JP2605336B2 - Evaporative fuel treatment system for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention adsorbs fuel evaporated from a fuel storage chamber such as a fuel tank of a vehicle to prevent the evaporated fuel from being released into the atmosphere. The present invention relates to an evaporative fuel processing device (hereinafter referred to as a canister).

[Conventional technology]

Conventionally, this type of canister has an adsorbent made of activated carbon or the like in a casing. The adsorbent adsorbs fuel vapor generated in a fuel tank of a vehicle and a float chamber of a carburetor, and adsorbs the fuel in the canister. The evaporated fuel thus desorbed by the intake pipe negative pressure is sucked into the intake pipe.

Also, in order to prevent a high concentration of evaporated fuel from being sucked into the intake pipe in the initial stage of desorption and to change the air-fuel ratio, an on-off valve controlled by various conditions of the vehicle is provided in the passage from the canister to the intake pipe. And a fixed orifice for controlling the flow rate of the evaporated fuel sucked into the intake pipe.

[Problems to be solved by the invention]

However, in the case of a large canister that processes a large amount of fuel vapor generated during gasoline refueling,
When the above-mentioned system is adopted, the concentration of the vaporized fuel to be desorbed is high, so that the desorbable condition for controlling the on-off valve becomes severe, and the desorption of the vaporized fuel adsorbed by the canister only in a region where the intake air amount is considerably large. Will be performed. Therefore, there is a problem that the flow rate of the entire evaporated fuel to be desorbed decreases, and the evaporated fuel adsorbed by the canister is not sufficiently desorbed.

The present invention has been made in view of the above problems, and can adsorb a large amount of high-velocity vaporized fuel generated at the time of refueling, and determine the influence of the vaporized fuel sucked from the canister into the intake pipe on the air-fuel ratio. The present invention provides an evaporative fuel processing apparatus capable of increasing the flow rate of the entire evaporative fuel desorbed by enlarging a suction air amount area where the evaporative fuel adsorbed by the canister can be desorbed, while increasing the amount of evaporative fuel adsorbed by the canister. With the goal.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, in a vehicular fuel vapor treatment device for adsorbing fuel vapor from a fuel tank with a fuel vapor adsorbent, a first space portion, a first vaporization portion, A first adsorbent chamber having a fuel adsorbent, a second space portion, a second evaporative fuel adsorbent, and a third space portion, in which the first evaporative fuel adsorbent is disposed, and the second evaporative fuel; The second adsorbent chamber in which the adsorbent is disposed is divided into two chambers by partition walls, and when adsorbing the fuel vapor, the first adsorbent chamber and the second adsorbent chamber are connected in series to form an evaporator. At the time of purging for supplying the fuel to the intake system of the vehicle, the second opening is opened to the second space portion, and the intake pipe negative pressure causes
A purge port for desorbing the evaporated fuel adsorbed by the evaporated fuel adsorbent into an intake pipe is provided, and the first adsorbent chamber and the second adsorbent chamber are connected in parallel; An inlet port opened to the first space for introducing fuel vapor generated at the time of refueling the fuel tank; and an air port opened to the third space and connected to the atmosphere, the evaporating generated at the time of refueling the fuel tank. In the pipe for introducing fuel to the introduction port, according to the operating state of the vehicle,
A three-way valve for switching between communication between a fuel tank and the introduction port and communication between the atmosphere and the introduction port is provided.

[Action]

According to the above configuration, a large amount of evaporative fuel generated at the time of refueling the fuel tank is diffused in the first space portion through the introduction port, and then adsorbed by the first evaporative fuel adsorbent, and further adsorbed by the adsorbent. The evaporative fuel that has leaked out without being adsorbed is diffused in the second space, and then adsorbed by the second evaporative fuel adsorbent. Therefore, the evaporative fuel is adsorbed by the adsorbent and then adsorbed by the second adsorbent without causing an increase in airflow resistance as in the case of being introduced into a large amount of evaporative fuel adsorbent generated during refueling. Therefore, the adsorption concentration of the first adsorbent is relatively higher than that of the second adsorbent.

