JPS6233093Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable bench valve carburetor, and more particularly to a variable bench valve carburetor provided with a low speed fuel system.

In order to respond to stricter automobile exhaust regulations and to save fuel consumption, improvements to the low-speed fuel system of carburetors are becoming important. Nothing that satisfies the requirements has yet to be obtained.

On the other hand, a fixed bench lily type carburetor uses a low-speed fuel system as shown in FIG. 1, for example.
In this low speed fuel system, the fuel metered in the slow jet 5 moves upward and enters the emulsion tube 8. On the other hand, the air entering from the first slow air bleed 6 enters the emulsion tube 8, passes through the bleed hole 9, mixes with fuel, becomes a gas-liquid mixed flow, rises, and further enters from the second slow air bleed 7. Mix with air. This gas-liquid mixed flow flows down the slow passage 10 and is supplied from the bypass hole 4 and the idle hole 3 into the intake path of the carburetor. Note that there is a throttle valve 1 attached to the throttle valve shaft 2 in a location close to the bypass hole 4 and the idle hole 3.

In such a low-speed fuel system, the air introduced into the emulsion tube 8 pushes the liquid fuel apart and passes through the bleed hole 9 intermittently. Flowing as a stream. Therefore, the amount of fuel in the gas-liquid mixture flow supplied to the intake passage from the idle hole 3 and the bypass hole 4 changes intermittently, resulting in a mixture with a highly fluctuating air-fuel ratio, which makes the engine run unsmoothly. At the same time, good results were not obtained in terms of fuel efficiency and exhaust composition.

Therefore, the opening of the second slow air bleed is enlarged and the slow passage 10 is made into a large diameter pipe.
Attempts have been made to equalize the gas-liquid mixed flow in the emulsion tube 10, but increasing the size of the second slow air bleed 7 reduces the load applied to the emulsion tube 8 and the slow jet 5. In addition to the effects of increased volume, this resulted in a decrease in the responsiveness of fuel supply to changes in intake passage negative pressure. Furthermore, in order to improve the mixing condition within the emulsion tube 8, a large number of small-diameter bleed holes 9 were provided, but it took time to manufacture the emulsion tube 8, resulting in high costs.

Furthermore, if the engine is stopped when the engine is operated at high speed and the temperature of the carburetor rises, bubbles will be generated in the fuel passage connected to the slow jet 5, and these bubbles will push up the fuel and overflow from the slow passage 10 into the intake passage. This has a serious drawback in that it causes so-called percolation, and the fuel that overflows into the intake passage enters the engine, making it difficult to restart it.

The main fuel system supplies fuel from the fixed bench lily, and the low-speed fuel system supplies fuel from near the throttle valve, so when the throttle valve opening is large during medium or high-speed operation, the fuel is supplied from the low-speed fuel system. This causes the fuel to be introduced into specific bubbles without being mixed well, making the engine run unsmoothly, and since fuel is supplied from two locations, the accuracy of fuel metering decreases, causing problems with the operating condition. Regardless of the situation, it was not possible to obtain a fuel flow rate that would allow a constant air-fuel ratio to be obtained.

The present invention eliminates the above-mentioned problems, provides a variable vent lily type carburetor that has a low-speed fuel system that is suitable for smooth engine rotation and prevention of percolation, and is easy to process and maintain. In a variable bench valve carburetor equipped with a low-speed fuel system for the purpose of A first slow air bleed is provided which communicates with the main emulsion tube and sucks air above the slow jet, and a plurality of bleed holes arranged in multiple stages in the axial direction are provided in the middle of the first slow air bleed. and a slow passage that surrounds the part of the first pipeline in which the bleed hole is provided and has a second slow air bleed at one end and an idle hole and a bypass hole at the other end. a diaphragm mechanism comprising an emulsion tube connected to a second conduit, wherein the slow passage is formed within a mounting surface of the diaphragm mechanism for driving the variable ventilate, and the second slow air bleed is located within the diaphragm mechanism. It is characterized in that it is formed so as to connect the atmospheric pressure chamber and the slow passage 10.

The variable bench lily type carburetor performs acceleration correction using the operating characteristics of the variable vent lily that forms the main system without adding an accelerator pump. For this reason, a variable bench valve carburetor with a low-speed fuel system needs to start the main system fuel quickly, and also make the main system fuel flow high, so that it can optimally increase the amount of fuel during acceleration. . This idea was made with attention to these points, and made it possible to achieve the desired purpose by reducing the fuel increase rate from the low-speed fuel system when the throttle valve opens.
Specifically, this is achieved by connecting the atmospheric pressure chamber of the diaphragm mechanism and the slow passage with a second air bleed so that when the throttle valve opens, the slow passage 10 becomes atmospheric pressure that is substantially unaffected by the intake pressure. Ru.

Fig. 2 is a sectional view of an embodiment of the variable bench lily type carburetor of the present invention, and Fig. 3 is a sectional view showing a longitudinal section along the low-speed fuel system of Fig. 2. The same reference numerals are given. The emulsion tube 8 for low-speed fuel is provided adjacent to the main emulsion tube 11, and its lower part is connected to the main emulsion tube 11 via the slow jet 5.
The upper part communicates with the first slow air bleed 6 through a passage indicated by a broken line. 1st
A plurality of bleed holes 9 are arranged in multiple stages in the axial direction in the middle part of the pipe that communicates the slow air bleed 6 and the slow jet 5, and a slow passage 10 is provided in the emulsion tube 8 surrounding this part. A second slow air bleed 7 opens in the raised position and communicates with an idle hole 3 and a bypass hole 4 that open in the intake passage near the throttle valve 2. In addition, 12 is a desk plate, 13
14 is a negative pressure chamber, 14 is a diaphragm, 15 is a spring, 17 is a negative pressure introduction hole, 19 is a ventilate part,
20 indicates the main air bleed.

The lower part of the emulsion tube 8 is sealed, and fuel is introduced through a horizontal hole communicating with the lower part of the main emulsion tube 11 provided at the lower part of the slow jet 5. Therefore, when the temperature of the carburetor rises, the amount of bubbles generated in the low-velocity fuel flow path is small, but even if bubbles are generated, they can easily escape from the first slow air bleed 6.
No percolation phenomenon occurs. On the other hand, the slow passage 10 communicating with the emulsion tube 8 is once connected in the horizontal direction as shown in FIG. 2, and then raised as shown in FIG. 3 to communicate with the second slow air bleed 7. The slow passage 10 communicates with the idle hole 3 and the bypass hole 4, and supplies the gas-liquid mixed flow sent from the emulsion tube 8 into the intake passage. Note that an air bleed 22 for adjusting low-speed fuel is provided in an air passage branched from the horizontal passage portion of the slow passage 10, thereby adjusting the amount of air introduced to more finely adjust the amount of low-speed fuel.

In Figure 2, the main fuel system is main jet 2.
1 controls the maximum fuel flow rate, and the intermediate fuel amount is controlled by moving a jet needle 18 inserted into the main emulsion tube 11 up and down together with a suction piston 16 that responds to the intake air amount. Further, the main emulsion tube 11 and the slow jet 5 communicate with each other directly above the main jet 21, and low-speed fuel is supplied to the emulsion tube 8 through the main jet 21 and the slow jet 5.

The bleed holes 9 are arranged in multiple stages in the axial direction of the conduit that communicates the first slow air bleed 6 and the slow jet 5, with two stages shown in FIG. 2 and one stage shown in FIG. A state in which a step bleed hole 9 is provided is shown.

In the low-speed fuel system configured in this way, the fuel measured by the slow jet 5 and the air taken in from the first slow air bleed 6 are separated from each other by the emulsion tube 8.
The fuel becomes a counterflow inside and passes through the bleed hole 9, and is conveyed to the slow passage 10 in a spray state.
That is, in the case of FIG. 1, the first slow air bleed 6
The fuel was made into fine particles by blowing the air sucked into the fuel into the fuel, but in this embodiment, the fuel is sucked up like a sprayer and ejected in the form of fine particles from the bleed hole 9. The air mixed in the gas-liquid mixed flow generated in this way is the air taken in from the second slow air bleed 7, and since this air is air from the atmospheric pressure of the diaphragm mechanism that is not affected by the intake pressure, the engine There is no pulsation caused by rotation, and changes in the mixing ratio are alleviated. Therefore, an air-fuel mixture uniformly containing particulate fuel can be supplied to the intake passage.

In addition, when the engine is stopped after high-speed operation when the temperature of the carburetor is rising, air bubbles are generated above and below the slow jet 5 and try to push up the fuel, but the first slow air bleed 6 Since the holes are open, air bubbles can easily rise and be discharged without causing percolation. In addition, since the occurrence of percolation can be prevented, it is possible to provide the bleed hole 9 below the fuel liquid level, and in engines equipped with a carburetor that does not use a choke valve, the fuel can be removed at the same time as the engine starts. is supplied, improving engine startability. Furthermore, when the throttle valve 1 opens, the slow passage 10
The second air bleed 7 introduces atmospheric pressure that is not affected by the intake pressure, thereby making it possible to sufficiently reduce the amount of fuel from the low-speed fuel system.

In addition, in this low-speed fuel system, since the slow passage 10 is formed within the mounting surface of the diaphragm 14 mechanism, the second slow air bleed 7 passage can be shortened, and the machining of the second slow air bleed 7 passage is easy. For example, as shown in Figure 3,
By inserting the chip on which the second slow air bleed 7 is formed, connection with the slow passage 10 is possible. In addition, the dust contained in the atmosphere that has flowed into the atmospheric pressure chamber of the diaphragm 14 mechanism will freely fall and accumulate in the vicinity of the entrance, as the flow of the atmosphere slows down at the entrance, and will accumulate at the second slow air bleed 7. As a result, even though the second slow air bleed 7 is exposed to the atmosphere, there is little possibility that the second slow air bleed 7 will become clogged with dust in the atmosphere. Easy to maintain.

