Abstract:
According to an aspect of the present invention, there is provided a float valve apparatus including: a housing including: a partition wall dividing an internal space into lower and upper spaces and having an opening therein; a ventilation pipe communicating the upper space with an outside; a valve seat formed at the opening; and a communication hole communicating the lower space with the outside; a float that is valve vertically slidably movable in the lower space and that upwardly floats in accordance with liquid flowing thereinto to open and close the opening; an upward urging spring urging the float valve from the housing toward the opening; and a support spring disposed inside the upward urging spring to support the float valve to not contact with a bottom surface of the housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from Japanese Patent Application No. 2008-133449 filed on May 21, 2008, and from Japanese Patent Application No. 2008-175732 filed on Jul. 4, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    An aspect of the present invention relates to a float valve apparatus suitable for use as a fuel fill-up control valve, a cut valve or a similar valve to be mounted on, for example, the fuel tank of a car. 
         [0004]    2. Description of the Related Art 
         [0005]    On the fuel tank of a car, there is mounted a fuel fill-up control valve which, when fuel is supplied up to the fill-up position of the fuel tank, closes the opening of the fuel tank communicating with the outside to stop the supply of the fuel. 
         [0006]    Also, there is provided a cut valve which not only releases fuel steam to a canister but also, when the car jolts heavily while running or the car rolls over, closes an opening communicating with the canister to prevent the fuel from leaking to the outside. 
         [0007]    As such fuel fill-up control valve and cut valve, there is employed a float valve apparatus structured such that it can be moved upward according to a rise in the liquid surface of the fuel to close the opening of the valve apparatus. 
         [0008]    However, in such float valve apparatus, when the car runs along a rough road, the float valve can collide with the bottom surface of a housing to generate a strange sound. 
         [0009]    JP-UM-H06-040552-A discloses a fuel leakage preventive valve structured such that a float valve disposed within a room formed in the housing can be moved up and down. Specifically, in the disclosed fuel leakage preventive valve, a separately-formed elastic buffer is interposed between the lower surface of the float valve and the receiving surface of the housing disposed opposed to the float valve lower surface. Since the lower surface of the float valve is elastically supported by the elastic buffer from the opposed receiving surface of the housing, even when the float valve is going to move up and down within the room due to the running vibration of the car or the like, the strong collision therebetween are buffered, and the generation of the loud strange sound is effectively reduced. 
         [0010]    JP-H07-035255-A discloses a fuel cut valve including: a valve housing mounted on the upper surface portion of a fuel tank; a valve port formed within the valve housing and communicating with the ventilation line for fuel steam through a downstream side passage projecting outwardly of the housing; and a float valve for detecting the liquid surface level inside the fuel tank to open or close the valve port. In this fuel cut valve, a slit is formed in the bottom portion of the valve housing, whereby a cantilever valve body support portion is formed as an integral portion. 
         [0011]    However, in JP-UM-H06-040552-A, since the elastic buffer for supporting the lower surface of the float valve is disposed outside a spring for urging the float valve upwardly, the outside diameter of the elastic buffer is large, which makes it difficult to set the load, free length and the like of the elastic buffer with high accuracy. Also, since, when the float valve is moved down in an inclined manner, the load concentrates on the local portion of the large outside diameter elastic buffer, there is raised a possibility that the collision of the float valve with the housing cannot be controlled sufficiently. 
         [0012]    In JP-H07-035255-A, when the valve housing is formed of hard resin from the viewpoint of heat resistance, the elasticity of the cantilever valve body support portion is poor, which lowers the hitting sound reduction effect when the valve housing is collided with the float valve. Also, when the cantilever valve body support portion is formed thin in order to enhance the elasticity thereof, it is easy to break. 
       SUMMARY OF THE INVENTION 
       [0013]    According to an aspect of the present invention, there is provided a float valve apparatus including: a housing including: a partition wall that divides an internal space of the housing into a lower space and an upper space and that has an opening formed therein; a ventilation pipe that is formed to communicate the upper space with an outside; a valve seat that is formed at the opening of the partition wall; and a communication hole that is formed to communicate the lower space with the outside; a float valve that is disposed to be slidably movable in a vertical direction in the lower space and that is configured to be upwardly floated by liquid flowing into the lower space through the communication hole so as to open and close the opening; an upward urging spring that is disposed between a lower surface of the float valve and a bottom surface of the housing to urge the float valve toward the opening; and a support spring that is disposed inside the upward urging spring to support the float valve so as to be prevented from contacting with the bottom surface of the housing in a state where the float valve is moved to a lower-most position. 