During the operation of the engine, the evaporative fuel adsorbed by the evaporative fuel adsorbent is desorbed by the negative pressure of the intake pipe generated, but the three-way valve communicates between the fuel tank side and the introduction port according to the operating state of the vehicle. And the communication between the atmosphere side and the introduction port are switched, and the atmosphere is introduced into the first space, so that the atmosphere port for introducing the atmosphere is switched to both the atmosphere port and the introduction port. If the amount of intake air is small, the vaporized fuel is mainly desorbed from the second vaporized fuel adsorbent having a low adsorption concentration. Evaporated fuel is desorbed from both the first and second evaporated fuel adsorbents. Therefore, by controlling the three-way valve, it is possible to control the concentration of the evaporative fuel released according to the operating state without limiting the conditions under which the fuel can be released, and to prevent fluctuations in the air-fuel ratio.

〔Example〕

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

In FIG. 1, a canister 100 includes a cylindrical casing 2 formed of a resin or an iron plate, and a cylindrical partition wall 3 disposed inside the casing 2 and formed of a resin or an iron plate. I have.

The inside of the casing 2 and the outer periphery of the partition 3 is filled with an adsorbent 6 made of, for example, activated carbon, and the adsorbent 6 forms an adsorbent layer 5. A filter 20 made of a nonwoven fabric or the like is provided on the lower surface of the adsorbent layer 5 in the drawing.
The bottom surface 30 of the partition wall 3 having the communication hole 30a is provided on the lower surface thereof. A filter 17 made of a nonwoven fabric or the like is also provided on the upper surface of the adsorption layer 5 in the drawing, and an upper holding plate 14 having a communication hole 14a is further provided on the upper surface thereof. The positions of the filter 20, the bottom surface 30 of the partition 3, the filter 17, and the upper holding plate 14 are fixed by being fixed to the inner peripheral surface of the outer casing 2.

Further, an adsorbent 4 by the adsorbent 6 is also formed inside the partition 3, and a filter 19 and a lower holding plate 16 having a communication hole 16 a are arranged on the lower surface of the adsorbent layer 4 in the drawing,
Further, an upper holding plate 15 having a filter 18 and a communication hole 15a is disposed above the adsorbent layer 4 in the drawing. A first space 7 is formed inside the partition 3 and below the adsorbent layer 4 in the drawing. A second space 8 is formed inside the casing 2 above the adsorbent layer 5, and a third space 9 is formed below the adsorbent layer 5. On the upper surface in the figure, the first introduction pipe 10 and the second
An introduction pipe 11 and a purge port 12 are formed. First
One end 10a of the introduction pipe 10 communicates with the fuel supply pipe 21a of the fuel tank 21 via the pipe 31, and the other end 10b communicates with the first space 7 through the second space 8 and the adsorbent layer 4. ing. Second
The introduction pipe 11 has a smaller diameter than the first introduction pipe 10 and has one end 11a.
Is connected to an upper port 21b of the fuel tank 21 via a pipe 32, and the other end 11b penetrates through the second space 8 to open to the adsorbent layer 4. Further, the purge port 12 is formed so as to communicate with the second space portion 8, one end 12 a communicates with the downstream side of the throttle valve 26 provided in the intake pipe 24, and the inside of the purge port 12 has a diameter of 0.6 mm to A stop 35 of about 1.0 mm is provided.

A switching valve 22 that is open only for a predetermined time only when fuel is supplied is provided at a connection portion of the fuel tank 21 with the fuel supply pipe 21a in the pipe 31. A three-way valve 27 is provided in the pipe 31. The three-way valve 27 is connected to the fuel tank 21 and the first introduction pipe 10 by a control circuit 28 to which a signal indicating an operation state such as an intake air amount is input. And the communication between the atmosphere and the first introduction pipe 10 are switched.

A control valve 29 is provided in the pipe 32.
29 controls the flow rate of the fuel vapor from the fuel tank 21 to the second introduction pipe 11. A control valve 23 is also provided in the pipe 33, and the control valve 23 controls the flow rate of the evaporated fuel sucked from the purge port 12 into the intake pipe 25.

An atmosphere port 13 is formed on the lower surface of the casing 2 in the drawing, and the atmosphere port 13 is open to the atmosphere.

 Next, the operation of the present embodiment will be described.

