VALVE ASSEMBLY FOR HIGH-PRESSURE FLUID RESERVOIR
TECHNICAL FIELD
[001] The present invention relates to a valve assembly for controlling fluid flow
to and from a high-pressure reservoir.
BACKGROUND
[002] Valves are employed in a multitude of industries to control flow of liquids
and/or gases. One application for such control valves appears in vehicles with stored
fuel to control a vehicle's evaporative emissions resulting from gasoline vapors
escaping from the vehicle's fuel system. Evaporative emissions of modern vehicles
are strictly regulated in many countries. To prevent fuel vapors from venting directly
to the atmosphere, a majority of vehicles manufactured since the 1970's include
specifically designed evaporative emissions systems. Additionally, in recent years
vehicle manufacturers began developing fully sealed fuel delivery to their engines.
[003] In a typical evaporative emissions system, vented vapors from the fuel
system are sent to a purge canister containing activated charcoal. The activated
charcoal used in such canisters is a form of carbon that has been processed to make it
extremely porous, creating a very large surface area available for adsorption of fuel
vapors and/or chemical reactions. 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.
SUMMARY
[004] An embodiment of the invention is a valve assembly for controlling fluid
flow between a first reservoir and a second reservoir. The valve assembly includes a
relief valve arranged inside the housing and configured to open the first fluid flow
path when a pressure inside the first reservoir is above a first predetermined pressure
value.
[005] The valve assembly also includes a solenoid assembly configured to open
a second fluid flow path when a rate of the fluid flow from the first reservoir to the
second reservoir is above a predetermined reference value.
[006] Furthermore, the valve assembly includes a flow restrictor configured to
open a third fluid flow path when the rate of the fluid flow from the first reservoir to
the second reservoir is below the predetermined reference value, and when the
pressure inside the first reservoir 12 is below a second predetermined pressure value.
[007] The above features and advantages and other features and advantages of
the present invention are readily apparent from the following detailed description of
the best modes for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[008] Figure 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 closed state, according to one embodiment of the invention;
[009] Figure 2 is a cross-sectional view of the valve assembly shown in Figure 1,
with a first flow path between the fuel tank and the purge canister shown in an open
state;
[0010] Figure 3 is a cross-sectional view of the valve assembly shown in Figure 1,
with a second flow path between the fuel tank and the purge canister shown in an
open state;
[0011] Figure 4 is a cross-sectional view of the valve assembly shown in Figure 1,
with a third flow path between the fuel tank and the purge canister shown in an open
state when the fuel tank is under pressure;
[0012] Figure 5 is a cross-sectional view of the valve assembly shown in Figure 1,
with a third flow path between the fuel tank and the purge canister shown in an open
state when the fuel tank is under vacuum; and
[0013] Figure 6 is a cross-sectional view of the valve assembly having an
armature that includes a separate piston and plunger, and the plunger is connected to
the piston via a catch mechanism.
DETAILED DESCRIPTION
[0014] Referring to the drawings wherein like reference numbers correspond to
like or similar components throughout the several figures, Figure 1 illustrates a
vehicle, schematically represented by numeral 10. Vehicle 10 includes a fuel tank 12
configured as a reservoir for holding fuel to be supplied to an internal combustion
engine 13 via a fuel delivery system which typically includes a fuel pump (not
shown), as understood by those skilled in the art. Vehicle 10 also includes a
controller 14 that is configured to regulate the operation of engine 13 and its fuel
delivery system. Fuel tank 12 is operatively connected to an evaporative emissions
control system 16 that includes a purge canister 18 adapted to collect fuel vapor
emitted by the fuel tank 12 and to subsequently release the fuel vapor to engine 13.
Controller 14 is also configured to regulate the operation of evaporative emissions
control system 16 in order to recapture and recycle the emitted fuel vapor. In
addition, controller 14 is adapted to regulate the operation of valve assembly 20, i.e.,
to selectively open and close the valve, in order to provide over-pressure and vacuum
relief for the fuel tank 12
[0015] Evaporative emissions control system 16 includes a valve assembly 20.
Valve assembly 20 is configured to control a flow of fuel vapor between the fuel tank
12 and the purge canister 18. Although valve assembly 20 as shown is located
between fuel tank 12 and purge canister 18, nothing precludes locating the valve
assembly in a different position, such as between the purge canister 18 and the engine
13. Valve assembly 20 includes a housing 22, which retains all internal components
of the valve assembly in a compact manner. Housing 22 connects to fuel tank 12 via
a connector 24, and to the purge canister via a connector 26. Housing 22
accommodates a relief valve 28. Relief valve 28 includes a piston 30, which may be
formed from a suitable chemically-resistant material such as an appropriate plastic or
aluminum. Relief valve 28 may also include a compliant seal 32, which may be
formed from a suitable chemically-resistant elastomeric material. Seal 32 may be an
inward-sloped dynamic pressure seal, i.e., such that the seal's outer edge or lip is
angled toward a central axis Yl. In operation, seal 32 makes initial contact with the
housing 22 along the seal's angled outer edge. After the initial contact with housing
22, the outer edge of seal 32 deflects to conform to the housing and hermetically
closes a passage 34. The inward slope of the seal's outer edge provides enhanced
control of fuel vapor flow at small openings between seal 32 and housing 22.
[0016] Piston 30 and 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. Piston 30 and seal 32 are urged to close passage 34 by a spring 36.
As shown in Figure 2, relief valve 28 is configured to facilitate opening a first fuel
vapor flow path being traversed by the fuel vapor flowing in a direction from the fuel
tank 12 toward the purge canister 18, represented by an arrow 38, when the fuel tank
12 is above a first predetermined pressure value. The first predetermined pressure
value is preferably a positive number, representing an extreme or over-pressure
condition of fuel tank 12.
[0017] The over-pressure condition of fuel tank 12 may depend on design
parameters typically specified according to appropriate engineering standards and
commonly includes a factor of safety to preclude operational failure of the fuel tank.
Pressure in the fuel tank 12 may vary in response to a number of factors, such as the
amount and temperature of the fuel contained therein. The first predetermined
pressure value may be established based on the design parameters of the fuel tank 12
and of the engine's fuel delivery system, as well as based on empirical data acquired
during testing and development.
[0018] Valve assembly 20 also includes a solenoid assembly 40 arranged inside
housing 22, and adapted to receive electrical power from a vehicle alternator or from
an energy-storage device (not shown), and be triggered or energized by a control
signal from controller 14. Solenoid assembly 40 includes an armature 42, a solenoid
spring 44, and a coil 46, as understood by those skilled in the art. Solenoid spring 44
is configured to generate a force sufficient to urge armature 42 out of the solenoid
assembly 40, when the solenoid assembly is not energized. Coil 46 is configured to
energize solenoid assembly 40, and to withdraw armature 42 into the solenoid
assembly by overcoming the biasing force of spring 44.
[0019] Valve assembly 20 additionally may include a flow restrictor 50. Flow
restrictor 50 is arranged inside the housing 22, and includes a piston 52 which may be
formed from a suitable chemically-resistant material such as an appropriate plastic or
aluminum. Flow restrictor 50 also includes a compliant seal 54, which may be
formed from a suitable chemically-resistant rubber. Seal 54 is an inward-sloped
dynamic pressure seal, i.e., such that the seal's outer edge or lip is angled toward a
central axis Y2. In operation, seal 54 makes initial contact with the housing 22 along
the seal's angled outer edge. After the initial contact with housing 22, the outer edge
of seal 54 deflects to conform to the housing and to hermetically close a passage 56.
The inward slope of the seal's outer edge provides enhanced control of fuel vapor
flow at small openings between seal 54 and housing 22.
[0020] Similar to the piston 30 and seal 32 above, piston 52 and seal 54 may be
combined into a unitary piston assembly via an appropriate manufacturing process
such as overmolding. Piston 52 and seal 54 are urged to close passage 56 by the
action of a spring 58. In the embodiment shown in Figure 1, flow restrictor 50 is
configured to be normally closed via the extension of armature 42 under the urging of
solenoid spring 44 in the absence of the control signal from controller 14. Referring
back to Figure 2, the normally closed position of the flow restrictor, combined with
the opening of relief valve 28 (as described above), also facilitates the opening of the
first flow fuel vapor flow path represented by arrow 38.
[0021] As shown in Figure 3, passage 56 is exposed when armature 42 is
withdrawn into solenoid assembly 40 in response to the solenoid assembly being
energized by the control signal from controller 14. Spring 58 is compressed by the
force of the flow of fuel vapor, and the flow restrictor 50 is pushed out of the way by
the vapor flow to thereby facilitate the opening of passage 56. Exposing passage 56
opens a second fuel vapor flow path to be traversed by the fuel vapor flowing in the
direction from the fuel tank 12 toward the purge canister 18, represented by arrow 60.
Fuel vapor flows in the direction represented by arrow 60 when a rate of fluid flow
from fuel tank 12 to purge canister 18 is greater than a predetermined reference value
in order to open passage 56.
[0022] The rate of fluid flow from fuel tank 12 may vary in response to a number
of factors, such as the amount, temperature and pressure of the fuel contained therein.
