阅读说明：本技术 用于脉冲提升泵控制的方法和系统 (Method and system for pulse-lift pump control ) 是由 迈克尔·乌里奇 罗斯·普西福尔 于 2019-06-21 设计创作，主要内容包括：本公开提供了“用于脉冲提升泵控制的方法和系统”。提供了用于校准燃料提升泵的方法和系统。在以脉冲模式操作时,脉冲的占空比斜变。相对于燃料压力的所得变化速率而基于施加的电压或电流的斜坡速率,在随后的燃料泵操作期间估计并施加校准增益或传递函数值。(The present disclosure provides "methods and systems for pulse-boost pump control. Methods and systems for calibrating a fuel lift pump are provided. When operating in the pulse mode, the duty cycle of the pulses is ramped. A calibration gain or transfer function value is estimated and applied during subsequent fuel pump operation based on the ramp rate of the applied voltage or current relative to the resulting rate of change of fuel pressure.)

1. A method for a fuel system, comprising:

operating the fuel lift pump in a pulse energy mode with a ramped duty cycle; and

adjusting a lift pump command ramp rate in response to a measured ramp rate of pressure downstream of the lift pump during the ramped duty cycle.

2. The method of claim 1, wherein the downstream pressure is a fuel rail inlet pressure.

3. The method of claim 2, wherein the rail inlet pressure is used for a port injected fuel rail.

4. The method of claim 1, the ramped duty cycle comprising one of a ramped voltage, a ramped current, and a ramped pump speed.

5. The method of claim 1, wherein the adjusting comprises increasing a ramp rate in proportion to a positive difference between a desired pressure ramp rate and the downstream pressure ramp rate.

6. The method of claim 4, wherein the adjusting further comprises adjusting a degree of scaling based on a pump temperature.

7. The method of claim 1, wherein the adjusting comprises:

converting the desired pressure ramp rate to a voltage ramp rate;

applying the voltage ramp rate to the lift pump;

learning a gain applied to a lift pump command based on a difference between an actual pressure ramp rate sensed while applying the voltage ramp rate and the desired pressure ramp rate; and

adjusting the lift pump command ramp rate based on the learned gain.

8. The method of claim 7, wherein the converting comprises converting via a steady state nominal characterization.

9. The method of claim 1, wherein operating the lift pump in the pulse energy mode comprises applying power to the lift pump for a duration of each pulse and then disabling the power, the power applied in response to a pressure below a threshold pressure at an inlet of a high pressure pump coupled downstream of the fuel lift pump.

10. A fuel system for a vehicle, comprising:

a lift pump coupled inside a fuel tank;

a fuel rail coupled downstream of the lift pump;

a pressure sensor coupled in a fuel line between an outlet of the lift pump and an inlet of the fuel rail; and

a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to:

calibrating the lift pump while operating in a continuous energy mode, wherein a voltage is continuously applied, the lift pump being calibrated relative to a sensed fuel pressure based on a desired fuel pressure corresponding to the continuously applied voltage;

calibrating the lift pump while operating in a pulse energy mode, wherein the applied voltage across each of a plurality of pulses ramps up at a rate based on a desired fuel pressure ramp rate, the lift pump calibrated based on the desired fuel pressure ramp rate and a sensed fuel pressure ramp rate; and

adjusting a lift pump command based on the calibration.

11. The system of claim 10, wherein adjusting the boost command comprises, while operating in the continuous energy mode, increasing the applied voltage in proportion to a positive difference between the desired fuel pressure and the sensed fuel pressure, and wherein adjusting the boost command further comprises, while operating in the pulsed energy mode, increasing the ramp rate of the applied voltage in proportion to a positive difference between the desired fuel pressure ramp rate and the sensed fuel pressure ramp rate.

12. The system of claim 10, further comprising a temperature sensor, wherein the controller includes further instructions that further adjust the lift pump command based on a sensed pump temperature.

13. The system of claim 12, wherein the lift pump command further increases as the sensed pump temperature increases.

14. The system of claim 10, wherein the fuel rail is coupled to a port fuel injector.

Technical Field

The present application relates generally to control schemes for lift fuel pumps of internal combustion engines that operate in a pulsed mode with intermittently applied current pulses.

Background

Some vehicle engine systems that utilize direct in-cylinder fuel injection include a fuel delivery system having multiple fuel pumps for providing appropriate fuel pressures to the fuel injectors. This type of fuel system (gasoline direct injection (GDI)) is used to improve the power efficiency and range over which fuel can be delivered to the cylinders. GDI fuel injectors may require high pressure fuel injection to produce enhanced atomization for more efficient combustion. As one example, GDI systems may utilize an electrically driven lower pressure pump (i.e., a fuel lift pump) and a mechanically driven higher pressure pump (i.e., a direct injection pump) disposed in series along a fuel passage between a fuel tank and a fuel injector, respectively. In many GDI applications, the lift fuel pump initially pressurizes fuel from the fuel tank to a fuel passage (which couples the lift fuel pump and the direct injection fuel pump), and a high pressure or direct injection fuel pump may be used to further increase the pressure of the fuel delivered to the fuel injectors. Various control strategies exist for operating the higher pressure pump and the lower pressure pump to ensure efficient fuel system and engine operation.

In one exemplary method, as shown by Ulrey and Pursifull in US 2016/0025030, voltage (and current) is provided to the lift fuel pump in a continuous or pulsed manner based on a number of parameters such as engine speed and load and the amount of fuel supplied to the engine. By switching between the two modes, fuel economy is improved via the pulse lift pump operation while avoiding the presence of fuel vapor at the high pressure pump inlet.

However, the inventors herein have recognized that switching between modes may make self-calibration of the fuel pump controller difficult. Generally, in a feedback system such as the fuel system described above, the open loop performance of the fuel system may be characterized at steady state (i.e., continuously powered). Centrifugal fuel pumps driven by electric motors have pressure versus flow characteristics for any given voltage. Since in automotive applications fuel lift pumps rarely operate at the high end of the flow range (such as at 20ml/s), lift pumps are typically calibrated by characterizing pump pressure as a function of voltage at the low end of the flow range (such as flow rates below 2 ml/s). The engine controller can control pump operation to a constant pressure and monitor voltage, or to a constant voltage and monitor pressure. In this way, the in-tank fuel lift pump may be characterized while operating in a steady state (i.e., continuous power mode). However, when in the pulsed mode, the pump may not be characterized because it has not reached steady state. The change in the pump over time is due to the following: the electrical resistance of the pump due to film formation or thermal conductivity of the pump windings (at the current temperature) may affect the pump characterization. Pump components, such as the brush/diverter interface and filming of the pump chamber, may wear over time as abrasive particles move through the pump chamber. This is particularly exacerbated when the abrasive particles are allowed to recirculate through the pump without filtration. Pressure control and therefore fueling accuracy may be affected if the pump is not properly characterized.

