U.S. patent application number 15/358746 was filed with the patent office on 2017-07-06 for isolation valve with fast depressurization for high-pressure fuel tank.
The applicant listed for this patent is Eaton Corporation. Invention is credited to Raymond Bruce McLauchlan, DANIEL LEE PIFER.
Application Number | 20170191580 15/358746 |
Document ID | / |
Family ID | 53181829 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170191580 |
Kind Code |
A1 |
PIFER; DANIEL LEE ; et
al. |
July 6, 2017 |
ISOLATION VALVE WITH FAST DEPRESSURIZATION FOR HIGH-PRESSURE FUEL
TANK
Abstract
An isolation valve includes a flow restrictor in a passage and
having an orifice and configured to provide a first, second, and
third flow paths. A spring may bias the flow restrictor to an open
position that opens the second flow path. A solenoid assembly may
include a coil and an armature moveable between an extended
position that moves the flow restrictor to close the first, second,
and third flow paths, and a retracted position that opens the first
flow path. The first flow path may include a path from a first
reservoir through the orifice to a second reservoir. The second
flow path may include a first flow direction from the first
reservoir to the second reservoir via a second path, the second
path including a space between the flow restrictor and the passage.
The third flow path may include a second flow direction from the
second reservoir to the first reservoir via the second path.
Inventors: |
PIFER; DANIEL LEE; (Chelsea,
MI) ; McLauchlan; Raymond Bruce; (Macomb Township,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Eaton Corporation |
Cleveland |
OH |
US |
|
|
Family ID: |
53181829 |
Appl. No.: |
15/358746 |
Filed: |
November 22, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14611637 |
Feb 2, 2015 |
9500291 |
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15358746 |
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13011511 |
Jan 21, 2011 |
8944100 |
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14611637 |
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12749924 |
Mar 30, 2010 |
8584704 |
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13011511 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02D 41/004 20130101;
F16K 24/04 20130101; F02M 25/0854 20130101; F16K 31/0658 20130101;
F02M 2025/0845 20130101; Y10T 137/8704 20150401; F16K 17/04
20130101; Y10T 137/87394 20150401; B60K 15/03519 20130101; F16K
17/0413 20130101; F16K 31/0655 20130101; Y10T 137/87016 20150401;
F02M 25/0836 20130101; F16K 39/024 20130101; Y10T 137/7761
20150401; F16K 1/44 20130101; B60K 2015/03302 20130101; Y10T
137/87338 20150401; F16K 31/0696 20130101 |
International
Class: |
F16K 31/06 20060101
F16K031/06; F02M 25/08 20060101 F02M025/08; F16K 17/04 20060101
F16K017/04 |
Claims
1-20 (canceled)
21. An isolation valve, comprising: a flow restrictor disposed in a
passage, the flow restrictor having an orifice and configured to
provide a first flow path, a second flow path, and a third flow
path; a flow restrictor spring that applies a biasing force to the
flow restrictor to bias the flow restrictor to an open position
that opens the second flow path; and a solenoid assembly,
including: a coil; and an armature that is moveable between (i) an
extended position that overcomes the biasing force of the flow
restrictor spring to move the flow restrictor to a closed position
that closes the first flow path, the second flow path, and the
third flow path, and (ii) a retracted position that opens the first
flow path, wherein when the coil is energized, the armature moves
to the retracted position to allow vapor to flow through the first
flow path at least until the biasing force of the flow restrictor
spring overcomes a vapor pressure in a first reservoir to open the
second flow path; wherein the first flow path includes a first path
from the first reservoir through the orifice to a second reservoir;
the second flow path includes a first flow direction from the first
reservoir to the second reservoir via a second path, the second
path including space between the flow restrictor and the passage;
and the third flow path includes a second flow direction from the
second reservoir to the first reservoir via the second path.
22. The isolation valve of claim 21, wherein the flow restrictor is
configured to open the third flow path while the coil is not
energized if a vapor pressure in the second reservoir is
sufficiently greater than the vapor pressure in the first reservoir
that a vapor pressure differential and the biasing force of the
flow restrictor spring overcome a biasing force of a solenoid
spring of the solenoid assembly.
23. The isolation valve of claim 21, including a pressure relief
valve configured to provide a fourth flow path, wherein the fourth
flow path includes a path from the first reservoir through the
pressure relief valve to the second reservoir if the vapor pressure
in the first reservoir is greater than a third predetermined
value.
24. The isolation valve of claim 21, including a seal, wherein in
the extended position of the armature, the seal is in contact with
the armature, a piston of the flow restrictor, and a wall of the
passage.
