JPH08189426A - Evaporation fuel treatment device for internal combustion engine - Google Patents

Abstract

PURPOSE: To prevent a large quantity of vapor from flowing in a canister by liquid surface fluctuation when the liquid surface of fuel is fluctuated in a fuel tank. CONSTITUTION: A differential pressure valve 5 which opens by detecting that pressure in a fuel tank 1 is raised to a prescribed value at the time of oiling, is arranged on the upper part of a fuel tank 1. The differential pressure valve 5 is connected to a canister 2 through breather passages 31, 7a, 7b. At the time of oiling, vapor in the fuel tank 1 is led to the canister 2 passing breather passages 32, 7a, 7b, and fuel component is collected by an activated carbon adsorbent 19 in the canister 2. In the evaporation fuel treatment device in an internal combustion engine provided with the constitution, a negative pressure regulating valve 6 for maintaining the breather passages 7a, 7b in closing condition during engine operation by detecting inner pressure of the breather passages 7a, 7b is arranged on the breather passages 7a, 7b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing device for preventing evaporative fuel generated in a fuel tank of an internal combustion engine from leaking to the atmosphere, and more particularly to evaporative fuel generated in a fuel tank of an automobile or the like. The present invention relates to an evaporated fuel treatment device having a mechanism for preventing the fuel from leaking into the atmosphere during refueling.

[0002]

2. Description of the Related Art In order to prevent evaporative fuel (hereinafter referred to as vapor) generated in a fuel tank of an automobile or the like from leaking to the atmosphere, an evaporative fuel processing apparatus has been conventionally used.

In this apparatus, a vapor passage that connects the inside of the fuel tank and the inside of the canister is formed, and the vapor generated in the fuel tank is introduced into the canister through the vapor passage. Then, the vapor is released into the atmosphere after most of the fuel components are collected by the activated carbon adsorbent contained in the canister.

On the other hand, the fuel component adsorbed by the activated carbon adsorbent is desorbed and absorbed by the air newly introduced from the outside, introduced into the intake passage of the engine intake system, and then burned together with the intake fuel. In the conventional evaporated fuel processing device, the vapor in the fuel tank is processed as described above.

In recent years, there has been a strong demand for a technique for preventing vapor in a fuel tank from leaking to the atmosphere. This is because vapor leakage has become a problem as a cause of air pollution. Under these circumstances, it is required to prevent the evaporative fuel from leaking out not only while the vehicle is traveling but also when the fuel tank is refueled.

In order to solve the above problems, the technique disclosed in the specification and drawings of US Pat. No. 4,714,172 has been proposed. In this evaporated fuel processing device in the prior art, as shown in FIG. 4, a breather passage 43 is provided between the fuel tank 41 and the canister 42, which communicates the both.
a and 43b are provided and the breather passages 43a and 43b are provided.
A diaphragm valve type differential pressure valve 44 is disposed midway. The differential pressure valve 44 includes a diaphragm valve 44
a, the opening end 43c of the breather passage 43b is closed by the diaphragm valve 44a.

The inside of the differential pressure valve 44 is divided into two pressure chambers by the diaphragm valve 44a, one of which is a first pressure chamber 44b and the other is a second pressure chamber 44c. A spring 44d is arranged in the first pressure chamber 44b, and the diaphragm valve 44a is opened by the urging force of the spring 44d to the open end 43c of the breather passage 43b.
Pressed to the side. The pressure passage 4 is provided in the first pressure chamber 44b.
One end of the pressure passage 45 is opened, and the other end of the pressure passage 45 is opened near the fuel supply port 46b of the fuel injection pipe 46. Therefore, the inside of the first pressure chamber 44 b and the inside of the fuel injection pipe 46 are connected by the pressure passage 45.

A seal portion 46a is provided on the inner peripheral wall surface of the fuel injection pipe 46. The seal portion 46a is arranged at a position closer to the fuel tank 41 than the opening portion 45a of the pressure passage 45. The inside of the second pressure chamber 44c communicates with the inside of the fuel tank 41 through the breather passage 43a.

The conventional evaporative fuel treatment system having the above-mentioned structure operates as follows. Other than when refueling, the above first
The diaphragm valve 44a is pressed against the open end portion 43c of the breather passage 43b located below the diaphragm valve 44a by the internal pressure of the pressure chamber 44b and the biasing force of the spring 44d. That is, the differential pressure valve 44 is kept closed. Therefore, the breather passages 43a and 43b are closed.