         [0014]    According to such configuration, for example, when liquid such as the fuel of a car flows into the housing and the liquid surface of the liquid rises up to a given height or more, the float valve is moved upward to close the opening formed in the partition wall, thereby being able to prevent the liquid from flowing into the upper space through the opening. For example, as applied to the fill-up control valve of the fuel tank of the car or to the cut-off valve thereof, the fill-up control in the fuel supply operation can be carried out and the leakage of the fuel to the outside can be prevented. 
         [0015]    Even when the liquid surface of the fuel varies suddenly due to the jolting movement of a car while it is running and the float valve is thereby caused to move down suddenly, the float valve is resiliently received by the support spring and thus the lower surface of the float valve is prevented from colliding with the bottom surface of the housing, which can reduce the hitting sounds of the float valve greatly. 
         [0016]    Since the support spring is disposed inside the upward urging spring and the outside diameter of the support spring is thereby set smaller than the outside diameter of the upward urging spring, the load of the spring, the free length of the spring and the like can be set with high accuracy. As a result of this, a proper clearance can be set between the lower surface of the float valve and the bottom surface of the housing, thereby being able to reduce the hitting sounds effectively. 
         [0017]    Since the support spring is disposed inside the upward urging spring, even when the float valve moves down in an inclined manner, the float valve is supported stably, which can attain the smooth lowering operation of the float valve. 
         [0018]    According to another aspect of the present invention, there is provided the float valve apparatus, wherein the float valve includes: a support spring storage recess that is formed in a central portion of the lower surface of the float valve to store the support spring therein and to have a depth larger than a free length of the support spring; an upward urging spring storage recess that is formed at an outer periphery of the support spring storage recess to store the upward urging spring; and a tubular partition wall that is formed to partition the support spring storage recess and the upward urging spring storage recess, wherein the housing includes a projection that is formed to protrude from a central portion of the bottom surface of the housing and that supports a lower end portion of the support spring, and wherein the support spring is inserted into the support spring storage recess so that the lower end portion thereof is supported by the projection. 
         [0019]    According to such configuration, since the support spring and upward urging spring are respectively stored into their associated support spring storage recess and upward urging spring storage recess which are formed with the partition wall between them, the two springs can be prevented from being twined with each other or from interfering with each other when they are assembled or used. This can enhance the assembling operation and also allows the springs to fulfill their spring operations in use. 
         [0020]    The support spring storage recess is formed to have a depth larger than the free length of the support spring, and the support spring is inserted into the support spring storage recess so that the lower end portion of the support spring is supported by the projection provided on the bottom surface of the housing. This can surely prevent mutual contact between the support spring and upward urging spring and also can prevent the support spring from flying out of its position to thereby be able to hold it at its given position surely. 
         [0021]    According to still another aspect of the prevent invention, there is provided the float valve apparatus, wherein the projection includes: a support portion that is formed at a proximal side thereof to support the lower end portion of the support spring and that is to slidingly contact with an inner periphery of the support spring storage recess when the float valve moves vertically; and an insertion portion that upwardly extends from the support portion to have a diameter reduced with respect to the support portion and that is to be inserted into an inner periphery of the support spring. 
         [0022]    According to such configuration, while the support portion of the projection is supporting the lower end of the support spring at a high position, the support spring can be supported stably by the insertion portion which is inserted into the inner periphery of the support spring. Since, when the float valve moves up and down, the support portion of the projection is slidingly contacted with the inner periphery of the support spring storage recess, the float valve can be prevented from inclining or de-centering, thereby being able to move the float valve up and down smoothly. 
         [0023]    According to still another aspect of the prevent invention, there is provided the float valve apparatus, wherein at least part of the projection is formed of a plurality of ribs radially projecting from a center axis thereof. 
         [0024]    According to such configuration, for example, since at least one of the support portion and insertion portion constituting the projection is made of plural ribs respectively projected radially, even when the fuel flows into the inner periphery of the tubular portion of the projection, the fuel can be discharged smoothly therefrom, which can reduce an influence on the rising and falling operation of the float valve. Also, when the support portion is made of radially extending plural ribs, the contact area of the tubular portion with the inner periphery of the peripheral wall is reduced, thereby reducing the sliding resistance of the float valve in the rising and falling operation thereof. 
         [0025]    According to still another aspect of the prevent invention, there is provided the float valve apparatus, wherein the float valve includes a support spring storage recess that is formed in a central portion of the lower surface of the float valve to store the support spring therein, and wherein an upper end portion of the support spring is fixed to an inner end portion of the support spring storage recess. 
         [0026]    According to such configuration, since the support spring is inserted into the support spring storage recess formed in the central portion of the lower surface of the float valve and the upper end portion of the support spring is fixed to the inner end portion of the support spring storage recess, the float valve and support spring are combined with each other. As a result of this, the support spring is allowed to rise and fall together with the float valve, which prevents that, when the float valve rises and falls, the support spring slidingly contacts with the inner periphery of the support spring storage recess and thus can provide resistance against the rising and falling operation of the float valve. 
         [0027]    According to still another aspect of the prevent invention, there is provided the float valve apparatus, wherein the support spring storage recess is formed to have a depth larger than a free length of the support spring, wherein the housing includes a projection that is formed to protrude from a central portion of the bottom surface of the housing, and wherein the projection slidingly contacts with an inner periphery of the support spring storage recess when the float valve moves vertically and contacts with a lower end portion of the support spring when the float valve moves downward. 
         [0028]    According to such configuration, the support spring is inserted into the support spring storage recess formed to have a depth larger than the free length of the support spring and also the projection provided on the bottom surface of the housing is inserted into the support spring storage recess. This can surely prevent mutual interference between the support spring and upward urging spring disposed outside the support spring. Since, when the float valve rises and falls, the projection is to be slidingly contacted with the inner periphery of the support spring storage recess, the rising and falling operation of the float valve is guided such that the float valve is prevented against inclination and de-centering, whereby the float valve can be moved up and down smoothly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]      FIG. 1  is an exploded perspective view of an embodiment of a float valve apparatus according to the invention. 
           [0030]      FIG. 2  is a section view of a float valve, a support spring, an upward urging spring and a lower cap respectively included in the float valve apparatus. 
           [0031]      FIG. 3  is a section view of the float valve apparatus, showing a state in which the float valve apparatus is mounted on a fuel tank, and the liquid surface of fuel exists in the lower position thereof and a float valve is lowered. 
           [0032]      FIG. 4  is a section view of the float valve apparatus, showing a state in which the fuel liquid surface rises and the float valve closes an opening. 
           [0033]      FIG. 5  is an explanatory view of the assembling procedure for the float valve apparatus. 
           [0034]      FIG. 6  is a section view of a float valve, a support spring, an upward urging spring and a lower cap respectively included in a second embodiment of a float valve apparatus according to the invention. 
           [0035]      FIG. 7  is a section view of the float valve apparatus according to the second embodiment, showing a state in which the float valve apparatus is mounted on a fuel tank, and the liquid surface of fuel exists in the lower position thereof and a float valve is lowered. 
           [0036]      FIG. 8  is a section view of the float valve apparatus according to the second embodiment, showing a state in which the fuel liquid surface rises and the float valve closes an opening. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0037]    Next, description will be given below of an embodiment of a float valve apparatus according to the invention with reference to  FIGS. 1 to 5 . 
         [0038]    As shown in  FIG. 1 , this float valve apparatus  10  includes a housing  20 , a float valve  40 , an upward urging spring  60  and a support spring  70 . 
         [0039]    Referring to  FIG. 3  together with  FIG. 1 , the housing  20  includes a housing main body  21 , an upper cap  22  and a lower cap  23 . In the upper portion of the housing main body  21 , a partition wall  24  is provided to divide the inside portion of the housing  20  into an upper space  25  and a lower space  26 . 
         [0040]    An opening  27  is formed in the partition wall  24 , and the lower edge portion of the opening  27  forms a valve seat  27   a.  A connecting pipe  28  and a connecting pipe  29  (respectively functioning as ventilation pipes) are formed on the side walls of the housing main body  21 . The base end sides of the connecting pipes  28  and  29  are respectively opened in the upper space  25  that is closed by the upper cap  22 . 
         [0041]    On the side wall upper portion of the housing main body  21 , a pair of flanges  30  and  30  are formed to respectively extend in the opposing directions (see  FIG. 1 ), and the float valve apparatus  10  is mounted onto the ceiling wall  80  of a fuel tank through the flanges  30 . The upper cap  22  is fixed to the upper surface of the housing main body  21  by thermal welding or by similar fixing means. 
         [0042]    Plural engaging pawls  31  are provided to project from the side wall lower portion of the housing main body  21 . Correspondingly to the engaging pawls  31 , tongue pieces  31  are provided on the lower cap  23  to erect therefrom; and engaging holes  33  into which the engaging pawls  31  are to be fitted are formed in the tongue pieces  32 . Therefore, when the tongue pieces  32  of the lower cap  23  are aligned to the engaging pawls  31  of the housing main body  21  and the lower cap  23  is pushed into the housing main body  21  toward the lower surface thereof, the engaging pawls  31  are fitted into the engaging holes  33  of the tongue pieces  32 , whereby the lower cap  23  is mounted onto the housing main body  21 . 
         [0043]    Referring now to  FIG. 2  together with  FIGS. 1 and 3 , the lower cap  23  has an upward urging spring receiving base  34  at the central portion of the bottom surface thereof and a disk-shaped projecting portion  34   a  at the central portion of the upward urging spring receiving base  34 . The upward urging spring  60  is supported so that the lower end portion thereof is contacted with the upward urging spring receiving base  34 . Further, a projection  35  having the cross section of a cross-like shape is formed on the central portion of the disk-shaped projecting portion  34   a  to erect therefrom. 
         [0044]    The projection  35  has a support portion  36  having a large diameter at the lower portion thereof and an insertion portion  37  having a reduced diameter at the upper portion thereof. The insertion portion  37  of the projection  35  is inserted into the inner periphery of the support spring  70 , while the lower end portion  70   b  of the support spring  70  is contacted with and supported by the upper end portion of the support portion  36 . 
         [0045]    Referring again to  FIG. 1 , the float valve  40  includes plural guide fins  41  in the lower portion thereof. The guide fins  41  are formed to have size matching to the inner periphery of the lower space  26  of the housing  20 . The float valve  40  includes a base portion  42  having a relatively large diameter and a head portion  43  having a slightly reduced diameter. The guide fins  41  are extended outwardly from the base portion  42  respectively. 
         [0046]    On the upper end face of the head portion  43 , a valve member  44  made of an elastic seal member is formed. As shown in  FIGS. 2 and 3 , a support spring storage recess  45  is formed on central portion of the lower surface of the float valve  40 . On the outer periphery of the support spring storage recess  45 , a tubular-shaped partition wall  46  is formed, and in the outer periphery of the partition wall  46 , an upward urging spring storage recess  47  is formed. The upward urging spring  60  is structured such that the upper end portion thereof is inserted into the upward urging spring storage recess  47  and the lower end portion thereof is contacted with and supported on the upper surface of the upward urging spring receiving base  34 . 
         [0047]    The support spring  70  is installed in the following manner: the insertion portion  37  of the projection  35  is inserted into the inner periphery of the support spring  70 ; the lower end portion  70   b  thereof is supported on and by the upper end portion of the support portion  36 ; and the upper end portion  70   a  thereof is inserted into the support spring storage recess  45 . The spring load of the support spring  70  is set to be three to forty times as large as the weight of the float valve  40 . 
         [0048]    As shown in  FIG. 3 , when the float valve  40  is lowered, the length L from the upward urging spring receive base  34  to the upper end portion  70   a  of the support spring  70  is set to be larger than the depth D from the lower surface of the float valve  40  to the inner end portion (the surface with which the support spring  70  contacts when the float valve  40  is lowered) of the support spring storage recess  45 . As a result of this, when the float valve  40  is moved down to the lower-most position, the upper end portion  70   a  of the support spring  70  is contacted with the inner end of the support spring storage recess  45 , thereby being able to form a clearance G between the lower surface of the float valve  40  and the upper surface of the upward urging spring receiving base  34 . 
         [0049]    Since the free length of the support spring  70  is set smaller than the depth D of the support spring storage recess  45  as shown in  FIG. 4 , even in a state where the float valve  40  floats up to close the opening  27  by the valve member  44 , the support spring  70  is prevented from being exposed from the support spring storage recess  45 . 
         [0050]    Next, description will be given below of the operation of the float valve apparatus  10 . 
         [0051]      FIGS. 3 and 4  show an example in which the float valve apparatus  10  is used as a fuel fill-up control valve for a fuel tank. As described above, the float valve apparatus  10  is mounted on the lower surface of the ceiling wall  80  of the fuel tank. Since the liquid surface of the fuel F is raised gradually as the fuel F is supplied, the air and fuel steam existing within the fuel tank must be discharged to the outside. In this case, in the float valve apparatus  10 , the air and fuel steam within the fuel tank are allowed to flow into a lower space  26  within the housing  20  from plural communication holes  38  respectively formed in the lower cap  23 , then flow through the opening  27  into the upper space  25 , and are sent to a canister disposed in the outside of the fuel tank through a ventilation line (not shown) which is connected to the connecting pipe  29 . 
         [0052]    Therefore, the air and fuel steam of the volume corresponding to the volume of the supplied fuel are discharged to the outside, whereby the supply of the fuel is progressed. As shown in  FIG. 4 , when the liquid surface of the fuel F comes near to the upper limit, the fuel flows into the lower space  26  of the housing  20  from the openings of the lower cap  23 , a floating force is applied to the float valve  40 , and the float valve  40  is floated by the floating force and by the urging force of the support spring  70 . 
         [0053]    When the liquid surface of the fuel F reaches the upper limit, the valve member  44  of the float valve  40  is contacted with the valve seat  27   a  of the opening  27  to close the opening  27 . As a result, the air and fuel steam within the fuel tank become unable to escape therefrom to the outside, and the internal pressure of the fuel tank is raised. Thus, the fuel supply using a fuel supply gun is automatically stopped by a known mechanism. That is, the fuel fill-up control in the fuel supply is carried out in this manner. 
         [0054]    On the other hand, while a car is running, especially, when the car is running along a rough road, the float valve  40  may be heavily moved up and down due to the vibration of the car. According to the float valve apparatus  10 , as shown in  FIG. 3 , when the float valve  40  moves down, the upper end portion  70   a  of the support spring  70  is contacted with the inner end of the support spring storage recess  45  so that the float valve  40  is supported to provide the clearance G between the lower surface of the float valve  40  and the upper surface of the upward urging spring receive base  34 . As a result, the lower end portion of the float valve  40  is prevented from colliding with the lower cap  23 , and the support spring  70  absorbs the vertical heavy movement of the float valve  40 , thereby preventing the generation of a big striking sound. 
         [0055]    Since the support spring  70  is situated inside the upward urging spring  60  and is formed to have a small spring diameter, the spring load, free length and the like thereof can be set with high accuracy. Further, even when the float valve  40  is moved down in an inclined state due to the inclination of the car, the movement of the float valve  40  is guided by the support portion  36  of the projection  35  inserted into the support spring storage recess  45 , whereby the float valve  40  is stably supported by the support spring  70 . As a result, the lower surface of the float valve  40  is surely prevented from colliding with the lower cap  23 . 
         [0056]    The depth D of the support spring storage recess  45  is set longer than the free length of the support spring  70 . And, the state in which the support spring  70  is stored in the support spring storage recess  45  is maintained even when the float valve  40  is floated to close the opening  27  as shown in  FIG. 4 . As a result, it is prevented that the support spring  70  and upward urging spring  60  is twined together to lead to the poor operation of the float valve. 
         [0057]    When assembling the float valve apparatus  10 , as shown in  FIG. 5 , the float valve  40  is set with the opening of the support spring storage recess  45  facing upwardly. In this state, after the support spring  70  is inserted into the support spring storage recess  45 , the upward urging spring  60  is inserted into the upward urging spring storage recess  47 . In this state, the float valve  40  is inserted into the housing main body  21  (not shown in  FIG. 5 ), and the lower cap  23  is pushed in downwardly as shown by an arrow mark in  FIG. 5 , and the float valve  40  is assembled to the housing main body  21 . Since the support spring  70  and upward urging spring  60  are respectively stored separately within the support spring storage recess  45  and upward urging spring storage recess  47  which are partitioned by the partition wall  46 , it is possible to prevent the support spring  70  and upward urging storage recess  60  from twining with each other and thus prevent such mutual twined state of them from interfering with the assembling operation of the float valve apparatus  10 . 
         [0058]    According to the present embodiment, since the projection  35  is made of ribs to have a cross-shaped cross section, the air, fuel steam and the fuel are allowed to flow into and out of the support spring storage recess  45  through clearances between the respective ribs. This can reduce the sliding resistance of the float valve  40  when the float valve  40  moves up and down. 
         [0059]    When a clearance is formed between the upper end portion  70   a  of the support spring  70  and the inner end of the support spring storage recess  45  in a state shown in  FIG. 4  where the float valve  40  is moved up, the support spring  70  may be caused to shake within the support spring storage recess  45 . Since the support spring  70  is itself elastic and also is small in mass, the shaking sounds of the support spring  70  are as low as can be neglected. In order to reduce the shaking sounds further, the lower end portion  70   b  of the support spring  70  may also be fixed to the upper surface of the support portion  36  of the projection  35 . 
         [0060]      FIGS. 6 to 8  respectively show another embodiment of a float valve apparatus according to the invention. The substantially same parts of the present embodiment as the above-mentioned embodiment are given the same designations and thus the description thereof is omitted here. 
         [0061]    Referring now to the structure of a float valve apparatus  10   a  according to the present embodiment, similarly to the above-mentioned embodiment, a support spring storage recess  45  into which a support spring  70  is to be inserted is formed in the central portion of the float valve  40 . Further, a cylindrically-shaped press-fit projection  48  is formed to downwardly project from the central portion of the inner end portion (inner upper surface) of the support spring storage recess  45  with a given height and to have a larger outside diameter than the inside diameter of the support spring  70 . 
         [0062]    When the support spring  70  is pushed into the outer periphery of the press-fit projection  48  so that the support spring  70  covers the outer periphery of the portion  48 , the press-fit projection  48  is press-fitted into the inner periphery of the support spring  70 , and the upper end portion  70   a  of the support spring  70  is fixed to the inner end portion of the support spring storage recess  45 , whereby the float valve  40  and support spring  70  are combined with each other. 
         [0063]    According to the present embodiment, the press-fit projection  48  to be press-fitted into the support spring  70  is formed to have a cylindrical shape. However, the press-fit projection  48  may also be a pillar-shaped or tubular-shaped press-fit projection and may have a polygonal shape such as a square shape, a pentagonal shape and a hexagonal shape; a press-fit projection having a cross-shaped cross section; or a press-fit projection having plural plate-shaped ribs radially erected therefrom. According to the press-fit projection having the above shape, there can be provided the following advantage: when the press-fit projection  48  is pushed into the inner periphery of the support spring  70 , the corner portions of the outer periphery of the press-fit projection are strongly pressure contacted with the inner periphery of the support spring  70  locally, and the upper end portion  70   a  of the support spring  70  is firmly fixed to the inner end portion of the support spring storage recess  45 . 
         [0064]    According to the present embodiment, the press-fit projection  48  is provided to project downwardly from the support spring storage recess  45 , and the upper end portion  70   a  of the support spring  70  is fixed to the inner end portion of the support spring storage recess  45  by pressure inserting the press-fit projection  48  into the inner periphery of the support spring  70 . However, this is not limitative as means for fixing the upper end portion  70   a  of the support spring  70  and the inner end portion of the support spring storage recess  45  to each other to thereby combine together the float valve  40  and support spring  70 . 
         [0065]    For example, the support spring  70  may be previously disposed in the inside of a metal mold for injection molding the float valve  40 . In this case, the upper end portion  70   a  of the support spring  70  may be fixed to the inner end portion of the support spring storage recess  45  by insert molding the support spring  70 , thereby combining the float valve  40  and the support spring  70  together. 
         [0066]    For example, a recess may be previously formed to extend upwardly from the support spring storage recess  45  with a given depth and to have a smaller inside diameter than the outside diameter of the support spring  70 . In this case, the upper end portion  70   a  of the support spring  70  and the inner end portion of the support spring storage recess  45  are fixed to each other by press-fitting the support spring  70  into the recess, thereby combining the float valve  40  and the support spring  70  together. 
         [0067]    For example, the upper end portion  70   a  of the support spring  70  may be bonded to the inner end portion of the support spring storage recess  45  using fuel-resisting adhesive. The upper end portion  70   a  of the support spring  70  may be connected to the inner end portion of the support spring storage recess  45  by welding. A pillar-shaped or tubular-shaped projection may be provided to project from the inner end portion of the support spring storage recess  45 ; the projection may be inserted into the upper end portion  70   a  of the support spring  70 ; and the leading end outer periphery of the projection may be caulked by welding or the like, thereby fixing the upper end portion  70   a  of the support spring  70  to the inner end portion of the support spring storage recess  45 . 
         [0068]    According to the present embodiment, the free length of the support spring  70  is set smaller than the depth D (see  FIG. 7 ) of the support spring storage recess  45 . Further, in the central portion of the bottom portion of the lower cap  23 , a projection  35   a  projecting upward is provided to have a slightly reduced diameter. This projection  35   a  is structured in the following manner: the outer periphery of the projection  35   a  slidingly contacts with the inner periphery of the support spring storage recess  45  when the float valve  40  rises and falls (see  FIGS. 7 and 8 ), and the lower end portion  70   b  of the support spring  70  is contacted with the upper end portion of the projection  35   a  (see  FIG. 7 ) when the float valve  40  falls. 
         [0069]    Next, description will be given below of the operation of the float valve apparatus  10  having the above structure. 
         [0070]    The rising and falling operations of the float valve  40  are similar to the embodiment shown in  FIGS. 1 to 5 . That is, as shown in  FIG. 7 , when the liquid surface of the fuel F is raised due to the supply of the fuel in a state where the float valve  40  is lowered, the fuel flows through a communication hole  38  into the lower space  26  and the float valve  40  is floated up; and the valve member  44  is contacted with the valve seat  27   a  to close the opening  27  when the liquid surface of the fuel F reaches the upper limit as shown in  FIG. 8 ; and after then, the fuel supply is automatically stopped due to the increased internal pressure of the fuel tank, thereby performing the fill-up control. 
         [0071]    In the float valve apparatus  10  according to the previously-described embodiment shown in  FIGS. 1 to 5 , the lower end portion  70   b  of the support spring  70  is supported by the projection  35  provided on the lower cap  23  (see  FIGS. 3 and 4 ), and the support spring storage recess  45  is formed to have a sufficient inside diameter in order to prevent the support spring  70  from slidingly contact with the inner periphery of the support spring storage recess  45  when the support spring  70  is inclined due to the rising and falling operation of the float valve  40 . If the support spring  70  slidingly contacts with the inner periphery of the support spring storage recess  45 , the resistance against the rising and falling operation of the float valve  40  might be generated and the accurate operation of the float valve  40  might be affected. 
         [0072]    On the other hand, in the float valve apparatus  10   a  according to the present embodiment, the upper end portion  70   a  of the support spring  70  is inserted into the support spring storage recess  45  formed in the central portion of the lower surface of the float valve  40 , and the upper end portion  70   a  is fixed to the inner end portion of the support spring storage recess  45 , thereby combining the float valve  40  and support spring  70  with each other. As a result, for example, as shown in  FIG. 8 , when the float valve  40  rises and falls, the support spring  70  rises and falls together with the float valve  40 , and the support spring  70  is surely prevented from slidingly contacting with the inner periphery of the support spring storage recess  45 . Therefore, the resistance against the rising and falling operation of the float valve  40  is surely prevented from being caused. 
         [0073]    Also, according to the present embodiment, the support spring  70  is inserted into the support spring storage recess  45  formed to have a depth larger than the free length of the support spring  70 , and the projection  35   a  provided on the bottom surface of the housing is inserted into the support spring storage recess  45 , thereby surely preventing the mutual interference between the support spring  70  and the upward urging spring  60  disposed outside the support spring  70 . Further, when the float valve  40  rises and falls, the projection  35   a  slidingly contacts with the inner periphery of the support spring storage recess  45  (see  FIG. 8 ). As a result, the rising and falling operation of the float valve  40  is guided, and the inclination and de-centering of the float valve  40  is prevented, thereby allowing the float valve  40  to rise and fall smoothly. 
         [0074]    According to an aspect of the present invention, there is provided the float valve apparatus in which the float valve is elastically received by the support spring even when the liquid surface of fuel varies suddenly to cause the float valve to move down. As a result, the lower surface of the float valve is prevented from colliding with the bottom surface of the housing, thereby reducing the hitting sounds of the float valve greatly. 
         [0075]    Also, since the support spring is disposed inside the upward urging spring, the outside diameter of the support spring can be set smaller than the outside diameter of the upward urging spring, the spring load, spring free length and the like can be set with high accuracy, and a proper clearance is surely interposed between the lower surface of the float valve and the bottom surface of the housing, thereby reducing the hitting sounds of the float valve effectively. 
         [0076]    Further, since the support spring is disposed inside the upward urging spring, even when the float valve lowers in an inclined manner, the float valve is supported stably and the lowering operation of the float valve is done smoothly.