JP2011079412A - Fuel shutoff valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel shutoff valve which surely prevents the leakage of fuel, even when fuel rapidly penetrates into a housing, without increasing the thickness of a float. <P>SOLUTION: This fuel shutoff valve is provided in a fuel tank and communicates the inside of the fuel tank with a canister. The fuel shutoff valve includes the housing and the float vertically movably provided in the housing. The housing includes an opening communicated with the canister. The float includes a valve member opening/closing the opening on the upper side. The float includes an air space having an opened lower side inside and a through-hole communicating the inside of the hosing with the air space on the upper side. The ratio of area of the through-hole to volume of the air space is ≤0.63. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention prevents a fuel cutoff gas, for example, fuel evaporative gas in a fuel tank of an automobile or the like from flowing out into the canister and adsorbing to the canister, or preventing fuel in the fuel tank from flowing out into the canister when the fuel oil level rises. The present invention relates to a fuel cutoff valve.

  An automobile or the like is provided with a fuel tank that stores fuel to be supplied to the combustion chamber of the engine. The fuel tank is provided with a ventilation system so that air commensurate with the increase or decrease of the fuel in the tank can enter and exit. This ventilation system is formed as a system that connects the inside of the fuel tank and the canister. If the fuel tank becomes full or more, the overflowed fuel flows out to the canister and wets the canister, making the canister unusable. . Therefore, a full tank control valve is provided in the upper part of the fuel tank so that when the fuel is full, the ventilation system is shut off so that air and fuel do not flow out to the canister.

  In addition to the full tank control valve, the fuel tank is provided with a fuel leakage prevention valve that is always open to the atmosphere to adjust the pressure fluctuation in the fuel tank and that closes when the vehicle tilts or rolls over. The full tank control valve and the fuel leakage prevention valve are provided separately, but for reasons such as cost increase, a fuel cutoff valve having the functions of both valves has been proposed.

  By the way, the float of the fuel shut-off valve is thin and heavy, and the material cost is high, and the molding time is required. Therefore, the float of the fuel shut-off valve is thin and the buoyancy can be obtained by utilizing the volume of the internal air space. Such a hollow float is mainly used.

  A float with a hollow air space inside has the advantage of being lightweight, and since the air volume in the air space is constant in the normal upright state of the float, a constant buoyancy generated due to the air in the air space Using this, there is an advantage that the valve closing operation by the float at the time of refueling can be performed stably. However, for example, when the vehicle inclines, rolls over, or falls down and fuel enters the housing that houses the float, part or all of the air in the air space is pushed out by the fuel. Buoyancy is reduced, the valve closing operation by the float is delayed, and the fuel leaks to the canister side.

  In order to eliminate the above problems, a fuel cutoff valve shown in FIG. 12 has been proposed. The fuel cutoff valve A includes a housing 1 and a float 3 housed in the internal space 2 of the housing 1.

  The housing 1 has an upper opening 4 above it, a lower opening 5 below it, and a lateral hole 6 on its upper peripheral wall surface. A flange 8 extending horizontally outward is formed on the upper outer peripheral wall of the housing 1. The flange 8 is attached to the upper wall surface of the fuel tank 7, and the housing 1 below the flange 8 is placed in the fuel tank 7. It is arranged in a form to be inserted into.

  Further, a seal portion 9 is formed on the lower surface of the upper opening 4 of the housing 1, and a connecting pipe having one end communicating with the upper opening 4 and the other end communicating with a canister (not shown) above the housing 1. 10 is provided. 12 actually has a diaphragm valve between the upper opening 4 and the connecting pipe 10 but is omitted.

  The float 3 is a cylindrical member whose upper part is closed, and a valve body 11 is attached to the upper part. A spring 12 is provided in the air space 3a, which is an internal space of the float 3, and assists the upward movement of the float 3. For example, when fuel in the fuel tank 7 enters the internal space 2 from the lower opening 5 during refueling or the like, the float 3 moves upward, and the upper valve body 11 comes into contact with the seal portion 9 on the lower surface of the upper opening 4. By closing the upper opening 4, the outflow of fuel from the upper opening 4 to the connecting pipe 10 is prevented.

