SYSTEM AND METHOD FOR PERFORMING EVAPORATIVE LEAK DIAGNOSTICS IN A VEHICLE

• US 20120215399A1
• Filed: 02/07/2012
• Published: 08/23/2012
• Est. Priority Date: 02/18/2011
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Jentz, Robert Roy, Clemens, David Allen, Dudar, Aed Mohammad, Kluzner, Michael Igor, DeZelia, Ann Irene
• Granted Patent: US 8,560,167 B2
• Time in Patent Office: Days
• US Class Current: 701/32.8
• CPC Class Codes: G01M 15/09 by monitoring pressure in fluid ducts, e.g. in lubrication or cooling parts
• CPC Class Codes: G01M 3/025 Details with respect to the testing of engines or engine parts
• CPC Class Codes: G01M 3/3263 using a differential pressure detector G01M3/3245, G01M3/3272 take precedence
• CPC Class Codes: G01M 3/34 by testing the possibility of maintaining the vacuum in containers, e.g. in can-testing machines

Abstract

A vehicle is provided with a fuel system, a controller, and a diagnostic module with an orifice, a pressure sensor, and a pump, the module connecting the fuel system to atmosphere. The controller measures a reference pressure across the orifice to provide a threshold, isolates the fuel system, and provides a code in response to comparing a series or measured pressures to the threshold. A method for performing an evaporative leak diagnostic is provided. A valve in a diagnostic module is commanded to a vent position. A pump is operated to measure a reference pressure across an orifice to provide a threshold. A valve is commanded to a test position. The pump is operated to place the fuel system in a low pressure state, and a series of pressures in the fuel system is measured. A diagnostic code is provided after comparing the series of pressures to the threshold.

Claims

1. A method for performing an evaporative leak diagnostic for a vehicle, comprising:

commanding a valve in a diagnostic module to a vent position, the valve connecting a fuel system to atmosphere;

operating a pump in the diagnostic module to measure a reference pressure across an orifice in the diagnostic module to provide a threshold;

commanding the valve to a test position;

operating the pump to place the fuel system in a low pressure state;

measuring a series of pressures in the fuel system; and

providing a diagnostic code after comparing the series of pressures to the threshold.

2. The method of claim 1 wherein the diagnostic code is a fault code when a slope of the series of pressure measurements indicates a future pressure measurement crossing the threshold.

3. The method of claim 2 wherein the slope is determined after a predetermined time.

4. The method of claim 1 wherein the diagnostic code is a fault code when at least one of the series of pressure measurements crosses the threshold within a predetermined time.

5. The method of claim 1 further comprising normalizing the series of pressure measurements with the reference pressure before comparison with the threshold.

6. The method of claim 1 wherein measuring the reference pressure across the orifice provides a second threshold.

7. The method of claim 6 further comprising providing a second diagnostic code after comparing the series of pressures to the second threshold.

8. The method of claim 1 further comprising isolating a tank in the fuel system at atmospheric pressure, and monitoring the pressure in the tank using a tank pressure sensor to perform a vapor generation test if the diagnostic code is a fault code.

9. A vehicle comprising:

a fuel system;

a diagnostic module having an orifice, a pressure sensor, and a pump, the module connecting the fuel system to atmosphere;

a controller configured to;

(i) measure a reference pressure across the orifice to provide a threshold;

(ii) isolate the fuel system in a low pressure state;

(iii) measure a series of pressures in the system; and

(iv) provide a code in response to comparing the series to the threshold.

10. The vehicle of claim 9 wherein the diagnostic module further comprises a changeover valve.

11. The vehicle of claim 10 wherein the controller is configured to command the changeover valve to a first position when measuring the reference pressure;

and

wherein the controller is configured to command the changeover valve to a second position when measuring the series of pressures.

12. The vehicle of claim 11 wherein the controller is configured to command the changeover valve to the first position and measure a second reference pressure for a test validation.

13. The vehicle of claim 9 wherein the controller is configured to provide a fault code as the code when a slope of the series of pressure measurements indicates a future pressure measurement crossing the threshold, wherein the slope is determined after a predetermined time.

14. The vehicle of claim 9 wherein the controller is configured to provide a fault code as the code when at least one of the series of pressure measurements crosses the threshold within a predetermined time.

15. The vehicle of claim 9 wherein the controller is configured to remain in a power on state after a vehicle shutdown event until the code is provided.

16. The vehicle of claim 9 wherein the controller is configured to measure the reference pressure using the orifice to provide a second threshold;

and

wherein the controller is configured to provide a second code by comparing the series of pressure measurements to the second threshold.

17. The vehicle of claim 9 wherein the fuel system further comprises a fuel tank connected to a canister by an isolation valve, the canister connected to an engine.

18. The vehicle of claim 9 wherein the fuel system further comprises a tank pressure sensor in communication with a fuel tank;

and

wherein the controller is configured to measure the pressure in the fuel tank using the tank pressure sensor to test for fuel tank integrity.

19. The vehicle of claim 9 wherein the controller is configured to test operation of a purge valve connecting the fuel system to an engine while the engine is operating, and test air flow to the module from atmosphere as entry conditions.

20. A vehicle comprising:

a first prime mover;

a fuel system having a fuel tank connected to a canister by an isolation valve, the canister connected to the first prime mover;

a second prime mover;

a diagnostic module having a changeover valve, an orifice, a pressure sensor, and a pump, the module connecting the fuel system to atmosphere;

a controller configured to;

(i) measure a reference pressure across the orifice to provide a threshold with the changeover valve in a first position;

(ii) command the isolation valve to a closed position and command the changeover valve to a second position to isolate the fuel system;

(iii) command the pump to place the fuel system in a low pressure state;

(iv) measure a series of pressures in the fuel system;

(v) provide a diagnostic code when at least one of the series of pressure measurements crosses the threshold within a predetermined time; and

(vi) provide a diagnostic code when a slope of the series of pressure measurements after another predetermined time indicates a future pressure measurement crossing the threshold.