Fuel tank pressure regulator

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/415,036, filed Oct. 31, 2016, which is expressly incorporated by reference herein.

The present disclosure relates to fuel tank vent valves, and particularly to venting apparatus for regulating discharge of fuel vapor from a fuel tank and admission of outside air into the fuel tank. More particularly, the present disclosure relates to a fuel tank pressure regulator including a fuel tank vent valve.

Vehicle fuel systems include valves associated with a fuel tank and are configured to vent pressurized or displaced fuel vapor from the vapor space in the fuel tank to a vapor recovery canister located outside of the fuel tank. The canister is designed to capture and store hydrocarbons entrained in fuel vapors that are displaced and generated in the fuel tank during a typical vehicle refueling operation or that are otherwise vented from the fuel tank.

A tank venting system in accordance with the present disclosure includes a vent apparatus for regulating flow of fuel vapor between a fuel tank and a fuel vapor recovery system in a vehicle. The flow of fuel vapor is controlled to maintain the pressure of fuel vapor in the fuel tank at a certain pressure level or within a certain pressure range during different modes of use.

A tank venting system in accordance with the present disclosure includes a vent apparatus for regulating flow of fuel vapor between a fuel tank and a fuel-vapor recovery system in a vehicle. The flow of fuel vapor is controlled to maintain the pressure of fuel vapor in the fuel tank at a certain pressure level or within a certain pressure range during different modes of use.

In illustrative embodiments, the vent apparatus includes a pressure-controlled valve configured to regulate a relatively large volume of pressurized fuel vapor flow from a fuel tank to a fuel-vapor recovery canister along a first vapor flow path under the pressure-controlled valve and an electronic bleed controller configured to regulate flow of a relatively small volume of fuel vapor flow from the fuel tank to the fuel-vapor recovery canister along a second vapor flow path through a pressurized-vapor bleed passageway formed in the pressure-controlled valve when the pressure-controlled valve is closed. By regulating the relatively small volume of fuel vapor flow from the fuel tank to the fuel-vapor recovery canister, the electronic bleed controller adjusts pressure applied to the pressure-controlled valve such that opening and closing of the pressure-controlled valve can be controlled by the electronic bleed controller.

In illustrative embodiments, the pressure-controlled valve is movable from a normally closed position arranged to block fuel vapor flow along the first vapor flow path to an opened position arranged to allow fuel vapor flow along the first vapor flow path. The pressure-controlled valve includes a deformable diaphragm that flexes in response to a pressure differential being applied to opposing sides of the pressure-controlled valve to move the pressure-controlled valve from the closed position to the opened position. A bias spring included in the electronic bleed controller is configured to encourage the pressure-controlled valve to move toward the normally closed position.

In illustrative embodiments, the pressure-controlled valve has a center portion formed to include a pressurized-vapor bleed passageway and a peripheral portion formed to include a valve-pressurization feed passageway. The electronic bleed controller is arranged normally to close the pressurized-vapor bleed passageway. Pressurized fuel vapor discharged into the vent apparatus from the fuel tank flows through the valve-pressurization feed passageway into a region above the pressure-controlled valve and applies a force to a topside of the pressure-controlled valve that cause the valve to move to a closed position to block flow of pressurized fuel vapor from the fuel tank to the fuel-vapor recovery canister along the first fuel vapor path through the vent apparatus.

In illustrative embodiments, in use, the pressure-controlled valve remains in the closed position until the electronic bleed controller is activated to open the pressurized-vapor bleed passageway to allow pressurized fuel vaper above the topside of the pressure-controlled valve to escape and pass through the pressurized-vapor bleed passageway and flow along the second vapor flow path through the vent apparatus to the fuel-vapor recovery canister. Such an escape of pressurized fuel vapor lowers the pressure of pressurized fuel vapor in the region above the topside of the pressure-controlled valve and causes the pressure-controlled valve to move from a closed position to an opened position thereby opening the first vapor flow path so that a large volume of pressurized fuel vapor can flow from the fuel tank to the fuel-vapor recovery canister through the vent apparatus along the first vapor flow path.

In illustrative embodiments, the vent apparatus includes a housing formed to include a tank pipe coupled to a fuel tank, a canister pipe coupled to a fuel-vapor recovery canister, and a valve compartment provided between the tank and canister pipes. The valve compartment is arranged to interconnect the tank and canister pipes in fluid communication to conduct pressurized fuel vapor discharged from the tank pipe into the canister pipe for delivery to the fuel-vaper recovery canister so that contaminants entrained in the pressurized fuel vapor can be trapped in the fuel-vaper recovery canister to block discharge of such contaminants from the fuel-vaper recovery canister to the atmosphere.

In illustrative embodiments, the pressure-controlled valve is mounted in the valve compartment formed in the housing to divide the housing into an upper chamber above the pressure-controlled valve and a lower chamber below the pressure-controlled valve. The valve-pressurization feed passageway has an inlet opening into the lower chamber and an outlet opening into the upper chamber. When the pressure-controlled valve is opened, the first vaper flow path established in the vent apparatus passes, in sequence, through the tank pipe, the lower chamber of the valve compartment, and the canister pipe. When the pressure-controlled valve is closed (and opened), the second vapor flow path established in the vent apparatus passes, in sequence, through the tank pipe, the lower chamber, the valve-pressurization feed passageway, the upper chamber, the pressurized-vapor bleed passageway, and the canister pipe.

In illustrative embodiments, the electronic bleed controller is movable from a closed position arranged to block fuel vapor flow along the second vapor flow path to an opened position arranged to allow pressurized fuel vapor flow along the second vapor flow path from the upper chamber into the canister pipe. The electronic bleed controller includes a bleed-passageway stopper located in the upper chamber and configured to move into and out of the pressurized-vapor bleed passageway and an electro-magnetic actuator configured to move the bleed-passageway stopper. A valve-mover controller is coupled to the electro-magnetic actuator to open and close the electronically-controlled valve under predetermined conditions.

Additional features of the present disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.

