Method and system for adjusting a direct fuel injector

Abstract

The present application relates to a method and system for adjusting a direct fuel injector, and a method and system for reducing direct injector fueling errors caused by injection variability in a transition region of a direct injector map are disclosed. Fuel injection can be scheduled based on engine operating conditions including engine temperature and driver demand, and the fuel injection includes using one or more direct injection fuel pulses and port injection fuel pulses. In response to any pulse of the direct injection fuel pulse having a pulse width located in a high variability transition region of the direct injector, the fuel injection can be adjusted by adjusting the number of injections and / or the split ratio so as not to operate in the transition region.

Description

Technical Field

[0001] The present invention generally relates to methods and systems for regulating operation of direct fuel injectors of an internal combustion engine. Background Art

[0002] Internal combustion engines can utilize direct fuel injection, in which fuel is injected directly into the engine cylinder to improve mixture preparation and reduce cylinder charge temperature. Direct fuel injection can replace or be in addition to intake port fuel injection, in which fuel is injected into the intake port upstream of the intake valve of the engine cylinder. The amount of time that the direct fuel injector is activated (direct injection pulse width) can be a function of the fuel pressure supplied to the injector, the engine speed, and the engine load. In order to take advantage of the benefits of direct injection, it can be advantageous to have full control over the pulse width range of the direct fuel injector. This includes a wide variety of operating conditions, including but not limited to fuel rail pressure, engine speed, and mass fuel flow.

[0003] However, between the ballistic region and the full lift region, the performance of the solenoid-controlled direct fuel injector may be limited in its flow characteristics. This region is generally referred to as the transition region of the direct fuel injector. In this region, the flow of the fuel injector is inaccurate and unpredictable, resulting in variability between shots (shot-to-shot) and between components. For example, the direct fuel injector may deliver more or less fuel than expected in the transition region. In addition, the variability in the transition region may not show a linear trend, making it difficult to know and compensate for the variability. Injector variability may cause cylinder torque output imbalance due to different amounts of fuel injected into each cylinder, and may also cause higher tailpipe emissions and reduced fuel economy due to the inability to properly meter the fuel to be injected into each cylinder. Therefore, there may be engine operating regions where direct fuel injectors cannot fully meet NVH, drivability and emission requirements.

[0004] Various methods have been developed to reduce direct injector variability. Ranga et al. show an exemplary method in US20160153391. Therein, direct fuel injection is divided into multiple injections, one of which has a pulse width that is small enough to be delivered in the impact area of ​​the direct injector. The transfer function of the injector is known based on the lambda value and the split ratio. Subsequent direct injections are adjusted based on the known transfer function.

[0005] However, the inventors herein have recognized potential problems with the method of '391 and other related methods. As an example, the variability of the injector in the transition region remains unmapped. Various methods update the transfer function based on the known injector variability in the impact region, where the injector pulse width is less than the injector pulse width in the transition region. However, there may still be a fueling error for a larger injection pulse width that is located outside the impact region but is less than the injection pulse width in the lift region. Therefore, NVH, drivability and emission issues may remain. As an example, in the impact region, increasing the electrical pulse width to the fuel injector increases the amount of mass delivered. Although there may be some variability in the increase, the variability can be known, and the shape or shift of the slope in the impact region can be adjusted to account for the variability. However, in the transition region, the increased pulse width may actually result in a decrease in the mass of fuel injected. Therefore, it may not be possible to simply shift and change the shape of the slope in the transition region. Since the slope in the transition region is different for each injector and is significantly different between shots, the variability is exacerbated. Summary of the invention

[0006] In one example, the above problem can be solved by a method for an engine method, the method comprising: delivering fuel to a cylinder as multiple direct injections over a combustion cycle; and in response to a fuel mass of one of the multiple direct injections being in a transition region of a direct injector map, updating one or more of a ratio of fuel delivered in each of the multiple direct injections and a number of the multiple injections to move the fuel mass of the one of the multiple direct injections out of the transition region. In this way, direct injector variability in the transition region can be solved.

[0007] As an example, the engine controller can determine the initial fuel injection profile based on the engine operating conditions. For example, this can include the total fuel mass to be delivered by direct injection, the number of direct injections for delivering the total fuel mass (e.g., by 2-4 injections), and the split ratio of multiple direct injections. The split ratio can include the ratio of the portion of the total fuel mass to be delivered by the first injection in multiple direct injections relative to the portion of the total fuel mass to be delivered by the second (and third, etc.) injection in multiple direct injections. The fuel injector pulse width to be commanded is then determined based on the split ratio (including the fuel mass to be delivered in each injection in multiple injections and based on the fuel rail pressure). If the pulse width of any injection is determined to be located within the transition region of the direct injector, the controller can update the injection distribution so as to operate outside the transition region. Specifically, the controller can modify the fuel mass delivered in each injection based on the position of the injection in the transition region and the distance between the injection and the adjacent impact region and lift region, thereby updating the split ratio. For example, the fuel mass of the injection close to the impact region can be reduced in order to move the injection from the transition region to the impact region. As another example, the fuel mass injected near the lift region can be increased to move the injection from the transition region to the lift region. In this way, the fuel mass of all injections can be adjusted to maintain the total fuel mass.

[0008] In yet a further example, additionally or optionally, the number of injections of the split injection can be updated. For example, in response to the pulse width of at least one of the multiple direct injections being within the transition region, the number of injections can be reduced. By combining the fuel masses of 2 or more injections, the pulse width can be moved to the full lift region (linear region). As another example, in response to the pulse width of a single direct injection being within the transition region, the number of injections can be increased. By splitting the fuel mass into 2 or more injections, the pulse width of the injection can be moved to the full lift region, while the pulse width of another injection can be moved to the impact region. Further, in an engine configured with direct injection and port injection, the split ratio of the portion of the total fuel mass to be delivered by direct injection relative to the portion to be delivered by port injection can be updated. In yet a further example, a combination of the above methods can be selected. The selection can be based on engine operating conditions (such as engine speed constraints and NVH constraints).

[0009] In this way, direct injector variability is reduced. The technical effect of adjusting the direct injected fuel mass based on the position of the injected pulse width on the direct injector operating area map is that the direct fuel injector cannot be operated at a pulse width where nonlinear fuel injector behavior occurs. At the same time, the total fuel mass can be maintained. Since the operation is performed outside the transition area of ​​the direct injector, the engine air-fuel ratio error and torque error can be reduced. In addition, the method can reduce engine emissions and NVH issues. Overall, drivability is improved.

[0010] It should be understood that the above summary of the invention is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the appended claims. Furthermore, the claimed subject matter is not limited to implementations that address any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the engine system.

[0012] Figure 2 A high level flow chart illustrating an exemplary method for adjusting fuel injection profile to move direct injector operation outside of the transition region.

[0013] Figure 3 A high level flow chart illustrating an exemplary method for updating direct injected fuel mass in order to move direct injector operation outside of a transition region is shown.

[0014] Figure 4 An exemplary direct injector performance map is shown.

[0015] Figure 5-Figure 6 An example of operating a direct injector outside of the transition region by adjusting the amount of direct injection is shown.

[0016] Figure 7-Figure 8 An example of operating a direct injector outside of the transition region by adjusting the fuel mass injected in each of multiple direct injections is shown.

[0017] Figure 9-10 An example of operating a direct injector outside of the transition region by adjusting the split ratio of fuel delivered via direct injection relative to fuel delivered via port injection is shown.

[0018] Fig.11 An exemplary fuel injection profile that may be applied to operate a direct injector outside of the transition region is shown. DETAILED DESCRIPTION

[0019] The following description relates to methods for improving engine systems such as Figure 1 Systems and methods for direct injector performance in an engine system) can be based on, for example, Figure 2-Figure 3 The control routine of the exemplary method operates the engine via a controller so that in a transition region ( Figure 4 ) externally operated direct fuel injectors. The split ratio of port injection fuel to direct injection fuel, the number of direct injections, and the split ratio of direct injection fuel ( Figure 5-Figure 11 ) to update the fuel injection distribution.

[0020] Figure 1 An example of a combustion chamber or cylinder of an internal combustion engine 10 coupled in a vehicle 5 is depicted. In some examples, the vehicle 5 may be a hybrid vehicle having multiple torque sources that may be used for one or more wheels 55. In other examples, the vehicle 5 is a conventional vehicle having only an engine, or an electric vehicle having only (multiple) motors. In the example shown, the vehicle 5 includes an engine 10 and a motor 52. The motor 52 may be a motor or a motor / generator (M / G). When one or more clutches 56 are engaged, the crankshaft 140 of the engine 10 and the motor 52 are connected to the wheels 55 through the transmission 54. In the depicted example, the first clutch 56 is disposed between the crankshaft 140 and the motor 52, and the second clutch 56 is disposed between the motor 52 and the transmission 54. The controller 12 may send a signal to the actuator of each clutch 56 to engage or disengage the clutch so as to connect or disconnect the crankshaft 140 with the motor 52 and its connected components, and / or to connect or disconnect the motor 52 with the transmission 54 and its connected components. The transmission 54 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain system can be configured in a variety of ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0021] The electric machine 52 receives power from the traction battery 58 to provide torque to the wheels 55. The electric machine 52 may also operate as a generator to provide power to charge the battery 58, such as during braking operations.

[0022] Engine 10 may be controlled at least partially by a control system including controller 12, and by input from a vehicle operator 130 via an input device 132. In this example, input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. Cylinder (also herein a "combustion chamber") 14 of engine 10 may include combustion chamber walls 136 in which a piston 138 is positioned. Piston 138 may be coupled to a crankshaft 140 so that reciprocating motion of the piston is translated into rotational motion of the crankshaft. Crankshaft 140 may be coupled to at least one drive wheel of a passenger vehicle via a transmission system. Additionally, a starter motor (not shown) may be coupled to crankshaft 140 via a flywheel to enable a starting operation of engine 10.

[0023] Cylinder 14 may receive intake air via a series of intake passages 142, 144, and 146. Intake passage 146 may communicate with other cylinders of engine 10 in addition to cylinder 14. In some examples, one or more of the intake passages may include a boosting device (such as a turbocharger or supercharger). For example, Figure 1 An engine 10 is shown configured with a turbocharger including a compressor 174 disposed between intake passages 142 and 144, and an exhaust turbine 176 disposed along exhaust passage 148. Exhaust turbine 176 may at least partially power compressor 174 via shaft 180, wherein the boost device is configured as a turbocharger. However, in other examples, such as examples where engine 10 is provided with a supercharger, exhaust turbine 176 may optionally be omitted, wherein a mechanical input from a motor or the engine may power compressor 174. A throttle valve 162 including a throttle plate 164 may be provided along the intake passage of the engine for varying the flow and / or pressure of intake air provided to the engine cylinders. For example, as Figure 1 As shown, throttle valve 162 may be positioned downstream of compressor 174 , or alternatively may be provided upstream of compressor 174 .

