JPS626277Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a down-draft type variable bench lily carburetor for internal combustion engines (hereinafter also referred to as engines) that eliminates temporal fluctuations in air-fuel ratio and improves idling stability.

In conventional variable bench lily carburetors, all fuel is led out to the bench lily portion even during idling operation. However, during idling, the flow rate of intake air is low, and the fuel nozzle and suction
Since the distance from the piston end face is short, most of the discharged fuel adheres to the suction piston end face, the outer periphery of the metering needle, and the wall of the intake passage below the fuel nozzle, and falls in the form of drops onto the top surface of the throttle valve. Otherwise, the air-fuel mixture intermittently flows on the side wall of the intake passage and is sucked into the engine intake pipe, causing the air-fuel ratio of the mixture to fluctuate greatly over time, making idling unstable and deteriorating drivability. Normally, as a countermeasure to this problem, a relatively high idling speed is set, which is less susceptible to fluctuations in the air-fuel ratio, but this has resulted in a worsening of the fuel consumption rate.

In order to solve the above-mentioned problems, this invention was developed to continuously flow fuel into the intake pipe during low intake air flow operation, including idling, without allowing fuel to adhere to the end face of the suction piston, the outer periphery of the metering needle, or the side wall of the intake passage. The object of the present invention is to provide a variable bench lily carburetor which allows the air to flow in to reduce temporal fluctuations in the air-fuel ratio and improves idling stability.

The present invention will be explained with reference to the drawings of the embodiment. In the variable ventilator carburetor body 1 shown in the figure,
2 is a float chamber, 3 is an intake passage, 4 is a throttle valve, and 5 is a ventilator.
is a fuel passage, which is connected from the float chamber 2 to the venturi portion 5. A fuel jet 7 is installed in the middle of the fuel passage 6.
The suction chamber 9 is formed above the throttle valve 4 by the intake passage side wall 3a and the bottom 8a of the suction piston 8. The suction chamber 9 is formed by a cylinder provided in the carburetor body 1 and the suction piston 8 which is slidable in contact with the inner wall surface of the cylinder. A compression spring 8b is inserted inside the suction chamber 9, and the suction piston 8
The suction piston 8 is constantly pushing the suction chamber 9 toward the intake passage side wall 3a. A negative pressure communication port 9a is provided in the bottom 8a of the suction piston 8, which communicates the suction chamber 9 with the venturi portion 5. An atmospheric chamber 10 is provided between the back surface of the sliding flange portion of the suction piston 8 and the carburetor body 1, and atmospheric air is introduced through an atmospheric communication port 10a provided near the intake passage inlet. A metering needle 11 is attached to the center of the bottom 8a of the suction piston 8 facing the venturi portion 5, and its free end is inserted inside the inner diameter of the fuel jet 7.

The fuel jet 7 has a jet portion 7a for metering fuel at its downstream portion, and a fuel nozzle 12 is connected to its tip. The fuel nozzle 12 is
It protrudes into the bench lily portion 5 at a position that does not interfere with the suction piston end face 8a in the idling position. A fuel bypass passage 13 has an inlet 12a at the bottom of the side wall of the fuel nozzle 12, passes through the side wall 3a of the intake passage to bypass the throttle valve 4, and has an outlet 13a on the downstream side thereof. An opening 13b communicating with the atmosphere is provided in the upper part of the fuel bypass passage 13, and an atmospheric jet 14 is provided. Similarly, a jet 15 is provided at the lower part of the passage. 16 is an air bleed passage;
The intake passage 3 has an inlet 16a near the inlet, and an outlet 12b that penetrates through the intake passage side wall 3a and is located on the side of the fuel nozzle 12, facing the inlet 12a of the fuel bypass passage 13. The inlet 16a and outlet 12b of the air bleed passage 16 are provided with jets 17 and 18, respectively.

When the variable bench lily carburetor 1 configured as described above operates in a low air amount region by minimizing the opening degree of the throttle valve 4, the suction piston 8 advances to the most forward position in FIG. The negative pressure in section 5 is maintained constant. The opening area of the fuel jet portion 7a is the same as that of the needle valve 11.
The fuel is metered in response to the lower intake air amount. The fuel led out to the fuel nozzle 12 is sucked by the strong negative pressure of the inlet 12a opened at the lower part of the nozzle side wall, and is drawn into the fuel bypass passage 1.
3 from the outlet 13a through the throttle valve 4
is constantly discharged downstream. In the above, since the jet 15 is provided at the lower part of the fuel bypass passage, the discharged fuel flows into the fuel bypass passage 13 while maintaining a constant flow rate without being affected by fluctuations in the intake pipe negative pressure. The inflowing fuel is air-bleeded from the atmospheric jet 14 and the air bleed passage 16, and is supplied to the downstream portion of the throttle valve 4 in a good atomized state.

When accelerating from steady state, atmospheric jet 1
4, the fuel in the fuel bypass passage 13 stagnates for a moment as the intake pipe negative pressure decreases, resulting in acceleration lean, but in the case of this device, the difference between the atmospheric pressure and the intake pipe negative pressure causes the intake pipe to stagnate. Since fuel is sent into the pipe, there is no stagnation of fuel and smooth running is possible.

Air bleed passage 16 is always stably filled with atmospheric air via jets 17 and 18, and bleed air flows from jet 18 into fuel nozzle 12.
Air is supplied. Fuel also adheres to the outer periphery of the metering needle 7 and flows toward the fuel nozzle 12, but this fuel is blown away by the bleed air jetted out from the jet 18, falls into the fuel nozzle 12, and is filled with fuel. It continuously flows into the bypass passage 13.

As described above, the fuel discharged from the fuel jet section during low air flow operation including idling is
It adheres to the end of the suction piston, the outer periphery of the metering needle, the side wall of the intake passage, etc., and falls onto the top of the throttle valve 4, or flows intermittently on the side wall of the ventilation passage, and is sucked into the engine. This prevents the fuel ratio from fluctuating over time.

As explained above, this invention provides a variable bench lily carburetor with a fuel bypass passage that has an inlet on the side of the fuel nozzle, bypasses the throttle valve and has an outlet on the side wall of the intake passage on the downstream side of the throttle valve; an air bleed passage having an atmospheric jet opening to the atmosphere at the top of the bypass passage; and an outlet having an inlet near the inlet of the intake passage and a jet at a side of the fuel nozzle opposite the inlet of the fuel bypass passage; By establishing
During low air flow operation, including idling, the fuel discharged from the fuel jet section is prevented from adhering to the end surface of the suction piston, the outer periphery of the metering needle, or the side wall of the intake passage, and is prevented from flowing directly from the fuel nozzle into the fuel bypass passage. Since the air-fuel mixture is continuously supplied to the engine intake pipe, fluctuations in the air-fuel ratio of the air-fuel mixture are reduced, which has the effect of improving idling stability. Therefore, the idling speed can be set low and the air-fuel ratio can be made leaner, which has the effect of improving the fuel consumption rate. Furthermore, stable engine combustion is obtained both during idling and during acceleration from idling, resulting in improved drivability.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of an embodiment of the variable bench lily carburetor according to this invention. 3a... Intake passage side wall, 4... Throttle valve, 5... Bench lily portion, 12... Fuel nozzle, 12a... Fuel bypass passage inlet, 12b...
...Air bleed passage outlet, 13...Fuel bypass passage, 14...Atmospheric jet, 15...Jet, 16...Air bleed passage.

Claims (1)

[Scope of utility model registration request] A fuel jet provided in a fuel passage that communicates from the float chamber to the bench lily of the down-draft intake passage, a suction piston that moves forward and backward across the bench lily depending on the load condition of the internal combustion engine, and a suction piston that moves forward and backward across the bench lily depending on the load condition of the internal combustion engine. An internal combustion engine having a suction chamber having an inner wall surface on which the outer periphery of the piston slides, and a metering needle having a base attached to the bottom of the suction piston and controlling the jet area of the fuel jet by movement of its free end. A variable bench lily carburetor for use in a carburetor, the fuel nozzle being coupled to the tip of the fuel jet and protruding into the vent lily portion, and having an inlet in a side portion of the fuel nozzle located in the carburetor body, downstream of the throttle valve. a fuel bypass passage having an outlet on a side wall of the intake passage; an atmospheric jet opening to the atmosphere at an upstream portion of the fuel bypass passage; and an atmospheric jet having an inlet near the entrance of the intake passage and discharging the fuel at a side of the fuel nozzle. A variable bench lily carburetor comprising: an air bleed passage having an outlet provided with a jet at a position opposite to an inlet of the bypass passage.