The detailed description particularly refers to the accompanying figures in which:

FIG. 1 is a perspective view of a vent apparatus made in accordance with the present disclosure for use in a tank venting system also including a fuel tank and a fuel-vapor recovery canister and suggesting that the vent apparatus includes a pressure-controlled valve formed to include a valve-pressurization feed passageway and a separate pressurized-vapor bleed passageway and suggesting that the vent apparatus also includes an electronic bleed controller that is located above the pressure-controlled valve and configured to control opening and closing of the pressurized-vapor bleed passageway to lower the pressure that is applied to a topside of the pressure-controlled valve as suggested in FIG. 8 to cause the pressure-controlled valve to move from a closed position as suggested in FIGS. 2 and 6 to an opened position as suggested in FIG. 9 to vent pressurized fuel vapor from a tank pipe of the vent apparatus to a canister pipe of the vent apparatus;

FIG. 2 is an enlarged sectional view of the vent apparatus of FIG. 1 after incorporation into a tank venting system to couple an inlet end of the tank pipe to a fuel tank and an outlet end of the canister pipe to a fuel-vapor recovery canister that is open to the atmosphere and showing that the pressure-controlled valve is a differential-pressure valve that is mounted in a valve compartment formed in a housing included in the vent apparatus to divide the valve compartment into an upper (chamber) portion above a topside of the pressure-controlled valve and a lower (chamber) portion below an underside of the pressure-controlled valve and showing the pressure-controlled valve in a closed position engaging an underlying valve seat provide in the housing as shown also in FIG. 4 to block flow of pressurized fuel vapor from a tank passageway that is coupled to the fuel tank to along a first vapor flow path a canister passageway that is coupled to the fuel-vapor recovery canister;

FIG. 3 is an exploded perspective assembly view of components included in the vent apparatus and showing that the pressure-controlled valve is formed to include a central pressurized-vapor bleed passageway and a peripheral valve-pressurization feed passageway and showing a small pliable pressure/vacuum valve that can be mounted on the topside of the pressure-controlled valve to cover the valve-pressurization feed passageway and regulate flow of fuel vapor therethrough as shown, for example, in FIGS. 6 (valve flap closed) and 7 (valve flap opened) and showing that the electronic bleed controller includes a bleed-passageway stopper that can be moved relative to the pressure-controlled valve to open and close the pressurized-vapor bleed passageway formed in the pressure-controlled valve;

FIG. 4 is an enlarged exploded perspective view of some components included in the vent apparatus of FIGS. 1-3 showing features of the pressure-controlled valve in more detail and showing the annular valve seat formed in the housing and components included in a test-condition valve opener that is coupled to the electronic bleed controller and used in accordance with the present disclosure to open the pressure-controlled valve during a pressurized On-Board Diagnostic (OBD) II test condition;

FIG. 5 is an enlarged perspective view of several of the vent apparatus components shown in FIG. 4 and showing some of the components that are included in the test-condition valve opener such as the three lift arms that are coupled to a center portion of the pressure-controlled valve and a companion valve-opening cage that is coupled to the bleed-passageway stopper of the electronic bleed controller to move up and down therewith and has three arm-lifter flanges that cooperate to be mated with the three lift arms after some relative lost motion between the arm-lifter flanges and the lift arms during upward movement of the bleed-passageway stopper from a closed position to an opened position as suggested in FIG. 10 ;

FIG. 6 is an enlarged perspective sectional view of the vent apparatus of FIG. 2 showing the pressure-controlled valve, the electronic bleed controller, and the test-condition valve opener that is linked to the electronic bleed controller;

FIG. 7 is an enlarged view taken from the circled region of FIG. 6 showing flow of pressurized fuel vapor (VT) from the fuel tank through the tank passageway, the lower (chamber) portion of the valve compartment, and up into the upper (chamber) portion of the valve compartment through the valve-pressurization feed passageway formed in the pressure-controlled valve past the opened pressure-vacuum valve;

FIG. 7A is a reduced side elevation view of or portion of FIG. 7 ;

FIG. 8 is a view similar to FIG. 7 showing upward movement of the bleed-passageway stopper (caused by actuation of the electronic bleed controller) to an opened position disengaging the pressure-controlled valve to allow pressurized fuel vapor extant in the upper (chamber) portion of the valve compartment to be discharged into the canister passageway formed in the canister pipe through the opened pressurized-vapor bleed passageway formed in the pressure-controlled valve so that the pressure over the pressure-controlled valve in the upper (chamber) portion of the valve compartment decreases relative to the combined pressure under the pressure-controlled valve in the lower (chamber) portion of the valve compartment and to cause in the canister passageway of the canister pipe the pressure-controlled valve to move upwardly from the closed position to the opened position;

FIG. 8A is a reduced side elevation view of a portion of FIG. 7 ;

FIG. 9 is a view similar to FIGS. 7 and 8 showing upward movement of the pressure-controlled valve to an opened position away from the underlying annular valve seat during a normal fuel-tank venting activity to allow pressurized fuel vapor from the fuel tank to flow from the tank passageway past the opened pressure-controlled valve into the canister passageway on its way to the fuel-vapor recovery canister;

FIG. 9A is a reduced side elevation view of a portion of FIG. 9 ;

FIG. 10 is a view similar to FIGS. 7-9 during exposure of the vent apparatus to a pressured On-Board Diagnostic (OBD) II test condition during a vent-apparatus performance test to cause the pressure-controlled valve to stay open to allow a pressure pump (not shown) and a sensor-type system (not shown) associated with an OBD II to test to see the whole fuel system; and

FIG. 10A is a reduced side elevation view of a portion of FIG. 10 .

A vent apparatus 10 includes, in series, a tank pipe 12 , valve housing 14 , and a canister pipe 16 as shown, for example, in FIGS. 1 and 2 . An inlet end 121 of tank pipe 12 is coupled to a fuel tank 18 to receive pressurized fuel vapor (V T ) discharged by fuel tank 18 as suggested in FIGS. 2 and 7-9 . An outlet end 160 of canister pipe 16 is coupled to a downstream fuel-vapor recovery canister 20 to discharge all pressurized fuel vapor (V d or V D ) that flows out of valve housing 14 and through canister pipe 16 into the downstream fuel-vapor recovery canister 20 for containment filtration so that only filtered air is discharged from fuel-vapor recovery canister 20 to the surrounding atmosphere 22 .

A pressure-controlled valve 24 is also included in vent apparatus 10 as shown diagrammatically in FIG. 1 and illustratively in FIGS. 2-4 . Pressure-controlled valve 24 is formed to include a valve-pressurization feed passageway 24 F and a separate pressurized-vapor bleed passageway 24 B as suggested in FIGS. 1-4 .

Pressure-controlled valve 24 is mounted in a valve compartment 26 formed in valve housing 14 for movement relative to valve housing 14 from a CLOSED POSITION shown, for example, in FIGS. 2, 6, 7, and 8 to a FIRST OPENED POSITION shown in FIG. 9 during normal fuel-tank venting activity and to a relatively larger SECOND OPENED POSITION shown in FIG. 10 during a vent-apparatus test-condition performance test. Pressure-controlled valve 24 is arranged to divide valve compartment 26 into separate lower and upper chambers 26 L, 26 U as suggested in FIG. 2 . A bottomside 241 of the movable pressure-controlled valve 24 cooperates with a lower interior wall of valve housing 14 to define lower chamber 26 L as suggested in FIG. 6 . A topside 242 of the movable pressure-controlled valve 24 cooperates with an upper interior wall of valve housing 14 to define upper chamber 26 U as suggested in FIGS. 2 and 6 .

