JP2000257514A - Evaporated fuel discharge suppressing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and surely prevent such state that a float valve sticks to an inlet part of an evaporated fuel passage in an evaporated fuel discharge suppressing device for suppressing the discharge of evaporated fuel from a fuel tank when oil is supplied into the fuel tank of an automobile. SOLUTION: This evaporated fuel discharge suppressing device is provided with a first communicating means 73 communicating the upstream of an opening and closing valve 33 with a pressure introducing passage 65 when pressure in the upstream of the opening and closing valve 33 is higher than pressure on the pressure introducing passage 65 side by a predetermined value or more and a second communicating means 75 communicating the upstream of the opening and closing valve 33 with the pressure introducing passage 65 when pressure on the pressure introducing passage 65 side is higher than pressure in the upstream of the opening and closing valve 33 by a predetermined value or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel emission control device for suppressing the release of evaporative fuel from a fuel tank when refueling the fuel tank of an automobile.

[0002]

2. Description of the Related Art Conventionally, as an evaporative fuel emission suppression device for suppressing the emission of evaporative fuel from a fuel tank when fuel is supplied to a fuel tank of an automobile, for example, Japanese Patent Application Laid-Open No. 8-18 / 1996
One disclosed in Japanese Patent No. 9423 is known. FIG.
Reference numeral 1 denotes an evaporative fuel release suppressing device disclosed in this publication, in which an evaporative fuel passage 4 is arranged by connecting a tank body 2 of a fuel tank 1 and a canister 3. I have.

[0003] In the tank body 2, when fuel in the tank body 2 exceeds a predetermined liquid level, an inlet 5 of the evaporative fuel passage 4 is formed.
Is disposed. An on-off valve 7 is interposed in the fuel vapor passage 4. The on-off valve 7 is a diaphragm valve having a positive pressure chamber 7a and a back pressure chamber 7b, and the fuel vapor passage 4 is interposed on the positive pressure chamber 7a side.

The pressure on the positive pressure chamber 7a side is changed to the back pressure chamber 7b.
When the pressure is higher than the pressure on the side by a predetermined value or more, the fuel vapor passage 4 is opened. On the back pressure chamber 7b side of the on-off valve 7, a pressure introduction passage 9 connected to the inlet 8a of the oil supply pipe 8 is provided.
Is open. And, the on-off valve 7 of the fuel vapor passage 4
And the pressure introduction passage 9 are connected by a communication passage 10.

A check valve 11 which is opened in the communication passage 10 when the pressure on the upstream side of the on-off valve 7 is higher than the pressure on the pressure introduction passage 9 by a predetermined value or more. In such an evaporative fuel emission suppression device, when a cap (not shown) of the refueling pipe 8 is removed at the start of refueling, the pressure on the back pressure chamber 7b side of the on-off valve 7 via the pressure introduction passage 9 becomes higher than the pressure on the positive pressure chamber 7a side. The pressure becomes smaller than the pressure by a predetermined value or more, the on-off valve 7 is opened, and the fuel vapor from the tank body 2 is adsorbed to the canister 3 through the fuel vapor passage 4.

When the internal pressure in the tank body 2 rises due to the start of refueling, and the pressure on the upstream side of the on-off valve 7 becomes higher than the pressure on the pressure introduction passage 9 side of the check valve 11 by a predetermined value or more, the communication passage 10, the check valve 11 is opened, and the fuel vapor in the tank main body 2 is guided to the inlet 8 a of the fuel supply pipe 8 through the pressure introducing passage 9, and the fuel supplied from the fuel supply gun 12 and the fuel tank 12. It is returned into the main body 2.

When the fuel is filled in the tank body 2, the inlet 5 of the fuel vapor passage 4 is closed by the float valve 6, and the on-off valve 7 is disconnected from the tank body 2 by the float valve 6. Pressure on the upstream side of the
The on-off valve 7 and the check valve 11 are closed. And
When a cap (not shown) is attached to the refueling pipe 8 upon completion of refueling, the pressure at the inlet 8 a of the refueling pipe 8 rises in the same manner as the pressure in the tank body 2, and the on-off valve 7 The pressure on the pressure introduction passage 9 side of the check valve 11 increases through the back pressure chamber 7b side and the communication passage 10.

[0008]

However, in such a conventional evaporative fuel emission control device, when fuel is filled in the tank body 2, the inlet portion 5 of the evaporative fuel passage 4 is closed by the float valve 6, Further, since the on-off valve 7 and the check valve 11 are closed, the pressure on the upstream side of the on-off valve 7 remains as a pressure equivalent to the atmospheric pressure.
However, there is a problem that the state is stuck to the inlet 5 of the fuel vapor passage 4.

Therefore, conventionally, for example, the float valve 6 is divided into upper and lower stages to prevent the float valve 6 from sticking. In this case, however, the float valve 6 becomes complicated and the manufacturing process becomes difficult. There is a problem that the cost increases and the responsiveness of the float valve 6 decreases. SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problem, and provides an evaporative fuel emission control device that can easily and reliably prevent a float valve from being stuck to an inlet of an evaporative fuel passage. With the goal.

[0010]

According to a first aspect of the present invention, there is provided an evaporative fuel release suppressing apparatus, comprising: a canister for adsorbing evaporative fuel from a fuel tank having a fuel supply pipe in a tank body; and an evaporator for connecting the tank body and the canister. A fuel passage, a float valve disposed in the tank body and closing an inlet of the evaporative fuel passage when fuel in the tank body exceeds a predetermined liquid level, and a positive pressure chamber and a back pressure chamber. An opening / closing valve for opening the fuel vapor passage when the pressure in the positive pressure chamber is higher than the pressure in the back pressure chamber by a predetermined value or more; A pressure introducing passage connecting the inlet of the oil supply pipe and the back pressure chamber side of the on-off valve, and the pressure when the pressure on the upstream side of the on-off valve is higher than the pressure on the pressure introducing passage by a predetermined value or more. The pressure introduction passage upstream of the on-off valve First communication means for communicating with the pressure introducing passage, and second communication for communicating the upstream side of the on-off valve with the pressure introducing passage when the pressure on the pressure introducing passage side is higher than a pressure on the upstream side of the on-off valve by a predetermined value or more. Means.

According to a second aspect of the present invention, there is provided the evaporative fuel release suppressing apparatus according to the first aspect, wherein the first communication means and the second communication means are formed integrally with the on-off valve. It has a positive pressure valve and a negative pressure valve housed in the room, and the negative pressure valve is arranged on the positive pressure valve. According to a third aspect of the present invention, there is provided the evaporative fuel release suppressing device according to the second aspect, wherein the positive pressure valve moves over a predetermined distance to the opening side of the pressure introduction passage opened to the valve chamber. In this case, there is provided a passage expanding means for opening the negative pressure valve to the pressure introduction passage side.

According to the first aspect of the present invention, when the cap is attached to the fuel supply pipe after the refueling is completed, the pressure at the inlet of the fuel supply pipe increases to the same pressure as the pressure in the tank body. Then, the second communication means is opened via the pressure introducing passage, and the pressure at the inlet of the fuel vapor passage rises to substantially the same pressure as the pressure in the tank body, and the sticking of the float valve to the inlet is eliminated. Is done.

According to a second aspect of the present invention, the positive pressure valve of the first communication means and the negative pressure valve of the second communication means are housed in a valve chamber formed integrally with the on-off valve. , A negative pressure valve is arranged. In the fuel vapor suppression device according to the third aspect, when the positive pressure valve moves over a predetermined distance to the opening side of the pressure introduction passage opened to the valve chamber due to the high pressure during high flow rate refueling, the passage expansion means The negative pressure valve is opened, and the passage area to the pressure introduction passage side is enlarged.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a first embodiment of an evaporative fuel emission control device according to the present invention. In this figure, reference numeral 21 indicates a fuel tank. The fuel tank 21 includes a tank main body 23 and a fuel supply pipe 25.