[0024] Exhaust passage 148 may receive exhaust gas from other cylinders of engine 10 in addition to cylinder 14. Exhaust gas sensor 128 is shown coupled to exhaust passage 148 upstream of emission control device 178. For example, sensor 128 may be selected from a variety of suitable sensors for providing an indication of exhaust air / fuel ratio, such as a linear oxygen sensor or UEGO (Universal or Wide Range Exhaust Gas Oxygen), a two-state oxygen sensor or EGO (as depicted), HEGO (Heated EGO), NOx, HC, or CO sensor. Emission control device 178 may be a three-way catalyst (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0025] Each cylinder of engine 10 may include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown as including at least one intake poppet valve 150 and at least one exhaust poppet valve 156 located at an upper region of cylinder 14. In some examples, each cylinder of engine 10 (including cylinder 14) may include at least two intake poppet valves and at least two exhaust poppet valves located at an upper region of the cylinder.

[0026] Controller 12 can control intake valve 150 through actuator 152. Similarly, controller 12 can control exhaust valve 156 through actuator 154. During some conditions, controller 12 can change the signals provided to actuators 152 and 154 to control the opening and closing of the corresponding intake valve and exhaust valve. The positions of intake valve 150 and exhaust valve 156 can be determined by corresponding valve position sensors (not shown). The valve actuator can be an electric valve actuation type or a cam actuation type or a combination thereof. The intake valve timing and exhaust valve timing can be controlled simultaneously, or any possibility of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing can be used. Each cam actuation system can include one or more cams, and can utilize one or more of the following: cam profile conversion (CPS), variable cam timing (VCT), variable valve timing (VVT) and / or variable valve lift (VVL) system, which can be operated by controller 12 to change valve operation. For example, cylinder 14 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 examples, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system.

[0027] Cylinder 14 may have a compression ratio, which is the ratio of volume when piston 138 is at bottom dead center to volume when piston 138 is at top dead center. In one example, the compression ratio is in the range of 9:1 to 10:1. However, in some examples using different fuels, the compression ratio may be increased. For example, this may occur when using a higher octane fuel or a fuel with a higher latent enthalpy of vaporization. If direct injection is used, the compression ratio may also be increased due to the effect of direct injection on engine knock.

[0028] In some examples, each cylinder of engine 10 may include a spark plug 192 for initiating combustion. Under select operating modes, ignition system 190 may provide an ignition spark to combustion chamber 14 via spark plug 192 in response to spark advance signal SA from controller 12. However, in some embodiments, spark plug 192 may be omitted, such as where engine 10 may initiate combustion by auto-ignition or by injection of fuel (as may be the case in some diesel engines).

[0029] In some examples, each cylinder of engine 10 may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder 14 is shown as including two fuel injectors 166 and 170. Fuel injectors 166 and 170 may be configured to deliver fuel received from fuel system 8. Fuel system 8 may include one or more fuel tanks, fuel pumps, and fuel rails. Fuel injector 166 is shown as being directly coupled to cylinder 14 for injecting fuel directly therein in proportion to the pulse width of signal FPW-1 received from controller 12 via electronic driver 168. In this manner, fuel injector 166 provides what is known as direct injection (hereinafter referred to as "DI") of fuel into combustion cylinder 14. Although Figure 1 Injector 166 is shown positioned to one side of cylinder 14, but may alternatively be located on top of the piston, such as near spark plug 192. Due to the lower volatility of some alcohol-based fuels, such a location may improve mixing and combustion when the engine is operated on alcohol-based fuels. Alternatively, the injector may be located on top of and near the intake valve to improve mixing. Fuel may be delivered to fuel injector 166 from a fuel tank of fuel system 8 via a high pressure fuel pump and fuel rail. Additionally, the fuel tank may have a pressure transducer that provides a signal to controller 12.

[0030] In some examples, direct fuel injector 166 may be solenoid controlled, wherein the amount of fuel delivered by the injector may be adjusted by varying a pulse width signal commanded to a solenoid coupled to the fuel injector. The inventors herein have recognized that a solenoid controlled direct injector may have unpredictable flow characteristics in a transition region of the direct fuel injector, between the impact region and the full lift region of injector operation. Specifically, in this region, the flow of the fuel injector may be inaccurate and unpredictable, resulting in shot-to-shot and part-to-part variability. In order to reduce cylinder torque output imbalances and undesirable tailpipe emissions due to injector variability, an engine controller may operate the direct injector outside of the transition region. As described in reference to Figure 2As described in detail, the engine controller can determine a fuel injection distribution, which includes the fuel mass to be delivered by the direct injector, the number of direct injections on a given fuel injection event, and the fuel split ratio in each injection of the number of direct injections. A pulse width signal can then be determined for each injection. If the pulse width signal of any direct injection falls into the transition region of the direct injector, the fuel injection distribution can be updated. Specifically, the pulse width signals of all direct injections can be adjusted to operate the direct injector outside the transition region. For example, the fuel mass in a given direct injection can be increased or decreased, the number of direct injections can be increased or decreased, and / or the fuel split ratio in the direct injection can be increased or decreased.

[0031] return Figure 1 , fuel injector 170 is shown arranged in intake passage 146 rather than in cylinder 14, in a configuration that provides so-called port fuel injection (hereinafter referred to as "PFI") into the intake port upstream of cylinder 14. Fuel injector 170 may inject fuel received from fuel system 8 in proportion to the pulse width of signal FPW-2 received from controller 12 via electronic driver 171. It should be noted that a single driver 168 or 171 may be used for both fuel injection systems, or as depicted, multiple drivers (e.g., driver 168 for fuel injector 166 and driver 171 for fuel injector 170) may be used.

[0032] In an alternative example, each of fuel injectors 166 and 170 may be configured as a direct fuel injector for injecting fuel directly into cylinder 14. In yet another example, each of fuel injectors 166 and 170 may be configured as a port fuel injector for injecting fuel upstream of intake valve 150. In yet other examples, cylinder 14 may include only a single fuel injector that is configured to receive different fuels in varying relative amounts from a fuel system as a fuel mixture, and is further configured to inject such a fuel mixture directly into the cylinder as a direct fuel injector, or to inject such a fuel mixture upstream of the intake valve as a port fuel injector. Therefore, it should be understood that the fuel system described herein should not be limited to the specific fuel injector configurations described herein by way of example.

[0033] Fuel can be delivered to the cylinder by two injectors during a single cycle of the cylinder. For example, each injector can deliver a portion of the total fuel injection that is burned in cylinder 14. In addition, the distribution and / or relative amount of fuel delivered from each injector can vary with operating conditions (such as engine load, knock and exhaust temperature, such as described below). Port injection fuel can be delivered during an open intake valve event, a closed intake valve event (e.g., generally before the intake stroke), and during both open and closed intake valve operations. Similarly, direct injection fuel can be delivered, for example, during the intake stroke and partially during the previous exhaust stroke, during the intake stroke, and partially during the compression stroke. Therefore, even for a single combustion event, the injected fuel can be injected from the intake port injector and the direct injector at different timings. In addition, for a single combustion event, multiple injections can be performed on the delivered fuel in each cycle. Multiple injections can be performed during the compression stroke, the intake stroke, or any appropriate combination thereof.

[0034] As mentioned above, Figure 1 Only one cylinder of a multi-cylinder engine is shown. Thus, each cylinder may similarly include its own set of intake / exhaust valves, (multiple) fuel injectors, spark plugs, etc. It should be appreciated that engine 10 may include any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more cylinders. Furthermore, each of these cylinders may include a plurality of Figure 1 Some or all of the various components described and depicted with reference to cylinder 14 .

[0035] Fuel injectors 166 and 170 may have different characteristics. These include size differences, for example, one injector may have a larger spray hole than the other injector. Other differences include, but are not limited to: different spray angles, different operating temperatures, different aiming, different injection timing, different spray characteristics, different locations, etc. In addition, depending on the distribution ratio of the fuel injected in injectors 170 and 166, different effects may be achieved.

[0036] The fuel tank in the fuel system 8 can hold fuels of different fuel types, such as fuels with different fuel qualities and different fuel components. The differences may include different alcohol contents, different water contents, different octane numbers, different heats of evaporation, different fuel blends and / or combinations thereof. An example of a fuel with different heats of evaporation may include gasoline as a first fuel type with a lower heat of evaporation and ethanol as a second fuel type with a higher heat of evaporation. In another example, the engine may use gasoline as the first fuel type, and use an alcohol-containing fuel blend such as E85 (which is about 85% ethanol and 15% gasoline) or M85 (which is about 85% methanol and 15% gasoline) as the second fuel type. Other feasible substances include water, methanol, a mixture of alcohol and water, a mixture of water and methanol, a mixture of alcohol, etc.

[0037] In yet another example, both fuels may be alcohol blends with different alcohol compositions, where the first fuel type may be a gasoline alcohol blend with a lower alcohol concentration, such as E10 (which is approximately 10% ethanol), and the second fuel type may be a gasoline alcohol blend with a higher alcohol concentration, such as E85 (which is approximately 85% ethanol). Furthermore, the first fuel and the second fuel may also differ in other fuel qualities, such as differences in temperature, viscosity, octane rating, etc. Furthermore, the fuel characteristics of one or both fuel tanks may change frequently, for example due to day-to-day variations in fuel tank refilling.

[0038] The controller 12 Figure 1 10 is shown as a microcomputer, which includes a microprocessor unit 106, input / output ports 108, an electronic storage medium for executable programs and calibration values ​​(in this particular example, shown as a non-volatile read-only memory chip 110 for storing executable instructions), a random access memory 112, a keyless memory (KAM) 114, and a data bus. In addition to those signals previously discussed, the controller 12 may also receive various signals from sensors coupled to the engine 10, including the following measurements: sensed mass air flow (MAF) from a mass air flow sensor 122; engine coolant temperature (ECT) from a temperature sensor 116 coupled to a cooling jacket 118; a surface ignition sensing signal (PIP) from a Hall effect sensor 120 (or other type) coupled to a crankshaft 140; a throttle position (TP) from a throttle position sensor; and an absolute manifold pressure signal (MAP) from a sensor 124. The controller 12 may generate an engine speed signal RPM based on the signal PIP. Manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum, or pressure, in the intake manifold.

[0039] The controller 12 is Figure 1Various sensors receive signals and use Figure 1 The controller may control various actuators of the controller to adjust engine operation based on the received signals and instructions stored on the memory of the controller. For example, the controller may adjust the fuel pulse width signal commanded to the direct fuel injector to operate the direct injector outside the transition region of the injector.