Pressure-controlled valve 24 is formed to include a valve-pressurization feed passageway 24 F and a separate pressurized-vapor bleed passageway 24 B as suggested diagrammatically in FIG. 1 and illustratively in FIGS. 2-5 . Valve-pressurization feed passageway 24 F functions to conduct pressurized fuel vapor (V T ) that has been discharged from fuel tank 18 and delivered into lower chamber 26 L of valve housing 14 via tank pipe 12 into upper chamber 26 U of valve housing 14 . Pressurized-vapor bleed passageway 24 B functions to conduct pressurized fuel vapor (V d ) from upper chamber 26 U into canister pipe 16 , for example, when pressure-controlled valve 24 is in the CLOSED POSITION and pressurized vapor bleed passageway 28 B has been opened as suggested in FIG. 8 . This bleed of pressurized fuel vapor from upper chamber 26 U lowers the pressure extant in upper chamber 26 U that is exposed to the topside 242 of pressure-controlled valve 24 as compared to the pressure that is exposed to the bottomside 241 of pressure-controlled valve 24 which pressure differential causes pressure-controlled valve 24 to move upwardly from the CLOSED POSITION shown in FIG. 8 through a first distance (h) to the FIRST OPENED POSITION shown in FIG. 9 .

An electronic bleed controller 28 is also included in vent apparatus 10 and used to open and close the pressurized-vapor bleed passageway 24 B formed in pressure-controlled valve 24 during a normal fuel-tank venting activity as suggested in FIGS. 7 and 8 . In illustrative embodiments, electronic bleed controller 28 is arranged to extend downwardly through upper chamber 26 U of valve compartment 26 and includes a bleed-passageway stopper 28 S that is arranged to engage a topside 242 of pressure-controlled valve 24 to block discharge of pressurized fuel vapor from upper chamber 26 U through the pressurized-vapor bleed passageway 24 B. When activated electronically, bleed controller 28 causes bleed-passageway stopper 28 S to rise upwardly to disengage topside 242 of pressure-controlled valve 24 so that pressurized fuel vapor (V d ) extant in upper chamber 26 U can escape through the now opened pressurized-vapor bleed passageway 24 B as shown in FIGS. 8 and 8A .

A test-condition valve opener 30 is also included in vent apparatus 10 and used to move the pressure-controlled valve 24 from the CLOSED POSITION through a relatively larger second distance (H) to the relatively larger SECOND OPENED POSITION in response to activation of the electronic bleed controller 28 during performance testing of the vent apparatus 10 as shown in FIGS. 10 and 10A . Test-condition valve opener 30 includes a valve-opening cage 32 that is coupled to bleed-passageway stopper 28 S to move therewith and upstanding lift arms 34 that are coupled to topside 242 of pressure-controlled valve 24 to move therewith. During performance testing, electronic bleed controller 28 is activated to move bleed-passageway stopper 28 S to a relatively high elevated position above topside 242 of pressure-controlled valve that is sufficient to cause valve-opening cage 32 to engage lift arms 34 and raise pressured-controlled valve 24 through the relatively larger distance (H) to the relatively high elevated position shown in FIG. 10 . However, during normal fuel-tank venting activity, electronic bleed controller 28 is activated only to move bleed-passageway stopper 28 S to a relatively lower elevated position above topside 242 of pressure-controlled valve 24 that is sufficient to move bleed-passageway stopper 28 S upwardly away from topside 242 to open pressurized-vapor bleed passageway 24 B as shown in FIGS. 9 and 9A . Such upward movement is not sufficient to cause valve-opening cage 32 to engage lift arms 34 and move pressure-controlled valve 24 away from the CLOSED POSITION.

An exploded perspective view of illustrative components that cooperate to form vent apparatus 10 is shown in FIG. 3 . A body 10 B is a monolithic component that comprises tank pipe 12 , valve housing 14 , and canister pipe 16 . A bottom housing cover 13 is arranged to underlie and mate with a bottom side 14 B of valve housing 14 . A top housing cover 15 is arranged to overlie and mate with a top side of 14 T valve housing 14 . Each cover 13 , 15 is welded to valve housing 14 . Valve housing 14 includes a laterally extending middle plate 14 MP located between covers 13 , 15 and formed to include an upwardly extending annular valve seat 14 S. A pressure-relief valve 36 is located between middle plate 14 MP and bottom cover 13 . A vacuum-relief valve 38 is located between middle plate 14 MP and pressure-controlled valve 24 . Electronic bleed controller 28 is coupled to top housing cover 15 and arranged to position bleed-passageway stopper 28 S above the pressurized-vapor bleed passageway 24 B formed in pressure-controlled valve 24 .

Pressure-controlled valve 24 of vent apparatus 10 is mounted for movement in a valve compartment 26 formed in a valve housing 14 and configured to regulate a relatively large volume of fuel-vapor flow from a fuel tank 18 to a fuel-vapor recovery canister 20 . Pressure-controlled valve 24 is formed to include a central pressurized-vapor bleed passageway 24 B and a peripheral valve-pressurization feed passageway 24 F as suggested in FIGS. 1-4 . Pressurized fuel vapor (V T ) from fuel tank 18 can flow from bottomside 241 of pressure-controlled valve 24 upwardly through the peripheral valve-pressurization feed passageway 24 F to push open a normally closed pressure-vacuum valve 25 mounted on a topside 242 of pressure-controlled valve 24 into an upper chamber 26 U that is bounded, in part, by the topside 242 of pressure-controlled valve 24 so that the upper chamber 26 U is filled with pressurized fuel vapor (V T ) that applies a downward valve-closing force (F closure ) to the topside 242 of pressure-controlled valve 24 as shown in FIGS. 7 and 7A . This valve-closing force (F closure ) causes the pressure-controlled valve 24 to close and generally remain closed.