The tank body 23 contains a volatile fuel such as gasoline or light oil. A cap 27 is attached to the inlet 25 a of the oil supply pipe 25. In the figure, reference numeral 29 indicates a canister that adsorbs fuel vapor from the fuel tank 21.

The canister 29 has a tank body 23
Is connected to the fuel passage 31. The fuel vapor passage 31 is opened on the upper surface of the tank body 23 via an on-off valve 33. As shown in FIG. 2, the on-off valve 33 is a diaphragm valve provided with a diaphragm 37 in a valve body 35.

That is, the inside of the valve body 35 of the on-off valve 33 is
A positive pressure chamber 39 and a back pressure chamber 41 are formed by being divided by the diaphragm 37. In the positive pressure chamber 39 of the valve body 35, a passage 45 that is connected to the canister 29 via a pipe 43 and forms a part of the evaporated fuel passage 31 is formed. This passage 45 is bent toward the diaphragm 37, and a valve seat 45a is formed at the end of the diaphragm 37.

On the other hand, the diaphragm 3 is located on the back pressure chamber 41 side.
A coil spring 47 for urging the valve 7 toward the valve seat 47 of the passage 45 is provided. The on-off valve 33 is opened when the pressure on the positive pressure chamber 39 side is higher than the pressure on the back pressure chamber 41 by a predetermined value or more, and is closed at other times. On the lower surface of the valve body 35 of the on-off valve 33, a float valve 49 is arranged.

The float valve 49 has a cylindrical guide part 51 integrally formed with the valve body 35, and a float 53 housed in the guide part 51. The float 53 is
It is urged upward by a coil spring 55. A flange portion 57 is formed on an upper portion of the guide portion 51. Then, the through hole 2 formed in the tank body 23
3a, the guide portion 51 is inserted and the flange portion 57 is inserted.
Are fixed to the upper surface of the tank body 23.

The guide portion 51 is partitioned from the positive pressure chamber 39 by a partition portion 59 formed integrally with the valve body 35. The partitioning portion 59 has a through-hole which is to be the entrance 61 of the fuel vapor passage 31. When the fuel in the tank body 23 exceeds a predetermined liquid level, the upper end of the float 53 comes into contact with the inlet 61 of the evaporative fuel passage 31 and the evaporative fuel passage 3
One inlet 61 is closed.

On the other hand, in this embodiment, a valve chamber 63 is integrally formed adjacent to the valve body 35 of the on-off valve 33.
As shown in FIG. 1, a pressure introduction passage 65 communicating with the inlet 25 a of the oil supply pipe 25 is opened in the valve chamber 63. That is, a passage 67 is formed in the valve chamber 63, and a pressure introduction passage 65 is formed by connecting the pipe 69 to the passage 67.

In the upper part of the valve chamber 63, a partition 71 is formed. The hole 7 formed in the partition 71
The valve chamber 63 is connected to the back pressure chamber 41 side of the on-off valve 33 via 1a. In this embodiment, a positive pressure valve 73 constituting the first communication means and a negative pressure valve 75 constituting the second communication means are arranged in the valve chamber 63.

That is, the positive pressure valve 73 communicates the positive pressure chamber 39 of the on-off valve 33 with the pressure introduction passage 65 when the pressure on the positive pressure chamber 39 side is higher than the pressure on the pressure introduction passage 65 by a predetermined value or more. The negative pressure valve 75 connects the inlet 61 to the pressure introducing passage 65 when the pressure on the pressure introducing passage 65 side is higher than the pressure of the inlet 61 of the evaporative fuel passage 31 by a predetermined value or more.

In this embodiment, as shown in FIG. 3, a through hole 77a is formed in a partition 77 formed between the positive pressure chamber 39 and the valve chamber 63. And this through hole 77
A cylindrical valve body 73a of the positive pressure valve 73 is disposed at a position surrounding the valve body a.