[0040] In this way, Figure 1The components implement an engine system, the engine system including: an engine cylinder; a direct injector for filling the cylinder with fuel; and a controller having computer-readable instructions stored on a non-volatile memory, the instructions being used to: estimate an initial fuel injection distribution for a combustion cycle of the cylinder based on engine speed-load and engine temperature, the initial fuel injection distribution including a plurality of direct injection fuel pulses, at least one of the plurality of direct injection fuel pulses having a pulse width in a transition region of the direct injector; during a first condition, modify the initial fuel injection distribution to a first modified fuel injection distribution having a smaller number of the plurality of direct injection fuel pulses, each of the smaller number of the plurality of direct injection fuel pulses having a smaller pulse width in a lift region of the direct injector; and during a second condition, modify the initial fuel injection distribution to a second modified fuel injection distribution, wherein the pulse width of a first group of the plurality of direct injection fuel pulses is reduced into an impingement region of the direct injector, and the pulse width of a second group of the plurality of direct injection fuel pulses is increased into a full lift region of the direct injector, while maintaining the number of the plurality of direct injection fuel pulses, wherein a total directly injected fuel mass in each of the first modified fuel injection distribution and the second modified fuel injection distribution is the same as the fuel mass in the initial fuel injection distribution. In one example, during a first condition, if a solution cannot be found by adjusting the fuel mass because the impact injection is below a minimum pulse width of the fuel injector, the fuel mass may be combined. A minimum pulse width must exist in the impact region because, under certain circumstances, small fuel pulses are too inaccurate between shots and between injectors, and the risk of the injector failing to open may increase. The multiple direct injection fuel pulses of the initial fuel injection distribution may include an initial number of direct injection fuel pulses, and wherein the modification during each of the first and second conditions is based on the initial number of direct injection fuel pulses, and further based on the relationship of the pulse width of at least one of the multiple direct injection pulses to an upper pulse width limit of the impact region and a lower pulse width limit of the lift region. The system may also include an intake port injector for filling the cylinder with fuel, wherein the controller includes additional instructions for the following operations: under a third condition, modifying the initial fuel injection distribution to a third modified fuel injection distribution, which includes adjusting the total direct injection fuel mass to move the pulse width of at least one of the multiple direct injection fuel pulses out of the transition region of the direct injector, and adjusting the intake port injection fuel mass based on the adjusted direct injection fuel mass.

[0041] Figure 1The component also implements an engine system, the engine system including: an engine cylinder; a direct injector for filling the cylinder with fuel; an intake port injector for filling the cylinder with fuel; and a controller having computer-readable instructions stored on a non-transitory memory, the instructions for: estimating an initial fuel injection distribution for a combustion cycle of the cylinder based on engine speed-load and engine temperature, the initial fuel injection distribution including an initial split ratio of direct injection fuel to intake port injection fuel delivered by a plurality of direct injection fuel pulses, at least one of the plurality of direct injection fuel pulses having a pulse width in a transition region of the direct injector; and modifying the initial fuel injection distribution to change the split ratio of direct injection fuel to intake port injection fuel so that at least one of the plurality of direct injection fuel pulses is moved out of the transition region. The modification may include: increasing or decreasing the intake port injection fuel mass relative to the total direct injection fuel mass based on a relationship of the pulse width of at least one of the plurality of direct injection pulses to an upper pulse width limit of the impact region of the direct injector and a lower pulse width limit of the lift region of the direct injector. Reducing the total direct injected fuel mass may include reducing the number of multiple direct injected fuel pulses so as to move the pulse width of each of the reduced number of direct injected fuel pulses into the lift region, and wherein increasing the total direct injected fuel mass includes increasing the number of multiple direct injected fuel pulses so as to move the pulse width of each of the increased number of direct injected fuel pulses into the impact region.

[0042] Now go to Figure 2 , an exemplary method 200 for modifying a fuel injection profile to operate a direct injector outside of a transition region of the direct injector is shown. Figure 2 The method may be included as executable instructions stored in a non-volatile memory. Figure 1 In addition, Figure 2 The method can provide Figure 5-Figure 11 Based on instructions stored in the controller's memory and in conjunction with sensors from the engine system (such as those referenced above) Figure 1 Based on signals received from sensors (described in the foregoing), the controller may execute instructions for performing method 200 and the remaining methods included herein. According to the method described below, the controller may employ engine actuators of the engine system to adjust engine operation.

[0043] At 202 , the method includes estimating and / or measuring engine operating conditions, which may include, for example, engine speed, engine load, engine temperature (e.g., inferred from engine coolant temperature), exhaust temperature, catalyst temperature (Tcat), desired torque, boost level, dilution demand, etc.

[0044] At 204, the method includes determining an initial fuel injection distribution based on estimated engine operating conditions. Determining the initial fuel injection distribution includes: at 206, determining an overall split ratio of fuel to be delivered by direct injection (DI) relative to fuel to be delivered by port fuel injection (PFI). The controller can determine the total fuel mass to be delivered on a given combustion cycle based on the driver torque demand and engine speed-load, and then determine the proportion of the portion of the total fuel mass to be delivered by the direct injector relative to the portion delivered by the port injector. As an example, during an engine cold start, during which the estimated engine coolant temperature before combustion begins in the engine is below a threshold (such as below the light-off temperature of the exhaust catalyst), a larger proportion of the fuel mass can be delivered as port injection relative to direct injection (at least for multiple combustion events since the engine was started from rest) to reduce particulate matter emissions caused by direct injection and cold start engine operation roughness. In contrast, during an engine hot start, during which the estimated engine coolant temperature is above a threshold before combustion begins in the engine, a larger proportion of the fuel mass may be delivered as direct injection relative to port injection (at least for a number of combustion events since the engine was started from rest) in order to take advantage of the higher performance and charge cooling effects of direct injection. It should be appreciated that in other examples, the entire commanded fuel mass may be delivered via port injection only or direct injection only.

[0045] In another example, the initial fuel injection distribution can be based on the combustion chamber temperature. Large DI injections (such as when the DI fuel mass is above a threshold amount) may hit the walls / pistons of the combustion chamber and produce particulate emissions. Therefore, when the combustion chamber temperature is high, the split ratio can be adjusted to reduce the DI fuel mass portion and increase the PFI fuel mass portion. As another example, the maximum flow limit of the injector can be considered in the initial fuel injection distribution, especially when the injector is cold, and fuel from two injectors is required to deliver the total fuel mass required to start the engine. This may be particularly true when dealing with an increased percentage of fuel ethanol. In another example, the engine start time can be considered when determining the initial fuel injection distribution. The DI injector can be injected during the compression stroke, which enables the engine to start on an earlier cylinder, thereby reducing the start time. Therefore, when a shorter start time is required, a larger portion of the total fuel mass can be delivered by direct injection. As another example, when determining the initial fuel injection distribution, the flow rate of the high pressure fuel pump (HPP) coupled to the direct injector can be considered. If the DI injectors are likely to flood the HPP, a larger portion of the total fuel mass may be delivered as PFI at engine start.

[0046] In one example, the amount of fuel to be delivered by the port injectors and the direct injectors is determined empirically and stored in a predetermined lookup table or function. For example, one table may correspond to determining the port injection amount and one table may correspond to determining the direct injection amount. The two tables may be indexed to engine operating conditions, such as engine speed and engine load, and other engine operating conditions. In addition, the table may output the amount of fuel injected into the engine cylinders at each combustion cycle via port fuel injection and / or direct injection.

[0047] As another example, the controller may make a logical determination (e.g., regarding the pulse width to be commanded to the solenoids of the port fuel injectors and direct fuel injectors) based on a logic rule as a function of the parameters (engine speed and load) and further based on the engine temperature. The controller may then generate a pulse width control signal that is sent to the injector solenoids.

[0048] Determining the initial fuel injection distribution also includes: at 208, determining the number of injections for delivering the fuel mass per combustion cycle. For example, within a given combustion cycle, one or more of the port injected fuel mass and the direct injected fuel mass can be delivered as multiple injections. In one example, within a given combustion cycle, the port injected fuel mass can be delivered as a single port injection, while the direct injected fuel mass can be delivered as multiple direct injections. The number of injections for multiple injections can be determined based on engine operating conditions. For example, during an engine cold start, the number of direct injections for delivering the direct injected fuel mass can be higher (per combustion cycle) relative to an engine hot start. During an engine cold start, the controller can use both PFI injected fuel and DI injected fuel. DI injected fuel can be used to promote catalyst heating. However, since DI fuel may increase emissions due to particulate contact with the combustion chamber, the DI fuel pulse can be divided into multiple injections.

[0049] The number of injections may also be based on the mass of fuel to be delivered. For example, when the mass of fuel to be delivered by the direct injector increases and exceeds the maximum pulse width of the direct injector, the fuel mass may be divided into multiple injections, each injection having a pulse width at or below the maximum pulse width. Similarly, when the mass of fuel to be delivered by the port injector increases and exceeds the maximum pulse width of the port injector, the fuel mass may be divided into multiple injections, each injection having a pulse width at or below the maximum pulse width. Multiple port injections may include multiple injections in the exhaust stroke (closed intake valve), intake stroke (open intake valve), or a combination thereof. Multiple direct injections may include multiple injections in the intake stroke, compression stroke, or a combination thereof.

[0050] By splitting the injection into multiple injections, the impact of the fuel with engine components (such as the piston and cylinder walls) is reduced. When the fuel hits these components, it can wash down the walls (which can damage the engine and put excess fuel into the oil), or it can burn and produce particulate emissions. Splitting the fuel into smaller pulses avoids this. Compression injection can also be used so that when the spark is delivered, the atomized fuel is in the vicinity of the spark plug.

[0051] Determining the initial fuel injection profile also includes, at 210, determining a split ratio of the fuel among the multiple injections. For example, over a given combustion cycle, where the direct injection fuel mass is delivered as a split direct injection including at least one intake stroke injection (DI_int) and at least one compression stroke injection (DI_comp), the controller may determine a proportion of the direct injection fuel mass delivered via the intake stroke injection relative to the direct injection fuel mass delivered via the compression stroke injection. Similarly, over a given engine cycle, where the direct injection fuel mass is delivered via multiple intake stroke injections or multiple compression stroke injections, a split ratio of the direct injection fuel mass in each injection may be determined. In one example, during an engine cold start, the direct injection fuel mass may be delivered as a split direct injection, where a larger portion of the direct injection fuel mass is delivered in the compression stroke and a smaller portion of the fuel mass is delivered in the intake stroke. In another example, during an engine cold start, the direct injection fuel mass may be delivered as a split compression stroke direct injection, where a larger portion of the fuel is delivered earlier during the compression stroke of the combustion cycle and a remaining smaller portion of the fuel is injected later during the compression stroke of the combustion cycle.

[0052] Can adjust the split ratio of injection and the quantity of multiple injections of split injection based on engine operating conditions (such as engine temperature, ambient temperature and alcohol content of injection fuel when engine starts).In addition, can further adjust the split ratio and quantity of injection based on exhaust catalyst temperature, PM load of exhaust PM filter and the smoke tendency of engine when engine starts.For example, along with the alcohol content of injection fuel increases, the quantity of compression stroke direct injection can be increased.As another example, along with engine temperature or ambient temperature reduce when engine cold start, the quantity of compression stroke injection applied during first combustion event can be increased.In one example, can advantageously use multiple compression stroke direct injection of alcohol fuel to heat engine and catalyst, thus promote catalyst activation and improve engine and catalyst performance under engine cold start condition, reduce the smoke load of direct injection simultaneously.

[0053] As an example, the controller can determine the control signals to be sent to the direct fuel injector actuator and the intake port fuel injector actuator, such as the pulse width of the signal determined based on the determination of engine speed and load, and further based on engine temperature, fuel alcohol content (or fuel octane grade) and engine PM load. The engine speed can be based on the output of the crankshaft sensor, and the engine load can be based on the operator torque demand. The controller can determine the pulse width to be commanded to each injector by directly considering the determination of engine speed-load and engine temperature, such as increasing the direct injection pulse width as the engine speed and engine load increase. Alternatively, the controller can determine the pulse width based on a calculation using a lookup table, in which the input is relative humidity and the output is pulse width.

[0054] It will be appreciated that after determining the DI:PFI split ratio, number of injections, and direct injection split ratio, the controller may determine a fuel pulse width signal for each injection command based on the fuel rail pressure and the fuel mass to be delivered in each injection.

