JP2943654B2 - Evaporative fuel emission prevention 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 preventing fuel vapor from being discharged from a fuel tank of an automobile at the time of refueling, and more particularly to an apparatus for preventing fuel vapor from being discharged from a fuel tank through a differential pressure valve to a canister. About.

[0002]

2. Description of the Related Art There has been proposed a technique for adsorbing evaporated fuel generated in a fuel tank to a canister during fuel supply to prevent discharge of fuel vapor into the atmosphere. (U.S. Pat.
No. 14,172). According to this technique, as shown in FIG. 5, the vehicle fuel tank 220 and the canister 222 are connected via the conduit 256 and the differential pressure valve 250.
The differential pressure valve 250 is controlled by the diaphragm 264.
And the high pressure side 254 of the differential pressure valve 250 are partitioned. The low pressure side 252 of the differential pressure valve communicates with the vicinity of the oil supply port of the inlet pipe 226 through a conduit 224, and a communication portion 224a is formed in the inlet pipe 226.
The high pressure side 254 of the differential pressure valve communicates with the fuel tank 220 side. When the fuel cap 228 is closed, the differential pressure valve low pressure side 252 and the differential pressure valve high pressure side 254 have the same pressure, and the elastic force of the spring 266 causes the fixed portion 256 of the differential pressure valve 250 to move. Section 258 to canister 2
The differential pressure valve 250 is urged toward the valve closing direction 22 and is closed. When the fuel cap 228 is opened due to fuel supply or the like, the differential pressure valve low pressure side 252 changes from high pressure (tank internal pressure) to low pressure (atmospheric pressure), and the differential pressure valve high pressure side 254 changes.
Becomes low pressure later than the differential pressure valve low pressure side 252. Then, due to the pressure difference between the low pressure side 252 and the high pressure side 254 of the differential pressure valve at the initial stage of opening the fuel cap 228, the differential pressure valve 2
50 is opened. Furthermore, when refueling, the differential pressure valve low pressure side 2
52 is low pressure (atmospheric pressure) since it is connected to the vicinity of the inlet filler port, and the high pressure side 254 of the differential pressure valve becomes positive pressure due to the fuel level rise due to fuel injection. The pressure difference between the low pressure side 252 and the high pressure side 254 of the differential pressure valve causes the differential pressure valve 250 to open. The fuel tank 220 communicates with a path connecting the canister 222 to the fuel tank 2.
The fuel vapor generated in 20 is guided to the canister 222,
It is adsorbed on activated carbon or the like of the canister 222 to prevent the evaporative fuel from being discharged to the atmosphere.

[0003]

However, when a differential pressure valve is used as in the above technique, liquid fuel flows from the vicinity of the inlet pipe filler port to the low pressure side of the differential pressure valve and accumulates due to fuel movement during turning of the vehicle or the like. . Alternatively, the evaporated fuel in the path connecting the low pressure side of the differential pressure valve and the inlet pipe is cooled and liquefied after the engine is stopped, and flows into the low pressure side of the differential pressure valve as liquid fuel and is accumulated. The liquid fuel accumulated on the low pressure side of the differential pressure valve has an undesired effect of making it difficult to open the differential pressure valve even if the differential pressure valve obtains a pressure difference during fuel supply.

[0004] Therefore, the present invention is to quickly return the liquid fuel flowing into the low pressure side of the differential pressure valve to the fuel tank by a communication means which enables communication between the low pressure side of the differential pressure valve and the fuel tank. It is still another object of the present invention to perform a valve-opening operation of a differential pressure valve during fueling without being affected by the communication means.

[0005]

According to a first aspect of the present invention, there is provided an apparatus for preventing evaporative fuel discharge, comprising: a fuel tank for an automobile; a canister for processing the evaporative fuel generated in the fuel tank; A path connecting the tank and the canister; and a differential pressure valve provided in the middle of the path to open and close the path by an opening / closing operation. The low pressure side of the differential pressure valve communicates with the fuel tank vicinity near the fuel tank. An evaporative fuel discharge prevention device in which the high pressure side of the differential pressure valve communicates with the fuel tank, wherein the low pressure side of the differential pressure valve and the fuel tank can communicate with each other, and the liquid fuel that flows into the low pressure side of the differential pressure valve is A communication means for returning the fuel into the fuel tank is provided.

[0006]

The liquid fuel flowing into the low pressure side of the differential pressure valve is returned to the fuel tank by the communication means which enables communication between the low pressure side of the differential pressure valve and the fuel tank.

[0007]

According to a second aspect of the present invention, there is provided an evaporative fuel emission preventing apparatus according to the first aspect, wherein:
At the time of fuel supply, there is provided a passing air flow rate limiting means for limiting the passing air flow rate of the evaporated fuel flowing to the low pressure side of the differential pressure valve through the communication means.

[0008]

The passing air flow restricting means restricts the passing air flow of the evaporated fuel flowing to the low pressure side of the differential pressure regulating valve through the fuel supply communication means.

[0009]

FIG. 1 is an overall view of an evaporative fuel discharge prevention device for a fuel tank for an automobile, FIG. 2 (a) shows a closed state of a differential pressure valve, and FIG. FIG. 3 shows the valve opening state of the differential pressure valve, and FIG. 4 shows the state of the fuel tank internal pressure at the time of fuel supply. According to FIG. 1, the fuel tank 20 is provided with an inlet pipe 26,
A fuel cap 28 is provided at a filler port of the inlet pipe 26 so as to seal the fuel tank 20. A differential pressure valve 50 is mounted on the upper surface of the fuel tank 20, and the low pressure side 52 of the differential pressure valve 50 is connected to the fuel pipe 20 through the conduit 24 near the fuel supply port of the inlet pipe 26. The high-pressure side 54 of the differential pressure valve 50 is connected to the fuel tank 20. Reference numeral 22 denotes a canister through which the fuel vapor in the fuel tank is guided through the differential pressure valve 50 and the conduit 30 when the differential pressure valve 50 is opened.

Referring to FIG. 2, the differential pressure valve 50 includes a main body case portion 56, a valve portion 58, and a lid portion 60. Case part 56
Is a differential pressure valve fixing portion that is connected to and connected to the fuel tank 20, and the valve portion 58 is a differential pressure valve movable portion in which the seal member 62 and the diaphragm 64 are integrally provided. The valve section 58, the diaphragm 64, and the lid section 60 form the above-described differential pressure valve low-pressure side 52, and the valve section 58, the diaphragm 64, and the main body case section 56 form the above-described differential pressure valve high-pressure side 54. That is, the low pressure side 52 of the differential pressure valve 50 and the differential pressure valve 5
0 is separated from the high-pressure side 54.

Above the case 56, the fuel tank 20
Conduit 56 which is part of the path connecting the
c is provided so as to be able to communicate with the canister 22. When the differential pressure valve 50 is closed, the conduit 56c is provided with a seal seat 56a that abuts against the seal member 62 of the valve portion 58 and hermetically blocks a path connecting the fuel tank 20 and the canister 22. Below the case portion 56, there is provided a known float 32 which rises with the rise of the fuel level when the fuel is supplied, and comes into contact with the float valve seal seat 56b of the case portion 56 to regulate the fuel level. I have. Reference numeral 34 denotes a spring that acts against the buoyancy of the float 32 when the buoyancy is generated downward in the plane of the drawing.

The valve portion 58 includes the seal seat 5 of the case portion 56.
6a, a seal member 62 for closing the differential pressure valve 50,
A diaphragm 64 that supports the valve portion 58 is provided integrally so that the valve portion 58 can move in the vertical direction. A guide piece 58a is provided on the valve portion 58 with a gap therebetween. The guide piece 58a is provided substantially at the center of the valve portion 58, preferably at the lowest position of the valve portion 58, at the low pressure side 52 and the high pressure side 54 of the differential pressure valve.
A communication hole 80 is provided as a communication means for communicating the.

The lid 60 is provided with a projection 60a, and the tip of the projection 60a has a diameter slightly smaller than the inner diameter of the communication hole 80 of the valve portion 58. Protrusions 82 are provided as passing air flow limiting means for limiting the passing air flow. In addition, a conduit 60b that is a part of a path that communicates with the vicinity of the oil supply port of the inlet pipe 26 is formed integrally with the lid 60.

Next, the operation of this embodiment will be described.
According to FIG. 2, when the fuel cap 28 is closed, the low pressure side 52 of the differential pressure valve and the high pressure side 54 of the differential pressure valve have the same pressure, and the differential pressure valve 50 has a spring provided in the space of the low pressure side 52 of the differential pressure valve. The sealing member 62 of the valve portion 58 is
Is urged against the seal seat 56a of the case portion 56 to close the valve, thereby sealingly shutting off the path connecting the fuel tank 20 and the canister 22. At this time, the liquid fuel flowing from the vicinity of the oil supply port of the inlet pipe 26 to the differential pressure reducing valve low-pressure side 52 through the conduit 24 and the conduit 60b, or the conduit 24 and the conduit 6
The liquid fuel generated by cooling and liquefying the fuel vapor in the pressure chamber 0b or in the low-pressure side 52 of the differential pressure valve falls into the fuel tank 20 through the communication hole 80 provided in the valve portion 58 and returns.

When the fuel cap 28 is opened by fuel supply or the like, according to FIG. 3, the fuel supply port of the inlet pipe 26 is opened to the atmosphere, and the low pressure side 52 of the differential pressure valve is connected to the inlet pipe 26 through the conduit 60 b of the lid 60. Since it is connected to the refueling port, from high pressure (tank pressure) to low pressure (atmospheric pressure)
become. The high pressure side 54 of the differential pressure valve communicates with the fuel tank 20, and the pressure becomes low later than the low pressure side 52 of the differential pressure valve. The differential pressure valve 50 is opened by the pressure difference between the differential pressure valve low pressure side 52 and the differential pressure valve high pressure side 54 at the initial stage of opening the fuel cap 28. When fuel is supplied, the pressure near the inlet port is low (atmospheric pressure), and the high pressure side 54 of the differential pressure valve becomes positive due to the rise in the fuel level due to fuel injection. The pressure difference between the low pressure side 52 and the high pressure side 54 of the differential pressure
0 opens the valve. When the differential pressure valve 50 is opened, the guide piece 58 a provided on the valve portion 58 is
0a, the valve portion 58 is supported by the diaphragm 64 and moves upward. Then, as shown by F in FIG. 3, the evaporated fuel generated in the fuel tank 20 is guided to the canister 22 through the conduit 56c of the case portion 56, and is adsorbed by the activated carbon in the canister 22 and processed.

At this time, as the valve portion 58 moves upward with the opening operation of the valve, the convex portion 82 provided at the tip of the convex portion 60a of the lid portion 60 is moved to the valve portion 58. The communication hole 80 provided in the communication hole 80 has a small opening area. As a result, the amount of air flow of the evaporated fuel flowing to the low pressure side 52 through the communication hole 80 is restricted. That is, the communication hole 80, the conduit 60b, and the conduit 24
And the amount of fuel vapor discharged from the inlet pipe 26 to the atmosphere can be suppressed. Then, the pressure drop in the fuel tank 20 due to the flow of the evaporated fuel to the differential pressure valve low pressure side 52 can be reduced, so that the differential pressure valve 50 can be kept open.

The above contents will be described with reference to FIG.
As shown by the solid line in FIG.
A state in which the gas space in the fuel tank 20 is pressurized by the rise in the fuel level, and the pressure in the fuel tank 20 gradually increases. That the fuel tank internal pressure between AB rises,
The low pressure (atmospheric pressure) near the oil supply port of the inlet pipe 26 causes the differential pressure valve low pressure side 52 and the differential pressure valve high pressure side 54
, And the differential pressure valve 50 reaches the valve opening pressure and opens.
The state in the fuel tank 20 between AB is a state in which the fuel vapor moves irregularly in the fuel tank 20 due to the momentum of the fuel injection. Therefore, the evaporated fuel canister 22
And the tank internal pressure further rises due to the fuel level rise even after the differential pressure valve 50 opens beyond the valve opening pressure.

The state in the fuel tank 20 between the BCs is such that the vaporized fuel starts to be introduced to the canister 22 through the differential pressure valve 50, the amount of the gas space in the fuel tank 20 reduced by the rise in the fuel level, and the state of the canister 22. The tank pressure is reduced until the amount of the evaporated fuel gradually approaches and is balanced. Further, between the BCs, the convex portion 82 fits into the communication hole 80 and the opening area of the communication hole 80 is reduced, so that the evaporated fuel is prevented from flowing to the differential pressure reducing valve low-pressure side 52 through the communication hole 80, The pressure drop in the fuel tank 20 due to the outflow of the evaporated fuel to the differential pressure valve low pressure side 52 is suppressed.
Then, the tank internal pressure is changed to the differential pressure valve 50 until the fueling of E is completed.
, The differential pressure valve 50 can be maintained in the open state, and the fuel vapor can be guided to the canister 22. If the convex portion 82 is not provided, and if the opening area of the communication hole 80 is too large, the low pressure side 5
As shown by the broken line in FIG. 4, there is a possibility that the valve opening pressure of the differential pressure regulating valve 50 cannot be maintained before the end of the fuel supply. The rapid change in the tank internal pressure of D is caused by the closing of the float 32 due to the filling of the fuel tank 20 and the auto-stop function of the fuel injection gun (not shown) following the closing of the valve. It occurs when refueling ends suddenly.

