Detecting faults within the normal range in fuel pressure sensors

Abstract

Method for operating a fuel system (8) of an internal combustion engine (10), comprising: during operation of a suction pump (208) in pulsed mode, adjusting a voltage level applied to the suction pump (208) based on an output signal of a pressure sensor (234) downstream of the suction pump (208), comprising: applying a first, higher voltage to the suction pump (208) when the output signal of the pressure sensor (234) decreases to a desired trough pressure, and applying a second, lower voltage to the suction pump (208) when the output signal of the pressure sensor (234) increases to a desired peak pressure, and monitoring the output signal for flattening; and in response to a detection of flattening, indicating a pressure sensor fault and operating the suction pump (208) independently of the output signal of the pressure sensor (234).

Description

AREA

[0001] The present description relates generally to methods for diagnosing an within-range failure of a pressure sensor located downstream of a fuel lift pump in an internal combustion engine and adjusting fuel system operation in response to the diagnosis. BACKGROUND ART / SUMMARY

[0002] Internal combustion engines may include a fuel system having a fuel system rail for distributing fuel to one or more fuel injectors, which may be direct injectors and / or port injectors. In a fuel system employing direct injectors, a fuel lift pump supplies fuel to a high pressure fuel pump, which in turn provides fuel at a high injection pressure to a fuel rail. The fuel rail is coupled to direct injectors that inject the fuel directly into combustion chambers of the internal combustion engine. In a fuel system using single nozzle per intake port fuel injection, a fuel lift pump delivers fuel at a lower injection pressure to a fuel rail. The fuel rail is coupled to the port injectors that inject the fuel into the engine intake upstream of intake ports of the combustion chambers. In a fuel system with fuel injection with one nozzle per intake port and direct injection, both injection with one nozzle per intake port and direct injection of fuel are performed.

[0003] Regardless of the type of fuel system, the fuel lift pump can be controlled to deliver fuel during what is referred to herein as continuous pump operation or operation in the continuous mode with a substantially constant delivery pressure by applying a voltage with a duty cycle of 100% and a voltage level that corresponds to the desired corresponds to a constant delivery pressure. As fuel flow demand changes, the voltage level can be adjusted to a different level and held constant or substantially constant (at 100% duty cycle) at the different voltage level, resulting in a different, substantially constant speed and delivery pressure of the Suction pump leads. In contrast, the fuel lift pump may also be controlled to output relatively high pressure intermittent pulses in what is referred to herein as pulsed pump operation or operation in a pulsed mode, wherein the duty cycle of the voltage applied to the lift pump is less than 100%. During pulsed pump operation, the level of voltage applied to the lift pump may alternate between a first, higher level and a second, lower level, with the second, lower level being very low (e.g., slightly above 0V). During the application of the first, higher voltage level to the lift pump, the speed of the lift pump is high and the discharge pressure of the lift pump is high, whereas during the application of the second, lower voltage level to the lift pump, the pump speed of the lift pump is very low (e.g. on a level slightly above zero, which may be desirable to maintain voltage supply to the lift pump rather than providing intermittent zero voltage) and the lift pump discharge pressure is very low. As a result, the lift pump discharge pressure over time during pulsed mode operation resembles a sawtooth wave, with the length of time between a valley of the wave and an adjacent peak of the wave following the valley being proportional to an application duration of voltage at the first, higher level and wherein the length of time between a peak of the wave and an adjacent trough of the wave subsequent to the peak is proportional to an application duration of voltage at the second, lower level.

[0004] In contrast to continuous pumping, pulsed pumping, in which the fuel lift pump is only energized during the duration of each pulse, is more energy efficient. Furthermore, when the pulse pump operation is performed instead of the continuous pump operation, the longevity of the fuel lift pump can be extended, and maintenance cost of the fuel lift pump can be reduced.

[0005] When the pulsed pump operation is performed, the engine controller can perform either open-loop or closed-loop control of the pump. When open-loop control is performed, voltage pulses having a predetermined pulse width (and thus a predetermined duty cycle) may be applied to the lift pump, and a measured or derived pressure downstream of the fuel lift pump (referred to herein as lift pump delivery pressure) has affected the regulation does not. In contrast, when closed loop control is performed, the head pressure is fed back to the controller and affects the duration of subsequent high voltage pulses applied to the lift pump (as well as the duration of the intervals between the high voltage pulses when a voltage slightly above 0V is applied) . In examples where the delivery pressure is measured by a pressure sensor that provides feedback to the controller, degradation of the pressure sensor may offset the reading of the pressure sensor, thereby causing the delivery pressure to vary from a desired or expected pressure, in turn affecting engine operation can affect. For example, failures within the expected normal range of sensor output (referred to as in-range failures) are much more difficult to detect than failures outside of the expected normal range of sensor output (referred to as out-of-range failures). Detection of within-range faults is particularly critical when the sensor is providing closed-loop feedback to control pulsed pump operation, since the fault will result in misadjustment of the voltage pulses applied to the lift pump.

[0006] One approach to addressing the detection of within-range faults in fuel pressure sensors is provided by Stavnheim et al. in US 6,526,948 B1, which deals with diagnosing fuel pressure sensors that are "stuck" within the normal range. Therein, a controller samples a fuel pressure sensor signal multiple times that includes pressure peaks and valleys. The controller then calculates an average pressure value and compares the measured values ​​with the average. If a reading falls within a threshold of the average value, this indicates that the pressure sensor is stuck within normal range (that is, not dynamically responding to changes in fuel pressure) and the controller will log a trouble code. Upon a certain number of logged errors, the controller initiates a minimum fueling algorithm that supplies just enough fuel to allow the vehicle to be driven out of a danger zone or to a service center.

[0007] However, the inventors of the present invention have recognized potential problems with this approach. For example, the method described above is limited to detecting a degraded pressure sensor that is not responding to pressure fluctuations. However, a degraded pressure sensor can measure higher or lower than actual pressure, but still respond to pressure fluctuations. Furthermore, by providing just enough fuel to drive the vehicle out of the danger zone or to a service center after detecting pressure sensor degradation, desired vehicle operation may not be available when the pressure sensor is degraded, negatively impacting driver satisfaction may have.

[0008] To address these issues, the inventors of the present invention have discovered methods and systems for diagnosing within-range pressure sensor failures and adjusting fuel system operation based on the diagnosis. In one example, the problems described above may be addressed by a method of operating a fuel system of an internal combustion engine, comprising: during operation of a lift pump in pulsed mode, adjusting a voltage level applied to the lift pump based on an output signal of a pressure sensor downstream of the lift pump and monitoring the output signal for flattening; and in response to a detection of flattening, indicating a pressure sensor failure and operating the lift pump independent of the output of the pressure sensor. In this way, faults that occur within the normal operating range of a pressure sensor located downstream of a fuel lift pump can be detected and control of the fuel lift pump can be switched from closed-loop to open-loop control upon detection of such faults. While open-loop control of the lift pump may be less fuel efficient than closed-loop control of the lift pump, this may not have a significant impact on drivability.

[0009] The method may further include dynamically determining a desired pressure of a pressure relief valve and a fuel vapor pressure of the fuel system to ensure accuracy of control of the lift pump as well as diagnosis of within-range pressure sensor errors. This may include: during steady-state engine operation with a requested delivery pressure of a fuel lift pump being below a first threshold, reducing a duty cycle of voltage pulses applied to a fuel lift pump until flattening of an output signal of a pressure sensor downstream of the lift pump is detected, and storing the pressure at which the output signal flattened out as the fuel system vapor pressure; during steady state operation of the internal combustion engine with a requested delivery pressure of the fuel lift pump being above a second threshold, increasing a duty cycle of voltage pulses applied to the lift pump until flattening of the output signal of the pressure sensor is detected, storing the pressure at which the output signal flattens out has, as a target pressure of a pressure relief valve; and adjusting lift pump operation based on the stored desired pressure and fuel vapor pressure. Dynamically determining the expected maximum and minimum physical values ​​of the fuel system in this manner can improve the overall accuracy of the fuel lift pump control and, in turn, improve the accuracy of diagnosing pressure sensor failures.

[0010] In yet another example consistent with the present disclosure, the lift pump may be controlled with a robust closed-loop control strategy. This may include: during pulsed operation of a lift pump, turning the lift pump OFF when a sensed head pressure increases to a desired peak pressure or a lift pump ON time reaches a calibrated maximum, and turning the lift pump ON when either the sensed head pressure reaches a desired valley pressure decreases or a volume of fuel taken in by the internal combustion engine reaches a predetermined volume. Such operation may advantageously reduce the possibility of the lift pump being "stuck" at a pressure below the target pressure when the lift pump is ON because the sensor is reading too low, or at a pressure above the target pressure when the lift pump is OFF , because the sensor measures values ​​that are too high. Optionally, the robust control strategy may also include: calibrating a sensor output upon detecting that the lift pump ON-time has reached a calibrated maximum or that the volume of fuel ingested by the engine has reached a predetermined volume, allowing accurate control of the lift pump can be performed even if the sensor is compromised.

[0011] It should be understood that the summary above 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 key or essential features of the claimed subject matter, the scope of which is defined uniquely in the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. character list figure 1 schematically shows an exemplary embodiment of a cylinder in an internal combustion engine of a vehicle. figure 2 schematically shows an exemplary embodiment of a fuel system used in the internal combustion engine of FIG figure 1 can be used. figure 3A- figure 3E show curves illustrating the sensed delivery pressure of a fuel lift pump as a function of time during pulsed pump operation of the fuel lift pump. figure 4 is a flow chart illustrating a routine for diagnosing an within-range failure of a pressure sensor downstream of a fuel lift pump and controlling operation of the fuel lift pump in response to the diagnosis. figure 5A shows a flow chart illustrating a routine for closed loop control of a fuel lift pump. figure 5B is a flow chart illustrating a routine for closed loop control of a fuel lift pump in accordance with a first example feedback control strategy used in connection with the routine of FIG figure 5A can be performed. figure 5C is a flow chart illustrating a routine for closed loop control of a fuel lift pump in accordance with a second example feedback control strategy used in conjunction with the routine of FIG figure 5A can be performed. figure 6 is a flowchart illustrating a routine for adjusting operation of a fuel system with a controller for determining a desired pressure relief valve pressure and fuel vapor pressure of the fuel system. figure 7 is a flowchart illustrating a routine for diagnosing an within-range failure of the output of a pressure sensor downstream of a fuel lift pump. figure8 shows a map of exemplary waveforms of relevant signals during adjustment of operation of a fuel system with a controller for determining a desired pressure of a pressure relief valve and fuel vapor pressure of the fuel system in accordance with the routine figure 6. figure 9 is a map showing example waveforms of relevant signals when an within-normal-range error is detected in the output of a pressure sensor downstream of a fuel lift pump in accordance with the routine figure 7 is diagnosed, the fault resulting in a flattening of the valleys in the pressure sensor output signal. figure 10 is a map showing example waveforms of relevant signals when an within-range error is detected in the output of a pressure sensor downstream of a fuel lift pump in accordance with the routine figure 7 is diagnosed, the fault resulting in a flattening of the peaks in the pressure sensor output signal. figure 11 is a flow chart illustrating a routine for robust closed loop control of a fuel lift pump. figure 12A- figure 12D show maps of example waveforms of relevant signals during robust closed-loop control of a fuel lift pump without calibration of the sensor output ( figure 12A and figure 12C) and with sensor output calibration ( figure 12B and figure 12D). In figure 12A- figure 12B the sensor measures values ​​that are too low, whereas the sensor in figure 12C- figure 12D measures values ​​that are too high. DETAILED DESCRIPTION

[0012] The following description relates to systems and methods for controlling a fuel lift pump in a fuel system of an internal combustion engine, such as that in figure 1 and diagnosing an within-range failure of a pressure sensor located downstream of the fuel lift pump and adjusting operation of the fuel system in response to the diagnosis. As in figure 2, the fuel system may include port fuel injectors as well as direct fuel injectors and associated fuel rails. However, the methods and systems described herein are also applicable to fuel systems that include port injectors and do not include direct injectors, and to fuel systems that include direct injectors and do not include port injectors, as well as to fuel systems that include other types of fuel injectors that pressurize fuel from a fuel lift pump record, tape. The suction pump can be operated in a pulsed mode with closed-loop feedback control (e.g. in accordance with the in figure 5A- figure 5A-5C) may be operated by applying voltage pulses to the lift pump until a desired fuel pressure is reached as measured by a pressure sensor downstream of the lift pump. Furthermore, a target pressure of a pressure relief valve of the fuel system and a fuel vapor pressure within the fuel system can be dynamically determined at a controller of the internal combustion engine by monitoring the sensed pressure downstream of the lift pump while in accordance with the in figure 6 and the routine shown in figure 8, the voltage applied to the lift pump is adjusted (e.g., the duty cycle of voltage pulses applied to the lift pump is adjusted). During the application of voltage pulses to the lift pump, the output of the pressure sensor downstream of the lift pump may have a sawtooth waveform, an example of which is shown in FIG figure 3A. During an within-normal error of the pressure sensor, the sawtooth waveform may flatten out at its peaks or valleys, depending on the nature of the within-normal error, as shown in FIG figure 3B- figure 3C. As in figure4, the controller may perform a routine in which the output of the pressure sensor downstream of the lift pump is monitored for flattening during pulsed pump operation with closed-loop control (e.g., in accordance with the figure 7 routine). In response to a flattening detection, in accordance with the figure 9 and figure The maps shown in Figure 10 indicate within normal range error of the pressure sensor and control the pump from closed loop operation (where the pressure sensor feedback is included in the control of the lift pump) to open loop pump operation (where the pressure sensor feedback is not included in the control the suction pump is involved) can be switched over. Alternatively, the lift pump may be operated in accordance with the robust closed-loop control strategy outlined in the routine figure 11 is shown. This strategy may include turning the lift pump OFF if it has been ON for a calibrated maximum ON time even if the pressure sensor output has not yet reached a desired peak pressure, and turning the lift pump ON when a volume of fuel is ingested has been reached a predetermined volume since the lift pump was turned OFF, even if the pressure sensor output has not yet reached a desired valley pressure, as in figure 12A- figure 12D. Optionally, as in figure 12B and figure 12D, the pressure sensor output can be calibrated when it is determined that the sensor is reading too high or too low, and the calibrated pressure sensor output can replace the pressure sensor output in the lift pump feedback control.

[0013] With respect to the terminology used in this detailed description, fuel injection with one nozzle per intake port may be abbreviated as PFI (Port Fuel Injection), while direct injection may be abbreviated as DI (Direct Injection). A high-pressure pump can be abbreviated as an HP pump (High Pressure Pump; alternatively HPP) or as a DI fuel pump. Likewise, a lift pump or fuel lift pump may also be referred to as a low pressure pump (abbreviated as LP pump or LPP; Low Pressure Pump). Also, fuel rail pressure, or the value of the pressure of fuel within a fuel rail, may be abbreviated as FRP (Fuel Rail Pressure). The direct injection fuel rail may also be referred to as a high pressure fuel rail, which may be abbreviated as an HP fuel rail. For brevity, the set pressure of the pressure relief valve is referred to herein as set pressure.

[0014] figure 1 shows an example of a combustion chamber or cylinder of the internal combustion engine 10 who is in a motor vehicle 5 can be included. The combustion engine 10 can be at least partly controlled by a control system that controls 12 includes, and by input from a vehicle operator 130 via an input device 132 to be controlled. In this example, the input device includes 132 an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. The cylinder 14 (here also as combustion chamber 14 called) of the internal combustion engine 10 can the combustion chamber walls 136 include where the piston 138 is positioned. The piston 138 can on the crankshaft 140 be coupled so that an alternating movement of the piston is translated into a rotational movement of the crankshaft. The crankshaft 140 can be coupled to at least one drive wheel of the passenger vehicle via a transmission system (not shown). Furthermore, a starter (not shown) can be connected to the crankshaft via a flywheel (not shown). 140 be coupled to a starting process of the internal combustion engine 10 to allow.

[0015] The cylinder 14 can be via a series of intake air ducts 142 , 144 and 146 absorb intake air. The intake air ducts 142 , 144 and 146can in addition to the cylinder 14 with other cylinders of the internal combustion engine 10 stay in contact. In some examples, one or more of the intake passages may include a charging device, such as a turbocharger or a supercharger. For example shows figure 1 the internal combustion engine 10 designed with a turbocharger that has a supercharger 174 , between the intake air ducts 142 and 144 is arranged, and an exhaust gas turbine 176 running along an exhaust duct 158 is arranged includes. The Compressor 174 can at least partially over a wave 180 through the exhaust gas turbine 176 be powered when the supercharging device is configured as a turbocharger. In other examples, such as when the internal combustion engine 10 is provided with a compressor, the exhaust gas turbine 176 however, optionally be omitted, with the compressor 174 can be powered by mechanical inputs from an electric motor or the internal combustion engine. A thrush 162 that have a throttle 164 may be provided along an intake passage of the internal combustion engine to vary the flow rate and / or pressure of intake air provided to the cylinders of the internal combustion engine. For example, the choke 162 the compressor 174 be positioned downstream, as in figure 1, or alternatively it may be the compressor 174 be provided upstream.

[0016] The exhaust manifold 148 can in addition to the cylinder 14 Exhaust gases from other cylinders of the internal combustion engine 10 record, tape. It is shown that the exhaust gas sensor 128 upstream of the emissions control device 178 to the exhaust duct 158 is coupled. the sensor 128 may 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; broadband or wide range lambda sensor), a two-state lambda sensor or EGO sensor ( as shown), a HEGO sensor (heated EGO sensor), a NOx, HC or CO sensor. At the emission control device 178 it may be a three-way catalyst (TWC), a NOx trap, various other emission control devices, or combinations thereof.

[0017] Each cylinder of the internal combustion engine 10 may include one or more intake valves and one or more exhaust valves. For example, the cylinder 14 as at least one inlet poppet valve 150 and at least one exhaust poppet valve 156 inclusive shown located in an upper portion of the cylinder 14 condition. In some examples, each cylinder of the internal combustion engine 10 holding the cylinder 14 includes at least two intake poppet valves and at least two exhaust poppet valves located in an upper portion of the cylinder.