[0055] At 212 , it may be determined whether any DI fuel pulses in the determined fuel injection profile are within a transition region of the direct injector (specifically, a direct injector operation map). Figure 4 As described in detail, the transition region is located between the impact region and the lift (or linear) region of the direct injector, and the direct injector variability in the transition region is higher than the direct injector variability in each of the impact region and the lift region. Determining whether any DI fuel pulse is within the transition region of the direct injector may include, for example, determining whether the pulse width signal for any DI fuel pulse is less than an upper threshold corresponding to the lift region of the direct injector and greater than a lower threshold corresponding to the impact region of the direct injector, the upper threshold and the lower threshold being selected based on the fuel rail pressure. In this way, the transition region includes a specific pulse width range at different fuel rail pressures. As the pressure across the DI injector changes, the characteristics of the injector change. Therefore, the transition region shifts and changes size at different fuel rail pressures. Therefore, calibration must be performed for each injector design (e.g., part number), but not for each injector individually. A set of extreme sample injectors can be used to calibrate the pulse width range at each pressure, and the calibration can then be used to cover the entire injector population. If no DI fuel pulse is located in the transition region, the method moves to 214 to deliver fuel according to the determined fuel injection distribution, and the method ends.

[0056] Temporarily go to Figure 4, a map 400 depicts an example map 400 of direct injector operating regions. The map 400 depicts injector pulse width along the x-axis and fuel mass along the y-axis. The relationship between commanded direct injector pulse width and actual delivered fuel mass is shown at curve 402 .

[0057] Curve 402 shows that a direct injector is located in its different regions (impact, transition, full lift) as the width of the electrical pulse applied to the injector increases. First, the fuel injector is not even open and a minimum electrical pulse is required to open the injector and enable the fuel to start flowing. Then, the impact region is the period of time when the needle is not fully open. In this region, small changes in the width of the electrical pulse result in large changes in the fuel mass (since the slope in this region is very steep). In the transition region, the needle may jump and fueling may be very unpredictable (between shots and between injectors). Then, the full lift region always has the same less steep slope and is therefore linear. For example, in the linear region, if a pulse width of 1 ms flows through 100 ml, a pulse width of 2 ms will flow through 200 ml.

[0058] At higher commanded fuel pulse widths, the injector operates in a lift region 406 where the fuel mass varies linearly with the commanded pulse width. At very small commanded fuel pulse widths, the injector operates in an impact region 404 where some variability may exist. Specifically, at very low commanded pulse widths, i.e., less than the injector's minimum pulse width, no fuel is delivered. However, thereafter, the fuel mass varies linearly with the commanded pulse width. In the region between the lift region and the impact region, specifically in the intermediate transition region 408, the injector operates with high variability. For example, based on the position of the pulse width within the transition region, the actual fuel mass delivered may be higher or lower than the expected fuel mass. Furthermore, the variability is nonlinear and difficult to predict or model, making it difficult to compensate for.

[0059] Specifically, in the impact region, increasing the electrical pulse width to the fuel injector increases the amount of mass delivered at a higher rate (steeper slope). While there may be some variability in this increase, the variability can be mapped, and the shape or shift of the slope in the impact region can be adjusted to take into account the mapped variability. For example, based on the variability, the slope can be made steeper or less steep. However, in the transition region, the increased pulse width may actually cause the mass of fuel injected to decrease. Because the shape and slope vary dramatically in the transition region (between shots and between injectors in an injector group), it may not be possible to simply shift and change the shape of the slope in the transition region. Because the slope in the transition region is different for each injector and significantly different between shots, the variability is exacerbated.

[0060] As described in detail herein, by updating the fuel injection profile to move the DI fuel pulse out of the transition region, fueling errors and resulting torque errors and emissions issues can be reduced. Thus, avoiding the transition region of the injector is not as simple as changing the pulse width of the injection to just jump from the end of the impact region to the beginning of the full lift region, because the fuel mass delivered in region 404 is significantly lower than the fuel mass delivered in region 406. This would result in a large jump in the fuel delivered to the engine. Therefore, updating the injector pulse width alone may not be sufficient to avoid the transition region. Instead, as described in reference Figure 3 and Figure 5-Figure 11 As described in detail in the example of , the fuel mass of each injection pulse of an initial fuel injection profile may need to be modified to maintain the total fuel mass delivered to the engine.

[0061] return Figure 2, if any DI fuel pulse of the initially determined fuel injection distribution is located within the transition region of the direct injector, then at 216, the method includes updating the fuel injection distribution to move the affected (multiple) DI fuel pulses out of the transition region. Updating the fuel injection distribution includes: at 218, updating the DI:PFI split ratio. For example, the proportion of the total fuel mass delivered by direct injection can be increased, while the proportion delivered by port injection is correspondingly reduced. As another example, the proportion of the total fuel mass delivered by direct injection can be reduced, while the proportion delivered by port injection is correspondingly increased. The controller can estimate the initial ratio of port injection fuel relative to direct injection fuel on a combustion cycle based on engine operating conditions (such as for a cold start of the engine), and then in response to the direct fuel injection at the initial ratio being located in the transition region of the direct injector map, the controller can update the initial ratio to move the direct fuel injection out of the transition region. The update can be based on the relationship between the pulse width of the direct fuel injection and each of the impact-transition boundary and the lift-transition boundary of the direct injector map. As an example, in response to a distance of a direct fuel injection pulse width from an impingement-transition boundary of a direct injector map being less than a distance of the direct fuel injection pulse width from a lift-transition boundary of the direct injector map, the controller may decrease the direct injected fuel mass to move the pulse width from a transition region of the direct injector map to an impingement region while increasing the port injected fuel mass. As another example, in response to a distance of a direct fuel injection pulse width from an impingement-transition boundary of a direct injector map being greater than a distance of the direct fuel injection pulse width from a lift-transition boundary of the direct injector map, the controller may increase the direct injected fuel mass to move the pulse width from a transition region of the direct injector map to a lift region while decreasing the port injected fuel mass. The initial ratio of the port injected fuel to the direct injected fuel may include multiple direct injections over a combustion cycle, and the increase and decrease may be based on the number of the multiple direct injections.

[0062] As described in detail below, the controller may adjust the number of multiple direct injections by reducing the number of multiple direct injections so as to move the pulse width from the transition region to the lift region. Here, the reduction may be in response to an unadjusted number of multiple direct injections being above a threshold. As another example, the controller may adjust the number of multiple direct injections by increasing the number of multiple direct injections so as to move the pulse width from the transition region to the impact region. Here, the increase may be in response to an unadjusted number of multiple direct injections being below a threshold. In one example, the multiple direct injections may include multiple direct injections in an intake stroke and / or a compression stroke of a combustion cycle, and the updating may also include updating a split ratio of the direct injected fuel delivered in the intake stroke relative to the direct injected fuel delivered in the compression stroke.

[0063] Additionally or optionally, updating the fuel injection distribution may include, at 220, updating the number of injections used to deliver the fuel mass. For example, the total number of direct injections may be increased by splitting some fuel pulses into multiple smaller fuel pulses. As another example, the total number of direct injections may be reduced by merging some fuel pulses into fewer, larger fuel pulses. Additionally or optionally, updating the fuel injection distribution may include, at 222, updating the split direct injection ratio of the fuel delivered in the multiple direct injection pulses. For example, the amount of total direct injected fuel mass delivered via compression stroke direct injection may be increased, while the fuel mass delivered via intake stroke direct injection may be decreased. As another example, the amount of total direct injected fuel mass delivered via compression stroke direct injection may be decreased, while the fuel mass delivered via intake stroke direct injection may be increased. As referenced in Figure 3 Methods and Figure 5-Figure 11 As described in the example of , yet further options are possible. The updating may be performed based on the position of the fuel mass of the DI fuel pulse in the transition region in relation to each of the lift region and the impingement region. In this way, the DI fuel pulse may be modified to operate the direct injector outside of the transition region, thereby reducing fueling errors and related problems.

[0064] In one example, during the first condition, the controller may update the fuel injection profile by adjusting the fuel mass between DI injections while maintaining the number of DI injections as it deviates as little from the base engine calibration as possible. In another example, since reducing the number of DI injections may reduce the effectiveness of multiple injections in reducing particulate emissions, the number of DI injections may be reduced during the second condition when the exhaust PM load is below a threshold. In yet another example, during the third condition, the DI / PFI split ratio may be modified, however, a limit may be imposed on the split ratio adjustment before it may begin to affect sideline spark and charge air cooling (power).

[0065] In yet a further example, a combination of the above methods may be selected. The selection may be based on engine operating conditions (such as engine speed constraints and NVH constraints). For example, an engine speed constraint may limit the total number of injections that the powertrain control module can inject. At higher engine speeds, the engine controller may not be able to handle the power consumption of multiple fuel injections. Therefore, at higher engine speeds, updating the injection distribution may include reducing the number of injections; or if the number of injections is increased, increasing the injection by a smaller amount (i.e., limiting the increased number of injections). As another example, additional fuel injection may increase ticking noise, which may have a negative impact on consumer perception. Therefore, when engine ticking noise already exists, updating the injection distribution may include reducing the number of injections; or if the number of injections is increased, increasing the injection by a smaller amount (i.e., limiting the increased number of injections).

[0066] At 224 , fuel is delivered according to the updated fuel injection profile. For example, the controller may determine the fuel pulse widths to command based on the updated fuel masses for the various pulses, and then send these signals to the corresponding fuel injectors. The method then ends.

[0067] Now go to Figure 3 , an exemplary method 300 for updating a fuel injection profile to move a DI fuel pulse out of a transition region of a direct injector is shown. Figure 3 The method can be used as Figure 2 The method may be performed as part of the method, such as at 216.

[0068] At 302, the method includes determining whether any DI fuel pulses of the initially determined fuel injection profile are within the transition region of the direct injector map. If not, the method moves to 322 to deliver fuel according to the unmodified fuel injection profile. This includes sending a pulse width signal to the fuel injector according to the initial fuel injection profile.

[0069] If one or more DI fuel pulses of the initial fuel injection profile are determined to have a fuel pulse width within the transition region, the method proceeds to 304 where the location of the affected DI fuel pulse(s) within the transition region of the injector is determined. For example, the distance of the affected DI fuel pulse(s) from each of the impingement region (specifically, the transition region and the boundary of the impingement region) and the lift region (specifically, the boundary of the transition region and the lift region) may be estimated. The controller may reference a direct injector map (such as Figure 4 An exemplary map of ) to estimate the distance.

[0070] At 305, it may be determined whether the fuel pulse in the transition region is closer to the impingement region relative to the lift region. For example, a first distance of the fuel pulse from the impingement-transition boundary and a second distance of the fuel pulse from the lift-transition boundary may be compared. If the first distance is less than the second distance, then the affected fuel pulse is determined to be closer to the impingement region. It should be appreciated that each DI fuel pulse in the transition region may be similarly evaluated.

