ISOLATION VALVE WITH INTEGRATED FLOAT
VALVE FOR HIGH-PRESSURE APPLICATIONS
TECHNICAL FIELD
[0001] The present teachings relate to a valve assembly for controlling fluid flow to
and from a high-pressure fuel tank, and more particularly to such a valve assembly that also
has a float valve integrated into the assembly.
BACKGROUND
[0002] High-pressure fluid reservoirs, such as high-pressure fuel tanks, may use an
isolation valve to open and close a vapor path between the fuel tank and a purge canister. In
a typical evaporative emissions system, vented vapors from the fuel system are sent to a
purge canister containing activated charcoal, which adsorbs fuel vapors. During certain
engine operational modes, with the help of specifically designed control valves, the fuel
vapors are adsorbed within the canister. Subsequently, during other engine operational
modes, and with the help of additional control valves, fresh air is drawn through the canister,
pulling the fuel vapor into the engine where it is burned.
[0003] For high-pressure fuel tank systems, an isolation valve may be used to isolate
fuel tank emissions and prevent them from overloading the canister and vapor lines. The
isolation valve itself may be a normally-closed, solenoid-operated valve that is opened to
allow vapor to flow out of the tank for depressurization or any other event requiring a
controlled vapor release.
[0004] Emissions systems may also include a fuel limit vent valve (FLVV) that vents
the fuel tank during refueling until the tank is filled to a desired. When the tank is full, the
FLVV closes, creating a pressure drop in a filler tube to initiate shutoff of a filler nozzle. The
isolation valve may work in conjunction with the FLVV by limiting vapor flow rate to a level
less than the maximum flow rate that the FLVV can handle. This prevents rushing fuel
vapors from "corking" the FLVV to a closed position. The control provided by the isolation
valve may also prevent corking of other vent valves (e.g., an over-pressure relief valve and/or
a vacuum relief valve) in the emissions system.
[0005] The isolation valve and the FLVV, along with other vent valves, may be
arranged in series with each other. However, there is a desire for a valve assembly that
combines the isolation valve function with a venting function to provide a more efficient,
compact assembly.
SUMMARY
[0006] A valve assembly for a high-pressure fluid reservoir according to one aspect of
the present teachings comprises an isolation valve having a selectively energizable coil, an
armature that is moveable between a first position when the coil is energized and a second
position when the coil is de-energized, and an isolation valve seal coupled to the armature.
The assembly also includes a float valve having a float with a passage at a bottom portion and
an orifice at a top portion of the float, wherein the isolation valve seal is aligned to open and
close the passage and wherein vapor flows through the passage and the orifice when the coil
is energized during a high pressure condition. A housing houses both the isolation valve and
the float valve and has a port that is opened and closed by the float valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 illustrates a valve assembly according one aspect of the teachings
during a high-pressure control condition where a coil in a solenoid valve is energized to open
an isolation valve and where a float valve is closed;
[0008] Figure 2 is a cross-sectional view of the valve assembly shown in Figure 1
during the high-pressure control condition where the coil is energized and both the isolation
valve and the float valve are open;
[0009] Figure 3 is a cross-sectional view of the valve assembly shown in Figure 1
during a refueling condition where the coil is de-energized, the isolation valve, and the float
valve is movable between an open position and a closed position;
[0010] Figure 4 illustrates a valve assembly according to another aspect of the
teachings;
[001 1] Figure 5 illustrates a valve assembly integrating an over-pressure relief valve
according to yet another aspect of the teachings;
[0012] Figure 6 illustrates a valve assembly integrating an over-pressure relief valve
according to a further aspect of the teachings.
DETAILED DESCRIPTION
[0013] Figure 1 is a cross-sectional view of an integrated valve assembly 10 for a
high-pressure fluid reservoir, such as a fuel tank 11, according to one aspect of the present
teachings during a high-pressure control condition. The valve assembly 10 can include an
isolation valve 12 and a float-operated vent valve 14, such as a fuel limit vapor valve
(FLVV). For illustrative purposes only, the float valve 14 in Figures 1 through 6 is an FLVV,
but those of ordinary skill in the art will understand that the float valve 14 can be another type
of valve and/or have a different function without departing from the scope of the teachings.
