METHOD AND SYSTEMS FOR A DUAL FUEL INJECTION SYSTEM

Abstract

Method for an engine (10), comprising: Determining engine operating conditions; Selecting a fuel injection schedule and fuel injection mode for the specific engine operating conditions; Adjusting the airflow into the engine (10) based on the total fuel injection quantity; in response to a report of impairment of a port fuel injection device (262), received during fuel supply to a cylinder (14) via each of a port fuel injection device (262) and a direct fuel injection device (252), limiting an intake air flow.

Description

AREA

[0001] The present application relates in general to systems and methods for adjusting the operation of an internal combustion engine having multiple fuel supply systems in order to maintain a combustion air-fuel ratio. GENERAL STATE OF THE ART / BRIEF OVERVIEW

[0002] Engines can be designed to supply fuel to an engine cylinder using one or more port and direct injection systems. Port fuel direct injection (PFDI) engines are capable of utilizing both fuel injection systems. For example, at high engine loads, fuel can be injected directly into an engine cylinder via a direct injection device, thus taking advantage of the charge air cooling properties of direct injection (DI). At lower engine loads and during engine starts, fuel can be injected into an intake manifold of the engine cylinder via a port fuel injection device, thereby reducing particulate emissions.Under other conditions, such as heavy loads, some of the fuel may be supplied to the cylinder via the port fuel injection system, while the remainder is supplied via the direct injection system. In such conditions, fuel from both the port fuel injection (PFI) and direct injection (DI) systems is required to maintain the desired air-fuel ratio.

[0003] DE 10 2009 000 426 A1 discloses a control device for an internal combustion engine. DE 10 2010 042 842 A1 discloses a method for operating an internal combustion engine. DE 10 2015 225 504 A1 discloses a method for compensating for errors in the fuel injection quantity during the operation of an internal combustion engine.

[0004] The inventors of the present invention have, however, identified a potential problem with PFDI systems. If the port fuel injection system ceases to function during engine operation, for example, due to problems with the port fuel injection circuitry, the engine can be damaged due to prolonged lean combustion. Specifically, the engine control system may not be able to react quickly enough when the port fuel injection system stops functioning while the direct fuel injection system continues to operate to meet the driver's torque demand. Consequently, the engine airflow may continue to be supplied based on the total fuel flow rate to provide engine torque, resulting in a leaner combustion than desired. Prolonged lean combustion can lead to misfires and engine damage.In contrast, in PFI-only systems, if the port fuel injection system is impaired, there is zero torque in the cylinder, and the engine control system is able to respond to the zero torque condition.

[0005] In one example, the above problem can be addressed, at least partially, by a procedure for an engine that includes: limiting an intake airflow in response to a report of impairment to a port fuel injection system received during fuel delivery to a cylinder via either a port or direct injection system. This will reduce engine impairment resulting from an interruption of port fuel injection in a PFDI system.

[0006] As an example, an engine can be configured with both port and direct fuel injection capabilities. Under conditions where fuel is supplied to the engine via either port or direct injection, the engine airflow can be adjusted based on the total fuel flow from the fuel injectors to provide a desired air-fuel ratio (e.g., stoichiometric air-fuel ratio). In response to a reported impairment of the PFI system, such as due to circuit impairment of a single port injector or a loss of electrical power to the port injection system, a direct injection fuel plan can be implemented, if feasible, to compensate for the loss of fuel injected into the intake manifold.For example, the direct injection pulse width can be lengthened, if possible, to compensate for at least some of the fuel injected into the intake manifold that should have been supplied, thereby providing as much torque as possible. Additionally, the engine airflow can be limited by reducing the opening of an intake throttle and / or by adjusting the camshaft timing. Specifically, the engine airflow limitation can be determined based solely on the amount of fuel supplied via direct injection, while ignoring the desired / commanded flow through the port fuel injector. For example, the intake throttle opening can be reduced to match (or be dependent on) the updated direct injection fuel pulse width, thus maintaining the desired air-fuel ratio (e.g., stoichiometric air-fuel ratio).

[0007] By limiting the engine airflow in a PFDI engine system in response to a reported impairment of the port fuel injection system, unintended lean combustion can be reduced. By adjusting the intake throttle position solely based on the directly injected fuel flow, and regardless of the desired (or anticipated) port fuel injection flow, the airflow can be appropriately limited in response to the interruption of port fuel injection. Limiting the airflow to maintain engine operation with a desired air-fuel ratio despite the impairment of the PFI system can extend engine performance and lifespan.

[0008] 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 mention important or essential features of the claimed subject matter, the scope of which is defined solely in the claims following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate disadvantages mentioned above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 schematically represents an exemplary embodiment of a cylinder of an internal combustion engine. Fig. Figure 2 schematically represents an exemplary embodiment of a fuel system designed for port fuel injection and direct injection, in which the engine consists of Fig. 1 can be used. Fig. Figure 3 shows a flowchart illustrating an exemplary procedure that can be implemented to limit airflow in a PFDI engine system in response to impairment of the PFI system. Fig. Figure 4 shows exemplary airflow settings in a PFDI engine system to reduce air-fuel ratio errors caused by impairment of port fuel injectors. Fig. Figure 5 shows an exemplary table of empirically determined intake manifold and direct fuel fractions (DI / PFI ratio). DETAILED DESCRIPTION

[0009] The following description concerns systems and methods for adjusting the operation of an internal combustion engine designed for either direct fuel injection or port fuel injection capability, such as the exemplary engine system from Fig. 1. An exemplary PFDI fuel system connected to the engine system made of Fig. 1 can be used, is in Fig. 2 shown. A fuel distribution ratio of port injection to direct injection can be determined based on engine operating conditions, such as using the engine speed / load table from Fig. 5. During certain engine operating conditions, fuel can be supplied to the engine via either port or direct injection. In response to a notification of PFI system impairment during fuel supply to the engine via either port or direct injection, an engine control unit may execute a routine, such as the exemplary routine from Fig. 3, to limit the airflow to the engine depending only on the directly injected fuel fraction, while disregarding the expected fuel fraction injected into the intake manifold. An example airflow setting is given with reference to Fig. Figure 4 shows how engine damage caused by prolonged lean combustion can be prevented.

[0010] Regarding the terminology used in this detailed description, a high-pressure pump or direct injection pump can be abbreviated as HPP (High Pressure Pump). Similarly, a low-pressure pump or suction pump can be abbreviated as LPP (Low Pressure Pump). Port fuel injection can be abbreviated as PFI (Port Fuel Injection), while direct injection can be abbreviated as DI. Additionally, fuel rail pressure, or the pressure of fuel within a fuel rail, can be abbreviated as FRP (Fuel Rail Pressure).

[0011] Fig. Figure 1 represents an example of a combustion chamber or cylinder of an internal combustion engine 10. The engine 10 can be controlled, at least partially, by a control system comprising the control unit 12 and by input from a driver 130 via an input device 132. In this example, the input device 132 includes an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The cylinder (here also referred to as the "combustion chamber") 14 of the engine 10 can include combustion chamber walls 136 in which a piston 138 is positioned. The piston 138 can be coupled to the crankshaft 140, so that an alternating motion of the piston is translated into a rotational motion of the crankshaft. The crankshaft 140 can be coupled to at least one drive wheel of the passenger car via a transmission system.Furthermore, a starter (not shown) can be coupled to the crankshaft 140 via a flywheel to enable a starting process of the engine 10.