[0071] If the affected DI fuel pulse is closer to the impingement region of the injector, then at 310, the method includes reducing the pulse width commanded for the affected DI fuel pulse to move it from the transition region to the impingement region. Due to the change in pulse width, the mass of fuel delivered in the affected fuel is reduced. In contrast, if the affected DI fuel pulse is closer to the lift region of the injector, such as when the second distance is less than the first distance, then at 308, the method includes increasing the pulse width commanded for the affected DI fuel pulse to move it from the transition region to the lift region. Due to the change in pulse width, the mass of fuel delivered in the affected fuel is increased.

[0072] In this way, in response to a DI fuel pulse (e.g., a fuel mass or fuel pulse width of an affected DI fuel pulse) being less than a distance of the affected fuel pulse from an impact-transition boundary of a direct injector map than a distance of the affected fuel pulse from a lift-transition boundary of the direct injector map, the controller may reduce the fuel mass of the injection of the plurality of direct injections to move the fuel mass from a transition region of the direct injector map to an impact region while increasing the fuel mass of another injection of the plurality of direct injections. In an alternative example, in response to a fuel mass being greater than a distance of the fuel mass from an impact-transition boundary of the direct injector map than a distance of the fuel mass from a lift-transition boundary of the direct injector map, the controller may increase the fuel mass of the injection of the plurality of direct injections to move the fuel mass from a transition region of the direct injector map to a lift region while reducing the fuel mass of another injection of the plurality of direct injections. Here, the increase and decrease may be based on the total number of the plurality of direct injections in the initial (unmodified) DI fuel injection profile, and the proportion of those injections that are located in the transition region.

[0073] The method moves from each of 308 and 310 to 320, where the method includes adjusting the pulse width commanded for each of the remaining DI fuel pulses (outside the transition region) and the PFI fuel pulses to maintain the total fuel mass. In other words, the total fuel mass delivered by the unmodified fuel injection profile and the modified fuel injection profile remains unchanged. In yet a further example, adjusting the pulse width may include: adjusting the direct injection fuel mass to move the affected pulses out of the transition region, and then adjusting the amount of fuel delivered to the cylinder via port injection over the combustion cycle to maintain the total fuel mass based on the updated DI fuel mass.

[0074] Additionally or optionally, the method may also move (from 302) to 314 to adjust the number of direct injections when adjusting the affected fuel pulses based on their location within the transition region. Specifically, at 314, it may be determined whether the DI fuel pulse in the transition region is part of a split direct injection. Split direct injection may be identified when a DI fuel mass is delivered within multiple intake stroke direct injections and / or compression stroke direct injections. As an example, a split direct injection may include 2-4 direct injections, which may be any combination of intake stroke direct injections and compression stroke direct injections.

[0075] If the affected DI fuel pulse is not part of a split direct injection, such as when the DI fuel pulse is a single direct injection of an unmodified fuel injection profile, then at 318, the method includes adjusting the fuel pulse width to split the affected DI fuel pulse into a plurality of smaller DI pulses, each of the plurality of smaller DI fuel pulses being located in an impingement region of the injector. By increasing the number of fuel pulses, the affected DI fuel pulse is moved out of the transition region, and each of the smaller fuel pulses is located in a less variable impingement region.

[0076] If the affected DI fuel pulse is part of a split direct injection, such as when the DI fuel pulse is one of multiple direct injections of an unmodified fuel injection profile, the method includes adjusting the fuel pulse width to combine the affected DI fuel pulse with at least one other DI fuel pulse (such as another DI fuel pulse in the transition region, a DI fuel pulse in the impingement region, or a DI fuel pulse in the lift region) into a larger DI pulse in the lift region of the injector at 316. By reducing the number of fuel pulses, the affected DI fuel pulse is moved out of the transition region, and the resulting larger fuel pulse is located in a more linear lift region.

[0077] Reference Figure 5 An example of adjusting the injection quantity to operate outside the transition region of a direct injector is shown. Map 500 depicts a direct injector map (such as Figure 4 406 . In this example, the initial (unmodified) fuel injection distribution includes multiple direct injections per combustion cycle. The map 500 depicts two DI fuel pulses 502a, 502b (both with the same fuel mass and therefore with the same pulse width) located in the transition region 408 of the injector map. In an alternative example, the DI fuel pulses 502a, 502b may be in the transition region and have different fuel masses. In order to avoid operation in the transition region 408, the number of fuel pulses is reduced by merging the fuel pulses 502a, 502b into a single fuel pulse 504 with a larger fuel mass and therefore with a larger pulse width. Specifically, the modified pulse width of the fuel pulse 504 is located in the lift region 406. In this way, by reducing the number of direct fuel injections per combustion cycle, the direct injector operation is moved out of the transition region and shifted into the lift region while maintaining the direct injection fuel mass.

[0078] Reference Figure 6 Another example of adjusting the injection quantity to operate outside the transition region of a direct injector is shown. Map 600 depicts a direct injector map (such as Figure 4 408 . In this example, the initial (unmodified) fuel injection profile includes a single direct injection per combustion cycle. The map 600 depicts a single DI fuel pulse 602 located in the transition region 408 of the injector map. To avoid operation in the transition region 408, the number of fuel pulses is increased by splitting the fuel pulse 602 into two fuel pulses 604a, 604b, each having a smaller fuel mass and therefore a smaller pulse width. In the depicted example, both fuel pulses 604a, 604b have the same fuel mass (and therefore the same pulse width) and are located in the impact region 404 of the injector map. In an alternative example, the DI fuel pulses 604a, 604b may be located in the impact region and have different fuel masses. In this way, direct injector operation is moved out of the transition region and into the impingement region by increasing the number of direct fuel injections per combustion cycle while maintaining direct injected fuel mass.

[0079] In this way, during a first condition, the controller may reduce the number of multiple injections by merging the one of the multiple direct injections with at least one other one of the multiple direct injections to move the fuel mass from the transition region to the lift region. Then, during a second condition, the controller may increase the number of multiple injections by splitting the one of the multiple direct injections into multiple direct injections in the impact region. In one example, during the first condition, the unadjusted number of the multiple injections is above a threshold number, and during the second condition, the unadjusted number of the multiple injections is below a threshold number.

[0080] refer to Figure 7 An example of adjusting the fuel mass in a fuel injection profile with multiple direct injections to operate outside the transition region of a direct injector is shown. Map 700 depicts a direct injector map (such as Figure 4 408). In this example, the initial (unmodified) fuel injection distribution includes multiple direct injections per combustion cycle. Map 700 depicts two DI fuel pulses 702a, 702b (both with the same fuel mass and therefore the same pulse width) located in the transition region 408 of the injector map. In an alternative example, DI fuel pulses 702a, 702b may be in the transition region and have different fuel masses. To avoid operation in the transition region 408, the fuel mass of each pulse in pulses 702a and 702b is adjusted while maintaining the total direct injection fuel mass and also while maintaining the total number of direct injections. Specifically, the fuel mass of pulse 702a is increased so as to provide a modified fuel pulse 704 in the lift region 406 of the injector. At the same time, the fuel mass of pulse 702b is reduced so as to provide a modified fuel pulse 706 in the impact region 404 of the injector. In this way, direct injector operation is moved out of the transition region by modifying the fuel mass and pulse width of each of the multiple direct fuel injections per combustion cycle.

[0081] In one example, the engine controller may modify each DI fuel pulse in the transition region based on the proximity of each pulse to the full lift-transition region boundary and the impact-transition region boundary. The modification may also be based on the total fuel mass to be delivered by direct injection, the total fuel mass of the affected pulse(s) in the transition region, the total number of direct injections, and the number of affected injections in the transition region. As an example, the controller may use an algorithm such as Figure 8 The fuel mass of each fuel pulse is modified using algorithm 800 depicted at and described in detail below.

[0082] The controller starts at Figure 8The total desired fuel mass to be injected (via direct injection) is determined as MFdes×Ndes in , where MFdes is the desired fuel mass to be injected at each injection and Ndes is the desired number of injections. The controller then converts the total desired fuel mass (MFdes×Ndes) into an equal number of direct injection fuel pulses separated between impact region injections and lift region injections. Assuming MFbe represents the "end of impact" fuel mass, MFls represents the "start of linearity" fuel mass (fuel mass in the lift region), and MFth represents a calibratable hysteresis for the transition region, the following equation should hold:

[0083] Ndes=Nb+Nl;

[0084] MFdes×Ndes=MFlinear×Nl+MFballistic×Nb;

[0085] where MFlinear and MFballistic are the modified fuel masses planned for injection in the lift region (also referred to herein as the linear region) and the kick region, respectively, and Nl and Nb are the number of pulses in each region, respectively.

[0086] The following conditions need to be met:

[0087] MFlinear≥MFl;

[0088] MFballistic≤MFb;

[0089] This can be written as follows:

[0090] 0=Delta(MFlinear)×Nl+Delta(MFballistic)×Nb.

[0091] When further calculations are made and assuming MFlinear = MFl and / or Fballistic = MFb, we finally arrive at the equation for floating point as:

[0092] Nb-float = (F32)Ndes×(MF Δl / MFtransition).

[0093] The optimal number of impact jets and linear jets will be as follows:

[0094] Nb=(U8)uclip(1UL,(U32)(Nb-float+0.5F),((U32)Ndes–1UL));

[0095] and:

[0096] Nl = Ndes – Nb;

[0097] The following will help in calculating MFlinear and MFballistic as follows:

[0098]

[0099] In this way, the fuel mass delivered in each DI fuel pulse may be modified to operate the direct injector outside of the transition region while maintaining the total fuel mass and total number of direct injections.

[0100] In one example, the multiple direct injections of the unmodified fuel injection profile may include multiple direct injections in the intake stroke and / or compression stroke of the combustion cycle. Here, updating the fuel mass may include updating the split ratio of the direct injected fuel delivered in the intake stroke relative to the direct injected fuel delivered in the compression stroke. In addition, the number of intake stroke injections and compression stroke injections may vary.

[0101] Reference Fig. 9 An example of adjusting the split ratio of fuel delivered via direct injection relative to fuel delivered via port injection to operate outside the transition region of a direct injector is shown. An unmodified direct injector map 900 and a modified direct injector map 910 are shown. Similar to Figure 4 Map 400 , maps 900 and 910 include an impact region 404 , a lift region 406 , and a transition region 408 .

[0102] In this example, the initial (unmodified) fuel injection profile includes an initial split ratio of 50% DI:50% PFI for multiple direct injections per combustion cycle. Map 900 depicts two DI fuel pulses 902 (both having the same fuel mass and therefore the same pulse width) that are located in the transition region 408 of the injector map and together constitute 50% DI of the initial fuel injection profile. In an alternative example, the DI fuel pulses 902 can be in the transition region and have different fuel masses. DI fuel pulses 902 are located in the transition region 408, near the boundary of the transition region and the lift region 406. In order to avoid operation in the transition region 408, the split ratio of DI:PFI fuel is adjusted by changing the DI percentage. Specifically, because the DI fuel pulse is closer to the lift region 406 (relative to the impact region 404), the percentage of the total fuel delivered by DI is increased from 50% to 70% in order to move the DI fuel pulse out of the transition region, as indicated by the modified pulse 904 in the lift region. At the same time, the total fuel mass is maintained by reducing the PFI percentage from 50% to 30%. In this way, direct injector operation is moved out of the transition region by increasing the percentage of fuel delivered by direct injection relative to fuel delivered by port injection over a given combustion cycle.

