Abstract:
An inlet valve assembly for a fuel pump comprises a valve assembly inflow path and valve assembly outflow path; a magnetic valve member situated in an intermediate flow path fluidly linking the inflow path and the outflow path; a magnetic pole adjacent the valve member; and a selectively energizable coil for generating a magnetic flux directly magnetically coupling the pole and the valve member; whereby the valve member opens and closes fluid communication between the inflow path and the outflow path in response to the energized state of the coil.

Description:
BACKGROUND 
       [0001]    The present invention relates to high pressure fuel pumps, and particularly to the inlet valve for feeding low pressure fuel to the high pressure pumping chamber. 
         [0002]    Single piston and multi-piston high pressure common rail fuel pumps have been implemented to provide the high fuel pressures required by modern direct injected gasoline and diesel engines. These engine mounted pumps are volume controlled to minimize parasitic losses while maintaining rail pressure. Volume control is achieved either by inlet throttling using a magnetic proportional control valve, or indirect digital control of the inlet valve by a magnetic actuator. Either execution requires that the pump be controlled by an electrical signal from the engine ECU. 
         [0003]    Because the indirect inlet valve actuator control requires a separate actuator for each pump piston, it has become common for multi-piston pumps to use a single inlet throttling proportional valve, in order to avoid a high part count and cost. Many modern single piston pumps use an indirect inlet valve actuator with a separate magnetically controlled armature assembly. These devices typically employ three separate components: inlet valve, magnetic armature, and the intervening engaging or connecting member. Different variants of this concept can be seen in U.S. Pat. Nos. 6,526,947, 7,513,240, 6,116,870, and 7,819,637. Due to the high complexity and precision of these devices, they typically account for at least ⅓ of the cost of a single piston pump. These digital type devices also suffer from high reciprocating mass and noise due to impact of the armature and valve assemblies during energizing and de-energizing events. 
       SUMMARY 
       [0004]    The primary purpose of the present invention is to reduce the cost and noise of a magnetically controlled inlet valve actuator for fuel pumps. 
         [0005]    The improved inlet valve assembly and associated pump, direct a magnetic flux path such that a magnetic force is directly applied to the inlet valve member when a coil is energized. As a result, direct actuation of the inlet valve is achieved, thereby eliminating the separate armature and armature to inlet valve connecting member, and reducing cost. By eliminating the separate armature and connecting member, reciprocating masses are reduced. Mass reduction minimizes impact generated noise and reduces response time for better controllability and lower power consumption. 
         [0006]    The disclosed embodiment of an fuel inlet valve assembly comprises a valve assembly inflow path and valve assembly outflow path; a magnetic valve member situated in an intermediate flow path fluidly linking the inflow path and the outflow path; a magnetic pole adjacent the valve member; and a selectively energizable coil for generating a magnetic flux directly magnetically coupling the pole and the valve member; whereby the valve member opens and closes fluid communication between the inflow path and the outflow path in response to the energized state of the coil. 
         [0007]    The disclosed fuel pump embodiment comprises a pump housing; a fuel inlet connection on the housing for delivering feed fuel into an inlet flow path in the housing; a pumping chamber and associated pumping mechanism in the housing for receiving feed fuel from inlet flow path through an inlet valve assembly, increasing the fuel pressure, and delivering pumped fuel to a discharge flow path; an outlet connection on the housing, in fluid communication with the discharge flow path through an outlet valve; wherein the inlet valve assembly includes a valve member directly magnetically coupled to a coil, whereby the coil is selectively energized to generate a magnetic flux path directly through the inlet valve member, thereby applying a magnetic force to the valve member to selectively open and close the valve member against a sealing surface in the inlet flow path. 
         [0008]    Preferably, the inlet valve assembly includes a central magnetic pole coaxially situated within and projecting from the coil; a portion of the inlet flow path passes inward through the projection of the pole into a central bore that opens at the end of the projection; the sealing surface is integrally formed in the pole around the opening of the central bore; and the inlet valve member is a flat plate having a periphery with a rim that provide magnetic flux paths transversely through the valve member and notches that form a portion of the inlet flow path when the valve member is open. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0009]    A representative embodiment will be described in detail with reference to the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a section view of a single piston common rail fuel pump suitable for incorporating the invention; 
           [0011]      FIG. 2  is a cross-sectional view of the pump of  FIG. 1 , in a different plane, showing an embodiment of the inlet valve assembly according to the invention; 
           [0012]      FIG. 3  is an enlarged section view of the inlet valve assembly of  FIG. 2 ; 
           [0013]      FIG. 4  is a section view through the pump, orthogonal to the view of  FIG. 3 , showing the inlet fuel flowpath from the inlet fitting to the inlet valve assembly; and 
           [0014]      FIG. 5  is an oblique view of the valve member, showing a periphery that includes a rim portion for accommodating transverse flux paths and notches for accommodating hydraulic flow. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    The basic functional aspects are evident from  FIGS. 1 and 2 . During the pump charging phase when piston  10  is reciprocally moving away from pumping chamber  7 , low pressure fuel enters the pump through inlet fitting  1 , passes around the pressure damper  2  and then into the pump housing  3  and a series of low pressure passages. It then enters into inlet annulus  4  assembly for the direct magnetically controlled inlet valve assembly  5 , passes around the direct magnetically controlled inlet valve  22  through the passage  6  and into the pumping chamber  7 . Upon completion of the charging phase the pumping camshaft acts upon a tappet  12 , urging the piston  10 , to slide in piston sleeve  11 . When the direct magnetically controlled inlet valve assembly  5  is energized with an electrical current to coil assembly  15 , a magnetic force is generated urging the inlet valve  22  to close and seal at surface  20 , thereby enabling fuel trapped in the pumping chamber  7  to compress and build pressure. When sufficient pressure is built, the outlet valve  9  will open, allowing high pressure discharge flow to pass from the pumping chamber through the high pressure passages  8  past the outlet valve  9  and into the high pressure line, rail, and finally to feed the fuel injectors. The pump is equipped with a relief valve  13  in case there is a system malfunction. 
         [0016]      FIGS. 3 and 4  provide more detail into the functional aspects of the preferred embodiment. When the direct magnetically controlled inlet valve assembly  5  is de-energized during the charging phase of the pump, valve member  22  opens and fuel is allowed to pass along inlet fluid flow path circuit  19 . During the charging phase fuel flows along path portion  19   a  from inlet fitting  1  to inlet valve inlet annulus  4 , through the inlet valve  5 , then along path portion  19   b  through passage  6  toward the pumping chamber. In the disclosed embodiment, the valve assembly  5  functions as both an inlet check valve and a quantity metering valve. During the charging phase, the downward movement of the pumping piston fills the pumping chamber with low pressure fuel from the inlet circuit  19 . During the high pressure pumping phase of the piston, highly pressurized fuel cannot be permitted to backflow through passage  19 ′ to the inlet fitting. During this phase the valve member  22  is closed against sealing surface  20 , due to both the energization of the coil and the high pressure fuel acting on the top surface of the valve member  22 . In order to control the quantity (volume) pumped at high pressure, the energization of the coil is timed to close the valve member  22  corresponding to a certain position on the upward stroke of the cam/piston. Prior to the valve closure, when the piston is moving upward, low pressure is being pushed backwards from the pumping chamber past the inlet valve  22  all the way to the pressure dampers  2  and inlet fitting  1 . The dampers absorb much of the pressure spike associated with this backflow. This can be considered a “pumping bypass” phase of the overall piston reciprocation cycle. The overall cycle thus comprises a charging phase, a pumping bypass phase, and a high pressure pumping phase. 