Vent apparatus 10 also includes an electronic bleed controller 28 actuated to open and close the central pressurized-vapor bleed passageway 24 B formed in pressure-controlled valve 24 at the option of a system operator. A system operator can use electronic bleed controller 28 to open the pressurized-vapor bleed passageway 24 B while pressure-controlled valve 24 is closed to change the differential pressure that is applied to pressure-controlled valve 24 so that pressure-controlled valve 24 is moved away from an annular valve seat 24 S to allow pressurized fuel vapor to flow from fuel tank 18 to fuel-vapor-recovery canister 20 past the opened pressure-controlled valve 24 along a first vapor flow path as suggested in FIGS. 9 and 9A . When electronic bleed controller 28 is actuated to allow a relatively small volume of pressurized fuel vapor (V d ) to flow downwardly through the central pressurized-vapor bleed passageway 24 B from the upper chamber 26 U provided above the topside 242 of pressure-controlled valve 24 along a second vapor flow path into the canister passageway 16 P to the fuel-vapor recovery canister 20 while pressure-control valve 24 remains closed, the differential pressure that is applied to bottomside 241 and topside 242 of the pressure-controlled valve 24 is changed to encourage movement of pressure-controlled valve 24 from the CLOSED POSITION upwardly through a small first distance (h) to a FIRST OPENED POSITION to allow free flow of pressurized fuel vapor from fuel tank 18 past the opened pressure-controlled valve 24 to fuel-vapor recovery canister 20 as shown in FIGS. 9 and 9A .

In illustrative embodiments, pressure-controlled valve 24 is a DIFFERENTIAL-PRESSURE valve that is located to divide a valve compartment 26 formed in a valve housing 14 into separate lower and upper chambers 26 L, 26 U as shown in FIG. 2 . Pressure-controlled valve 24 moves up and down in valve compartment 26 in response to changes in pressure that are applied to the topside 242 and bottomside 241 of pressure-controlled valve 24 as shown in FIGS. 7-9 . An outer section of the underside 241 of pressure-controlled valve 24 is exposed to pressurized fuel vapor (V T ) conducted from fuel tank 18 through a tank passageway 12 P formed in tank pipe 12 . The outer section is formed to include the valve-pressurization feed passageway 24 F to conduct pressurized fuel vapor (V T ) from fuel tank 18 into upper chamber 26 U of valve compartment 26 when pressure-controlled valve 24 is closed as shown in FIGS. 7 and 7A . An inner portion of the bottomside 241 of pressure-controlled valve 24 is exposed to atmospheric air conducted from fuel-vapor recovery canister 20 through a canister passageway 16 P formed in canister pipe 16 as shown in FIGS. 7 and 7A . The topside 242 of pressure-controlled valve 24 is exposed to pressurized fuel vapor (V T ) that passes from lower chamber 26 L of valve compartment 26 that is coupled to tank passageway 12 P into upper chamber 26 U of valve compartment 26 through the valve-pressurization feed passageway 24 F that is formed in the outer section of pressure-controlled valve 24 and past an opened pressure/vacuum valve 25 mounted on the topside 242 of pressure-controlled valve 24 as shown in FIGS. 2-5 .

Valve housing 14 is formed to include an annular valve seat 24 S that faces upwardly toward the underside 241 of pressure-controlled valve 24 and opens into the canister passageway 16 P formed in valve housing 14 and in canister pipe 16 as shown in FIG. 2 . When the pressure of fuel vapor in upper chamber 26 U of valve compartment 26 is greater than the effective pressure in lower chamber 26 L of valve compartment 26 , such a TOP-HEAVY differential pressure causes pressure-controlled valve 24 to move downwardly in valve compartment 26 to assume a closed position engaging annular valve seat 24 S and blocking flow of pressurized fuel vapor from tank passageway 12 P into canister passageway 16 P as shown in FIGS. 7 and 7A . However, if the pressure of fuel vapor in upper chamber 26 U of valve compartment 26 is lesser than the effective pressure in lower chamber 26 L of valve compartment 26 , such a BOTTOM-HEAVY differential pressure causes pressure-controlled valve 24 to move upwardly in valve compartment 26 to an OPENED POSITION disengaging annular valve seat 24 S and allowing flow of pressurized fuel vapor from tank passageway 12 P into canister passageway 16 P through a fluid-conducting interface 14 I provided in valve housing 14 under the opened pressure-controlled valve 24 between the tank and canister passageways 12 P, 16 P as shown in FIGS. 9 and 9A . In this way, pressurized fuel vapor (V T ) can flow from fuel tank 18 into fuel-vapor recovery canister 20 for filtering treatment before the resultant filtered vapor is discharged to the atmosphere 22 .

A center portion 24 C of pressure-controlled valve 24 is formed to include a pressurized-vapor bleed passageway 24 B that opens into canister passageway 16 P when pressure-controlled valve 24 is closed as shown in FIG. 4 . The pressurized-vapor bleed passageway 24 B is normally closed by a bleed-passageway stopper 28 S that is included in electronic bleed controller 28 to prevent any flow of pressurized fuel vapor from upper chamber 26 U of valve compartment 26 through the pressurized-vapor bleed passageway 24 B into canister passageway 16 P. When the pressurized-vapor bleed passageway 24 B is closed by bleed-passageway stopper 28 S, upper chamber 26 U of valve compartment 26 is filled with pressurized fuel vapor (V T ) that has flowed into that upper chamber 26 U through the valve-pressurization feed passageway 24 F formed in pressure-controlled valve 24 to create the TOP-HEAVY differential pressure that moves pressure-controlled valve 24 to the closed position as shown in FIGS. 7 and 7A . However, if the bleed-passageway stopper 28 S is moved relative to valve housing 14 by an electronic actuator 28 to open the pressurized-vapor bleed passageway 24 B as shown in FIGS. 8 and 8A , then pressurized fuel vapor (V d ) will be discharged from upper chamber 26 U of the valve compartment 26 through the opened pressurized-vapor bleed passageway 24 B into canister passageway 16 P for discharge to fuel-vapor recovery canister 20 . Such discharge will lower the pressure in upper chamber 26 U until it is lesser than the pressure in lower chamber 26 L and such a BOTTOM-HEAVY differential pressure will cause pressure-controlled valve 24 to move upwardly through first distance (h) to an opened position so that pressurized fuel vapor (V D ) can flow easily from fuel tank 18 past the opened pressure-controlled valve 24 along the first vapor flow path to fuel-vapor recovery canister 20 as shown in FIGS. 9 and 9A .

Pressure/vacuum valve 25 is located in upper chamber 26 U and is shown, for example, in FIGS. 2-5 and 7 . Valve 25 is a fuel-tank vapor flow blocker that regulates flow through valve-pressurization feed passageway 24 F as suggested in FIGS. 7-10 . Valve 25 includes a strip anchor 25 A coupled to divider plate 243 of center portion 24 C of pressure-controlled valve 24 and a pliable strip 25 S cantilevered to strip anchor 25 A as shown in FIG. 5 . Pliable strip 25 S is movable in response to pressure changes to open and close valve-pressurization feed passageway 24 F. Valve 25 opens under pressure of fuel tank vapor (V T ) and allows that pressurized fuel vapor (V T ) to flow through valve-pressurized feed passageway 24 F into upper chamber 26 U of valve compartment 26 . This allows pressure to get into upper chamber 26 U above pressure-controlled valve 24 so that pressure-controlled valve 24 will remain closed until electronic bleed controller 28 moves bleed-passageway stopper 28 S upwardly to open pressurized-vapor bleed passageway 24 B formed in pressure-controlled valve 24 . Under tank vacuum conditions in fuel tank 18 , pressure/vacuum valve 25 stays closed and does not allow vacuum to reach upper chamber 26 U. That keeps pressure-controlled valve 24 from opening by itself under tank vacuum conditions.

