Methods for controlling fuel injection in diesel engines

Abstract

Procedure, comprehensive: Reducing the total number of fuel injections provided to a cylinder in a given cylinder cycle in response to a reduction in pressure in a fuel distributor (222), including reducing the total number of pre-fuel injections during high engine load conditions and reducing the total number of main fuel injections during low engine load conditions.

Description

Area

[0001] The present description generally relates to methods for controlling fuel injection into an internal combustion engine, which has multiple injections per cylinder per combustion cycle. General state of the art / Summary

[0002] In diesel combustion engines, the fuel injection profile can include multiple injection events within a single injection cycle, such as at least one pre-injection followed by at least one main injection, to reduce ignition delay, exhaust emissions, and combustion noise. Additionally, a common distributor fuel system can be used in diesel engines, which may include a high-pressure fuel pump that delivers fuel to a fuel distributor associated with a group of cylinders. The fuel distributor system maintains sufficient fuel pressure for injection while distributing fuel to the injectors, which all share the fuel in the common distributor.The distributor volume acts as an accumulator in the fuel system, dampening pressure fluctuations from the pump and fuel injection cycles to maintain a nearly constant pressure at the fuel injector nozzle. The accuracy of any fuel injection event depends on the ability to maintain a sufficiently constant fuel distributor pressure; therefore, any deviation in distributor pressure from the intended value can lead to inaccurate fuel delivery, which in turn can negatively affect engine performance.

[0003] However, if the engine is operated at high engine speeds and load conditions that demand a higher fuel injection quantity, the fuel pump may not be able to supply enough fuel to the fuel rail to maintain the high fuel rail pressure. Thus, the engine may be throttled during high engine speeds and load conditions if the high-pressure fuel pump is unable to maintain sufficient rail pressure. Alternatively, the fuel pump size can be increased to supply enough fuel during periods of high fuel demand. However, this results in high parasitic losses in the pump. An example of an approach to prevent variation in rail pressure is shown by McCormick et al. in US patent application US 2003 / 0089334A1.In this system, the pre-injection timing is determined based on the fuel pressure in the common distributor and the engine's operating condition. When the common fuel distributor pressure is high, the pre-injection timing is advanced to maintain the interval between the pre-injection and the main fuel injection. However, the inventors of the present invention have recognized potential problems with this approach. For example, advancing the pre-injection timing at high engine speed / load can still impair engine performance if the fuel pump capacity is insufficient to supply enough fuel to the common distributor, thus leading to an inability to maintain high pressure in the fuel distributor. Further prior art can be found in DE 10 2013 202 663 A1.

[0004] The object of the present invention is therefore to provide improved methods for controlling fuel injection in an internal combustion engine. This object is achieved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0005] The inventors of the present invention have recognized that by reducing the actual total number of pre- and / or main fuel injections supplied to a cylinder when a deviation in the distributor pressure is detected (e.g., when the actual fuel distributor pressure is lower than a target fuel distributor pressure), less fuel is returned from the injection devices to the fuel tank after the fuel injections, and more fuel can be retained in the fuel distributor to maintain the fuel distributor pressure. Accordingly, the problems described above can be addressed, at least in part, by a method comprising: reducing the total number of fuel injections supplied to a cylinder in a given cylinder cycle in response to a threshold reduction in the pressure in a fuel distributor.In this way, sufficient fuel can be provided to maintain engine operation at high load / speed while maintaining a relatively constant high pressure in the fuel distributor.

[0006] As an example, during high engine speed and load conditions, a target fuel rail pressure (e.g., using an engine lookup table) can be obtained. If the actual fuel rail pressure is lower than the target pressure, the number of injections can be reduced to maintain the required fuel quantity by preventing fuel return from the injectors. Simultaneously, depending on the engine load conditions, the pre-injection and / or main injection timing can be adjusted to supply sufficient fuel to the combustion chamber to accommodate changes in engine torque demand and maintain a constant common rail pressure.

[0007] In one example, during high engine load conditions (e.g., when high torque is demanded) and when the actual fuel rail pressure falls below a threshold pressure, the total number of pre-injections can be reduced to prevent the peak cylinder pressure from exceeding a pressure limit. Additionally, the remaining pre-injection pulse width can be reduced, and its injection timing can be retarded to reduce combustion noise. Simultaneously, the main injection timing can be advanced relative to the engine compression stroke to reduce ignition retardation. By shifting the pre-injection timing closer to the main injection timing, cylinder pressure can be increased to promote fuel combustion. Furthermore, the main injection pulse width can be increased to provide sufficient fuel supply to meet the increased engine torque demand.

[0008] In another example, the actual fuel rail pressure may drop during low-load conditions, such as when the fuel pump is malfunctioning or when the fuel temperature is above a threshold (or when the fuel viscosity is below a threshold). Under these conditions, it may be desirable to maintain the pre-injections to reduce engine noise and instead reduce one or more of the main injections to decrease engine power output. Furthermore, the pre-injection timing can be advanced, and a smaller pulse width can be provided. The main injection timing can be retarded to increase exhaust gas temperature. A larger quantity of main fuel injection can be provided based on the desired total fuel quantity.In this way, a precise amount of fuel can be delivered to the engine while the fuel distributor pressure is maintained at a relatively constant pressure.

[0009] It is understood that the foregoing summary is provided to introduce, in simplified form, a selection of concepts that are further described in the detailed description. It is not intended to identify important or essential features of the claimed subject matter, the scope of which is defined solely by the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address the disadvantages mentioned above or in any part of this disclosure. Brief description of the drawings Fig. Figure 1 shows a schematic representation of an engine. Fig. Figure 2 shows a detailed illustration of a fuel system that supplies fuel to the engine. Fig. Figure 3 presents a flowchart of an exemplary method for controlling the fuel injection profile according to the present disclosure. Fig. Figure 4 illustrates a timing diagram demonstrating a fuel injection adaptation that allows a large quantity of fuel to be delivered during a high engine torque demand while keeping the fuel rail pressure constant. Fig. Figure 5 illustrates exemplary fuel injection profile adjustments. Detailed description

[0010] The following description concerns systems and methods for controlling a fuel injection profile in an engine system, such as the engine system from Fig. 1, using a single direct-injection fuel system, such as the fuel system from Fig. 2. A controller can be designed to execute a control routine, such as the exemplary routine from Fig. 3, to accurately detect any deviation in the fuel rail pressure and to provide adjustments for the pre- and main injection profiles. A prospective example of a fuel injection profile delivering fuel with a reduced number of pre-injections is shown in Fig. Figure 4 illustrates the examples of fuel injection adjustments for the pilot and main fuel injection profiles in response to a deviation in the fuel rail pressure. Fig. Figure 5 illustrates this. In this way, sufficient fuel can be supplied to the combustion chamber during high loads while maintaining the fuel rail pressure, thus reducing the likelihood of the engine being throttled due to lower fuel rail pressure.