         [0017]    In a known manner, the electromagnetic coil assembly  15  is analogous to a solenoid, with a multi-winding coil situated around an axially extending, ferromagnetic cylinder or rod  21  (hereinafter referred to as magnetic pole). One end of the pole projects from the coil. When an electrical current is passed through the coil assy  15 , a magnetic field is generated, which flows about the magnetic circuit along magnetic flux lines across radial air gap  23 , generating an axial force onto the face of the valve  22  via the varying magnetic air gap  16 . When the magnetic force exceeds the force of the inlet valve return spring  24 , the valve  22  will close against valve sealing surface  20 . The magnetic pole  21  integrally defines sealing surface  20  and is also a part of the magnetic flux path  32 . Preferably, an inlet valve stop  14  aids in positioning of the valve  22  for accurate stroke control. 
         [0018]    First magnetic break  17  and second magnetic break  18  surround the sealing face  20  to direct the correct magnetic flow path and avoid a magnetic short circuit. Both breaks  17  and  18  should be fabricated from a non-magnetic material and for best performance valve stop  14  should also be fabricated from a non-magnetic material. Breaks  17  and  18  surround the projecting portion of the magnetic pole to prevent magnetic flux from travelling radially to the housing from the pole and thereby short-circuiting the valve member  22 . The breaks therby assure that the flux circuit passes through the coils, the magnet pole, through the sealing surface  20  and air gap  16 , through the inlet valve member  22 , across radial air gap  23 , through conductive ring  31  and pump housing  3 , back to the coil  15 . In an alternative embodiment, the sealing surface  20 ′ is not unitary with the pole  21 ; it could be integrated with the second magnetic break  18 . 
         [0019]      FIG. 5  shows additional features which contribute to efficient performance of the disclosed inlet valve assembly. The periphery of the valve member  22  includes a plurality of magnetic flow rim sections or lobes  26  which control the radial air gap  23 , and a plurality of hydraulic flow notches  25  which facilitate adequate fuel flow along fluid flow path  19  when the valve opens. The lobes have a rim diameter (max OD) and the notches have a base diameter (min OD). The base diameter is larger than the ID of the valve sealing surface  20 , so when the valve  22  is closed during the pumping stroke no flow can pass from pumping chamber across the valve  22  back to the inlet annulus  4 ′. The min OD should also be at approximately the same diameter as the diameter of the sealing surface  20  to allow sufficient magnetic force across magnetic air gap  16 . When valve  22  opens during the charging stroke, fuel flows from the inlet annulus  4 ′ through the notches and through the radial air gap  23 . The notches are provided because the air gap  23  must be minimized to maintain sufficient magnetic force, but as a result the annular flow area would otherwise be too small to permit the necessary inlet flow rate to the pumping chamber. 
         [0020]    As a stand-alone unit, the disclosed fuel inlet valve assembly  5  shown in  FIGS. 3 and 4  can be considered as providing a controlled intermediate flow path within the overall pump inlet flow path  19 . A magnetic valve member  22  is situated within the intermediate flow path. The intermediate flow path comprises a valve assembly inflow path  19 ′ fluidly connected to inlet path  19   a  and starting at inlet annulus  4 , and valve assembly outflow path  19 ″ starting downstream of the valve member  22  and ending at flow path  19   b  into passage  6 . The magnetic pole  21  is a rod or cylinder or the like coaxially situated within the magnetic coil  15  and includes one end  27  projecting from the coil  15 . A portion  19 ′ of the inflow path passes through transverse holes  28  in the projection of the pole and into a central bore  29 , which opens through a sealing face  20  integrally formed at the end of the projection. The inlet valve member  22  is a flat plate that constitutes an armature in relation to the coil  15  and has a sealing face  30  that confronts the sealing surface  20  through a magnetic air gap  16 . When lifted off the sealing surface  20 , the valve member  22  opens fluid communication from the inflow path  19 ′ (upstream of the sealing surface  20 ) to the outflow path  19 ″ (downstream of the sealing surface). The valve member  22  includes a periphery with a rim  26  that provides magnetic flux paths transversely through the valve member and notches  25  that form another portion of the valve assembly outflow flow path when the valve member is open.