[0103] Reference Fig.10 Another example of adjusting the split ratio of fuel delivered via direct injection relative to fuel delivered via port injection to operate outside the transition region of a direct injector is shown. An unmodified direct injector map 1000 and a modified direct injector map 1010 are shown. Similar to Figure 4 4 , 1000 and 1010 include an impact region 404 , a lift region 406 , and a transition region 408 .

[0104] In this example, the initial (unmodified) fuel injection profile includes an initial split ratio of 50% DI:50% PFI for multiple direct injections per combustion cycle. Map 1000 depicts two DI fuel pulses 1002 (both having the same fuel mass and therefore the same pulse width) located in the transition region 408 of the injector map and together constituting 50% DI of the initial fuel injection profile. In an alternative example, the DI fuel pulses 1002 may be in the transition region and have different fuel masses. DI fuel pulses 1002 are located in the transition region 408, near the boundary of the transition region and the impact region 404. In order to avoid operation in the transition region 408, the split ratio of DI:PFI fuel is adjusted by changing the DI percentage. Specifically, since the DI fuel pulse is closer to the impact region 404 (relative to the lift region 406), the percentage of the total fuel delivered by DI is reduced from 50% to 30% in order to move the DI fuel pulse out of the transition region, as indicated by the modified pulse 1004 in the impact region. At the same time, the total fuel mass is maintained by increasing the PFI percentage from 50% to 70%. In this way, direct injector operation is moved out of the transition region by reducing the percentage of fuel delivered by direct injection relative to fuel delivered by port injection over a given combustion cycle.

[0105] It should be recognized that although Figure 5-Figure 10 The example depicts adjustment of one of the number of injections, the DI:PFI split ratio, and the fuel mass of multiple direct injections, but this is not meant to be limiting. In still further examples, various combinations of the above methods may be used. For example, during selected conditions, the number of direct injections and the DI:PFI split ratio may be modified. As another example, during other conditions, each of the number of injections, the DI:PFI split ratio, and the fuel mass of multiple direct injections may be modified.

[0106] For example, during a first condition, in response to a pulse width signal of a single direct injection fuel pulse of a combustion cycle being within a transition region of the direct injector, the controller may move to operating with multiple direct injection fuel pulses on the combustion cycle, each of which has a pulse width signal outside the transition region. In contrast, during a second condition, in response to a pulse width signal of one of the multiple direct injection fuel pulses of the combustion cycle being within the transition region of the direct injector, the controller may move to operating with a single direct injection fuel pulse on the combustion cycle, the pulse width signal of the single direct injection fuel pulse being outside the transition region. In one example, during the first condition, the pulse width signal of each of the multiple direct injection fuel pulses is within the impingement region of the direct injector, while during the second condition, the pulse width signal of the single direct injection fuel pulse is within the lift region of the direct injector. In another example, during each of the first condition and the second condition, the total fuel mass delivered by direct injection on the combustion cycle is maintained. Additionally, during a third condition, in response to a pulse width signal of one of a plurality of direct injection fuel pulses of a combustion cycle being within a transition region of the direct injector, the controller may adjust a pulse width signal of each of the plurality of direct injection fuel pulses to move out of the transition region while maintaining a pulse number of the plurality of direct injection fuel pulses.

[0107] As an example, a first condition (where the number of injections is increased) includes the engine operating at a lower engine speed and / or a lower PM load, a second condition (where the number of injections is decreased) includes the engine operating at a higher speed, a higher PM load, and / or at least one of the multiple injections in the impingement region is too small (e.g., less than or at a minimum pulse width of the injector), and a third condition includes the PM load being above a threshold and / or the engine NVH being above a threshold. The shifting and adjusting during each of the first, second, and third conditions may include, for example, adjusting the total fuel mass delivered by direct injection over the combustion cycle, the method further comprising adjusting the fuel mass delivered by port injection over the combustion cycle based on the adjusted total fuel mass delivered by direct injection.

[0108] In yet another example, during a first condition, the controller may modify the initial fuel injection profile to a first modified fuel injection profile having a smaller number of multiple direct injection fuel pulses, each of the smaller number of multiple direct injection fuel pulses having a smaller pulse width in the lift region of the direct injector; and during a second condition, the controller may modify the initial fuel injection profile to a second modified fuel injection profile, wherein the pulse width of a first group of the multiple direct injection fuel pulses is reduced into the impact region of the direct injector, while the pulse width of a second group of the multiple direct injection fuel pulses is increased into the lift region of the direct injector, while maintaining the number of the multiple direct injection fuel pulses. Here, the total direct injection fuel mass in each of the first modified fuel injection profile and the second modified fuel injection profile may be the same as the fuel mass in the initial unmodified fuel injection profile. As an example, the first condition may include one or more of a higher engine speed and a higher PM load, while the second condition may include one or more of a lower engine speed, higher engine NVH, and at least one of the injections of the initial fuel injection profile operating at or near the minimum pulse width of the injector. The plurality of direct injection fuel pulses of the initial fuel injection profile may include an initial number of direct injection fuel pulses, and the modification during each of the first condition and the second condition may be based on the initial number of direct injection fuel pulses, and further based on a relationship of a pulse width of at least one of the plurality of direct injection pulses to an upper pulse width limit of the impingement region and a lower pulse width limit of the lift region. Further, during a third condition, the controller may modify the initial fuel injection profile to a third modified fuel injection profile, including adjusting the total direct injection fuel mass to move the pulse width of at least one of the plurality of direct injection fuel pulses out of a transition region of the direct injector, and adjusting the port injection fuel mass based on the adjusted direct injection fuel mass.

[0109] In yet another example, during a first condition, in response to a pulse width of one of a plurality of direct injection fuel pulses of a combustion cycle being within a transition region of a direct injector map, the controller may reduce the number of the plurality of direct injection fuel pulses while maintaining a split ratio of the direct injection fuel to the port injection fuel; and during a second condition, in response to a pulse width of one of a plurality of direct injection fuel pulses of a combustion cycle being within a transition region of the direct injector, the controller may adjust the split ratio of the direct injection fuel to the port injection fuel. As an example, adjusting the split ratio may include increasing the split ratio of the direct injection fuel to the port injection fuel within the combustion cycle when more fuel mass is needed in the impinged DI injection (because it is less than the minimum allowed pulse width of the injector). In another representation, rather than splitting the DI pulse into an impinged region and a linear region, the pulse is split into two impinged injections and then the remaining mass is placed in the PFI system, thereby changing the number of DI injections and reducing the split ratio of the direct injection fuel to the port injection fuel within the combustion cycle. Adjusting the split ratio may also include maintaining the number of the plurality of direct injection fuel pulses in the combustion cycle. Alternatively, adjusting the split ratio may include adjusting the number of multiple direct injection fuel pulses in a combustion cycle, and the mass of fuel delivered in each of the multiple direct injection fuel pulses. In one example, during a first condition, the pulse width of each of the reduced number of multiple direct injection fuel pulses is located in the full lift region of the direct injector. The number of DI pulses may be maintained by adding more fuel to avoid a minimum pulse width, or by taking away fuel so that all DI injectors may be located in the impingement region. In another representation, the number of DI pulses may be reduced, and additional mass may be placed in the PFI system. In yet another representation, the number of DI pulses may be increased by taking fuel from the PFI system to place the fuel in the DI system, thereby increasing the number of DI injections and increasing the split ratio of direct injected fuel to port injected fuel within the combustion cycle.

[0110] refer to Fig.11 An exemplary modified fuel injection profile is shown in which a number of different adjustments may be applied to move the direct injection fuel pulse out of the transition region. Fig.11Map 1100 shows exemplary fuel injection profiles 1102-1104 that may be used during engine operation in response to an initial fuel injection profile 1101 having a DI fuel pulse within a transition region of an operating map for a direct injector. Each injection profile depicts injection timing relative to a cylinder piston position or cylinder stroke. Based on the position of the cylinder piston at any time during the engine cycle, fuel may be injected into the cylinder during an intake stroke (I), a compression stroke (C), a power stroke (P), or an exhaust stroke (E). The injection profile also describes whether fuel is injected via port injection (shaded blocks), single or multiple direct injections (striped blocks), or both.

[0111] The initial fuel injection distribution can be determined based on engine operating conditions (including engine speed, driver torque demand, engine temperature and fuel alcohol content). In one example, the initial fuel injection distribution can be an engine cold start fuel injection distribution. The initial fuel injection distribution includes: during a given combustion cycle, during the closed intake valve event (i.e., during the exhaust stroke of the previous cylinder combustion event), a portion of the fuel is injected as an intake port injection (shaded block), and the remaining portion of the fuel is injected as an intake stroke direct injection and two compression stroke direct injections (oblique stripe blocks). The injection amount can be adjusted so that 35% of the fuel injection can be delivered as an intake port injection during the closed intake valve event (e.g., during the exhaust stroke), another 35% of the fuel injection can be delivered as an intake stroke direct injection, and the remaining 30% of the fuel injection can be delivered as multiple compression stroke direct injections. Here, the fuel mass in the second (most recent combustion cycle) compression stroke injection can correspond to the pulse width located in the transition region of the direct injector.

[0112] To avoid the transition region, the initial fuel injection distribution can be updated to a first modified fuel injection distribution (Updated Fuel Injection Distribution_A) in which the number of compression stroke direct injections is increased by dividing the first (earlier in the combustion cycle) compression stroke DI pulse into two smaller compression stroke DI pulses. In addition, the total amount of DI fuel delivered in the compression stroke is reduced, while the amount of DI fuel delivered in the intake stroke is correspondingly increased. The proportion of fuel delivered by intake port injection is not changed, allowing the overall DI:PFI ratio to be maintained. Therefore, in this example, by increasing the number of direct injections, and by changing the ratio of the fuel mass delivered in each direct injection, the compression stroke DI fuel pulses predicted to be in the transition region are moved into the impact region. In one example, the first modified fuel injection distribution can be selected in response to the injection mode. If the engine is in a mode that requires catalyst heating, the DI compression injection size and injection timing are very important. Other fueling parameters (such as DI intake fuel mass) can be adjusted without affecting emissions, just like changing the DI compression injection.

[0113] To avoid the transition region, the initial fuel injection profile may alternatively be updated to a second modified fuel injection profile (Updated Fuel Injection Profile_B) in which the number of compression stroke direct injections is reduced by merging the first compression stroke DI pulse and the second compression stroke DI pulse into a single compression stroke DI pulse, while also reducing the total amount of fuel delivered in the compression stroke. The amount of DI fuel delivered in the intake stroke is increased a small amount until the maximum pulse width of the direct injector is reached. The remaining fuel mass adjustment is achieved by increasing the proportion of fuel delivered via port injection, resulting in a reduction in the overall DI:PFI ratio. Thus, in this example, compression stroke DI fuel pulses predicted to be in the transition region are moved into the impact region by reducing the number of direct injections, and by changing the ratio of the fuel mass delivered in each direct injection, and reducing the ratio of DI:PFI fuel. In one example, the second modified fuel injection profile may be selected in response to maintaining the same fuel-air control. If it is necessary to move fuel mass out of the DI injection in order to ensure that the DI pulse is not located in the transition region, the PFI may be increased in response thereto.

[0114] To avoid the transition region, the initial fuel injection profile may alternatively be updated to a third modified fuel injection profile (Updated Fuel Injection Profile_C) in which the number of compression stroke direct injections is reduced by merging the first and second compression stroke DI pulses with the intake stroke DI fuel pulse to provide a single intake stroke DI pulse while also increasing the total amount of fuel delivered by direct injection. The proportion of fuel delivered by port injection is correspondingly reduced, resulting in an increase in the overall DI:PFI ratio. Thus, in this example, compression stroke DI fuel pulses predicted to be in the transition region are moved into the impingement region by reducing the number of direct injections, and by changing the ratio of the fuel mass delivered in each direct injection and increasing the ratio of DI:PFI fuel. In one example, the third modified fuel injection profile may be selected in response to maintaining the same fuel-air control and the driver demand torque being at a higher load requiring DI charge air cooling.

[0115] In another example, at higher engine loads, such as when more power, more air charge cooling, or advanced spark is needed, the controller may increase the split ratio of direct injected fuel to port injected fuel within the combustion cycle. In contrast, at lower engine loads, such as when PM load or exhaust emissions are above a threshold load, the controller may decrease the split ratio of direct injected fuel to port injected fuel within the combustion cycle.

[0116] In yet other examples, the controller may continue to adjust the fuel mass until a solution that places the pulse in the full lift region and the impingement region cannot be found. At this point, the number of injectors may be reduced by one and a solution determined. The controller may repeatedly adjust the number of pulses and then the number of injectors until the distribution drops to 1 injection. If the injection is still in the transition region, the DI / PFI split ratio may be changed (e.g., increased or decreased) to move the DI injection out of the transition region.

[0117] In yet another example, in the absence of an option to allow the number of injections to be maintained, the controller may combine the fuel pulses while redistributing them between the impact region and the full lift region. Thus, the controller may prioritize maintaining the number of pulses and redistribute the fuel mass to the full lift region and the transition region. If a solution cannot be achieved because the injection in the impact region is below the minimum pulse width of the injector, the number of pulses may be reduced so that full lift injection can be achieved.

[0118] Further, when more direct injected fuel mass is needed to allow the controller to split the transition region injection into the impingement region injection and the full lift region injection, the controller may increase the split ratio of the direct injected fuel to the port injected fuel within the combustion cycle. In contrast, when less direct injected fuel mass is needed in order to move the injection out of the transition region (e.g., because the number of DI injectors has been reduced), the controller may decrease the split ratio of the direct injected fuel to the port injected fuel within the combustion cycle.

[0119] In this way, direct injector variability is reduced, thereby allowing for reductions in gaseous and particulate emissions. For example, gaseous and particulate emissions can be reduced without reducing the number of multiple injections on a dual fuel engine (PFDI). The technical effect of adjusting one or more of the number of direct injection fuel pulses, fuel mass, and split ratio based on the position of the fuel pulse relative to the transition region of the direct injector is that direct injection can be provided outside the highly variable transition region while maintaining the total fuel mass to be injected on a given combustion cycle. In addition, the amount of calibration effort required for the engine is reduced relative to the effort required to map the fuel mass separated between fuel pulses in a feed-forward manner. Due to operation outside the inaccurate transition region of the direct injector, engine air-fuel ratio errors and torque errors can be reduced, thereby improving drivability.

[0120] An exemplary method for an engine includes: delivering fuel to a cylinder as multiple direct injections over a combustion cycle; and in response to a fuel mass of one of the multiple direct injections being located in a transition region of a direct injector map, updating one or more of a ratio of fuel delivered in each of the multiple direct injections and a number of the multiple injections to move the fuel mass of the one of the multiple direct injections out of the transition region. In the previous examples, additionally or optionally, the transition region is located between an impingement region and a lift region of the direct injector map, and wherein a direct injector variability in the transition region is higher than a direct injector variability in each of the impingement region and the lift region. In any or all of the previous examples, additionally or optionally, the updating is based on a position of the fuel mass relative to each of an impingement-transition boundary and a lift-transition boundary of the direct injector map. In any or all of the previous examples, additionally or optionally, the updating includes: in response to the distance of the fuel mass from the impact-transition boundary of the direct injector map being less than the distance of the fuel mass from the lift-transition boundary of the direct injector map, reducing the fuel mass of the injection of the multiple direct injections so as to move the fuel mass from the transition region of the direct injector map to the impact region, while increasing the fuel mass of another injection of the multiple direct injections. In any or all of the previous examples, additionally or optionally, the updating also includes: in response to the distance of the fuel mass from the impact-transition boundary of the direct injector map being greater than the distance of the fuel mass from the lift-transition boundary of the direct injector map, increasing the fuel mass of the injection of the multiple direct injections so as to move the fuel mass from the transition region of the direct injector map to the lift region, while reducing the fuel mass of another injection of the multiple direct injections. In any or all of the previous examples, additionally or optionally, increasing and decreasing the number based on the multiple direct injections. In any or all of the previous examples, additionally or optionally, updating the number of injections of the multiple direct injections includes: during a first condition, reducing the number of multiple injections by merging the injection of the multiple direct injections with at least another injection of the multiple direct injections to move fuel mass from the transition region to the lift region; and during a second condition, increasing the number of multiple injections by splitting the injection of the multiple direct injections into multiple direct injections in the impact region. In any or all of the previous examples, additionally or optionally, during the first condition, the unadjusted number of the multiple injections is above a threshold number, and wherein under the second condition, the unadjusted number of the multiple injections is above a threshold number. In any or all of the previous examples, additionally or optionally, the multiple direct injections include multiple direct injections in an intake stroke and / or a compression stroke of a combustion cycle, and wherein updating further includes updating a split ratio of direct injected fuel delivered in an intake stroke relative to direct injected fuel delivered in a compression stroke.In any or all of the previous examples, additionally or optionally, the method further comprises adjusting the amount of fuel delivered to the cylinder via port injection over the combustion cycle based on the update. In any or all of the previous examples, additionally or optionally, the method may be implemented in a hybrid vehicle system.

[0121] Another exemplary method includes: during a first condition, in response to a pulse width signal of a single direct injection fuel pulse of a combustion cycle being within a transition region of the direct injector, shifting to operate with multiple direct injection fuel pulses on the combustion cycle, the pulse width signal of each of the multiple direct injection fuel pulses being outside the transition region; and during a second condition, in response to a pulse width signal of one of the multiple direct injection fuel pulses of the combustion cycle being within the transition region of the direct injector, shifting to operate with a single direct injection fuel pulse on the combustion cycle, the pulse width signal of the single direct injection fuel pulse being outside the transition region. In the previous example, additionally or optionally, during the first condition, the pulse width signal of each of the multiple direct injection fuel pulses is within the impingement region of the direct injector, and wherein during the second condition, the pulse width signal of the single direct injection fuel pulse is within the lift region of the direct injector. In any or all of the previous examples, additionally or optionally, during each of the first condition and the second condition, the total fuel mass delivered by direct injection on the combustion cycle is maintained. In any or all of the previous examples, additionally or optionally, the method further includes, during a third condition, in response to a pulse width signal of one of a plurality of direct injection fuel pulses of a combustion cycle being within a transition region of the direct injector, adjusting a pulse width signal of each of the plurality of direct injection fuel pulses to move out of the transition region while maintaining a pulse number of the plurality of direct injection fuel pulses. In any or all of the previous examples, additionally or optionally, the second condition includes being above a threshold engine speed, and the third condition includes being below a threshold engine speed or above a threshold engine NVH level. In any or all of the previous examples, additionally or optionally, the shifting and adjusting during each of the first condition, the second condition, and the third condition includes adjusting a total fuel mass delivered by direct injection over the combustion cycle, the method further including adjusting a fuel mass delivered by port injection over the combustion cycle based on the adjusted total fuel mass delivered by direct injection.

[0122] Another exemplary system includes: an engine cylinder; a direct injector for filling the cylinder with fuel; and a controller having computer-readable instructions stored on a non-volatile memory, the instructions being used to: estimate an initial fuel injection profile for a combustion cycle of the cylinder based on engine speed-load and engine temperature, the initial fuel injection profile including a plurality of direct injection fuel pulses, at least one of the plurality of direct injection fuel pulses having a pulse width in a transition region of the direct injector; during a first condition, modify the initial fuel injection profile to a first modified fuel injection profile having a smaller number of the plurality of direct injection fuel pulses, each of the smaller number of the plurality of direct injection fuel pulses having a larger pulse width in a lift region of the direct injector; and under a second condition, modify the initial fuel injection profile to a second modified fuel injection profile, wherein the pulse width of a first group of the plurality of direct injection fuel pulses is reduced into an impact region of the direct injector, and the pulse width of a second group of the plurality of direct injection fuel pulses is increased into a lift region of the direct injector, while maintaining the number of the plurality of direct injection fuel pulses, wherein a total directly injected fuel mass in each of the first modified fuel injection profile and the second modified fuel injection profile is the same as the fuel mass in the initial fuel injection profile. In the previous examples, additionally or optionally, the first condition includes being above a threshold engine speed, and the second condition includes being below a threshold engine speed. In any or all of the previous examples, additionally or optionally, the plurality of direct injection fuel pulses of the initial fuel injection profile includes an initial number of direct injection fuel pulses, and wherein the modification during each of the first and second conditions is based on the initial number of direct injection fuel pulses, and further based on a relationship of a pulse width of at least one of the plurality of direct injection pulses to an upper pulse width limit of the impact region and a lower pulse width limit of the lift region. In any or all of the previous examples, additionally or optionally, the method further includes an intake port injector for filling the cylinder with fuel, wherein the controller includes further instructions for the following operations: during a third condition, modifying the initial fuel injection profile to a third modified fuel injection profile, including adjusting the total direct injection fuel mass to move the pulse width of at least one of the plurality of direct injection fuel pulses out of a transition region of the direct injector, and adjusting the intake port injection fuel mass based on the adjusted direct injection fuel mass.

[0123] Another exemplary method includes: estimating an initial ratio of port injected fuel to direct injected fuel over a combustion cycle based on engine operating conditions; and in response to direct fuel injection at the initial ratio being in a transition region of a direct injector map, updating the initial ratio to move the direct fuel injection out of the transition region. In the previous example, additionally or optionally, the transition region is between an impingement region and a lift region of the direct injector map, and wherein direct injector variability in the transition region is higher than direct injector variability in each of the impingement region and the lift region. In any or all of the previous examples, additionally or optionally, the updating is based on a relationship of a pulse width of the direct fuel injection to each of an impingement-transition boundary and a lift-transition boundary of the direct injector map. In any or all of the previous examples, additionally or optionally, the updating includes: in response to the distance of the direct fuel injection pulse width from the impact-transition boundary of the direct injector map being less than the distance of the direct fuel injection pulse width from the lift-transition boundary of the direct injector map, reducing the direct injected fuel mass to move the pulse width from the transition region of the direct injector map to the impact region while increasing the port injected fuel mass. In any or all of the previous examples, additionally or optionally, the updating also includes: in response to the distance of the direct fuel injection pulse width from the impact-transition boundary of the direct injector map being greater than the distance of the direct fuel injection pulse width from the lift-transition boundary of the direct injector map, increasing the direct injected fuel mass to move the pulse width from the transition region of the direct injector map to the lift region while reducing the port injected fuel mass. In any or all of the previous examples, additionally or optionally, the initial ratio of the port injected fuel to the direct injected fuel includes a plurality of direct injections over the combustion cycle, and wherein the increasing and decreasing are based on the number of the plurality of direct injections. In any or all of the previous examples, additionally or optionally, updating also includes adjusting the number of multiple direct injections by reducing the number of multiple direct injections so as to move the pulse width from the transition region to the lift region. In any or all of the previous examples, additionally or optionally, reducing the unadjusted number in response to the multiple direct injections being above a threshold. In any or all of the previous examples, additionally or optionally, updating also includes adjusting the number of multiple direct injections by increasing the number of multiple direct injections so as to move the pulse width from the transition region to the impact region. In any or all of the previous examples, additionally or optionally, increasing the unadjusted number in response to the multiple direct injections being below a threshold. In any or all of the previous examples, additionally or optionally, the multiple direct injections include multiple direct injections in an intake stroke and / or a compression stroke of the combustion cycle, and wherein updating also includes updating a split ratio of the direct injected fuel delivered in the intake stroke relative to the direct injected fuel delivered in the compression stroke.In any or all of the previous examples, additionally or alternatively, the method may be implemented in a hybrid vehicle system.