Disclosure of Invention

In one example, the above-mentioned problem may be solved by a method for a fuel system, the method comprising: operating the lift fuel pump in a pulse energy mode, including ramping up voltage (or current, or power or speed) during the pulse mode; and calibrating the lift pump based on the ramp rate during the pulse relative to the estimated rate of change of the fuel pressure. In this way, the lift pump may be characterized even when operated in a pulsed mode.

As one example, during operation of the fuel lift pump in a pulsed mode, duty cycle pulses applied to an electric (DC) motor of the lift pump may be ramped up gradually. The pump is typically controlled by a voltage at a cyclic duty at a frequency of, for example, 10 kHz. Such short electrical pulses occurring every 0.0001 seconds are not what we say. These rapidly occurring pulses are used for an effective applied voltage of the pump motor. What we say is a pulse is an effective voltage that can be applied for 0.25 seconds to restore pressure and then shut off for 8 to 0.5 seconds until pressure again needs to be restored. Within this 0.1 to 0.4 second voltage pulse, this may include a ramp-up of the applied voltage, or alternatively, a ramp-up of the applied power, current, or pump speed. In one example, the rate at which the pump pulses ramp up may be based on the ramp speed that achieves the greatest electrical savings. Alternatively, the pressure rate may be further limited to limit the rate of pressure change during the scheduled injection. At the same time, the resulting rate of fuel pressure rise (i.e., the derivative indicative of the rate of fuel pressure rise) may be estimated. The fuel pump is then characterized based on the ramp rate of the applied voltage ramp (during the pulse) relative to the rate of change of the fuel pressure. In one example, the pump gain factor is determined based on a ratio of applied pulses to a measured rate of pressure rise. During subsequent fueling, the pump operation is adjusted according to the newly learned gain factor.

In this way, the fuel lift pump may be operated in a pulsed mode to reduce energy consumption while providing a robust characterization of the lift pump. A technical effect of applying ramped pulses is that changes in the applied pulses (e.g., voltage or current or velocity) can be better correlated with changes in the resulting fuel pressure. This may allow for better calibration of the fuel pump. This in-line calibration can compensate for manufacturing or time-dependent variations such as brush/commutator filming, motor temperature, and pump chamber wear. By reliably and accurately calibrating the pump, fuel pressure control performance and therefore overall engine fuel economy are improved. By calibrating the pump without interrupting the pulse mode of lift pump operation, the pulse mode can be extended over a longer portion of the drive cycle, thereby improving the associated fuel economy benefits.

It should be appreciated that the summary above is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by 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.

Drawings

FIG. 1 shows a schematic diagram of an exemplary fuel system coupled to an engine.

FIG. 2 depicts a high level flow chart of an exemplary method for calibrating a fuel lift pump when operating in a pulsed mode of operation or a continuous mode of operation.

Fig. 3 shows an exemplary unit ramp response.

Fig. 4-5 illustrate exemplary calibration profiles for a fuel lift pump.

FIG. 6 illustrates an exemplary method for pressure control of a fuel lift pump via pulses.

FIG. 7 shows a prophetic example of a lift pump calibration event.

FIG. 8 illustrates an exemplary method for learning a pump transfer function based on a difference between a desired pressure ramp rate and an actual pressure ramp rate according to the present disclosure.

FIG. 9 shows a block diagram of a control loop for adjusting the ramp rate commanded to the lift pump based on the measured pressure ramp rate downstream of the lift pump during application of the ramped duty cycle.

Detailed Description

The following detailed description provides information regarding the fuel lift pump, its associated fuel and engine systems, and several control strategies for calibrating the lift fuel pump. A simplified schematic diagram of an exemplary engine system including a lift fuel pump is shown in FIG. 1. The engine controller may be configured to execute a control routine (such as the exemplary routine of fig. 2) to calibrate the lift pump independent of the operating mode of the pump (i.e., when in the pulsed mode or the continuous mode). The method of fig. 2 is also described in detail with reference to fig. 8 to 9. An exemplary cell response of the pump is shown graphically in fig. 3. Exemplary calibration profiles for a lift pump that may be generated when operating in a pulsed mode are shown in fig. 4-5. An exemplary method for pressure control of a lift pump via ramping the applied pulses is shown in fig. 6. An exemplary fuel system operation including a calibration event when operating in a pulsed mode is shown in FIG. 7.

With respect to terminology used throughout the detailed description, a higher-pressure fuel pump or a direct-injection fuel pump (which provides pressurized fuel to injectors attached to a direct-injection fuel rail) may be referred to simply as a DI or HP pump. Similarly, the lower pressure pump (the compression pump, which is typically at a lower pressure than the DI pump) or the lift fuel pump (which provides pressurized fuel from the tank to the DI pump) may be referred to simply as the LP pump. An electromagnetic spill valve, which may be electronically energized to allow operation of a check valve and de-energized to open (or vice versa), may also be referred to as a fuel quantity regulator, a magnetic solenoid valve, a digital feed valve, and the like.

Fig. 1 shows a direct injection fuel system 150 coupled to an internal combustion engine 110, which may be configured as part of a propulsion system for a vehicle 5. The internal combustion engine 110 may include a plurality of combustion chambers or cylinders 112. Fuel may be provided directly to the cylinder 112 via the in-cylinder direct injector 120. Engine 110 may also receive intake and exhaust products of combusted fuel, as schematically shown by the arrows in FIG. 1. For simplicity, the intake and exhaust systems are not shown in FIG. 1. Engine 110 may include any suitable type of engine, including a gasoline engine or a diesel engine. In other embodiments, the fuel combusted may include other individual fuels or combinations of different fuels.

In some examples, the vehicle 5 may be a hybrid vehicle having multiple torque sources available to one or more wheels 55. In other examples, the vehicle 5 is a conventional vehicle having only an engine, or an electric vehicle having only an electric machine. In the illustrated example, the vehicle 5 includes an engine 110 and a motor 52. The electric machine 52 may be a motor or a motor/generator. When the one or more clutches 56 are engaged, the crankshaft 40 of the engine 110 and the electric machine 52 are connected to the wheels 55 via the transmission 54. In the depicted example, the first clutch 56 is disposed between the crankshaft 40 and the electric machine 52, while the second clutch 56 is disposed between the electric machine 52 and the transmission 54. Controller 170 may send signals to an actuator of each clutch 56 to engage or disengage the clutch to connect or disconnect crankshaft 40 from motor 52 and components connected thereto, and/or to connect or disconnect motor 52 from transmission 54 and components connected thereto. The transmission 54 may be a gearbox, a planetary gear system, or another type of transmission. The powertrain may be configured in various ways, including a parallel, series, or series-parallel hybrid vehicle.