A vehicle fuel system 11 comprises a fuel tank 18 , a fuel-vapor recovery canister 20 , a vent apparatus 10 , a first fluid-conducting conduit 10 C for conducting fuel vapor between fuel tank 18 and vent apparatus 10 , and a second fluid-conducting conduit 20 C for conducting fuel vapor between vent apparatus 10 and fuel-vaper recovery canister 20 as suggested in FIGS. 2 and 7-9 . Vent apparatus 10 is a tank venting system that comprises a valve housing 14 and a pressure-controlled valve 24 associated with valve housing 14 as suggested in FIGS. 1 and 2 .

Valve housing 14 is formed to include a tank-side inlet 141 adapted to be coupled in fluid communication to fuel tank 18 and a canister-side outlet 142 adapted to be coupled in fluid communication to fuel-vapor recovery canister 20 as suggested in FIG. 6 . Valve housing 14 also is formed to include a valve seat 24 S at a fluid-conducting interface 14 I to intercept fluid flowing through valve housing 14 between tank-side inlet 141 and canister-side outlet 142 as suggested in FIGS. 9 and 9A .

In an illustrative embodiment, shown, for example, in FIGS. 2, 6, and 7 , fuel vapor (V T ) is conducted between fuel tank 18 and tank-side inlet 141 of valve housing 14 via first fluid-conducting conduit 18 C and tank pipe 12 . Lower chamber 26 U of valve compartment 26 and an interior region formed in tank pipe 12 cooperate to form tank passageway 12 P as suggested in FIG. 2 . Canister passageway 16 P is formed by an interior region between bottom cover 13 and middle plate 14 MP of valve housing 14 and an interior region formed in canister pipe 16 as suggested in FIGS. 2 and 6 .

Pressure-controlled valve 24 has a first side 241 exposed to fuel vapor flowing into valve housing 14 through tank-side inlet 141 and canister-side outlet 142 and an opposite second side 242 exposed to fuel vapor extant in fuel tank 18 that is communicated to the opposite second side 242 via a valve-pressurization feed passageway 24 F exposed to fuel vapor extant in fuel tank 18 as suggested in FIGS. 2 and 6 . Pressure-controlled valve 24 is mounted for movement relative to valve housing 14 to a closed position shown in FIGS. 2, 6, 7, and 7A wherein the first side 241 engages valve seat 24 S to block flow of fuel vapor between the tank and canister passageways 12 P, 16 P and an opened position wherein the first side 241 disengages valve seat 24 S to allow flow of fuel vapor between the tank and canister passageways 12 P, 16 P as shown in FIGS. 9 and 9A .

Tank venting system 10 also comprises an electronic bleed controller 28 that is configured to provide valve-opening means for lowering pressure of fuel vapor exposed to the opposite second side 242 of pressure-controlled valve 24 by venting pressurized fuel vapor (V T ) that has been communicated via the valve-pressurization feed passageway 24 F to the opposite second side 242 of pressure-controlled valve 24 into canister passageway 16 P through a pressurized-vapor bleed passageway 24 B for as pressurized vapor (V d ) as suggested in FIGS. 8 and 8A discharge into the atmosphere 22 in response to an electrical input. This causes pressure-controlled valve 24 to move from the closed position away from valve seat 24 S to the opened position as suggested in FIGS. 9 and 9A to allow pressurized fuel vapor (V D ) to flow from tank passageway 12 P into canister passageway 16 P through the fluid-conducting interface 14 I provided between tank and canister passageways 12 P, 16 P at valve seat 24 S.

Valve housing 14 is formed to include a valve compartment 26 containing pressure-controlled valve 24 as suggested in FIGS. 2 and 6 . Pressure-controlled valve 24 is arranged to divide valve compartment 26 into a lower chamber 26 L bounded in part by first side 241 of pressure-controlled valve 24 and arranged to provide tank passageway 12 P and a separate upper chamber 26 U bounded in part by second side 242 of pressure-controlled valve 24 that is exposed to pressurized fuel vapor discharged from valve-pressurization feed passageway 24 F. Pressure-controlled valve 24 is formed to include the pressurized-vapor bleed passageway 24 B to allow pressurized fuel vapor (V d ) to flow from the separate upper chamber 26 U of valve compartment 26 into canister passageway 16 P for discharge into fuel-vapor recovery canister 20 when the valve-opening means 28 is activated by the electrical input to vent pressurized fuel vapor (V d ) from the separate upper portion 26 U of valve compartment 26 through pressurized-vapor bleed passageway 24 B into canister passageway 16 P.

The valve-opening means 28 includes a bleed-passageway stopper 28 S and a stopper mover 73 arranged to apply a force to yieldably to urge bleed-passageway stopper 28 S to a bleed-blocking position engaging pressure-controlled valve 24 to block discharge of pressurized fuel vapor from the separate upper chamber 26 U portion of valve compartment 26 into canister passageway 16 P as suggested in FIGS. 2 and 6 . The valve-opening means 28 also includes test-condition valve opener 30 means for moving bleed-passageway stopper 28 S in opposition to the force applied by stopper mover from the bleed-blocking position away from pressure-controlled valve 24 to a bleed-allowing position and moving pressure-controlled valve 24 away from the closed position to hold pressure-controlled valve 24 in the opened position during a pressurized onboard diagnostics test condition as suggested in FIGS. 10 and 10A .

The test-condition valve opener means 30 includes a lift arm 34 and a valve-opening cage 32 as shown, for example, in FIGS. 3-5 . Lift arm 34 is coupled to pressure-controlled valve 24 and located in the separate upper chamber 26 U of valve compartment 26 as shown in FIGS. 9 and 9A . Valve-opening cage 32 is coupled to bleed-passageway stopper 28 S to move therewith as suggested in FIG. 5 . Valve-opening cage 32 includes a separate arm-lifter flange 32 F for each of the lift arms 34 and a ring-shaped flange support 32 S that is coupled to each of the circumferentially spaced-apart arm-lifter flanges 32 F and anchored to bleed-passageway stopper 28 S as shown in FIG. 5 . Valve-opening cage 32 is arranged to cause each arm-lifter flange 32 F to engage and move a companion lift arm 34 relative to valve housing 14 following movement of bleed-passageway stopper 28 S away from bleed-blocking position to a bleed-allowing position to cause pressure-controlled valve 24 to move to and be supported in an opened position during the pressurized onboard diagnostics test condition as suggested in FIGS. 10 and 10A . As shown in FIG. 5 , flange support 32 S comprises three radially extending and circumferentially spaced-apart flange-support posts 32 P. Each post 32 P is arranged to interconnect bleed-passageway stopper 28 S and one of the arm-lifter flanges 32 F. Flange support 32 S also comprises three arc-shaped rims 32 R and each rim 32 R interconnects a pair of adjacent arm-lifter flanges 32 F.

