Leak detection assembly

• US 5,635,630 A
• Filed: 05/21/1996
• Issued: 06/03/1997
• Est. Priority Date: 12/23/1992
• Status: Expired due to Fees

• Current Assignee: Chrysler Corporation (Stellantis NV)
• Original Assignee: Chrysler Corporation (Stellantis NV)
• Inventors: Busato, Murray, Cook, John, Blomquist, William B., Dawson, Gary D.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): WIGGINS, JOHN DAVID
• Application Number:
  US08/651,095
• Time in Patent Office: 378 Days
• Field of Search: 73/40, 73/40.5 R, 73/117.3, 73/118.1, 73/47, 123/518, 123/519, 123/520
• US Class Current: 73/40.50R
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/0818 having means for pressurising the evaporative emission space
• CPC Class Codes: F04B 9/1215 the return stroke being obtained by a spring

Abstract

An assembly for testing an evaporative emission control system of an automotive vehicle which controls emission of volatile fuel vapors. The assembly is used to determine if a leak is present in a portion of the system which includes a vapor collection canister. The leak detection assembly incorporates a vacuum actuated canister vent control valve which seals the evaporative system so the leak detection test can be performed. A vacuum actuated pump which performs a leak detection test. An engine control unit initializes the pump by drawing air into a pump cavity and also closes the vent control valve. After the initialization period, the pump is activated to pressurize the evaporative emission control system. Once a control pressure is achieved, the cycle rate starts to drop off. If no leak exists in the system, the pump will eventually stop pumping. If there is a leak, the pump will continue to pump at a rate that will be representative of the flow characteristics of the size of the leak. After the test has been concluded, the vent control valve will unseal the system after the vacuum has been bled out through the orifice/check valve that has been holding the seal during the test.

Claims

1. In an automotive vehicle evaporation emission control system including:

a fuel tank;

a canister for collecting volatile fuel vapors from the fuel tank;

an atmospheric vent coupled to the canister by a conduit;

an engine including a combustion chamber utilizing fuel from the fuel tank;

an intake manifold connected to the engine, the intake manifold creating a vacuum during operation of the engine;

a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold;

a vacuum actuated pump attached to the conduit and in communication with the canister;

the vacuum actuated pump including a housing having a diaphragm disposed within the housing defining a pump actuation cavity and a pump chamber, a spring disposed within the pump actuation cavity between the housing and the diaphragm for urging the diaphragm outward into the pump chamber in a pump stroke, a pair of one way check valves disposed in the pump chamber, the valves orientated to direct flow from the pump chamber through the conduit to the evaporative emission control system wherein the pump is used to pressurize the evaporative emission control system; and

a leak detection assembly comprising;

a vent control valve operative to selectively prevent communication between the canister and the atmospheric vent coupled to the vacuum actuated pump, the vent control valve including a housing, a diaphragm disposed within the housing and defining a vacuum chamber, a valve including a head portion, a seal element connected to the head portion, the valve connected to the diaphragm, the housing further having an orifice defining a valve seat; and

a vacuum line connecting the vacuum chamber to the pump actuation cavity such that a vacuum drawn in the pump actuation cavity draws a corresponding vacuum in the vacuum chamber to draw down the diaphragm which causes the seal element to engage the valve seat and closes the vent control valve, thereby defining the normally-closed position of the vent control valve set during a leak test of the evaporative emission control system.

2. A leak detection assembly as set forth in claim 1 including a check valve disposed on the vacuum line connecting the pump actuation cavity with the vacuum chamber.

3. A leak detection assembly as set forth in claim 2 wherein the check valve includes a body having a interior chamber, a plurality of ports connected to said body to allow communication with the chamber, a wall member disposed within the chamber dividing the chamber into separate portions, a one way valve member sealing an orifice in the wall member to allow fluid flow in one direction only, the wall member further including a second orifice, having a predetermined size, operative to retard fluid flow in at least one direction.

4. A leak detection assembly as set forth in claim 3 including a sintered filter placed adjacent the second orifice.

5. A leak detection assembly as set forth in claim 1 wherein the vent control valve includes a spring disposed within the vacuum chamber and acting upon the diaphragm, the spring operative to urge the diaphragm and corresponding valve outward to maintain the vent control valve in an open position when the pressure in the vacuum chamber is substantially atmospheric.

