JP2860081B2 - Motorcycle vaporizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carburetor for a motorcycle having an air vent passage communicating a float chamber with the outside air.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional carburetor, which is mounted on an internal combustion engine in a tilted forward position and in which a carburetor passage 2 is inclined substantially downward. It is. As prior art, there is Japanese Utility Model Laid-Open No. 3-87857.

[0003] An air vent passage 20 is formed in the carburetor body 1, and the front end of the air vent passage 20 is connected to the passage 2.
6 and the outside air through an air vent hose (not shown).
The upper end of the front wall 11a of the float chamber 11 opens toward the upper air region of the chamber 11.

Since the air vent passage 20 communicates the inside of the chamber 11 with the atmosphere, the pressure in the chamber is always kept constant (atmospheric pressure) with respect to a change in the amount of fuel in the chamber 11. Thereby, the smooth supply of fuel from the chamber 11 to the main jet 7 and the like is maintained, and an appropriate air-fuel ratio is always obtained.

[0005]

Position of the opening 20a of the air vent passage 20 [SUMMARY OF THE INVENTION] is a top also the oil level L ₁ of the normal running, the height of the degree in the normal deceleration that does not Hitakara fuel It is located in.

However, at the time of rapid deceleration, the fuel in the chamber 11 is pushed extremely forward, and the virtual line L ₂ shown in FIG.
In some cases, the fuel may enter the air vent passage 20 in such a case.

[0007] Once the fuel in the air vent passage 20 from entering, even oil level and even then accelerated returns substantially to the state of the L _1, fuel air vent passage 20 is not escape immediately, for a while the air vent It remains with the passage 20 closed. Thus, the air vent passage 20
When the fuel is accelerated in a closed state, the pressure in the chamber 11 decreases with a decrease in the amount of fuel in the chamber 11, and it becomes impossible to supply fuel to the main jet 7 smoothly. Therefore, the air-fuel ratio changes, and the acceleration performance decreases.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent fuel from entering the air vent passage at the time of sudden deceleration and to maintain an appropriate air-fuel ratio even during subsequent acceleration, thereby maintaining acceleration performance.

[0009]

In order to achieve the above object, the invention according to claim 1 of the present application provides a float chamber 1
In a carburetor of a motorcycle having an air vent passage communicating the inside of the carburetor with the outside air, an air vent passage 20 is provided on both left and right sides near the upper end of the carburetor body 1 in which the carburetor passage 2 is inclined substantially downward. The pair of air vent passages 20 are connected to a common passage 26 on the front side of the carburetor passage 2 and reach the upper end of the front wall 11a of the rear float chamber 11 at the rear end of each air vent passage 20. The extension pipes 24 protruding into the float chamber 11 are connected to each other. Each extension pipe 24 protrudes rearward in the float chamber 11 by a certain distance, and its opening 24a is opened during normal operation or during rapid deceleration. It is characterized in that it is located at an air area position where the fuel is not immersed even with respect to the fuel level.

According to a second aspect of the present invention, in the carburetor for a motorcycle according to the first aspect, instead of the extension pipe 24 connected to the rear end of the air vent passage 20, the meat formed on the float chamber side wall 11b. Extension passage 30 in protruding portion 27
Is formed.

[0011]

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a carburetor of a motorcycle to which the present invention is applied. Since the carburetor is of a down-draft type mounted in a forward leaning position, the carburetor passage 2 is almost in a downward position. The upper end of the carburetor passage 2 is connected to an air cleaner via an intake pipe, and the lower end is connected to an intake port of a cylinder head via an intake communication pipe. That is, in the carburetor passage 2, the air flows downward from above.

In the carburetor body 1, a piston valve 4 for forming a venturi 3 in the carburetor passage 2 is provided, and a throttle valve (butterfly valve) 5 is provided downstream.
At the rear of the carburetor body 1, a main jet 7 and a fuel needle valve 8 are provided.

A float chamber 11 is formed by fixing a chamber case 10 on the rear side of the vaporizer main body 1. The float chamber 11 stores fuel therein and opens and closes the needle valve 8. The needle valve 8 is appropriately opened by the raising / lowering action of the float 14, and fuel flows into the chamber 11 from the fuel inlet 16 through the needle valve 8.
It is adjusted to keep the oil level L ₁ of the inner at a constant level.

The air vent passage 20 is located near the upper end in the carburetor body 1 and is formed as a pair on both left and right sides of the carburetor passage 2 as shown in FIG. The passage 26 communicates with the atmosphere via an air vent hose (not shown).

As shown in FIG. 2, each of the air vent passages 20 linearly extends rearward with a slight downward slope and reaches the upper end of the front wall 11a of the chamber 11. At the rear end of the air vent passage 20, a brass extension tube 24 is press-fitted. The extension tube 24 protrudes rearward in the chamber 11 by a fixed distance, and the rear end opening 24a is
Open in the air area.

The position of the opening 24a is positioned higher than the normal running oil level L ₁ at the time, and also positioned it than to come to the rear with respect to the oil surface L ₂ at the time of rapid deceleration ing. Furthermore, for the oil surface L ₃ during rapid acceleration it is positioned so as to come in front. That is, the position of the opening 24a is set so as to be always located in the air region of the chamber 11 without being immersed in fuel during normal running, sudden deceleration, and sudden acceleration.
Specifically, a substantially central portion in the front-rear direction width W of the oil surface L ₁ in the chamber 11, since the amount of variation in the vertical direction (increase amount) is small in the deceleration and any oil level change of the acceleration, the front and rear The opening 24a is located above the center of the width W in the direction.

