JP3312467B2 - Evaporative fuel processor for internal combustion engines - 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 an internal combustion engine.

[0002]

2. Description of the Related Art A main activated carbon layer, an auxiliary activated carbon layer having a smaller capacity than the main activated carbon layer, and a fuel vapor diffusion suppression space formed between the main activated carbon layer and the auxiliary activated carbon layer are provided. 2. Description of the Related Art A canister is known in which an evaporative fuel chamber connected to a passage is communicated with the atmosphere via a main activated carbon layer, then an evaporative fuel diffusion suppression space, and then a sub-active carbon layer (see Japanese Patent Application Laid-Open No. 5-33734). In this canister, a fuel vapor diffusion suppression space is provided between the main activated carbon layer and the sub-activated carbon layer, thereby controlling the release of the vapor fuel to the atmosphere.

That is, in this canister, the fuel vapor generated in the fuel tank is sent to the fuel vapor chamber, and then the fuel vapor flows into the main activated carbon layer and is adsorbed by the activated carbon in the main activated carbon layer. On the other hand, when the fuel vapor chamber is communicated with the negative pressure generation region in the engine intake passage, the fuel vapor released from the main activated carbon layer is purged into the engine intake passage. The purging action of the fuel vapor into the engine intake passage is not performed when the engine is stopped, whereas the fuel vapor continues to be fed into the canister even when the engine is stopped, so that the largest amount of the fuel vapor is transferred to the activated carbon in the main activated carbon layer. The adsorption is performed when the engine is stopped.

[0004] When the amount of fuel vapor adsorbed on the activated carbon in the main activated carbon layer increases, a part of the fuel vapor is desorbed from the activated carbon in the main activated carbon layer and tends to diffuse into the auxiliary activated carbon layer. Since the evaporative fuel diffusion suppression space is provided between the auxiliary activated carbon layer and the auxiliary activated carbon layer, the amount of evaporative fuel diffused into the auxiliary activated carbon layer is small, and thus the amount of evaporative fuel adsorbed by the activated carbon in the auxiliary activated carbon layer is small. . If the amount of the evaporated fuel adsorbed in this manner is small, the amount of the evaporated fuel released from the activated carbon in the auxiliary activated carbon layer and released into the outside air becomes extremely small. It can be suppressed.

[0005]

On the other hand, when the operation of the engine is started and the fuel vapor chamber is connected to the negative pressure generating region in the engine intake passage, the air flows into the auxiliary activated carbon layer and first the auxiliary The evaporative fuel is desorbed from the activated carbon in the activated carbon layer, and then the desorption action of the evaporative fuel from the activated carbon in the main activated carbon layer is started. However, when such a sub-activated carbon layer is provided, the overall flow resistance increases, so that the amount of air flowing into the main activated carbon layer is reduced, and thus the air is adsorbed by activated carbon in the main activated carbon layer having a large capacity. There is a problem that a large amount of evaporated fuel cannot be desorbed in a short time.

[0006]

According to the present invention, there is provided a main activated carbon layer, a sub activated carbon layer having a smaller capacity than the main activated carbon layer, and a layer formed between the main activated carbon layer and the sub activated carbon layer. And a fuel vapor chamber connected to the inside of the fuel tank and the engine intake passage is communicated with the atmosphere via the main activated carbon layer, then the vapor fuel diffusion suppressing space, and then the auxiliary activated carbon layer. In the evaporative fuel treatment device, the evaporative fuel chamber is communicated with the air chamber only through the main activated carbon layer without passing through the auxiliary activated carbon layer, and the air chamber is provided with an atmosphere release valve for controlling communication between the air chamber and the atmosphere, The air on-off valve is kept closed until a predetermined period elapses after the engine is started, and the air release valve is kept open when the predetermined period elapses.

