Evaporative emission control system with vent valve

• US 5,437,257 A
• Filed: 02/28/1994
• Issued: 08/01/1995
• Est. Priority Date: 02/28/1994
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Rich, Gregory E., Giacomazzi, Roy A., Turner, Kenneth W., Przeklas, Chester W.
• Primary Examiner(s): MILLER, CARL STUART
• Application Number:
  US08/202,626
• Time in Patent Office: 519 Days
• Field of Search: 123/520, 123/198 D, 123/516, 123/518, 123/519, 123/521
• US Class Current: 123/520
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0836 Arrangement of valves controlling the admission of fuel vapour to an engine, e.g. valve being disposed between fuel tank or absorption canister and intake manifold

Abstract

An evaporative emission control system of an internal combustion engine'"'"'s fuel system including a vent valve. The vent valve provides a mechanism for closing the evaporative emission control system creating a pressure differential between system and atmospheric under various conditions whereby the system can be automatically diagnosed. The vent valve relieves pressure or vacuum in the system that exceeds a threshold necessary to detect the presence of leaks. The vent valve includes a vacuum actuator providing a low restriction flow path for system purges.

Claims

1. An evaporative emission control system for a vehicle having an internal combustion engine with an intake manifold and a fuel system, comprising:

a canister having a cavity with a first opening for transferring fuel evaporate between the fuel system and the cavity, a second opening for transferring fuel evaporate from the cavity to the intake manifold and a third opening for venting the cavity to atmosphere; and

a vent valve for controlling flow between the cavity and atmosphere including;

a housing having a canister port in communication with the third opening of the canister cavity, an atmosphere port in communication with the atmosphere, an actuator port in communication with the intake manifold and parallel first and second flow paths between the canister port and the atmosphere port;

a first normally closed valve disposed in the first flow path including an operator responsive to subatmospheric pressure in the evaporative emission control system for opening the first normally closed valve;

a second normally closed valve disposed in the second flow path including an operator in communication with the actuator port responsive to superatmospheric pressure in the evaporative emission control system and responsive to subatmospheric pressure in the actuator port from the intake manifold for opening the second normally closed valve.

2. An evaporative emission control system for a vehicle having an internal combustion engine with an intake manifold and a fuel tank, comprising:

a vapor storage canister;

a vapor line connected between the fuel tank and the canister for conveying fuel vapors and air between the fuel tank and the canister;

a vent line connected between the canister and atmosphere, wherein evaporative emission control system internal pressure in the canister is communicated to the vent line;

a purge line connected between the canister and the intake manifold for conveying fuel vapor and air from the canister to the intake manifold;

a vent valve connected to the vent line for controlling flow between the canister and the atmosphere, the vent valve comprising first and second parallel flow paths, the first flow path including a first normally closed valve and a first valve operator exposed to pressure in the vent line and the second flow path including a second normally closed valve and a second valve operator exposed to pressure in the vent line;

a vacuum line connected between the intake manifold and the second valve operator exposing the second valve operator to pressure in the intake manifold;

the first valve operator being responsive to subatmospheric pressure in the evaporative emission control system lower than a first subatmospheric reference value for opening the first normally closed valve thereby enabling flow between the canister and the atmosphere; and

the second valve operator being responsive to each of a superatmospheric pressure in the evaporative emission control system exceeding a superatmospheric reference value and a subatmospheric pressure in the vacuum line from the intake manifold lower than a second subatmospheric reference value for opening the second normally closed valve thereby enabling flow between the canister and atmosphere.

3. An evaporative emission control system for a vehicle having an internal combustion engine with an intake manifold and a fuel tank, comprising:

a vapor storage canister;

a vapor line connected between the fuel tank and the canister for conveying fuel vapors and air between the fuel tank and the canister;

a vent line connected between the canister and atmosphere;

a purge line connected between the canister and the intake manifold, the purge line including a normally closed purge valve that is opened during engine operation exposing the canister to subatmospheric pressure in the intake manifold to purge fuel vapor from the canister by enabling air flow therethrough from the vent line to the intake manifold;

a vent valve in the vent line for controlling flow between the canister and the atmosphere, the vent valve comprising first and second parallel flow paths, the first flow path including a first normally closed valve and a first valve operator exposed to pressure in the vent line and the second flow path including a second normally closed valve and a second valve operator exposed to pressure in the vent line;

a vacuum line connected between the intake manifold and the second valve operator exposing the second valve operator to pressure in the intake manifold;

the first valve operator being responsive to subatmospheric pressure in the evaporative emission control system lower than a first subatmospheric reference value for opening the first normally closed valve thereby enabling flow between the canister and the atmosphere; and

the second valve operator being responsive to each of a superatmospheric pressure in the evaporative emission control system exceeding a superatmospheric reference value and a subatmospheric pressure in the vacuum line from the intake manifold lower than a second subatmospheric reference value for opening the second normally closed valve thereby enabling flow between the canister and atmosphere,

whereby flow between the canister and atmosphere is enabled when the vent valve is opened in response to subatmospheric pressure in the intake manifold lower than the second subatmospheric reference value during engine operation and when the pressure in the evaporative emission control system exceeds the superatmospheric reference value or is lower than the first subatmospheric reference value to enable collection and purging of fuel vapor and the vent valve being closed when the engine is off and the pressure in the evaporative emission control system is between the superatmospheric reference value and the first subatmospheric reference value to enable diagnosis of the evaporative emission control system.

4. An evaporative emission control system for a vehicle having an internal combustion engine with an intake manifold and a fuel tank, comprising:

a vapor storage canister;

a vapor line connected between the fuel tank and the canister for conveying fuel vapors and air between the fuel tank and the canister;

a vent line connected between the canister and atmosphere;

a purge line connected between the canister and the intake manifold, the purge line including a normality closed purge valve that is opened during engine operation exposing the canister to subatmospheric pressure in the intake manifold to purge fuel vapor from the canister by enabling air flow therethrough from the vent line to the intake manifold;

a vent valve in the vent line for controlling flow between the canister and the atmosphere, the vent valve comprising first and second parallel flow paths, the first flow path including a first normally closed valve and a first valve operator exposed to pressure in the vent line and the second flow path including a second normally closed valve and a second valve operator exposed to pressure in the vent line;

a vacuum line connected between the intake manifold and the second valve operator exposing the second valve operator to pressure in the intake manifold;

the first valve operator including a first diaphragm having a first valve element with an orifice therethrough biased toward a first valve seat by a first spring;

the first valve operator being responsive to subatmospheric pressure in the evaporative emission control system lower than a first subatmospheric reference value equal to the spring'"'"'s biasing force for opening the first normally closed valve thereby enabling flow between the canister and the atmosphere;

the second valve operator including a second diaphragm having a second valve element biased toward a second valve seat by a second spring; and

the second valve operator being responsive to each of a superatmospheric pressure in the evaporative emission control system exceeding a superatmospheric reference value equal to the second spring'"'"'s biasing force and a subatmospheric pressure in the vacuum line from the intake manifold lower than a second subatmospheric reference value equal to the second spring'"'"'s biasing force for opening the second normally closed valve thereby enabling flow between the canister and atmosphere,

whereby flow between the canister and atmosphere is enabled when the vent valve is opened in response to subatmospheric pressure in the intake manifold lower than the second subatmospheric reference value during engine operation and when the pressure in the evaporative emission control system exceeds the superatmospheric reference value or is lower than the first subatmospheric reference value to enable collection and purging of fuel vapor and the vent valve being closed when the engine is off and the pressure in the evaporative emission control system is between the superatmospheric reference value and the first subatmospheric reference value to enable diagnosis of the evaporative emission control system.