FIG. 4 is a diagram showing the relationship between the fuel flow rate and the intake air amount for the devices shown in FIGS. 2 and 3, with the intake air amount and fuel flow rate plotted on the horizontal and vertical axes, respectively. 31 is the required characteristic curve, 32 is the fuel supply situation from the low-speed fuel system of this embodiment, 33 is the fuel supply situation of the main fuel system, and 34 is the situation when the low-speed fuel system having the structure shown in FIG. 1 is used. The fuel supply status 35 also indicates the fuel supply status of the main fuel system.

In general, in a variable bench lily type carburetor equipped with a suction piston, the negative pressure generated in the vent lily remains almost constant even if the amount of intake air changes, so during medium to high speed operation The negative pressure transmitted is equivalent. Therefore, as shown by the dashed line 34, the ratio of the low speed fuel amount is relatively large. On the other hand, the amount of fuel supplied to the low-speed fuel system of this embodiment changes as shown by a dashed line 32. That is, when the intake air amount increases due to high-speed operation, the slow passage 10 increases with negative pressure in the intake passage.
Since the negative pressure of the air bleed also decreases, the amount of fuel passing through the bleed hole 9 decreases, but since the slow passage 10 is substantially at atmospheric pressure via the second air bleed, the rate of decrease is lower than that of the conventional low speed. This is more noticeable than in the fuel system. The reason for this is that even when the throttle valve 1 opens, the intake pressure remains lower than atmospheric pressure due to the variable bench lily 16, but the atmospheric pressure chamber of the diaphragm mechanism is not affected by this and maintains the slow passage 10 at atmospheric pressure. It is from.

Note that, as a matter of course, the viscosity and specific gravity of liquid fuel are much higher than those of air, so the lower the negative pressure, the lower the proportion of fuel passing through the bleed hole 9. That is, since the bleed holes 9 are arranged in multiple stages in the axial direction in the middle part of the pipe that communicates the first slow air bleed 6 and the slow jet 5, Fuel and air are ejected from the upper bleed hole 9, and only fuel is ejected from the lower bleed hole 9. However, as the amount of air increases, air is ejected from the upper bleed hole 9, and the lower bleed hole 9 ejects fuel and air. Fuel and air will come out from the bleed hole.
As a result, as the amount of air increases, fuel from the low speed fuel system decreases. That is, as the engine speed increases and the fuel supply from the main fuel system increases, the fuel supply from the low-speed fuel system can be reduced. By reducing the amount of fuel supplied from the low-speed fuel system during high-speed operation in this way, the unevenness of the air-fuel ratio of the air-fuel mixture to each cylinder of the engine as described above is greatly improved, and the amount of fuel is reduced. Accuracy is improved and the engine rotates more smoothly.

That is, there is a noticeable difference in the change in the amount of low-speed fuel in the low-speed fuel system of this embodiment compared to the case of the conventional variable bench valve carburetor.

As described above, the variable bench lily type carburetor of this embodiment is provided with a first slow air bleed directly above the slow jet in the low speed fuel system, and a shaft in the middle of the pipe connecting the slow jet and the first slow air bleed. By providing a plurality of bleed holes arranged in multiple stages in the direction, and surrounding the part where the bleed holes are provided with an emulsion tube having a slow passage branched horizontally, the fuel is supplied from a low-speed fuel system. In addition to improving fuel atomization and uniformity, it also reduces the proportion of low-speed fuel supplied during medium and high-speed operation, allowing the engine to rotate smoothly over the entire operating range and preventing percolation. It has this effect. Therefore, the advantage of purifying the exhaust composition and saving fuel consumption is also obtained.

The low-speed fuel control device for the carburetor of the present invention smoothes engine rotation over the entire operating range, and
This has the effect of preventing percolation and facilitating processing and maintenance.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the low-speed fuel system of a conventional fixed bench lily type carburetor, FIG. 2 is a sectional view of an embodiment of the variable bench lily type carburetor of the present invention, and FIG.
The figure is a sectional view, and FIG. 4 is a fuel flow characteristic diagram. 1...throttle valve, 5...slow jet, 6...
1st slow air bleed, 8... emulsion tube, 9... bleed hole, 10... slow passage.

Claims (1)

[Scope of utility model registration request] In a variable bench valve carburetor provided with a low-speed fuel system, the low-speed fuel system is provided adjacent to a main emulsion tube, and a lower part thereof communicates with the main emulsion tube via a slow jet for metering fuel. and a first pipe line in which a first slow air bleed for sucking air is provided above the slow jet, and a plurality of bleed holes arranged in multiple stages in the axial direction are provided in an intermediate portion thereof. and a second slow passage which surrounds the part of the first conduit where the bleed hole is provided and which is connected to a second slow air bleed at one end and an idle hole and a bypass hole at the other end. The slow passage is formed within the mounting surface of the driving diaphragm mechanism of the variable ventilary, and the second slow air bleed is formed between the atmospheric pressure chamber of the diaphragm mechanism and the A variable bench lily type vaporizer characterized by being formed so as to connect with a slow passage.