Fuel vapor control system

An anti-pollution mechanism usable on the filler tubes of automotive fuel tanks to prevent vaporous hydrocarbons from escaping from the tank through the tube, especially at the instant when the closure cap at the mouth of the tube is initially opened such as required during refueling. A vapor escape line extends from the fuel tank to a vapor collection canister. A pressure-operated valve in the escape line is automatically opened in response to opening of the cap on the filler tube such that vapors and fumes escape through the line instead of flowing out of the tube mouth.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a pressure responsive valve mechanism for 
preventing undesired escape of fuel vapor from the fuel tank in an 
automotive vehicle during refueling. 
2. Description of Prior Developments 
During normal operation of automotive vehicles such as cars, trucks, buses 
and vans, the fuel tank often becomes slightly pressurized due to the 
accumulation of fuel vapor in the confined space above the liquid fuel. 
This pressurized condition is especially likely during hot weather periods 
when the fuel vapor pressure is higher. When liquid fuel is added to the 
fuel tank, the pressurized vapor has an open path to the atmosphere via 
the opened closure cap at the mouth of the fuel tank filler tube. The 
pressurized vapor can flow rapidly out through the tube, thereby polluting 
the ambient atmosphere. Such escape of the vapor can be detected as an 
audible hissing sound associated with rapid outflow of fuel vapors through 
the filler tube. 
A venting mechanism shown in U.S. Pat. No. 4,572,394 issued to T. 
Tanahashi, et al addresses the problem of fuel vapor escape during 
refueling by providing a canister of activated charcoal around the mouth 
of the filler tube. In contrast, the newly proposed mechanism described in 
detail below is adapted to use a conventional activated charcoal canister 
used for venting the fuel tank during normal vehicle operation. Moreover, 
the newly proposed arrangement locates a control valve remote from the 
fuel tank and filler tube where possible clog-up due to atmospheric 
contamination is not as likely as in the case of the patented arrangement 
of Tanahashi, et al. 
Also, the newly-proposed arrangement includes a rigid rugged guide 
structure for a fuel dispenser nozzle, whereas the arrangement of the '394 
patent includes a rubber bellows guide structure for the nozzle. Service 
life of the guide structure in U.S. Pat. No. 4,572,394 could be a problem. 
SUMMARY OF THE INVENTION 
The present invention concerns a mechanism that is responsive to opening 
movement of a fuel tank closure cap to automatically open an auxiliary 
valve in a vapor escape line leading from the fuel tank to a vapor 
collector such as an activated charcoal canister. The operation is such 
that when the cap is opened, any accumulated vapor in the tank is directed 
away from the filler tube through an alternate escape route which exits 
through the vapor collector, thereby overcoming the pollution problem. 
The newly proposed mechanism includes a control valve operated by pressures 
existing on opposite faces of a movable partition within the control valve 
housing. The partition is preferably a diaphragm, although it could be a 
piston or a bellows. One operating face of the partition is exposed to the 
pressure existing in the fuel tank. The other control face of the 
partition is in fluid pressure communication with the filler tube at a 
point near its mouth. 
When the filler tube is closed by a removable cap, the pressures on 
opposite faces of the partition are equalized. One face of the partition 
is in axial registry with an outlet port in the valve housing, such that 
the partition is closed against the port by the area differential 
resulting from the area of the outlet port which is in contact with only 
one side of the partition. As an alternative, or as a supplementary 
feature, a compression spring can be positioned against the partition to 
normally hold it in a closed position against the outlet port. 
When the cap at the mouth of the filler tube is operated to open the filler 
tube preparatory to a refueling operation, atmospheric pressure is 
communicated to the control face of the partition through a control line 
leading from the mouth of the filler tube to the valve housing. The 
relatively lower atmospheric pressure on the control face of the partition 
enables the partition to be deflected to an open condition by the higher 
pressure of the fuel vapor such that pressurized vapor can then flow from 
the fuel tank through the opened valve. The action is such that 
pressurized vapor is drawn away from the filler tube and routed through a 
filter, thereby lessening the potential for polluting the atmosphere.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
The drawing shows a fuel storage system for use within an automotive 
vehicle. The system includes a fuel tank 10 having an upwardly angled 
filler tube 12 that terminates in an open mouth 14. A radial flange 16 
extends from the tube mouth to form a radial sealing surface for an 
annular seal 17 carried on a removable closure cap 19. 
Cap 19 includes an outer manually-engageable portion 20 located beyond the 
end of tube 12, a relatively large diameter plug section 22 fitting into 
the open mouth of tube 12, and a relatively small diameter plug section 24 
extending axially from section 22. A single helical groove is formed in 
the side surface of cap section 22 for meshed engagement with a helical 
spline 25 on the inner side surface of filler tube 12. The construction is 
such as to permit cap 19 to be inserted into and onto the fuel filler tube 
with a manual screw-on turning motion. The cap can be completely removed 
from the filler tube with a reverse screw-off motion. When the cap is 
fully inserted onto the tube, seal 17 has sealing engagement with flange 
16. 
A fuel nozzle guide structure 27 is welded or otherwise fixedly mounted 
within tube 12 in axial spaced relation to tube mouth 14. Guide structure 
27 includes a hollow cylinder 29 having radial end flanges 30 and 31 
attached to the inner surface of tube 12. An annular deflectable flap seal 
33 is mounted onto flange 31, as by a crimping operation. Seal 33 has an 
internal diameter that is less than the internal diameter of cylinder 29, 
such that when cap 19 is fully inserted into tube 12 the inner annular 
edge of seal 33 will sealably engage the cylindrical side surface of cap 
section 24. 
An L-shaped bleed passage 35 extends from the end face of plug section 24 
to the outer cylindrical side surface of plug section 24, thereby forming 
a pressure connection between lower main space 26 within tube 12 and upper 
annular space 28 within tube 12, i.e. the space between seal 33 and the 
tube mouth 14. The diameter of plug section 22 is made to be slightly 
smaller than the internal diameter of the tube mouth 14, such that the 
pressure in annular space 28 is communicated to a spigot fitting 40 
suitably attached to the wall of tube 12. An annular clearance 37 exists 
between the outer surface of cap section 22 and the inner surface of the 
tube 12. 
A normally-closed valve 42 is operatively located between fuel tank 10 and 
a vapor collector 44 such as a charcoal canister. Valve 42 is located in a 
vapor escape line designated diagrammatically by numeral 43. In practice 
the vapor escape line can be formed by two sections of small diameter 
tubing, e.g. five eighth inch diameter tubing, telescoped onto spigot 
structures 45, 46, 47 and 48 that extend from the fuel tank, valve 
housing, and vapor collector, respectively. This arrangement is 
particularly advantageous in those vehicles normally equipped with a vapor 
collector as no additional collector is required to carry out the 
invention. 
Valve 42 includes a housing 41 that is subdivided into a flow chamber 49 
and a control chamber 50 by an imperforate flexible diaphragm or partition 
52. As shown in full lines, the partition is deflected rightwardly to 
sealably engage the wall of an outlet port 54, thereby preventing vapor 
flow from fuel tank 10 to collector 44. 
A compression spring 55 may be located in chamber 50 to augment the force 
provided by the pressure of the fluid vapor in that chamber. The effective 
force on the left face of partition 52 is or may be normally greater than 
the force on the partition right face, due to the presence of spring 55 
and also due to the fact that the effective area of the partition right 
face is decreased by its area of contact with flow port 54. 
A control line 56 such as a one eighth inch diameter hose extends from a 
spigot structure 57 on valve housing 41 to the spigot 40 on filler tube 
12. When cap 19 is in a closed position (as shown) the pressures on 
opposite faces of partition 52 will be equalized except for pressure 
surges that are damped out by the small diameter bleed passage 35. Spring 
55 and the differential partition area due to port 54 will maintain 
partition 52 in a closed condition. 
When cap 19 is manually unscrewed from tube 12, seal 17 will move axially 
away from tube flange 16, thereby opening a vent path through annular 
clearance 37. With seal 33 still engaged with plug section 24 of the cap, 
the pressure in control chamber 50, which is typically greater than 
ambient, will be quickly vented through the associated line 56 and 
clearance space 37, thereby enabling the pressure in flow chamber 49 to 
deflect partition 52 leftwardly away from port 54. An escape path is 
thereby formed for vapor otherwise trapped within tank 10. Vapor will 
begin to flow from tank 10 through vapor line 43 before plug section 24 of 
cap 19 moves out of contact with seal 33. Any pressurized vapor in tube 
space 26 will tend to be drawn downwardly from the tube into tank 10, 
rather than escaping upwardly through the tube. 
Structure 27 serves as a mounting surface for seal 33, and also as a guide 
structure for a conventional fuel dispenser nozzle (not shown). After cap 
19 is completely removed from tube 12 the fuel nozzle is inserted into 
tube 19 to feed liquid fuel, e.g. gasoline, through the tube into the 
tank. Hollow cylinder 29 will encircle the lower end portion of the 
nozzle, while seal 33 is sealably engaged against the nozzle side surface. 
Seal 33 will prevent the upflow of fumes or vapors through tube 12 during 
the refueling operation. 
Seal 33 could be located on flange 30 instead of on flange 31. However, in 
its illustrated position the seal is in a shielded portion, such that when 
the fuel nozzle is initially inserted into the filler tube 19, structure 
27 acts as a protector for seal 33 so that the tip of the nozzle is not 
likely to forcibly engage or destroy the seal. 
The drawing shows a particular system embodying the invention. It will be 
appreciated that variations in the system could be used while still 
practicing the invention.