Apparatus and methods for estimating vehicle fuel composition

• US 7,159,623 B1
• Filed: 09/22/2005
• Issued: 01/09/2007
• Est. Priority Date: 09/22/2005
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Carr, Mark D., Graham, Christopher R., Dulzo, Joseph R., Jess, Richard B., MacEwen, Ian J., Sell, Jeffrey A., Matthews, Onassis, Svestka, Michael J., Verdejo, Julian R.
• Primary Examiner(s): Douglas; Steven O.
• Application Number:
  US11/232,704
• Time in Patent Office: 474 Days
• Field of Search: 141/83, 141/94, 141/95, 141/192, 141/198, 123/497, 123/516, 123/41.31
• US Class Current: 141/94
• CPC Class Codes: F02D 19/061 by controlling fuel injectors
• CPC Class Codes: F02D 19/0628 Determining the fuel pressure, temperature or flow, the fuel tank fill level or a valve position
• CPC Class Codes: F02D 19/0665 Tanks, e.g. multiple tanks
• CPC Class Codes: F02D 19/084 Blends of gasoline and alcohols, e.g. E85
• CPC Class Codes: F02D 19/088 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 41/0032 Controlling the purging of the canister as a function of the engine operating conditions
• CPC Class Codes: F02P 5/1527 with means allowing burning of two or more fuels, e.g. super or normal, premium or regular
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A method of estimating composition of fuel in the fuel tank of a vehicle. A refuel event is detected. Fuel consumption is monitored during a plurality of stages after the refuel event. A plurality of fuel trim shift values are determined relative to the stages. The fuel trim shift values are used to estimate a fuel composition change. This method eliminates a need for a hardware fuel composition sensor and also provides dynamic filtering of fuel trim values.

Claims

1. A method of estimating composition of fuel in the fuel tank of a vehicle, said method comprising:

detecting a refuel event;

monitoring fuel consumption during a plurality of stages after the refuel event;

determining a plurality of fuel trim shift values relative to the stages; and

using the fuel trim shift values to estimate a fuel composition change.

2. The method of claim 1 further comprising scheduling one of said stages based on an amount of fuel consumed after the refuel event.

3. The method of claim 1 further comprising monitoring vehicle engine speed and fuel level change to detect the refuel event.

4. The method of claim 1 further comprising filtering the fuel trim shift values at a frequency based on a frequency of an exhaust sensor of the vehicle.

5. The method of claim 4 wherein the filtering frequency is a multiple of the exhaust sensor frequency.

6. The method of claim 1 further comprising determining a plurality of limits on a fuel composition estimate, said determining performed based on the following relationship:

x_e3=x_e1k+x_e2(1−

k) where

7. A method of estimating composition of fuel in the fuel tank of a vehicle, said method comprising:

detecting a refuel event; and

estimating a change in the fuel composition relative to an amount of fuel consumed after the refuel event, said estimating performed using a fuel trim shift value;

said estimating step performed one or more times until said estimated change in the fuel composition approaches or reaches a stable value.

8. The method of claim 7 wherein said estimating comprises using a change in a fuel/air ratio relative to a baseline value to determine an ethanol percent change.

9. The method of claim 7 further comprising:

scheduling a plurality of stages in which to perform said estimating step;

performing said estimating step in one or more of the stages; and

ending said estimating before performing said estimating step in all of the stages.

10. The method of claim 7 further comprising:

freezing a closed-loop fuel control long-term multiplier; and

using a short term integrator to control fuel trim while the long-term multiplier is frozen.

11. The method of claim 7 further comprising:

determining an O2 metric based on a signal of an exhaust sensor of the vehicle; and

performing said estimating step based at least partly on the O2 metric.

12. The method of claim 11 further comprising filtering said fuel trim shift value using a filter having a frequency that changes with a frequency of the exhaust sensor.

13. A system for estimating composition of fuel in the fuel tank of a vehicle having an engine, said system comprising:

means for detecting a refuel event;

means for scheduling a plurality of stages after the refuel event based on amounts of fuel consumption;

means for monitoring fuel consumption during the stages;

means for determining a fuel trim adjustment to control a fuel-air ratio to the engine; and

means for estimating a fuel composition change relative to one of the stages using the fuel trim adjustment.

14. The system of claim 13 further comprising means for expediting the estimating means;

wherein said expediting means causes said estimating means to estimate the fuel composition change as one of two predefined fuel compositions.

15. The system of claim 13 wherein said means for determining a fuel trim adjustment comprise means for measuring a degree to which a closed loop fuel control system of the vehicle controls air and fuel near stoichiometry.

16. The system of claim 13 wherein said estimating means makes estimates relative to fewer than all of the scheduled stages based on at least one previous estimate.

17. A system for estimating composition of fuel in the fuel tank of a vehicle having an engine, said system comprising a control module that:

detects a refuel event; and

using a fuel trim shift value, estimates a change in the fuel composition relative to an amount of fuel consumed after the refuel event;

wherein said control module estimates the change until the estimated change approaches or reaches a stable value.

18. The system of claim 17 wherein the vehicle includes a plurality of cylinder banks, each bank associated with a corresponding exhaust sensor;

wherein said control module uses a fuel trim shift value for each bank to estimate the change.

19. The system of claim 17 wherein said control module selects one of the bank fuel trim shift values based on maintaining long-term accuracy of the estimating.

20. A method of maintaining closed-loop control of fuel to a vehicle engine at stoichiometry, said method comprising:

determining a plurality of fuel trim shift values;

filtering the fuel trim shift values using a filter having a frequency that changes based on a frequency of an exhaust sensor of the vehicle; and

evaluating the filtered fuel trim shift values using an O2 metric based on the exhaust sensor frequency.

21. The method of claim 20 further comprising:

monitoring fuel consumption in a plurality of stages after a refueling event;

determining the fuel trim shift values relative to the stages; and

using the fuel trim shift values to estimate a fuel composition change.

22. The method of claim 21 wherein the fuel trim shift values comprise a frozen long-term multiplier and a short term integrator.