Abstract:
A purge control system for an electric vehicle including a fuel tank, a purge canister coupled to the fuel tank, an internal combustion engine coupled to the purge canister, a microgenerator coupled to the purge canister, and where said microgenerator uses fuel in the purge canister to generate electrical energy.

Description:
TECHNICAL FIELD 
     The present invention relates generally to the recovery of evaporative emissions for a vehicle. More specifically, the present invention relates to a method and apparatus including a microgenerator or an array of microgenerators to recover evaporative emissions from vehicle fuel tank to generate power. 
     BACKGROUND OF THE INVENTION 
     In today&#39;s automotive market, vehicles are typically equipped with a fuel evaporation control system to eliminate evaporative emissions from a fuel tank to the environment. The evaporative emissions are collected in a purge canister such as a charcoal canister where carbon granules store the vapor when the engine in the vehicle is turned off. After the engine has been started, the canister will be regenerated and the vapors will enter the engine to be used in normal operation. If a vehicle is left unused for an extended period of time, the canister may saturate with fuel, and vapors may be released into the atmosphere. An extended period of disuse of the vehicle will also affect the electrical system, specifically the battery. Parasitic currents are drawn from the battery when the vehicle is off to maintain memory in various electronic devices, through the polling of wireless communication services, and the battery is also naturally discharging through internal battery parasitic currents. The battery after this extended period of disuse may expend all of its electrical energy and fail to start the vehicle when desired by an operator. 
     SUMMARY OF THE INVENTION 
     The present invention includes a method and apparatus that uses a microgenerator or array of microgenerators to utilize fuel stored in a canister supplemented by fuel from the vehicles fuel system to charge the battery in a vehicle. During extended periods of vehicle disuse, this will prevent the canister from being saturated and the battery from discharging. Formerly wasted fuel vapors discharged to the atmosphere are now used to charge the battery. 
     A microgenerator comprises a gas turbine supplied with fuel and air that rotates a generator to produce electrical power. The microgenerator may further include AC/DC and DC/AC converters to condition the power as needed. The microgenerator will have dimensions of substantially under one inch in area and one-tenth of an inch in volume, but any other dimensions are within the scope of the present invention including larger and smaller dimensions. Microgenerators may be arrayed in series or parallel, depending on the required voltage and current outputs. Alternatively, a microgenerator may consist of a fuel cell supplied with fuel and air. 
     The present invention further includes a method and apparatus to determine the state of charge (SOC) of a battery in a vehicle. The SOC is defined as the percentage of the full capacity of a battery that is still available for further discharge. The SOC determination is used by the microgenerator(s) to regulate the charging of the battery. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic drawing of a microgenerator of the present invention; 
     FIG. 2 is a diagrammatic drawing of an array of microgenerators of the present invention; and 
     FIG. 3 is a diagrammatic drawing of the fuel control system of the present invention; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is a diagrammatic drawing of a microgenerator  10  used in the present invention. Fuel  12  and air  14  enter a gas turbine  16 . The gas turbine  16  rotates a motor/generator (MOGEN)  18  to generate electricity. The MOGEN  18  may comprise any known type of generator including, but not limited to, electrostatic, induction and permanent magnet generators. The electrical current output of the MOGEN  18  is rectified and conditioned by a converter  20  to provide regulated DC power. In the preferred embodiment of the present invention, the converter  20  comprises a series of rectifier diodes. 
     FIG. 2 is a diagrammatic drawing of an array  22  of microgenerators  10  of the present invention. The array  22  is configured to produce desired voltage and current outputs. Voltage and current are controlled by controlling the rate of fuel feed into the microgenerator(s)  10 . 
     FIG. 3 is a diagrammatic drawing of a vehicle  30  containing a fuel control system  32  of the present invention. The fuel control system  32  includes a fuel tank  34  used to hold fuel such as gasoline or diesel fuel. A purge line  36  is connected to the fuel tank  34  and a purge canister  38 . The purge canister includes carbon to absorb fuel vapor when the vehicle  30  is in an off state. The purge canister  38  is coupled to an internal combustion engine  42  by a purge line  40 . During operation of the engine  42 , the vacuum created by the engine draws air through the purge canister  38  and purge line  40  to pull fuel vapor into the engine  42 , regenerating the purge canister  38  and burning the fuel vapor in the engine  42 . 
     The present invention further includes a purge line  44  to the microgenerator  10 . The microgenerator  10  is further coupled to the fuel tank  34  by fuel line  46 . In the preferred embodiment of the present invention, a controller  48  controls the microgenerator operation in response to the operating condition of the vehicle  30 . If the controller  48  determines that the vehicle  30  has been in an extended period of disuse and the purge canister  38  is saturated, the microgenerator  10  will be operated by the fuel vapors in the purge canister  38  supplemented by fuel from the main tank to generate power to charge the battery  50 . Vapor is drawn from the purge canister  38  by applying a vacuum to across a control valve. The vacuum causes air to be drawn into the purge canister  38  to draw the vapors from storage in the purge canister  38 . The power generated by the microgenerator  10  in the preferred embodiment will be used to charge a battery  50 . The battery  50  is preferably charged at substantially 12 to 14  volts by the microgenerator  10 . The battery  50  SOC is monitored by the controller  48 . In alternate embodiments of the present invention, the microgenerator  10  will power vehicle accessory loads  52  directly. Vehicle accessory loads  52  include, but are not limited to, clocks, electronic controllers, vehicle electronics, and sensors. In this manner the purge canister  38  may be regenerated before fuel vapor is released to the environment and the battery  50  may be recharged before it is fully discharged by the accessory loads  52 . 
     While this invention has been described in terms of some specific embodiments, it will be appreciated that other forms can readily be adapted by one skilled in the art. Accordingly, the scope of this invention is to be considered limited only by the following claims.