[0018] The inlet valve 150 can via an actor 152 through the controller 12 to be controlled. Likewise, the exhaust valve 156 about the actor 154 through the controller 12 to be controlled. Under some conditions, the controller 12 those of the actors 152 and 154 The signals provided vary to control the opening and closing of the respective intake and exhaust valves. The position of the intake valve 150 and the exhaust valve 156can be determined by appropriate valve position sensors (not shown). The valve actuators may be of the electric valve actuation type, or of the cam actuation type, or a combination thereof. Intake and exhaust valve timing may be controlled simultaneously, or any of variable intake cam timing, variable exhaust cam timing, dual independent variable cam timing, or fixed cam timing may be used. Each cam actuation system may include one or more cams and one or more of cam profile switching (CPS), variable cam timing (VCT), variable valve timing (VVT), and / or variable valve lift ( Variable Valve Lift - WL) by the controller 12 can be operated to vary valve operation. For example, the cylinder 14 alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and / or VCT. In other examples, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system.

[0019] The cylinder 14 may have a compression ratio, which is the volume ratio between the pistons 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 other fuels are used, the compression ratio may be increased. This can occur, for example, when fuels with a higher octane number or fuels with a higher latent enthalpy of vaporization are used. The compression ratio may also be increased when using direct injection due to its effect on engine knock.

[0020] In some examples, each cylinder of the internal combustion engine 10 a spark plug 192 contain to initiate combustion. The ignition system 190 can of combustion chamber 14 via the spark plug 192 an ignition spark in response to a spark advance signal SA from the controller 12 provide under selected operating modes. In some embodiments, the spark plug 192 however accounted for, such as when the internal combustion engine 10 combustion can initiate by auto-ignition or by fuel injection, which can occur in some diesel engines.

[0021] In some examples, each cylinder of the internal combustion engine 10 be configured with one or more fuel injectors to provide fuel thereto. As a non-limiting example, the cylinder includes 14 shown two fuel injectors 166 and 170 . The fuel injectors 166 and 170 can be designed from the fuel system 8 deliver fuel consumed. As below with reference to figure 2 running, the fuel system can 8 include one or more fuel tanks, fuel pumps and fuel rails.

[0022] Shown is the fuel injector 166 directly to the cylinder 14 coupled to fuel proportional to the pulse width of the signal FPW- 1 that from the controller 12 via an electronic driver 168 is received to inject directly into it. In this way, the fuel injector 166 Direct injection of fuel into the combustion cylinder 14 ready. While the injector 166 the representation of figure 1 after on one side of the cylinder 14 is positioned, it may alternatively be located above the piston, such as near the position of the spark plug 192. Such a position can improve mixing and burning when operating the internal combustion engine with an alcohol-based fuel, since some alcohol-based fuels have lower volatility. Alternatively, the injector may be located above and near the intake valve to improve mixing. Fuel can fuel injector 166 from a fuel tank of the fuel system 8 are supplied via a lift pump and / or a high-pressure fuel pump and a fuel rail. Furthermore, the fuel tank can have a pressure converter, which the controller 12 provides a signal.

[0023] The fuel injector 170 is in one design, the injection of fuel with one nozzle per intake port in the intake port upstream of the cylinder 14 provides in the intake air duct 146 instead of in the cylinder 14 shown arranged. The fuel injector 170 can from the fuel system 8 consumed fuel proportional to the pulse width of the signal FPW- 2 that from the controller 12 via the electronic driver 171 is received, inject. It should be noted that a single electronic driver 168 or 171 can be used for both fuel injection systems or multiple drivers as shown, for example the electronic driver 168 for the fuel injector 166 and the electronic driver 171 for fuel injector 170 , can be used.

[0024] In an alternate example, each of the fuel injectors 166 and 170 as a direct fuel injector for injecting fuel directly into the cylinder 14 be designed. In yet another example, each of the fuel injectors 166 and 170 as port fuel injectors for injecting fuel to the intake valve 150 be configured upstream. In still other examples, the cylinder 14 include only a single fuel injector configured to receive different fuels in varying relative amounts as a fuel mixture from the fuel systems and further configured to inject that fuel mixture either as a direct in-cylinder fuel injector or as a port fuel injector upstream of the intake valves. Accordingly, it should be understood that the fuel systems described herein are not intended to be limited by the specific fuel injector configurations described herein by way of example.

[0025] Fuel may be delivered to the cylinder through both injectors during a single cycle of the cylinder. For example, each injector may provide a portion of a total fuel injection that is in the cylinder 14is burned. Further, the distribution and / or relative amount of fuel delivered by each injector may vary with operating conditions such as engine load, knock, and exhaust gas temperature, as described hereinafter. The fuel injected into the intake passage may be delivered during an open intake valve event, a closed intake valve event (eg, substantially prior to the intake stroke), as well as during both open and closed intake valve operation. Likewise, directly injected fuel may be delivered, for example, during an intake stroke as well as 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 may be injected at different times from port and direct injectors. Additionally, multiple injections of the fuel supplied may be performed per cycle in a single combustion event. The multiple injections may be performed during the compression stroke, intake stroke, or any suitable combination thereof.

[0026] As described above, shows figure 1 only one cylinder of a multi-cylinder engine. Thus, each cylinder may equally have its own set of intake / exhaust valves, fuel injectors, spark plug, etc. It is understood that the engine 10 any suitable number of cylinders, including 2, 3, 4, 5, 6, 8, 10, 12 or more cylinders. Furthermore, each of these cylinders may contain some or all of the various components listed in figure 1 with reference to the cylinder 14 are described and illustrated.

[0027] The fuel injectors 166 and 170 can have different properties. These include differences in size; for example, one injector may have a larger injection orifice than the other. Other differences include: different spray angles, different operating temperatures, different targets, different injection timings, different spray characteristics, different positions, etc. In addition, depending on the distribution ratio of the injected fuel between the injectors 170 and 166 different effects can be achieved.

[0028] The regulator 12 is in figure 1 shown as a microcomputer having a microprocessor unit 106 , input / output connectors 108 , an electronic storage medium for executable programs and calibration values, illustrated in this particular example for storing executable instructions as non-volatile read-only memory 110, random access memory 112 , a keep-alive memory 114 and includes a data bus. The regulator 12 can receive various signals from to the motor in addition to the signals previously discussed 10 paired sensors, including measurement of inducted mass air flow (MAF) from a mass air flow sensor 122 ; engine coolant temperature (ECT) from a temperature sensor 116 , attached to a cooling sleeve 118 is coupled; a Profile Ignition Pickup (PIP) signal from a Hall Effect sensor 120 (or some other kind) attached to the crankshaft 140 is coupled; throttle position (TP) from a throttle position sensor; and a manifold absolute pressure (MAP) signal from a sensor 124 . The MAP signal may be used to provide an indication of vacuum or pressure in the intake manifold. An engine speed signal, RPM, can be generated by the controller 12 can be generated from the signal PIP.

[0029] In some examples, the vehicle 5 be a hybrid vehicle with multiple sources of torque, the one or more vehicle wheels 55be available. In other examples, it may be the vehicle 5 be a conventional vehicle with only an internal combustion engine or an electric vehicle with only electrical machine(s). In the example shown, the vehicle includes 5 an internal combustion engine 10 and an electric machine 52 . With the electric machine 52 it can be an electric motor or an electric motor / generator. The crankshaft 140 of the combustion engine 10 and the electric machine 52 are about the gearbox 54 with the vehicle wheels 55 connected if one or more clutches 56 are engaged. In the example shown, there is a first clutch 56 between the crankshaft 140 and the electric machine 52 provided and a second clutch 56 between the electric machine 52 and the gearbox 54 provided. The control 12 can send a signal to an actuator of each clutch 56 send to engage or disengage the clutch to so the crankshaft 140 with or from the electrical machine 52 and to connect or disconnect the components connected thereto and / or around the electric machine 52 with or from the gearbox 54 and the associated components to connect or disconnect. At the gearbox 54 it can be a manual transmission, a planetary gear system or another type of transmission. The powertrain can be configured in a variety of ways, including as a parallel, series, or series-parallel hybrid vehicle.

[0030] The electric machine 52 takes electrical power from a traction battery 58 on to the vehicle wheels 55 provide torque. The electric machine 52 can also be operated as a generator, for example to generate electrical power to charge the battery during braking 58 to provide.

[0031] figure 2 schematically illustrates an exemplary embodiment of the fuel system 8 the end figure 1. The actuators of the fuel system 8 can by a controller, such as the controller 12 the end figure 1, operated to some or all of those referred to in figure 4- figure 7 to perform the operations described.

[0032] The fuel system 8 may be an internal combustion engine, such as the exemplary internal combustion engine 10 the end figure 1, fuel from a fuel tank 202 provide. In the illustrated embodiment, the fuel system is a PFDI fuel system and thus includes a first low pressure fuel rail 240 , the fuel to one or more port injectors 242 outputs, and a second high pressure fuel rail 250 , the fuel to one or more direct injectors 252 gives. In other examples, the fuel system 8 however, be a PFI or DI fuel system. For example, the fuel may contain one or more hydrocarbon components and also optionally contain an alcohol component. The fuel can go to the fuel tank 202 via a fuel filler port 204 to be provided.

[0033] A fuel lift pump (LPP) 208 in connection with the fuel tank 202 can be operated to get fuel from the fuel tank 202 a first fuel channel 230 to supply As shown, the first fuel passage 230 a first end coupled to the output of the lift pump and a second end coupled to the first fuel rail such that fuel pumped into the first fuel passage by the LPP is delivered to the first fuel rail 240 and hence the port injectors 242 can be supplied. In one example, the LPP 208 electrically powered and at least partially within the fuel tank 202be arranged. As shown, a check valve 209 downstream from an outlet of the LPP 208 be positioned. The check valve 209 can fuel flow from the LPP 208 to the first fuel channel 230 allow while allowing fuel flow in the opposite direction from the first fuel channel 230 back to the LPP 208 blocked. The pressure downstream of the check valve 209 can differ from the pressure downstream of the LPP 208 and upstream of the check valve 209 differentiate; References herein to pressure in the first fuel passage refer to pressure in the first fuel passage downstream of the check valve 209 .

[0034] A pressure relief valve 211 may be trapped in the fuel system to bleed off excess pressure. In the example shown is the pressure relief valve 211 in a canal 231 arranged having a first end connected to the first fuel passage 230 is coupled, and a second end that connects to the fuel tank 202 is coupled to allow fuel to flow from the first fuel passage in the event that the pressure of the fuel system exceeds a target pressure of the pressure relief valve 230 to the fuel tank 202 flows back. The pressure relief valve may be a passive valve that opens and closes in response to fluid pressure to which it is subjected; alternatively, the pressure relief valve may be an actively controlled valve, and the controller may send a signal to an actuator of the pressure relief valve to open or close the valve in response to a fluid pressure, such as fuel system delivery pressure. The target pressure is the pressure at which the pressure relief valve passively opens (or actively opens) to relieve pressure from the fuel system (e.g., by returning fuel to the fuel tank). The value of the target pressure may be fixed by the geometry of the pressure relief valve or may be varied by an actuator of the pressure relief valve in response to a signal from the controller.

[0035] Although shown that the first fuel rail 240 Fuel to four port injectors 242 emits, it is understood that the first fuel rail 240 Can deliver fuel to any suitable number of fuel injectors. As an example, the first fuel rail 240 fuel to one of the fuel injectors 242 for each cylinder of the internal combustion engine. In other examples, the first fuel channel 230 Fuel via two or more first fuel rails to the port injectors 242 submit. For example, if the cylinders of the internal combustion engine are laid out in a V-type configuration, the first fuel passage may lead to two first fuel rails, each of which may supply fuel to respective port injectors.

[0036] In the illustrated example, a second fuel passage branches off upstream of the first fuel rail 232 from the first fuel channel. A first end of the second fuel passage is coupled to the first fuel passage upstream of the first fuel rail, while a second end of the second fuel passage is coupled to the second fuel rail. A direct injection fuel pump (HPP) 228 , by the LPP 208 receiving fuel pumped from the fuel tank is in the second fuel gallery 232 arranged. In one example, the HPP 228 be a mechanically driven positive displacement pump. The HPP 228 can via the second fuel rail 250 with the direct fuel injectors 252 stay in contact. Through the LPP 208 in the first fuel channel 230 pumped fuel can flow through the HPP 228 from the first fuel channel 230 into the second fuel channel 232 be pumped and also by the HPP pump 228be pressurized before being sent for direct injection into the internal combustion engine via the direct fuel injectors 252 to the first fuel rail 250 flows. The second fuel rail 250 may be a high pressure fuel rail; for example, fuel in the second fuel rail 250 be stored at a higher pressure than the pressure in the first fuel rail 240 stored fuel because at the HPP 228 further pressurization of the fuel takes place.

[0037] The various components of the fuel system 8 associated with an internal combustion engine control system, such as the controller 12 , in connection. For example, the controller 12 from various sensors related to the fuel system 8 in addition to the sensors described above with reference to figure 1 receive signals indicative of operating conditions. The signals may include signals from one or more pressure sensors located in the fuel system, such as the pressure sensors 234 , 235 and 236 . The signals can also include a signal from a fuel level sensor 206 include, the one in the fuel 202 amount of fuel stored. The control 12 may also be provided by one or more fuel composition sensors in addition or as an alternative to an indication of a fuel composition based on a signal from an exhaust gas sensor (such as the sensor 128 the end figure 1) is derived, receive signals indicative of fuel composition. For example, an indication of the fuel composition in the fuel tank 202 stored fuel by the fuel composition sensor 210 to be provided. The fuel composition sensor 210 may further include a fuel temperature sensor. Additionally or alternatively, one or more fuel composition sensors may be provided at any suitable location along the fuel passages between the fuel storage tank and the fuel injectors.

[0038] in the in figure 2, the fuel system includes a pressure sensor 236 , which is connected to the second fuel rail 250 is coupled, and one or more of a pressure sensor 234 , connected to the first fuel channel 230 is coupled, and a pressure sensor 235 , which is connected to the first fuel rail 240 is coupled. The pressure sensor 234 can be used to determine a fuel line pressure of the first fuel passage 230 downstream of the suction pump and thus to determine the delivery pressure of the suction pump. The pressure sensor 235 can be used to determine the pressure level within the first fuel rail 240 to eat. The pressure sensor 236 can be used to determine the pressure level in the second fuel rail 250 to eat. The positions of the figure The pressure sensors shown in FIG. 2 are for example purposes only and are not limiting; Instead of or in addition to the pressure sensors shown, other pressure sensors can be used in the fuel system 8 be positioned to measure the pressure at different locations therein. The various recorded pressures can be sent as signals to the controller 12 be transmitted. In some examples, other types of sensors may be at different locations in the fuel system 8 be located and pressures within the fuel system can be inferred based on the output of these sensors.

[0039] As used herein, the term "delivery pressure" refers to the fuel pressure downstream of the lift pump, specifically downstream of the check valve 209 in the example fuel system figure 2 and upstream of any DI pump or other type of pump that may be included in the system. In an example where the fuel system includes a pressure sensor in the first fuel passage (e.g. the pressure sensor 234) and does not include a pressure sensor in the first fuel rail, the delivery pressure relates to the pressure measured in the first fuel passage. In an example where the fuel system includes a pressure sensor in the first fuel rail (e.g. the pressure sensor 235 ) but does not include a pressure sensor in the first fuel passage, the delivery pressure relates to the pressure in the first fuel rail. In an example where the fuel system includes a pressure sensor in both the first fuel passage and the first fuel rail, the fuel rail pressure may be related to only one of the pressure in the first fuel passage and the pressure in the first fuel rail.

[0040] The control 12 is designed to operate by each of the LPP 208 and HPP 228 to adjust an amount, pressure, flow rate, etc. of fuel supplied to the internal combustion engine. For example, the controller 12 vary a pressure setting, a pump stroke amount, a pump duty cycle command, and / or a fuel flow rate of the fuel pumps for delivering fuel to different locations of the fuel system. During both injection with one nozzle per intake port and direct injection, the LPP 208 through the controller 12 be controlled to the first fuel rail 240 and / or the HPP 228 deliver fuel based on pressure in one or more of the first fuel passage, the first fuel rail, and the second fuel rail. A driver electronically connected to the controller 12 coupled can be used to send a control signal to the LPP 208 to send to the output (e.g. speed and / or discharge pressure) of the LPP 208 set. During direct injection, the amount of fuel delivered to the direct fuel injectors via the HPP 228 is fed, adjusted by the output of the LPP 208 and HPP 228 set and coordinated.

[0041] The control 12 can the LPP 208 control it to operate in a continuous mode or a pulsed mode. Likewise, the controller 12 the HPP 228 control it to operate in a continuous mode or a pulsed mode. During the operation of the LPP 208 in the continuous mode, a constant, non-zero voltage is applied to the lift pump to the first fuel rail 240 To supply fuel with a constant fuel pressure. The operation of the HPP 228 in the continuous mode can be performed in a similar manner. On the other hand, during the operation of the LPP 208 in the pulsed mode, the LPP may be activated (i.e. turned ON) but be provided with zero voltage or a voltage slightly greater than zero voltage. Then the LPP 208 Pulses with higher voltage are supplied. During the application of each higher voltage pulse, the voltage supplied to the LPP is ramped from a lower positive voltage (e.g. 0V or substantially 0 V) is increased to a higher positive voltage (e.g. 8-12 V), held at the higher voltage for a duration (e.g. 30-300 ms) and then decreased from the higher voltage back to the lower voltage.

[0042] In accordance with a first example feedback control strategy, a duty cycle of the voltage pulses is fixed. The duty cycle of the voltage pulses determines the relative duration of the application of the lower voltage and the higher voltage to the lift pump (and hence the pulse width of the pulses). In such cases, a higher voltage to be supplied to the lift pump may be selected based on the fixed duty cycle (which dictates the duration of the higher voltage pulses). For example, the LPP 208be pulsed with 8V if the interval between the higher voltage pulses (during which the lower voltage is applied) is between 0 and 50 milliseconds. Alternatively, if the interval between the higher voltage pulses is between 50 and 100 milliseconds, the LPP 208 can be pulsed at 10V. In another example, the LPP 208 be pulsed with 12 V if the interval between the higher voltage pulses is between 100 and 250 milliseconds.