25. The isolation valve of claim 21, wherein the passage includes a
funnel-shaped portion and a piston of the flow restrictor is
configured to move in the funnel-shaped portion.
26. The isolation valve of claim 25, wherein the funnel-shaped
portion includes a maximum diameter proximate the first reservoir
and a minimum diameter proximate the second reservoir.
27. The isolation valve of claim 21, wherein the passage includes a
step.
28. The isolation valve of claim 21, wherein the passage includes a
plurality of steps and an inner diameter of the passage is
different at each step.
29. The isolation valve of claim 28, wherein the plurality of steps
includes at least three steps.
30. The isolation valve of claim 21, wherein the passage includes a
tapered wall.
31. The isolation valve of claim 21, wherein the passage include a
plurality of tapered walls.
32. The isolation valve of claim 21, wherein the passage includes
one or more guide ribs disposed around a perimeter of the
passage.
33. The isolation valve of claim 32, wherein at least one of the
one or more guide ribs includes an upper end with a tapered
lead-in.
34. The isolation valve of claim 32, wherein the armature is
engaged with at least one of the one or more guide ribs.
35. An isolation valve, comprising: a flow restrictor disposed in a
passage having a funnel-shaped portion, the flow restrictor
including: an orifice; and a piston configured to move in the
funnel-shaped portion; a flow restrictor spring configured to apply
a biasing force on the flow restrictor to bias the piston to an
open position; and a solenoid assembly, including: a coil; and an
armature that is moveable between (i) an extended position that
overcomes the biasing force of the restrictor spring to move the
flow restrictor to a closed position and to close the orifice, and
(ii) a retracted position to open the orifice, wherein when the
coil is energized, the armature moves to the retracted position to
allow vapor to flow through the orifice at least until the biasing
force of the flow restrictor spring overcomes a vapor pressure;
and, the open position of the flow restrictor allows vapor to flow
through a space between the flow restrictor and the funnel-shaped
portion of the passage.
36. The isolation valve of claim 35, wherein the passage includes
one or more guide ribs disposed around a perimeter of the passage,
and at least one of the one or more guide ribs includes an upper
end with a tapered lead-in.
37. An isolation valve, comprising: a flow restrictor disposed in a
passage having a stepped portion, the flow restrictor having: an
orifice; and a piston configured to move in the stepped portion; a
flow restrictor spring that applies a biasing force on the flow
restrictor to bias the piston to an open position; and a solenoid
assembly, including: a coil; and an armature that is moveable
between (i) an extended position that overcomes the biasing force
of the restrictor spring to move the flow restrictor to a closed
position and to close the orifice, and (ii) a retracted position to
open the orifice, wherein when the coil is energized, the armature
moves to the retracted position to allow vapor to flow through the
orifice at least until the biasing force of the flow restrictor
spring overcomes a vapor pressure; and, the open position of the
flow restrictor allows vapor to flow through a space between the
flow restrictor and the stepped portion of the passage.
38. The isolation valve of claim 37, wherein the stepped portion
includes a plurality of steps and an inner diameter of the passage
is different at each step.
39. The isolation valve of claim 37, wherein the stepped portion
includes at least three steps and an inner diameter of the passage
is different at each step.
40. The isolation valve of claim 37, wherein the passage includes
one or more guide ribs disposed around a perimeter of the passage,
and at least one of the one or more guide ribs includes an upper
end with a tapered lead-in.
Description
REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 14/611,637 filed on Feb. 2, 2015, now U.S.
Pat. No. 9,500,291, which is a continuation-in-part of U.S. patent
application Ser. No. 13/011,511 filed on Jan. 21, 2011, now U.S.
Pat. No. 8,944,100, which is a continuation-in-part of U.S. patent
application Ser. No. 12/749,924 filed on Mar. 30, 2010, now U.S.
Pat. No. 8,584,704, which are all incorporated by reference.
TECHNICAL FIELD
[0002] The present teachings relates 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 can be
depressurized quickly.
BACKGROUND
[0003] 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 (e.g., vapor vent 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.
[0004] 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 valve that is opened to allow vapor
flow for tank depressurization or any other event where vapor
release is desired. The vapor flow rate may be controlled to, for
example, prevent corking of vent valves elsewhere in the emissions
system.
[0005] There is a desire for an isolation valve that can be used in
high-pressure fuel tanks and that can depressurize quickly in a
controlled manner to allow user access to the fuel tank within a
reasonable amount of time.