When refueling, first, the fuel injection pipe 46
The oil supply cap 46c is removed. Next, the refueling nozzle 48 is inserted into the fuel injection pipe 46, and the periphery of the refueling nozzle 48 is sealed by the seal portion 46a. Therefore, from the seal portion 46a, the oil supply port 46b
The inside of the fuel injection pipe 46 on the side is opened to the atmospheric pressure. Since the first pressure chamber 44b communicates with the inside of the fuel injection pipe 46, its internal pressure becomes equal to the atmospheric pressure.

On the other hand, in the fuel tank 41, the fuel level rises due to the injected fuel and the internal pressure of the fuel tank 41 increases. As a result, the fuel tank 4
The inside of the second pressure chamber 44c communicating with the inside of the first pressure chamber 44c has a higher pressure than the inside of the first pressure chamber 44b.
There is a pressure difference between the internal pressures of b and 44c.

The high-pressure vapor in the second pressure chamber 44c urges the diaphragm valve 44a upward against the internal pressure of the first pressure chamber 44b and the urging force of the spring 44d to open the differential pressure valve 44. . As a result, the fuel tank 4
The vapor in 1 is introduced into the canister 42 through the breather passages 43a and 43b, and the fuel component is collected by the activated carbon adsorbent 49 contained therein. That is, the vapor does not leak outside during refueling.

In the following specification, the processing for collecting the evaporated fuel generated in the fuel tank at the time of refueling without leaking to the atmosphere as described above is OR.
VR processing (ORVR; Onboard Refueling Vapor Recove
ry).

[0014]

In the prior art, the float valve 47 is provided in the fuel tank 41, and the fuel tank 41 and the breather passage 4 are connected via the float valve 47.
3a is connected. The float valve 47 prevents the fuel from flowing into the differential pressure valve 44 side when an excessive amount of fuel is supplied to the fuel tank 41 or when the liquid level of the fuel fluctuates during traveling of the vehicle.

However, when the liquid level fluctuation is large and abruptly occurs, the fuel may reach the differential pressure valve 44 before the float valve 47 is closed, and the differential pressure valve 44 may be opened. was there. In such a case, a large amount of vapor flows into the canister 42 via the differential pressure valve 44, and the amount of vapor in the canister 42 is rapidly increased. As a result, excessive vapor is supplied from the canister 42 to the engine intake system, which adversely affects vapor control for supplying vapor from the canister 42 to the engine intake system. Further, the differential pressure valve 44 is often arranged in the upper part of the fuel tank 41 in order to save space, and this is a particularly serious problem in the evaporated fuel treatment device having such a configuration.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an evaporated fuel treatment apparatus for an internal combustion engine, which solves the above-mentioned problems of the prior art.

[0017]

In order to achieve the above-mentioned object, the present invention makes the adsorbent in the canister adsorb the evaporated fuel from the fuel tank through the vapor passage and the adsorbed fuel in the canister during operation of the internal combustion engine. In an evaporated fuel processing apparatus for an internal combustion engine for purging into an intake passage of an internal combustion engine through a purge passage, a breather passage that communicates the inside of a fuel tank with the inside of a canister and introduces the evaporated fuel in the fuel tank into the canister during refueling, and the breather. A first pressure-sensitive valve which is arranged in the middle of the passage and opens upon detection of an increase in the internal pressure of the fuel tank during fueling, and the breather passage between the first pressure-sensitive valve and the canister. The gist of the present invention is to include a second pressure sensitive valve that is arranged and holds the breather passage in a closed state when the internal combustion engine is operating.

[0018]

In the evaporative fuel treatment system having the above structure, the second pressure sensitive valve is kept closed during operation of the internal combustion engine. Therefore, the breather passage from the fuel tank to the canister is closed.

As a result, even when the fuel level in the fuel tank fluctuates and the evaporated fuel in the fuel tank flows into the breather passage while the vehicle is running, the evaporated fuel flows into the canister side by the second pressure sensitive valve. Is suppressed.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied as an automobile fuel vapor treatment apparatus will be described below with reference to FIGS.

FIG. 1 is a schematic explanatory view showing the entire system when the evaporated fuel processing device of the present invention is mounted on a vehicle. As shown in the figure, one end of a vapor passage 3 for introducing vapor generated inside the fuel tank 1 into the canister 2 is opened and connected to the fuel tank 1. The other end of the vapor passage 3 is connected to the canister 2 via a tank internal pressure control valve 4 provided above the canister 2. The tank internal pressure control valve 4 opens when the internal pressure of the fuel tank 1 becomes a predetermined value or more.