[0043] In contrast, in a second example feedback control strategy, the LPP is turned ON (e.g., operated at a high voltage) when it is sensed that a desired valley head pressure has been reached, and turned OFF (e.g., operated at a voltage near 0V) when it is sensed that a desired peak delivery pressure has been reached.

[0044] Operating the LPP in the pulsed mode can effectively ensure lower power consumption by the LPP while providing faster response time when the LPP is actuated. Furthermore, operation in the pulsed mode can reduce the longevity of the LPP 208 to enhance. The operation of the HPP 228 in the pulsed mode can be performed in a similar manner.

[0045] A pump electronics module (PEM) of the LPP 208 may provide electrical power to an electric motor coupled to the LPP. In one example, a controller, such as the controller, reads 12 the end figure 1, emits the output of a fuel pressure sensor that senses the delivery pressure of the LPP and issues a fuel pump command (FPC) to the PEM that varies with, and is determined based on, the output of the fuel pressure sensor, among other factors. The FPC may be encoded as a 150 Hz duty cycle that conveys the intended duty cycle of a field effect transistor (FET) of the LPP to the PEM, for example. Alternatively, the PEM can communicate the FPC via a serial interface, such as a CAN bus or LIN bus. The PEM takes the commanded FET duty cycle and applies the duty cycle to the FET at a frequency such as 9.8 kHz. This results in an effective voltage being applied to the pump's brushed DC motor. Thus, if the vehicle voltage supply is 12V and the desired rms voltage to be applied to the LPP is 6V, the FET can be turned on for 0.00005 seconds and off for 0.00005 seconds (i.e. with one duty cycle be operated by 50 %). The PEM current has some value; the pump motor current is generally a current that is on average greater than the average current of the PEM due to current circulating through a diode while the FET is off. (The instantaneous current of the PEM is essentially equal to the instantaneous current of the pump motor while the FET is on. While the FET is off, the instantaneous current of the PEM is zero, but the current through the inductance of the electric motor is a positive value.) The PEM references its electrical energy from the vehicle's battery, which may be a 12V battery, and the vehicle's alternator system. If no "current shaping" or "soft start" measures are taken, the peak PEM current is, for example, 30 to 35 amps. However, by not immediately applying a full step voltage of full battery / alternator voltage, the peak value of this inrush current can be reduced, e.g. B. to the level of the steady current. For example, the RMS voltage applied to the pump motor can be shaped such that the peak inrush current remains below 10 amps.

[0046] If the LPP 208 is operated in the pulsed mode, a sawtooth pressure pattern can be observed at the delivery pressure, which can be seen with reference to FIG figure 3A- figure3C will be discussed in more detail. For example, the pulsed mode can produce a rapid pressure rise to 6.5 bar followed by a ramp down to 4.5 bar as fuel is consumed. While this pressure change may not be used in direct injection systems, knowledge of the actual pressure may be desirable in PFI systems.

[0047] In the continuous mode of operation, control of the LPP (e.g., controlling the voltage level applied to the LPP) may be closed-loop control based on feedback from one or more pressure sensors (e.g., the pressure sensors 234 , 235 and 236 ) or an open-loop control that is performed independently of and does not take into account the feedback from the pressure sensors. Likewise, in the pulsed continuous mode of operation, control of the LPP (e.g. control of the voltage level and / or duty cycle of the pulses applied to the LPP) may be closed loop control based on feedback from one or more pressure sensors (e.g. the pressure sensors 234 , 235 and 236 ) or an open-loop control that is performed independently of and does not take into account the feedback from the pressure sensors. If the pulsing of the LPP 208 performed independently of the feedback, the LPP can be run at slightly higher power than required. Despite the slightly higher performance that the LPP 208 provided during operation in the open loop pulsed mode, however, the LPP may effectively consume significantly less power in the open loop pulsed mode compared to the power consumption during operation of the lift pump in the continuous mode.

[0048] figure 1- figure 2 show exemplary layouts with relative positioning of the various components. If such elements are shown as directly touching or directly coupled to each other, they may be referred to as directly touching or directly coupled, respectively, in at least one example. Likewise, elements shown contiguous or adjacent to one another may be contiguous or adjacent to one another, respectively, in at least one example. For example, components that are in face-sharing contact with one another may be referred to as being in face-sharing contact. As another example, elements that are positioned apart from one another with only space therebetween and no other components may be referred to as such in at least one example. As yet another example, elements depicted above / below one another, on opposite sides of one another, or to the left / right of one another may be referred to as such relative to one another. Further, as shown in the figures, in at least one example, a top element or point of an element may be referred to as a "top" of the component and a bottom element or point of the element may be referred to as a "bottom" of the component . As used herein, top / bottom, upper / lower, above / below may refer to a vertical axis of the figures and may be used to describe the positioning of elements of the figures relative to one another. Thus, in one example, elements shown above other elements are positioned vertically above the other elements. As yet another example, shapes of the elements depicted in the figures may be referred to as having those shapes (such as circular, straight, planar, curved, rounded, beveled, angled, or the like). Further, elements that are depicted as intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Additionally, an element represented inside another element or outside another element may be referred to as such in an example.

[0049] figure 3A- figure 3E depict traces representing sensed and actual delivery pressure of a fuel lift pump (e.g., the LPP 208 the endfigure 2) during pulsed operation as a function of time. figure 3A illustrates a waveform representing both sensed and actual pressure during pulsed operation when a pressure sensor sensing discharge pressure is functioning properly. figure 3B illustrates two waveforms representing sensed and actual discharge pressure, respectively, during pulsed operation with the first exemplary feedback control strategy when the pressure sensor that senses discharge pressure is degraded and over-reading. figure 3C illustrates two waveforms representing sensed and actual discharge pressure, respectively, during pulsed operation with the first example feedback control strategy when the pressure sensor that senses discharge pressure is degraded and reading too low. figure 3D illustrates two waveforms representing sensed and actual discharge pressure, respectively, during pulsed operation with the second exemplary feedback control strategy when the pressure sensor that senses discharge pressure is degraded and over-reading. figure 3E illustrates two waveforms representing the sensed and actual discharge pressure, respectively, during pulsed operation with the second example feedback control strategy when the pressure sensor that senses the discharge pressure is degraded and reading too low values.

[0050] As in figure 3A- figure 3E, application of voltage pulses to a fuel lift pump results in delivery pressures that produce a waveform having a sawtooth pattern when plotted against time. In some examples, during pulsed operation of the lift pump, in accordance with the first example feedback control strategy, the duty cycle of the pulses applied to the lift pump (and optionally the level of the supply voltage) is selected (e.g., preprogrammed into the controller, determined dynamically at the controller). or determined at the controller based on engine operating conditions) that the application of each pulse of supply voltage to the lift pump produces a rapid increase in discharge pressure until a desired peak pressure is reached. However, in accordance with the second exemplary feedback control strategy, a predetermined high voltage is applied to the lift pump when it is sensed that a desired valley lift pressure has been reached, whereas a predetermined low voltage (e.g., 0V or slightly greater than 0V) is applied to the lift pump is applied when it is sensed that a desired peak delivery pressure has been reached, such that the sensed delivery pressure dictates the duration of each higher voltage pulse. It is understood that other feedback control strategies can be used without departing from the scope of this disclosure.

[0051] in the in figure 3A- figure 3E, the desired peak pressure (indicated by the dashed line 307 shown) selected to be below a set pressure relief valve pressure (indicated by the dashed line 302 shown) and the desired valley pressure (indicated by the dashed line 305 shown) was chosen to be above the vapor pressure of the fuel (indicated by the dashed line 304 shown) is located. The target pressure and fuel vapor pressure may represent the maximum and minimum physical pressures of the fuel system, respectively. For example, as above with reference to FIG figure2 discusses at the target pressure around the pressure at which the pressure relief valve opens to relieve pressure from the fuel system (e.g., by returning fuel to the fuel tank). Further, the fuel is in thermodynamic equilibrium between its gas and liquid phases, with the fuel vapor being at a certain pressure (e.g., vapor pressure) that depends on the fuel composition and temperature. In the absence of additional fueling by the lift pump while fuel is being injected by the fuel injectors, the delivery pressure decreases to the fuel vapor pressure and cannot decrease any further. Fuel vapor pressure can vary from near zero absolute pressure in cold ambient temperatures to 600+ kPa absolute pressure during warm restarts. The fuel vapor pressure is the minimum pressure that can be obtained in the fuel system as long as liquid fuel is present in the system, which is always the case in real vehicles. Undissolved air may also be present in the line, making the pressure slightly higher than the fuel vapor pressure, but the fuel vapor pressure still sets the minimum pressure.

[0052] Driving the lift pump motor causes the head pressure to increase such that the head pressure ultimately appears as a rising ramp when plotted against time. When the lift pump motor is OFF and the voltage applied to the lift pump is substantially 0 V and the fuel is PFI injected or DI pumped at a constant rate out of this zone of low fuel pressure, the delivery pressure will ultimately appear as a downward slope when plotted against time. If fuel consumption (via PFI injections or DI pumps) increases, the downward slope becomes steeper and vice versa.

[0053] in the in figure 3A shown exemplary diagram 300 the feedback control of the lift pump is working properly and the pressure sensor, which records the delivery pressure, is measuring accurately (e.g. it is not impaired). Because the pressure sensor measures accurate values, the signal output by the pressure sensor accurately represents the actual discharge pressure. The waveform represents accordingly 306 , which has a sawtooth pattern, represents both the signal output by the pressure sensor and the actual discharge pressure. As shown, the waveform has 306 sharpen 306a at a desired peak pressure (through the dashed line 307 shown) that is less than the target pressure 302 of the pressure relief valve (providing a margin between the peak pressure and the set pressure). Furthermore, the waveform 306 Valleys 306b at a pressure higher than the fuel vapor pressure 304 is. However, in other examples, the desired peak pressure may be set equal to the target pressure and / or the duty cycle of the pulses may be set such that the troughs of the waveform are equal to the fuel vapor pressure.

[0054] In contrast, the pressure sensor in the in figure 3B shown exemplary diagram 320 affected and measures compared to the actual discharge pressure (through the waveform 308 shown) too high values ​​(through the waveform 309 shown). In this example, the first example feedback control strategy is performed. Accordingly, the waveform 309 the same shape as the waveform 308 but it is shifted up the chart because the controller adjusts the voltage pulses applied to the lift pump in response to the (higher) sensed lift pressure. Specifically, the controller has reduced the duty cycle of the voltage pulses applied to the lift pump to a lower value relative to the duty cycle that would have been selected given an accurate sensor reading. As a result, insufficient voltage is supplied for the actual discharge pressure (waveform 308 ) the desired peak pressure 307 is reached, and the actual discharge pressure decreases relative to the discharge pressure during sensor operation at nominal pressure (e.g. as indicated by the waveform 306 the end figure3A). Furthermore, in the illustrated example, the actual delivery pressure has decreased to such an extent that after applying a voltage pulse to the lift pump during fuel injection by fuel injectors, the pressure decreases to the fuel vapor pressure and for a duration (e.g. until it is due to the application of the next voltage pulse begins to increase again) remains at the fuel vapor pressure, so the waveform 308 appears flattened at each valley. It comes to the flattening of the valleys, since the actual pressure is not below the fuel vapor pressure 304 can fall, which is the physical minimum value of the system. This flattening contrasts with the pressure characteristic of the actual head pressure when the sensor is functioning properly, where the actual head pressure will continue to decrease until the next voltage pulse is applied, resulting in a sharp transition in the pressure signal from negative slope to positive slope at the valley pressure, so e.g. B. the pressure signal remains at its minimum value for less than a threshold duration. The normal, peaked valleys that make up the waveform 308 would occur if the pressure were allowed to drop below the fuel vapor pressure are shown by dashed lines. Similar to the waveform 308 the waveform appears 309 flattened out at each valley, but the flattening occurs at a measured pressure that is higher than the fuel vapor pressure because the sensor is reading too high a value.

[0055] in the in figure 3C example diagram shown 330 the pressure sensor in the fuel line is degraded and measures compared to the actual supply pressure (by the waveform 310 shown) too low values ​​(by the waveform 311 shown). Here again the first exemplary feedback control strategy is performed. Accordingly, the waveform 311 the same shape as the waveform 310 up, but it's shifted down the chart. In this case, the controller adjusts the voltage pulses applied to the lift pump in response to the (lower) sensed discharge pressure by adjusting the duty cycle of the voltage pulses applied to the lift pump relative to the duty cycle that would have been selected if the signal provided by the pressure sensor was correct would have been is increased to a higher value. As a result, the actual delivery pressure (waveform 310 ) relative to the discharge pressure during sensor operation at nominal pressure overall (e.g. as indicated by the waveform 306 the end figure 3A). Therefore, the LPP 208 more voltage is supplied than is required to achieve the desired peak pressure, which is undesirable because it lowers efficiency and increases power consumption. As shown, the peaks of the waveform are located 310 at a pressure higher than the desired peak pressure 307 . Furthermore, in the illustrated example, the actual delivery pressure has increased to such an extent that when a voltage pulse is applied to the lift pump, the pressure increases to the target pressure of the pressure relief valve. The voltage then remains for a duration (e.g., until it begins to decrease again due to fuel injection by the fuel injectors / pumping by the DI pump) so that the waveform 310 appears flattened at each peak. This is in contrast to the pressure characteristic of the actual delivery pressure when the sensor is functioning properly, where the actual delivery pressure will continue to increase until fuel is consumed via the injection of fuel into the engine by the fuel injectors, resulting in a sharp positive slope transition in the pressure signal leads to a negative slope at the peak pressure, so that e.g. B. the pressure signal remains at its maximum value for less than a threshold duration. The peak flattens as the actual pressure exceeds the target pressure 302 cannot exceed. The normal, non-flattened peaks that would occur if the pressure were allowed to exceed the target pressure are shown in dashed lines. Similar to the waveform310 the waveform appears 311 flattened out at each peak, but the flattening occurs at a measured pressure that is lower than the target pressure because the sensor is reading too low a value.

[0056] As used herein, "flattening" of sensed head pressure and actual head pressure refers to an event where the pressure waveform transitions from a non-zero slope to a zero slope and remains at zero slope (e.g., remains constant) for more than a threshold duration ). For example, the detected pressure for a valley (as in figure 3B) transition from a negative slope to a zero slope and then to a positive slope or for a spike (as in figure 3C) inverted, in each case remaining at the zero slope for a threshold duration. The threshold duration may be predetermined during manufacture of the internal combustion engine and stored in non-volatile memory of the control system. Further, the threshold duration may be proportional to the duty cycle of the voltage pulses applied to the lift pump and, in particular, may be less than the duration (pulse width) of each voltage pulse. Flattening of the pressure waveform may alternatively be referred to as clipping the waveform at the peaks and valleys or plateauing the waveform at its maximum and minimum values.

[0057] While the in figure 3B- figure 3C associated with the pulsed operation of the LPP in accordance with the first exemplary feedback control strategy include those in FIG figure 3D figure 3E shows example diagrams of the pulsed operation of the LPP in accordance with the second example feedback control strategy. in the in figure 3D shown exemplary diagram 340 the pressure sensor is degraded and measures compared to the actual discharge pressure (through the waveform 312 shown) too high values ​​(through the waveform 313shown). In this example, the second example feedback control strategy is performed. At the beginning of the curve, the delivery pressure decreases because only a minimum voltage (e.g. slightly above 0) is applied to the lift pump and fuel injection occurs. Were the pressure sensor working properly, it would correctly detect that the actual head pressure is reaching the desired valley pressure, at which point the controller would increase the voltage applied to the lift pump to a higher voltage. However, because the pressure sensor reads too high, the controller does not increase the voltage applied to the lift pump to a higher voltage when the actual lift pressure reaches the desired valley pressure; as shown, the sensed head pressure is still above the desired valley pressure at this point and thus pulsing the lift pump to the higher voltage is not triggered. The actual discharge pressure thus continues to decrease until the detected discharge pressure reaches the desired valley pressure. In the illustrated example, the actual delivery pressure decreases to the fuel vapor pressure before the sensed delivery pressure has decreased to the desired valley pressure due to the extent to which the pressure sensor is reading too high. When the actual delivery pressure reaches the fuel vapor pressure, it cannot decrease any further and thus remains constant at the fuel vapor pressure. The detected delivery pressure also remains constant as shown, but at a higher value. Because the higher value is greater than the desired valley pressure, the controller does not increase the voltage applied to the lift pump to a higher voltage and thus the actual lift pressure is stuck at the fuel vapor pressure. This can cause the combustion engine to stall. A similar problem can occur if the fuel vapor pressure is higher than the fuel vapor pressure stored on the controller. For example, if the actual fuel vapor pressure has increased above the desired valley pressure (which may occur due to a rapid rise in fuel temperature), the sensed pressure will not decrease to the desired valley pressure even if the pressure sensor is functioning properly. Here again, the controller does not increase the voltage applied to the LPP to a higher voltage as it waits for the head pressure to decrease to the desired valley pressure, which can result in an engine stall.

[0058] in the in figure 3E shown exemplary diagram 350 the pressure sensor is degraded and measures compared to the actual discharge pressure (through the waveform 314 shown) too low values ​​(by the waveform 315shown). In this example, the second example feedback control strategy is performed. At the beginning of the course, the delivery pressure decreases because only a minimum voltage (e.g. slightly above 0) is applied to the LPP and fuel injection occurs. If the pressure sensor were working properly, it would correctly sense that the actual head pressure is reaching the desired valley pressure, at which point the controller would increase the voltage applied to the LPP to a higher voltage. However, because the pressure sensor is reading too low, the controller does not increase the voltage applied to the LPP to a higher voltage when the sensed head pressure reaches the desired valley pressure, which occurs before the actual head pressure has decreased to the desired valley pressure. The actual head pressure thus does not reach the desired valley pressure and instead begins to increase in response to the LPP being pulsed to the higher voltage. In the illustrated example, the actual discharge pressure increases to the desired pressure relief valve pressure before the sensed discharge pressure has increased to the desired peak pressure due to the extent to which the pressure sensor is reading too low. When the actual delivery pressure reaches the set pressure of the pressure relief valve, it cannot increase any further and thus remains constant at the set pressure of the pressure relief valve. The discharge pressure sensed also remains constant as shown, but at a lower value. Because the lower value is lower than the desired peak pressure, the controller continues to apply the higher voltage to the LPP and thus the actual discharge pressure is stuck at the pressure relief valve set pressure. This disadvantageously leads to increased fuel consumption and reduced fuel system longevity as the delivery pressure is maintained higher than required for current engine operating conditions.

[0059] In the sensor degradation examples described above, the sensor (e.g., the sensor 234 or 235 the end figure 2) Measure values ​​within the operating range of the instrument and the error will not be detected by previously described methods. In contrast, consistent with the present disclosure, a flattening of the discharge pressure waveform (e.g., discharge pressure remaining constant for more than a threshold duration) may indicate degradation of the pressure sensor even when the pressure sensor output is within its normal operating range, such as is described in more detail here. Moreover, detection of such flattening alone may indicate degradation of the pressure sensor, such that detection of other parameters (e.g., magnitudes of sensed discharge pressure) may not be necessary. Accordingly, the control carried out for the pressure sensor diagnosis can advantageously be simplified.

[0060] Now will open figure 4, an example routine 400 for diagnosing an within-range failure of a pressure sensor located downstream of a fuel lift pump in a fuel system. Instructions for running the routine 400 and the other routines disclosed herein (e.g., the routines 500 , 510 , 530 , 600 , 700 and 1100 ) can be controlled by a controller (such as the controller 12 the end figure 1) based on instructions stored in non-volatile memory of the controller and in conjunction with internal combustion engine sensors such as those referred to above with reference to FIG figure 1- figure 2 described sensors, received signals are executed. In executing the routines disclosed herein, the controller may send signals to various engine actuators to cease operation of the engine, as described below.

[0061] at 402 includes the routine of performing closed loop feedback control of voltage pulses applied to the lift pump. Feedback control of the voltage pulses involves the controller receiving feedback from a pressure sensor downstream of the lift pump (e.g. the pressure sensor234 or 235 off figure 2) receives and adjusts the voltage applied to the lift pump based on feedback from the pressure sensor (e.g., via adjustment of an actuator of the lift pump). The feedback control may be performed in accordance with the first or second exemplary feedback control strategy discussed herein, or another control strategy.

[0062] at 404 includes the routine of determining whether entry conditions for diagnosing an within-range failure of a pressure sensor are met. Entry conditions may include a pressure sensor output being within a predetermined normal operating range. For example, if the pressure sensor is degraded such that the output is outside of the normal operating range (e.g., an out-of-range pressure sensor fault), a diagnosis of within-range faults is not necessary. When an out-of-range fault occurs, a corresponding OBD flag may be set at the controller, and thus determining whether the entry conditions for diagnosing within-normal faults are met may involve the controller checking the status of that OBD -Flags checked. Further, the entry conditions may include steady state operation of the engine and / or the temperature of the engine (eg, engine coolant temperature) exceeding a threshold. If the entry conditions are not met, for example due to the presence of an out-of-range sensor error, the routine ends. Otherwise the routine proceeds to 406 .

[0063] at 406 includes the routine of detecting the delivery pressure of the suction pump with a pressure sensor. This can include continuous detection of the delivery pressure of the suction pump during the entire operation of the internal combustion engine. After 406 the routine proceeds to 408.

[0064] at 408 the routine includes that the controller outputs the detected delivery pressure in accordance with the routine figure 7, discussed below, is monitored for flattening, for example.

[0065] If flattening is detected at 410, the routine continues to 412 and indicates an within-range error of the pressure sensor. In one example, indicating that the pressure sensor has failed within the normal range may include the controller setting an OBD flag. Further, at 412, the routine includes switching the fuel lift pump from a closed loop control scheme to an open loop control scheme in which the lift pump is energized using a non-zero steady state voltage and pressure sensor feedback is not considered. Switching to open loop lift pump control allows the fuel system to continue to operate even if the pressure sensor is degraded, albeit at a lower efficiency than closed loop lift pump operation when the pressure sensor is not degraded. After 412 the routine ends.

[0066] Back at 410 , if no flat is detected, the routine continues to 414 . at 414 the controller maintains closed loop control of the lift pump. After 414 the routine ends 400 .

[0067] Now, referring to figure 5A shows an example routine 500 for performing closed loop control of a fuel lift pump.

[0068] at 502 includes the routine 500 Measuring or estimating internal combustion engine operating conditions (e.g., fuel composition, fuel flow rate from injectors, and current lift pump delivery pressure).

[0069] at 504 includes the routine of determining desired pressure and fuel vapor pressure. In one example, the target pressure and fuel vapor pressure may be referenced below with reference to FIG figure6 described manner can be determined dynamically by the controller. In another example, the target pressure may include a predetermined value stored in non-volatile memory of the controller, the predetermined value being based on characteristics of the pressure relief valve (e.g., the pressure relief valve 211 the end figure 2) as well as properties of the fuel system, and the fuel vapor pressure can be calculated as a function of the detected fuel temperature and fuel composition.

[0070] at 506 includes the routine of determining the desired peak and valley lift pump discharge pressure. The desired peak lift pressure is a desired maximum lift pump output pressure, while the desired valley lift pressure is a desired minimum lift pump output pressure. The desired peak discharge pressure may be below the target pressure by a predetermined margin; likewise, the desired valley delivery pressure may be above the fuel vapor pressure by a predetermined margin.

[0071] at 508 The routine involves performing closed loop feedback control of the lift pump to achieve the desired peak and valley lift pressure, for example in accordance with the first exemplary feedback control strategy described herein (see figure 5B), the second exemplary feedback control strategy described here (see figure 5C) or the third exemplary feedback control strategy described here (see figure 11). After 508 the routine ends.

[0072] figure 5B shows an example routine 510 for performing the first example feedback control strategy described herein. The routine 510 can be in conjunction with the routine 500 the end figure 5A can be performed at 508, for example.

[0073] at 512 the routine includes determining the magnitude of non-zero voltage pulses for application to the lift pump and the duty cycle of the pulses that corresponds to the routine 500 at 506 certain desired peak and valley discharge pressures. For example, the voltage and / or duty cycle at the controller may be determined via a look-up table stored in non-volatile memory of the controller, given values ​​of parameters such as fuel vapor pressure, target pressure, desired peak and valley lift pump lift pressure, fuel injection rate , DI pump rate, etc., indicating the appropriate voltage and duty cycle. Alternatively, the voltage and / or duty cycle may be determined at the controller via functions that take values ​​of parameters (e.g., fuel vapor pressure, desired pressure, desired peak and valley delivery pressure, fuel injection rate, DI pumping rate, etc.) as inputs and the output the appropriate voltage and / or duty cycle for the pulses. The specified voltage and duty cycle may be selected such that each voltage pulse applied to the lift pump increases the delivery pressure to the desired peak pressure and such that the next voltage pulse is applied as the delivery pressure decreases from the desired peak pressure to the desired valley pressure. In some examples, the same non-zero effective voltage is always applied during pulsed operation of the lift pump, while the duty cycle of the pulses is varied as engine operating conditions change.

[0074] at 514 includes the routine applying voltage pulses to the lift pump, the pulses having the magnitude and duty cycle determined at 512 . For example, the controller may send a signal to an actuator of the lift pump, which in turn applies voltage pulses of the particular magnitude to the work pump at the particular duty cycle.

[0075] at 516 includes the routine monitoring the discharge pressure of the lift pump (e.g. with a pressure sensor such as the pressure sensor 234 or 235 the end figure2). The lift pump delivery pressure may be monitored over a duration, such as a duration beginning when a voltage pulse is applied and ending when the next voltage pulse is applied. Alternatively, the delivery pressure of the suction pump can be continuously monitored during the entire operation of the internal combustion engine.

[0076] at 516 the routine proceeds to 518 to determine if the sensed peak and valley discharge pressures are within (eg, approximately equal to) a predetermined normal range of the desired peak and valley discharge pressures, respectively, of the lift pump. Determining whether the sensed peak and valley discharge pressures are within the predetermined normal range may include: calculating a difference between the sensed peak discharge pressure and the desired peak discharge pressure at the controller and comparing the absolute value of the difference to a threshold and calculating a difference between the sensed valley discharge pressure and the desired valley head at the controller and comparing the absolute value of the difference to a threshold. If it is determined at 514 that the sensed peak and valley lift pressure are within the predetermined normal range of the desired peak and valley lift pressure, the routine continues to 520 and control maintains the current operation (e.g., continues to carry out regulation of the fuel lift pump closed loop control without adjusting the duty cycle / voltage of the pulses). Following 520, the routine returns 500 return.

[0077] However, if it is determined at 518 that the sensed peak and valley delivery pressure are not approximately equal to the desired peak and valley delivery pressure, the routine proceeds to 518 . at 518 the routine includes determining whether the sensed peak and valley delivery pressures are greater than the desired peak and valley delivery pressures, respectively (eg, greater than a predetermined amount).

[0078] If the sensed peak and valley lift pressures are greater than the desired peak and valley lift pressures, respectively, the routine continues to 524 and the duty cycle of the pulses applied to the lift pump is decreased. For example, the controller may send a signal to an actuator of the lift pump to reduce the duty cycle of voltage pulses applied to the lift pump. The reduction in duty cycle may be selected by the controller to be proportional to the difference between the sensed peak and valley delivery pressure and the desired peak and valley delivery pressure, in some examples. In this manner, the controller may reduce the total amount of voltage applied to the fuel lift pump, thereby reducing the lift pump discharge pressure. Following 524, the routine returns.

[0079] If, back at 522, it is instead determined that the sensed peak and valley lift pressures are less than the desired peak and valley lift pressures, respectively, the routine proceeds to 526 and the duty cycle of the pulses applied to the lift pump is increased. For example, the controller may send a signal to an actuator of the lift pump to increase the duty cycle of voltage pulses applied to the lift pump. The increase in duty cycle may be selected by the controller to be proportional to the difference between the sensed peak and valley delivery pressure and the desired peak and valley delivery pressure, in some examples. In this manner, the controller may increase the total amount of voltage applied to the fuel lift pump, thereby increasing the lift pump's peak and valley discharge pressure. Following 526, the routine returns.

[0080] In some examples, the routine 500 performed in an iterative manner during closed loop control of the lift pump, allowing the controller to continually adjust the amount of voltage applied to the fuel lift pump as the desired peak and valley lift pressures vary.

[0081] figure 5C shows an example routine 530 for performing the second exemplary feedback control strategy described herein. The routine 530 can be in conjunction with the routine 500 the end figure5A can be performed at 508, for example.

[0082] at 532 includes the routine of determining a higher and lower voltage level to be applied to the lift pump during pulsed operation. The higher voltage level can be a predetermined voltage level that quickly raises the head pressure to the desired peak pressure (e.g., 8-12V), whereas the lower voltage level can be a predetermined voltage level that is low enough to power the lift pump remains (e.g. greater than 0 V and less than 0.3 V) and which does not significantly increase the fuel pressure. When the higher voltage level is applied to the lift pump, the lift pump can be considered to be in an ON state, but when the lower voltage level is applied to the lift pump, the lift pump can be considered to be in an OFF state, although still to a minimal extent voltage is applied.

[0083] After 532 the routine continues to 534 and control applies the predetermined higher voltage to the lift pump.

[0084] After 534 the routine proceeds to 536 and control determines whether the sensed discharge pressure is equal to the desired peak discharge pressure. If not, the routine continues to monitor the sensed discharge pressure until it equals the desired peak discharge pressure. If the pressure sensor malfunctions and measures too low values, as described above with reference to figure 3E, this can result in the sensed discharge pressure never reaching the desired peak discharge pressure. In this case, the routine would be stuck at 534 and fuel economy and fuel system longevity would be negatively impacted.

[0085] Once control determines that the sensed displacement pressure is equal to the desired peak displacement pressure, the routine proceeds to 538 and control determines whether the sensed displacement pressure is equal to the desired valley displacement pressure. If not, the routine continues to monitor the sensed head pressure until it equals the desired valley head pressure. If the pressure sensor malfunctions and measures too high values, as described above with reference to figure 3D, this can result in the sensed head pressure never reaching the desired valley head pressure. In this case, the routine would be stuck at 538 and the engine could potentially stall due to lack of adequate fuel pressure.

[0086] It is understood that the implementation of the routine 530 may be interrupted and / or suspended by the controller to switch to a different fuel system control strategy or to turn off the combustion engine.

[0087] figure 6 shows an example routine 600 to determine the desired pressure (eg, maximum physical pressure in the fuel system for current engine operating conditions) and fuel vapor pressure (eg, minimum physical pressure of the fuel system for current engine operating conditions). In accordance with the routine 600 the controller may initiate a determination of the desired pressure during engine operating conditions where the desired peak and valley lift pump discharge pressures are relatively high. Further, the controller may initiate a fuel vapor pressure determination when the desired peak and valley lift pump delivery pressures are relatively low. In this manner, dynamic determination of desired pressure and fuel vapor pressure may be performed intermittently during engine operation in a manner that takes advantage of variations in desired peak and valley lift pump delivery pressure to make active adjustments to engine operation in conjunction with performing the dynamic determination minimize.

[0088] at 602 the routine begins by measuring and / or estimating engine operating conditions, such as those above for the routine 500 in the manner described at 502.

[0089] at 604includes the routine of determining whether the engine is operating at steady state and is warmed up. For example, the engine may be determined to be operating at steady state if the engine speed remains substantially constant for at least a threshold duration. Further, the engine may be determined to be warmed up if it is determined that the engine temperature is greater than a threshold temperature (eg, based on an output of an engine coolant temperature sensor). The routine 600 returns if the engine is not warmed up and not in steady state operation. Otherwise, if the engine is warmed up and operating at steady state, the routine continues to 606 .

[0090] at 606 includes the routine of determining whether the entry conditions for determining the desired pressure are met. In one example, the entry conditions for determining the desired pressure include peak delivery pressure being greater than a threshold and / or valley delivery pressure being greater than a threshold. In another example, the entry conditions for determining the desired pressure include engine load being greater than a threshold. If it is determined at 606 that the entry conditions for determining the desired pressure are not met, the routine continues to 608 to determine whether the entry conditions for determining the fuel vapor pressure are met, which will be explained in more detail below. Otherwise, if the entry conditions for determining the desired pressure are met at 606 , the routine proceeds to 610 .

[0091] at 610 The routine includes increasing the duty cycle of voltage pulses applied to the fuel lift pump until the sensed discharge pressure of the pump levels off. Flattening can be in accordance with the routine 700 the end figure 7, which is discussed below. Flattening of the sensed delivery pressure represents that a physical limit of the fuel system is being reached. In this example, the physical limit is the target pressure. The pressure in the fuel system cannot exceed this pressure; when the pressure in the fuel system reaches the set pressure, the pressure relief valve opens and fuel flows back to the fuel tank. The pressure relief valve remains open until the pressure in the fuel system decreases to the desired pressure, at which time the pressure relief valve closes.

[0092] at 612 includes the routine of setting the target pressure to the pressure at which flattening occurred. In this way, the controller determines the highest possible delivery pressure. For example, because the fuel pressure sensor can become clogged or otherwise compromised, this reading may change over time. It is therefore advantageous that the controller periodically recalculates this value. For example, knowing the maximum pressure of the system can help the controller discriminate within normal range pressure sensor failures, as discussed below with reference to FIG figure 7 described in detail. Additionally, knowing the target pressure with high accuracy may allow the controller to set the desired peak delivery pressure to be a small margin (e.g., 20 kPa) below the target pressure. By way of non-limiting example, if the desired pressure is determined to be 650 kPa, the desired peak delivery pressure may be set at 630 kPa. Accordingly, the duty cycle of the voltage pulses applied to the fuel lift pump to achieve the desired peak delivery pressure can be reduced, thereby improving fuel economy.

[0093] After 612 the routine goes to 614. at 614 includes the routine returning to normal closed-loop control of the lift pump (e.g., by executing the routine 500 the end figure5A). For example, this may include the controller determining a lift pump activation duty cycle that adjusts the peak lift pressure to the desired peak lift pressure and controlling an actuator of the lift pump to adjust the duty cycle of the voltage pulses applied to the lift pump to the determined duty cycle. The adjustment may include reducing the duty cycle of the lift pump voltage pulses so that the discharge pressure remains below the desired pressure. After 614 the routine proceeds to 608.

[0094] at 608 includes the routine of determining whether entry conditions for determining fuel vapor pressure are met. In one example, entry conditions for determining fuel vapor pressure include peak delivery pressure being less than a threshold and / or valley delivery pressure being less than a threshold. In another example, entry conditions for determining fuel vapor pressure include engine load being less than a threshold. If it is determined at 608 that the entry conditions for determining fuel vapor pressure are not met, the routine ends 600 . Otherwise, if the entry conditions for determining fuel vapor pressure are met, the routine goes to 616 .

[0095] at 616 involves the routine of reducing the duty cycle of the voltage pulses applied to the fuel lift pump until the pump discharge pressure levels off (e.g. as measured by the pressure sensors 234 or 235 the end figure 2). Flattening can be in accordance with the routine 700 the end figure 7, which is discussed below. Flattening of the sensed delivery pressure represents that a physical limit of the fuel system is being reached. In this example, the physical limit is fuel vapor pressure.

