Abstract:
The disclosure relates to a valve comprising a body defining at least an admission duct and an outlet duct for a fluid and receiving a valve member that is movable by means of an actuator member fastened to the body to move between a closed position closing the outlet duct and an open position leaving it open, the valve member having a central portion secured to a central portion of a substantially plane diaphragm that has a peripheral portion associated in leaktight manner with a support element secured to the body in such a manner as to co-operate with the support element to define a chamber, the valve member and the diaphragm being pierced by an opening providing permanent communication between the chamber and the outlet duct, the diaphragm being elastically deformable and being dimensioned to urge the valve member into its closed position.

Description:
The present invention relates to a valve suitable for use in particular for controlling the flow rate of a fluid in a fluid transport circuit, such as the circuit feeding a motor vehicle engine with fuel, for example. 
     BACKGROUND OF THE INVENTION 
     Such a valve generally comprises a body defining an inlet duct and an outlet duct for a fluid and receiving a valve member that is movable between a closed position in which it closes the outlet duct and an open position in which it is spaced apart therefrom by means of an actuator member fastened to a support element secured to the body. By way of example, the actuator member is an electromagnetic actuator member associated with a spring for returning the valve member into its closed position. 
     When the valve member is in the closed position, the pressure acting on the valve member beside the inlet duct differs from the pressure acting on the valve member beside the outlet duct. The force that results from this pressure difference tends to hold the valve member in its closed position by adding to the return force exerted by the spring. To bring the valve member into its open position, the electromagnetic actuator member therefore needs to provide sufficient force to overcome the combined action of the spring and of the pressure difference. This requires an electromagnetic member that is dimensioned accordingly, thereby presenting relatively large size and relatively high levels of electricity consumption. In addition, the force that needs to be delivered is not constant and depends on the pressure difference that exists between the two faces of the valve member. 
     To mitigate that drawback, it is known to use flexible sleeves of elastomer material, each having one end closed by the valve member and an opposite end connected to the support element in such a manner as to form a chamber. The chamber communicates with the outlet duct via an opening formed through the valve member so that the same pressure exists both in the chamber and in the outlet duct. The valve member is returned to the closed position by a spring interposed in the sleeve between the valve member and the support element. As a result the valve has a relatively large number of parts, thereby lengthening the duration and the complexity of assembly. In addition, assembling the sleeve and the spring is quite difficult. Furthermore, given the shape of the sleeve and the deformation to which it is subjected, the sleeve is made of an elastomer, which presents only limited ability to withstand fuel, unless it is prohibitively expensive. The flexibility of the sleeve also makes it necessary to provide means for guiding the valve member. 
     OBJECT OF THE INVENTION 
     It would therefore be advantageous to have a valve of structure that is simpler than that of prior art valves, but without sacrificing effectiveness. 
     BRIEF SUMMARY OF THE INVENTION 
     To this end, the invention provides a valve comprising a body defining at least an admission duct and an outlet duct for a fluid and receiving a valve member that is movable by means of an actuator member fastened to the body to move between a closed position closing the outlet duct and an open position leaving it open, the valve member having a central portion secured to a central portion of a substantially plane diaphragm that has a peripheral portion associated in leaktight manner with a support element secured to the body in such a manner as to co-operate with the support element to define a chamber, the valve member and the diaphragm being pierced by an opening providing permanent communication between the chamber and the outlet duct, the diaphragm being elastically deformable and being dimensioned to urge the valve member into its closed position. 
     Thus, the diaphragm co-operates with the support element to form a chamber at the same pressure as the outlet chamber, thus making it possible to limit the force that needs to be exerted on the valve member in order to bring it into its open position. The substantially plane shape of the diaphragm makes it possible for the valve to be compact in structure. In addition, the resilient return of the valve member into the closed position is provided by the diaphragm itself, so there is no need to add a spring dedicated to providing this effect. In order to perform these functions, the diaphragm is relatively stiff, thus also enabling it to guide the valve member. Another advantage of using a resilient return diaphragm lies in the fact that during movement of the valve member towards its open position, the force exerted by the diaphragm increases rapidly and tends to slow the valve member down as it arrives in the open position. This helps limit the noise made by the valve in operation. Such a diaphragm is made of materials that are relatively stiff, and in particular of metals that present relatively good ability to withstand fuel at lesser cost. 