[0007]

The air flows into the sub-activated carbon layer because the air release valve is kept closed until a predetermined period elapses after the engine is started. The vaporized fuel adsorbed on the fuel is almost completely desorbed. When a predetermined period elapses after the engine is started, the atmosphere is directly opened from the air chamber into the main activated carbon layer because the atmosphere release valve is kept open. Since the flow resistance of the main activated carbon layer is small, a large amount of air flows in the main activated carbon layer at this time, and thus the fuel vapor is rapidly desorbed from the activated carbon in the main activated carbon layer.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, reference numeral 1 denotes a canister, 2 denotes a fuel tank, 3 denotes an engine body, and 4 denotes an intake passage provided with a throttle valve 5. The main activated carbon layer 6 in the canister 1
And a sub-activated carbon layer 8 separated from the main activated carbon layer 6 by the partition wall 7. The auxiliary activated carbon layer 8 has a considerably smaller capacity than the main activated carbon layer 6, and has a considerably large flow path resistance. The main activated carbon layer 6 is formed between the pair of filters 9 and 10, and the sub activated carbon layer 8 is formed between the pair of filters 11 and 12.
It is formed between them. An evaporative fuel chamber 13 is formed above the main activated carbon layer 6, and an air chamber 14 is formed below the main activated carbon layer 6. Further, an atmosphere chamber 15 communicating with the atmosphere is formed above the auxiliary activated carbon layer 8,
A fuel vapor diffusion suppression space 16 is formed below the auxiliary activated carbon layer 8. In addition, the auxiliary activated carbon layer 8 and the diffusion suppression space 16
A stop aperture 17 is formed between them.

The fuel vapor chamber 13 is connected to the intake passage 4 via a purge pipe 18 on the one hand, and a pressure control valve 19 for controlling the pressure in the fuel tank 2 and a fuel fuel supply pipe 20 on the other hand. It is connected to the upper space of the fuel tank 2. The pressure control valve 19 has a diaphragm 22 for controlling the opening and closing of the valve port 21. When the pressure in the fuel tank 2 exceeds a certain pressure, the pressure control valve 19 opens and the fuel vapor in the fuel tank 2 is released. The fuel is fed into the fuel vapor chamber 13 through the fuel vapor supply pipe 20.

The tip of the fuel injection pipe 23 of the fuel tank 2 projects into a recess 24 formed in the vehicle body.
A lid 25 that can cover the recess 24 is rotatably attached to the vehicle body. A detection switch 26 that can detect the open / closed state of the lid 25 is attached to the lid 25. An on-off valve 28 rotatable around a pivot 27 is attached to the fuel injection pipe 23.
Reference numeral 8 denotes a position normally shown in FIG. 1, that is, the lower end opening of the fuel supply nozzle guide 29 is closed by a spring force of a spring (not shown), and the evaporated fuel passage 30 connecting the upper space of the fuel tank 2 and the evaporated fuel chamber 13 is shut off. Resting in position.

When fuel is to be injected into the fuel tank 2, the lid 25 is first opened and then the fuel cap 31
Is removed, and then the refueling nozzle is
Is inserted into. At this time, the opening and closing valve 28 is rotated clockwise because the tip of the oil supply nozzle contacts the opening and closing valve 28. As a result, the evaporated fuel in the fuel tank 2 is fed into the evaporated fuel chamber 13 through the evaporated fuel passage 30 so that the on-off valve 28 opens the evaporated fuel passage 30. When refueling is completed and the refueling nozzle is withdrawn, the on-off valve 28 returns to the position shown in FIG. 1 again.

On the other hand, the atmosphere chamber 1 formed in the canister 1
An atmosphere port 32 communicating with the atmosphere is formed in 4, and an atmosphere opening valve 33 for controlling the opening and closing of the atmosphere port 32 is arranged in the atmosphere port 32. The atmosphere release valve 33 is controlled by an output signal of the electronic control unit 40. The electronic control unit 40 is composed of a digital computer, and is connected to a RAM (random access memory) 42, a ROM (lead-on memory) 43, a CPU (microprocessor) 44, and a power supply which are interconnected by a bidirectional bus 41. Backup RAM 45, input port 4
6 and an output port 47. The input port 46 is connected to the detection switch 26 and a rotation speed sensor 48 for generating an output signal indicating the engine rotation speed. The input port 46 receives an on / off signal of an ignition switch 49. On the other hand, the output port 47 is
Is connected to the atmosphere release valve 33 via the

First, consider the case where the operation of the engine is stopped. At this time, when the pressure in the fuel tank 2 becomes higher than the opening pressure of the pressure control valve 19, the evaporative fuel generated in the fuel tank 2 is discharged via the evaporative fuel supply pipe 20 and the pressure control valve 19 to the evaporative fuel chamber 13. Then, the evaporated fuel flows into the main activated carbon layer 6 and is adsorbed by the activated carbon in the main activated carbon layer 6. At this time, the fuel vapor chamber 13
Therefore, the concentration of the evaporated fuel adsorbed on the activated carbon gradually increases from the air chamber 14 toward the evaporated fuel chamber 13.

By the way, in the activated carbon, the adsorbed fuel vapor is diffused mainly by two methods. For example, if a difference occurs in the concentration of the evaporated fuel adsorbed on the main activated carbon layer 6, the evaporated fuel moves along the surface of the activated carbon toward a lower concentration. That is, the evaporated fuel diffuses along the surface of the activated carbon so that the concentration of the evaporated fuel in the main activated carbon layer 6 becomes uniform. This is the first diffusion method.

On the other hand, when the concentration of the fuel vapor in the air around the activated carbon decreases, the fuel vapor adsorbed on the activated carbon desorbs from the activated carbon and jumps out into the air. Next, the evaporated fuel also diffuses in the air so as to have a uniform concentration. This is the second diffusion method. Therefore, as described above, when the fuel vapor in the fuel tank 2 is fed into the main activated carbon layer 6, the concentration difference initially occurs in the main activated carbon layer 6, but as the time elapses, the concentration of the evaporated fuel in the main activated carbon layer 6 increases. Becomes uniform. By the way, as shown in FIG. 1, when a diffusion control space 16 is formed between the main activated carbon layer 6 and the sub-activated carbon layer 8, the activated carbon layer is interrupted in the diffusion control space 16, so that the above-described operation from the main activated carbon layer 6 to the sub-activated carbon layer 8 is performed. The diffusion of the evaporated fuel by the first diffusion method will not occur.

On the other hand, the inside of the diffusion suppressing space 16 is filled with air containing evaporated fuel, and the evaporated fuel in this air gradually diffuses into the sub-activated carbon layer 8 through the throttle opening 17. However, the amount of fuel vapor flowing into the auxiliary activated carbon layer 8 through the throttle opening 17 is small, and it takes a considerable time for the fuel vapor to diffuse to the end of the auxiliary activated carbon layer 8 on the atmosphere chamber 15 side. Thus, almost no fuel vapor is released from the auxiliary activated carbon layer 8 into the atmosphere. Therefore, even if only the diffusion suppression space 16 is provided, the emission of the evaporated fuel to the atmosphere is considerably suppressed. If the throttle opening 17 is further provided, the emission of the evaporated fuel to the atmosphere is further suppressed.

On the other hand, when the operation of the engine is started and the fuel vapor chamber 13 is connected to the negative pressure generating area of the intake passage 4 via the purge pipe 18, the atmosphere in the atmosphere chamber 15 is released from the secondary activated carbon layer 8 and the throttle opening. 17, the diffusion suppression space 16, the main activated carbon layer 6, the fuel vapor chamber 13, and the purge pipe 18 are supplied into the adsorption passage 4. At this time, first, the evaporated fuel adsorbed on the activated carbon in the auxiliary activated carbon layer 8 is desorbed, and thus all the evaporated fuel adsorbed on the activated carbon in the auxiliary activated carbon layer 8 is eliminated in a short time. Can be Therefore, immediately after the engine is stopped, no evaporated fuel is adsorbed on the activated carbon in the auxiliary activated carbon layer 8 at all. As a result, even if the evaporated fuel diffuses into the auxiliary activated carbon layer 8 while the engine is stopped, the evaporated fuel is surely adsorbed by the activated carbon in the auxiliary activated carbon layer 8 and thus the emission of the evaporated fuel to the atmosphere is prevented. It can be suppressed.

