Conductive foam vapor sensing

• US 5,560,347 A
• Filed: 02/27/1995
• Issued: 10/01/1996
• Est. Priority Date: 05/02/1994
• Status: Expired due to Term

• Current Assignee: General Motors Corporation (General Motors Company)
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Reddy, Sam R., Gokhale, Kalyan P.
• Primary Examiner(s): Moulis, Thomas N.
• Application Number:
  US08/395,140
• Time in Patent Office: 582 Days
• Field of Search: 123/518, 123/519, 123/520, 123/198 D, 55/270
• US Class Current: 123/520
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: G01N 27/12 of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid , for detecting components in the fluid

Abstract

An apparatus for use in diagnosing an evaporative emission canister collection and purge system. An EVAP system of a vehicle is diagnosed through the use of a mechanism wherein a change in conductivity occurs in response to a change in concentration of fuel vapor in the variably conductive mechanism. By sensing the change in conductivity, a diagnostic mechanism determines whether the vapor collection and purge systems are operating correctly.

Claims

1. A vapor handling system comprising:

a vapor storage container;

a repeatedly enableable variably conductive vapor sensing mechanism associated with the vapor storage container including a polymeric foam material containing carbon particles having an electrical conductivity related property proportional to a concentration of fuel vapor in the vapor storage container; and

a vent conduit exiting the vapor storage container and opening to atmosphere including a normally open valve and a relief valve the normally open valve being selectively closable and in combination with the variably conductive vapor sensing mechanism operating in diagnosing the vapor handling system.

2. A vapor handling system according to claim 1 wherein the normally open valve and the relief valve are interconnected in parallel in the vent conduit.

3. A vapor handling system according to claim 2 further comprising a two-part diagnostic test associated with the variably conductive vapor sensing mechanism and the normally open valve.

4. A vapor handling system according to claim 3 further comprising a vapor collection mechanism and a purge mechanism wherein the two-part diagnostic test includes a first part wherein the vapor handling system'"'"'s vapor collection and purge mechanisms and system integrity are tested and a selectively conducted second part wherein the vapor handling system'"'"'s integrity is retested.

5. A fuel vapor handling system comprising:

a fuel vapor storage container;

an adsorbent in the fuel vapor storage container;

a repeatedly enableable variably conductive vapor sensing mechanism associated with the fuel vapor storage container including a polymeric foam material containing carbon particles; and

a vent conduit exiting the fuel vapor storage container and opening to atmosphere including a normally open valve that is selectively closable during a diagnostic routine conducted on the fuel vapor handling system.

6. A fuel vapor handling system comprising:

a fuel vapor storage container;

a variably conductive vapor sensing mechanism associated with the fuel vapor storage container including a polymeric foam material containing carbon particles;

a vent conduit communicating with the fuel vapor storage container and opening to atmosphere including a normally open valve and a relief valve;

a vapor collection conduit communicating with the fuel vapor storage container;

a purge conduit communicating with the fuel vapor storage container, wherein vapor is collected in the fuel vapor storage container and purged therefrom through interaction with the vent conduit;

an automatic and repeatedly enabled test capable of diagnosing the vapor collection and purge functions and the fuel vapor handling system'"'"'s integrity

and being capable of a further degree of selectively conducted diagnosis of the integrity of the fuel vapor handling system.

7. A fuel vapor handling system comprising:

a fuel vapor storage container capable of containing a variable amount of fuel vapor;

an adsorbent capable of repeatedly adsorbing and desorbing the variable amount of fuel vapor positioned in the fuel vapor storage container;

a polymeric foam material containing carbon particles positioned in the fuel vapor storage container adjacent the adsorbent and having an electrical conductivity related property continuously and repeatedly variable in proportion to a concentration of the variable amount of fuel vapor in the storage container during adsorption and desorption of the variable amount of fuel vapor; and

a sensor adjacent to the polymeric foam material to selectively monitor the conductivity related property.

8. A fuel vapor handling system according to claim 7 wherein the polymeric foam material contains coconut based activated carbon particles.

9. A fuel vapor handling system according to claim 7 further comprising a diagnostic system that communicates with the sensor to diagnose the fuel vapor handling system based on the conductivity related property.

10. A fuel vapor handling system according to claim 9 wherein the diagnostic system determines the extent to which the canister is loaded with the variable amount of fuel vapor.

11. An evaporative emission control system for a vehicle operating under variable ambient conditions having an engine and a computer containing engine operational data and a fuel system with a fuel tank containing fuel and having a system with fuel vapor collection and purge functions comprising:

a fuel vapor storage canister carrying a repeatedly variable concentration of fuel vapor including;

a polymeric foam material containing coconut based activated carbon particles having a conductivity that repeatedly varies in proportion to the concentration of fuel vapor in the canister;

a sensor capable of generating a conductivity related signal representative of the concentration of fuel vapor in the canister; and

a diagnostic system to determine whether the evaporative emission control system is operating to transfer fuel vapor to and from the canister by performing a multiple part diagnostic test including;

a first stage that is conducted under all ambient conditions and is enabled after every start of the engine and is capable of determining whether the fuel vapor collection and purge functions are operating correctly; and

a second stage that is conducted under some ambient conditions and is enabled when a sufficient manifold air temperature increase since engine start is detected and when a vapor generation factor, defined as 0.0014 (100-%Full)EXP(0.041MAT), is greater than 1 wherein %Full is a percentage that the fuel tank is full and MAT is the manifold air temperature increase since engine start.

12. A fuel vapor handling system for use in a vehicle having a fuel tank and an engine with a manifold operating under variable ambient conditions comprising:

a fuel vapor storage container;

a variably conductive polymeric foam containing carbon particles positioned in the fuel vapor storage container;

a sensor positioned in contact with the variably conductive polymeric foam;

a vapor collection conduit communicating with the fuel vapor storage container;

a purge conduit communicating with the fuel vapor storage container, wherein fuel vapor is collected in the fuel vapor storage container from the vapor collection conduit during a vapor collection function and purged therefrom through the purge conduit during a purge function;

a vent conduit communicating with the fuel vapor storage container and opening to atmosphere including a selectively closable normally open valve and a pressure relief valve; and

a diagnostic system communicating with the sensor, the purge valve and the normally open valve including;

a first stage that is conducted under all ambient conditions and is enabled after every start of the engine and is capable of determining whether the fuel vapor collection and purge functions are operating correctly; and

a second stage that is conducted under some ambient conditions and is enabled when a sufficient manifold air temperature increase since engine start is detected and when a vapor generation factor, defined as 0.0014 (100-%Full)EXP(0.041MAT), is greater than 1 wherein %Full is a percentage that the fuel tank is full and MAT is the manifold air temperature increase since engine start.

13. A method of diagnosing a fuel vapor handling system having a vapor collection function, a purge function and a vapor storage container with an adsorbent, a repeatedly enableable variably conductive vapor sensing mechanism and a vent conduit opening to atmosphere and being selectively closable by a normally open valve comprising the steps of:

a. closing the normally open valve;

b. reopening the normally open valve;

c. reading conductivity of the variably conductive vapor sensing mechanism over a period of time; and

d. determining whether the reading of the variably conductive vapor sensing mechanism is indicative of a properly operable vapor collection function and a properly operable purge function based on the conductivity of the variably conductive vapor sensing mechanism.

14. A method of diagnosing A fuel vapor handling system of a vehicle having a fuel tank carrying fuel with a manifold conducting air operating under variable ambient conditions and including a fuel vapor storage container;

a variably conductive polymeric foam containing carbon particles positioned in the fuel vapor storage container;

a sensor positioned in contact with the variably conductive polymeric foam;

a vapor collection conduit communicating with the fuel vapor storage container;

a purge conduit communicating with the fuel vapor storage container, wherein fuel vapor is collected in the fuel vapor storage container from the vapor collection conduit during a vapor collection function and purged therefrom through the purge conduit during a purge function; and

a vent conduit communicating with the fuel vapor storage container including a selectively closable normally open valve and a pressure relief valve comprising the steps of;

a. closing the normally open valve after the engine is started;

b. waiting a period of time sufficient to draw fuel vapor into the fuel vapor storage container;

c. opening the normally open valve;

d. reading the sensor;

d. determining whether the sensor reading indicates a conductivity indicative of proper operation of the vapor collection and purge functions;

e. waiting a time sufficient for the air conducted in the manifold to experience an increase in temperature;

f. determining an actual amount of the increase in temperature;

g. determining a level of the fuel in the fuel tank;

h. determining whether the increase in temperature and the level of the fuel are sufficient to enable a second stage test;

i. when a second stage test is enabled reclosing the normally open valve and determining whether the fuel vapor handling system is securely closed based on the sensed conductivity of the variably conductive vapor sensing mechanism; and

j. reopening the normally closed valve.