  A plurality of slightly larger through holes 13 are provided on the upper side wall of the float 3. The through hole 13 has a function of quickly discharging the air in the air space 3a to the outside of the float 3 when the fuel in the fuel tank 7 enters the internal space 2 from the lower opening 5 regardless of the speed of the fuel that enters. It is what you have. By providing this through hole 13, the effect of buoyancy generated due to the air in the air space 3a is eliminated, and the float 3 is moved upward by the buoyancy due to the volume of the float 3 itself and the urging force of the spring 12, thereby The opening 4 is closed. As a result, the same stable valve closing characteristic can be obtained even when the float is in the normal upright state, or when the vehicle is tilted or rolls over or falls (see Patent Document 1).

Recently, there has been a strong demand to prevent fuel leakage when the fuel tank inclines or the fuel suddenly enters the housing that houses the float when the fuel tank is inclined or when refueling. If the fuel cutoff valve A answers such a request, it is necessary to increase the volume of the float 3 and increase the buoyancy of the float 3 itself. However, for example, if the wall thickness is increased in order to increase the volume of the float 3, the material cost increases accordingly.
In addition, it is necessary to provide a shielding plate at the fuel intrusion portion to alleviate rapid fuel intrusion. In this case, there is a problem that the number of parts increases and the cost increases.

Japanese Patent No. 3393788

  The object of the present invention is to more reliably prevent fuel leakage even when fuel suddenly enters the housing without increasing the thickness of the float and without increasing the number of parts. It is providing the fuel cutoff valve which can do.

  In order to achieve the above object, the present invention adopts the following configuration.

  The invention according to claim 1 is a fuel cutoff valve that is provided in the fuel tank and communicates between the inside of the fuel tank and the canister, and includes a housing and a float that is provided in the housing so as to be movable up and down. The housing has an opening that communicates with the canister, the float has a valve member that opens and closes the opening above the float, and the float has an air space that is open at the bottom. And having a through hole communicating with the inside of the housing and the air space above the housing, the ratio of the area of the through hole to the volume of the air space being 0.63 or less.

  In addition, “below” of “0.63 or less” means that zero is not included, and the lower limit value is the minimum value of holes that can be manufactured. The reason for not including zero is that a known example is included when the ratio is zero, and that the float rising speed is high when the fuel rising speed in FIG. 6 is large and when the fuel rising speed is small in FIG. It is because it becomes impossible to change.

  In the invention which concerns on Claim 2, the said through-hole consists of two or more, It is characterized by the above-mentioned.

  The invention according to claim 3 is characterized in that the through holes are provided at equal intervals on the same circle.

  In the invention which concerns on Claim 4, the said through-hole is provided in the inclined form so that the opening end by the side of the said opening part may leave | separate from the said opening part.

  In the invention according to claim 5, the float is provided with an upper float having the valve member and a small opening above it, and is provided at the lower part of the upper float so as to engage with the upper float and move up and down. The lower float which has the 2nd valve member which opens and closes the said small opening part above it is characterized by the above-mentioned.

  The invention according to claim 6 is characterized in that the through hole is provided in the lower float.

  In the invention according to claim 1, the ratio of the area of the through hole to the volume of the air space in the float is set to 0.63 or less, so that the housing for storing the float when the fuel tank is inclined or when refueling is performed. When the fuel suddenly enters the air and the amount of fuel flowing into the air space of the float becomes larger than the amount of air discharged from the air space through the through hole, buoyancy is generated in the air space, and the buoyancy is reduced. Since it is added as a new force that moves up the float, the upward movement speed of the float can be increased, and the amount of fuel leaking from the opening to the canister can be reduced because the valve is closed early. As a result, it becomes unnecessary to increase the buoyancy of the float itself by increasing the thickness of the float as in the prior art, and the problem of an increase in material costs can be eliminated.

  Even if fuel suddenly enters the housing that houses the float, the amount of fuel flowing into the air space of the float hollow portion is less than the amount of air discharged from the air space through the through hole. Since no buoyancy is generated in the air space, the valve closing operation can be stably performed under a valve closing condition based on a preset buoyancy due to the volume of the float itself and the biasing force of the spring.

  In the invention according to claim 2, by providing a plurality of through holes, in addition to the effect of the invention according to claim 1, for example, even if an adverse effect such as clogging of one through hole occurs, the remaining one is not used. The operation of the present invention can be continued.

  In the invention according to claim 3, by providing the through holes at equal intervals on the same circle, in addition to the effect of the invention according to claim 2, the center of gravity of the float can be maintained in the center, and the vertical movement of the float can be maintained. It can be stabilized.

  In the invention according to claim 4, in addition to the effects of the invention according to claims 1 to 3, the through hole is provided in an inclined shape so that the opening end on the opening side is separated from the opening. It is possible to reduce the risk that fuel mixed in the discharged air flows out from the opening to the canister side.

  In the invention according to claim 5, the float is provided above and below the upper float having a valve member and a small opening, and engages with the upper float at the lower part of the upper float and is movable up and down. The effect of the invention according to claim 1 even in the fuel cutoff valve in which the full tank control valve and the fuel leakage prevention valve are integrated by forming from the lower float having the second valve member that opens and closes the small opening. The same effect can be achieved.

  In the invention according to claim 6, by providing the through hole in the lower float, in addition to the effect of the invention according to claim 5, the distance between the through hole and the opening can be increased by the height of the upper float. The risk of fuel mixed in the air flowing out from the opening to the canister side can be further reduced.

Overall sectional view of the fuel shut-off valve The figure which shows roughly the calculated volume of the air space in the float Float plan view It is the A section enlarged view of FIG. 2, and is a diagram schematically showing the calculated area of the through hole Perspective view of upper float Diagram showing the upward movement of the float when the fuel rise speed is high Diagram showing the upward movement of the float when the fuel rise speed is low The figure which shows the other through-hole provided in a float Schematic diagram of experimental equipment Graph diagram showing experimental results Figure showing experimental data Cross-sectional view of a conventional fuel cutoff valve

  The fuel shut-off valve of the present invention may be used for any application. In the following, the fuel shut-off valve used for a fuel system for an automobile and having an upper float 45 and a lower float 55 will be described. The fuel cutoff valve 20 includes a housing 30, an upper float 45, a lower float 55, a first valve member 50, a second valve member 59, and the like disposed in the housing 30.

  The housing 30 is a cylindrical resin member that is open at the bottom and has an internal space 31. A connecting pipe 32 communicating with a canister (not shown) is integrally formed above the housing 30, and an opening 33 (corresponding to the opening of the present invention) is formed between the internal space 31 and the connecting pipe 32. The In addition, a circular first seal portion 34 with which a first valve member 50 (corresponding to the valve member of the present invention) abuts is formed below the opening 33.

  In the housing 30, a plurality of vertical ribs 35 are provided at equal intervals in the vertical direction along the inner wall surface, and the vertical ribs 35 are provided between the inner wall surface of the housing 30 and the outer peripheral surface of the lower float 55. A space is secured to form a passage for fuel evaporative gas and the like, and the vertical movement of the lower float 55 is guided at the inner peripheral end thereof.

  A bottom member 36 is attached to the bottom of the housing 30 by means such as heat welding. The bottom member 36 is provided with a plurality of lower openings 37 for allowing fuel or the like to enter the internal space 31. The lower opening 37 is for allowing fuel to enter the internal space 31 when refueling or when the vehicle is tilted or rolls over. The upper float 45 and the lower float 55 are moved by the fuel that enters the internal space 31. The opening 33 is closed by the first valve member 50 provided above the upper float 45 to prevent the fuel from flowing out into the canister. The bottom member 36 may be included in a part of the housing 30.

  In addition, a plurality of, for example, two lateral holes 38 are provided on the side wall surface above the housing 30, and the fuel evaporative gas in the fuel tank 40 enters the internal space 31 through the lateral holes 38 and opens the opening 33. And it is discharged to a canister (not shown) through the connecting pipe 32.

  Further, a flange 39 is integrally formed on the outer peripheral portion of the housing 30. A mounting opening 40 a is provided on the upper wall surface of the fuel tank 40, and the fuel cutoff valve 20 is inserted into the fuel tank 40 at a lower portion thereof through the mounting opening 40 a, and the flange 39 is formed on the upper wall surface of the fuel tank 40. Mounted in a fixed form. Note that the housing 30 may have a multi-divided structure in which the lower part is a case member that houses a float and the connecting pipe 32 and the flange 39 part are cap members.

  A resin float F made up of an upper float 45 and a lower float 55 is accommodated in the housing 30 so as to be movable up and down. FIG. 5 shows a perspective view of the upper float 45. The upper float 45 includes a disk-shaped member 46 and a leg member 47. The leg members 47 are a plurality of, for example, four, members on the outer peripheral bottom surface of the disk-like member 46, each having an arcuate cross section. A vertically long and rectangular engagement groove 48 is provided in which four locking pieces 58 formed on the outer peripheral surface are engaged.

  The disk-shaped member 46 has an upper small-diameter disk part 46a, a lower large-diameter disk part 46b, and a columnar part 46c that connects the small-diameter disk part 46a and the large-diameter disk part 46b. A first valve member 50 that is donut-shaped and made of rubber is fitted into the columnar portion 46c. The first valve member 50 abuts on the first seal portion 34 formed on the upper portion of the housing 30 when the lower float 55 moves up, and prevents the fuel or the like from flowing out to the opening 33 side. In this case, the first valve member 50 is fitted with a space in the front-rear and left-right directions, and the first valve member 50 and the first seal portion 34 are kept in close contact with each other even when the upper float 45 is inclined. Do well.

  A cylindrical hollow portion 51 is formed at the center of the upper wall of the small-diameter disk portion 46a of the upper float 45. The cylindrical hollow portion 51 is a hollow annular body, and has a small-diameter small opening portion 52 that opens in the vertical direction at the upper end thereof, and is below the small opening portion 52, and is formed in the cylindrical hollow portion. A second seal portion 53 is formed at the upper tip of 51.

  The lower float 55 is a hollow cylindrical member that is open downward, and has a large-diameter cylindrical portion 56 below and a small-diameter cylindrical portion 57 above. The large-diameter cylindrical portion 56 has a large-diameter air space 56a (corresponding to the air space of the present invention) that is open downward, and the outer peripheral portion of the large-diameter cylindrical portion 56 is formed on the inner surface of the housing 30. Guided by vertical vertical ribs 35 provided.

  The small-diameter cylindrical portion 57 extends upward from the upper wall of the large-diameter cylindrical portion 56, and an upper space 57a that is open downward is formed therein, and the upper outer peripheral surface projects radially and outward. A plurality of, for example, four locking pieces 58 are provided at substantially equal intervals, and a second valve member 59 having a columnar shape and an arc-shaped tip is erected at the center of the upper surface of the small diameter cylindrical portion 57. .

  A spring 60 is interposed between the lower float 55 and the bottom member 36. The spring 60 itself does not have a force to move up the lower float 55, but acts as a force to quickly move up the lower float 55 together with a buoyancy generated by the fuel when the fuel enters the housing 30.

  The assembly of the upper float 45 and the lower float 55 is performed as follows. First, the first valve member 50 is fitted into the columnar portion 46 c which is a groove portion of the upper float 45. Next, the upper float 45 is placed on the upper part of the lower float 55, and a force is applied from the upper part of the upper float 45 in the state as it is to move the upper float 45 downward. Then, the leg member 47 is spread outward by the locking piece 58, and the upper float 45 is pushed along the outer periphery of the small-diameter cylindrical portion 57 of the lower float 55, and finally the four leg members 47 are engaged with each other. Four locking pieces 58 provided on the outer periphery of the upper portion of the small diameter cylindrical portion 57 enter the groove 48, and both members are snap-fit engaged. At the same time, the second valve member 59 of the lower float 55 is fitted into the cylindrical hollow portion 51 of the upper float 45.

  As a result, the upper float 45 is connected to the upper part of the second valve member 59 of the lower float 55 in a pivot shape while being connected to be freely movable up and down without being separated from the lower float 55.

  The engagement groove 48 has a length S (see FIG. 5), and when the opening 33 where the first valve member 50 of the upper float 45 abuts against the first seal portion 34 is closed, the lower float 48 is closed. The second valve member 59 is movable by a length S from a position where the second valve member 59 is opened to a position where the small opening 52 of the upper float 45 is closed.

  The upper float 45 and the lower float 55 operate as follows. When fuel enters the internal space 31 from the lower opening 37, for example, when fuel is supplied to the fuel tank 40, both the upper float 45 and the lower float 55 move upward, and the second valve member 59 having a small diameter in the lower float 55 While abutting against the second seal portion 53 of the float 45 and closing the small opening portion 52, the first valve member 50 of the upper float 45 is formed on the first seal portion 34 formed below the opening portion 33. The large-diameter opening 33 is closed by contact, and fuel is prevented from flowing into a canister (not shown) through the connecting pipe 32.

  When the first valve member 50 and the second valve member 59 are closed, the force with which the second valve member 59 having a small diameter comes into contact with the second seal portion 53 due to the pressure in the fuel tank 40 is a large diameter. When the pressure of the first valve member 50 is considerably smaller than the force of contact with the first seal portion 34 and the pressure in the fuel tank 40 decreases even slightly, the lower float 55 moves down by its own weight, and the second valve member 59 having a small diameter. And the second seal portion 53 come out of contact with each other, and the inside of the fuel tank 40 communicates with the atmosphere through the small opening 52 and the lateral hole 38.

  As a result, the pressure in the fuel tank 40 decreases, the contact between the first valve member 50 and the first seal portion 34 is released, and the large-diameter opening 33 opens to the atmosphere. The pressure drops rapidly. Further, when the fuel in the fuel tank 40 is full, even if the lower opening 37 is blocked by the fuel, the fuel evaporative gas generated in the fuel tank 40 flows from the lateral hole 38 toward the connecting pipe 32. The pressure in the fuel tank 7 does not become excessively high.

  In the present invention, a through hole 65 (in the through hole of the present invention) is formed on the upper wall surface of the lower float 55 (in the case of a single float as shown in FIGS. 6 and 7, the upper wall surface of the float F) in the vertical direction. Equivalent). One or a plurality of through holes 65 may be provided. In the case of a plurality of through holes 65, the through holes 65 may be provided at arbitrary positions on the upper wall surface of the lower float 55, or may be provided at equal intervals on the same circle as shown in FIG. Also good. If the through holes 65 are provided at equal intervals on the same circle, the through holes 65 are evenly arranged with respect to the center of the float, so that the center of gravity of the float can be maintained at the center, and the vertical movement of the float is stabilized. be able to. Further, the through hole 65 is not limited to a cylindrical shape having a constant cross section, and may have a conical shape or an indefinite cross section. Further, the direction is not limited to the vertical direction, but may be inclined or lateral. There may be.

  The present inventor has a problem that when the fuel tank 40 is inclined or when fuel is suddenly infiltrated into the internal space 31 of the housing 30, the valve closing operation of the float is delayed and the fuel easily flows out to the canister side. On the other hand, when the fuel tank 40 tilts or refuels, the amount of fuel flowing into the air space 56a of the lower float 55 exceeds the amount of air discharged from the air space 56a through the through hole 65. Based on the knowledge that buoyancy occurs in the air space 56a (buoyancy increases as the ratio increases), an invention characterized by the numerical range described in claim 1 is created.

  That is, the present inventor is the buoyancy generated in the air space 56a by setting the ratio of the area of the through hole 65 to the volume of the air space 56a of the float to 0.63 or less (not including zero), The buoyancy of the magnitude | size which can close the opening part 33 before the fuel flows out from the opening part 33 to the canister side when the fuel tank 40 inclines or refuels is found.

  Here, the calculated volume of the air space 56 a of the float is the air space 56 a communicating with the lower end portion of the through hole 65 that opens to the air space 56 a, and the air space below the lower end portion of the through hole 65. The air space 56a has a volume of 56a and excludes a portion of the air space 56a where air does not flow upward. If this is shown in FIG. 2, in FIG. 2 (A), it is the volume (the volume of the air space 56a excluding the upper space 57a) indicated by oblique lines, and the small-diameter cylindrical portion 57 as shown in FIG. 2 (B). In such a case that extends downward, the volume is in a range indicated by oblique lines (the volume of the air space 56a excluding the upper space 57a).

  Further, the calculated area of the through hole 65 here is a cross-sectional area indicated by hatching if the through hole 65 has a cylindrical shape with the same diameter as shown in FIG. For example, a conical shape having a different cross section, such as 4 (B), has a minimum cross-sectional area as shown by hatching.

  Regarding the critical significance of the numerical limitation of the present invention, using the experimental device of FIG. 9, the characteristic diagram of the amount of oil supply leakage (mL / test) with respect to the through hole area / air space volume (%) of FIG. 10, and the data table of FIG. explain.

  In the experimental apparatus, the fuel cutoff valve 20 was provided on the upper wall surface of the fuel tank 40 having the fuel supply cylinder 41, and the connecting pipe 32 of the fuel cutoff valve 20 was communicated with the canister 43 through the recovery can 44. Then, the fuel was rapidly supplied from the fuel gun 42 and the amount of leakage flowing out from the fuel cutoff valve 20 was measured with the recovery can 44. In this case, the amount of fuel supplied from the fuel gun suddenly is 38 L / min (10 gallons / min), which is legally determined in the United States, and 45 L / min, which is the amount of fuel normally used in Japan. (Approximately the maximum value) was used.

Then, as shown in Figure 11, the volume of the air space 56a of the float F and 14cm ^3, 0.008 cm ² of area of the through holes ^{65, 0.018cm 2, 0.035cm 2,} 0.053cm 2, 0. 071cm ^2, 0.088cm ^2, as eight 0.106cm ² and ^{0.141cm 2 No (1) ~No (} 8), each percentage, i.e., 0.06%, 0.13%, 0. The leakages of 25%, 0.38%, 0.50%, 0.63%, 0.76% and 1.01% were measured.

  The leakage amount of each ratio (%) is shown in FIGS. As shown in FIG. 10, the leakage amount increases sharply as the rate increases in No (1) to No (6), and shows a maximum value at No (6) (rate of 0.63%), and thereafter. No (7) and No (8) are almost flat. Thus, it can be seen that when the ratio of the area of the through hole 65 to the volume of the air space 56a of the float F is set to 0.63 or less (excluding zero), the amount of leakage rapidly decreases. The reason for this is that the float F closes early due to the buoyancy generated in the air space in addition to the buoyancy of the float itself.

  6 and 7 will describe the float raising operation when the fuel rising speed is high and when the fuel rising speed is low. In this example, a single float is used instead of the float composed of the upper float 45 and the lower float 55 as shown in FIG. 1, and the ratio of the area of the through hole 65 to the volume of the air space 56a of the float is 0.63. Use the following. Only the float is different from that of FIG. 1, and the others are common and are given the same reference numerals.

  FIG. 6 shows a large fuel rising speed at which the fuel suddenly enters the internal space 31 of the housing 30. 6A shows a state when the float F is moved upward, FIG. 6B shows a state when the float F is closed, and FIG. 6C shows an outline of buoyancy acting on the float F. FIG.

  As shown by an arrow, when fuel suddenly enters the internal space 31 of the housing 30 from the lower opening 37, the fuel that enters moves upward between the float F and the housing 30 toward the opening 33, and The air enters the air space 56a. The fuel that enters the air space 56a acts to push out the air in the air space 56a from the through hole 65. However, since the through hole 65 is small and sufficient air is not discharged, the range of the height h of the air space 56a is not reached. 6B, a buoyancy B as shown by the oblique lines in FIG. 6C is newly generated, and the buoyancy B is applied to the float F in addition to the buoyancy A of the float F itself and the urging force of the spring 60. As a result, the upward movement speed of the float F increases, the valve closing time of the opening 33 is shortened, and the valve closing state shown in FIG.

  The height of the fuel entering the housing 30 is H1, and since the upward movement speed of the float F is fast and the valve closing time is short, the height is lower than the height H2 shown in FIG.

  Next, FIG. 7 shows a time when the fuel rising speed at which the fuel enters the internal space 31 of the housing 30 relatively slowly is small. 7A shows the state when the float F is moved upward, FIG. 7B shows the state when the float F is closed, and FIG. 7C shows the outline of the buoyancy acting on the float F.

  When the fuel enters the inner space 31 of the housing 30 through the lower opening 37 relatively slowly as indicated by an arrow, the fuel that enters moves up between the float F and the housing 30 toward the opening 33 and also floats F Enters the air space 56a. The fuel that enters the air space 56 a pushes the air in the air space 56 a from the through hole 65 and rises at substantially the same speed as the fuel that moves up between the float F and the housing 30. Therefore, the valve closing force acting on the float F becomes the buoyancy A of the float F itself and the urging force of the spring 60, and rises at a speed approximately the same as the fuel rise speed. As a result, the upward movement speed of the float F becomes slower than that in FIG. 6, and the fuel height H2 when the valve is closed becomes higher than H1 in FIG.

  FIG. 8 shows a modification of the through hole. When the upper opening 65 a of the through hole 65 is close to the upper opening 33 of the housing 30, the fuel flowing out of the through hole 65 (for example, fuel contained in the air) easily flows out of the opening 33. In this example, the through hole 65 is provided in an inclined shape so that the upper opening 65a, which is the opening end on the opening 33 side, is separated from the opening 33. By adopting such a shape, the above-described disadvantages are provided. Can be reduced. The through hole 65 may be provided in the lateral direction on the side wall surface of the float F.

  It should be noted that the present invention is not limited to the configuration of the above-described embodiments, and the design can be changed as appropriate without departing from the scope of the invention. For example, the fuel cutoff valve does not use the upper float and the lower float as shown in FIG. 1, but may be a full tank control valve and a fuel leakage prevention valve using a single float.

DESCRIPTION OF SYMBOLS 20 ... Fuel cutoff valve 30 ... Housing 31 ... Internal space 32 ... Connection pipe 33 ... Opening part 34 ... First seal part 35 ... Vertical rib 36 ... Bottom member 37 ... Lower opening 38 ... Side hole 39 ... Flange 40 ... Fuel tank 40a ... Installation opening 41 ... Fuel cylinder 42 ... Fuel gun 43 ... Canister 44 ... Recovery can 45 ... Upper float 46 ... Disk member 46a ... Small diameter disk part 46b ... Large diameter disk part 46c ... Columnar part 47 ... Leg member 48 ... engagement groove 50 ... first valve member 51 ... cylindrical hollow part 52 ... small opening 53 ... second seal part 55 ... lower float 56 ... large diameter cylindrical part 56a ... air space 57 ... small diameter cylindrical part 57a ... Upper space 58 ... locking piece 59 ... second valve member 60 ... spring 65 ... through hole 65a ... upper opening F ... float

Claims (6)

A fuel shut-off valve provided in the fuel tank and communicating between the fuel tank and the canister,
A housing and a float provided in the housing so as to be movable up and down;
The housing has an opening communicating with the canister;
The float has a valve member that opens and closes the opening above the float,
The float has an air space whose lower part is opened inside, and a through hole that communicates the inside of the housing and the air space above the float.
A ratio of the area of the through hole to the volume of the air space is 0.63 or less.   The fuel cutoff valve according to claim 1, wherein the through hole includes a plurality of through holes.   The fuel cutoff valve according to claim 2, wherein the through holes are provided at equal intervals on the same circle.   The fuel cutoff valve according to any one of claims 1 to 3, wherein the through hole is provided in an inclined shape so that an opening end on the opening side is separated from the opening.   The float has an upper float having the valve member and a small opening above the float, and is provided at the lower part of the upper float so as to be able to move up and down and engage with the upper float, and the small opening above the float. The fuel cutoff valve according to any one of claims 1 to 4, further comprising a lower float having a second valve member that opens and closes.   The fuel cutoff valve according to claim 5, wherein the through hole is provided in the lower float.

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