Abstract:
A method of relieving hot soak pressure in a fuel rail of a fuel injected internal combustion engine includes pressurizing fuel with a fuel pump when the engine is operating, and conveying the pressurized fuel through a check valve that prevents backflow of fuel from the fuel rail toward the fuel pump. A bypass path is in fluid communication between a location downstream of the check valve and a location downstream of the fuel pump and upstream of the check valve. The bypass path is opened when the engine is not operating so as to relieve fuel pressure downstream of the check valve to a level below a system operating pressure. Apparatuses are provided for carrying out the method.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/898,614, filed Jan. 31, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to fuel systems for combustion engines, and more particularly to fuel pressure control in a returnless fuel system for a fuel-injected engine. 
       BACKGROUND OF THE INVENTION 
       [0003]    A returnless fuel system is often used to store, pressurize, and deliver fuel to a fuel-injected internal combustion engine. The fuel is stored in a fuel tank, pressurized by a fuel module in the tank, and delivered through a system check valve and a fuel line to an engine fuel rail. The check valve prevents backflow from the fuel rail to the fuel tank to maintain fuel in the fuel rail for continuous availability to fuel injectors downstream of the fuel rail. 
         [0004]    A pressure regulator in fluid communication between the check valve and fuel rail maintains a system operating pressure. An upstream end of the pressure regulator is in fluid communication with the fuel line upstream of the fuel rail and downstream of the check valve, and a downstream end of the pressure regulator is in open communication with the fuel tank. When fuel pressure supply by the fuel module exceeds engine fuel pressure demand, the pressure regulator exhausts some fuel from the supply line back to the tank. 
         [0005]    But fluid pressure in the fuel rail rises during hot soak conditions, which typically occur for a period after a hot engine is deactivated, especially during hot weather. Some fuel rail pressure is desirable to suppress formation of fuel vapor in the fuel rail. But pressure in the fuel rail at or above a relatively high system operating pressure could lead to several issues, including reduced durability of pressurized components, fuel injector leakage, and difficulty in re-opening the fuel injectors upon engine restart. 
       SUMMARY OF THE INVENTION 
       [0006]    An apparatus according to one implementation provides pressurized fuel for delivery to a fuel injected engine. The apparatus includes a fuel pump to pressurize fuel, and a check valve in downstream fluid communication with the fuel pump to prevent backflow of fuel through the check valve toward the fuel pump. The apparatus also includes a fuel pressure control apparatus in parallel fluid communication across the check valve and in downstream fluid communication with the fuel pump, wherein the control apparatus is configured to prevent flow of fuel therethrough when the fuel pump is operating and to permit flow of fuel therethrough so as to relieve fuel pressure downstream of the check valve to a level below a system operating pressure when the fuel pump is not operating. 
         [0007]    According to another implementation, a method of relieving hot soak pressure in a fuel rail of a fuel injected internal combustion engine includes pressurizing fuel with a fuel pump when the engine is operating, and conveying the pressurized fuel through a check valve that prevents backflow of fuel from the fuel rail toward the fuel pump. The method also includes opening a bypass path in fluid communication between a location downstream of the check valve and a location downstream of the fuel pump and upstream of the check valve, when the engine is not operating so as to relieve fuel pressure downstream of the check valve to a level below a system operating pressure. 
         [0008]    At least some of the objects, features and advantages that may be achieved by at least certain embodiments of the invention include providing a method and apparatus that yields relatively low pressure in a fuel rail, enables increases in durability of pressurized components, reduces fuel injector leakage, and eases re-opening of fuel injectors upon engine restart, and is of relatively simple design, economical manufacture and assembly, rugged, durable, reliable, and in service has a long useful life. 
         [0009]    Of course, other objects, features and advantages will be apparent in view of this disclosure to those skilled in the art. Various other methods and apparatuses embodying the invention may achieve more or less than the noted objects, features or advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic view of a presently preferred form of an apparatus to supply pressurized fuel to a fuel injected engine; 
           [0011]      FIG. 2  is a schematic view of a first modification to the apparatus of  FIG. 1 ; 
           [0012]      FIG. 3  is a schematic view of a second modification to the apparatus of  FIG. 1 ; 
           [0013]      FIG. 4  is a schematic view of a third modification to the apparatus of  FIG. 1 ; 
           [0014]      FIG. 5  is a schematic view of a presently preferred form of a pressure control valve; and 
           [0015]      FIG. 6  is a schematic view of another presently preferred form of a pressure control valve. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0016]    Referring in more detail to the drawings,  FIG. 1  illustrates a fuel supply apparatus  10  to supply pressurized fuel to a fuel injected engine  12 . In general, the apparatus  10  is configured to supply fuel to the engine  12  at a system operating pressure, and to restrict/relieve fuel pressure at the engine  12  to a pressure below the system operating pressure when fuel is not being supplied to the engine  12 . The apparatus  10  may be a portion of a fuel delivery module (not shown), which is adapted to be carried within a fuel tank (not shown). The apparatus  10 , fuel delivery module, and fuel tank may be part of an overall fuel system to store, pressurize, and deliver fuel to the engine  12 . 