The fuel supplied to the fuel supply pipe 21a of the fuel tank 21 is about 3
It flows into the fuel tank 21 at a flow rate of 0 to 40 / min. At this time, the switching valve 22 is open, and the evaporated fuel generated during refueling flows into the pipe 31.

Here, the three-way solenoid valve 27 is switch-controlled by the control circuit 28 to which a signal indicating the refueling state is input so that the fuel tank 21 side and the first introduction pipe 10 of the canister 100 are communicated. The evaporated fuel flowing into the inside is introduced into the canister 100 through the first introduction pipe 10.

The evaporated fuel introduced through the first introduction pipe 10 is discharged from the open end 10b of the first introduction pipe 10 to the first space 7. The discharged fuel vapor is supplied to the partition wall 3 acting as a deflection plate.
Collides with the inner wall of the bottom part 30 of the
Flow velocity decreases. The distance from the opening end 10b of the first introduction pipe 10 to the inner wall of the bottom portion 30 is set to about 6 mm.

Thereafter, the evaporated fuel flows upward from below the adsorbent layer 4 through the communication hole 16a of the lower holding plate 16 via the filter 19,
The adsorption phenomenon proceeds gradually.

Here, since the evaporated fuel collides with the inner wall of the bottom portion 30 and diffuses in the first space portion 7 and then flows through the adsorbent layer 4, the evaporative fuel having a high flow velocity directly flows through the adsorbent layer. As described above, the evaporated fuel is adsorbed in the entire area of the adsorbent layer 4 without passing through without being adsorbed sufficiently, and the utilization efficiency of the adsorbent layer 4 becomes extremely high.

Next, the evaporated fuel leaked from the adsorbent layer 4 is discharged to the second space 8 and diffused, and then flows downward from above the adsorbent layer 5 and is adsorbed. Also in this case, since the evaporated fuel passes through the adsorbent layer 5 after being once diffused in the space 8, the utilization efficiency of the adsorbent 6 is increased.

On the other hand, the fuel evaporated from the fuel stored in the fuel tank 21 passes through the upper port 21b and the pipe 32 to the second inlet pipe 11
The switching valve 29 is set so as to open when the amount of fuel vapor passing through the pipe 32 exceeds a predetermined amount. Since the flow rate of the fuel vapor from the fuel stored in the fuel tank 21 is smaller than that of the fuel vapor generated in the refueling, the diameter of the second introduction pipe 11 is small, and
The open end 11b of 11 is directly opened in the adsorbent layer 4. Therefore, the fuel vapor introduced from the second introduction pipe 11 is adsorbed by the adsorbent layer 4.

During operation of the engine, a negative pressure is generated in the intake pipe 25, and the negative pressure is supplied from the pipe 33 and the purge port 12 to the canister 10.
Introduced in 0. At this time, the three-way valve 27 is controlled to be switched by the control circuit 28 in accordance with the driving state of the vehicle.For example, in the initial stage of desorption of the evaporated fuel or when the intake air amount is small, the three-way valve 27 is The three-way valve 27 communicates between the atmosphere side and the first introduction pipe 10 after the elapse of a predetermined time and the amount of intake air is large after the communication between the 21 side and the first introduction pipe 10 is performed. It has become.

Therefore, for example, in the initial stage of desorption or when the amount of intake air is small, the atmosphere is introduced into the canister 100 from the atmosphere port 13 by the suction pipe negative pressure, and the atmosphere is introduced into the third space 9, the adsorbent layer 5, the first Sequentially pass through the space portion 7 of FIG. By this atmosphere, the evaporated fuel mainly adsorbed to the adsorbent layer 5 having a low adsorption concentration is desorbed, and the evaporated fuel is supplied to the purge port.
It flows into 12. The evaporated fuel that has flowed into the purge port 12 passes through the pipe 33, and its flow rate is adjusted by the switching valve 23, and is sucked into the intake pipe 25.

Further, for example, after a lapse of a predetermined desorption time and when the amount of intake air is large, the three-way valve 27 communicates with the atmosphere side and the first introduction pipe 10, so that the atmosphere is reduced to the atmosphere port 13 by the suction pipe negative pressure. And the first introduction pipe 10. The air introduced from the atmosphere port 13 passes through the third space portion 9, the adsorbent layer 5, and the second space portion 8 sequentially, and the air introduced from the first introduction pipe 10 receives the first space portion 7, It sequentially passes through the agent layer 4 and the second space 8. Therefore, the evaporated fuel that has been adsorbed by both the adsorbent layer 4 and the adsorbent layer 5 is desorbed, flows into the purge port 12, passes through the pipe 33, and the flow rate thereof is changed by the switching valve 23. It is metered and sucked into the intake pipe 25.

