Anti-siphon and anti-leanout fuel valve
The present invention is directed to fuel delivery systems for internal combustion engines, and more particularly to a fuel flow control valve for disposition between a fuel pump and a fuel supply. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     In some conventional internal combustion engine fuel delivery systems, a fuel pump disposed on or adjacent to the engine draws fuel under vacuum from a remote tank or other fuel supply. Fuel delivery systems of this character are particularly prevalent in marine applications, and can also be employed in automotive and other like applications. The fuel line between the supply tank and the engine can be punctured or severed, whereupon the fuel may be siphoned from the tank. The fuel filter, normally disposed within the tank or in-line and upstream of the fuel pump, can become clogged, starving the fuel pump and engine for fuel, leaning out the air/fuel mixture at the engine, and potentially causing serious damage such as cease-up at the engine. 
     It is therefore a general object of the present invention to provide a fuel flow control valve for disposition between the fuel supply and the fuel pump that will prevent fuel from siphoning out of the fuel supply if the fuel line to the pump becomes punctured or severed. Another object of the present invention is to provide a fuel flow control valve that will prevent lean-out of fuel at the engine in the event of plugging at the fuel filter or other obstruction in the fuel line. A further object of the present invention is to provide an anti-leanout fuel flow control valve that automatically resets when the engine turns off, so that the engine can be restarted and operated in a &#34;limp home&#34; mode. 
     A flow control valve for an internal combustion engine fuel delivery system in accordance with the present invention includes a valve body having a fuel inlet for connection to a fuel supply and a fuel outlet for connection to the pump, so that the pump can draw fuel under vacuum from the supply through the valve and deliver fuel to an engine. A valve element is disposed within the valve body between the inlet and the outlet, and springs urge the valve element to a closed position within the valve body. A diaphragm is also disposed within the valve body between the valve element and the fuel outlet, and is coupled to the valve element such that suction vacuum applied by a fuel pump to the valve body outlet operates the diaphragm to open the valve element against forces applied by the valve springs to permit flow of fuel from the supply through the valve to the pump. The diaphragm is coupled to the valve element by a resilient detent mechanism responsive to vacuum at the valve outlet above a preselected level for releasing the coupling engagement between the diaphragm and the valve element, such that the valve is closed by the springs to terminate flow of fuel to the valve outlet. 
     In the preferred embodiment of the invention, a valve stem extends from the valve element, and link arms extend from the diaphragm for external engagement with the valve stem. A split spring ring surrounds the link arms and urges the link arms into a recess on the valve stem for directly coupling the diaphragm to the valve element. A first spring is disposed between the valve body and the valve element for directly urging the valve element toward a closed position, and a second spring is disposed between the valve body and the diaphragm for urging the valve element toward a closed position through the diaphragm/element coupling. When suction vacuum at the valve outlet exceeds the capacity of the split ring, the ring expands and the link arms move out of the recess on the valve stem, so that the valve element is closed by the first spring independent of the diaphragm to terminate flow of fuel to the engine. When the engine and pump have stopped, release of suction vacuum at the valve outlet allows the second spring to urge the diaphragm away from the valve element. A conical camming surface on the valve stem expands the split ring sufficiently that the split ring and link arms re-engage the recess in the valve stem. Thus, when the engine is restarted, suction vacuum at the valve outlet reopens the valve through the diaphragm, and the engine may be operated in a low-power &#34;limp home&#34; mode, in which engine demand and suction at the valve outlet do not release the spring detent and reclose the valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention, together with additional objects, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawing in which: 
     FIG. 1 is a schematic diagram of an internal combustion engine fuel delivery system in accordance with a presently preferred implementation of the invention; 
     FIG. 2 is a sectional view diametrically bisecting a fuel flow control valve in accordance with a presently preferred embodiment of the invention; 
     FIGS. 3 and 4 are fragmentary sectional views similar to that of FIG. 2 showing the valve in differing modes of operation; and 
     FIG. 5 is a sectional view taken substantially along the line 5--5 in FIG. 4. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     FIG. 1 illustrates an internal combustion engine fuel delivery system 10 that includes a fuel pump 12 mounted on an engine 14. Fuel pump 12 has an inlet connected by a line 15 to a flow control valve 16 mounted on a fuel supply tank 20, and thence by a line 17 to a fuel filter 18 both disposed within tank 20. The outlet of pump 12 is connected to deliver fuel under pressure to a fuel rail 22 mounted on engine 14. A plurality of fuel injectors 24 extend between fuel rail 22 and the engine air intake manifold 26 for delivering fuel to the cylinders of engine 14. Fuel pump 12 thus draws fuel under suction or vacuum from supply tank 20 through filter 18 and valve 16, and delivers fuel under pressure to fuel rail 22. 
     Fuel flow control valve 16 is illustrated in greater detail in FIG. 2 as comprising a valve body 28 having an inlet fitting 30 for connection to fuel supply 20 and an outlet fitting 32 for connection to pump 12. A valve element 34 is centrally disposed within housing 28 in alignment with inlet fitting 32. A coil spring 36 urges valve element 34 against a seat 38 that surrounds an opening 37 in a transverse wall 39 within housing 28. A valve stem 40 is monolithically integral with or fastened to valve element 34, coaxially projecting upwardly therefrom (in the orientation of FIG. 2) through opening 37 toward outlet fitting 32. 