[0124] Another exemplary method includes: during a first condition, in response to a pulse width of one of a plurality of direct injection fuel pulses of a combustion cycle being within a transition region of a direct injector map, reducing the number of a plurality of direct injection fuel pulses while maintaining a split ratio of direct injection fuel to port injection fuel; and during a second condition, in response to a pulse width of one of a plurality of direct injection fuel pulses of a combustion cycle being within a transition region of a direct injector map, adjusting the split ratio of direct injection fuel to port injection fuel. In any or all of the previous examples, additionally or optionally, adjusting the split ratio includes: increasing the split ratio of direct injection fuel to port injection fuel within a combustion cycle when more power, air charge cooling, or advanced spark is needed, such as at higher engine loads; and decreasing the split ratio of direct injection fuel to port injection fuel within a combustion cycle at lower loads when PM load is above a threshold. In any or all of the previous examples, additionally or optionally, when more direct injection fuel mass is needed to move the pulse in the plurality of direct injection fuel pulses out of the transition region, the split ratio of the direct injection fuel to the port injection fuel within the combustion cycle is increased; and when less direct injection fuel mass is needed to move the pulse in the plurality of direct injection fuel pulses out of the transition region, the split ratio of the direct injection fuel to the port injection fuel within the combustion cycle is reduced. In any or all of the previous examples, additionally or optionally, adjusting the split ratio includes maintaining the number of the plurality of direct injection fuel pulses in the combustion cycle. In any or all of the previous examples, additionally or optionally, adjusting the split ratio includes adjusting the number of the plurality of direct injection fuel pulses in the combustion cycle, and the mass of fuel delivered in each of the plurality of direct injection fuel pulses. In any or all of the previous examples, additionally or optionally, during the first condition, the pulse width of each of the plurality of direct injection fuel pulses of the reduced number is located in the lift region of the direct injector. In any or all of the previous examples, additionally or optionally, the first condition includes a higher engine load and the second condition includes a lower engine load.

[0125] Another exemplary engine system includes: an engine cylinder; a direct injector for filling the cylinder with fuel; an intake port injector for filling the cylinder with fuel; and a controller having computer readable instructions stored on a non-transitory memory, the instructions for: estimating an initial fuel injection profile for a combustion cycle of the cylinder based on engine speed-load and engine temperature, the initial fuel injection profile including an initial split ratio of direct injected fuel to intake port injected fuel delivered by a plurality of direct injection fuel pulses, at least one of the plurality of direct injection fuel pulses having a pulse width in a transition region of the direct injector; and modifying the initial fuel injection profile to change the split ratio of the direct injection fuel to the intake port injected fuel such that at least one of the plurality of direct injection fuel pulses is moved out of the transition region. In any or all of the previous examples, additionally or optionally, the modifying includes: increasing or decreasing the intake port injected fuel mass relative to the total direct injected fuel mass based on a relationship of the pulse width of at least one of the plurality of direct injection pulses to an upper pulse width limit of a pulse width in an impingement region and a lower pulse width limit of a pulse width in a lift region of the direct injector. In any or all of the previous examples, additionally or optionally, reducing the total direct injected fuel mass includes reducing a number of multiple direct injected fuel pulses so as to move a pulse width of each pulse in the reduced number of direct injected fuel pulses into a lift region, and wherein increasing the total direct injected fuel mass includes increasing a number of multiple direct injected fuel pulses so as to move a pulse width of each pulse in the increased number of direct injected fuel pulses into an impact region.

[0126] In another representation, the engine is coupled in a hybrid vehicle system.

[0127] Note that the exemplary 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 a non-volatile memory and can be executed by a control system that includes a controller 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, multi-tasking, multi-threading, etc. Therefore, the various actions, operations, and / or functions shown may be performed in the order shown, performed in parallel, or omitted in some cases. Similarly, the order of processing is not necessary to achieve the features and advantages of the exemplary embodiments described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be performed repeatedly, depending on the specific strategy used. In addition, the described actions, operations, and / or functions can graphically represent the code in the non-volatile memory of a computer-readable storage medium that will be programmed into the engine control system, wherein the described actions are performed by executing instructions in a system including various engine hardware components combined with an electronic controller.

[0128] It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific embodiments should not be considered limiting, as many variations are possible. For example, the above-described techniques can be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

[0129] The following claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or a "first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amendment of the present claims or by presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, are also deemed to be included in the subject matter of the present disclosure.

Claims

1. A method for an engine, comprising: delivering fuel to the cylinder as multiple direct injections over a combustion cycle; as well as In response to a fuel mass of one of the plurality of direct injections being within a second region of a direct injector map, updating a ratio of fuel delivered in each of the plurality of direct injections and / or a quantity of the plurality of direct injections to move the fuel mass of the one of the plurality of direct injections out of the second region, wherein updating the ratio or updating the quantity is selected based on operating conditions of the engine; wherein the direct injector map describes the mass of fuel injected as a function of fuel injector pulse width; wherein the second region is located between the first region and the third region of the direct injector map; wherein the first region includes a region where fuel is not injected for the fuel injector pulse width and a region where a first linear relationship exists between the amount of injected fuel and the fuel injector pulse width; wherein the second region includes a region where there is a non-linear relationship between the amount of fuel injected and the fuel injector pulse width; wherein the third region includes a region where a second linear relationship exists between the amount of injected fuel and the fuel injector pulse width, The first region, the second region, and the third region are different from each other. 2 . The method of claim 1 , wherein direct injector variability in the second region is higher than direct injector variability in each of the first region and the third region. 3 . The method of claim 2 , wherein the updating is based on a position of the fuel mass relative to each of a first boundary between the first region and the second region and a second boundary between the second region and the third region of the direct injector map.

4. The method of claim 3, wherein the updating comprises: In response to the distance of the fuel mass from the first boundary of the direct injector map being less than the distance of the fuel mass from the second boundary of the direct injector map, reducing the fuel mass of the one of the multiple direct injections to move the fuel mass from the second region to the first region of the direct injector map while increasing the fuel mass of another of the multiple direct injections.

5. The method of claim 4, wherein the updating further comprises: In response to the distance of the fuel mass from the first boundary of the direct injector map being greater than the distance of the fuel mass from the second boundary of the direct injector map, increasing the fuel mass of the one of the multiple direct injections to move the fuel mass from the second region to the third region of the direct injector map while decreasing the fuel mass of another of the multiple direct injections. The method of claim 5 , wherein said increasing and said decreasing are based on said number of said multiple direct injections.

7. The method of claim 1 , wherein updating the number of the multiple direct injections comprises: during a first condition, reducing the number of the plurality of direct injections by merging the one of the plurality of direct injections with at least another of the plurality of direct injections to move the fuel mass from the second region to the third region; as well as During a second condition, the number of the multiple direct injections is increased by dividing the one of the multiple direct injections into multiple direct injections in the first region. 8 . The method of claim 7 , wherein during the first condition, an unadjusted number of the multiple direct injections is above a threshold number, and wherein during the second condition, the unadjusted number of the multiple direct injections is below the threshold number.

9. The method of claim 1 , wherein the multiple direct injections include multiple direct injections in an intake stroke and a compression stroke of the combustion cycle, and wherein the updating further includes updating a split ratio of the direct injected fuel delivered in the intake stroke relative to the direct injected fuel delivered in the compression stroke. 10 . The method of claim 1 further comprising adjusting an amount of fuel delivered to the cylinder via port injection within the combustion cycle based on the update.

11. An engine system, comprising: Engine cylinders; a direct injector for filling the cylinder with fuel; as well as A controller having computer readable instructions stored on a non-transitory memory, the instructions for: estimating an initial fuel injection profile for a combustion cycle of the cylinder based on engine speed-load and engine temperature, the initial fuel injection profile comprising a plurality of direct injection fuel pulses, at least one of the plurality of direct injection fuel pulses having a pulse width in a second region of a direct injector map, wherein the direct injector map describes a mass of fuel injected as a function of a fuel injector pulse width; wherein the second region is between a first region and a third region of the direct injector map; wherein the first region comprises a region where no fuel is injected for the fuel injector pulse width and a region where a first linear relationship exists between an amount of fuel injected and the fuel injector pulse width; wherein the second region comprises a region where a non-linear relationship exists between an amount of fuel injected and the fuel injector pulse width; wherein the third region comprises a region where a second linear relationship exists between an amount of fuel injected and the fuel injector pulse width, wherein the first region, the second region, and the third region are different from one another; during a first condition, modifying the initial fuel injection profile to a first modified fuel injection profile having a smaller number of a plurality of direct injection fuel pulses, each of the smaller number of a plurality of direct injection fuel pulses having a pulse width in the third region of the direct injector map; as well as During a second condition, the initial fuel injection distribution is modified to a second modified fuel injection distribution, wherein the pulse width of the first group of the plurality of direct injection fuel pulses is reduced to the first region of the direct injector map and the pulse width of the second group of the plurality of direct injection fuel pulses is increased to the third region of the direct injector map while maintaining the number of the plurality of direct injection fuel pulses. 12 . The system of claim 11 , wherein a total directly injected fuel mass in each of the first modified fuel injection profile and the second modified fuel injection profile is the same as the fuel mass in the initial fuel injection profile.

13. The system of claim 11 wherein the first condition comprises above a threshold engine speed and the second condition comprises below a threshold engine speed.

14. The system of claim 11, wherein the plurality of direct injection fuel pulses of the initial fuel injection profile includes an initial number of direct injection fuel pulses, and wherein the modification during each of the first condition and the second condition is based on the initial number of direct injection fuel pulses and further based on a relationship of the pulse width of at least one of the plurality of direct injection pulses to an upper pulse width limit of the first region and a lower pulse width limit of the third region.

15. The system of claim 11 further comprising a port injector for filling the cylinder with fuel, wherein the controller includes further instructions for: During a third condition, the initial fuel injection profile is modified to a third modified fuel injection profile, which includes adjusting a total directly injected fuel mass to move the pulse width of at least one of the plurality of direct injected fuel pulses out of the second region of the direct injector, and adjusting a port injected fuel mass based on the adjusted total directly injected fuel mass.

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