         [0017]    The engine  12  may be a fuel injected internal combustion engine for an automotive vehicle. The engine  12  may include one or more fuel manifolds or rails (not shown) for receiving fuel from the fuel system, and one or more fuel injectors (not shown) in downstream fluid communication with the fuel rail(s) for receiving fuel from the rail(s), and injecting it into combustion chambers of the engine  12 . Although any suitable type of engine is contemplated, the engine  12  may be a relatively high performance engine, a spark-ignition direct-injection (SIDI) type of engine, or the like. More particularly, the engine  12  may be an eight cylinder gasoline fuel engine capable of generating over 500 horsepower. Accordingly, such an engine may use relatively high fuel pressure at the fuel injectors. Thus, fuel system operating pressure may also be relatively high. 
         [0018]    The apparatus  10  may include a fuel reservoir  14  that defines a volume of fuel within a normally larger volume of fuel in the fuel tank. The reservoir includes a bottom wall  16  and sidewalls  18 ,  20  extending therefrom. The reservoir  14  may further include a check valve  22  disposed in the bottom wall  16  to admit an initial volume of fuel into the reservoir  14  from the fuel tank. The reservoir  14  also includes an inlet port  24  disposed in the bottom wall  16  to admit fuel into the reservoir  14  from the fuel tank. The inlet port  24  may also be communicated to a fuel screen (not shown) disposed just outside the reservoir  14 . 
         [0019]    The apparatus  10  includes a fuel pump  26  having one or more inlets  28 , which may draw fuel therein through a suction side fuel screen  30  disposed in the reservoir  14 . The pump  26  operates to pressurize fuel and includes one or more outlets  32  through which pressurized fuel flows toward the engine  12 . The fuel pump  26  may supply fuel at a higher rate than the engine&#39;s maximum fuel demand. Any suitable fuel pump may be used, such as a fuel pump driven by an electrical motor. But, more specifically, a variable speed electric motor fuel pump may be used, such as a pulse-width modulated pump, a three phase brushless pump, or the like. The fuel pump  26  may provide any suitable fuel pressures, which may include 200-700 kPa or any other suitable range(s). A fuel system operating pressure may be controlled by monitoring the actual pressure in the engine fuel rail and comparing it to a desired fuel rail pressure, and then adjusting speed of the fuel pump  26  to increase or decrease fuel pump output as need to achieve the desired fuel rail pressure. Those skilled in the art will recognize that any suitable apparatus may be used to enable such closed loop control, such as pressure and/or flow sensors, processors, memory, software, and the like (not shown). 
         [0020]    In addition to, or instead of, the variable speed pump, one or more pressure relief valves can be placed in a suitable location in the system to augment or replace the aforementioned pressure control functionality. For example, a fuel pump can be operated at a substantially constant speed to provide maximum fuel output and pressure downstream to the engine and to a bypass fuel regulator that exhausts fuel in excess of demand. 
         [0021]    The apparatus  10  may also include a jet pump  34 . The jet pump  34  includes an outlet  36  in fluid communication with the reservoir  14 , and an inlet  38  in fluid communication with the inlet port  24  of the reservoir  14 . The jet pump  34  also includes a jet inlet  40  in downstream fluid communication with the fuel pump outlet(s)  32  through a jet path  42 . An anti-siphon valve  44  may be placed in the jet conduit or path  42  to prevent vacuum from being pulled through the fuel pump  26  from its inlet  28  to its outlet  32 . In turn, the jet pump  34  draws fuel through the reservoir inlet  24  at a rate sufficient to keep the pump inlet(s)  28  supplied with fuel. 
         [0022]    The apparatus  10  also includes a check valve  46  disposed in downstream fluid communication with the fuel pump  26 . More specifically, the check valve  46  includes an outlet  48 , and an inlet  50  in fluid communication with the outlet(s)  32  of the fuel pump  26  and is configured to prevent flow of fuel through the check valve  46  back toward the fuel pump  26 . Any suitable type of check valve may be used, such as a ball check valve, stem valve, umbrella valve, or the like, with or without a return spring. The check valve  46  is provided to automatically limit flow to a direction generally from the fuel pump  26  toward the engine  12 . 