Further, the fuel tank 1 is provided with a differential pressure valve 5 which opens at the time of refueling. The differential pressure regulating valve 5 is connected to the canister 2 by a breather passage 7 via a negative pressure regulating valve 6 in the middle thereof. Therefore, when the differential pressure regulating valve 5 and the negative pressure regulating valve 6 are opened, the vapor of the fuel tank 1 is introduced into the canister 2 through the breather passage 7. The differential pressure valve 5 constitutes the first pressure sensitive valve of the present invention, and the negative pressure adjusting valve 6 constitutes the second pressure sensitive valve.

The amount of vapor passing through the breather passage 7 during the ORVR process is extremely large compared to the amount of vapor passing through the vapor passage 3. Therefore, the passage cross-sectional area of the breather passage 7 is about 10 times larger than that of the vapor passage 3.

The interior of the canister 2 is connected by a purge passage 8 to a surge tank 9 forming a part of the engine intake system. A purge amount control valve 11 is provided in the purge passage 8. The purge amount control valve 11 is an ECU (Elec
The open / close drive is controlled by a control signal from the tronic control unit 10 to control the purge amount supplied to the engine intake system.

The interior of the canister 2 is divided into two chambers by a partition plate 15 extending in the vertical direction, and the main chamber 16 located below the tank internal pressure control valve 4 and the atmosphere side control valve 14 are divided.
A sub chamber 1 located below the main chamber 16 and having an internal volume smaller than that of the main chamber 16
7 and 7 are formed respectively. An air layer 18 is formed above the main chamber 16 and the sub chamber 17, and an adsorbent layer 20 filled with an activated carbon adsorbent 19 is formed below the air layer 18. Filters 20a and 20b are provided above and below the adsorbent layer 20, and the activated carbon adsorbent 19 is filled between the filters 20a and 20b. A space below the filter 20b is a diffusion chamber 21, and the diffusion chamber 21 connects the main chamber 16 and the sub chamber 17 to each other. A vapor introducing port 22 for introducing the vapor generated in the fuel tank 1 into the canister 2 is formed on the upper surface of the canister 2 above the main chamber 16. Further, on the right side of the vapor introduction port 22, a check ball type vapor relief valve 23 for ventilating when the inside of the fuel tank 1 becomes a negative pressure.
Are formed.

The vapor introducing port 2 is provided on the upper surface of the canister 2.
The tank internal pressure control valve 4 is arranged so as to cover 2. The tank internal pressure control valve 4 has a diaphragm valve 4a.
The diaphragm valve 4a closes the tip opening of the vapor introducing port 22.
Further, the inside of the tank internal pressure control valve 4 is vertically divided by a diaphragm valve 4a, and a back pressure chamber 4b is formed above the diaphragm valve 4a and a positive pressure chamber 4c is formed below the diaphragm valve 4a. An atmosphere opening port 24 is provided on the side surface of the back pressure chamber 4b to maintain the inside thereof at atmospheric pressure. Further, the inside of the positive pressure chamber 4c communicates with the inside of the fuel tank 1 through the vapor passage 3.

The diaphragm valve 4a is provided in the back pressure chamber 4
The tank internal pressure control valve 4 is kept closed until the internal pressure of the fuel tank 1 becomes equal to or higher than a predetermined value because it is pressed toward the tip opening side of the vapor introduction port 22 by the spring 4d provided at b.

Further, one end of the breather passage 7 is opened and connected to the upper surface of the canister 2 which is located above the main chamber 16. A purge passage 8 is similarly connected to the left side of the opening position of the breather passage 7.

Further, a ventilation port 25 is formed on the upper surface of the canister 2 above the sub chamber 17. Then, the atmosphere side control valve 14 has the same ventilation port 25.
Is arranged so as to cover. The atmosphere side control valve 14 is formed by arranging the atmosphere release control valve 12 and the atmosphere suction control valve 13 at positions facing each other on the left and right.

An atmospheric pressure chamber 12b is formed on the left side of the diaphragm valve 12a provided in the atmosphere opening control valve 12, and a negative pressure chamber 13b is formed on the right side of the diaphragm valve 13a provided in the atmosphere intake control valve 13. . The space sandwiched by both diaphragm valves 12a and 13a is partitioned by a partition wall 28 into two pressure chambers. One of the pressure chambers is a positive pressure chamber 12d of the atmosphere opening control valve 12, and the other is an atmospheric pressure chamber 13d of the atmosphere suction control valve 13. Further, a pressure port 28a is formed in a part of the partition wall 28, and an opening portion at the tip thereof is closed by the diaphragm valve 13a. The diaphragm valve 13a is provided with a pressure port 28a by a spring 13c provided in the negative pressure chamber 13b.
The atmosphere suction control valve 13 is closed because it is urged toward the tip opening side. Then, when the vapor is purged to the engine intake system side, when the pressure difference between the negative pressure acting on the negative pressure chamber 13b and the internal pressure of the atmospheric pressure chamber 13d reaches a predetermined value, the atmosphere intake control valve 13 opens.

An atmosphere opening port 29 is formed above the atmosphere side control valve 14, and the inside of the atmospheric pressure chamber 12b is always kept at atmospheric pressure. A pressure passage 30 that connects the inside of the negative pressure chamber 13b to the inside of the main chamber 16 in the canister 2 is connected to the side portion of the negative pressure chamber 13b, and the pressure generated in the purge passage 8 is introduced into the negative pressure chamber 13b. ing.

Atmospheric pressure chamber 13d of the atmospheric suction control valve 13
Atmospheric air intake passage 27 is provided in the opening. When purging the vapor in the canister 2 into the surge tank 9, the outside air is introduced into the canister 2 through the atmosphere suction passage 27.

The atmosphere side control valve 14 has a canister 2
An atmosphere opening passage 26 is provided for leading out the vapor in which the fuel component is collected. During the ORVR process, a large amount of air (vapor in which the fuel component is collected) is released to the outside through the atmosphere opening passage 26, so that the atmosphere opening passage 2
6 has a passage cross-sectional area which is substantially equal to that of the breather passage 7. Further, the front end opening of the atmosphere opening passage 26 is closed by the diaphragm valve 12 a of the atmosphere opening control valve 12. And the diaphragm valve 12a is
Since the spring 12c disposed in the atmospheric pressure chamber 12b is biased toward the opening side of the atmosphere opening passage 26, the atmosphere opening control valve 12 is kept closed until the internal pressure of the canister 2 becomes a predetermined value or more. To be done.

Next, the main structure related to the ORVR process will be described with reference to FIG. Fuel tank 1
A fitting insertion hole 31 is formed in the upper part of the, and a cylindrical breather pipe 32 forming a part of the breather passage is inserted into the fitting insertion hole 31.
Fixed. A float valve 33 is formed below the breather pipe 32.

Further, the differential pressure regulating valve 5 is provided above the fuel tank 1 so as to cover the upper end opening 32a of the breather pipe 32.
Is provided. The diaphragm valve 5a provided in the differential pressure valve 5 closes the upper end opening 32a of the breather pipe 32. As described above, in the present embodiment, the differential pressure valve 5 is
The structure is integrated with the float valve 33.

The inside of the differential pressure valve 5 is vertically divided by a diaphragm valve 5a. A first pressure chamber 5b is formed on the upper side of the diaphragm valve 5a and a second pressure chamber 5c is formed on the lower side. The diaphragm valve 5a is moved by the urging force of the spring 5d arranged in the first pressure chamber 5b.
It is pressed against the upper end opening 32 a of the breather pipe 32.

Closed by diaphragm valve 5a
Area S of the upper end opening 32a of the breather pipe 32₇Is the first
Diaphragm valve 5a pressure receiving area S on the pressure chamber 5b side₆of
It is set to occupy 60% or more. Such a configuration
The reason is as follows. That is, the differential pressure valve 5
Diaphragm valve 5a according to the internal pressure change of the material tank 1
Change in urging force (hereinafter referred to as urging force change ΔF)
Is detected to open and close. But before
Area S₇Is small, the urging force change ΔF is also small.
The differential pressure valve 5 is opened and closed by detecting this.
In order to make it possible, the elastic force of the spring 5d is inevitable.
Minimize the valve closing force to keep the differential pressure valve 5 closed.
There is a need. However, in such a configuration, due to vehicle vibration, etc.
The diaphragm valve 5a vibrates and the differential pressure valve 5 opens.
There is a risk that Therefore, in this embodiment, the differential pressure
In order to obtain a stable closed state of the valve 5, the area S₇Is the area
S ₆Of 60% or more.

The first pressure chamber 5b is connected to the inside of the fuel injection pipe 36 provided in the fuel tank 1 by the pressure passage 34. A throttle 36 is provided at the tip of the fuel injection pipe 36.
a is formed. Then, when the fuel passes through the throttle 36a, the flow direction of the vapor inside the fuel injection pipe 36 is restricted to the direction from the fuel filler port 36b to the fuel tank 1 side. Therefore, it is possible to prevent the vapor from leaking to the outside from the fuel filler port 36b.

The breather passage 7 is composed of a first breather passage 7a on the fuel tank 1 side of the negative pressure adjusting valve 6 and a second breather passage 7c on the canister 2 side. In addition,
The first and second breather passages 7a and 7b form the breather passage of the present invention. The upstream (right side in the figure) end of the first breather passage 7a is opened and connected to the second pressure chamber 5c of the differential pressure valve 5, and the downstream end thereof is a negative pressure chamber 6c of a negative pressure adjusting valve 6 described later. It is connected to the. On the other hand, the upstream end of the second breather passage 7b is opened and connected to the negative pressure chamber 6c of the negative pressure adjusting valve 6, and the downstream end is opened and connected to the canister 2.

The negative pressure adjusting valve 6 is arranged so as to cover the downstream end of the first breather passage 7a. The negative pressure adjusting valve 6 is provided with a diaphragm valve 6a, and the diaphragm valve 6a closes the downstream opening end portion 7c of the first breather passage 7a.

Further, the inside of the negative pressure adjusting valve 6 is divided into upper and lower pressure chambers by the diaphragm valve 6a, and the atmospheric pressure chamber 6b is provided above the diaphragm valve 6a.
However, negative pressure chambers 6c are formed on the lower side. Above the negative pressure regulating valve 6 corresponding to the atmospheric pressure chamber 6b side,
Atmosphere opening port 37 for maintaining the atmospheric pressure chamber 6b at atmospheric pressure
Are formed. A spring 6d is provided in the atmospheric pressure chamber 6b, and the urging force of the spring 6d causes
The diaphragm valve 6a is pressed against the downstream opening end 7c of the first breather passage 7a.

The evaporative fuel treatment system of the present embodiment having the above construction operates as follows. First, a case where the ORVR processing is not performed, that is, a vapor processing process other than during refueling will be described with reference to FIG.

When the fuel evaporates in the fuel tank 1 and the internal pressure of the fuel tank 1 increases above a predetermined pressure value, the tank internal pressure control valve 4 opens. Then, a vapor flow from the fuel tank 1 to the canister 2 is formed in the vapor passage 3. Therefore, the vapor of the fuel tank 1 is introduced to the canister 2 side via the tank internal pressure control valve 4. At this time, since the internal pressures of the first pressure chamber 5b and the second pressure chamber 5c of the differential pressure valve 5 are equal, the differential pressure valve 5 is kept closed and the breather passage 7 is closed.

In the vapor that has reached the inside of the canister 2, first, the fuel components are collected by the activated carbon adsorbent 19 filled in the adsorbent layer 20 on the main chamber 16 side. Subsequently, the vapor reaches the diffusion chamber 21 via the adsorbent layer 20. further,
The vapor is introduced into the sub-chamber 17 through the diffusion chamber 21, and the adsorbent layer 20 on the sub-chamber 17 side collects the fuel components that cannot be collected by the adsorbent layer 20 on the main chamber 16 side. Since the vapor flows inside the canister 2 along the U-shaped movement path, the time during which the vapor contacts the activated carbon adsorbent 19 of the adsorbent layer 20 becomes long, and the fuel component is effectively collected.

Most of the fuel components are adsorbent layer 20.
The vapor collected by the activated carbon adsorbent 19 is opened to the atmosphere opening control valve 12 and is discharged to the outside through the atmosphere opening passage 26. At this time, the air intake control valve 13
Since the internal pressure of the negative pressure chamber 13b is a positive pressure larger than the internal pressure of the atmospheric pressure chamber 13d, the atmosphere suction control valve 13 does not open. Therefore, the vapor does not leak to the outside from the air intake passage 27 via the air intake control valve 13.

On the other hand, when the fuel tank 1 is cooled by long-time parking or the like, the generation of vapor in the fuel tank 1 is stopped, and the pressure inside the canister 2 becomes relatively high, the positive pressure chamber 4c. The pressure is negative. Therefore, the check ball moves upward, and the vapor relief valve 2
Since 3 is opened, the vapor in the canister 2 is returned to the fuel tank 1 through the vapor passage 3.

Next, the fuel component collected in the canister 2 is supplied to the engine intake system as follows.
When the engine is started, the vicinity of the opening of the purge passage 8 on the surge tank 9 side turns to negative pressure, and every time the purge amount control valve 11 is driven to open by the control signal of the ECU 10, the canister is provided inside the purge passage 8. A vapor flow from 2 to the surge tank 9 is formed. Therefore, the inside of the canister 2 has a negative pressure, and the atmosphere intake control valve 13
Is opened, and outside air is introduced into the canister 2 through the atmosphere suction passage 27. Then, the fuel component adsorbed on the activated carbon adsorbent 19 is released by the outside air,
Be absorbed.

