JP3441574B2 - Vaporizer air vent device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air intake device for an engine, and more particularly to an air vent device for a carburetor of a motorcycle in which ram pressure is applied to improve the efficiency of charging the air-fuel mixture. Things. 2. Description of the Related Art In a motorcycle or the like, when a vehicle is running, wind from the front is taken into an intake passage, the pressure in the passage is made higher than the atmospheric pressure (this pressure is called ram pressure), and this ram pressure is reduced. Developed an air vent device for a carburetor that was introduced into the venturi of the carburetor and also introduced into the float chamber of the carburetor via the air vent passage branched from the intake passage to apply ram pressure to the venturi and the float chamber. Have been. By applying such ram pressure, a high-density air-fuel mixture is supercharged, the efficiency of charging the air-fuel mixture of the engine is improved, and the output during high-speed running is improved. However, in such an air vent device for a carburetor utilizing ram pressure, when the engine is stopped or at a low speed, fuel vaporized from the carburetor in a high-temperature state flows back into the intake passage via the air vent passage. Mixed.
For this reason, at the time of engine restart and 20-30 km /
When the vehicle travels at a low speed of less than or equal to h (low air amount range), the air-fuel mixture becomes over-rich with respect to a predetermined optimum air-fuel ratio, and the startability is reduced, the engine stalls, or so-called bumping (the rotational speed does not increase even if the throttle opening is increased) State, and the combustion efficiency also worsens. An air vent structure for a carburetor that addresses such problems is disclosed in Japanese Utility Model Laid-Open No. 2-126066 and Japanese Patent Laid-Open No. 6-185414. In the prior art described in the above-mentioned utility model publication, a valve for shutting off the passage when the engine is stopped is provided in the middle of the air vent passage to prevent the backflow of vaporized fuel from the float chamber of the carburetor to the intake passage side. Have been. In the prior art disclosed in the above-mentioned patent publication, an air release passage is branched from an air vent passage for introducing a ram pressure, and switching means for these passages is provided so that the passage is provided when the engine is stopped and the engine speed is 20 to 30 km / h or less. During low-speed running, the vaporizer float chamber is switched to the atmosphere opening side to prevent backflow of vaporized fuel to the intake passage side. However, in the air vent device for a carburetor as disclosed in each of the above publications, a switching shutoff valve, a branch passage to the atmosphere, and switching means such as a solenoid valve and a controller. Is required, the number of parts increases and the layout and structure become complicated,
There were drawbacks such as an increase in cost. The present invention has been made in view of the above-mentioned drawbacks of the prior art, and is intended to prevent a backflow of vaporized fuel to an intake passage side at the time of starting an engine or running at a low speed, and to easily maintain a good combustion efficiency. It is an object of the present invention to provide an air vent device for a carburetor having a structure. [0008] In order to achieve the above object, an air vent device for a carburetor according to the present invention introduces ram pressure due to traveling wind into a venturi of a carburetor through an intake passage. An air vent device for a carburetor, which is also introduced into a float chamber of the carburetor via an air vent passage branched from an intake passage, wherein a cooling means for cooling the inside of the passage is provided in the middle of the air vent passage. To provide an air vent device for a vaporizer. In a preferred embodiment, the cooling means comprises a metal cooling pipe. In a further preferred embodiment, the cooling pipe is provided with an outlet for an internal gas or a drain liquid. The fuel evaporated from the carburetor when the engine is stopped or running at low speed is cooled by the cooling pipe while flowing backward through the air vent passage, and does not enter the intake passage. FIG. 1 is an explanatory diagram showing a basic configuration of an embodiment of the present invention. A carburetor 2 that sends an air-fuel mixture to a motorcycle engine 1 has a venturi (not shown) connected to an intake passage 6 via an air cleaner 3 and a float chamber 19 (see FIG. 4) connected to an air vent passage 4. To the intake passage 6. The intake passage 6 has a ram chamber whose opening end is directed forward and takes in the traveling wind to generate a ram pressure higher than the atmospheric pressure. The air vent passage 4 is made of rubber or resin, and a cooling pipe 5 made of stainless steel or the like is interposed between the air vent passage 4 and the cooling pipe 5. According to the air vent device of the carburetor having such a configuration, when the motorcycle travels, traveling wind from the front is introduced into the intake passage 6, passes through the air cleaner 3 as ram pressure, and flows through the carburetor 2.
And sent to the float chamber of the vaporizer 2 through the air vent passage 4. As a result, the venturi of the carburetor 2 and the float chamber become ram pressure, the high-density mixture is supercharged to the engine 1, and the output of the engine is increased as compared with the case where the atmospheric pressure is lower than the ram pressure. When the engine 1 is stopped or at a low speed, the fuel vaporized in the float chamber of the carburetor 2 flows back through the air vent passage 4 due to the hot air of the engine, but is cooled and liquefied by the cooling pipe 5 on the way, or becomes heavy and rises. The backflow action is suppressed, and the mixing in the intake passage 6 is prevented. In this case, as shown in the figure, if the air vent passage 4 is formed so that the upstream side (front side of the vehicle) of the traveling wind flowing inside the air vent path 4 is higher than the downstream side (rear side), the fuel vaporized when the engine is stopped. Backflow to the intake passage side can be more effectively suppressed, and fuel cooled by the cooling pipe 5 can be returned to the float chamber side of the carburetor 2. FIG. 2 is an explanatory diagram showing the configuration of another embodiment of the present invention. In this example, a cooling pipe 5 is provided in a horizontal portion of the air vent passage 4, and an outlet 7 including a drain port 7a and a gas port 7b is provided in the cooling pipe 5. The top of the air vent passage 4 connected to the intake passage 6
As shown, it is at a position higher than the cooling pipe 5. When the engine 1 is stopped, the fuel cooled and liquefied by the cooling pipe 5 is discharged to the outside from the lower drain port 7a, and the vaporized fuel is discharged to the outside from the upper gas port 7b. Thus, the backflow of the vaporized fuel into the intake passage can be reliably prevented. Also, by appropriately selecting the diameter of the discharge port 7, the air vent pressure can be adjusted. Although the above two embodiments are applied to a motorcycle, they can be applied to other vehicles. FIG. 3 is a plan view showing a more specific embodiment of the air vent device for a vaporizer according to the present invention, and FIG. 4 is a side view thereof. In this example, the front cover 1
In the lower part of the headlamp 11 provided at the
2 are provided. The inlet 12 branches into the intake passages 6 forming the ram chambers on the left and right sides, and penetrates the left and right main frames 16 of the vehicle body and communicates with the air cleaner 3. Fresh air that has passed through the air cleaner 3 is introduced into a venturi section of the downdraft type carburetor 2,
4, the main jet 18 is driven by the negative pressure of the intake air.
Then, the fuel in the float chamber 19 is sucked to form an air-fuel mixture having a predetermined air-fuel ratio. This air-fuel mixture is supplied into the combustion chamber from an intake port 21 of the engine 1 through an intake pipe 20, and after combustion, is discharged outside through an exhaust port 23 through an exhaust port 22. Due to the cooling structure of the water-cooled motorcycle, the cooling efficiency may be different between the left and right sides of the vehicle body. In this embodiment, a radiator fan 31 is provided on the right side of the vehicle body.
And the upper right part rises due to the entanglement with the rotation direction of the radiator fan 31. As described above, it is difficult to obtain the air vent cooling effect of the cooling pipe in the location where the radiator fan is exposed to the hot air.
Therefore, the cooling pipe 5 of the air vent passage 4 needs to avoid hot air from the radiator 30, and the cooling pipe 5 is provided slightly to the left of the vehicle body. The traveling wind introduced through the inlet 12 is introduced into the ram chamber (intake passage 6) from the left and right inlets 12a. At this time, since the constriction 60 is formed near the inlet 12a, the traveling wind is generated. Is deflected downward as indicated by arrow B. Therefore, behind the constriction 60 in the intake passage 6, the dynamic pressure due to the wind speed disappears, and only the high pressure (ram pressure) is applied. Therefore, the connection port 4a of the air vent passage 4 is provided behind the constriction 60, and the ram pressure can be taken out of the air vent passage 4 obliquely forward. The air vent passages 4, which are taken out of the intake passages 6 on the right and left sides inclining forward and upward, are connected to the cooling pipe 5, bypass the handlebar stem (head pipe) 13 in the center, and pass through the filter 15 After removing dust and the like from the traveling wind through the float chamber 19, the float chamber 19 in the vaporizer 3 is removed.
Communicate with The handle stem 13 is connected to a front wheel 17 via a front fork. A drain pipe 14 is connected to a left end of the cooling pipe 5. This drain pipe 14
In order to prevent the ram pressure from dropping significantly, for example, at least one-third or less of the equivalent diameter of the total cross-sectional area of the air vent passage 4 at the most narrowed diameter portion (see the portion A in FIG. 2) upstream of the drain hole. The diameter is set so that the drain function is sufficiently achieved. By providing such a drain pipe, when the engine is stopped, the fuel evaporated from the vaporizer 2 and cooled by the cooling pipe 5 of the air vent passage 4 can be discharged to the outside via the drain pipe 14. As described above, in the present invention, the fuel vaporized from the carburetor is liquefied when the engine is stopped, or the fuel is raised by cooling only by interposing the cooling pipe in the middle of the air vent passage. Can be suppressed to prevent mixing into the intake passage. Therefore, as compared with the conventional structure which requires a switching valve or a shutoff valve and its accompanying parts, the startability of the engine is improved by using an inexpensive device having a simple structure and the combustion efficiency is improved by effectively using the fuel. Can be enhanced. In this case, if raising the upstream side of the air vent passage, backflow of fuel cooled by cooling tubes Ru can be further effectively prevented. According to the present invention, since the cooling pipe is provided with the discharge port, the fuel cooled by the cooling pipe can be discharged to the outside from the discharge port to reliably prevent the fuel from entering the intake passage . Also, select the diameter of the discharge port appropriately.
Thereby, the air vent pressure can be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram of a basic configuration of an embodiment of the present invention. FIG. 2 is an explanatory view of a basic configuration of another embodiment of the present invention. FIG. 3 is a plan view showing an example of an air vent device for a vaporizer according to the present invention. FIG. 4 is a side view of the air vent device of FIG. 3; [Description of Signs] 1: engine, 2: carburetor, 3: air cleaner, 4: air vent passage, 5: cooling pipe, 6: intake passage, 7: exhaust port.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 5/08

Claims (1)

(57) [Claims 1] A ram pressure caused by traveling wind is introduced into a venturi of a carburetor through an intake passage, and an air vent passage made of rubber or resin branched from the intake passage. the air vent apparatus for a carburetor is introduced to the float chamber of the carburetor Te, said air vent provided with a cooling means for cooling the intermediate in the path of the passage, the cooling means is made of a metal cooling pipe, the An air vent device for a vaporizer, wherein a drain for a drain liquid is provided in a cooling pipe .