JPH0311405Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an evaporative fuel processing device for a vehicle internal combustion engine.

[Prior art]

To prevent air pollution, an adsorption device adsorbs and captures fuel vapor generated in a fuel storage container such as a fuel tank of a vehicle or a float chamber of a carburetor, and the adsorbed fuel vapor is absorbed into the intake air during engine operation. Vaporized fuel processing devices are well known that utilize pressure to purge (hereinafter referred to as purge) into the intake air stream in the intake passage of a carburetor and combust it in an engine combustion chamber. This device includes a canister containing an adsorbent such as activated carbon, and fuel vapor temporarily adsorbed and captured by the adsorbent is guided to a purge port of a vaporizer via a fuel vapor transfer conduit.

When purging evaporated fuel, an extra amount of fuel is added to the intake airflow in addition to the fuel metered in the carburetor, resulting in an overrich air-fuel ratio that interferes with smooth engine operation. and exhaust emissions deteriorate. This tendency is particularly noticeable during idling operation, where the amount of intake air per revolution of the engine is small. Therefore, in conventional devices, the purge port is provided upstream of the throttle valve in the closed state, so that purge is not performed during idle operation (for example, JP-A-53-5317, JP-A-53
-44719, Utility Model Application Publication No. 53-32215).

However, in order to always ensure the maximum adsorption capacity of the canister and to be able to adsorb a sufficient amount of evaporated fuel whenever necessary, it is desirable to purge adsorbed fuel as quickly as possible during engine operation. . For this purpose, it is necessary to improve the purge efficiency during engine operation.

[Purpose of invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fuel vapor processing device that can appropriately purge fuel vapor over a wide range of operating ranges from engine idle operation to high load operation.

[Summary of the structure and operation of the device]

Therefore, in the present invention, (1) the purge port is branched into a first purge port that opens on the upstream side of the throttle valve in the fully closed position and a second purge port that opens on the downstream side, and connects them to each other through a communication path. (2) A temperature-sensitive valve is provided to close the second purge port when the temperature is high.

With this configuration, during idling operation when the throttle valve is fully closed, air flows from the first purge port on the upstream side of the throttle valve to the second purge port on the downstream side of the throttle valve through the communication passage. 2
The fuel vapor discharged from the purge port is diluted by this airflow and then sucked into the engine.
Therefore, it is possible to perform purging during idling without substantially changing the air-fuel ratio. Furthermore, since the second purge port is shut off by the temperature-sensitive valve when the temperature is high, the air-fuel ratio during idling is prevented from becoming excessively rich, and smooth idling rotation can be ensured. It is preferable that the opening area of the first purge port on the upstream side of the throttle valve be larger than the opening area of the second purge port on the downstream side. Preferably a hole. In this way, it becomes possible to gradually change the purge amount according to the throttle valve opening degree, and the purge amount can be ensured even under high load.

〔Example〕

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

Referring to FIG. 1, this evaporated fuel processing apparatus includes a canister 10 containing activated carbon particles as an adsorbent. The interior of the canister 10 is connected to a fuel tank 16 via a conduit 12 and an inlet check valve 14, and is connected to a fuel tank 16 via a conduit 18.
It is connected to the float chamber 22 of the carburetor 20 by. A solenoid type outer vent switching valve 26 controlled by an ignition switch 24 is provided in the middle of the conduit 18, and when the engine is stopped, the evaporated fuel in the float chamber 22 is transferred to the canister 10.
When the engine is running, the conduit 18 is shut off and the fuel vapor in the float chamber is released from the inner vent 28 into the intake air stream. A fuel vapor transfer conduit 31 is connected to the canister 10 via an outlet check valve 30.

According to the present invention, a first purge port 32 and a second purge port 34 are formed in the wall of the main body of the vaporizer 10, and these purge ports 32, 34 are communicated with each other by a communication passage 36. . As shown, the first purge port 32 is positioned to open into the intake passage 40 upstream of the throttle valve 38 in the fully closed state,
The second purge port 34 is located downstream of the throttle valve 38. As shown in Figure 2, the first
The cross-sectional shape of the purge port 32 is an elongated hole extending in the axial direction of the intake passage 40 of the carburetor 20. In the example shown in FIG. 2a, the rate of increase in the flow path area of the first purge port 32 as the throttle valve 38 opens is uniform, and in the example shown in FIG. 2b, it increases gradually, and in the example shown in FIG.
In this example, it appears to be decreasing gradually. As shown in FIG. 1, the upper end of the fuel vapor transfer pipe 31 is connected to a communication passage 36
connected to any position. The second purge port 34 is provided with a wax-type temperature-sensitive valve 42, which closes the second purge port 34 when the ambient temperature exceeds a set value. The temperature-sensitive valve 42 may be a bimetal type or another type, and can be used to control the temperature of the vaporizer 20 body, the air cleaner 44
It may also be activated in response to internal intake air temperature, fuel temperature, etc. In order to simplify the drawing, the liquid fuel system of the carburetor 20 is omitted in FIG. 1.

The operation of this device is as follows.

While the engine is stopped, fuel vapor generated in the fuel tank 16, carburetor float chamber 22, fuel piping, etc. is adsorbed by the adsorbent of the canister 10 and is temporarily captured.

During engine operation, fuel vapor collected in the canister 10 is sucked out into the intake air stream in response to the intake vacuum acting on the first purge port 32 and the second purge port 34. Referring to FIG. 3, which shows the combined negative pressure acting on the two purge ports 32 and 34, the throttle valve 38 opens slightly from the fully closed position corresponding to idle to the first purge port.
When the throttle valve is in the angle range up to the angle θ where the purge port 32 is exposed, negative pressure acts only on the second purge port 34, and the first purge port 3
2 is under almost atmospheric pressure. Therefore, a portion of the intake air flows from the first purge port 32 to the communication path 36.
and to the second purge port 34, and this air flow dilutes the fuel vapors discharged from the canister 10 to the second purge port 34. Therefore, even during idling operation or low load operation, it is possible to purge fuel vapor while avoiding malfunction of engine rotation due to excessive enrichment of the air-fuel ratio.

When the throttle valve opening exceeds θ, the intake negative pressure also acts on the first purge port 32, so the composite negative pressure increases as the throttle valve opening increases, and the purge amount also increases accordingly. Since the first purge port 32 has an elongated cross-sectional shape, the amount of purge increases as the throttle valve opening increases during medium to high loads. Therefore, the purge amount does not decrease during high load.

Next, when the engine reaches a high temperature, fuel vapor from the carburetor float chamber 22 flows into the inner vent 28.
Since the intake air is drawn into the engine, the air-fuel ratio becomes rich, and during idling operation with a small amount of intake air, there is a risk that the air-fuel ratio may become excessively rich, resulting in poor idling. However, in the device of the present invention, the temperature-sensitive valve 42 operates to close the second purge port 34 when the temperature is high, so the purge of fuel vapor is cut off during idling operation and at high temperatures. This state is shown in the shaded area in FIG. In addition, in the above explanation,
Although the fuel supply system for an internal combustion engine has been described as consisting of a carburetor, the present invention is not limited to application to an internal combustion engine equipped with a carburetor, but can also be applied to an internal combustion engine equipped with a fuel supply system such as an electronically controlled fuel injection system. Needless to say, this also applies to internal combustion engines.

[Effect of idea]

According to the present invention, it is possible to purge fuel vapor over a wide range of operating ranges from engine idling to high-load operation, so the fuel vapor adsorbed by the adsorption device can be quickly discharged. , the adsorption capacity of the adsorption device can be maintained to the maximum. Therefore, the effect of preventing pollution is remarkable. Moreover, during idling operation, fuel vapor is not purged at high temperatures where fuel evaporation is active and the purge concentration is high, and the purged fuel vapor is sufficiently diluted by the air flow, so it does not cause engine malfunction. , without deteriorating exhaust emissions.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of the evaporated fuel processing device of the present invention, Fig. 2 illustrates the cross-sectional shape of the first purge port, and Fig. 3 shows the relationship between the throttle opening and the purge port synthetic negative pressure. It is a graph. 10...Canister, 16...Fuel tank, 2
0... Carburizer, 22... Float chamber, 31... Fuel vapor transfer conduit, 32... First purge port, 3
4...Second purge port, 36...Communication path, 38
...Throttle valve, 40...Intake passage, 42...
Temperature-sensitive valve.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. An adsorption device for adsorbing and collecting fuel vapor generated in a fuel storage container, and a fuel vapor purge port formed in the main body of a fuel supply device and opening into an intake passage of the fuel supply device. , a fuel vapor transfer conduit that guides the fuel vapor adsorbed by the adsorption device to the purge port of the fuel supply device, and when the engine is not in operation, the adsorption device collects the fuel vapor generated in the fuel storage container; In an evaporative fuel processing device for an internal combustion engine, which is configured to release fuel vapor adsorbed in an adsorption device into an intake air stream by an intake negative pressure during engine operation, the purge port is located upstream of a throttle valve in a fully closed state. A first purge port opens downstream of the fully closed throttle valve, and a second purge port opens downstream of the fully closed throttle valve.
a purge port, the first purge port and the second purge port communicate with each other through a communication path connected to the fuel vapor transfer conduit, and the second purge port is configured such that the second purge port is closed when the temperature is high. An evaporated fuel processing device for an internal combustion engine, characterized in that it is provided with a temperature-sensitive valve. 2. The evaporated fuel processing device according to claim 1, wherein the opening area of the first purge port is larger than the opening area of the second purge port. 3. The evaporated fuel processing device according to claim 2, wherein the cross-sectional shape of the first port is an elongated hole extending in the axial direction of the intake passage of the fuel supply device.