TITLE OF INVENTION
[0001] Controlling Fuel Vapor Venting In A Fuel Tank.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to systems for controlling the venting of
fuel vapor from a fuel tank and particularly from an on-board motor vehicle fuel
tank. Currently, fuel vapor emission control systems are required on light truck
passenger motor vehicles. Fuel tanks for such vehicles are often molded of
plastic material and configured to conform around structural members of the
vehicle such as stiffener members for the vehicle undercarriage or body floor.
This often results in the upper or top wall of the tank having a valley formed
therein often running longitudinally with respect to the vehicle chassis and which
effectively divides the vapor dome within the tank into two or more compartments
when the fuel level is not less than that of the lowest level of the valley.
[0003] This compartmentalized vapor dome within the tank has caused
problems in providing venting of the fuel vapor from the tank and has resulted in
the need for a plurality of vapor vent valves with one valve provided in each
separate compartment of the vapor dome.
[0004] Where the fuel vapor vent valves are float operated and are installed in
the tank externally through access openings in the upper wall of the tank, it has
proven costly and cumbersome to provide the interconnection of the plurality of
vent valves to the remote vapor storage device such as a charcoal filled canister.
Furthermore, where the tank has a trough or valley formed in the upper surface
thereof, it has been required to provide draining of the liquid fuel from the vent
valves and lines when the fuel level falls below the lowest level of the valley upon
withdrawal of fuel from the tank.
[0005] Thus, it has been desired to provide a way or means of eliminating the
need for access openings in the tank wall to install vent valves and to minimize
the number of conduit and interconnections thereof required to provide venting of
the compartmentalized vapor domes in the fuel tank and to insure drainage of the
liquid fuel from the vent system in order to prevent blocking of vapor flow to the
storage canister.
[0006] Referring to FIG. 2, a known system has the fuel tank indicated
generally at 1 which has an upper wall having an upper level 2 and a lower level 3
such that a separate vapor dome 4 is formed within the tank when the fuel rises
above the undersurface of the level 3.
[0007] A first vapor vent valve 5 is disposed within the vapor dome 4 adjacent
the undersurface of the upper level 2; and, a second vapor vent valve 6 is
disposed adjacent the undersurface of the tank top level 3 and the outlets of the
respective valves 5, 6 are interconnected by a conduit 7 which passes beneath
the undersurface of the lower level 3. A second conduit 12 is connected to
conduit 7 through an access opening 8 in the lower level 3 of the upper wall, and,
conduit 12 is connected to a vapor storage canister 9 which has an outlet 10
adapted for connection to the air inlet of an engine. The canister 9 typically has a
purge air inlet 11 for admitting atmospheric air to purge the canister upon engine
startup.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention relates to vapor venting of fuel tanks such as for
motor vehicles and particularly relates to fuel tanks having a multilevel upper wall
and more particularly to tanks having a valley formed in the upper wall for
conforming to structural members of the vehicle and thus having a
compartmentalized vapor dome. The present invention provides for vapor vent
valving in each compartment of the vapor dome interiorly of the tank to eliminate
external hose connections along the outer surface of the tank top. The system of
the present invention employs a vapor vent valve in each vapor dome
compartment and the vent valves are disposed completely interiorly of the tank
with the outlets interconnected; and, a single vapor vent line exits through the
upper wall of the tank for connection to a storage canister. The interconnecting
lines within the tank include a drain valve disposed at the lowest level of the lines
passing under valley formed in the upper tank wall. In one embodiment of the
invention the drain valve is a one-way pressure operated valve and in an alternate
form the dram valve is float operated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009| FIG. 1 is a pictorial schematic of a system with a fuel tank having a
multilevel upper wall Configuration as connected to a vapor storage canister;
[0010] FIG. 2 is a cross-section of a fuel tank with interior vent valves of the
prior art;
[0011] FIG. 3 is a cross-section of a float operated drain valve employed in the
present invention; and,
[0012| FIG. 4 is a cross-section of a one-way drain valve employed in an
alternate arrangement of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring to FIG. 1, the system of the present invention is indicated
generally at 20 and includes a fuel tank indicated generally at 22 having the upper
wall thereof formed in a first or highest level 24, a second lower level 26 spaced
therefrom and interconnected by a third or lowest level 28 forming a valley
between levels 24 and 26 such as for conforming to the undercarriage or under
floor structure of a vehicle. It will be understood however, that the first and
second levels 24, 26 may alternatively be at the same level as shown in dashed
outline in PIG. 1.
[0014] An access opening 30 is formed in the second level 26 of the upper
wall of the tank and has received therein a module 32 and which is secured about
the opening 30 by an annular flange 34 which is sealed about the opening by any
suitable expedient, as for example, weidment. I he module 32 may include a fuel
pump 36 and a vapor vent valve 38 which is preferably of the float operated type.
and which has an inlet 40 for receiving fuel vapor therein and at least one outlet
42 which is connected to an externally extending conduit 44 which is also
connected to the inlet of storage canister 46. Storage canister 46 has an outlet
conduit 48 adapted for connection to the air inlet of an engine and nas an
atmospheric air inlet 50 for providing atmospheric purge air flow through the
canister during engine operation.
[0015] A second vapor vent valve, which in the presently preferred practice of
the invention is float Operated, but may also be pressure operated is disposed in
the vapor dome under tank wall portion 24 as denoted by reference numeral 52.
The vent valve 52 has an outlet which is connected through conduit or hose 54 to
the outlet 42 of vent valve 38. The conduit 54 passes under the lowest level
section 28 of the tank upper wail; and, conduit 54 has a drain valve indicated
generally at 56 disposed therein and located under the lowest section 28 of the
upper tank wall as shown in FIG. 1.
[0016] Referring to FIG. 3, the drain valve 56 is shown in one embodiment
having a body 58 with an annuiar outwardly extending flange 60 formed adjacent
the upper end thereof which flange is secured to the conduit 54 by snap-locking
within an annular receptacle 62 preferably formed internally with a portion of
conduit 54 and sealed by labyrinth seal 64. The body has a valve seat 66
disposed therein which communicates with the interior of the conduit 54 via flow
passage 67.
[0017] A float 68 is slidably disposed within the body and has a flexible
membrane valve member 70 provided on the upper end thereof for contacting and
closing against valve seat 66 upon the fuel level in the tank rising to the ievei of
the lower surface of the lowest portion 28 of the tank upper wall. Membrane
valve number 70 is partially attached to the float 68 about support 69 on the float;
and, a centrally located curved surface 71 makes contact with the undersurface of
valve member 70 to urge the central region thereof into contact with the valve
seat 66.
[0018] Referring to FIG. 4, an alternate embodiment of the drain valve is
illustrated generally at 156 and has a resilient membrane valve member attached
to the conduit 154 which has a plurality of drain holes 158 formed therein with the
membrane valve member 160 attached thereover on the lower surface of the
conduit 154. The membrane 160 is shown in solid outline and FIG. 4 has closed
over the drain holes 158 formed in the lower surface of the conduit and is moved
to the open position shown in dashed outline in FIG. 4 under the gravitational
force or pressure resulting from the weight of liquid fuel accumulating in the
conduit 154, thus permitting drainage.
[0019] The present invention thus provides a system for venting fuel vapor in a
fuel tank having a multilevel upper wall with vapor vent valves disposed
completely within the tank and positioned to vent vapor from the various
compartments of the vapor dome formed by the contours of the upper wall of the
tank and has the outlets of the vent valves interconnected. A drain valve is
provided in the upper conduit interconnecting the vent valve outlets at the lowest
level of the upper wall of the tank to drain liquid fuel accumulating in the conduit
as the tank is refilled and the liquid level rises above the level of the lowest region
of the upper wall of the tank. The drain valve comprises a float operated valve in
one embodiment and a fluid pressure operated one-way valve in another
embodiment.
[0020] Although the invention has hereinabove been described with respect to
the illustrated embodiments, it will be understood that the invention is capable of
modification and variation and is limited only by the following claims.
WE CLAIM:
1. A system for venting fuel vapor from a vehicle engine fuel tank of the type
having the upper wall thereof configured to a plurality of different levels
comprising:
(a) a first vapor vent valve having an inlet and outlet disposed within
the tank at a first of said plurality of levels of the upper wall;
(b) a second vapor vent valve having an inlet and outlet disposed within
the tank at a second of said plurality of levels of the upper wall;
(c) a storage reservoir disposed remotely from the tank and operably
connected for preventing escape to the atmosphere of fuel vapor
and adapted to flow vapor to the engine air inlet during engine
operation;
(d) a first conduit connecting the outlet of said first vent valve and the
outlet of said second vent valve, wherein said first conduit passes
under a third of said plurality of levels lower than said first and
second levels;
(e) a drain valve disposed in said first conduit and operative to drain
liquid fuel trapped in the first conduit to the tank when the fuel level
therein descends below said third level; and,
(f) a second conduit connecting said first and second vent valve outlets
to said reservoir.
2. The system defined in claim 1, wherein said first and second vent valve
are float operated
3. The system defined in claim 1, wherein said drain valve is float operated.
4. The system defined in claim 1, wherein said tank top has a saddle-like
configuration.
5. The system defined in claim 1, wherein said drain valve is a one-way
valve.
6. A system for controlling fuel vapor emissions in a motor vehicle comprising:
(a) a fuel tank having a first portion of the upper wall and a second
portion of the upper wall spaced therefrom and disposed at a
significantly lower level than said first portion;
(b) a first float operated vapor vent valve disposed within said tank on
said first portion;
(c) a second float operated vapor vent valve disposed within said tank
on said lower level, and a first conduit connecting to the outlet of
said first and second vent valve;
(d) a storage reservoir disposed remotely from the tank for containing
fuel vapor during vehicle motor shutdown, said reservoir adapted for
connection to the vehicle motor air inlet for providing stored vapor to
the air inlet during engine operation; and,
(e) a second conduit connecting the outlet of said first and second vent
valves with said reservoir;
(f) a drain valve operative to drain liquid fuel from said second conduit
when the fuel level in the tank descends below said lower level.
7. The system defined in claim 6, wherein said drain valve is float operated.
8. The system defined in claim 6. wherein said first conduit passes beneath a
third portion of the tank at a third level below said lower level and said
drain valve is disposed at said third level.
9. A method of controlling fuel vapor emission from a motor vehicle fuel tank
having a multilevel upper wall comprising:
(a) disposing a first vapor vent valve in the uppermost level of said
multilevel upper wail and disposing a second vapor vent valve in a
second level lower than said uppermost level;
(b) disposing a conduit under a third lowest level of said upper wall and
connecting the outlet of said first vent valve and the outlet of said
second vent valve with said conduit and connecting the outlets of
said valves to a vapor reservoir remote from the tank with the
reservoir adapted for connection to the air inlet of the vehicle motor;
and
(c) disposing a drain valve in said tank at said third lowest level of said
upper wall and draining liquid from the said conduit when the fuel
level in the tank descends below said third lowest level.
10. The method defined in claim 9. wherein said step of connecting a drain
valve in the third lowest level includes disposing said drain valve between
said first and second vent valves.
11. The method defined in claim 9. wherein said step of disposing said second
valve includes disposing said valve in a valley in the tank top.
12. The method defined in claim 9 wherein said step of disposing a drain valve
includes disposing a one-way valve.
13. The method defined in claim 9, wherein said step of disposing a drain
valve includes disposing a float operated valve.
14. A method of controlling fuel vapor emission from a motor vehicle fuel tank
having a plurality of regions of the upper wall thereof at a higher level and
disposed on opposite sides of a lower level region, the method comprising:
(a) disposing a first vent valve in one of said regions and disposing a
second vent valve in another of said regions;
(b) disposing a conduit under the lower level region of said upper wall
and connecting the outlet ot said first vent valve and the outlet of
said second vent valve with said conduit;
(c) communicating the outlets of said valves to a vapor reservoir
remote from the tank with the reservoir adapted for connection to
the air inlet of the motor vehicle; and,
(d) disposing a drain valve in said tank in said lower level region of the
upper wall and draining liquid from the conduit when the fuel level in
the tank descends below the said lower level region of the upper
wall.
15. The method defined in claim 14, wherein said step of disposing a drain
valve includes disposing a float operated valve.
16. A method of controlling fuel vapor emission from a fuel tank having a
saddle shaped upper wall forming plural separated vapor dome regions
when the fuel level is above the lowest level of the upper wall, comprising:
(a) disposing a first vent in one of said vapor dome regions and
disposing a second vent valve in another of said vapor dome
regions;
(b) disposing a conduit under the said lowest level of the upper wall and
connecting the outlet of the first and second vent valve to said
conduit;
(c) communicating the outlets of said first and second vent valves with
a vapor reservoir remote from the tank; and,
(d) disposing a drain valve in said tank in the region of the lowest level
of the upper wall and draining liquid from said conduit when the fuel
level in the tank descends below said lowest level of the tank upper
wall.
17. The method defined in claim 16, wherein the step of disposing a drain
valve includes disposing a float operated valve.
18. The method defined in claim 17, wherein the step of communicating the
outlets of said first and second vent valves includes connecting the conduit
to said reservoir.

A fuel vapor venting system for fuel tanks having a saddle-shaped upper
wall. A vapor vent valve is disposed entirely within the tank in each vapor dome
compartment formed by the upper tank wall. The vent valves are interconnected
by a conduit passing under the lowest portion of the upper tank wall and a drain
valve installed in the lowest point of the conduit. The drain valve may be
pressure operated or float operated.