The predetermined reference value of the rate of fluid flow may be set at, for
example, approximately 260 liters per minute (LPM), but may also be established in
relation to a higher or a lower predetermined reference value. The reference value is
typically predetermined or established in accordance with operating parameters of a
particular engine's fuel delivery system, as understood by those skilled in the art. The
predetermined rate of fluid flow, however, must be sufficiently high to compress
spring 58 and thereby expose passage 56, and the rate of spring 58 should therefore be
selected accordingly.
[0023] Piston 52 and seal 54 are urged to close passage 56 by a spring 58. Relief
valve 28 is configured to open a third fuel vapor flow path represented by arrow 62A,
as shown in Figure 4, and arrow 62B, as shown in Figure 5. Arrow 62A represents
the third fuel vapor flow path being traversed by the fuel vapor flowing in the
direction from the fuel tank 12 toward the purge canister 18, and arrow 62B
represents the third fuel vapor flow path being traversed by the fuel vapor flowing in a
direction from the purge canister 18 toward the fuel tank 12. Fuel vapor flows in the
direction represented by arrow 62B when the rate of the fluid flow from fuel tank 12
to purge canister 18 is below the first predetermined reference value.
[0024] As shown in Figure 6, armature 42 may also be composed of separate
parts, a piston 42A and a plunger 42B in order to reduce operational hysteresis of the
armature during the opening and closing of the passage 56. Friction may develop
between the armature 42 and a bore 72 of the solenoid assembly 40 during the
operation of the valve assembly 20. Particularly, such friction may impact the
opening and closing instance of the third fuel vapor flow path represented by arrow
62B shown in Figure 5 as the flow restrictor 50 is pushed out of the way by the vapor
flow. In order to address such a possibility, as shown in Figure 6, the plunger 42B is
connected to the piston 42A via a catch mechanism 74. Accordingly, the catch
mechanism 74 is configured to maintain the connection between the plunger 42B and
the piston 42A.
[0025] The catch mechanism 74 is configured to permit the plunger 42B to move
or translate away from the flow restrictor 50 for a distance 76 that is sufficient to open
the third fuel vapor flow path 62B without the need for the piston 42A to also be
displaced away from the flow restrictor. Therefore, the separate piston 42A and
plunger 42B permit friction between the piston 42A and the bore 72 to not impact the
initial opening of the third fuel vapor flow path 62B. A stop plate 78 is provided to
limit travel of the piston 42A within the bore 72.
[0026] As shown in the embodiment of Figure 6, a plunger spring 80 is
additionally provided to preload the plunger 42B against the stop plate 78. The
plunger spring 80 is configured to press plunger 42B against seal 54 and maintain the
normally closed position of the flow restrictor 50 when solenoid assembly 40 is not
energized. The plunger spring 80 permits the force of gravity to be employed in
pulling the piston 42A against the stop plate 78 when the valve assembly 20 is
oriented as shown in Figures 106. Accordingly, in the situation when the valve
assembly 20 is oriented to employ the force of gravity in such manner, the solenoid
spring 44 becomes optional. In such a case, the plunger spring 80 is additionally
configured to perform all the described functions of the solenoid spring 44.
[0027] As shown in Figure 4, passage 64 is exposed when armature 42 is
withdrawn into solenoid assembly 40 in response to the solenoid assembly being
energized by the control signal from controller 14. The force of the flow of fuel vapor
in the third fuel vapor flow path 62A is insufficient to compress spring 58. Spring 58
is thus permitted to extend and urge the flow restrictor 50 to close passage 56 while at
the same time exposing passage 64. In this example, the third fuel vapor flow path
represented by arrow 62A is opened when the rate of fluid flow is lower than the
predetermined reference value of approximately 260 LPM, but may also be
established in relation to a higher or a lower reference value. However, to expose
passage 64, the rate of fluid flow in the third fuel vapor flow path should be incapable
of compressing spring 58; therefore, the rate of spring 58 should be selected
accordingly.
[0028] As noted above, relief valve 28 is additionally configured to open the third
fuel vapor flow path being traversed by the fuel vapor flowing in the direction
represented by arrow 62B when the fuel tank 12 is below a second predetermined
pressure value (shown in Figure 5). The first predetermined pressure value is greater
than the second predetermined pressure value. While the first predetermined pressure
value is preferably a positive number, representing an extreme or over-pressure
condition of fuel tank 12, the second predetermined pressure value is preferably a
negative number i.e., signifying that the fuel tank 12 is under a vacuum. This vacuum
in the fuel tank 12 is sufficient to overcome the force of spring 44, and thereby expose
passage 64 to open the third fuel vapor flow path. Spring 44 is specifically designed
to permit opening of the third fuel vapor flow path at a specific vacuum set point of
the fuel tank 12. As such, the rate of solenoid spring 44 generates a force that is
sufficient to close passage 64 when the fuel tank 12 is at positive pressure, but is
insufficient to close the same passage when the fuel tank is under vacuum.
[0029] In the embodiments shown in Figures 1 through 5, valve assembly 20 also
includes a cover 66, which in this example is configured as a single-piece component.
Cover 66 locates relative to the housing 22 with the aid of a flange 22A nesting inside
a channel 66A. Cover 66 engages and interconnects with housing 22 via tabbed
extensions 68 that are configured to provide a snap-fit against the housing. Valve
assembly 20 additionally includes a static seal 70 adapted to hermetically seal cover
66 against housing 22. As shown in Figures 1-5, and as understood by those skilled in
the art, seal 70 is of an O-ring type.
[0030] While the best modes for carrying out the invention have been described in
detail, those familiar with the art to which this invention relates will recognize various
alternative designs and embodiments for practicing the invention within the scope of
the appended claims.
CLAIMS
1. A valve assembly 20 configured for controlling fluid flow between a
first reservoir 12 and a second reservoir 18, the valve assembly 20 comprising:
a relief valve 28 configured to open a first fluid flow path 38 when a pressure
inside the first reservoir 12 is above a first predetermined pressure value;
a solenoid assembly 40 configured to open a second fluid flow path 60 when a
rate of the fluid flow from the first reservoir 12 to the second reservoir 18 is above a
predetermined reference value; and
a flow restrictor 50 configured to open a third fluid flow path 62 when the rate
of the fluid flow from the first reservoir 12 to the second reservoir 18 is below the
predetermined reference value, and when the pressure inside the first reservoir 12 is
below a second predetermined pressure value.
2. The valve assembly of claim 1, wherein the solenoid assembly 40
includes an armature 42 configured to selectively open and close the flow restrictor
50, and the armature 42 includes a piston 42A and a plunger 42B, and wherein the
piston 42A is connected to the plunger 42B by a catch mechanism 74 configured to
permit the plunger 42 to translate away from the flow restrictor 50 such that the third
fluid flow path 62 is opened without displacing the piston 42A.
3. The valve assembly of claim 2, further comprising a plunger spring 80
configured to press the plunger 42B against the flow restrictor 50 to maintain the flow
restrictor 50 in a closed position, and comprising a coil 46 configured to energize the
armature 42 and overcome the plunger spring 80 to open the flow restrictor 50.
4. The valve assembly of claim 3, further comprising a solenoid spring 44
configured to generate a force sufficient to close the restrictor 50 by displacing the
armature 42, and the coil 46 is additionally configured to overcome the solenoid
spring 44.
5. The valve assembly according to claim 1, further comprising a housing
22 including the first 38, second 60, and third 62 fluid flow paths, wherein the relief
valve 28, the solenoid assembly 40, and the flow restrictor 50 are arranged inside the
housing 22.
6. The valve assembly according to claim 1, wherein the first
predetermined pressure value is greater than the second predetermined pressure value.
7. The valve assembly according to claim 3, wherein the coil 46 is
configured to overcome the plunger spring 80 when the rate of the fluid flow is below
the predetermined reference value.
8. The valve assembly according to claim 3, wherein the plunger spring
80 is configured to generate a force sufficient to close the third fluid flow path 62
when the pressure inside the first reservoir 12 is a positive value, but insufficient to
close the third fluid flow path 62 when the pressure inside the first reservoir 12 is a
negative value.
9. The valve assembly according to claim 1, further comprising a spring
58 configured to urge the flow restrictor 50 to open, wherein the flow restrictor 50 is
configured to be normally closed.
10. The valve assembly according to claim 1, wherein at least one of the
relief valve 28 and the flow restrictor 50 includes an inward-sloped pressure seal 54
configured to seal the corresponding relief valve 28 and the flow restrictor 50 against
the housing 22.
11. The valve assembly according to claim 1, further comprising a cover
66 configured to retain the relief valve 28, the flow restrictor 50, and the solenoid
assembly 40 inside the housing 22.
12. The valve assembly according to claim 11 wherein the cover 66
engages and interconnects with the housing 22 via a snap-fit.
13. The valve assembly according to claim 11, further comprising a static
seal 70 configured to seal the cover 66 against the housing 22.
14. The valve assembly according to claim 13, wherein the static seal 70 is
an O-ring type seal.