In the above embodiment, a communication hole as communication means is provided in a valve portion which is a movable portion of a differential pressure valve, a convex portion which is a means for restricting a flow rate of air is provided in a lid portion of the differential pressure valve, and the convex portion is communicated. Although it is fitted into the hole to limit the amount of air passing through the communication hole, it is not always necessary to fit the air if the amount of air flowing through the communication hole can be limited. Further, as long as the communication means returns the liquid fuel flowing into the low pressure side of the differential pressure valve into the fuel tank of the differential pressure valve, the communication means may be provided at a position other than the movable portion of the differential pressure valve. For example, the liquid fuel may be returned into the fuel tank by directly connecting the low pressure side of the differential pressure valve and the fuel tank by a pipe that allows communication between the low pressure side of the differential pressure valve and the fuel tank. Further, the liquid fuel may be returned into the fuel tank by using a material having fuel permeability for the differential pressure valve as the communication means.

Further, in the above embodiment, a communication hole as communication means is provided in the movable portion of the differential pressure valve, and a convex portion as air flow restriction means is provided in the lid portion to limit the amount of air passing through the communication hole. However, a communication hole as communication means may be provided at a position other than the movable part of the differential pressure valve, and a passing air volume restriction means may be provided at the movable part of the differential pressure valve to limit the amount of air passing through the communication hole.

[0021]

According to the first aspect of the present invention, the liquid fuel which has flowed into the low pressure side of the differential pressure valve is returned to the fuel tank by the communication means which enables communication between the low pressure side of the differential pressure valve and the fuel tank. In addition, the liquid fuel is not accumulated on the low pressure side of the differential pressure valve, so that the valve opening operation of the differential pressure valve can be performed smoothly. Further, in the evaporative fuel discharge device according to the second aspect of the present invention, the flow rate of the evaporative fuel flowing to the low pressure side of the differential pressure valve through the fuel refueling communication means is restricted by the flow rate restricting means. The valve opening pressure can be maintained, and the fuel vapor can be guided to the canister. Further, the amount of evaporative fuel discharged from the inlet pipe to the atmosphere can be suppressed by the passing air flow restricting means.

[Brief description of the drawings]

FIG. 1 is an overall view of an apparatus for preventing fuel vapor from being discharged from an automobile fuel tank.

FIGS. 2A and 2B show an embodiment of an evaporative fuel emission prevention device according to the present invention, in which FIG. 2A shows a closed state of a differential pressure valve, and FIG.

FIG. 3 is a view showing an embodiment of an evaporative fuel emission prevention device according to the present invention, and showing a valve opening state of a differential pressure valve.

FIG. 4 is a diagram showing a state of a fuel tank internal pressure at the time of fuel supply.

FIG. 5 is a diagram showing a conventional technique.

[Explanation of symbols]

 20 220 220 Fuel tank 22 222 Canister 50 250 Differential pressure valve 52 252 Differential pressure valve low pressure side 54 254 Differential Pressure valve high pressure side 80 ... communicating hole (communicating means) 82 ... convex part (passing air volume limiting means)

Claims (2)

(57) [Claims] An automobile fuel tank, a canister for processing fuel vapor generated in the fuel tank, a path connecting the fuel tank and the canister, and a path provided in the middle of the path to open and close the fuel tank. An evaporative fuel discharge prevention device having a differential pressure valve for communicating and shutting off a path, a low pressure side of the differential pressure valve communicating with a fuel supply port vicinity of the fuel tank, and a high pressure side of the differential pressure valve communicating with the fuel tank. An evaporative fuel discharge prevention device, further comprising communication means for enabling communication between the low pressure side of the differential pressure valve and the fuel tank and returning liquid fuel flowing into the low pressure side of the differential pressure valve to the inside of the fuel tank. 2. An evaporative fuel discharge prevention device according to claim 1, further comprising a passing air flow restricting means for restricting a passing air flow of the evaporative fuel flowing to the low pressure side of the differential pressure valve through the communication means when supplying fuel. .