     A diaphragm assembly 42 is mounted to valve body 28 by a valve cover 44. Diaphragm assembly 42 includes a resilient diaphragm 46 of elastomeric construction having a plate element 48 centrally mounted thereto. Two or more link arms 50 project downwardly from plate 48 for external engagement with valve stem 40 on diametrically opposed sides thereof. Link arms 50 have diametrically opposed inward bends 52 that are embraced by a split spring ring 55 (FIGS. 2 and 5). A coil spring 54 is captured in compression between transverse wall 39 in valve body 28 and plate 48 on diaphragm assembly 42 coaxially surrounding valve seat 38 and valve element 34. A cylindrical or partitioned wall 56 extends from transverse wall 39 concentrically with opening 37 and valve stem 40. Wall 56 functions both to maintain position of spring 54 and as a stop against movement of diaphragm assembly 42, as will be described. Diaphragm assembly 42 thus divides valve assembly 16 into a lower chamber surrounded by valve body 28 through which fuel flows, and an upper chamber that is referenced to atmosphere through an opening 58 in cover 44. A check valve 60 is carried by transverse wall 39 between inlet fitting 30 and outlet fitting 32 for relieving vacuum within valve body 28, as will be described. Thus, if fuel line 15 between pump 12 and valve 16 becomes severed or punctured, fuel cannot be siphoned out of supply tank 20. 
     In operation with engine 14 and pump 12 turned off, flow control valve 16 assumes the configuration illustrated in FIG. 2. Split spring ring 55 urges bends 52 of link arms 50 into a recess 62 on valve stem 40, thus forming a spring detent that couples diaphragm assembly 42 to valve element 34. Valve element 34 is urged to the normally closed position illustrated in FIG. 2 by coil spring 36 that acts directly on valve element 34, and coil spring 54 that acts on valve 34 through link arms 50 and valve stem 40. When engine 14 and pump 12 are started, the suction vacuum applied by pump 12, normally between about one and five inches of mercury, pulls diaphragm assembly downwardly against the forces applied by springs 36,54, thus operating through spring detent 64 to urge valve 34 downwardly and open flow from inlet fitting 30 to outlet fitting 32 as illustrated in FIG. 3. Fuel thus flows freely through valve assembly 16 under normal operating and load conditions as long as the suction vacuum remains between one and five inches of mercury. 
     In the event that fuel filter 18 becomes clogged or fuel line 17 is otherwise obstructed, increased fuel pump suction vacuum applies additional force pulling diaphragm assembly 42 downwardly in the orientation of the drawings. When this force exceeds the capacity of split ring 55 in spring detent 64, the camming action of recess 62 expands split spring ring 55 diametrically outwardly, so that bends 52 and link arms 50 are released from detent 64 and move downwardly along the external surface of valve stem 40, as shown in FIG. 4. Since diaphragm assembly 42 is no longer directly coupled to valve element 34. Valve element 34 is urged by spring 36 against seat 38, thereby closing valve assembly 16 and terminating flow of fuel through the valve to fuel pump 12 (except for small amount through valve 60, which is too small to run the engine). Downward motion of diaphragm assembly 42 is stopped by the upper edge of wall 56 so that suction on the diaphragm assembly does not push the valve open. Rather than running in an excessively lean condition that might damage the engine, the fuel pump and engine are starved for fuel and the engine ceases operation. 
     Thus, when the vacuum applied by the fuel pump exceeds the preselected level associated with resiliency of split ring 55, such as a level of five inches of mercury, valve assembly 16 is closed and engine operation ceases. When this occurs, pump 12 no longer applies vacuum to the valve outlet, and coil spring 54 urges diaphragm assembly 42 and link arms 50 upwardly. As this occurs, link arms 50 and split ring 55 are diametrically expanded by motion along the conical camming surface 66 of valve stem 40 until bends 52 of link arms 50 again engage notch 62 on valve stem 40. Thus, spring detent 64 is automatically reset and re-engaged when engine and fuel pump operation terminates. Check valve 60, which is normally closed with a pressure drop of less than one inch of mercury, releaves vacuum down to one inch of mercury within chamber 37 of valve assembly 16. With valve assembly 16 again in the configuration of FIG. 2, the engine and fuel pump may be restarted. Of course, with the clogged fuel filter or other obstruction remaining in the fuel line, the engine cannot be operated under high load or flow control valve 16 will again assume the configuration of FIG. 4 and terminate engine operation. However, the engine can be operated under low load so that the boat or other vehicle can &#34;limp home.&#34; 
     A cut in line 15 and resultant fuel siphon effect would not cause a vacuum at 32 greater than one inch of mercury. This would therefore be insufficient to cause diaphragm 42 to move against the preload on spring 54 or cause flow through valve 60. There would be no fuel leakage through the cut in line 15.