Pressure-controlled valve 24 includes a center portion 24 C that is arranged to engage the underlying valve seat 24 S when pressure-controlled valve 24 is in the closed position as shown in FIGS. 2 and 6 . Center portion 24 C is formed to include the pressurized-vapor bleed passageway 24 B as shown in FIG. 4 . Center portion is also formed to include the valve-pressurization feed passageway 24 F as shown in FIG. 4 .

Pressure-controlled valve 24 further includes a rim portion 24 R coupled to valve-housing 14 and a web portion 24 W arranged to interconnect center portion 24 C and rim portion 24 R as suggested in FIG. 4 . Web portion 24 W is arranged to support center portion 24 C for movement relative to valve seat 24 S to engage valve seat 24 S and align pressurized-vapor bleed passageway 24 B in fluid communication with canister passageway 16 P in the closed position of pressure-controlled valve 24 as shown in FIGS. 7, 7A, 8, and 8A and disengage valve seat 24 S in the opened position of pressure-controlled valve 24 as shown in FIGS. 9, 9A, 10, and 10A .

Center portion 24 C comprises a divider plate 243 having a peripheral edge 243 E coupled to web portion 24 W as suggested in FIG. 7A . Divider plate 243 is formed to include a seal-receiving aperture 244 opening into the separate upper chamber 26 U of valve compartment 26 and into canister passageway 16 P when pressure-controlled valve 24 is in the closed position as suggested in FIGS. 7 and 7A . Center portion 24 C also includes a seal ring 245 formed to include the pressurized-vapor bleed aperture 24 B and arranged to extend through the seal-receiving aperture 244 and remain coupled to divider plate 243 to move therewith during movement of pressure-controlled valve 24 between the closed and opened positions as suggested in FIGS. 7-9 . Seal ring 245 includes a lower flange 245 L and an upper flange 245 U as shown in FIG. 5 . Lower flange 245 L is arranged to lie between valve seat 24 S and divider plate 243 to establish a sealed connection therebetween when pressure-controlled valve 24 is in the closed position as suggested in FIGS. 7-9 . Upper flange 245 U is arranged to mate with the valve-opening means 28 to establish a sealed connection therebetween when the valve-opening means 28 is arranged to block flow of pressurized fuel vapor from upper chamber 26 U of valve compartment 26 through pressurized-vapor bleed passageway 24 B into canister passageway 16 P. Divider plate 243 is formed to include the valve-pressurization feed passageway 24 F in a location between 24 W web portion and seal ring 245 as suggested in FIGS. 4 and 5 .

Valve housing 14 is formed to include a valve compartment 26 containing pressure-controlled valve 24 as suggested in FIGS. 2 and 6 . Pressure-controlled valve 24 is arranged to divide valve compartment 26 into a lower chamber 26 L bounded in part by first side 241 of pressure-controlled valve 24 and a separate upper chamber 26 U bounded in part by second side 241 of pressure-controlled valve 24 . Lower chamber 26 L is arranged to communicate with tank passageway 12 P when pressure-controlled valve 24 is in the closed and opened positions as suggest in FIGS. 6-10 and with canister passageway 16 P when pressure-controlled valve 24 is in the opened position as suggested in FIGS. 9 and 10 .

Pressure-controlled valve 24 is formed to include the valve-pressurization feed passageway 24 F to conduct pressurized fuel vapor from tank passageway 12 P to the separate upper chamber 26 U of valve compartment 26 to supply pressurized fuel vapor from fuel tank 18 to the opposite second side 241 of pressure-controlled valve 24 as suggested in FIG. 7 . Valve-pressurization feed passageway 24 F has a first opening in first side 241 of pressure-controlled valve 24 and an opposite second opening in second side 242 of pressure-controlled valve 24 as suggested in FIGS. 2, 7, and 7A .

Pressure-controlled valve 24 is also formed to include the pressurized-vapor bleed passageway 24 B to allow pressurized fuel vapor (V d ) to flow from the separate upper chamber 26 U of valve compartment 26 into canister passageway 16 P for discharge into fuel-vapor recovery canister 20 when the valve-opening means 28 is actuated by the electrical input as suggested in FIGS. 8 and 8A . This causes pressurized fuel vapor (V d ) to vent from the separate upper chamber 26 U of valve compartment 26 through pressurized-vapor bleed passageway 24 B into canister passageway 16 P.

Divider plate 243 is made of a plastics material and formed to include valve-pressurization feed passageway 24 F as shown, for example, in FIG. 4 . Seal ring 245 is coupled to divider plate 243 to move therewith and formed to include pressurized-vapor bleed passageway 24 B as suggest in FIGS. 2 and 3 . Seal ring 245 is arranged to mate with valve seat 24 S upon movement of pressure-controlled valve 24 to the closed position as suggested in FIGS. 7 and 7A . Web portion 24 W is a pliable diaphragm having a radially inner portion coupled to a peripheral portion of divider plate 243 and a radially outer portion coupled to rim portion 24 R to support pressure-controlled valve 24 for movement in valve compartment 26 relative to valve housing 14 between the closed and opened positions.

Pressurized-vapor bleed passageway 24 B is arranged to conduct fuel vapor between canister passageway 16 P and upper chamber 26 U of valve compartment 26 when pressure-controlled valve 24 is in the closed position. Valve-pressurization feed passageway 24 F is arranged to conduct fuel vapor between tank passageway 12 P and upper chamber 26 U of valve compartment 26 when pressure-controlled valve 24 is in the closed position.

Bleed-passageway stopper 28 S is located in the separate upper chamber 26 U of valve compartment 26 for up-and-down movement relative to center portion 24 C of pressure-controlled valve 24 between a bleed-blocking position shown in FIGS. 6 and 7 engaging center portion 24 C to block discharge of pressurized fuel vapor from the separate upper chamber 26 U of valve compartment 26 into canister passageway 16 P through pressurized-vapor bleed passageway 24 B and a bleed-allowing position shown in FIGS. 8 and 9 disengaging center portion 24 C to allow discharge of pressurized fuel vapor from the separate upper chamber 26 U of valve compartment 26 into canister passageway 16 P. Such fuel vapor discharge lowers pressure of fuel vapor exposed to the opposite second side 242 of pressure-controlled valve 24 to a level that is below the level of pressure of pressurized fuel vapor in lower chamber 26 L of valve compartment 26 that is applied to first side 241 of pressure-controlled valve 24 so that pressure-controlled valve 24 is moved from the closed position to an opened position to allow pressurized fuel vapor (V T ) extant in tank passageway 12 P to flow into canister passageway 16 P through the fluid-conducting interface 14 I provided between fuel and canister passageways 12 P, 16 P.