[0012] Cylinder 14 can draw in intake air via a series of intake air ducts 142, 144, and 146. Intake air duct 146 can communicate with other cylinders of engine 10 in addition to cylinder 14. In some examples, one or more of the intake ducts may include a charging device, such as a turbocharger or a supercharger. For example, shows Fig. 1. The engine 10 is designed with a turbocharger comprising a compressor 174, arranged between the intake ports 142 and 144, and an exhaust turbine 176, arranged along an exhaust port 148. The compressor 174 can be driven, at least partially, by the exhaust turbine 176 via a shaft 180 when the charging device is designed as a turbocharger. In other examples, such as when the engine 10 is equipped with a supercharger, the exhaust turbine 176 can be optionally omitted, with the compressor 174 being driven by mechanical inputs from an electric motor or the engine itself. A throttle 162, which includes a throttle valve 164, can be provided along an intake port of the engine to vary the flow rate and / or pressure of the intake air supplied to the engine cylinders. For example, the throttle 162 can be positioned downstream of the compressor 174, as shown in Fig. 1 shown, or alternatively it can be provided upstream of compressor 174.

[0013] The exhaust channel 148 can receive exhaust gases from other cylinders of the engine 10 in addition to those from cylinder 14. The exhaust gas sensor 128 is shown to be coupled to the exhaust channel 148 upstream of the emission control device 178. The sensor 128 can be selected from various suitable sensors for providing an indication of an exhaust air-fuel ratio, such as a linear lambda sensor or UEGO sensor (Universal Exhaust Gas Oxygen Sensor; wide-range or broad-band lambda sensor), a dual-state lambda sensor or EGO sensor (as shown), a HEGO sensor (heated EGO sensor), a NOx, HC, or CO sensor. The emission control device 178 can be a three-way catalytic converter (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0014] Each cylinder of the engine 10 can include one or more intake valves and one or more exhaust valves. For example, cylinder 14 is shown to include at least one intake control valve 150 and at least one exhaust control valve 156, which are arranged in an upper region of the cylinder 14. In some examples, each cylinder of the engine 10, including cylinder 14, can include at least two intake control valves and at least two exhaust control valves, which are arranged in an upper region of the cylinder.

[0015] The inlet valve 150 can be controlled by the controller 12 via the actuator 152. Likewise, the exhaust valve 156 can be controlled by the controller 12 via the actuator 154. Under certain conditions, the controller 12 can vary the signals provided to the actuators 152 and 154 to control the opening and closing of the corresponding inlet and exhaust valves. The position of the inlet valve 150 and exhaust valve 156 can be determined by appropriate valve position sensors (not shown). The valve actuators can be of the electrically actuated type, the cam-actuated type, or a combination thereof. The inlet and exhaust valve actuation can be controlled simultaneously, or any of the following options can be used: variable inlet cam actuation, variable exhaust cam actuation, dual independent variable cam actuation, or fixed cam actuation.Each cam actuation system can include one or more cams and use one or more cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift (VVL) systems, operated by the control unit 12, to vary valve operation. For example, cylinder 14 can 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 can be controlled by a common valve actuator or actuation system, or by a variable valve timing actuator or actuation system.

[0016] Cylinder 14 can have a compression ratio that is the volume ratio between piston 138 at bottom dead center and at top dead center. In one example, the compression ratio is in the range of 9:1 to 10:1. However, in some examples where different fuels are used, the compression ratio can be higher. This can occur, for example, when using fuels with a higher octane rating or fuels with a higher latent heat of vaporization. The compression ratio can also be higher when using direct injection due to its effect on engine knock.

[0017] In some examples, each cylinder of the engine 10 may include a spark plug 192 to initiate combustion. The ignition system 190 can provide a spark to the combustion chamber 14 via the spark plug 192 in response to a spark advance signal (SA) from the control unit 12 under selected operating modes. However, in some embodiments, the spark plug 192 may be omitted, such as when the engine 10 can initiate combustion by auto-ignition or by fuel injection, as may be the case with some diesel engines.

[0018] In some examples, each cylinder of the engine 10 can be configured with one or more fuel injection devices to supply it with fuel. As a non-limiting example, cylinder 14 is shown to include two fuel injection devices 166 and 170. The fuel injection devices 166 and 170 can be configured to deliver fuel drawn from the fuel system 8. As described in reference to Fig. As shown in Figure 2, the fuel system 8 can include one or more fuel tanks, fuel pumps, and fuel distributors. It is shown that the fuel injection device 166 is directly coupled to the cylinder 14 to inject fuel directly into it, proportional to the pulse width of the signal FPW-1 received by the controller 12 via the electronic driver 168. Thus, the fuel injection device 166 provides so-called direct injection (hereinafter referred to as "DI") of fuel into the combustion cylinder 14. While the injection device 166 is in Fig. The fuel injector 166, shown positioned on one side of cylinder 14, can alternatively be located above the piston, such as near the spark plug 192. Such a position can improve mixing and combustion when the engine is operated with an alcohol-based fuel, as some alcohol-based fuels have lower volatility. Alternatively, the injector can be located above and near the intake valve to improve mixing. Fuel can be supplied to the fuel injector 166 from a fuel tank of the fuel system 8 via a high-pressure fuel pump and fuel distributor. Furthermore, the fuel tank can include a pressure converter that provides a signal to the control unit 12.

[0019] The fuel injection device 170 is shown in a configuration that provides so-called port fuel injection (hereinafter referred to as "PFI") into the intake manifold upstream of cylinder 14, arranged in the intake port 146 instead of in cylinder 14. The fuel injection device 170 can inject fuel taken from the fuel system 8 proportionally to the pulse width of the FPW-2 signal received by the controller 12 via the electronic driver 171. It should be noted that a single driver 168 or 171 can be used for both fuel injection systems, or, as shown, several drivers can be used, for example, driver 168 for fuel injection device 166 and driver 171 for fuel injection device 170.

[0020] In an alternative example, each of the fuel injection devices 166 and 170 can be configured as a direct fuel injection device for injecting fuel directly into cylinder 14. In yet another example, each of the fuel injection devices 166 and 170 can be configured as a port fuel injection device for injecting fuel upstream of the intake valve 150. In still further examples, cylinder 14 can contain only a single fuel injection device, which is configured to receive different fuels in varying relative quantities as a fuel mixture from the fuel systems, and which is further configured to inject this fuel mixture either as a direct fuel injection device directly into the cylinder or as a port fuel injection device upstream of the intake valves.It is understood that the fuel systems described here are not to be limited by the specific designs of fuel injection devices described here as examples.

[0021] Fuel can be supplied to the cylinder by either injection device during a single cylinder cycle. For example, each injection device can provide a portion of the total fuel injection that is burned in cylinder 14. Furthermore, the distribution and / or relative amount of fuel supplied by each injection device can vary with operating conditions, such as engine load, knocking, and exhaust gas temperature, as described below. Fuel injected into the intake manifold can be supplied during an open intake valve event, a closed intake valve event (e.g., essentially before the intake stroke), and during operation with both the open and closed intake valves.Similarly, directly injected fuel can be supplied, for example, during an intake stroke, partially during a preceding exhaust stroke, during the intake stroke, and partially during the compression stroke. Thus, even in a single combustion event, injected fuel can be injected from the intake manifold and direct injection systems at different times. Furthermore, multiple injections of the supplied fuel can be performed per cycle during a single combustion event. These multiple injections can occur during the compression stroke, the intake stroke, or any suitable combination thereof.

[0022] The fuel injection devices 166 and 170 can have different characteristics. These include differences in size; for example, one injection device may have a larger injection orifice than the other. Other differences include, but are not limited to, different spray angles, different operating temperatures, different target orientations, different injection timings, different spray characteristics, different positions, etc. Furthermore, different effects can be achieved depending on the distribution ratio of the injected fuel between the injection devices 170 and 166.

[0023] Fuel tanks in fuel system 8 can contain different types of fuel, such as fuels with different fuel properties and compositions. These differences can include varying alcohol content, water content, octane ratings, heats of vaporization, fuel blends, and / or combinations thereof. An example of fuels with different heats of vaporization could be gasoline as the primary fuel type, with a lower heat of vaporization, and ethanol as the secondary fuel type, with a higher heat of vaporization. In another example, the engine could use gasoline as the primary fuel type and an alcoholic fuel blend, such as E85 (approximately 85% ethanol and 15% gasoline) or M85 (approximately 85% methanol and 15% gasoline), as the secondary fuel type.Other possible substances include water, methanol, a mixture of alcohol and water, a mixture of water and methanol, a mixture of alcohols, etc.

