Patent Publication Number: US-6666192-B2

Title: Fluid control valve and system

Description:
BACKGROUND 
     The present disclosure generally relates to fluid control valves and systems. Fluid control valves may be used in systems for the controlled feeding of volatile fuel components present in the free space of a fuel tank into an intake manifold of an internal combustion engine. A system of this type is disclosed U.S. Pat. No. 4,901,702. The system includes a vent line connecting the free space to the atmosphere. In the vent line there is disposed a storage chamber containing an absorption element, as well as a line connecting the storage chamber to the intake tube, which can be shut off by an electromagnetic check valve. Between the check valve and the intake tube there is disposed an auxiliary valve with a control chamber. The auxiliary valve can be closed by a vacuum actuator in dependence upon the pressure difference between the control chamber and the atmosphere. During low engine operating speeds in the near idling range, the flow rate of volatile fuel components through the apparatus is reduced so as to prevent the excessive enrichment of the mixture fed to the engine; at high engine operating speeds when the differential pressure between the engine and the tank is reduced, the non-return valve employed is wide open. 
     Another system of this type is disclosed in U.S. Pat. No. 5,284,121. This system comprises a pneumatically actuated purge control valve for opening or closing a flow line which connects an upper space of the fuel tank with the intake pipe, a controller for controlling the operation of the valve, a throttle section formed in series with the purge control valve, and pressure and temperature sensors which are located on the upstream side of the throttle section for detecting a pressure and a temperature of the evaporated fuel. When a value detected by the pressure sensor exceeds a predetermined value of pressure for providing a critical pressure ratio at which a flow rate of the evaporated fuel at the throttle section substantially equals to a sonic velocity, the controller opens the pneumatically actuated purge control valve to cause a purged flow of the evaporated fuel whose flow rate is constant. Simultaneously, the controller calculates a purged flow rate of the evaporated fuel from the detected values of the pressure and temperature sensors and a time period during which the purge control valve is opened. On the basis of the calculated purged flow rate, a reduction correction is made to an amount of the fuel to be supplied to the engine in order to maintain an air-fuel ratio in the optimum condition. 
     U.S. Pat. No. 5,460,137 provides another system of this type. This system includes a venting line that connects the free space of the fuel tank to the atmosphere. Along this line is interposed a storage chamber containing an absorption element having at least one line which connects the storage chamber to the intake manifold and which can be sealed by an electromagnetically actuated valve. The valve includes a seat and a Laval-type nozzle arranged downstream of the seat. The Laval-type nozzle allows the valve to employ a valve seat having a relatively small orifice cross section while maintaining generally the same mass throughput as a valve employing a relatively large valve seat with a standard cylindrical nozzle. The relatively small orifice cross section allows the valve to employ relatively small actuating forces to open and close the valve, thereby allowing the valve to be held in the closed position during clocked control for a longer period of time so that the excessive enrichment of the fuel-air mixture can be avoided. 
     SUMMARY 
     Disclosed herein is a fluid control valve comprising a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile. 
     Also disclosed herein is a system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold. The system comprises a storage chamber in fluid communication with the free space of the fuel tank, and a valve in fluid communication between the storage chamber and the engine manifold. The valve includes a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile. 
    
    
     The above described and other features are exemplified by the following figures and detailed description. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the figures, which are exemplary embodiments, and wherein the like elements are numbered alike: 
     FIG. 1 is a schematic view of an exemplary system for the controlled feeding of volatile fuel components from the free space of a fuel tank to an engine manifold; 
     FIG. 2 is a perspective view of the fluid control valve of FIG. 1; 
     FIG. 3 is a cross-sectional view of the fluid control valve of FIG. 2; 
     FIG. 4 is a cross-sectional view of the outlet port of FIG. 3; and 
     FIG. 5 is another cross-sectional view of the outlet port of FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, an exemplary embodiment of a system  10  for the controlled feeding of volatile fuel components from a free space  12  of a fuel tank  14  to an intake manifold  16  of an internal combustion engine  18  is shown. The system  10  includes an air filter  20  and a throttle valve  22 , which may be located inside the intake manifold  16 . System  10  also includes a fluid control valve  24  having an outlet port  26  in fluid communication with intake manifold  16  and an inlet port  28  in fluid communication with an outlet  30  of an absorption element  32 . Absorption element  32  is located within a storage chamber  34 , and may be an activated carbon filter or the like. An inlet  36  of absorption element  32  is in fluid communication with the free space  12  of fuel tank  14  and with a diagnostic unit  38 . Diagnostic unit  38  is in electrical communication with fluid control valve  24  and may in communication with the indicating instruments  40 . 
     During the operation of the internal combustion engine  18 , volatile fuel components from the free space  12  of the fuel tank  14  pass into the storage chamber  34  via the inlet  36  of absorption element  32  and are taken up by the absorption element  32 . Vacuum in the intake manifold  16  of the internal combustion engine  18  draws the volatile fuel components from chamber  34  through the outlet  30  of absorption element  32  and through the fluid control valve  24 . The volatile fuel components are fed from fluid control valve  24  to the manifold  16  in the flow direction  42  towards the throttle valve  22 . The flow of volatile fuel components from chamber  34  to the intake manifold  16  can be sealed by fluid control valve  24 . 
     Fluid control valve  24  is controlled (i.e., opened and closed) in response to various signals received from diagnostic unit  38 . The Diagnostic unit  38  monitors various environmental and vehicle variables to estimate the amount of fuel vapors stored in the absorption element  32 . The diagnostic unit  38  serves to monitor and control the fluid control valve  24 . The passage of volatile fuel components into the intake manifold  16  is regulated as a function of input variables such as the position of the throttle valve  22 , the speed of rotation of the internal combustion engine  18 , and/or the composition of the exhaust gas. 
     Referring to FIG. 2, a perspective view of an exemplary embodiment of the fluid control valve  24  is shown. Fluid control valve  24  includes a housing  100  that is, preferably, cylindrical in shape and molded from plastic. Inlet port extends along a radial surface  102  of housing  100 , generally parallel to a longitudinal axis  104  of the outlet port  26 . Also extending from radial surface  102 , diametrically opposite inlet port  28 , is a mounting bracket  106 . Extending from an end surface  108  of housing  100  is a terminal housing  110 . An opposite end surface  112  of housing  100  is formed in part by a flange  109  that extends outward from radial surface  102 . Outlet port  26  is received within an aperture formed by flange  109 . 
     Inlet port  28  includes a first tubular section  114  that extends generally parallel to longitudinal axis  104 , and a second tubular section  116  that extends generally perpendicular to longitudinal axis  104 . Second tubular section  116  is attached to first tubular section  114  at an end  118  of first tubular section  114  proximate end surface  112  of housing  100 . An end  120  of first tubular section  114  proximate end surface  108  of housing is configured to receive tubing from system  10  (e.g., tubing from outlet  30  of absorption element  32  as shown in FIG.  1 ). Second tubular section  116  includes a plug  122  disposed in an end thereof. Plug  122  seals the end of second tubular section  116  to prevent the volatile fuel components from escaping as they pass through first tubular section  114  and second tubular section  116  into housing  100 . Preferably, inlet port  28  is integrally molded with housing  100 . 
     Mounting bracket  106  includes two legs  124  that extend from radial surface  102 . Each leg  124  includes a generally “C” shaped guide  126  formed on an end of leg  124  distal from radial surface  102 . The “C” shaped guides  126  include slots  128  that are arranged in opposition to each other, such that a mounting plate (not shown) may be slidably received within slots  128  to secure fluid control valve  24  to the mounting plate. Preferably, mounting bracket  106  is integrally molded with housing  100 . 
     Terminal housing  110  is configured to retain an electrical terminal (not shown) for electrically coupling fluid control valve  24  and diagnostic unit  38  (FIG.  1 ). Preferably, terminal housing  110  is integrally molded with housing  100 . 
     Outlet port  26  includes a generally flat, circular end cap  130  and a nozzle portion  132  that extends from end cap  130  along longitudinal axis  104 . A free end  134  of nozzle portion  132  is configured to receive tubing from system  10  (e.g., tubing to inlet manifold  16  as shown in FIG.  1 ). 
     Referring to FIG. 3, a cross-sectional view of fluid control valve  24  is shown. Received in housing  100  is a tubular guide  200  around which a coil winding assembly  202  is disposed. The tubular guide  200  slidably supports a valve plunger  204  that is formed of a ferrous material (e.g., steel). Valve plunger  204  and coil winding assembly  202  form an actuator  205  for opening and closing fluid control valve  24 . Also extending within tubular guide  200  is a stop member  206 , which is prevented from axial movement by frictional engagement with housing  100  or by mechanical engagement with an end cap  208  disposed in housing  100 . Tubular guide  200  is retained at one end by a spacer  210 , which abuts housing  100 , and the other end of tubular guide  200  is retained by an annular wall  212 . Valve plunger  204  extends through an aperture in annular wall  212 . 
     Disposed on one end of valve plunger  204  is a sealing device  214 . Disposed on the opposite end of valve plunger  204  is a spring  216 , which extends between valve plunger  204  and stop member  206 . Spring  216  biases valve plunger  204  towards outlet port  26 . In the embodiment shown, sealing device  214  is a resilient stopper including a lip  218  extending axially from its periphery. In the closed position of fluid control valve  24 , as shown in FIG. 3, spring  216  forces sealing device  214 , via valve plunger  204 , into contact with a valve seat  220  formed on outlet port  26 , thus preventing the flow of volatile fuel components through valve  24 . While sealing device  214  is shown here as a resilient stopper including lip  218 , it will be recognized that sealing device  214  may include a resilient stopper having a flat sealing surface (e.g., without lip  218 ). Alternatively, sealing device  214  may include a surface formed on valve plunger  204 , or any device that interfaces with valve seat  220  to form a fluid-tight seal. 
     Outlet port  26  includes a flange  222  extending axially from the periphery of end cap  130 , and nozzle portion  132 , which extends through end cap  130 . Preferably, flange  222 , end cap  130  and nozzle portion  132  are integrally molded. End cap  130  is received within the circular opening formed by flange  109  of housing  100  to form a generally flat, coplanar surface with flange  109 . Valve seat  220  is formed on a generally flat end surface of nozzle portion  132 . The inside surface of nozzle portion  132  is shaped to form a nozzle  224 , as will be described in further detail hereinafter. 
     Coil winding assembly  202  includes a plurality of wire turns (windings)  226  disposed around a coil bobbin  228 . Coil winding assembly  202  is retained at one end by annular wall  212  and at an opposite end by the inside wall of housing  100 . The windings  226  are electrically coupled to a terminal  232  mounted within terminal housing  110 . The flow of current through windings  226  induces a magnetic force on valve plunger  204 , causing valve plunger  204  to move towards stop member  206 , against the force of spring  216 , thereby separating sealing device  214  from valve seat  220  and placing fluid control valve  24  in an open position. 
     In the open position, volatile fuel components can flow past sealing device  214  and valve seat  220 . The fluid path through fluid control valve is indicated by arrows  234 , and extends from inlet port  28  through a notch  236  disposed in flange  222  into a chamber formed by flange  222 , end cap  130 , and annular wall  212 . From this chamber, fluid passes between the sealing device  214  and valve seat  220  (when valve  24  is open) into the nozzle portion  132 , where the fluid passes through the nozzle  224  and out of fluid control valve  24 . 
     During use, the windings  226  are supplied with a pulse-width modulated direct current having a variably duty cycle. This causes the fluid control valve  24  to open and close at the frequency of the pulse-width modulated direct current, and the relative time periods that the valve is open and closed depends on the duty cycle. This is known as “pulse width modulated control”. As the duty cycle increases, the amount or volume of flow per unit time will increase and vice versa. 
     Referring to FIG.  4  and FIG. 5, FIG. 4 is a longitudinal section of outlet port  26 , as indicated at  4 — 4  in FIG. 5, and FIG. 5 is a transverse section of outlet port  26 , as indicated at  5 — 5  in FIG.  4 . As shown in FIG.  4  and FIG. 5, nozzle  224  includes, in the direction of fluid flow, a cylindrical entrance section  300 , a convergent section  302 , a throat  304 , a divergent section  306 , and a cylindrical exit section  308 . Cylindrical entrance section  300  has a diameter d 1 , which extends perpendicular to longitudinal axis  104 , and a length L 1 , which is measured along longitudinal axis  104 . Cylindrical exit section  308  has a diameter d 3 , which extends perpendicular to longitudinal axis  104 , and a length L 4 , which is measured along longitudinal axis  104 . In the present embodiment, diameter d 1  is equal to diameter d 3 , and length L 1  is smaller than or equal to length L 4 . It will be recognized, however, that the diameters d 1  and d 3  and the lengths L 1  and L 2  may be varied as needed for a specific application. Preferably, L 1  is selected to prevent the turbulence created by the flow bending 90 degrees at the valve seat entrance from extending into the convergent section  302 . Preferably, L 1  is selected to have laminar flow in the convergent portion of the semi-circular profile restriction. 
     Within convergent section  302 , the inside diameter of the nozzle  224  decreases from the diameter d 1  at the cylindrical entrance section  300  to a diameter d 2  at the throat  304 , over a length L 2 , as measured along longitudinal axis  104 . As shown in FIG. 4, the profile of the convergent section  302 , from diameter d 1  to diameter d 2 , is formed by a radius r 1 . Within divergent section  306 , the inside diameter of the nozzle  224  increases from the diameter d 2  at the throat  304  to the diameter d 3  at the cylindrical exit section  308 , over a length L 3 , as measured along longitudinal axis  104 . The profile of the divergent section  306 , from diameter d 2  to diameter d 3 , is formed by the radius, r 1 . Thus, the convergent and divergent sections  302  and  304 , are formed by a semi-circular profile having a radius r 1 . The throat  304  is the cross sectional flow area at the apex of this semi-circular profile. Throat  304  has a diameter d 2 , which is less than d 1  and d 3 . 
     The transition between cylindrical entrance section  300  and convergent section  302 , as indicated at  310 , and the transition between divergent section  306  and cylindrical exit section  308 , as indicated at  312 , may be blended to prevent fluid turbulence in these regions. Similarly, edges at inlet and outlet cross sections  314  and  316  of nozzle  224  may be radiused to prevent fluid turbulence in these regions. 
     The throat diameter d 2  is selected based on the maximum required flow through the fluid control valve  24 . For example, referring to FIG.  1  and FIG. 4, throat diameter d 2  may be selected to set the maximum flow of volatile fuel components through valve  24  required by the application at the relatively high differential pressures existent during idle operation of internal combustion engine  18 . 
     After the diameter d 2  is selected, the diameter d 1  is then selected to insure that the nozzle will have enough flow to allow for choked flow at the lower differential pressures existent during wide throttle operation of internal combustion engine  18 . Preferably, diameter d 1  can be greater than or equal to about 1.2 times diameter d 2 . More preferably, d 1  can be greater than or equal to about 1.4 times diameter d 2 . The maximum dimension of d 1  may be set to insure that the smallest force available to open valve  24  (e.g., the magnetic force induced by windings  226  on valve plunger  204 ) is greater than the maximum vacuum force on the sealing device  214  (FIG.  3 ). 
     The radius r 1  is then selected to insure that the convergent, divergent semi-circular profile will create a choked flow at low vacuum levels. The radius r 1  may also be selected to accommodate d 1 , d 2 , and L 1  in the space available for nozzle  224 . That is, the radius r 1  may be selected to insure that the semi-circular profile creates a convergent section  302  wherein the diameter decreases from d 1  to d 2 , and to insure that the lengths L 1 , L 2 , and L 3  fit within the overall length available for nozzle  224 . For the application described herein, the radius r 1  can be less than or equal to about 100 millimeters, with less than or equal to about 64 millimeters preferred. Also for the application described herein, the radius r 1  can be greater than or equal to about 5 millimeters, with greater than about 9.6 millimeters preferred. 
     Rather than employing a Laval-type or Venturi-type nozzle, valve  24  employs a relatively simple nozzle design. Nozzle  224  employs a semi-circular profile to form the convergent and divergent sections of the nozzle. Use of the semi-circular profile allows the nozzle to be designed without regard for the angles of the convergent and divergent sections, which must be considered in the design of a Laval-type or a Venturi-type nozzle. In addition, because the angles of the convergent and divergent sections are not important in manufacturing tolerance considerations, manufacturing of a valve  24  including the nozzle  224  is simplified from that possible with valves including nozzles of the Laval-type or Venturi-type. 
     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. For example, while nozzle  224  is described herein as being used in a fluid control valve  24  employing an electromagnetic actuator  205 , it will be appreciated that nozzle  224  may be used in a fluid control valve  24  employing a pneumatic actuator such as that described in U.S. Pat. No. 5,284,121. In another example, while inlet port is described herein as extending parallel to longitudinal axis  104 , it will be appreciated that inlet port may extend at an angle to longitudingal axis  104 , such as described in U.S. Pat. No. 4,830,333. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.