[0096] at 618 includes the routine setting the fuel vapor pressure to the pressure at which flattening occurs as determined at 616 . In this way, the controller determines the lowest delivery pressure that is possible for the fuel system. Fuel temperature can fluctuate during vehicle operation, changing fuel vapor pressure. Determining fuel vapor pressure in accordance with the routine 600 may be more accurate than calculating fuel vapor pressure based on sensed or inferred fuel composition and temperature. Knowing the fuel vapor pressure at a given point in time with high accuracy can allow the fuel system to operate at a small pressure above the fuel vapor pressure without risk of losing the desired pressure margin between the vapor pressure and the injection pressure due to temperature variation. For example, this method could be used in place of the hot injector compensation method, metering less fuel than intended since operating at a greater pressure (e.g., 50 or 100 kPa) above the fuel vapor pressure. Further, knowing the system's minimum pressure can help the controller discriminate within normal range pressure sensor errors, as referred to below with reference to FIG figure 7 described in more detail.

[0097] at 620 includes the routine returning to normal closed-loop control of the lift pump (e.g., by executing the routine 500 the end figure 5A). For example, this may include the controller determining a lift pump activation duty cycle that adjusts the peak lift pressure to the desired peak lift pressure and controlling an actuator of the lift pump to adjust the duty cycle of the voltage pulses applied to the lift pump to the determined duty cycle. The adjustment may include increasing the duty cycle of the lift pump voltage pulses so that the lift pressure remains above the fuel vapor pressure. After 620 the routine returns.

[0098] figure 7 shows an example routine 700used to diagnose an within-range fault in fuel pressure sensors. An within-range fault can occur when the pressure sensor output appears to be within an expected normal range (e.g., the sensor output voltage is non-zero and an out-of-range check according to industry standards does not indicate that the pressure sensor output is outside of normal range). When an within-range fault occurs, the pressure sensor output corresponds to a pressure that is higher or lower than the actual delivery pressure, but still within a normal pressure range of the fuel system.

[0099] at 702 includes the routine of determining a threshold duration for which the sensed pressure remains constant during proper sensor operation. As above with reference to figure 3A- figure 3E, for example, during pulsed operation of the lift pump, the discharge pressure varies in a sawtooth pattern that includes sharp peaks and valleys. The threshold duration may be a longest duration that the pressure is expected to remain at a peak or valley pressure for current operating conditions. The threshold duration can be determined empirically, e.g. B. during manufacture of the vehicle, and stored in non-volatile memory of the controller, z. B. in a lookup table that stores threshold durations corresponding to different operating conditions such as different pulse widths of the voltage pulses applied to the lift pump. As below with reference to figure 9, the threshold duration at any given time may be significantly less than the pulse width of the voltage pulses applied to the lift pump at that time.

[0100] at 704 includes the routine of monitoring the detected discharge pressure (e.g. as measured by the sensor 234 or 235 the end figure 2). In some examples, the monitoring may be stopped once the sensed head pressure remains constant for longer than the threshold duration, even if it occurs before the end of application of the first voltage pulse during the monitoring. In other examples, the monitoring may be performed during the application of a predetermined number of voltage pulses to the lift pump regardless of whether the sensed pump pressure remains constant for more than the threshold duration before all of the predetermined number of voltage pulses have been applied. The predetermined number can be one, two, three, or any other number of voltage pulses.

[0101] at 706 the routine includes determining if the sensed discharge pressure is greater than a threshold duration, e.g. the threshold duration determined at 702, has remained constant. In some examples, the fact that the sensed delivery pressure remains constant longer than the threshold duration creates an interrupt. In response to a determination that the sensed head pressure has remained constant for longer than the threshold duration, the routine proceeds to 708 and control indicates an within-range fault (eg, by setting an OBD flag). Following step 708 the routine returns.

[0102] Returning to 706, if the sensed pressure does not remain constant for more than a threshold duration while monitoring, the routine continues to 710 and control indicates that there is no within-range pressure sensor fault (e.g., by not providing an OBD flag sets). Following 710, the routine returns.

[0103] Now, referring to figure 8 an exemplary map 800 shown, the relevant signals during the dynamic determination of the target pressure and fuel pressure of a fuel system z. B. in accordance with the routine 600 the end figure 6 illustrates. The map 800 sets the target pressure in the course 802 , the fuel vapor pressure at history 804 , the desired (e.g. commanded) discharge pressure at history 806 , the voltage applied to the suction pump at history 808 , the recorded delivery pressure of the suction pump at history810 , the engine load at history 812 and the engine temperature during history 814 For all of the above traces, the x-axis represents time, with time increasing from left to right along the x-axis. The Y-axis of each gradient corresponds to the specified parameter, with the value increasing from bottom to top. In addition, that line 816 represents a first, higher engine load threshold, the line 818 represents a second, lower engine load threshold and the line 820 represents a threshold for the engine temperature.

[0104] The expected physical behavior of the fuel system is that the target pressure 802 of the pressure relief valve is constant throughout its service life. In contrast, the fuel vapor pressure varies 804 depends on the fuel composition and is closely linked to the fuel temperature. Thus, it changes significantly as the vehicle warms up during operation. However, between fuel composition specification and design measures, it is expected that the maximum fuel vapor pressure will be limited to a worst-case value. In normal operation, the desired peak pressure is set to be below the target pressure 802 of the pressure relief valve and the desired valley pressure is set to be above the fuel vapor pressure 804 lies. However, in order to determine the values ​​of each, the controller can willfully disregard this normal target.

[0105] Between t0 and t1, the fuel lift pump may be operated with a closed loop control scheme, e.g. B. in accordance with the routine 500 the end figure 5A The controller, such as the controller 12 the end figure 1, sends a signal to an actuator of the lift pump, causing the actuator to deliver pulses of non-zero voltage with a duty cycle that achieves a desired discharge pressure characteristic 806 manufactures to apply to the suction pump. As shown, the desired discharge pressure characteristic 806 vary with engine load. The energizing voltage pulses applied to the lift pump to achieve the desired head pressure characteristic 806 are in progress 808 shown. The delivery pressure of the fuel lift pump, which is determined by a sensor (e.g. the pressure sensor 234 or 235 the end figure 2) is measured and at course 810 illustrated increases in response to the application of voltage to the lift pump. Between energizing pulses, when zero voltage is applied to the lift pump, the lift pump discharge pressure decreases due to engine fuel consumption.

[0106] It may be beneficial to dynamically determine fuel vapor pressure and target pressure to maximize fuel economy, as discussed above with reference to FIG figure 6 described in detail. However, in order to proceed to dynamically determining either the fuel vapor pressure or the target pressure, the engine must be operating at steady state and warmed up, and the appropriate entry conditions must be met. In the map 800 In the example shown, the engine operates at steady state between t0 and t1, and thus the engine load remains 812 essentially constant. Furthermore, the internal combustion engine temperature 814 higher than that indicated by the dashed line 820 threshold shown, indicating that the engine is warmed up. Additionally, the engine load is above the first, higher threshold 816 . The entry conditions for determining the target pressure are therefore met at t1. However, in other examples, additional entry conditions may need to be met before the desired pressure is determined.

[0107] Between t1 and t2 of the map 800 the controller determines the target pressure 802, which is the maximum delivery pressure possible due to the presence of the pressure relief valve in the fuel system. To determine the maximum lift pressure, the controller increases the duty cycle of the voltage pulses applied to the fuel lift pump at t1 as shown 808 . This increase is not in response to a change in engine operating conditions (e.g., an increase in engine load) or an increase in desired (e.g., requested or commanded) boost pressure; instead, the increase is performed solely for the purpose of determining the maximum delivery pressure of the fuel system that corresponds to the target pressure of the pressure relief valve. Although, for example, the internal combustion engine load 812 remains substantially constant between times t0 and t1, the controller still increases the duty cycle of the voltage pulses applied to the fuel lift pump to perform the dynamic determination of the desired pressure.

[0108] If the detected delivery pressure 810 the target pressure 802 is reached, the waveform of the detected discharge pressure develops a flat-top characteristic. In the illustrated example, the delivery pressure reaches the target pressure during the application of the first voltage pulse having an increased pulse width. However, in other examples, the increase in duty cycle may be performed incrementally such that the sensed delivery pressure does not reach the target pressure until several voltage pulses have been applied, which advantageously reduces the steepness of the increase in pressure supplied to the fuel injectors. Further, incrementally increasing the duty cycle provides detection of flattened peaks while minimizing the increase in delivery pressure so that the delivery pressure remains closer to the optimal delivery pressure at the current engine operating conditions.

[0109] In the map 800 the target pressure is 650 kPa and the sensed discharge pressure waveform flattens out (remains constant) at 650 kPa for a non-trivial duration. This specific target pressure is just an example; the target pressure will vary depending on the characteristics of the pressure relief valve and fuel system.

[0110] In the illustrated example, the controller continues to monitor the sensed discharge pressure after flattening has been detected; specifically, a further voltage pulse is applied after an instance of flattening has been detected, so that the head pressure signal flattens twice at the peak. The application of one or more additional voltage pulses with an increased pulse width relative to the nominal pulse width even after detecting a first instance of flattening may be beneficial in that it may reduce false-positive flattening detection (e.g., when it an anomaly occurs resulting in a transient flattening of the sensed discharge pressure signal, which does not represent the actual set pressure). However, in other examples, the controller may end the process of determining the target pressure once flattening is detected and update the stored target pressure to the pressure at which flattening occurred. This may limit the amount of time that the voltage applied to the lift pump is increased by the controller to perform the sensing and therefore improve fuel economy.

[0111] Upon detecting the flattening of the sensed discharge pressure waveform, the controller compares the pressure at which the sensed discharge pressure flattened to a predetermined target pressure stored in non-volatile memory. Because the desired pressure is subject to change over time (e.g., if the pressure relief valve becomes clogged or other fuel system parameters change), it may be desirable to periodically re-evaluate the desired pressure; to this end, the routine 600 be carried out intermittently or optionally continuously during the pulsed operation of the suction pump. In other examples, the routine 600 only be carried out if the pulsed operation of the suction pump is initiated.

[0112] At t2, the controller ends the process of determining the target pressure and returns the operation of the lift pump to the routine 500 the end figure 5A with closed loop control scheme. For example, as shown, the controller can change the duty cycle of the voltage pulses applied to the lift pump 808 decrease to a value reflecting current engine operating parameters (e.g., the same value applied from time t0 to t1).

[0113] Between t2 and t3, the engine load increases 812 to a level lower than the second threshold 818 is. The decrease in engine load may occur due to a change in engine operation (e.g., a transition to idling or vehicle descent). Furthermore, the internal combustion engine temperature 814 higher than that indicated by the dashed line 820 threshold shown, indicating that the engine is warmed up. Therefore, at t3, the entry conditions for determining the fuel vapor pressure are met. However, in other examples, additional entry conditions may need to be met before the fuel vapor pressure is determined. For example, since fuel vapor pressure is dependent on fuel temperature in the fuel system, entry conditions may include fuel temperature remaining substantially constant for at least a threshold duration.

[0114] After determining that the entry conditions are met at t3, the controller modifies the operation of the lift pump to determine the fuel vapor pressure by the duty cycle of the voltage pulses applied to the fuel lift pump 808 is reduced. This reduction is not in response to a change in engine operating conditions (e.g., a decrease in engine load) or a decrease in desired (e.g., requested or commanded) boost pressure; instead, the reduction is performed solely for the purpose of determining the maximum delivery pressure of the fuel system that corresponds to the target pressure of the pressure relief valve. Although, for example, the internal combustion engine load 812 remains substantially constant from the period immediately prior to t3 to t3, at t3 the controller nevertheless reduces the duty cycle of the voltage pulses applied to the lift pump to perform the dynamic determination of fuel vapor pressure.

[0115] If the delivery pressure 810 the fuel vapor pressure 804 is reached, the waveform of the detected discharge pressure develops a flattened valley property. In the illustrated example, the delivery pressure reaches the fuel vapor pressure after the application of the first voltage pulse having a reduced pulse width and before the application of a second voltage pulse having a reduced pulse width. However, in other examples, the duty cycle reduction may be performed incrementally such that the sensed delivery pressure does not reach the fuel vapor pressure until multiple voltage pulses have been applied, advantageously reducing the steepness of the decrease in pressure supplied to the fuel injectors. Further, incrementally reducing the duty cycle provides the detection of flattened valleys while minimizing the decrease in delivery pressure so that the delivery pressure remains closer to the optimal delivery pressure at the current engine operating conditions.

[0116] In the map 800 For example, the fuel vapor pressure is 300 kPa and the detected delivery pressure waveform flattens out (remains constant) at 300 kPa for a non-trivial duration. This specific fuel vapor pressure is just an example; fuel vapor pressure varies depending on fuel system operating conditions (e.g., fuel temperature). Therefore, it may be beneficial to periodically re-evaluate the fuel vapor pressure.

[0117] In the illustrated example, the controller continues to monitor the sensed discharge pressure after flattening has been detected; specifically, a further voltage pulse is applied after an instance of flattening has been detected, so that the head pressure signal flattens twice at the valley. As discussed above with respect to determining the target pressure, applying one or more additional voltage pulses with a reduced pulse width relative to the nominal pulse width, even after detecting a first instance of flattening, can be beneficial in that it eliminates a false positive detection of flattening (e.g. when an anomaly occurs that results in a transient flattening of the sensed delivery pressure signal which is not indicative of actual fuel vapor pressure). However, in other examples, the controller may end the process of determining the fuel vapor pressure once flattening is detected and update the stored fuel vapor pressure to the pressure at which the flattening occurred. This may limit the amount of time that the boost pressure is modified from the requested boost pressure to perform the determination and thereby improve engine operation.

[0118] After detecting the flattening of the sensed discharge pressure waveform, the controller stores the pressure at which the sensed discharge pressure flattened as fuel vapor pressure in non-volatile memory. The routine 600 can be performed intermittently or optionally continuously during the pulsed operation of the lift pump to improve the accuracy of the closed-loop control. In other examples, the routine 600 only be carried out if the pulsed operation of the suction pump is initiated.

[0119] After determining the fuel vapor pressure, the controller returns operation of the lift pump to the routine 500 the end figure 5A with closed loop control scheme. For example, the controller can change the duty cycle of the voltage pulses applied to the lift pump 808 set to a value that reflects current engine operating parameters (e.g., the current characteristic of the desired lift pump delivery pressure determined by the history 806 is shown).

[0120] While the map 800 For example, dynamically determining target pressure, followed shortly thereafter by dynamically determining fuel vapor pressure, this sequence of events is exemplary only. Dynamically determining the desired pressure may be performed anytime the appropriate entry conditions (including engine load above the first, higher threshold) are met, and similarly dynamically determining the fuel vapor pressure may be performed anytime when the appropriate entry conditions (including engine load below the second, lower threshold) are met.

[0121] In examples where the vehicle in which the fuel system is included is a hybrid vehicle, the engine load may be increased or decreased if it is desirable to determine the desired pressure or fuel vapor pressure even if the engine load is not within the appropriate normal range ( e.g., above the first, higher threshold or below the second, lower threshold) by adding or subtracting an amount of load to the engine via the electric machine and battery. For example, instead of waiting for the engine load to exceed the first, higher threshold to determine the target pressure, the engine load may be increased above the first, higher threshold and the excess engine power may be used via the electric machine (operating in a generator mode ) are converted into electrical energy and stored in the energy storage device. Conversely, instead of waiting for the engine load to fall below the second, lower threshold to determine the fuel vapor pressure, the engine load may be reduced below the second, lower threshold, and the battery and electric machine (operating in an electric motor mode) may Provide supplemental torque to vehicle wheels such that the requested torque is still provided to the vehicle wheels despite the decrease in engine load.

[0122] Further, in examples where the vehicle in which the fuel system is included is a hybrid vehicle and the robust feedback control strategy is performed, a volume of fuel ingested by the engine may be monitored while the lift pump is OFF. If the volume of fuel ingested by the engine while the lift pump is OFF reaches a predetermined volume before an output signal from the pressure sensor has decreased to a desired valley pressure, the lift pump can be turned ON, the value of the output signal from the pressure sensor can stored as the first stored value and dynamically determining a fuel vapor pressure of the fuel system may be requested. If the volume of fuel ingested by the engine while the lift pump is OFF exceeds an expected amount for the current operating conditions, as discussed above, but the desired valley pressure has not yet been reached, this indicates that either the sensor is inaccurate or the fuel vapor pressure has changed (e.g., has risen above the desired valley pressure). To determine which of these problems is present, the controller may perform dynamic determination of fuel vapor pressure by reducing fuel rail pressure until it cannot be reduced any further. To do this without including desired engine operation during conditions where the requested engine output torque is above a threshold, the motor / generator may be used to supplement engine output torque. Thus, if a requested vehicle wheel torque is above a first threshold, the controller may send signals to actuators to mechanically couple an engine crankshaft to the electric motor / generator and reduce engine load until the pressure sensor output signal remains constant for at least a first threshold duration , while electrical energy is converted to torque with the electric motor / generator and the torque is provided to the vehicle wheels. The pressure at which the output signal remains constant may then be stored as the updated fuel vapor pressure, and if the updated fuel vapor pressure is less than the first stored value, the controller may indicate that the pressure sensor is reading too high. In this case, a calibration of the sensor output can then be performed, taking into account the difference between the updated fuel vapor pressure and the first stored value. Otherwise, the controller may indicate that the pressure sensor is measuring correct values ​​and is not degraded, and then perform feedback control of the lift pump based on the updated fuel vapor pressure.

[0123] Likewise, during pulsed operation of the lift pump, an ON time of the lift pump may be monitored; if the lift pump ON time reaches a calibrated maximum ON time before the pressure sensor output has increased to a desired peak pressure, the lift pump may be turned OFF, the value of the pressure sensor output stored as a second stored value, and dynamically determining a target pressure of the pressure relief valve can be requested. If the lift pump remains ON for a calibrated maximum ON time as discussed above, but the desired peak pressure has not yet been reached, this indicates that either the sensor is reading inaccurately or the pressure relief valve setpoint pressure has changed (e.g. from has decreased from the stored value). To determine which of these problems is present, the controller may perform dynamic determination of the desired pressure by increasing the fuel rail pressure until it cannot be increased any further. To do this without including desired engine operation during conditions where the requested engine output torque is below a threshold, the motor / generator may be used to absorb excess engine output torque. Thus, if a requested vehicle wheel torque is below a second threshold, the controller may send signals to actuators to mechanically couple the crankshaft to the electric motor / generator to increase engine load until the pressure sensor output signal remains constant for at least a second threshold duration, during converting part of the output torque of the internal combustion engine into electrical energy with the electric motor / generator and storing the electrical energy on the battery, and storing the pressure at which the output signal remains constant as the updated target pressure. If the updated target pressure is greater than the second stored value, the controller may indicate that the pressure sensor is reading too low. In this case, the sensor output can then be calibrated, taking into account the difference between the updated target pressure and the second stored value. Otherwise, the controller may indicate that the pressure sensor is measuring correct values ​​and is not degraded, and then perform feedback control of the lift pump based on the updated target pressure.

