JP2590957B2 - Fuel vapor emission prevention device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel vapor emission prevention device for an internal combustion engine.

[Conventional technology]

In order to suppress the emission of fuel vapor generated in the fuel tank to the atmosphere and to make effective use of these, a canister filled with activated carbon or the like is used as an adsorption means.
A configuration in which steam generated in a tank during engine operation or due to a rise in temperature is processed by a first canister, and steam generated during refueling is processed by a second canister is disclosed in U.S. Pat.
No. 884,204.

In the invention described in this publication, the second canister for adsorbing a large amount of steam generated during refueling has a larger capacity since the first canister that adsorbs the vapor generated during operation or the like has a larger amount of vapor generated. However, from the viewpoint of avoiding excessive purge of a large amount of steam from the second canister to the intake manifold and preventing excessive exhaust emissions,
A restrictor (restrictor) for forming a reduced flow region is provided in a conduit for purging adsorbed vapor from the second canister to the intake manifold, and the second restrictor is provided with a purge amount smaller than the vapor purge amount from the first canister. It is characterized in that adsorbed vapor is desorbed from the canister.

[Problems to be solved by the invention]

However, in the fuel vapor emission prevention device disclosed in the above publication, the flow rate restricting member is provided in the purge conduit of the second canister although the capacity of the second canister is larger than that of the first canister. It takes a considerable amount of time for the adsorbed fuel to be desorbed, and in the case where refueling is performed frequently, the second canister is left with insufficient desorption to produce new fuel vapor and has a sufficient adsorption capacity. And fuel vapor tends to be wasted to the atmosphere. Furthermore, as a result of the fuel vapor being left in the canister for a long time, the activated carbon in the canister is rapidly deteriorated and the desorption efficiency is reduced, so that short-term replacement of the activated carbon is required as an essential requirement. Alternatively, there is a contradictory problem that when the size of the canister is increased in consideration of early deterioration in advance, the mountability is deteriorated.

[Means for solving the problem]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel vapor emission prevention device which can solve the above-mentioned problems and can stably adsorb and desorb fuel vapor over a long period of time and can also reduce the size of a canister. It is in.

According to the present invention, in order to achieve the above object, first fuel vapor adsorbing means connected to a fuel tank having a level sensor for adsorbing fuel vapor generated in the tank and discharging the fuel vapor into an intake passage of an internal combustion engine, A second fuel vapor adsorbing means for adsorbing fuel vapor at the time of refueling and discharging the fuel vapor to the intake passage.
A sub-purge pipe having a valve device for connecting the second fuel vapor adsorbing means and the intake passage is further provided, and the valve device is opened according to an output signal at the time of detecting a predetermined refueling state of the level sensor, and the sub-purge pipe is closed. A feature of the present invention is that a quick purge is performed via the power supply.

〔Example〕

 Hereinafter, the present invention will be described with reference to the drawings.

In FIG. 1, a fuel tank 10 has a fuel supply pipe 12 for fuel supply, and a cap 14 is screwed to an inlet end thereof. A fuel pipe (not shown) for supplying fuel to the engine 15 and a return pipe (not shown) for returning surplus fuel are inserted into the fuel tank 10.

In the example shown in FIG. 1, two canisters 20 and 22 filled with activated carbon are provided.

The first canister 20 is connected to the fuel tank by the evaporation pipe 24.
Connected to the upper space of 10. A check valve (not shown) in the middle of the evaporation pipe 24 or at the entrance of the first canister 20
Is arranged. This check valve is bidirectional, and allows the flow of fuel vapor from the fuel tank 10 to the first canister 20 when the pressure of the fuel vapor in the fuel tank 10 becomes high due to thermal expansion or the like. When the pressure in the fuel tank 10 becomes lower than the atmospheric pressure due to a decrease or the like, the first
This allows air to flow from the canister 20 to the fuel tank 10. Therefore, when the cap 14 is closed and the pressure in the fuel tank 10 increases, the fuel vapor is adsorbed on the first canister 20. The first canister 20 has a fuel vapor inlet 28, an outlet 30, and an air inlet 32,
The outlet 30 is connected to a position downstream of the throttle valve 38 in the intake passage 36 of the engine 15 by a purge pipe 34. An electromagnetic valve 40 is provided in the middle of the pipe 34 and is opened by a control device (CPU) 42 according to the operating conditions of the engine 15. solenoid valve
When the valve 40 is opened, the fuel vapor adsorbed on the first canister 20 is purged into the intake passage 36 by the manifold negative pressure, and is burned by the engine 15.

The second canister 22 is connected above the oil supply pipe 12 by a breather pipe 44. The second canister 22 is a fuel vapor inlet
An outlet 48 is connected to the intake passage 36 similarly to the first canister 20 by a pipe 52 having an outlet 46, an air inlet 50, and an air inlet 50.

That is, the fuel vapor adsorbed by the first canister 20 is substantially equally distributed in the intake passage 36 through the purge pipe 34, and the fuel vapor adsorbed by the second canister 22 is transmitted through the pipe 52 joining the purge pipe 34. The above flow of adsorbed fuel vapor, which may be purged, will be referred to as the main purge line.
As can be understood from FIG. 1, the main purge line can be opened and closed in accordance with the opening and closing of the solenoid valve 40.

In accordance with the present invention, the second canister 22 is provided with a sub-purge line. That is, an outlet 58 different from the outlet 48 is formed in the second canister 22, and is connected to the intake passage 36 via the sub-purge pipe 60 having the electromagnetic valve 62.

The sub-purge line regenerates the second canister 22 adsorbing a large amount of fuel vapor generated immediately after or immediately after refueling, that is, purges the adsorbed fuel vapor into the intake passage 36 at once. For this reason, the diameter of the sub-purge line is made larger than that of the main purge line so that the sub-purge line can flow in a large amount (up to 10 times).

An example of an operation example of the apparatus according to the present invention will be described. A control flowchart shown in FIG. 2 is an interrupt routine executed when fuel supply is full in a main routine for executing fuel injection control, air-fuel ratio control, and the like. It can be. First, in step 201, a state corresponding to fuel filling is determined. This is detected by, for example, a level sensor 70 provided in the fuel tank 10. If YES in this step, the routine proceeds to step 202, where the electromagnetic valve 62 is opened and the electromagnetic valve 40 is closed. That is, the main purge line is closed and the sub-purge line is opened, and at the time of refueling, the fuel vapor adsorbed by the second canister 22 passes through the sub-purge pipe 60 and is quickly purged into the intake passage 36 so that the canister can be regenerated in a short time.
Next, at step 203, it is determined whether or not the reproduction is sufficient. That is, the passage flow rate (purge flow rate) is measured by, for example, the flow sensor 64 provided in the sub-purge pipe 60, and the step 202 is repeated until a predetermined flow rate is reached. If a predetermined amount has flowed, the process proceeds to step 204, where the electromagnetic valve 62 is closed and the electromagnetic valve 4
Open 0. That is, the main purge line is opened and the sub-purge line is closed, returning to the normal state, and this routine ends. It should be noted that if the answer is NO in step 201, steps 202 and 203 are skipped and the routine proceeds to step 204, where the routine ends with the solenoid valves 62 and 40 in the normal state.

The purge flow rate in the short-time regeneration is determined from the HC (hydrocarbon) purge characteristic diagram of the activated carbon shown in FIG. It was confirmed that a flow rate of about 17 per gram may be set. Of course, it is needless to say that it is effective to increase the purge flow rate as much as possible if it is acceptable for the apparatus.

In order to explain the advantage of regenerating the canister in a short time, FIG. 4 shows a difference in durability deterioration between a purged one immediately after the adsorption and a purged one after being left for 4 hours. As can be clearly understood from this figure, the deterioration shows a significant deterioration depending on the standing time. On the other hand, it can be understood that the gas immediately purged shows almost no deterioration.

In addition, in the operation example of the present apparatus, switching between the sub purge line and the main purge line is performed depending on whether the purge flow rate has reached a predetermined amount, but without depending on the purge flow rate, that is, without providing a flow sensor, for example, It goes without saying that the same canister regeneration effect can be obtained by switching the line after a predetermined time has elapsed.

Even when the solenoid valve 40 is not provided in the main purge line, it is possible to regenerate the second canister in a short time by opening and closing the sub-purge line independently of the main purge line (open). No change.

By the way, although the purge amount may fluctuate considerably due to the opening and closing of the sub-purge line, the fluctuation of the air-fuel ratio due to these fluctuations is detected by the O ₂ sensor 80 and under the control of the control device (CPU) 42 It can be said that there is almost no problem because the fuel supply is properly controlled by the EFI injector and the A / F can be effectively optimized.

〔The invention's effect〕

As described above, according to the present invention, the second canister, which has adsorbed a large amount of fuel vapor generated during refueling, can be purged very quickly without time, so that the adsorption / desorption capacity is dramatically improved and maintained. This can lead to the possibility of downsizing the canister.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing the entire fuel vapor emission prevention device according to the present invention, FIG. 2 is a diagram showing a control flowchart,
FIG. 3 is a diagram showing the HC purge characteristics of activated carbon, and FIG. 4 is a diagram showing the difference in durability between the case where the purge was performed immediately after adsorption and the case where the purge was performed after standing for 4 hours. 10: fuel tank, 12: refueling pipe, 20: first canister, 22: second canister, 34: purge pipe, 36: intake passage, 40: solenoid valve, 42: control device ( CPU), 60: Sub-purge pipe, 62: Solenoid valve.

Claims (1)

(57) [Claims] A first fuel vapor adsorbing means connected to a fuel tank having a level sensor for adsorbing fuel vapor generated in the tank and discharging the fuel vapor into an intake passage of the internal combustion engine; And a second fuel vapor adsorbing means for adsorbing the fuel vapor and discharging the fuel vapor to the intake passage. A sub-purge pipe having a valve device for connecting the second fuel vapor adsorbing means to the intake passage. A fuel vapor discharge prevention device characterized in that a valve device is opened according to an output signal at the time of detection of a predetermined refueling state of a level sensor, and quick purge is performed via a sub-purge pipe.