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

Fuel may be provided to engine 110 via injector 120 by a direct injection fuel system, indicated generally at 150. In this particular example, the fuel system 150 includes a fuel storage tank 152 for storing on-board fuel, a low pressure fuel pump 130 (e.g., a fuel lift pump), a high pressure fuel pump or Direct Injection (DI) pump 140, a fuel rail 158, and various fuel passages 154 and 156. In the example shown in fig. 1, a fuel passage 154 carries fuel from the low pressure pump 130 to the DI pump 140, and a fuel passage 156 carries fuel from the DI pump 140 to a fuel rail 158. Due to the location of the fuel passages, passage 154 may be referred to as a low pressure fuel passage, while passage 156 may be referred to as a high pressure fuel passage. As such, the fuel in passage 156 may exhibit a higher pressure than the fuel in passage 154. In some examples, fuel system 150 may include more than one fuel storage tank and additional passages, valves, and other devices for providing additional functionality to direct injection fuel system 150.

In the present example of FIG. 1, the fuel rail 158 may distribute fuel to each of the plurality of direct fuel injectors 120. Each of the plurality of fuel injectors 120 may be positioned in a corresponding cylinder 112 of the engine 110 such that fuel is directly injected into each corresponding cylinder 112 during operation of the fuel injectors 120. Alternatively (or in addition), engine 110 may include a fuel injector positioned at or near an intake port of each cylinder such that fuel is injected into one or more intake ports of each cylinder along with charge air during operation of the fuel injector. This configuration of injectors may be part of a port fuel injection system, which may be included in fuel system 150. In the illustrated embodiment, engine 110 includes four cylinders that are fueled via direct injection only. However, it should be appreciated that the engine may include a different number of cylinders and a combination of both port and direct fuel injection.

Low-pressure fuel pump 130 may be operated by controller 170 to provide fuel to DI pump 140 via fuel low-pressure passage 154. Low-pressure fuel pump 130 may be configured as a pump that may be referred to as a fuel lift pump. As one example, low pressure fuel pump 130 may include an electric pump motor, whereby the pressure increase across the pump and/or the volumetric flow rate through the pump may be controlled by varying the power provided to the pump motor to increase or decrease the motor speed. For example, as the controller 170 reduces the power (e.g., voltage or current) provided to the LP pump 130, the volumetric flow rate and/or pressure increase across the pump may be reduced. Alternatively, the volumetric flow rate and/or pressure increase across the pump may be increased by increasing the power (e.g., voltage or current) provided to the pump 130. As one example, the power supplied to the low-pressure pump motor may be obtained from an alternator or other on-board energy storage device (not shown), whereby the control system provided by the controller 170 may control the electrical load used to power the low-pressure pump. Thus, by varying the voltage and/or current provided to the low pressure fuel pump 130 as indicated at 182, the flow rate and pressure of the fuel provided to the DI pump 140 and ultimately to the fuel rail 158 may be adjusted by the controller 170.

The low pressure fuel pump 130 may be fluidly coupled to the check valve 104, which may facilitate fuel delivery and maintain fuel rail pressure. Filter 106 may be fluidly coupled to outlet check valve 104 via a low pressure passage 154. The filter 106 may remove small impurities that may be contained in the fuel that may potentially damage the fuel storage and transportation components. With the check valve 104 upstream of the filter 106, the compliance of the low pressure passage 154 may be increased because the volume of the filter may be physically large. In addition, the pressure relief valve 155 includes a ball and spring mechanism that seats and seals at a particular pressure differential to release the fuel, thereby limiting the fuel pressure at 154. The passage 159 supports the lift pump operation, the purpose of which is to fill the reservoir within the tank. As can be seen in fig. 1, check valve 104 is oriented such that fuel backflow from DI pump 140 to low pressure pump 130 is substantially reduced (i.e., eliminated). In some embodiments, fuel system 150 may include a series of check valves fluidly coupled to low-pressure fuel pump 130 to further prevent fuel from leaking back upstream of the valves. In this context, upstream flow refers to the flow of fuel traveling from the fuel rail 158 toward the low pressure pump 130, while downstream flow refers to the nominal fuel flow direction from the low pressure pump toward the fuel rail.

Next, fuel may be delivered from check valve 104 to a high pressure fuel pump (e.g., DI pump) 140. The DI pump 140 may increase the pressure of the fuel received from the check valve 104 from a first pressure level generated by the low pressure fuel pump 130 to a second pressure level that is higher than the first level. The DI pump 140 may deliver high pressure fuel to a fuel rail 158 via a high pressure fuel line 156. The operation of the DI pump 140 may be adjusted based on the operating conditions of the vehicle to provide more efficient fuel system and engine operation.

The DI pump 140 may be controlled by a controller 170 to provide fuel to the fuel rail 158 via the high pressure fuel passage 156. As one non-limiting example, DI pump 140 may utilize a flow control valve, a solenoid actuated "spill valve" (SV), or a fuel quantity regulator (FVR) to enable the control system to vary the effective pumping quantity per pump stroke. The relief valve may be separate from (i.e., integrally formed with) the DI pump 140 or may be part of the DI pump. The DI pump 140 may be mechanically driven by the engine 110, as opposed to a motor-driven low pressure fuel pump or fuel lift pump 130. The pump pistons of the DI pump 140 may receive mechanical input from the engine crankshaft or camshaft via the cam 146. In this manner, the DI pump 140 may operate according to the principles of a cam-driven single cylinder pump. Further, the angular position of the cam 146 may be estimated (i.e., determined) by a sensor located near the cam 146, which communicates with the controller 170 via connection 185. Specifically, the sensor may measure the angle of the cam 146 (measured in degrees in the range of 0 to 360 degrees) from the circular motion of the cam 146. While the cam 146 is shown in fig. 1 as being external to the DI pump 140, it is understood that the cam 146 may be included in the system of the DI pump 140.

As such, the fuel system described above may be applied to DI, PFI, or PFDI configurations. When applied to a DI system, intermittent lift pump operation does not affect DI injection pressure. When applied to PFI and PFDI systems, intermittent lift pump operation can affect PFI injection pressure, but this is allowed.

As depicted in FIG. 1, a fuel pressure sensor 148 is disposed downstream of the fuel lift pump 130. The sensor may be referred to as a lift pump pressure sensor or a low pressure sensor.

As shown in FIG. 1, the fuel rail 158 includes a fuel rail pressure sensor 162 for providing an indication of the fuel rail pressure to a controller 170. An engine speed sensor 164 may be coupled to crankshaft 40 and may be used to provide an indication of engine speed to controller 170. The indication of engine speed may be used to identify the speed of the DI pump 140 because the pump 140 is mechanically driven by the engine 110, for example, via the crankshaft or camshaft. Exhaust gas sensor 166 may be used to provide an indication of exhaust gas composition to controller 170. As one example, gas sensor 166 may include a universal exhaust gas sensor (UEGO). Exhaust gas sensor 166 may be used as feedback by controller 170 to adjust the amount of fuel delivered to engine 110 via injector 120. In this manner, the controller 170 may control the air/fuel ratio delivered to the engine to a prescribed set point.

In addition, the controller 170 may receive other engine/exhaust parameter signals from other engine sensors such as engine coolant temperature, engine speed, throttle position, absolute manifold pressure, emission control device temperature, and the like. Further, the controller 170 may provide feedback control based on signals received from the fuel sensor 148, the pressure sensor 162, the engine speed sensor 164, and the like. For example, the controller 170 may send signals via connection 184 that adjust the current level, current ramp rate, pulse width of the Solenoid Valve (SV) of the DI pump 140, etc. to adjust the operation of the DI pump 140. Further, controller 170 may send signals to adjust the fuel pressure set point and/or the fuel injection amount and/or timing of the fuel pressure regulator based on signals from fuel sensor 148, pressure sensor 162, engine speed sensor 164, and/or the like. Other sensors not shown in fig. 1 may be positioned around engine 110 and fuel system 150.

Controller 170 may individually actuate each of injectors 120 via fuel injection driver 122. Controller 170, driver 122, and other suitable engine system controllers may comprise a control system. Although the driver 122 is shown external to the controller 170, in other examples, the controller 170 may include the driver 122 or the controller may be configured to provide the functionality of the driver 122. In this particular example, the controller 170 includes an electronic control unit that includes one or more of an input/output device 172, a Central Processing Unit (CPU)174, a Read Only Memory (ROM)176, a Random Access Memory (RAM)177, and a Keep Alive Memory (KAM) 178. The storage medium ROM 176 may be programmed with computer readable data representing non-transitory instructions executable by the processor 174 for performing the methods described below as well as other variations that are anticipated but not specifically listed. For example, the controller 170 may contain stored instructions for implementing various control schemes for the DI pump 140 and the LP pump 130 based on several measured conditions from the aforementioned sensors. As another example, the controller 170 receives signals from the various sensors of FIG. 1 and employs the various actuators of FIG. 1 to adjust engine operation based on the received signals and instructions stored in the controller's memory.

As shown in FIG. 1, the direct injection fuel system 150 is a non-return fuel system and may be a mechanical non-return fuel system (MRFS) or an electronic non-return fuel system (ERFS). In the case of MRFS, the fuel rail pressure may be controlled as well as you have a pressure regulator (relief valve 155) located at the fuel tank 152. In an ERFS, a pressure sensor 162 may be installed at the fuel rail 158 to measure the fuel rail pressure; however, the open-loop approach described herein puts the pressure sensor 162 to diagnostic purposes only, and thus the inclusion of a pressure sensor is discretionary. The signal from pressure sensor 162 may be fed back to controller 170, which controls driver 122, driver 122 adjusting the voltage to DI pump 140 to provide the correct pressure and fuel flow rate to the injectors.

Although not shown in fig. 1, in other examples, the direct injection fuel system 150 may include a return line whereby excess fuel from the engine is returned to the fuel tank via a return line via a fuel pressure regulator. A fuel pressure regulator may be connected in series with the return line to regulate fuel delivered to the fuel rail 158 at a set point pressure. To regulate the set-point fuel pressure, the fuel pressure regulator may return excess fuel to the fuel tank 152 via a return line when the fuel rail pressure reaches the set-point. It should be appreciated that the operation of the fuel pressure regulator may be adjusted to change the fuel pressure set point to adapt it to operating conditions.

Various techniques may be used to control the energy input into lift fuel pump 130 of FIG. 1, where energy is provided to the pump via connection 182 as previously described. For example, the lift fuel pump may alternate between operating in a continuous mode and a pulsed mode based on engine operating conditions to reduce power consumption while also reducing fuel vapor formation at the DI pump inlet. In the context of the present disclosure, continuous pump operation (also referred to herein as continuous mode) includes supplying a substantially constant current (i.e., power or energy) to the lift pump. However, as the fuel flow demand changes, the current may then be adjusted to a different level, where the different level remains substantially constant while providing the desired fuel flow. In contrast, pulsed pump operation (also referred to herein as a pulse mode) includes supplying current to the lift pump for a limited duration. In this context, the limited duration may be a threshold such as 0.3 seconds or another suitable amount depending on the engine and fuel system. Between pump pulse events, no current is supplied to the lift pump, thereby stopping pump operation between pulse events.

For example, the lift pump "on" duration may be adjusted as a function of the DI pump inlet pressure. The lift pump may be sized to have a large dynamic range corresponding to the fuel consumption dynamic range of the engine. For example, at one engine speed and load, the engine may consume 25cc/sec, while at another operating condition, the engine consumes 0.3 cc/sec. By adjusting the operating mode of the lift pump, the injection pump (herein the DI pump) can supply fuel at different pressures without compromising the ability to control the fuel pressure in the fuel rail. For example, the lift pump may be operated intermittently while the valve on the inlet side of the injection pump is adjusted to maintain a desired pressure in the fuel rail.

The fuel lift pump may also need to be calibrated intermittently. Where the engine controller can typically control pump operation to a constant pressure and monitor voltage, or to a constant voltage and monitor pressure, while the pump is in a continuous mode. However, when in the pulse mode, the pump may not be characterized because it has not reached a steady state pressure. The open-loop pump characterization may vary due to the resistance of the pump, as the thermal conductivity (at the current temperature) of the film formation or pump windings may affect the pump characterization. Pump components, such as the brush/diverter interface and filming of the pump chamber, may wear over time as abrasive particles move through the pump chamber. This is particularly exacerbated when the abrasive particles are allowed to recirculate through the pump without filtration. If the pump is not properly characterized, fuel pressure control, and thus fueling accuracy, may be affected.

As described in detail herein with reference to fig. 2, the lift pump may be calibrated while operating in the pulse mode by ramping up (within a pulse) the applied voltage and monitoring the resulting rate of change of fuel pressure. In one example, when operating the lift pump in a pulsed mode, the controller 170 may send control signals to the electric motor of the pump 130 to ramp up the applied pulses gradually while observing the rate of increase of the fuel pressure via the pressure sensor 162. Based on the ratio of the pulse ramp rate to the rate of fuel pressure increase, a pump gain value may be determined. This value (which may be, for example, a multiplier) may then be applied to the commanded pump pulse during subsequent pump operations, thereby self-adjusting for changes in pump performance.

Turning now to FIG. 2, an exemplary method 200 for operating a fuel lift pump in different modes (e.g., selecting between continuous and pulsed modes) based on engine operating conditions and adjusting a calibration routine of the pump based on the selected pump operating mode is shown. To obtain the power savings associated with intermittently operating the lift pump, the primary mode is the intermittent mode. Under certain rare conditions, continuous operation can be selected in which there is little impact on typical power consumption, and therefore little impact on fuel economy. The instructions for performing method 200 and the remaining methods included herein may be executed by a controller based on instructions stored on a memory of the controller in conjunction with signals received from sensors of an engine system, such as the sensors described above with reference to fig. 1. The controller may employ an engine actuator of the engine system to adjust engine operation according to the method described below.

At 202, the method includes estimating and/or measuring engine operating conditions. These engine operating conditions include, for example, driver torque demand, engine speed, engine load, engine fuel flow rate (actual or desired), ambient conditions such as ambient air temperature, pressure and humidity, fuel rail pressure, manifold airflow and pressure, and exhaust air-fuel ratio.

At 204, the method includes selecting a pump operating mode based on the estimated operating conditions. The lift pump may be operated intermittently in a pulsed mode, wherein the pump is intermittently turned on and off, and wherein the pump speed goes to zero during the off period. Alternatively, the lift pump may be operated in a continuous mode, wherein the lift pump is continuously operated at a certain level. In one example, engine speed and engine load are used to index a table that outputs a particular desired pattern. The desired mode may be determined empirically by performing tests at different engine operating conditions. As an example, the lift pump may be operated in a pulse mode at lower engine speeds and engine loads. Under these conditions, the fuel flow to the engine is low and the lift pump has the ability to supply fuel at a rate higher than the fuel consumption rate of the engine. Thus, the lift pump may be turned off while the engine continues to operate (i.e., combust an air-fuel mixture) for a duration (e.g., 1 to 8 seconds) before the lift pump has to be restarted.

As another example, the lift pump may be operated in a continuous mode during periods of higher engine speeds and engine fuel injection rates. In one embodiment, the lift pump is continuously operated when the lift pump off time falls below a threshold time (such as 0.5 seconds). However, if desired, the off time level that triggers operation of the continuous lift pump may be adjusted to 0.3 or 0.8 seconds as desired. In another embodiment, the lift pump is continuously operated when the average fuel flow rate injected to the engine exceeds a predetermined level.

At 206, it may be determined whether a pulse mode of lift pump operation has been selected. If so, at 210, the method includes applying a pulsed current duty cycle to the lift pump. Alternatively, pulses of voltage or power are provided. Whether in continuous or intermittent mode, an effective voltage is applied across the pump by cycling the pump power at a fast rate (e.g., 10 kHz). For example, the controller may power the electric motor of the lift pump for a predetermined duration, the predetermined duration being shorter than the threshold. The amplitude of the pulse may be adjusted based on a desired engine fuel flow (or DI fuel pressure), which in turn is determined based on current engine operating conditions. For example, as the required fuel flow increases, the frequency of the pressure recovery pulses may increase. The pulse duration is largely constant, but may vary as the duration continues until the predetermined pressure level is reached (or will be reached). The lift pump may be powered at the determined pulse level for the determined pulse duration, and the power supply may then be terminated. In other words, between the end of the current pulse and the start of the next pulse, the pump does not receive any power and does not operate. It should be appreciated that at the beginning of the next pulse, the size of the pulse (including the amplitude and duration of the pulse) may be varied to meet the current fuel flow demand based on the current engine operating conditions. Typically, the pulse is terminated when the target pressure is reached or will be reached.

If not, at 208, it may be determined that a continuous mode of lift pump operation has been selected. Thus, at 212, the method includes applying a continuous current (or voltage or power) duty cycle to the lift pump. For example, the controller may power the electric motor of the lift pump at a level based on a desired engine fuel flow (or DI fuel pressure), which in turn is determined based on current engine operating conditions. For example, as the pressure or fuel flow demand increases, the output of the continuous pump operation may increase. The lift pump may be provided with power at a determined level and the power supply may not be terminated. It should be appreciated that if engine operating conditions change and result in different fuel flow requirements, the magnitude of the power provided to the lift pump electric motor may be varied while maintaining continuous pump operation. For example, in response to an increase in fuel flow or pressure demand, pump output may be increased and then maintained at an increased level until further changes in engine operating conditions require further changes in pump output.

When operating in a pulsed mode, wherein a pulsed current or voltage or power is provided to the lift pump, at 214, it may be determined whether a pump calibration condition has been met. Likewise, when operating in a continuous mode, where continuous current or voltage or power is provided to the lift pump, at 216, it may be determined whether the pump calibration condition has been met.

If the pump calibration condition is not satisfied, the method moves to 222 to maintain pump operation. Otherwise, if the pump calibration conditions are met while operating in the pulsed mode, the method moves to 218 to calibrate the pump while in the pulsed mode. This includes adjusting the slope of the applied voltage ramp to adjust the pressure rate to a desired rate.

For example, if the desired pressure rate is 1000kPa/s, then the pump voltage is increased at a rate that results in a pressure rate of 1000 kPa/s. However, since the pump requires some time to respond (i.e., spin up), the actual pressure ramp is delayed. However, even if the pressure command is delayed, the commanded rate is the same as the resulting rate. Now, if the pump performance is lower than the nominal performance, the actual rate is lower than the commanded rate. By adjusting the gain, the commanded rate and the actual rate can be made the same, thereby compensating for the varying performance during pulsed operation.

The resulting rate of rise of fuel pressure is recorded while ramping up the power supplied to the pump during the pulse. The method then moves to 220. The inventors herein have recognized that a fuel lift pump can be characterized by ramping up the applied voltage even when the pulse duration is short (e.g., about 0.2 seconds). Specifically, the resulting pressure ramps up at a rate corresponding to pump performance, allowing the pump to be calibrated. However, it should be understood that the ramping up of the applied voltage during the pulse mode is different from the step response evaluation, as may be used when in the continuous mode.

For example, the controller ramps up to the desired pressure at a preprogrammed rate. The pressure is mapped to the voltage via a steady state characterization between the commanded pressure, the current flow rate, and the applied voltage. In a nominal pump (no gain adjustment is required), the commanded pressure rate is equal to the measured pressure rate, so the appropriate gain is one.

At 220, a pump gain value is calculated based on the voltage ramp rate relative to the fuel pressure rise rate. For example, a ratio of the voltage ramp rate to the rate of fuel pressure rise is determined and used to calculate a multiplier. In one example, the controller may collect at least two data points on a given pulse. Additional data points may also be collected on the same pulse or on multiple consecutive pulses to enable mapping of monotonic causal relationships. The at least two data points collected on a given pulse may include a first pressure data point (P1) collected at a first point in time (T1) when fuel pressure first rises above a threshold set at or near a valley pressure (fpump _ P _ gag _ des) or at a lowest fuel pressure. The data points may also include a second pressure data point (P2) collected at a second time point (T2) where the applied pump voltage becomes zero. This may correspond to approaching the highest pressure in the pulse. In some examples, the second data point may be collected when the pressure reaches an upper threshold or peak pressure, however, for a weak pump, the pressure may not reach the peak pressure. The slope is then calculated as the rise in pressure as a function of voltage operation. In other words, the derivative of the pressure change is determined. The slope can be calculated as: the slope is (P2-P1)/(T2-T1) in kPa/sec.

If the expected pressure rate is 1000kPa/s and the measured pressure rate is 800kPa/s, the "adjustment factor" needs to be increased. And the most likely adjustment is 1/0.8-1.25.

If the pump calibration conditions are met while in the continuous mode, the method moves to 224 to calibrate the pump while in the continuous mode. This includes adjusting the duty cycle of the applied power to maintain a constant voltage or constant current. At the same time, the fuel pressure resulting from the applied constant voltage is determined. The method then moves to 226.

In some examples, the pump may be calibrated in a continuous mode via step response assessment, where the level of the applied constant voltage is stepped up or stepped down, and the resulting rise or fall in pressure is recorded, respectively. However, it should be understood that the step response evaluation for continuous mode calibration is different from the ramp pulse evaluation for pulsed mode calibration.

At 226, a pump correction factor, such as a gain value, is calculated based on the applied voltage relative to the resulting fuel pressure. For example, a multiplier may be calculated using a ratio of the applied voltage relative to the resulting fuel pressure. As an alternative example, a multiplier or addend is calculated using the difference between the expected fuel pressure based on the applied voltage and the actual fuel pressure resulting from the applied voltage.

In one example, the controller may collect at least two data points for the duration of the continuous mode. Additional data points may also be collected to enable mapping of monotonic causal relationships. The at least two data points collected over the duration of time may include a first pressure data point (P1) collected at a first point in time (T1) and a second pressure data point (P2) collected at a second point in time (T2) after a threshold duration has elapsed. A multiplier is then calculated from the difference between the pressures. That is, the multiplier is calculated as: the multiplier f (P2-P1) is in kPa. Alternatively, the addend is calculated as: the addend is f (P2-P1) in kPa. In one example, the controller may measure the pressure rate from two ordered pressure pairs and time data points. The controller may then calculate the slope. The controller may then adjust the gain factor to bring the slope closer to the desired slope.

From each of 220 and 226, the method then moves to 228 to adjust subsequent pump operations based on the learned pump correction factor (e.g., gain value). As an example, in the case where the learned correction coefficient is a multiplier, the subsequent pump operation may be corrected via a multiplier. For example, the commanded signal may be multiplied by a multiplier to determine the actual signal to be provided to the lift pump. As another example, an addend may be added to the commanded signal to determine the actual signal to be provided to the lift pump. The method then ends.

Thus, if the ramp response of the fuel lift pump follows first order control system dynamics, a unit ramp response will be observed. FIG. 3 shows a graph 300 of the unit ramp response of a fuel lift pump. Graph 300 depicts an expected ramp response at curve 302 (dashed line) and an actual ramp response at curve 304 (solid line). As shown, the unit ramp response c (t) follows the unit ramp signal for all positive values of t. However, there is a deviation of T units from the input signal.

FIG. 3 illustrates the response of an exemplary system to a ramp input. Note that in this case the slope is preserved, and the measured value lags the commanded value. The expected pressure is similar to 320. The measured pressure is similar to 304. If the slopes are the same, no gain adjustment is needed.

An embodiment of the method of fig. 2 is illustrated with reference to the control loops of fig. 8, and 9. Fig. 8 illustrates at 800 various steps that may be used to calibrate the lift pump during the pulse energy mode of operation. Specifically, at 802, a desired pressure ramp is determined. Where the pressure is mapped as a function of time and the desired ramp rate is represented by the expected slope. At 804, the desired pressure ramp is converted to a voltage ramp via a steady state nominal characterization. Thus, fuel pump data is plotted as a function of voltage versus pressure. At 806, a voltage ramp is applied to the fuel pump. Herein, the voltage is applied according to time, wherein the voltage increases for the duration of a given pulse. It should be appreciated that in alternative examples, the pump speed or applied current may be ramped up. At 808, the actual pressure ramp is measured. For example, the actual pressure ramp rate (solid line) resulting from the voltage ramping pulse is compared to the desired pressure ramp rate (dashed line, the desired pressure ramp rate determined prior to 802). The gain factor or value is determined based on the difference between the commanded pressure ramp rate and the actual (measured or sensed) pressure ramp rate (e.g., based on a positive difference between the slopes of the two lines). The gain value is a proportional function via which the commanded pressure ramp rate (i.e., the applied voltage command) can be multiplied to actually obtain the desired pressure ramp rate. Exemplary profiles in which the gains are 0.8 and 1.2, respectively, are shown in fig. 4-5.

Fig. 9 depicts the method of fig. 8 as a block diagram. Map 900 depicts an expected slope at 902. The expected slope refers to the desired pressure ramp rate. This, along with the estimated expected initial pressure, is used to determine the resulting pressure at 904. The steady state pressure to voltage characterization at 906 allows for the determination of a corresponding voltage ramp rate. The comparator uses the error between the actual pressure ramp rate and the commanded pressure ramp rate to determine a gain adjustment that is used with the commanded voltage ramp rate to determine the final command for the voltage applied at 910. In this way, the controller may: converting the desired pressure ramp rate to a voltage ramp rate; applying a voltage ramp rate to the lift pump; learning a gain applied to the lift pump command based on a difference between an actual pressure ramp rate sensed while the voltage ramp rate is applied and a desired pressure ramp rate; and finally adjusting the ramp rate of the lift pump command based on the learned gain.

Exemplary calibration profiles for the fuel lift pump are shown with reference to fig. 4-5. Specifically, map 400 of FIG. 4 shows lower pump performance than nominal output, while map 500 of FIG. 5 shows higher pump performance than nominal output. In fig. 4 and 5, the commanded voltage is shown at curves 406, 506 (solid line) and the commanded pressure change is shown at curves 402, 502 (solid line). In contrast, the actual voltage is shown at curves 408, 508 (dashed lines) and the actual measured pressure change is shown at curves 404, 504 (dashed lines). In both cases, the first time point of data collection T1 is selected around the trough pressure, while the second time point of data collection T2 is selected when the application of the voltage signal is stopped. The pressure points collected at T1 and T2 were designated P1 and P2, respectively. All curves are shown over time.

In the example shown in fig. 4, the ratio of the actual rate of rise of the fuel pressure relative to the rate of rise of the applied pulse voltage is lower than the ratio of the commanded rate of rise of the fuel pressure relative to the commanded rate of rise of the applied pulse voltage. The ratio is 0.8. In other words, the multiplier is determined to be 0.8.

As an example, a nominal pump may produce a pressure ramp rate very close to the commanded ramp rate of 1200 kPa/s. In the example of FIG. 4, the measured pressure rise rate was 763 kPa/s. This corresponds to a pressure ramp rate of 228kPa (763kPa/s) in 0.299 seconds. Therefore, the actual feed forward characteristic of the pump is determined to be 0.8 times the nominal characteristic. In the example of FIG. 5, the measured pressure rise rate was 1958 kPa/s. This corresponds to a pressure ramp rate of 280kPa (1958kPa/s) in 0.143 seconds. Thus, the actual feed forward characteristic of the pump is determined to be 1.2 times the nominal characteristic. Turning now to FIG. 6, a map 600 depicts fuel rail pressure control via a pulse lift pump operation. Curve 604 depicts the rate of change of the fuel rail pressure, while curve 602 depicts the change in the input current or voltage applied to the fuel lift pump during the pulsed mode of operation. All curves are depicted over time.

