Abstract:
A vent valve for a fuel tank of a motor vehicle includes a housing, a cage in the housing, a movable float, and a sealing arrangement with an at least three-stage reopening operation. The sealing arrangement includes multiple movable supports defining openings of varying cross-sectional area sequentially operable.

Description:
TECHNICAL FIELD 
     The invention relates to a vent valve for the fuel tank of a motor vehicle. Such a valve serves, for example, to ensure an aeration and venting of the tank during the operation of the vehicle, or to limit the fill level of fuel during fueling. 
     BACKGROUND 
     Valves for the latter use are also known as fill limit vent valves (FLVV). They have a float that is directly or indirectly connected to a sealing arrangement which seals a valve housing vent opening, connected with the environment, for example, when during fueling the fuel level has reached a predetermined height. A problem with this type of valve is that during the operation of the vehicle the float can be lifted by fuel splashing up, and the vent opening of the valve can be sealed. Thereby, due to vaporizing fuel, an internal pressure can build up exerting a force on the sealing arrangement, which in the simplest case is a disk of elastomer material, the force exceeding the weight of the float, such that the vent opening remains closed at least for a certain duration. Thus, the danger exists of the tank being damaged by the internal pressure. 
     To reduce this danger, among others, two-stage valves are used. In these valves, known, for example, from US 2005/0126633 A1, a sealing arrangement is present, in which initially a smaller opening cross-section is released, which due to the smaller surface upon which the internal pressure can act, requires a lower force expenditure. The internal pressure can be reduced until the weight of the float is sufficient to remove the sealing arrangement from a second, larger opening cross-section that corresponds, for example, approximately to the cross-sectional area of the vent opening. Because the first opening cross-section cannot be selected to be too large, in order to enable the opening of the first stage during greater internal pressures, it takes a relatively long time until the internal pressure is reduced to a value that permits the opening of the second valve stage. 
     SUMMARY 
     An objective of the disclosure is to propose a vent valve, which is improved with respect to its re-opening behavior after a closure of the vent opening caused by a pressure inside the tank. 
     This objective and others are attained by a vent valve such as a FLVV which comprises at least a three-stage sealing arrangement. Thereby, in general, a faster re-opening is possible. Thus, a first stage can be provided with a relatively small opening cross-section, which opens with high pressures inside the tank. Because, however, at least two further valve stages are provided, depending on the design and the number of the stages, an opening of the next stage occurs after a short time, such that the decrease in pressure is further accelerated due to the respectively larger opening cross-section. 
     A sealing arrangement may include multiple supports, arranged one after the other along the central longitudinal axis, where said supports, are each penetrated by a through channel running coaxially to the central longitudinal axis. A sealing element is arranged on each support, coaxially to the central longitudinal axis, both on the upper sides facing towards the vent opening, and on the lower sides facing the float. It would be conceivable thereby that the supports and the sealing elements present thereon are formed as one piece, for example, formed as an injection molded part. Preferably, however, the sealing elements are separate parts which in view of their sealing function are composed, for example, of a soft and elastic material. 
     The supports are movable, in each case, relative to each other and relative to the float, in the direction of the central longitudinal axis of the valve housing, by a predetermined distance between a closed position and an open position. In this way, it is guaranteed that the supports and their sealing elements can be removed from each other in a chronological sequence (open position) and—with floats rising upwards—can be again brought close to each other, and finally pressed against each other, the uppermost support closing the vent opening (closed position). In the each case of the closed position of a support, the sealing element on the upper side thereof bears against the sealing element on the lower side of an adjacent support, and in the case of the uppermost support lying nearest to the vent opening, the sealing element on the upper side thereof bears against a counter-sealing element, this being a lower-side sealing element of a support or a sealing element encompassing the vent opening. Thereby, in each case, two sealing elements cooperate to surround an opening having a cross-section. The size of the respective opening cross-sections following one another, which ultimately represent the individual stages of the valve, decreases towards the float, the gradation of the individual opening cross-sections permitting a large range with regards to the opening characteristics of the valve. 
