Abstract:
Prior art fuel line check valves remain closed after engine off and cool down. Diurnal heating and the resultant pressure increase in the fuel line causes fuel vapor emissions through small openings in the fuel line (e.g., at the injector tips). The invention provides a check valve for a vehicle fuel line which opens in response to engine cooling and remains open while the engine is off to relieve subsequent increasing pressure in the fuel line due to diurnal heating thereof.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a divisional application of Divisional U.S. Ser. No. 11/805,354, filed May 23, 2007, which claims priority to U.S. Ser. No. 11/263,013, filed Oct. 31, 2005, now abandoned. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to vehicle fuel line check valves and, more particularly, to a fuel line check valve that opens to relieve increasing fuel line pressure, and hence the escape of fuel vapors, caused by diurnal heating of the fuel line when the engine is not running. 
       BACKGROUND OF THE INVENTION 
       [0003]    A vehicle fuel line system basically includes a fuel tank, a fuel pump and a fuel line that leads from the tank to the vehicle engine to deliver fuel thereto. A fuel regulator is used to maintain the proper amount of pressure in the fuel line and returns excess fuel to the fuel tank. Starting the engine also starts the fuel pump which pumps fuel from the tank and into the fuel line. Pressure builds in the fuel line to maintain the regulated amount of fuel running to the engine. In present day fuel line systems, a check valve that is normally closed is positioned in or near the fuel pump such that when the engine is turned off, the valve closes to maintain the pressure in the fuel line. This is done to prevent a rapid decrease in pressure which would result in boiling of the fuel in the fuel line due to the latent heat of the recently turned off engine. Should the fuel boil, fuel vapors would replace liquid fuel at the fuel injectors resulting in the engine being unable to start until the vapor is purged and replaced by liquid fuel at the injector tips. 
         [0004]    While this method has worked well at preventing fuel boiling for this reason, a normally closed valve which remains closed even after engine cooling also undesirably prevents the relief of increasing pressure caused by diurnal heating of the fuel in the fuel lines (e.g., when the vehicle spends a cool night followed by a day without running and sitting in the hot sun). Thus, in a vehicle that has cooled down and then heated back up due to diurnal heating, fuel vapors may form that, due to the high pressure build-up in the fuel line caused by the heat and a normally closed valve, will leak out of the fuel line at seal locations such as the injector tips. While fuel vapor emissions due to diurnal heating have been tolerated in the past, present day federal and state emission regulations prohibit or at least significantly reduce previously accepted emission levels. 
         [0005]    There therefore exists a need for a fuel line valve and method that will relieve pressure build-up caused by diurnal heating of a previously cooled engine, and thereby significantly reduce or eliminate fuel vapors from escaping the fuel line due to this phenomenon. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention addresses the above need by providing a fuel line valve and method that is closed when the engine is initially turned off, opens once the engine has cooled, and remains open during subsequent diurnal heating of the off engine. More particularly, the invention provides a fuel line check valve system and method for reducing or eliminating fuel vapor emissions from a fuel line of an engine caused by diurnal heating. When the engine and fuel pump are running, the valve is open by the flow of fuel being pumped therethrough. When the engine (and hence also the fuel pump) is turned off, the valve immediately closes due to the high back pressure in the fuel line. This is desirable since the high back pressure will prevent the boiling of the fuel in the fuel line due to the hot engine. As the engine cools, the back pressure decreases until it reaches a threshold pressure that allows the valve to bias back to the open position. Should diurnal heating cause the fuel line temperature and pressure to increase, the open valve allows the release of this pressure so that vapors are not forced under pressure out of the fuel line and into the atmosphere. The threshold pressure at which the valve opens is set according to the specific fuel line system design and requirements. In one preferred embodiment, the pressure threshold is set to be about 25 kPa. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1  is a schematic representation of a vehicle fuel line system; 
           [0009]      FIG. 2A  is an enlarged, cross-sectional view of a valve according to one embodiment of the present invention with the valve shown in the normally open, relaxed condition; 
           [0010]      FIG. 2B  is the view of  FIG. 2A  showing the valve in the extended open position; 
           [0011]      FIG. 2C  is the view of  FIG. 2A  showing the valve in the closed position; 
           [0012]      FIG. 3  is an enlarged, cross-sectional view of a valve according to a second embodiment of the invention; 
           [0013]      FIG. 4A  is an enlarged, cross-sectional view of a valve according to a third embodiment of the invention; 
           [0014]      FIG. 4B  is an enlarged, fragmented view of the area of detail labeled  4 B in  FIG. 4A ; 
           [0015]      FIG. 5A  an enlarged, cross-sectional view of a valve according to a fourth embodiment of the invention; and 
           [0016]      FIG. 5B  is an enlarged, fragmented view of the area of detail labeled  5 B in  FIG. 5A . 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to  FIG. 1 , a typical vehicle fuel line system is designated generally by the reference numeral  10 . A typical vehicle fuel line system basically includes a fuel tank  12 , a fuel pump  14 , a fuel filter  16 , and a fuel regulator  18  with a fuel line  20  leading from the tank to the intake manifold  22  of the vehicle engine  24 . Although a particular arrangement of the fuel line system is shown in  FIG. 1 , it is understood that the exact design and placement of fuel line components used with the present invention may vary according to the requirements of the vehicle application. In the system shown in  FIG. 1 , the fuel line  20  connects to a fuel rail  26  that has a plurality of fuel injectors  28  that are operable to deliver fuel into the intake manifold  22 . 
         [0018]    A fuel line check valve  30  according to a first embodiment of the invention is seen in  FIGS. 2A-2C . Valve  30  is positioned in fluid communication with the fuel line between the pump  14  and intake manifold  22 , preferably adjacent or in the fuel pump outlet  15  (see  FIG. 1 ). Valve  30  is a spring biased ball valve which is biased in the open position seen in  FIG. 2A . At rest with no forces acting thereon, valve spring  32 , which is connected to and between valve seat  34  and valve plate  36 , biases ball  38  in spaced relation to the valve seat  34 . An opening having a spacing “S” is thus created about the circumference of valve ball  38  in the normally open, unbiased condition of valve  30 . 
         [0019]      FIG. 2B  shows valve  30  in the extended open position which occurs when the engine and fuel pump  14  are running and fuel is flowing through valve as indicated by the arrows “F”. The force of the fuel F flowing through the valve causes the spring  32  to extend which increases the original spacing S between the ball  38  and valve seat  34 . 
         [0020]      FIG. 2C  shows valve  30  in the biased closed position which occurs when the pressure in the fuel line downstream of the valve (toward engine  24 ) is a predetermined amount higher than the pressure upstream of the valve (toward pump  14 ). The pressure differential that occurs immediately after the engine is shut off is sufficient to cause the valve  30  to close as seen in  FIG. 2C . This will maintain the pressure in the downstream line  20  until the engine begins to cool. Maintaining the pressure for this period of time is desirable since the pressure prevents the boiling of the fuel in the downstream fuel line  20  due to the heat of the recently turned off engine. As the engine cools, the pressure in the downstream fuel line  20  lowers. At the valve opening pressure (e.g., about 25 kPa), valve  30  will open to the unbiased, relaxed position seen in  FIG. 2A  and the upstream and downstream pressures will move toward a state of equilibrium. Conversely and as discussed above, prior art fuel line valves are biased to remain closed, even after engine cooling. When the pressure in the fuel line begins to build back up due to diurnal heating, fuel vapors are forced out of any tiny openings in the fuel line system (e.g., at part interfaces of the fuel injectors). As explained, these vapor emissions are undesirable and are significantly reduced or eliminated with the present invention wherein the check valve is biased in the open position seen in  FIG. 2A . As such, diurnal heating and rising pressure in the downstream fuel line  20  will be relieved at spacing S of open check valve  30  which thus allows movement toward pressure equilibrium despite rising temperature of the downstream fuel line  20 . Fuel vapors will therefore not be forced out tiny openings in the fuel line system as is the case with the prior art, normally closed check valves. 
         [0021]      FIGS. 3-5B  show several alternate embodiments of the inventive valve. In  FIG. 3 , a prior art normally closed valve has been modified to a normally open valve  130 . In particular, a lower valve sleeve  131  including a second spring  133  has been attached to the upper valve sleeve  135 . The second spring  133  is positioned between lower flange  131   a  and the base  132   a  of the pintle  132 . An O-ring  134  at the opposite end of the pintle is positioned to open and close with respect to valve seat  136 . Second spring  133  is sufficient to overcome the opposite (closing) bias of first spring  137  and thus biases valve  130  to the normally open position as shown. This embodiment thus shows how a normally closed check valve can be retrofitted to become a normally open check valve. 
         [0022]      FIGS. 4A  and B show another embodiment of the invention designated generally by the reference numeral  230  wherein a prior art, primary check valve  232  is positioned in the fuel pump end cap  200 . When fuel is flowing through the pump, primary check valve lifts off seat  234  and is open. When the engine and fuel pump are turned off, the high back pressure in the downstream fuel line causes primary check valve to move against valve seat  234  and close. The invention provides a secondary valve  240  positioned inside the primary check valve  232 . As seen best in  FIG. 4B , secondary valve  240  includes a spring  242  extending between a ball  244  and flange  246  which surrounds passageway  248  that is in fluid communication with primary valve inlet  250 . When the fuel pump is on and fuel is flowing, the primary and secondary valves  230 ,  240  are both open and fuel may flow through and out openings  252  in valve  240 . When the engine and fuel pump are turned off, primary valve  230  closes as explained above and secondary valve  240  also closes by ball  244  being forced against the bias of spring  242  to seat on smaller diameter opening  248 . As the engine and fuel line cool down and pressure in the downstream fuel line decreases, the bias of spring  242  will act against ball  244  which will unseat itself from opening  248 , thereby allowing the downstream pressure to be relieved. As such, fuel vapors will not be trapped and forced out of tiny openings in the downstream fuel line as explained above. 
         [0023]      FIGS. 5A and 5B  show yet another embodiment of the invention wherein a prior art ball check valve  330  is positioned at inlet  210  of fuel pump end cap  200 . Valve  330  has a valve head in the form of a ball  334 . When the fuel pump is on and fuel is flowing therethrough, ball  334  unseats itself from valve seat  336  and the valve is thus open. Upon turning the engine and fuel pump off, the backpressure in the upstream fuel line causes ball  334  to move against valve seat  336  and close the valve. The invention provides a secondary valve  340  positioned in an opening  212  extending radially outward of the pump end cap outlet  214 . As seen best in  FIG. 5B , secondary valve  340  includes a spring  342  extending between flange  344  and ball  346 . Spring  342  biases ball  346  against flange  348  which includes one or more through holes  349  making valve  340  normally open. When the fuel pump is on and fuel is flowing through primary valve  332 , secondary valve  340  closes since it is located radially outward of the fuel path through pump outlet  214 . When the engine and fuel pump are turned off, the high backpressure in the upstream fuel line will close primary valve  332  and also secondary valve  340  by the back pressure causing ball  346  to move against the bias of spring  342  and seat against valve outlet  350 . As the engine cools and the pressure in the upstream fuel line lowers, the force of the ball against spring  342  is lowered such that the spring starts biasing ball  346  in the opposite direction, i.e., toward valve flange  348 . When the ball  346  is seated against valve flange  348 , upstream pressure caused by diurnal heating may be relieved through openings  349 . 
         [0024]    It is noted that in the embodiments of  FIGS. 4A-5B , the valves  230  and  330  are of higher flow restriction than valves  30  and  130  due to small openings  252 ,  349 , in valves  230 ,  330 , respectively. This design not only aids in the closing of the valve upon shutting the engine off, but also impedes siphoning of fuel from the fuel tank in the event of the downstream fuel line being severed (with resultant rapid decrease in pressure) in a collision, for example. 
         [0025]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims