JP2743238B2 - 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 an apparatus for treating fuel vapor from a fuel tank mounted on a motor vehicle, and more particularly, to a vent passage for guiding fuel vapor in a fuel tank to a canister, and an intake air for an engine from the canister. The present invention relates to an evaporative fuel processing apparatus provided with a purge line including a purge passage for purging fuel vapor in a passage.

[0002]

2. Description of the Related Art Conventionally, in this type of apparatus, a two-way valve having a built-in positive pressure valve and a negative pressure valve is interposed in a vent passage, and the internal pressure of the tank is adjusted to a predetermined positive pressure by evaporation of fuel in the fuel tank. When the pressure rises above, the positive pressure valve is opened and the fuel vapor in the tank is guided to the canister.On the other hand, when the tank internal pressure falls below a predetermined negative pressure, the negative pressure valve is opened and the atmosphere from the canister side into the tank. Introduced to prevent deformation of the tank. In addition, a bypass valve is interposed in the vent passage in parallel with the 2-way valve, and when refueling the fuel tank, the bypass valve is opened to reduce the tank internal pressure from a positive pressure state to atmospheric pressure, and the fuel vapor in the tank is reduced. There is also known one that can be prevented from being released into the atmosphere from a filler port. Further, a pressure sensor for detecting the internal pressure of a fuel tank is provided, and an alarm is activated when the internal pressure of the tank rises to a reference value or more due to clogging of a vent passage or the like (Japanese Patent Laid-Open No. Hei 2 (1990)). 102360).

[0003]

If a leak occurs due to looseness of the joint between the fuel tank and the vent passage, fuel vapor is released from the leaked portion into the atmosphere. In this case, a bypass valve interposed in parallel with the two-way valve in the vent passage is temporarily opened during operation of the engine to apply a negative pressure of the intake air of the engine to the fuel tank, thereby causing the internal pressure of the purge line including the fuel tank to increase. Is detected by a pressure sensor, and the presence or absence of a leak is determined from the degree of pressure reduction,
It is conceivable to activate the alarm when it is determined that there is a leak. However, simply activating the alarm means that the fuel vapor continues to leak from the leak location until the repair is completed, which is not sufficient as a measure against the leak. The present invention has been made in view of the above circumstances, and provides a device that can detect when a leak has occurred and that can minimize the leakage of fuel vapor from a leak location. For that purpose.

[0004]

In order to achieve the above object,
The present invention includes a purge line including a vent passage for guiding fuel vapor in a fuel tank to a canister, and a purge passage for purging fuel vapor from the canister to an intake passage of an engine.The vent passage includes a positive pressure valve and a negative pressure valve. In an evaporative fuel treatment device having a built-in two-way valve and a bypass valve parallel to the valve, whether or not there is a leak based on an output value of a pressure sensor that detects an internal pressure on a fuel tank side upstream of the bypass valve And a control means for holding the bypass valve open when the determination means determines that there is a leak.

[0005]

[Action] If the bypass valve is not opened, the tank internal pressure becomes 2
Unless the pressure rises to the set pressure of the positive pressure valve of the way valve, the fuel vapor in the tank is not led out to the canister, and when a leak occurs, the fuel vapor is released into the atmosphere from the leak location. However, in the present invention, when the leak occurs, the bypass valve is opened and held based on the determination result of the determination means. Therefore, the upstream side and the downstream side of the two-way valve are communicated via the bypass valve, and the tank internal pressure is reduced. Is prevented from rising to a positive pressure, and the emission of fuel vapor from the leak location to the atmosphere is suppressed.

It is to be noted that the determination means is provided by temporarily opening and closing the bypass valve so as to reduce the internal pressure on the fuel tank side by applying an engine intake negative pressure to the fuel tank side upstream of the bypass valve. If it is configured that the presence or absence of a leak is determined based on a change in the internal pressure on the fuel tank side detected by the pressure sensor after the above, it is advantageous that the presence or absence of a leak on the fuel tank side can be accurately determined. .

[0007]

Referring to FIG. 1, reference numeral 1 denotes a fuel tank mounted on an automobile. Fuel vapor in the tank 1 is purged into an intake passage 4 of an engine 3 through a purge line 2.

The purge line 2 includes a canister 5 having an adsorbent layer 5a for adsorbing fuel vapor, a vent passage 6 for guiding fuel vapor in the fuel tank 1 to the canister 5, and an intake passage 4 for supplying fuel vapor from the canister 5 to the intake passage 4. Throttle valve 4a
A purge passage 7 for purging at a downstream portion of the tank. A positive pressure valve that opens in the vent passage 6 when the tank internal pressure rises above a predetermined positive pressure and opens when the tank internal pressure falls below a predetermined negative pressure. A well-known two-way valve 8 having a built-in negative pressure valve and a bypass valve 9 parallel to the valve 8 are provided.
0, and an atmosphere introduction valve 11 was connected to the canister 5.

