Patent Application
20050045160
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Turning to the drawings,
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
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'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 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.
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.