Valve seat 24 S is ring-shaped and extends around a vertical central axis as shown in FIG. 4 . Bleed-passageway stopper 28 S is arranged to be moved up and down relative to center portion 24 C of pressure-controlled valve 24 along a vertical stopper-motion axis that is coextensive with vertical central axis 14 A as suggested in FIGS. 3 and 8-10 .

Divider plate 243 arranged to lie above valve seat 24 S and formed to include a seal-receiving aperture 244 opening into lower chamber 16 L of valve compartment 26 and into canister passageway 16 P. Seal ring 245 is arranged to extend through the seal-receiving aperture 244 and formed to include the pressurized-vapor bleed aperture 24 B.

Seal ring 245 includes a sleeve 245 S, a lower flange 245 L, and an upper flange 245 U as shown in FIG. 5 . Sleeve 245 S is formed to define pressurized-vapor bleed passageway 24 B and arranged to extend through the seal-receiving 244 aperture formed in divider plate 243 . Lower flange 245 L is coupled to a lower end of sleeve 245 S and arranged to mate with valve seat 24 S to establish a sealed connection therebetween to block flow of pressurized fuel vapor (V T ) between the tank and canister passageways 12 P, 16 P when pressure-controlled valve 24 is in the closed position.

Upper flange 245 U is coupled to an opposite upper end of sleeve 245 S to face into the separate upper portion 26 U of valve compartment 26 . Upper flange 245 U is arranged to mate with the valve-opening means 28 to establish a sealed connection therebetween to block flow of pressurized fuel vapor (V d ) from the separate upper chamber 26 U of valve compartment 26 through pressurized-vapor bleed passageway 24 B into canister passageway 16 P until the valve-opening means 28 is actuated by the electrical input.

The valve-opening means is provided by an electronic bleed controller 28 associated with pressure-controlled valve 24 and arranged to lie normally in a flow-blocking position to block flow of pressurized fuel vapor from valve-pressurization feed passageway 24 F to canister passageway 16 P through pressurized-vapor bleed passageway 24 B. Electronic bleed controller 28 is arranged to move from the flow-blocking position shown in FIGS. 7 and 7A to a flow-allowing position shown in FIGS. 8 and 8A to allow flow of pressurized fuel vapor (V d ) from valve-pressurization feed passageway 24 F to the canister passageway 16 P through pressurized-vapor bleed passageway 24 B to lower pressure of pressurized fuel vapor exposed to the opposite second side 242 of pressure-controlled valve 24 in response to the electrical input to cause pressure-controlled valve 24 to move from the closed position shown in FIGS. 8 and 8A away from valve seat 24 S to the opened position shown in FIGS. 9 and 9A to allow pressurized fuel vapor to flow from tank passageway 12 P into canister passageway 16 P.

Valve-pressurization feed passageway 24 F has an inlet 24 FI formed in first side 241 of pressure-controlled valve 24 to receive pressurized fuel vapor discharged from tank passageway 12 P and an outlet 24 FO formed in the opposite second side 242 of pressure-controlled valve 24 to communicate pressurized fuel vapor to the opposite second side 242 as suggested in FIGS. 7 and 7A . Valve-pressurization feed passageway 24 F is arranged to lie in spaced-apart relation to pressurized-vapor bleed aperture 24 B as suggested in FIG. 7A .

Pressure-controlled valve 24 includes a perimeter rim 24 R coupled to valve housing 14 , a center portion 24 C arranged to lie in confronting relation to valve seat 24 S of valve housing 14 and formed to include the valve-pressurization feed passageway 24 F and the pressurized-vapor bleed aperture 244 , and a web portion 24 W as suggested in FIG. 4 . Web portion 24 W is arranged to interconnect center portion 24 C and perimeter rim 24 R as suggested in FIG. 7 . Web portion 24 W is arranged to support center portion 24 C for movement relative to valve seat 24 S to engage valve seat 24 S and align the pressurized-vapor bleed aperture 24 B in fluid communication with canister passageway 16 P in the closed position of pressure-controlled valve 24 as suggested in FIG. 7A and disengage valve seat 24 S in the opened position of pressure-controlled valve 24 as suggested in FIG. 8A .

Valve housing 14 includes a body 10 B including valve seat 24 S, a tank pipe 12 that is formed to include a portion of the tank passageway 12 P, and a canister pipe 16 that is formed to include a portion of the canister passageway 16 P as suggested in FIG. 3 . Valve housing 14 also includes a cap 15 coupled to body 10 B to form a valve compartment 26 containing pressure-controlled valve 24 to allow movement of pressure-controlled valve 24 between the closed and opened positions as suggested in FIGS. 7 and 9 . Pressure-controlled valve 24 is arranged to divide valve compartment 26 into a lower chamber 26 L bounded in part by first side of pressure-controlled valve 24 and a separate upper chamber 26 U bounded in part by the opposite second side 242 of pressure-controlled valve 24 . Valve-pressurization feed passageway 24 F is formed in pressure-controlled valve 24 to communicate with upper chamber 26 U of valve compartment 26 . An inlet end of pressurized-vapor bleed passageway 24 B is arranged to communicate with upper chamber 26 U of valve compartment 26 . An outlet end of pressurized-vapor bleed passageway 24 B is arranged to communicate with canister passageway 16 P.

Valve-opening means 28 includes a bleed-passageway stopper 28 S that is located in upper chamber 26 U of valve compartment 26 . Bleed-passageway stopper 28 S is aligned to lie in close proximity to the inlet end of pressurized-vapor bleed passageway 24 B formed in pressure-controlled valve 24 and move relative to pressure-controlled valve 24 during movement of the electronically controlled electronic bleed controller 28 between the flow-allowing and flow-blocking positions to regulate flow of pressurized fuel vapor from upper portion 26 U of valve compartment 26 to canister passageway 16 P via the pressurized-vapor bleed passageway 24 B.

Pressure-controlled valve 24 is arranged to lie between the electronically controlled pressure-bleed valve 28 and valve seat 24 S included in valve housing 14 as shown in FIG. 2 . Valve compartment 26 contains the pressure-controlled valve 24 and interconnects valve-pressurization feed passageway 24 F and pressurized-vapor bleed passageway 24 B in fluid communication. Upper chamber 26 U arranged to communicate pressurized fuel vapor from valve-pressurization feed passageway 24 L to pressurized-vapor bleed passageway 24 B.

