Abstract:
An evaporative emissions canister is used in an automotive evaporative emission system to separate liquid fuel entrained with fuel vapor and to control emission of fuel vapors to the atmosphere, the system including a fuel tank coupled to an automotive engine. The canister includes an integrally molded housing having side walls, a top wall and a bottom wall; a hydrocarbon-adsorbing material disposed therein so as to provide a vapor adsorbent chamber for adsorbing hydrocarbon fuel vapor flowing therethrough; and a liquid-fuel trap located above the vapor adsorbent chamber for separating fuel vapor and liquid fuel. A method is provided for preventing or reducing hydrocarbon emissions to the atmosphere.

Description:
This application is continuation-in-part of U.S. patent application Ser. No. 10/655,240, filed Sep. 3, 2003 now abandonded. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a fuel system for an internal combustion engine and, particularly, to a method and an evaporation emissions canister which includes an integral liquid fuel trap for improved separation of liquid fuel which is entrained along with the fuel vapor from the fuel tank to the evaporative emissions canister in the fuel system. 
   Presently, fuel systems employed in the automotive industry contain an evaporative emissions canister to control evaporative emissions from the automotive fuel tank. Examples of evaporative emissions canisters are described in U.S. Pat. No. 4,203,401 to Kingsley et al.; U.S. Pat. No. 4,658,796 TO Yoshida et al.; U.S. Pat. No. 4,683,862 to Fornuto et al.; U.S. Pat. No. 5,119,791 to Gifford, et to Cotton; U.S. Pat. No. 5,924,410 to Dumas et al.; U.S. Pat. No. 5,957,114 to Johnson et al; U.S. Pat. No. 6,136,075 to Bragg et al; U.S. Pat. No. 6,237,574 to Jamrog et al.; and RE38, 844 to Hiltzik et al. 
   Typically, the evaporative emissions canisters include an adsorbent material such as activated carbon to adsorb the fuel vapors emitted from the fuel tank. The carbon filled canister adsorbs the fuel vapor until it becomes saturated, at which time, fresh air drawn through the canister removes the fuel vapor therefrom and sends it to the engine by means of suitable conduits and flow control devices. Such fuel systems not only permit the vapor to flow to the canister but also have the potential to allow liquid fuel entrained with the fuel vapor to travel from the fuel tank to the canister where it saturates at least a portion of the adsorbent carbon bed causing the carbon to become non-functional until the liquid is evaporated and purged from the carbon bed. This decreases the overall working capacity of the adsorbent material and the efficiency of the canister resulting in possible emissions to the atmosphere. To prevent this, some fuel systems incorporate a device inside the fuel tank where the liquid fuel is trapped and returned to the tank. Such devices are not entirely satisfactory since small amounts of liquid fuel are entrained with the fuel vapor and enter the emissions canister where it has the potential to reduce the effectiveness of the emissions canister. Emissions canisters have been provided with a liquid fuel trap, which is designed to allow the liquid fuel to enter the canister but will not allow it to enter the adsorbent material bed. Once the liquid enters the liquid fuel trap it simply sits there until it either evaporates on its own due to the properties of the gasoline or it will be drawn out of the canister during the purge cycle of the vehicle and conveyed back to the engine where it is consumed. However, such canisters generally require that an additional welding step be performed in the manufacture of the canister/liquid fuel trap system, wherein a seal is created between the fuel trap and the canister. Typically, the fuel trap is installed into the canister via a plastic welding process such as vibration welding, ultrasonic welding, etc. The manufacture of such evaporative emissions canisters is both time consuming and economically unattractive. 