The operation will be described. During normal running is kept fuel generally horizontal oil level L ₁ in the chamber 11, the air vent passage 20 is functioning normally, adjusted so as to maintain always the atmospheric pressure in the chamber 11 to variations in fuel I do.

[0019] During rapid deceleration, the fuel within the chamber 11 as the oil level L ₂ of FIG. 2 is asked to the front wall side. However, fuel does not intrude from the rear end opening 24a of the extension pipe 24, the air vent passage 20 functions normally, and the inside of the chamber is kept at atmospheric pressure. Therefore, even if the vehicle accelerates after the rapid deceleration, it is possible to maintain good acceleration performance with an appropriate air-fuel ratio.

[0020] When rapid acceleration from the normal operation, although the fuel in the chamber is as asked by the oil surface L ₃ to the rear wall side, the opening 24a of the extension tube 24 also in this case not Hitakara fuel .

When the vehicle goes down a steep hill, the entire vaporizer further leans forward from the position shown in FIG. 1, causing a fuel forward phenomenon similar to that during deceleration in the chamber 11. Up to 15 slopes on the road slope
Since about 20%, and is not initially thought that tilts up oil level L ₂ of FIG. In other words, even when going down steep hills,
First, fuel does not enter the air vent passage 20. The same is true when the vehicle climbs a steep slope, and the fuel does not enter the air vent passage 20.

In this embodiment, as shown in FIG. 3, since the air vent passage 20 is provided as a pair on the left and right, when the vehicle body leans to the left or right, the opening of the extension pipe 24 located on the leaning side. Even if 24a is immersed in fuel, the other is always higher and exposed to the air region, keeping the inside of the chamber 11 at atmospheric pressure.

[0023]

[Other embodiments]

(1) FIGS. 4 and 5 show that a built-up portion 27 is formed on the side wall 11 b of the chamber 11, and an extension passage 30 that is continuous from the air vent passage 20 is formed in the build-up portion 27. the rear end opening 30a, as in the case of the extension tube 24, higher than the oil level L ₁ at the time of normal running, and at the rear with respect to the oil surface L ₂ at the time of sudden deceleration, further rapid acceleration and it is positioned so as to come forward with respect to the oil surface L ₃ in.

[0024]

[0025]

As described above, the invention according to the first aspect of the present invention relates to a carburetor of a motorcycle having an air vent passage 20 for communicating the inside of the float chamber 11 with the outside air. At the ends, extension passages 24, 30 extending into the chamber 11 are extended,
Opening 24a of the extension passage 24 and 30, the 30a, since the position is allowed so as not Hitakara fuel against normal operation one of the fuel oil level at the time of and during rapid deceleration L _1, L _2, rapid At the time of deceleration, fuel does not flow into the extension passages 24 and 30. Even during the acceleration immediately after the deceleration, the air vent passage 20 naturally functions normally to maintain the inside of the chamber 11 at the atmospheric pressure, and to obtain an appropriate air-fuel ratio and Acceleration performance due to this can be maintained.

An extension pipe 24 is provided at the rear end of the air vent passage 20.
Therefore, it is possible to easily manufacture the carburetor simply by adding a pipe without changing the shape of the conventional carburetor body. Also, a pair of air vent passages 20 are provided on both left and right sides of the carburetor body 1, and the two air vent passages 20 communicate with a common passage 26 in front of the carburetor passage 2,
6 communicates with the atmosphere, so that when the vehicle turns left or right, even if fuel enters one air vent passage 20, the other air vent passage 20 is reliably open. Therefore, the float chamber 11 can be maintained at the atmospheric pressure.

According to the second aspect of the present invention, instead of the extension pipe 24, the overlay portion 27 formed on the chamber side wall 11b is provided.
Since the extension passage 30 is formed therein, material can be saved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a carburetor of a motorcycle to which the present invention is applied.

FIG. 2 is a partial longitudinal sectional view cut along a cutting plane passing through an air vent passage.

FIG. 3 is a schematic sectional view taken along the line III-III of FIG. 1;

FIG. 4 shows a modification of the present invention, and is the same partial longitudinal sectional view as FIG.

FIG. 5 is a sectional view taken along line VV of FIG. 4;

FIG. 6 is a longitudinal sectional view of a conventional example.

FIG. 7 is a sectional view taken along a section passing through an air vent passage.
3 is a partial vertical sectional view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vaporizer main body 2 Vaporizer passage 11 Float chamber 20 Air vent passage 24 Extension pipe (an example of extension passage) 27 Overlay portion 30 Extension passage

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 5/08 F02M 5/02

Claims (2)

(57) [Claims] 1. In a carburetor of a motorcycle having an air vent passage 20 communicating the outside of the float chamber 11 with outside air, the air vent passage 20 is provided in the carburetor body 1 in which the carburetor passage 2 is inclined substantially downward. A pair of air vent passages 20 are formed on the left and right sides near the upper end, and the two air vent passages 20
Is connected to the common passage 26 on the front side and reaches the upper end of the front wall 11a of the float chamber 11 on the rear side,
An extension pipe 24 protruding into the float chamber 11 is connected to the rear end of each air vent passage 20, and each extension pipe 24 protrudes rearward within the float chamber 11 by a certain distance, and its opening 24a is formed. Wherein the fuel is not immersed in any of the fuel levels during normal operation and sudden deceleration, and is positioned in an air area position.
Wheel car carburetor. 2. The motorcycle carburetor according to claim 1, wherein the extension pipe is connected to a rear end of the air vent passage.
A vaporizer for a motorcycle, wherein an extension passage 30 is formed in a built-up portion 27 formed in a side wall 11b of the float chamber in place of the vaporizer 4.