Further, the outside air (vapor) that has absorbed the fuel component is introduced into the purge passage 8 and flows into the surge tank 9 via the purge amount control valve 11. In the surge tank 9, the vapor is mixed with the combustion air that has passed through the air cleaner 35 and supplied into a cylinder (not shown). Then, the vapor mixed with the combustion air is used in the fuel tank 1
The fuel is combusted in a cylinder (not shown) together with the fuel discharged from the fuel injection valve 40 via the internal fuel pump 38.

Next, the ORVR process will be described with reference to FIG. When refueling, first, the fuel injection pipe 36
Refueling cap 36 attached to the refueling port 36b of the
c is removed, and then the oil supply nozzle 39 is connected to the oil supply port 36.
It is inserted into the fuel injection pipe 36 from b. At this time, since the inside of the first pressure chamber 5b of the differential pressure valve 5 is communicated with the vicinity of the fuel filler port 36b of the fuel injection pipe 36 by the pressure passage 34,
The internal pressure of the first pressure chamber 5b becomes equal to the atmospheric pressure.

When fuel is injected into the fuel tank 1 from the refueling nozzle 39, the fuel level in the fuel tank 1 rises and the amount of vapor in the fuel tank 1 increases. As a result, the internal pressure in the fuel tank 1 increases. The high-pressure vapor of the fuel tank 1 lifts the diaphragm valve 5a upward against the internal pressure (atmospheric pressure) of the first pressure chamber 5b of the differential pressure valve 5 and the biasing force of the spring 5d to open the differential pressure valve 5. Speak. As a result, the vapor of the fuel tank 1 passes through the breather pipe 32 and the differential pressure valve 5,
It flows into the breather passage 7a side. Further, the vapor reaches the negative pressure adjusting valve 6, and the diaphragm valve 6a provided in the negative pressure adjusting valve 6 is connected to the internal pressure of the atmospheric pressure chamber 6b and the spring 6d.
The negative pressure adjusting valve 6 is opened by lifting upward against the urging force of. The vapor that has passed through the negative pressure adjusting valve 6 is further
It is introduced into the canister 2 through the breather passage 7b.

After the vapor is introduced into the canister 2, the fuel component is collected and discharged to the outside, and the collected fuel component is supplied to the engine intake system, the ORVR process is not performed. The description is omitted because it is the same as the case.

The configuration of the evaporated fuel processing apparatus and the vapor processing process according to this embodiment have been described above in detail.
Next, the operation and effect of this embodiment in which the negative pressure adjusting valve 6 is provided between the first breather passage 7a and the second breather passage 7b will be described in comparison with the prior art.
First, the flow of vapor that occurs when the fuel level in the fuel tank 1 fluctuates while the vehicle is traveling in the prior art will be described with reference to FIG.

As described above, the fuel in the fuel tank 41 repeats the liquid level fluctuation while the vehicle is traveling.
When the fluctuation amount of the liquid level fluctuation is large, the fuel flows through the float valve 47 to the second pressure chamber 44c of the differential pressure valve 44.
Reach inside.

If the fuel flowing into the second pressure chamber 44c has a valve closing force (hereinafter referred to as valve closing force F ₁ ) of the differential pressure valve 44 that is larger than the force that pushes up the diaphragm valve 44a, the differential pressure valve will be used. 44 does not open. Therefore,
The vapor does not flow out to the downstream side of the differential pressure regulating valve 44.
The valve closing force F ₁ is the difference between the force (F _S1 + P ₁ · S ₁ ) for urging the diaphragm valve 44a downward and the force (P ₂ · S ₂ + P ₁ · S ₃ ) for urging it upward. Can be represented by Here, F _S1 is the elastic force of the spring 44d, P
₁ is the internal pressure of the fuel tank 41, S ₁ is the pressure receiving area of the diaphragm valve on the side of the first pressure chamber 44b, and P ₂ is the breather passage 43.
b internal pressure, S ₂ is the opening area of the breather passage 43b, S ₃
Indicates the pressure receiving area of the diaphragm valve on the second pressure chamber 44c side. Therefore, the valve closing force F ₁ can be expressed by the following equation.

[0055]

[Equation 1]

Since S ₃ = S ₁ -S ₂ in the equation (1), the equation (1) becomes the following equation.

[0057]

[Equation 2]

The second term on the right side of the equation (2) (P ₁ −
Since P ₂ ) is very small, the equation (2) can be further approximated by the following equation.

[0059]

(Equation 3)

That is, the valve closing force F₁Is the first of the differential pressure valve 44
The elastic force of the spring 44d arranged in the pressure chamber 44b
Are almost equal. Therefore, the elasticity of the spring 44d
Force F _S1If is increased, the vapor flows out to the downstream side of the differential pressure valve 5.
Can be prevented.