[0024] In yet another example, both fuels could be alcohol mixtures with varying alcohol compositions. The first fuel could be a gasoline-alcohol mixture with a lower alcohol concentration, such as E10 (which consists of approximately 10% ethanol), while the second fuel could be a gasoline-alcohol mixture with a higher alcohol concentration, such as E85 (which consists of approximately 85% ethanol). Additionally, the first and second fuels could differ in other fuel properties, such as temperature, viscosity, octane rating, etc. Furthermore, the fuel properties of one or both fuel tanks can frequently vary, for example, due to daily fluctuations in refueling.

[0025] Control 12 is in Fig. 1 is shown as a microcomputer comprising a microprocessor unit 106, input / output ports 108, an electronic storage medium for executable programs and calibration values, which in this specific example is shown as a non-volatile read-only memory chip 110 for storing executable instructions, random access memory 112, keep-alive memory 114 and a data bus.In addition to the signals discussed previously, the control unit 12 can receive various signals from sensors coupled to the engine 10, including the measurement of mass air flow (MAF) from a mass air flow sensor 122; the engine coolant temperature (ECT) from a temperature sensor 116 coupled to a cooling sleeve 118; a profile ignition pickup signal (PIP) from a Hall effect sensor 120 (or other type) coupled to the crankshaft 140; the throttle position (TP) from a throttle position sensor; and a manifold absolute pressure (MAP) signal from a sensor 124. An engine speed signal (RPM) can be generated by the control unit 12 from the PIP signal. The manifold pressure signal MAP from a manifold pressure sensor can be used to provide an indication of the vacuum or pressure in the intake manifold.The controller 12 receives signals from the various sensors. Fig. 1 and suspends the various actuators Fig. 1. To adjust engine operation based on received signals and instructions stored in the controller's memory. For example, based on a pulse width signal commanded by the controller to a driver coupled to the direct injection device, a fuel pulse can be delivered by the direct injection device to a corresponding cylinder.

[0026] As described above, shows Fig. 1. This refers to only one cylinder of a multi-cylinder engine. Accordingly, each cylinder can contain its own set of intake / exhaust valves, fuel injection device(s), spark plug, etc. It is understood that the engine 10 can contain any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12, or more. Furthermore, each of these cylinders can contain some or all of the various components that are described in Fig. 1 are described and illustrated with reference to cylinder 14.

[0027] Fig. Figure 2 schematically represents an exemplary embodiment 200 of a fuel system, such as the fuel system 8 from Fig. 1. The fuel system 200 can be operated to supply fuel to an engine, such as engine 10. Fig. 1. The fuel system 200 can be operated by a control system such that it performs some or all of the functions referred to in Fig. 3 processes described.

[0028] The fuel system 200 includes a fuel storage tank 210 for storing fuel on board the vehicle, a low-pressure fuel pump (LPP) 212 (also referred to here as the fuel suction pump 212), and a high-pressure fuel pump (HPP) 214 (also referred to here as the fuel injection pump 214). Fuel can be supplied to the fuel tank 210 via a fuel filling channel 204. In one example, the LPP 212 can be an electrically driven low-pressure fuel pump located at least partially within the fuel tank 210. The LPP 212 can be controlled by a controller 222 (e.g., the controller 12 from Fig. 1) to supply fuel to the HPP 214 via fuel channel 218. The LPP 212 can be designed as a so-called fuel suction pump. As an example, the LPP 212 can be a turbine pump (e.g., centrifugal pump) that has an electric (e.g., DC) pump motor, whereby the pressure rise at the pump and / or the volume flow through the pump can be controlled by varying the electrical power supplied to the pump motor, thereby increasing or decreasing the motor speed. For example, the rise in volume flow and / or pressure at the suction pump can be decreased if the control reduces the electrical power supplied to the suction pump 212. The rise in volume flow and / or pressure at the pump can be increased by increasing the electrical power supplied to the suction pump 212.As an example, the electrical power supplied to the low-pressure pump motor can be obtained from an alternator or other energy storage device on board the vehicle (not shown), with the control system being able to manage the electrical load used to power the low-pressure pump. Thus, by varying the voltage and / or current supplied to the low-pressure fuel pump, the flow rate and pressure of the fuel supplied at the inlet of the high-pressure fuel pump 214 are adjusted.

[0029] The LPP 212 can be fluid-coupled to a filter 217, which can remove minor impurities contained in the fuel that could potentially damage the fuel handling components. A check valve 213, which facilitates fuel supply and maintains fuel line pressure, can be fluidically positioned upstream of the filter 217. The check valve 213 upstream of the filter 217 can increase the compliance of the low-pressure channel 218, as the filter may have a physically large volume. Additionally, a pressure relief valve 219 can be used to limit the fuel pressure in the low-pressure channel 218 (e.g., the output from the suction pump 212). The relief valve 219 can have a ball-spring mechanism that, for example, engages and seals at a predetermined pressure differential.The target pressure differential at which the relief valve 219 is designed to open can assume various suitable values; as a non-restrictive example, the target value can be 6.4 bar or 5 bar (g). An opening 223 can be used to allow air and / or fuel vapor to escape from the suction pump 212. This escape at the opening 223 can further be used to drive a jet pump, which is used to transfer fuel from one location to another within the tank 210. In one example, an opening check valve (not shown) can be arranged in series with the opening 223. In some embodiments, the fuel system 8 can include one or more (e.g., a series of) check valves fluidly coupled to the low-pressure fuel pump 212 to prevent fuel from flowing back upstream from the valves.In this context, upward flow refers to a fuel flow moving from the fuel distributors 250, 260 towards the LPP 212, while downward flow refers to the nominal fuel flow direction from the LPP towards the HPP 214 and from there to the fuel distributors.

[0030] Fuel drawn in through the LPP 212 can be discharged at a lower pressure into a fuel channel 218, which leads to an inlet 203 of the HPP 214. The HPP 214 can then discharge fuel into a first fuel distributor 250, which is coupled to one or more fuel injectors of a first group of direct injection devices 252 (here also referred to as the first injection device group). Fuel drawn in through the LPP 212 can also be discharged to a second fuel distributor 260, which is coupled to one or more fuel injectors of a second group of port fuel injection devices 262 (here also referred to as the second injection device group).The HPP 214 can be operated to increase the pressure of the fuel supplied to the first fuel rail above the suction pump pressure, with the first fuel rail coupled to the high-pressure direct injection unit. As a result, high-pressure direct injection (DI) can be possible while pre-fuel injection (PFI) can operate at a lower pressure.

[0031] While it has been shown that each of the first fuel distributor 250 and the second fuel distributor 260 supplies fuel to four fuel injectors of the respective injector group 252, 262, it is understood that each fuel distributor 250, 260 can supply fuel to any suitable number of fuel injectors. For example, the first fuel distributor 250 can supply fuel to one fuel injector of the first injector group 252 for each cylinder of the engine, while the second fuel distributor 260 can supply fuel to one fuel injector of the second injector group 262 for each cylinder of the engine. The controller 222 can actuate each of the port fuel injectors 262 individually via a port fuel injector driver 237 and each of the direct fuel injectors 252 individually via a direct fuel injector driver 238.The controller 222, the drivers 237, 238, and other suitable motor system controllers can comprise a control system. While the drivers 237, 238 are shown outside of the controller 222, it is understood that in other examples the controller 222 may include the drivers 237, 238 or may be designed to provide the functionality of the drivers 237, 238. The controller 222 may include additional components not shown, such as those in the controller 12. Fig. 1 are included.