6. In an automotive vehicle evaporation emission control system including:

a fuel tank;

a canister for collecting volatile fuel vapors from the fuel tank;

an atmospheric vent coupled to the canister by a conduit;

an engine including a combustion chamber utilizing fuel from the fuel tank;

an intake manifold connected to the engine, the intake manifold creating a vacuum during operation of the engine;

a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold;

a vacuum actuated pump attached to the conduit and in communication with the canister;

the vacuum actuated pump including a housing having a diaphragm disposed within the housing defining a pump actuation cavity and a pump chamber, a spring disposed within the pump actuation cavity between the housing and the diaphragm for urging the diaphragm outward into the pump chamber in a pump stroke, a pair of one way check valves disposed in the pump chamber, the valves orientated to direct flow from the pump chamber through the conduit to the evaporative emission control system wherein the pump is used to pressurize the evaporative emission control system; and

a leak detection assembly comprising;

a vent control valve operative to selectively prevent communication between the canister and the atmospheric vent coupled to the vacuum actuated pump, the vent control valve including a housing, a diaphragm disposed within the housing and defining a vacuum chamber, a valve including a head portion and a stem portion, the stem portion connected to the diaphragm, a seal element connected to the head portion, the housing further having an orifice defining a valve seat;

a spring disposed within the vacuum chamber and acting upon the diaphragm, the spring operative to urge the diaphragm and valve connected thereto outward to maintain the vent control valve in an open position when the pressure in the vacuum chamber is substantially atmospheric; and

a vacuum line connecting the vacuum chamber to the pump actuation cavity such that a vacuum drawn in the pump actuation cavity draws a corresponding vacuum in the vacuum chamber to draw down the diaphragm which causes the seal element to engage the valve seat and closes the vent control valve, thereby defining the normally-closed position of the vent control valve set during a leak test of the evaporative emission control system.

7. A leak detection assembly as set forth in claim 6 including a check valve disposed on the vacuum line connecting the vacuum chamber with the pump actuation cavity for maintaining the vacuum in the vacuum chamber during operation of the pump.

8. A leak detection assembly as set forth in claim 7 wherein the check valve includes a body having a interior chamber, a plurality of ports connected to the body to allow communication with the chamber, a wall member disposed within the chamber dividing the chamber into separate portions, a one way valve member sealing an orifice in the wall member to allow fluid flow in one direction only, the wall member further including a second orifice, having a predetermined size operative to retard fluid flow in at least one direction.

9. A leak detection assembly as set forth in claim 8 including a sintered filter placed adjacent the second orifice.

10. In an automotive vehicle evaporation emission control system including:

a fuel tank;

a canister for collecting volatile fuel vapors from the fuel tank;

an atmospheric vent coupled to the canister by a conduit;

an engine including a combustion chamber utilizing fuel from the fuel tank;

an intake manifold connected to the engine, the intake manifold creating a vacuum during operation of the engine;

a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold;

a vacuum actuated pump attached to the conduit and in communication with the canister;

the vacuum actuated pump including a housing having a diaphragm disposed within the housing defining a pump actuation cavity and a pump chamber, a spring disposed within the pump actuation cavity between the housing and the diaphragm for urging the diaphragm outward into the pump chamber in a pump stroke, a pair of one way check valves disposed in the pump chamber, the valves orientated to direct flow from the pump chamber through the conduit to the evaporative emission control system wherein the pump is used to pressurize the evaporative emission control system; and

a leak detection assembly comprising;

a vent control valve coupled with the vacuum actuated pump for selectively sealing off the conduit and preventing communication between the canister and the atmospheric vent, the vent control valve including a housing, a diaphragm disposed within the housing and defining a vacuum chamber, a valve including a head portion and a stem portion, the stem portion connected to the diaphragm, a seal element connected to the head portion, the housing further having an orifice defining a valve seat;