[0011] Fig. Figure 1 shows a schematic diagram of an internal combustion engine 10 comprising a plurality of cylinders, one of which is in Fig. Figure 1 shows the engine 10 being controlled by an electronic engine control unit 12. The engine 10 includes a combustion chamber 30 and cylinder walls 32 with a piston 36 positioned therein and connected to a crankshaft 40. According to the illustration, the combustion chamber 30 communicates with an intake manifold 44 and an exhaust manifold 48 via a corresponding intake valve 52 and exhaust valve 54. The intake and exhaust valves can each be actuated by an intake cam 51 and an exhaust cam 53, respectively. The position of the intake cam 51 can be determined by an intake cam sensor 55. The position of the exhaust cam 53 can be determined by an exhaust cam sensor 57.

[0012] The fuel injection device 66 is positioned, as shown, to inject fuel directly into the combustion chamber 30, a process known to those skilled in the art as direct injection. The fuel injection device 66 delivers fuel proportionally to the pulse width of the FPW signal from the controller 12. Fuel is supplied to the fuel injection device 66 by a fuel system, as shown in Fig. 2 shown. Excess fuel from the fuel injection device 66 (e.g. after a pre-fuel injection) can be returned to the fuel tank 204 via the fuel return line 250.

[0013] The intake manifold 44 is shown connected to an optional electronic throttle 62, which sets the position of the throttle valve 64 to control the airflow from the intake charge chamber 46. The compressor 162 draws air from the air inlet 42 to supply it to the charge chamber 46. Exhaust gases cause the turbine 164 to rotate, which is coupled to the compressor 162 via the shaft 161. In some examples, an intercooler may be provided. The compressor speed can be adjusted by setting the position of an adjustable guide vane control 72 or a compressor bypass valve 158. In alternative examples, a wastegate 74 may replace or be used in addition to an adjustable guide vane control 72. The adjustable guide vane control 72 sets the position of turbine guide vanes with variable geometry.Exhaust gases can pass through turbine 164, supplying some energy to rotate the turbine 164 when the guide vanes are in an open position. Exhaust gases can pass through turbine 164 and transfer increased power to the turbine 164 when the guide vanes are in a closed position. Alternatively, the wastegate 74 allows exhaust gases to bypass turbine 164, thus reducing the amount of energy supplied to the turbine. The compressor bypass valve 158 allows the compressed air at the compressor 162 outlet to be recirculated to the compressor 162 inlet. In this way, the efficiency of the compressor 162 can be reduced to influence the compressor 162 flow and reduce the possibility of compressor pumping.

[0014] Combustion is initiated in the combustion chamber 30 when the fuel ignites without a specific ignition source, such as a spark plug, as the piston 36 approaches top dead center of the compression stroke and the cylinder pressure increases. In some examples, a wideband lambda sensor (Universal Exhaust Gas Oxygen Sensor - UEGO sensor) 126 may be connected to the exhaust manifold 48, which is located upstream of the emission device 70. In other examples, the UEGO sensor may be located downstream of one or more exhaust aftertreatment devices. Furthermore, in some examples, the UEGO sensor may be replaced by a NOx sensor that incorporates both NOx and oxygen sensing elements.

[0015] At lower combustion engine temperatures, the glow plug 68 can convert electrical energy into heat energy, thus raising the temperature in the combustion chamber 30. Raising the temperature of the combustion chamber 30 can make it easier to ignite a cylinder-air-fuel mixture via compression.

[0016] The emission control device 70 can, in one example, include a particulate filter and catalyst bricks. In another example, multiple emission control devices, each with several bricks, can be used. The emission control device 70 can, in one example, include an oxidation catalyst. In other examples, the emission control device can include a lean NOx trap or selective catalytic reduction (SCR) and / or a diesel particulate filter (DPF).

[0017] Exhaust gas recirculation (EGR) can be supplied to the internal combustion engine via the EGR valve 80. The EGR valve 80 is a three-way valve that either closes or allows exhaust gas to flow from the emission device 70 downstream to a location in the internal combustion engine's air intake system upstream of the compressor 162. In alternative examples, EGR can flow from the turbine 164 upstream to the intake manifold 44. EGR can bypass the EGR cooler 85, or alternatively, EGR can be cooled by passing through the EGR cooler 85. In other examples, a high-pressure and a low-pressure EGR system can be provided.

[0018] Control unit 12 is in Fig. Figure 1 shows a conventional microcomputer comprising: a microprocessor unit 102, input / output channels 104, read-only memory 106, random access memory 108, keep-alive memory 110 and a conventional data bus.According to the diagram, the control unit 12 receives different signals from the sensors connected to the internal combustion engine 10, in addition to the signals previously explained, including: the engine coolant temperature (ECT) from a temperature sensor 112 connected to the cooling sleeve 114; a position sensor 134 coupled to an accelerator pedal 130 to detect the accelerator pedal position set by the foot 132; a measurement of the engine manifold pressure (MAP) from a pressure sensor 121 coupled to the intake manifold 44; a boost pressure from a pressure sensor 122; exhaust oxygen concentration from an exhaust gas sensor 126; an engine position sensor from a Hall effect sensor 118 detecting the position of the crankshaft 40; a measurement of the mass of air flowing into the engine from a sensor 120 (e.g.,a hot-wire air mass meter); and a measurement of the throttle device position from a sensor 58. Atmospheric pressure can also be acquired for processing by the controller 12 (sensor not shown). In a preferred aspect of the present description, the engine position sensor 118 generates a predetermined number of evenly spaced pulses at each revolution of the crankshaft, from which the engine speed (RPM) can be determined.

[0019] During operation, each cylinder in the internal combustion engine 10 is typically subjected to a four-stroke cycle: The cycle includes the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. During the intake stroke, the exhaust valve 54 generally closes and the intake valve 52 opens. Air is drawn into the combustion chamber 30 via the intake manifold 44, and the piston 36 moves toward the bottom of the cylinder to increase the volume within the combustion chamber 30. The position at which the piston 36 is near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber 30 has reached its maximum volume) is typically referred to by those skilled in the art as bottom dead center (BDC). During the compression stroke, the intake valve 52 and the exhaust valve 54 are closed. The piston 36 moves toward the cylinder head to compress the air within the combustion chamber 30.The point at which the piston 36 is closest to the cylinder head at the end of its stroke (e.g., when the combustion chamber 30 has its smallest volume) is typically referred to by those skilled in the art as top dead center (TDC). In a process subsequently referred to as injection, fuel is introduced into the combustion chamber. In some examples, fuel may be injected into a cylinder a multitude of times during a single cylinder cycle. In a process subsequently referred to as ignition, the injected fuel is ignited by auto-ignition, resulting in combustion. During the power stroke, the expanding gases push the piston 36 back to bottom dead center (BDC). The crankshaft 40 converts piston movements into a torque of the rotating shaft. Finally, during the exhaust stroke, the exhaust valve 54 opens to discharge the burnt air-fuel mixture to the exhaust manifold 48, and the piston returns to TDC.It should be noted that the above is merely an example and that the timing of the opening and / or closing of the intake and exhaust valves may vary, for example, to provide positive or negative valve overlap, late intake valve closing, or various other examples. Furthermore, a two-stroke cycle may be used instead of a four-stroke cycle in some examples.

[0020] With reference to Fig. Figure 2 shows a detailed illustration of a fuel system that supplies fuel to the engine. The fuel system consists of Fig. 2 can be designed to turn the engine off Fig. 1. Fuel is supplied and can be controlled by a control unit 12, e.g. according to the procedure from Fig. 3.