   Typically, evaporative emissions canisters with incorporated liquid fuel traps have been manufactured by mounting the liquid fuel trap into of the canister, providing a basin for any invasive liquid fuel. For example, U.S. Pat. No. 5,119,791 to Gifford, et al. specifically teaches the use of a liquid trap with a vapor storage canister wherein the liquid-fuel trap consists of a cup that forms an interior cavity at the bottom of, and surrounded by, the carbon adsorbent bed. The fuel vapor with entrained liquid fuel emitted from the fuel tank is directed to the liquid-fuel trap through a fill tube. The liquid fuel settles out in the cup where it remains until it is later vaporized. The fuel vapor enters the carbon bed through a grid. During purge, vacuum is applied to a central purge tube that extends all the way through the carbon bed and cup into a plenum located below the cup. It is apparent from the above that there exists a need in the art for an automotive evaporative emissions canister which effectively prevents liquid fuel from entering and saturating the carbon bed in the canister, and which also eliminates the requirement for an additional sealing step between the fuel separator and the canister in the manufacturing process. Furthermore, it is desirable to provide an evaporative emissions canister having a simple construction, which does not require the insertion of the associated tubes all the way into the chambers of the evaporative emissions canister. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, the liquid-fuel trap is incorporated into the evaporative emissions canister body by simply pressure fitting the liquid-fuel trap into an open chamber located directly above the adsorbent chamber in the canister housing. The liquid-fuel trap, when incorporated into the evaporative emissions canister in accordance with the invention, as described below, directs the liquid fuel to the liquid-fuel trap by gravity while allowing the fuel vapor to flow to the adsorbent material where it is adsorbed and stored until it is purged to the engine where it is consumed. Since the liquid-fuel trap is secured in the evaporative emissions canister by pressure fitting the liquid-fuel trap directly into the canister housing, the need for a separate welding step is eliminated, thereby reducing labor and capital costs associated with welding equipment and operators. 
   Accordingly, it is a primary object of this invention to provide an improved evaporative emissions system, which incorporates a liquid-fuel trap in the fuel system, which is operative to prevent liquid fuel from entering the carbon bed. 
   It is another object of the invention to provide an evaporative emissions canister, which eliminates the requirement for an additional step in the manufacturing process to provide a seal between the fuel separator and the canister. 
   It is yet another object of the invention to simplify the manufacture of an evaporative emissions canister having a liquid-fuel trap incorporated therein, wherein the evaporative emissions canister does not require additional purge tubes that protrude all the way into and through the adsorbent chamber of the canister housing. 
   These objects as well as other objects, features and advantages of the present invention will be apparent to those skilled in the art from the following detailed description, appended claims and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of an evaporative emission system of a combustion engine in accordance with the present invention; 
       FIG. 2  is a side view of an evaporative emissions canister of the evaporative emissions systems of  FIG. 1 ; 
       FIG. 3  is an enlarged view of Section A of  FIG. 2 ; 
       FIG. 4  is a perspective view of the evaporative emissions canister of the invention; 
       FIG. 5  is a perspective view of a liquid-fuel trap of the present invention; 
       FIG. 6  is a side view of a liquid-fuel trap of the present invention; 
       FIG. 7  is a top view of the liquid-fuel trap of  FIG. 4 ; and 
       FIG. 8  is a bottom view of the liquid-fuel trap of  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Vehicle fuel systems require liquid traps to prevent liquid fuel from entering the carbon bed of the vapor canister. Without the liquid trap, there is the potential for liquid fuel to enter the adsorbent bed in the canister where the adsorbent material would quickly degrade to a point that it would no longer be useful. 
   It has now been found that an evaporative emissions canister manufactured in accordance with the present invention and positioned between the fuel tank and the engine of an automotive vehicle, effectively separates the fuel vapor from any liquid fuel entrained therewith. More specifically, the evaporative emissions canister of the present invention incorporates a liquid-fuel trap directly into the housing of the evaporative emissions canister, wherein the liquid-fuel trap is disposed above the adsorbent chamber containing the adsorbent material so that the fuel vapor and any accompanying liquid fuel are in open communication with the liquid-fuel trap without the need for any additional tubular hardware to direct the fuel vapor and the liquid fuel to other destinations within the evaporative emissions canister. As more fully described below, the liquid fuel is separated from the fuel vapor immediately upon entering the evaporative emissions canister providing a simpler and more effective separation of the liquid fuel vapor from the fuel vapor. 