In this aspect, the isolation valve 12 is disposed beneath the FLVV 14. However, as shown in
Figure 5, the isolation valve 12 may be disposed above the FLVV 14 as well. The isolation
valve 12 and the FLVV 14 may be disposed together in a housing 16 to form an integrated
unit.
[0014] The isolation valve 12 can be a solenoid-operated valve having a coil 18 and
an armature 20 that actuates based on the energized or de-energized state of the coil 18.
Electrical terminals 22 link the coil 18 to a controller (not shown) that controls the electrical
signals sent to the coil 18. The armature 20 may include a narrower piston portion 24. An
isolation valve seal 26 is attached to the piston portion 24 and may be biased toward to a
closed position by an armature spring 28 to close a passage 30.
[0015] Although the isolation valve seal 26 may be attached to the armature 20 by
being formed as an integral part thereof, the isolation valve seal 26 may also be formed as a
separate component. In the teachings shown in Figures 1 through 6, the isolation valve seal
26 can be separate and independent from the armature 20 and can be attached to the piston
portion 24 via an engagement structure 26a, such as a hook or catch, that engages with a
corresponding engagement structure 24a, such as a ledge, on the piston portion 24.
[0016] In certain aspects of the teachings, the armature spring 28 may bias the
isolation valve seal 26 by engaging a flange on the seal 26. Note that the armature spring 28
in this aspect does not touch the armature 20 or piston portion 24 itself. This allows the
isolation valve seal 26 to be decoupled from the armature 20 and not be affected by friction
between the armature 20 and other components within the isolation valve 12 (e.g., the piston
portion 24) that may cause response delays or hysteresis. Moreover, biasing the isolation
valve seal 26 alone ensures that the passage 30 is securely closed even if the armature 20
itself is not in a fully sealing position. In other words, the decoupled isolation valve seal 26
does not depend on perfect operation of the armature 20 to reliably open and close the
isolation valve 12.
[0017] The float valve 14 may include a float 32 that may be biased by a float spring
34 toward a closed position. The float 32 itself may have a seal 36 that contacts a seat 38 to
restrict vapor access to a port 40 that links the valve assembly 10 with another component in
the emissions system, such as a canister (not shown). The housing 16 may include one or
more spillover windows 41, which allow fuel to enter the float valve 14 and lift the float 32
quickly once fuel reaches the edge of the window 41. Vapor may also flow from the tank 11
through the window 4 1 into the valve assembly 20 during operation of the isolation valve 12,
which will be explained in greater detail below.
[0018] In one aspect of the teachings, the float 32 can be hollow and the passage 30
opened and closed by the isolation valve 12 is disposed at the bottom of the float 32. The
hollow float structure allows vapor to flow through the float 32 as well as around it when the
isolation valve 12 is open. A float orifice 42 at the top of the float 32 can act as a flow
restrictor to provide controlled vapor flow from the valve assembly 10 into the port 40 to
prevent corking of other valves in the emissions system. In one aspect, the float valve 14 can
close the port 40 when a fuel level in the tank 11 reaches a predetermined level or when the
vapor pressure within the valve assembly 10, combined with the biasing force of the float
spring 34, is high enough to overcome the weight of the float 32 and push it upward against
the float seal 36. Note that when the float 32 is in the closed position, vapor can still flow
through the float orifice 42 to relieve pressure in the fuel tank 11.
[0019] In one aspect, the float valve 14 may also include an optional liquid/vapor
discriminator 44 that closes the float orifice 42. The discriminator 44 blocks liquid fuel from
entering the port 40.
[0020] The operation of the valve assembly 10 will now be explained. Figure 1
shows the valve assembly 10 during a high tank pressure condition where controlled release
of the tank pressure is desired. The controller (not shown) sends an electrical signal through
the terminals 22 to energize the coil 18. The resulting magnetic field can pull the armature 20
into the isolation valve 12 (downward in the illustration shown in Figure 1) against the
biasing force of the armature spring 28, drawing the piston portion 24 and its attached
isolation valve seal 26 away from the passage 30, allowing vapor to flow through the float 32.
