JPS6149499B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automotive fuel evaporation prevention device (hereinafter referred to as a canister) in which a container contains activated carbon that adsorbs fuel vapor generated from an automobile fuel tank, etc. This relates to a canister equipped with a pipe, and its purpose is to effectively utilize the entire activated carbon contained in the container for fuel vapor adsorption.

An automotive canister generally includes a fuel vapor inlet that communicates with a fuel vapor generation source such as a fuel tank, and a mixture outlet that communicates with an intake passage such as a carburetor.
It consists of activated carbon embedded in a container with an air inlet that communicates with the atmosphere.When the engine is stopped, the activated carbon adsorbs fuel vapor introduced into the canister from the fuel tank, etc., preventing it from being released into the atmosphere. When the engine is operating, air is sucked into the canister under negative pressure in the intake passage, the adsorbed fuel vapor is desorbed from the activated carbon by this air, and a mixture of air and fuel vapor is supplied to the intake passage.

Incidentally, even when the engine is operating, the fuel tank and the like may be heated and a large amount of fuel vapor may be generated. In this case, in the above canister, the fuel vapor introduced into the canister from the fuel vapor inlet is led out from the air-fuel mixture outlet without contacting the activated carbon, and is supplied to the intake passage and taken into the engine. Become. As a result, the air-fuel ratio of the intake air-fuel mixture becomes significantly richer than a predetermined value during engine acceleration, etc., leading to engine malfunction and deteriorating exhaust gas.

In order to prevent the occurrence of such troubles, a fuel vapor inflow pipe having a large number of small holes on the pipe wall is provided inside the container, one end of which is connected to the fuel vapor inlet, and the other end is connected to the bottom of the canister. There is a canister protruding into the activated carbon. In this canister, fuel vapor enters the fuel vapor inlet pipe from the fuel vapor inlet and flows into the activated carbon through the small hole, so that the fuel vapor is directly led out from the mixture outlet without contacting the activated carbon. It is possible to prevent this from occurring. However, a problem with this canister is that much of the activated carbon within the container is not effectively utilized for fuel adsorption.

To explain this situation in more detail, in conventional canisters of this type, one end of a thin fuel vapor inlet pipe with the same diameter is connected to the fuel vapor inlet of the container, and the tip side is directed toward the bottom of the canister. The pipe is inserted into an activated carbon layer, and the pipe is not filled with activated carbon. In such conventional canisters, the airflow resistance of the activated carbon layer is much larger than that in the hollow fuel vapor inlet pipe;
The fuel vapor that enters the pipe from the fuel vapor inlet hardly flows out from the small hole at the top of the pipe, and most of it flows out from the small hole at the tip. Therefore, the upper part of the activated carbon layer is not effectively used for fuel adsorption. In addition, the fuel vapor that flows out from the small hole at the tip of the pipe is adsorbed only at the bottom of the activated carbon layer, and the activated carbon in this area quickly reaches the limit of its adsorption capacity, and the vapor that is not adsorbed is released into the atmosphere, causing the device to lose its original capacity. The purpose will not be achieved. Therefore, the present invention provides a fuel vapor inflow pipe that is connected to a fuel vapor inlet and guides fuel vapor into the activated carbon layer, and has a diameter larger than the diameter of the inlet and has a large number of small holes for fuel vapor distribution. using
In addition, by filling this pipe with activated carbon and inserting it into the activated carbon layer, the above-mentioned problems in the conventional device can be solved.

That is, in the canister of the present invention, by filling the fuel vapor inflow pipe with activated carbon, the outflow of fuel vapor into the activated carbon layer is not unevenly distributed in the small holes at the tip of the pipe, as in conventional devices, but is carried out through the pipe. A large amount of water flows out from the small pores at the top of the pores, and the area of the activated carbon layer used for adsorption can be expanded. Further, since the diameter of the pipe is made larger than that of the conventional pipe, there is no possibility that the flow resistance of the fuel vapor within the pipe becomes excessive and obstructs the flow.

Embodiments of the present invention will be described below in comparison with conventional examples.

FIG. 1 shows the structure and fuel vapor flow of an embodiment of the present invention, in which a punching metal 2a having a large number of holes is fixed in a shelf shape to a step formed at the lower part of the canister container 1. Along with being
On top of that is glass wool 3a which is a filter member.
is placed thereon, and granular activated carbon is further filled in a layered manner on top of it. A glass wool 3b is placed on the top surface of the activated carbon layer 4, and a punching metal 2b is placed on top of the glass wool 3b, and a lid 5 is fixed to the upper opening of the container 1 with the punching metal 2b pressed downward. ing.

The lid 5 is provided with a thick valve base portion 5a,
A fuel vapor introduction pipe 6 and an air-fuel mixture outlet pipe 7 are connected to the base portion 5a. Although not shown, the fuel vapor introduction pipe 6 is communicated with the fuel tank via a fuel vapor distribution pipe, and the mixture outlet pipe 7 is communicated with the intake passage of the carburetor via the mixture distribution pipe.

The valve base portion 5a includes a check valve 9 for controlling the flow of fuel vapor from the fuel vapor introduction pipe 6 and a check valve for controlling the flow of the air-fuel mixture from the inside of the container 1 to the air-fuel mixture outlet pipe 7. 10 are provided. Check valve 9
shows a check ball 9a and a valve seat 9c provided with this ball 9a at the opening of the fuel vapor introduction pipe 6.
It consists of a spring 9b for pressing against the
When the fuel vapor pressure in the fuel tank reaches a predetermined value, fuel vapor is allowed to flow into the container 1 through the fuel vapor inlet 9d, and the flow of vapor in the opposite direction is blocked. Check valve 10 is check ball 10
a and this pole 10a to the air-fuel mixture outlet 10d
and a spring 10b for pressing against the valve seat 10c provided in the air-fuel mixture outlet pipe 7, when the engine intake passage negative pressure reaches a predetermined value.
allow the air-fuel mixture to flow into the air, but block the flow of the air-fuel mixture in the opposite direction. On the other hand, a pipe 11 communicating with the atmosphere is attached to the center of the bottom of the container 1, forming an air inlet 11a.

One end of a fuel vapor inflow pipe 12 is fixed to the lower surface of the valve base portion 5a at a position communicating with a fuel vapor inlet 9d provided with a check valve 9. The diameter of this pipe 12 is larger than the diameter of the introduction port 9d, and the tip, that is, the lower end thereof, passes through the center of the punching metal 2b and the glass wool 3b and is inserted into the activated carbon layer 4, and the lower end opening is inserted into the activated carbon layer 4. It is located almost in the center of Also this pipe 1
In the activated carbon layer insertion part 2, small hole groups 12a, 1 for fuel vapor circulation are provided at circumferential positions in upper and lower three stages, respectively.
2b and 12c are bored. This pipe 12 is also filled with activated carbon to the same level as the activated carbon layer 4, and the top surface is filled with glass wool 31b.
is placed.

When the engine is stopped, the fuel vapor generated in the fuel tank opens the check valve 9 when it reaches a predetermined pressure, enters the fuel vapor inlet pipe 12, and passes through the small hole groups 12a, 12b, 12c and the lower end opening. It enters the activated carbon layer 4 and is adsorbed. When the engine is running, when the negative pressure in the carburetor passage reaches a predetermined value, the check valve 10 is opened, and air is sucked into the container 1 from the air inlet 11a.
The adsorbed fuel vapor is desorbed from the activated carbon by this air, and the mixture passes through the mixture outlet 10d and into the pipe 7.
It is then supplied to the vaporizer. Note that even if a large amount of fuel vapor is generated when the engine is stopped and flows into the container by opening the check valve 9, it will directly flow into the air-fuel mixture outlet 10d because it is blocked from the air-fuel mixture outlet 10d by the fuel vapor inflow pipe 12. Not derived from

On the other hand, FIG. 2 shows a typical example of a conventional canister, and to explain the difference from the above-mentioned embodiment of the present invention, it is provided in the valve base portion 5a in communication with the fuel vapor inlet 9d. The fuel vapor inflow pipe 13 has the same diameter as the inlet 9d, penetrates the center of the punching metal 2b and the glass wool 3b, and is erected in the activated carbon layer 4, with its lower end located at the bottom of the activated carbon layer 4. ing. In addition, in the part of the pipe 13 located in the activated carbon layer 4, small hole groups 13a, 13b, 13c are formed at circumferential positions in five upper and lower stages, respectively.
13d and 13e are bored. Activated carbon is not stored in the pipe 13, and the pipe 13 is hollow.

