Abstract:
A flow regulating valve for a diesel engine in which a unitary valve element has three positions for controlling flow from a unit injector fuel injection system in response to valve inlet pressure. The valve has a first position wherein flow is blocked below about 10 psi, a second position between about 10 psi and 20 psi wherein flow is substantially unrestricted, and a third position above about 20 psi wherein flow is restricted to minimize return flow to a fuel supply and minimize fuel cooling requirements.

Description:
FIELD OF THE INVENTION 
   The invention relates to internal combustion engines and more particularly to flow regulating valves for such engines. 
   BACKGROUND OF THE INVENTION 
   Internal combustion engines of the diesel type are an essential part of the automotive and agriculture industries. The fundamental diesel process depends upon the heat of compression to ignite an air fuel mixture where fuel has been injected at or near top dead center during the compression stroke of the engine. Over the years, a wide variety of systems have been proposed and adopted to achieve the end of a predetermined quantity of fuel under high pressure at a predetermined time in the engine cycle to achieve the necessary performance and emission goals for the diesel engine. These fuel systems include high pressure common rail systems (HPCR), unit injectors, distributor systems, and multiple unit injector pump systems. One of the common requirements of all such systems is the ability to have a solid column of fuel from a fuel supply to the fuel injection system, i.e. no trapped air in the fuel supply. This is necessary to provide the correct quantity and timing of injected fuel but also to lubricate the close tolerance moving parts of the fuel injection system. 
   To this end, it is necessary to rapidly fill the line from a fuel supply to the fuel injection system prior to engine startup so that initial operation is on the basis of a solid column of fuel in the system. At the same time, the fuel supply to the fuel injection system must not be above certain flow levels during engine operation since most fuel injection systems have a return flow feature for fuel that is not consumed by the engine. The process of pressurizing fuel for delivery to the combustion chambers of an engine produces heat which is transferred to the fuel. Any fuel, not consumed by the engine, goes back to the fuel tank. In the event of an excess of fuel passing to the fuel injection system, the heat input to the fuel can be significant and require fuel coolers to avoid the adverse consequences of fuel that has been heated to a significant temperature. 
   In no system is the requirement for a solid column of fuel more important than in the class of fuel system comprising unit injectors in which the injection pressure is derived from a cam actuated plunger to achieve ultra high injection pressures. In such a system, a common inlet passage or chamber is positioned adjacent each of the injectors and solenoid valves control the timing and quantity of fuel admitted to each of the plungers for injection into the engine combustion chamber. Such a system has a pressure adjacent the injectors at a level about 100 psi. Under some conditions, after shut down of the engine, air can enter into the system so that it is possible to have fuel/air or air entering the injection chamber which has an adverse affect on engine performance. 
   Accordingly, there exists a need in the internal combustion engine art for a fuel system that minimizes, if not eliminates aeration of the fuel but limits return flow under engine operating conditions. Furthermore there exists a need in the art for a simplified unitary valve accomplishing these functions. 
   SUMMARY OF THE INVENTION 
   The invention, in one form is a fuel system for an internal combustion engine receiving fuel for operating said engine with a series of timed, quantitatively selected fuel charges. The fuel system has a fuel injection system for pressurizing fuel for delivery to the engine. A supply and a return line extend between the fuel injection system and a fuel supply. At least one pump is interposed in the supply line for receiving fuel from the fuel supply and delivering the flow to the fuel injection system. A flow regulating valve is interposed in the return line. The flow regulating valve includes a housing having an inlet and outlet and a chamber interconnecting said inlet and outlet. A valve element is displaceable in the chamber between a first position wherein flow is blocked, a second position wherein flow is substantially unrestricted, and a third position where flow is restricted, the valve element being displaceable between the positions in response to the inlet pressure at said valve. 
   The invention, in another form, is a flow regulating valve for a fluid having a housing with an inlet and outlet and a chamber connecting the inlet and outlet. A valve element is displaceable in the chamber between a first position where flow is blocked, a second position where flow is substantially unrestricted and a third position where flow is restricted, the valve element being displaceable between the first, second and third positions as a function of given pressure ranges. 
   The invention, in still another form, is an internal combustion engine and a fuel supply for operating said engine with a series of timed, quantitatively selected fuel charges. A fuel system has a fuel injection system for pressurizing fuel for delivery to the engine. A supply and a return line extend between the fuel injection system and the fuel supply. At least one pump is interposed in the supply line for receiving fuel from the fuel supply and delivering the flow to the fuel injection system. A flow regulating valve is interposed in the return line. The flow regulating valve includes a housing having an inlet and outlet and a chamber interconnecting said inlet and outlet. A valve element is displaceable in the chamber between a first position wherein flow is blocked, a second position wherein flow is substantially unrestricted, and a third position where flow is restricted, the valve element being displaceable between the positions in response to the inlet pressure at said valve. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of a fuel system for an internal combustion engine with a valve embodying the present invention; 
       FIG. 2  is a enlarged cross-section view of a flow regulating valve incorporated in  FIG. 1  in a first position; 
       FIG. 3  is an enlarged cross-section view of the valve of  FIG. 2  in a second position; and 
       FIG. 4  is an enlarged cross-section view of the valve of  FIG. 2  in a third position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows an internal combustion engine  11  of the diesel type. Engine  11  has a fuel injection system  10  supplied with fuel from an appropriate fuel supply  12  such as a tank by way of a supply line or conduit  14  A priming pump  18  and transfer pump  19  are connected in series in supply conduit  14  to deliver fuel to the fuel injection system  10 . A return line or conduit  16  connects excess fuel that has not been consumed by the engine  11  to the fuel supply  12  to complete the loop. 
   A flow regulating valve  20  is interposed in conduit  16  between the fuel injection system  10  and the fuel supply  12 . Although the priming pump  18  is shown away from the fuel supply  12 , it should be apparent to those skilled in the art that the pump may be in one of a number of positions. 
   The fuel injection system  10  may be one of a number of fuel injection systems adaptable for supplying predetermined fuel charges at a predetermined time to the combustion chamber of engine  11 . For purpose of illustrating the invention, the fuel injection system  10  is a unit injector system where plungers for individual cylinders receive a fuel charge that is timed and metered by solenoid valves (not shown). The plungers are cam actuated to inject the fuel into the combustion chamber of the engine  11  for compression ignition operation. The solenoid valves permit a control of when the fuel charge is injected and the quantity of the fuel charge. Details of this control system are not shown to simplify the understanding of the present invention. Lines  14  and  16  extend to a common passage or chamber adjacent the internal combustion engine  11  so that any excess fuel not consumed by the individual injectors is passed by way of line  16  to the fuel supply  12 . As discussed above, the hydrodynamic process of pressurizing the fuel by the pumps  18  and  19 , and passing through the injection system causes a heat increase in the fuel. In order to minimize the need for fuel coolers, the valve  20  is incorporated in the system. 
   Referring now to  FIG. 2 , the valve  20  has a housing  24  having an inlet  26  and an outlet  28 . A chamber  30 , herein illustrated as cylindrical, interconnects inlet  26  and outlet  28 . Appropriate threads  32  and  34  respectively connect the upstream and downstream end of valve  20  to the supply line  14 . Although the valve  20  is illustrated in the form of a threaded fitting, the valve  20  could also be integrated within another component, such as a fuel filter header or cylinder head casting (not shown), wherein that component would serve at least a portion of the function of the housing  24  in the illustrated embodiment. 
   A valve element  34  is positioned within cylindrical chamber  30  for linear displacement between the inlet  26  and outlet  28 . Valve element  34  has a cylindrical outer diameter  36  to allow free displacement within cylindrical chamber  30 . For manufacturing purposes, a seat element  38  is positioned within the upstream end of cylindrical chamber  30 . Seat element  38  has a tapered seat  40  leading to inlet  26 . Valve element  34  has an upstream end  42  displaceable towards inlet  26  that incorporates an annular groove  44  receiving an appropriate resilient O-ring  46  to provide an effective seal against seat  40  to prevent flow from the inlet  26  to the outlet  28  when the valve element  34  is in a first position as illustrated in  FIG. 2 . 
