Abstract:
A fuel pressure regulator is provided between the outlet of the fuel pump and an inlet of a jet pump to control the flow of fuel to the jet pump. Desirably, during low voltage conditions in a vehicle, the flow of fuel to the jet pump may be temporarily restricted or terminated to decrease the amount of fuel diverted from the engine and thereby increase the flow rate of fuel to the engine and improve the performance of the engine. The regulator may also function to bypass fuel delivered from the fuel pump in excess of the engine fuel demand to control the pressure of and limit the maximum pressure of fuel supplied to the engine.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to vehicle fuel systems and more particularly to a fuel flow and pressure regulator for a fuel system with a jet pump. 
     BACKGROUND OF THE INVENTION 
     Electric motor fuel pumps have been used to supply the fuel demand for engines in various applications. In some applications, the fuel pump may be disposed within a reservoir within the fuel tank and may draw fuel directly from the reservoir for delivery to the engine. To provide fuel within the reservoir and available for the fuel pump, some of these fuel systems utilize a portion of fuel discharged under pressure from the fuel pump to operate a jet pump which creates a pressure drop adjacent an inlet of the reservoir to draw fuel from the fuel tank into the reservoir. 
     In prior fuel systems, the flow path providing fuel from the fuel pump to the jet pump is always fully open and therefore, a significant portion of fuel discharged from the fuel pump is always routed through the jet pump. Undesirably, during low voltage conditions, such as when the vehicle is started in cold weather, a lower than normal voltage may be provided to the fuel pump causing the fuel pump to run at a lower than normal speed and thereby discharge fuel at a relatively low flow rate. Thus, a lower flow rate of fuel is available for the engine, and to compound this problem, a portion of the fuel discharged from the fuel pump is routed away from the engine and to the jet pump as previously described. Thus, during low voltage conditions, an undesirably low fuel flow rate may be provided to the vehicle engine. Therefore, there is a need to improve the flow rate of fuel to the engine during low voltage and other conditions in the vehicle wherein the fuel pump has a low output flow rate. 
     SUMMARY OF THE INVENTION 
     In a fuel system a fuel pressure regulator is provided between the outlet of the fuel pump and an inlet of a jet pump to control the flow of fuel to the jet pump. Desirably, during low voltage conditions in a vehicle, the flow of fuel to the jet pump may be temporarily restricted or terminated to decrease the amount of fuel diverted from the engine and thereby increase the flow rate of fuel to the engine and improve the performance of the engine. The regulator may also function to bypass fuel delivered from the fuel pump in excess of the engine fuel demand to control the pressure of fuel downstream of the fuel pump delivered to the engine. 
     Objects, features and advantages of this invention include providing a fuel pressure regulator which controls the maximum pressure of fuel delivered to the engine, bypasses excess fuel discharged from the fuel pump, controls the flow of fuel to a jet pump, may restrict or terminate the flow of fuel to a jet pump during low voltage conditions, improves the performance of the engine during low voltage conditions, is reliable, durable, of relatively simple design and economical manufacture and assembly, and has a long, useful service life. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and advantages of this invention will be apparent from the following detailed description of the preferred embodiments and best mode, appended claims and accompanying drawings in which: 
     FIG. 1 is a diagrammatic view of a fuel system embodying the present invention; 
     FIG. 2 is a cross sectional view of the fuel pressure regulator of FIG. 1 shown in a closed position; 
     FIG. 3 is a cross sectional view of the fuel pressure regulator in an open position; and 
     FIG. 4 is a cross sectional view of the fuel pressure regulator shown in its bypass position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring in more detail to the drawings, FIG. 1 illustrates a vehicle fuel system  6  with a fuel supply module  8  having a fuel pressure regulator  10  disposed downstream of a fuel pump  12  and upstream of a jet pump  14  to control the flow rate and maximum pressure of fuel delivered to an engine  16  and the flow of fuel to the jet pump  14 . The fuel pump  12 , jet pump  14  and fuel pressure regulator  10  are disposed within a fuel reservoir  24  within a fuel tank  20 . Fluid flow through the jet pump  14  provides a pressure drop which draws fuel through an inlet  22  and discharges it into reservoir  24  so that fuel is available at an inlet  40  of the fuel pump  12 . 
     The jet pump  14  has a housing  26  with a first, or low pressure inlet  28  communicating with and surrounding the inlet  22  of the reservoir  24  and through which fuel in the fuel tank  20  is drawn into the fuel reservoir  24 . The housing  26  also has a second, or high pressure inlet  30  in communication with the fuel pressure regulator  10  through a conduit  32  through which pressurized fuel is routed to the jet pump  14 . A venturi tube  34  is preferably press fit into the housing  26  and is constructed to receive the pressurized fuel which flows through the high pressure inlet  30 . The venturi tube  34  has a reduced diameter portion or throat  36 , and fuel flow therethrough creates a pressure drop within the jet pump housing  26  to draw fuel from the fuel tank  20  through the low pressure inlet  28  and into the reservoir  24 . Fuel which flows through the venturi tube  34  is also discharged into the reservoir  24  and may thereafter be drawn into the fuel pump  12 . 
     The fuel pump  12  draws fuel through its inlet  40 , increases the pressure of the fuel and discharges fuel under pressure through an outlet  42  for delivery to the engine  16  and the jet pump  14  as controlled by the fuel pressure regulator  10 . The fuel pump  12  may be of substantially any kind or construction capable of drawing fuel from the reservoir  24  and discharging fuel under pressure for delivery to the engine  16  such as a positive displacement type or gear rotor fuel pump such as disclosed in U.S. Pat. No. 4,697,995, or a turbine type fuel pump such as disclosed in U.S. Pat. No. 5,257,916, the disclosures of each of which is disclosed herein by reference in its entirety. Preferably, a fuel filter  44  surrounds the inlet  40  of the fuel pump  12  to remove contaminants from the fuel before it is drawn into the fuel pump  12 . The outlet  42  of the fuel pump  12  is connected to a fuel line  46  through which fuel is delivered to a fuel rail  48  and injectors  50  of the engine. 
     The fuel pressure regulator  10  is connected to the fuel line  46  downstream of the fuel pump  12  through a T-fitting  52  so that its inlet  54  receives the pressurized fuel discharged from the fuel pump  12 . The fuel pressure regulator  10  has a housing  56  comprising a cap  58  press fit over a body  60  and preferably ultrasonically welded or otherwise sealed thereto. The cap  58  and body  60  are typically molded and formed of a plastic material suitable for use in hydrocarbon fuels such as polyphenelene sulfide, nylon, acetal or other polymers. As best shown in FIG. 1, the cap  58  preferably has two or more spokes  62  defining bypass outlets  64  between them and interconnecting a rim  66  received over the body  60  and a central hub  68  which has a throughbore  70  in which a stop  72  is press fit. The body  60  has a generally annular cavity which defines the regulator inlet  54  and a throughbore which defines an outlet  74  communicated with the high pressure inlet  30  of the jet pump  14  by the conduit  32 . 
     The housing  56  carries a diaphragm  80  which has a relatively thin and flexible central portion and a circumferentially continuous peripheral rib  82  received in a groove in the body  60  and retained therein by the cap  58  to provide fluid tight seals between them and the diaphragm  80 . Preferably, to permit increased displacement of the diaphragm  80  it has a circumferentially continuous annular pleat or bellows  84  sized to permit, by gathering and ungathering thereof, full working travel of the diaphragm central portion. The diaphragm  80  is yieldably biased towards the body  60  by a spring  86  retained at its upper end by an annular shoulder  88  of the cap  58 . The lower end of the spring  86  bears on a retainer  90  disposed between the spring  86  and the diaphragm  80 . The retainer  90  has a radially outwardly extending flange  92  engaged by the spring  86  and an axially extending annular sidewall  94  defining a throughbore  96  of the retainer  90 . The diaphragm  80  has a central opening  98  which opens into the throughbore  96  of the retainer  90 . 
     A valve  100  is slidably carried within the bore  96  of the retainer  90  and opening  98  of the diaphragm  80  and has a valve stem  102  and a valve head  104  with a first face  106  engageable with a valve seat  108  of the body  60  surrounding the outlet  74 . The valve  100  is movable between a closed position (FIG. 2) with, the first face  106  engaged with the valve seat  108  to prevent fluid flow through the outlet  74  and an open position (FIG. 3) spaced from the valve seat  108  to permit fluid flow through the outlet  74  and to the jet pump  14 . To selectively permit fluid flow from the regulator inlet  54  through the diaphragm opening  98 , a raised annular rim  110  of a second face  112  of the valve head  104  is selectively engageable with the diaphragm  80  surrounding the opening  98 . The second face  112  of the valve head  104  is normally held in contact with and against the diaphragm  80  by the pressure of fuel in the inlet  54  of the fuel pressure regulator  10  to prevent fuel flow through the diaphragm opening  98 . The valve stem  102  is preferably elongate and extends through the diaphragm opening  98  and retainer bore  96 . The valve  100  normally seals the diaphragm opening  98  and forms part of the working surface of the diaphragm  80 . 
     Under normal operating conditions, the fuel pump  12  will supply fuel at a sufficient pressure and a flow rate which exceeds the maximum fuel demand of the engine. Under these conditions, the fuel at the inlet  54  of the fuel pressure regulator  10  will be at a high enough pressure to displace the diaphragm  80  and valve  100  away from the valve seat  108  of the body  60  to permit fuel to flow through the outlet  74  of the regulator  10  and to the high pressure inlet  30  of the jet pump  14 . Even with this fuel flow to the jet pump  14 , the fuel which continues through the fuel line  46  downstream of the fuel pressure regulator  10  is sufficient for the operation of the engine and supplied to the engine at a pressure controlled by the pressure regulator. 
     Preferably, to accommodate a sudden increase in fuel demand and to ensure an adequate fuel supply to the engine  16  even during high fuel demand conditions, the fuel pump  12  delivers fuel at a rate greater than needed for the operation of the engine  16  and the jet pump  14 . To maintain the pressure of the fuel delivered to the engine  16  generally constant, fuel discharged from the fuel pump in excess of the engine&#39;s fuel demand and the jet pump fuel demand is bypassed by the fuel pressure regulator  10  to either the fuel tank  20  or the reservoir  24 . Bypass fuel flow or fuel overpressure relief, such as to accommodate hot fuel expansion, occurs only when the rim  10  of the valve head  104  is disengaged from the diaphragm  80 . As shown in FIG. 4, when an overpressure condition exists at the inlet  54  of the regulator  10 , the diaphragm  80  will be displaced beyond the point where the valve stem  102  engages the stop  72  carried by the cap  58 . Upward travel of the diaphragm  80  beyond this point causes the diaphragm  80  to separate from the second face  112  of the valve head  104  to permit fuel flow through the diaphragm opening  98 , the bore  96  of the retainer  90  and into the cap  58 . Fuel then flows back into the fuel tank  20  or reservoir  24  through the openings or bypass outlets  64  defined between the spokes  62  of the cap  58 . 
     During low voltage conditions or other conditions wherein the fuel pump  12  discharges fuel at a lower than desired rate, the fuel pump  12  may not deliver sufficient fuel to operate both the engine  16  and the jet pump  14 . In these situations, the fuel discharged from the fuel pump  12  and received at the inlet  54  of the fuel pressure regulator  10  will be insufficient to significantly, if at all, displace the diaphragm  80  and valve  100  relative to the valve seat  108  to at least substantially restrict the flow of fuel through the outlet  74  and to the jet pump  12 . Thus, in these conditions, substantially all, if not all, of the fuel delivered from the fuel pump  12  is supplied to the engine  16  to ensure satisfactory operation of the engine  16 . When the fuel pump  12  delivers a sufficiently high flow rate of fuel, the valve head  104  will be displaced from the valve seat  108  to permit fuel flow to the jet pump  14  to power the jet pump  14 . 
     Thus, the fuel pressure regulator  10  controls the flow of fuel to the jet pump  14 , the pressure of fuel delivered to the engine  16 , and controls the pressure of fuel in the system, and limits the maximum pressure of fuel in the system by bypassing excess fuel delivered from the fuel pump  12 . During low voltage conditions, for example, the parasitic fuel loss to the jet pump  14  is at least substantially reduced and may be eliminated, to provide to the engine  16  substantially all of the fuel delivered from the fuel pump  12 . During other operating conditions, the regulator  10  permits fuel flow to the jet pump  14  to draw fuel into the reservoir  24 .