JPS5929761A - Preventing device for fuel vapor transpiration in internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent air-fuel mixture from becoming excessively thick even when the temperature of the fuel is high and to maintain an air-fuel ratio at an appropriate value to prevent worsening of exhaust emission, by stopping introduction of a purge air to an adsorptive layer and stopping separation of fuel vapor from the adsorptive layer. CONSTITUTION:When the temperature of the air in a fuel tank 1 is below a set temperature, purge air is introduced only from a purge air introducing part 11, through the open air releasing port C of a 3-way electromagnetic valve 36, a port A and a hose 34, and the adsorbed vapor fuel is separated from two adsorptive layers 9a and 9b. Meanwhile, when the temperature of the fuel exceeds a set temperature, the purge air introducing part 11 is closed, an auxiliary purge air introducing part 33 is opened, and the purge air is introduced from only the auxiliary purge air introducing part through the open air releasing port C, a port B, and a hose 35, whereby the adsorbed vaporized fuel is separated from only the adsorptive layer 9a but not separated from the adsorptive layer 9b.

Description

[Detailed description of the invention] The present invention relates to a fuel vapor evaporation prevention device for an internal combustion engine.

Conventional devices of this type include those shown in Figures 1 and 2 (Nissan Motor Co., Ltd. Regulations - Service Bulletin).
(Refer to the introduction of the 440 (SAY-1) Tll type car published in June 1981), and its composition is as follows.

One end of a fuel vent line 3 equipped with a gas valve 2 is connected to the upper space of the fuel tank 1, and the other end of this fuel vent line 3 is connected to an inlet space 5 provided in the upper center of the canister 4. It is. In the canister 4, an inlet space 5 and an outlet space 6 surrounding the inlet space 5 with a partition plate are filled with filters γ and 8 having mesh plates 7' and 8'', respectively, for adsorption filled with an adsorbent such as activated carbon. The lower surface of this adsorption layer 9 is opened to the atmosphere by means of a filter 10 having a mesh plate 10', and is connected to an outlet space 6 of the canister 4, which serves as a purge air introduction section 11. is connected to one end of the purge passage 13 through the nosiege control valve 12, and in addition to this purge passage 13, A1.1 is the throttle valve 1 of the intake passage 15 of the engine 14.
6 is connected to the downstream part. 17 is an air cleaner. The purge control valve 12 has a chamber 13 communicating with the purge passage 13.
A valve hole 19 with an orifice connected to the outlet space 6 protrudes into the interior, and this valve hole 19 is equipped with a diaphragm 20 that can be opened and closed to adjust its opening area. The compression spring 21 is fully disposed on the diaphragm 20, and the diaphragm 20 is operated in the valve opening direction.
A negative pressure working chamber 22 is formed above 0. The negative pressure working chamber 22 is connected to the intake passage 15 from the vicinity of the throttle valve 16, which is located upstream of the throttle valve 16 when the throttle valve is fully closed, such as during idling, and when the throttle valve 16 opens, the throttle valve Negative pressure (hereinafter, this negative pressure will be referred to as throttle negative pressure) is led from a negative pressure outlet 23 located at the lower ylt of the engine 16 to a negative pressure passage 24.

In such a configuration, the fuel evaporated in the fuel tank 1 is adsorbed by the adsorbent of the M absorption layer 9 from the canister 40 through the opening 5 of the canister 40 via the check valve 2 and the fuel vent line 3. When the negative pressure generated in the intake passage 15 downstream of the throttle valve 16 during engine operation is introduced into the outlet space 6 of the canister 4 via the purge control valve 12, the evaporated fuel adsorbed on the adsorption layer 9 is adsorbed. Together with the purge air introduced from the nozzle air introduction part 11 on the lower surface of R9, it is sucked into the intake passage 15 and subjected to a re-combustion process. However, when the engine is stopped, the diaphragm 20 is moved upward by the force of the spring 21 and the purge control valve 12 is opened, but since the engine is stopped and no negative pressure is generated in the intake passage 15, the purge action is not performed. No air is introduced into the canister 4 either.

In addition, at low rotation speeds and low loads such as during idle linking, the throttle negative pressure is small and only the negative pressure downstream of the throttle valve 16 is applied downward to the diaphragm 20 through the purge passage, so the diaphragm 20 moves down and the purge control valve 12 is activated. As a result of closing, at this time as well, the -ji operation is not performed and the nitrogen gas is not introduced into the canister 4.

However, when such a conventional device uses a so-called composite fuel consisting of a complete mixture of hakasolin and alcohol (methanol, ethanol, etc.), the evaporation characteristics become uneven. In other words, when the fuel temperature in the fuel tank is at a predetermined high temperature (40 to 60 @ C), a large amount of alcohol vapor from the fuel tank is adsorbed by the canister and the canister is filled with a large amount of fuel vapor, resulting in concentrated purge. There is a problem in that the air-fuel mixture is discharged into the engine intake system, enriching the air-fuel ratio and worsening exhaust emissions, especially CO emissions.

The present invention has been made in view of this more conventional problem. By clogging when the air pressure is higher than the above, the introduction of purge air to some of the adsorption layers is stopped and all fuel vapor is desorbed from the adsorption layers, thereby preventing enrichment of the air-fuel ratio. The present invention provides a fuel vapor evaporation prevention device for an internal combustion engine that completely prevents deterioration of C#1 gas emission characteristics.