A tank venting system 18 C, 10 , 20 C is provided to control flow of air and fuel vapor between a fuel tank 18 and an emission control system including a fuel-vapor recovery canister 20 as suggested in FIG. 2 . Tank venting system 18 C, 10 , 20 C is used onboard a vehicle (not shown) including an engine and a purge vacuum source coupled to engine and canister 20 .

Both pressure-controlled valve 24 and bleed-passageway stopper 28 S are controlled by electronic bleed controller 28 . Pressure-controlled valve 24 is configured to selectively allow a relatively large volume of fuel vapor to flow from tank 12 to canister 20 to relieve unwanted tank pressure conditions as suggested in FIG. 9 . Bleed-passageway stopper 28 S is configured to selectively allow a relatively small volume of fuel vapor (V d ) to flow to atmosphere 22 via canister 20 and thereby control pressures applied to pressure-controlled valve 24 as suggested in FIGS. 8 and 9 .

Electronic bleed controller 28 is an actuator that is directly coupled to bleed-passageway stopper 28 S and indirectly coupled to pressure-controlled valve 24 via a lost-motion connector provided by test-condition valve opener 30 as shown in FIGS. 10 and 10A . Direct connection of actuator 28 with stopper 28 S and indirect connection of actuator 28 with pressure-controlled valve 24 causes stopper 28 S to be opened ahead of pressure-controlled valve 24 so that pressures applied to pressure-controlled valve 24 assist actuator 28 in opening pressure-controlled valve 24 . By adjusting pressures applied to the pressure-controlled valve 24 , stopper 28 S can reduce force needed to move the pressure-controlled valve 24 to the opened position. Accordingly, the power required to control flow through tank venting system 18 C, 10 , 20 C is less than if controlling a relatively-large volume flow valve with only a directly connected electronic actuator.

In the illustrated embodiment, tank pipe 12 extends directly from lower chamber 26 L and canister pipe 16 extends directly from upper chamber 26 U such that tank pipe 12 and canister pipe 16 are offset from one another and pressure losses incurred during movement of fluid from pipes 12 , 16 into/out of valve-receiving space 26 are minimized.

Illustrative components included in vent apparatus 10 are shown in FIG. 3 . A top housing cover 15 is ultrasonically welded to a top side 14 T of valve housing 14 of body 10 B and a bottom housing cover 15 is ultrasonically welded to a bottom side 14 B of valve housing 14 . An assembly 80 comprising a lid 81 , an O-ring 82 , a plate 83 , a can 24 , and an electronic bleed controller 28 comprising a coil assembly 72 and a stopper mover 73 mounted for movement in a vertical passageway 72 P formed in coil assembly 72 is shown in FIG. 3 . Stopper mover 73 comprises a rod 75 , a mover past 74 coupled to bleed-passageway stopper 28 S, and a coiled compression spring 76 interposed between and in contact with rod 75 and mover post 74 .

Electronic bleed controller 28 is configured to be electronically controlled by a controller actuator 70 as suggested in FIG. 1 . Electronic bleed controller 28 includes a coil assembly 72 , a mover post 74 , and a bias spring 76 as shown in FIGS. 1 and 2 . Coil assembly 72 is configured to be energized by controller actuator 70 to retract mover post 74 . Mover post 74 is mounted for movement within coil assembly 72 for movement between an extended and a retracted position. Mover post 74 is coupled directly to bleed-passageway stopper 28 S and indirectly to pressure-controlled valve 24 via lost-motion coupler 30 such that retraction of mover post 74 opens, first bleed-passageway stopper 28 S as suggested in FIGS. 8 and 8A and then pressure-controlled valve 24 as suggested in FIGS. 10 and 10A . Bias spring 76 biases mover post 74 toward the extended position.

In illustrative embodiments, vacuum-relief valve 38 and pressure-relief valve 30 are incorporated into vent apparatus 10 to accommodate fault modes of the vent apparatus 10 . Vacuum-relief valve 38 is configured to allow vapor to flow from canister 20 (and atmosphere 22 ) to tank 12 upon a large enough vacuum pressure developing in tank 12 . Pressure-relief valve 36 is configured to allow vapor to flow from tank 12 to canister 20 (and atmosphere) upon a large enough pressure developing in tank 12 .

In operation, to open the pressure-controlled valve 24 thereby allowing a relatively large flow of fuel vapor to move from tank 12 to canister 20 , an electrical signal is generated by controller actuator 70 associated with opening of bleed-passageway stopper 28 S. The electrical signal may be generated in response to a user opening an outer fuel door of a vehicle indicative that the use may be about to refuel the vehicle. Upon receipt of the electrical signal, electronic bleed controller 28 begins to retract bleed-passageway stopper 28 S to allow a relatively small flow of fuel vapor (V d ) from upper chamber 26 U of valve-receiving space 26 toward canister 20 and atmosphere 22 as suggested in FIGS. 8 and 8A .

The relatively small flow of fuel vapor (V d ) changes the pressure applied to pressure-controlled valve 24 to make the pressure-controlled valve 24 easier to open because of differential pressure applied to the deformable diaphragm 24 W. As bleed-passageway stopper 28 S continues to retract, the lost-motion connector 30 is engaged and the pressure-controlled valve 24 is opened during a test condition.

Vent apparatus 10 provides a fuel management isolation valve system in which the pressure feed 24 F and pressure bleed 24 B are located in the pressure-controlled valve 24 and electronic bleed controller 28 engages and retracts or pulls open a diaphragm seal established by pressure-controlled valve 24 . A one millimeter feed orifice 24 F is formed in pressure-controlled valve 24 outside of the main seal area in contact with valve seat 24 S. A bleed orifice 24 B is now at the center of pressure-controlled valve 24 and is sealed by a bleed-passageway stopper 28 S coupled to electronic bleed controller 28 . When the coil is energized the armature 73 will move about 0.5 millimeter to move stopper 28 S to open bleed orifice 24 B and begin to decay the pressure on top of pressure-controlled valve 24 in upper chamber 26 U. As this occurs, pressure-controlled valve 24 will begin to blow open on its own and the armature continues to pull in to the coil core until the pressure-controlled valve 24 is full open. The pressure-controlled valve 24 is then held open by armature/cage connections until the coil is allowed to de-energize. Pressure-controlled valve 24 opens on its own in this way and the bleed size is minimized. Therefore a smaller coil is required in this design to initiate bleed of pressure from upper chamber 26 and to hold pressure-controlled valve 24 open under OBDII pressure-testing conditions.