Air filter assembly for automotive fuel vapor recovery system

In a vehicle with an internal combustion engine and a fuel vapor recovery system including a carbon canister connected to the fuel tank for collecting fuel vapors from the fuel tank as the tank is being refilled, an air filtering apparatus is provided to supply a flow of clean and dry purge air to the canister for the purging of vapors therefrom. The air filtering apparatus includes gradually spaced baffle means and filter element means and is remotely connected in the evaporative emission control system by hoses connected to the air inlet and air outlet of the canister.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an air filter for an automotive vehicle fuel 
vapor recovery system, which includes structures for gradually separating 
unwanted particles of dust, moisture, soot, and the like from the vapor 
recovery system purge air stream. 
2. Disclosure Information 
Conventional fuel vapor recovery systems used in automotive vehicles 
typically include a carbon canister used to recover excess fuel vapor 
generated in the fuel tank. Activated carbon in the carbon canister 
adsorbs the fuel vapor and temporarily retains the vapor until the 
canister is purged. During vehicle operation, at times determined by 
programmed vehicle calibration, the fuel vapor adsorbed by the activated 
carbon is desorbed by introducing outside air, or purge air, to the 
canister. The fuel vapor thus desorbed is fed to the engine for 
utilization in combustion. The present invention ensures that the air used 
to purge the carbon canister, or purge air, is dry and cleaned of 
particulate matter. This invention has been approved through theoretical 
calculations, computer simulations, and laboratory and road testing, and 
is involved in a current production program. 
Filtering of-purge air introduced to a vapor recovery system to purge the 
carbon canister is not new. For the mentioned purpose, prior art examples 
teach the use of one or more assemblies comprising either a filter medium, 
baffle means, or both. 
U.S. Pat. No. 5,058,693 to Murdock et al, U.S. Pat. No. 5,024,687 to 
Waller, and U.S. Pat. No. 5,638,768 to Gimby each disclose a remote fuel 
vapor recovery system filter assembly comprising the combination of baffle 
and filter element means. Both '693 and '687 include simple baffle means 
comprising no more than two independent baffle entities. The present 
invention discloses a plurality of mating and nonmating planar baffles, 
the increased complexity of which is matched by increased functional 
efficiency. Patent '768 provides a self-cleaning air filter comprising a 
filter element of various embodiments. In each embodiment, this mentioned 
element, so that it may be cleaned by the invention's filter cleaning 
member, is apparently a thin, firm, screen-like entity, and the filter 
includes provisions for function upon "occlusion" of this element. The 
present invention is comprised of a robust and hearty (thick, wide and 
tall) filter element and a baffle area, and has been proven to be able to 
last the average lifetime usage of vehicles (approximately 150,000 miles) 
without any cleaning. 
There are two primary and novel factors contributing to the long-lasting 
functionality of our invention. The first is found in the design of the 
baffle section. The plurality of baffles are designed such that the 
particles, having wide size and inertial distributions, are dislodged from 
the air stream as it travels from inlet towards the filter section. This 
occurs due to decreased baffle spacing between baffles and the 
corresponding increase in mobility demand placed on the air flow. The 
second primary and novel quality of our invention is found in the 
implementation of a filter element so that the smallest particles (those 
that survive the baffle section) are generally lodged in the upper half of 
the filter element and eventually, due to gravity, vibration, etc., will 
migrate to the lower portions of the element. This occurrence will ensure 
the thorough cleaning of the air and the long-lasting function of the air 
filter assembly. 
U.S. Pat. No. 4,693,393 to DeMinco et al and U.S. Pat. No. 5,501,198 to 
Korama disclose examples of filtering systems integrally combined within a 
carbon canister by comprising only baffle means and only filter element 
means, respectively. U.S. Pat. No. 5,149,347 to Turner et al also 
discloses a separator device comprising only a baffle section, which is 
remotely connected to the carbon canister. It is apparent that any 
structure comprising only baffle means or only filter means will not 
bet-as effective and robust as the present invention comprising both 
baffle and particulate filter means. 
It is a feature of the present invention that both graduated baffle 
separation means and filter element means are included in a filter 
assembly. This assures a maximum degree of separation of particles, 
foreign matter, such as soot and road dust, moisture, and the like from 
the fresh air therein otherwise present. 
SUMMARY OF THE INVENTION 
The fuel vapor storage system (FVSS) of an automotive vehicle is used to 
contain, clean, and utilize the fuel filled air necessarily displaced upon 
filling of the fuel tank, so as not to introduce fuel vapor filled air to 
the atmosphere. The primary component in this system is the carbon 
canister. This canister, filled with activated carbon, functions by 
adsorbing the fuel vapor of any air introduced thereto. Proper function of 
the carbon canister and corresponding canister vent valve (CW) is 
accomplished best when periodically flushed with clean (purge) air. 
The clean air mentioned prior is provided by outside air that has been 
filtered by the present inventive air filter assembly. Traditional FVS 
systems comprise either a filter with only filter element means, a filter 
with only baffle means, or, most commonly, no filter means at all. The 
present filter invention integrates both filter element and baffle means 
in such a way that substantially all necessary matter is separated from 
the purge air flow. 
It is an object of the present invention to clean air by filtering it 
through the graduated baffle section-comprising a plurality of mating and 
nonmating baffle sets, the spaces between which gradually 
decreases-thereby forcing the air to travel an increasingly tortuous path. 
This prescribed path includes many turns and changes of direction and 
causes particles beyond a certain size (approximately 15 .mu.m-20 .mu.m) 
due to the inertial properties associated with their size, gravity, and 
the speed of the air stream, to separate from the ongoing stream of air. 
It is a further object of the present invention to further clean air by 
filtering it through a filter media section comprising a filter element 
snugly disposed between retaining ribs. The filter element section is 
prescribed to filter substantially all remaining particles in the air 
stream, and particularly those between 1 .mu.m and 20 .mu.m in size. The 
preferred filter media is open cell reticulated foam, and the preferred 
style is an reticulated open cell laminated foam with between 30 and 65 
p.p.i. (pores per inch). 
It is an advantage of the present invention that substantially all 
particles, including, but not limited to, moisture (rain, snow, mist, 
condensation et al) and other matter (dirt, soot, road dust, dirt et al) 
will be separated from the air stream. The removal of these particles from 
the air flow ensures proper function of a fuel vapor recovery system 
(FVSS) by avoiding increased system restriction and premature canister 
vent valve (CVV) and carbon canister failures. 
It is a further advantage that the present invention is durable, under 
normal to severe conditions, lasting the entirety of a vehicle's life, 
about 150,000 miles, without requiring cleaning, changing, replacement, or 
adjustments of any kind. This is primarily made possible by the even 
distribution of separated particles throughout the filter assembly, due to 
the filter (for the finest particles) being located after the baffle 
section which is gradually designed for this same distribution purpose. 
It is yet a further advantage of the present invention that robustness is 
achieved in two primary ways. First, our air filter assembly may be 
remotely connected within the FVSS for easy access and for nondisturbance 
of the balance of the components therein. Secondly, due to specialty of 
design, our filter assembly can remain fully functional even after the 
inlet or outlet side of the assembly is tilted by plus or minus 
approximately 45.degree.. 
It is yet a further advantage of the present invention to be mountable in a 
variety of vehicles, automotive and other, due to its diverse mounting 
structures. These structures include molded mounting locations and 
universal clips. 
Other features, objects, and advantages of the present invention will 
become apparent to the reader of the specification.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
FIG. 1 shows an automotive powerplant having an FVSS integrally disposed 
therein. Although some of the powerplant's specific components, geometry, 
and component names may differ from vehicle to vehicle, the primary 
structure and structural components will remain constant. 
Primary components of the automotive powerplant are fuel tank 10 and 
internal combustion engine 12. Liquid fuel enters the vehicle by first 
being introduced to the fuel inlet opening 14 then traveling through fuel 
filler tube 16 into fuel tank 10. Fuel is sent by fuel pump 18 through 
fuel filter 20 and to engine 12 by way of fuel line 22, fuel rail 24, and 
fuel injectors 26. optionally, some systems will recycle fuel unused by 
engine 12 by sending it back to fuel tank 10 via the fuel return line 28. 
There are generally two primary circumstances wherein fuel vapor filled air 
is forced out of fuel tank 10. The first circumstance is during the above 
outlined filling of tank 10 and the other occurs when the fuel vapor in 
the tank expands (usually due to increased temperature of the fuel and/or 
fuel vapor) and forces some of the fuel vapor out of the tank. In either 
case, the fuel vapor filled air is sent through fuel recovery line 30 to 
carbon canister 32 where it is cleaned of its vapor before being sent to 
the atmosphere. Carbon canister 32 is filled with activated carbon which 
adsorbs the fuel vapor from the air flow. 
Periodically, carbon canister 32, after absorbing and cleaning the fuel 
vapor filled air, must be desorbed, or purged, of the fuel vapor therein. 
This refreshing is done so that the canister can accommodate and absorb 
additional fuel vapor from fuel tank 10. 
Atmospheric air, to be used as purge air, is forced into and out of 
canister 32 and then sent through vapor purge line 34, and canister purge 
valve 36, directly to engine 12 for utilization. 
As mentioned above, the outdoor air used as purge air must be cleaned of 
substantially all matter and moisture before it is introduced to canister 
vent valve 38 (CVV) and carbon canister 32. This is the purpose of the air 
filter assembly 40. 
The preferred design of the air filter assembly 40, best viewed in FIG. 3, 
is composed of two primary components: a closure panel 42, which can be 
made to be removable, and a base 44. Closure panel 42 further comprises 
inner surface 46 strategically equipped with a plurality of baffles. Base 
44 further comprises of an air inlet 48, a baffle section 50, a filter 
element 52 contained within filter section 54, and air outlet 56. Filter 
52 is cubic in shape, thereby facilitating production efforts. 
Air enters air filter assembly 40 only by way of air inlet 48 and exits 
only by way of air outlet 56. Immediately after being introduced to baffle 
section 50 of the assembly, air is forced to maneuver under a first 
nonmating baffle 60, extending inward from the inner surface 46 of the 
closure panel 42, and over a second nonmating baffle 62, extending inward 
from the floor of base 64. From here the air flow continues on to maneuver 
the first mating baffle set 66, the third nonmating baffle 68, the second 
mating baffle set 70, and the fourth and final nonmating baffle sets 72. 
As mentioned above, the larger particles (matter, moisture, et al), due to 
their developed inertia, will be unable to survive the increasingly 
demanding path prescribed in baffle section 50. This increasingly 
demanding path is designed in such a way that the Stokes Number of the air 
flowing through said baffle area 50 remains relatively unchanged. The 
unwanted particles will therefore fall out of the continuing air stream 
and become disposed in the corresponding retention area 74. The particles 
will remain in retention area 64 unless evaporated or otherwise 
disintegrated by natural means. 
After leaving baffle section 50, purge air enters the filter section 
comprised primarily of filter element 52 and retention ribs 80. Filter 
element 52 is preferably a reticulated open cell foam and is designed so 
as to separate any remaining (usually very small, less than 20 .mu.m) 
particles from the air stream. Retention ribs 80 assure the proper 
locating of the filter element 52 during manufacture. Upon leaving filter 
section 54, the clean air then travels out of air outlet 56 and through 
canister vent line 58 to carbon canister 32 for the purging thereof. 
For the purpose of allowing flexible mounting and locating configuration of 
filter assembly 40, a plurality of sockets 82 is integrally formed upon a 
plurality of outer surfaces of the enclosure 84 to permit the manual 
attachment of mounting brackets 86 to the enclosure. 
As witnessed by simulation, testing, and actual usage, a filter assembly 40 
according to the present invention functions excellently in accomplishing 
the purpose of its design. The increasingly tortuous baffle section 50 
removes particles which will generally be decreasing in size. Any smaller 
particles that survive this portion will most likely be trapped in the 
foam media of the filter element 52. Due to this dual stage filtering 
process, only a very clean air flow is sent on to the CVV and carbon 
canister 32 for successful purging. 
While the invention has been shown and described in its preferred 
embodiments, it will be clear to those skilled in the art which they 
pertain that many changes and modifications may be made thereto with out 
departing from the scope of the invention.