Abstract:
A fuel pump for an automotive application includes two separate pumping chambers within each of which a piston is reciprocated in order to pump fuel to an engine for the automobile. The dual cylinder arrangement increases the output capacity of the fuel pump.

Description:
FIELD 
       [0001]    The present disclosure relates to fuel pumps. More particularly, the present disclosure relates to dual piston direct injection fuel pumps. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Conventional gasoline engines are designed to use an electronic fuel injection system, replacing the traditional mechanical carburation systems. Port-Fuel Injection (PFI), where the fuel is injected through each intake port, is currently one of the popular systems used today. Although PFI provides a drastic improvement in response and quality, it is still limited due to the fuel and air mixing prior to entering the engine&#39;s cylinder. 
         [0004]    In order to further increase response time and combustion efficiency, while lowering the fuel consumption and increasing output, designers are turning towards direct injection systems. Gasoline direct injection engines are engineered to inject the gasoline directly into the engine&#39;s cylinder in a manner similar to diesel direct injection engines. 
         [0005]    Direct injection systems are designed to allow greater control and precision, resulting in better fuel economy. This is accomplished by enabling combustion of an ultra-lean mixture under many operating conditions. Direct injection is also designed to allow higher compression ratios and to deliver higher performance with lower fuel consumption. 
         [0006]    In a direct injection system, the gasoline is highly pressurized because it is injected via a common rail fuel line directly into the combustion chamber of each cylinder. In PFI systems, or low pressure applications, turbine impeller fuel pumps can be used to deliver fuel from the fuel tank to the fuel rails and cylinders of the engine. However, conventional turbine impeller fuel pumps cannot deliver fuel at the pressures required by the direct injection systems. Piston type fuel pumps are more capable of delivering the fuel at these higher fuel pressures. 
         [0007]    Current designs for piston type fuel pumps incorporate a single piston/cylinder design. The newer designs for vehicle engines include engines that have higher outputs and/or engines for flex fuel vehicles. These newer designs for engines require a higher flow rate of fuel and the current single piston/cylinder designs for fuel pumps are not able to meet this increased flow rate requirement. 
         [0008]    One typical solution is to add a second fuel pump to an engine which would then double the amount of fuel delivery. Although this does solve the problem, adding a second fuel pump is expensive and packaging space to mount the second pump is limited. 
       SUMMARY 
       [0009]    The present disclosure provides a fuel pump which meets the increase in flow rate requirements without adding a second pump. The pump design of the present disclosure is a dual piston design which makes use of one pump which has twice the delivery rate. Even though the dual piston pump is larger in size due to the second cylinder, the overall packaging required to mount the pump is less than the overall packaging for a second pump. 
         [0010]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0011]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0012]      FIG. 1  is a side view of an automobile incorporating a direct fuel injection system in accordance with the present disclosure; 
           [0013]      FIG. 2  is a schematic view of a direct fuel injection system in accordance with the present disclosure; 
           [0014]      FIG. 3  is a side view of the fuel tank module illustrated in  FIGS. 1 and 2 ; 
           [0015]      FIG. 4  is a top view of the fuel pump in accordance with the present disclosure; 
           [0016]      FIG. 5  is a side view partially in cross-section of the fuel pump illustrated in  FIG. 4 ; and 
           [0017]      FIG. 6  is a schematic diagram of the fuel pump illustrated in  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0019]      FIGS. 1-3  illustrate a vehicle  10 , such as an automobile, having an engine  12  and a direct fuel injection system  14 . Direct fuel injection system  14  comprises a fuel tank  16 , a fuel tank module  18 , a fuel supply line  20 , a fuel injector rail  22 , a plurality of fuel injectors  24  and a direct injection pump  26 . 
         [0020]    Fuel tank  16  is typically located in the rear of vehicle  10  with fuel tank module  18  being located within fuel tank  16 . Fuel supply line  20  extends from fuel tank module  18  to direct injection pump  26  which is typically located on or near engine  12  located in the front of vehicle  10 . Direct injection pump increases the fuel pressure between fuel supply line  20  and fuel injector rail  22 . Each fuel injector  24  is in communication with fuel injector rail  22  to receive fuel which is then injected directly into one of the cylinders of engine  12 . 
         [0021]    Direct fuel injection system  14  does not have a fuel return line from fuel injector rail  22  to fuel tank  16 . Because of this, a fuel pump  30  within fuel tank module has its voltage varied to adjust the amount of fuel supplied to direct injection pump  22  which then supplies pressurized fuel to fuel injector rail  22  to maintain a specified fuel pressure within direct fuel injection system  14  as is dictated by the fuel demand from engine  12 . 
         [0022]    Referring to  FIG. 3 , fuel tank module  18  includes a flange  40  that mounts fuel tank module  18  to a specified mounting location on fuel tank  16 . Flange  40  forms a seal, such as with an O-ring, with fuel tank  16  when fuel tank module  18  is secured to fuel tank  16 . First and second reservoir rods  42 ,  44  position a fuel reservoir  46  at the bottom interior wall of fuel tank  16 . From the top flange  40 , an engine fuel line connector  48  protrudes to deliver fuel to fuel supply line  20  and eventually to engine  12  through fuel injector rail  22  and fuel injectors  24 . 
         [0023]    Referring now to  FIGS. 4-6 , direct injection fuel pump  26  is illustrated in greater detail. Direct injection fuel pump  26  comprises a cylinder head  60 , a lower housing  62 , a pair of pistons  64 , a pair of cams  66  and an engine camshaft  68 . 
         [0024]    Cylinder head  60  defines two pumping cylinders  70 . Each piston is disposed within a respective cylinder  70  and reciprocates within its respective cylinder  70  to pump fuel. Cylinder head  60  defines an inlet  72  leading to cylinders  70  and an outlet  74  leading from cylinders  70 . An inlet check valve  76  is disposed between inlet  72  and each cylinder  70  and an outlet check valve  78  is disposed between outlet  74  and each cylinder  70  as illustrated in  FIG. 6 . Thus, during the reciprocal movement of pistons  64 , fuel is supplied to each cylinder  70  through inlet  72  and check valves  76  and fuel is pumped by each piston  64  from cylinders  70  through check valves  78  and through outlet  74 . Inlet  72  receives fuel from fuel supply line  20  and outlet  74  delivers fuel to fuel injector rail  22 . 
         [0025]    Lower housing  62  is sealingly attached to cylinder head  60 . The pair of cams  66  are rotatably disposed on the engine camshaft  68 . Each cam  66  engages an end of a respective piston  64  and each cam  66  has an exterior contour which provides the reciprocal movement of pistons  64  in cylinders  70  when cams  66  are rotated. A return spring or biasing member  82  attached to each piston  64  urges piston  64  into contact with its respective cam  66 . Engine camshaft  68  causes rotation of cams  66  and the pumping of fuel by pistons  64  in cylinders  70 .