivered fuel quantity based on feedback from the exhaust sensors. In a PFDI engine, air-fuel ratio errors can be attributed to components of the fuel injection system (such as components of the port fuel injection system and / or the direct fuel injection system). By identifying the contribution of fuel supply error to each fuel injection system (e.g., the port fuel injection system or the direct fuel injection system), appropriate fuel supply calibration can be provided, and therefore any deviation in the air-fuel ratio can be quickly calibrated. This enables improvements in catalytic converter efficiency and engine performance.

[0004] A variety of methods can be used to identify the source of fuel supply errors in a PFDI system (e.g., port fuel injection or direct fuel injection). Surnilla et al., in US 9,631,573, illustrate an example method that provides a non-intrusive fuel system calibration routine to identify fuel supply errors in each of two fuel injection systems. This method determines the fuel supply error based on the ratio of the change in air-fuel ratio under different engine operating conditions to the change in the fuel fraction of each fuel injection system. Furthermore, the fuel supply error of one fuel supply system can be distinguished from that of the other by allocating different portions of the air-fuel ratio error to each fuel supply system based on the corresponding fuel fraction delivered by the fuel supply system.

[0005] The inventors of this paper have recognized the potential problems with the above-described method. Specifically, Surnilla's method is only able to detect and distinguish the air-fuel ratio error associated with each fuel injection system when the variation in the fuel share injected by each fuel injection system is sufficiently large and / or when the mass of fuel injected is considerably large. With lower injected fuel masses and smaller fuel share variations, even if the total air-fuel ratio error is determined, it may be difficult to resolve the error contribution of each injection system. Even if the error is resolved, the confidence factor of the learned error may be low. For example, a more accurate error estimate can be achieved when the fuel share ratio of the direct injection system to the port injection system is 20%:80% compared to 40%:60%. Furthermore, since fuel supply errors are identified non-invasively, there may be limited injection events where the variation in injected fuel mass and / or fuel share is sufficient to provide reliable test results. If the variation in injected fuel mass and / or fuel share is invasively altered to provide the desired test conditions, vehicle driving performance can be affected. As yet another example, the purging of the fuel vapor canister of the fuel system can be delayed until calibration is complete to reduce the air-fuel ratio offset caused by purging. Therefore, if the canister is not purged frequently, it may become unable to hold further fuel vapors, leading to emissions degradation. This problem can be exacerbated in hybrid vehicles where shorter engine operating times already limit canister purging opportunities. Summary of the Invention

[0006] The inventors have recognized that measurable variations in the air-fuel ratio can be provided by intrusively adjusting the fuel share supplied by each fuel injection system, while maintaining the fuel share within a selected upper and lower limit for each injection system based on engine operating conditions. By intrusively adjusting the fuel share of each fuel injection system, sufficient variation in the fuel share of each fuel injector can be provided, thereby enabling reliable detection and differentiation of air-fuel ratio errors via a non-intrusive calibration routine to be implemented. In one example, fuel supply errors in a PFDI system can be known through a method for an engine, comprising: delivering fuel in the cylinder cycle via direct injectors and port injectors; increasing the direct injection fuel share to the upper limit when the current share is closer to the lower limit than the upper limit; and decreasing a first fuel share supplied by the direct injectors to the lower limit when the current share is closer to the upper limit than the lower limit. In this way, the source of fuel supply errors can be reliably identified and addressed in a timely manner.

[0007] As an example, the initial fuel share value can be learned and adjusted in a timely manner via a non-intrusive fuel calibration routine. An invasive routine can be initiated in response to a predetermined amount of time elapsed since the last (non-intrusive) fuel adjustment. Here, for example, the upper and lower limits of the fuel share for each fuel injection system can be determined based on engine speed-load conditions. The upper and lower limits can be selected to allow for significant changes in fuel share without degrading vehicle driving performance. The controller can then compare the previously adjusted fuel share value with the upper and lower limits and select the fuel share to apply to the current adjustment based on the distance of the previously adjusted fuel share value from each of the corresponding upper and lower limits. For example, if it is determined that the previously adjusted fuel share value for the direct injection system is further away from the upper limit, then the upper limit fuel share value can be applied to the direct injection system during the current adjustment. Otherwise, if it is determined that the previously adjusted fuel share value for the direct injection system is further away from the lower limit, then the lower limit fuel share value can be invasively applied to the direct injection system during the current adjustment. In one example, the previous non-intrusive adjustment may have been performed with 40% direct injection and 60% port injection. During the subsequent invasive adjustment, the upper and lower limits of direct injection can be determined to be 80% and 20%, respectively. Therefore, the invasive adjustment can be performed with 80% direct injection and 20% port injection, and the previously known air-fuel ratio error can be updated based on the most recently known air-fuel ratio error.

[0008] In this way, by adjusting the fuel share applied to each fuel injection system based on dynamically selected upper and lower limits, significant variations in fuel share can be provided by each injection system. The technical effect of actively providing significant variations constrained by predetermined limits is that fuel system calibration can be implemented, where fuel supply errors can be known with high confidence. Furthermore, by performing intrusive fuel share adjustments only when fuel trimming is required, the engine can operate at the desired / pre-calibrated fuel share value as close as possible to its intended value. Additionally, the amount of time required for fuel trimming can be reduced without compromising accuracy, enabling more frequent fuel tank purging. Improved fuel tank purging frequency reduces emissions.

[0009] It should be understood that the above overview is provided to introduce some concepts in a simplified form, which are further described in the specific embodiments. This is not intended to identify the key or essential features of the claimed subject matter, the scope of which is uniquely defined by the appended claims. Furthermore, the claimed subject matter is not limited to embodiments that address any shortcomings mentioned above or in any part of this disclosure. Attached Figure Description

[0010] Figure 1 A schematic diagram of the engine system is shown.

[0011] Figure 2 It shows that it is connected to Figure 1 A schematic diagram of the dual-fuel injector system of the engine system.

[0012] Figure 3A An example table of adapted fuel multipliers is shown.

[0013] Figure 3B A graphical representation of the error contributions of inlet-injected fuel and directly injected fuel, determined via a non-invasive calibration routine, is shown.

[0014] Figure 4 This is a high-level flowchart illustrating an example routine for performing fuel system calibration in a dual-fuel injector system.

[0015] Figure 5 This is a flowchart demonstrating an example routine for adaptively learning fuel supply errors in a dual-fuel injector system.

[0016] Figure 6 This is a flowchart illustrating an example routine for invasively adjusting the fuel share of an injector in a dual-fuel injector system.

[0017] Figure 7 A diagram illustrating an example fuel system calibration in a dual-fuel injector system is shown. Detailed Implementation

[0018] The following description pertains to the calibration of systems using dual-fuel injectors (such as...) Figure 2 Fuel system) of engines (such as Figure 1 Systems and methods for the fuel system in an engine system. The controller can be configured to execute control routines (such as...) Figures 4 to 6 (Example routines) thereby identifying and distinguishing the sources of fuel supply errors between the engine's direct injectors and port injectors by performing non-invasive and invasive fuel system calibrations in a timely manner. The identified fuel supply errors can be used to update the adaptive fuel multiplier table, such as... Figure 3A The table. The initial error set can be obtained in a timely manner via non-intrusive routines, such as... Figure 3B As shown. The error can then be updated via an intrusive routine. Figure 7 The illustrations here demonstrate predictive fuel system calibration, where fuel supply errors are determined based on non-invasive and invasive calibration routines. In this way, fuel supply errors caused by different fuel injection systems can be identified and differentiated, thereby improving fuel injection accuracy and reducing air-fuel ratio errors.

[0019] Figure 1A schematic diagram of a spark-ignition internal combustion engine 10 with a dual-injector system is shown, wherein the engine 10 is configured with both direct fuel injection and port fuel injection. The engine 10 can be included in a vehicle 5 that can be configured for propulsion on a road. The engine 10 includes multiple cylinders, one of which, cylinder 30 (also referred to as combustion chamber 30), is in… Figure 1 As shown in the figure. The cylinder 30 of the engine 10 is shown to include a combustion chamber wall 32, in which a piston 36 is located and connected to a crankshaft 40. A starter motor (not shown) may be coupled to the crankshaft 40 via a flywheel (not shown), or alternatively, direct engine starting may be used.

[0020] Combustion chamber 30 is shown communicating with intake manifold 43 and exhaust manifold 48 via intake valve 52 and exhaust valve 54, respectively. In addition, intake manifold 43 is shown to have throttle valve 64, which adjusts the position of throttle plate 61 to control airflow from intake passage 42.

[0021] Intake valve 52 can be operated by controller 12 via actuator 152. Similarly, exhaust valve 54 can be activated by controller 12 via actuator 154. During certain conditions, controller 12 can change the signals provided to actuators 152 and 154 to control the opening and closing of the corresponding intake and exhaust valves. The positions of intake valve 52 and exhaust valve 54 can be determined by corresponding valve position sensors (not shown). The valve actuators can be electric valve actuated, cam actuated, or a combination thereof. Intake and exhaust valve timing can be controlled simultaneously, or any of the following can be used: variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing. Each cam actuation system may include one or more cams and can utilize one or more of a cam profile change (CPS) system, variable cam timing (VCT) system, variable valve timing (VVT) system, and / or variable valve lift (VVL) system operable by controller 12 to change valve operation. For example, cylinder 30 may alternatively include an intake valve controlled by electric valve actuation and an exhaust valve controlled by cam actuation including CPS and / or VCT. In other embodiments, the intake and exhaust valves may be controlled by common valve actuators or actuation systems, or by variable valve timing actuators or actuation systems.

[0022] In another embodiment, four valves per cylinder can be used. In yet another example, two intake valves and one exhaust valve per cylinder can be used.

[0023] Combustion chamber 30 can have a compression ratio, which is the volume ratio of piston 36 when it is at the bottom center to when it is at the top center. In one example, the compression ratio can be approximately 9:1. However, in some examples using different fuels, the compression ratio can be increased. For example, the compression ratio can be between 10:1 and 11:1, or between 11:1 and 12:1, or greater.

[0024] In some embodiments, each cylinder of the engine 10 may be configured with one or more fuel injectors for supplying fuel to the cylinder. For example... Figure 1 As shown, cylinder 30 includes two fuel injectors 66 and 67. Fuel injector 67 is shown as being directly coupled to combustion chamber 30 to deliver injected fuel directly therein in proportion to the pulse width of the signal DFPW received from controller 12 via electronic actuator 68. In this way, direct fuel injector 67 provides so-called direct injection of fuel into combustion chamber 30 (hereinafter referred to as "DI"). Although Figure 1 Injector 67 is shown as a side injector, but it can also be located on top of the piston, such as near spark plug 91. This location improves mixing and combustion due to the lower volatility of some alcohol-based fuels. Alternatively, the injector can be located at the top and near the intake valve to improve mixing.

