JPS626099B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable vent lily type carburetor for use in an internal combustion engine.

A conventional variable bench lily type carburetor is equipped with a spring-biased movable suction piston that forms a variable bench lily portion in the carburetor intake air passage, and the negative pressure chamber of the movable suction piston is connected to the negative pressure downstream of the vent lily portion. The atmospheric pressure chamber of the movable suction piston is communicated with the atmospheric pressure region upstream of the bench lily section, and the negative pressure acting in the negative pressure chamber and the atmospheric pressure acting in the atmospheric pressure chamber are connected to the movable suction piston. The movable suction piston moves to a position where the force acting in the direction of opening the piston and the force of the spring in the direction of closing the suction piston are balanced, so that a substantially constant negative pressure is generated downstream of the bench lily portion. That is, the cross-sectional area of the bench lily portion is varied so that the flow velocity of intake air passing through the bench lily portion is approximately constant. In such a variable bench lily type carburetor, it is difficult to achieve combustion stability and engine speed stability in an operating range where the amount of intake air is small unless fuel atomization is sufficient. In order to cope with this and promote atomization of the fuel, the flow velocity of the air passing through the vent lily portion may be increased, and for this purpose, the spring may be strengthened and the opening area of the vent lily portion may be reduced. However, if the suction piston is slightly closed in this way, the flow resistance becomes large during high load operation that requires high output, resulting in a disadvantage that high charging efficiency cannot be obtained and it is difficult to produce engine output.

In view of the above, the present invention secures a large opening area of the bench lily during high-load operation requiring high output, while increasing the flow velocity of the intake air passing through the bench lily when the amount of intake air is relatively small. Therefore, it is an object of the present invention to provide a variable bench lily type carburetor that promotes atomization of fuel.

That is, the present invention is provided with a movable suction piston that forms a variable bench lily portion in the intake air passage of the carburetor, and communicates the negative pressure chamber of the movable suction piston with a negative pressure generating region downstream of the vent lily portion. In a variable bench lily type carburetor, the atmospheric pressure chamber of the suction piston is communicated with the atmospheric pressure region upstream of the bench lily portion, and the suction piston reciprocates to change the cross-sectional area of the bench lily portion.
a negative pressure passage that communicates the negative pressure generation region downstream of the variable bench lily portion with the atmospheric pressure chamber; a throttle disposed in the atmospheric hole that communicates the atmospheric pressure chamber of the suction piston with the atmospheric pressure region; A throttle disposed in the pressure passage, an on-off valve disposed in the negative pressure passage, and a connecting means for operating the on-off valve according to the opening degree of the throttle valve, and when the opening degree of the throttle valve is below a predetermined value. The on-off valve is opened to introduce negative pressure into the atmospheric pressure chamber of the suction piston, and the atmospheric vent is extended to the center of the intake passage, and the variable vent lily type carburetor is opened toward the upstream side. It is.

Next, the variable bench lily type carburetor of the present invention will be explained based on the drawings.

In Fig. 1, 1 is the carburetor housing, 2 is the throttle valve, 3 is the throttle valve shaft, 4 is the float chamber, 5 is the movable metering needle fixed to the right end of the suction piston 7, and 6 is the metering jet. , 8 is a compression spring that always biases the suction piston 7 in the closing direction; 9 is a cover; 10 is an atmospheric vent that communicates the atmospheric pressure chamber 12 of the suction piston with the atmospheric pressure region upstream of the bench lily; As shown in FIG. 2, it is composed of a pipe, and its inlet 14 extends to the center of the intake passage where the intake air flow rate is high and opens toward the upstream side, and the atmospheric air vent 10 is equipped with a throttle 20. This opening is therefore subjected to the dynamic pressure of the intake air. In FIG. 1 again, 11 is the bench lily part;
Reference numeral 13 denotes a negative pressure chamber, which communicates with a negative pressure generation area downstream of the bench lily portion through a hole 18 formed at the bottom of the suction piston 7. 15 is an on-off valve; 17 is a negative pressure passage communicating with the atmospheric pressure chamber 12 downstream of the vent lily and upstream of the throttle valve 2; and 16 is a throttle provided in the negative pressure passage. As shown in FIG. 3, the on-off valve 15 disposed in the negative pressure passage 17 operates in conjunction with the throttle valve 2, and opens when the throttle valve opening is below a certain level. That is, one end of the link 24 engages with the cam 19 fixed to the throttle valve shaft 3, and the other end of the link 24 is connected to the lower end of the rod extending downward from the valve body of the on-off valve 15. It is rotatably mounted. 21
25 is an intake passage, and 25 is a spring that urges the on-off valve 15 upward. When the opening degree of the throttle valve 2 is below a predetermined value and the on-off valve 15 is open, the atmospheric pressure chamber 12 is communicated with the atmosphere via the throttle 20 on the one hand, and is connected to the atmosphere downstream of the bench lily through the throttle 16 on the other hand. Since the atmospheric pressure chamber 12 is communicated with the pressure generation area, a negative pressure intermediate between the negative pressure generated in the negative pressure generation area and the atmospheric pressure is generated in the atmospheric pressure chamber 12 . Therefore, compared to the case where atmospheric pressure is applied in the atmospheric pressure chamber 12, the suction piston 7
moves further to the right, sandwiching the opening cross-sectional area of the bench lily portion 11, and the flow velocity of the intake air passing through the bench lily portion 11 becomes faster. As described above, according to the present invention, when the opening degree of the throttle valve is small, that is, when the amount of intake air is relatively small, the flow velocity of the intake air flowing through the bench lily portion 11 can be greatly increased compared to the conventional art. can promote atomization of fuel.

On the other hand, when the throttle valve opening increases, the on-off valve 15 closes, and the introduction of negative pressure into the atmospheric pressure chamber 12 is stopped, and the atmospheric pressure chamber 12 is communicated with the atmosphere through the atmospheric vent 10, allowing high-speed, high-load operation. High filling efficiency can be ensured at times. Furthermore, since the dynamic pressure of the intake air is applied to the entrance of the atmospheric air vent, it is more effective in increasing the filling efficiency.

According to the present invention, it is possible to increase the flow velocity of the intake air flowing inside the bench lily portion when the amount of intake air is relatively small, and promote atomization of the fuel, while ensuring high charging efficiency at high speed and high load. Therefore, combustion in the engine is stabilized, rotational fluctuations are reduced, and output is improved.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a vertical cross-sectional view showing the overall outline, and FIGS. 2 and 3 are enlarged cross-sectional views of main parts of FIG. 1. DESCRIPTION OF SYMBOLS 1... Carburetor housing, 2... Throttle valve, 3... Throttle valve shaft, 7... Suction piston, 8... Compression spring,
10... Atmospheric ventilation hole, 11... Bench lily part, 12...
Atmospheric pressure chamber, 13... Negative pressure chamber, 14... Inlet, 15... Open/close valve, 16... Throttle, 17... Negative pressure passage, 19... Cam, 21... Intake passage, 23... Fulcrum, 24... Link, 25... Spring.

Claims (1)

[Scope of Claims] 1. A movable suction piston forming a variable bench lily portion in the intake air passage of the carburetor, communicating the negative pressure chamber of the movable suction piston with a negative pressure generating region downstream of the vent lily portion; In a variable bench lily type carburetor, the atmospheric pressure chamber of the movable suction piston is communicated with an atmospheric pressure region upstream of the bench lily portion, and the suction piston reciprocates to change the cross-sectional area of the bench lily portion. a negative pressure passage that communicates between the negative pressure generation area of the suction piston and the atmospheric pressure chamber; a throttle disposed in an atmospheric vent that communicates the atmospheric pressure chamber of the suction piston with the atmospheric pressure area; with an aperture placed in
An on-off valve disposed in the negative pressure passage, and a connecting means for operating the on-off valve according to the opening degree of the throttle valve,
When the opening degree of the throttle valve is below a predetermined value, the opening/closing valve is opened to guide negative pressure into the atmospheric pressure chamber of the suction piston, and the atmospheric vent is extended to the center of the intake passage, and A variable bench lily type carburetor that opens toward the front. 2. The variable vent lily type carburetor according to claim 1, wherein one end of the negative pressure passage opens downstream of the variable vent lily portion and upstream of the throttle valve.