Abstract:
An emissions control system is described for an internal combustion engine, having a vapor sorbent material within the fuel tank cap subjected to an active purge.

Description:
[0001]    This non-provisional application relies on the filing date of provisional U.S. Application Ser. No. 60/747,036 filed on May 11, 2006, which is incorporated herein by reference, having been filed within twelve (12) months thereof, and priority thereto is claimed under 35 USC §119(e). 
     
     BACKGROUND 
       [0002]    The use of sorbtion materials (sorbents) such as activated carbon to remove contaminants from air is well known. Specialized activated carbons have been developed for example as described by U.S. Pat. No. 5,538,929 which discloses a phosphorus-treated activated carbon. Sorbents may be placed within suitable air-handling systems to clean the air passing through the material. Such systems are sometimes known as vapor adsorbers. 
         [0003]    Another well known sorbent use is for capturing hydrocarbon vapors that would otherwise escape from the fuel systems of internal combustion engines. An example is a sorbent canister suitably placed in an automobile to trap gasoline vapors that might otherwise escape from the gasoline tank or from engine components, particularly during periods of non-use. 
         [0004]    U.S. Pat. No. 6,959,696 discloses both an actively purged canister and a passively purged canister for small internal combustion engines. The actively purged design embodies a carbon canister that is connected by a tube to the throttle body of the internal combustion engine that induces airflow. 
       SUMMARY 
       [0005]    This invention relates to a method of providing vapor emissions control for small engines, using a sorbent contained in the cap of the fuel tank. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  illustrates a fuel tank having an emissions control device according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0007]      FIG. 1  illustrates a cross section view of a fuel tank  100  showing the tank partially filled with fuel  110 , and above the fuel, a vapor space  120 . Liquid fuel from tank  100  may be conveyed through fuel line  115  to an internal combustion engine  200 . Details of the internal combustion engine are not shown, but are well known to those skilled in the art. Fuel delivered through fuel line  115  will typically pass through components (not shown) such as a filter, a fuel pump, and a fuel injection or carburetion system. Some of these components may be contained within fuel tank  100 , such as a filter or a pump. There may be an additional fuel recirculation line (not shown). 
         [0008]    Fuel tank  100  is provided with a fuel cap  130 , which has a vent such as a hole  150  to allow pressure within the tank to be released to the atmosphere. To prevent fuel vapors from reaching the atmosphere, a sorbent material  140  is provided within gas cap  130 . The sorbent material may, for example, be activated carbon. 
         [0009]    When the fuel tank  100  heats up, for example during the day, gases within the vapor space  120  expand and pass through the cap  130  must first pass through sorbent  140 , which adsorbs fuel vapors. When the fuel tank cools, for example at night, the pressure within the fuel tank reduces and fresh air comes in through hole  150 , passing through the sorbent  140  and entering the fuel tank  100 . As the fresh air is drawn in through the sorbent  140 , it removes some of the adsorbed fuel from the sorbent  140 , restoring it within the vapor space  120 . Such purging is termed “passive purging.” 
         [0010]    It would be useful if the sorbent  140  could be purged actively. To accomplish this, according to the invention, during operation of engine  200 , vapors  120  are drawn through purge line  125  and into a low pressure point in the engine, for example a venturi point or other reduced pressure location within the engine air intake system, such as within the throttle body. When the engine is operating, airflow is induced through the purge line  125 , which causes air to enter the tank through the gas cap and vent hole  150 , and purge sorbent  140 , sweeping gas vapor from the sorbent, and delivering it to the combustion chamber of the engine. 
         [0011]    With the invention disclosed herein, the purge line is connected to and draws air from the fuel tank, which in turn draws air through the sorbent device located within the fuel cap. The sorbent device itself is not connected to the purge line. 
         [0012]    The invention uses a sorbent device or canister that is fitted to a fuel tank. The sorbent device or canister could be part of the screw cap, or could be a separate device. A fuel cap containing a sorbent is currently marketed by ITW Fastex, but it does not have a means to actively purge the sorbent. 
         [0013]    Methods of making and using the emission control system in accordance with the invention should be readily apparent from the mere description of the structure and its varied appearances as provided herein. No further discussion or illustration of such methods, therefore, is deemed necessary. 
         [0014]    While preferred embodiments of the invention have been described and illustrated, it should be apparent that many modifications to the embodiments and implementations of the invention can be made without departing from the spirit or scope of the invention. It is to be understood therefore that the invention is not limited to the particular embodiments disclosed (or apparent from the disclosure) herein, but only limited by the claims appended hereto.