     Sealing elements interacting with each other can, in principle, be formed arbitrarily. Thus, it is conceivable for instance, that a sealing element is a two-dimensional seat, or also a seat formed in the shape of a ring projection, and that a sealing element interacting therewith is a ring-shaped sealing lip or a sealing ring having a level sealing area. It is critical only that a sealing element pair interacts such that an opening cross-section is surrounded in a sealing manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantageous embodiments are explained in more detail in the following description, which refers to the attached drawings. They show: 
         FIG. 1  a longitudinal section through a first embodiment of a vent valve with a three-stage sealing arrangement, comprising two supports, 
         FIG. 2  a longitudinal section through the sealing arrangement as in  FIG. 1 , 
         FIG. 3  a perspective view of the sealing arrangement as in  FIG. 1 , 
         FIG. 4  a perspective, exploded longitudinal sectional representation of the valve from  FIG. 1 , 
         FIG. 5  a perspective representation of the sealing arrangement corresponding to  FIG. 3 , with a different reciprocal position of the supports, 
         FIG. 6  a longitudinal section through the sealing arrangement as in  FIG. 5 , 
         FIG. 7  a perspective, longitudinal sectional view of the valve from  FIG. 1 , 
         FIG. 8  a perspective view of a second embodiment of a four-stage sealing arrangement, where the total of three supports thereof are axially removed from each other, 
         FIG. 9  a side view of the sealing arrangement from  FIG. 8 , wherein the supports bear against one another, 
         FIG. 10  a side view of the sealing arrangement from  FIG. 9 , rotated by 90° about its central longitudinal axis, and 
         FIG. 11  a longitudinal section taken along the line XI-XI in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Detailed reference will now be made to the drawings in which examples embodying the present invention&#39;s various aspects will be shown. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description refer to like or similar parts. 
     A vent valve according to the disclosure, valve  1  for short, comprises, for example, a cylindrical housing  2 , on the underside of which a base  3  is molded, and which on its upper side is closed with a cover  4 . At an approximately central position, the cover  4  has a connection piece  5 , which defines a vent opening  6 . On the cover  4 , a flange  7  is attached, with which the valve  1  can be fixed to an upper tank wall. The housing  2  thereby extends through a tank opening into the interior of the tank. The flange  7  has a connection  8 , with which a vent line can be connected. A ventilation channel  9 , which is connected with the vent opening  6 , passes through the connection  8 . A gas-tight seal is attained between the connection piece  5  of the cover  4  and the flange  7  using an O-ring  10 , which is inserted in a peripheral groove  11  of the connection piece  5 . 
     A cage  12 , having an approximately cylindrical peripheral wall ( 12   a ), is molded onto the underside of the cover  4 , where the underside of the cage is open and receives a sealing arrangement  13  (or  70  in the case of  FIGS. 8-11 ) in an axially movable manner. The sealing arrangement  13  (also  70 ) is connected with a float  14 , which is movable in the direction of the central longitudinal axis  15  of the housing  2 . The float  14  has a hollow interior and a central peg  16  that extends approximately to the lower end of the float, where the peg is held in a guide sleeve  17  in an axially movable manner. The guide sleeve  17  is molded onto the base  3 , the interior of the guide sleeve being connected via an opening  18  in the base with the interior of the tank. Approximately plate-shaped ribs  19  protrude radially inwards from the inner wall of the float  14 . A helical compression spring  20  is arranged within the central space of the float surrounded by the ribs  19 , where the helical compression spring acts upon the float  14  with a force directed upwards, i.e., towards the vent opening  6 . The float  14  has an upper longitudinal section  22  with a reduced diameter. A flange  23 , projecting radially outwards, is molded onto the face side of the longitudinal section  22 , where the under side of the flange has a stop face  24  running approximately in a radial plane (radial with respect to the central longitudinal axis  15 ). 
     In the face side  26  of the longitudinal section  22 , there is a central recess  25  from the base of which a peg  27 , which is arranged coaxially to the central longitudinal axis  15 , extends outward in the axial direction. The peg  27  ends at an axial distance before the face side  26  of the longitudinal section  22 . The recess  25  is ring-shaped, in cross-section or viewed from the top, due to the presence of the peg  27 . A sealing element  28  is arranged in the recess  25 . This is formed, for example, by a circular disk-shaped plate  29  and several webs  30 . The webs  30  are arranged on the underside, or on the side of the plate  29  facing away from the vent opening  6 , and are uniformly distributed over its perimeter. The webs  30  are radially broadened and project to a certain extent beyond the edge  31  of the plate  29 . The webs  30  are arranged in the ring-shaped recess  25 . The plate  29  bears with its underside against the peg  27 . The webs  30  extend, in each case, into a window  32  ( FIG. 4 ) assigned to them in the longitudinal section  22 . The windows  32  extend in the direction of the central longitudinal axis  15 , which results in a certain axial mobility of the sealing element  28 . The webs  30  have a stop face  33 , running approximately in a radial plane, which stop face interacts with the upper edge region  34  ( FIG. 4 ) of a window  32 . Furthermore, the sealing element  28  is guided in the recess  25  with a certain radial play, such that the plate  29  can easily tilt or adopt an oblique position relative to the central longitudinal axis  15 . 