[0025] Fuel injector 66 is shown arranged in intake manifold 43, a configuration that provides so-called fuel-to-intake port injection (hereinafter referred to as "PFI"), which delivers fuel into the intake port upstream of cylinder 30 instead of directly into cylinder 30. The intake port fuel injector 66 delivers the injected fuel in proportion to the pulse width of the signal PFPW received from controller 12 via electronic actuator 69.

[0026] Fuel can be transported through a fuel tank, fuel pump, and fuel rail (in...) Figure 2 The high-pressure fuel system 200 (described in detail below) is supplied to fuel injectors 66 and 67. Further, as... Figure 2 As shown, the fuel tank and the rail may each have a pressure transducer that provides signals to the controller 12.

[0027] In one example, exhaust gas flows through exhaust manifold 48 into emission control device 70, which may include multiple catalyst blocks. In another example, multiple emission control devices may be used, each having multiple blocks. In one example, emission control device 70 may be a three-way catalyst.

[0028] An exhaust sensor 76 is shown coupled to the exhaust manifold 48 upstream of the emission control unit 70 (wherein sensor 76 can correspond to a variety of different sensors). For example, sensor 76 can be any of many known sensors used to provide an indication of the exhaust air-fuel ratio, such as a linear oxygen sensor, UEGO, dual-state oxygen sensor, EGO, HEGO, or HC or CO sensor. In this specific example, sensor 76 is a dual-state oxygen sensor that provides the signal EGO to controller 12, which converts the signal EGO into a dual-state signal EGOS. A high voltage state of signal EGOS indicates that the exhaust is stoichiometrically rich and a low voltage state of signal EGOS indicates that the exhaust is stoichiometrically lean. Signal EGOS can be used to help maintain the average air / fuel ratio at stoichiometric levels during stoichiometric uniform operating modes during feedback air / fuel control. A single exhaust sensor can serve 1, 2, 3, 4, 5, or other numbers of cylinders. In one example, sensor 76 can measure the oxygen content in the exhaust oxygen sensor in the pre-catalytic converter and provide feedback on the air-fuel ratio error in the engine to controller 12.

[0029] The distributorless ignition system 88 responds to the spark advance signal SA from the controller 12 and provides an ignition spark to the combustion chamber 30 via the spark plug 91.

[0030] The controller 12 can operate the combustion chamber 30 in various combustion modes (including homogeneous air / fuel mode and stratified air / fuel mode) by controlling injection timing, injection quantity, spray pattern, etc. Furthermore, a combination of stratified and homogeneous mixtures can be formed in the combustion chamber. In one example, stratification can be formed by operating injector 66 during the compression stroke. In another example, a homogeneous mixture can be formed by operating one or both of injectors 66 and 67 during the intake stroke (which may be open valve injection). In yet another example, a homogeneous mixture can be formed by operating one or both of injectors 66 and 67 before the intake stroke (which may be closed valve injection). In other examples, multiple injections from one or both of injectors 66 and 67 can be used during one or more strokes (e.g., intake, compression, exhaust, etc.). Even further examples, as described below, could involve using different injection timing and mixture patterns under different conditions.

[0031] The controller 12 can control the amount of fuel delivered by the fuel injectors 66 and 67, such that the homogeneous, stratified, or combined homogeneous / stratified air / fuel mixture in the combustion chamber 30 can be selected as stoichiometric, stoichiometrically rich, or stoichiometrically lean. For example, the amount of fuel delivered can be changed by adjusting the pulse width control signal commanded by the controller to each fuel injector actuator, the control signal being selected based on engine speed-load conditions.

[0032] Controller 12 in Figure 1 The controller 12 is shown as a conventional microcomputer, including a central processing unit (CPU) 102, input / output (I / O) ports 104, read-only memory (ROM) 106, random access memory (RAM) 108, keep-alive memory (KAM) 110, and a conventional data bus. The controller 12 is shown receiving various signals from sensors coupled to the engine 10, including, in addition to those previously discussed: a measurement of the introduced mass airflow (MAF) from the mass airflow sensor 118; the engine coolant temperature (ECT) from the temperature sensor 112 coupled to the cooling sleeve 114; the surface ignition sensing signal (PIP) from the Hall effect sensor 38 coupled to the crankshaft 40; the throttle position (TP) from the throttle position sensor 58; and the absolute manifold pressure signal (MAP) from the sensor 122. The engine speed signal (RPM) is generated by the controller 12 from the PIP signal in a conventional manner, and the manifold pressure signal (MAP) from the manifold pressure sensor provides an indication of vacuum or pressure in the intake manifold. During stoichiometric operations, the sensor is able to provide an indication of engine load. Furthermore, the sensor, along with engine speed, is able to provide an estimate of the charge (including air) directed to the cylinders. In one example, sensor 38, also used as an engine speed sensor, produces a predetermined number of equally spaced pulses with each rotation of the crankshaft.

[0033] In some examples, the engine can be coupled to an electric motor / battery system in a hybrid vehicle. Furthermore, in some examples, other engine configurations may be used, such as a diesel engine with multiple fuel injectors. Furthermore, the controller 12 can communicate conditions such as component degradation to the lights, or alternatively to the display panel 171.

[0034] As mentioned above, Figure 1 Only one cylinder of a multi-cylinder engine is shown, and each cylinder has its own intake / exhaust valve assembly, fuel injector, spark plug, etc. Furthermore, in the example embodiment described herein, the engine can be coupled to a starter motor (not shown) for starting the engine. For example, the starter motor can be powered when the driver turns the key in the ignition switch to the drive lever. The starter motor disengages after the engine has started, for example, after the engine 10 reaches a predetermined speed after a predetermined time. Further, in the disclosed embodiment, an exhaust gas recirculation (EGR) system can be used to deliver a desired portion of the exhaust gas from the exhaust manifold 48 to the intake manifold 43 via an EGR valve (not shown). Alternatively, a portion of the combustion gases can be retained in the combustion chamber by controlling the exhaust valve timing.

[0035] In some examples, vehicle 5 may be a hybrid vehicle having multiple torque sources available for one or more wheels 55. In other examples, vehicle 5 may be a conventional vehicle with only an engine or an electric vehicle with only one or more electric motors. In the example shown, vehicle 5 includes an engine 10 and an electric motor 152. The electric motor 152 may be a motor or a motor / generator (M / G). When one or more clutches 56 are engaged, the crankshaft 40 of engine 10 and the electric motor 152 are connected to the wheels 55 via a transmission 154. In the depicted example, a first clutch 56 is disposed between the crankshaft 40 and the electric motor 152, and a second clutch 56 is disposed between the electric motor 152 and the transmission 154. Controller 12 may send signals to the actuators of each clutch 56 to engage or disengage the clutch, thereby connecting or disconnecting the crankshaft 40 from the electric motor 152 and components connected to the electric motor 152, and / or connecting or disconnecting the electric motor 152 from the transmission 154 and components connected to the transmission 154. The transmission 154 may be a gearbox, a planetary gear system, or other type of transmission. The powertrain can be configured in various ways, including in parallel, series, or series-parallel hybrid vehicles.

[0036] Electric motor 152 receives power from traction battery 158 to provide torque to wheel 55. Electric motor 152 can also operate as a generator to provide power, for example, to charge battery 158 during braking operations.

[0037] Controller 12 receives from Figure 1 The system uses signals from various sensors and employs methods based on the received signals and instructions stored in the controller's memory. Figure 1 Various actuators are used to regulate engine operation. For example, based on the engine speed signal received from the crankshaft speed sensor, the controller can select a pulse width signal to command each of the fuel injectors 66 and 67.

[0038] Figure 2 A dual-injector single-fuel system 200 with high-pressure and low-pressure fuel rail systems is shown. The fuel system 200 can be coupled to an engine, such as... Figure 1 Engine 10. The previously described components can be similarly numbered.

[0039] Fuel system 200 may include a fuel tank 201 and a low-pressure or booster pump 202, which supplies fuel from fuel tank 201 to high-pressure fuel pump 206 via low-pressure passage 204. Booster pump 202 also supplies fuel at a lower pressure to low-pressure fuel rail 211 via low-pressure passage 208. Therefore, low-pressure fuel rail 211 is specifically coupled to booster pump 202. Fuel rail 211 supplies fuel to intake injectors 215a, 215b, 215c, and 215d. High-pressure fuel pump 206 supplies pressurized fuel to high-pressure fuel rail 213 via high-pressure passage 210. Therefore, high-pressure fuel rail 213 is coupled to each of the high-pressure pump (206) and booster pump (202).

[0040] High-pressure fuel rail 213 supplies pressurized fuel to fuel injectors 214a, 214b, 214c, and 214d. Fuel rail pressures in fuel rails 211 and 213 can be monitored by pressure sensors 220 and 217, respectively. In one example, booster pump 202 can be an electronic non-return pump system capable of intermittent operation in pulse mode. Engine block 216 can be coupled to intake passage 222 with intake air throttle valve 224.

[0041] The booster pump 202 may be equipped with a check valve 203, which allows the low-pressure passages 204 and 208 (or alternative compliant elements) to maintain pressure while the booster pump 202 has its input energy reduced to the point where the flow through the check valve 203 is stopped.

[0042] Direct fuel injectors 214a to 214d and port fuel injectors 215a to 215d inject fuel into engine cylinders 212a, 212b, 212c, and 212d located in engine block 216, respectively. Therefore, each cylinder can receive fuel from two injectors, which are positioned in different locations. For example, as in the earlier... Figure 1 As discussed herein, one injector can be configured as a direct injector, which is connected to supply fuel directly to the combustion chamber, while the other injector is configured as an intake manifold injector, which is connected to the intake manifold and delivers fuel to the intake passage upstream of the intake valve. Therefore, cylinder 212a receives fuel from both the intake manifold injector 215a and the direct injector 214a, while cylinder 212b receives fuel from both the intake manifold injector 215b and the direct injector 214b.

[0043] Similar to Figure 1The controller 12 can receive fuel pressure signals from fuel pressure sensors 220 and 217, which are respectively connected to fuel rails 211 and 213. Fuel rails 211 and 213 may also include one or more temperature sensors for sensing fuel temperature within the fuel rails. The controller 12 can also control the operation of intake and / or exhaust valves or throttle valves, engine cooling fan, spark ignition, injectors, and fuel pumps 202 and 206 to control engine operating conditions. The controller 12 can further receive a throttle opening angle signal indicating the intake air throttle position via throttle position sensor 238.

[0044] like Figure 2 As shown, fuel pumps 202 and 206 can be controlled by controller 12. Controller 12 can adjust the amount or rate of fuel fed into fuel rails 211 and 213 by the booster pump 202 and the high-pressure fuel pump 206 via corresponding fuel pump controls (not shown). By shutting down pumps 202 and 206, controller 12 can also completely stop the fuel supply to fuel rails 211 and 213.

