Abstract:
A stationary fuel storage system that includes a stationary fuel tank that defines a tank volume adapted to store a quantity of fuel. An evaporative emission device is disposed outside of the tank volume and defines a device volume that is in fluid communication with the atmosphere. A mass of fuel vapor adsorbing material is disposed within the device volume and a vent conduit provides fluid communication between the fuel tank and the evaporative emission device.

Description:
[0001]     This application is a divisional of patent application Ser. No. 10/411,477 filed on Apr. 10, 2003, now U.S. Pat. No. ______ which claims the benefit of prior filed co-pending provisional patent application No. 60/372,268 filed on Apr. 12, 2002, both of which are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to internal combustion engine emission control, and more particularly to control of fuel evaporative emissions utilizing a control device containing activated carbon.  
       BACKGROUND INFORMATION  
       [0003]     Fuel tanks are often employed to provide fuel to engines, such as internal combustion engines, diesel engines, combustion engines, and the like. In many cases, the fuel tanks, as well as the engines, are mobile. For example automobile engines and lawn mower engines include a fuel tank that is permanently attached to and moves with the automobile or the lawn mower.  
         [0004]     Other fuel tanks remain stationary and serve to store fuel for use in one or more stationary applications. For example, farms often include a large fuel tank that stores fuel that can be used with vehicles, tractors, lawn equipment, snow equipment, and the like. Another example of a detachable fuel storage tank is a fuel tank used in marine applications. Thus, the fuel tank does not have a permanent connection between it and an engine. Rather, an outlet from the tank allows fuel to be drawn from the tank and delivered to the desired location.  
         [0005]     Stationary tanks may be subjected to daily ambient temperature changes that may cause the release of hydrocarbons or gasoline. Such emissions are known as “diurnal” emissions. Fuel tanks are typically vented to the atmosphere to prevent pressure buildup in the tank.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention provides a stationary fuel storage system that includes a stationary fuel tank that defines a tank volume adapted to store a quantity of fuel. An evaporative emission device is disposed outside of the tank volume and defines a device volume that is in fluid communication with the atmosphere. A mass of fuel vapor adsorbing material is disposed within the device volume and a vent conduit provides fluid communication between the fuel tank and the evaporative emission device.  
         [0007]     The invention also provides a stationary evaporative emission control system that includes an evaporative emission device having a mass of fuel vapor adsorbing material and a stationary fuel tank having a tank volume. An atmospheric vent provides fluid communication between the evaporative emission device and the atmosphere and a vent conduit provides fluid communication between the fuel tank and the evaporative emission device. The vent conduit enables flow from the fuel tank to the evaporative emission device in response to an increase in pressure within the fuel tank and enables flow from the evaporative emission device to the fuel tank in response to a decrease in pressure within the fuel tank. The device volume and the tank volume are sized relative to one another, and a portion of fuel vapor passing from the evaporative emission device to the atmosphere is substantially reduced.  
         [0008]     The invention further provides a stationary fuel storage system that includes a stationary fuel tank that defines a tank volume adapted to store a quantity of fuel and a passive evaporative emission device. A first flow path provides fluid communication between the passive evaporative emission device and the atmosphere. A mass of fuel vapor adsorbing material is disposed within the device volume and a vent conduit provides fluid communication between the fuel tank and the evaporative emission device such that fuel vapor is able to flow between the tank and the evaporative emission device.  
         [0009]     The invention also provides a fuel storage system that includes a fuel tank that defines a tank volume adapted to store a quantity of fuel and an evaporative emission device that defines a device volume. A vent aperture provides fluid communication between the fuel tank and the evaporative emission device such that the evaporative emission device is in direct fluid communication with only the atmosphere and the fuel tank.  
         [0010]     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description and drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic view of an internal-combustion-engine-powered device having a fuel vapor control system embodying the invention.  
         [0012]      FIG. 2  is a schematic view of another internal-combustion-engine-powered device having a fuel vapor control system embodying the invention.  
