JPH10244845A - Fuel cutoff valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a pressure difference between an upper and a lower space of a float valve body and to prevent fuel from flowing between them. SOLUTION: A fuel cutoff valve 20 has a case body 21a and a float valve body 40 which is moved up or down by a floating force increased or decreased by liquid fuel in a fuel tank to close or open a communicating hole 23a at a closing part 42a. The float valve body 40 has projecting fins 46 made on the side thereof which slide on the inner wall of a float room S to guide the float valve body 40. A stepwise part 48 forming a throttle 48a is formed between the fins 46. The stepwise part 48 prevents the liquid fuel from flowing into the upper valve room Sa, providing ventilation, having a height less than one third of the height H1 of the float valve body 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cutoff valve for preventing fuel from flowing out of a fuel tank when the liquid level in the fuel tank of an automobile rises.

[0002]

2. Description of the Related Art FIG. 9 shows a fuel cutoff valve of this type. FIG. 9 is a sectional view showing a conventional fuel cutoff valve 100. As shown in FIG. The fuel cutoff valve 100 has a case 110 disposed above the inside of the fuel tank. The case 110 is formed of a synthetic resin such as polyacetal or nylon, and is provided with a valve chamber 1.
The valve chamber 120 has a float valve 130.
Is stored. The float valve 130 has a closing projection 131 for opening and closing the communication hole 110 a at an upper portion thereof, and is biased by a coil spring 142. The communication hole 11
Oa is connected to the canister via a communication pipe (not shown).

With the structure of the fuel cutoff valve 100, when the fuel in the fuel tank does not enter the valve chamber 120, the float valve 130 is located below (the state of FIG. 9), and the inside of the fuel tank is closed by a case. 110 through holes 110
b, connecting to the canister via the valve chamber 120, the communication hole 110a, and the communication pipe.

[0004] On the other hand, when fuel enters the valve chamber 120, the float valve 130 rises due to the buoyancy accompanying the rise in the level of the liquid fuel. When the closing protrusion 131 on the upper part of the float valve 130 protrudes into the communication hole 110a and closes the communication hole 110a, the fuel is prevented from flowing out to the communication pipe.

[0005] In the fuel cutoff valve 100, the fuel in the fuel tank is agitated by rocking the fuel tank,
When the temperature in the fuel tank increases and the vapor pressure increases, the difference between the space above and below the float valve 130, that is, the lower valve chamber 120a communicating with the fuel tank and the upper valve chamber 120b communicating with the communication hole 110a. Pressure increases. Such a differential pressure raises the float valve 130 and causes the closing protrusion 13
1 acts as a force to close the communication hole 110a. In order to prevent this, a passage gap 133 is provided between the outer wall surface of the float valve 130 and the inner wall surface of the case 110.

[0006]

However, if the passage area of the passage gap 133 is too large, the liquid fuel in the fuel tank flows into the upper valve chamber 120b through the passage gap 133 and further passes through the communication hole 110a to the canister. It easily leaks to the side.

As described above, the passage gap 133 needs to have a passage area so as to reduce the pressure difference between the inside of the fuel tank and the upper valve chamber 120b and at the same time prevent the flow of the liquid fuel. There is a problem that the formation in a predetermined range requires a strict allowable dimension and the production is troublesome.

The present invention solves the above-mentioned problems of the prior art, and provides a simple fuel cut-off valve capable of reducing the differential pressure between the space above and below the float valve body and preventing fuel flow therebetween. It is intended to be provided in a configuration.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention provides a case body forming a valve chamber connected to a communication passage for communicating the inside of a fuel tank to the outside. And, housed in the valve chamber, has a closing portion for opening and closing the communication path at the upper portion, by moving up and down by increasing or decreasing the buoyancy with the liquid fuel in the fuel tank entering and exiting the valve chamber, A float valve body that opens and closes the communication passage with the closing portion, wherein the float valve body has a cylindrical float body that forms a float chamber, and an outer wall portion of the float body. And has a fin projecting along the vertical direction, a plurality of the fins are arranged spaced apart from each other in the circumferential direction of the float body,
The tops of the plurality of fins slide on the inner wall surface of the valve chamber to guide the float body in the up-down direction and to ventilate the space above and below the valve chamber partitioned by the float body. A guide portion that forms a gap between the fins, and an aperture forming the outer wall of the float body and forming an aperture portion that is provided between the fins and narrows a part of the ventilation gap. And a step portion.