The valve body 73a is urged toward the partition 77 by a coil spring 79, and the positive pressure valve 73 is closed by the contact of the valve body 73a with the partition 77. On the other hand, a through hole 73c is formed in the bottom surface 73b of the valve body 73a of the positive pressure valve 73, and a negative pressure valve 75 is disposed in the through hole 73c. In the valve body 73a of the positive pressure valve 73, a cylindrical valve body 75 of the negative pressure valve 75 is provided at a position surrounding the through hole 73c.
a is arranged.

The valve body 75a is urged toward the passage 67 by the coil spring 81, and the negative pressure valve 75 is closed by contact with the bottom surface 73b of the valve body 75a. In this embodiment, a pressing portion 75b is arranged on the opposite side of the valve body 75a of the negative pressure valve 75, and a protruding portion serving as a flow path expanding means is provided at a position facing the pressing portion 75b in the valve chamber 63. 63a are formed.

The projecting portions 63a are formed at intervals of, for example, 60 degrees around the passage 67. When the positive pressure valve 73 moves to the passage 67 side over a predetermined distance, the negative pressure valve It is collided with the pressing portion 75b. In FIG. 1, reference numeral 83 denotes an evaporative fuel passage that guides the evaporative fuel in the fuel tank 21 to the canister 29 except during refueling.

The evaporative fuel passage 83 has a positive / negative pressure valve 8
5, 87 are arranged, and float valves 89, 9 are provided at the inlet.
1 is arranged. In the evaporative fuel emission control device described above, the pressure in the tank main body 23 and the pressure in the fuel supply pipe 25 are the same during normal running, so that the pressure on the positive pressure chamber 39 side of the on-off valve 33 and the back pressure chamber 41 side 4 becomes the same, and FIG.
As shown in FIG. 7, the on-off valve 33 is closed.

When the cap 27 of the refueling pipe 25 is removed for refueling, as shown in FIG.
And the negative pressure valve 75 is closed, so that the evaporated fuel is supplied through the pressure introduction passage 65 to the inlet 2 of the fuel supply pipe 25.
It is prevented from being guided to 5a and emitted to the outside. next,
When the internal pressure in the tank body 23 rises due to the start of refueling, the pressure of the on-off valve 33 on the positive pressure chamber 39 side becomes higher than the pressure on the back pressure chamber 41 by a predetermined value or more, as shown in FIG. The on-off valve 33 opens, and the fuel vapor from the tank body 23 is adsorbed to the canister 29 through the fuel vapor passage 31.

At this time, the pressure on the upstream side (positive pressure chamber 39) of the on-off valve 33 becomes larger than the pressure on the pressure introduction passage 65 side of the positive pressure valve 73 by a predetermined value or more, and the positive pressure valve 73 is opened. The fuel vapor in the tank main body 23 is guided to the inlet 25a of the fuel supply pipe 25 through the pressure introducing passage 65, and is returned to the tank main body 23 together with the fuel supplied from the fuel supply gun or the like.

This prevents an increase in the amount of fuel vapor due to the mixture of outside air. In this embodiment, at the time of high flow rate refueling, as shown in FIG. 7, the high pressure due to the high flow rate refueling causes the positive pressure valve 73 to move beyond a predetermined distance to the passage 67 side, and the negative pressure valve 75 to be pressed by the pressing portion 75b. Collides with the negative pressure valve 7
5 is opened. Thereby, the passage area is enlarged, and at the time of high flow rate refueling, the circulating flow rate to the inlet 25a side of the refueling pipe 25 increases, and the entrainment of the outside air from the inlet 25a of the refueling pipe 25 is reduced.

Next, when fuel is filled in the tank main body 23, as shown in FIG.
1 is closed by the float valve 49. Then, when the cap 27 is attached to the refueling pipe 25 by the end of refueling,
The pressure at the inlet 25a of the oil supply pipe 25 rises to the same level as the pressure in the tank body 23, and the pressure introduction passage 65 and the valve chamber 6
3 and the back pressure chamber 41 side of the on-off valve 33 and the positive pressure valve 73
, The pressure on the pressure introduction passage 65 side increases.