a spring disposed within the vacuum chamber and acting upon the diaphragm, the spring operative to urge the diaphragm and valve connected thereto outward to maintain the vent control valve in an open position when the pressure in the vacuum chamber is substantially atmospheric;

a vacuum line connecting the vacuum chamber to the pump actuation cavity such that a vacuum drawn in the pump actuation cavity draws a corresponding vacuum in the vacuum chamber to draw down the diaphragm which causes the seal element to engage the valve seat to close the vent control valve, thereby defining the normally-closed position of the vent control valve set during a leak test of the evaporative emission control system; and

a check valve including a body having an interior chamber, a plurality of ports connected to said body to allow communication with the chamber, a wall member disposed within the chamber dividing the chamber into separate portions, a one way valve member sealing an orifice in the wall member to allow fluid flow in one direction only, the wall member further including a second orifice, having a predetermined size, operative to retard fluid flow in at least one direction.

11. A leak detection assembly for an evaporative emission control system in an automotive vehicle including a fuel tank, a canister for collecting volatile fuel vapors from the fuel tank, an intake manifold connected to an engine of the automotive vehicle to create a vacuum during operation of the engine and a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold, said leak detection assembly comprising:

a vacuum actuated pump in communication with the canister;

a vacuum actuated canister vent control valve operative to selectively allow and prevent communication between the canister and said vacuum actuated pump; and

means interconnecting said vacuum actuated pump and said vacuum actuated vent control valve.

12. A leak detection assembly as set forth in claim 11 wherein said vacuum actuated vent control valve comprises a housing, a diaphragm disposed within said housing to define a vacuum chamber, and a valve connected to said diaphragm to close said vacuum actuated vent control valve during a leak detection assembly test of the evaporative emission control system.

13. A leak detection assembly as set forth in claim 12 including a spring disposed within said vacuum chamber to urge said diaphragm and said valve outward to maintain said vacuum actuated vent control valve in an open position when the pressure in said vacuum chamber is substantially atmospheric.

14. A leak detection assembly as set forth in claim 12 wherein said housing has an orifice defining a valve seat.

15. A leak detection assembly as set forth in claim 14 wherein said valve has a head portion and a seal element connected to said head portion to engage said valve seat.

16. A leak detection assembly for an evaporative emission control system in an automotive vehicle including a fuel tank, a canister for collecting volatile fuel vapors from the fuel tank, an intake manifold connected to an engine of the automotive vehicle to create a vacuum during operation of the engine and a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold, said leak detection assembly comprising:

a pump in communication with the canister;

a vacuum actuated canister vent control valve operative to selectively allow and prevent communication between the canister and said pump;

wherein said vacuum actuated vent control valve is integrally associated with said pump by being disposed to selectively open and close a passage extending between an inlet port of said pump and an outlet port of said pump.

17. A leak detection assembly for an evaporative emission control system in an automotive vehicle including a fuel tank, a canister for collecting volatile fuel vapors from the fuel tank, an intake manifold connected to an engine of the automotive vehicle to create a vacuum during operation of the engine and a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold, said leak detection assembly comprising:

a vacuum actuated pump in communication with the canister;

a vacuum actuated canister vent control valve operative to selectively allow and prevent communication between the canister and said vacuum actuated pump;

a vacuum line interconnecting said vacuum actuated pump and said vacuum actuated vent control valve; and

a check valve disposed on said vacuum line to allow one way fluid flow to maintain a vacuum to keep said valve in a closed position during operation of said vacuum actuated pump.

18. A leak detection assembly for an evaporative emission control system in an automotive vehicle including a fuel tank, a canister for collecting volatile fuel vapors from the fuel tank, an intake manifold connected to an engine of the automotive vehicle to create a vacuum during operation of the engine and a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold, said leak detection assembly comprising:

a pump in communication with the canister;

a vacuum actuated canister vent control valve operative to selectively allow and prevent communication between the canister and said pump;

a vacuum line interconnecting said pump and said vacuum actuated vent control valve;

a check valve disposed on said vacuum line to allow one way fluid flow to maintain a vacuum to keep said valve in a closed position during operation of said pump; and

wherein said check valve includes a body having an interior chamber, a plurality of ports connected to said body to allow communication with said interior chamber, a wall member disposed within said interior chamber and dividing said interior chamber into separate portions, a one way valve member sealing an orifice in said wall member to allow fluid flow in one direction only, said wall member further including a second orifice having a predetermined size and operative to retard fluid flow in at least one direction.