[0010] The fuel cutoff valve of the present invention includes a case body forming a valve chamber, and the valve chamber is connected to a communication passage for communicating the inside of the fuel tank with the outside (for example, a canister). The fuel vapor in the fuel tank is released to the outside through the communication passage. Further, in the fuel cutoff valve, when the liquid level of the fuel in the fuel tank becomes equal to or higher than a predetermined liquid level, the liquid fuel in the fuel tank flows into the valve chamber, and the float valve body which has increased the buoyancy by the liquid fuel is formed. To rise. Due to the rise of the float valve body, the closing portion provided at the upper part of the float valve body closes the communication passage and prevents the fuel in the fuel tank from flowing out.

In the float valve body, a plurality of fins constituting a guide portion are arranged on the outer wall of the float body at predetermined intervals in the outer peripheral direction. The top of the fin slides on the inner wall surface of the valve chamber and acts as a guide when the float valve body moves in the vertical direction. Further, between the fins, there is a ventilation gap for ventilating the space above and below the float valve body. The ventilation gap is a throttle portion in which a part of the passage area is narrowed by a throttle forming step projecting from the outer wall of the float main body.

As described above, the throttle portion is not formed over the entire length of the float main body in the vertical direction, but is formed only on a part thereof, and since the passage length is short, the pressure difference between the upper and lower spaces of the float valve body is reduced. Is reduced, whereby the force in the closing direction of the float valve body can be reduced.

[0013] Even if the passage length of the throttle portion is reduced,
Because liquid fuel is difficult to pass through the throttle due to its viscosity,
The effect of preventing the liquid fuel from flowing through the throttle is hardly reduced.

As described above, the length of the passage in the vertical direction of the throttle portion is determined by the factor for preventing the liquid fuel in the fuel tank from flowing to the communication path through the ventilation gap and the space above and below the float valve element is quickly ventilated. And the factor for reducing the differential pressure. That is, the upper limit of the passage length of the throttle portion is preferably not more than １ ／ of the height of the outer wall surface of the float valve body in order to ensure air permeability between the upper and lower spaces of the float valve body, Further, in order to prevent the flow of the liquid fuel in the fuel tank, it is preferable that the ratio is 1/6 or more.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the present invention will be described below.

FIG. 1 is a sectional view showing a fuel cutoff valve 20 according to one embodiment of the present invention. The fuel cutoff valve 20 is mounted on an upper wall of a fuel tank (not shown), and is connected to a canister through a communication pipe. The fuel cutoff valve 20 has a case 21. The case 21 includes a case body 21a and the case body 21a.
And a case upper portion 21b for being attached to the upper wall of the fuel tank by ultrasonic welding.

The case body 21a includes an upper wall 23 having a communication hole 23a connected to the canister side, and an upper wall 23.
And a side wall portion 24 formed integrally with the side wall. A lower case opening 26 is formed in a lower portion of the side wall portion 24.
The case lower opening 26 is closed by the bottom plate 30.

A plurality of claw portions 30 are provided on the outer peripheral portion of the bottom plate portion 30.
The bottom plate portion 30 is supported by the side wall portion 24 by engaging the claw portion 30a with the case lower notch 24a of the side wall portion 24. The space surrounded by the case body 21a and the bottom plate 30 is a float chamber S
It has become.

A vent hole 28 is formed in the upper part of the side wall portion 24, and fuel vapor in the fuel tank is led to the float chamber S through the vent hole 28. Further, a fuel communication hole 31 is formed in the bottom plate portion 30, and the liquid fuel in the fuel tank is introduced into the float chamber S via the fuel communication hole 31.

In the float chamber S, a float valve body 40 is provided.
Is stored. The float valve body 40 has a cylindrical wall portion 41.
And a float body 43 integrally formed of resin and surrounded by the upper surface portion 42, and an inner space thereof is a buoyancy chamber 44. At the upper part of the float main body 43, a closing part 42a for opening and closing the communication hole 23a is formed. The float valve element 40 is supported by a spring 45 provided between the float valve element 40 and the bottom plate 30.

FIG. 2 is an enlarged view of a side portion of the fuel cutoff valve 20, and FIG. 3 is a perspective view showing a float valve body 40. FIG.
3 and FIG. 3, a fin 46 protrudes from the outer wall portion 41a of the cylindrical wall portion 41 along the vertical direction and has a length substantially equal to the height H1 of the outer wall portion 41a. Fins 46
Are formed at predetermined intervals in the circumferential direction of the float main body 43, and the tops 46a of the fins 46 slide on the inner wall surface of the float chamber S, respectively. It acts as a guide part for guiding by resistance.