     The sealing element  13 , already mentioned above, which has an essentially circular contour, is composed essentially of a lower support  36  and an upper support  37 . The supports  36 ,  37  are arranged after each other along the central longitudinal axis  15  and are in each case penetrated by a throughchannel  35  or  48 , respectively, running coaxially to the central longitudinal axis  15 . On the upper sides facing towards the vent opening  6 , and on the lower sides of the support  36 ,  37  facing the float  14 , in each case, a sealing element  45 ,  51 ,  57 ,  55  is arranged that is coaxial with respect to the central longitudinal axis  15 . The supports  36 ,  37  are, in each case, movable in the direction of the central longitudinal axis  15  of the valve housing  2  relative to each other and relative to the float by a predetermined distance between a closed position and an open position. In the closed position of the lower support  36 , its upper-side sealing element  51  formed as a planar seat bears against the lower-side sealing element  57  of the upper support  37 , which sealing element projects in the shape of a ring lip. In the closed position of the upper support  37 , its upper-side sealing element  55 , which is a ring lip projecting from the upper side of the support  37 , interacts with a sealing element  56  ( FIG. 1 ) formed as a planar seat surrounding the vent opening  6 . The lower-side sealing element  45  of the lower support  36 , which sealing element is a projecting ring lip, interacts with the sealing element  28  present on the float  14 . In each case, two sealing elements  55 / 56 ,  51 / 57 ,  45 / 28  assigned to each other cooperate to define an opening cross-section  61 ,  62 ,  63 , the size of the successive opening cross-sections decreasing towards the float  14 . Therefore, the opening cross-section  62  (sealing element pair  51 / 57 ) is smaller than the opening cross-section  61  (sealing element pair  55 / 56 ) and larger than the opening cross-section  63  (sealing element pair  45 / 28 ). The named sealing element pairs  55 / 56 ,  51 / 57 ,  45 / 28  form the three stages of the valve. 
     The lower support  36  is formed essentially from a circular disk  38  and multiple arms  39  distributed over its periphery, which are formed in the manner of wall sections curved in an arc-shaped manner, extending downwards from its edge  38   a  in the direction of the central longitudinal axis  15 . Projections  40 , protruding radially inwards, are molded onto the free ends of the arms  39 . For fixing the lower support  36 , it is placed on the longitudinal section  22  of the float  14 , the projections  40  with angled surfaces  42  striking on the flange  23  and in the process being moved radially outwards. After the projections  40  are past the flange  23 , they move radially inwards again. The projections  40  then interact with the stop face  24  of the flange  23  in the sense of an axially active undercut, whereby the support  36  is fixed on the longitudinal section  22  with axial play. 
     The arms  39 , three in total, are separated from each other in the peripheral direction by recesses  43  and uniformly distributed in the peripheral direction. The circular disk  38  is centrally penetrated by a through channel  35  extending coaxially to the central longitudinal axis  15 . An inner region ( FIG. 2 ) of the circular disk  38 , bordering on the through channel  35 , is composed of an elastomer material. This material projects on the lower side of the circular disc  38  in the form of the sealing element  45  that opens in a funnel-shaped manner. The cross-sectional area of the through channel  35  is smaller than the cross-sectional area of the vent opening  6 . The axial length of the arms  39  and the axial position of the projections  40  located on them are chosen such that the lower support  36  is held on the float or on its longitudinal section  22  in an axially movable manner. Therefore, when the float—assuming a closed valve—moves downwards, the sealing element  28  can move away from the sealing element  45  of the support  36 , whereby the opening cross-section  63  is released. On the upper side, an essentially tubular section-shaped part  46  is inserted in the circular disk  38 , which part surrounds the upper longitudinal section of the through channel  35 , and on the upper face side of which a radially extending flange  47  is molded, which bears against the upper side of the circular disk  38 . The upper side of the flange  47  forms the sealing element  51 , which interacts with the sealing element  57  of the upper support  37 . 
     The upper support  37  is formed essentially from a circular ring  49 , on the underside of which the arms  50  are molded that extend axially or in the direction of the central longitudinal axis  15 , and that are also formed like wall sections curved in an arc-shaped manner. The arms  50  are uniformly distributed over the periphery of the circular ring  49 . Projections  52 , which protrude radially inwards, are molded on their free ends. The projections  52  engage behind a stop face  64  ( FIG. 2 ) facing the float  14 , on the underside of the lower support  36 . 
     Regardless of whether the sealing arrangement  13  comprises two or more supports, it is advantageous if a region  65  of a support, where the region supports a stop face  64  or is engaged from behind by a projection, is set back radially inwards at least by an extent corresponding to the thickness of an arm. In the exemplary embodiment according to  FIGS. 1 through 7 , this is accomplished in that windows  53 , opening upwards, are present in the arms  39  of the lower support  36 , where in each case, an arm  50  of the upper support  37  can be at least partially slid into the windows. The length of the arms  50  and the axial position of the projections  52  are dimensioned in the axial direction such that the second support  37  is fixed in an axially movable manner to the first support  36 . Thus, it is guaranteed that the upper-side sealing element  51  of the lower support  36  and the lower-side sealing element  57  of the upper support  37  are brought into mutual contact and can be removed again from each other. 
     The circular ring  49  supports an elastomer element  54 , which is essentially formed as a funnel opening towards the vent opening  6 , the upper edge of the funnel projecting axially above the circular ring  49  forming the sealing element  55 , which interacts with the sealing element  56  surrounding the vent opening  6 . The lower edge of the elastomer element  54  that forms the sealing element  57 , also expands in a funnel-like manner and extends beyond the lower side of the support  37 . 
     The fixing of the sealing arrangement  13  in the cage  12  with axial mobility is accomplished in that locking projections  58 , protruding radially outwards on the first support, engage in windows  59 , which are present in the cage  12 , and in each case, interact with the lower edge  66  ( FIG. 6 ) of a window  59 . The locking projections  58  are arranged on wall regions  60  of the first support  36 , which connect two arms  39  to one another that are adjacent in the peripheral direction. 
     The valve described above or its sealing arrangement  13  is embodied in a three-staged manner. Naturally, more than 3 stages are also conceivable, for instance 4, 5 or even more, which, for example, are realized in the manner described above. A continuous opening of the vent opening can be attained through a larger number of stages, i.e., the pressure differences between the individual stages are lower, the more stages are present. 
     In the following, the mode of operation of the valve  1  is briefly explained: The vent opening  6  is closed when the float  14  moves upwards, for instance, due to an increasing level of fuel. In the closed state, the sealing element  28  or its plate  29 , respectively, is pressed against the lower-side sealing element  45  of the lower support  36 , the upper side of the flange  47  or the sealing element  51  is pressed against the lower-side sealing element  57  of the upper support  37 , and its upper-side sealing element  55  is pressed against the sealing element  56  surrounding the vent opening  6 . With absent or reduced pressure inside the tank, the weight of the float  14  is sufficient to move the sealing arrangement  13  collectively axially downwards, whereby the vent opening  6  is released. However, if during the closure of the vent opening  6 , pressure builds up inside the tank, the multiple stage quality of the sealing arrangement  13 , or of the valve  1 , come into action. Initially, the sealing element  28  is removed from the lower support, whereupon the opening cross-section  63  is released and gas (fuel vapor/air mixture) can flow to the outside via the through channels  35 ,  48 , which are connected to one another, and via the vent opening  6 , whereby the pressure inside the tank is partially reduced. The float  14  bears with its flange  23  against the projections  40  of the lower support  36 , such that this support is loaded with the weight of the float. When the pressure inside the tank has reached an appropriate limit, the force exerted by the weight of the float  14  onto the lower support  36  is sufficient to move it axially downwards, whereby the opening cross-section  62  is released. Now a substantially greater flow of gas can leave the interior of the tank via the through channel  48  and the vent opening  6 . Now a pressure value is quickly attained at which the force exerted by the weight of the float  14  and the weight of the first support  36  on the second support  37  is sufficient to move the second support  37  axially downwards, too. The lower support  36  thereby bears against the projections  52  of the upper support  37 . The latter is thereby also moved axially downwards, where its upper-side sealing element  55  is removed from the sealing element  56  encompassing the vent opening  6 , and the opening cross-section  61  is released. Thereupon, an aeration and ventilation of the tank is again possible, whereupon pressure still remaining inside the tank can be completely relieved via the vent opening  6 , whose flow cross-section is slightly smaller than the opening cross-section  61 . 
     In the  FIGS. 8 through 11  an alternate sealing arrangement  70  is shown that can be used in the type of valve described in the preceding. The sealing arrangement  70  has four stages, it comprises in total three supports, namely an upper support  71 , a middle support  72  arranged below it, and lastly, arranged below this a lower support  73 . The upper support  71  has a form which corresponds to that of the upper support  37  of the exemplary embodiment described above. The projections  52  present on the arms  50  engage behind a stop face  67  present on the lower side of the middle support  72 . Accordingly, the same individual parts or individual parts acting in the same way are provided with the same reference numbers. The middle support  72  is formed in an approximately disk-shaped manner and is penetrated by a central through channel  74  extending coaxially to the central longitudinal axis  15  of the valve  1  or of the sealing arrangement  70 . The diameter of the through channel  74  is smaller than the smallest diameter of the through channel  48  of the upper support  71 . The middle support  72  comprises marginal arms  75 , i.e., arms that have a radial distance to the central longitudinal axis  15  and a distance in the peripheral direction and that are formed, for instance, in the manner of arc-shaped wall segments, on the free ends of which arms, in each case, a projection  76  extending radially inwards is present, which engages behind a stop face  77  ( FIG. 11 ) present on the lower support  73 . The arms  75  have a window  78  opening upwards, are therefore U-shaped, as can be seen in the side view according to  FIGS. 9 and 10 . 
     The lower support  73  is formed similarly to the middle support  72 . Its total of three arms  79  uniformly distributed in the peripheral direction are provided on their free ends with a projection  80  extending radially inwards, which in the assembled state engages behind the flange  23  of the float  14 . Windows  82  opening upwards are present in the arms  79 . A projection  83 , bridging the windows  82 , is molded onto the outer side of the arms  79  where in the assembled state said projection projects into a window  59  present in the cage  12  and interacts with the lower edge  66  ( FIG. 4 ,  7 ) of this window in the sense of a stop. Those regions of a support  72 ,  73  which are engaged from behind by the arms  50 ,  75  of a support  71 ,  72  arranged above, or by the projections  52 ,  76  molded onto the arms, are set back radially inwards. In the case of the middle support  72 , these are the regions  85  extending in the peripheral direction between the arms  75 , or in the case of the lower support  73 , the regions  86 . The extent by which the regions  85 ,  86  are offset radially inwards, corresponds approximately to the thickness of the arms  50  or the arms  75 . This embodiment is advantageous in that the sealing arrangement  70 , as well as the sealing arrangement  13  described above, have a small overall width and a small outer circumference and correspondingly require a small installation space. 
     The upper-side sealing element  86  of the middle support  72  interacting with the lower-side sealing element  57  of the upper support  71 , is formed by a region of the upper side of the support  72  surrounding the through channel  74  and its upper-side outlet opening, respectively. On the lower side of the support  72 , an elastomer element  87  is arranged that has an edge projecting downwards surrounding the through channel  74  or its lower-side outlet opening, which edge forms a sealing element  88 . The sealing element  88  interacts with an upper-side sealing element  89  of the lower support  73 . The sealing element  89  is formed by a surface region that surrounds the central through channel  90  of the lower support  73  or its upper-side outlet opening. On the lower side of the lower support  72 , an elastomer element  92  is also arranged at which also an edge projecting downwards, which surrounds the through channel  90  or its lower-side outlet opening, and forms a sealing element  93  interacting with the sealing element  28  of the float  14 . The sealing elements  55 / 56 ,  57 / 86 ,  88 / 89  and  93 / 28  interacting with one another, their size decreasing in the direction towards the float  14 . The four-stage mode of operation of a valve equipped with the sealing arrangement  70  corresponds to that of the valve operating in a three-stage manner described above, except that due to the additional stage, it is optimized especially with regards to a fast re-opening after the development of pressure inside the tank. 
     While preferred embodiments have been shown and described, those skilled in the art will recognize that changes and modifications may be made to the embodiments without departing from the scope and spirit of the invention. For example, specific styles and dimensions of various elements of the illustrated embodiments and materials used for the elements may be altered to suit particular applications or industry regulations. It is intended that all such changes and modifications as such fall within the scope of the appended claims and their equivalents.