At the same time, the pressure on the upstream side (positive pressure chamber 39) of the on-off valve 33 whose communication with the inside of the tank body 23 is cut off by the float valve 49 is reduced, so that the on-off valve 33 and the positive pressure valve 73 are closed. . And, as shown in FIG.
Due to the pressure from the pressure introducing passage 65, the negative pressure valve 75 is opened, and the pressure on the upstream side (positive pressure chamber 39) of the on-off valve 33 rises to almost the same pressure as the pressure in the tank body 23, and the inlet 61
The sticking of the float valve 49 to is eliminated.

In the evaporative fuel emission control device configured as described above, when the refueling is completed, the cap 27 is attached to the refueling pipe 25.
Is mounted, the pressure at the inlet 25a of the refueling pipe 25 becomes
The pressure rises in the same manner as the pressure in the tank body 23, and the negative pressure valve 75 is opened by the pressure from the pressure introduction passage 65, and the on-off valve 33
The pressure on the upstream side (positive pressure chamber 39) of the fuel tank 31 rises to almost the same pressure as the pressure in the tank body 23, and the sticking of the float valve 49 to the inlet 61 is eliminated.
It is possible to easily and reliably prevent the float valve 49 from being stuck to the inlet portion 61.

Further, in the above-described evaporative fuel emission suppression device, the positive pressure valve 73 constituting the first communication means and the negative pressure valve 75 constituting the second communication means are formed integrally with the on-off valve 33. Since the negative pressure valve 75 is disposed in the positive pressure valve 73 and housed in the valve chamber 63, the first communication means and the second communication means can be configured without using separate piping, and the apparatus can be made compact. can do.

Further, in the above evaporative fuel emission suppression device, the high pressure during high flow rate refueling causes the positive pressure valve 73 to
When the negative pressure valve 75 collides with the pressing portion 75b over a predetermined distance to the side of the passage 67 opened to the valve chamber 63, the negative pressure valve 75 is opened, and the passage area is enlarged. The circulating flow rate of the pipe 25 toward the inlet 25a is increased, and the entrainment of outside air from the inlet 25a of the oil supply pipe 25 can be reduced.

Thus, the generation of steam can be reduced, and the size of the canister 29 can be reduced. FIG. 10 shows a second embodiment of an evaporative fuel emission control device according to the present invention. In this embodiment, a tank body 23 and a canister 29 are connected by an evaporative fuel passage 31.

At the inlet 61 of the evaporative fuel passage 31, when the fuel in the tank body 23 exceeds a predetermined liquid level, the inlet 6
A float valve 49 for closing 1 is arranged. An on-off valve 33 composed of a diaphragm valve is interposed in the evaporative fuel passage 31. The on-off valve 33 has a positive pressure chamber 39 and a back pressure chamber 41, and the fuel vapor passage 31 is interposed on the positive pressure chamber 39 side.

The pressure on the positive pressure chamber 39 side is changed to the back pressure chamber 41.
The fuel vapor passage 31 is opened when the pressure is higher than the pressure on the side by a predetermined value or more. A pressure introducing passage 65 is arranged to connect the inlet 25 a of the oil supply pipe 25 and the back pressure chamber 41 side of the on-off valve 33. In this embodiment, the on-off valve 3
When the pressure on the upstream side of the valve 3 is higher than the pressure on the pressure introduction passage 65 side by a predetermined value or more, the upstream side of the on-off valve 33 is connected to the pressure introduction passage 6.
The first communication means 101 communicating with the first communication means 5 is arranged.

The first communication means 101 is provided between the upstream side of the on-off valve 33 in the fuel vapor passage 31 and the pressure introduction passage 65.
And a first communication path 103 for connecting A first check valve 105 that opens when the pressure on the upstream side of the on-off valve 33 is higher than the pressure on the pressure introducing passage 65 by a predetermined value or more is disposed in the first communication passage 103.

