JPH0322544Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an evaporated fuel emission prevention device for an internal combustion engine, and more particularly to a device for adsorbing fuel vapor into two charcoal canisters and purging it into the intake system.

[Conventional technology]

A large-capacity charcoal canister has a large canister ventilation resistance, so in order to increase the purge flow rate and improve the purge efficiency, it is necessary to increase the diameter of the air hole of the canister. but,
When the diameter of the air hole is increased, there is a problem in that the fuel vapor adsorbed in the charcoal canister tends to escape from the air hole. In addition, there is a problem in that the internal pressure of the canister decreases, and the adsorption efficiency of the canister decreases.

Therefore, a first coal canister for adsorbing fuel vapor generated from a first fuel vapor generation source such as a fuel tank, and a second fuel vapor generation source such as a carburetor float chamber are provided. It is proposed that a second charcoal canister for adsorbing vapor is placed in parallel, and the purge passages of these canisters are provided in parallel, and they are merged into one line in the middle and connected to the purge port of the carburetor. (For example, Japanese Patent Application Laid-Open No. 55-23348). However, due to changes in each canister over time, that is, changes in ventilation resistance, the purge amount of fuel vapor becomes unbalanced, and the purge flow rate increases for the one with lower ventilation resistance, while the purge amount decreases for the other, resulting in a decrease in adsorption efficiency. , there is a problem.

Furthermore, a system in which two such carbon canisters are connected in series through a fuel vapor discharge pipe has also been proposed (for example, Utility Model Application No. 59-24961). According to this, although the problem of unbalance in the purge amount of the two coal canisters is solved,
There is a problem in that airflow resistance increases during purging, making it difficult to increase purge efficiency.

[Problem that the invention attempts to solve]

In this invention, in an evaporative fuel emission prevention device equipped with two charcoal canisters, the internal pressure of each canister is increased to increase the fuel vapor adsorption efficiency of the canister, and when one canister overflows, the overflowed fuel vapor is is adsorbed to the other canister to increase the overall adsorption capacity.

[Means for solving problems]

In order to realize such an object, the present invention includes a first coal canister connected to a first fuel vapor generation source that generates a relatively large amount of fuel vapor, and a first fuel vapor generation source that generates a relatively large amount of fuel vapor. a second charcoal canister connected to a second fuel vapor generation source that generates a relatively small amount of fuel vapor compared to the second charcoal canister;
In the evaporative fuel emission prevention device in which the atmospheric port side of the first carbon dioxide canister is connected to the purge port side of the second carbon dioxide canister via a connecting pipe, the connecting pipe is connected to the A check valve is provided to prevent outflow and allow inflow from the atmosphere into the connecting pipe, and the purge port sides of the first and second coal canisters are connected to the intake pipe of the internal combustion engine through their respective purge passages. An evaporative fuel emission prevention device is provided, which is characterized in that the evaporative fuel discharge prevention device is connected to the evaporative fuel discharge prevention device.

[Effect]

When fuel vapor in the first carbon canister overflows, it flows into the second carbon canister through the connecting pipe and is adsorbed by the second carbon canister. The valve opens and fresh air is introduced into the first charcoal canister located upstream.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of an evaporative fuel emission prevention device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings.

In the figure, the intake system consists of an air cleaner 1, a carburetor 2, and an intake manifold 3 from upstream, and is connected to an engine body 4. Fuel vapor generated at a first fuel vapor generation source such as the fuel tank 6, which generates a relatively large amount of fuel vapor, passes through a first fuel vapor introduction pipe 14 to a first coal canister on the upstream side. It is adsorbed by activated carbon 11 in 10. The fuel vapor generated at the second fuel vapor generation source, which generates a relatively small amount of fuel vapor compared to the first fuel vapor generation source such as the fuel float chamber 7 of the carburetor 2, is transferred to the second fuel vapor introduction pipe. 24 and is adsorbed by the activated carbon 21 in the second charcoal canister 20 on the downstream side. Note that 27 is an outer vent control valve. The internal upper purge chambers 12 and 22 of each coal canister 10 and 20 are connected to purge ports 16 and 26 provided upstream of the throttle valve 5 of the carburetor 2 through respective purge passages 15 and 25, respectively. When the throttle valve 5 is opened during engine operation and negative pressure is generated in the purge ports 16 and 26, the fuel vapor adsorbed on the activated carbon in each of the charcoal canisters 10 and 20 is transferred to the vaporizer 2. Purge inward.

The atmospheric communication chamber 13 on the lower side inside the first carbon dioxide canister 10 is connected to the purge chamber 22 on the upper side inside the second carbon dioxide canister 20 via the connecting pipe 30.
is connected to. This connecting pipe 30 extends downward from the first charcoal canister 10, but at least a portion of the connecting pipe 30 is installed at a position higher than the upper part of the first charcoal canister 10. Further, a pipe 31 branched from this connecting pipe 30 is opened to the atmosphere via a check valve 32 and a filter 33. This check valve 32
prevents fuel vapor from flowing out from the connecting pipe 30 to the atmosphere, and allows fresh air to flow into the connecting pipe 30 from the atmosphere. The atmosphere communication chamber 23 on the lower side of the interior of the second carbon canister 20 is opened to the atmosphere through an atmosphere port 28 .

