JPS6143258A - Variable venturi type carburetor - Google Patents

Abstract

PURPOSE:To improve the response performance of fuel control in acceleration and deceleration by allowing an air bleed passage to communicate to an atmospheric chamber in the piston operation part of a variable venturi type carburetor. CONSTITUTION:A needle valve 4 is fixed at the lower edge of a suction piston 3 installed onto the upstream side of a throttle valve 6. The piston 3 is operated by introducing a negative pressure into a negative-pressure chamber 15 from a suction hole 18 formed at the lower edge surface of the piston 3. The atmospheric chamber 16 on the other side of the negative-pressure chamber 15 communicates to a suction passage 2 on the upstream side of the piston 3 through a passage 19. The atmospheric chamber 16 further communiates to an air bleed hole 27 through a valve 40 and a passage 43. When a valve 38 is opened according to a variety of inputs and the valve 40 is opened and the piston 3 moves leftward immediately in acceleration, a negative pressure is temporarily generated in the atmospheric chamber 16, and the air bleed supplied from the hole 27 is reduced, and dense mixed gas is supplied. In deceleration when the piston 3 immediately moves rightward, a high pressure is temporarily generated in the atmospheric chamber 16, and a large amount of air is supplied from the opening 27, and lean mixed gas is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a variable venturi carburetor, and more particularly to a variable venturi carburetor in which the air-fuel ratio is controlled by air bleed.

Conventional technology A suction piston that changes the venturi area in response to the amount of intake air, a needle connected to the suction piston, a fuel passage extending in the axial direction of the needle so that the needle can enter, and a fuel passage provided in the fuel passage. A variable Pencil type carburetor is known which is equipped with a metering jet that cooperates with a needle and an air bleed passage for supplying air into the fuel passage (Japanese Patent Application Laid-open No. 58-106158, Japanese Patent Application Laid-Open No. 58-1999). -107849, etc.].

Problems to be Solved by the Invention In the variable venturi type carburetor described in the above publication, the amount of fuel is metered in an annular gap between a metering jet and a needle that moves together with a suction piston, and air bleed occurs during warm-up, etc. By changing the amount, the air-fuel ratio is further controlled. For this purpose, a flow control valve with a conical surface is used, which continuously changes the passage area according to the temperature of the engine coolant, and after warming up, obtains a constant air-fuel ratio that is at or slightly leaner to the stoichiometric air-fuel ratio. It looks like this. The air introduction portion of the conventional air bleed passage was formed upstream of the venturi in the intake passage or outside the carburetor.

Furthermore, after warming up, there is a demand for setting the air-fuel ratio to be even leaner, and for that purpose it is necessary to introduce a larger amount of bleed air. However, when accelerating with a lean air-fuel ratio by introducing a large amount of bleed air, there is a problem in that responsiveness is poor and a sense of acceleration is not felt.

Means for Solving the Problems In order to solve the above problems, the present invention introduces air through an air bleed passage into an atmospheric pressure chamber formed opposite to a negative pressure chamber formed on one side of the suction piston. It is characterized by connecting parts.

The working atmospheric pressure chamber is communicated with air through a hole and is normally at approximately atmospheric pressure, but if the suction piston moves rapidly, the pressure inside the atmospheric pressure chamber may temporarily decrease due to the action of the piston. It becomes a depressurized state or an accelerated state. Since the pressure is reduced during acceleration, the amount of air bleed is reduced, the air-fuel ratio is increased, and the acceleration response is improved.

Embodiment Referring to FIG. 1, numeral 1 is a carburetor main body, 2 is an intake passage extending vertically, 3 is a suction piston that moves back and forth in the horizontal direction within the intake passage 2, and 4 is attached to the tip surface of the suction piston 3. a throttle valve 7 provided in the intake passage 2 downstream of the suction piston 3;
respectively indicate the carburetor float chamber, and the suction piston 3
A venturi portion 8 is formed between the tip surface of the carburetor and the wall of the carburetor body. A hollow cylindrical casing 9 is fixed to the carburetor body 1, and a guide sleeve 10 extending in the axial direction of the casing 9 inside the casing 9 is attached. A bearing 12 is inserted into the guide sleeve 10, and the outer end of the guide sleeve 10 is closed by a blind cover 13.

On the other hand, a guide rod 14 is fixed to the suction piston 3, and the guide rod 14 is inserted into the bearing 12.
It is inserted movably in the axial direction of 4. Since the suction piston 3 is thus supported by the casing 9 via the bearing 12, the suction piston 3 can move smoothly in its axial direction. The interior of the casing 9 is divided by the suction piston 3 into a negative pressure chamber 15 and an atmospheric pressure chamber 16 opposite thereto. 17 is inserted. The negative pressure chamber 15 is connected to the venturi section 8 through a suction hole 18 formed in the suction piston 3, and the atmospheric pressure chamber 16 is connected to the carburetor main body l.
suction piston 3 through an air hole 19 formed in
It is connected within the upstream intake passage 2.

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor body 1 so that the needle 4 can enter therein, and a metering jet 21 is provided within this fuel passage 20. A fuel passage 20 upstream of the metering jet 21 is connected to the float chamber 7 via a downwardly extending fuel pipe 22.
The fuel in the float chamber 7 is sent into the fuel passage 20 via this fuel/mother inlet 22. Further, a hollow cylindrical O/O is disposed coaxially with the fuel passage 20 toward the intake passage 2.
, e-ru 23 are fixed. This nozzle 23 protrudes into the venturi portion 8 from the inner wall surface of the vaporizer main body, and the nozzle 23
The upper half of the tip of the piston 3 further protrudes from the lower half toward the suction piston 3.

The needle 4 extends through the nozzle 23 and the metering jet 21, and the fuel is metered into the annular gap formed between the needle 4 and the metering jet 21 and then supplied from the nozzle 23 into the intake passage 2. Ru.

As shown in FIGS. 1 to 3, the weighing jet 21
An annular air passage (chamber) 24 is formed around the metering jet 21, and a plurality of air bleed holes 25 are formed through the metering jet 21 to communicate the annular air passage 24 with the inside of the metering jet 21. An air bleed hole 25II is also formed downstream of the metering jet 21. Air bleed passages 26,27 formed in the carburetor body 1 in the annular air passage 24
connected to. These air bleed passages 26, 27 are formed separately in the carburetor body 1 and open into the annular air passage 24 in mutually opposing directions, and in the vicinity of the annular air passage 24, the air bleed passages The air bleed passage 26 is oriented vertically downward, and the other air bleed passage 27 is oriented vertically upward.

The air bleed passages 26, 27 do not necessarily have to face each other in the above-mentioned vertical relationship; the air bleed passages 26, 27 can also face each other in a horizontal relationship, or other arrangements are possible.

A flow control valve 30 is arranged in the air bleed passage 26,
An on-off valve 31 is arranged in the other air bleed passage 27 . Although omitted in Figure 1, JP-A-58-106
As shown in Japanese Patent No. 158, the air bleed passage 26
The negative pressure control valve that responds to engine negative pressure is the flow control valve 3.
can be connected in parallel with o.

The flow control valve 30 includes a bushing rod 33 with a conical surface that is actuated by the wax 32.
An air bleed hole 34 is formed corresponding to the conical surface 3. The air intake hole 35 of this flow control valve is connected upstream of the venturi portion 8 of the intake passage 2. 36 and 37 are the inlet and outlet of engine cooling water. This flow rate control valve 30 is of a known type, and is of a type that increases the amount of air bleed as the engine cooling water temperature rises.

Therefore, when the engine cooling water temperature is low, the air-fuel ratio is set to be rich because the amount of air bleed from now on is small, and as the temperature rises and the amount of air bleed increases, the air-fuel ratio becomes lean. Then, the air bleed amount becomes the maximum constant value.

The on-off valve 31 is for further diluting the air-fuel ratio (to about 21, for example), and operating negative pressure is introduced from the intake manifold via the solenoid valve 38. Solenoid valve 38
are controlled by a computer 39 which receives detection signals from the engine coolant temperature sensor a1 rotational speed sensor b1 throttle opening sensor C and others. The valve body 40 of the on-off valve 31 is biased by a spring 41 to normally close an air bleed passage 43 formed in the valve body, and opens when operating negative pressure is introduced under the control of the computer 39. For example, the valve may be opened when driving in a city, and may remain open during acceleration and deceleration within a small range of accelerator operation. However, the acceleration pump and the like can operate even during such acceleration. The air introduction portion of the air bleed passage 43 of this on-off valve 31 is connected to the atmospheric pressure chamber 16 described above.

In the variable venturi type carburetor having the above configuration, the suction piston 3 moves according to the amount of intake air, and the venturi portion 8
The area of the passageway is made variable. That is, when the throttle 6 is opened wide and the amount of intake air increases, the venturi section 8
When the flow rate increases and the negative pressure becomes large, this negative pressure enters the negative pressure chamber 15 from the suction hole 18 and moves the suction piston 3 to the left in FIG. When the amount of intake air is small, the suction piston 3 moves to the right. In this way, the negative pressure in the venturi section 8 is always approximately constant. The atmospheric pressure chamber 16 is connected to the intake passage 2 through an air hole 19.
It may be connected to the upper part of the inner venturi part and not constricted above the venturi part 8)! It is at atmospheric pressure. However, the suction piston 3 operates responsively to changes in the amount of intake air, and operates very quickly during acceleration and deceleration. When the suction piston 3 moves quickly in this way, the pressure in the atmospheric pressure chamber 16 changes instantaneously due to the action of the piston.

It can be seen from FIG. 1 that during acceleration when the suction piston 3 moves to the left, the atmospheric pressure chamber 16 becomes under negative pressure. Since the air introduction of the on-off valve 31 is connected to this atmospheric pressure chamber 16, when the engine is accelerated with the on-off valve 31 open, the air-fuel ratio is diluted by increasing the amount of air bleed. However, the bleed air disappears and the air-fuel ratio instantly shifts to the rich side. Therefore, acceleration response is improved.

However, this is irrelevant when the on-off valve 31 is closed. Conversely, during deceleration, the atmospheric pressure chamber 16 is pressurized and more bleed air is supplied, which improves the feeling of deceleration and reduces the amount of unburned fuel discharged.

Note that the air introduction section 35 of another air bleed passage 26 can also be connected to the atmospheric pressure chamber 16.

Details of the invention As explained above, according to the present invention, responsiveness is improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a variable venturi type carburetor according to the present invention, Fig. 2 is an enlarged view of the metering jet section of Fig. 1, and Fig. 3 is a sectional view taken along the line ■-■ in Fig. 2. . 1... Carburetor body, 3... Suction piston, 4
... Needle, 15... Negative pressure chamber, 16... Atmospheric pressure chamber, 20... Fuel passage, 21... Metering jet, 2
4... Annular air passage, 26. 27... Air bleed passage, 30... Flow rate control valve, 31... Opening/closing valve. □□-12□□7"- -, -7 Single layer V Figure 2 Figure 3

Claims (1)

[Claims] A carburetor main body having an intake passage, a suction piston that can move back and forth laterally into the intake passage, a negative pressure chamber and an atmospheric pressure chamber formed on each side of the suction piston, and a needle attached to the suction piston. A variable venturi carburetor having an accessible fuel passage, a metering jet disposed in the fuel passage and cooperating with the needle, and an air bleed passage for supplying air into the fuel passage, A variable venturi type carburetor, characterized in that an air intake portion of the air bleed passage is connected to the atmospheric pressure chamber.