         [0023]    The apparatus  10  may also include a pre-filter pressure control valve  52  of any suitable type. The pressure control valve  52  may be any suitable pressure relief valve, such as a spring-loaded ball check valve, as shown. Alternatively, the pressure control valve  52  may be any suitable type of pressure regulator. The pressure control valve  52  can be configured to open at any suitable pressure, such as on the order of about 600-700 kPa where the maximum system operating pressure is about 600-700 kPa. Accordingly, the pressure control valve  52  can itself maintain, or can help maintain, system operating pressure. In any case, the pressure control valve  52  includes an inlet  54  in downstream fluid communication with the fuel pump outlet(s)  32  and may be upstream of the inlet  50  of the check valve  46 . The pressure control valve  52  also includes an outlet  56  that may openly exhaust fuel back to the fuel tank and back into the reservoir  14  upstream of the fuel pump inlet(s)  28 . 
         [0024]    The apparatus  10  may also include a pressure side fuel filter  58 , which may be positioned downstream of the check valve  46 . The fuel filter  58  may of any suitable type, shape, and size. But the fuel filter  58  may include a generally cylindrical, corrugated fibrous element (not separately shown). In any case, the fuel filter  58  includes an outlet  60 , and an inlet  62  in downstream fluid communication with the fuel pump  26 , pressure control valve  52 , and check valve  46 . 
         [0025]    The apparatus  10  further includes a bypass path  64 , which may be connected in parallel fluid communication across the check valve  46  and the filter  58 . The bypass path  64  may include a fuel pressure control apparatus  66  therein to control fuel pressure at the engine  12 . The control apparatus  66  is configured to prevent flow of fuel therethrough when the fuel pump  26  is operating and to permit flow of fuel therethrough when the fuel pump  26  is not operating, so as to relieve fuel pressure downstream of the check valve  46  to a level below the system operating pressure. 
         [0026]    The fuel pressure control apparatus  66  includes an inlet  68  in downstream fluid communication with the check valve  46  and the filter  58 , and an outlet  70  in upstream fluid communication with the check valve  46  and downstream fluid communication with the fuel pump  26 . In other words, the control apparatus outlet  70  is tied into a downstream side of the fuel pump outlet(s)  32  instead of being openly exhausted back into the reservoir  14  at an upstream side of the fuel pump inlet(s)  28 . More specifically, the outlet  70  is shown as being in fluid communication downstream of the pressure control valve inlet  54  and upstream of the check valve inlet  50 . However, the outlet  70  may instead or also be in fluid communication upstream of the pressure control valve inlet  54 , or connected to the jet path  42  upstream of the anti-siphon valve  44 . 
         [0027]    The control apparatus  66  may include any suitable pressure control valve  72 , such as a pressure relief valve, pressure regulator valve, or the like. For example, typical pressure regulator valves are preloaded by a calibrated spring to open at an upper limit of a preset pressure range and to close at a lower limit of that range. 
         [0028]    More specifically, and referring to  FIG. 5 , the pressure control valve may also be a flow-through pressure regulator  172 , which is a device well known to those of ordinary skill in the art, and any suitable type of flow-through pressure regulator may be used. As shown in  FIG. 5 , a typical flow-through regulator  172  includes an inlet  174 , an oppositely disposed outlet  176 , and a stationary valve head  184  therebetween. Also, a diaphragm  186  has a flow-through aperture  188  that defines a valve seat  190  for cooperation with the valve head  184 , and a spring  192  for urging the diaphragm valve seat  190  into sealed engagement with the valve head  184 . In operation, when inlet pressure exceeds outlet pressure and spring pressure, the diaphragm  186  will move away from the valve head  184  to permit fluid flow through the regulator  172  to control and regulate the fuel pressure at the inlet  174 . 
         [0029]    Any other types of pressure regulator valve may also be used, including a standard type of regulator valve. As shown in  FIG. 6 , a typical standard regulator  272  includes an outlet tube  276  centrally disposed at one end of the regulator  272 , and an inlet  274  disposed at the same end of the regulator  272  radially outside of the outlet tube  276 . Also, a valve head  284  is yieldably biased to engage a seat  290  on the outlet tube  276  and is movably carried by a diaphragm  286 , which is urged toward the outlet tube  276  by a spring  292 . In operation, when inlet pressure exceeds spring pressure, the diaphragm  286  will move away from the valve seat  290  to permit fluid flow through the regulator  272 . In this standard regulator, back flow of fuel into the outlet tube  276  will tend to open the regulator  272  not close it. Accordingly, the check valve  78  ( FIG. 2  or  3 ) may be used downstream of the outlet tube  276  of the standard regulator  272  to prevent back flow through the regulator  272 . 
         [0030]    In any case, the pressure control valve  72  includes an inlet  74  in downstream fluid communication with the filter  58  and check valve  46  and an upstream regulator inlet in communication with the engine  12 . The pressure control valve  72  also includes an outlet  76  in downstream fluid communication with the fuel pump  26  and upstream fluid communication with the check valve  46  and filter  58 . 
         [0031]    The pressure control valve  72  is configured to open at a pressure below the system operating pressure. For example, if the typical system operating pressure is on the order of about 600 kPa, then the valve  72  can be set to open at a pressure on the order of about 400 kPa. Also, during normal operation of the fuel pump  26 , the pressure on the outlet  76  of the control valve  72  will be somewhat greater than the pressure on the inlet  74  of the control valve  72 , due to system pressure losses such as filter pressure drop. Accordingly, fuel will not pass in the forward direction through the control valve  72  and its outlet  76  when the fuel pump  26  is operating normally. But, when the fuel pump  26  is not operating, such as after the engine  12  is deactivated, the control valve  72  can allow fuel to pass therethrough. This is because once pressure from the fuel pump  26  drops to substantially zero, the check valve  46  allows pressure between the fuel pump  26  and check valve  46  to drop to substantially zero. Accordingly, pressure at the outlet  76  of the control valve  72  will also drop, wherein the control valve  72  may open to relieve system pressure downstream of the check valve  46 . Unlike conventional configurations, wherein a pressure regulator is set to open at the system operating pressure, here the control valve  72  opens below the system operating pressure such as to relieve hot soak pressures in the fuel rail of the engine  12 . This also reduces fuel pressure in the fuel rail when the engine and fuel pump are not operating. 
         [0032]      FIG. 2  illustrates another presently preferred embodiment of a fuel supply apparatus  210 . This embodiment is similar in many respects to the embodiment of  FIG. 1  and like numerals between the embodiments generally designate like or corresponding elements throughout the several views of the drawing figures. Additionally, the description of the common subject matter generally may not be repeated here. 
         [0033]    The fuel supply apparatus  210  includes a control apparatus  266  including the pressure control valve  72 , which may be a standard type of regulator, and additionally includes a check valve  78  downstream of the pressure control valve  72  and upstream of the fuel pump  26 . More particularly, the check valve  78  includes an inlet  80  in downstream fluid communication with the outlet  76  of the pressure control valve  72 , and an outlet  82  in upstream fluid communication with the check valve inlet  50  and filter inlet  62  and downstream fluid communication with the pump outlet(s)  32 . The check valve  78  is configured to prevent flow of fuel through the check valve  78  from the fuel pump  26  to the pressure control valve  72 . Any suitable type of check valve may be used, such as a ball check valve, stem valve, umbrella valve, or the like, with or without a return spring. 
         [0034]      FIG. 3  illustrates another presently preferred embodiment of a fuel supply apparatus  310 . This embodiment is similar in many respects to the embodiment of  FIGS. 1 and 2  and like numerals between the embodiments generally designate like or corresponding elements throughout the several views of the drawing figures. Additionally, the description of the common subject matter generally may not be repeated here. 
         [0035]    In this fuel supply apparatus  310 , the fuel filter  58  and check valve  46  are reversed, wherein the fuel filter  58  is disposed upstream of the check valve  46 . Also, in this configuration, the jet pump  34  may be in fluid communication downstream of the filter  58  and upstream of the check valve  46 . More specifically, although the jet inlet  40  of the jet pump  34  is still in upstream fluid communication with the check valve inlet  50 , it is in downstream fluid communication with the fuel filter outlet  60 . Accordingly, the fuel filter  58  is not pressurized when the fuel pump  26  is not operating, such as during heat soak after engine shutdown, and the jet pump  34  receives filtered fuel. 
         [0036]      FIG. 4  illustrates another presently preferred embodiment of a fuel supply apparatus  410 . This embodiment is similar in many respects to the embodiment of  FIGS. 1 through 3  and like numerals between the embodiments generally designate like or corresponding elements throughout the several views of the drawing figures. Additionally, the description of the common subject matter generally may not be repeated here. 
         [0037]    This fuel supply apparatus  410  is nearly identical to that of  FIG. 3 , except the pressure control apparatus  66  does not include the separate check valve  78 . Accordingly, the pressure control valve  72  may be a flow-through type of regulator. 
         [0038]    The various apparatuses  10 ,  210 ,  310 ,  410  may also include any other suitable components. For example, any suitable conduit may interconnect the various components, and any suitable clamps, connectors, fittings, and the like may also be used. 
         [0039]    While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all the possible equivalent forms or ramifications of the invention. For example, any two or more of the embodiments described above may be combined in any suitable manner to define one or more additional embodiments. It is understood that the terms used herein are merely descriptive, rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.