US 3884204 A
A vapor loss control system for a vehicle fuel supply system includes a first vapor recovery circuit from a vapor space of a gas tank to an air purged canister having a first predetermined volume of vapor adsorbing active material; and wherein the outlet of the canister is connected to a ported vacuum connection in a carburetor for selectively purging said first canister during each engine operation at a rate to purge said first canister for subsequent recovery of vapors. The system further includes a second vapor recovery circuit with second larger volume vapor adsorbing canister in communication with a normally closed, unrestricted vent port on the filler neck of the tank which is opened during fuel fill operation to direct tank vapors into the second canister; and wherein means including a flow restrictor communicate the outlet of the second larger volume canister with the intake manifold to produce a rate of recovery of vapors from the second canister sufficient to purge it between tank fill operations without excessive enrichment of fuel flow into the intake manifold.
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Description (OCR text may contain errors)
United States Patent [191 Krautwurst et al.
[ TANK FILL VAPOR CONTROL  Inventors: Homer V. Krautwurst; Cristian F.
Schulitz, both of Rochester, NY.
 Assignee: General Motors Corporation,
22 Filed: Apr. 15, 1974 21 Appl. No.: 461,010
Primary Examiner-Manuel A. Antonakas Assistant Examiner-James W. Cramson, Jr. Attorney, Agent, or FirmJ. C. Evans [451 May 20, 1975  ABSTRACT A vapor loss control system for a vehicle fuel supply system includes a first vapor recovery circuit from a vapor space of a gas tank to an air purged canister having a first predetermined volume of vapor adsorbing active material; and wherein the outlet of the canister is connected to a ported vacuum connection in a carburetor for selectively purging said first canister during each engine operation at a rate to purge said first canister for subsequent recovery of vapors. The system further includes a second vapor recovery circuit with second larger volume vapor adsorbing canister in communication with a normally closed, unrestricted vent port on the filler neck of the tank which is opened during fuel fill operation to direct tank vapors into the second canister; and wherein means including a flow restrictor communicate the outlet of the second larger volume canister with the intake manifold to produce a rate of recovery of vapors from the second canister sufficient to purge it between tank fill operations without excessive enrichment of fuel flow into the intake manifold.
3 Claims, 3 Drawing Figures PATENTEI] HAY 2 0 I975 SHEET 10? 2 TO FUEL PUMP TANK FILL VAPOR CONTROL This invention relates to evaporation control systems for limiting gasoline vapor discharge into the atmosphere from the fuel supply of an internal combustion engine and more particularly to systems having vapor collection canisters therein with active vapor adsorbing material to adsorb and store fuel vapors and means for selectively withdrawing the adsorbed fuel vapors for consumption in the engine combustion process.
Evaporation control systems for collecting vapors from the fuel supply components including the fuel tank and carburetor fuel bowl of an internal combustion engine include means for adsorbing and storing fuel vapors in a charcoal canister as generated from the fuel bowl during heat soak periods of engine operation and as generated from the fuel tank under elevated ambient temperature conditions. These collected vapors are drawn from the canister when the engine is running and subsequently consumed in the engine combustion process. Typically, such systems connect the canister to a source of vacuum in the intake fuel supply system of the vehicle which is used to draw the collected vapors from the canister at a rate that will serve to purge the active material of canister adsorbed vapors during each engine operation to condition the canister for collection of subsequently generated vapors The purge rate is selected to prevent excessive enrichment of a predetermined air-fuel supply from a carburetor to the intake manifold of the engine.
Such systems are satisfactory for their intended purpose under circumstances where fuel vapors are directed out the filler neck of a gas tank directly to atmosphere when the tank is being filled with fuel. In order to improve vapor collection, it has been proposed that the filler neck be sealed during the fill phase of operation and that fill generated vapors be directed to an evaporative control canister. Thus, the canister must adsorb substantially greater volumes of vapor each time that the tank is filled. In order to effectively purge the canister in such systems, the purge rate must be elevated in order to purge both daily adsorption of fuel vapor emissions from the fuel tank and the fuel bowl and the added charge of fill generated vapors. Such purge rates can affect engine operation or increase engine exhaust emissions of unburned hydrocarbons or both.
Accordingly, it is an object of the present invention to improve collection of fuel vapor emissions from a vehicle fuel supply system by the provision of first canister means having an inlet for collection of vapors generated during daily vehicle operation from a fuel tank and carburetor bowl and wherein means are provided to purge vapors from the first canister means for consumption in the engine at a rate to condition the first canister means for collection of subsequently generated vapors; and by the further provision of second canister means connected to the fuel tank by means for collection of vapors generated during gas tank fill operations without affecting the cycle of collection and purge of vapors from the first canister means; and wherein the second canister means is connected to means for purging such vapors at a reduced rate into the intake manifold of the engine to avoid adverse engine operation or production of increased exhaust emissions of unburned hydrocarbons.
Another object of the present invention is to provide an improved two canister evaporative emission control system for collecting fuel vapors from a fuel supply system for the vehicle including a first small capacity canister operative to collect vapors generated within a fuel tank and from a fuel bowl of the carburetor during engine operation and including means for purging collected vapors from the small capacity canister during each engine operation to condition the canister for subsequent collection of vapors generated from the tank and carburetor bowl and wherein means are provided to direct vapors from the tank into a second larger volume canister during a fuel fill phase of operation without passage of additional vapors into the smaller canister with means being provided to purge the larger volume canister into the intake manifold of an engine at a lesser rate than the purge rate from the first canister to avoid adverse engine operation or increased exhaust emission of unburned hydrocarbons from the engine during its operation.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.
IN THE DRAWINGS FIG. 1 is a diagrammatic view of an evaporative loss control system including two vapor collection canisters in accordance with the present invention;
FIG. 2 is a view in vertical section taken along the line 22 of FIG. 1 looking in the direction of the arrows; and
FIG. 3 is an enlarged fragmentary sectional view of a sealed fuel filler neck used in the present invention.
Referring now to the drawings, in FIG. 1 a fuel tank 10 is illustrated having a dome 12 thereon defining an interior fuel air vapor space 14, in which fuel vapors generated during vehicle operation are collected. A vent conduit 16 from the space 14 is connected across an orifice 17 to the inlet 18 of a reduced volume fuel vapor collection canister 20 sized to be located easily within the engine compartment of a vehicle. The canister 20 is of a conventional configuration having an interior volume 22 filled in part with an active vapor adsorbing material 24 such as activated charcoal or carbon. The canister 20 includes a purge fitting 26 to the interior volume 22 and in communication with air ambient the canister 20. The canister 20 further includes an outlet 28 therefrom communicated across a restrictor 30 to a vapor conduit 32 that is connected to a ported vacuum source defined by first and second ports 34, 36 located within a bore 38 of a carburetor 40 for supplying a predetermined air-fuel ratio to the intake manifold 41 of an internal combustion engine. The bore 38 includes a throttle valve 42 therein which, when positioned in an idle position, as illustrated in FIG'. 1, is located below the port 34 and above the port therein such as activated charcoal or carbon and includes an inlet 54 at one end thereof and an air purge connection 56 at the opposite end thereof in communication with air ambient the canister 46 at the rear of the vehicle. The canister 46 further includes an outlet 58 connected by a purge conduit 60 across a restrictor 62 to a carburetor port 64 below throttle valve 42 to be exposed to the intake manifold pressure of the vehicle. A vent conduit 65 communicates the carburetor fuel bowl 66 with the canister 20 during engine soak conditions.
In the illustrated arrangement, the inlet 54 to the large volume canister 46 is connected by an intake con duit 67 to a side fitting 68 on the end of a filler neck 70. A vent port 72 is located in the filler neck 70 to communicate the fitting 68 with the interior thereof at a point adjacent the upper open end 74 of the filler neck.
A seal cap assembly 76 is located on the open end 74 of the filler neck and includes a gasket 78 to seal the end of neck 70. The cap 76 which is representatively shown as a cap that is suitable for association with the system of the present invention is illustrated with a diagrammatically shown seal 80 thereon that coacts with an internally located reduced diameter 82 on the filler neck 70 interiorly thereof located between the open end 74 of the filler neck and the interior of the tank to seal the vent port 72 when the cap 76 is in place on the filler neck 70. Accordingly, vapor flow from the tank 10 is maintained through the small capacity canister during normal vehicle operation and the vent port 72 is only open when the cap 76 is removed from the filler neck 70.
As shown in FIG. 3, a fuel fill nozzle 84 is positioned in the open end 74 during a fill phase of operation with the seal cap 76 removed from the filler neck 70. A suitable seal component such as a bellows 86 is connected between the nozzle 84 and the filler neck 70 to completely seal the system during this phase of operation. Accordingly, fuel vapors that are directed into the tank 10 during fill from nozzle 84 are directed through the unrestricted port 72 rather than the restricted vent 16 from the vapor space 14 of the tank 10 so that vapors are accumulated in the larger volume of the canister 46 during the fill operation. During this period of time, only a limited flow of vapors will pass into the canister 20 so that the vapor adsorbing capacity of the charcoal material 24 therein will not be overloaded with vapors during the fill phase of operation. The volume of the activated charcoal 52 in the large volume canister 46 is selected to accommodate the large volume vapors produced during the tank fill of operation. Once the seal cap 76 is in place on the filler neck 70, the larger rear canister 46 is purged to remove the vapor therefrom at a rate which removes adsorbed vapor from the rear canister so as to accommodate vapors produced during a subsequent tank fill cycle of operation. This period of time is of a duration to permit a reduced purge rate as compared to the purge rate from the canister 20 so that the vapors drawn through the port 64 will not adversely effect exhaust emissions from the engine. The two canister system is better than a single large canister located in the front of the vehicle which has to be purged at increased rates to accommodate both fill generated vapors and engine operation generated vapors. Such rates can adversely affect the exhaust emission levels from the engine.
An additional advantage of the rear mounting of the canister 46 is that vibrational forces on the canister 46 are reduced enabling it to be constructed of a less expensive plastic material than high strength plastic such as nylon 66 as required for the front canister.
While the embodiments of the present invention, as herein disclosed, constitute a preferred form, it is to be understood that other forms might be adopted.
What is claimed is:
1. In an internal combustion engine, an evaporation control system for limiting vapor loss from a fuel supply including a fuel tank having a vapor space and an airfuel supply carburetor for directing a predetermined fuel charge into the intake manifold of an internal combustion engine comprising: means for adsorbing vapor generated from the tank during normal vehicle operation including a first canister means having a first predetermined volume, means for communicating the interior of said first canister means with an engine carburetor for purging vapor from said first canister means during engine operation for consumption in the engine, second vapor adsorbing means for adsorbing vapors produced within said tank during a fill phase of operation including second canister means having a second predetermined volume greater than said first predetermined volume to adsorb increased volume of vapors produced during tank fill operation, and means for purging vapors from said second canister means for consumption with the engine during engine operation at a lesser rate than the rate of withdrawal of vapors from said first canister means thereby to avoid excessive enrichment of the air-fuel mixture to the intake manifold of the internal combustion engine so as to prevent excessive exhaust emissions therefrom.
2. In an internal combustion engine, an evaporation control system to limit vapor loss from a fuel tank comprising: a vent space within said tank having a vent thereon, a first canister having a first predetermined volume therein filled with vapor adsorbing material, said first canister having a purge connection thereto in communication with air ambient said first canister and including an inlet and outlet therefrom located on the opposite end of said canister from said purge connection, means communicating the inlet of said first canister with said vent, carburetor means for supplying a predetermined air-fuel ratio to the intake manifold of the vehicle including a bore therethrough having a throttle valve therein, port means located within said bore at points above and below said throttle valve under idle conditions, means for communicating the outlet of said first canister with said carburetor port means including a restriction for establishing a predetermined rate of purge through said first canister during engine operations to withdraw vapors from said first canister for passage through said carburetor bore into the engine for consumption therein, said restriction controlling flow of vapors from said first canister at a rate to prevent excessive enrichment of the air-fuel ratio to the engine during operation thereof, a second canister having a volume therein filled with vapor adsorbing material greater than said first predetermined volume, said second canister including an inlet and outlet on one end thereof and a purge connection on the opposite end thereof, a fill neck on said tank having an unrestricted vent port thereon at one end thereof, seal cap means on said filler neck for blocking communication between said unrestricted vent port and the interior of said tank following a tank fuel fill operation, a supply conduit for communicating the unrestricted vent port with the inlet to said second canister, said unrestricted vent port being opened during a sealed tank fuel fill operation and having vapors from said tank directed therethrough for adsorption on said greater volume of adsorbing material in said second canister, and means for connecting the outlet of said second canister with engine intake manifold vacuum including a restrictor having a reduced flow area to cause vapors to be purged from said second canister at a rate reduced from that of the purge rate from said first canister to prevent excessive flow of vapor into the intake maniduring the fill phase of operation.