However, increasing the elastic force F _{S1 in} order to prevent the outflow of vapor increases the internal pressure of the fuel tank 1 during refueling more than necessary. As a result, it becomes difficult to inject fuel into the fuel tank 1. That is, in the prior art, it was not possible to prevent the vapor from flowing out without lowering the oil supply property.

Next, the operation of this embodiment equipped with the negative pressure adjusting valve 6
Applications and effects will be described with reference to FIG. Fuel tank
When the differential pressure valve 5 opens due to the fluctuation of the liquid level in the cylinder 1, the vapor
The negative pressure regulating valve 6 on the downstream side is reached. Where negative
The diaphragm valve 6a of the pressure adjusting valve 6 is connected to the first breather.
The force pressed by the open end 7c of the path 7a is F₂(Hereafter, closed
Valve force F ₂), The same valve closing force F₂Is a positive value (F₂> 0)
If so, the negative pressure adjusting valve 6 does not open, and therefore
Vapor flows into the canister 2 through the laser passage 7b.
There is no such thing.

The valve closing force F ₂ is a force (F _S2 + P ₀ · S) for urging the diaphragm valve 6a of the negative pressure adjusting valve 6 downward.
₄ ) and the force that urges upward {P ₃ · (S ₄ −S ₅ ) + P
₂ · S ₅ }. here,
F _S2 is the elastic force of the spring 6d arranged in the atmospheric pressure chamber 6b, P ₀ is the internal pressure (atmospheric pressure) of the atmospheric pressure chamber 6b, S ₄ is the diaphragm valve pressure receiving area on the atmospheric pressure chamber 6b side, and P ₃ is the Two
The internal pressure of the breather passage 7b, S ₅ is the area of the downstream opening end portion 7c of the first breather passage 7a, and P ₂ is the first breather passage 7a.
The internal pressure is shown respectively. Therefore, the F ₂ can be expressed by the equation (4).

[0064]

[Equation 4]

In the equation (4), since the differential pressure valve 5 is opened by the internal pressure of the fuel tank 1, the internal pressure P ₂ of the first breather passage 7a is equal to the internal pressure P ₁ of the fuel tank 1.
Therefore, the equation (4) becomes the following equation.

[0066]

(Equation 5)

Further, since (P ₃ −P ₁ ) is very small, the equation (5) can be approximated to the following equation.

[0068]

(Equation 6)

In equation (6), the diaphragm valve area S ₄ of the atmospheric pressure chamber 6b can be changed in design,
Assuming that this is a times the area S ₅ of the downstream opening end 7c of the first breather passage 7a (hereinafter, a is referred to as an enlargement ratio), the equation (6) is as follows.

[0070]

(Equation 7)

After the engine is started, as shown in FIG. 3, a negative pressure (P ₃ -P ₀ <inside the second breather passage 7b).
Since 0) has occurred, a · (P ₀ in equation (7)
-P ₃ ) ・ S ₅ (hereinafter referred to as urging force F ₃ ) is a positive value (F
₃ > 0). Thus, the diaphragm valve 6a of the negative pressure control valve 6 is in addition to the elastic force F _S2 of the spring 6d disposed in the atmospheric pressure chamber 6b, it will be pressed downward by the urging force F _3. As a result, the negative pressure adjusting valve 6 is kept closed. That is, the vapor is the same as the negative pressure adjusting valve 6.
Will not flow downstream. Therefore, even if the liquid level of the fuel tank 1 changes while the vehicle is traveling, the vapor does not flow into the canister 2 through the second breather passage 7b. Further, the value of the enlargement factor a in the equation (7) is
If a ≧ 10, it is possible to reliably prevent the vapor from flowing out to the downstream side of the negative pressure adjusting valve 6. In this embodiment, the enlargement ratio a is set to a = 10.

By the way, when the engine is stopped from the operating state, the purge amount control valve 11 is closed. During operation of the engine, the inside of the second breather passage 7b has a negative pressure. Therefore, when the engine is stopped and the purge amount control valve 11 is closed, the second breather passage 7b is closed as shown in FIG.
Breather passage 7b is weak negative pressure (P ₃ -P _{0 <0)}
Will be held in. Therefore, the negative pressure control valve 6 by the biasing force F ₃ during refueling is held in the open state, refueling resistance is concerned be decreased.

