Identifying in-range fuel pressure sensor error

Patent metadata

Field	Value
Publication number	US-10189466-B2
Application number	US-201615365669-A
Country	US
Kind code	B2
Filing date	Nov 30, 2016
Priority date	Nov 30, 2016
Publication date	Jan 29, 2019
Grant date	Jan 29, 2019

Abstract

Methods and systems are provided for diagnosing an in-range error of a pressure sensor arranged downstream of a lift pump in a fuel system of a vehicle. In one example, a method may include performing feedback control of the lift pump based on output of the pressure sensor, monitoring the pressure sensor output for flattening during the application of the voltage pulses, and adjusting operation of the fuel system depending on whether the pressure sensor output flattens for at least a threshold duration, which is indicative of an in-range error. The method may further include dynamically learning a setpoint pressure of a pressure relief valve of the fuel system and a fuel vapor pressure within the fuel system by monitoring pressure sensor output while adjusting the duty cycle of voltage pulses applied to the lift pump.

First claim

The invention claimed is:

1. A method of operating an engine fuel system, comprising:
during pulsed operation of a lift pump, turning the lift pump OFF when a sensed delivery pressure increases to a desired peak pressure, turning the lift pump OFF when an ON time of the lift pump reaches a calibrated maximum, turning the lift pump ON when the sensed delivery pressure decreases to a desired trough pressure, and turning the lift pump ON when a volume of fuel ingested by an engine reaches a predetermined volume.

2. The method of claim 1 , further comprising determining the predetermined volume as a function of a difference between the desired peak pressure and the desired trough pressure and a stiffness of the fuel system.

3. The method of claim 2 , wherein the predetermined volume is set equal to a quotient of the difference between the desired peak pressure and the desired trough pressure and the stiffness of the fuel system.

4. The method of claim 3 , further comprising determining the stiffness of the fuel system as a function of a density of fluid within the fuel system.

5. The method of claim 1 , further comprising, in response to the ON time of the lift pump reaching the calibrated maximum, indicating an in-range error of a pressure sensor and initiating calibration of the sensed delivery pressure, the calibration including adding an offset to the sensed delivery pressure.

6. The method of claim 5 , wherein the offset is equal to the difference between a setpoint pressure of a pressure relief valve and the sensed delivery pressure when the ON time reaches the calibrated maximum.

7. The method of claim 1 , further comprising, in response to the volume of fuel ingested by the engine reaching the predetermined volume, indicating an in-range error of a pressure sensor and initiating calibration of the sensed delivery pressure, the calibration including subtracting an offset from the sensed delivery pressure.

8. The method of claim 7 , wherein the offset is equal to the difference between the sensed delivery pressure when the volume of fuel ingested by the engine reaches the predetermined volume and a fuel vapor pressure of the fuel system.

9. A method of operating an engine fuel system, comprising:
while performing closed-loop control of a lift pump based on an output signal of a pressure sensor arranged downstream of the lift pump, 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 a 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 a pressure at which the output signal remained constant, and performing subsequent closed-loop control of the lift pump based on the calibrated output signal.

10. The method of claim 9 , 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 equal to a difference between a setpoint pressure of a pressure relief valve and the pressure at which the output signal remained constant while the lift pump was ON.

11. The method of claim 10 , 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 equal to a 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.

12. The method of claim 9 , further comprising determining the first threshold duration by subtracting an ON time of the lift pump prior to the output signal reaching the pressure at which it remained constant from a calibrated maximum ON time.

13. The method of claim 12 , further comprising determining the second threshold duration based on a current rate of fuel ingestion by an engine and a difference between a predetermined volume of fuel and a volume of fuel ingested by the lift pump since the lift pump was turned OFF prior to the output signal reaching the pressure at which it remained constant.

14. The method of claim 13 , wherein the predetermined volume of fuel is determined as a function of a difference between a desired peak delivery pressure and a desired trough delivery pressure and a stiffness of the fuel system.

15. The method of claim 14 , wherein the predetermined volume is set equal to a quotient of the difference between the desired peak pressure and the desired trough pressure and the stiffness of the fuel system, and where the stiffness of the fuel system is determined as a function of a density of fluid within the fuel system.

16. A hybrid vehicle, comprising:
a powertrain comprising an engine, a motor/generator, a battery, and a transmission coupled to vehicle wheels;
a fuel system comprising a fuel tank, a fuel lift pump, a pressure sensor arranged downstream of an output of the lift pump in the fuel system, and a pressure relief valve; and
a controller including non-transitory memory with instructions stored therein which are executable by a processor to:
during pulsed operation of the lift pump, monitor a volume of fuel ingested by the 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 trough pressure, turn the lift pump ON, store a value of the output signal of the pressure sensor as a first stored value, and request dynamic learning of a fuel vapor pressure of the fuel system;
if a requested vehicle wheel torque is above a first threshold, mechanically couple a crankshaft of the engine to the motor/generator, decrease engine load until the output signal of the pressure sensor remains constant for at least a first threshold duration while converting electrical energy to torque with the motor/generator and providing the torque to the vehicle wheels, and store a pressure at which the output signal remains constant as an updated fuel vapor pressure; and
if the updated fuel vapor pressure is less than the first stored value, indicate that the pressure sensor is reading high.

17. The hybrid vehicle of claim 16 , wherein the controller further comprises instructions stored in non-transitory memory and executable by the processor to:
during pulsed operation of the lift pump, monitor an ON time of the lift pump;
if the ON time of the lift pump reaches a calibrated maximum ON time before the output signal of the pressure sensor has increased to a desired peak pressure, turn the lift pump OFF, store the value of the output signal of the pressure sensor as a second stored value, and request dynamic learning of a setpoint pressure of the pressure relief valve;
if a requested engine output torque is below a second threshold, mechanically couple the crankshaft to the motor/generator, increase engine load until the output signal of the pressure sensor remains constant for at least a second threshold duration while converting a portion of engine output torque to electrical energy with the motor/generator and storing the electrical energy at the battery, and store the pressure at which the

Assignees

• Ford Global Tech Llc

Inventors

• Ulrey Joseph Norman
• Pursifull Ross Dykstra
• Woodring Christopher Arnold

Classifications

• F02D41/3863

  by controlling the flow out of the common rail, e.g. using pressure relief valves · CPC title

• F02D41/26

  using computer, e.g. microprocessor · CPC title

• F02D41/3854

  with elements in the low pressure part, e.g. low pressure pump · CPC title

• F02D29/02

  peculiar to engines driving vehicles; peculiar to engines driving variable pitch propellers · CPC title

• F02D2200/0602

  Fuel pressure · CPC title