[0124] figure 9 shows an exemplary map 900 , the relevant signals for diagnosing an error lying within the normal range of a pressure sensor that detects the delivery pressure of a suction pump, z. B. in accordance with the routine 700 the end figure 7 illustrates. The map 900 shows the commanded lift pump discharge pressure at history 902 , the voltage applied to the suction pump at history 904 , the detected discharge pressure at history 906 , an indication of whether entry conditions have been met, on history 912 and an indication of a within-normal error in history 916 . In addition, the target pressure is symbolic as the dashed line 908 shown and fuel vapor pressure symbolized as the dashed line 910 shown. For all of the above, the X-axis represents time, with time increasing from left to right along the X-axis. The y-axis of the gradients 902 , 904 and 906 corresponds to the specified parameter, with the value increasing from bottom to top.

[0125] From t0 to t1, the controller performs closed-loop control of voltage pulses applied to the lift pump (eg, in accordance with the first or second example feedback control strategies described herein). As with history 904 shown, the applied voltage pulses have a pulse width 905 on. The pulsed operation generates as with course 906shown is a waveform for the sensed discharge pressure with a sawtooth shape. Before t1, the entry conditions for diagnosing an within-range failure of the pressure sensor are not met. For example, the engine temperature is below a threshold, the engine is not operating at steady state, and / or other entry conditions are not met. Also, during this period, an within-normal pressure sensor failure is not indicated (eg, an OBD flag indicating an within-normal pressure sensor failure is not set).

[0126] At time t1, control returns as in History 912 indicates that the entry conditions for diagnosing an within-range fault of the pressure sensor have been met (e.g., in response to measured and / or derived signals representing values ​​for engine load, engine temperature, etc.). In response to this indication, the controller initiates a routine for diagnosing an within-range failure of the pressure sensor, such as the routine 700 the end figure 7. This may include first determining a threshold duration for which the detected feed pressure remains constant during proper sensor operation. In the map 900 an example threshold duration at 918 is shown. The threshold can optionally be determined on the controller depending on the pulse width, e.g. B. as a fraction of the pulse width. For example, the controller may make a logical determination of an appropriate threshold duration for current engine and fuel system operating conditions based on logic rules as a function of pulse width. In the example shown, is the threshold duration 918 smaller than the pulse width 905 . It is understood that the threshold duration can be significantly less than the pulse width (e.g., less than 1 / 100 of the pulse width) without departing from the scope of this disclosure.

[0127] From t1 to t2, the controller performs the diagnostic routine by monitoring the sensed head pressure to determine whether it remains constant (eg, levels off) for longer than the threshold duration. As with history 906 shown, the sensor operates within the normal range with the expected sawtooth output until just before t2. However, just prior to t2, an within-range error of the sensor begins to occur; at t2, the detected delivery pressure has remained constant for the threshold duration. In this example, the flattening occurs at the bottom of the waveform, indicating that the pressure sensor is reading too high. However, when performing the diagnostic, the controller may ignore the magnitude of the pressure at which the flattening occurs and thus not distinguish between flattening of the valley and the peak (e.g., the diagnostic will be independent of the magnitude of the pressure at which the detected signal remains constant). Such operation can advantageously simplify the control strategy.

[0128] Upon detecting at t2 that the sensed discharge pressure has remained constant for the threshold duration, the controller indicates an within-range error of the pressure sensor, as at history 916 is shown. Further, at t2, the controller switches from closed loop control of the lift pump, where voltage pulses are applied to the lift pump, to open loop control of the lift pump, where a non-zero steady state voltage is applied to the lift pump. Like history, for example 904As shown, starting at t2, a non-zero steady state voltage is applied to the lift pump. In response to the application of the non-zero steady-state voltage, the sensed delivery pressure increases to a pressure greater than an average pressure of the sawtooth waveform and then remains substantially constant at that pressure (assuming a constant fuel injection rate). However, the delivery pressure may vary in response to variance in fuel injection rate that occurs during open-loop operation of the fuel pump. By switching to open-loop control of the lift pump when an within-range pressure sensor error is detected, control no longer relies on the inaccurate feedback from the pressure sensor. This in turn improves the robustness of the lift pump control and reduces the likelihood of an inappropriate amount of fuel being delivered to the engine cylinders.

[0129] At the one in the map 900 In the example shown, an error of the pressure sensor that is within the normal range is indicated as soon as the sensed discharge pressure has remained constant for the threshold duration. In other examples, such as that in the map 1000 the end figure 10, the controller may continue to monitor the sensed discharge pressure during the application of multiple voltage pulses to ensure that the sensed flattening is not accidental.

[0130] Now, referring to figure 10 another exemplary map 1000 shown, the relevant signals for diagnosing an error lying within the normal range of a pressure sensor that detects the delivery pressure of a suction pump, z. B. in accordance with the routine 700 the end figure 7 illustrates. The map 1000 shows the commanded lift pump discharge pressure at history 1002 , the voltage applied to the suction pump at history 1004 , the detected discharge pressure at history 1006 , an indication of whether entry conditions have been met, on history 1012 and an indication of a within-normal error in history 1016 . In addition, the target pressure is symbolic as the dashed line 1008 shown and fuel vapor pressure symbolized as the dashed line 1010 shown. For all of the above, the X-axis represents time, with time increasing from left to right along the X-axis. The y-axis of the gradients 1002 , 1004 and 1006 corresponds to the specified parameter, with the value increasing from bottom to top.

[0131] From t0 to t1, the controller performs closed-loop control of voltage pulses applied to the lift pump, as above with respect to the map 900 described. While those in the map 900 However, the closed-loop control shown is performed in accordance with either the first or second exemplary feedback control strategy is that in the map 1000 For example, the closed-loop control shown is inconsistent with the second exemplary feedback control strategy (since the control does not "stick" when the desired peak pressure is not achieved due to flattening). However, in other examples, an error within the normal range may be detected when peak flattening occurs during closed-loop control of the lift pump in accordance with the second example feedback control strategy.

[0132] Prior to t1, entry conditions for diagnosing an within-bounds fault of the pressure sensor are not met and no within-bounds fault is indicated. As with history 1006 shown, however, there is an error within the normal range, as evidenced by the flattening of the peaks of the sensed pressure signal.

[0133] At time t1, control returns as in History 912indicates that the entry conditions for diagnosing an within-range fault of the pressure sensor have been met, and initiates a routine for diagnosing an within-range fault, such as the routine 700 the end figure 7. As above with reference to the map 900 discussed, this may include first determining a threshold duration for which the sensed discharge pressure remains constant during proper sensor operation; an example threshold duration is shown at 1018 . In the example shown, is the threshold duration 1018 smaller than the pulse width 1005 of the voltage pulses applied to the suction pump.

[0134] From t1 to t2, the controller performs the diagnostic routine by monitoring the sensed head pressure to determine whether it remains constant (eg, levels off) for longer than the threshold duration. As noted above, by the time the diagnostic routine is initiated, an error within the normal range is occurring; upon application of the first voltage pulse applied during the diagnostic routine, the sensed discharge pressure rises and then levels off, lasting longer than the threshold duration 1018 remains constant. While the control at the in the map 900 The example diagnostic routine shown indicates a fault within the normal range once flattening is detected for the threshold duration, the map shows 1000 Figure 12 shows an example diagnostic routine in which control waits until multiple discrete instances of flattening have been detected before indicating an within-normal-range fault. Specifically, in the example shown, the controller does not indicate an error within the normal range until the sensed discharge pressure remains constant for the threshold duration a third time, which occurs at t2. This example is not limiting; in other examples, the controller may wait until flattening has occurred one, two, three, four, five or more times before indicating an error that is within the normal range. Alternatively, another routine for detecting flattening of the sensed pressure signal may be performed by the controller without departing from the scope of this disclosure.

[0135] After indicating the error within the normal range as in the map 900 switches the control from closed loop control of the lift pump to open loop control of the lift pump. Like history, for example 1004 As shown, a non-zero steady-state voltage is applied to the lift pump after t2. As shown, the steady state voltage is not applied until the sensed discharge pressure has decreased by some amount from the flattened peak pressure; such operation may be appropriate since the desired discharge pressure may be less than the peak pressure during pulsed operation of the lift pump. However, in other examples, the steady state voltage may be applied once the within-normal fault is detected, or the voltage may be increased to the steady state voltage, or another strategy to transition from pulsed operation to continuous operation of the lift pump may be used. In any event, the sensed delivery pressure increases in response to the application of the non-zero steady-state voltage to a pressure greater than an average pressure of the sawtooth waveform and then remains substantially constant at that pressure (assuming a constant fuel injection rate). However, the delivery pressure may vary in response to variance in fuel injection rate that occurs during open-loop operation of the fuel pump.

[0136] The routine 700 and the maps 900 and 1000are associated with diagnosing an within-range pressure sensor failure and adjusting the lift pump control from closed-loop to open-loop control accordingly. Alternatively, instead of transitioning to open-loop control of the lift pump when an within-range pressure sensor error occurs, an example feedback control strategy, referred to herein as robust control, may be employed.

[0137] figure 11 shows an example routine 1100 to perform robust control of a fuel lift pump in accordance with the third example feedback control strategy. This robust control strategy may advantageously allow closed loop feedback control of the lift pump to persist even in the event of pressure sensor degradation or an increase in fuel vapor pressure that has not been detected by the controller, while minimizing stalls and over fuel consumption. The routine 1100 can be in conjunction with the routine 500 the end figure 5A can be performed at 508, for example.

[0138] at 1102 includes the lift pump ON routine. As above for the routine 530 discussed, this may include, for example, the controller adjusting an actuator of the lift pump to apply a predetermined higher voltage level to the lift pump that rapidly raises the lift pressure to that specified in the routine 500 certain desired peak pressure (e.g. 8-12V).

[0139] After 1102 the routine proceeds to 1104 and control determines whether the sensed discharge pressure is less than the desired peak discharge pressure. For example, the controller may receive a signal from a pressure sensor indicative of discharge pressure and compare this sensed discharge pressure to the stored value of the previously determined desired peak discharge pressure. If the answer at 1104 is YES, indicating that either the head pressure has not yet reached the desired peak pressure or the sensor output is inaccurate, the routine proceeds to 1106 .

[0140] at 1106 the controller determines whether the amount of time that the lift pump has been ON is less than a calibrated maximum value. The calibrated maximum value may be a predetermined value stored in memory, or alternatively during execution of the routine 1100 responsive to various engine operating parameters (e.g., fuel consumption rate, engine speed, voltage level applied to the lift pump, etc.) at the controller. The calibrated maximum value represents the maximum duration that the lift pump should remain in the ON state during conditions where pressure sensor degradation or other failure is preventing the sensed discharge pressure from reaching the desired peak pressure. If the answer at 1106 is YES, the routine returns to 1104. Otherwise, if the answer at 1106 is NO, indicating that the lift pump has already been ON for at least the calibrated maximum duration, the routine returns to 1102 or optionally transitions to 1108 .

[0141] at 1108 the controller calibrates the output of the pressure sensor to produce a more accurate indication of the actual discharge pressure. If the lift pump remains ON for at least the calibrated maximum duration, this may be due to flattening of the signal from the sensor, reflecting that the actual discharge pressure is equal to the pressure relief valve set pressure. Such flattening can be done, for example, in accordance with the method figure7 to be determined. In an example calibration strategy, after determining that the lift pump has remained ON for the calibrated maximum duration, control proceeds to determining whether the sensed supply has remained constant (eg, leveled off) for longer than a threshold duration. If so, the controller then determines a pressure offset as the difference between the desired pressure relief valve pressure and the pressure at which the sensed discharge pressure flattened out and calibrates the output of the pressure sensor by adding the offset to the sensed discharge pressure. Thus, the calibrated delivery pressure generated at the controller at any given time can be equal to the sum of the offset and the currently sensed delivery pressure. The calibrated boost pressure can then replace the sensed boost pressure in the feedback control performed by the controller, which can advantageously improve the accuracy of the lift pump control and thereby improve fuel economy. This example calibration strategy is in figure 12B, discussed below, and is appropriate when the pressure sensor is consistently reading too low. However, other methods of calibrating sensed head pressure may be performed without departing from the scope of this disclosure.

[0142] After 1108 the routine goes to 1110. Further, if the answer at 1104 is NO, indicating that the sensed discharge pressure has reached the desired peak discharge pressure, the routine proceeds to 1110 . at 1110 includes the lift pump OFF routine. As above with reference to the routine 530 discussed, may include, for example, the controller setting an actuator of the lift pump to apply a predetermined lower voltage level to the lift pump that is low enough to keep the lift pump energized (e.g., greater than 0V and less than 0.3 V), and does not significantly increase the fuel pressure. However, in other examples, turning the lift pump OFF may include the controller setting an actuator of the lift pump to apply 0V to the lift pump. The predetermined lower voltage level may, for example, via execution of the routine 500 to be determined. By turning the lift pump OFF when the lift pump ON duration has reached the calibrated maximum duration, regardless of whether the sensed discharge pressure has reached the peak discharge pressure, the pulsed operation of the lift pump can continue even if the pressure sensor is degraded. For example, if the sensor is degraded and reading too low, the sensed discharge pressure may remain unchanged at a level below the desired peak pressure when normal closed-loop control of the lift pump (e.g., the routine from figure 5C) is performed since the control strategy cannot turn the lift pump OFF until the desired peak pressure has been reached. In contrast, the robust control strategy relies on routine 1100 the lift pump control "backs off" when the lift pump has reached the calibrated maximum ON time, regardless of whether the head pressure has reached the desired peak head pressure.

[0143] After 1110 the routine proceeds to 1112 and control determines a target pressure drop ΔP between the peak and valley pressures and a system stiffness S. The target pressure drop ΔP represents the desired amount that the discharge pressure decreases during the period beginning when the lift pump is turned OFF and ends when the lift pump is turned ON again, and may equal, for example, the difference between the desired peak pressure and the desired valley pressure. The system stiffness S may represent the bulk modulus of the fluid within the fuel system (e.g., fuel or fuel and air). The bulk modulus can depend on the density of the fluid within the fuel system and can be given by the equation = ρ d P d ρ be shown, where ρ is the density of the fluid in the fuel system, P is the pressure in the fuel system (z. B. the delivery pressure). The value of S may be obtained at the controller via a lookup table stored in memory at the controller, or alternatively may be obtained at the controller as a function of currently sensed parameter values ​​such as sensed head pressure as well as known dimensions of the fuel system (eg The volume of a fuel passage within the fuel system) stored in memory at the controller can be calculated. Notably, since the equation relies on the rate of change of the sensed discharge pressure rather than the magnitude of the sensed discharge pressure, it may be possible to accurately determine S even when the pressure sensor output is offset due to deterioration.

[0144] After 1112 the routine proceeds to 1114 and control determines a volume V of fuel ingested by the engine while the lift pump is OFF that should trigger an OFF to ON state transition of the lift pump. V can be determined at the controller as a function of ΔP and S, for example via the equation = in a non-limiting example Δ P s . The specific volume V represents the volume of fuel that, when ingested by the internal combustion engine (e.g. via fuel injection), from the point in time when the delivery pressure is at the desired peak pressure, given the current stiffness S of the fuel system, the delivery pressure from that desired peak pressure should reduce to the desired valley pressure. If the volume V of fuel has been ingested by the engine since the lift pump was turned OFF, with the head pressure at the desired peak pressure, and the head pressure sensed is still greater than the desired valley pressure, this may indicate that the pressure sensor is compromised (e.g. reading too high) or the fuel vapor pressure is higher than the value stored in the controller.

[0145] After 1114 the routine proceeds to 1116 and control determines whether the sensed head pressure is greater than the desired valley head pressure. If the answer at 1116 is NO, indicating that the sensed head pressure has reached the desired valley pressure, the routine returns to 1102 to turn the lift pump ON and another voltage pulse is applied to the lift pump. However, it is understood that the routine 1100 can be interrupted at any time (e.g., via a system interrupt) to terminate the lift pump's robust feedback control.

[0146] Otherwise, if the answer at 1116 is YES, the routine continues to 1118 and control determines whether the volume of fuel ingested by the engine since the lift pump was turned OFF is greater than the volume V determined at 1114 . The volume of fuel ingested by the engine since the lift pump was turned OFF may be equal to the amount of fuel consumed during the period beginning when the lift pump was turned OFF and ending after the execution of 1118 by the fuel system has been injected into the internal combustion engine and can be determined at the controller depending on sensed values ​​and / or data stored in memory regarding the regulation of the fuel injectors during the relevant period.

[0147] If the answer at 1118 is NO, the routine returns to 1116. Otherwise, if the answer at 1118 is YES, the routine returns to 1102 or optionally transitions to 1120 before returning to 1102 .

[0148] at 1120the controller calibrates the output of the pressure sensor that senses the discharge pressure to produce a more accurate indication of the actual discharge pressure. If the volume of fuel ingested by the engine since the lift pump was turned OFF is greater than the volume V, this may occur due to flattening of the signal from the sensor reflecting the actual delivery pressure equal to the fuel vapor pressure is. Such flattening can be done, for example, in accordance with the method figure 7 to be determined. In an example calibration strategy, after determining that the volume of fuel ingested by the engine since the lift pump was turned OFF is greater than volume V, control proceeds to determining whether the sensed inflow is longer than a threshold duration has remained constant (e.g. has flattened out). If so, the controller then determines a pressure offset as the difference between the pressure at which the sensed delivery pressure flattened out and the fuel vapor pressure, and calibrates the output of the pressure sensor by subtracting the offset from the sensed delivery pressure. Thus, the calibrated delivery pressure generated at the controller at a given point in time can be equal to the currently recorded delivery pressure minus the offset. The calibrated delivery pressure may then replace the sensed delivery pressure in the feedback control performed by the controller, which may beneficially improve engine operation by reducing the likelihood of stalling due to low fuel rail pressure. This example calibration strategy is in figure 12D, discussed below, and is appropriate when the pressure sensor is consistently reading too high.

[0149] After 1120 the routine returns to 1102 or optionally ends if the controller supports robust feedback control of the lift pump, e.g. B. ended due to shutdown of the internal combustion engine. By returning to 1102 and turning ON the lift pump when the volume of fuel ingested by the engine reaches a predetermined level, regardless of whether the sensed lift pressure has decreased to the desired valley lift pressure, the pulsed operation of the lift pump can continue even if the pressure sensor is impaired. For example, if the sensor is degraded and reading too high, the sensed head pressure may remain unchanged at a level above the desired valley pressure when normal closed-loop control of the lift pump (e.g., the routine from figure 5C) is performed since the control strategy cannot turn ON the lift pump until the desired valley pressure has been reached. In contrast, the robust control strategy relies on routine 1100 the suction pump control "reverse" when a certain amount of fuel has been taken up by the combustion engine, regardless of whether the delivery pressure has reached the desired peak delivery pressure. Such control may advantageously reduce engine stalls due to insufficient fuel delivery pressure.

[0150] It is understood that in the case of calibration of the detected delivery pressure during execution of the routine 1100 is initiated during a given period of operation, the calibrated discharge pressure and the sensed discharge pressure on subsequent iterations of the routine 1100 can replace during this period of operation. Depending on the accuracy of the calibrated delivery pressure, further calibration may be performed during subsequent execution of the routine 1100 not be necessary. Alternatively, if the pressure sensor degradation worsens, further calibration may be performed.

[0151] figure 12A- figure 12D show example maps depicting relevant signals during control of the lift pump in accordance with the third example feedback control strategy, e.g. B. in accordance with the routine 1100 the end figure11 illustrate. For simplicity, in the illustrated maps, the engine is operating at steady state, fuel is being ingested by the engine at a constant rate, and the magnitude of each voltage pulse applied to the lift pump is the same.

[0152] First up figure 12A, which shows an example map 1200 shows that the voltage applied to the suction pump at course 1202 , the actual delivery pressure of the suction pump with history 1204 and the sensed lift pump discharge pressure at history 1206 represents. For all of these traces, the x-axis represents time, with time increasing from left to right along the x-axis. The Y-axis of each gradient corresponds to the specified parameter, with the value increasing from bottom to top. In addition, that line 1208 represents the (actual) target pressure of the pressure relief valve, the line 1210 represents the desired peak delivery pressure, the line 1212 represents the desired valley head and the line 1214 represents the (actual) fuel vapor pressure.

[0153] Shortly after t0, the recorded delivery pressure reaches the desired valley delivery pressure 1212 ; in response, the controller turns ON the lift pump (e.g., by sending a signal to an actuator of the lift pump). However, the pressure sensor that records the delivery pressure measures values ​​that are too low; the sensed delivery pressure is lower than the actual delivery pressure by a first amount. Accordingly, the lift pump is turned ON when the actual head pressure is higher than the desired valley head pressure. Here, the first magnitude happens to be less than the difference between the desired pressure relief valve pressure and the desired peak pressure. Accordingly, when the sensed discharge pressure reaches the desired peak pressure, the actual discharge pressure has not yet reached the pressure relief valve target pressure. In response to detecting that the sensed discharge pressure has reached the desired peak pressure, the controller turns the lift pump OFF. Before turning OFF, the suction pump was ON for a period of time 1216 long switched ON that is shorter than a calibrated maximum ON time 1218 the suction pump is. After the lift pump is turned off, the actual delivery pressure decreases at a rate that corresponds to the rate at which fuel is being ingested from the fuel system by the internal combustion engine.

[0154] At t1, the pressure sensor is further degraded and begins to measure even lower values ​​such that the sensed discharge pressure is lower than the actual discharge pressure by a second amount, the second amount being greater than the first amount. The second magnitude happens to be greater than the difference between the desired pressure relief valve pressure and the desired peak pressure. The sensed head pressure increases to the desired valley pressure at t2 before the actual head pressure has decreased to the desired valley pressure (because the pressure sensor reads too low). Here, the controller turns the lift pump ON again at t2 after detecting that the sensed head pressure has reached the desired valley pressure.

[0155] At t3, the actual delivery pressure reaches the pressure relief valve set pressure, causing the pressure relief valve to open and vent excess fuel pressure. However, since the difference between the actual discharge pressure and the sensed discharge pressure is greater than the difference between the target pressure of the pressure relief valve and the desired peak discharge pressure, the sensed discharge pressure has not yet reached the desired peak pressure at t2. Accordingly, the lift pump remains ON, the actual discharge pressure remains constant (levels off) at the current setpoint pressure of the pressure relief valve, and the sensed discharge pressure remains constant (levels off) at a pressure below the desired peak pressure.

[0156] At t4, the controller recognizes that the lift pump has exceeded the calibrated maximum ON time 1218 has remained ON for a long time, and turns OFF the lift pump in response thereto, as above with respect to the routine 1100discussed. Accordingly, although the sensed discharge pressure has not reached the desired peak pressure, the length of time that the lift pump has been ON without reaching the desired peak value indicates that the output of the sensor may be inaccurate and the controller turns the lift pump OFF , allowing pulsed operation to continue. Such operation is in contrast to the second exemplary feedback control strategy discussed herein, in which the lift pump is turned OFF when the sensed lift pressure reaches the desired peak pressure, which can result in the lift pump continuing to be ON even though the actual lift pressure exceeded the desired peak pressure and has reached the set pressure of the pressure relief valve.

[0157] After t4, the controller continues to turn ON the lift pump when the sensed head pressure has decreased to the desired valley pressure and continues to turn OFF the lift pump when the calibrated maximum ON time has been reached. As shown, since the extent to which the sensor is under reading remains constant after t4, the lift pump remains the calibrated maximum ON time each time a voltage pulse is applied 1218 long switched ON. Thus, although the sensor is degraded and under-measures, the robust feedback control strategy allows the pulsed operation of the lift pump to be performed, thereby improving fuel economy.

[0158] figure 12B shows an example map 1240 , which illustrates the same signals as the map 1200 and also depicts lift pump operation in accordance with the third example feedback control strategy. In the map 1240 however, at t3, after detecting that the lift pump has remained ON for the calibrated maximum ON time, the controller initiates a calibration of the pressure sensor output. The history 1242 represents the calibrated pressure sensor output.

[0159] In the example shown, the controller determines the calibrated pressure sensor output by adding an offset 1244 to the sensed discharge pressure, which is equal to the difference between the set pressure of the pressure relief valve and the pressure at which the sensed discharge pressure leveled off between t2 and t3. From t3 onwards, the feedback control based on the calibrated pressure sensor output 1242 carried out instead of the recorded delivery pressure 1206 . Accordingly, if the sensed discharge pressure reaches the desired valley pressure at t4, the controller does not turn ON the lift pump; instead, the lift pump remains OFF until the calibrated pressure sensor output reaches the desired valley pressure at t5. Likewise, the lift pump is turned OFF as soon as the calibrated pressure sensor output reaches the desired peak pressure at t6, although the sensed discharge pressure has not yet reached the desired peak pressure. As shown, the calibrated pressure sensor output corresponds 1242 from t3 the actual discharge pressure 1204 , so that the suction pump can be controlled accurately and efficiently despite the erroneous output of the pressure sensor.

[0160] figure 12C shows an example map 1260 , which illustrates the same signals as the map 1200 and also depicts lift pump operation in accordance with the third example feedback control strategy. However, while the maps 1200 and 1240 To illustrate lift pump operation during sensor degradation causing the sensor to read too low, the map illustrates 1260 lift pump operation during sensor degradation causing the sensor to read too high. The map 1260 also illustrated in the course 1262 the volume of fuel ingested by the internal combustion engine and provides example values ​​for actual delivery pressure and sensed delivery pressure. Specifically, in the illustrated non-limiting example, the desired valley head is 400 kPa and the desired peak head is 600 kPa.

[0161] Shortly after t0, the sensed head pressure has decreased to the desired valley pressure and thus the controller turns ON the lift pump. Since the sensor measures values ​​that are too high, the actual delivery pressure at this point in time is lower than the desired valley pressure by a first amount. Here the first magnitude happens to be less than the difference between the desired valley pressure and the fuel vapor pressure. Accordingly, when the sensed delivery pressure reaches the desired valley pressure, the actual delivery pressure has not yet reached the fuel vapor pressure and thus the signals have not flattened out. After the lift pump is turned ON, the actual discharge pressure decreases at a rate that corresponds to the magnitude of the voltage applied to the lift pump.

[0162] At t1, the sensed discharge pressure reaches the desired peak pressure and in response the controller turns the lift pump OFF. Because the pressure sensor measures values ​​that are too high, the actual discharge pressure has not yet reached the desired peak pressure. Accordingly, the delivery pressure is lower than the requested delivery pressure for the current engine operation.

[0163] At t2, the pressure sensor degrades further and begins to measure even higher values ​​such that the sensed discharge pressure is higher than the actual discharge pressure by a second amount, the second amount being greater than the first amount. The second magnitude happens to be greater than the difference between the desired valley pressure and the fuel vapor pressure. The actual delivery pressure decreases to the desired valley pressure slightly before t2 and then reaches the fuel vapor pressure at t2, causing the signal to flatten out. Because the pressure sensor is reading too high and because the second magnitude is greater than the difference between the desired valley pressure and the fuel vapor pressure, the sensed delivery pressure levels off at a pressure that is higher than the desired valley pressure. Because the sensed lift pressure has not reached the desired valley pressure, the controller does not turn ON the lift pump and the actual lift pressure remains at the fuel vapor pressure. If this were to continue for too long, the internal combustion engine could stall.

[0164] To prevent stalling, control monitors as above with reference to the routine 1100 discusses the volume of fuel ingested by the engine and compares it to a volume V of fuel ingested by the engine while the lift pump is OFF, which should trigger an OFF to ON state transition of the lift pump. As stated above, the volume V can be equal to the quotient of the intended pressure drop ΔP between the desired peak pressure and the desired valley pressure and a system stiffness S . In the example shown, the intended pressure drop ΔP is 200 kPa and the system stiffness is 100 kPa / cm 3 and the volume V is therefore 2 cm 3 . For example, the history 1262 assume that at t1 2 cm 3 Fuel was added at t4 4 cm 3 fuel have been included and so on; this is illustrative only and does not represent actual cumulative amounts of fuel ingestion that would occur over the course of engine operation. In other examples, the controller may reset the ingested volume of fuel V to 0 each time the lift pump is turned OFF.

[0165] At t1, when the lift pump was turned OFF, the volume of fuel taken was 2 cm 3 . At t4, the ingested volume of fuel 4 cm 3 reached, and thus 2 cm 3 Fuel has been ingested since the lift pump was turned OFF. Since the volume V to trigger a transition of the state of the suction pump to 2 cm 3is set, the controller turns ON the lift pump at t4. Accordingly, although the sensed discharge pressure has not reached the desired peak pressure, once the volume V has been taken, the lift pump is turned ON so that the pulsed operation can continue. Such operation is in contrast to the second example feedback control strategy discussed herein, in which the lift pump is turned ON again when the sensed lift pressure reaches the desired valley pressure, which can result in the lift pump continuing to be OFF even though the actual lift pressure reaches fuel vapor pressure has.

[0166] After t4, the controller continues to turn OFF the lift pump when the sensed delivery pressure has increased to the desired peak pressure, and turns ON the lift pump when the volume of fuel ingested by the engine since the lift pump was turned OFF is 2 cm 3 achieved. Thus, although the sensor is degraded and measuring too high values, the robust feedback control strategy allows the pulsed operation of the lift pump to be performed, thereby improving fuel economy.

[0167] figure 12D shows an example map 1280 , which illustrates the same signals as the map 1260 and also depicts lift pump operation in accordance with the third example feedback control strategy. In the map 1280 however, after recognizing that the volume V of fuel has been ingested since the lift pump was turned OFF, the controller initiates a calibration of the output of the pressure sensor. The history 1282 represents the calibrated pressure sensor output.

[0168] In the example shown, the controller determines the calibrated pressure sensor output by subtracting an offset 1284 of the sensed delivery pressure, which is equal to the difference between the pressure at which the sensed delivery pressure leveled off between t3 and t4 and the fuel vapor pressure. From t4, the feedback control is based on the calibrated pressure sensor output 1282 carried out instead of the recorded delivery pressure 1206 . Accordingly, when the sensed discharge pressure reaches the desired peak pressure at t5, the controller does not turn ON the lift pump; instead, the lift pump remains OFF until the calibrated pressure sensor output reaches the desired peak pressure at t6. Likewise, once the calibrated pressure sensor output reaches the desired valley pressure at t7, the lift pump is turned OFF even though the sensed head pressure has not yet reached the desired valley pressure. As shown, the calibrated pressure sensor output corresponds 1282 from t4 the actual discharge pressure 1204 , so that the suction pump can be controlled accurately and efficiently despite the erroneous output of the pressure sensor.

[0169] Consistent with the foregoing, a method for a method of during operation of a lift pump in the pulsed mode includes adjusting a voltage level applied to the lift pump based on an output signal from a pressure sensor downstream of the lift pump and monitoring the output signal for flattening; and in response to a detection of flattening, indicating a pressure sensor failure and operating the lift pump independent of the output of the pressure sensor. In a first example of the method, monitoring the output signal for flattening includes comparing a period of time during which a slope of the output signal is zero to a threshold period. A second example of the method optionally includes the first example and further includes wherein operating the lift pump independent of the output of the pressure sensor comprises: operating the lift pump in a continuous mode in which a non-zero continuous voltage is applied to the lift pump. A third example of the method optionally includes one or more of the first and second examples and further includes wherein operating the lift pump independently of the output of the pressure sensor comprises: operating the lift pump in a pulsed mode in which the voltage level applied to the lift pump is not set based on the output of the pressure sensor. A fourth example of the method optionally includes one or more of the first through third examples and further includes wherein adjusting the voltage level applied to the lift pump based on the output of the pressure sensor includes adjusting a duty cycle of the voltage pulses based on the output. A fifth example of the method optionally includes one or more of the first through fourth examples and further includes wherein adjusting the duty cycle of the voltage pulses based on the output signal comprises: increasing the duty cycle when a peak pressure of the output signal is less than a desired peak pressure, and reducing the duty cycle when the peak pressure is greater than the desired peak pressure. A sixth example of the method optionally includes one or more of the first through fifth examples and further includes wherein adjusting the voltage level applied to the lift pump based on the output of the pressure sensor comprises: applying a first, higher voltage to the lift pump when the output of the pressure sensor decreases to a desired valley pressure, and applying a second, lower voltage to the lift pump when the output of the pressure sensor increases to a desired peak pressure. A seventh example method optionally includes and further includes one or more of the first through sixth examples, wherein the pressure sensor error is an error within the normal range, the method further comprising: in response to the output signal exceeding an expected operating range of the pressure sensor increases or decreases below, indicating an out-of-range fault of the pressure sensor, and operating the lift pump independent of the output of the pressure sensor.

[0170] Further consistent with the foregoing, an additional method of operating a fuel system of an internal combustion engine may include: during steady state operation of the internal combustion engine with a requested delivery pressure of a fuel lift pump being below a first threshold, reducing a duty cycle of voltage pulses applied to a fuel lift pump until flattening of an output signal of a pressure sensor downstream of the lift pump is detected, and storing the pressure at which the output signal has flattened as a fuel vapor pressure of the fuel system; during steady state operation of the internal combustion engine with a requested delivery pressure of the fuel lift pump being above a second threshold, increasing a duty cycle of voltage pulses applied to the lift pump until flattening of the output signal of the pressure sensor is detected, storing the pressure at which the output signal flattens out has, as a target pressure of a pressure relief valve; and adjusting lift pump operation based on the stored desired pressure and fuel vapor pressure.

[0171] In a first example of the additional method, adjusting lift pump operation based on the stored target pressure and fuel vapor pressure includes setting a desired peak lift pump lift pressure to be less than the stored target pressure by a first predetermined amount, and setting a desired lift pump valley pressure to be is greater than the stored fuel vapor pressure by a second predetermined amount. A second example of the additional method optionally includes the first example and further includes wherein adjusting operation of the lift pump based on the stored desired pressure and fuel vapor pressure further comprises: applying a first, higher voltage while operating the lift pump in a pulsed mode the lift pump each time the pressure sensor output decreases to the desired valley pressure; and applying a second, lower voltage to the lift pump each time the pressure sensor output increases to the desired peak pressure. A third example of the additional method optionally includes one or more of the first and second examples, and further includes wherein adjusting lift pump operation based on the stored target pressure and fuel vapor pressure comprises: determining a duty cycle of voltage pulses that, when applied to the lift pump, produces an output signal having a maximum value at the desired peak lift pressure and a minimum value at the desired valley lift pressure, and applying voltage pulses to the lift pump at the determined duty cycle. A fourth example of the additional method optionally includes one or more of the first through third examples and further includes wherein the requested fuel lift pump delivery pressure is directly proportional to engine load. A fifth example of the additional method optionally includes one or more of the first through fourth examples and further includes during the application of voltage pulses to the lift pump at the determined duty cycle, monitoring the output signal of the pressure sensor for flat and indicating a pressure sensor fault in response to a detection of flat and operating the lift pump independently of the output of the pressure sensor. A sixth example of the additional method optionally includes one or more of the first through fifth examples and further includes wherein operating the lift pump independent of the output of the pressure sensor comprises: operating the lift pump in a continuous mode in which a non-zero continuous voltage is applied applying the lift pump, or operating the lift pump in a pulsed mode in which the voltage pulses applied to the lift pump are not adjusted based on the output of the pressure sensor.

[0172] Also consistent with the foregoing description, a hybrid vehicle includes a powertrain including an engine, an electric motor / generator, a battery, and a transmission coupled to vehicle wheels; a fuel system including a fuel tank, a fuel lift pump, a pressure sensor disposed downstream of an outlet of the lift pump in the fuel system, and a pressure relief valve; a controller including non-transitory memory with instructions stored therein executable by a processor to: responsive to a request to dynamically determine a fuel vapor pressure of the fuel system during pulsed operation of the lift pump where the requested vehicle wheel torque is above a first threshold, mechanically coupling a crankshaft of the engine to the motor / generator, reducing engine load until an output signal of the pressure sensor remains constant for at least a first threshold duration while electrical energy is converted to torque with the motor / generator and the torque is provided to the vehicle wheels, and Storing the pressure at which the output signal remains constant as the fuel vapor pressure. In a first example for the hybrid vehicle, the controller further includes instructions stored in non-transitory memory and executable by a processor to: responsive to a request to dynamically determine a desired pressure relief valve pressure during pulsed operation of the lift pump, wherein the requested output torque of the engine is below a second threshold, mechanically coupling the crankshaft to the motor / generator, increasing the engine load until the output of the pressure sensor remains constant for at least a second threshold duration while converting a portion of the output torque of the engine to the motor / generator into electrical energy is converted and the electric power is stored at the battery, and storing the pressure at which the output signal remains constant as the target pressure. A second example hybrid vehicle optionally includes and further includes the first example, wherein the controller further comprises instructions stored in non-transitory memory and executable by a processor to: perform closed-loop control of the lift pump based on an output of the pressure sensor is, monitoring the output signal; in response to the output signal remaining constant for at least a threshold duration, indicating an error within the normal range, and switching from closed-loop to open-loop control of the lift pump, wherein lift pump operation is discontinued independent of the pressure sensor output. A third example hybrid vehicle optionally includes one or more of the first and second examples, and further includes, wherein the instructions stored in non-transitory memory and executable by the processor to switch from closed-loop control to open-loop control of the lift pump, wherein lift pump operation is adjusted independent of the output of the pressure sensor, comprise instructions for applying a non-zero steady state voltage to the lift pump. A fourth example hybrid vehicle optionally includes and further includes one or more of the first through third examples, wherein the controller further comprises instructions stored in non-transitory memory and executable by a processor to: after storing the pressure at which the output signal remains constant as fuel vapor pressure adjusting a duty cycle of voltage pulses applied to the lift pump based on a desired pressure margin between fuel vapor pressure and lift pump discharge pressure.

[0173] In addition, consistent with the foregoing description, a method of operating a fuel system of an internal combustion engine during pulsed operation of a lift pump includes turning OFF the lift pump when a sensed discharge pressure increases to a desired peak pressure or an ON time of the lift pump reaches a calibrated maximum, and turning ON the lift pump when either the sensed delivery pressure decreases to a desired valley pressure or a volume of fuel ingested by the engine reaches a predetermined volume. A first example of this method includes determining the predetermined volume as a function of a difference between the desired peak pressure and the desired valley pressure and a stiffness of the fuel system. A second example of this method optionally includes the first example and further includes wherein the predetermined volume is set equal to the quotient of the difference between the desired peak and desired valley pressures and the stiffness of the fuel system. A third example of this method optionally includes one or more of the first and second example and further includes determining the stiffness of the fuel system as a function of a density of fluid within the fuel system. A fourth example of this method optionally includes one or more of the first through third examples and further includes, in response to the lift pump ON-time reaching the calibrated maximum, indicating an error of the pressure sensor within the normal range and initiating a calibration of the sensed Discharge pressure, wherein the calibration includes adding an offset to the sensed discharge pressure. A fifth example of this method optionally includes one or more of the first through fourth examples and further includes where the offset is equal to the difference between a desired pressure of a pressure relief valve and the sensed discharge pressure when the ON time has reached the calibrated maximum. A sixth example of this method optionally includes one or more of the first through fifth examples, and further includes, in response to the volume of fuel ingested by the engine reaching the predetermined volume, indicating an error of the pressure sensor within the normal range and initiating a calibration the sensed discharge pressure, wherein the calibration includes subtracting an offset from the sensed discharge pressure. A seventh example of this method optionally includes one or more of the first through sixth examples and further includes wherein the offset is equal to the difference between the sensed delivery pressure when the volume of fuel ingested by the internal combustion engine has reached the predetermined volume and a fuel vapor pressure of the fuel system is.

[0174] Yet another method consistent with the present disclosure while performing closed loop control of a lift pump based on an output signal of a pressure sensor disposed downstream of the lift pump includes monitoring the output signal; in response to the output signal remaining constant for at least a first threshold duration while the lift pump is ON, turning the lift pump OFF, calibrating the output signal based on the pressure at which the output signal remained constant, and performing subsequent closed-loop control of the lift pump based on the calibrated output signal; in response to the output signal remaining constant for at least a second threshold duration while the lift pump is OFF, turning the lift pump ON, calibrating the output signal based on the pressure at which the output signal remained constant, and performing subsequent closed loop control of the lift pump based on the calibrated output signal. A first example of this method includes wherein calibrating the output signal based on the pressure at which the output signal remained constant while the lift pump was ON comprises adding a first offset to the output signal, the first offset being equal to the difference between a desired pressure of a pressure relief valve and the pressure at which the output signal remained constant while the lift pump was ON. A second example of this method optionally includes the first example and further includes wherein calibrating the output signal based on the pressure at which the output signal remained constant while the lift pump was OFF comprises subtracting a second offset from the output signal, the second Offset is equal to the difference between the pressure at which the output signal remained constant while the lift pump was OFF and a fuel vapor pressure of the fuel system. A third example of this method optionally includes one or more of the first and second example and further includes determining the first threshold duration by subtracting a lift pump ON time before the output signal reached the pressure at which it remained constant from a calibrated maximum ON -Time. A fourth example of this method optionally includes one or more of the first through third examples and further includes determining the second threshold duration based on a current rate of fuel uptake by the internal combustion engine and a difference between a predetermined volume of fuel and a volume of fuel consumed by the lift pump has been picked up since the lift pump was turned OFF before the output signal reached the pressure at which it remained constant. A fifth example of this method optionally includes one or more of the first through fourth examples and further includes wherein the predetermined volume of fuel is determined as a function of a difference between a desired peak delivery pressure and a desired valley delivery pressure and a stiffness of the fuel system. A sixth example of this method optionally includes one or more of the first through fifth examples and further includes wherein the predetermined volume is set equal to the quotient of the difference between the desired peak pressure and the desired valley pressure and the stiffness of the fuel system, and wherein the stiffness of the fuel system is determined as a function of a density of fluid within the fuel system.

[0175] Additionally, consistent with the foregoing description, a hybrid vehicle includes a powertrain including an engine, an electric motor / generator, a battery, and a transmission coupled to vehicle wheels; a fuel system including a fuel tank, a fuel lift pump, a pressure sensor disposed downstream of an outlet of the lift pump in the fuel system, and a pressure relief valve; and a controller including non-transitory memory having instructions stored therein executable by a processor to: during pulsed operation of a lift pump, monitor a volume of fuel ingested by the internal combustion engine while the lift pump is OFF; if the volume of fuel ingested by the engine while the lift pump is OFF reaches a predetermined volume before an output signal of the pressure sensor has decreased to a desired valley pressure, turning ON the lift pump, storing the value of the output signal of the pressure sensor as the first stored one value and request dynamically determining a fuel vapor pressure of the fuel system; if a requested vehicle wheel torque is above a first threshold, mechanically coupling an engine crankshaft to the motor / generator, reducing engine load until the pressure sensor output signal remains constant for at least a first threshold duration while converting electrical energy to torque with the motor / generator and the torque is provided to the vehicle wheels, and storing the pressure at which the output signal remains constant as the updated fuel vapor pressure; and if the updated fuel vapor pressure is less than the first stored value, indicating that the pressure sensor is reading too high. In a first example for the hybrid vehicle, the controller further includes instructions stored in non-transitory memory and executable by a processor to: monitor an ON time of the lift pump during pulsed operation of the lift pump; if the lift pump ON time reaches a calibrated maximum ON time before the pressure sensor output has increased to a desired peak pressure, turning the lift pump OFF, storing the value of the pressure sensor output as the second stored value, and requesting dynamic determination of a target pressure of the pressure relief valve; if the requested engine output torque is below a second threshold, mechanically coupling the crankshaft to the electric motor / generator, increasing the engine load until the pressure sensor output remains constant for at least a second threshold duration while sharing a portion of the engine output torque with the electric motor / generator converting the generator into electrical energy and storing the electrical energy at the battery, and storing the pressure at which the output signal remains constant as the updated target pressure; and if the updated target pressure is greater than the second stored value, indicating that the pressure sensor is reading too low. A second example hybrid vehicle optionally includes and further includes the first example, wherein the controller further comprises instructions stored in non-transitory memory and executable by a processor to: in response to an indication that the pressure sensor is measuring too high, initiating a calibration of the pressure sensor output, the calibration including subtracting a first offset from the pressure sensor output. A third example hybrid vehicle optionally includes one or more of the first and second examples and further includes wherein the controller further comprises instructions stored in non-transitory memory and executable by a processor to: responsive to an indication that the pressure sensor measures too low values, initiating a calibration of the pressure sensor output, the calibration including adding a second offset to the pressure sensor output.A fourth example hybrid vehicle optionally includes and further includes one or more of the first through third examples, wherein the controller further comprises instructions stored in non-transitory memory and executable by a processor to: set the first offset equal to the difference between the first stored value and the updated fuel vapor pressure and setting the second offset equal to the difference between the updated target pressure and the second stored value.

[0176] In accordance with the methods and systems disclosed herein, within-range failures of a pressure sensor measuring discharge pressure of a lift pump can be accurately detected. In response to detecting an within-range failure of the pressure sensor, the lift pump control may change from a closed-loop control strategy, wherein a duty cycle of voltage pulses applied to the lift pump is adjusted based on feedback from the pressure sensor, to an open-loop control strategy, wherein the voltage applied to the lift pump is independent of feedback from the pressure sensor. Notably, the detection of within-range errors may include detection of flattening of sensed pressure without regard to the magnitude of the sensed pressure, which has the technical effect of detecting pressure sensor degradation even when the pressure sensor is operating within its expected operating range, and which can advantageously reduce the complexity of the control. Further, switching from closed-loop control to open-loop control of the lift pump upon detection of a fault within the normal range may allow the fuel system to continue to provide a commanded pumping pressure despite the pressure sensor malfunctioning. Alternatively, consistent with the methods and systems disclosed herein, a robust feedback control strategy may be implemented that allows pulsed, closed-loop operation of the lift pump to continue even when flattening of the pressure sensor output has indicated the sensor is degraded.

[0177] In another representation, a method consistent with the present disclosure may include: adjusting operation of a fuel lift pump of a fuel system of an internal combustion engine with a controller to dynamically determine a desired pressure of a pressure relief valve in the fuel system and a fuel vapor pressure of the fuel system; adjusting operation of the lift pump to maintain a first desired margin between a maximum delivery pressure and the target pressure and a second desired margin between a minimum delivery pressure and the fuel vapor pressure; and monitoring the lift pressure with a pressure sensor located downstream of the lift pump for a deviation from an expected slope of the sensed lift pressure signal. The deviation may include the signal having a zero slope for more than a predetermined threshold duration.

[0178] Note that the example control and estimation routines included herein can be used with various engine and / or vehicle system designs. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and executed by the control system including the controller in combination with the various sensors, actuators and other engine hardware. The specific flows described herein may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and / or functions illustrated may be performed in the order illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not mandatory to achieve the features and advantages of the embodiments described herein; rather, it is provided for ease of illustration and description. One or more of the illustrated acts, processes, and / or functions may be performed repeatedly depending on the particular strategy employed. Further, the acts, operations, and / or functions described may graphically represent code that is programmed into non-transitory memory of the computer-readable storage medium in the engine control system, wherein the acts described are performed by executing the instructions in a system that uses the various engine hardware components in combination with the electronic controller includes to be carried out.

[0179] It should be understood that the configurations and routines disclosed herein are exemplary in nature and are not to be construed as limiting to these specific embodiments as numerous variations are possible. For example, the above technique can be applied to V-6, 1-4, 1-6, V-12, opposed 4, and other internal combustion engine types. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and arrangements and other features, functions and / or properties disclosed herein.

[0180] The following claims particularly set out certain combinations and sub-combinations which are believed to be novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations 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 claims, whether broader, narrower, equal, or different in scope to the original claims, are also considered to be included within the subject matter of the present disclosure. QUOTES INCLUDED IN DESCRIPTION

[0000] This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Patent Literature Cited

[0000] US6526948B1

[0006]

Claims

[1] Method for operating a fuel system of an internal combustion engine, comprising: During operation of a suction pump in pulsed mode, setting a voltage level applied to the suction pump based on an output signal from a pressure sensor downstream of the suction pump and monitoring the output signal for flattening; and In response to a detection of flattening, a pressure sensor error is indicated and the suction pump is operated independently of the pressure sensor's output signal. [2] Method according to claim 1, wherein monitoring the output signal for flattening comprises comparing a time period during which the slope of the output signal is zero with a threshold period. [3] Method according to claim 2, wherein operating the suction pump independently of the output signal of the pressure sensor comprises: operating the suction pump in a continuous mode in which a non-zero constant voltage is applied to the suction pump. [4] Method according to claim 2, wherein operating the suction pump independently of the output signal of the pressure sensor comprises: operating the suction pump in a pulsed mode in which the voltage level applied to the suction pump is not set on the basis of the output signal of the pressure sensor. [5] Method according to claim 1, wherein adjusting the voltage level applied to the suction pump based on the output signal of the pressure sensor comprises adjusting a duty cycle of the voltage pulses based on the output signal. [6] Method according to claim 5, wherein adjusting the duty cycle of the voltage pulses based on the output signal comprises: increasing the duty cycle when a peak pressure of the output signal is less than a desired peak pressure, and decreasing the duty cycle when the peak pressure is greater than the desired peak pressure. [7] Method according to claim 1, wherein adjusting the voltage level applied to the suction pump based on the output signal of the pressure sensor comprises the following: Applying a first, higher voltage to the suction pump when the output signal of the pressure sensor decreases to a desired valley pressure, and applying a second, lower voltage to the suction pump when the output signal of the pressure sensor increases to a desired peak pressure. [8] Method according to claim 2, wherein the pressure sensor error is an error within the normal range, the method further comprising: indicating an error of the pressure sensor that is outside the normal range in response to the output signal increasing above or decreasing below an expected operating range of the pressure sensor and operating the suction pump independently of the output signal of the pressure sensor. [9] Hybrid vehicle, comprising: a powertrain comprising an internal combustion engine, an electric motor / generator, a battery and a transmission coupled to vehicle wheels; a fuel system comprising a fuel tank, a fuel suction pump, a pressure sensor arranged downstream of an outlet of the suction pump in the fuel system, and a pressure relief valve; a controller that includes non-volatile memory with instructions stored therein, which can be executed by a processor to do the following: In response to a request for dynamic determination of a fuel vapor pressure of the fuel system during pulsed operation of the suction pump, where the requested vehicle wheel torque is above a first threshold, mechanical coupling of a crankshaft of the internal combustion engine to the electric motor / generator, reduction of the internal combustion engine load until an output signal of the pressure sensor remains constant for at least a first threshold duration, while electrical energy is converted into torque by the electric motor / generator and the torque is supplied to the vehicle wheels, and storage of the pressure at which the output signal remains constant as fuel vapor pressure. [10] Hybrid vehicle according to claim 9, wherein the control further comprises instructions which are stored in non-volatile memory and which can be executed by a processor to: In response to a request for dynamic determination of a setpoint pressure of the pressure relief valve during pulsed operation of the suction pump, where the requested output torque of the internal combustion engine is below a second threshold, mechanical coupling of the crankshaft to the electric motor / generator, increasing the internal combustion engine load until the output signal of the pressure sensor remains constant for at least a second threshold duration, while part of the output torque of the internal combustion engine is converted into electrical energy by the electric motor / generator and the electrical energy is stored in the battery, and storing the pressure at which the output signal remains constant as the setpoint pressure. [11] Hybrid vehicle according to claim 10, wherein the control further comprises instructions which are stored in non-volatile memory and which can be executed by a processor to: During the operation of a closed-loop control system for a suction pump based on the output signal of the pressure sensor, monitor the output signal; In response to the fact that the output signal remains constant for at least a threshold duration, indicating an error within the normal range and switching from closed-loop control of the suction pump to open-loop control, whereby the suction pump operation is set independently of the output signal of the pressure sensor. [12] Hybrid vehicle according to claim 11, wherein the instructions stored in non-volatile memory and executable by the processor for switching from closed-loop control of the suction pump to open-loop control, wherein the suction pump operation is set independently of the output signal of the pressure sensor, include instructions for applying a non-zero constant voltage to the suction pump. [13] Hybrid vehicle according to claim 11, wherein the instructions stored in non-volatile memory and executable by the processor for switching from closed-loop control of the suction pump to open-loop control, wherein the suction pump operation is set independently of the output signal of the pressure sensor, include instructions for applying pulses of a non-zero voltage to the suction pump during a duty cycle that is not set on the basis of the output signal of the pressure sensor. [14] Hybrid vehicle according to claim 9, wherein the control further comprises instructions which are stored in non-volatile memory and which can be executed by a processor to: after storing the pressure at which the output signal remains constant, as fuel vapor pressure, set a duty cycle of voltage pulses applied to the suction pump based on a desired pressure range between the fuel vapor pressure and a delivery pressure of the suction pump. [15] Hybrid vehicle according to claim 10, wherein the control further comprises instructions which are stored in non-volatile memory and which can be executed by a processor to: after storing the pressure at which the output signal remains constant as the setpoint pressure, set a duty cycle of voltage pulses applied to the suction pump based on a desired pressure range between the setpoint pressure and a delivery pressure of the suction pump.