[0032] The HPP 214 can be a positive displacement pump driven by the engine. As a non-restrictive example, the HPP 214 could be a Bosch HDP5 high-pressure pump that uses a magnetically activated control valve (e.g., fuel volume regulator, solenoid valve, etc.) to vary the effective pump volume for each pump stroke. The HPP's outlet check valve is mechanically controlled and not electronically controlled by an external control unit. Unlike the LPP 212, which is driven by an electric motor, the HPP 214 can be mechanically driven by the engine. The HPP 214 includes a pump piston 228, a pump compression chamber 205 (also referred to here as the compression chamber), and a stage chamber 227. The pump piston 228 receives a mechanical input from the engine crankshaft or camshaft via the cam 230, thus operating the HPP according to the principle of a cam-driven single-cylinder pump. A sensor (in Fig. 2 (not shown) can be positioned near the cam 230 to allow the determination of the angular position of the cam (e.g. between 0 and 360 degrees), which can be passed on to the control 222.

[0033] A suction pump fuel pressure sensor 231 can be positioned along the fuel channel 218 between the suction pump 212 and the high-pressure fuel pump 214. In this configuration, measured values ​​from sensor 231 can be interpreted as indicating the fuel pressure of the suction pump 212 (e.g., the outlet fuel pressure of the suction pump) and / or the inlet pressure of the high-pressure fuel pump. Measured values ​​from sensor 231 can be used to assess the operation of various components in the fuel system 200, to determine whether sufficient fuel pressure is being supplied to the high-pressure fuel pump 214 so that the high-pressure fuel pump draws in liquid fuel and not fuel vapor, and / or to minimize the average electrical power delivered to the suction pump 212.

[0034] The first fuel distributor 250 includes a first fuel distributor pressure sensor 248 for providing the control unit 222 with a value for the direct injection fuel distributor pressure. Similarly, the second fuel distributor 260 includes a second fuel distributor pressure sensor 258 for providing the control unit 222 with a value for the intake manifold injection fuel distributor pressure. An engine speed sensor 233 can be used to provide the control unit 222 with a value for the engine speed. This engine speed value can be used to determine the speed of the high-pressure fuel pump 214, since the pump 214 is mechanically driven by the engine 202, for example via the crankshaft or the camshaft.

[0035] The first fuel distributor 250 is coupled to an outlet 208 of the HPP 214 along the fuel channel 278. A check valve 274 and a pressure relief valve (also known as a pump relief valve) 272 can be positioned between the outlet 208 of the HPP 214 and the first (DI) fuel distributor 250. The pump relief valve 272 can be coupled to a bypass channel 279 of the fuel channel 278. The outlet check valve 274 opens to allow fuel to flow from the high-pressure pump outlet 208 into a fuel distributor only when a pressure at the outlet of the direct injection fuel pump 214 (e.g., a compression chamber outlet pressure) is higher than the fuel distributor pressure. The pump relief valve 272 can limit the pressure in the fuel channel 278 downstream of the HPP 214 and upstream of the first fuel distributor 250.For example, the pump relief valve 272 can limit the pressure in the fuel channel 278 to 200 bar. The pump relief valve 272 allows fuel to flow from the DI fuel distributor 250 towards the pump outlet 208 when the fuel distributor pressure is greater than a predetermined pressure. The valves 244 and 242 work together to keep the low-pressure fuel distributor 260 pressurized at a predetermined low pressure. The pressure relief valve 242 helps to limit the pressure that can develop in the fuel distributor 260 due to the thermal expansion of the fuel.

[0036] Based on the engine operating conditions, fuel can be supplied by one or more port fuel injectors 262 and direct fuel injectors 252. For example, under high-load conditions, fuel can be supplied to a cylinder via direct injection only during each engine cycle, with the port fuel injectors 262 deactivated. In another example, under medium-load conditions, fuel can be supplied to a cylinder via either direct or port fuel injection during each engine cycle. Yet another example: during low-load conditions, engine starts, and warm-up idling, fuel can be supplied to a cylinder via port fuel injection only during each engine cycle, with the direct fuel injectors 252 deactivated.An example of an engine speed / load table that can be accessed by control 222 to determine a fuel supply schedule is given with reference to . Fig. 5 shown and with reference to the procedure from Fig. 3 described.

[0037] It should be noted that the high-pressure pump 214 is made of Fig. Figure 2 is presented as an illustrative example of a possible design for a high-pressure pump. Fig. The two components shown can be removed and / or modified, while additional components not currently shown can be added to pump 214 while still maintaining the ability to deliver high-pressure fuel to a direct injection fuel distributor and a port fuel distributor.

[0038] The controller 12 can also control the operation of each of the fuel pumps 212 and 214 to adjust the quantity, pressure, flow rate, etc., of fuel supplied to the engine. For example, the controller 12 can vary a pressure setting, pump stroke quantity, pump duty cycle command, and / or fuel flow rate of the fuel pumps to supply fuel to different points in the fuel system. A driver (not shown) electronically coupled to the controller 222 can be used to send a control signal to the low-pressure pump as needed to adjust the output (e.g., speed, flow rate, and / or pressure) of the low-pressure pump.

[0039] Under conditions where an engine cylinder receives fuel via both port and direct injection, impairment of the port fuel injection system may occur. This can happen, for example, due to a loss of electrical power to the PFI system or due to circuit damage to an individual port fuel injector. However, the engine can still receive fuel via the direct injection system. As referenced in Fig. As described in section 3, under such conditions, the engine airflow can be limited in response to the loss of PFI fuel flow in order to maintain the combustion air-fuel ratio. By limiting the airflow so that it depends only on the directly injected fuel flow and is independent of the fuel flow injected into the intake manifold (actual or anticipated), the occurrence of lean combustion is reduced.

[0040] Thus, the components made of Fig. 1-2 A system comprising: an engine cylinder; a port fuel injection device; a direct fuel injection device; an intake throttle; and a controller with computer-readable instructions stored in non-volatile memory to: in response to a port fuel injection device impairment signal received during fuel delivery to the cylinder via the port fuel injection device only, switch to fuel delivery to the cylinder via the direct fuel injection device only; and limit an intake airflow. For example, limiting may involve reducing the opening of the intake throttle when a pulse width commanded to the direct fuel injection device increases. Limiting may be adjusted to maintain the cylinder's air-fuel ratio from before the switchover.In one example, the specification of the impairment of the intake manifold injection device may include impairment of an electrical circuit coupled to the intake manifold injection device and loss of electrical power to the intake manifold injection device. Fig. Figure 3 illustrates an exemplary procedure 300 for limiting engine airflow in response to problems with the PFI fuel system. Instructions to execute the procedure 300 can be carried out by a controller based on instructions stored in a memory of the controller and in conjunction with signals from sensors of the engine system, such as those described above with reference to Fig. 1 and Fig. The controller can receive signals from the two sensors described below. It can then use motor actuators of the engine system to adjust engine operation according to the procedures described below. For example, the controller can send a signal to an actuator of the engine system's intake throttle to limit the airflow.

[0041] At 302, engine operating conditions can be determined by the control unit. These conditions can include engine load, engine temperature, engine speed, driver torque demand, etc. Depending on the estimated operating conditions, a variety of engine parameters can be determined. For example, at 304, a fuel injection schedule can be determined. This involves determining the amount of fuel to be supplied to a cylinder (e.g., based on the torque demand) and the fuel injection timing. Furthermore, a fuel injection mode and a fuel split ratio between port and direct injection can be determined for the current engine operating conditions.In one example, under high engine loads, direct injection (DI) of fuel into an engine cylinder via a direct injection device can be selected to utilize the charge air cooling properties of DI, allowing engine cylinders to operate at higher compression ratios without unwanted engine knocking. If direct injection is selected, the control unit can determine whether the fuel is to be delivered as a single injection or split into multiple injections, and furthermore, whether the injection(s) is / are to be delivered during an intake stroke and / or a compression stroke. In another example, under lower engine loads (low engine speed) and during engine starts (especially cold starts), port fuel injection (PFI) of fuel into an intake manifold of the engine cylinder via a port fuel injection device can be selected to reduce particulate emissions.If port fuel injection is selected, the control unit can determine whether fuel is to be delivered during a closed intake valve event or an open intake valve event. There may be other conditions under which some fuel is delivered to the cylinder via the port fuel injection system, while the remainder is delivered via the direct injection system. Determining the fuel injection schedule can also involve setting a pulse width for each fuel injection system and a duration between injection pulses based on the estimated engine operating conditions.