When the pressure of fuel vapor in the fuel tank 6 becomes high and flows into the first coal canister 10, the check valve 32 is closed.
The internal pressure of the charcoal canister 10 increases,
Adsorption efficiency is increased. The residual pressure in the first carbon dioxide canister 10 flows into the second carbon dioxide canister 20 through the connecting pipe 30. Since the piping is installed at a higher position, it is advantageous for increasing the internal pressure of the first charcoal canister 10. This provides the same effect of increasing internal pressure as when the diameter of the canister's atmospheric hole is made smaller.
When fuel vapor exceeding the adsorption capacity of the first upstream carbonate canister 10 is introduced from the fuel tank 6, it is guided to the downstream second carbonate canister 20 via the connecting pipe 30. . In this way, the second charcoal canister 20 is connected to the carburetor 2.
The fuel vapor generated in the fuel float chamber 7 is introduced through the outer vent control valve 27 and adsorbed therein, and the fuel vapor that overflowed the first coal canister 10 is introduced and acts to be adsorbed. In this manner, even if the fuel vapor in the first coal canister 10 overflows, the check valve 32 is closed, so there is no risk of the fuel vapor being discharged into the atmosphere.

Conversely, during purging, the insides of the first and second carbon canisters 10 and 20 become negative pressure, so the check valve 32 opens and fresh air passes through the filter 33 and flows into the first carbon canister. At the same time, fresh air is introduced into the second carbon canister 20 from the atmosphere port 28, and the fuel vapor adsorbed on the respective activated carbons 11 and 21 is vaporized from the fuel vapor release pipes 15 and 25. It is inhaled into the container 2. In this way, since fresh air is introduced into the first and second coal canisters 10 and 20 from separate air inlet ports during purging, it is the same as when the diameter of the air holes in the canisters is increased. This increases the purge flow rate and improves the purge efficiency.

Furthermore, by providing an appropriate throttle 34 in the connecting pipe 30 that communicates the first and second coal canisters 10 and 20, it is possible to reduce the It is possible to promote the increase in internal pressure, and at the time of purging, the second charcoal canister 2
Due to the influence of the air flow from the 0 side to the first charcoal canister 10 side, it is possible to reduce the amount of air introduced.

Note that, as is clear from the above description, the first carbon dioxide canister 10 is connected to a fuel vapor generation source that generates more fuel vapor, such as the fuel tank 6, and the second carbon dioxide canister 20 is connected to a fuel vapor generation source that generates more fuel vapor. is connected to a fuel vapor source, such as a fuel float chamber 7, which produces less fuel vapor. In addition, the purge passages 15 and 25 are independent passages, and as shown in the figure, the purge passages 15 and 25 are independent passages.
The purge port 16 connected to the second channel canister 20 is connected to the purge port 2 connected to the second channel canister 20
Throttle valve 5 is installed slightly downstream of 6.
It is desirable to start purging on the first charcoal canister 10 side at an earlier point in time when the first charcoal canister 10 opens.

In this way, in the embodiment, the purge passages 15, 25
are connected to the intake pipe 2 through independent passages, so the airflow resistance of each of the charcoal canisters 10 and 20 will differ over time or due to changes in the adsorption state, resulting in unbalanced purge amounts. Even if this occurs, there will be no possibility that the purge amount of one side will be extremely reduced compared to the other, resulting in a drop in adsorption efficiency.

[Effect of idea]

According to the present invention, in a device equipped with two serially connected charcoal canisters, the first charcoal canister 10 on the upstream side has a small diameter hole when adsorbing fuel vapor. Similarly, the internal pressure is increased and the adsorption efficiency is increased, and during purging, the purge flow rate can be increased to increase the purge efficiency, similar to when the diameter of the atmospheric hole is increased. Moreover, the fuel vapor overflowing from the first carbon dioxide canister 10 is adsorbed by the second carbon dioxide canister 20, thereby substantially increasing the capacity of the canister. Furthermore, in the present invention, since the check valve 32 is provided in the connecting pipe 30, the fuel vapor that overflows in the first coal canister 10 does not escape to the atmosphere and is captured in the second coal canister 20. Ru. Therefore, it is possible to prevent harmful fuel vapor components from being released into the atmosphere.

[Brief explanation of the drawing]

The figure is a schematic diagram of an evaporative fuel emission prevention device for an internal combustion engine according to the present invention. 6...Fuel tank (first fuel vapor generation source),
7...Float chamber (second fuel vapor generation source), 1
0...First channel canister, 20...Second channel canister, 15, 25...Purge passage, 30...Connecting pipe, 34...Check valve.

Claims (1)

[Scope of utility model registration request] a first charcoal canister connected to a first fuel vapor source that generates a relatively large amount of fuel vapor; and a second carbon canister that generates a relatively small amount of fuel vapor compared to the first fuel vapor source. a second charcoal canister connected to the fuel vapor generation source, and an atmospheric port side of the first charcoal canister is connected to a purge port side of the second charcoal canister via a connecting pipe. In the evaporative fuel emission prevention device consisting of
The connecting pipe is provided with a check valve that prevents outflow from the connecting pipe to the atmosphere and allows inflow from the atmosphere into the connecting pipe, and a check valve is provided on each of the purge port sides of the first and second coal canisters. An evaporative fuel emission prevention device characterized in that it is connected to an intake pipe of an internal combustion engine via a barge passage.