FIG. 7 shows a prophetic example of a timeline 700 of a fuel lift pump calibration event. The fuel lift pump may be coupled to an engine of a vehicle system. The calibration is performed independently of the operating mode (pulsed or continuous) of the lift pump. The curve 702 depicts engine speed. As the operator torque request increases to accelerate the vehicle, the engine speed increases. Curve 704 indicates the operating mode (pulsed or continuous) of the fuel lift pump. The pump voltage applied by the engine controller to the motor of the pump is depicted at curve 706. The Fuel Rail Pressure (FRP) is depicted at curve 708. The inlet pressure of a high pressure DI fuel pump coupled downstream of the lift pump is shown at curve 710. An indication of whether the fuel lift pump calibration is enabled (on) or disabled (off) is shown at curve 712. All curves are shown along the x-axis as a function of time.

Before t1, the engine is operated in a medium speed-load range. Thus, the fuel pump operates in a continuous mode. The target fuel rail pressure is achieved by applying a constant voltage to the pump. The HPP inlet pressure is also maintained above a non-zero threshold 711, ensuring that there is no fuel vapor at the inlet. At this time, the calibration condition is not considered to be satisfied.

At t1, the torque request changes, resulting in a transition to a higher engine speed-load range. The fuel pump is maintained in continuous mode while the applied voltage is increased to achieve a higher target rail pressure. The HPP inlet pressure remains above threshold 711.

At t2, the pump calibration condition is satisfied while continuing to operate in the continuous mode. For example, a threshold duration may have elapsed since the last pump calibration. The pump is calibrated by recording the applied first constant voltage v1 and the resulting fuel rail pressure p 1. At t3, the torque request changes, resulting in a transition to a lower engine speed-load range. The fuel pump is maintained in continuous mode while the applied voltage is reduced to achieve a lower target rail pressure. Since the calibration mode is still on, another calibration data point is collected by recording the applied second constant voltage v2 and the resulting fuel rail pressure p 2. The pump is then calibrated based on the ratio or difference between the expected value of p1 versus p1 (the expected value based on applied voltage v1) and the expected value of p2 versus p2 (the expected value based on applied voltage v 2). In one example, the pump calibration multiplier or addend is calculated using the average of two data points.

At t4, the calibration condition ends. Further, the engine shifts to a lower engine speed-load range due to the change in torque demand, requiring the lift pump operation to shift from continuous mode to pulsed mode. Wherein the pump is operated intermittently. Specifically, at t4, the pump is turned off and the HPP inlet pressure begins to gradually decay toward the threshold 711. When the HPP inlet pressure is within the threshold 711 range, the pump is turned on by providing a voltage pulse. In the depicted example, three pulses are provided between t4 and t5 to maintain the HPP inlet pressure above threshold 711 and provide the desired fuel rail pressure.

At t5, the pump calibration condition is satisfied while continuing to operate in the pulsed mode. For example, a threshold duration may have elapsed since the last pump calibration in pulse mode. The pump is calibrated by ramping up the next pulse. After t5, the voltage is applied in the first pulse at a ramp rate depicted by slope s 1. At the same time, the rate of change of the HPP inlet pressure is learned, in particular as derivative d 1. Two further pulses are provided between t5 and t6, and the voltage slopes s2 and s3 are provided accordingly, and the corresponding pressure derivatives d2 and d3 are learned. The pump was then calibrated based on the ratio of s1 to d1, the ratio of s2 to d2, and the ratio of s3 to d 3. In one example, the pump calibration multiplier is calculated using the average of three data points.

At t6, the calibration condition ends. Since the torque demand does not change significantly, the engine remains in the pulse mode of lift pump operation. Further, pump operation is adjusted based on the learned pump calibration.

It should be understood that while the figure shows a ramped voltage applied across the duty cycle of the pulses, in alternative examples, the ramped duty cycle may include a power, speed, or current ramped over the duration of a given pulse.

In this way, fuel lift pump calibration may be enabled even if the pump is operating in a pulsed mode. By ramping the pulse, the effect of the voltage change on the fuel pressure change can be learned even if the magnitude and duration of the applied voltage is low. A technical effect of correlating the ramp rate of the voltage applied to a given fuel pump pulse with a corresponding change in fuel pressure is that the voltage-pressure relationship can be used to calibrate the lift pump. By calibrating the pump while ramping the applied voltage, the disturbing effects of pump resistance on pump characterization are reduced. At the same time, the fuel economy benefits of the pulsed mode of pump operation may be realized. By performing the calibration during the drive cycle, pump performance is improved.

An exemplary method for a fuel system includes: operating the fuel lift pump in a pulse energy mode with a ramped duty cycle; and adjusting a lift pump command ramp rate in response to a measured ramp rate of pressure downstream of the lift pump during the ramped duty cycle. In the foregoing example, additionally or alternatively, the downstream pressure is a fuel rail inlet pressure. In any or all of the foregoing examples, additionally or alternatively, the rail inlet pressure is used for a port injected fuel rail. In any or all of the foregoing examples, additionally or alternatively, the downstream pressure is a pump outlet pressure estimated downstream of the fuel lift pump and upstream of a high pressure fuel pump. In any or all of the foregoing examples, additionally or optionally, the adjusting comprises increasing the ramp rate in proportion to a positive difference between the desired pressure ramp rate and the downstream pressure ramp rate. In any or all of the foregoing examples, additionally or optionally, the adjusting further comprises adjusting a degree of the scaling based on the pump temperature. In any or all of the foregoing examples, additionally or optionally, the adjusting comprises: converting the desired pressure ramp rate to a voltage ramp rate; applying the voltage ramp rate to the lift pump; learning a gain applied to a lift pump command based on a difference between an actual pressure ramp rate sensed while applying the voltage ramp rate and the desired pressure ramp rate; and adjusting the lift pump command ramp rate based on the learned gain. In any or all of the foregoing examples, additionally or alternatively, the converting comprises converting via a steady-state nominal characteristic. In any or all of the foregoing examples, additionally or optionally, operating the lift pump in the pulse energy mode includes applying power to the lift pump for a duration of each pulse, and then disabling the power, the power applied in response to a pressure below a threshold pressure at an inlet of a high-pressure pump coupled downstream of the fuel lift pump.

Another exemplary method for a fuel system includes: ramping up the applied voltage within the pulse at a ramp rate based on a desired ramp rate of the fuel pressure while operating the fuel lift pump in the pulse energy mode; monitoring a resulting ramp rate of fuel pressure measured downstream of the lift pump; and adjusting a lift pump command based on the measured ramp rate of fuel pressure relative to the desired ramp rate. In the foregoing example, additionally or alternatively, the applied voltage within the pulse ramps up at a higher rate as the desired ramp rate of fuel pressure increases. In any or all of the preceding examples, additionally or optionally, the lift pump command comprises a commanded ramp rate, and wherein the adjusting comprises increasing a gain applied to the lift pump command as the desired ramp rate exceeds the measured ramp rate. In any or all of the foregoing examples, additionally or alternatively, the fuel pressure measured downstream of the lift pump includes one of a lift pump outlet pressure, a port injected fuel rail inlet pressure, and a high pressure fuel pump inlet pressure. In any or all of the foregoing examples, additionally or optionally, operating in the pulse energy mode includes applying power to the lift pump for a duration of each pulse, the power applied in response to a pressure below a threshold pressure at an inlet of a high-pressure pump coupled downstream of the fuel lift pump, and then disabling the power. In any or all of the foregoing examples, additionally or optionally, the lift pump command is further adjusted according to one or more of a pump temperature, a fuel temperature, and a height.