[0021] The fuel system 200 includes a fuel tank 204 for storing fuel on board the vehicle, a low-pressure pump or suction pump 206, a high-pressure pump 256, and a fuel distributor 222. Fuel can be supplied from the fuel tank 204 to the low-pressure pump 206, which then pumps fuel to the high-pressure fuel pump 256. The fuel in the high-pressure fuel pump 256 is then directed to the fuel distributor 222, which in turn supplies pressurized fuel to the fuel injectors 66. The fuel distributor 222 can supply fuel to one cylinder bank of a vehicle via the fuel injectors 66. In other examples, another fuel distributor (not shown) supplies fuel to a second cylinder bank of the vehicle via fuel injectors.

[0022] The high-pressure pump 256 can include a fuel pump chamber 212, a camshaft 216, and a piston 202. The camshaft 216 is driven by the engine and provides a driving force to the piston 202, which is operated with fuel in the pump chamber 212. The low-pressure pump 206 can, for example, be an electronic non-return pumping system that can be operated intermittently in a pulse mode.

[0023] The fuel rail pressure in the fuel rail 222 can be monitored by the pressure sensor 220 and controlled via the adjusting valves 208 and 226. In one example, the fuel rail pressure control valve 226 can be partially open during operating conditions, allowing at least some of the fuel supplied by the fuel pump 256 to be returned to the fuel tank 204. In another example, the fuel rail pressure control valve 226 can be at least partially open by an additional amount during certain conditions to reduce the fuel pressure in the fuel rail 222. Under other operating conditions, the fuel rail pressure control valve 226 can be at least partially closed to increase the fuel pressure in the fuel rail 222.In another example, the fuel rail pressure control valve 226 can be controlled separately from the fuel pump flow metering valve 208, so that the fuel pressure in the fuel rail 222 can be adjusted by a valve or a combination of valves to provide a desired fuel pressure response. The fuel pump flow metering valve 208 can be used to control the amount of fuel flowing into the high-pressure fuel pump 256. Additionally, the check valve 210, positioned between the low-pressure pump 206 and the high-pressure pump 256, allows fuel to flow only to the high-pressure pump 256 in one direction and limits backflow from the high-pressure fuel pump 256.

[0024] The fuel temperature is monitored by temperature sensors 230 and 231. Sensor 231 detects the fuel temperature before the fuel pump 256 performs work on the fuel. Sensor 230 detects the fuel temperature after the fuel pump 256 performs work on the fuel. Sensor 230 can be positioned on the fuel distributor 222 if required. In some examples, the fuel temperature in a fuel return line 250 can be detected via temperature sensor 233. Similarly, Fig. The control unit 12 can receive fuel pressure signals from the control pressure sensor 220, which is coupled to the fuel distributor 222. The fuel distributor 222 can also contain one or more temperature sensors to detect the fuel temperature within the fuel distributor. The control unit 12 can also activate the fuel pump 206 to supply fuel to the fuel pump flow metering valve 208. The control unit 12 can further control the operations of the intake and / or exhaust valves or throttles, the engine cooling fan, the spark ignition, the injection device, and fuel pumps 206 and 256 to control engine operating conditions. Additionally, the control unit 12 can regulate the quantity or velocity of fuel into the fuel distributor 222 through the suction pump 206 and the high-pressure fuel pump 256 by means of appropriate fuel pump controllers (not shown).

[0025] The fuel injection devices 66 can be operationally coupled to and controlled by the control unit 12, as shown in Fig. Figure 2 shows that the amount of fuel injected by each injection device and the injection timing can be determined by the control unit 12 based on an engine map stored in the control unit 12, using the engine speed and / or the intake throttle angle or the engine load. Each injection device can be controlled via an electromagnetic valve (not shown) coupled to the injection device.

[0026] As described above, fuel can be supplied by the fuel injection device 66 via a plurality of injections during a combustion cycle. The plurality of injections may include multiple injections during the compression stroke, multiple injections during the intake stroke, or a combination of some direct injections during the compression stroke and some during the intake stroke. The fuel injection may also include a number of pre-injections prior to the main injection and / or one or more post-injections. The pre-injection(s) typically begin during a compression stroke at a predetermined crank angle before top dead center (BTDC) and prior to the main injection(s). The pre-injection typically injects a substantially smaller quantity of fuel, e.g.,1-20% of the total injected fuel, depending on the required total quantity, compared to the subsequent main injection, which can be up to 55-95% of the total fuel. The main injection can be administered before or after the TP (Temperature Boost), but it is usually administered after the TP. Additionally, under selected conditions, more than one pre-injection and / or more than one main injection can be performed during the compression stroke of the compression-ignition engine. The timing and duration of the pre- and main injections can be adjusted based on various parameters, such as noise, vibration, and harshness (NVH) parameters, peak cylinder pressure, engine load conditions, etc.Post-injection is provided to regenerate particulate filters in diesel engines and is generally carried out after the TP (Torque Transfer) with up to 10% of the total fuel. The sum of the pre-injection and main injection quantities, which may also include part of the post-injection, is the total amount of fuel required to keep the engine running in order to meet the driver's torque demand under a given operating condition. The required total amount of fuel can be determined by control unit 12, for example, based on an estimated engine operating condition. As described herein with reference to the... Fig. 3-5, the number of pre-fuel injections and / or main fuel injections during selected conditions can be reduced or eliminated depending on whether the estimated fuel rail pressure falls above or below a target fuel rail pressure.

[0027] With reference to Fig. Section 3 now illustrates an exemplary routine 300, which is executed by a controller to adjust the number of pre- and / or main injections based on a deviation in the fuel rail pressure from a setpoint. The reduction in the number of pre-injections can be instructed during a high engine torque demand if the actual fuel rail pressure deviates from a setpoint fuel rail pressure. Alternatively, the reduction in the number of main injections can be instructed during a low engine torque demand if the actual fuel rail pressure deviates from a setpoint fuel rail pressure. In one example, the setpoint fuel rail pressure can be a fuel rail pressure high enough to maintain an instructed fuel injection profile.Instructions for carrying out the procedure 300 and the other procedures contained herein can be executed by a controller based on instructions stored in a memory of a controller and in conjunction with signals received from sensors of the engine system, such as the pressure sensor 220 of the fuel distributor 222 in . Fig. 2 and the pedal position sensor 134, the MAP pressure sensor 121, the boost pressure sensor 122, the Hall effect sensor 118, the throttle position sensor 58, etc., which are described above with reference to Fig. 1 are described. The control system can use motor actuators of the motor system to adjust the motor operation according to the procedures described below.

[0028] At 302, engine operating conditions can be estimated and / or measured. These can include, for example, engine speed, engine load, driver torque demand, fuel injection parameters, fuel pressure, fuel temperature, ambient pressure, and ambient temperature.

[0029] Based on the operating conditions, a pre-fuel injection profile can be determined for the 304. The fuel injection(s) may include injections used as an ignition source (instead of ignition) for a subsequent main combustion and / or to reduce combustion noise, control emissions, etc. The pre-injection profile involves determining the number of pre-injections, the timing of each injection, the amount of fuel delivered in each injection, and the duration of each injection. It is understood that all fuel injections delivered before a main injection are referred to here as pre-injections. As an example, the pre-injection quantity may be 1–20% of the total injected fuel, depending on the required total fuel quantity and the minimum delivery quantity of the fuel injector at a given distributor pressure.In one example, the amount of pre-injection can be 4 mg or less. The pre-injection quantity can be determined based on engine operating conditions. For example, only a small amount of pre-fuel may be delivered during low loads, and a larger amount may be delivered during high load conditions. As an example, pre-injection may be initiated at 40 degrees of crank angle (CAD) before the TP (Throttle Point) and may end at 32 CAD before the TP.

[0030] In another example, the number of pre-injections can be determined using a lookup table indexed based on the engine speed and torque delivered in response to a torque demand. The table can contain a multitude of cells, each containing a value representing the total number of pre-injections delivered to an engine cylinder during a single cylinder cycle and over the course of an engine cycle. The table may include an increased number of pre-injections at lower engine speeds and loads to reduce engine noise under such conditions. For example, a table value corresponding to an engine torque of 1000 rpm and an engine speed of 500 rpm might hold an empirically determined value of 2.The value 2 can include two pre-fuel injections during one cylinder cycle.

[0031] In another example, the number of pre-injections can be determined using a different lookup table indexed based on an estimated fuel rail pressure at a given engine torque. In other examples, engine speed can also serve as a basis for adjusting the number of pre-injections. For instance, at a fuel rail pressure of 1400 bar, when the engine torque is 500 Nm, the number of pre-injections might be two. However, if the fuel rail pressure drops to 1200 bar with a similar engine torque of 500 Nm, only one pre-injection might be provided. Thus, if the fuel pressure changes, the number of pre-injections can be reduced. Once the pre-injection profile has been determined, the procedure proceeds to 306.

[0032] For the 306, a main fuel injection profile can be determined based on the estimated engine operating conditions. Determining the main fuel injection profile involves determining the number of injections, the timing of each injection, the amount of fuel delivered in each injection, and the duration of each injection. Accordingly, the main injection(s) may include an injection used for the main combustion event in the cylinder. As an example, the pre-injection(s) may provide 55–98% of the total fuel, depending on the total fuel quantity required and the minimum delivery quantity of the fuel injector at a given distributor pressure. In one example, the main injection quantity may be 10 mg or more.In another example, the amount of fuel to be injected into the engine can be determined using a lookup table, also indexed based on engine speed and load. For instance, at lower engine speeds and loads, the control unit can inject a smaller amount of fuel in the main injection, and at higher engine speeds and loads, it can inject a larger amount of fuel in the main injection. In yet another example, determining the main fuel injection profile can also involve determining whether the fuel is delivered as a single injection or as multiple smaller injections via a split injection strategy to reduce peak cylinder pressure below a cylinder pressure limit.In one example, the main fuel injection can be divided into a first injection, which can be delivered at a slightly earlier time than the planned main injection, and a second injection, which is delivered at a slightly later time relative to the main injection time. Once the main injection profile has been determined, the procedure proceeds to 308.

[0033] At 308, a target fuel rail pressure (FRP) can be determined. The target FRP can be determined using a lookup table indexed based on the fuel quantity and the actual number of pre-injections and main injections. For example, a correlation value between the specified pulse width and the amount of fuel injected for pre- and main injections can be learned by the control unit.

[0034] This relationship can then be used to determine an estimated FRP at a given engine operating condition. Alternatively, the target fuel pressure can be derived from a graph based on the engine speed and torque at a given engine operating condition. Once the estimated FRP value has been determined, the procedure proceeds to 310.

[0035] At 310, it can be determined whether the actual FRP is lower than the target FRP. The actual FRP can be measured via the pressure sensor, as shown in Fig. 2 described. The fuel rail pressure can be affected by various factors, such as fuel temperature and fuel viscosity. In one example, the actual FRP may be lower than the target FRP under certain conditions, such as when the fuel viscosity is below a threshold and / or the fuel temperature is above a threshold. If the actual FRP is equal to or greater than the target FRP, the procedure proceeds to 316, injecting fuel according to the specified fuel injection profiles, and the procedure ends.

[0036] If the actual FRP is less than the target FRP, the procedure proceeds to 312, thereby reducing the actual number of pre- and / or main injections. In some examples, the number of pre- and / or main injections can be reduced in response to the actual FRP being less than the target FRP by any amount, whereas in other examples, the number of pre- and / or main injections can be reduced in response to the actual FRP being less than the target FRP by a threshold amount, such as at least 5% less than the target FRP. Accordingly, fuel in the fuel rail can be preserved by reducing the return fuel from the injector to the fuel tank during pre-injections. In one example, pre-injections can be reduced based on the target FRP. For example, the number of pre-injections can be reduced to their minimum, e.g.,The number of main injections can be reduced to just one pre-injection. In another example, pre-injections can be eliminated to increase the FRP to its target value. Alternatively or additionally, the number of main injections can be reduced to increase the FRP to the target FRP. The number of main injections can be reduced to their minimum, e.g., to one main injection.

[0037] As an example, the fuel injection profile for a vehicle under a selected operating condition can be set to three injections, consisting of two pre-injections and one main injection. If an actual fuel injection pressure (FRP) lower than the target FRP is detected, such as during a high engine load condition, the control unit can adjust the total number of fuel injections to reduce them to one. Additionally, by reducing the number of pre-injections to one and maintaining the number of main injections, the peak cylinder pressure can be limited to mitigate cylinder degradation, while the FRP can be increased to the target FRP by reducing fuel return from the injector to the fuel tank.

[0038] It is also possible for the actual fuel-to-fuel ratio (FRP) to fall below the target FRP, even under low-load conditions, such as when the fuel pump is malfunctioning, the fuel temperature is relatively high, or the fuel viscosity is low. During low-load conditions, when the actual FRP is below the target FRP, one of the main injections can be omitted while maintaining the number of pre-injections (e.g., transitioning from two pre-injections and two main injections to two pre-injections with one main injection). Alternatively, in a case where the original fuel injection profile is set to two main injections without pre-injections, one of the main injections can be omitted in response to the actual FRP falling below a target FRP, leaving only one main injection.Due to lower load conditions, the cylinder pressure can be well below a cylinder pressure limit. Therefore, it may be desirable to maintain the main injections to reduce engine noise and instead omit one of the main injections, as this prevents the cylinder pressure from exceeding the pressure limit. During high load conditions, the control unit can reduce the number of main injections, allowing the cylinder to operate at or above the cylinder pressure limit for a predetermined number of engine cycles—for example, below a number of cycles that could impair engine performance.

[0039] Therefore, the decision as to whether to omit at least one or more of the pre- and / or main injections when a pressure deviation in the fuel-air mixture (FRP) is detected (e.g., when the actual FRP is lower than the target FRP) can depend on the vehicle operating conditions. For example, if the vehicle is operating under a high load condition (e.g., when high torque is required) and the actual FRP falls below a target FRP, one or more pre-injections may be omitted to prevent the peak cylinder pressure from exceeding a pressure limit. Conversely, if the vehicle is operating under a low load condition and the actual FRP falls below the target FRP, one or more main injections may be omitted to reduce the engine's power output.

[0040] Furthermore, if the actual fuel rail pressure is lower than the nominal fuel rail pressure, the number of pre- and / or main injections for each cylinder of the engine can be reduced, as shown in Figure 313. In other examples, the number of pre- and / or main injections can be reduced for only a subset of the engine's cylinders, as shown in Figure 315. For example, in a four-cylinder engine, the number of pre- and / or main injections can be reduced in two of the cylinders, while maintaining the number of pre- and / or main injections in the other two cylinders. The decision as to how many cylinders have their number of pre- and / or main injections reduced can be based on the difference between the nominal fuel rail pressure and the actual fuel rail pressure, with the number of pre- and / or main injections being reduced as the difference increases (e.g.,The number of cylinders experiencing reduced pre- and / or main injections increases (the actual fuel rail pressure decreases relative to the set value). In another example, in an engine with two fuel rails (e.g., a V8 engine), the two fuel rails may operate at different pressures under certain conditions (e.g., if a first high-pressure pump feeding a first fuel rail is aged or impaired, while a second high-pressure pump feeding a second fuel rail is neither aged nor impaired). Under such conditions, cylinders receiving fuel from a fuel rail with a lower fuel rail pressure may experience reduced pre- and / or main injections, while cylinders receiving fuel from a fuel rail with a higher (e.g.,The target fuel distributor pressure is supplied, and the pre- and / or main injections cannot be reduced.

[0041] Once the number of pre- and / or main injections has been reduced, the pulse width of the pre- and / or main injection can be increased in step 314, and the injection timing can be adjusted based on the required fuel quantity. For example, if a pre-injection is omitted when engine torque demand is high, the remaining pre-injection pulse width can be increased, and its injection timing can be further delayed to reduce combustion noise. Simultaneously, the main injection timing can be advanced relative to the engine compression stroke to reduce ignition retardation. By advancing the pre-injection timing closer to the main injection timing, the cylinder temperature can be increased to promote fuel combustion.To provide sufficient fuel supply to meet the increased engine torque demand, the pulse width of the main injection can be increased. This allows the actual fuel-to-fuel ratio (FRP) to be increased.

[0042] In cases where the main injection is omitted during low engine load conditions, the main injection timing can be advanced further, and a smaller pulse width can be provided. Alternatively, the timing of the pre-injection can remain unchanged while the pulse width is adjusted to a smaller pulse width. The main injection timing can be delayed to increase the exhaust gas temperature. A larger quantity of main injection can be provided based on the desired total fuel quantity.

[0043] In another example, the pulse width of the pre- and / or main injection can be determined based on the desired total fuel quantity and the target fuel-to-gas ratio (FRP). In yet another example, the timing and quantity of the pre- and / or main fuel injection can be adjusted by the control unit via an open-loop control system without feedback from any sensors. For example, the timing and quantity of the pre- and / or main injection can be determined using a lookup table indexed based on engine load and engine torque demand. In another example, the timing and quantity of the pre- and / or main injection can be adjusted based on a measured peak cylinder pressure.For example, a peak cylinder pressure limit can be defined for specific engine operating conditions, and fuel injection parameters can be adjusted when the cylinder pressure approaches or reaches this limit. For instance, the fuel injection timing can be adjusted and / or the fuel injection quantity reduced to prevent exceeding the peak cylinder pressure limit. The pulse width and / or timing of the pre- and / or main injection can be adjusted for cylinders / injectors where the number of corresponding main or pre-injections has been reduced.

[0044] In this way, a precise amount of fuel can be delivered to the engine while maintaining a relatively constant fuel rail pressure at or above a set pressure. By reducing the number of pre- and / or main injections when a deviation in the fuel rail pressure is detected, more fuel can be retained in the fuel rail, as fuel can be returned from the injectors to the fuel tank. As a result, the fuel rail pressure can be maintained at a relatively constant level. Furthermore, while the fuel injection adjustments described here involved reducing the number of pre- and / or main injections, in some examples, post-injection can be adjusted in response to a fuel rail pressure falling below the set pressure.Post-injection can be performed to initiate the regeneration of one or more aftertreatment devices, such as particulate filters. If the fuel distributor is unable to reach the target distributor pressure, regeneration can be delayed until the distributor pressure rises to the target pressure. In this way, post-injection can be reduced or eliminated during low distributor pressure conditions, allowing the distributor pressure to remain at or above the target pressure for accurate fuel injection to meet torque demands.

[0045] With reference to Fig. Figure 4 shows an exemplary timing diagram of a pre-fuel adjustment that allows for a constant fuel rail pressure. Diagram 400 shows an engine torque request at 402, a fuel rail pressure at curve 404, and a control command to a high-pressure (HP) fuel pump at curve 408. The lower curve of diagram 400 shows representative fuel injection timing for one cylinder. The pre-injection timing is shown as 412x (black bars), and the main injection timing is shown as 414x, with reference to their positions from top dead center (TDC) along the X-axis.It is understood that more than one fuel injection event may occur between t0 and t5 by other cylinders, and that the injection timing sequence shown in the lower part of diagram 400 is intended to illustrate a representative fuel injection profile for a particular cylinder at each defined time point, and that other similar fuel injection events may occur during the period shown. Fig. The events shown in the 4-time graphs can take place. All curves are plotted as a function of time along the x-axis. The time markers t0-t5 represent significant points in time during engine operation.

[0046] Between t0 and t1, the engine operates at a lower torque with a lower engine torque demand, so the engine torque requirement is lower than the threshold demand, which is determined based on the maximum capacity of the high-pressure pump. The fuel rail pressure is maintained at a nominal operating pressure above the target fuel pressure (FRP) by pressurizing the fuel in the fuel rail via the operation of the high-pressure pump. Consequently, at t1, the high-pressure pump valve command remains at its nominal setting to supply sufficient fuel to the fuel rail and maintain the fuel rail pressure (404) constant and above the target fuel pressure (406).At t1, the control determines that the total amount of fuel delivered to the cylinder is divided into 3 injections, comprising two pre-injections 412a, 412b, which are delivered before TP, and one main injection 414a, which is delivered after TP.

[0047] In one example, the first pre-injection 412a can be delivered at 40 degrees of crank angle (CAD) before the tipping point (TP), and the second pre-injection 412b can be delivered at approximately 15 CAD before the TP. Furthermore, the main injection 414a can be introduced into the cylinder precisely at the TP for a relatively short duration d2.

[0048] Other embodiments may include different fuel injection profiles, such as different timings than those in Fig. shown. Furthermore, the duration of each injection can be adjusted relative to the one in Fig. The amounts shown may vary to deliver higher or lower quantities of fuel.

[0049] Between t2 and t3, the engine torque demand increases above a threshold requirement. To meet this increased engine torque demand and maintain a constant fuel rail pressure above the target FRP, the high-pressure pump command increases to its maximum capacity, allowing more fuel to be supplied to the fuel rail. Based on the increased engine torque, the control unit can retain the existing injection profile and adjust only the injection timing and pulse width of the pilot and main injections. In this case, the pilot injection timings (412c, 412d) are advanced to prevent ignition retard and avoid combustion noise. Furthermore, the control unit advances the main injection timing (414b) to just before the start of the TP (e.g., 5 CAD before the TP).The duration of the first main injection 414b is increased from d2 to d3 (where d3 > d2), so that the injector remains open for a longer period and more fuel can be injected into the engine cylinder. However, due to the large amount of fuel injected, the fuel pump is unable to supply sufficient fuel to the fuel rail, and therefore the fuel rail pressure begins to drop below the target FRP (i.e., the threshold pressure) at t3.

[0050] At t4, the engine torque demand remains high, and to meet this demand above the threshold, a large amount of fuel is required. Therefore, the high-pressure fuel pump operates at its maximum capacity. Due to the fuel pump's inability to deliver fuel at a rate higher than its maximum capacity, the pressure in the fuel rail remains lower than the target fuel pressure (FRP) (i.e., the threshold pressure). In response to the actual FRP falling below the target FRP, the control unit at t4 adjusts the pre-injection profile by eliminating one of the pre-injections. Thus, the timing of the remaining pre-injection (412e) is delayed to bring it closer to the main injection, preventing ignition retardation, and its pulse width can be increased to provide sufficient fuel for the pre-combustion phase in the cylinder.The timing of the main fuel injection 414c is advanced to an earlier point relative to the piston's bottom dead center (DPC) position (e.g., 20 CAD before DPC) for a longer duration d4, where d4 is the longest and d2 is the shortest, such that d4 > d3 > d2. This increases the pulse width for the main fuel injection 414c to deliver sufficient fuel to the combustion chamber. Consequently, eliminating the pre-injection increases the fuel rail pressure to achieve a value above the target fuel rail pressure (FRP) at t5.

[0051] In this way, the actual number of pre-injections can be reduced once the deviation of the fuel rail pressure (from the target FRP) is detected, in order to bring the FRP back to its intended value. This allows a precise volume of fuel to be delivered through the injectors to provide sufficient fuel for combustion and generate the desired torque output. Furthermore, this approach can reduce the time spent during pressure shifts between different operating conditions, thereby improving engine performance.

[0052] With reference to Fig. Figure 5 shows an exemplary timing diagram of fuel injection adjustments in response to a deviation in the fuel pressure (FRP). Diagram 500 shows several injection strategies (trajectories 502-512) where the pre- and main injection profiles are adjusted in response to the actual FRP falling below the target FRP. The pre-injection timing is shown as black bars and the main injection timing is shown as white bars, with reference to their positions from top dead center (TDC) along the x-axis. T1 represents a time when the fuel rail pressure is above or around the target FRP, while T2 represents a time when the actual FRP falls below the target FRP.

[0053] The curve 502 shows an initial injection profile (also referred to as the "original" injection profile) at T1, which includes two pre-injections (black bars) with a pulse width P1 for both pre-injections and two main injections (white bars) with pulse widths of e0 and e1 for the first and second main injections, respectively. At T2, a deviation of the actual fuel-air mixture (FRP) from the target FRP is detected, such as during a high engine torque demand, and the control unit then adjusts the injection profiles so that the number of pre-injections is reduced to one. By omitting a pre-injection, the remaining pre-injection quantity is increased to a pulse width PW2, where PW2 > PW1, and the pre-injection timing is retarded so that it is closer to the main injection timing. In another example, the remaining pre-injection quantity can be reduced to reduce combustion noise.The first main injection at T2 remains unchanged with a pulse width of e0. To increase the fuel injection quantity, the pulse width of the second main injection is increased to e2, where e2 > e1. In this way, a large amount of fuel can be delivered while the fuel rail pressure is kept above the target FRP.

[0054] At time point T1, curve 504 shows a similar initial injection profile to curve 502, with two pre-injections (with a pulse width P1) and two main injections with pulse widths of e0 and e1 for the first and second main injections, respectively. At T2, a reduction in fuel rail pressure is detected. Therefore, the control unit can adjust the fuel injection profile to reduce the number of fuel injection events. In the example timing scenario shown in curve 504, one injection event can be eliminated. By maintaining the pre-injections, the engine noise can be kept at a relatively low level.Reducing the number of main injection events can, however, lead to an increase in peak cylinder pressure. Therefore, eliminating one main injection while maintaining the number of pre-injections can only be performed under certain conditions, such as low load conditions. As shown, the pre-injection timings are adjusted so that they are further delayed, and the first main injection is eliminated. In one example, the amount of fuel injected in the pre-injections can be reduced. Furthermore, the remaining main injection quantity can be increased to the pulse width e3, where e3 > e1 > e0, and the main injection timing can be delayed to reduce the NOx level.

[0055] The curve 506 shows an initial injection profile at T1 with only one pre-injection (with a pulse width P1) and two main injections with pulse widths e0 and e1 corresponding to the first and second main injections, respectively. Similar to the fuel adjustments in 504, the first main injection is eliminated at T2. The timing of the pre-injection and the second main injection can be delayed. Furthermore, the remaining main injection quantity can be increased to a pulse width e3, where e3 > e1 > e0, and the main injection timing can be delayed to reduce the NOx level.

[0056] The curve 508 shows an initial injection profile at T1 with two pre-injections (with a pulse width P1) and one main injection with a pulse width e2. At T2, if a deviation from the target fuel-to-fuel ratio (FRP) is detected, one of the pre-injections can be eliminated. By omitting a pre-injection, the remaining pre-injection quantity is increased to a pulse width PW2, where PW2 > PW1, and the pre-injection timing is retarded so that it is closer to the main injection timing. To increase the fuel injection quantity, the pulse width of the second main injection is increased to e3, where e3 > e2.

[0057] The curve 510 shows an initial injection profile at T1 with a pre-injection with a pulse width P1 and a main injection with a pulse width e2. At T2, if a deviation from the target fuel-fuel ratio (FRP) is detected, the pre-injections can be eliminated. To increase the fuel injection quantity, the pulse width of the second main injection is increased to e3, where e3 > e2. The main injection timing is also advanced to prevent ignition retardation.

[0058] The curve 512 shows an initial injection profile at T1 with two main injections, each with a pulse width of e1 and e2 for the first and second main injections, respectively. At T2, if a deviation from the target fuel-fuel ratio (FRP) is detected, one of the main injections can be eliminated. To increase the fuel injection quantity, the pulse width of the remaining main injection is increased to e3, where e3 > e2 > e1. The main injection timing is also advanced to prevent ignition retardation.

[0059] In some examples, a staged approach can be used to reduce the number of fuel injection events. For instance, with respect to the timing diagram described above, the approach illustrated in graph 502 (e.g., omitting a pre-injection to perform one pre-injection and two main injections) can be initiated in response to the FRP falling below the target FRP. If the FRP then does not increase to the target FRP, one of the main injections can be omitted, so that the injection profile resembles that in graph 506 (e.g., one pre-injection and one main injection). If the FRP still does not increase to the target value, the pre-injection can be omitted, so that only the main injection occurs, without any pre-injections.Other approaches are within the scope of disclosure, such as first omitting one of the main injections, then omitting one of the pre-injections, and then omitting the other pre-injection. If reducing the number of fuel injection events does not cause the fuel rail pressure to reach the target pressure, at least in some examples, the engine may be throttled or other actions may be taken. In one example, if the system is unable to maintain the fuel rail pressure at the target pressure when the engine load is below a certain threshold, this may indicate that the fuel pump is malfunctioning, and the control unit may notify the driver by illuminating a Malfunction Indicator Light (MIL).Additionally or alternatively, an inability to maintain the distributor pressure at the set pressure during low load conditions may indicate a potential fuel system leak, and thus the control system may be designed to shut down the engine to prevent a fuel leak during this condition.

[0060] By measuring the fuel rail pressure in real time during engine operation and adjusting the number of pre-injections at high engine load / fuel pump capacity, higher engine power levels can be achieved with lower-capacity pumps. In particular, the approach described here can enable the delivery of high engine power even with an aging high-pressure fuel pump. For example, a new high-pressure fuel pump may have sufficient capacity to pressurize the fuel rail for multiple pre-injections, even under high torque demand. However, as the high-pressure fuel pump ages, its capacity may decrease.Instead of throttling the engine when high torque is required as the pump ages, the approach described here allows for a reduction in fuel injection events at high engine loads / high torque demand, thereby enabling the delivery of the requested engine power.

[0061] Accordingly, in an example, a fuel injection device can be controlled, during a first condition involving an engine operating at a fuel rail pressure greater than a threshold pressure, in response to a first command to inject fuel for a first cylinder cycle, to inject a first quantity of fuel via a pre-injection, a second quantity of fuel via a first main injection, and a third quantity of fuel via a second main injection. The pre-injection can occur before the first main injection, and the first main injection can occur before the second main injection, and the first fuel quantity can be smaller than the second fuel quantity.During a second condition, which involves the engine operating at a fuel rail pressure lower than a threshold pressure, the fuel injection device can be controlled, in response to a second command to inject fuel for a second cylinder cycle, to inject a fourth quantity of fuel via a second pre-injection and a fifth quantity of fuel via a single third main injection. The first condition may involve the engine operating within a first engine speed / load range, and the second condition may involve the engine operating within the same first engine speed / load range (e.g., the engine may operate within substantially the same engine speed / load range under both the first and second conditions).

[0062] The first engine speed / load range can involve a relatively high engine speed / load, such as greater than 2000 rpm and greater than 50% of the maximum rated engine load. The first condition can further involve operation of a high-pressure fuel pump at a first performance level, and the second condition can further involve operation of the high-pressure fuel pump at a second performance level. The second performance level can reflect an aged high-pressure fuel pump relative to a new high-pressure fuel pump, which would result in the first performance level. In another example, the first condition can involve an unaffected fuel pump flow meter valve (e.g., valve 208 from...). Fig.2) and the second condition may involve a malfunctioning fuel pump flow meter. The malfunctioning fuel pump flow meter may involve a valve that is unable to move to a fully open position, thus limiting the fuel flow to the high-pressure fuel pump. In this way, malfunctioning fuel system components (e.g., the fuel pump) can cause the fuel distributor to fail to reach the target distributor pressure, and thus one or more fuel injection events may be eliminated to allow the target distributor pressure to be reached. Other parameters that can cause the target distributor pressure to fail include fuel temperature (e.g., higher than a threshold temperature) and fuel viscosity (e.g., a relatively low viscosity).

[0063] In another example, the first condition might involve the engine operating within a first speed / load range, and the second condition might involve the engine operating within a second speed / load range. In such an example, the first speed / load range could be smaller than the second speed / load range.

[0064] Thus, as described above, reducing the number of fuel injection events in response to a drop in distributor pressure due to the elimination of some fuel recirculation events can reduce the total volume of fuel removed from the distributor. Reducing the total volume of fuel removed from the distributor can allow the fuel distributor to remain at higher pressures, thereby enabling the delivery of a more accurate fuel injection quantity. However, such a configuration can result in larger pressure drops at the fuel distributor during each main injection event, relative to a fuel injection profile where multiple fuel injections occur during each cylinder cycle.Therefore, under certain conditions it may be desirable to maintain or even increase the number of pre-injections to provide smaller pressure drops at the fuel rail, which can result in a more consistent rail pressure. Such conditions can include high engine speeds, fuel rail diagnostics, and other situations.

[0065] One example provides a method that involves reducing the total number of fuel injections delivered to a cylinder in a given cylinder cycle in response to a threshold reduction in the pressure in a fuel rail. In a first example, the pressure threshold reduction involves the pressure in the fuel rail falling below a set pressure by at least a threshold amount. Reducing the total number of fuel injections involves reducing the total number of pre-fuel injections delivered to the cylinder in the given cylinder cycle relative to the total number of pre-fuel injections delivered in a previous cylinder cycle.In a second example, which optionally includes the first example, the method further includes one or more instances of increasing an injection pulse width and adjusting an injection timing of a remaining pre-fuel injection supplied to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel rail. In a third example, which optionally includes one or both of the first and second examples, the method further includes one or more instances of increasing an injection pulse width and adjusting an injection timing of at least one main fuel injection supplied to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel rail.In a fourth example, which optionally includes one or more of each from the first through third examples, reducing the total number of power injections involves reducing the total number of main fuel injections delivered to the cylinder in the given cylinder cycle relative to the total number of main fuel injections delivered in a previous cylinder cycle. In a fifth example, which optionally includes one or more of each from the first through fourth examples, the method further involves increasing an injection pulse width and adjusting an injection timing of a remaining main fuel injection delivered to the cylinder in the given cylinder cycle in response to the pressure reduction in the fuel rail.In a sixth example, which optionally includes one or more of each of the first to fifth examples, the method further includes one or more of adjusting an injection pulse width and adjusting an injection timing of at least one pre-fuel injection provided to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel distributor.

[0066] An example provides a method that includes the following: during a first condition, when the fuel rail pressure is above a threshold pressure, supplying fuel to a cylinder in a first cylinder cycle via two pre-fuel injection events and at least one main fuel injection event; and in response to the fuel rail pressure falling below the threshold pressure, supplying fuel to the cylinder in a second cylinder cycle via only one pre-fuel injection event and at least one main fuel injection event. In a first example, the method further includes adjusting the timing and pulse width of one or more of the single pre-fuel injection event and the at least one main fuel injection event in response to the fuel rail pressure falling below the threshold pressure.In a second example, which optionally includes the first example, the first condition involves the engine torque demand being less than a threshold demand, and the fuel rail pressure falling below the threshold pressure in response to the engine torque demand increasing above the threshold demand. In a third example, which optionally includes one or both of the first and second examples, the method further involves pressurizing a fuel rail by operating a high-pressure pump, and the threshold demand is determined based on the maximum capacity of the high-pressure pump.In a fourth example, which optionally includes one or more of each of the first to third examples, the cylinder is a first cylinder and the method further includes: during the first condition, where the fuel rail pressure is above the threshold pressure, supplying fuel to a second cylinder in a third cylinder cycle of the second cylinder via two pre-fuel injection events and at least one main fuel injection event; and in response to the fuel rail pressure falling below the threshold pressure, supplying fuel to the second cylinder in a fourth cylinder cycle of the second cylinder via only one pre-fuel injection event and at least one main fuel injection event.In a fifth example, which optionally includes one or more of each of the first through fourth examples, the cylinder is a first cylinder and the method further includes: during the first condition, when the fuel rail pressure is above the threshold pressure, supplying fuel to a second cylinder in a third cylinder cycle of the second cylinder via two pre-fuel injection events and at least one main fuel injection event; and in response to the fuel rail pressure falling below the threshold pressure, supplying fuel to the second cylinder in a fourth cylinder cycle of the second cylinder via two pre-fuel injection events and at least one main fuel injection event.

[0067] An example provides a procedure that includes the following: during a first condition, injecting a first quantity of fuel into a cylinder of the engine via a first pre-injection, a second quantity of fuel via a first main injection, and a third quantity of fuel via a second main injection, wherein the first pre-injection, the first main injection, and the second main injection are performed during a first cylinder cycle; and during a second condition, injecting a fourth quantity of fuel via a second pre-injection and injecting a fifth quantity of fuel via a single third main injection, wherein the third main injection and the second pre-injection are performed during a second cylinder cycle. In a first example, the first pre-injection is performed before the first main injection, and the first main injection is performed before the second main injection.In a second example, which optionally includes the first example, the first fuel quantity is smaller than the second fuel quantity. In a third example, which optionally includes one or both of the first and second examples, the first condition is that the fuel viscosity is above a threshold viscosity, and the second condition is that the fuel viscosity is below the threshold viscosity. In a fourth example, which optionally includes one or more of each of the first through third examples, the first condition is that the fuel temperature is below a threshold temperature, and the second condition is that the fuel temperature is above the threshold temperature.In a fifth example, which optionally includes one or more of each from the first four examples, the first condition involves the operation of a high-pressure fuel pump at a first power level, and the second condition involves the operation of the high-pressure fuel pump at a second power level. In a sixth example, which optionally includes one or more of each from the first five examples, the first condition involves an unaffected fuel pump flow meter, and the second condition involves an impaired fuel pump flow meter. In a seventh example, which optionally includes one or more of each from the first six examples, the first condition involves the fuel rail pressure being higher than a threshold pressure, and the second condition involves the fuel rail pressure being lower than the threshold pressure.

[0068] It should be noted that the control and estimation routines contained herein can be used with various engine and / or vehicle system configurations. The control procedures and routines disclosed herein can be stored as executable instructions in non-volatile memory and can be executed by the control system, which includes the control unit in combination with the various sensors, actuators, and other engine hardware. The specific routines described herein can represent one or more from any number of processing strategies, such as event-driven, interrupt-driven, multitasking, multithreading, and the like. Accordingly, various illustrated operations, steps, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Likewise, the processing sequence is not strictly necessary to achieve the features and advantages of the exemplary embodiments described here, but is provided for easier illustration and description. One or more of the illustrated actions, operations, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, operations, and / or functions can graphically represent code that is to be programmed in the non-volatile memory of the computer-readable storage medium in the engine control system, whereby the described actions are carried out by executing the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0069] It is understood that the interpretations and routines disclosed herein are exemplary and that these specific embodiments are not to be interpreted restrictively, as numerous variations are possible. For example, the foregoing technology can be applied to V-6, I-4, I-6, V-12, 4-cylinder boxer, and other engine types. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations and other features, functions, and / or properties disclosed herein.

Claims

[1] Procedure, encompassing: Reducing the total number of fuel injections provided to a cylinder in a given cylinder cycle in response to a reduction in pressure in a fuel distributor (222), including reducing the total number of pre-fuel injections during high engine load conditions and reducing the total number of main fuel injections during low engine load conditions. [2] Method according to claim 1, wherein the pressure reduction includes a threshold reduction of the pressure, comprising that the pressure in the fuel distributor (222) falls below a target pressure by at least a threshold amount, and wherein reducing the total number of pre-fuel injections during high engine load conditions includes reducing a total number of pre-fuel injections supplied to the cylinder in the specified cylinder cycle relative to a total number of pre-fuel injections performed in a previous cylinder cycle. [3] Method according to claim 2, further comprising one or more of increasing an injection pulse width and adjusting an injection timing of a remaining pre-fuel injection provided to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel distributor (222). [4] Method according to claim 2, further comprising one or more of increasing an injection pulse width and adjusting an injection timing of at least one main fuel injection provided to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel distributor (222). [5] Method according to claim 1, wherein reducing the total number of main fuel injections during low engine load conditions comprises reducing a total number of main fuel injections supplied to the cylinder in the specified cylinder cycle relative to a total number of main fuel injections performed in a previous cylinder cycle. [6] Method according to claim 5, further comprising one or more of increasing an injection pulse width and adjusting an injection timing of a remaining main fuel injection provided to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel distributor (222). [7] Method according to claim 5, further comprising one or more of adjusting an injection pulse width and adjusting an injection timing of at least one pre-fuel injection which is provided to the cylinder in the specified cylinder cycle in response to the pressure reduction in the fuel distributor (222). [8] Method according to claim 1, wherein the amount of fuel injected in each pre-fuel injection of a cylinder cycle is less than the amount of fuel injected in each main fuel injection of the corresponding cylinder cycle. [9] Procedures, comprehensive: During a first condition, injecting a first quantity of fuel into a cylinder of an engine (10) via a first pre-injection, a second quantity of fuel via a first main injection, and a third quantity of fuel via a second main injection, wherein the first pre-injection, the first main injection, and the second main injection are carried out during a first cylinder cycle; and During a second condition, a fourth fuel quantity is injected via a second pre-injection and a fifth fuel quantity is injected via a single third main injection, wherein the third main injection and the second pre-injection are carried out during a second cylinder cycle, the first fuel quantity being smaller than the second fuel quantity and larger than the fourth fuel quantity. [10] Method according to claim 9, wherein the first pre-injection is carried out before the first main injection, and the first main injection is carried out before the second main injection. [11] Method according to claim 9, wherein the first condition includes that the fuel viscosity is above a threshold viscosity and the second condition includes that the fuel viscosity is below the threshold viscosity. [12] Method according to claim 9, wherein the first condition includes that the fuel temperature is below a threshold temperature and the second condition includes that the fuel temperature is above the threshold temperature. [13] Method according to claim 9, wherein the first condition includes operation of a high-pressure fuel pump (256) at a first power level and the second condition includes operation of the high-pressure fuel pump (256) at a second power level. [14] Method according to claim 9, wherein the first condition includes an unaffected fuel pump flow meter (208) and the second condition includes an impaired fuel pump flow meter (208). [15] Procedure which includes the following: During a first condition where the fuel distributor pressure is above a threshold pressure, fuel is supplied to a first cylinder in a first cylinder cycle via two pre-fuel injection events and at least one main fuel injection event; In response to the fuel rail pressure falling below the threshold pressure, fuel is supplied to the first cylinder in a second cylinder cycle via only one pre-fuel injection event and at least one main fuel injection event; During the first condition, where the fuel rail pressure is above the threshold pressure, fuel is supplied to a second cylinder in a third cylinder cycle of the second cylinder via two pre-fuel injection events and at least one main fuel injection event; and In response to the fuel distribution pressure falling below the threshold pressure, fuel is supplied to the second cylinder in a fourth cylinder cycle of the second cylinder via only one pre-fuel injection event and at least one main fuel injection event.

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