[0042] In one example, the specified fuel plan may include a split ratio between fuel supplied via port injection and direct injection, where the split ratio is determined using a lookup table from the control unit, such as the exemplary table from Fig. 5, is determined. With reference to Fig. Figure 5 shows a Table 500 for determining port and direct injection fuel fractions for a total amount of fuel delivered to an engine during one engine cycle. The table from Fig. 5 can provide a basis for determining a mode of fuel system operation (DI only, PFI only, or PFI and DI combined (PFDI)), as described in the procedure from Fig. 3. The vertical axis represents the engine speed, and the engine speeds are listed along the vertical axis. The horizontal axis represents the engine load, and the engine load values ​​are listed along the horizontal axis. In this example, table cells 502 contain two values ​​separated by a comma. Values ​​to the left of the commas represent port fuel injection fuel fractions, and values ​​to the right of the commas represent direct fuel injection fuel fractions. For example, for the table value corresponding to 2000 rpm and a load of 0.2, the empirically determined values ​​are 0.4 and 0.6. The value of 0.4, or 40%, is the port fuel injection fuel fraction, and the value of 0.6, or 60%, is the direct fuel injection fuel fraction.Consequently, if the desired fuel injection mass is 1 gram of fuel during an engine cycle, 0.4 grams of fuel are port-injected fuel and 0.6 grams are direct-injected fuel. In other examples, the table may contain only a single value in each cell, and the corresponding value can be determined by subtracting the table value from one. For example, if the cell containing 2000 rpm and a load of 0.2 has a single value of 0.6 for a direct-injection fuel fraction, then the port-injection fuel fraction is 1 - 0.6 = 0.4.

[0043] In this example, it can be observed that the port fuel injection fraction is highest at lower engine speeds and loads. In the illustrated example, table cell 504 represents an engine speed / load condition where all fuel is supplied via port injection only. Direct injection is deactivated under this speed / load condition. The direct fuel injection fraction is highest at medium engine speeds and loads. In the illustrated example, table cell 506 represents an engine speed / load condition where all fuel is supplied via direct injection only. Port fuel injection is deactivated under this speed / load condition.The port fuel injection fraction increases at higher engine speeds when the timing for direct fuel injection into a cylinder can be reduced due to a shorter time between cylinder combustion events. It can be observed that if the engine speed changes without a change in engine load, the port and direct fuel injection fractions can change.

[0044] With renewed reference to Fig. 3 includes the procedure at 306 Determining whether a Port Fuel Injection (PFI) Only mode has been selected, based on the current engine operating conditions. For example, PFI-only fuel delivery may be requested during low engine load and low engine temperature conditions, as well as during engine starts. If a PFI Only mode is selected, the procedure at 312 includes activating the port fuel injectors and selectively disabling the direct fuel injectors. The control unit can then supply fuel to an engine cylinder via the port fuel injectors according to the specified fuel delivery schedule. For example, the port fuel injector control unit (such as the port fuel injectors 262 from Fig. 1) Command a pulse width corresponding to the specified fuel quantity. A timing for port fuel injection can be set relative to the cylinder's intake valve actuation based on whether open-valve or closed-valve port fuel injection has been selected in the specified fuel delivery plan.

[0045] In the 314, the procedure involves adjusting the airflow into the engine based on the intake manifold fuel injection quantity to control the air-fuel ratio. For example, the control unit can retrieve a desired air-fuel ratio and then, depending on the total amount of fuel supplied via the intake manifold injection device (e.g., depending on the intake manifold injection pulse width), calculate a desired airflow that provides the desired air-fuel ratio. In one example, the desired air-fuel ratio is a stoichiometric air-fuel ratio. The desired airflow can be provided as a desired intake throttle position (e.g., throttle opening degree) or a desired cam position (e.g., desired VCT actuation).In one example, the control system can determine the throttle position pulse width by a determination that directly considers the intake manifold fuel injection quantity or intake manifold injection pulse width and the desired air-fuel ratio, such as increasing the throttle opening with increasing intake manifold fuel injection quantity for a given air-fuel ratio, increasing the throttle opening with increasing desired air-fuel ratio for a given quantity of fuel injected into the intake manifold, or increasing the throttle opening with increasing intake manifold fuel injection quantity and increasing combustion air-fuel ratio.Alternatively, the controller can determine the airflow based on a calculation using a lookup table, where the inputs are the intake manifold injection pulse width and the desired air-fuel ratio, and the output is an intake throttle position that provides the desired air-fuel ratio. As another example, the controller can make a logical determination (e.g., regarding the position of the intake throttle or intake cam) based on logic rules that depend on the intake manifold injection pulse width and the desired air-fuel ratio. The controller can then generate a control signal that is sent to the intake throttle or the VCT mechanism (or the intake cams).

[0046] If no PFI-only mode is selected, routine 308 includes determining whether a direct injection-only (DI-only) mode has been requested. Fuel delivery via DI only may be desirable, for example, under high engine load and / or high engine temperature conditions. If a DI-only mode is confirmed, direct injection devices can be enabled at 316, while port injection devices remain disabled. Fuel can then be supplied via the direct injection devices (such as the direct injection devices 252 from Fig. 1) be injected into the engine cylinder. The control unit can set an injection pulse width of the direct injection devices to deliver fuel via the direct injection devices according to the specified fuel delivery plan. For example, the direct injection device control unit can command a pulse width corresponding to a specific amount of fuel. Direct injection control can be set relative to the cylinder piston position based on whether injection during the intake and / or compression stroke has been selected, as well as based on the number of injections selected per injection cycle in the specified fuel delivery plan.

[0047] In the 318, the procedure involves adjusting the airflow into the engine based on the direct fuel injection quantity to control the air-fuel ratio. For example, the control unit can retrieve a desired air-fuel ratio and then, depending on the total amount of fuel supplied via the direct injection device (e.g., depending on the direct injection pulse width), calculate a desired airflow that provides the desired air-fuel ratio. In one example, the desired air-fuel ratio could be a stoichiometric air-fuel ratio. The desired airflow can be provided as a desired intake throttle position (e.g., degree of throttle opening) or a desired cam position (e.g., desired VCT actuation).In one example, the control unit can determine the throttle position by a process that directly considers the direct injection fuel quantity or pulse width and the desired air-fuel ratio, such as increasing the throttle opening with increasing direct fuel injection quantity for a given air-fuel ratio, increasing the throttle opening with increasing desired air-fuel ratio for a given quantity of directly injected fuel, or increasing the throttle opening with increasing direct fuel injection quantity and increasing air-fuel ratio. Alternatively, the control unit can determine the airflow based on a calculation using a lookup table, where the inputs are direct injection pulse width and desired air-fuel ratio, and the output is an intake throttle position that provides the desired air-fuel ratio.As another example, the control unit can make a logical determination (e.g., regarding the position of the intake throttle or intake camshaft) based on logic rules that depend on the direct injection pulse width and the desired air-fuel ratio. The control unit can then generate a control signal that is sent to the intake throttle or the VCT mechanism (or the intake camshaft).

