Patent Publication Number: US-2007095934-A1

Title: Horizontal spool for direct needle closing

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      The application claims priority to U.S. Provisional Application No. 60/727,935 which was filed on Oct. 18, 2005. 
    
    
     BACKGROUND OF THE INVENTION  
      This invention generally relates to valve assembly for actuating a needle valve. More particularly, this invention relates to a spool valve actuateable for opening and closing a fuel injector needle valve.  
      A fuel injector for a vehicle provides for the selective injection of fuel into a combustion chamber. The fuel injector typically includes a needle valve that opens and closes to control the flow of fuel into the combustion chamber. Opening and closing of the fuel injector is timed with the combustion cycle of the engine and therefore speeds up or slows down depending on engine speed. The needle valve is desired to open and close quickly to facilitate properly timed injection of fuel.  
      A conventional fuel injector includes a spool valve movable parallel to the opening and closing movement of the needle valve. A solenoid device moves the spool valve within a valve body to control high pressure fluid flow to a top portion of the needle valve. The control of fluid flow by the spool valve provides a pressure imbalance that subsequently controls movement of the needle valve.  
      Disadvantageously, the parallel orientation of the spool valve requires complex fluid flow passages that are difficult and expensive to fabricate. Further, the parallel orientation and movement of the spool valve relative to the needle valve, and in some fuel injectors to an intensifier piston can detrimentally affect the opening and closing operation and time of the spool valve.  
      Accordingly, it is desirable to design and develop a valve for controlling the opening and closing of a needle valve that is less expensive to machine and less susceptible to operation of other valves within the fuel injector device.  
     SUMMARY OF THE INVENTION  
      A needle valve assembly includes a direct needle control valve including a spool movable transverse to the direction of needle valve movement.  
      An example fuel injector includes an intensifier piston disposed within an intensifier valve body. The high pressure fuel is controlled by a needle valve. The needle valve moves between an opened and closed position along an axis common to the intensifier piston. A needle control valve includes a spool that moves in a direction transverse to movement the needle valve and the intensifier piston.  
      The spool valve moves transverse to the axial movement of the needle valve within a valve body. The valve body is disposed between the intensifier piston and needle valve. Movement of the spool within the valve body provides for the selective communication of high-pressure fuel to the top of the needle valve. The spool valve is also movable to communicate a low vent pressure to the top of the needle valve. The selective communication of fuel pressure to the top of the needle valve results in the balance or imbalance of fuel pressures on the needle valve. The differences in communication of fuel pressure provide for the opening and closing of the needle valve.  
      The direct needle control valve provides for the durable actuation of the needle valve without substantial interference caused by the axial movement of the intensifier and the needle valve during operation.  
      These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional view of an example fuel injector assembly.  
       FIG. 2  is an enlarged cross-sectional view of an example direct needle control valve.  
       FIG. 3  is a sectional view of the example needle control valve. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Referring to  FIG. 1 , an example fuel injector assembly  10  includes an intensifier body  12  that defines an intensifier bore  14  within which an intensifier piston  18  moves along a longitudinal axis  15 . A sleeve  20  is attached to the intensifier body  12  and defines a high-pressure fuel passage  25  from the intensifier bore  14  to an outlet  28 . The sleeve  20  also holds a needle valve body  26 . The needle valve body  26  defines a needle valve bore  24  within which a needle valve  22  moves. The needle valve  22  moves between an open position that allows high-pressure fuel to exit the outlet  28 , and a closed position where no fuel is allowed to exit the outlet  28 .  
      Movement of the needle valve  22  is controlled by regulating a pressure differential about a head  23  of the needle valve  22 . The needle valve is biased by a spring  30  towards the closed position. Fuel pressure on either side of the head  23  of the needle valve  22  provides for the selective opening and closing of the needle valve  22 . The pressure at the above the head portion  23  of the needle valve  22  is controlled by the direct needle control valve  34 .  
      The direct needle control valve  34  includes a spool valve  40 . When the pressure above and below the head portion  23  is equal the bias force of the spring  30  provides a downward closing force on the needle valve  22 . When the spool valve  40  is opened to vent, the fuel pressure above the spool valve head  23  is lower than the pressure below the spool valve head  23 . This difference in pressure drives the spool valve  22  upwardly to an open position that allows fuel to exit the outlet  28 .  
      Fuel pressure is communicated to the outlet  28  through the fuel passages  25  that go around both the direct needle control valve  34  and the needle valve body  26 . This high pressure fuel is generated by action of the intensifier piston  18 .  
      Both the intensifier piston  18  and the needle valve  22  move along the first longitudinal axis  15 . This intensifier piston  18  movement along the first longitudinal axis  15  increases the fuel pressure. Movement of the needle valve  22  provides for the fuel flow.  
      Axial movement along the axis  15  can cause disruption that may affect operation of the direct needle control valve  34 . However, the example direct needle control valve  34  includes the spool  40  that moves along an axis  17  that is transverse to the longitudinal axis  15 . This transverse movement along the axis  17  substantially prevents movement along the longitudinal axis  15  from affecting control and actuation of the spool valve  40 .  
      Referring to  FIG. 2 , the example direct needle control valve  34  includes the spool valve  40 . The spool valve  40  moves along the axis  17  within a bore  41  defined by a valve body  38 . The valve body  38  is disposed such that the bore  41  is transverse to the longitudinal axis  15 . The spool valve  40  is biased towards a position allowing the communication of high-pressure fuel to the needle valve bore  24 . This communication provides the desired pressure balance that results in the needle valve  22  being biased to the closed position. The spool valve  40  is biased in this position by a biasing spring  44 .  
      Actuation of a solenoid  36  generates a magnetic force that acts on the spool valve  40  to move the spool valve  40  towards the solenoid  46  against the biasing force of the spring  44  to communicate a vent or low pressure with the top of the needle valve bore  24 . The low pressure at the needle valve bore  24  creates the desired pressure imbalance that allows opening of the needle valve  22 .  
      The valve body  38  includes an inlet  46  and an outlet  48 . The fluid flows in two directions through the outlet  48 . High pressure fuel flows into the bore  24  through this outlet  48 . Also, when the spool valve  40  is in a position that provides for communication of vent to the bore  24 , high pressure fluid will exit through this outlet  48 .  
      The valve body  38  is sandwiched between a top inlet plate  58  and a bottom outlet plate  60 . The top inlet plate  58  includes a throttle opening  52  that is sized to provide the desired fluid flow into the valve body bore. Similarly, the outlet plate  60  includes a throttle opening  54  that is sized to provide the desired fuel flow into the needle valve bore  24 . Sizing of the throttle opening  52 ,  54  for both the inlet plate  58  and the outlet plate  60  are determined according to application specific requirements. The size of these throttle openings  52 ,  54  is determined to provide the desired fuel flow based on pressures to provide the desired opening and closing times of the needle valve  22 .  
      The spool valves  40  includes a throttle passage  56 . This throttle passage  56  is used to tailor opening and closing movement of the spool valve  40  within the valve body  38 . This provides the desired actuation times of the needle valve  22 .  
      The top inlet plate  58  includes a relief  68 . The relief  68  provides and prevents a downward crushing force on the valve body  48  that may affect movement of the valve body  40 . The direct needle control valve assembly  34  is sandwiched between the intensifier body  12  and the needle valve body  26 . Accordingly, the relief  68  prevents any crushing force or other undesired forces on the valve body  34  that may affect free movement of the spool valve  40 .  
      The control valve assembly  34  also includes an end plate  62 . The end plate  62  is spaced apart from the valve body  38  by a first shim plate  64 . This first shim plate  64  is used to tailor the stroke of the spool valve  40 . In addition, a second shim plate  66  is disposed between the solenoid  36  and valve body  38 . This second shim plate  66  is provided to tailor the air gap between the spool valve  40  and the solenoid  36 . This air gap is tailored to provide the desired reaction times and movement of the spool valve  40  in response to actuation and energization of the solenoid  36 .  
      The end plate  62  and the solenoid  36  are held against the valve body  38  by securement rings  70 . The securement rings  70  encircle the valve assembly  34  at the top and bottom. The example securement rings  70  provide the clamping force required to maintain the desired air gaps between the end plate  62  and the solenoid  36 . As the valve assembly  34  is disposed transversely, the compressive forces provided by the threaded interface between the sleeve  20  and body  12  cannot hold the valve assembly  34  together. The rings  70  hold the valve assembly together in the transverse direction. Further, the rings  70  secure the endplate  62  and solenoid  36  together in a subassembly to aid and simplify assembly.  
      The example securement rings  70  are fabricated from a metal banding material, however, any material that provides the desired clamping force, and that maintains the relative position of the valve assembly  34  components over the desired operation life is within the contemplation of this invention.  
      Referring to  FIG. 3 , another sectional view of the example control valve assembly  34  is illustrated and shows the vent passage  50 . The vent passage  50  is disposed in a different plane than the inlet passage  46  and the outlet passage  48 . The reason that the vent passage  50  is in a different plane is to reduce the possibility of leakage or any type of fluid communication between the vent  50  and the inlet  46 . As appreciated, the recess  68  provided to prevent crushing forces on the valve body  38  also represents a fluid communication path therefore the vent  50  must be disposed in an orientation to prevent such undesired communication.  
      The horizontal orientation of the control valve assembly  34  eases manufacturing process time and expense. The example valve body  38  is greatly simplified as both the inlet  46  and outlet  48  can be machined in a single set up and is disposed within a common plane. No odd or irregular angles are required for these passages. Further, the vent passage  50  may also be fabricated in the same setup. Although the vent passage  50  is shown in an orientation different than those of the inlet  46  and outlet  48 , the vent passage  50  maybe machined in such a manner to avoid the recess  68  and thereby provides the required function in a simplified manufacturing and assembly step.  
      Further, the spool valve  40  movement along the horizontal axis  17  substantially prevents any communication of movement or vibrations that may occur along the longitudinal axis  15  due to movement of the intensifier piston  18  and the spool valve  22 .  
      Accordingly, the example spool valve assembly  34  for controlling the needle valve  22  according to this invention provides a durable, dependable and easily manufactured and assembled control valve to operate a needle valve. Further, the horizontal construction substantially eliminates effects that may be transmitted to effects and vibrations created by the intensifier piston  18  and spool valve  22  that could affect operation of digital valve assembly  34 .  
      Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.