[0045] like Figure 2 As shown, injectors 214a to 214d and 215a to 215d can be operatively coupled to and controlled by controller 12. The amount of fuel injected from each injector and the injection timing can be determined by controller 12 from an engine map stored in controller 12 based on engine speed and / or intake throttle angle or engine load. Each injector can be controlled via a solenoid valve coupled to the injector (not shown).

[0046] During a single combustion cycle of a cylinder, both injectors can deliver fuel to the cylinder. For example, each injector can deliver a portion of the total fuel injected for combustion in cylinder 30. Furthermore, the distribution and / or relative amount of fuel delivered from each injector can vary with operating conditions such as engine load and engine speed. Intake port injection fuel can be delivered during intake valve opening events, intake valve closing events (e.g., substantially before the intake stroke), and during intake valve opening and closing operations. Similarly, direct injection fuel can be delivered during the intake stroke and partly during the preceding exhaust stroke, for example, during the intake stroke and partly during the compression stroke. Thus, even for a single combustion event, the injected fuel can be injected from the intake port injector and the direct injector at different timings. Furthermore, for a single combustion event, multiple injections of the delivered fuel can be performed in each cycle. Multiple injections can be performed during the compression stroke, the intake stroke, or any suitable combination thereof.

[0047] When determining the amount of fuel to be delivered to the cylinder, controller 12 can be configured to determine a short-term air-fuel ratio correction factor, Lambse, to adjust fuel delivery to compensate for rich or lean fuel supply errors, such as those detected by exhaust sensor 76. Lambse is typically the integral of the output signal from exhaust sensor 76, and is an average uniform value when cylinder 30 operates in stoichiometric mode and there is no steady-state air-fuel ratio error or offset. For typical operating examples, Lambse can range from 0.75 to 1.25.

[0048] The long-term air-fuel ratio adaptive correction factor Kamrf (also referred to herein as the adaptive fuel multiplier) can be used to store fuel calculation correction values ​​in an adaptive fuel multiplier table based on engine speed and load or air charging temperature. These correction values ​​are used to adjust fuel delivery to cylinder 30, as described below:

[0049]

[0050] Where Fuel_mass is the mass of fuel delivered to the engine, air_mass is the mass of air introduced into the engine cylinders, Kamrf is the adjusted fuel multiplier, stoich_afr is the stoichiometric air-fuel ratio for the fuel supplied to the engine, and Lambse is a short-term air-fuel ratio correction factor used to adjust fuel delivery to compensate for rich or lean fuel supply errors, such as those detected by exhaust sensor 76. Specifically, Lambse is the fuel correction multiplier formed by a proportional / integral controller that uses the air-fuel ratio error as the basis for controlling the engine's air-fuel ratio.

[0051] Table 300 includes an X-axis that vertically divides the table into multiple cells indexed by engine speed. Table 300 also includes a Y-axis that horizontally divides the table into multiple cells indexed based on engine load. Thus, the X-axis is identified as engine speed, and the Y-axis is identified as engine load. The table can be stored in the KAM of controller 12 and used as feedforward fuel correction (e.g., direct injection fuel correction) throughout the engine operating range. The table is initially filled with 1s, and the 1s are incremented or decremented based on exhaust sensor feedback. Table values ​​can be limited or reduced to predetermined values, such as between 0.75 and 1.25. Thus, for multiple engine speed and load combinations, the amount of fuel delivered to the engine cylinders can be adjusted based on the values ​​in the table. The table output value is the variable Kamrf. If the engine has multiple cylinder banks, multiple Kamrf values ​​can be provided. Kamrf can be an indication of engine air-fuel ratio error. The values ​​in Table 300 are based on the error between the desired engine air-fuel ratio and the engine air-fuel ratio, such as that determined via an oxygen sensor. The values ​​in Table 300 can be increased or decreased based on the lambse value or air-fuel ratio error between the desired air-fuel ratio and the engine air-fuel ratio determined by an oxygen sensor such as exhaust sensor 76.

[0052] Furthermore, the amount of fuel delivered via the port fuel injection system and the direct fuel injection system (also referred to herein as fuel share) is determined empirically and stored in predetermined lookup tables or functions. For example, one table may correspond to determining the port injection amount, and another table may correspond to determining the direct injection amount. Both tables can be indexed to engine operating conditions such as engine speed and engine load, as well as other engine operating conditions. Additionally, the tables may output the fuel amount to be injected into the engine cylinders via port fuel injection and / or direct injection in each cylinder cycle.

[0053] Furthermore, the relationship between the fuel share and Kamrf for each injection system under various engine speed-load conditions can be stored in a lookup table and updated each time a new Kamrf is determined, so that the air-fuel ratio error can be updated according to the fuel share delivered by each fuel injection system. Furthermore, the controller 12 can also update the KAM with a new fuel share value each time a fuel supply error is detected (such as when a change in the amount of fuel delivered by each fuel injection system is detected).

[0054] The inventors have recognized that fuel supply errors in PFDI fuel systems can be distinguished between port injection and direct injection systems by allocating a portion of the air-fuel error based on the proportion of fuel injected into the cylinder. For example, in Figures 4 to 6As described in detail, the engine air-fuel ratio error can be non-invasively obtained via a non-invasive fuel system calibration routine, which includes determining the difference between the commanded air-fuel ratio and the actual air-fuel ratio, as measured by exhaust sensor 76. A portion of the air-fuel ratio error (DI_Kamrf) can then be allocated to the direct fuel injection system by calculating the ratio between the change in the air-fuel ratio error and the change in the fuel share provided by the direct injection system (also referred to herein as percentage DI (DI%)). Similarly, a portion of the air-fuel ratio error (PFI_Kamrf) can be allocated to the intake fuel injection system by calculating the ratio between ΔKamrf and the change in the fuel share provided by the intake fuel injection system (also referred to herein as percentage PFI (PFI%)). It should be understood that percentage PFI can be calculated as (100% - percentage DI) because the fuel shares contributed by both the intake fuel injection system and the direct fuel injection system must be equal to 1.

[0055] In one example, if it is determined that DI_Kamrf is greater than PFI_Kamrf, the fuel supply error can be attributed to the direct fuel injection system. However, if the opposite is true, the fuel supply error can be attributed to the intake manifold fuel injection system.

[0056] Furthermore, due to non-intrusive fuel error being known (such as...) Figure 5 The routines described in detail in the text depend on variations in engine speed and engine load conditions, so the percentage DI may not provide sufficient variation for non-invasive fuel system calibration to be performed. Therefore, to provide sufficient variation in the percentage DI, invasive fuel system calibration (such as that described in the text) can be performed. Figure 6 (The routine described in detail in [the document]). In one example, the previously adjusted percentage DI obtained from the non-invasive fuel system calibration routine can be retrieved and compared with the upper and lower limits of the percentage DI determined based on engine speed-load conditions. The invasive fuel system calibration routine may further include changing the new percentage DI value to the upper limit when the previous percentage DI value is further away from the lower limit, and changing the new percentage DI value to the lower limit when the previous percentage DI is further away from the lower limit. As previously mentioned, once the new percentage DI is determined, the non-invasive fuel calibration routine can be implemented to identify fuel supply errors between the port fuel injection system and the direct fuel injection system. By invasively changing the percentage DI, the accuracy of fuel error information obtained during non-invasive fuel calibration can be increased. In this way, fuel supply errors contributed by the two fuel supply systems can be accurately identified and quickly addressed, resulting in improved engine performance. Now refer to [the document]. Figure 3BThe diagram illustrates a graphical representation of the fuel error contributions from port injection and direct injection, as initially known via non-invasive or invasive calibration routines. In each case, the fuel share of direct injection (and the corresponding fuel share of port injection) is commanded to operate the engine at a target air-fuel ratio, and the actual share of fuel delivered is then inferred based on air-fuel ratio feedback from exhaust sensors and its deviation from the target air-fuel ratio. Specifically, the value of the adjusted fuel error multiplier (Kamrf) is plotted relative to the fuel shares of direct injection and port injection.

[0057] The X-axis represents the proportion of fuel directly injected into the engine cylinders. The proportion of directly injected fuel ranges from 0 (e.g., no fuel is directly injected) to 1 (e.g., all fuel is directly injected during a cylinder cycle in which direct injection is performed). The Y-axis represents the proportion of fuel injected through the intake manifold into the engine cylinders. The proportion of fuel injected through the intake manifold ranges from 0 (e.g., no fuel is injected through the intake manifold) to 1 (e.g., all fuel is injected through the intake manifold during a cylinder cycle in which direct injection is performed).

[0058] A first Kamrf value of 1.05 is shown at position 320. As indicated by dashed line 355, the portion of fuel injected directly at position 320 is 0.25, and as indicated by dashed line 356, the portion of fuel injected via the intake manifold is 0.75. The fuel share values ​​of 0.25 and 0.75 add up to 1. Therefore, the total amount or mass of fuel injected into the cylinder during a cylinder cycle multiplied by the direct fuel share equals the mass of fuel directly injected during the cylinder cycle. Similarly, the total mass of fuel injected into the cylinder during a cylinder cycle multiplied by the intake manifold fuel share equals the mass of fuel injected via the intake manifold during the cylinder cycle. A second Kamrf value of 0.92 is shown at position 322. The portion of fuel injected directly at position 322 is 0.5, and the portion of fuel injected via the intake manifold is 0.25 of the total amount of fuel injected during the cycle of the receiving cylinder.

[0059] The change in Kamrf from 320 to 322 is 1.05 - 0.92 = 0.13. The slope of the change in Kamrf relative to the change in the direct injection share is 0.13 / (0.25 - 0.5) = -0.52. The slope of the change in Kamrf relative to the change in the intake manifold injection share is 0.13 / (0.75 - 0.25) = 0.26. Therefore, the change in Kamrf relative to the intake manifold injection share is greater than that of the direct injection share. Therefore, if the change in Kamrf relative to the direct injection share exceeds a threshold, the direct fuel injector transfer function can be adjusted and / or the direct fuel injection system can be indicated to be in a deteriorated state.

[0060] In this way, the adjusted fuel error multiplier Kamrf can serve as the basis for determining the degradation or error of the intake manifold fuel injection system. Furthermore, the same adjusted fuel error multiplier can serve as the basis for determining the degradation error of the direct fuel injection system.

