JP2900704B2 - Evaporative fuel processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor treatment system.
And relates to a fuel vapor treatment system that releases treated evaporative fuel generated in a fuel tank (vapor) in the air intake system.

[0002]

2. Description of the Related Art Conventionally, as disclosed in Japanese Patent Application Laid-Open No. 61-277762, a diffusion chamber is provided in a purge passage connecting an intake passage and a canister of an internal combustion engine, and the concentration of vapor purged into the intake passage is varied. There is an evaporative fuel processing device configured to suppress the generation of fuel.

[0003]

When the purge flow rate changes, the concentration of vapor to be purged changes. By providing a diffusion chamber as in the prior art, the change in vapor concentration to be purged can be suppressed. However, in order to obtain a sufficient suppression effect, it is necessary to increase the capacity of the diffusion chamber. If the purge flow rate becomes relatively large with respect to the capacity of the diffusion chamber, the replacement of the vapor in the diffusion chamber becomes faster and the change in the vapor concentration cannot be sufficiently suppressed, and the air-fuel ratio control cannot be performed by the air-fuel ratio feedback control. There was a problem that performance deteriorated.

[0004] The present invention has been made in view of the above points,
By providing a purge pump and a recirculation passage between a fuel tank and a purge control valve, it is possible to sufficiently suppress a change in the concentration of vapor to be purged, and to provide an evaporative fuel processing apparatus that prevents deterioration of control performance of an air-fuel ratio. The purpose is to:

[0005]

According to the present invention, there is provided an evaporative fuel processing apparatus for purging evaporative fuel generated in a fuel tank into an intake passage of an internal combustion engine by controlling a purge amount with a purge control valve. In the device, the fuel tank side
A purge pump fuel vapor et forcibly sucked to be discharged into the purge control valve, a portion of the purge pump or al ejection out the vapor refluxing to the suction side of the purge pump
A recirculation passage for mixing with the fuel vapor from the fuel tank side is provided in a purge passage connecting the fuel tank and a purge control valve.

[0006]

In the present invention, the purge control valve is forcibly supplied with fuel vapor from the fuel tank side by the purge pump, and a part of the fuel vapor is returned to the suction side of the purge pump through the return passage so as to be supplied to the fuel tank. Since the fuel vapor is mixed with the fuel vapor from the side, the fuel vapor is agitated and the concentration becomes uniform, and the change in the fuel vapor concentration is sufficiently suppressed even when the purge flow rate is large.

[0007]

FIG. 1 is a block diagram showing an embodiment of the apparatus according to the present invention. In FIG. 1, reference numeral 10 denotes an intake passage, and reference numeral 11 denotes a throttle valve. In the intake passage 10, an intake manifold and an internal combustion engine main body are arranged in the direction indicated by an arrow.

The fuel tank 12 is connected to a canister 14 by a vapor passage 13. The canister 14 is filled with activated carbon that adsorbs vapor, and has an air opening port 1.
Five. Purge port 16 of the cab two static 14 is connected to the front chamber 18a of the first diffusion chamber 18 by the purge passage 17. The first diffusion chamber 18 is separated into a front chamber 18a and a rear chamber 18b by a shielding plate 18c having a communication passage.

A rear chamber 18b of the first diffusion chamber 18 is connected to a purge pump 20, and the purge pump 20 is connected to a second diffusion chamber 22 by a purge passage 21. The vapor inhaled from the second
Discharge is performed toward the diffusion chamber 22. The second diffusion chamber 22 is connected to a purge control valve 23, and the purge control valve 23 is connected by a purge passage 24 to a purge port 25 of the intake passage 10 immediately downstream of the throttle valve 11.

The purge control valve 23 is an electromagnetic valve (VSV), and performs opening and closing operations by varying the duty ratio under the control of an electronic control circuit (ECU) 26.

Further, a pressure regulator 30 is attached to the second diffusion chamber 22. The pressure regulator 30 controls the pressure of the second diffusion chamber 22 and the pressure introduction path 31.
When the pressure difference from the pressure of the purge passage 24 introduced by the pressure exceeds a predetermined value, a part of the vapor of the second diffusion chamber 22 is taken out, and the rear chamber 18 of the first diffusion chamber 18 is passed through the reflux passage 32.
Reflux to b.

Here, the vapor generated in the fuel tank 12 reaches the canister 14 through the vapor passage 13 and is captured by the activated carbon.

The air sucked from the atmosphere opening port 15 of the canister 14 by the purge pump 20 desorbs the vapor trapped in the activated carbon of the canister 14 and then enters the first diffusion chamber 18 from the purge passage 17. First diffusion chamber 1
8, the air is purged to the intake passage 10 through a purge pump 20, a purge passage 21, a second diffusion chamber 22, a purge control valve 23, and a purge passage 24.

Here, when the purge flow rate is relatively large with respect to the capacity of the first and second diffusion chambers 18 and 22,
Since the pressure difference increases, a part of the vapor in the second diffusion chamber 22 is returned to the first diffusion chamber 18 through the return passage 32 by the pressure regulator 30 and mixed with the vapor in the rear chamber 18b, so that the vapor concentration is averaged. .

For example, the purge port 1 of the canister 14
When the vapor concentration of _{No. 6} suddenly changes from the concentration C ₀ to C ₁ at time t ₀ as shown in FIG. 2A, the vapor concentration of the purge port 25 of the intake passage 10 is delayed as shown by the solid line in FIG. gradually changes from time t ₁ with a time τ. The change of the vapor concentration C shown by the solid line is obtained by using the time t from the time t ₁ assuming that the purge flow rate of the purge port 25 is Q and the total volume of the first and second diffusion chambers 18 and 22 is V. Is represented by

[0016] _{C ≒ C 1 - (C 1} -C 0) exp (-Q a · t / V) The first, the case of using the second diffusion chamber 18, 22 FIG. 2 (B without reflux ) Is indicated by a broken line, and the change in the vapor concentration C in this case is expressed by the following equation.

C ≒ C ₀ + Q _a (C ₁ -C ₀ ) t / V By refluxing in this manner, the diffusion chambers 18 and 2
The change in the vapor concentration to be purged is sufficiently suppressed without increasing the volume of 2, and the vapor concentration gradually changes,
The air-fuel ratio feedback control can follow, and the control performance of the air-fuel ratio can be prevented from deteriorating.

By the way, as shown in FIG.
A check valve 40 may be provided in the purge port 16 of No. 4 and connected to the purge passage 17. In this case, the purge control valve 23 maintains the valve closed during the purge cut, so that the vapor recirculated through the recirculation passage 32 can be prevented from flowing back to the canister 14.

[0019]

As described above, according to the evaporative fuel processing apparatus of the present invention, the change in the concentration of the vapor to be purged can be sufficiently suppressed, and the control performance of the air-fuel ratio can be prevented from being deteriorated. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the device of the present invention.

FIG. 2 is a diagram for explaining the device of the present invention.

FIG. 3 is a configuration diagram of a modified example of the device of the present invention.

DESCRIPTION OF SYMBOLS 10 Intake passage 12 Fuel tank 14 Canister 18 First diffusion chamber 20 Purge pump 22 Second diffusion chamber 23 Purge control valve 30 Pressure regulator 32 Reflux passage

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Kisokoro 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (56) References JP-A-61-277862 (JP, A) JP-A-58-58 155269 (JP, A) Japanese Utility Model 2-115955 (JP, U) Japanese Utility Model hei 2-78755 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02M 25/08 F02M 25 / 08 301

Claims (1)

(57) [Claims] An evaporative fuel processing apparatus for purging evaporative fuel generated in a fuel tank into a suction passage of an internal combustion engine by controlling a purge amount with a purge control valve to process the evaporative fuel from the fuel tank side. to inhalation and purge pump that discharges to the purge control valve, a portion of the purge pump or al ejection out the vapor from the fuel tank side refluxed to the intake side of the purge pump
And a recirculation passage to be mixed with fuel vapor, the evaporative fuel processing system characterized by having a fuel vapor passage <br/> path connecting the aforementioned fuel tank and the purge control valve.