The bypass valve 9, the purge control valve 10, and the air introduction valve 11 are controlled to open and close by a controller 12 comprising a microcomputer.
In the predetermined operation state, the purge control valve 10 and the air introduction valve 11 are opened to generate an airflow from the air introduction valve 11 to the purge passage 7 through the adsorption layer 5a in the canister 5 due to the negative pressure of the intake air of the engine 3. Then, the fuel adsorbed by the adsorbent layer 5a is vaporized by this air flow and purged into the intake passage 4 through the purge passage 7, and the opening of the fuel filler lid is detected to open the bypass valve 9 at the time of refueling. Even if the tank internal pressure is a positive pressure, the pressure is reduced to the atmospheric pressure by opening the bypass valve 9 so that the fuel vapor can be prevented from being released into the atmosphere from the filler port.

Further, a pressure sensor 13 for detecting the internal pressure of the fuel tank 1 is provided, and an output signal of the sensor 13 is input to the controller 12, so that a leak test is sometimes performed during the operation of the engine. In detail, at the time of the leak inspection, the fuel tank 1 is temporarily opened to the atmosphere by opening the bypass valve 9 while keeping the purge control valve 10 and the atmosphere introduction valve 11 open as shown in FIG. After that, the bypass valve 9 is closed, and a vapor check for detecting the generation state of the fuel vapor from the degree of increase of the tank internal pressure at this time is performed. Next, while the purge control valve 10 is opened, the air introduction valve 11 is closed, the bypass valve 9 is opened, and the intake negative pressure of the engine 3 is applied to the fuel tank 1 to reduce the tank internal pressure to a predetermined negative pressure. Then, the bypass valve 9 is closed for a predetermined time to perform a leak check. At this time, if no leak has occurred, the tank internal pressure is maintained in a reduced pressure state only by increasing the generation of fuel vapor, but if a leak has occurred, the tank internal pressure increases significantly as indicated by the dotted line. Then, the determination reference value of the tank internal pressure is corrected according to the steam generation state detected by the vapor check, and the determination reference value is compared with the tank internal pressure detected by the pressure sensor 13 at the time of the leak check to determine whether there is a leak. judge.

When it is determined that there is no leak due to the tank internal pressure being equal to or less than the determination reference value, the purge control valve 10 and the atmosphere introduction valve 11 are opened while the bypass valve 9 is closed to return to the normal purge state. Returning, when it is determined that the tank internal pressure exceeds the determination reference value and there is a leak, the bypass valve 9 is switched to the open state and held. According to this, the tank internal pressure is maintained at or below the atmospheric pressure, and the release of fuel vapor from the leak location to the atmosphere is suppressed.

Although the internal pressure of the fuel tank 1 is detected by the pressure sensor 13 in the above embodiment, the pressure in the vent passage 6 upstream of the bypass valve 9 may be detected. In the above embodiment, the purge control valve 10 was closed during the leak check, but may be opened.

[0013]

As is apparent from the above description, according to the present invention, when a leak occurs, the tank internal pressure is maintained below the atmospheric pressure by opening the bypass valve, and the fuel vapor from the leak location to the atmosphere is released. Has the effect of suppressing the release of

[Brief description of the drawings]

FIG. 1 is a system diagram of an example of the apparatus of the present invention.

FIG. 2 is a time chart for explaining its operation.

[Explanation of symbols]

1 fuel tank 2 purge line 3
Engine 4 Intake passage 5 Canister 6
Vent passage 7 Purge passage 8 2-way valve 9
Bypass valve 12 Controller 13 Pressure sensor

Continuation of the front page (72) Inventor Yasunari Seki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda Technical Research Institute Co., Ltd. (56) References JP-A-2-102360 (JP, A) JP-A-61-53451 (JP, A) Japanese Utility Model Showa 63-102962 (JP, U)

Claims (2)

(57) [Claims] A purge line for purging fuel vapor from the canister to an intake passage of the engine; a purge line for purging the vapor from the canister to an intake passage of the engine; a positive pressure valve and a negative pressure valve in the vent passage; In the evaporative fuel treatment device having a two-way valve having a built-in valve and a bypass valve arranged in parallel with the valve, a leak is detected based on an output value of a pressure sensor for detecting an internal pressure on a fuel tank side upstream of the bypass valve. An evaporative fuel processing apparatus comprising: a determination unit for determining the presence / absence; and a control unit for opening and holding a bypass valve when the determination unit determines that there is a leak. 2. The fuel cell system according to claim 1, wherein the determining means applies an intake negative pressure of the engine to a fuel tank upstream of the bypass valve so as to reduce the internal pressure of the fuel tank and then open and close the bypass valve. 2. The evaporative fuel processing apparatus according to claim 1, wherein the presence / absence of a leak is determined based on a change in internal pressure on the fuel tank side detected by the pressure sensor after the detection.