   The evaporative emission canister of the invention includes a first chamber for receiving a mixture of fuel vapor having liquid fuel entrained therewith. The first chamber comprises: 
   a top member having an inner surface and an outer surface, the top member terminating in a circumferential edge thereof defining a circumferential perimeter of the top member. The first chamber further includes a continuous side member having an inner surface and an outer surface, said side member extending vertically from the circumferential edge of the top member in a downward direction defining a first cavity for receiving a mixture of fuel vapor having liquid fuel entrained therewith; 
   a first tubular member extending upwardly from said housing and in operable communication with said fuel vapor-receiving chamber, said first tubular member providing a passage throughwhich said fuel vapor having said liquid fuel entrained therewith flows into said fuel vapor-receiving chamber; 
   a first port in operable communication with the first chamber, the first port extending upwardly from the top of the first chamber in an oppositional direction from the continuous side member and provides a passageway through which the fuel vapor having liquid fuel entrained therewith flows into said first chamber; 
   a second tubular member extending upwardly from said housing and in operable communication with said fuel-receiving chamber, said second tubular member providing a passage throughwhich fuel vapor flows from said evaporative emissions canister to an automotive engine where said fuel vapor is consumed; 
   a second port in operable communication with the first chamber, the second port extending upwardly from the top member of the first chamber and parallel to the first port providing a passageway through which fuel vapor flows from the evaporative emissions canister to an automotive engine where the fuel vapor is consumed; and 
   a circumferential groove formed in the inner surface of the top member, the circumferential groove being parallel to the circumferential edge of the top member. 
   The evaporative emissions canister further comprises a second chamber positioned below the first chamber and in open communication with the first chamber, the second chamber comprises: 
   a bottom member defining the lower perimeter of the second chamber; 
   a continuous side member having an inner surface and an outer surface extending vertically from the bottom member in an upward direction defining a second cavity of the evaporative emissions canister; 
   a second top member adjacent the first chamber; 
   a partition extending downwardly to a predetermined distance from the second top member dividing the second chamber into a first compartment and a second compartment, the first compartment being directly below and in open communication with the first chamber, and the second compartment being directly below the second top member; 
   a third tubular member extending upwardly from said housing, said third tubular member providing a passage throughwhich fresh air is admitted to said housing during a purging stet, and throughwhich air from an air/fuel mixture is vented to the atmosphere in a venting step; 
   a third port in operable communication with the second chamber, the third port extending upwardly from the second top member providing a passageway through which fresh air from the second compartment is vented to the atmosphere upon adsorption of fuel vapor from the liquid fuel trap, and for permitting air to flow into the second compartment upon desorption of fuel vapor from the first compartment, during a purging step; and 
   a liquid-fuel trap located in the first chamber for separating liquid fuel from fuel vapor and retaining the liquid fuel until it is evaporated forming additional fuel vapor. 
   The liquid-fuel trap comprises: 
   a second bottom member; 
   a continuous side member defining a circumferential wall having an inner surface, an outer surface and a rim defining the upper edge of the continuous side member, the continuous side member extending vertically from the bottom member in an upward direction; 
   a plurality of parallel rib members extending vertically along at least a portion of the outer surface of the continuous side member of the liquid-fuel trap wherein the liquid-fuel trap is secured in the first chamber by pressure exerted by the plurality of ribs on the interior surface of the sidewall of the first chamber to secure the liquid-fuel trap in the first chamber. The ribs are spaced apart exhibiting open access between each of the ribs to allow the flow of fuel vapor from the first chamber to the second chamber. The circumferential upper rim of the side member of the liquid-fuel trap is inserted into the corresponding circumferential groove in the inner surface of the top of the first chamber to provide a seal thereat. Since the canister is typically installed on its side in the vehicle, the seal prevents the liquid fuel from entering the second chamber while allowing the fuel vapor to flow freely to the second chamber through the opening in the bottom of the liquid-fuel trap. The liquid fuel remains in the liquid-fuel trap until it evaporates and subsequently passes as fuel vapor into the adsorbent chamber, or is purged along with the adsorbed fuel vapor into the automotive engine where it is consumed. In a particularly preferred aspect of the present invention, each of said first, second and third ports is an external port and there is no need for additional tubular purge member extending through the adsorbent material and to the bottom of the adsorbent chamber of the evaporative emissions canister. 
   Turning to the drawings,  FIG. 1  is a schematic illustration of an evaporative emissions system for an automotive vehicle. As illustrated in  FIG. 1 , the evaporative emissions system  10  includes an evaporative emissions canister  14  containing a bed of adsorbent material  42 . Fuel vapor including a small amount of liquid fuel vented from the fuel tank  12  flows through the fuel vapor line  16  which communicates with fuel tank  12  via port  18  and with canister  14  via port  19 . Fuel vapor containing anywhere from a minor amount to a relatively significant amount of liquid fuel is vented from the fuel tank  12  where it flows through fuel vapor line  16  to the canister  14 . In accordance with the present invention, the liquid fuel is separated from the fuel vapor allowing the fuel vapor to be adsorbed by the bed of adsorbent material  42 . The adsorbed fuel vapor is then purged from the adsorbent material  42  as necessary by applying engine vacuum on the bed of adsorbent material  42 , drawing air through the adsorbent material  42  containing the fuel vapor. The desorbed fuel vapor is then fed to the engine  26  through engine vacuum line  17 , and consumed. More specifically, one end of the fuel vapor load line  16  is connected to the fuel tank  12  via port  18  and the other end is connected to the canister  14  via port  19 . The fuel vapor, including a minor amount of liquid fuel enters the canister at port  19  where the fuel vapor is separated from any liquid fuel entrained therewith. Upon entering the evaporative emissions canister  14 , the liquid fuel is directed by gravity into the liquid-fuel trap  48  where it remains until it evaporates, while the fuel vapor is passed on to the adsorbent chamber  46  where it is adsorbed on the adsorbent material  42 . The liquid fuel, upon evaporation, may pass into the adsorbent chamber where it is adsorbed on the adsorbent material, or it may pass directly to the engine  26  for consumption along with the adsorbed fuel vapor from the adsorption chamber  46  during a purge step. 
   When the adsorbent material  42  becomes saturated with the fuel vapor, engine controller  34  commands fuel vapor valve  30  to close the fuel vapor load line  16  so that the fuel vapor is desorbed from the adsorbent material  42  and drawn by vacuum through an engine vacuum port  28  connecting engine vacuum line  17  to the engine  26  where the desorbed fuel vapor is consumed. The vacuum created by opening the fresh air valve  32  also causes fresh air from the atmosphere to be drawn into the canister  14  through fresh air line  22  connected to canister  14  via port  24 . Upon removal of the fuel vapor from the adsorbent material  42 , the fuel vapor valve  30  is opened so that additional fuel vapor from the fuel tank  12  can be transported via fuel vapor load line  16  to the canister  14  and adsorbed by the adsorbent material  42 . Fresh air is then forced back through fresh air line  22  to the atmosphere. The fresh air valve  32  is opened and closed by the engine controller  34  to prevent fuel vapor from escaping into the atmosphere. However, the fresh air valve  32  typically remains open until routine or diagnostic steps are performed on the automotive vehicle. 
   As shown in  FIG. 2 , the canister  14  includes a housing having a side portion  36 , a top portion  38  and a bottom portion  40 . The canister  14  further includes a liquid fuel trap  48  secured in a fuel vapor-receiving chamber  49  located above the adsorbent chamber  46 . The adsorbent chamber  46  includes a partition  52  that divides the adsorbent chamber into two compartments  46   a  and  46   b , both of which contain adsorbent material  42 . The adsorbent material  42  in the first compartment  46   a , which is located directly below the first chamber, adsorbs and stores the fuel vapor as it enters the compartment  46   a . During a purge step, the fuel vapor valve is actuated to draw fresh air from the fresh air valve through the second compartment  46   b  via port  24  where the fresh air travels through the adsorbent material  42  and around the bottom of the partition  52  displacing the fuel vapor adsorbed and stored in the compartment  46   a . The displaced fuel vapor proceeds to the automotive engine  26  through engine vacuum line  17 , where it is consumed. Fuel vapor entering the canister  14  through port  19  is passed into the adsorbent chamber  46 , which contains the adsorbent material  42  while the liquid fuel accompanying the fuel vapor is drawn by gravity to the fuel trap  48  above the chamber  46 . At the liquid fuel trap  48 , a seal is maintained between the fuel trap  48  and the adsorbent chamber  46  by creating a torturous path for the liquid molecules via a groove  50  inside the fuel vapor-receiving chamber  49 , into which the fuel trap  48  is pressed. The liquid fuel entrained with the fuel vapor from the fuel tank  12  is separated from the fuel vapor by gravity wherein the fuel vapor is directed to the adsorbent material  42  and the liquid fuel is directed to the fuel trap  48  where the liquid remains until it evaporates. Upon evaporation, the liquid fuel in the form of fuel vapor is directed into the bed of adsorbent material  42  in chamber  46  where it becomes adsorbed on the adsorbent material  42 , or it is directed to the engine during the purge stage. Typically, a porous material separates the liquid-fuel trap chamber  20  from the adsorbent chamber  46  to promote even flow of the fuel vapor therethrough. As illustrated in  FIG. 5 , the outer surface of the bottom member  54  of the liquid-fuel trap may include a plurality of finger members  72  to further facilitate the flow of fuel vapor through the porous material  70 . 
   The fuel tank vapor load line  16  is connected to canister  14  via port  19 . Engine purge line  17  is also connected to the canister  14  via port  24 . Communication between the canister  14  and each of the fuel tank  12  and the engine  26  is controlled by valve  30 . When the valve  30  is open between the fuel tank  12  and the canister  14 , fuel vapor from the fuel tank  12  is transported to the canister  14  and when the valve  30  is open between the canister  14  and the engine  26 , desorbed fuel vapor is drawn from the adsorbed material  42  in the canister  14  via vapor line  17  having one end connected to canister port  21  and the other end connected to by engine port  28  where the desorbed fuel vapor is consumed. The engine&#39;s vacuum serves to draw fresh air through the fresh air vent line  22  into the canister  14  for the purpose of desorbing fuel vapor from the bed of adsorbent material  42 . The desorbed fuel vapor is then routed to the engine  26  through fuel vapor line  17  where it is consumed by the engine  26 . The air drawn into the bed of adsorbent material  42  to desorb the fuel vapor is then vented to the atmosphere through fresh air line  22  connected to the canister  14  by fresh air vent port  24 . 
   The liquid fuel trap  48  is located above the adsorbent material chamber  46  and separates any liquid fuel, which is swept along with the fuel vapor into the canister  14 . The fuel vapor separated from the liquid fuel continues on to the adsorbent material chamber  46  where it is adsorbed by the adsorbent material  42 . The liquid fuel swept into the liquid fuel trap  48  is pulled there by gravity where it remains until it eventually evaporates. The vapor created by the evaporation of the liquid fuel then passes on to the bed of adsorbent material  42  where it becomes adsorbed, or it is purged to the engine  26  through fuel vapor line  17 , depending on the direction of flow dictated by the engine controller  34  at the time. 
   The liquid fuel trap  48  comprises: 
   A bottom member  54  defining the bottom of the liquid-fuel trap  48 ; a continuous side member  56  defining a circumferential wall having an inner surface  58 , an outer surface  60  and a circumferential rim  62  defining the upper edge of the continuous side member  56 , the continuous side member  56  extending vertically from the bottom member  54  in an upward direction, and 
   a plurality of parallel rib members  64  extending vertically along at least a portion of the outer surface  60  of the continuous side member  56  of the liquid-fuel trap  48  wherein the liquid-fuel trap  48  is secured in the liquid-fuel trap chamber  20  by pressure exerted by the plurality of rib members  64  on the interior surface of the sidewall  56  of the liquid-fuel trap chamber  20  to secure the liquid-fuel trap  48  in the liquid-fuel trap chamber  20 . The rib members  64  are spaced apart exhibiting open access between each of the rib members to allow the flow of fuel vapor from the liquid-fuel trap chamber  20  to the adsorbent chamber  46 . 
   In order to keep the adsorbent material  42  inside the adsorbent material chamber  46 , a barrier member  70  may be disposed between the fuel vapor-retaining chamber  49  and the adsorbent chamber  46  to prevent the adsorbent material  42  from escaping the adsorbent chamber  46  and entering the fuel vapor-retaining chamber  49 . Typically the barrier member  70  is a porous material such as a foamed polymeric material, a fibrous material, or the like. In order to provide a surface area and maintain the barrier member  70  relatively flat, the bottom member  54  of the liquid-fuel trap  48  includes a plurality of finger elements  72  extending downwardly from the outer surface of the bottom member  54  of the liquid-fuel trap  48  adjacent the barrier member  70 . 
   The circumferential upper rim  62  of the side member  56  of the liquid-fuel trap  48  is inserted into the corresponding circumferential groove  50  in the inner surface of the top portion  38  of the liquid-fuel trap chamber  20  to provide a seal  66  thereat. The seal  66  prevents the liquid fuel from entering the adsorbent chamber  46  while allowing the fuel vapor to flow freely to the adsorbent chamber  46  through the aperture  68  in the bottom  54  of the liquid-fuel trap  48 . The aperture  68  typically includes a wall portion  74  extending upward from the circumferential rim  76  of the aperture  68 . The liquid fuel remains stored in the liquid-fuel trap  48  until it evaporates and subsequently passes as fuel vapor into the adsorbent chamber  46 , or is purged along with the adsorbed fuel vapor into the automotive engine  26  where it is consumed. 
   The evaporative emissions canister of the present invention is manufactured from any material possessing the desirable properties and characteristics, such as flexibility, fuel resistance, heat resistance, pressure resistance, weatherability, dimensional stability, and high impact strength. Typically, such material is a polymeric material, more preferably, a polyamide material such as nylon or an aromatic polyamide such as aramid. 
   Typically, the evaporative emissions canister, including the various parts thereof, is molded in one piece to provide a continuous unitary structure thereby preventing the need for any assembly steps. 
   The liquid-fuel trap, including the various parts thereof, is also manufactured as a unitary structure, but in a separate molding operation from that of the evaporative emissions canister. 
   The adsorbent material useful in the invention may be any of the conventional materials effective to adsorb hydrocarbon materials such as fuel vapor. Preferable, the adsorbent material is carbon and most preferably activated carbon. The carbon can be in any desired form having an effective particle size sufficient to maximize the adsorbance of the fuel vapor in the canister. 
   Typically, the evaporative emissions canister will include a volume compensator, as is well known in the art, located at the bottom of the canister housing to limit shifting of the adsorbent material, particularly during operation of the automotive vehicle. 
   While the present invention has been fully illustrated and described in detail, other designs, modifications and improvements will become apparent to those skilled in the art. Such designs, modifications and improvements are considered to be within the spirit of the present invention, the scope of which is determined only by the scope of the appended claims.