[0048] If neither the PFI-only nor the DI-only mode is selected, the routine at 310 includes confirming that fuel delivery via both DI and PFI (also referred to here as PFDI mode) has been requested. If it is determined that fuel delivery via both direct injection and port injection has been selected, the controller at 320 can activate both the port and direct injection devices. Furthermore, the controller can send a signal to actuators coupled to the direct injection device and the port injection device of each cylinder to deliver fuel based on the specified fuel delivery plan. Each injection device can provide a portion of the total fuel injection that is burned in the cylinder. As referred to in Fig. As described in section 5, a fuel split ratio between PFI and DI injection can be retrieved from a lookup table, and control signals can be sent to the injection devices to supply fuel according to the specified split ratio. Accordingly, the distribution and / or the relative quantity of fuel supplied by each injection device can vary based on operating conditions such as engine load, knock tendency, engine speed, exhaust gas temperature, etc. For example, the direct injection control unit can command a first pulse width corresponding to the first portion of the total fuel quantity to be supplied via direct injection. The control unit can also command a second pulse width to the port injection unit corresponding to the second, remaining portion of the total fuel quantity to be supplied via port injection.Direct injection control can be set with respect to the cylinder piston position based on whether injection during the intake and / or compression stroke has been selected, as well as based on the number of injections selected per injection cycle in the specified fuel delivery plan. Similarly, port injection control can be set with respect to the intake valve actuation based on whether injection with the intake valve closed or open has been selected.

[0049] In the 322, the procedure involves adjusting the airflow into the engine based on the total fuel injection quantity to control the air-fuel ratio. For example, the control unit can retrieve a desired air-fuel ratio and then, depending on the total amount of fuel supplied via the direct injection and port injection systems (e.g., based on the sum of the direct injection pulse width and the port injection pulse width), calculate a desired airflow that provides the desired air-fuel ratio. In one example, the desired air-fuel ratio is a stoichiometric air-fuel ratio. The desired airflow can be provided as a desired intake throttle position (e.g., throttle opening degree) or a desired cam position (e.g., desired VCT actuation).In one example, the control unit can determine the throttle position by a determination that directly considers the total fuel injection quantity and the desired air-fuel ratio, such as increasing the throttle opening as the total fuel injection quantity and the combustion air-fuel ratio increase. Alternatively, the control unit can determine the airflow based on a calculation using a lookup table, where the inputs are the commanded total fuel injection quantity and the desired air-fuel ratio, and the output is an intake throttle position that provides the desired air-fuel ratio. As another example, the control unit can make a logical determination (e.g.,The control unit determines the position of the intake throttle or intake camshaft based on logic rules that depend on the commanded total fuel injection quantity (or a sum of the direct and port injection pulse widths) and the desired air-fuel ratio. The control unit can then generate a control signal that is sent to the intake throttle or the VCT mechanism (or the intake camshafts).

[0050] From 314, the procedure proceeds to 324 during operation in PFI-only mode to determine whether a PFI system impairment is indicated. In one example, a PFI system impairment may be indicated as a response to a circuit failure of a single port fuel injector. In another example, a PFI system impairment may be indicated as a response to a loss of electrical power to the PFI system. If no PFI system impairment is indicated, the procedure at 336 involves continuing fuel delivery to the cylinder via port fuel injection according to the specified schedule and maintaining the airflow settings.

[0051] If a malfunction of the PFI system is detected, the procedure at 326 involves disabling the port fuel injectors while selectively activating the direct fuel injectors. The remaining amount of fuel that should have been supplied via port fuel injectors is then supplied via direct fuel injectors. For example, the control unit can command a direct fuel pulse width corresponding to the amount of fuel that should have been supplied via the malfunctioning direct fuel injector according to the originally determined fuel delivery schedule. The control unit's torque / airflow limiting logic can be informed that the PFI system has been disabled. If the direct fuel injectors cannot supply the entire fuel mass, the airflow can be limited to prevent engine damage.

[0052] At 328, the airflow is adjusted as needed based on the direct fuel injection quantity to maintain the air-fuel ratio. For example, the airflow settings can be maintained as they were originally determined based on the port fuel injection quantity, such as when the commanded direct fuel injection quantity matches the port fuel injection quantity that was originally commanded. This means that if the direct fuel injection is able to fully compensate for the lack of port fuel injection, the airflow settings can be maintained and there will be no deviation in the air-fuel ratio.In another example, airflow can be limited based on the direct fuel injection quantity, such as when the commanded direct fuel injection quantity is less than the corresponding port fuel injection quantity that was originally commanded. This means that if the direct fuel injection is unable to fully compensate for the lack of port fuel injection, the airflow can be limited to reduce the occurrence of deviation towards a lean air-fuel ratio. Limiting the airflow can involve reducing the opening of an intake throttle or adjusting a VCT (Variable Control Valve) actuator to vary the intake camshaft timing, thereby reducing the intake airflow. For example, in response to the commanded direct fuel injection quantity, the control unit can send a signal to the intake throttle actuator to move the throttle to a less open position.

[0053] In one example, the control unit can determine the updated throttle position corresponding to the limited airflow by a determination that directly considers the direct fuel injection quantity, such as increasing the throttle opening to a position as the direct fuel injection quantity increases. Alternatively, the control unit can decrease the throttle opening from an initial opening based on a difference between the commanded direct fuel injection quantity and the initially determined port fuel injection quantity, further reducing the throttle opening as the difference increases. The control unit can alternatively update the airflow based on a calculation using a lookup table, where the inputs are the commanded direct fuel injection quantity and the output is an intake throttle position that provides the desired air-fuel ratio. As another example, the control unit can make a logical determination (e.g.,The control unit can determine the position of the intake throttle or intake camshaft based on logic rules that depend on the commanded direct fuel injection quantity and the desired air-fuel ratio. The control unit can then generate a control signal that is sent to the intake throttle or the VCT mechanism (or the intake camshafts).

[0054] If the direct injection (DI) fuel delivery plan were not adjusted to compensate for the loss of port fuel injection, the engine would produce zero torque due to a malfunction in the port fuel system. In response to the zero torque, the airflow would be immediately stopped by the control unit. For example, the throttle would be closed. If, for example, the DI fuel delivery plan were not updated, the engine would still produce torque, but the combustion would be very lean. This lean combustion could very quickly lead to engine damage. If the lack of port fuel injection (PFI) were so severe that the engine produced no torque, the throttle would be opened, as the torque strategy attempts to match the desired torque to the actual torque the engine is producing.

[0055] Referring again to 322, the procedure proceeds to 330 during operation in PFDI mode, with fuel supplied via each of the port and direct injection systems, to determine whether there is a reported impairment of the PFI system. In one example, impairment of the PFI system may be reported as a response to a circuit failure of a single port injection device. In another example, impairment of the PFI system may be reported as a response to a loss of electrical power to the PFI system. If no impairment of the PFI system is reported, the procedure proceeds to 336 to continue port and direct fuel supply to the cylinder according to the specified plan and to maintain the airflow settings.

[0056] If a PFI system impairment is detected, the procedure at 332 involves disabling the port fuel injectors while updating the direct injection fuel schedule to immediately compensate for the PFI impairment. The remaining amount of fuel that should have been supplied via port fuel injection is then supplied via direct injection. For example, the control unit may send a signal to extend the direct injection pulse width by an amount equal to the amount of fuel that, according to the originally determined fuel delivery schedule, still needs to be supplied via the impaired port fuel injector. Alternatively, the direct injection schedule may be updated to meet the driver's torque demand following the port fuel injector impairment as closely as possible.It is understood that the updated direct injection (DI) fuel plan may not be able to fully compensate for the port fuel injection (PFI) shortfall due to the difference in direct fuel delivery relative to port fuel delivery (PFI) delivery within a fuel delivery cycle. For example, if the DI injectors are only designed to provide 70% of the required fuel mass when the engine is running at high engine speed and load, then the DI injectors will not be able to deliver sufficient fuel. Therefore, the air mass must be rapidly limited to prevent engine damage. Additionally, the PFI injector is designed to inject for a total of 720 degrees (with the intake valve open and closed), but the DI injector can only begin injecting once the intake valve opens and is then limited by the ignition timing.This means the operating window for DI injection is much smaller than the operating window for PFI injection.