[0021] At this stage, pressurized vapor in the tank 11 can flow through the spillover
window 4 1 into the valve assembly 10. At this stage, the combined forces from the float
spring 34 and the vapor pressure within the valve assembly 10 may be high enough to push
the float 32 upward so that the float seal 36 presses against the port seat 38. At this point, a
controlled amount of vapor may flow out of the tank 11 into the port 40 through the float
orifice 42, allowing the tank 11 to depressurize while keeping the vapor flow rate below a
maximum flow rate to prevent corking of other valves in the emissions system and allow
continued venting.
[0022] Figure 2 is a cross-sectional view of the valve assembly 10 shown in Figure 1
after tank depressurization has taken place. This may occur after, for example, the tank
pressure is low enough to allow greater vapor flow without corking or prior to a refueling
operation. At this stage, the coil 18 is still energized, keeping the armature 20 retracted in the
isolation valve 12 and the piston portion 24 in the open position. However, since the vapor
pressure in the tank 11, and therefore the valve assembly 10, is lower, there is less pressure
holding the float 32. The weight of the float 32 can overcome the biasing force of the float
spring 34 as well as the lower vapor pressure in the assembly 10, allowing the float 32 to
drop to an open position as shown in Figure 2 and completely open the port 40. As a result,
vapor can flow through the spillover window 4 1 directly into the port 40, bypassing the other
components in the valve assembly 10.
[0023] The integrated structure of the valve assembly 10 allows the same assembly 10
to handle venting during a refueling process as well as tank pressure control. Figure 3 is a
cross-sectional view of the valve assembly shown in Figure 1 after refueling. At this stage,
the coil 18 is still energized, with the armature 20 in the retracted position. Also, the isolation
valve seal 26 rests against the passage 30 at the bottom of the float 32 and the float valve 14
is in an open position because the weight of the float 32 and the pressure drop across the float
seal 36 overcome the biasing force of the float spring 34. Moreover, the fuel level in the tank
is not high enough to fill the float valve 14 and lift the float 32. As a result, vapor flows
freely through the port 42.
[0024] During refueling, vapor continues to flow freely through the port 42. When
the fuel level in the tank 11 rises high enough to reach the edge of the spillover window 41,
liquid fuel spills through the window 4 1 into the float valve 14. As a result, the float 32 can
quickly rise until the float seal 36 reaches the port seat 38 to essentially close off the port 40.
The resulting vapor drop in the rest of the emissions system may initiate shutoff of a refueling
nozzle (not shown). If the valve assembly includes a liquid/vapor discriminator 44, the rising
fuel level can cause the discriminator 44 to close the float orifice 42, sealing the port 40.
Since the risk of undesirable liquid fuel entering the emissions system via the port 40 may be
high when the tank is full, the discriminator 44 prevents even a small amount of liquid fuel
from entering the port 40 by blocking the float orifice 42. However, the discriminator 44 is
not required to create the pressure drop in the port 40 necessary to induce nozzle shutoff.
[0025] Note that in an alternative aspect of the teachings as shown in Figure 4, the
isolation valve 12 can be disposed above the float valve 14 instead of below it. To
accommodate this new orientation while maintain the same functionality, the piston portion
24 and isolation valve seal 26 may be disposed to hang inside float 32. When the coil 18 is
de-energized, the isolation valve 12 can be biased to the closed position by the armature
spring 28. In this aspect, the armature spring 28 can engage the piston portion 24 instead of
the isolation valve seal 26, but the isolation valve seal 26 can still move independent of the
piston portion 24. When the coil 18 is energized, the armature 20 and piston portion 24 may
move downward, pushing the isolation valve seal 26 downward to the open position.
[0026] Figures 5 and 6 illustrate additional aspects of the present teachings. Figure 5
illustrates an example of the valve assembly 10 in Figure 1 with the addition of an integrated
over-pressure relief (OPR) valve 50, while Figure 6 illustrates an example of the valve
assembly in Figure 4 with the integrated OPR valve 50. In both aspects, the OPR valve 50
can have a valve plate 52 and a seal 54 covering an OPR orifice 56. The valve plate 52 can
be biased closed by a resilient member 58, such as a spring. The biasing force of the resilient
member 58 may be selected so that the OPR valve 50 opens when the vapor pressure in the
fuel tank 11 reaches above a selected level, thereby relieving excessive tank pressure.