In this embodiment, the pressure introducing passage 6
When the pressure on the fifth side is higher than the pressure on the upstream side of the on-off valve 33 by a predetermined value or more, a second communication means 107 for communicating the upstream side of the on-off valve 33 with the pressure introducing passage 65 is provided. The second communication means 107 has a second communication path 109 connecting the upstream side of the on-off valve 33 in the fuel vapor path 31 and the pressure introduction path 65.

A second check valve 111 is provided in the second communication passage 109 and opens when the pressure on the pressure introduction passage 65 side is higher than the pressure on the upstream side of the on-off valve 33 by a predetermined value or more. . In the evaporative fuel emission suppression device of this embodiment, the pressure in the tank main body 23 and the pressure in the fuel supply pipe 25 are the same during normal running, so the pressure on the positive pressure chamber 39 side of the on-off valve 33 and the back pressure chamber The pressure on the side 41 becomes the same, and the on-off valve 33 is closed.

When the cap 27 of the refueling pipe 25 is removed for refueling, the first check valve 105 of the first communication means 101 is closed, so that the fuel vapor passes through the pressure introducing passage 65. Inlet section 2 of oil supply pipe 25 through
It is prevented from being guided to 5a and emitted to the outside. next,
When the internal pressure in the tank body 23 rises due to the start of refueling, the pressure of the on-off valve 33 on the positive pressure chamber 39 side becomes larger than the pressure on the back pressure chamber 41 by a predetermined value or more, and
Is opened, and the fuel vapor from the tank body 23 is adsorbed by the canister 29 through the fuel vapor passage 31.

At this time, the pressure on the upstream side of the on-off valve 33 is applied to the check valve 10 disposed in the first communication means 101.
5 is greater than the pressure on the side of the pressure introduction passage 65 by a predetermined value or more.
5 is opened, the fuel vapor in the tank main body 23 is guided to the inlet 25a of the fuel supply pipe 25 through the pressure introduction passage 65, and is returned to the tank main body 23 together with the fuel supplied from the fuel supply gun 113 and the like. .

As a result, an increase in fuel vapor due to the mixing of outside air is prevented. Next, when the fuel is filled in the tank body 23, the inlet 61 of the evaporative fuel passage 31 is closed by the float valve 49, and when the pressure on the upstream side of the on-off valve 33 decreases, the on-off valve 33 and the check valve 105 close. Can be Next, when the refueling is completed, the cap 27 is attached to the refueling pipe 25.
Is mounted, the pressure at the inlet 25a of the refueling pipe 25 becomes
The pressure rises in the same manner as the pressure in the tank main body 23, the second check valve 111 of the second communication means 107 is opened via the pressure introduction passage 65, and the pressure on the upstream side of the on-off valve 33 becomes the pressure in the tank main body 23. Rises to almost the same pressure as
The sticking of the float valve 49 to is eliminated.

Therefore, it is possible to prevent the float valve 49 from sticking to the inlet portion 61 of the fuel vapor passage 31.

[0047]

As described above, according to the first aspect of the present invention, when the cap is attached to the fuel supply pipe due to the end of the fuel supply, the pressure at the inlet of the fuel supply pipe becomes the pressure inside the tank body. And the second communication means is opened through the pressure introducing passage, and the pressure on the upstream side of the on-off valve rises to substantially the same pressure as the pressure in the tank body, and the float valve to the inlet is opened. Since the sticking is eliminated, it is possible to easily and reliably prevent the float valve from sticking to the inlet of the evaporative fuel passage.

According to a second aspect of the present invention, the positive pressure valve of the first communication means and the negative pressure valve of the second communication means are accommodated in a valve chamber formed integrally with the on-off valve. , The negative pressure valve is arranged, so that the first communication means and the second communication means
Can be configured without using separate piping, and the apparatus can be made compact. In the fuel vapor suppression device according to the third aspect, when the positive pressure valve moves over a predetermined distance to the opening side of the pressure introduction passage opened to the valve chamber due to the high pressure during high flow rate refueling, the passage expansion means Since the negative pressure valve is opened and the passage area to the pressure introduction passage side is enlarged, the circulating flow to the inlet side of the oil supply pipe increases during high flow refueling, and external air is trapped from the inlet of the oil supply pipe. Can be reduced.