19. A leak detection assembly as set forth in claim 18 including a sintered filter placed adjacent said second orifice.

20. A leak detection assembly for an evaporative emission control system in an automotive vehicle including a fuel tank, a canister for collecting volatile fuel vapors from the fuel tank, an intake manifold connected to an engine of the automotive vehicle to create a vacuum during operation of the engine and a purge valve disposed between the canister and the intake manifold operative to allow flow of the fuel vapors from the canister to the intake manifold, said leak detection assembly comprising:

a pump in communication with the canister;

a vacuum actuated vent control valve operative to selectively allow and prevent communication between the canister and said pump;

a line interconnecting said pump and said vacuum actuated vent control valve; and

a check valve disposed on said line to allow one way fluid flow to maintain a vacuum to keep said vacuum actuated vent control valve in a closed position during operation of said pump.

21. A leak detection assembly as set forth in claim 20 wherein said vacuum actuated vent control valve comprises a housing, a diaphragm disposed within said housing to define a vacuum chamber, and a valve connected to said diaphragm to close said vacuum actuated vent control valve.

22. A leak detection assembly as set forth in claim 21 wherein said housing has an orifice defining a valve seal.

23. A leak detection assembly as set forth in claim 22 wherein said valve has a head portion and a seal element connected to said head portion to engage said valve seat.

24. A leak detection assembly as set forth in claim 23 including a spring disposed within said vacuum chamber to urge said diaphragm and said valve outward to maintain said vacuum actuated vent control valve in an open position when the pressure in said vacuum chamber is substantially atmospheric.

25. A leak detection assembly as set forth in claim 20 wherein said check valve includes a body having an interior chamber, a plurality of ports connected to said body to allow communication with said interior chamber, a wall member disposed within said interior chamber and dividing said interior chamber into separate portions, a one way valve member sealing an orifice in said wall member to allow fluid flow in one direction only, said wall member further including a second orifice, having a predetermined size, operative to retard fluid flow in at least one direction.

26. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that said positive displacement reciprocating pump comprises a housing that is divided by a movable wall into an air pumping chamber space and a vacuum chamber space, a one-way valve through which said inlet port communicates with said air pumping chamber space such that air can enter, but not exit, said air pumping chamber space via said inlet port, a second one-way valve through which said outlet port communicates with said air pumping chamber space such that air can exit, but not enter, said air pumping chamber space via said outlet port, said pump further comprising a mechanical spring that acts on said movable wall in a sense urging said movable wall to compress air in said air pumping chamber space, means for repeatedly causing said vacuum chamber space to be alternately communicated to intake manifold vacuum and to atmosphere such that during communication of said vacuum chamber space to intake manifold vacuum, said movable wall executes an intake stroke against force exerted thereon by said mechanical spring to draw air from atmosphere into said air pumping chamber space through said inlet port and first one-way valve, and during communication of said vacuum chamber space to atmosphere, said mechanical spring forces said movable wall to execute a compression stroke to force some of the air from said air pumping chamber space through said second one-way valve and said outlet port into said evaporative emission space, and said vacuum chamber space is in communications with a vacuum actuator for operating said vent control valve such that when vacuum is delivered to said vacuum chamber space, it is also conveyed to said vacuum actuator to cause said vent control valve to close, thereby defining the normally-closed position of said vent control valve set during a leak test of the evaporative emission control system.

27. An automotive vehicle as set forth in claim 26 characterized further in that vacuum is conducted to said vacuum actuator via the parallel combination of an orifice and a third one-way valve organized and arranged such that said third one-way valve organized and arranged such that said third one-way valve allows vacuum to pass into, but not from, said vacuum actuator whereby vacuum is promptly conveyed to said vacuum actuator when said vacuum chamber space is communicated to vacuum, but is delayed in leaving said vacuum actuator when said vacuum chamber space is communicated to atmosphere.

28. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and further in that said positive displacement reciprocating pump comprises a housing that is divided by a movable wall into an air pumping chamber space and a vacuum chamber space, inlet means including a one-way valve communicating an inlet of said air pumping chamber space to atmosphere such that air can enter, but not exit, said air pumping chamber space via said inlet means, outlet means including a second one-way valve communicating an outlet of said air pumping chamber space to said evaporative emission space such that air can exit, but not enter said air pumping chamber space via said outlet means, and said valve means comprises a vent valve having a vent valve inlet in fluid communication with said outlet means at a location between said evaporative emission space and the one-way valve of said outlet means and a vent valve outlet in fluid communication with said inlet means at a location between atmosphere and the one-way valve of said inlet means;

characterized further in that said pump further comprises a mechanical spring that acts on said movable wall in a sense during said movable wall to compress air in said air pumping chamber space, sand means for repeatedly causing said vacuum and to atmosphere such that during communication of said vacuum chamber space to intake manifold vacuum, said movable wall executes an intake stroke against force exerted thereon by said mechanical spring to draw air from atmosphere into said air pumping chamber space through said inlet means, and during communication of said vacuum chamber space to atmosphere, said mechanical spring forces said movable wall to execute a compression stroke to force some of the air from said air pumping chamber space through said outlet means into said evaporative emission space, spring means resiliently biasing said vent valve open, and vacuum actuator means including a check valve and an orifice fluidly connected in parallel with each other between said vacuum chamber space and a vacuum actuator of said vacuum actuator means such that when vacuum is applied to said vacuum chamber space, it is concurrently applied to said vacuum actuator to cause said vent valve to immediately close, and to cause vacuum sufficient to keep said vent valve closed to continue to be applied to said vacuum actuator for a certain amount of time after vacuum ceases to be applied to said vacuum chamber space, thereby defining the normally-closed position of said vent control valve set during a leak test of the evaporative emission control system.

29. An automotive vehicle comprising an internal combustion engine and a fuel system for said engine which comprises a fuel tank for storing volatile liquid fuel for the engine and an evaporative emission control system which comprises a collection canister that in cooperative combination with head space of said tank cooperatively defines an evaporative emission space wherein fuel vapors generated from the volatilization of fuel in said tank are temporarily confined and collected until periodically purged by means of a canister purge valve to an intake manifold of the engine for entrainment with induction flow of combustible mixture into combustion chamber space of the engine and ensuing combustion in said combustion chamber space, valve means via which said evaporative emission space is selectively communicated to atmosphere, said vehicle further comprising means, including pump means, for distinguishing between integrity and non-integrity of said evaporative emission control system, under conditions conducive to obtaining a reliable distinction between such integrity and non-integrity, against leakage of volatile fuel vapor from that portion thereof which includes said tank, said canister, said valve means, and said canister purge valve, characterized in that said pump means comprises a positive displacement reciprocating pump having a mechanism that, while said valve means is closed to prevent communication of said evaporative emission space to atmosphere and while said canister purge valve is closed to prevent communication of said evaporative emission space to said intake manifold, executes reciprocating motion comprising an intake stroke and a compression stroke and that comprises means to intake air during each occurrence of the intake stroke for creating a measured charge volume of air at given pressure and means to compress said measured charge volume of air to pressure greater than such given pressure and force a portion thereof into said evaporative emission space on each occurrence of the compression stroke, and characterized further in that said positive displacement reciprocating pump comprises a housing that is divided by a movable wall into an air pumping chamber space and a vacuum chamber space, inlet means including a one-way valve communicating an inlet of said air pumping chamber space to atmosphere such that air can enter, but not exit, said air pumping chamber space via said inlet means, outlet means including a second one-way valve communicating an outlet of said air pumping chamber space to said evaporative emission space such that air can exit, but not enter, said air pumping chamber space via said outlet means, and said valve means comprises a vacuum actuated vent valve having a vent valve inlet in fluid communication with said outlet means at a location between said evaporative emission space and the one-way valve of said outlet means and a vent valve outlet in fluid communication with said inlet means at a location between atmosphere and the one-way valve of said inlet means.