[0027] Although the examples above focus on an isolation valve for a fuel tank, those
of ordinary skill in the art will recognize that the valve assembly can be used in any
application where controlled pressure release and valve shutoff are desired. Thus, the above
description should not be read to be limited to fuel emissions systems.
[0028] It will be appreciated that the above teachings are merely exemplary in nature
and is not intended to limit the present teachings, their application or uses. While specific
examples have been described in the specification and illustrated in the drawings, it will be
understood by those of ordinary skill in the art that various changes may be made and
equivalents may be substituted for elements thereof without departing from the scope of the
present teachings as defined in the claims. Furthermore, the mixing and matching of features,
elements and/or functions between various examples is expressly contemplated herein so that
one of ordinary skill in the art would appreciate from this disclosure that features, elements
and/or functions of one example may be incorporated into another example as appropriate,
unless described otherwise, above. Moreover, many modifications may be made to adapt a
particular situation or material to the teachings of the present disclosure without departing
from the essential scope thereof. Therefore, it is intended that the present teachings not be
limited to the particular examples illustrated by the drawings and described in the
specification as the best mode presently contemplated for carrying out the teachings of the
present disclosure, but that the scope of the present disclosure will include any embodiments
falling within the foregoing description and the appended claims.
CLAIMS
What is claimed is:
1. A valve assembly for a high-pressure fluid reservoir, comprising:
an isolation valve having
a coil that is selectively energizable,
an armature that is moveable between a first position when the coil is
energized and a second position when the coil is de-energized, and
an isolation valve seal coupled to the armature;
a float valve having a float with a passage at a bottom portion and an orifice at
a top portion, wherein the isolation valve seal is aligned to open and close the passage and
wherein vapor flows through the passage and the orifice when the coil is energized; and
a housing that houses both the isolation valve and the float valve, the housing
having a port that is opened and closed by the float valve.
2. The valve assembly of claim 1, wherein the coil is energized during a high
pressure condition when controlled pressure release is desired.
3. The valve assembly of claim 1, wherein the isolation valve further comprises
an armature spring that biases the armature to the second position, and wherein when the coil
is energized, the armature overcomes a biasing force of the armature spring when moving to
the first position.
4. The valve assembly of claim 1, wherein the first position is a retracted position
and the second position is an extended position.
5. The valve assembly of claim 1, wherein the isolation valve seal closes the
passage when the armature is in the first position.
6. The valve assembly of claim 1, wherein the isolation valve is disposed below
the float valve, and wherein the armature pushes the float downward and the isolation valve
seal closes the passage in the float when the coil is de-energized and the armature is in the
second position.
7. The valve assembly of claim 1, wherein the isolation valve is disposed above
the float valve, and wherein the armature pulls the float upward and the isolation valve seal
closes the passage in the float when the coil is de-energized and the armature is in the second
position.
8. The valve assembly of claim 1, wherein the isolation valve seal is a separate,
independent component from the armature.
9. The valve assembly of claim 8, wherein the armature includes a narrower
piston portion that couples the isolation valve seal with the armature.
10. The valve assembly of claim 8, wherein the isolation valve further comprises
an armature spring that biases the isolation valve seal to the second position without
contacting the armature itself, wherein when the coil is energized, the armature overcomes a
biasing force of the armature spring when moving to the first position.
11. The valve assembly of claim 8, wherein the isolation valve seal and the piston
portion each have an engagement structure that engages the isolation valve seal with the
piston portion.
12. The valve assembly of claim 1, further comprising a spillover window
disposed in the housing near the isolation valve.
13. The valve assembly of claim 1, further comprising a liquid/vapor
discriminator disposed in the float valve, wherein the discriminator is aligned to open and
close the orifice.
14. The valve assembly of claim 13, wherein the float is hollow, and wherein the
liquid/vapor discriminator is disposed inside the float.
15. The valve assembly of claim 1, further comprising an over-pressure relief
valve.
16. The valve assembly of claim 15, wherein the over-pressure relief valve is
disposed in the housing.
17. The valve assembly of claim 15, wherein the housing includes an over¬
pressure orifice and the over-pressure relief valve includes:
a valve plate;
a seal disposed on the valve plate; and
a resilient member that biases the valve plate to close the over-pressure orifice.