An embodiment of the present invention will be described below with reference to FIGS. 3 to 5.

Fig. 3 is a cross-sectional view of a canister used in the present invention, Fig. 4 is a diagram showing the overall configuration of a fuel vapor evaporation prevention device using the canister, and Fig. 5 is a three-way electromagnetic device used in the device of Fig. 4. It is a figure showing the composition of a valve.

First, the canister is configured to have a sub-purge air introduction section 33 in addition to the purge air introduction section 11, and this sub-purge air introduction section 33 has a mesh-like structure.
The adsorption layer is formed between the filters 31 and 32, each having a double purge nitrogen introduction section 33, and has two metal surfaces 9a and 9b.

The purge air introduction section 11 and the sub-purge air introduction section 33 of this canister are connected to a three-way [magnetic valve 36 (Fig. 5) (7) two bows] A,
]3. The three-way solenoid valve 36 is connected to a power source 39 via an ignition switch 37 and a fuel temperature switch 38, and selects the boat A when the power is on and the boat B when the power is on. It operates in such a way that it communicates with the atmosphere opening boat C.

The same reference numerals as in other FIGS. 1 and 2 indicate the same elements.

Next, the operation will be explained.

Now that the ignition switch 3γ is on and the engine is in operation, the fuel temperature in the fuel tank 1 is the fuel temperature switch 38.
It is assumed that the temperature is below the set temperature (for example, 3 U'C). In this case, since the fuel temperature switch 38 is off, the three-way solenoid valve 36
is not energized, boats A and C are in communication, and boats 1-B are blocked.

Also, when the fuel temperature exceeds the set temperature, the fuel temperature switch 38
is turned on, so the 30,000-ton solenoid valve 36 is energized and the valve body 36a
moves downward against the spring 36b in FIG. 5, and boats B and C communicate with each other, making boat A feel blocked.

Therefore, if the fuel temperature in the fuel tank 1 is lower than the set temperature, the purge air is introduced only from the purge air introduction part 11 through the boat C and the hose 34 of the three-way TIE magnetic valve 36. The vaporized fuel adsorbed is desorbed from both the M absorption layers 9a and 9b. On the other hand, when the fuel temperature is υ higher than the set temperature, the purge air introduction section 11 is closed and the sub purge air introduction section 33 is closed. is opened and the purge air is introduced only from the sub purge air introduction part 33 via the atmosphere release boat C1 boat B and the hose 35, so the adsorbed evaporated fuel is desorbed only from the adsorption layer 9a and adsorbed. It does not desorb from the layer 9b. Therefore, the total amount of desorption is reduced, and the purge mixture t discharged into the intake passage 15 does not become over-concentrated.

Note that even if the purge air introduction part 33 of the adsorption layer 9a is opened without controlling the opening/closing of the inlet 11 of the adsorption M9b, there is an effect of not over-enriching the purge air-fuel mixture.

Alternatively, the sub purge air introduction section may be open to the atmosphere at all times, and the purge air introduction section 11 may be controlled to open and close.

As described above, the present invention provides a plurality of P Yanista adsorption layers and purge air introduction sections, and when the fuel tank internal combustion f1 degree is higher than a predetermined value, Since the purge air introduction part of TI5 was blocked to stop the purge air introduction to some of the adsorption layers and the fuel vapor film m from the adsorption layers was stopped, the fuel temperature was high in the canister e, Even when multiple fuels are adsorbed in the M layer, the purge air-fuel mixture does not become excessively rich, and the engine air-fuel ratio can be maintained at an appropriate value to prevent deterioration of exhaust emissions.

[Brief explanation of drawings]

Figure 1 is a schematic diagram AA showing the structure of a conventional combustion engine combustion engine vapor evaporation prevention device, Figure 2 is a vertical 1rfr side view showing the four structures of the canister in the same device, and Figure 3 is a side view of the present invention. A vertical sectional view showing the structure of a canister used in the invention device, FIG. 4 is an explanatory view showing an embodiment of the present invention, and FIG. 5 is a whip sectional view showing the trpt structure of the three-way Tl magnetic valve used in the same embodiment. Out. 1... Fuel tank, 2... Check valve, 4
... Canister, 5... Inlet nitrogen gap, 6...
- Between outlet walls, 7.8.10, 31.32...filter, 11. 33...Purge air introduction part, 12...) 1 valve for pressure control, 13...Purge passage, 14...
Engine, 33...Sub purge air introduction section, 36...3
directional solenoid valve, 37...ignition switch,
38...Fuel temperature switch. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] Fuel evaporated in a fuel tank is drawn into a canister filled with adsorbent and stored therein, and when the engine is running, purge air is passed through the canister to mix it with the purge air and remove the fuel. A fuel vapor supply device for an internal combustion engine in which steam is introduced into an engine intake system, which includes a plurality of adsorption layers in the canister, a purge air introduction section that guides purge air to all of these adsorption layers, and a part of the adsorption layers that contains purge air. In addition, a sub-purge air introduction section is provided in the fuel tank, and when the detection means detects that the fuel temperature is above a predetermined value, only the sub-purge air introduction section of the canister is provided. 1. A fuel vapor evaporation prevention device for an internal combustion engine, characterized in that it is provided with a control means for fully opening barge air to flow through only a portion of the adsorption layer through full-open continuous detonation.