         [0013]      FIG. 3  is a schematic view of another internal-combustion-engine-powered device having a fuel vapor control system embodying the invention.  
         [0014]      FIG. 4  is a schematic view of another internal-combustion-engine-powered device having a fuel vapor control system embodying the invention.  
         [0015]      FIG. 5  is a schematic view of a fuel tank venting system embodying the invention.  
         [0016]      FIG. 6  is a graphical representation of a diurnal cycle for a vapor control system.  
         [0017]      FIG. 7  is a graphical representation of the mass of a vapor control device subjected to several diurnal cycles.  
         [0018]      FIG. 8  is a lawn tractor having an internal combustion engine embodying the invention.  
         [0019]      FIG. 9  is a walk-behind lawnmower having an internal combustion engine embodying the invention.  
         [0020]      FIG. 10  is a portable generator having an internal combustion engine embodying the invention.  
         [0021]      FIG. 11  is a portable pressure washer having an internal combustion engine embodying the invention.  
         [0022]      FIG. 12  is a snowthrower having an internal combustion engine embodying the invention.  
         [0023]      FIG. 13  is an automatic backup power system having an internal combustion engine embodying the invention.  
         [0024]      FIG. 14  is a multi-cylinder, V-twin internal combustion engine embodying the invention.  
         [0025]      FIG. 15  is a single cylinder internal combustion engine embodying the invention.  
         [0026]     Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIG. 1  schematically illustrates a vapor control system  10  for use with a device  12  having an internal combustion engine  14 . In  FIG. 1 , the system  10  is illustrated as configured for use in a walk-behind type lawn mower  12   a  (see  FIG. 9 ), but could alternatively be a riding lawnmower  12   b  (See  FIG. 8 ), a portable generator  12   c  (see  FIG. 10 ), a pump, such as the type commonly used in a portable pressure washer  12   d  (see  FIG. 11 ), a snowthrower  12   e  (see  FIG. 12 ), a stand-alone generator, such as the type commonly used for an automatic backup power system  12   f  (see  FIG. 13 ), or the like. The engine  14  can be a multi-cylinder engine, such as a V-twin or opposed-cylinder engine  14   a  (see  FIG. 14 ), or a single-cylinder engine  14   b  (see  FIG. 15 ).  
         [0028]     The system  10  includes an engine intake assembly  16 , a fuel tank assembly  18 , an evaporative emission control device  22 , and an engine control device  26 . The intake assembly  16  fluidly communicates with the control device  22  through a vapor line  30 , and the fuel tank assembly  18  fluidly communicates with the control device  22  through a vent line  34 . All of the above components are mounted to or otherwise carried by the device  12 .  
         [0029]     The engine intake assembly  16  conveys intake air from the atmosphere toward an engine combustion chamber  38 . As the air travels through the intake assembly  16 , combustible fuel is mixed with the air to form an air/fuel mixture or charge. The charge is then delivered to the combustion chamber  38  where it is ignited, expands, and is subsequently discharged from the combustion chamber  38  through an engine exhaust system (not shown). The engine intake assembly  16  includes an air filter element  40 , an evaporative valve  42  downstream of the filter element  40 , a purge tube  46  downstream of the valve  42  and coupled to the vapor line  30 , and a venturi section  50  downstream of the purge tube  46 . Some embodiments of the engine intake assembly  16  may be configured for operation without the evaporative valve  42 . The venturi section  50  includes an aperture  54  that communicates with a carburetor  58 . The carburetor  58  receives fuel from the fuel tank assembly  18  via a fuel line  60  and regulates the delivery of the fuel to the intake assembly  16  as is well known in the art. A throttle valve  62  is located downstream of the venturi section  50  and regulates the delivery of the air/fuel mixture to the combustion chamber  38 .  
         [0030]     The fuel tank assembly  18  includes a fuel tank  66  having a filler opening  70  that is covered by a removable, sealed filler cap  74 . The fuel tank  66  also includes a vent opening  78  coupled to the vent line  34  and including a rollover check valve  82  and/or a liquid vapor separator. Liquid fuel  86  such as gasoline is stored in the fuel tank  66  and flows toward the carburetor  58  along the fuel line  60 . The check valve  82  substantially prevents the liquid fuel  86  from flowing through the vent line  34  should the fuel tank  66  become overturned.  
         [0031]     The control device  22  includes a first opening  90  communicating with the vent line  34 , a second opening  94  communicating with the vapor line  30 , and a third opening  98  communicating with the atmosphere. The control device  22  contains a mass of activated carbon  102  or any other suitable composition that is able to store (e.g. through adsorption) fuel vapor as described further below. The engine control device  26  is operatively coupled to the valve  42  by a mechanical linkage  104  (shown only schematically in the Figures) such that, when the engine  14  is running, the valve  42  is in an open position (shown in phantom in  FIG. 1 ), and when the engine  14  is not running, the valve  42  is in a closed position (shown in solid lines in  FIG. 1 ). As illustrated in  FIG. 1 , the engine control device  26  takes the form of an operator bail  106  of a lawnmower  12   a  (see  FIG. 9 ). In alternative embodiments, the engine control device  26  may include an air vane of a mechanical governor (not shown) of the engine  14 . Various other configurations of the engine control device  26  are also possible, provided they operate substantially as described above. Preferably, the engine control device  26  is operator or mechanically actuated, thereby reducing the cost and complexity associated with the addition of electronically or microprocessor controlled components.  
         [0032]     The vapor control system  10  is configured to reduce engine emissions that are associated with the evaporation of the liquid fuel  86  that is stored in the fuel tank  66  and that remains in the carburetor  58  when the engine  14  is not running. When the device  14  is not in use, some of the liquid fuel  86  in the fuel tank  66  may evaporate, releasing fuel vapors into the empty space of the tank  66 . To control the emission of fuel vapors, the vapors are carried out of the fuel tank  66  toward the evaporative emission control device  22  along the vent line  34 . Once the fuel vapors reach the control device  22 , the vapor is adsorbed by the activated carbon  102  such that air emitted from the control device  22  to the atmosphere via the third opening  98  contains a reduced amount of fuel vapor.  
         [0033]     Fuel vapors from the liquid fuel  86  remaining in the carburetor when the device  12  is not in use are also conducted to the control device  22 . As described above, when the engine  14  is not running, the evaporative valve  42  is in the closed position such that fuel vapor cannot travel upstream along the engine intake assembly  16  and out the filter element  40  to the atmosphere. Fuel vapors are essentially trapped between the valve  42  and the throttle valve  62 , such that they must travel along the vapor line  30  toward the control device  22  when the engine  14  is not running. These vapors are adsorbed by the activated carbon  102  in the same manner as the fuel vapors resulting from evaporation of the liquid fuel  86  in the fuel tank  66 .  
         [0034]     As the device  12  is subjected to extended periods of non-use, the carbon  102  in the control device  22  becomes saturated with fuel vapors. As a result, it is necessary to “purge” or remove the vapors from the carbon. This purging occurs while the device  12  is in use and the engine  14  is running. When the engine  14  is started, the engine control device  26  opens the valve  42  such that intake air can enter the venturi section  50 . As the engine  14  runs, atmospheric air is drawn through the intake assembly toward the combustion chamber. As the air passes through the intake assembly  16  it flows over the purge tube  46 , thereby creating a vacuum in the vapor line  30 . In response to the formation of the vacuum in the vapor line  30 , atmospheric air is drawn into the control device  22  through the third opening  98 . The atmospheric air then removes fuel vapor from the activated carbon  102  and continues along the vapor line  30  toward the purge tube  46 . The vapor-laden air then mixes with the intake air and is subsequently delivered to the combustion chamber  38  for ignition.  