In order to prevent the fuel vapor from being released to the atmosphere, the fuel is first adsorbed on the activated carbon in the auxiliary activated carbon layer 8 when the purge operation of the fuel into the intake passage 4 is started. It is necessary to desorb the evaporated fuel. However, the flow resistance of the auxiliary activated carbon layer 8 is large, and
Is provided, the flow path resistance is further increased, so that the amount of air flowing in the sub-activated carbon layer 8 and the main activated carbon layer 6 becomes small. Therefore, if the air that has passed through the sub-activated carbon layer 8 is allowed to flow into the main activated carbon layer 6 even after all the fuel vapor has been desorbed from the activated carbon in the sub-activated carbon layer 8, the total evaporated fuel can be removed from the activated carbon in the main activated carbon layer 6. Takes a long time to desorb.

Therefore, in the embodiment according to the present invention, as shown in FIG. 2, the atmosphere opening valve 33 is kept closed until a certain period To elapses after the start of the engine. After that, the atmosphere release valve 33 is kept open until the engine is stopped. This fixed period To is a period necessary for desorbing all the evaporated fuel from the activated carbon in the auxiliary activated carbon layer 8. The certain period To varies depending on the volume of the auxiliary activated carbon layer 8 and the type of activated carbon, but is about 20 to 40 minutes.

On the other hand, when a predetermined period To elapses after the engine is started and the air release valve 33 is opened, the air is released from the air chamber 14.
Flows into the fuel vapor chamber 13 through the main activated carbon layer 6. At this time, air no longer flows in the secondary activated carbon layer 8.
As described above, the flow resistance of the main activated carbon layer 6 is small. Therefore, at this time, a large amount of air flows in the main activated carbon layer 6 from the air chamber 14 to the fuel vapor chamber 13. As a result, all the fuel vapor can be desorbed from the activated carbon in the main activated carbon layer 6 in a short time.

When the on-off valve 28 is opened by the refueling nozzle during refueling, the fuel vapor in the fuel tank 2 is fed into the main activated carbon layer 6 through the fuel vapor passage 30. Next, when fuel is blown out from the refueling nozzle, the pressure in the fuel tank 2 increases, and a large amount of fuel vapor is generated.
This evaporated fuel is sequentially sent into the main activated carbon layer 6. At this time, if the atmosphere on-off valve 33 is kept closed, the pressure in the fuel tank 2 becomes considerably high due to the large flow path resistance in the canister 1, and as a result, the pressure from the refueling nozzle in response to this pressure is increased. The fuel injection operation will be automatically stopped.

Therefore, in the embodiment according to the present invention, when the lid 25 is opened for refueling, the air release valve 33 is opened immediately. When the atmosphere release valve 33 is opened, the pressure in the fuel tank 2 does not increase so much because the flow path resistance in the canister 1 decreases, and thus the fuel injection operation stops during refueling by the refueling nozzle. You will not be swayed.

FIG. 4 shows a routine for controlling the atmosphere release valve. This routine is executed by interruption every predetermined time. In the embodiment shown in FIG. 1, power is continuously supplied to the electronic control unit 40 even when the engine is stopped. Referring to FIG. 4, first, at step 100, it is determined whether or not the ignition switch 49 is on. When it is ON, the routine proceeds to step 101, where the engine speed N is 400 rpm. p. m, that is, whether the engine has been started. N> 400 r.
p. When it reaches m, the routine proceeds to step 102, where the count value T is incremented by one, and then at step 103, it is determined whether or not the count value T has become larger than a predetermined value To. If T <To, the routine proceeds to step 107, where the atmosphere release valve 33 is closed, and T
If ≧ To, the routine proceeds to step 104, where the atmosphere release valve 33 is set.
Is opened.

On the other hand, when it is determined in step 100 that the ignition switch 49 is not turned on, or in step 101, N ≦ 400 r. p. When it is determined to be m, the routine proceeds to step 105, where the count value T is set to zero, and then at step 106, it is determined whether or not the detection switch 26 is on. When the detection switch 26 is off, that is, when the lid 25 is closed as shown in FIG. 1, the routine proceeds to step 107, where the atmosphere release valve 33 is closed. On the other hand, when the detection switch 26 is turned on, that is, when the lid 25 is opened, the routine proceeds to step 104, where the atmosphere release valve 33 is opened.

When the activated carbon in the sub-activated carbon layer 8 deteriorates due to aging, the adsorption capacity of the activated carbon decreases. Therefore, it is preferable that the period To shown in FIG. 2 necessary for desorbing all the fuel vapor from the activated carbon in the sub-activated carbon layer 8 is gradually shortened as the activated carbon deteriorates. FIG. 3 shows the relationship between the optimum engine To and the cumulative operating time ΔT of the engine. In the second embodiment shown in FIG. 5, the period To is determined based on the relationship shown in FIG. Note that the cumulative running distance of the vehicle may be used instead of the cumulative driving time ΔT.

FIG. 5 shows a routine of the second embodiment for controlling the atmosphere release valve, and this routine is executed by interruption every predetermined time. Referring to FIG. 5, first, at step 200, it is determined whether or not the ignition switch 49 is on. If it is on, the routine proceeds to step 201, where the engine speed N is 400 r. p.
m, that is, whether the engine has been started. N> 400 r. p. Step 20 when m
Proceeding to 2, the count value T is incremented by one,
Next, at step 203, the cumulative operation time ΔT is incremented by one. Next, at step 204, the period To is determined from the cumulative operation time ΔT based on FIG. 3, and then at step 205, it is determined whether or not the count value T has become larger than a predetermined value To. T <
In the case of To, the routine proceeds to step 209, where the atmosphere release valve 33 is set.
Is closed, and when T ≧ To, the routine proceeds to step 206, where the atmosphere release valve 33 is opened.

On the other hand, when it is determined in step 200 that the ignition switch 49 is not turned on, or in step 201, N ≦ 400r. p. When it is determined that it is m, the process proceeds to step 207, where the count value T is set to zero, and then in step 208, it is determined whether or not the detection switch 26 is on. When the detection switch 26 is off, that is, when the lid 25 is closed as shown in FIG. 1, the routine proceeds to step 209, where the atmosphere release valve 33 is closed. On the other hand, when the detection switch 26 is turned on, that is, when the lid 25 is opened, the routine proceeds to step 206, where the atmosphere release valve 33 is opened.

[0028]

According to the present invention, all the fuel vapor adsorbed on the activated carbon in the main activated carbon layer can be desorbed in a short time while suppressing the release of the fuel vapor into the atmosphere.

[Brief description of the drawings]

FIG. 1 is an overall view of a fuel vapor processing apparatus.

FIG. 2 is a time chart of opening / closing control of an atmosphere release valve.

FIG. 3 is a diagram illustrating a valve closing period To of an atmosphere release valve.

FIG. 4 is a flowchart for controlling an atmosphere release valve.

FIG. 5 is a flowchart showing a second embodiment for controlling the atmosphere release valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Canister 2 ... Fuel tank 3 ... Engine main body 4 ... Intake passage 6 ... Main activated carbon layer 8 ... Secondary activated carbon layer 13 ... Evaporated fuel chamber 14 ... Air chamber 16 ... Diffusion suppression space 33 ... Atmospheric release valve

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B01D 53/04 ZAB B60K 15/077 F02M 25/08

Claims (1)

(57) [Claims] 1. A fuel cell system comprising: a main activated carbon layer; a sub-activated carbon layer having a smaller capacity than the main activated carbon layer; and a fuel vapor diffusion suppression space formed between the main activated carbon layer and the sub-activated carbon layer. In the evaporative fuel treatment device in which the evaporative fuel chamber connected to the passage is communicated with the main activated carbon layer, then the evaporative fuel diffusion suppression space, and then through the auxiliary activated carbon layer to the atmosphere, the evaporative fuel chamber is connected to the sub-active carbon layer. Communication with the air chamber only through the main activated carbon layer without intervening, an air release valve for controlling the communication between the air chamber and the atmosphere is provided in the air chamber,
An evaporative fuel for an internal combustion engine that keeps the atmosphere on-off valve closed until a predetermined period elapses after the engine is started, and holds the atmosphere opening valve open when the predetermined period elapses. Processing equipment.