[0057] At 334, the procedure involves adjusting, specifically limiting, the intake airflow based on the updated direct fuel injection schedule and independent of the originally determined port fuel injection schedule, to reduce the likelihood of deviation towards a lean air-fuel ratio. For example, the airflow can be limited based on the updated direct fuel injection quantity. This means that since direct fuel injection is not able to fully compensate for the lack of port fuel injection, the airflow is limited to reduce the occurrence of deviation towards a lean air-fuel ratio. Limiting the airflow may involve reducing the opening of an intake throttle or adjusting a VCT (Variable Control Valve) actuator to vary the intake camshaft timing, thereby reducing the intake airflow.For example, in response to the updated direct fuel injection quantity, the control unit can send a signal to the intake throttle actuator to move the throttle to a less open position.

[0058] In one example, the control unit can determine the updated throttle position corresponding to the restricted airflow by a setting that directly accounts for the direct fuel injection quantity, such as increasing the throttle opening to a certain position as the direct fuel injection quantity increases. Alternatively, the control unit can decrease the throttle opening from an initial opening based on a difference between the commanded direct fuel injection quantity and the originally commanded total fuel injection quantity, further reducing the throttle opening as the difference increases. The control unit can also, alternatively, update the airflow based on a calculation using a lookup table, where the inputs are the commanded direct fuel injection quantity (rather than the originally commanded port fuel injection quantity) and the output is an intake throttle position that provides the desired air-fuel ratio.As another example, the control unit can make a logical determination (e.g., regarding the position of the intake throttle or intake camshaft) based on logic rules that depend on the updated commanded direct fuel injection quantity and the desired air-fuel ratio. The control unit can then generate a control signal that is sent to the intake throttle or the VCT mechanism (or the intake camshaft). It is understood that the control unit ignores the originally commanded port fuel injection quantity in response to the indication of a port fuel system malfunction.

[0059] For example, in both the 328 and 334 engines, the control unit can adjust one or more engine operating parameters based on a torque deficit between the actual engine torque at the reduced intake throttle opening (or limited airflow) and the commanded torque. An example of this could involve lowering an alternator setpoint, disabling the vehicle's air conditioning, and advancing the ignition timing towards the MBT (to provide less spark reserve).

[0060] Unlike the PFI-only mode, where loss of port fuel injection results in zero torque, loss of port fuel injection in PFDI mode does not result in zero torque, and therefore the control unit would not close the throttle. If the control system were to compensate for the reduced torque by increasing the throttle position (to increase airflow and therefore torque), the result would be a deviation towards a lean air-fuel ratio without a significant increase in torque. In this example, increasing the direct fuel injection quantity in response to the port fuel injection impairment signal reduces torque errors. By then limiting the intake airflow based on the direct injection quantity, and regardless of the originally commanded port fuel injection quantity, a lean combustion is avoided.According to this, prolonged lean combustion could impair engine performance and possibly lead to engine damage.

[0061] An example of a fuel and airflow setting is shown in Fig. Figure 4 shows a characteristic map 400, representing an engine speed profile at curve 402, a fuel supply to a cylinder via port injection at curve 404, a fuel supply to the same cylinder via direct injection at curve 406, an intake throttle position at curve 408, and an air-fuel ratio (AFR) in relation to stoichiometry at curve 410.

[0062] In the illustrated example, based on engine operating conditions (e.g., low engine speed / load range), the engine cylinder before t1 can only receive fuel via port fuel injection, while direct fuel injection is selectively deactivated (graphs 402, 404). This means the cylinder operates in port fuel injection only mode. The throttle opening is adjusted depending on the port fuel injection quantity (graph 408) to operate the cylinder with an air-fuel ratio (graph 410) at or around stoichiometry (dashed horizontal line).

[0063] At t1, there is an increase in driver demand, and in response, the engine moves into a higher RPM / load range where the probability of knocking is higher. In this RPM / load range, the engine receives fuel only via direct injection. Thus, between t1 and t2, the engine cylinder can only receive fuel via direct injection, while port fuel injection is selectively deactivated (graphs 402, 404). This means the cylinder operates in direct injection-only mode. The throttle opening is adjusted depending on the direct fuel injection quantity (graph 408) to maintain an air-fuel ratio at or near stoichiometric for the cylinder.

[0064] At t2, there is a decrease in driver demand, and in response, the engine moves into a mid-range engine speed / load range. In this speed / load range, fuel is supplied to the engine via both port and direct fuel injection, with a port-to-direct fuel split ratio determined based on engine speed and load. This means the cylinder operates in a PFDI (Port Fuel Injection Direct Injection) mode. In this example, the cylinder receives fuel at a split ratio that has a higher port-to-direct fuel split, with the ratio varying as engine speed / load and driver torque demand change.The throttle opening is adjusted depending on the total fuel injection quantity (sum of the fuel injected into the intake manifold and directly) in order to operate the cylinder with a combustion air-fuel ratio at or around stoichiometry.

[0065] At t3, during operation with either port or direct injection fuel, it can be determined that the PFI fuel system is malfunctioning. This malfunction may be due to a problem with the circuitry or electrical power supply of the port injection unit, for example. As a result of the malfunction, there is an immediate drop in the amount of fuel delivered to the cylinder via port injection (curve 404, solid line), even though the commanded amount is greater (curve 405, dashed line). To compensate for the lack of port injection fuel and meet the driver's torque demand, at t3 the amount of direct injection fuel (curve 406, solid line) is increased relative to the originally commanded amount (curve 407, dashed line).In the illustrated example, however, the increase in direct injection fuel quantity is less than the loss in port injection fuel quantity. This means that the updated direct injection pulse width is unable to compensate for the loss of port fuel injection. If the throttle opening were maintained according to the original fuel schedule (dashed curve 409), the cylinder would run leaner than intended, as indicated by the deviation towards a lean air-fuel ratio in dashed curve 411. Prolonged lean combustion could impair engine performance and reduce engine life.

[0066] To address this problem, in response to the indication of impairment to the intake manifold fuel system at t3, the intake airflow is limited. Specifically, the throttle opening is reduced to limit the airflow based solely on the updated amount of directly injected fuel (curve 406), rather than on the originally commanded amount of fuel injected into the intake manifold (curve 405). By limiting the airflow based only on the updated amount of directly injected fuel, the air-fuel ratio is maintained at or around the desired air-fuel ratio (in this case, stoichiometry).

[0067] At t4, a command to shut down the engine is received. In response to the shutdown request, the fuel supply to the cylinder is deactivated and the engine begins to coast to idle. Additionally, the throttle opening is reduced to a fully closed position.

[0068] At t5, a command to restart the engine is received. In response to the restart request, fuel supply to the cylinder is reactivated. Under the low engine speed / load conditions of the restart, only port fuel injection is desired, as indicated by the dashed line 405, and no direct injection is desired. However, due to the impairment of the PFI system (indicated at t3), it is not possible to supply fuel via port injection. Therefore, at t5, fuel is supplied only via direct injection. The direct injection pulse width and fuel quantity are adjusted to compensate for the total desired port fuel injection quantity.

[0069] This means that the direct injection pulse width is able to fully compensate for the loss of the intake manifold fuel injection and meet the torque requirements of the driver when restarting.

[0070] The throttle opening is adjusted depending on the amount of fuel injected directly (which in this case is the same as the originally intended amount of intake manifold injection fuel) in order to operate the cylinder with an air-fuel ratio at or around stoichiometry.

[0071] In T6 mode, there is an increase in driver demand, and in response, the engine operates in a higher RPM / load range where the probability of knocking is higher. In this RPM / load range, fuel is supplied to the engine exclusively via direct injection. Therefore, according to T6, the engine cylinder can only receive fuel via direct injection. The throttle opening is adjusted depending on the direct fuel injection quantity to maintain an air-fuel ratio at or near stoichiometric in the cylinder.

[0072] This prevents deviations to a lean air-fuel ratio in a PFDI engine system caused by the sudden impairment of a PFI system component. By adjusting the amount of directly injected fuel in response to the impairment of the port fuel injection system, engine torque can still be generated. By limiting the intake airflow based solely on the directly injected fuel, while ignoring the commanded port fuel injection, engine damage due to prolonged lean operation is reduced.

