Not Applicable.
Not Applicable.
The present invention relates in general to bleed elements in evaporative emission canisters for vehicle fuel systems, and, more specifically, to a deflector for retaining a carbon scrubber element.
Evaporative emissions systems are used in conjunction with the fuel systems of gasoline-powered vehicles to prevent release of hydrocarbon fuel vapors into the atmosphere. A typical carbon canister design uses a bleed emission treatment section to provide reduced emissions occurring during the diurnal (i.e., inactive) state of the vehicle. A large primary carbon bed handles the majority of fuel vapor during vehicle use and refueling. A bleed emission region close to the atmospheric vent uses an activated carbon scrubber element to capture low concentration hydrocarbon vapor from being expelled into the environment. Typically, the activated carbon element is held by a plastic molded tube generally open at both ends. This tube provides structure protecting the relatively fragile carbon element. An O-ring seal between this tube and the venting access of the mating shell has been used to assure a tight seal. Another separate molded piece is placed around the bleed tube to act as a bleed deflector or flow diverter so that vapors are routed through a zig-zag path to double back for entry into the bleed tube.
Very limited packaging space is available within the carbon canister. Therefore, it would be desirable to eliminate the separate bleed tube, o-ring seal, and any compliance media packed around the carbon element that is often used to protect the fragile element.
In one aspect of the invention, a deflector is provided for mounting a carbon scrubber element at an atmospheric port of an evaporative emissions canister. A substantially cylindrical shell has an open end and a closed end. A spacer plate extends outwardly from the shell. An elastomeric ring is overmolded by an interior surface of the shell at a longitudinal position intermediate of the open end and the closed end. The elastomeric ring has an inner diameter configured to sealingly receive the carbon element. A plurality of vapor apertures are formed in the shell located longitudinally between the spacer plate and the elastomeric ring. A plurality of elastomeric ribs are overmolded by the interior surface of the shell and located longitudinally between the vapor apertures and the closed end. The elastomeric ribs are configured to be spaced around the carbon element to suspend the carbon element spaced away from the shell without blocking a gaseous flow from the vapor vents to the carbon element. The open end of the shell is configured to sealingly connect with the atmospheric port.
Deflector 21 has a spacer plate 23 with flexible fingers that contact walls 11 and 12. Adsorbent carbon pellets are retained below spacer plate 23, and air and fuel vapors are allowed to pass from cavity 13 through spacer plate 23 into a cylindrical gap 24 between deflector 21 and bleed tube 20. The air and fuel vapors traverse down gap 24 and into an opening 25 at the lower end of bleed tube 20 for scrubbing by element 16 before the scrubbed air moves out through port 15.
In order to ensure a robust seal so that only gases that have passed through element 16 are allowed to vent to atmosphere, O-rings 26 and 27 are placed between bleed tube 20 and an outlet collar 28. The relatively high parts count of this prior art structure may make it particularly difficult to assemble and install all the subcomponents for the evaporative emissions unit. The present invention provides one molded part that performs the functions of both the deflector and the bleed tube while integrating support and cushioning for the carbon scrubber element all in one bleed element assembly that is easily installed in the evaporative emissions unit.
As shown in
Second end 32 of carbon element 30 is retained by a plurality of elastomeric ribs 44 which are also over-molded within the interior surface of shell 34. Ribs 44 are located longitudinally between vapor apertures 40 and closed end 36. At least four ribs 44 are spaced around element 30 to suspend it away from shell 34 without blocking the gaseous flow entering vapor apertures 40 and progressing to second end 32 of element 30. Since elastomeric ring 41 sealingly receives carbon element 30 continuously around the circumference of element 30, and since the only flow path through element 30 is between the opposite ends 31 and 32, no additional O-rings or seals are needed to prevent vapor leakage to open end 35. Ribs 44 are disposed both radially and longitudinally against element 30 and may have any desired shapes suitable for overmolding such as pips, dimples, bumps, or elongated sections.
In a preferred embodiment, elastomeric ribs 44 each comprises an L-shaped body with a first arm 45 over-molded by the interior cylindrical surface of shell 34, wherein first arm 45 extends longitudinally away from closed end 36. The L-shaped body further comprises a second arm 46 that is over-molded into closed end 36 and extends radially toward the center axis. Thus, any movements or vibrations of element 30 (either axial or radial) are cushioned by ribs 44 and ring 41, and a foam sock as shown in prior art
Elastomeric ring 41 and elastomeric ribs 44 may preferably be comprised of MBR rubber which may be over-molded using conventional techniques within a deflector body comprised of nylon or polypropylene blends, for example. Preferably, the shell and spacer plate are integrally molded as one piece. More specifically, ring 41 and ribs 44 may be loaded into a molding tool which then receives molten thermoplastic to form the deflector in a manner that captures ring 41 and ribs 44.
The inner walls of canister 50, including walls 52 and 53, preferably include a plurality of stop ribs 55 shown in
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