         [0035]     The embodiment of the invention illustrated in  FIG. 1  is configured such that as the speed of the engine  14  is increased, the rate at which the activated carbon  102  is purged also increases. Specifically, as the engine&#39;s speed is increased, the velocity of the intake air in the vicinity of the purge tube  46  also increases, which in turn increases the vacuum in the vapor line  30 . The pressure drop that occurs as atmospheric air is drawn across the air filter element  40  also increases the vacuum in the vapor line  30 . A greater vacuum in the vapor line  30  causes a greater amount of atmospheric air to flow through the control device  22 , resulting in increased purging of the activated carbon  102 . Furthermore, at higher engine speeds, a greater amount of fuel is supplied to the intake air by the carburetor  58 . As such, the additional fuel introduced to the intake air in the form of fuel vapor flowing from the purge tube  46  is a relatively low percentage of the total amount of fuel in the final air/fuel mixture that is delivered to the combustion chamber  38 . This configuration provides a consistent and predictable air/fuel mixture during engine  14  operation.  
         [0036]     Referring now to  FIG. 2 , an alternative embodiment of the invention is illustrated wherein like parts have been given like reference numerals. The vapor control system  10  illustrated in  FIG. 2  is similar to that illustrated in  FIG. 1  and includes an engine intake assembly  16 , a fuel tank assembly  18 , an evaporative emission control device  22 , and an engine control device  26 . However in contrast to the system  10  of  FIG. 1 , the system  10  of  FIG. 2  is configured such that the control device  22  is purged primarily during low speed operation of the engine  14  as described further below.  
         [0037]     As illustrated in  FIG. 2 , the engine intake assembly  16  includes an aperture  108  that communicates with the vapor line  30 . The aperture  108  is positioned such that it is substantially aligned with the throttle valve  62 . As a result, when the throttle valve  62  is in a closed position (e.g. when engine speed is lowest), the velocity of the intake air passing over the aperture  108  is at a maximum due to the relatively small opening (e.g. cross-sectional area) through which the intake air travels. As described above with respect to the purge tube  46 , high velocity intake air moving past the aperture  108  creates a vacuum in the vapor line  30  that results in the purging of the control device  22 . When the throttle valve  62  is opened, the velocity of the intake passing over the aperture  108  is reduced due to the larger opening (e.g. cross-sectional area) through which the intake air travels resulting in a reduction of flow velocity near the walls of the intake assembly  16 . Lower velocity air traveling over the aperture  108  results in a weaker vacuum in the vapor line  30  and less purging of the control device  22 .  
         [0038]      FIGS. 3 and 4  illustrate a further alternate vapor control system  10  including an additional mass of activated carbon  110  embedded in the filter element  40 . As a result, the system  10  illustrated in  FIGS. 3 and 4  does not require an evaporative valve  42  as described further below. The system  10  may be configured such that the control device  22  is primarily purged in a manner similar to the system  10  of  FIG. 1 , (e.g. at high engine speeds, see  FIG. 3 ) or in a manner similar to the system  10  of  FIG. 2 , (e.g. at low engine speeds, see  FIG. 4 ).  
         [0039]     The additional mass of activated carbon  110  embedded in the filter element  40  substantially stores (e.g. through adsorption) fuel vapors that are produced by liquid fuel remaining in the carburetor  58  when the device  12  is not in use. Conversely, when the device  12  is in use, atmospheric air is drawn through the filter element  40  and the activated carbon  110 . Fuel vapors stored in the carbon  110  are released to the intake air and continue through the engine intake assembly  16  toward the combustion chamber  38 . Although the illustrated additional mass of activated carbon  110  is embedded within the filter element  40 , the carbon  110  may also be located at other positions along the intake assembly  16  between the filter element  40  and the purge tube  46 , as long as substantially all of the intake air passes through the carbon  110  before reaching the purge tube  46 . Because the additional mass of activated carbon  110  embedded in the air filter  40  primarily adsorbs vapors from the relatively small quantity of liquid fuel that remains in the carburetor  58  after engine  14  shutdown, the additional mass of carbon  110  will generally be smaller than the mass of carbon  102  contained in the control device  22 . However in certain devices  12  with relatively small fuel tanks  66 , the additional mass of carbon  110  may be approximately equal to the mass of carbon  102  contained in the control device  22 .  
         [0040]     A further embodiment of the invention is illustrated in  FIG. 5 . The system  10  of  FIG. 5  is specifically sized and configured such that the vapor line  30  is unnecessary. The system of  FIG. 5  is “passively purged” as described further below such that the fuel tank  66 , the vent line  34  and the evaporative control device  22  cooperate to store (e.g. through adsorption) fuel vapors resulting from the evaporation of the liquid fuel in the fuel tank  66 , and to purge the control device  22  by drawing atmospheric air through the control device  22 . Specifically, as the various components begin to heat up, (e.g. during engine running or increased ambient temperatures) the gasses and vapors in the fuel tank  66  expand and are vented through the vent line  34  to the control device  22  where the vapors are subsequently adsorbed by the activated carbon  102 . As the components cool down (e.g. when the engine is stopped or the ambient temperature decreases) or when the fuel  86  level drops, atmospheric air is drawn into the control device  22  and through the carbon  102 , thereby purging the vapors from the carbon  102  and returning them to the fuel tank  66 .  
         [0041]      FIG. 6  illustrates a diurnal test cycle of 24 hours that is used to determine whether the present invention is capable of controlling evaporative emissions during a hypothetical summer day.  FIG. 6  depicts the hypothetical ambient temperatures to which an evaporative emission control system may be subjected. The temperatures range from an overnight temperature of approximately 65° F., up to a mid-day temperature of about 105° F., followed by a return to approximately 65° F. Other test temperatures are possible depending on the specific environment and the type of use the system  10  is to be subjected to.  
         [0042]      FIG. 7  illustrates the performance of a hypothetical vapor control system operating over a period of several diurnals. The figure illustrates the mass of the evaporative control device  22  along the ordinate, and the number of diurnal cycles along the abscissa. As illustrated, the control device  22  is initially at a “dry mass” associated with a relatively low amount of fuel vapor stored within the carbon  102 . As the diurnal cycle begins and the ambient temperature increases, some of the liquid fuel  86  stored in the fuel tank  66  begins to evaporate and the fuel vapors begin to expand. This expansion forces the vapors out of the tank  66  via the vapor line  34  and into the control device  22 . As the fuel continues to evaporate and expand, the mass of the control device  22  begins to increase as the carbon  102  adsorbs fuel vapors. As the ambient temperature begins to decrease near the latter portion of an individual diurnal cycle, the liquid fuel and the fuel vapors begin to cool, such that a portion of the vapors begin to contract and/or condense into liquid fuel, thereby forming a vacuum in the fuel tank  66 . Atmospheric air is drawn into the control device  22  and through the activated carbon  102  to fill the vacuum in the fuel tank  66 , thus purging the fuel vapors from the carbon  102  as discussed above. As the fuel vapors are purged from the device  22 , the mass of the device  22  decreases.  
         [0043]     It is believed that over the course of several diurnal periods, the average mass of the device  22  (illustrated by the dashed line in  FIG. 7 ) will increase until the average mass of the device  22  reaches an equilibrium value (e.g. after about 3 diurnals as illustrated in  FIG. 7 ). Preferably the equilibrium mass value is achieved before the control device  22  reaches a completely saturated condition to control the release of fuel vapors into the atmosphere. While operating in this equilibrium regime, the device  22  captures at least a portion of the fuel vapors emitted during the first portion of the diurnal period (e.g. during ambient temperature increase), stores the vapors, and then returns the vapors to the fuel tank  66  during the latter portion of the diurnal period (e.g. during ambient temperature decrease).  
         [0044]     A hypothetical system that is designed to operate substantially as described above will theoretically maintain the equilibrium mass value for an extended period of time (e.g. 30 days or more) without requiring any form of active purging. The specific number of diurnals required to reach equilibrium conditions, as well as the level of vapor control during the equilibrium period will vary based upon the specific system design parameters. Such a system would presumably provide effective vapor control during extended periods of non-use that are commonly associated with the devices  12  illustrated in  FIGS. 8-13 , as well as additional devices. Various active purge methods such as those described above may also be utilized to provide additional purging of the control device  22 .