   Valve element  34  has a pair of radial, intersecting passages  48  and  50  which extend from the periphery of valve element  34  radially inward. An annular recess  52  is formed in the interior of valve element  34  and a plurality of axial passages  54  connect radial passages  48  and  50  to the recess  52 . A single, central passage  56  connects the intersection of radial passages  48  and  50  to the recess  52 . As described later, the cross-sectional flow area of passages  54  individually are greater then the cross-sectional flow area of passage  56  and collectively are approximately eight times the flow area of central passage  56 . 
   The valve element  34  is biased against seat  40  by a coil spring  58  having one end acting against the end wall  53  of recess  52 . However, it should be apparent to those skilled in the art, however, that many forms of yieldable biasing components may be employed to hold valve element  34  against seat  40 . 
   As illustrated herein, an annular element  60  is positioned in chamber  30  adjacent outlet  28  and has a flange  62  forming an abutment for the other end of spring  58 . Annular element  60  has a central recess  64  open to outlet  28 . A plurality of radial passages  66  connect the outer periphery of element  60  to recess  64 . A central axial passage  68  extends from recess  64  through an end wall  70  of element  60  to the recess  52  of valve element  34 . Central passage  68  is sized and positioned so that it aligns with central passage  56  on valve element  34  but does not overlap or interconnect with passages  54  when valve element  34  abuts element  60  in the position illustrated in  FIG. 4 . 
   Before engine operation, the valve  20  is in the first position illustrated in  FIG. 2  wherein the valve element  34  is against seat  40  to block flow through line  16  to the fuel supply  12  to maintain a residual fuel pressure in the fuel injection system  10 , and to prevent fuel from flowing back to the fuel supply  12 . The spring constant of the spring  58  and valve areas exposed to the upstream pressure are set so that the valve  34  fully unseats at about ten pounds per square inch (psi) to the second position shown in  FIG. 3 , where the valve element  34  is in between the position of  FIG. 2  and  FIG. 4 . In the position of  FIG. 3 , the flow in line  16  passes around the circumference of the valve element  34  and radially inward through passages  48  and  50 . The flow then passes through the plurality of passages  54  and the central passage  56  to flow freely to outlet  28  via passages  66  and  68  in element  60 . 
     FIG. 3  shows the valve element  34  in a position intermediate valve seat  40  and the end wall  70  of outlet element  60 . The areas exposed to pressure and the spring constant of spring  58  are selected so that in this position between valve seat  40  and end wall  70 , the flow through from the inlet  26  to the outlet  20  is substantially fee flowing at pressures from about 10 psi to 20 psi, thus allowing any air trapped in the fuel to be effectively purged to the fuel supply  12 . 
     FIG. 4  shows the valve element  34  in its third position wherein the valve element  34  abuts the end wall  70  of outlet element  60  to block flow through passages  54  but permit flow through central passage  56  in valve element  34 . This position, which is selected to be at above approximately 20 psi, permits flow on a restricted basis such that fuel is supplied to the fuel injection system at a desired pressure, as a function of the flow rate of the transfer pump  19 , and the size of the central passage  56 . 
   Although the values of the pumps  18 ,  19  and fuel injection system  10  can vary according to the particular type of system and the output of the pressurization device within the fuel injection system, the following values may be found in a system incorporating flow limiting valve  20 . As an example of a typical system, the pump  18  can generate 30 psi and a maximum of 0.25 gallons per minute (gpm). The transfer pump  19  within can generate 90 psi and 2 gpm during the running of the engine  11 . The valve  20  is sized so that the maximum flow through conduit  16 , during operation of engine  11 , is below approximately 10 milliliters per second. By making the flow area of passages  54  approximately 8 times the flow area of passage  56 , the fuel injection system  10  is quickly purged of air and primed prior to start-up of engine  11 , but flow is limited during engine operation. Furthermore, the functions of blocking flow during non-operation to maintain an at-rest minimum fuel system pressure, permitting relatively free flow to purge any entrained air and prime the fuel injection system  10 , and the flow limiting feature in the third position illustrated in  FIG. 4  are provided by a single, simplified hydro mechanical valve, without the need for complicated electronic algorithms and other sophisticated control systems. 
   Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.