In this conventional device, fuel vapor from the fuel tank enters the activated carbon 14 through each small hole group of the fuel vapor inflow pipe 13. The flow of steam in the activated carbon layer 4 has two elements: the flow as a fluid and the spread due to diffusion, but according to the inventors' experiments, the flow as a fluid is dominant and the diffusion is almost negligible. In the activated carbon layer 4, the steam is
It flows along the paths A′, B′, C′, D′, and E′. However, the inside of the fuel vapor inflow pipe 13 of the conventional device is hollow, and the flow resistance outside the pipe filled with activated carbon is much greater than that inside the pipe.
Only a small amount of the fuel vapor that has flowed into the pipe flows out from the small hole group at the top, and most of it flows out from the small hole group at the bottom, with the largest amount of vapor flowing along the path indicated by arrow E'. However, since the amount of activated carbon in route E' is small, once these activated carbons start adsorbing steam, they soon reach the limit of their adsorption capacity, and the unadsorbed steam is released into the atmosphere through the air introduction pipe 11. As a result, the original purpose of the device cannot be achieved. On the other hand, since the amount of fuel vapor flowing out from the upper small hole group 13a and the like to the activated carbon layer 4 is small, it hardly advances in the lateral direction and flows down toward the bottom of the activated carbon layer 4. Therefore, only a portion of the activated carbon layer 4 is effectively used for fuel vapor adsorption.

On the other hand, in the canister of the present invention, the fuel vapor inflow pipe 12 is also filled with activated carbon as shown in FIG.
Fuel vapor flows out evenly from a, 12b, 12c and the lower end opening, and flows within the activated carbon layer 4 along the paths indicated by arrows A, B, C, and D. In particular, since a larger amount of steam flows out from the upper small hole group 12a etc. than from the upper small hole group of the pipe 13 of the conventional device (FIG. 2), the amount of steam flowing out in the lateral direction also increases. Furthermore, since the paths A to D of the steam flowing through the activated carbon have similar lengths, the steam does not concentrate locally, especially at the bottom of the activated carbon layer 4. Therefore, in this device, the entire activated carbon layer 4 is effectively utilized for adsorption, so that the adsorption capacity is improved, and a situation where fuel vapor is released into the atmosphere at the beginning of the adsorption process does not occur. . Also, the diameter of the fuel vapor inflow pipe 12 is the fuel vapor inlet 9d.
Since the diameter is sufficiently larger than the diameter of the pipe, even in a pipe whose outlet is narrowed by a group of small holes, steam will not become overcrowded and the flow will not be obstructed.

Note that the diameter of the fuel vapor inflow pipe 12 depends on the diameter of the fuel vapor inlet 9d and the diameter of the container 1.
It is desirable that it be about 3 to 5 times the introduction port 9d. If the pipe diameter is made too large, the extraction of the air-fuel mixture will be inhibited in the vapor desorption process. Further, in the above embodiment, the lower end of the fuel vapor introduction pipe 12 was positioned in the vertical direction of the activated carbon layer 4, but the pipe 12 was made even longer.
The lower end may be located at the bottom. Further, the entire lower end of the pipe may be open, or the lower end may be bottomed and a group of small holes for steam circulation may be provided in the bottom.

As described above, the canister of the present invention is a canister with improved performance in which a fuel vapor inlet pipe is provided in the container to communicate with the fuel vapor inlet and feed fuel vapor into the activated carbon layer. The canister of the present invention provides a small, high-performance canister by effectively utilizing the entire activated carbon inside the container for fuel vapor adsorption. This prevents fuel vapor from being locally concentrated and can more completely prevent the release of fuel vapor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a vertical cross section and a flow of fuel vapor in an embodiment of the apparatus of the present invention, and FIG. 2 is a diagram showing a vertical cross section and a flow of fuel vapor in a conventional example. 1... Container, 4... Activated carbon layer, 9d... Fuel inlet, 10d... Air mixture outlet, 11a... Air inlet, 12, 13... Fuel inlet pipe, 12
a, 12b, 12c, 13a, 13b, 13c,
13d, 13e...Small holes of fuel inflow pipe.

Claims (1)

[Claims] 1. Activated carbon is contained in a container having a fuel vapor inlet communicating with a fuel vapor generation source, a mixture outlet communicating with an intake passage of an internal combustion engine, and an air inlet communicating with the atmosphere. A fuel evaporation prevention device for an automobile comprising a fuel vapor inflow pipe having a large number of small holes for fuel vapor distribution in the pipe wall, one end connected to the fuel inlet, and the other end protruding into the activated carbon, A fuel evaporation prevention device for an automobile, characterized in that the diameter of the fuel vapor inflow pipe is larger than the diameter of the fuel vapor inlet, and the pipe is also filled with activated carbon.