Thus, the generation of steam can be reduced, and the size of the canister can be reduced.

[Brief description of the drawings]

FIG. 1 is a piping system diagram showing a first embodiment of a fuel vapor emission suppression device according to the present invention.

FIG. 2 is an enlarged sectional view showing a main part of the fuel vapor emission control device of FIG. 1;

FIG. 3 is an enlarged sectional view showing a valve chamber of the fuel vapor emission control device of FIG.

FIG. 4 is an explanatory diagram showing a state of a main part of the evaporated fuel emission suppression device of FIG. 1 during normal traveling.

FIG. 5 is an explanatory diagram showing a state of a main part when a cap is removed in the evaporative fuel emission control device of FIG. 1;

FIG. 6 is an explanatory diagram showing a state of a main part at the time of refueling in the fuel vapor emission suppression device of FIG. 1;

FIG. 7 is an explanatory diagram showing a state of a main part at the time of refueling in the fuel vapor emission suppression device of FIG. 1;

FIG. 8 is an explanatory diagram showing a state of a main part of the fuel vapor suppression device of FIG. 1 when the fuel tank is full.

FIG. 9 is an explanatory diagram showing a state of a main part when a cap is mounted in the evaporative fuel emission control device of FIG. 1;

FIG. 10 is a piping diagram showing a second embodiment of the fuel vapor emission suppression device according to the present invention.

FIG. 11 is a piping diagram showing a conventional fuel vapor emission control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Fuel tank 23 Tank main body 25 Oil supply pipe 25a Inlet part 29 Canister 31 Evaporative fuel passage 33 Open / close valve 39 Positive pressure chamber 41 Back pressure chamber 49 Float valve 61 Inlet part 63 Valve chamber 65 Pressure introduction passage 73 Positive pressure valve 75 Negative pressure valve

Claims (3)

[Claims] 1. A canister (29) for adsorbing fuel vapor from a fuel tank (21) having an oil supply pipe (25) in a tank body (23); and the tank body (23) and the canister (29). An evaporative fuel passage (31) connected thereto; and an inlet (61) of the evaporative fuel passage (31) disposed in the tank main body (23) when fuel in the tank main body (23) exceeds a predetermined liquid level. ), A positive pressure chamber (39) and a back pressure chamber (41), and the fuel vapor passage (31) is interposed on the positive pressure chamber (39) side. An on-off valve (33) for opening the fuel vapor passage (31) when the pressure on the pressure chamber (39) side is higher than the pressure on the back pressure chamber (41) by a predetermined value or more; 25) and the back pressure chamber of the on-off valve (33). A pressure introduction passage (65) connecting the pressure introduction passage (65) to the pressure introduction passage (65) by a predetermined value or more than a pressure on the pressure introduction passage (65) side by a predetermined value or more; First communication means (73, 101) for communicating the upstream side of the pressure introducing passage (65) with the pressure introducing passage (65);
Second communication means (75, 107) for communicating the upstream side of the on-off valve (33) to the pressure introduction passage (65) when the pressure on the upstream side of (3) is higher than the upstream pressure by a predetermined value or more. An evaporative fuel emission control device characterized by the above-mentioned. 2. The evaporative fuel emission control device according to claim 1, wherein the first communication means and the second communication means are provided in a valve chamber (63) formed integrally with the on-off valve (33). An evaporative fuel emission control device, comprising a positive pressure valve (73) and a negative pressure valve (75) housed therein, wherein the negative pressure valve (75) is arranged on the positive pressure valve (73). 3. The evaporative fuel emission control device according to claim 2, wherein the positive pressure valve (73) is arranged at a predetermined distance from an opening side of the pressure introduction passage (65) opened to the valve chamber (63). An evaporative fuel emission control device comprising: a passage expanding means for opening the negative pressure valve (75) to the pressure introduction passage (65) when moved over.