Abstract:
An evaporative emissions canister for use in an automotive evaporative emission system to control emission of fuel vapors to the atmosphere, the system including a fuel tank coupled to an automotive engine, the canister comprising: a housing having side walls, a top wall and a bottom wall; a hydrocarbon-adsorbing material disposed so as to provide a vapor adsorbent chamber for adsorbing hydrocarbon fuel vapor flowing therethrough; and separating means located adjacent the vapor adsorbent chamber for separating fuel vapor and liquid fuel.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a fuel system for an internal combustion engine and, particularly, to 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 to the evaporative emissions canister in the fuel system.  
         [0002]     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. 5,408,977 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; and U.S. Pat. No. 6,237,574 to Jamrog 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 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. This decreases the overall working capacity of the canister resulting in possible emissions to the atmosphere. To prevent this, most fuel systems have a liquid fuel trap which is designed to allow the liquid to enter the canister but will not allow it to enter the carbon 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.  
         [0003]     Evaporative emissions canisters with incorporated fuel traps have been manufactured by mounting the fuel trap onto the top 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. 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.  
         [0004]     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.  
         [0005]     Accordingly, it is a primary object of this invention to provide an improved evaporative emissions system which incorporates a vapor/liquid separator in the fuel system which is operative to prevent liquid fuel from entering the carbon bed.  
         [0006]     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 seam between the fuel separator and the canister.  
         [0007]     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.  
       SUMMARY OF THE INVENTION  
       [0008]     In the past, canisters with incorporated fuel traps have been manufactured by mounting the fuel trap into the top of the canister creating the basin. Typically, a seal is created between the canister and the fuel trap by a plastic welding process such as vibration welding, ultrasonic welding, etc. The creation of the seal between the canister and the fuel trap is undesirable in that it requires an additional time consuming and, therefore, manufacturing step. The liquid trap of the present invention does not require “outside help” for installation into the system.  
         [0009]     In accordance with the present invention, the liquid fuel trap is incorporated directly into the evaporative emissions canister body by pressure fitting the fuel trap into the canister housing, wherein the seal is maintained by creating a torturous path for the liquid molecules via a groove inside the canister into which the fuel trap or basin is located, thereby eliminating the vibration welding step. The elimination of the welding step also reduces labor and capital costs because there is no need for welding equipment or operators. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic illustration of an evaporative emission system of a combustion engine according to the present invention;  
         [0011]      FIG. 2  is a perspective view of an evaporative emissions canister of the evaporative emissions systems of  FIG. 1 ; and  
         [0012]      FIG. 3  is an enlarged view of Section A of  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     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 canister. If this were to happen, the carbon bed would quickly degrade to a point that it would no longer be useful.  
         [0014]     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 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  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 burned. 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. The fuel vapor is passed on to the adsorbent chamber  46  where it is adsorbed on the adsorbent material  42 , while the liquid fuel is drawn by gravity to a liquid fuel trap  48  where it remains until it evaporates.  
         [0015]     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.  
         [0016]     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  and an adsorbent chamber  46 . The fuel vapor entering the canister  14  is passed into the adsorbent chamber  46  which contains an 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 canister  14 , 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. The vapor from the liquid fuel trap  48  is directed into the bed of adsorbent material  42  in chamber  46  where it becomes adsorbed on the adsorbent material  42 .  
         [0017]     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  20 . 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  connected to the engine  26  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 .  
         [0018]     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.  
         [0019]     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 but is typically in the form of carbon particles having an effective particle size sufficient to maximize the adsorbance of the fuel vapor in the canister.  
         [0020]     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.