JP3262626B2 - Evaporative fuel processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor treatment system for a motor vehicle.

[0002]

2. Description of the Related Art In an automobile, an evaporative fuel treatment device is used to prevent gasoline vapor from flowing into the atmosphere.

As this device, there is a device having a structure shown in FIG. In FIG. 5, 1 is a fuel tank, 2 is one end opened to the upper air chamber of the fuel tank 1, and the other end is an adsorbent 3
The fuel vapor passage 5, which communicates with the tank port 4a of the main canister 4 filled with, is connected at one end to the purge port 4b of the main canister 4, and the other end is connected to the negative pressure port 6 of the intake pipe of the engine (not shown). It is a purge line that communicates.

[0004] Reference numeral 7 denotes a sub-canister, which is connected to the main canister 4 separately and in series. 8 is an adsorbent filled in the sub-canister 7, and 9 is an atmospheric port on the downstream side of the sub-canister 7.

As shown in FIG. 2B of Japanese Utility Model Laid-Open Publication No. 61-25568, a system in which the main and sub canisters are arranged in series to provide a large-capacity canister as a whole. .

[0006]

In the above prior art,
When the vehicle is left for a long time and the temperature rises in the daytime and the gasoline in the tank 1 evaporates, the evaporated gasoline vapor is adsorbed by the adsorbent 3 of the main canister 4 through the evaporative fuel passage 2.

When the temperature falls at night, the generation of gasoline vapor decreases, but the adsorbent 3 of the main canister 4
The evaporated fuel adsorbed on the sub-canister 7 is diffused and adsorbed on the adsorbent 8 of the sub-canister 7. When the temperature decreases, the pressure in the tank 1 decreases, and air enters the tank from the atmosphere port 9 through the sub-canister 7 and the main canister 4.

When the engine is left for a long time, the vapor of the main canister 4 diffuses and flows to the sub-canister 7, and a large amount of fuel vapor is adsorbed by the adsorbent 8 of the sub-canister 7. When the temperature in the tank rises in this state, the pressure of the fuel vapor in the tank rises, and the air in the tank is released from the main canister 4 through the sub-canister 7 to the atmosphere. For this reason, there is a problem that a large amount of evaporative fuel flows out of the air port 9 together with the air and pollutes the air.

Therefore, the present applicant has previously proposed a device in which a throttle portion is provided in a communication passage between the main canister 4 and the sub-canister 7 to suppress the diffusion of fuel vapor from the main canister 4 to the sub-canister 7. 4-4-2625
issue).

However, when the flow area of the throttle portion is reduced, the above diffusion can be suppressed. However, the purge amount of the evaporated fuel in both canisters 4 and 7 is suppressed, and the flow area of the throttle portion is increased. Then the opposite is true,
There was a problem that none of them could be satisfied.

Accordingly, an object of the present invention is to provide an evaporative fuel treatment apparatus which can solve such problems.

[0012]

In order to achieve the above-mentioned object, the present invention provides an evaporative fuel processing apparatus comprising a main canister and a sub canister in an upper air chamber of a fuel tank via an evaporative fuel passage. A part that connects a main canister and a sub canister in series in a series connection
A throttle portion is formed by a first vent hole which is always open and a second vent hole having a check valve, and the check valve is normally closed. The valve is opened only by the airflow in the direction.

[0013]

[Advantage] Adsorbent (21) in main canister chamber (12)
When the evaporated fuel adsorbed in the tank flows and diffuses into the sub-canister chamber (13), it flows only through the first ventilation hole (31), and the diffusion is suppressed. When the air flows from the sub-canister chamber (13) into the main canister chamber (12), the check valve (33) is opened, and the air flows through the first and second ventilation holes (31) and (32). Atmosphere flows in through the passage having a large area, and the amount of the inflow becomes larger than the amount of the evaporated fuel flowing into the sub-canister chamber (13).

[0014]

Next, a first embodiment of the present invention shown in FIGS. 1 to 3 will be described. Reference numeral 10 denotes a canister case, in which a cylindrical partition 11 having a lower end opening is integrally formed.
A main canister chamber 12 is formed in an outer peripheral portion, and a sub canister chamber 13 is formed in a central portion.

A first diffusion chamber 14 is formed above the main canister chamber 12, and a second diffusion chamber 15 partitioned from the first diffusion chamber 14 is formed above the sub canister chamber 13.

The first diffusion chamber 14 is formed with a tank pipe 16 communicating with an air chamber of a fuel tank (not shown) and a purge pipe 17 communicating with an intake cylinder of the engine. The second diffusion chamber 15 has an atmosphere pipe 18 opened to the atmosphere.
Are formed in communication.

Reference numeral 19 denotes an upper filter, and reference numeral 20 denotes a lower filter, between which an adsorbent 21 for a main canister is filled. A cover 22 is welded and fixed to the lower end of the case 10.
A spring 24 is compressed and interposed between plates 23 provided on the lower surface of the substrate to hold the adsorbent 21.

The lower end of the opening of the partition 11 is formed short so as not to reach the lower filter 20, and a flow gap d is formed between the lower end of the opening and the lower filter 20. The gap d allows the main canister chamber 12 to communicate with the lower canister. Sub canister 1
3 is in communication.

Reference numeral 25 denotes a throttle portion, which is press-fitted and fixed at a lower portion inside the partition 11, and filters 26 and 27 are provided on the upper and lower surfaces thereof. Reference numeral 28 denotes an upper filter installed in the upper part of the sub-canister chamber 13, and a space between the filter 28 and the filter 26 is filled with an adsorbent 29 for the sub-canister.

As shown in the enlarged views of FIGS. 2 and 3, the aperture 25 has a mounting hole 30 at its center, a second vent 32 at its outer periphery, and a first vent 31 at its outer periphery. Are formed penetrating in the vertical direction, respectively.

Reference numeral 33 denotes a check valve, which is formed by a flap seal made of an elastic material.
2 is provided so as to elastically close the lower surface, so that the airflow from below to above in the second ventilation hole 32 is blocked, and the airflow from above to below flows.

Next, the operation of this embodiment will be described. During the stop of the engine, the evaporated fuel generated in the air chamber of the fuel tank diffuses in the first diffusion chamber 14 through the tank pipe 16, flows downward in the drawing, and flows into the adsorbent 21 in the main canister chamber 12. Is adsorbed.

When the concentration of the vaporized fuel adsorbed by the adsorbent 21 is further increased and the concentration of the vaporized fuel adsorbed by the adsorbent 21 is increased, the vaporized fuel flows through the flow gap d.
Into the lower part of the partition 11 through the first
The air enters the sub-canister chamber 13 through the vent hole 31 and is adsorbed by the adsorbent 29.

At this time, the flow direction of the fuel vapor flows upward in the drawing at the throttle section 25, and the valve section 33 of the check valve 33
b is pushed toward the second ventilation hole 32, so that the valve 3
3b closes the second ventilation hole 32. Therefore, only the first ventilation hole 31 is provided in the circulation part, and the fuel vapor in the main canister chamber 12 is suppressed from diffusing into the sub-canister chamber 13.

Therefore, the amount of evaporated fuel adsorbed by the adsorbent 13 in the sub-canister chamber 13 is suppressed, and the amount of evaporated fuel flowing out to the atmosphere through the atmosphere pipe 18 is also reduced. Next, at the time of purging by the engine operation, air is introduced from the air pipe 18 and the air is introduced into the adsorbent 2 in the sub-canister chamber 13.
After passing through the nine layers, it flows downward in the drawing at the throttle portion 25, enters the main canister chamber 12 through the flow gap d, and flows out of the purge pipe 17 to the intake cylinder of the engine.

At this time, the circulation pressure of the atmosphere acts on the second ventilation hole 32 to open the valve portion 33b of the check valve 33, and the atmosphere is changed to the first atmosphere.
The air flows into both the ventilation hole 31 and the second ventilation hole 32. For this reason, the amount of air introduced from the atmosphere pipe 18 increases, and the desorbing action of the evaporated fuel adsorbed by the adsorbent 29 in the sub-canister chamber 13 and the adsorbent 21 in the main canister chamber 12 increases, so that a large amount of evaporated fuel Are purged.

As a result, the adsorbing efficiency in the next adsorbing operation is improved, and the amount of fuel vapor flowing out from the atmospheric pipe 18 is reduced. In the above embodiment, both the main canister chamber 12 and the sub canister chamber 13 are incorporated in the case to reduce the number of parts and the space for mounting on the vehicle. As shown, the main canister and the sub-canister may be formed separately and applied to those directly connected.

The second embodiment shown in FIG. 4 is different from the conventional structure shown in FIG. 5 in that the throttle section 25 of the present invention and the check valve 33 are provided in the communication passage 34 which connects the main canister 4 and the sub-canister 7. Is provided.

The valve portion of the check valve 33 is closed when the fuel vapor flows in the direction of the sub-canister 7, and is opened when the air flows in the direction of the main canister 4, as in the above embodiment. ing.

The second embodiment has the same functions and effects as the first embodiment.

[0031]

As described above, according to the present invention, at the time of adsorbing the evaporated fuel, the flow area of the throttle portion is reduced to suppress the diffusion of the evaporated fuel to the sub-canister. As a result, the amount of fuel vapor flowing out to the atmosphere is reduced, which is effective for air pollution control measures. Further, at the time of purging, the flow area of the throttle section is increased, and the amount of air flowing into the canister is increased to increase the purge amount. As a result, the re-adsorption performance of the adsorbent can be improved, and the amount of evaporative fuel discharged to the atmosphere can be further reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of a diaphragm.

FIG. 3 is a sectional view taken along line AA in FIG. 2;

FIG. 4 is a schematic sectional view showing a second embodiment of the present invention.

FIG. 5 is a system diagram of a conventional structure.

[Explanation of symbols]

 12 Main Canister Chamber 13 Sub Canister Chamber 25 Restrictor 31 First Vent Hole 32 Second Vent Hole 33 Check Valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02M 25/08 311 F02M 25/08 301

Claims (1)

(57) [Claims] 1. An apparatus in which a main canister and a sub-canister are connected in series to an upper air chamber of a fuel tank via an evaporative fuel passage, and a throttle section is provided at a portion where the main canister and the sub-canister are connected in series , The throttle portion is formed by a first ventilation hole that is always open and a second ventilation hole having a check valve, and the check valve is always closed, and the valve is opened only by airflow from the sub canister to the main canister. An evaporative fuel treatment apparatus characterized in that: