Abstract:
A pressure control valve includes a valve body having an axial flow path, a valve seat integrated into the valve body, a retention cup positioned within the flow path, a spring received and guided by the flow passage, and an armature connected to the spring. The spring maintains the armature positioned in the retention cup keeping the flow path open. A solenoid moves the armature from the retention cup to the valve seat blocking the flow path. The pressure control valve may be used for controlling a high-pressure single-piston pump and has the capability for controlling pressure or flow with a commanded input electrical voltage or current, while simplifying the component design and reducing the amount of components and, thus, the complexity of the assembly process. The pressure control valve may be used, for example, to manage the fuel rail pressure of a gasoline direct injection internal combustion engine.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to electromechanical actuators; more particularly, to pressure control valves for application in gasoline internal combustion engines; and most particularly, to a pressure control valve for application in a fuel system of a gasoline direct injection engine. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electromechanical actuators for applications in internal combustion engines are well known, and are typically used to control the flow and/or pressure of the supplied fluid through one or several fluid passages. In some cases it is desired that the control pressure or flow output is proportional to an input electrical signal to the coil of the electromagnet. In most specialized cases, the valve design must be customized to the needs of a specific application, for example, for very fast on and off pressure cycling requirements in fuel delivery and control systems, such as gasoline direct injection (GDI) engines. Another typical requirement for valve applications in GDI engines includes tight tolerances for the consistency in the pressure response times. 
         [0003]    For example, a high-pressure single-piston pump driven via a pulley or directly from one of the engine shafts manages the GDI fuel rail pressure control. The pressure pulsations of such a pump are controlled entirely or partially by a normally open on/off control valve that creates pumping and spilling flow conditions. Such valve is typically synchronized to the camshaft that will trigger the valve according to the angle of the cam and the required flow or pressure delivery to the fuel rail assembly and injectors. 
         [0004]    Different control valves exist in the art to achieve different kinds of performances. Material selected for the control valve has to be corrosion resistant to different blends of fuel and typically the design configuration makes such pump an expensive component that increases the overall system cost considerably. 
         [0005]    Pressure control valves for high-pressure pumps that are able to deliver fuel from a fuel tank to a fuel rail assembly at a high-pressure must manage the occurring magnetic, mechanical, and hydraulic forces adequately to produce the desired pressure or flow output. Factors such as friction, hydraulic stiction, component misalignment, under-over damping, inertia, or mass must be minimized in order to reduce actuator performance variation and to enhance part reliability. 
         [0006]    What is needed in the art is a pressure control valve that significantly simplifies the component design and reduces the amount of components used thereby reducing the complexity and cost of the assembly process. 
         [0007]    It is a principal object of the present invention to provide a pressure control valve for controlling a high-pressure single-piston pump that has a low mass armature geometry and an integral seat with in line flow configuration for improved flow behavior and that is designed to reduce the pump packaging. 
       SUMMARY OF THE INVENTION 
       [0008]    Briefly described, a pressure control valve for controlling a high-pressure single-piston or multiple-piston pump has the capability for controlling pressure or flow with a commanded input electrical voltage or current, while simplifying the component design and reducing the amount of components and, thus, the complexity of the assembly process. The pressure control valve in accordance with the invention may be used for, but is not limited to, applications in the automobile industry, for example, to manage the fuel rail pressure of a gasoline direct injection (GDI) internal combustion engine. 
         [0009]    The pressure control valve in accordance with the invention includes a spring that biases the armature section to keep the valve normally open. The armature mechanical net load may be set in spring preload to prevent self-closure caused by reverse flow. 
         [0010]    Utilization of a ball armature in accordance with the invention simplifies the valve design by reducing the number of components. The ball armature is self guided and, therefore, controls the occurring radial forces with tight clearances. The armature stroke may be determined by a retention cup positioned in line with the flow within the housing. Accordingly, a flow path that minimizes the force created by the back flow may be created making the design of the control valve robust for applications at different engine speeds. Consequently, the control valve in accordance with the present invention may have a fast response with low variation. 
         [0011]    The magnetic ball armature is moved from an open position to a closed position by an electromagnetic field created with a solenoid. The coil of the solenoid is kept dry by positioning it outside of the valve body and by over molding the spool the coil is wound around with a plastic material. Using a dry coil design improves the body leakage performance and reduces hydrocarbon emissions typically carried by fuel vapors. Furthermore, the core of the solenoid is cooled by the flow of the fuel through the pressure control valve. Accordingly the pressure control valve in accordance with the invention has a self-cooling design. 
         [0012]    Still further, the outlet port of the pressure control valve is designed to be received by the inlet port of a high-pressure single-piston pump, which may reduce the pump packaging and simplify the assembly process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0014]      FIG. 1  is a schematic diagram of a prior art fuel system of a gasoline direct injection engine in accordance with the invention; and 
           [0015]      FIG. 2  is a cross-sectional view of a pressure control valve in accordance with the invention. 
       
    
    
       [0016]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    Referring to  FIG. 1 , a prior art fuel system  10  of a gasoline direct injection (GDI) engine includes a fuel tank  12 , a pressure control valve  20 , a high-pressure pump  14 , and a fuel rail assembly  16 . Fuel rail assembly  16  includes a fuel rail  18 , a plurality of fuel injectors  22 , a pressure limiting valve  24  and a high-pressure sensor  26  that monitors the pressure in fuel rail  18 . Pressure limiting valve  24  allows fuel to return to fuel tank  12  in the case that the pressure in fuel rail  18  overcomes a preset pressure limit of valve  24 . A low-pressure pump  28  is incorporated within fuel tank  12 . A low-pressure line  32  connects low-pressure pump  28  with pressure control valve  20  and pressure limiting valve  24 , while a high-pressure line  34  connects high-pressure pump  14  with fuel rail  18 . 
         [0018]    Fuel injectors  22  are adapted to receive fuel from fuel rail  18  and to deliver fuel directly into the combustion chamber of each cylinder (not shown). High-pressure pump  14  may be a single-piston reciprocating pump that has a piston (not shown) that draws fluid, in this case fuel, into a chamber when stroked in one direction and expels fluid from the chamber when stroked in the other direction. Thus, pump  14  delivers a single charge of fuel during each stroking cycle. 
         [0019]    Fuel tank  12  stores the fuel required for operating the DIG engine. Low-pressure pump  28  delivers fuel with low pressure from tank  12  to high-pressure pump  14  via low-pressure line  32 . High-pressure pump  14  delivers highly pressurized fuel to fuel rail  18  via high-pressure line  34 . High-pressure fuel pump  14  is typically driven mechanically by the engine via a pulley or directly from one of the engine shafts. 
         [0020]    Pressure control valve  20  is positioned between fuel pump  28  and high-pressure pump  14  and typically controls entirely or partially the pressure pulsations of high-pressure pump  14  and creates pumping and spilling flow conditions and, therefore, is operated as a fuel-metering device. Pressure control valve  20  controls flow and pressure of the fuel to fuel rail  18 . Pressure control valve  20  is an on/off valve that is normally open allowing flow from fuel tank  12  to pump  14  and vice versa. Pressure control valve  20  may be controlled by an electric actuator, such as an electromagnet, and may continuously adjust the flow from low-pressure pump  28  to high-pressure pump  14 . If pressure control valve  20  is operated in an open position, fuel flow from low-pressure pump  28  to high-pressure pump  14  or in inverse direction is enabled. If pressure control valve  20  is operated in a closed position, fuel flow from low-pressure pump  28  to high-pressure pump  14  is interrupted, high-pressure pump  14  pressurizes fuel previously suctioned in, and flow of the pressurized fuel to fuel rail  18  only is enabled. Pressure control valve  20  may enable pressurization of the fuel from about 4 to 6 bars at an outlet of low-pressure valve  28  to about 40 to 200 bars at an outlet of high-pressure pump  14 . 
         [0021]    Referring to  FIG. 2 , a pressure control valve  40  in accordance with the invention includes a valve body  42 , an armature, such as a magnetic ball  44 , that is retained by a retention cup  46  and permanently connected to a spring  48 , and a solenoid  50  positioned around valve body  42 . Pressure control valve  40  extends axially along an axis  60 . In a preferred embodiment, valve body  42  includes an inlet segment  52  forming an inlet port  54 , an outlet segment  56  forming an outlet port  58 , and a center segment  62  connecting inlet segment  52  with outlet segment  56 . Inlet port  54  is in controlled fluid communication with a fuel tank through a low-pressure line, such as fuel tank  12  and low-pressure line  32  shown in  FIG. 1 . Outlet port  58  is in direct fluid communication with an inlet port of a high-pressure pump, such as high-pressure pump  14  shown in  FIG. 1 . 
         [0022]    Inlet segment  52  has preferably a cylindrical shape and includes cylindrical center bore  64  that extends along axis  60 . Cylindrical bore  64  includes a first section  641  positioned proximate to an upper end  521  and having a first diameter  642  and a second section  643  having a second diameter  644  that is larger than first diameter  642 . Consequently, cylindrical bore  64  includes a shoulder  645  where first section  641  meets second section  643 . Second section  643  receives and guides spring  48  and shoulder  645  is utilized to retain the position of spring  48  in an axial direction. At the outer circumference, inlet segment  52  may include connection features  646  that may enable preferably quick connection of inlet segment  52  to a low-pressure line of a fuel system, such as low-pressure line  32  of fuel system  10  shown in  FIG. 1 , for receiving fuel from a fuel tank, such a fuel tank  12  shown in  FIG. 1 . Connection features  646  are not limited to quick connection features but may be, for example, threads. A lower end  522  of inlet segment  52  is designed as a valve seat  66  and is preferably conically tapered. Valve seat  66  has a size adapted to the diameter of ball  44 . This ensures that flow  74  through bore  64  can be completely stopped when ball  44  is positioned in valve seat  66 . Integrating valve seat  66  in inlet segment  52  reduces the number of components compared to prior art pressure control valves. 
         [0023]    Center segment  62  has preferably a cylindrical shape and includes a cylindrical center bore  68  that extends along axis  60 . Bore  68  is designed to receive and retain inlet segment  52  and outlet segment  54 . The size of bore  68  is adapted to the size of an outer circumference of inlet segment  52  and outlet segment  54  and to allow flow around ball  44 . Retention cup  46  may be secured to the inner wall of center segment  62  that is formed by bore  68 . 
         [0024]    Outlet segment  56  has preferably a cylindrical shape and includes a cylindrical center bore  72  that extends along axis  60 . An outer circumference of outlet segment  56  is preferably adapted to the size of an inlet port of a high-pressure pump, such as pump  14  shown in  FIG. 1  and enables connection of pressure control valve  40  to a high-pressure pump, such as pump  14  shown in  FIG. 1 . The outer circumference of outlet segment  56  may include a groove  561  for receiving an o-ring. The axial length of outlet segment  56  that is inserted into a high-pressure pump may be shorter compared to prior art pressure control valves resulting in material and therefore manufacturing cost savings. 
         [0025]    Center bore  64  of inlet segment  52 , center bore  68  of center segment  62 , and center bore  72  of outlet segment  56  are in fluid communication and, thus, form a centered axial flow path  78  of valve  40  that extends from inlet port  54  to outlet port  58 . Flow  74  is possible in both directions from inlet port  54  to outlet port  58  and from outlet port  58  to inlet port  54  when ball  44  is positioned in retention cup  46  and, thus, when valve  40  is open. Flow  74  is stopped when ball  44  is positioned in valve seat  66  and, thus, when valve  40  is closed. The flow direction is determined by the movement of a piston in a high-pressure pump, such as pump  14  in  FIG. 1 . For example, during the downward stroke of the piston, flow  74  from inlet port  54  to outlet port  58  occurs, and during the upward stroke of the piston, flow  74  from outlet port  58  to inlet port  54  occurs. By positioning retention cup  46  and valve seat  66  in flow path  78 , the forces on the ball  44  created during the upward stroke of the piston of the pump can be minimized. 
         [0026]    Ball  44  is in a preferred embodiment movable by solenoid  50  from a first position in which ball  44  is positioned in retention cup  46  and a second position in which ball  44  is positioned in valve seat  66  and, therefore, from an open position to a closed position of valve  40 . Spring  48  is preferably designed to normally maintain ball  44  positioned in retention cup  46  to keep valve  40  open even when the flow  74  from outlet port  58  to inlet port  46  occurs. Spring  48  maintains ball  44  in retention cup  46  and keeps valve  40  open until an electrical signal is sent. A current sent via an electrical connector  76  to solenoid  50  energizes valve  40  by creating a magnetic field that moves ball  44  from its position in retention cup  46  to valve seat  66 , thereby blocking flow path  78  and stopping flow  74  towards inlet port  54  and, thus, closing valve  40 . The force needed to move ball  44  into valve seat  66  may be lower compared to forces applied in prior art control pressure valves, since flow  74  towards inlet port  54  assists upward movement of ball  44  from retention cup  46  to valve seat  66 . In a preferred embodiment, solenoid  50  is an electromagnet including a coil  82  wound around a spool  84 . Spool  84  may be over molded with a plastic material  86  to protect coil  82  from the environment, for example, from corrosive fluids. By positioning solenoid  50  around the outer circumference of valve body  42 , the core of solenoid  50  or coil  82  is cooled instantly by flow  74  passing through flow path  78 . 
         [0027]    Referring now to  FIGS. 1 and 2 , pressure control valve  40  is used, in the preferred embodiment, in a fuel system of a gasoline direct injection (GDI) engine, such as fuel system  10  illustrated in  FIG. 1 . Pressure control valve  40  may replace prior art pressure control valve  20  and may be integral with high-pressure pump  14 . Pressure control valve  40  may be triggered by an electronic signal sent from an electronic control unit (not shown), which determines the time and duration of fuel injection by fuel injectors  22  in accordance with operating parameters of the engine, such as engine speed, load, temperature, etc. During an injection event, normally open pressure control valve  40  is closed by supplying a current to solenoid  50  and creating a magnetic field that moves ball  44  upwards from its position in retention cup  46  to valve seat  66  thereby blocking flow path  78  and stopping flow  74  towards inlet port  52 . The upward stroke of the piston of high-pressure pump  14  compresses the previously suctioned in fuel and pressurized fuel flows through a discharge bore of pump  14  and then via high-pressure line  34  to fuel rail  18 . Once the pump  14  is pressurized, the valve  40  can be de-energized and the high pressure could keep the valve  40  closed until the next charging event comes; this allows to reduce the power and heat on the valve. Between each injection event when pressure control valve  40  is open, an amount of fuel is drawn from fuel tank  12  through flow path  78  of pressure control valve  40  into an inlet port of high-pressure pump  14  during the downward stroke of the piston, and flows back into fuel tank  12  through flow path  78  during the upward stroke of the piston of pump  14 . 
         [0028]    While pressure control valve  40  has been described for application in a fuel system of a gasoline direct injection (GDI) engine other applications are possible. 
         [0029]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the on not be limited to the described embodiments, but will have full scope defined language of the following claims.