Further, between the fins 46, the float valve body 4
A ventilation path 47 for ventilating between the upper valve chamber Sa and the lower valve chamber Sb, which is partitioned by zero. The ventilation path 47 is provided with a step portion 48 which protrudes from the outer wall 41a of the float main body 43 and forms a narrowed portion 48a which narrows a part of the ventilation path 47. This step 48
Is that the vertical passage length h1 of the throttle portion 48a is 1/1 / the height H1 of the float body 43 in the vertical direction.
It is formed so as to be 4 to 1/3. The reason why the passage length h1 of the throttle portion 48a is formed in this manner will be described later.

Next, the operation of the fuel cutoff valve 20 will be described. In the fuel cutoff valve 20, when the fuel level in the fuel tank has not reached the cutoff level FL, the float valve body 40 is at the position shown in FIG. 1, and the inside of the fuel tank has the vent hole 28, the float chamber S, Communication hole 23a,
It communicates with the canister through the communication pipe.

On the other hand, when the fuel level rises due to the refueling of the fuel tank and exceeds the cutoff level FL, the liquid fuel F enters the buoyancy chamber 44 through the fuel communication hole 31 and the float valve body The buoyancy is generated in 40, and the float valve body 40 rises. Then, the closing portion 42a at the distal end of the float valve body 40 rises from the state shown in FIG.
Block 3a. As a result, the fuel cutoff valve 20 closes the space between the fuel tank and the canister.

The case upper part 21b has an upper chamber 51 for communicating the communication hole 23a with the communication pipe inside. The upper chamber 51 is provided with a check valve (not shown). The check valve includes a ball and a spring that urges the ball in a valve closing direction.
0 closes the communication hole 23a, and acts as a release valve for releasing the tank internal pressure when the tank internal pressure exceeds a predetermined value.

In the fuel cutoff valve 20, when the fuel in the fuel tank is swung and the fuel in the fuel tank is agitated, or when the temperature in the fuel tank rises and the vapor pressure becomes high, the fuel cutoff valve 20 shown in FIG. As shown in FIG. 7, the gas flows from the lower valve chamber Sb to the upper valve chamber Sa via the ventilation path 47 between the outer periphery of the float valve body 40 and the inner wall surface of the case body 21a. The pressure difference with the chamber Sa is reduced, and the force in the direction to close the float valve body 40 is reduced. In this case, the narrowed portion 48a of the air passage 47 does not act to increase the pressure difference because the portion where the passage area is reduced is short.

On the other hand, when the fuel tank swings when the fuel level of the fuel tank is high, the throttle portion 48a allows the liquid fuel in the fuel tank to move from the lower valve chamber Sb to the upper valve chamber Sb.
a. As described above, the squeezing section 48a
Prevents the flow of the liquid fuel and prevents the float valve body 4 from flowing.
The passage area and the passage length are set so as not to obstruct the differential pressure difference above and below 0. In order to examine the operation and effect of the throttle portion 48a, a test described below was performed.

FIG. 4 is a sectional view showing a float valve body 40 used for the test, and FIG. 5 is a sectional view showing a conventional float valve body 130. The length h1 of the throttle portion 48a of the float valve body 40 shown in FIG.
The gap W1 of the narrowed portion 48a was 1 mm, and the gap W2 of the air passage 47 above it was 2 mm. On the other hand, the conventional float valve element 130 shown in FIG.
The gap W3 was 1 mm over the entire length.

FIG. 6 is a diagram showing a test apparatus for measuring the amount of fuel leak of the fuel cutoff valve 20. FIG. 6 shows a fuel tank T having a fuel cut-off valve 20 mounted on an upper portion thereof.
Is placed on top. The pedestal P is connected to a driving device (not shown) that can swing the fuel tank T at a swing angle of ± 20 °.

Now, the cutoff level F in the fuel tank T
Fill with fuel instead of fuel so that it is lower than L by -3mm to -22mm, swing angle ± 20 °, frequency 0.7
Hz and the regulator pressure were set to about 2.5 kPa, and the amount of fuel leakage for 30 minutes was examined. As a result, in both the case of the liquid level of −3 mm from the cutoff liquid level FL and the case of the liquid level of −22 mm, the leak amount could be suppressed to the same level as the conventional one. That is, it has been found that even if the passage length of the throttle portion 48a is shorter than in the conventional case, the amount of fuel passing through the ventilation path 47 can be suppressed to the same amount as in the related art.

On the other hand, the pressure limit at which the float valve body 40 of the fuel cutoff valve 20 closes due to the differential pressure was examined by the following test. That is, air pressure was applied to the upper part of the fuel tank, and the air pressure when the float valve body 40 was closed was examined. As a result, it was found that the air pressure of the fuel cutoff valve 20 was 24 kPa, and the air pressure of the conventional fuel cutoff valve was higher than that of 17 kPa.

As described above, the passage length h1 of the throttle portion 48a is obtained.
Is determined in consideration of an element that makes it difficult for the liquid fuel in the fuel tank T to flow through the throttle portion 48a and an element that quickly vents the space above and below the float valve body 40 to reduce the differential pressure. For example, the fuel cutoff valve 60 shown in FIG. 7 which is a passage shorter than the throttle portion 48a may be used. That is, in FIG. 7, on the side of the float valve body 61,
Fins 62 are formed, and a step portion 64 that forms a narrowed portion 63 is formed between the fins 62. The length h2 of the constricted portion 63 is about 1/6 of the height H1 of the side wall portion of the float valve body 61. As described above, if the length of the throttle portion 63 is 1/6 or more of the height H1 of the side wall portion of the float valve body 61 in order to prevent the flow of the liquid fuel in the fuel tank, And the air permeability can be enhanced.

The present invention is not limited to the above-described embodiment, but can be embodied in various modes without departing from the gist thereof. For example, the following modifications are possible.

(1) FIG. 8 is a sectional view showing a fuel cutoff valve 90 according to another embodiment. 8, an inclined portion 94 is formed from the upper surface portion 92 of the float valve body 91 to the upper portion of the cylindrical wall portion 93. The inclined portion 94 forms a ventilation path 96 connected to the throttle portion 95, and acts so that when liquid fuel enters the upper valve chamber Sa, it quickly escapes to the lower valve chamber Sb via the inclined portion 94. I do. Therefore, it is possible to avoid a state in which the liquid fuel accumulates on the upper part of the float valve body 91 and the float valve body 91 becomes difficult to close due to its own weight.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a fuel cutoff valve 20 according to one embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a main part of a fuel cutoff valve 20;

FIG. 3 is a perspective view showing a float valve body 40.

FIG. 4 is a sectional view showing a float valve body 40;

FIG. 5 is a sectional view showing a conventional float valve element.

FIG. 6 shows an apparatus for testing fuel leakage of the fuel cutoff valve 20.

FIG. 7 shows a fuel cutoff valve 60 according to another embodiment.
FIG.

FIG. 8 is a sectional view showing a fuel cutoff valve 90 according to still another embodiment.

FIG. 9 is a sectional view showing a conventional fuel cutoff valve.

[Explanation of symbols]

 Reference Signs List 20 fuel cutoff valve 21 case 21a case body 21b case upper part 23a communication hole 23 upper wall part 24 side wall part 24a case lower notch 26 case lower opening 28 vent hole 30 bottom plate part 30a Claw part 31 ... Fuel communication hole 40 ... Float valve body 41 ... Cylindrical wall part 41a ... Outer wall part 42 ... Top part 42a ... Closed part 43 ... Float body 44 ... Buoyancy chamber 45 ... Spring 46 ... Fin 46a ... Top part 47 ... Ventilation path 48a ... throttle section 48 ... step section 51 ... upper chamber 60 ... fuel cutoff valve 70 ... float valve body 76 ... fin 78a ... throttle section 78 ... step section 90 ... fuel cutoff valve 91 ... float valve body 91 ... cylinder -Shaped wall portion 92: upper surface portion 92b: inclined portion 97a: throttle portion

Claims (2)

[Claims] 1. A case main body forming a valve chamber connected to a communication passage for communicating the inside of a fuel tank to the outside, and a closing portion housed in the valve chamber and opening and closing the communication passage at an upper portion thereof. And a float valve body that opens and closes the communication path at the closing portion by increasing and decreasing the buoyancy with the liquid fuel in the fuel tank that moves into and out of the valve chamber to move in the vertical direction. In the above, the float valve body has a cylindrical float main body forming a float chamber, and a fin protruding from an outer wall portion of the float main body along the up-down direction. A plurality of the fins are arranged in the circumferential direction so as to be separated from each other, and the tops of the plurality of fins slide on the inner wall surface of the valve chamber to guide the float body in the vertical direction, and are partitioned by the float body. A guide portion for forming a ventilation gap between the fins for ventilating the upper and lower spaces of the chamber; and an outer wall portion of the float body, and one of the ventilation gaps protruding between the fins. And a throttle forming step portion forming a throttle portion for narrowing the portion. 2. The throttle forming step portion according to claim 1, wherein a vertical path length of the throttle portion is a half of a vertical height of the float body.
Fuel cut-off valve formed to be 1/6 of