[0061] In this way, Figures 1 to 2 The components implement a system comprising: an engine including cylinders; a port fuel injector (PFI) in fluid communication with the cylinders; a direct fuel injector (DI) in fluid communication with the cylinders; an exhaust oxygen sensor for estimating air-fuel ratio errors in the cylinders; and a controller. The controller may include executable instructions stored in a non-transitory memory for: estimating a split ratio of fuel delivered via the PFI to the DI over a cylinder cycle based on engine speed and load; commanding fuel according to the estimated split ratio in response to a threshold change in the estimated split ratio that is higher than the DI fuel share since the last estimated split ratio; and updating the estimated split ratio based on one of an upper and lower limit of the direct injector, said upper and lower limits being estimated based on engine speed and load, and commanding fuel according to the updated split ratio in response to a threshold change in the estimated split ratio that is lower than the DI fuel share since the last estimated split ratio and an elapsed threshold duration. In one example, the estimated split ratio includes the fuel share of a first direct injection and the fuel share of a second intake port injection, and wherein updating the estimated split ratio based on one of the upper and lower limits of the direct injectors includes: reducing the fuel share of the first direct injection to the lower limit and correspondingly increasing the fuel share of the second intake port injection when the fuel share of the first direct injection is closer to the upper limit of the direct injector; and increasing the fuel share of the first direct injection to the upper limit and correspondingly decreasing the fuel share of the second intake port injection when the fuel share of the first direct injection is closer to the lower limit of the direct injector. In a further example, the controller may include further instructions for: allocating the estimated air-fuel ratio error after the command fuel based on the estimated split ratio between the intake port injector and the direct injector, according to the rate of change of the air-fuel ratio error relative to the estimated split ratio; and allocating the estimated air-fuel ratio error after the command fuel based on the updated split ratio between the intake port injector and the direct injector, according to the rate of change of the air-fuel ratio error relative to the updated split ratio. In yet another further example, allocating the air-fuel ratio error includes assigning a first portion of the air-fuel ratio error to the direct injector and assigning a remaining second portion of the air-fuel ratio error to the intake injector, wherein the controller includes further instructions for: restricting the operation of the direct injector in response to the first portion exceeding the second portion; and restricting the operation of the intake injector in response to the second portion exceeding the first portion.

[0062] Now for reference Figure 4This illustrates an example routine for calibrating a PFDI fuel system. The instructions for performing routine 400 and the remaining methods included herein may be based on instructions stored in the controller's memory and combined with those from sensors in the engine system (such as those referenced above). Figure 1 and Figure 2 The signal received by the described sensor is controlled by a controller (such as...) Figure 1 and Figure 2 The controller 12) executes the commands. According to the method described below, the controller can use the engine actuator of the engine system to regulate engine operation.

[0063] At point 402, engine operating conditions can be estimated and / or inferred. These operating conditions may include, for example, engine speed, engine load, driver torque demand, environmental conditions (e.g., ambient temperature and humidity, and atmospheric pressure), MAP, MAF, MAT, engine temperature, boost level, etc.

[0064] Once the engine operating condition is estimated, the method proceeds to step 404, where it determines whether a threshold duration has elapsed since the last iteration of the non-invasive fuel system calibration routine. In one example, fuel system calibration may be performed periodically, such as at least once per driving cycle, after a predetermined number of miles driven or after a predetermined duration of engine operation. Non-invasive fuel system calibration can be performed in a timely manner using a fuel share value selected based on engine speed-load variations.

[0065] If the threshold duration has not yet elapsed, the method proceeds to step 416, where the fuel supply to the cylinders continues to be adjusted based on the most recent fuel multiplier table. This may include applying the most recent adaptive fuel multiplier (Kamrf) based on estimated engine speed / load conditions, and applying the corresponding direct fuel share and intake manifold fuel share based on the most recent Kamrf value. In one example, the controller may use a lookup table (such as...) stored in the controller's memory. Figure 3A The method retrieves the most recent Kamrf value from the table. Then the method ends.

[0066] If sufficient time has elapsed since the last iteration of fuel system calibration, method 400 proceeds to 406, where a non-invasive PFDI fuel system calibration routine is performed, as referenced. Figure 5 Described. A non-invasive fuel system calibration routine may include learning and updating the adaptive fuel multiplier value Kamrf at each calibration run. Further, for example, a deteriorated fuel injector may be indicated when DI_Kamrf or PFI_Kamrf exceeds a threshold. Still further, as described in detail below, fuel supply errors between the intake fuel injection system and the direct fuel injection system can be identified by comparing DI_Kamrf with PFI_Kamrf.

[0067] At point 408, after the calibration routine is completed, the adaptive fuel multiplier table is updated in the controller's memory based on the non-intrusive PFDI fuel system. In one example, such as a reference... Figure 3A As shown in the table, the adaptive fuel multiplier table can be indexed based on engine speed and engine load and can provide Kamrf as an output value. In one example, it is based on the commanded air-fuel ratio and, for example, via an exhaust sensor (e.g., Figure 1 The air-fuel ratio error determined by the gas sensor 76) can be updated by increasing or decreasing the Kamrf value from the previous Kamrf value. In another example, the change in the DI percentage can also be updated. (As in...) Figure 4 As described in detail, the adaptive fuel multiplier can further update information about the status of each fuel injection system. For example, a flag can be set for direct fuel injection systems when DI_Kamrf exceeds a threshold. Similarly, a flag can be set for intake fuel injection systems when PFI_Kamrf exceeds a threshold. Alternatively, each time a flag is set, the error counter for each fuel injection system can be incremented, such that a malfunction indicator lamp (MIL) can be provided to warn the vehicle operator that the corresponding deteriorated fuel injector needs repair or replacement when the error count reaches a threshold.

[0068] At 410, it can be determined whether the percentage DI (i.e., the fuel share provided by the direct fuel injection system) has changed significantly since the last fuel calibration. A significant change may include a change in the percentage DI above a threshold, large enough to warrant a timely re-implementation of non-invasive fuel system calibration. Alternatively, the threshold change may include the number of calibrable counts up to maturity and the number of calibrable counts that maturity could fail before performing invasive DI calibration. For example, it can be determined that non-invasive fuel system calibration may optionally be repeated every 10 seconds. Thus, non-invasive calibration may require a significant change in fuel share to detect the corresponding measured air-fuel ratio error and reliably attribute it to a change in DI fuel supply or PFI fuel supply. Therefore, if the change in the percentage DI is significant, invasive fuel system calibration is not required, and the method proceeds to 416, where the fuel multiplier table continues to be updated based on the timely running of the non-invasive calibration routine, and the fuel supply to the cylinders continues to be adjusted based on the most recent fuel multiplier table.

[0069] However, if no significant percentage DI change is detected, the method proceeds to 411. At 411, it can be determined whether the elapsed time since the last fuel adjustment has exceeded a threshold duration. In one example, determining the duration since the last fuel adjustment may include determining whether any fuel correction values ​​(such as Kamrf, percentage DI, etc.) have been recently updated, and if so, starting a timer and determining whether the elapsed time since the timer started has exceeded the threshold duration. In another example, it may also include determining whether any fuel supply error has occurred in the fuel injection system, and if so, determining the elapsed time since then (e.g., as measured via a timer). In response to each of the threshold duration elapsed since the last fuel adjustment and a threshold change less than the DI percentage, the method proceeds to 412 to perform an intrusive PFDI fuel system calibration routine. Otherwise, the method returns to 411, where the timer continues to increment until the threshold duration is reached.

[0070] At position 412, if referenced Figure 6 The described procedure involves performing an invasive PFDI fuel system calibration routine. This routine may include retrieving the last adjusted percentage DI value and comparing it to the upper and lower limits of the percentage DI injector, which are dynamically determined based on real-time engine speed / load conditions. Furthermore, if the previously adjusted percentage DI value is further away from the upper limit, the percentage DI may be actively switched to the upper limit; or if the previously adjusted percentage DI value is further away from the lower limit, the percentage DI may be actively switched to the lower limit. By invasively adjusting the percentage DI, sources of fuel supply errors (e.g., port fuel injection systems and / or direct fuel injection systems) can be accurately identified.

[0071] In this way, the adaptive fuel error learning strategy first attempts to learn about the fuel supply error without any intrusive percentage DI change. If the adaptive strategy does not detect a sufficient change in percentage DI, the controller forces a percentage DI change and runs the engine with an alternative percentage DI to allow the adaptive fuel strategy to learn about the fuel supply error more reliably.

[0072] After the invasive fuel system calibration is completed, the method proceeds to 414, where the fuel multiplier table is updated based on the invasive fuel system information. Similar to step 408, updating the fuel multiplier table may include updating based on the commanded air-fuel ratio and, for example, via an exhaust sensor (e.g., Figure 1The Kamrf value is incremented or decremented based on the air-fuel ratio error between the actual air-fuel ratios determined by the gas sensor 76. In one example, the Kamrf value learned during non-invasive calibration can be replaced with the Kamrf value learned during invasive calibration. In another example, the Kamrf value learned during non-invasive calibration can be updated to a weighted average of the Kamrf values ​​learned during invasive and non-invasive calibration. As yet another example, the Kamrf value learned during non-invasive calibration can be updated based on the difference between the Kamrf value learned during non-invasive calibration and the Kamrf value learned during invasive calibration. Invasive and non-invasive calibrations can then work together to mature the long-term fuel trim value. As more updates to the trim occur, the gain decreases until the final long-term fuel trim is determined. Updating the adaptive fuel multiplier can further include updating a new percentage DI value for a given engine speed-load condition.

[0073] At point 416, subsequent engine fuel supply events can be adjusted based on an updated table. In one example, the fuel share of each fuel injection system in the lookup table can be adjusted based on the updated Kamrf value. In another example, if degradation is indicated in one of the fuel injection systems, the operation of the degraded fuel injection system can be limited to prevent further damage to the injectors, and thus the operation of the undegraded fuel injection systems can be temporarily increased.

[0074] In one example, updating the injector's transfer function may include assigning a first portion of the measured air-fuel ratio error to the direct injector based on the rate of change of the air-fuel ratio relative to the increased or decreased direct injection fuel share, and assigning a second portion of the air-fuel ratio error to the intake injector based on the rate of change of the air-fuel ratio error relative to the intake port injection fuel share. Further, the controller may update the direct injector's transfer function based on the first portion of the air-fuel ratio error; and update the intake injector's transfer function based on the second portion of the air-fuel ratio error. The controller can then restrict the operation of the direct injector when the first portion is greater than the second portion, and restrict the operation of the intake injector when the second portion is greater than the first portion. In this way, additional fuel supply errors are avoided.

[0075] Now for reference Figure 5 This illustrates example routine 500 for performing non-invasive fuel system calibration. In one example, Figure 5 The routines can be used as Figure 4A portion of the routine (such as at 406) is executed. Specifically, routine 500 describes a method for identifying and isolating sources of deterioration in dual-injection, single-fuel systems (e.g., duct fuel injection systems or direct fuel injection systems). Further, routine 500 also describes mitigation measures for situations where deterioration of a given fuel injection system is determined. A trigger may be initiated in response to the detection of a significantly large percentage change in DI. Figure 5 Non-invasive fuel system calibration routines. Furthermore, the source of fuel supply errors (e.g., inlet fuel injection systems or direct fuel injection systems) can be accurately identified, and fuel supply errors caused by specific injection systems can be resolved immediately.

[0076] At position 502, the engine operates in a closed-loop air-fuel control mode. In one example, the closed-loop control mode can be activated during idling and cruise operation, and can be based on data from exhaust sensors (such as...). Figure 1 The sensor 76 receives signals to adjust fuel injection. During closed-loop air-fuel control, the controller can determine the desired engine air-fuel ratio based on various engine operating conditions such as driver-demanded torque, engine speed, and other conditions using index tables and / or functions. In one example, the air-fuel ratio can be maintained at a stoichiometric ratio. Fuel is supplied to provide the desired engine air-fuel ratio and from exhaust sensors (e.g., [missing information]). Figure 1 Feedback from the exhaust sensor 76 is used to adjust the fuel share for each fuel injector. Depending on the fuel share, fuel can be injected through the intake manifold, directly, or a combination of both. Once the engine is operating in closed-loop mode, the process continues to 504.

[0077] At point 504, the fuel multiplier (Kamrf) is adjusted based on estimated engine speed and engine load conditions. In one example, the Kamrf value can be adjusted based on whether the exhaust sensor is monitoring lean or rich fuel mixture combustion products in the exhaust system. In another example, if the short-term air-fuel ratio correction factor lambse indicates a lean air-fuel ratio over an extended time period, the adjusted fuel multiplier (Kamrf) can increase from its initial value to a richer air-fuel ratio, and vice versa. Additionally, the fuel multiplier can be adjusted for multiple engine speeds and load conditions. Furthermore, the fuel shares of port-injected fuel and direct-injected fuel can be stored in the same table, which stores the adjusted fuel multiplier. (Previous reference) Figure 3B An example fuel multiplier adjustment is described. The method then proceeds to step 506 after adjusting the fuel multiplier.

[0078] At point 506, it can be determined whether any adjusted fuel multipliers are out of range. In one example, the controller can determine whether the Kamrf value stored in the adaptive fuel multiplier table is between 0.75 and 1.25. Alternatively, the method can also determine whether a sufficient number of adjusted fuel multipliers have been stored in memory (e.g., at least two different adjusted fuel multipliers and their corresponding direct injection fuel shares and port injection fuel shares have been stored in memory). If the fuel multipliers are within range, the method proceeds to point 510. Otherwise, the method proceeds to point 508, where multiple fuel multipliers continue to be updated in the closed-loop air-fuel control mode for different engine speed-load conditions, and the method ends.

[0079] At point 510, the fuel multiplier change rate based on the change rate of fuel share in inlet fuel injection (PFI_Kamrf) and the fuel multiplier change rate based on the change rate of fuel share in direct fuel injection (DI_Kamrf) are determined. The relationship between the adjusted fuel multiplier change rate and the change rate of fuel share in direct injection can be expressed as:

[0080]

[0081] Where DI_Kamrf is the slope of the rate of change of Kamrf relative to the change in the direct injection fuel share, and Kamrf is the adjusted fuel multiplier, and di frac This refers to the direct injection fuel share. Furthermore, the relationship between the rate of change of the adjusted fuel multiplier and the rate of change of the intake manifold injection fuel share can be expressed as:

[0082]

[0083] Where PFI_Kamrf is the slope of the Kamrf change rate relative to the change in the fuel share injected into the intake manifold, where Kamrf is the adjusted fuel multiplier, and di frac This refers to the direct injection fuel share. Further, for example, information about the Kamrf and its corresponding direct fuel injector and port fuel injector fuel shares can be stored as sub-tables in an adaptive multiplier table. These sub-tables can be indexed based on the direct fuel injector and port fuel injector fuel shares. Additionally, the range of direct fuel and port fuel shares can be from 0 (e.g., no fuel is directly injected) to 1 (e.g., all fuel is directly injected during a cylinder cycle where direct injection is performed).

[0084] As an example, based on the first estimated engine speed-load condition, the first Kamrf value can be determined to be 1.05. In another example, the first Kamrf value can also be inferred from a lookup table (e.g., an adaptive fuel multiplier table). Furthermore, the fuel share values ​​for direct fuel injection and port fuel injection can be determined from a sub-table. Therefore, based on a Kamrf value of 1.05, the first Kamrf value can be determined to be 1.05. frac and PFI frac The values ​​are determined to be 0.25 and 0.75, respectively. Under the second engine speed-load condition, the second Kamrf can be determined to be 0.92. In this case, the fuel share values ​​for direct fuel injection and port fuel injection can be determined to be di, respectively. frac =0.5 and pfi frac =0.25.

[0085] Based on the determined first and second Kamrf values, DI_Kamrf and PFI_Kamrf can be calculated. For example, DI_Kamrf can be (1.05-0.92) / (0.25-0.5) = -0.52. And PFI_Kamrf can be calculated as (1.05-0.92) / (0.75-0.25) = 0.26.

[0086] For reference Figure 3A As illustrated in the example, by determining the slope of the rate of change of Kamrf relative to the change in the fuel share of the intake manifold injection and the slope of the rate of change of Kamrf relative to the fuel share of the direct injection system, engine fuel supply errors can be allocated between the intake manifold fuel injection system and the direct fuel injection system. For example, the larger the absolute value of the slope of the rate of change of Kamrf relative to the change in the fuel share of the direct injection system, the greater the amount of fuel supply error attributed to the direct fuel injection system. Once DI_Kamrf and PFI_Kamrf are determined, the method proceeds to step 512.

[0087] At point 512, it can be determined whether the absolute value of PFI_Kamrf exceeds a threshold. In one example, the threshold may be a predetermined number provided by the vehicle manufacturer. In another example, the threshold may be known and adjusted based on vehicle operating conditions (e.g., engine speed, engine load, etc.). If the absolute value of PFI_Kamrf exceeds the threshold, the method proceeds to point 514, where PFI degradation is indicated. Indicating PFI degradation may include warning the vehicle operator by activating the malfunction indicator lamp (MIL). In another example, PFI degradation may be indicated via a display panel (such as...) Figure 1The indication is made via display panel 171. Indicating PFI degradation may further include limiting PFI operation at 516 and correspondingly increasing DI operation. For example, the operating range of port fuel injection may be reduced, and direct fuel injection may be used instead of the port fuel injector during operating conditions where port fuel injection was previously used. As another example, after determining the initial DI:PFI fuel share based on engine operating conditions, in response to the indication of PFI degradation, the PFI fuel share may be reduced while the DI share increases accordingly. The reduction in the PFI fuel share may be determined based on the difference between the known absolute value of PFI_Kamrf and a threshold, with the PFI fuel share (from the initial value) decreasing further as the difference increases. The method then ends.

[0088] However, if the absolute value of PFI_Kamrf does not exceed the threshold, the method proceeds to step 518, where it is determined whether the absolute value of DI_Kamrf exceeds the threshold. Similar to the threshold used to evaluate the PFI system, the threshold can be a predetermined number provided by the vehicle manufacturer. In another example, the threshold can be known and adjusted based on vehicle operating conditions (e.g., engine speed, engine load, etc.). The threshold for DI_Kamrf can be the same as or different from the threshold for PFI_Kamrf.

[0089] If the absolute value of DI_Kamrf exceeds the corresponding threshold, the method proceeds to step 520, where DI degradation is indicated. Further, at step 522, the method includes restricting DI operation while correspondingly increasing PFI operation. For example, the operating range of direct fuel injection can be reduced, and port fuel injection can be used instead of direct fuel injection during operating conditions where direct fuel injection was previously used. As another example, after determining the initial DI:PFI fuel share based on engine operating conditions, in response to the indication of DI degradation, the DI fuel share can be reduced while the PFI share is increased accordingly. The reduction in the DI fuel share can be determined based on the difference between the known absolute value of DI_Kamrf and the threshold, with the DI fuel share (from the initial value) decreasing further as the difference increases. The method then terminates.

[0090] If neither the absolute values ​​of DI_Kamrf nor PFI_Kamrf exceed their respective thresholds, then method 500 proceeds to 524, where it is determined whether the absolute value of PFI_Kamrf is greater than the absolute value of DI_Kamrf. For example, it can be determined whether PFI_Kamrf exceeds DI_Kamrf by a threshold amount. If PFI_Kamrf is greater than DI_Kamrf (e.g., greater than the threshold amount), the controller can determine that fuel supply errors, such as those measured based on feedback from the air-fuel ratio sensor, are attributable to the intake manifold fuel injection system. Therefore, at 526, the transfer function of the intake manifold fuel injection system can be updated accordingly (e.g., by adjusting the offset or slope function of the intake manifold fuel injection system).

[0091] However, if PFI_Kamrf is not greater than DI_Kamrf, the method proceeds to step 528, where it is determined whether the absolute value of DI_Kamrf is greater than the absolute value of PFI_Kamrf. For example, it can be determined whether DI_Kamrf exceeds PFI_Kamrf by a threshold amount. If DI_Kamrf is greater than PFI_Kamrf (e.g., greater than the threshold amount), the controller can determine that fuel supply errors, such as those measured based on feedback from the air-fuel ratio sensor, are attributable to the direct fuel injection system. Therefore, at step 530, the transfer function of the direct fuel injection system can be updated accordingly (e.g., by adjusting the offset or slope function of the direct fuel injection system).

[0092] Returning to the earlier example, the absolute values ​​of DI_Kamrf and PFI_Kamrf could be 0.52 and 0.26, respectively. Therefore, the variation in Kamrf is greater relative to the fuel share of the direct fuel injector (i.e., DI_Kamrf > PFI_Kamrf). Consequently, fuel supply errors can be attributed to the direct fuel injection system, and the transfer function of the direct fuel injection system can be further adjusted, for example, by adjusting the slope or offset of the transfer function. Therefore, the commanded direct injector pulse width during subsequent fuel supply events can be increased or decreased.

[0093] If it is determined at 528 that DI_Kamrf is not greater than PFI_Kamrf, meaning that DI_Kamrf and PFI_Kamrf are within each other's range, then proceed to 530. At 530, fuel continues to be supplied from both the direct fuel injection system and the intake fuel injection system according to the previously updated transfer function, and the method ends.

[0094] From each of 526 and 532, the method moves to 534. At 534, the fuel supply to both the intake manifold fuel and the direct injection system during subsequent fuel supply events can be based on one or more modified transfer functions. In one example, the total fuel quantity and the share of fuel delivered via each of the intake manifold injectors and the direct injectors can be incremented or decremented according to the modified transfer function, such that the commanded fuel quality better matches the desired fuel quality for a given engine operating condition. Furthermore, updated values ​​of various fuel correction factors (such as the fuel multiplier Kamrf), changes in percentage DI, and fuel injector transfer functions can be stored in the controller's memory, such as in a lookup table, according to engine speed and load.

[0095] In this way, by performing non-invasive calibration routines, the source of fuel supply errors in the fuel injection system can be quickly identified without affecting driving performance, and mitigation measures can be provided to prevent further fuel supply errors. In one example, the controller can increase the operation of the first non-degraded fuel injection system in the presence of a second degraded fuel injection system. Furthermore, fuel injection deterioration indication can allow for timely provision of fuel system maintenance services.

[0096] Now for reference Figure 6 The illustration shows an example routine for performing invasive fuel system calibration. In one example, Figure 6 The routines can be used as Figure 4 A portion of the routine (such as at 412) is executed. The method allows for the implementation of an intrusive fuel conditioning strategy, enabling the proactive induction of sufficient variation in the percentage DI (i.e., the share of fuel supplied by the direct fuel injection system) to reliably identify fuel supply errors without degrading driving performance.

[0097] At point 602, the percentage upper and lower limits of the DI system (also referred to herein as DI upper and lower limits) can be determined based on estimated engine operating conditions (e.g., engine speed-load conditions). The upper and lower limits can be selected to reduce the impact of intrusive changes in fuel share on NVH, driving performance, emissions, and engine torque. In one example, the upper and lower limits of the direct injection fuel share can be provided in a lookup table based on engine speed and engine load indices. In one example, the upper and lower limits could be 67% and 41% respectively during a first engine speed-load condition. In another example, the upper and lower limits could be 15% and 0% respectively during a second engine speed-load condition. Both the upper and lower limits can be separate speed / load calibration maps. Various design considerations can be made when selecting values ​​for these maps. For example, at idle engine speed / load, both the lower and upper limits could be 0% DI. This is because some engines / vehicles cannot tolerate NVH from a DI fuel system when the vehicle is stationary at idle. The earlier references of 67% and 41% can be applied when a DI fuel system uses up 67% of its fuel, but a PFI injection system will not provide sufficient charge cooling at any point below 47%, so these limits will protect fuel flow limits and combustion knock limits. Once the percentage DI upper and lower limits are determined, the method proceeds to 604.

[0098] At position 604, the percentage DI from the last adjustment can be retrieved. In one example, this can be obtained from a previous non-intrusive PFDI fuel system (such as...). Figure 4 Step 408 and Figure 5 The adaptive fuel multiplier table (such as) updated during step 510) Figure 3A The last adjusted percentage DI is retrieved from the table. In another example, the last adjusted percentage DI can be a pre-calibrated value set by the vehicle manufacturer. In one example, the last adjusted DI percentage could be 58% during the first engine speed-load condition and 0% during the second engine speed-load condition, where 58% DI means that 58% of the fuel mass is supplied by the direct fuel injectors and the remaining (100% - 58%) 42% of the fuel mass is supplied by the port fuel injectors, while 0% DI means that 100% of the fuel mass is supplied by the port fuel injectors (e.g., during low load conditions). Once the last adjusted percentage DI is retrieved, the method proceeds to 606.

[0099] At 606, it can be determined whether the previously adjusted percentage DI is further away from the DI upper limit relative to the lower limit. For example, a first difference between the previously adjusted percentage DI value and the DI upper limit and a second difference between the previously adjusted percentage DI value and the DI lower limit can be compared. If the first difference is greater than the second difference, it can be determined that the previously adjusted percentage DI is further away from the DI upper limit. Otherwise, if the first difference is less than the second difference, it can be determined that the previously adjusted percentage DI is further away from the DI lower limit. If the previously adjusted percentage DI is further away from the upper limit, at 608, the method includes adjusting the percentage DI based on the percentage DI upper limit adjustment command. For example, the percentage DI can be actively changed from the previously adjusted percentage DI value to the DI upper limit value. However, if the previously adjusted percentage DI is closer to the upper limit, the method proceeds to 610, where the percentage DI is adjusted based on the lower limit adjustment command. For example, the percentage DI can be actively changed from the previously adjusted percentage DI value to the DI lower limit value. If the first difference and the second difference are the same, the upper limit can be selected as the default value due to the preference for using direct injection operation.

[0100] In this manner, the controller can deliver fuel in the cylinder cycle via both the direct injector and the port injector; and when the current share is closer to the lower limit than the upper limit, the direct injection fuel share is increased to the upper limit, while when the current share is closer to the upper limit than the lower limit, the first fuel share provided by the direct injector is decreased to the lower limit. Here, the direct injection fuel share increases or decreases relative to the port injection fuel share, where each of the upper and lower limits is used for the direct injector and is based on engine operating conditions including engine speed, load, and operator torque demand. The controller can then update the transfer function of the direct injector based on the air-fuel ratio error relative to the increased or decreased fuel share. Additionally, the port injection fuel share can be based on the direct injection fuel share, and the controller can further update the transfer function of the port injector based on the air-fuel ratio error relative to the port injection fuel share.

[0101] It should be understood that the increase or decrease of the fuel share is performed in response to the threshold duration that has elapsed since the last update of the transfer function of the direct injector. Therefore, if no threshold duration has elapsed since the last update of the transfer function, the controller may continue to deliver fuel in the cylinder cycle at the current share via the direct injector and port injectors, and based on the current share (e.g., ... Figure 5 The rate of change of the air-fuel ratio error (described in detail) is used to non-invasively but timely update the transfer function of the direct injector.

[0102] In one example, adjusting the new percentage DI to the upper limit prevents intake manifold fuel injection at higher engine speeds / loads, thus reducing engine power consumption. In another example, adjusting the new percentage DI to the lower limit under low load conditions allows more fuel to be delivered through the intake manifold fuel injection system, avoiding negative impacts on NVH. Once a sufficient change in the percentage DI value is detected, non-invasive fuel calibration can be performed, such as... Figure 5 As described in detail. Furthermore, by executing an intrusive fuel calibration routine, controller software (e.g., powertrain control software) may require less time to adjust for fuel errors. Still further, by reducing the time spent running the fuel system calibration routine, fuel tank purging capability can be improved, since the fuel purging system does not need to be activated until fuel system calibration is complete.

[0103] Referring to an earlier example, during the first engine speed-load condition, the previously adjusted percentage DI could be 58% (current fuel share), with an upper limit of 67% and a lower limit of 41%. The first difference between the previously adjusted percentage DI and the upper limit (67% - 58% = 9%) is less than the second difference between the previously adjusted percentage DI and the lower limit (58% - 41% = 17%). Therefore, the percentage DI is forced to the lower limit, that is, from 58% to 41%. Here, although the engine speed-load condition ensures the use of 58% DI, the controller actively reduces the applied percentage DI to 41%, while correspondingly increasing the applied percentage PFI to provide a measurable change in the DI fuel share that enables accurate fuel supply error detection. As another example, during the second engine speed-load condition, the previously adjusted percentage DI could be 0%, which is further away from the upper limit (15%) and closer to the lower limit (0%). Therefore, during the second engine speed-load condition, the applied percentage DI can be actively adjusted to the upper limit, that is, from 0% to 15%. Here, although engine speed-load conditions ensure no DI is used, the controller actively increases the applied DI to 15% while correspondingly reducing the applied percentage PFI, in order to provide a measurable change in the DI fuel share that enables accurate fuel supply error detection.

[0104] In one example, the current share determined solely based on engine operating conditions includes a threshold change below the direct injection fuel share since the last update of the transfer function. In contrast, each of the increased and decreased fuel shares includes a threshold change above the direct injection fuel share. By proactively providing a threshold change above the direct injection fuel share, significant changes in the DI fuel share are provided, allowing fuel supply errors to be known with a higher confidence factor.

[0105] From each of 608 and 610, the method moves to 612 to adaptively determine the fuel multiplier for each of the DI and PFI fuel systems based on feedback from the exhaust air-fuel ratio sensor, as previously described in Figures 4 to 5 The location is described in detail. For example, based on the invasive provision of (above a threshold) changes in DI fuel share and the corresponding changes in air-fuel ratio, the fuel supply error of the DI system can be known and the adaptive multiplier of the DI fuel system can be determined accordingly.

[0106] In this way, the amount of time required for the engine controller to adjust for fuel errors is reduced. Fuel errors can be non-invasively identified by enabling the engine to operate at the desired or pre-calibrated percentage DI as close to the target value as possible. Fuel errors can be identified more reliably only when fuel trimming requires adjustment, by forcing the engine to operate at the updated percentage DI, while reducing the frequency and duration of invasive identification. With more accurate identification of adaptive fuel errors and fuel trimming, canister purging can be performed in a timely manner.

[0107] Now for reference Figure 7 The example illustrates fuel system calibration diagnostics. The example includes identifying fuel supply errors via a non-invasive fuel system calibration routine (between t0 and t3) and identifying fuel supply errors via an invasive fuel system calibration routine (between t4 and t5) by invasively adjusting the percentage DI. Map 700 depicts engine speed at curve 702, percentage DI at 704, percentage PFI at curve 707, adaptive fuel multiplier at 708, engine air-fuel ratio at curve 709, DI transfer function update at 710, and invasive fuel supply error diagnostic request at 712. All curves are plotted relative to time along the x-axis. Time markers t1-t6 depict key time points during fuel system calibration.

[0108] Before t1, the engine operates in a low-speed, low-load region (curve 702), where the engine cylinders are supplied with a higher share of port-injected fuel (curve 707) relative to the directly injected fuel (curve 704), thus maintaining engine operation at a target exhaust air-fuel ratio (such as at or near stoichiometry). The DI percentage at this point is DI_1. Since port-injected fuel evaporates well under lower engine loads, a larger port-injection share at lower engine loads is desirable, and the direct injection fuel pump can be reduced when the direct injection fuel quantity is low. The engine air-fuel ratio feedback correction lambse value oscillates around a value of 1. The adaptive fuel multiplier Kamrf fluctuates around the desired value (around 1.00), and the controller continues to update the DI and PFI fuel quantities based on the fuel multiplier value according to the engine speed-load conditions. Between t0 and t1, the DI fuel share does not change significantly, and therefore no fuel calibration is performed. Therefore, the DI transfer function is not updated, and no intrusive diagnostic requests are performed. If indicated by the direct injector transfer function update state, the direct injector transfer function has not been updated. The direct injection fuel share, the intake port injection fuel share, and the adaptive fuel multiplier are stored in memory (not shown).

[0109] At t1, the engine torque demand requested by the vehicle operator may increase (e.g., due to increased accelerator pedal pressure). Therefore, engine speed increases and a higher proportion of the total fuel mass is delivered as directly injected fuel. The percentage DI increases from DI_1 to DI_2, while the percentage PFI decreases accordingly to maintain the exhaust air-fuel ratio at the stoichiometric level. The change in percentage DI at t1 (from DI_1 to DI_2) is large enough to trigger a non-intrusive fuel calibration routine. The change in exhaust sensor output (and the resulting change in air-fuel ratio) is compared to the change in the commanded percentage DI. The controller detects a rich air-fuel ratio error and, based on its comparison with the change in percentage DI, reduces Kamrf to a lower value (e.g., Kamrf decreases from 1.00 to 0.92). A rich error indicates that more fuel is delivered than commanded, but it is not yet clear whether the excess fuel is due to the direct injector or the port injector (or both). The rate of change of the fuel multiplier is compared to each of the rates of change of the PFI fuel share (PFI_Kamrf) and the DI fuel share (DI_Kamrf). Based on the fact that DI_Kamrf has a larger absolute value than PFI_Kamrf, the known fuel supply error can be attributed to the direct fuel injection system.

[0110] In response to the fuel supply error caused by the direct fuel injection system's indication, at t2, the transfer function of the DI fuel system is updated (curve 710). After t2, the DI fuel percentage is determined based on the updated transfer function, such that the DI percentage applied under constant engine load (DI_3) is less than the corresponding DI fuel share (DI_2) provided before t2. As a result of the correction, the air-fuel ratio returns to 1.0. Additionally, the Kamrf value can be updated in the adaptive multiplier table. The non-invasive calibration routine can then be terminated. At t3, the reduced operator torque demand causes an increase in the PFI percentage and a corresponding decrease in the DI percentage. Since the decrease in the DI percentage is not significantly greater at this point, the non-invasive calibration is not restarted.

[0111] At t4, for example, since the threshold duration has elapsed since the last fuel adjustment, the conditions for the intrusive fuel system calibration routine can be considered met. Therefore, the percentage DI (DI_3) of the last adjustment is retrieved. The controller can then determine the upper limit of the percentage DI (DI_4 at curve 703) and the lower limit of the percentage DI (DI_5 at curve 705) based on the engine speed-load condition. The controller then compares the last adjusted percentage DI (DI_3) with the upper and lower limits of the percentage DI (DI_4 and DI_5) to select the one further away from the limit. In this example, at t4, the controller can determine that the last adjusted percentage DI is further away from the lower limit. Therefore, at t5, the intrusive routine is initiated, where the percentage DI (curve 704) is adjusted to the lower limit (DI_5). By changing the percentage DI based on the lower limit, a sufficiently large percentage DI change can be achieved, allowing the non-intrusive routine to learn about fuel supply errors in the PFDI system. Between t5 and t6, as at t1-t2, the adaptive fuel multiplier is adjusted based on feedback regarding the change in air-fuel ratio. The change in the adaptive fuel multiplier is then correlated with the change in the DI percentage (D3 to D5) command to detect DI fuel supply errors. The DI transfer function is then updated based on this information, so that after t6, the engine can resume fuel supply based on the engine operating condition with the updated transfer function.

[0112] In this way, the engine controller can estimate each of the current direct injection (DI) fuel share, DI upper limit, and DI lower limit as the operator's torque demand changes. Then, during a first condition, the controller can command the current DI fuel share and learn the DI transfer function based on the air-fuel ratio error relative to the current DI fuel share (non-intrusively, as shown at t1 to t3). In contrast, during a second condition, the controller can command one of the DI upper and lower limits and learn the DI transfer function based on the air-fuel ratio error relative to the commanded upper or lower limit (intrusively, as shown at t4 to t6). In one example, during the first condition, the current DI fuel share includes a threshold change in fuel share higher than the last commanded DI fuel share, while during the second condition, the current DI fuel share includes a threshold change in fuel share lower than the last commanded DI fuel share. In another example, the first condition includes a threshold duration lower than the elapsed duration since the last learning of the DI transfer function, and the second condition includes a threshold duration higher than the elapsed duration since the last learning of the DI transfer function. In the foregoing example, the command during the second condition may include commanding the DI upper limit when the current DI fuel share is further away from the DI upper limit than the lower limit, and commanding the DI lower limit when the current DI fuel share is further away from the DI lower limit than the upper limit, wherein commanding the DI upper limit includes increasing the current DI fuel share to the DI upper limit, and wherein commanding the DI lower limit includes decreasing the current DI fuel share to the DI lower limit. In a further example, during the first condition, the target DI fuel share is commanded non-intrusively, while during the second condition, one of the upper limit and the DI limit is commanded intrusively, while overriding the current DI fuel share, and wherein during each of the first and second conditions, the engine operates in closed-loop air-fuel ratio control to determine the air-fuel ratio error. In a further example, the air-fuel ratio error is in the form of an adjusted fuel multiplier, and the method further includes: during a first condition, commanding the port injection (PFI) fuel share based on the current DI fuel share, and obtaining the PFI transfer function based on the air-fuel ratio error relative to the commanded PFI fuel share; and during a second condition, commanding the port injection (PFI) fuel share based on one of the commanded upper and lower limits of the DI, and obtaining the PFI transfer function based on the air-fuel ratio error relative to the commanded PFI fuel share. In another example, the engine is coupled to a hybrid vehicle, and the method further includes: during the first condition, being able to purge fuel vapor from the canister to the engine intake port later during the vehicle's driving cycle, and during the second condition, being able to purge fuel vapor from the canister to the engine intake port earlier during the vehicle's driving cycle.

[0113] In this way, the contribution of fuel supply error from the direct injection system can be better separated from the contribution of fuel supply error caused by the port injection system. Engine performance can be improved by accurately identifying and promptly addressing errors. The reliability and confidence factor of fuel error awareness can be improved by enabling invasive fuel share adjustment, providing a target variation in DI fuel share. Engine NVH, drivability, and emissions can be maintained even when invasive operations are performed, by adjusting invasive fuel share according to calibrated upper and lower limits. Engine drivability is improved by selectively and intermittently performing invasive calibration only when fuel trimming (or fuel trimming) is required, allowing the engine to operate at the desired / pre-calibrated fuel share for longer portions of the driving cycle. By coordinating the use of invasive and non-invasive fuel supply error awareness routines, the amount of time required for fuel trimming can be reduced, allowing canister purging to begin earlier in the driving cycle, since fuel purging can only be initiated after fuel trimming is complete. Therefore, this enables a more complete canister purging to be performed. The technical advantage of identifying the contribution of fuel supply errors from each fuel injection system is that any deviation in the air-fuel ratio can be compensated in a timely manner, resulting in improved catalytic converter efficiency and engine performance.

[0114] One example method includes: delivering fuel in a cylinder cycle via a direct injector and a port injector; increasing the direct-injection fuel share to the upper limit when the current share is closer to the lower limit than the upper limit; and decreasing a first fuel share provided by the direct injector to the lower limit when the current share is closer to the upper limit than the lower limit. In the foregoing example, additionally or optionally, the direct-injection fuel share increases or decreases relative to the port-injection fuel share, and each of the upper and lower limits is used for the direct injector and is based on engine operating conditions including engine speed, load, and operator torque requirements. In any or all of the foregoing examples, additionally or optionally, the method further includes updating the transfer function of the direct injector based on an air-fuel ratio error relative to the increased or decreased fuel share. In any or all of the foregoing examples, additionally or optionally, the port-injection fuel share may be based on the direct-injection fuel share, and the method further includes updating the transfer function of the port injector based on an air-fuel ratio error relative to the port-injection fuel share. In any or all of the foregoing examples, additionally or optionally, the fuel share is increased or decreased in response to a threshold duration that has elapsed since the last update of the transfer function of the direct injector. In any or all of the foregoing examples, additionally or optionally, the current share includes a threshold change below the direct injection fuel share since the last update of the transfer function, and wherein each of the increased and decreased fuel shares includes a threshold change above the direct injection fuel share. In any or all of the foregoing examples, additionally or optionally, the method further includes delivering fuel in the cylinder cycle via the direct injector and the port injector at the current share in response to a threshold duration that has elapsed since the last update of the transfer function, and updating the transfer function of the direct injector based on the rate of change of the air-fuel ratio error relative to the current share. In any or all of the foregoing examples, additionally or optionally, a first portion of the air-fuel ratio error is assigned to the direct injector based on the rate of change of the air-fuel ratio relative to the increased or decreased direct injection fuel share, and a second portion of the air-fuel ratio error is assigned to the intake injector based on the rate of change of the air-fuel ratio error relative to the intake port injection fuel share; the transfer function of the direct injector is updated based on the first portion of the air-fuel ratio error; and the transfer function of the intake injector is updated based on the second portion of the air-fuel ratio error. In any or all of the foregoing examples, additionally or optionally, the method further includes restricting the operation of the direct injector when the first portion is greater than the second portion, and restricting the operation of the intake injector when the second portion is greater than the first portion.

[0115] Another example method for an engine includes: estimating each of a current direct injection (DI) fuel share, a DI upper limit, and a DI lower limit as the operator's torque demand changes; during a first condition, commanding the current DI fuel share and obtaining the DI transfer function based on an air-fuel ratio error relative to the current DI fuel share; and during a second condition, commanding one of the DI upper and lower limits and obtaining the DI transfer function based on an air-fuel ratio error relative to the commanded upper or lower limit. In the foregoing examples, additionally or optionally, during the first condition, the current DI fuel share includes a threshold change in fuel share higher than the last commanded DI fuel share, and wherein during the second condition, the current DI fuel share includes a threshold change in fuel share lower than the last commanded DI fuel share. In any or all of the foregoing examples, additionally or optionally, the first condition includes a threshold duration lower than the elapsed duration since the last known DI transfer function, and wherein the second condition includes a threshold duration higher than the elapsed duration since the last known DI transfer function. In any or all of the foregoing examples, additionally or optionally, the command during the second condition includes commanding the DI upper limit when the current DI fuel share is further away from the DI upper limit than the lower limit, and commanding the DI lower limit when the current DI fuel share is further away from the DI lower limit than the upper limit, wherein commanding the DI upper limit includes increasing the current DI fuel share to the DI upper limit and wherein commanding the DI lower limit includes decreasing the current DI fuel share to the DI lower limit. In any or all of the foregoing examples, additionally or optionally, during the first condition, the target DI fuel share is commanded non-intrusively, wherein during the second condition, one of the upper limit and the DI limit is commanded intrusively while overriding the current DI fuel share, and wherein during each of the first and second conditions, the engine operates in closed-loop air-fuel ratio control to determine the air-fuel ratio error. In any or all of the foregoing examples, additionally or optionally, the air-fuel ratio error is in the form of an adjusted fuel multiplier, and the method further includes: during a first condition, commanding the port injection (PFI) fuel share based on the current DI fuel share and obtaining the PFI transfer function based on the air-fuel ratio error relative to the commanded PFI fuel share; and during a second condition, commanding the port injection (PFI) fuel share based on one of the commanded upper and lower limits of DI, and obtaining the PFI transfer function based on the air-fuel ratio error relative to the commanded PFI fuel share. In any or all of the foregoing examples, additionally or optionally, the engine is coupled to a hybrid vehicle, and the method further includes: during the first condition, being able to purge fuel vapor from the canister to the engine intake port later during the vehicle's driving cycle; and during the second condition, being able to purge fuel vapor from the canister to the engine intake port earlier during the vehicle's driving cycle.