[0073] However, since the negative pressure generated in the second breather passage 7b while the engine is stopped is small, the urging force F ₃ of such time is extremely small as compared with the biasing force F ₃ in the engine operation. Therefore, if the elastic force F _S2 of the spring 6d arranged in the atmospheric pressure chamber 6b is set to a small value in advance so that the biasing force F ₃ generated during refueling is offset, the refueling property will not deteriorate.

In the present embodiment, as described in detail above, even when the liquid level of the fuel tank 1 changes while the vehicle is traveling, the vapor of the fuel tank 1 is changed to the canister 2.
Never flow into. Therefore, the amount of vapor in the canister 2 does not suddenly increase, and the problem that the stability of the purge control for purging the vapor of the canister 2 into the engine intake system or the stability of the air-fuel ratio control of the engine intake system is impaired is avoided. You can

Further, the negative pressure adjusting valve 6 in this embodiment is
When refueling, the valve is opened and the vapor in the fuel tank 1 is replaced by the canister 2
And acts to close the breather passage 7 except when refueling. However, the operation of the negative pressure adjusting valve 6 does not require any external energy supply. Therefore, in the present embodiment, it is possible to simplify and reduce the cost of the evaporated fuel treatment apparatus, as compared with the case where the same operation is realized by providing the electromagnetic valve or the like.

The present invention can be embodied as follows. (1) In this embodiment, the enlargement ratio a is set to a = 10. However, when the evaporated fuel treatment apparatus of the present invention is embodied in a vehicle in which the liquid level fluctuation in the fuel tank 1 is large and the pressure fluctuation is large, this may be changed to 10 times or more. With this configuration, the valve closing force F ₂ of the negative pressure adjusting valve 6 is increased, so that the vapor can be reliably prevented from flowing out to the canister 2 side. (2) The position where the negative pressure adjusting valve 6 is provided may be between the differential pressure regulating valve 5 and the canister 2. However, if the negative pressure adjusting valve 6 is provided near the differential pressure regulating valve 5, The amount of vapor flowing into the first breather passage 7a due to the liquid level fluctuation can be made minute. (3) In the present embodiment, the differential pressure valve 5 is integrated with the float valve 33, but both may be separate bodies.

Although the embodiments of the present invention have been described above, technical ideas other than the claims which can be understood from each embodiment will be described below together with their effects. (A) In the invention described in claim 1, the second pressure sensitive valve is a differential pressure valve that is opened and closed by a pressure difference between the internal pressure of the breather passage 7 and the atmospheric pressure, and the evaporated fuel of the internal combustion engine is characterized. Processing equipment. With this configuration, it is not necessary to separately provide a drive source or the like for driving the second pressure sensitive valve to open and close, so that the cost and size of the device can be reduced.

[0078]

According to the present invention, even if the liquid level of the fuel in the fuel tank changes, the evaporated fuel does not flow into the canister through the breather passage. Therefore, the concentration of the evaporated fuel in the canister does not suddenly increase, and the stability of the purge control for purging the evaporated fuel into the engine intake system is not impaired.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a system when an evaporated fuel processing device according to an embodiment of the invention is mounted on a vehicle.

FIG. 2 is an explanatory view showing an evaporated fuel treatment device of the same embodiment.

FIG. 3 is an explanatory diagram showing a change in internal pressure of a second breather passage.

FIG. 4 is an explanatory diagram showing a conventional evaporated fuel processing device.

[Explanation of symbols]

1 ... Fuel tank, 2 ... Canister, 3 ... Vapor passage, 5
... differential pressure valve (first pressure sensitive valve), 6 ... negative pressure regulating valve (second pressure sensitive valve), 7a ... first breather passage (breather passage), 7
b ... 2nd breather passage (breather passage), 8 ... Purge passage, 19 ... Activated carbon adsorbent, 32 ... Breather pipe (breather passage).

Claims (1)

[Claims] 1. An evaporative fuel for an internal combustion engine, wherein the evaporated fuel from a fuel tank is adsorbed by an adsorbent in a canister through a vapor passage, and the adsorbed fuel in the canister is purged through an purge passage into an intake passage of the internal combustion engine during operation of the internal combustion engine. In the processing device, a breather passage that communicates the inside of the fuel tank with the inside of the canister and introduces the evaporated fuel in the fuel tank into the canister at the time of refueling, and a breather passage that is arranged in the middle of the breather passage so that the fuel tank internal pressure has a predetermined value A first pressure-sensitive valve that opens upon detection of the rise and a breather passage that is disposed between the first pressure-sensitive valve and the canister and that keeps the breather passage closed during operation of the internal combustion engine. A second pressure-sensitive valve for controlling an evaporated fuel processing apparatus for an internal combustion engine, comprising: