JPH05340315A - Vapor fuel processor - Google Patents

Abstract

PURPOSE:To prevent deterioration of control performance of an air-fuel ratio by fully suppressing variation of the concentration of vapor which is purged. CONSTITUTION:Vapor is forcibly sucked from a canister 14 by a purge pump 20, and then discharged to a purge control valve 23. A part of vapor discharged from the purge pump 20 to the purge control valve 23 is circulated in the suction side of the purge pump 20, and mixed with the vaport sucked by the canister 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for adsorbing evaporated fuel (vapor) on a canister, desorbing the vapor from the canister and discharging the evaporated fuel to an intake system for processing.

[0002]

2. Description of the Related Art Conventionally, as described in Japanese Patent Laid-Open No. 61-277862, a diffusion chamber is provided in a purge passage connecting an intake passage of an internal combustion engine and a canister, and fluctuation of vapor concentration for purging the intake passage. There is an evaporated fuel processing device configured to suppress the above.

[0003]

When the purge flow rate changes, the concentration of vapor to be purged changes. By providing a diffusion chamber as in the conventional case, it is possible to suppress the change in concentration of vapor to be purged. However, in order to obtain a sufficient suppressing 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 vapor in the diffusion chamber will become faster, and it will not be possible to sufficiently suppress changes in the vapor concentration, and the air-fuel ratio feedback control cannot be applied to control the air-fuel ratio. There was a problem that performance deteriorated.

The present invention has been made in view of the above points,
Provided is an evaporative fuel treatment apparatus which is provided with a purge pump and a recirculation passage between a canister and a purge control valve to sufficiently suppress changes in vapor concentration to be purged and prevent deterioration of air-fuel ratio control performance. With the goal.

[0005]

SUMMARY OF THE INVENTION An evaporated fuel processing apparatus according to the present invention is an evaporated fuel processing apparatus for processing evaporated fuel stored in a canister by purging it into an intake passage of an internal combustion engine by controlling a purge amount with a purge control valve. In the above, the purge pump forcibly sucking vapor from the canister and discharging it to the purge control valve, and a part of the vapor discharged from the purge pump to the purge control valve are returned to the suction side of the purge pump. A recirculation passage for mixing with the vapor sucked from the canister is provided in the purge passage connecting the canister and the purge control valve.

[0006]

In the present invention, the purge control valve is forcibly supplied with vapor from the canister by the purge pump, and a part of this vapor is recirculated to the intake side of the purge pump through the recirculation passage and mixed with the vapor from the canister. Therefore, the purge gas is agitated to have a uniform concentration, and the change in vapor concentration is sufficiently suppressed even when the purge flow rate is large.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the device of the present invention. In the figure, 10 is an intake passage, 11 is a throttle valve, and there are an intake manifold and an internal combustion engine main body in the direction of the arrow of the intake passage 10.

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 the atmosphere opening port 1
Have five. The purge port 16 of the caster 14 is connected to the front chamber 18 a of the first diffusion chamber 18 by the purge passage 17. The first diffusion chamber 18 is a shield plate 1 having a communication passage.
A front chamber 18a and a rear chamber 18b are separated by 8c.

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

The purge control valve 23 is a solenoid valve (VSV), and is controlled by an electronic control circuit (ECU) 26 to change the duty ratio and perform an opening / closing operation.

A pressure regulator 30 is attached to the second diffusion chamber 22. The pressure regulator 30 includes a pressure in the second diffusion chamber 22 and a pressure introducing passage 31.
When the pressure difference between the pressure in the purge passage 24 and the pressure in the purge passage 24 exceeds a certain value, a part of the vapor in 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.

The vapor generated in the fuel tank 12 reaches the canister 14 through the vapor passage 13 and is trapped by the activated carbon.

Further, 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 room 1
The intake passage 10 is purged from 8 through the purge pump 20, the purge passage 21, the second diffusion chamber 22, the purge control valve 23, and the purge passage 24.

Here, when the purge flow rate becomes relatively large with respect to the capacities of the first and second diffusion chambers 18 and 22,
Since the differential pressure increases, a part of the vapor in the second diffusion chamber 22 is returned to the first diffusion chamber 18 through the reflux passage 32 by the pressure regulator 30 and mixed with the vapor in the rear chamber 18b to average the vapor concentration. ..

For example, the purge port 1 of the canister 14
When the vapor concentration of _{No. 6} suddenly changes from 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. 2B. It gradually changes from time t ₁ with time τ. When 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, the change in the vapor concentration C shown by the solid line is expressed by the following equation using the time t from the time t _1. It 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 of the vapor concentration C in this case is expressed by the following equation.

C.apprxeq.C ₀ + Q _a (C ₁ -C ₀ ) t / V By performing reflux in this way, the diffusion chambers 18, 2
The change in vapor concentration to be purged is sufficiently suppressed without increasing the volume of 2 and the vapor concentration gradually changes,
It is possible to follow the air-fuel ratio feedback control and prevent deterioration of the air-fuel ratio control performance.

By the way, as shown in FIG. 3, the canister 1
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 is kept 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 fuel vapor processing apparatus of the present invention, it is possible to sufficiently suppress the change in purged vapor concentration and prevent the deterioration of the air-fuel ratio control performance, and it is extremely useful in practice. ..

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a 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.

[Explanation 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Kisho 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Automobile Co., Ltd.

Claims (1)

[Claims] 1. An evaporative fuel processing apparatus for processing evaporative fuel stored in a canister by purging an intake passage of an internal combustion engine by controlling a purge amount with a purge control valve, and forcibly inhaling vapor from the canister. A purge pump that discharges to the purge control valve, and a reflux passage that causes a portion of the vapor discharged from the purge pump to the purge control valve to flow back to the suction side of the purge pump and mix with the vapor sucked from the canister. An evaporative fuel treatment apparatus is provided in a purge passage that connects the canister and the purge control valve.