BRIEF SUMMARY
[0006] An isolation valve according to one example of the present
teachings may include a flow restrictor disposed in a passage
having non-parallel sides, the flow restrictor having an orifice. A
flow restrictor spring may apply a biasing force on the flow
restrictor to bias the flow restrictor to an open position. A
solenoid assembly may include having a coil and an armature that
may be moveable between (i) an extended position that overcomes the
biasing force of the restrictor spring to move the flow restrictor
to a closed position and to close the second orifice, and (ii) a
retracted position to open the orifice. If the coil is energized,
the armature may move to the retracted position to allow vapor to
flow through the orifice at least until the biasing force of the
flow restrictor spring overcomes a vapor pressure. The open
position of the flow restrictor may allow vapor to flow through a
space between the flow restrictor and the passage.
[0007] An isolation valve according to another example of the
present teachings may include a body including a passage having
non-parallel sides and a flow restrictor disposed in the passage.
The flow restrictor may include an orifice, an open position in
which the flow restrictor allows vapor flow in a space between the
flow restrictor and the passage, and/or a closed position in which
the flow restrictor prevents vapor flow between the flow restrictor
and the passage. The isolation valve may include an armature that
may be movable between (i) an extended position in which the
armature prevents vapor flow through the orifice, and (ii) a
retracted position, in which the armature allows vapor flow through
the orifice.
[0008] A method of operating an isolation valve according to
another example of the present teaching may include providing an
isolation valve body including a passage having non-parallel sides;
providing an flow restrictor in the passage. The flow restrictor
may include an orifice and a piston that may be movable between (i)
an open position in which the flow restrictor allows vapor flow in
a space between the flow restrictor and the passage, and (ii) a
closed position in which the flow restrictor prevents vapor flow
between the flow restrictor and the passage. The method may include
providing an armature that may be movable between (i) an extended
position in which the armature prevents vapor flow through the
orifice, and (ii) a retracted position, in which the armature
allows vapor flow through the orifice. The method may include
moving the armature to the retracted position to allow vapor to
flow through the orifice, reducing a vapor pressure via vapor
flowing through the orifice, and/or moving the piston gradually
from the closed position toward the open position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a cross-sectional view of a valve assembly
configured for controlling fuel vapor flow between a fuel tank and
a purge canister, with the valve shown in a completely closed
state, according to one example of the present teachings.
[0010] FIG. 1A is a magnified cross-sectional view of a
depressurizing valve according one example of the present
teachings.
[0011] FIG. 2 is a cross-sectional view of the valve assembly shown
in FIG. 1 when a solenoid in the valve assembly is energized during
a start of a depressurization process conducted before refueling of
the fuel tank.
[0012] FIG. 3 is a cross-sectional view of the valve assembly shown
in FIG. 1 when the solenoid is energized and the depressurizing
valve is in an open position while the flow restrictor is in a
closed position.
[0013] FIG. 4 is a cross-sectional view of the valve assembly shown
in FIG. 1 where both the depressurizing valve and the flow
restrictor are both in an open position.
[0014] FIG. 5 is a cross-sectional view of a valve assembly
according to another example of the present teachings.
[0015] FIG. 5A is a cross-sectional view of a valve assembly
according to another example of the present teachings.
[0016] FIG. 5B is a cross-sectional view of a valve assembly
according to another example of the present teachings.
DETAILED DESCRIPTION
[0017] Referring to the drawings, FIG. 1 generally illustrates a
fuel system, schematically represented by numeral 10. The system 10
may include a fuel tank 12 and a controller 14 that may regulate
the operation of an engine (not shown) and its fuel delivery system
(not shown). Fuel tank 12 may be operatively connected to an
evaporative emissions control system that includes a purge canister
18 that may collect fuel vapor from the fuel tank 12 and
subsequently release the fuel vapor to the engine. In addition,
controller 14 may regulate the operation of a valve assembly 20 to
selectively open and close the valve assembly 20, which may provide
over-pressure relief and/or vacuum relief for the fuel tank 12.
Valve assembly 20 may be connected to tank 12 via tank connector 24
and/to canister 18 via canister connector 26.
[0018] The valve assembly 20 itself may control fuel vapor flow
between the fuel tank 12 and the purge canister 18. Although the
valve assembly 20 shown in the figures is located between the fuel
tank 12 and the purge canister 18, nothing precludes the valve
assembly 20 from being located elsewhere, such as between the purge
canister 18 and the engine.
[0019] The valve assembly 20 may include a housing 22 that retains
internal components of the valve assembly 20 in a compact manner.
The valve assembly 20 may include a relief valve 28. The relief
valve 28 may include a piston 30, which may be formed from a
suitable chemically-resistant material such as an appropriate
plastic or aluminum. The relief valve 28 may also include a
compliant seal 32, which may be formed from a suitable
chemically-resistant elastomeric material. During operation, the
seal 32 may make initial contact with the housing 22 along the
seal's outer edge. After the initial contact with housing 22, the
outer edge of seal 32 may deflect to conform to the housing and
seal a passage 34.
[0020] The piston 30 and the seal 32 may be combined into a unitary
piston assembly via an appropriate manufacturing process, such as
overmolding, as understood by those skilled in the art. The piston
30 and the seal 32 may be biased to close the passage 34. A spring
36 or other resilient member may bias the piston and the seal 32.
The relief valve 28 may generally be used to open a vapor path
between the fuel tank 12 and the purge canister 18 to relieve an
extreme or over-pressure condition in the fuel tank 12. Additional
details of the operation of the relief valve 28 in conjunction with
the rest of the valve assembly 20 are described in
commonly-assigned, U.S. Pat. No. 8,584,704 on Mar. 30, 2010, the
disclosure of which is incorporated by reference herein in its
entirety.
[0021] The description below will now focus on operation of the
valve assembly 20, and particularly a solenoid assembly 40 and
components that operate in conjunction with it, during a
depressurization operation prior to refueling.
[0022] The solenoid assembly 40 includes an armature 42, a solenoid
spring 44, and a coil 46. The energization and de-energization of
the coil 46 may be controlled by a signal from the controller 14.
The solenoid spring 44 may generate a force sufficient to urge the
armature 42 out of the solenoid assembly 40 when the coil 46 is not
energized. When the coil 46 is energized, the resulting magnetic
forces overcome the biasing force of the solenoid spring 44 and
pull the armature 42 into the solenoid assembly 40, exposing a
small orifice 49 in a flow restrictor 50 to allow vapor flow
through the orifice 49 (see, e.g., FIG. 2).
[0023] In one example of the present teachings, the flow restrictor
50 may be arranged inside the housing 22 and may include a piston
portion 52, which may be formed from a suitable
chemically-resistant material such as an appropriate plastic or
aluminum. The flow restrictor 50 may also include a compliant seal
55, which may be formed from a suitable chemically-resistant
rubber. During valve operation, the seal 55 may initially contact
the housing 22 along the seal's outer edge. After initial contact
with the housing 22, the outer edge of seal 55 may deflect to
conform to the housing 22 and hermetically close a passage 56
leading to the canister connector 26.
[0024] In one aspect of the present teachings, the size of the
small orifice 49 in the flow restrictor 50 is selected to allow
only a selected amount of flow at a maximum specified tank pressure
because the size of the passage 56 is may be large enough to
prevent "corking." More particularly, without the small orifice 49
slowing vapor flow through the passage 56, the force from rushing
fuel vapors may force other valves in the system 10, such as a fuel
limit vent valve (not shown) in the fuel tank 12, to "cork" into a
closed position. Thus, the reduced size of the small orifice 49 in
the flow restrictor 50 may control the vapor flow to a level that
prevents corking. Vapor control may be desired for other purposes
as well without
[0025] Referring again to FIG. 2, when a user wishes to refuel the
tank, the user may wish to depressurize the fuel tank first so that
the potentially high pressure in the tank 12 is lowered to a
specified acceptable level. However, the size of the small orifice
49 may restrict the vapor flow rate to a level that is not high
enough to depressurize the tank in a reasonable amount of time. On
the other hand, allowing unrestricted vapor flow through the
isolation valve 10 may cause other valves in the system to cork,
such as explained above.
[0026] To provide closer control over vapor flow, the flow
restrictor 50 may include a depressurization valve 50a, as shown in
FIG. 1A, to allow faster tank depressurization. The
depressurization valve 50a may be a poppet valve, wherein the small
orifice 49 is in the poppet valve rather than the piston 52. The
depressurization valve 50a may have its own associated seal 57 that
seats against the piston 52. In examples of the present teachings,
the depressurization valve 50a may disposed in an intermediate
orifice 50b in the piston 52. In one aspect of the present
teachings, the size of the intermediate orifice 50b may be selected
to allow increased vapor flow while still limiting the flow enough
to prevent corking of fuel venting valves. The depressurization
valve 50a may be biased toward an open position by a
depressurization spring 50c supported by the piston 52. In one
aspect of the present teachings, the spring 50c may have a biasing
force that is greater than the spring 54 biasing the flow
restrictor 50 itself.
[0027] The flow restrictor 50 may have two effective orifice sizes
that may be opened when the solenoid assembly 40 is energized: (1)
a small orifice 49 in the depressurization valve 50a that may
ensure vapor flow rate between the tank and the canister is less
than a maximum flow rate to prevent corking of fuel tank venting
valves during normal valve operation; and, (2) an intermediate
orifice 50b in the piston 52 that, in combination with the small
orifice 49, may allow faster tank depressurization, such as before
a refueling operation. Also, a difference in biasing forces between
the springs 54, 50c may allow the depressurization valve 50a to
open at a given vapor pressure while the flow restrictor 50 remains
in a closed position, which may allow vapor to flow simultaneously
through the small orifice 49 and the intermediate orifice 50b.
[0028] In examples of the present teachings, a user may
depressurize the tank 12 by, for example, pushing a button on the
interior of the vehicle to send a control signal from the
controller 14. The signal may energize the coil 46, which may
create a magnetic force that withdraws the armature 42 to open the
small orifice 49 and creates a flow path through the flow
restrictor 50 and the passage 56. High tank pressure may create a
high vapor flow rate, which provide enough initial force to
compress both springs 54, 50c, keeping the piston 52 and the
depressurization valve 50a pushed downward against the large
passage 56 and restricting flow to only through the small orifice
49.
[0029] Referring to FIG. 3, if the spring force of the
depressurization spring 50c biasing the depressurization valve 50a
to an open position is larger than the spring force of the
restrictor spring 54 biasing the flow restrictor 50 to an open
position, and since the vapor pressure may drop soon after a small
amount of vapor escapes through the small orifice 49, the
depressurization spring 50c may force the depressurization valve
50a to an open position. The open position of the depressurization
valve 50A may allow for increased vapor flow by creating two flow
paths out of the tank 12, which may include one through the small
orifice 49 and one through the intermediate orifice 50b (e.g., in
the space between the depressurization valve 50a and the piston
52). The intermediate orifice 50b, which may be larger than small
orifice 49, may allow an increased flow rate out of the tank, which
may allow the tank 12 to depressurize to a desired level quicker
than through the small orifice 49 alone.
[0030] Referring to FIG. 4, the vapor pressure may drop low enough
so that the restrictor spring 54 overcomes the vapor pressure from
the tank and pushes the flow restrictor 50 open as well, which may
open a flow path through the large passage 56. As shown in FIG. 4,
the large passage 56 may be exposed when the armature 42 is
withdrawn into the solenoid assembly 40 in response to a tank
depressurization signal, such as noted above. This combination of
lower tank pressure and withdrawn armature 42 may allow the
restrictor spring 54 to extend, which may push the flow restrictor
50 upward against the armature 42 to close the small orifice 49 and
intermediate orifice 50b and open the large passage 56. At this
point, the tank pressure may be low enough to keep the vapor flow
at a lower level during the final stages of the tank
depressurization process, which may prevent corking in the fuel
vent valves.
[0031] The varying opening sizes 49, 50b, 56, used both alone and
in combination, and the different biasing forces of the springs 44,
50c may provide fast, yet controlled, tank depressurization while
still keeping the vapor flow rate low enough to prevent corking of
fuel vent valves in the emissions system.
[0032] FIG. 5 shows a further example of the present teachings that
may increase the vapor flow rate through the valve assembly 20.
This particular example may omit a separate depressurization valve
and additional orifice sizes. Instead, this example may provide for
modification of the configuration of the passage 56, the
characteristics of the restrictor spring 54, and/or the weight of
components of flow restrictor 50 (e.g., piston 52) to permit vapor
flow to increase gradually through the passage 56.
[0033] For instance, the passage 56 may include sides that may not
be parallel. Passage 56 may comprise generally cylindrically shaped
sides that may include arcuate sections. In an example of the
present teachings, passage 56 may be funnel-shaped, which may
include some or all arcuate sections of passage 56 being tapered.
When the coil 46 is initially energized to initiate tank
depressurization, the armature 42 may withdraw into the solenoid
assembly 40, allowing vapor to initially flow through the small
orifice 49. As the vapor pressure drops, the biasing force of the
restrictor spring 54 may lift the piston 52 from the passage 56 to
allow some of the vapor to bypass the flow restrictor 50 directly
into the passage 56. However, the funnel shape of the passage 56
restricts the amount of vapor flowing through the passage 56,
thereby preventing corking of the fuel vent valves. As a difference
in pressure is reduced, the restrictor spring 54 may gradually
force the flow restrictor 50 up the funnel-shaped passage 56 to a
wider point, which may allow even more vapor to flow under and/or
around the flow restrictor 50 into the passage.
[0034] In previous examples of the present teachings, flow
restrictor 50 may generally operate in a binary fashion, such that
flow restrictor 50 is either opened or closed at a predetermined
pressure. In this example of the present teachings, a funnel-shaped
passage 56 may permit gradual opening and/or gradual closing of
flow restrictor 50, which may allow for reduced depressurization
time without causing other vent valves to cork. Additionally or
alternatively, a funnel-shaped passage 56 may allow for orifice 49
to be smaller and a smaller orifice 49 may be opened via a lower
amount of force, which may allow for using a smaller solenoid
assembly 40.
[0035] In a further example of the present teachings, such as
generally illustrated in FIG. 5A, passage 56 may include a sloped
section 56a, but may include non-sloped sections (e.g., may not be
entirely funnel-shaped). A passage 56 with a sloped portion 56a may
function in a similar manner as a funnel-shaped passage. For
example, and without limitation, sloped portion 56a may gradually
increase the width and/or circumference of passage 56, which may
allow for gradual opening and closing of flow restrictor 50, and/or
faster depressurization.
[0036] In a further example of the present teachings, such as
generally illustrated in FIG. 5B, passage 56 may include a stepped
portion 56b. Stepped portion may include one or more steps (e.g.,
two, three, four, or more steps) that may gradually increase the
width and/or circumference of passage 56.
[0037] In examples of the present teachings, such as generally
illustrated in FIGS. 5A and 5B, piston 52 of flow restrictor 50 may
include an elongated, hollow body with a generally cylindrical
shape that may include a flow path between orifice 49 and passage
56. Seal 55 may be disposed generally between housing 22 and piston
52 and/or may define a minimum diameter of the small orifice 49.
The flow restrictor spring 54 may be disposed around the outside of
piston 52 and may engage a flange 52a of piston 52. The flange 52a
may extend radially outward from the body of piston 52 and/or may
extend around all or part of the circumference of piston 52. The
flow restrictor spring 54 may also engage a recess 22a of body 22
that may be disposed, for example, about half between the top and
bottom of piston 52 when piston 52 is in the closed position.
[0038] In the closed position, armature 42 may be biased by
solenoid spring 44 to contact piston 52 and/or seal 55 to keep
small orifice 49 closed. If solenoid assembly 40 is sufficiently
energized or activated, such as in response to a signal from
controller 14, armature 42 may be lifted off of seal 55 to expose
small orifice 49. Small orifice 49 may start allowing a balancing
of pressure and/or depressurization, and spring 54 may start moving
piston 52 toward an open position at a predetermined pressure
difference. Spring 54 may be a helical spring. As depressurization
continues, piston 52 may move in passage 56 such that the gap
between piston 52 and passage 56 increases via the sloped portion
56a and/or the stepped portion 56b. As the gap increases, a greater
vapor flow rate may be permitted, which may allow for faster
depressurization.
[0039] In other words, the shape of the passage 56 itself, in
combination with the piston 52 diameter, may naturally create a
passage 56 with a variable size to control vapor flow. Thus, the
combination of the funnel-shaped, sloped, and/or stepped passage 56
and the selected biasing force of the restrictor spring 54 against
the piston 52 may gradually adjust the amount of vapor released
from the fuel tank 12 while adjusting the vapor flow rate via the
position of the flow restrictor 50 in the passage 56 to prevent
corking of fuel vent valves in the emissions system.
[0040] In an example of the present teachings, the weight of one or
more components of flow restrictor 50, such as piston 52, may be
configured such that one or more of the solenoid spring 44 and the
flow restrictor spring 54 may be omitted (e.g., portions of valve
assembly 20 may be controlled via gravity).
[0041] The foregoing descriptions of specific examples of the
present teachings have been presented for purposes of illustration
and description. They are not intended to be exhaustive or to limit
the teachings to the precise forms disclosed, and various
modifications and variations are possible in light of the above
teaching. It is believed that various alterations and modifications
of the exemplary aspects of the present teachings may become
apparent to those skilled in the art from a reading and
understanding of the specification. It is intended that all such
alterations and modifications are included in the present
disclosure, insofar as they come within the scope of the present
teachings as defined by the claims appended hereto and their
equivalents.
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