Figure 2 in this embodiment, the adsorbent layer 4 and 5 as shown in FIG. 3 to 6 divided into A ₁ to A _6, the adsorption residual rate after desorption and after adsorption of the adsorbent at that respective points The adsorption concentration of the adsorbent becomes lower in accordance with the flow of a large amount of evaporative fuel generated during refueling, and the evaporative fuel is almost uniformly desorbed from each adsorbent.

FIG. 4 shows the desorption characteristics of the adsorbent layer 4 (arrow B) and the desorption characteristics of the adsorbent layer 5 (arrow C) shown in FIG. The evaporated fuel desorbed from the adsorbent layer 4 has a high HC concentration, and the evaporated fuel desorbed from the adsorbent layer 5 has a low HC concentration. Therefore, by controlling the three-way valve 27, the HC concentration can be controlled according to the driving state of the vehicle.

As described above, according to the present embodiment, a large amount of fuel vapor generated at the time of refueling and having a high inflow rate diffuses in the first space 7 through the first introduction pipe 10 and then diffuses into the adsorbent layer 4, 5, the gas is effectively adsorbed almost uniformly as a whole, so that the flow resistance is not increased unlike a case where a large amount of fuel vapor is directly introduced into the adsorbent layer.

Further, the fuel vapor from the fuel stored in the fuel tank 21 is also directly introduced into the inhalant layer 4 through the second introduction pipe 11 and is adsorbed.

Further, the fuel vapor adsorbed by the adsorbent layers 4 and 5 is
During engine operation, the intake pipe is depressurized by negative pressure, but by switching the three-way valve 27 according to the operating state of the vehicle,
Atmosphere port to which atmosphere is introduced is atmosphere port 13 and atmosphere port
Since it is switched to both the 13 and the first introduction pipe 10, for example, in the initial stage of desorption or when the amount of intake air is small, the vaporized fuel adsorbed in the adsorbent layer 5 having a low adsorption concentration is mainly desorbed. After the lapse of a predetermined time of desorption and when the amount of intake air is large, it is possible to desorb the evaporated fuel adsorbed on both the adsorbent layer 4 and the adsorbent layer 5 having a high adsorption concentration.
Therefore, without limiting the conditions under which the canister 100 can be desorbed, it is possible to control the concentration of the evaporative fuel that is desorbed in accordance with the operation state, and to prevent a change in the air-fuel ratio.

The signals input to the control circuit 28 for switching the three-way valve 27 include an intake air amount, an intake negative pressure, a fuel tank
The remaining fuel, cooling water temperature, oxygen amount in exhaust gas, throttle position, engine speed, fuel injection amount, etc. in the fuel cell 21 can be considered.

Further, the three-way valve 27 is not limited to being controlled by the control circuit 28, and may use a pressure valve that operates with intake negative pressure.

It should be noted that the present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist thereof. Hereinafter, a modified example will be described.

In the embodiment shown in FIG.
36, the adsorbent layer 4, the adsorbent layer 5, the first space 7,
A second space portion 8 and a third space portion 9 are formed, and a first introduction port 10,
A second inlet pipe 11 and an atmosphere port 13 are formed, and a purge port 12 is formed on the lower surface of the housing 2. Further, the first introduction port 10 is connected to the first space 7 and the second introduction pipe 11.
Represents the adsorbent layer 4, the atmosphere port 13 communicates directly with the third space 9, and the purge port 12 communicates directly with the second space 8. Since other configurations are the same as those of the above embodiment, the same functional components are denoted by the same reference numerals.

In the above configuration, a large amount of evaporative fuel generated at the time of refueling flows into the first space 7 through the three-way valve 27 and diffuses, and then is adsorbed by the adsorbent layer 4. And the adsorbent layer 4
The evaporated fuel that has leaked out is diffused in the second space portion 8 and then adsorbed by the adsorbent layer 5. Therefore, the adsorbent layer 4
Is relatively higher than the adsorption concentration of the adsorbent layer 5.

During engine operation, the evaporated fuel adsorbed by the intake pipe negative pressure is desorbed. For example, in the initial stage of desorption or when the amount of intake air is small, the three-way valve 27 connects the first introduction port 10 to the fuel tank side. The atmosphere is introduced through the atmosphere port 13 and sequentially passes through the third space 9, the adsorbent layer 5, and the second space 8. Therefore, the evaporated fuel having a low adsorption concentration adsorbed on the adsorbent layer 5 is desorbed and is sucked from the purge port 12 into the intake pipe. Further, after a lapse of a predetermined time of desorption and when the amount of intake air is large, the three-way valve 27 communicates between the atmosphere side and the first introduction port 10, so that the atmosphere is reduced to the atmosphere port 13 and the It is introduced from both of the introduction ports 10. Therefore, the evaporated fuel that has been adsorbed to both the adsorbent layer 4 and the adsorbent layer 5 having a high adsorption concentration is desorbed and is drawn from the purge port 12 into the intake pipe. Therefore,
By controlling the three-way valve 27, it is possible to control the concentration of the evaporated fuel that is desorbed according to the operating state without limiting the desorbable condition of the canister 100, and to prevent the fluctuation of the air-fuel ratio. it can.

〔The invention's effect〕

As described above, according to the present invention, a large amount of evaporated fuel can be effectively adsorbed, and a large amount of adsorbed evaporated fuel can be desorbed at the time of purging. In addition, a large amount of evaporative fuel generated at the time of refueling can be effectively adsorbed, and by controlling the three-way valve, without limiting the conditions under which the canister can be detached,
The concentration of the evaporated fuel that is desorbed can be controlled in accordance with the operation state, and fluctuations in the air-fuel ratio can be prevented.

[Brief description of the drawings]

1 to 5 relate to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the structure of the present embodiment, FIG. 2 is a characteristic diagram showing the adsorption residual ratio after adsorption and desorption of the adsorbent of this embodiment, and FIG. FIG. 4 is a diagram showing the respective positions, FIG. 4 is a diagram showing the desorption characteristics of the present embodiment, FIG. 5 is a diagram showing the flow of each desorption in the desorption characteristics shown in FIG. 4, and FIG.
The figure is a sectional view showing another embodiment of the present invention. 100 ... canister, 2 ... casing, 3 ... wall, 4 ...
Adsorbent layer, 5 ... adsorbent layer, 7 ... first space, 8 ... second
Of the space part, 9 ... third space part, 10 ... first introduction pipe, 11 ...
2nd inlet pipe, 12 …… Purge port, 13 …… Air port, 21
... fuel tank, 25 ... intake pipe, 27 ... three-way valve.

Claims (1)

(57) [Claims] An evaporative fuel processing apparatus for a vehicle, wherein an evaporative fuel from a fuel tank is adsorbed by an evaporative fuel adsorbent, wherein a first space portion, a first evaporative fuel adsorbent,
A first adsorbent chamber having a second space portion, a second evaporative fuel adsorbent, and a third space portion, in which the first evaporative fuel adsorbent is disposed, and in which the second evaporative fuel adsorbent is disposed; The second adsorbent chamber is divided into two chambers by a partition, and the first adsorbent chamber and the second adsorbent chamber are connected in series at the time of adsorbing the evaporative fuel, so that the evaporative fuel is removed from the vehicle. At the time of purging to be supplied to the intake system, the air is opened to the second space and the intake pipe negative pressure causes
A purge port for desorbing the evaporated fuel adsorbed by the evaporated fuel adsorbent into an intake pipe is provided, and the first adsorbent chamber and the second adsorbent chamber are connected in parallel; An introduction port that opens into the first space to introduce fuel vapor generated when the fuel tank is refueled;
An air port which is open to the third space portion and communicates with the atmosphere, wherein a fuel tank is provided in a pipe for introducing evaporated fuel generated at the time of refueling of a fuel tank to the introduction port, according to a driving state of the vehicle. An evaporative fuel processing device for a vehicle, comprising: a three-way valve for switching between communication between a gas inlet side and the inlet port and communication between an air side and the inlet port.