[0073] An exemplary method for an engine comprises: limiting an intake air flow in response to a report of impairment of a port fuel injection device received during fuel delivery to a cylinder via any port or direct injection device. In the preceding example, the method further comprises, or optionally, increasing the amount of fuel supplied via the direct injection device in response to the report. In any or all of the preceding examples, limiting the intake air flow further comprises, or optionally, reducing an intake throttle opening. In any or all of the preceding examples, limiting is further comprised, or optionally, solely based on the amount of fuel supplied to the cylinder via the direct injection device.In any or all of the preceding examples, limiting is additionally or optionally independent of the amount of fuel supplied to the cylinder via the port fuel injection system. In any or all of the preceding examples, limiting the intake air flow additionally or optionally includes setting a variable cam timing. In any or all of the preceding examples, limiting is additionally or optionally set to maintain a combustion air-fuel ratio prior to the specification. In any or all of the preceding examples, specifying the impairment of the port fuel injection system additionally or optionally includes specifying the impairment of a circuit coupled to the port fuel injection system.In any or all of the preceding examples, the specification of the impairment of the intake manifold injection device additionally or optionally includes a specification of a loss of electrical power to the intake manifold injection device. In any or all of the preceding examples, the method additionally or optionally further includes adjusting one or more engine operating parameters based on a torque deficit between the actual torque at the restricted airflow and the commanded torque.

[0074] Another exemplary procedure for an engine comprises: supplying fuel to a cylinder via each of a port and a direct injection device during operation at an air-fuel ratio; and, in response to loss of electrical power to the port injection device, continuing to supply fuel to the cylinder via the direct injection device while reducing an intake throttle opening to maintain the air-fuel ratio.

[0075] Another exemplary procedure for an engine comprises: in response to a notification of impairment of a port fuel injection device, which during the supply of fuel to a cylinder is received only via a port fuel injection device, supplying fuel to the cylinder only via a direct injection device and limiting an intake air flow.

[0076] Another exemplary procedure for an engine comprises: supplying fuel to a cylinder via each of a port and a direct injection device while operating at an air-fuel ratio; and, in response to a loss of electrical power to the port injection device, continuing to supply fuel to the cylinder via the direct injection device while maintaining the air-fuel ratio. In the preceding example, maintaining the air-fuel ratio additionally or optionally includes reducing an intake throttle opening to maintain the air-fuel ratio.In any or all of the preceding examples, the method additionally or optionally comprises, in response to a loss of electrical power to the port fuel injector during fuel delivery to the cylinder via the port fuel injector only, increasing the fuel delivery to the cylinder via the direct fuel injector while reducing the intake throttle opening to maintain the air-fuel ratio that existed before the loss of electrical power. In any or all of the preceding examples, the intake throttle opening is additionally or optionally reduced based on only one quantity of fuel being supplied to the cylinder via the direct fuel injector.In any or all of the preceding examples, the method additionally or optionally includes adjusting one or more engine operating parameters based on a torque deficit between the actual engine torque at the reduced intake throttle opening and the commanded torque. In any or all of the preceding examples, the adjustment additionally or optionally includes shedding one or more electrical loads (including lowering an alternator setpoint and disabling the air conditioning) and advancing the ignition timing to or towards the MBT (to operate the engine with less spark reserve).

[0077] Another exemplary engine system comprises: an engine cylinder; a port fuel injection device; a direct fuel injection device; an intake throttle; a controller with computer-readable instructions stored in non-volatile memory to: in response to a port fuel injection device impairment signal received while fuel is being supplied to the cylinder via the port fuel injection device only, switch to supplying fuel to the cylinder via the direct fuel injection device only; and limit an intake airflow. In the preceding example, limiting additionally or optionally involves reducing the opening of the intake throttle when a pulse width commanded to the direct fuel injection device increases. In any or all of the preceding examples, limiting is additionally or optionally set to maintain the cylinder's air-fuel ratio from that prior to the switchover.In any or all of the preceding examples, the indication of impairment of the intake manifold injection device additionally or optionally includes impairment of an electrical circuit coupled to the intake manifold injection device and loss of electrical power to the intake manifold injection device.

[0078] It should be noted that the exemplary control and estimation routines included herein can be used with various engine and / or vehicle system designs. The control methods and routines disclosed herein can be stored as executable instructions in non-volatile memory and executed by the control system, including the controller, 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 actions, operations, and / or functions can be performed in the illustrated sequence or in parallel, or in some cases, omitted.Similarly, the processing sequence is not strictly necessary to achieve the features and advantages of the exemplary embodiments described here, but is provided to facilitate illustration and description. One or more of the illustrated actions, processes, and / or functions can be performed repeatedly, depending on the specific strategy employed. Furthermore, the described actions, processes, and / or functions can graphically represent code to be programmed into non-volatile memory of the computer-readable storage medium in the engine control system, with the described actions being executed by carrying out the instructions in a system that includes the various engine hardware components in combination with the electronic control unit.

[0079] It is understood that the interpretations and routines disclosed herein are exemplary in nature and that these specific embodiments are not to be interpreted in a limiting sense, as numerous variations are possible. For example, the foregoing technology can be applied to V6, I4, I6, V12, 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.

[0080] The following claims describe, in particular, certain combinations and subcombinations that are considered novel and not obvious. These claims may refer to "one" element, "a first" element, or the equivalent thereof. Such claims are to be understood as including one or more such elements and 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 amending the present claims or by filing new claims in this or a related application.Such patent claims, regardless of whether they have a broader, narrower, the same or different scope compared to the original patent claims, are also considered to be included in the subject matter of the present disclosure.

Claims

[1] Method for an engine (10), comprising: Determining engine operating conditions; Selecting a fuel injection schedule and fuel injection mode for the specific engine operating conditions; Adjusting the airflow into the engine (10) based on the total fuel injection quantity; in response to a report of impairment of a port fuel injection device (262) received during fuel supply to a cylinder (14) via each of a port fuel injection device (262) and a direct fuel injection device (252), limiting an intake air flow. [2] Method according to claim 1, further comprising, in response to the specification, increasing the amount of fuel supplied via the direct injection device (252). [3] Method according to claim 1, wherein limiting the intake airflow includes reducing an intake throttle opening. [4] Method according to claim 1, wherein the limitation is based only on a quantity of fuel supplied to the cylinder (14) via the direct injection device (252). [5] Method according to claim 1, wherein the limiting is independent of the amount of fuel supplied to the cylinder (14) via the intake manifold injection device (262). [6] Method according to claim 1, wherein limiting the intake air flow includes adjusting a variable cam control. [7] Method according to claim 1, wherein the limiting is adjusted to maintain a combustion air-fuel ratio of before the specification. [8] Method according to claim 1, wherein the specification of the impairment of the intake manifold injection device (262) includes a specification of an impairment of a circuit coupled to the intake manifold injection device (262). [9] Method according to claim 1, wherein the specification of the impairment of the intake manifold injection device (262) includes a specification of a loss of electrical power to the intake manifold injection device (262). [10] Method according to claim 1, further comprising adjusting one or more engine operating parameters based on a torque deficit between the actual torque at the limited intake air flow and the commanded torque. [11] Engine system, comprising: one engine cylinder (14); a port fuel injection device (262); a direct injection device (252); an intake throttle (162); a controller (12) with computer-readable instructions stored on non-volatile memory for the following: in response to a report of impairment of the intake manifold injection device (262), which is received only via the intake manifold injection device (262) during fuel supply to the cylinder (14), Transition to fuel supply to the cylinder (14) only via the direct injection device (252); and Limiting an intake airflow. [12] System according to claim 11, wherein limiting includes reducing the opening of the intake throttle (162) when a pulse width commanded to the direct injection device (252) increases. [13] System according to claim 11, wherein the limiting is adjusted to maintain an air-fuel ratio of the cylinder (14) from before the transition. [14] System according to claim 11, wherein the specification of the impairment of the intake manifold injection device (262) includes impairment of an electrical circuit coupled to the intake manifold injection device (262) and loss of electrical power to the intake manifold injection device (262).

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