[0116] Another example system includes: an engine including cylinders; a port fuel injector (PFI) in fluid communication with the cylinders; a direct fuel injector (DI) in fluid communication with the cylinders; an exhaust oxygen sensor for estimating air-fuel ratio errors in the cylinders; and a controller including executable instructions stored in a non-transitory memory for: estimating a split ratio of fuel delivered via the PFI to the DI over the cylinder cycle based on engine speed and load; commanding fuel according to the estimated split ratio in response to a threshold change in the estimated split ratio that is higher than the DI fuel share since the last estimated split ratio; and updating the estimated split ratio based on one of an upper and lower limit of the direct injector, the upper and lower limits being estimated based on engine speed and load, and commanding fuel according to the updated split ratio in response to a threshold change in the estimated split ratio that is lower than the DI fuel share since the last estimated split ratio and the elapsed duration of the threshold. In the foregoing examples, additionally or optionally, the estimated split ratio includes the fuel share of the first direct injection and the fuel share of the second intake port injection, and wherein the updated estimated split ratio based on one of the upper and lower limits of the direct injectors includes: reducing the first direct injection fuel share to the lower limit and correspondingly increasing the second intake port injection fuel share when the first direct injection fuel share is closer to the upper limit of the direct injector; and increasing the first direct injection fuel share to the upper limit and correspondingly decreasing the second intake port injection fuel share when the first direct injection fuel share is closer to the lower limit of the direct injector. In any or all of the foregoing examples, additionally or optionally, the controller includes further instructions for: allocating the estimated air-fuel ratio error after the command fuel based on the estimated split ratio between the intake port injector and the direct injector according to the rate of change of the air-fuel ratio error relative to the estimated split ratio; and allocating the estimated air-fuel ratio error after the command fuel based on the updated split ratio between the intake port injector and the direct injector according to the rate of change of the air-fuel ratio error relative to the updated split ratio. In any or all of the foregoing examples, additionally or optionally, allocating the air-fuel ratio error includes assigning a first portion of the air-fuel ratio error to the direct injector and assigning a remaining second portion of the air-fuel ratio error to the port injector, wherein the controller includes further instructions for: limiting direct injector operation in response to the first portion exceeding the second portion; and limiting port injector operation in response to the second portion exceeding the first portion. In a further representation, the engine is coupled to a hybrid vehicle system.

[0117] In a further embodiment, one method includes: delivering fuel over the cylinder cycle via a direct injector and a port injector, wherein a first fuel share provided by the direct injector is set as one of an upper limit and a lower limit of the direct injector, the upper and lower limits being based on engine operating conditions; and updating the transfer function of the direct injector based on an air-fuel ratio error relative to the first fuel share. In the foregoing example, the method additionally or optionally further includes: estimating a target fuel share provided by the direct injector based on engine speed and load; setting the first fuel share as the upper limit of the direct injector when the difference between the target fuel share and the upper limit is greater than the difference between the target fuel share and the lower limit; and setting the first fuel share as the lower limit of the direct injector when the difference between the target fuel share and the upper limit is greater than the difference between the target fuel share and the lower limit. In any or all of the foregoing examples, additionally or optionally, the operating conditions include engine speed and load.

[0118] Note that the example control and estimation routines included herein can be used with various engine and / or vehicle system configurations. The control methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be executed by a control system including controllers combined with various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more of any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, etc. Therefore, the various actions, operations, and / or functions described can be executed in the order shown, in parallel, or omitted in some cases. Similarly, the processing order is not required to realize the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. Depending on the specific strategy used, one or more of the shown actions, operations, and / or functions can be repeatedly executed. Furthermore, the described actions, operations, and / or functions can be graphically represented as code encoded into a non-transitory memory of a computer-readable storage medium in an engine control system, wherein the described actions are realized by cooperating with the electronic controller to execute instructions in a system including various engine hardware components.

[0119] It should be understood that the configurations and procedures disclosed herein are exemplary in nature, and these specific embodiments are not considered limiting, as many variations are possible. For example, the above-described technology can be applied to V-6, I-4, I-6, V-12, opposed 4-cylinder, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and constructions disclosed herein, as well as other features, functions, and / or properties.

[0120] The appended claims specifically point to certain combinations and sub-combinations that are considered novel and non-obvious. These claims may relate to a “one” element or a “first” element or its equivalent. These claims should be understood to include combinations of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics may be claimed by amending existing claims or by filing new claims in this or related applications. These claims, whether broader, narrower, identical, or different in scope from the original claims, are considered to be included within the subject matter of this disclosure.

Claims

1. A method for an engine, comprising: Fuel is delivered during the cylinder cycle via direct injectors and port injectors; When the current direct injection fuel share is closer to the lower limit than the upper limit, the direct injection fuel share will be increased to the upper limit; as well as When the current direct injection fuel share is closer to the upper limit than the lower limit, the first fuel share provided by the direct injector will be reduced to the lower limit.

2. The method of claim 1, wherein the direct injection fuel share increases or decreases relative to the intake manifold injection fuel share, and wherein each of the upper and lower limits is used for the direct injector and is based on engine operating conditions including engine speed, load, and operator torque requirements.

3. The method according to claim 2, further comprising: The transfer function of the direct injector is updated based on the air-fuel ratio error relative to the increased or decreased fuel share.

4. The method of claim 3, wherein the intake manifold fuel injection ratio is based on the direct injection fuel ratio, the method further comprising: The transfer function of the intake injector is updated based on the air-fuel ratio error relative to the fuel fraction injected into the intake manifold.

5. The method of claim 3, wherein the increase or decrease of the fuel share is in response to a threshold duration elapsed since the last update of the transfer function of the direct injector.

6. The method of claim 5, wherein the current direct injection fuel share includes a threshold change in the direct injection fuel share below the last update of the transfer function, and wherein each of the increased and decreased fuel shares includes a change in the direct injection fuel share above the threshold.

7. The method of claim 5, further comprising: In response to a duration less than the threshold that has elapsed since the last update of the transfer function, fuel is delivered in the cylinder cycle via the direct injector and the port injector at the current direct injection fuel share, and the transfer function of the direct injector is updated based on the rate of change of the air-fuel ratio error relative to the current direct injection fuel share.

8. The method of claim 4, wherein updating the transfer function comprises: Based on the rate of change of the air-fuel ratio relative to the increased or decreased direct injection fuel share, a first portion of the air-fuel ratio error is assigned to the direct injector, and based on the rate of change of the air-fuel ratio error relative to the intake manifold injection fuel share, a second portion of the air-fuel ratio error is assigned to the intake manifold injector. The transfer function of the direct injector is updated based on the first portion of the air-fuel ratio error; as well as The transfer function of the intake manifold injector is updated based on the second portion of the air-fuel ratio error.

9. The method of claim 8, further comprising: When the first portion is larger than the second portion, the operation of the direct injector is restricted, and when the second portion is larger than the first portion, the operation of the intake injector is restricted.

10. The method of claim 3, wherein the air-fuel ratio error is in the form of an adjusted fuel multiplier, the method further comprising: During the first condition, based on the current direct injection fuel share, i.e., the DI fuel share, the intake port injection fuel share, i.e., the PFI fuel share, is commanded, and based on the air-fuel ratio error relative to the commanded PFI fuel share, the PFI transfer function is obtained. as well as During the second condition, the intake manifold fuel injection (PFI) fuel share is commanded based on one of the upper and lower limits of the command (DI), and the PFI transfer function is obtained based on the air-fuel ratio error relative to the commanded PFI fuel share.

11. The method of claim 10, further comprising: During the first condition, fuel vapor is purged from the canister to the engine intake port later during the vehicle's driving cycle, and during the second condition, the fuel vapor is purged from the canister to the engine intake port earlier during the vehicle's driving cycle.

12. A system for an engine, comprising: An engine, which includes cylinders; The intake manifold fuel injector, or PFI, is in fluid communication with the cylinder. The direct injector (DI) is in fluid communication with the cylinder. An exhaust oxygen sensor is used to estimate the air-fuel ratio error in the cylinder. and The controller, comprising executable instructions stored in non-transitory memory, is used for: Based on engine speed and load, estimate the fuel split ratio in the cylinder cycle relative to the fuel delivered by DI via the PFI; In response to the estimated split ratio including changes in DI fuel share above a threshold since the last estimated split ratio, fuel is commanded according to the estimated split ratio, and In response to the estimated split ratio including the change in DI fuel share below a threshold since the last estimated split ratio and the elapsed threshold duration, the estimated split ratio is updated based on one of the upper and lower limits of the direct injector, the upper and lower limits being estimated based on the engine speed and load, and fuel is commanded according to the updated split ratio; The estimated split ratio includes the fuel share of the first direct injection and the fuel share of the second intake injection, and the estimated split ratio is updated based on one of the upper and lower limits of the direct injectors by: When the fuel share of the first direct injection is closer to the upper limit of the direct injector, the fuel share of the first direct injection is reduced to the lower limit and the fuel share of the second intake injection is increased accordingly. as well as When the fuel share of the first direct injection is closer to the lower limit of the direct injector, the fuel share of the first direct injection is increased to the upper limit and the fuel share of the second intake injection is reduced accordingly.

13. The system of claim 12, wherein the controller includes further instructions for: Based on the rate of change of the air-fuel ratio error relative to the estimated split ratio, the estimated air-fuel ratio error is allocated after the commanded fuel according to the estimated split ratio between the intake fuel injector and the direct injector; and Based on the rate of change of the air-fuel ratio error relative to the updated split ratio, the estimated air-fuel ratio error is allocated after the command fuel according to the updated split ratio between the intake fuel injector and the direct injector.

14. The system of claim 13, wherein allocating the air-fuel ratio error comprises assigning a first portion of the air-fuel ratio error to the direct injector and assigning a remaining second portion of the air-fuel ratio error to the intake fuel injector, and wherein the controller includes further instructions for: In response to the first part exceeding the second part, direct injection operation is restricted; and In response to the second part exceeding the first part, the operation of the intake fuel injector is restricted.

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