     Other characteristics and advantages of the invention appear on reading the following description of a particular, non-limiting reservoir of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       Reference is made to the sole accompanying FIGURE which shows, in section, a portion of a valve in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the FIGURE, the valve in accordance with the invention comprises a body given overall reference  1 , defining an admission duct  2  and an outlet duct  3 , each having one end that opens out into a housing  4  of the body  1 . The outlet duct  3  is shaped to have a segment  33  that converges (relative to the fluid flow direction represented by arrows S) in the vicinity of said end. The end is surrounded in the housing  4  by a seat  5  against which there bears a valve member given overall reference  6  that is associated, in a manner described in greater detail below, with a support element given overall reference  7  that is secured to the body  1  so as to extend inside the housing  4  in line with the outlet duct  3 . 
     The support element  7  has a tubular portion  8  with one end adjacent to the seat  5  that is terminated by a collar  9 . The support element  7  is made of a non-magnetic material. 
     An electromagnetic actuator member  10  of known type is mounted on the support element  7 . In conventional manner, the electromagnetic actuator  10  comprises a core  11  mounted in the tubular portion  8 , and a coil  12  mounted on the tubular portion  8  and connected to electrical power supply means (not shown). Specifically, the core  11  is embedded in the support element  7 , while the coil is made by winding a conductor directly onto the tubular portion  8 . The electromagnetic actuator member  10  also comprises, in known manner, a field-closing bell  13 . The core  11  has one end projecting from the tubular portion  8  into a chamber  14  that is formed in the collar  9  so as to be open to the outside of the collar  9  and so as to lead into the tubular portion  8 . 
     The valve member  6  has a rigid strength member of magnetic steel, shaped as a disk with a domed center. The valve strength member  6  thus has an annular peripheral portion  16  that is plane with a projecting surface  16 . 1  from which there extends a circular central portion  17  that is plane and concentric with the peripheral portion  16 . The peripheral portion  16  and the central portion  17  are connected to each other by a frustoconical portion  15 . 
     Damper studs  18  of elastomer material project from the surface  16 . 1  of the peripheral portion  16 . On its opposite side, the peripheral portion  16  possesses a projecting surface  16 . 2  from which there extends an annular sealing element  19 , e.g. of elastomer material, for pressing against the seat  5 . The damper studs  18  and the sealing element  19  in this example are hot-stuck onto the valve strength member  6 . 
     The central portion  17  of the valve member has a convex surface pressed against the central portion  20  of a diaphragm given overall reference  21  made of a disk of relatively rigid material such as a metal such as stainless steel or a copper alloy, . . . . 
     The diaphragm  21  is substantially plane and has a peripheral portion  22  bearing in leaktight manner against an annular bearing surface  23  surrounding the chamber  14  in such a manner that the diaphragm  21  closes the chamber  14 . The annular bearing surface  23  in this example is formed by a bead that provides a line bearing against the peripheral portion  22  of the diaphragm  21 . The collar  9  possesses a rim  27  projecting from the annular bearing surface  23  to position the diaphragm  21  laterally. 
     The diaphragm  21  possesses a surface  28  facing the surface  16 . 1  of the valve member  6 . 
     The central portions  20 ,  17  of the diaphragm  21  and of the valve strength member  6  are united in this example by a tubular rivet  24  defining a passage  26 . The rivet  24  is received in a central opening of the diaphragm  21  and of the valve strength member  6 , and serves to center the valve member  6  relative to the diaphragm  21 . The rivet  24  presses the central portion  20  of the diaphragm  21  and the central portion  17  of the valve strength member  6  against each other. 
     The valve member  6  also has a central projection beside the outlet duct  3  presenting an outside surface that is complementary in shape to the shape of the converging segment  33 . This projection is formed by one end  25  of the rivet  24 . 
     The diaphragm  21  is elastically deformable between a rest state corresponding substantially to a position in which the valve is closed (as shown in the FIGURE), in which the valve member  6  presses against the seat  5 , and a deformed state corresponding to an open position in which the valve member is separated from its seat  5 . 
     When the valve is in its closed position, the diaphragm is lightly prestressed to press the valve member  6  against the seat  5 . In addition, this prestress serves in particular to compensate for any low level of suction in the housing  4 . The surface  16 . 1  of the peripheral portion  16  of the valve strength member  6  and the surface  28  of diaphragm  21  are subjected to the admission pressure, while the surfaces opposite thereto of the diaphragm  21  and of the valve member  6  are subjected to the pressure of the outlet duct  3 . The fluid under pressure, in association with the prestress and the stiffness of the diaphragm  21 , thus exerts both a force on the peripheral portion  20  of the diaphragm  21 , which force tends to press the diaphragm against the annular bearing surface  23 , and a force on the valve member  6 , tending to press it against its seat  5 . The area ratio of the surfaces  16 . 1  and  28  is designed in such a manner that the forces acting in opposite directions are equivalent. This makes it possible to achieve very good sealing both of the chamber and of the valve. 
     When the valve is in its closed position, the chamber  14  and the outlet duct  3  are at the same pressure, i.e. the pressure that exists in the outlet duct  3 , because of the passage  26  that provides permanent communication between the chamber  14  and the outlet duct  3 . 
     The valve member  6  is moved into its open position when the coil  12  is excited, thereby causing the diaphragm  21  to deform towards its deformed state. Since this deformation is substantially symmetrical, the valve member  6  is shifted parallel to itself. The portion extending between the peripheral portion  16  and the central portion  17  accommodate the major fraction of the deformation of the diaphragm  21  such that the contacting surfaces of the valve member  6  and of the diaphragm  21  remain unchanged during deformation of the diaphragm  21 . Because of the rapid increase in the opposing force exerted by the diaphragm  21 , the damper studs  18  come into contact with the support element  7  at a speed that is relatively slow. When the valve member  6  is in its open position, the damper studs  18  are in contact with the support element  7  that forms an abutment stopping the movement of the valve member  6 . 
     In this position, the horn-shaped projection  25  guides the lines of fluid flow within the converging segment  33  of the outlet duct  3 , thereby limiting fluid disturbances in this location and increasing the fluid flow rate while suction is relatively weak in the outlet duct  3 . 
     When the coil  12  ceases to be excited, the diaphragm  21  returns to its rest state, thereby bringing the valve member  6  into the closed position. Because the chamber  14  is in communication with the opposite face of the valve member  6 , the suction effect that occurs on the valve member  6  is limited, thus making it possible to achieve a relatively low level of noise when the valve member  6  comes to press against the seat  5 . 
     Naturally, the invention is not restricted to the embodiment described and variant embodiments can be applied thereto without going beyond the ambit of the invention as defined by the claims. 
     In particular, the annular bearing surface may be plane and it is possible to interpose an annular sealing element between the annular bearing surface and the peripheral portion of the diaphragm. The outer edge of the peripheral portion of the diaphragm may be engaged in a groove in the support element, or it may be fastened thereto in a manner that does not hinder deformation of the diaphragm. 
     In addition, the diaphragm may be dimensioned so that the force needed for holding it in its deformed state is substantially equal to that exerted by the electromagnetic actuator member. It is then possible to omit any additional positive abutment for defining the open position of the valve member  6 . 
     The actuator member may be mounted on the outside of the body  1 , the support element then being formed, for example, by a portion of the body that serves only for bearing against the peripheral portion of the diaphragm. 
     A plastics material or a composite material may also be used for the diaphragm. 
     The diaphragm and the valve member may be connected together by fastener means other than a rivet, for example by adhesive or by welding. 
     The horn-shaped projection from the valve member may be made on a conventional valve member, e.g. being integral therewith. 
     The valve member may also be formed of a disk having its central portion surmounted by a cylinder.