An exemplary fuel system for a vehicle includes: a lift pump coupled within a fuel tank; a fuel rail coupled downstream of the lift pump; a pressure sensor coupled in a fuel line between an outlet of the lift pump and an inlet of the fuel rail; and a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to: calibrating the lift pump while operating in a continuous energy mode, wherein a voltage is continuously applied, the lift pump being calibrated relative to a sensed fuel pressure based on a desired fuel pressure corresponding to the continuously applied voltage; calibrating the lift pump while operating in a pulse energy mode, wherein the applied voltage across each of a plurality of pulses ramps up at a rate based on a desired fuel pressure ramp rate, the lift pump calibrated based on the desired fuel pressure ramp rate and a sensed fuel pressure ramp rate; and adjusting a lift pump command based on the calibration. In the foregoing example, additionally or optionally, adjusting the boost command comprises, while operating in the continuous energy mode, increasing the applied voltage in proportion to a positive difference between the desired fuel pressure and the sensed fuel pressure, and wherein adjusting the boost command further comprises, while operating in the pulsed energy mode, increasing the ramp rate of the applied voltage in proportion to a positive difference between the desired fuel pressure ramp rate and the sensed fuel pressure ramp rate. In any or all of the foregoing examples, additionally or optionally, the system further comprises a temperature sensor, wherein the controller comprises further instructions that further adjust the lift pump command based on the sensed pump temperature. In any or all of the foregoing examples, additionally or optionally, the lift pump command further increases as the sensed pump temperature increases. In any or all of the foregoing examples, additionally or alternatively, the fuel rail is coupled to a port fuel injector.

In another expression, the vehicle system is a hybrid vehicle system.

Note that the example control and estimation routines included herein may be used with various engine and/or vehicle system configurations. The control methods and routines disclosed herein may be stored as executable instructions in a non-transitory memory and may be executed by a control system, including a controller, in conjunction with various sensors, actuators, and other engine hardware. The specific routines 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 sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and/or functions may graphically represent code to be programmed into the non-transitory memory of a computer readable storage medium in the engine control system, with the described acts being implemented by executing instructions in the system including the various engine hardware components and the electronic controller.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

As used herein, unless otherwise specified, the term "about" is to be construed as meaning ± 5% of the range.

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

According to the invention, a method for a fuel system comprises: operating the fuel lift pump in a pulse energy mode with a ramped duty cycle; and adjusting a lift pump command ramp rate in response to a measured ramp rate of pressure downstream of the lift pump during the ramped duty cycle.

According to one embodiment, the downstream pressure is a fuel rail inlet pressure.

According to one embodiment, the rail inlet pressure is used for a port injected fuel rail.

According to one embodiment, the ramped duty cycle comprises one of a ramped voltage, a ramped current and a ramped pump speed.

According to one embodiment, said adjusting comprises increasing the ramp rate in proportion to a positive difference between the desired pressure ramp rate and said downstream pressure ramp rate.

According to one embodiment, the adjusting further comprises adjusting the degree of scaling based on the pump temperature.

According to one embodiment, the adjusting comprises: converting the desired pressure ramp rate to a voltage ramp rate; applying the voltage ramp rate to the lift pump; learning a gain applied to a lift pump command based on a difference between an actual pressure ramp rate sensed while applying the voltage ramp rate and the desired pressure ramp rate; and adjusting the lift pump command ramp rate based on the learned gain.

According to one embodiment, the converting includes converting via a steady state nominal characterization.

According to one embodiment, the above-described invention is further characterized by operating the lift pump in the pulse energy mode including applying power to the lift pump for the duration of each pulse and then disabling the power, the power being applied in response to a pressure below a threshold pressure at an inlet of a high pressure pump coupled downstream of the fuel lift pump.

According to the invention, a method for a fuel system comprises: ramping up the applied voltage within the pulse at a ramp rate based on a desired ramp rate of the fuel pressure while operating the fuel lift pump in the pulse energy mode; monitoring a resulting ramp rate of fuel pressure measured downstream of the lift pump; and adjusting a lift pump command based on the measured ramp rate of fuel pressure relative to the desired ramp rate.

According to one embodiment, the applied voltage within the pulse ramps up at a higher rate as the desired ramp rate of fuel pressure increases.

According to one embodiment, the lift pump command comprises a commanded ramp rate, and wherein the adjusting comprises increasing a gain applied to the lift pump command as the desired ramp rate exceeds the measured ramp rate.

According to one embodiment, the fuel pressure measured downstream of the lift pump comprises one of a lift pump outlet pressure, a port injection fuel rail inlet pressure, and a high pressure fuel pump inlet pressure.

According to one embodiment, the above-described invention is further characterized by operating in the pulse energy mode including applying power to the lift pump for the duration of each pulse and then disabling the power, the power being applied in response to a pressure below a threshold pressure at an inlet of a high-pressure pump coupled downstream of the fuel lift pump.

According to one embodiment, the lift pump command is further adjusted according to one or more of pump temperature, fuel temperature and altitude.

According to the present invention, there is provided a fuel system for a vehicle, the fuel system having: a lift pump coupled within a fuel tank; a fuel rail coupled downstream of the lift pump; a pressure sensor coupled in a fuel line between an outlet of the lift pump and an inlet of the fuel rail; and a controller having computer readable instructions stored on a non-transitory memory that, when executed, cause the controller to: calibrating the lift pump while operating in a continuous energy mode, wherein a voltage is continuously applied, the lift pump being calibrated relative to a sensed fuel pressure based on a desired fuel pressure corresponding to the continuously applied voltage; calibrating the lift pump while operating in a pulse energy mode, wherein the applied voltage across each of a plurality of pulses ramps up at a rate based on a desired fuel pressure ramp rate, the lift pump calibrated based on the desired fuel pressure ramp rate and a sensed fuel pressure ramp rate; and adjusting a lift pump command based on the calibration.

According to one embodiment, the above invention is further characterized in that adjusting the boost command comprises, while operating in the continuous energy mode, increasing the applied voltage in proportion to a positive difference between the desired fuel pressure and the sensed fuel pressure, and wherein adjusting the boost command further comprises, while operating in the pulsed energy mode, increasing the ramp rate of the applied voltage in proportion to a positive difference between the desired fuel pressure ramp rate and the sensed fuel pressure ramp rate.

According to one embodiment, the above invention is further characterized by a temperature sensor, wherein the controller includes further instructions that further adjust the lift pump command based on the sensed pump temperature.

According to one embodiment, the lift pump command is further increased as the sensed pump temperature increases.

According to one embodiment, the fuel rail is coupled to a port fuel injector.